Evaluation of the mechanical properties of implant-supported permanent crowns manufactured by additive and subtractive techniques: an in vitro study

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The number of studies evaluating the surface roughness and fracture resistance of these materials is limited. This study aims to evaluate these features of implant-supported crowns produced by additive manufacturing using an experimental setup as close to clinical conditions as possible, and to compare the results with those of crowns produced by subtractive manufacturing methods. Crowns produced in three different thicknesses were used to determine the optimal wall thicknesses applicable in clinical practice. Methods In this in vitro study, two composite resins and one hybrid ceramic were used. A total of 180 crowns, produced in three different thicknesses (1.0, 1.5, and 2.0 mm), were cemented onto titanium abutments. Half of the crowns were designated as experimental, whereas the other half served as control groups (n = 10 for each material and thickness group). The samples in the experimental group were subjected to thermal aging to simulate one year of clinical aging. Surface roughness measurements were taken using a profilometer, and a universal testing machine was employed to assess fracture resistance. Two-way ANOVA was used to compare group means, Duncan’s post-hoc test was used for the comparative evaluation of subgroups, and a t-test was used to compare surface roughness results before and after thermal aging. Results Compared with those produced by the subtractive manufacturing technique, the crowns produced via the additive manufacturing technique presented lower surface roughness and lower fracture resistance values. Thermal aging did not significantly affect these parameters across all test groups (p > 0.05). There was no difference between the two manufacturing techniques at 1.0 mm (p > 0.05), whereas crowns produced using the subtractive manufacturing technique at thicknesses of 1.5 and 2.0 mm presented greater fracture resistance than those produced with the additive manufacturing technique (p < 0.01). Conclusions It was concluded that implant-supported permanent crowns produced by the additive manufacturing technique using composite resin meet clinical requirements regarding surface roughness and fracture resistance. 3D printing Additive manufacturing CAD/CAM Dental crowns Fracture resistance Figures Figure 1 Figure 2 Figure 3 Background Computer-aided design/computer-aided manufacturing (CAD/CAM) techniques consist of additive manufacturing, also known as three-dimensional (3D) printing, and subtractive manufacturing, also known as milling [ 1 ]. Although both techniques are used in dentistry, CAD/CAM technology was considered more of a subtractive manufacturing technique until recently due to its widespread use [ 2 ]. Compared to subtractive manufacturing, additive manufacturing offers advantages such as higher accuracy, speed, better surface quality, cost-effectiveness, less waste material, and ease of intraoral repair. Despite these advantages, additive manufacturing has not been as widely used as subtractive manufacturing for producing permanent crown restorations until recently because of the lack of sufficiently durable and workable materials. In recent years, several 3D printable materials have been introduced to the market for permanent crown restorations, making it possible to take advantage of additive manufacturing to produce permanent restorations [ 3 ]. The routine use of implants to compensate for tooth loss has increased the importance of implant-supported crowns [ 4 , 5 ]. The development of composite resin materials suitable for additive manufacturing has contributed to the widespread use of 3D printers in the production of implant-supported permanent crowns. According to the most recent reviews, the number of studies in the literature on the mechanical properties of permanent crowns produced with 3D printers using composite resin is currently limited [ 1 , 6 ]. All of the few studies evaluating surface roughness have been conducted on samples prepared in forms other than crowns, such as bars, disks and rectangular blocks [ 7 – 10 ]. To the best of the authors' knowledge, this is the first study to evaluate the surface roughness of samples prepared in the form of crowns via additive manufacturing. The number of studies evaluating the fracture resistance of permanent crown restorations manufactured using 3D printing technology is also limited [ 3 , 9 , 11 – 13 ]. Among these five studies, only two were performed on implant-supported crowns, one screw-retained and one cement-retained [ 12 , 13 ]. The experimental setup of the only study conducted on implant-supported cement-retained crowns differed from our study regarding crown form and method of applying fracture load [ 12 ]. The aim of this study is to compare the fracture resistance and surface roughness of implant-supported cement-retained crowns produced with two composite resin materials used in additive manufacturing and one with a polymer-infiltrated ceramic network used in subtractive manufacturing. This study also evaluated the effects of thermal aging on these parameters. By performing experiments using crown samples produced with different wall thicknesses, we also attempted to determine the optimal thickness of implant-supported crowns produced from these materials that could withstand the maximum occlusal chewing force. Studies evaluating the fracture resistance of crowns should be performed with an experimental setup that simulates the clinical conditions as much as possible to guide clinical practice. This study attempted to use an experimental setup as close to clinical conditions as possible, especially for fracture loading experiments, with the aim of simulating the worst-case scenario that could be encountered in the clinic. The null hypotheses were that the manufacturing technique had no effect on the surface roughness and the fracture resistance of the implant-supported permanent crown materials, and one year of thermal aging had no effect on the surface roughness and the fracture resistance of the implant-supported permanent crown materials. Methods Design and preparation of crown samples Before crown design and manufacturing, implant analogs (PS IMPA 57821, BEGO, Bremen, Germany) were embedded in 15x15x20 mm polymethyl methacrylate (PMMA) based self-curing pink acrylic blocks. The abutments were screwed to implant analogs (PS TIA 57851, BEGO, Bremen, Germany) with a torque of 25 N/cm and retightened after ten minutes. One of the abutments was scanned using the 3Shape EScanner (3Shape, Copenhagen, Denmark), and the data obtained were transferred to the 3Shape Dental Design program (3Shape) for crown design. The crowns were designed with three different thicknesses, 1.0, 1.5, and 2.0 mm, with equal thicknesses of the occlusal, buccal, lingual, and proximal walls (Fig. 1). Care was taken to ensure that the supporting structures were not located in the center of the occlusal region where the force would be applied during fracture testing. The cement space was set to 50 µm. Figure 1. Cross-sectional CAD designs of crown restorations with wall thicknesses of 1.0, 1.5, and 2.0 mm. A total of 180 crowns were produced, 20 for each thickness in each material group. Ten of these 20 samples were designated the control, and 10 were designated the experimental group. The total sample size was determined by statistical power analysis using G*Power Software version 3.1 (effect size of 0.3, α = 0.05, observed power = 0.90). Hybrid ceramic VITA Enamic blocks (VE, VITA Zahnfabrik; Bad Säckingen, Germany) were selected for subtractive manufacturing. A 5-axis milling CAD/CAM device (ImesCore 350i Loader, Eiterfeld, Germany) was used for subtractive manufacturing. The crowns were cleaned in an ultrasonic cleaner after their support was removed with a cutoff wheel. For additive manufacturing, VarseoSmile Crown Plus (VS, Bego, Bremen, Germany) and Crowntec (CT, Saremco Dental AG Rebstein, Switzerland) composite resins were utilized. DLP-based 3D printers, Varseo XS (Bego, Bremen, Germany) for VS, and MAX UV (Asiga, Sydney, Australia) for CT were used. The layer thickness was selected as 50 µm. The printing orientation was determined to be 0 degrees since it was reported that marginal adaptation is better than other build angles [ 14 ]. After production was completed, the CT crowns were cleaned with a 96% ethanol-soaked cloth, and the VS crowns were cleaned in an ultrasonic bath containing 96% ethanol. The crowns were cured in a polymerization device (Otoflash G171-6, NK Optik, Baierbrunn, Germany) with 2000 × 2 light exposures for CT and 1500 × 2 light exposures for VS according to the manufacturers’ recommendations. The inner surfaces of the CT and VS crowns were airborne-particle abraded (Zhermack Sand S24R, Marl, Germany) at 1.5 bar pressure with Al 2 O 3 (Korox, BEGO, Bremen, Germany) from a distance of 10 mm for 10 s. The particle size of Al 2 O 3 was 110 µm for CT, whereas it was 50 µm for VS. The outer surfaces of the abutments were airborne-particle abraded with the same sandblasting machine at 1.5 bar pressure with 50 µm particle-sized Al 2 O 3 from a distance of 10 mm for 15 s. The VE group crowns were treated with 4.5% hydrofluoric acid (IPS Ceramic Etching Gel; Ivoclar AG, Schaan, Liechtenstein) for 60 s. Surface polishing was applied to all the crowns. The Vita Enamic Polishing Set (VITA Zahnfabrik; Bad Säckingen, Germany) was used for VE and the Diacomp Twist composite polishing set (Eve Gmbh, Keltern, Germany) was used for CT and VS. Polishing of the restorations was finished using a cotton bur. The screw access holes of the abutments were sealed with polytetrafluoroethylene (PTFE) tape, Teflon. The PTFE tape was inserted into the access hole cavity and firmly compacted with an amalgam plugger until the hole was completely covered [ 15 ]. Silane (UltraDent Products GmbH, Cologne, Germany) and then a bonding agent (Gluma, Kulzer GmbH, Hanau, Germany) were applied to the inner surfaces of the crowns and the same operator cemented the crowns with finger pressure using dual-cure resin cement (Els Cem, Saremco Dental AG, Rebstein, Switzerland) [ 12 , 16 ]. The buccal, lingual, palatal and occlusal surfaces of the crowns were light-cured for 40 s to ensure polymerization. Surface roughness measurements To ensure the measurements could be made on the same line before and after aging, the lines were marked by notching the acrylic blocks for each sample. Before the thermal aging process, the surface roughness of the crowns in the experimental group was measured using a contact profilometer (Mahrsurf M300C, Mahr, Gottingen, Germany). The measurements were made with a measurement length of 1.75 mm and a speed of 0.5 mm/s. To obtain reliable results during the measurements, the device was calibrated with a reference calibration block after every 10 test sample measurements. The measurements were repeated 3 times. The surface roughness values were determined by calculating the arithmetic average of these three measurements. Thermal aging process Thermal aging was performed in a thermal cycler (SD Mechatronik Thermocycler, Julabo GmbH, FT 200, Seelbach, Germany) at 30-second intervals between 5–55ºC for 10,000 cycles, corresponding to one year of aging [ 17 ]. During the aging period, the control group samples were kept in distilled water in a heating cabinet (Kottermann Labortechnik, Uetze, Germany) at 37ºC. After the thermal aging process was complete, the surface roughness measurements of the crowns in the experimental group were repeated 3 times with the same contact profilometer device from the locations where the first measurements were made, and the average Ra values of postthermal aging were calculated. Fracture resistance measurements All the samples in the control and experimental groups were subjected to a fracture resistance test using a universal testing machine (Lloyd-LRX, Lloyd Instruments, Fareham, UK)(Fig. 2). A spherical tip with a diameter of 5.0 mm was used during loading. Force was applied at a rate of 1 mm/min vertically to the center of each crown, corresponding to the point where the screw hole was located. The force application was continued until fracture occurred, and the fracture loads of the samples were recorded in Newtons by a computer program (Nexygen 4.0, Lloyd Instruments Ltd., Fareham, UK). Figure 2. Measuring fracture resistance by a universal testing machine. Statistical analysis Statistical analysis of the obtained data was performed with the SPSS 23.0 (SPSS Inc., Chicago, IL, USA) package program. The fracture resistance and surface roughness values were evaluated with the two-way ANOVA. Duncan’s post-hoc test was used for the comparative evaluation of subgroups. Dependent samples t-tests were performed to assess the effect of thermal aging on surface roughness. Results Surface roughness The descriptive statistics of the surface roughness measurements and t-test results (p values) are presented in Table 1 . Two-way ANOVA test indicated that the material type was a factor influencing surface roughness. Although no difference in surface roughness values was found between the crowns produced by additive manufacturing (VS and CT), the surface roughness values of crowns produced through subtractive manufacturing (VE) were found to be greater than those of VS and CT. Material thickness did not affect the surface roughness across all three material groups. Additionally, no statistically significant difference was observed in the roughness values obtained before and after thermal aging for all material and thickness groups (p > 0.05). Table 1 Descriptive statistics of the surface roughness measurements (Ra, µm) and t-test results (p values) Before thermal aging After thermal aging P value Group mm Mean ± SD Median (min-max) Mean ± SD Median (Min-Max) CT 1.0 0.141 ± 0.038 0.126 (0.098–0.214) 0.138 ± 0.036 0.138 (0.090–0.199) 0,699 1.5 0.146 ± 0.031 0.144 (0.102–0.198) 0.142 ± 0.036 0.136 (0.090–0.207) 0,579 2.0 0.136 ± 0.026 0.136 (0.089–0.183) 0.137 ± 0.023 0.141 (0.101–0.179) 0,736 VS 1.0 0.147 ± 0.038 0.138 (0.105–0.225) 0.148 ± 0.039 0.145 (0.085–0.222) 0,879 1.5 0.137 ± 0.028 0.137 (0.098–0.175) 0.142 ± 0.028 0.144 (0.103–0.189) 0,111 2.0 0.135 ± 0.027 0.133 (0.092–0.177) 0.127 ± 0.029 0.117 (0.093–0.169) 0,116 VE 1.0 0.166 ± 0.015 0.167 (0.144–0.191) 0.168 ± 0.014 0.170 (0.145–0.195) 0,324 1.5 0.178 ± 0.018 0.171 (0.155–0.214) 0.182 ± 0.022 0.178 (0.156–0.216) 0,375 2.0 0.176 ± 0.021 0.175 (0.144–0.210) 0.173 ± 0.021 0.168 (0.146–0.211) 0,226 SD: Standard Deviation CT: Crowntec VS: VarseoSmile Crown Plus VE: Enamic Fracture resistance The results of the fracture resistance measurements for the control and experimental groups are shown in Table 2 . The two-way ANOVA test results of fracture resistance indicated that the material type and wall thickness significantly differed (p < 0.01). In each material group, an increase in wall thickness resulted in a statistically significant difference in fracture resistance (p 0.05). In evaluating the wall thickness and material together, the comparative Duncan post hoc analysis revealed that there was no statistically significant difference in the fracture resistance values of the three materials at a thickness of 1.0 mm. It was also found that VE exhibited greater fracture resistance than VS and CT in 1.5 and 2.0 mm thicknesses (Table 3 , Fig. 3). No difference in fracture resistance was found between VS and CT for all three wall thicknesses. Table 2 Descriptive statistics of the fracture resistance measurements (N). SD: Standard Deviation CT: Crowntec VS: VarseoSmile Crown Plus VE: Enamic Control Group Experimental Group Group mm Mean ± SD Median (Min-Max) Mean ± SD Median (Min-Max) 1.0 425.2 ± 66.3 444.1 (326.1- 542.6) 413.8 ± 76.7 395.6 (321.3- 553.5) CT 1.5 670.7 ± 74.8 676.7 (563.0- 791.8) 657.1 ± 70.8 665.9 (513.3-736.9) 2.0 909.7 ± 97.4 892.5 (781.6- 1063.2) 902.4 ± 100.3 912.0 (756.5-1051.8) 1.0 444.1 ± 82.9 420.5 (349.8-622.8) 434.3 ± 72 423.1 (328.5-592.2) VS 1.5 688.3 ± 70.8 687.3 (584.0-841.7) 676.4 ± 69.4 679.4 (578.8- 794.3) 2.0 953.1 ± 89.8 939.5 (824.5-1109.1) 935.2 ± 92.9 939.2 (782.3-1059.2) 1.0 503.4 ± 51.5 506.0 (425.6-613.4) 480.5 ± 65.1 459.3 (413.6-574.7) VE 1.5 930.7 ± 83.6 937.6 (806.1- 1063.1) 898.4 ± 92.5 914.0 (782.8- 1012.7) 2.0 1291.3 ± 127.8 1296.4 (1042.7-1503.2) 1245.2 ± 144.9 1229.2 (968.5-1447.1) Table 3 Duncan post-hoc analysis results of the fracture resistance values of the experimental and control groups (N). mm CT VS VE 1.00 mm 419.50 ± 70.00 d 439.20 ± 75.76 d 491.90 ± 58.29 d 1.50 mm 663.90 ± 71.21 c 682.30 ± 68.51 c 914.50 ± 87.37 b 2.00 mm 906.00 ± 96.30 b 944.10 ± 89.40 b 1268.00 ± 135.07 a Rows and columns with the same letter indicate that the difference is not statistically significant. CT: Crowntec VS: VarseoSmile Crown Plus VE: Enamic Discussion Surface roughness Surface roughness quantitatively describes the degree of unevenness or irregularities found on the surface of a material [ 1 ]. The increase in the surface roughness of crown restorations, causes the increase of wear on the antagonist teeth, the adhesion of microorganisms and therefore results in stains, formation of plaque, loss of color stability, soft tissue reaction, and so negatively affects the aesthetic success and survival of the restoration [ 18 ]. Clinical studies have determined that 0.2 µm surface roughness of restorations in the mouth is the threshold value, especially in terms of bacterial plaque retention [ 19 , 20 ]. In this study, the surface roughness of the CT and VS groups was found to be significantly lower than that of the VE group. Although there were some differences between the groups, sufficiently smooth surfaces meeting the clinically accepted value (< 0.2 µm) could be obtained for the crowns in all three material groups with the surface polishing process applied before the thermal aging process. According to the most recent reviews, the number of studies in the literature on the surface roughness of permanent crowns produced with 3D printers using composite resins is currently limited [ 1 , 6 ]. All of the few studies evaluating the surface roughness of crown materials have been conducted on samples prepared in forms other than crowns. In a study comparing the surface roughness of samples produced from different crown materials, the surface roughnesses of disks produced from two 3D printable composite resins (CT and VS) and one resin nanoceramic used in subtractive manufacturing were compared. The surface roughnesses of disks produced from all three materials were clinically unacceptable before the polishing process but generally became acceptable after polishing [ 9 ]. In another study conducted by Bozoğulları et al., the surface roughness of samples in the shape of rectangular rods produced with 3D printable composite resin (CT) was lower than that produced with polymer infiltrated ceramic mesh (VE), as in our study [ 8 ]. In this study, it was also determined that there was no statistically significant difference between the surface roughness values measured before and after thermal aging. In the three studies we encountered in the literature, thermal aging did not cause a statistically significant change in surface roughness values as in our study [ 8 , 21 , 22 ]. According to the surface roughness results obtained in this study, the null hypothesis that "the manufacturing technique has no effect on the surface roughness of implant-supported permanent crowns" is rejected, and the hypothesis that "one year of thermal aging has no effect on the surface roughness of implant-supported permanent crown materials" is accepted. Fracture resistance The mechanical resistance of prosthetic restorations against masticatory forces is one of the most important factors affecting the survival and clinical success of restorations. The maximum bite force is defined as "the maximum force that a person can reach while clenching their teeth without causing pain in the periodontal tissues" [ 23 , 24 ]. The maximum bite force reaches its highest value in the molar tooth region and decreases as it moves anteriorly, reaching 1/3 or even 1/4 of the maximum value at its lowest point [ 25 ]. In an in vivo study, the maximum bite force for molar teeth was found to be 490 N in men and 402 N in women, whereas in another study, it was found to be 522 N for men and 441 N for women [ 24 , 26 ]. In a study evaluating the situation for incisors, the maximum bite force was reported to be as low as 190 N in men and 50 N in women [ 27 ]. The results of some in vivo studies have shown that the maximum bite force to which implant-supported crowns are exposed is close to the maximum bite force exposed by natural teeth and is usually slightly lower [ 28 – 30 ]. Since the fracture resistance values of all three materials with a thickness of 1.0 mm evaluated in our study were found to be slightly below the maximum bite force determined in clinical studies, it can be concluded that it would not be appropriate to use 1.0 mm and below thicknesses in restorations in the molar region. The fracture resistance values of restorations with wall thicknesses of 1.5 mm and 2.0 mm produced from different materials presented in Table 2 revealed that the crowns manufactured from VE blocks exhibited significantly greater performance than the crowns manufactured from composite resin materials (p < 0.01). When the fracture resistance values of the VS and CT crowns are compared, it is evident that these two materials do not exhibit a statistically significant difference in all three thicknesses. According to these results, it can be concluded that it will be safe enough to choose a wall thickness of 1.5 mm and above for implant-supported crowns to be used in the molar region for all three materials, and crowns with a wall thickness of 1.0 mm can be used in the anterior regions when necessary. There are a limited number of studies in the literature comparing the fracture resistance values of crowns produced using subtractive and additive techniques [ 3 , 9 , 11 – 13 ]. According to the authors' knowledge, 5 studies in the literature can be compared with this study in terms of fracture resistance. Two of these studies were performed on implant-supported crowns, and the other three used CAD/CAM fabricated resin dies as abutments. In the study conducted by Diken Türksayar et al., one of the two studies using implant-supported crowns, screw-retained abutments were used and the fracture resistances of crowns produced from VE, VS and CT were compared. In this study, crowns in the form of a natural tooth were used, but no information was given about the wall thickness of the crowns [ 13 ]. The fracture resistance of the crowns was measured only after thermomechanical aging. Consistent with our study, the fracture resistance of the crowns in the VE group was greater than that in the VS and CT groups. In the study conducted by Dönmez and Okutan, cement-retained implant-supported crowns were used [ 12 ]. Four groups of crowns, including those produced from VE and CT materials, were produced in an anatomical tooth form. The wall thickness of the crowns was designed to be 2 mm on the proximal surface, 2.5 mm on the buccal and palatal surfaces, and a minimum of 1.5 mm on the occlusal surface. The fracture resistance of the crowns was measured by applying vertical force to the buccal and palatal cusps without any prior aging process. No significant difference was found among the fracture resistances of the groups. In one of the studies where CAD/CAM produced dies were used as abutments, Zimmerman et al. used SLA-produced dies. In this study, crowns produced from five different subtractively manufactured crown materials, including VE and one type of 3D permanent crown material were used [ 11 ]. Like in our study, a crown form with homogeneous wall thicknesses was preferred and crowns with walls of 0.5, 1.0 and 1.5 mm were produced. The fracture resistance of the crowns was measured after thermomechanical aging. In our study, it was concluded that the fracture resistance increased as the wall thickness increased and was influenced by the type of production material. Unlike our study, it was concluded that 3D material was more fracture resistant than VE at thicknesses of 1.0 and 1.5 mm. In the study conducted by Suksuphan et al. 3D-printed dies were used [ 3 ]. Three crown material groups including VE and VS were used in this study. Similar to our study, instead of an anatomical tooth form, a crown form with homogeneous wall thickness was selected and the crowns were produced at thicknesses of 0.8, 1.0 and 1.5 mm. The fracture resistance of the crowns was evaluated without any prior aging process. As in our study, the fracture resistance of VE was found to be greater than that of VS and the fracture resistance was observed to increase proportionally with the restoration thickness. Çakmak et al. used milled epoxy resin dies in their study. In this study which compared VE, VS, and CT, an anatomical tooth form that differed from that used in our study was selected [ 9 ]. The minimum axial thickness for the crowns was 1.5 mm, and the minimum occlusal thickness was 2.0 mm. Mechanical aging was applied to the experimental group, and the fracture resistance was subsequently measured. It was concluded that mechanical aging negatively affects fracture resistance. They reported that the VE group had greater fracture resistance than the other groups did; however, unlike our findings and those of Diken et al., they concluded that the CT group had greater fracture resistance than the VS group did. According to the fracture resistance results obtained in this study, the hypothesis of “the manufacturing technique has no effect on the fracture resistance of implant-supported permanent crowns” is rejected, and the hypothesis of “one-year thermal aging has no effect on the fracture resistance of implant-supported permanent crown materials.” is accepted. Notably, the results obtained in the studies we reached in the literature are not consistent with each other and with our results except for one. The results of the study by Türksayar et al. are qualitatively similar to our study but they differ quantitatively [ 13 ]. To understand the source of differences among the results obtained in the studies we summarized above, it would be useful to briefly discuss the characteristics of the study setups used in the fracture resistance tests. Experimental setup The main factors that can affect the results of studies evaluating the fracture resistance of crowns are the properties of the material used in production and the fracture load position (central or cusp) applied during the test [ 31 ]. The E-modulus of the supporting structure (dies or abutments) also has a very important role in fracture resistance [ 32 , 33 ]. It would be appropriate to add the crown form and wall thickness used in the experiment to the parameters that may affect the results. A fracture test setup is formed by the combination of all these parameters and factors, and significantly affects the results obtained from the study. Unless the experimental setups used in such experiments are standardized, it will not be possible to objectively compare the results obtained from studies conducted with great effort and to derive information that will guide clinical applications from these results. In our study, an attempt was made to create an experimental setup as close as possible to clinical conditions. Crowns with homogeneous wall thickness were produced from materials routinely used in clinical practice, using devices and usage parameters in accordance with the recommendations of the material manufacturers. In the fracture load tests, the loading force was applied to the center of the occlusal surfaces of the crowns, the point where the screw hole is located. Thus, the weakest point of the crown was selected and the measurement was made according to the worst-case scenario. Our study is different from existing studies in some ways and, in our opinion, has an experimental setup that simulates clinical conditions as well as possible. Limitations One year of aging did not cause a significant difference in terms of either roughness or fracture resistance. Thermal aging applications for longer periods may be useful for comparing the clinical durability and survival of crown restorations produced from different materials and production technologies. Although the fact that crowns with homogeneous thicknesses on each wall were preferred in our study rather than in the form of natural teeth may seem to be a limitation, this form was preferable for evaluating the effect of thickness on fracture resistance more precisely. Conclusions 1. The implant-supported permanent crowns produced by additive manufacturing techniques using composite resin meet the clinical requirements regarding surface roughness and fracture resistance. 2. Although the wall thickness of implant-supported crowns does not affect surface roughness, fracture resistance increases proportionally with wall thickness. On the basis of the masticatory force information obtained from in vivo studies, the wall thickness of crowns produced using composite resin with additive manufacturing should be 1.5 mm or greater in the molar region, and crowns with lower wall thickness can be used in the anterior regions. 3. One year of thermal aging has no effect on the fracture resistance and surface roughness of implant-supported permanent crown materials. Abbreviations 3D Three-dimensional CAD/CAM Computer-Aided Design/Computer-Aided Manufacturing CT Saremco Crowntec PMMA Polymethyl methacrylate PTFE polytetrafluoroethylene VE Enamic VS VarseoSmile Crown Plus Declarations Acknowledgments The authors thank BEGO GmbH & Co for providing the implant abutments and analogs for this study. Author contributions Nilufer Ipek Sahin: Conceptualization, methodology, validation, investigation, resources, data curation, writing - original draft, writing - review & editing, visualization. Emre Tokar: Conceptualization, methodology, data curation, review & editing, supervision, project administration. Funding This study was funded by The Gazi University Scientific Research Projects Coordination Unit with the project code TDK-2023-8510. Data availability The data that support the findings of this study are available from the corresponding author upon reasonable request. Ethics approval and consent to participate Not applicable. Consent for publication Not applicable. Competing interests The authors declare no competing interests. References Pot GJ, Van Overschelde PA, Keulemans F, Kleverlaan CJ, Tribst JPM. Mechanical properties of additive-manufactured composite-based resins for permanent indirect restorations: a scoping review. Materials. 2024;17:3951. Kessler A, Hickel R, Reymus M. 3D printing in dentistry-state of the art. Oper Dent. 2020;45:30-40. Suksuphan P, Krajangta N, Didron PP, Wasanapiarnpong T, Rakmanee T. 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Fracture load of CAD/CAM-fabricated and 3D-printed composite crowns as a function of material thickness. Clin Oral Investig. 2019;23:2777–84. Donmez MB, Okutan Y. Marginal gap and fracture resistance of implant-supported 3D-printed definitive composite crowns: An in vitro study. J Dent. 2022;124:104216. Diken Türksayar AA, Demirel M, Donmez MB, Olcay EO, Eyüboğlu TF, Özcan M. Comparison of wear and fracture resistance of additively and subtractively manufactured screw-retained, implant-supported crowns. J Prosthet Dent. 2024;132:154-164. Farag E, Sabet A, Ebeid K, El Sergany O. Build angle effect on 3D-printed dental crowns marginal fit using digital light-processing and stereo-lithography technology: an in vitro study. BMC Oral Health. 2024;11;24(1):73. Maluly-Proni AT, Anchieta RB, Suzuki TY, Garcia de Oliveira F, Guedes AP, Rocha EP, et al. Sealing the screw access channel with polytetrafluoroethylene tape: advantages of the technique. Int J Oral Maxillofac Implants. 2017;32(5):1132–1134. Yildiz C, Vanlioğlu BA, Evren B, Uludamar A, Özkan YK. Marginal-internal adaptation and fracture resistance of CAD/CAM crown restorations. Dent Mater J. 2013;32:42-47. Gale MS, Darvell BW. Thermal cycling procedures for laboratory testing of dental restorations. J Dent. 1999;27:89-99. Al‐Dwairi ZN, Tahboub KY, Baba NZ, Goodacre, CJ, Özcan M. A comparison of the surface properties of CAD/CAM and conventional polymethylmethacrylate (PMMA). J Prosthodont. 2019;28:452-457. Bollen CM, Papaioanno W, Van Eldere J, Schepers E, Quirynen M, van Steenberghe D. The influence of abutment surface roughness on plaque accumulation and peri-implant mucositis. Clin Oral Implants Res. 1996;7:201-11. Bollen CM, Lambrechts P, Quirynen M. Comparison of surface roughness of oral hard materials to the threshold surface roughness for bacterial plaque retention: a review of the literature. Dent Mater. 1997;13:258-69. Baytur S, Diken Turksayar AA. Effects of post-polymerization conditions on color properties, surface roughness, and flexural strength of 3D-printed permanent resin material after thermal aging. J Prosthodont. 2023; https://doi.org/10.1111/jopr.13818 Acar B, Egilmez F. Effects of various polishing techniques and thermal cycling on the surface roughness and color change of polymer-based CAD/CAM materials. Am J Dent. 2018;31:91-96. Floystrand F, Kleven E, Gudbrand O. A novel miniature bite force recorder and its application. Acta Odontol Scand. 1982;40:209-214. Apostolov N, Chakalov I, Drajev T. Measurement of the maximum bite force in the natural dentition with a gnathodynamometer. Journal of Medical and Dental Practice. 2014;1:70-75. Helkimo E, Carlsson G, Carmell Y. Bite force in patients with functional disturbances of masticatory system. J Oral Rehabil. 1975;2:397. Bakke M, Holm B, Jensen BL, Michler L, Möller E. Unilateral, isometric bite force in 8-68-year-old women and men related to occlusal factors. Scand J Dent Res. 1990;98:149-58. Osborn JW, Mao J. A thin bite-force transducer with three-dimensional capabilities reveals a consistent change in bite-force direction during human jaw-muscle endurance tests. Arch Oral Biol. 1993;38:139-44. Al-Omiri MK, Sghaireen MG, Alhijawi MM, Alzoubi IA, Lynch CD, Lynch E. Maximum bite force following unilateral implant-supported prosthetic treatment: within-subject comparison to opposite dentate side. J Oral Rehabil. 2014;41:624-629. Al-Zarea BK. Maximum bite force following unilateral fixed prosthetic treatment: a within-subject comparison to the dentate side. Med Princ Pract. 2015;24:142-6. Singhal M, Budakoti V, Pratap H, Chourasiya P, Waghmare A. A comparative evaluation of bite pressure between single implant prosthesis and natural teeth: an in-vivo study. Journal of Dental Implants. 2022;12:86-94. Rekow ED, Harsono M, Janal M, Thompson VP, Zhang G. Factorial analysis of variables influencing stress in all-ceramic crowns. Dent Mater. 2006;22:125-32. Scherrer SS, de Rijk WG. The fracture resistance of all-ceramic crowns on supporting structures with different elastic moduli. Int J Prosthodont. 1993;6:462-7. Thompson VP, Rekow DE. Dental ceramics and the molar crown testing ground. J Appl Oral Sci. 2004;12:26-36. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-5919920","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":408618865,"identity":"1a49be7e-935b-4a93-9732-c2bd1cf15829","order_by":0,"name":"Nilufer Ipek Sahin","email":"","orcid":"","institution":"Gazi University Health Sciences Institute","correspondingAuthor":false,"prefix":"","firstName":"Nilufer","middleName":"Ipek","lastName":"Sahin","suffix":""},{"id":408618866,"identity":"befc3194-b69c-4d8e-8d9d-983d9c56ebe9","order_by":1,"name":"Emre Tokar","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA9ElEQVRIiWNgGAWjYPCCBAYG9gYgbQDEB4jRcACkhecAXAtjA3FaJBLgPPxa+MXOPnz8oSJN3nzm84sffxQwyPHdSGB/XIFHi+TsdGODA2dyDOfczimWkDBgMJa8kcDYeAaPFoPbaWwSB9sqGGdI5yRIGBgwJG4AacHnMvvbaew/gFrsZ0ieSf6RYMBQT1CLgXQaG8PBtpzEGRLsxyQOGDAkGBDSInE7jVnizJm05Bk8OWyWDQYShjPPPGyciU8L/+w0xg8VFcm2M9iPP77544+NPN/x5AMf8WlBAjygeJQAYiJiEgrYHxCrchSMglEwCkYYAADTuVGkP2mmrgAAAABJRU5ErkJggg==","orcid":"","institution":"Gazi University","correspondingAuthor":true,"prefix":"","firstName":"Emre","middleName":"","lastName":"Tokar","suffix":""}],"badges":[],"createdAt":"2025-01-28 16:53:16","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5919920/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5919920/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":75153684,"identity":"5f519f03-8a3c-4238-9c12-75ed1aaa9e3a","added_by":"auto","created_at":"2025-01-31 09:50:54","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":2533014,"visible":true,"origin":"","legend":"\u003cp\u003eCross-sectional CAD designs of crown restorations with wall thicknesses of 1.0, 1.5, and 2.0 mm.\u003c/p\u003e","description":"","filename":"figure1.png","url":"https://assets-eu.researchsquare.com/files/rs-5919920/v1/119f5550a5308914f707b42f.png"},{"id":75153683,"identity":"0b541ebb-b0e4-4fd4-b9f9-0aaabcc4c55b","added_by":"auto","created_at":"2025-01-31 09:50:54","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":681006,"visible":true,"origin":"","legend":"\u003cp\u003eMeasuring fracture resistance by a universal testing machine.\u003c/p\u003e","description":"","filename":"figure2.png","url":"https://assets-eu.researchsquare.com/files/rs-5919920/v1/551e6e16b9d62c59fba4a2d4.png"},{"id":75154092,"identity":"7fa25647-a757-4842-baec-03ff01e4ec60","added_by":"auto","created_at":"2025-01-31 09:58:54","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":181197,"visible":true,"origin":"","legend":"\u003cp\u003eFracture resistance of crowns with different thicknesses. (a) 1.0 mm, (b) 1.5 mm, (c) 2.0 mm.\u003c/p\u003e","description":"","filename":"figure3.png","url":"https://assets-eu.researchsquare.com/files/rs-5919920/v1/2ca9fc6813aa722a914131c4.png"},{"id":98777387,"identity":"1b755955-bacb-4ce0-ad2d-ca977b41f33c","added_by":"auto","created_at":"2025-12-22 12:26:41","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3486388,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5919920/v1/48356b4e-3433-4361-bb6a-33ac1bd64767.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Evaluation of the mechanical properties of implant-supported permanent crowns manufactured by additive and subtractive techniques: an in vitro study","fulltext":[{"header":"Background","content":"\u003cp\u003eComputer-aided design/computer-aided manufacturing (CAD/CAM) techniques consist of additive manufacturing, also known as three-dimensional (3D) printing, and subtractive manufacturing, also known as milling [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Although both techniques are used in dentistry, CAD/CAM technology was considered more of a subtractive manufacturing technique until recently due to its widespread use [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eCompared to subtractive manufacturing, additive manufacturing offers advantages such as higher accuracy, speed, better surface quality, cost-effectiveness, less waste material, and ease of intraoral repair. Despite these advantages, additive manufacturing has not been as widely used as subtractive manufacturing for producing permanent crown restorations until recently because of the lack of sufficiently durable and workable materials. In recent years, several 3D printable materials have been introduced to the market for permanent crown restorations, making it possible to take advantage of additive manufacturing to produce permanent restorations [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. The routine use of implants to compensate for tooth loss has increased the importance of implant-supported crowns [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. The development of composite resin materials suitable for additive manufacturing has contributed to the widespread use of 3D printers in the production of implant-supported permanent crowns.\u003c/p\u003e \u003cp\u003eAccording to the most recent reviews, the number of studies in the literature on the mechanical properties of permanent crowns produced with 3D printers using composite resin is currently limited [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. All of the few studies evaluating surface roughness have been conducted on samples prepared in forms other than crowns, such as bars, disks and rectangular blocks [\u003cspan additionalcitationids=\"CR8 CR9\" citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. To the best of the authors' knowledge, this is the first study to evaluate the surface roughness of samples prepared in the form of crowns via additive manufacturing. The number of studies evaluating the fracture resistance of permanent crown restorations manufactured using 3D printing technology is also limited [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan additionalcitationids=\"CR12\" citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. Among these five studies, only two were performed on implant-supported crowns, one screw-retained and one cement-retained [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. The experimental setup of the only study conducted on implant-supported cement-retained crowns differed from our study regarding crown form and method of applying fracture load [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe aim of this study is to compare the fracture resistance and surface roughness of implant-supported cement-retained crowns produced with two composite resin materials used in additive manufacturing and one with a polymer-infiltrated ceramic network used in subtractive manufacturing. This study also evaluated the effects of thermal aging on these parameters. By performing experiments using crown samples produced with different wall thicknesses, we also attempted to determine the optimal thickness of implant-supported crowns produced from these materials that could withstand the maximum occlusal chewing force.\u003c/p\u003e \u003cp\u003eStudies evaluating the fracture resistance of crowns should be performed with an experimental setup that simulates the clinical conditions as much as possible to guide clinical practice. This study attempted to use an experimental setup as close to clinical conditions as possible, especially for fracture loading experiments, with the aim of simulating the worst-case scenario that could be encountered in the clinic.\u003c/p\u003e \u003cp\u003eThe null hypotheses were that the manufacturing technique had no effect on the surface roughness and the fracture resistance of the implant-supported permanent crown materials, and one year of thermal aging had no effect on the surface roughness and the fracture resistance of the implant-supported permanent crown materials.\u003c/p\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eDesign and preparation of crown samples\u003c/h2\u003e \u003cp\u003eBefore crown design and manufacturing, implant analogs (PS IMPA 57821, BEGO, Bremen, Germany) were embedded in 15x15x20 mm polymethyl methacrylate (PMMA) based self-curing pink acrylic blocks. The abutments were screwed to implant analogs (PS TIA 57851, BEGO, Bremen, Germany) with a torque of 25 N/cm and retightened after ten minutes. One of the abutments was scanned using the 3Shape EScanner (3Shape, Copenhagen, Denmark), and the data obtained were transferred to the 3Shape Dental Design program (3Shape) for crown design. The crowns were designed with three different thicknesses, 1.0, 1.5, and 2.0 mm, with equal thicknesses of the occlusal, buccal, lingual, and proximal walls (Fig.\u0026nbsp;1). Care was taken to ensure that the supporting structures were not located in the center of the occlusal region where the force would be applied during fracture testing. The cement space was set to 50 \u0026micro;m.\u003c/p\u003e \u003cp\u003eFigure 1. Cross-sectional CAD designs of crown restorations with wall thicknesses of 1.0, 1.5, and 2.0 mm.\u003c/p\u003e \u003cp\u003eA total of 180 crowns were produced, 20 for each thickness in each material group. Ten of these 20 samples were designated the control, and 10 were designated the experimental group. The total sample size was determined by statistical power analysis using G*Power Software version 3.1 (effect size of 0.3, α\u0026thinsp;=\u0026thinsp;0.05, observed power\u0026thinsp;=\u0026thinsp;0.90).\u003c/p\u003e \u003cp\u003eHybrid ceramic VITA Enamic blocks (VE, VITA Zahnfabrik; Bad S\u0026auml;ckingen, Germany) were selected for subtractive manufacturing. A 5-axis milling CAD/CAM device (ImesCore 350i Loader, Eiterfeld, Germany) was used for subtractive manufacturing. The crowns were cleaned in an ultrasonic cleaner after their support was removed with a cutoff wheel.\u003c/p\u003e \u003cp\u003eFor additive manufacturing, VarseoSmile Crown Plus (VS, Bego, Bremen, Germany) and Crowntec (CT, Saremco Dental AG Rebstein, Switzerland) composite resins were utilized. DLP-based 3D printers, Varseo XS (Bego, Bremen, Germany) for VS, and MAX UV (Asiga, Sydney, Australia) for CT were used. The layer thickness was selected as 50 \u0026micro;m. The printing orientation was determined to be 0 degrees since it was reported that marginal adaptation is better than other build angles [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. After production was completed, the CT crowns were cleaned with a 96% ethanol-soaked cloth, and the VS crowns were cleaned in an ultrasonic bath containing 96% ethanol. The crowns were cured in a polymerization device (Otoflash G171-6, NK Optik, Baierbrunn, Germany) with 2000 \u0026times; 2 light exposures for CT and 1500 \u0026times; 2 light exposures for VS according to the manufacturers\u0026rsquo; recommendations.\u003c/p\u003e \u003cp\u003eThe inner surfaces of the CT and VS crowns were airborne-particle abraded (Zhermack Sand S24R, Marl, Germany) at 1.5 bar pressure with Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e (Korox, BEGO, Bremen, Germany) from a distance of 10 mm for 10 s. The particle size of Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e was 110 \u0026micro;m for CT, whereas it was 50 \u0026micro;m for VS. The outer surfaces of the abutments were airborne-particle abraded with the same sandblasting machine at 1.5 bar pressure with 50 \u0026micro;m particle-sized Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e from a distance of 10 mm for 15 s. The VE group crowns were treated with 4.5% hydrofluoric acid (IPS Ceramic Etching Gel; Ivoclar AG, Schaan, Liechtenstein) for 60 s.\u003c/p\u003e \u003cp\u003eSurface polishing was applied to all the crowns. The Vita Enamic Polishing Set (VITA Zahnfabrik; Bad S\u0026auml;ckingen, Germany) was used for VE and the Diacomp Twist composite polishing set (Eve Gmbh, Keltern, Germany) was used for CT and VS. Polishing of the restorations was finished using a cotton bur. The screw access holes of the abutments were sealed with polytetrafluoroethylene (PTFE) tape, Teflon. The PTFE tape was inserted into the access hole cavity and firmly compacted with an amalgam plugger until the hole was completely covered [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. Silane (UltraDent Products GmbH, Cologne, Germany) and then a bonding agent (Gluma, Kulzer GmbH, Hanau, Germany) were applied to the inner surfaces of the crowns and the same operator cemented the crowns with finger pressure using dual-cure resin cement (Els Cem, Saremco Dental AG, Rebstein, Switzerland) [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. The buccal, lingual, palatal and occlusal surfaces of the crowns were light-cured for 40 s to ensure polymerization.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eSurface roughness measurements\u003c/h3\u003e\n\u003cp\u003eTo ensure the measurements could be made on the same line before and after aging, the lines were marked by notching the acrylic blocks for each sample. Before the thermal aging process, the surface roughness of the crowns in the experimental group was measured using a contact profilometer (Mahrsurf M300C, Mahr, Gottingen, Germany). The measurements were made with a measurement length of 1.75 mm and a speed of 0.5 mm/s. To obtain reliable results during the measurements, the device was calibrated with a reference calibration block after every 10 test sample measurements. The measurements were repeated 3 times. The surface roughness values were determined by calculating the arithmetic average of these three measurements.\u003c/p\u003e\n\u003ch3\u003eThermal aging process\u003c/h3\u003e\n\u003cp\u003eThermal aging was performed in a thermal cycler (SD Mechatronik Thermocycler, Julabo GmbH, FT 200, Seelbach, Germany) at 30-second intervals between 5\u0026ndash;55\u0026ordm;C for 10,000 cycles, corresponding to one year of aging [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. During the aging period, the control group samples were kept in distilled water in a heating cabinet (Kottermann Labortechnik, Uetze, Germany) at 37\u0026ordm;C.\u003c/p\u003e \u003cp\u003eAfter the thermal aging process was complete, the surface roughness measurements of the crowns in the experimental group were repeated 3 times with the same contact profilometer device from the locations where the first measurements were made, and the average Ra values of postthermal aging were calculated.\u003c/p\u003e\n\u003ch3\u003eFracture resistance measurements\u003c/h3\u003e\n\u003cp\u003eAll the samples in the control and experimental groups were subjected to a fracture resistance test using a universal testing machine (Lloyd-LRX, Lloyd Instruments, Fareham, UK)(Fig.\u0026nbsp;2). A spherical tip with a diameter of 5.0 mm was used during loading. Force was applied at a rate of 1 mm/min vertically to the center of each crown, corresponding to the point where the screw hole was located. The force application was continued until fracture occurred, and the fracture loads of the samples were recorded in Newtons by a computer program (Nexygen 4.0, Lloyd Instruments Ltd., Fareham, UK).\u003c/p\u003e \u003cp\u003eFigure 2. Measuring fracture resistance by a universal testing machine.\u003c/p\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003eStatistical analysis\u003c/h2\u003e \u003cp\u003eStatistical analysis of the obtained data was performed with the SPSS 23.0 (SPSS Inc., Chicago, IL, USA) package program. The fracture resistance and surface roughness values were evaluated with the two-way ANOVA. Duncan\u0026rsquo;s post-hoc test was used for the comparative evaluation of subgroups. Dependent samples t-tests were performed to assess the effect of thermal aging on surface roughness.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003eSurface roughness\u003c/h2\u003e \u003cp\u003eThe descriptive statistics of the surface roughness measurements and t-test results (p values) are presented in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. Two-way ANOVA test indicated that the material type was a factor influencing surface roughness. Although no difference in surface roughness values was found between the crowns produced by additive manufacturing (VS and CT), the surface roughness values of crowns produced through subtractive manufacturing (VE) were found to be greater than those of VS and CT. Material thickness did not affect the surface roughness across all three material groups. Additionally, no statistically significant difference was observed in the roughness values obtained before and after thermal aging for all material and thickness groups (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eDescriptive statistics of the surface roughness measurements (Ra, \u0026micro;m) and t-test results (p values)\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003eBefore thermal aging\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003eAfter thermal aging\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eP value\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGroup\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003emm\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMedian (min-max)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eMedian (Min-Max)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003eCT\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.141\u0026thinsp;\u0026plusmn;\u0026thinsp;0.038\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.126 (0.098\u0026ndash;0.214)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.138\u0026thinsp;\u0026plusmn;\u0026thinsp;0.036\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.138 (0.090\u0026ndash;0.199)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0,699\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.146\u0026thinsp;\u0026plusmn;\u0026thinsp;0.031\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.144 (0.102\u0026ndash;0.198)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.142\u0026thinsp;\u0026plusmn;\u0026thinsp;0.036\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.136 (0.090\u0026ndash;0.207)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0,579\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.136\u0026thinsp;\u0026plusmn;\u0026thinsp;0.026\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.136 (0.089\u0026ndash;0.183)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.137\u0026thinsp;\u0026plusmn;\u0026thinsp;0.023\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.141 (0.101\u0026ndash;0.179)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0,736\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003eVS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.147\u0026thinsp;\u0026plusmn;\u0026thinsp;0.038\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.138 (0.105\u0026ndash;0.225)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.148\u0026thinsp;\u0026plusmn;\u0026thinsp;0.039\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.145 (0.085\u0026ndash;0.222)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0,879\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.137\u0026thinsp;\u0026plusmn;\u0026thinsp;0.028\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.137 (0.098\u0026ndash;0.175)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.142\u0026thinsp;\u0026plusmn;\u0026thinsp;0.028\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.144 (0.103\u0026ndash;0.189)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0,111\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.135\u0026thinsp;\u0026plusmn;\u0026thinsp;0.027\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.133 (0.092\u0026ndash;0.177)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.127\u0026thinsp;\u0026plusmn;\u0026thinsp;0.029\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.117 (0.093\u0026ndash;0.169)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0,116\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003eVE\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.166\u0026thinsp;\u0026plusmn;\u0026thinsp;0.015\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.167 (0.144\u0026ndash;0.191)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.168\u0026thinsp;\u0026plusmn;\u0026thinsp;0.014\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.170 (0.145\u0026ndash;0.195)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0,324\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.178\u0026thinsp;\u0026plusmn;\u0026thinsp;0.018\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.171 (0.155\u0026ndash;0.214)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.182\u0026thinsp;\u0026plusmn;\u0026thinsp;0.022\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.178 (0.156\u0026ndash;0.216)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0,375\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.176\u0026thinsp;\u0026plusmn;\u0026thinsp;0.021\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.175 (0.144\u0026ndash;0.210)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.173\u0026thinsp;\u0026plusmn;\u0026thinsp;0.021\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.168 (0.146\u0026ndash;0.211)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0,226\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eSD: Standard Deviation CT: Crowntec VS: VarseoSmile Crown Plus VE: Enamic\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eFracture resistance\u003c/h3\u003e\n\u003cp\u003eThe results of the fracture resistance measurements for the control and experimental groups are shown in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. The two-way ANOVA test results of fracture resistance indicated that the material type and wall thickness significantly differed (p\u0026thinsp;\u0026lt;\u0026thinsp;0.01). In each material group, an increase in wall thickness resulted in a statistically significant difference in fracture resistance (p\u0026thinsp;\u0026lt;\u0026thinsp;0.01). Thermal aging had no effect on fracture resistance (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05). In evaluating the wall thickness and material together, the comparative Duncan post hoc analysis revealed that there was no statistically significant difference in the fracture resistance values of the three materials at a thickness of 1.0 mm. It was also found that VE exhibited greater fracture resistance than VS and CT in 1.5 and 2.0 mm thicknesses (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, Fig.\u0026nbsp;3). No difference in fracture resistance was found between VS and CT for all three wall thicknesses.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eDescriptive statistics of the fracture resistance measurements (N). SD: Standard Deviation CT: Crowntec VS: VarseoSmile Crown Plus VE: Enamic\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026minus;\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026minus;\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003eControl Group\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003eExperimental Group\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGroup\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003emm\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMedian (Min-Max)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eMedian (Min-Max)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e425.2\u0026thinsp;\u0026plusmn;\u0026thinsp;66.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026minus;\" colname=\"c4\"\u003e \u003cp\u003e444.1 (326.1- 542.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e413.8\u0026thinsp;\u0026plusmn;\u0026thinsp;76.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026minus;\" colname=\"c6\"\u003e \u003cp\u003e395.6 (321.3- 553.5)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCT\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e670.7\u0026thinsp;\u0026plusmn;\u0026thinsp;74.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026minus;\" colname=\"c4\"\u003e \u003cp\u003e676.7 (563.0- 791.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e657.1\u0026thinsp;\u0026plusmn;\u0026thinsp;70.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026minus;\" colname=\"c6\"\u003e \u003cp\u003e665.9 (513.3-736.9)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e909.7\u0026thinsp;\u0026plusmn;\u0026thinsp;97.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026minus;\" colname=\"c4\"\u003e \u003cp\u003e892.5 (781.6- 1063.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e902.4\u0026thinsp;\u0026plusmn;\u0026thinsp;100.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026minus;\" colname=\"c6\"\u003e \u003cp\u003e912.0 (756.5-1051.8)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e444.1\u0026thinsp;\u0026plusmn;\u0026thinsp;82.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026minus;\" colname=\"c4\"\u003e \u003cp\u003e420.5 (349.8-622.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e434.3\u0026thinsp;\u0026plusmn;\u0026thinsp;72\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026minus;\" colname=\"c6\"\u003e \u003cp\u003e423.1 (328.5-592.2)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e688.3\u0026thinsp;\u0026plusmn;\u0026thinsp;70.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026minus;\" colname=\"c4\"\u003e \u003cp\u003e687.3 (584.0-841.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e676.4\u0026thinsp;\u0026plusmn;\u0026thinsp;69.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026minus;\" colname=\"c6\"\u003e \u003cp\u003e679.4 (578.8- 794.3)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e953.1\u0026thinsp;\u0026plusmn;\u0026thinsp;89.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026minus;\" colname=\"c4\"\u003e \u003cp\u003e939.5 (824.5-1109.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e935.2\u0026thinsp;\u0026plusmn;\u0026thinsp;92.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026minus;\" colname=\"c6\"\u003e \u003cp\u003e939.2 (782.3-1059.2)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e503.4\u0026thinsp;\u0026plusmn;\u0026thinsp;51.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026minus;\" colname=\"c4\"\u003e \u003cp\u003e506.0 (425.6-613.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e480.5\u0026thinsp;\u0026plusmn;\u0026thinsp;65.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026minus;\" colname=\"c6\"\u003e \u003cp\u003e459.3 (413.6-574.7)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVE\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e930.7\u0026thinsp;\u0026plusmn;\u0026thinsp;83.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026minus;\" colname=\"c4\"\u003e \u003cp\u003e937.6 (806.1- 1063.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e898.4\u0026thinsp;\u0026plusmn;\u0026thinsp;92.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026minus;\" colname=\"c6\"\u003e \u003cp\u003e914.0 (782.8- 1012.7)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e1291.3\u0026thinsp;\u0026plusmn;\u0026thinsp;127.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026minus;\" colname=\"c4\"\u003e \u003cp\u003e1296.4 (1042.7-1503.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e1245.2\u0026thinsp;\u0026plusmn;\u0026thinsp;144.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026minus;\" colname=\"c6\"\u003e \u003cp\u003e1229.2 (968.5-1447.1)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eDuncan post-hoc analysis results of the fracture resistance values of the experimental and control groups (N).\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003emm\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCT\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eVS\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eVE\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1.00 mm\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e419.50\u0026thinsp;\u0026plusmn;\u0026thinsp;70.00 \u003csup\u003ed\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e439.20\u0026thinsp;\u0026plusmn;\u0026thinsp;75.76 \u003csup\u003ed\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e491.90\u0026thinsp;\u0026plusmn;\u0026thinsp;58.29 \u003csup\u003ed\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1.50 mm\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e663.90\u0026thinsp;\u0026plusmn;\u0026thinsp;71.21 \u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e682.30\u0026thinsp;\u0026plusmn;\u0026thinsp;68.51 \u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e914.50\u0026thinsp;\u0026plusmn;\u0026thinsp;87.37 \u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2.00 mm\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e906.00\u0026thinsp;\u0026plusmn;\u0026thinsp;96.30 \u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e944.10\u0026thinsp;\u0026plusmn;\u0026thinsp;89.40 \u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1268.00\u0026thinsp;\u0026plusmn;\u0026thinsp;135.07 \u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eRows and columns with the same letter indicate that the difference is not statistically significant. CT: Crowntec VS: VarseoSmile Crown Plus VE: Enamic\u003c/p\u003e "},{"header":"Discussion","content":"\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003eSurface roughness\u003c/h2\u003e \u003cp\u003eSurface roughness quantitatively describes the degree of unevenness or irregularities found on the surface of a material [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. The increase in the surface roughness of crown restorations, causes the increase of wear on the antagonist teeth, the adhesion of microorganisms and therefore results in stains, formation of plaque, loss of color stability, soft tissue reaction, and so negatively affects the aesthetic success and survival of the restoration [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. Clinical studies have determined that 0.2 \u0026micro;m surface roughness of restorations in the mouth is the threshold value, especially in terms of bacterial plaque retention [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn this study, the surface roughness of the CT and VS groups was found to be significantly lower than that of the VE group. Although there were some differences between the groups, sufficiently smooth surfaces meeting the clinically accepted value (\u0026lt;\u0026thinsp;0.2 \u0026micro;m) could be obtained for the crowns in all three material groups with the surface polishing process applied before the thermal aging process.\u003c/p\u003e \u003cp\u003eAccording to the most recent reviews, the number of studies in the literature on the surface roughness of permanent crowns produced with 3D printers using composite resins is currently limited [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. All of the few studies evaluating the surface roughness of crown materials have been conducted on samples prepared in forms other than crowns.\u003c/p\u003e \u003cp\u003eIn a study comparing the surface roughness of samples produced from different crown materials, the surface roughnesses of disks produced from two 3D printable composite resins (CT and VS) and one resin nanoceramic used in subtractive manufacturing were compared. The surface roughnesses of disks produced from all three materials were clinically unacceptable before the polishing process but generally became acceptable after polishing [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn another study conducted by Bozoğulları et al., the surface roughness of samples in the shape of rectangular rods produced with 3D printable composite resin (CT) was lower than that produced with polymer infiltrated ceramic mesh (VE), as in our study [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. In this study, it was also determined that there was no statistically significant difference between the surface roughness values measured before and after thermal aging.\u003c/p\u003e \u003cp\u003eIn the three studies we encountered in the literature, thermal aging did not cause a statistically significant change in surface roughness values as in our study [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eAccording to the surface roughness results obtained in this study, the null hypothesis that \"the manufacturing technique has no effect on the surface roughness of implant-supported permanent crowns\" is rejected, and the hypothesis that \"one year of thermal aging has no effect on the surface roughness of implant-supported permanent crown materials\" is accepted.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003eFracture resistance\u003c/h2\u003e \u003cp\u003eThe mechanical resistance of prosthetic restorations against masticatory forces is one of the most important factors affecting the survival and clinical success of restorations. The maximum bite force is defined as \"the maximum force that a person can reach while clenching their teeth without causing pain in the periodontal tissues\" [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. The maximum bite force reaches its highest value in the molar tooth region and decreases as it moves anteriorly, reaching 1/3 or even 1/4 of the maximum value at its lowest point [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. In an in vivo study, the maximum bite force for molar teeth was found to be 490 N in men and 402 N in women, whereas in another study, it was found to be 522 N for men and 441 N for women [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e, \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. In a study evaluating the situation for incisors, the maximum bite force was reported to be as low as 190 N in men and 50 N in women [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. The results of some in vivo studies have shown that the maximum bite force to which implant-supported crowns are exposed is close to the maximum bite force exposed by natural teeth and is usually slightly lower [\u003cspan additionalcitationids=\"CR29\" citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eSince the fracture resistance values of all three materials with a thickness of 1.0 mm evaluated in our study were found to be slightly below the maximum bite force determined in clinical studies, it can be concluded that it would not be appropriate to use 1.0 mm and below thicknesses in restorations in the molar region. The fracture resistance values of restorations with wall thicknesses of 1.5 mm and 2.0 mm produced from different materials presented in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e revealed that the crowns manufactured from VE blocks exhibited significantly greater performance than the crowns manufactured from composite resin materials (p\u0026thinsp;\u0026lt;\u0026thinsp;0.01). When the fracture resistance values of the VS and CT crowns are compared, it is evident that these two materials do not exhibit a statistically significant difference in all three thicknesses. According to these results, it can be concluded that it will be safe enough to choose a wall thickness of 1.5 mm and above for implant-supported crowns to be used in the molar region for all three materials, and crowns with a wall thickness of 1.0 mm can be used in the anterior regions when necessary.\u003c/p\u003e \u003cp\u003eThere are a limited number of studies in the literature comparing the fracture resistance values of crowns produced using subtractive and additive techniques [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan additionalcitationids=\"CR12\" citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. According to the authors' knowledge, 5 studies in the literature can be compared with this study in terms of fracture resistance. Two of these studies were performed on implant-supported crowns, and the other three used CAD/CAM fabricated resin dies as abutments.\u003c/p\u003e \u003cp\u003eIn the study conducted by Diken T\u0026uuml;rksayar et al., one of the two studies using implant-supported crowns, screw-retained abutments were used and the fracture resistances of crowns produced from VE, VS and CT were compared. In this study, crowns in the form of a natural tooth were used, but no information was given about the wall thickness of the crowns [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. The fracture resistance of the crowns was measured only after thermomechanical aging. Consistent with our study, the fracture resistance of the crowns in the VE group was greater than that in the VS and CT groups.\u003c/p\u003e \u003cp\u003eIn the study conducted by D\u0026ouml;nmez and Okutan, cement-retained implant-supported crowns were used [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Four groups of crowns, including those produced from VE and CT materials, were produced in an anatomical tooth form. The wall thickness of the crowns was designed to be 2 mm on the proximal surface, 2.5 mm on the buccal and palatal surfaces, and a minimum of 1.5 mm on the occlusal surface. The fracture resistance of the crowns was measured by applying vertical force to the buccal and palatal cusps without any prior aging process. No significant difference was found among the fracture resistances of the groups.\u003c/p\u003e \u003cp\u003eIn one of the studies where CAD/CAM produced dies were used as abutments, Zimmerman et al. used SLA-produced dies. In this study, crowns produced from five different subtractively manufactured crown materials, including VE and one type of 3D permanent crown material were used [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Like in our study, a crown form with homogeneous wall thicknesses was preferred and crowns with walls of 0.5, 1.0 and 1.5 mm were produced. The fracture resistance of the crowns was measured after thermomechanical aging. In our study, it was concluded that the fracture resistance increased as the wall thickness increased and was influenced by the type of production material. Unlike our study, it was concluded that 3D material was more fracture resistant than VE at thicknesses of 1.0 and 1.5 mm.\u003c/p\u003e \u003cp\u003eIn the study conducted by Suksuphan et al. 3D-printed dies were used [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Three crown material groups including VE and VS were used in this study. Similar to our study, instead of an anatomical tooth form, a crown form with homogeneous wall thickness was selected and the crowns were produced at thicknesses of 0.8, 1.0 and 1.5 mm. The fracture resistance of the crowns was evaluated without any prior aging process. As in our study, the fracture resistance of VE was found to be greater than that of VS and the fracture resistance was observed to increase proportionally with the restoration thickness.\u003c/p\u003e \u003cp\u003e\u0026Ccedil;akmak et al. used milled epoxy resin dies in their study. In this study which compared VE, VS, and CT, an anatomical tooth form that differed from that used in our study was selected [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. The minimum axial thickness for the crowns was 1.5 mm, and the minimum occlusal thickness was 2.0 mm. Mechanical aging was applied to the experimental group, and the fracture resistance was subsequently measured. It was concluded that mechanical aging negatively affects fracture resistance. They reported that the VE group had greater fracture resistance than the other groups did; however, unlike our findings and those of Diken et al., they concluded that the CT group had greater fracture resistance than the VS group did.\u003c/p\u003e \u003cp\u003eAccording to the fracture resistance results obtained in this study, the hypothesis of \u0026ldquo;the manufacturing technique has no effect on the fracture resistance of implant-supported permanent crowns\u0026rdquo; is rejected, and the hypothesis of \u0026ldquo;one-year thermal aging has no effect on the fracture resistance of implant-supported permanent crown materials.\u0026rdquo; is accepted.\u003c/p\u003e \u003cp\u003eNotably, the results obtained in the studies we reached in the literature are not consistent with each other and with our results except for one. The results of the study by T\u0026uuml;rksayar et al. are qualitatively similar to our study but they differ quantitatively [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. To understand the source of differences among the results obtained in the studies we summarized above, it would be useful to briefly discuss the characteristics of the study setups used in the fracture resistance tests.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003eExperimental setup\u003c/h2\u003e \u003cp\u003eThe main factors that can affect the results of studies evaluating the fracture resistance of crowns are the properties of the material used in production and the fracture load position (central or cusp) applied during the test [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. The E-modulus of the supporting structure (dies or abutments) also has a very important role in fracture resistance [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e, \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. It would be appropriate to add the crown form and wall thickness used in the experiment to the parameters that may affect the results. A fracture test setup is formed by the combination of all these parameters and factors, and significantly affects the results obtained from the study. Unless the experimental setups used in such experiments are standardized, it will not be possible to objectively compare the results obtained from studies conducted with great effort and to derive information that will guide clinical applications from these results.\u003c/p\u003e \u003cp\u003eIn our study, an attempt was made to create an experimental setup as close as possible to clinical conditions. Crowns with homogeneous wall thickness were produced from materials routinely used in clinical practice, using devices and usage parameters in accordance with the recommendations of the material manufacturers.\u003c/p\u003e \u003cp\u003eIn the fracture load tests, the loading force was applied to the center of the occlusal surfaces of the crowns, the point where the screw hole is located. Thus, the weakest point of the crown was selected and the measurement was made according to the worst-case scenario. Our study is different from existing studies in some ways and, in our opinion, has an experimental setup that simulates clinical conditions as well as possible.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003eLimitations\u003c/h2\u003e \u003cp\u003eOne year of aging did not cause a significant difference in terms of either roughness or fracture resistance. Thermal aging applications for longer periods may be useful for comparing the clinical durability and survival of crown restorations produced from different materials and production technologies.\u003c/p\u003e \u003cp\u003eAlthough the fact that crowns with homogeneous thicknesses on each wall were preferred in our study rather than in the form of natural teeth may seem to be a limitation, this form was preferable for evaluating the effect of thickness on fracture resistance more precisely.\u003c/p\u003e \u003c/div\u003e"},{"header":"Conclusions","content":"\u003cp\u003e1. The implant-supported permanent crowns produced by additive manufacturing techniques using composite resin meet the clinical requirements regarding surface roughness and fracture resistance.\u003c/p\u003e\n\u003cp\u003e2. Although the wall thickness of implant-supported crowns does not affect surface roughness, fracture resistance increases proportionally with wall thickness. On the basis of the masticatory force information obtained from in vivo studies, the wall thickness of crowns produced using composite resin with additive manufacturing should be 1.5 mm or greater in the molar region, and crowns with lower wall thickness can be used in the anterior regions.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003cspan\u003e3. One year of thermal aging has no effect on the fracture resistance and surface roughness of implant-supported permanent crown materials.\u003cbr\u003e\u003c/span\u003e\u003c/p\u003e\n"},{"header":"Abbreviations","content":"\u003cp\u003e3D Three-dimensional\u003c/p\u003e\n\u003cp\u003eCAD/CAM Computer-Aided Design/Computer-Aided Manufacturing\u003c/p\u003e\n\u003cp\u003eCT Saremco Crowntec\u003c/p\u003e\n\u003cp\u003ePMMA Polymethyl methacrylate\u003c/p\u003e\n\u003cp\u003ePTFE polytetrafluoroethylene\u003c/p\u003e\n\u003cp\u003eVE Enamic\u003c/p\u003e\n\u003cp\u003eVS VarseoSmile Crown Plus\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors thank BEGO GmbH \u0026amp; Co for providing the implant abutments and analogs for this study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNilufer Ipek Sahin: Conceptualization, methodology, validation, investigation, resources, data curation, writing - original draft, writing - review \u0026amp; editing, visualization.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eEmre Tokar: Conceptualization, methodology, data curation, review \u0026amp; editing, supervision, project administration.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was funded by The Gazi University Scientific Research Projects Coordination Unit with the project code TDK-2023-8510.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe data that support the findings of this study are available from the corresponding author upon reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003ePot GJ, Van Overschelde PA, Keulemans F, Kleverlaan CJ, Tribst JPM. Mechanical properties of additive-manufactured composite-based resins for permanent indirect restorations: a scoping review. Materials. 2024;17:3951. \u003c/li\u003e\n\u003cli\u003eKessler A, Hickel R, Reymus M. 3D printing in dentistry-state of the art. Oper Dent. 2020;45:30-40.\u003c/li\u003e\n\u003cli\u003eSuksuphan P, Krajangta N, Didron PP, Wasanapiarnpong T, Rakmanee T. Marginal adaptation and fracture resistance of milled and 3D-printed CAD/CAM hybrid dental crown materials with various occlusal thicknesses. J Prosthodont Res. 2024;68:326-335.\u003c/li\u003e\n\u003cli\u003eNouh I, Kern M, Sabet AE, Aboelfadl AK, Hamdy AM, Chaar MS. Mechanical behavior of posterior all-ceramic hybrid-abutment-crowns versus hybrid-abutments with separate crowns-a laboratory study. Clin Oral Implants Res. 2019;30:90-98.\u003c/li\u003e\n\u003cli\u003ePjetursson BE, Valente NA, Strasding M, Zwahlen M, Liu S, Sailer I. A systematic review of the survival and complication rates of zirconia-ceramic and metal-ceramic single crowns. Clin Oral Implants Res. 2018;16:199-214.\u003c/li\u003e\n\u003cli\u003eBalestra D, Lowther M, Goracci C, Mandurino M, Cortili S, Paolone G, et al. 3D printed materials for permanent restorations in indirect restorative and prosthetic dentistry: a critical review of the literature. Materials. 2024;17(6):1380. \u003c/li\u003e\n\u003cli\u003eBorella PS, Alvares LAS, Ribeiro MTH, Moura GF, Soares CJ, Zancop\u0026eacute; K, et al. Physical and mechanical properties of four 3D-printed resins at two different thick layers: An in vitro comparative study. Dent Mater. 2023;39(8):686.\u003c/li\u003e\n\u003cli\u003eBozoğulları HN, Temizci T. Evaluation of the color stability, stainability, and surface roughness of permanent composite-based milled and 3D printed CAD/CAM restorative materials after thermocycling. \u003cem\u003eApplied Sciences\u003c/em\u003e. 2023;13(21):11895.\u003c/li\u003e\n\u003cli\u003e\u0026Ccedil;akmak G, Donmez MB, Molinero-Mourelle P, Kahveci \u0026Ccedil;, Abou-Ayash S, Peutzfeldt A, et al. Fracture resistance of additively or subtractively manufactured resin-based definitive crowns: effect of restorative material, resin cement, and cyclic loading. Dent Mater. 2024;40(7):1072-1077. \u003c/li\u003e\n\u003cli\u003eTokar E, Nezir M, Polat S, \u0026Ouml;zcan S. Evaluation of optical and mechanical properties of crown materials produced by 3D printing. Adv Clin Exp Med. 2024; https://doi.org/10.17219/acem/189856.\u003c/li\u003e\n\u003cli\u003eZimmermann M, Ender A, Egli G, \u0026Ouml;zcan M, Mehl A. Fracture load of CAD/CAM-fabricated and 3D-printed composite crowns as a function of material thickness. Clin Oral Investig. 2019;23:2777\u0026ndash;84. \u003c/li\u003e\n\u003cli\u003eDonmez MB, Okutan Y. Marginal gap and fracture resistance of implant-supported 3D-printed definitive composite crowns: An in vitro study. J Dent. 2022;124:104216.\u003c/li\u003e\n\u003cli\u003eDiken T\u0026uuml;rksayar AA, Demirel M, Donmez MB, Olcay EO, Ey\u0026uuml;boğlu TF, \u0026Ouml;zcan M. Comparison of wear and fracture resistance of additively and subtractively manufactured screw-retained, implant-supported crowns. J Prosthet Dent. 2024;132:154-164.\u003c/li\u003e\n\u003cli\u003eFarag E, Sabet A, Ebeid K, El Sergany O. Build angle effect on 3D-printed dental crowns marginal fit using digital light-processing and stereo-lithography technology: an in vitro study. BMC Oral Health. 2024;11;24(1):73. \u003c/li\u003e\n\u003cli\u003eMaluly-Proni AT, Anchieta RB, Suzuki TY, Garcia de Oliveira F, Guedes AP, Rocha EP, et al. Sealing the screw access channel with polytetrafluoroethylene tape: advantages of the technique. Int J Oral Maxillofac Implants. 2017;32(5):1132\u0026ndash;1134.\u003c/li\u003e\n\u003cli\u003eYildiz C, Vanlioğlu BA, Evren B, Uludamar A, \u0026Ouml;zkan YK. Marginal-internal adaptation and fracture resistance of CAD/CAM crown restorations. Dent Mater J. 2013;32:42-47.\u003c/li\u003e\n\u003cli\u003eGale MS, Darvell BW. Thermal cycling procedures for laboratory testing of dental restorations. J Dent. 1999;27:89-99.\u003c/li\u003e\n\u003cli\u003eAl‐Dwairi ZN, Tahboub KY, Baba NZ, Goodacre, CJ, \u0026Ouml;zcan M. A comparison of the surface properties of CAD/CAM and conventional polymethylmethacrylate (PMMA). J Prosthodont. 2019;28:452-457.\u003c/li\u003e\n\u003cli\u003eBollen CM, Papaioanno W, Van Eldere J, Schepers E, Quirynen M, van Steenberghe D. The influence of abutment surface roughness on plaque accumulation and peri-implant mucositis. Clin Oral Implants Res. 1996;7:201-11.\u003c/li\u003e\n\u003cli\u003eBollen CM, Lambrechts P, Quirynen M. Comparison of surface roughness of oral hard materials to the threshold surface roughness for bacterial plaque retention: a review of the literature. Dent Mater. 1997;13:258-69.\u003c/li\u003e\n\u003cli\u003eBaytur S, Diken Turksayar AA. Effects of post-polymerization conditions on color properties, surface roughness, and flexural strength of 3D-printed permanent resin material after thermal aging. J Prosthodont. 2023; https://doi.org/10.1111/jopr.13818\u003c/li\u003e\n\u003cli\u003eAcar B, Egilmez F. Effects of various polishing techniques and thermal cycling on the surface roughness and color change of polymer-based CAD/CAM materials. Am J Dent. 2018;31:91-96.\u003c/li\u003e\n\u003cli\u003eFloystrand F, Kleven E, Gudbrand O. A novel miniature bite force recorder and its application. Acta Odontol Scand. 1982;40:209-214.\u003c/li\u003e\n\u003cli\u003eApostolov N, Chakalov I, Drajev T. Measurement of the maximum bite force in the natural dentition with a gnathodynamometer. Journal of Medical and Dental Practice. 2014;1:70-75.\u003c/li\u003e\n\u003cli\u003eHelkimo E, Carlsson G, Carmell Y. Bite force in patients with functional disturbances of masticatory system. J Oral Rehabil. 1975;2:397.\u003c/li\u003e\n\u003cli\u003eBakke M, Holm B, Jensen BL, Michler L, M\u0026ouml;ller E. Unilateral, isometric bite force in 8-68-year-old women and men related to occlusal factors. Scand J Dent Res. 1990;98:149-58.\u003c/li\u003e\n\u003cli\u003eOsborn JW, Mao J. A thin bite-force transducer with three-dimensional capabilities reveals a consistent change in bite-force direction during human jaw-muscle endurance tests. Arch Oral Biol. 1993;38:139-44.\u003c/li\u003e\n\u003cli\u003eAl-Omiri MK, Sghaireen MG, Alhijawi MM, Alzoubi IA, Lynch CD, Lynch E. Maximum bite force following unilateral implant-supported prosthetic treatment: within-subject comparison to opposite dentate side. J Oral Rehabil. 2014;41:624-629.\u003c/li\u003e\n\u003cli\u003eAl-Zarea BK. Maximum bite force following unilateral fixed prosthetic treatment: a within-subject comparison to the dentate side. Med Princ Pract. 2015;24:142-6.\u003c/li\u003e\n\u003cli\u003eSinghal M, Budakoti V, Pratap H, Chourasiya P, Waghmare A. A comparative evaluation of bite pressure between single implant prosthesis and natural teeth: an in-vivo study. Journal of Dental Implants. 2022;12:86-94.\u003c/li\u003e\n\u003cli\u003eRekow ED, Harsono M, Janal M, Thompson VP, Zhang G. Factorial analysis of variables influencing stress in all-ceramic crowns. Dent Mater. 2006;22:125-32.\u003c/li\u003e\n\u003cli\u003eScherrer SS, de Rijk WG. The fracture resistance of all-ceramic crowns on supporting structures with different elastic moduli. Int J Prosthodont. 1993;6:462-7. \u003c/li\u003e\n\u003cli\u003eThompson VP, Rekow DE. Dental ceramics and the molar crown testing ground. J Appl Oral Sci. 2004;12:26-36. \u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"3D printing, Additive manufacturing, CAD/CAM, Dental crowns, Fracture resistance","lastPublishedDoi":"10.21203/rs.3.rs-5919920/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5919920/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e \u003cp\u003eThe development of composite resin materials that can be used with additive manufacturing techniques has contributed to the widespread use of 3D printers for producing implant-supported permanent crowns. The number of studies evaluating the surface roughness and fracture resistance of these materials is limited. This study aims to evaluate these features of implant-supported crowns produced by additive manufacturing using an experimental setup as close to clinical conditions as possible, and to compare the results with those of crowns produced by subtractive manufacturing methods. Crowns produced in three different thicknesses were used to determine the optimal wall thicknesses applicable in clinical practice.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eIn this in vitro study, two composite resins and one hybrid ceramic were used. A total of 180 crowns, produced in three different thicknesses (1.0, 1.5, and 2.0 mm), were cemented onto titanium abutments. Half of the crowns were designated as experimental, whereas the other half served as control groups (n\u0026thinsp;=\u0026thinsp;10 for each material and thickness group). The samples in the experimental group were subjected to thermal aging to simulate one year of clinical aging. Surface roughness measurements were taken using a profilometer, and a universal testing machine was employed to assess fracture resistance. Two-way ANOVA was used to compare group means, Duncan\u0026rsquo;s post-hoc test was used for the comparative evaluation of subgroups, and a t-test was used to compare surface roughness results before and after thermal aging.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eCompared with those produced by the subtractive manufacturing technique, the crowns produced via the additive manufacturing technique presented lower surface roughness and lower fracture resistance values. Thermal aging did not significantly affect these parameters across all test groups (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05). There was no difference between the two manufacturing techniques at 1.0 mm (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05), whereas crowns produced using the subtractive manufacturing technique at thicknesses of 1.5 and 2.0 mm presented greater fracture resistance than those produced with the additive manufacturing technique (p\u0026thinsp;\u0026lt;\u0026thinsp;0.01).\u003c/p\u003e\u003ch2\u003eConclusions\u003c/h2\u003e \u003cp\u003eIt was concluded that implant-supported permanent crowns produced by the additive manufacturing technique using composite resin meet clinical requirements regarding surface roughness and fracture resistance.\u003c/p\u003e","manuscriptTitle":"Evaluation of the mechanical properties of implant-supported permanent crowns manufactured by additive and subtractive techniques: an in vitro study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-01-31 09:50:50","doi":"10.21203/rs.3.rs-5919920/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"5416aebd-0120-4d77-9b10-9c78f8d66fd9","owner":[],"postedDate":"January 31st, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-12-22T04:39:19+00:00","versionOfRecord":[],"versionCreatedAt":"2025-01-31 09:50:50","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-5919920","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5919920","identity":"rs-5919920","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}