Digital Versus Conventional Altered Cast Techniques For Constructing Mandibular Distal Extension Removable Partial Dentures Using Digitally Fabricated Frameworks: A clinical comparative parallel study of alveolar bone height changes

Digital Versus Conventional Altered Cast Techniques For Constructing Mandibular Distal Extension Removable Partial Dentures Using Digitally Fabricated Frameworks: A clinical comparative parallel study of alveolar bone height changes | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Digital Versus Conventional Altered Cast Techniques For Constructing Mandibular Distal Extension Removable Partial Dentures Using Digitally Fabricated Frameworks: A clinical comparative parallel study of alveolar bone height changes Abdullah S. A. AboZied, Marwa Ahmed Aboelez, Aisha Z. H. Mostafa, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7739601/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Background Conventional altered cast technique for distal extension removable partial dentures (RPDs) involve multiple clinical and laboratory steps. To overcome the limitations of conventional method and enhance bone support and load distribution, digital workflows have been introduced in RPD fabrication. Methods Twenty-two patients (n=22) of age ranging from 50 to 60 years were included in this parallel clinical study. Each patient received a maxillary complete denture and a mandibular bilateral distally extended RPD made with digitally constructed frameworks. Patients were randomly and equally divided into two groups (n=11) based on the altered cast method used: Group I : Digitally fabricated altered cast and Group II : Conventionally fabricated altered cast. Alveolar bone height changes of the residual ridge and around abutment teeth were assessed using CBCT at three intervals: 1 st 6 months (T1), 2 nd 6 months (T2) and 12 months (T3) post-insertion. Data were collected and statistically analyzed using SPSS software version 25. Results There was no statistically significant difference in bone resorption around abutment teeth in two groups at T1, T2 and T3 intervals after RPD insertion where ( P value= .837, .423, .550) respectively. There was no statistically significant difference in bone resorption of residual alveolar ridge in two groups at T1, T2 and T3 intervals after RPD insertion where ( P value= .850, .649, .949) respectively. Within each group the comparison of alveolar bone height changes around abutment teeth and of residual ridge revealed significant difference between time intervals. Conclusion Both digital and conventional altered cast techniques utilizing digitally constructed metal frameworks demonstrated comparable effectiveness of maintaining alveolar bone height of residual ridges and around abutment teeth of distally extended RPDs. Clinical trial registry number (No. NCT05899712) (06/09/ 2023) Digital altered cast Conventional altered cast Distal extension RPD Alveolar bone height Abutment teeth Residual ridge resorption CBCT Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Background Removable partial dentures (RPDs) remain a cornerstone in the rehabilitation of partially edentulous patients, particularly in cases involving distal extension (free-end saddle) scenarios [ 1 , 2 ]. These prostheses are widely utilized in clinical practice due to their cost-effectiveness and ability to restore function and aesthetics [ 3 ]. If partial dentures are designed to give the optimal support, stability, and retention, it can provide favorable outcomes for individuals using them [ 4 , 5 ]. Mandibular distal extension RPD face special difficulties due to unequal support from the remaining dentition and edentulous ridge. This disparity frequently leads to unequal stress distribution, which may accelerate alveolar bone resorption and increase abutment tooth movement [ 6 , 7 ]. The conventional altered cast method has been used to address these problems by creating a functional impression of the edentulous region during framework try-in. This approach can improve stress distribution and denture base adaptation to the ridge [ 8 , 9 ]. When the denture base is appropriately extended using the altered cast technique it evenly distributes force and receives support from the teeth and the denture base. Typically, a selective pressure impression is used to create a well-fitted RPD with a proper extension base for Kennedy class I and II arches [ 10 , 11 ]. Compared to the conventional method, the digitally altered cast impression approach may decrease inter-operator variability and increase accuracy. For RPDs with distal extensions, the altered cast impression technique is often used. This method helps ensure the denture base receives proper support from the soft tissues while maintaining an accurate relationship with the tooth abutments [ 12 , 13 ]. The fabrication of removable partial denture (RPD) frameworks has undergone significant advancements with the integration of digital technologies in prosthodontics [ 14 , 15 ]. The application of intraoral scanning, computer-aided design (CAD), and additive or subtractive manufacturing techniques such as 3D printing and milling has enhanced the precision and efficiency of RPD production. These digital workflows have the potential to minimize operator-dependent variability and improve the passive fit of prosthetic components, thereby contributing to improved clinical outcomes [ 16 , 17 ]. Digital technology has transformed the way removable partial dentures (RPDs) are made. One of the recent advancements is the use of intraoral scanners (IOS) to take digital impressions, which are now being used in clinical practice for the fabrication of RPDs [ 18 – 20 ]. Alternative technologies for additively constructing cobalt chromium and titanium frameworks, such as selective laser sintering (SLS) and selective laser melting (SLM), show potential in reducing fabrication defects [ 21 , 22 ]. Peng et al. [ 23 ] reported that RPD frameworks created using SLM showed greater accuracy than those created using conventional techniques. When fabricating RPD frameworks, SLM and SLS are frequently utilized to construct the detailed and complicated structure of the framework as intended [ 24 , 25 ]. Removable partial dentures (RPDs) may have a great influence on the health of supporting oral structures. One of the concerns associated with long-term RPD wear is the potential for alveolar bone resorption, particularly in the regions surrounding abutment teeth. Understanding the extent and pattern of this bone loss is essential for improving prosthetic design and patient outcomes [ 26 ]. Excessive stress on the abutment teeth and residual ridge can accelerate alveolar bone resorption. Minimizing this effect helps to conserve alveolar bone loss to patients using RPDs [ 27 ]. The long-term impact of RPDs on alveolar bone remains a clinical concern. The lack of posterior abutments in distal extension cases often leads to uneven load distribution, accelerating bone resorption beneath the denture base [ 28 ]. With the advent of cone-beam computed tomography (CBCT), a more accurate three-dimensional assessment of bone changes has become possible, allowing for a deeper understanding of the resorptive patterns associated with prolonged RPD use [ 29 , 30 ]. Since no previous clinical study had compared alveolar bone resorption around abutments and in residual ridges associated with mandibular class I removable partial dentures (RPDs) fabricated using digitally and conventionally altered cast techniques, the goal behind this study was to evaluate the two methods used for mandibular class I RPD construction. The null hypothesis for this research was that there was no difference between digital and conventional altered cast technique regarding the changes of abutment teeth and residual ridge alveolar bone. Methods Study design Twenty two patients (Ten females and Twelve males) with completely edentulous maxilla and partially edentulous mandibles with retaining anteriors and first premolar teeth were included in a comparative parallel randomized clinical trial. They were choosen from the outpatient clinic of the Prosthodontic Department, Faculty of Dentistry, Mansoura University with ages between [50–65] years. Figure 1 displays the study procedures' flowchart. All experiments were performed in accordance with relevant guidelines and regulations. Faculty of dentistry ethics board committee approved this clinical investigation, and it was given the ethical approval number (A0203023 RP).The study's protocol was registered in clinicaltrials.gov (Identifier: NCT05899712; registration date: September 6, 2023). Data collection The inclusion criteria included patients with completely edentulous maxillae and partially edentulous mandibles retaining anteriors and first premolar teeth. Premolars were required to be healthy, with good periodontal and bone support. Good crown/root ratio not greater than 1:2, confirmed radiographically. Patients with severe ridge resorption or undercuts, systemic diseases affecting bone metabolism (e.g., diabetes, osteoporosis) were excluded. The presentation of this study complied with the requirements set out by CONSORT (consolidated standards for reporting randomized trials). Sample size Sample size estimation was performed using G*Power software (version 3.1; Heinrich Heine University Düsseldorf), based on data from a previously published study [ 28 ]. With a significance level (α) of 0.05 and a power of 80%, the minimum required sample size was determined to be 11 participants per group.Written informed consent was obtained from all participants after they received comprehensive information regarding the study’s objectives and procedures. Randomization and blinding Participants were divided into two groups according to the patient's gender; thirteen males and nine females were chosen at random for each group (n = 11) to ensure an equal gender distribution.Participant allocation was conducted using a simple randomization technique with computer-generated random number tables in SPSS software (version 25; IBM Corp.), following the establishment of a defined sampling frame. To ensure blinding, treatment procedures and follow-up assessments were performed by two independent clinicians, each of whom was blinded to the group assignments throughout the study duration. The group allocation was also concealed from the participants. Participants were equally assigned to two groups based on the altered cast technique: Group I: Digitally fabricated altered cast and Group II: Conventionally fabricated altered cast. Prosthodontic procedures Each patient received a maxillary complete denture and a mandibular class I RPD fabricated using the altered cast technique with digitally constructed frameworks. Mandibular teeth and alveolar ridge mucosa were scanned using an intraoral scanner (IOS) (MEDIT i700; MEDIT) Fig. 2 A. Digital surveying of the 3D model was performed to determine the optimal path of insertion, measuring amount of undercuts and cast tilting if needed to plan necessary mouth preparations Fig. 2 B. Mouth preparation followed this sequence: Mesial occlusal rest seats and guiding planes were prepared on teeth number 34 and 44. Cingulum rests were prepared on teeth number 33 and 43. A final intraoral scan of the prepared teeth and alveolar ridge mucosa was performed using an IOS (MEDIT i700; MEDIT) Fig. 2 C. RPD frameworks were designed using Partial CAD 3.1 (EXOCAD, Rijeka), with a standardized design applied to all cases for consistency. A single laboratory fabricated all mandibular RPDs and maxillary complete dentures. Framework components, including RPA clasps, lingual bar, mesh work as denture base minor connector and cingulum rest as indirect retainer according to RPD design principles for distal extension cases Fig. 2 D. The finalized design was exported as an STL file and transferred to a rapid prototyping system (M270; EOS) to 3D print the resin try-in and master cast. The resin framework was tried intraorally. Final Co-Cr frameworks (Cobalt Chrome SP2; EOS GmbH) were fabricated using selective laser melting with 0-degree built orientation, then polished and seated on the 3D-printed master cast. Intraoral try-in of the metal framework was performed using disclosing media to check for interferences, verify component contact, and confirm complete seating. A light-cured acrylic special tray was adapted over the printed meshwork framework and cured. The tray was placed intraorally to verify peripheral extensions, which were refined with modeling compound and selectively trimmed to accommodate impression material. Zinc oxide eugenol (ZOE) impression material was applied to the fitting surface and the tray was seated. Occlusal rests and indirect retainers were fully seated during the impression. According to the technique of producing the altered cast, patients were classified into two equal groups. Group I: Digital altered cast construction [ 13 ] The fitting surface of the impression was scanned extra-orally Fig. 3 A. Then, STL file of the altered impression scan was selected then clicked on "Invert the normal" This command turned the fitting surface of impression into active surface Fig. 3 B. The original scan used to create the RPD framework was opened in the IOS software, and the distal extension denture base area was erased to accommodate the altered cast impression. The impression was seated intraorally, and IOS was used to scan the labial, buccal, and distal areas with the framework in place. Scanning continued until the dentition and impression material aligned in the software Fig. 3 C. Full arch scan with framework and the framework with the altered impression scan were imported into Meshmixer (Autodesk). Once both models were loaded, the align tool was used to match them accurately through selected common landmarks like teeth, clasps, and rest. After confirming the alignment, the digital altered cast was virtually merged with the tooth cast Fig. 3 D and fabricated using additive manufacturing (AM). After 3D printing of digital altered cast, it was duplicated into stone cast to continue the rest of RPD construction steps. Group II: Conventional altered cast construction [ 8 ] Edentulous ridges were removed from the duplicated master cast 1 mm distal to the abutments using a jeweler’s saw, and the cut surfaces were roughened with a bur to ensure stone adhesion. The altered impression was seated on the cast, and the framework was checked for proper fit; sticky wax was applied to stabilize framework Fig. 4 A, B. A line was marked 2 mm below the impression border, along which beading wax was applied. The cast was then boxed with wax to a height of 13 mm above the highest point of the impression, and all edges were sealed to prevent stone leakage Fig. 4 C. The boxed impression was filled with dental stone and left to set. After setting, all boxing materials and the impression were removed to retrieve the altered cast Fig. 4 D. Jaw relation of maxillary complete denture opposes class I removable partial denture for both groups was done. Try in of dentures was done to evaluate vertical dimension, esthetics and phonetics. Flasking of waxed denture to produce final prosthesis. Compression mold technique was used to produce mandibular class I RPD and maxillary complete denture. The flask is heated to 70°C for 7 hours then 100°C for 3 hours (The total 10 hours). Once the finished denture has been delivered. All the following were checked, fit of denture base, denture stability, retention, soft tissue adaptation, abutment tooth adaptation, vertical dimension of occlusion, esthetics and phonetics Fig . 5A, B. Radiographic evaluation The alveolar bone height changes of abutment teeth and residual ridge was measured using CBCT at following periods: (T0) at RPD insertion, (T6) six months after RPD insertion and (T12) twelve months after RPD insertion. CBCT images were obtained using the CBCT machine (Carestream CS 8100 3D CBCT, Carestream Dental) at 90 kVp and 3.2 mA. Alveolar bone resorption was assessed using Real Guide software (3Diemme). CBCT image fusion was performed to establish a consistent reference point (the abutment apex) using a horizontal line tangential to the apex and perpendicular to the long axis. Coronal views were used to measure mesial and distal bone heights, while sagittal views assessed buccal and lingual heights. Vertical lines parallel to the abutment’s long axis were used to measure the distance from the crestal bone to the apex in all directions. Measurements were performed twice by the same calibrated examiner, two weeks apart, to evaluate reproducibility [ 18 ] Fig. 6 . CBCT scans adjusted to capture the entire mandibular residual ridge and analyzed using Real Guide software. Images were aligned to a standardized reference plane, with a horizontal line tangential to the superior border of the mandibular canal. Vertical lines were drawn perpendicular to this plane at measurement sites. Alveolar bone height was measured as the vertical distance from the alveolar crest to the superior border of the mandibular canal at 10, 20, and 30 mm from the last abutment tooth Fig. 7 . Measurements were performed twice by the same calibrated examiner, two weeks apart, and intra-examiner reliability was confirmed using the Intraclass Correlation Coefficient (ICC) [ 19 ]. Measurements of alveolar bone height changes Alveolar bone height changes were calculated as follows: T1 = T0–T6 (first 6 months), T2 = T6–T12 (second 6 months), and T3 = T0–T12 (total 12 moths). Statistical methods Statistical analysis. The data was analyzed using the IBM SPSS software program version 20.0 (Armonk, NY: IBM Corp). The data distribution's normality was assessed using the Shapiro-Wilk test. The parametric data (quantitative data) was presented as a mean, and standard deviation. A significant level of 5% was utilized. For normally distributed quantitative variables, an independent t -test was utilized to evaluate and compare abutment bone changes and residual ridge bone changes between the two independent groups (digital and conventional) to determine the significance of the differences. For within-group comparison of bone changes at different times, after 1st 6 months, 2nd 6 months, and total 12 months of denture insertion, a repeated ANOVA test was utilized, followed by a paired t -test to determine significant differences between each pair. A P value of less than .05 was considered statistically significant. Results Twelve males and ten females, ages 50 to 65, were recruited as the research subjects. Two sets of patients were randomly selected. All subjects attended regular appointments without any dropouts because of the motivation during the brief evaluation period. The subject enrolled in the groups of the study as the following: Group I : Digitally fabricated altered cast includes 11 patients [6 male (54.5%) and 5 females (45.5%)]. Group II : Conventionally fabricated altered cast: includes 11 patients [5 male (45.5%) and 6 females (54.5%)]. There was no statistically significant difference between groups regarding sex (Mann-Whitney Test, P = .677), age (independent t -test, P = .954). There was no statistically significant difference between the two groups regarding crown root ratio of the abutment teeth (independent t -test, P = .631), residual ridge size category (Mann-Whitney Test, P = .672), and thickness of the mucosa (independent T-test, P = .753). Analytical analysis, between groups comparisons, comparing alveolar bone resorption around abutment teeth between the two study groups, using independent t-test, revealed that no statistically significant difference between the bone resorption around abutment teeth in the two groups at the intervals T1, T2 and T3 of RPD insertion where ( P value = .837, .423, .550) respectively. Comparing the residual alveolar ridge bone resorption between two study groups, using independent t-test, revealed that no statistically significant difference between the bone resorption of residual alveolar ridge in the two groups after the intervals T1, T2 and T3 of RPD insertion where ( P value = .850, .649, .949) respectively Table 1 . Table 1 Comparison between means of crestal alveolar bone resorption around abutment teeth and residual alveolar ridge in the two groups. Group I (Digital) Group II (Conventional) Independent t-test Mean ± SD Mean ± SD P value Abutment bone loss T1 (1st 6 months) 0.173 ± 0.011 0.175 ± 0.022 0.837 T2 (2nd 6 months) 0.258 ± 0.014 0.265 ± 0.026 0.423 T3 (12 months) 0.431 ± 0.019 0.441 ± 0.044 0.550 Ridge bone loss T1 (1st 6 months) 0.398 ± 0.043 0.401 ± 0.041 0.850 T2 (2nd 6 months) 0.512 ± 0.027 0.508 ± 0.023 0.649 T3 (12 months) 0.911 ± 0.052 0.909 ± 0.049 0.949 Within each group comparison, alveolar bone resorption around abutment teeth at T1 and T2 revealed significant difference within time intervals. Within each group comparison, of the residual alveolar ridge bone resorption at T1 and T2 revealed significant difference within time intervals Table 2 . Table 2 Group I (Digital) Group II (Conventional) Abutment bone loss Ridge bone loss Abutment bone loss Ridge bone loss Mean ± SD Mean ± SD Mean ± SD Mean ± SD T1 (1st 6 months) 0.173 ± 0.011 0.398 ± 0.043 0.175 ± 0.022 0.401 ± 0.041 T2 (2nd 6 months) 0.258 ± 0.014 0.512 ± 0.027 0.265 ± 0.026 0.508 ± 0.023 paired t-test P value P = 0.001* P = 0.001* P = 0.001* P = 0.001* P: difference between T1 & T2 Discussion The present study compared alveolar bone resorption around abutments and in residual ridges associated with mandibular class I removable partial dentures (RPDs) fabricated using digitally and conventionally altered cast techniques. Both techniques utilized IOS, and frameworks fabricated by selective laser melting (SLM). The results demonstrated no statistically significant differences in bone resorption between the two groups at 6 and 12 months post-insertion. Therefore, the null hypothesis that no difference would be found between digital and conventional altered cast technique regarding the preservation of abutment teeth and residual ridge alveolar bone were accepted. Free-end saddle RPDs rely on both abutment teeth and the residual ridge for support, which respond differently to chewing forces. This mismatch leads to uneven force distribution, increasing the risk of abutment tooth mobility, crestal bone loss, and residual ridge resorption [ 7 ]. The altered cast impression technique reduces vertical movement of denture bases, which has significant benefits for alveolar bone health. Through lowering stresses on abutments, less periodontal damage, and reduce bone loss. It improves force distribution and denture fit, minimizing pressure and trauma to the residual ridge, which helps slow bone resorption and preserve ridge shape [ 9 ]. The radiographic evaluation of alveolar bone level and density is capable of predicting the potential longevity of RPD abutment teeth. Earlier diagnosis of at-risk teeth facilitates enhanced treatment planning and perhaps superior outcomes [ 2 ]. The application of CAD/CAM technology in production of RPDs presents several advantages, such as enhanced fitting accuracy, accelerated fabrication, a reduction in the number of laboratory steps, and a decrease in potential sources of error. This fabrication method offers the advantage of preserving digital data and images of the individual’s dentures, facilitating future replacements, particularly for elderly individuals or those with Alzheimer’s who may frequently misplace their dentures [ 14 , 20 ]. The crown root ratio (CRR) of the abutment teeth was at most 1:2 to be suitable as an abutment for the removable partial denture (RPD). A high CRR suggests an increased probability of losing bone support, which result in reduced resistance to masticatory loads and lateral forces exerted by the RPD. This study included patients with good abutment teeth with at most CRR 1:2 [ 31 ]. Using 0-degree built orientation during SLM of the RPD framework resulted in optimal framework adaptation. That’s why 0 degree-built ordination was used to construct Co-Cr frameworks of this study [ 25 ]. No statistically significant differences were found between the two groups in terms of bone resorption around abutments at any time interval. Similarly, no significant differences were observed between the groups in residual alveolar ridge resorption at corresponding time intervals. These findings indicated that both digital and conventional altered cast techniques offer comparable outcomes in preserving bone levels within the first year following RPD insertion [ 8 , 9 ]. The modified cast technique captures the edentulous ridge in a functional position, resulting in a denture base that conforms closely to the mucosa. This adaptation promotes a more even distribution of occlusal stresses. Research has shown that dentures created with the modified cast procedure provide enhanced stability and support, essential for maintaining the integrity of the residual ridge over time [ 10 ]. In the management of mandibular Kennedy Class I cases, the application of the broad stress distribution (BSD) philosophy significantly reduced alveolar bone resorption, with an average bone loss of 0.19 mm observed radiographically compared to 0.72 mm in cases without load distribution, while the altered cast technique demonstrated bone loss of 0.17 mm around abutment teeth which considered comparable outcome to broad stress distribution (BSD) philosophy [ 27 ]. The comparable outcomes between the two fabrication methods provide valuable clinical insight. With the advent of digital workflows in prosthodontics, the use of digitally altered casts can offer practical advantages, such as reduced clinical and laboratory time, better reproducibility, and enhanced comfort [ 12 , 13 ]. Digital altered cast technique may be considered a viable and efficient alternative for RPD fabrication [ 14 , 15 ]. Despite the lack of intergroup differences, both groups exhibited statistically significant increases in bone resorption over time. Clinical investigations indicate that RPDs fabricated using the modified cast approach exhibit reduced mobility and enhanced periodontal health of abutment teeth in comparison to those produced with standard procedures [ 32 , 33 ]. Abutment teeth with direct retainers, especially in distal positions, showed the greatest decline in periodontal health. This highlights the need for careful abutment selection and consistent periodontal maintenance to minimize long-term bone loss around these teeth in RPD wearers [ 34 ]. The increased bone loss around abutments through time may be related to the impact of RPD on the periodontal health of abutment teeth. This consistent with a study revealed that removable partial dentures (RPDs) can adversely result in higher plaque formation, bleeding during probing, and greater probing depth which can lead to increased bone loss over time. Nonetheless, via carefully planned prosthetic interventions and proper oral and denture hygiene management, periodontal infections can be averted [ 5 ]. Removable partial dentures (RPDs) contribute to alveolar bone resorption, especially in abutment teeth, with an average bone loss of .38 mm observed over a short period of six months, whereas the use of the altered cast technique resulted in a reduced bone loss of only .17 mm around abutment teeth [ 26 ]. long-term RPD use contributes to progressive alveolar bone resorption, with the severity influenced by denture design, duration of wear, and anatomical location [ 28 ]. This highlights the necessity for appropriate denture design, consistent monitoring, and ongoing care to avoid long-term bone loss in RPD users. However, it's essential to consider the limitations of this study, including the relatively short follow-up period and sample size. Future researches with extended observation periods and larger cohorts are necessary to validate these findings and assess the long-term implications of digital fabrication techniques in RPDs. Conclusion Despite the limitations of this comparative clinical study, the following conclusions can be drawn: Both digital and conventional altered cast impression techniques, when used for fabricating distally extended RPDs with digitally constructed metal frameworks, showed similar effectiveness in maintaining alveolar bone height around abutment teeth and residual ridges over a one-year observation period. Moreover, The accuracy of digital impressions used for fabricating distally extended RPDs with digitally constructed metal frameworks presents a viable alternative to traditional methods, effectively preserving bone integrity. Abbreviations CD Complete Denture RPD Removable Partial Denture CBCT Cone-Beam Computed Tomography CAD/CAM Computer-Aided Design/Computer-Aided Manufacturing SPSS Statistical Package for the Social Sciences CONSORT Consolidated Standards of Reporting Trials CI Confidence Interval P value P – Probability value Declarations Patient consent Informed patient consent was provided. Ethics approval and consent to participate Approval to conduct this study was given by the Institution Ethics Committee, the Faculty of Dentistry, Mansoura University, Egypt (Approval No: A0203023 RP), and the trial was registered on ClinicalTrials.gov (Identifier: NCT05899712; registration date: September 6, 2023). Participants’ agreements were taken by signing the informed consent to undergo Consent for publication Not Applicable. Competing interests The authors declare no competing interests. Funding Open access funding provided by The Science, Technology & Innovation Funding Authority (STDF) in cooperation with The Egyptian Knowledge Bank (EKB). Author Contribution ASA: Conceptualization, methodology, and manuscript writing. MAA: DataCollection. AZH: Data curation, supervision, and writing draft preparation. MFM:Supervision, writing, reviewing, and editing. All authors read and approvedthe final manuscript. Acknowledgements The authors thank all patients for their participation in this study. Data Availability The datasets used in the current study are available from the corresponding author upon request. References Oh KC, Jeon J, Kim JH. Fabrication of a removable partial denture combining conventional and digital techniques. 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BMC Oral Health. 2018;18(1):120. 10.1186/s12903-018-0578-3 . Nishiyama H, Taniguchi A, Tanaka S, Baba K. Novel fully digital workflow for removable partial denture fabrication. J Prosthodont Res. 2020;64(1):98–103. 10.1016/j.jpor.2019.05.002 . Pereira ALC, de Medeiros AKB, de Sousa Santos K, de Almeida ÉO, Barbosa GAS, Carreiro AFP. Accuracy of CAD-CAM systems for removable partial denture framework fabrication: A systematic review. J Prosthet Dent. 2021;125(2):241–8. 10.1016/j.prosdent.2020.01.003 . Akl MA, Stendahl CG. Removable partial denture frameworks in the age of digital dentistry: A review of the literature. Prosthesis. 2022;4(2):184–201. 10.3390/prosthesis4020019 . Tregerman I, Renne W, Kelly A, Wilson D. Evaluation of removable partial denture frameworks fabricated using 3 different techniques. J Prosthet Dent. 2019;122(4):390–5. 10.1016/j.prosdent.2018.10.013 . Peng P-W, Hsu C-Y, Huang H-Y, Chao J-C, Lee W-F. Trueness of removable partial denture frameworks additively manufactured with selective laser melting. J Prosthet Dent. 2022;127(1):122–7. 10.1016/j.prosdent.2020.06.035 . Kim S, Oh KC, Kim J-H. Accuracy of Mandibular Removable Partial Denture Frameworks Fabricated by 3D Printing and Conventional Techniques. Materials. 2024;17(13):3148. 10.3390/ma17133148 . Elhadery SS, Alhajj MN, Yunus N, Ibrahim N, Abidin ZZ, Ahmad SF et al. Adaptation of cobalt chromium frameworks fabricated by conventional versus selective laser melting techniques: An in vitro and clinical assessment. J Prosthet Dent. 2024;15:S0022-3913(24)00212-9. 10.1016/j.prosdent.2024.03.020 Knezović-Zlatarić D, Čelebić A, Brujić S. Alveolar bone loss on abutment and non-abutment teeth in relation to removable partial denture wearing. A six month follow up study. Acta Stomatol Croatica: Int J Oral Health Dent. 2003;37(2):179–84. Abd El-Khalik MM, El Mekawy NH, El-Kasaby SS. Mandibular Kennedy Class I partial denture management by broad stress distribution philosophy (radiographic assessment). J Indian Prosthodont Soc. 2016;16(3):282–7. 10.4103/0972-4052.179263 . Ozan O, Orhan K, Aksoy S, Icen M, Bilecenoglu B, Sakul BU. The effect of removable partial dentures on alveolar bone resorption: a retrospective study with cone-beam computed tomography. J Prosthodont. 2013;22(1):42–8. 10.1111/j.1532-849X.2012.00877.x . Menezes CC, Janson G, da Silveira Massaro C, Cambiaghi L, Garib DG. Precision, reproducibility, and accuracy of bone crest level measurements of CBCT cross sections using different resolutions. Angle Orthod. 2016;86(4):535–42. 10.2319/040115-214.1 . Kaaber L, Matzen LH, Spin-Neto R, Schropp L. Low‐dose, standard, and high‐resolution cone beam computed tomography for alveolar bone measurements related to implant planning: An ex vivo study in human specimens. Clin Oral Implants Res. 2024;35(11):1394–405. 10.1111/clr.14326 . Tada S, Allen P, Ikebe K, Zheng H, Shintani A, Maeda Y. The impact of the crown-root ratio on survival of abutment teeth for dentures. J Dent Res. 2015;94(9 Suppl):S220–5. 10.1177/0022034515589710 . Frank RP, Brudvik JS, Noonan CJ. Clinical outcome of the altered cast impression procedure compared with use of a one-piece cast. J Prosthet Dent. 2004;91(5):468–76. 10.1016/S0022391304000769 . Rashid H. Altered cast technique: Improving tissue support for the distal extension bases. J Pak Dent Assoc. 2013;22:280. Almeida ML, de Oliveira ÉPS, Tôrres CP, Calderon PDS, Carreiro A, Gurgel BV. Evaluation of periodontal parameters on Removable Partial Denture abutment teeth with direct and indirect retainers: A 48-month follow-up. J Int Acad Periodontol. 2020;22(2):10–7. Additional Declarations No competing interests reported. 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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-7739601","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":541933937,"identity":"930d5be7-7681-481b-8d69-3a0b649904f3","order_by":0,"name":"Abdullah S. A. AboZied","email":"","orcid":"","institution":"Mansoura University","correspondingAuthor":false,"prefix":"","firstName":"Abdullah","middleName":"S. A.","lastName":"AboZied","suffix":""},{"id":541933938,"identity":"17c47e22-8dc4-47d4-b1b5-b4a6191a3a0f","order_by":1,"name":"Marwa Ahmed Aboelez","email":"data:image/png;base64,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","orcid":"","institution":"Mansoura University","correspondingAuthor":true,"prefix":"","firstName":"Marwa","middleName":"Ahmed","lastName":"Aboelez","suffix":""},{"id":541933939,"identity":"f2aadd4f-f6d2-47c6-9f77-1d1dd8d8b0ed","order_by":2,"name":"Aisha Z. H. Mostafa","email":"","orcid":"","institution":"Mansoura University","correspondingAuthor":false,"prefix":"","firstName":"Aisha","middleName":"Z. H.","lastName":"Mostafa","suffix":""},{"id":541933942,"identity":"fba95aa1-e7cb-49b8-a371-f3528ba3f61f","order_by":3,"name":"Mohammed M. Fouad","email":"","orcid":"","institution":"Mansoura University","correspondingAuthor":false,"prefix":"","firstName":"Mohammed","middleName":"M.","lastName":"Fouad","suffix":""}],"badges":[],"createdAt":"2025-09-29 08:23:41","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7739601/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7739601/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":95624007,"identity":"f8be51da-21e2-4c65-9560-b5d4d2ff0007","added_by":"auto","created_at":"2025-11-11 10:11:14","extension":"docx","order_by":0,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":758292,"visible":true,"origin":"","legend":"","description":"","filename":"manuscriptabdCopy.docx","url":"https://assets-eu.researchsquare.com/files/rs-7739601/v1/9e9d5755908fe68d64d4bddb.docx"},{"id":95624004,"identity":"098a36b1-923a-4d8c-a221-ff4760c2accf","added_by":"auto","created_at":"2025-11-11 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10:11:15","extension":"html","order_by":18,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":117854,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-7739601/v1/45f9749d5010b8972555ab6c.html"},{"id":95657280,"identity":"1c4f52f6-4930-4f95-b3f2-c9a6b3861938","added_by":"auto","created_at":"2025-11-11 16:20:28","extension":"jpeg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":71347,"visible":true,"origin":"","legend":"\u003cp\u003eFlowchart of study procedures.\u003c/p\u003e","description":"","filename":"floatimage1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7739601/v1/6036cde07498e629270d4fd8.jpeg"},{"id":95624017,"identity":"6a89f22f-8a38-44a5-8451-723306b91c46","added_by":"auto","created_at":"2025-11-11 10:11:14","extension":"jpeg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":559225,"visible":true,"origin":"","legend":"\u003cp\u003eA, Scanned mandibular edentulous ridge and teeth. B, Digital surveying using AiDENTAL. C, Final intraoral scan after mouth preparations. D, Final design of mandibular class I RPD framework.\u003c/p\u003e","description":"","filename":"floatimage2.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7739601/v1/1d4169ed3f69d8e80383fc60.jpeg"},{"id":95624014,"identity":"2244f736-38bb-42be-a6aa-2d8748d0ac53","added_by":"auto","created_at":"2025-11-11 10:11:14","extension":"jpeg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":546371,"visible":true,"origin":"","legend":"\u003cp\u003eA, Scanned altered impression extraoral. B, active surface of altered impression. C, Scanned altered impression intraorally. D, Digital altered cast\u003c/p\u003e","description":"","filename":"floatimage3.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7739601/v1/a2f0a5f386f530385669ecff.jpeg"},{"id":95624011,"identity":"89d6b329-fef3-49ed-a0db-f2950540929d","added_by":"auto","created_at":"2025-11-11 10:11:14","extension":"jpeg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":88505,"visible":true,"origin":"","legend":"\u003cp\u003eConventional altered cast. A,B Sectioned master cast after repositioning of the metal framework. C, Boxing of altered impression. D, Conventional altered cast.\u003c/p\u003e","description":"","filename":"floatimage4.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7739601/v1/4b58882175dbb586bf3f5f52.jpeg"},{"id":95624006,"identity":"7657c229-2426-4b09-bbda-2ac7d227cda6","added_by":"auto","created_at":"2025-11-11 10:11:14","extension":"jpeg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":15355,"visible":true,"origin":"","legend":"\u003cp\u003eA, Finished mandibular class I RPD after delivery. B, Maxillary complete denture opposed by mandibular class I RPD.\u003c/p\u003e","description":"","filename":"floatimage5.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7739601/v1/2f2ac949730684fa9be2fcdf.jpeg"},{"id":95656595,"identity":"8424c8d5-93a2-4e3f-92ed-aa1e7a6499d3","added_by":"auto","created_at":"2025-11-11 16:19:09","extension":"jpeg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":232554,"visible":true,"origin":"","legend":"\u003cp\u003eAlveolar bone height measurements around abutment teeth.\u003c/p\u003e","description":"","filename":"floatimage6.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7739601/v1/09c86f66536dcd1aa9f3dfb4.jpeg"},{"id":95624012,"identity":"18131189-f208-4dc3-8560-21ea4ecb11de","added_by":"auto","created_at":"2025-11-11 10:11:14","extension":"jpeg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":100742,"visible":true,"origin":"","legend":"\u003cp\u003eAlveolar bone height measurements in residual alveolar ridge.\u003c/p\u003e","description":"","filename":"floatimage7.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7739601/v1/594ef711fa0782ff273018f6.jpeg"},{"id":106394486,"identity":"ef025280-806e-446f-a6cb-30964cf47016","added_by":"auto","created_at":"2026-04-08 07:44:00","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2446364,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7739601/v1/7780ee8f-8c02-4cc4-ab52-8c5f0504ad8b.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Digital Versus Conventional Altered Cast Techniques For Constructing Mandibular Distal Extension Removable Partial Dentures Using Digitally Fabricated Frameworks: A clinical comparative parallel study of alveolar bone height changes","fulltext":[{"header":"Background","content":"\u003cp\u003eRemovable partial dentures (RPDs) remain a cornerstone in the rehabilitation of partially edentulous patients, particularly in cases involving distal extension (free-end saddle) scenarios [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. These prostheses are widely utilized in clinical practice due to their cost-effectiveness and ability to restore function and aesthetics [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. If partial dentures are designed to give the optimal support, stability, and retention, it can provide favorable outcomes for individuals using them [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Mandibular distal extension RPD face special difficulties due to unequal support from the remaining dentition and edentulous ridge. This disparity frequently leads to unequal stress distribution, which may accelerate alveolar bone resorption and increase abutment tooth movement [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. The conventional altered cast method has been used to address these problems by creating a functional impression of the edentulous region during framework try-in. This approach can improve stress distribution and denture base adaptation to the ridge [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. When the denture base is appropriately extended using the altered cast technique it evenly distributes force and receives support from the teeth and the denture base. Typically, a selective pressure impression is used to create a well-fitted RPD with a proper extension base for Kennedy class I and II arches [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Compared to the conventional method, the digitally altered cast impression approach may decrease inter-operator variability and increase accuracy. For RPDs with distal extensions, the altered cast impression technique is often used. This method helps ensure the denture base receives proper support from the soft tissues while maintaining an accurate relationship with the tooth abutments [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThe fabrication of removable partial denture (RPD) frameworks has undergone significant advancements with the integration of digital technologies in prosthodontics [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. The application of intraoral scanning, computer-aided design (CAD), and additive or subtractive manufacturing techniques such as 3D printing and milling has enhanced the precision and efficiency of RPD production. These digital workflows have the potential to minimize operator-dependent variability and improve the passive fit of prosthetic components, thereby contributing to improved clinical outcomes [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. Digital technology has transformed the way removable partial dentures (RPDs) are made. One of the recent advancements is the use of intraoral scanners (IOS) to take digital impressions, which are now being used in clinical practice for the fabrication of RPDs [\u003cspan additionalcitationids=\"CR19\" citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. Alternative technologies for additively constructing cobalt chromium and titanium frameworks, such as selective laser sintering (SLS) and selective laser melting (SLM), show potential in reducing fabrication defects [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. Peng et al. [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e] reported that RPD frameworks created using SLM showed greater accuracy than those created using conventional techniques. When fabricating RPD frameworks, SLM and SLS are frequently utilized to construct the detailed and complicated structure of the framework as intended [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e].\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003eRemovable partial dentures (RPDs) may have a great influence on the health of supporting oral structures. One of the concerns associated with long-term RPD wear is the potential for alveolar bone resorption, particularly in the regions surrounding abutment teeth. Understanding the extent and pattern of this bone loss is essential for improving prosthetic design and patient outcomes [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. Excessive stress on the abutment teeth and residual ridge can accelerate alveolar bone resorption. Minimizing this effect helps to conserve alveolar bone loss to patients using RPDs [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. The long-term impact of RPDs on alveolar bone remains a clinical concern. The lack of posterior abutments in distal extension cases often leads to uneven load distribution, accelerating bone resorption beneath the denture base [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. With the advent of cone-beam computed tomography (CBCT), a more accurate three-dimensional assessment of bone changes has become possible, allowing for a deeper understanding of the resorptive patterns associated with prolonged RPD use [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e].\u003c/p\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eSince no previous clinical study had compared alveolar bone resorption around abutments and in residual ridges associated with mandibular class I removable partial dentures (RPDs) fabricated using digitally and conventionally altered cast techniques, the goal behind this study was to evaluate the two methods used for mandibular class I RPD construction. The null hypothesis for this research was that there was no difference between digital and conventional altered cast technique regarding the changes of abutment teeth and residual ridge alveolar bone.\u003c/p\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003eStudy design\u003c/h2\u003e\u003cp\u003eTwenty two patients (Ten females and Twelve males) with completely edentulous maxilla and partially edentulous mandibles with retaining anteriors and first premolar teeth were included in a comparative parallel randomized clinical trial. They were choosen from the outpatient clinic of the Prosthodontic Department, Faculty of Dentistry, Mansoura University with ages between [50\u0026ndash;65] years. Figure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e displays the study procedures' flowchart. All experiments were performed in accordance with relevant guidelines and regulations. Faculty of dentistry ethics board committee approved this clinical investigation, and it was given the ethical approval number (A0203023 RP).The study's protocol was registered in clinicaltrials.gov (Identifier: NCT05899712; registration date: September 6, 2023).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003eData collection\u003c/h3\u003e\n\u003cp\u003e\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003eThe inclusion criteria included patients with completely edentulous maxillae and partially edentulous mandibles retaining anteriors and first premolar teeth. Premolars were required to be healthy, with good periodontal and bone support. Good crown/root ratio not greater than 1:2, confirmed radiographically. Patients with severe ridge resorption or undercuts, systemic diseases affecting bone metabolism (e.g., diabetes, osteoporosis) were excluded. The presentation of this study complied with the requirements set out by CONSORT (consolidated standards for reporting randomized trials).\u003c/p\u003e\u003c/div\u003e\u003c/p\u003e\n\u003ch3\u003eSample size\u003c/h3\u003e\n\u003cp\u003eSample size estimation was performed using G*Power software (version 3.1; Heinrich Heine University D\u0026uuml;sseldorf), based on data from a previously published study [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. With a significance level (α) of 0.05 and a power of 80%, the minimum required sample size was determined to be 11 participants per group.Written informed consent was obtained from all participants after they received comprehensive information regarding the study\u0026rsquo;s objectives and procedures.\u003c/p\u003e\n\u003ch3\u003eRandomization and blinding\u003c/h3\u003e\n\u003cp\u003e\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003eParticipants were divided into two groups according to the patient's gender; thirteen males and nine females were chosen at random for each group (n\u0026thinsp;=\u0026thinsp;11) to ensure an equal gender distribution.Participant allocation was conducted using a simple randomization technique with computer-generated random number tables in SPSS software (version 25; IBM Corp.), following the establishment of a defined sampling frame. To ensure blinding, treatment procedures and follow-up assessments were performed by two independent clinicians, each of whom was blinded to the group assignments throughout the study duration. The group allocation was also concealed from the participants. Participants were equally assigned to two groups based on the altered cast technique: Group I: Digitally fabricated altered cast and Group II: Conventionally fabricated altered cast.\u003c/p\u003e\u003c/div\u003e\u003c/p\u003e\n\u003ch3\u003eProsthodontic procedures\u003c/h3\u003e\n\u003cp\u003e\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003eEach patient received a maxillary complete denture and a mandibular class I RPD fabricated using the altered cast technique with digitally constructed frameworks. Mandibular teeth and alveolar ridge mucosa were scanned using an intraoral scanner (IOS) (MEDIT i700; MEDIT) Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eA. Digital surveying of the 3D model was performed to determine the optimal path of insertion, measuring amount of undercuts and cast tilting if needed to plan necessary mouth preparations Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eB. Mouth preparation followed this sequence: Mesial occlusal rest seats and guiding planes were prepared on teeth number 34 and 44. Cingulum rests were prepared on teeth number 33 and 43. A final intraoral scan of the prepared teeth and alveolar ridge mucosa was performed using an IOS (MEDIT i700; MEDIT) Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eC. RPD frameworks were designed using Partial CAD 3.1 (EXOCAD, Rijeka), with a standardized design applied to all cases for consistency. A single laboratory fabricated all mandibular RPDs and maxillary complete dentures. Framework components, including RPA clasps, lingual bar, mesh work as denture base minor connector and cingulum rest as indirect retainer according to RPD design principles for distal extension cases Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eD.\u003c/p\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe finalized design was exported as an STL file and transferred to a rapid prototyping system (M270; EOS) to 3D print the resin try-in and master cast. The resin framework was tried intraorally. Final Co-Cr frameworks (Cobalt Chrome SP2; EOS GmbH) were fabricated using selective laser melting with 0-degree built orientation, then polished and seated on the 3D-printed master cast. Intraoral try-in of the metal framework was performed using disclosing media to check for interferences, verify component contact, and confirm complete seating.\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003eA light-cured acrylic special tray was adapted over the printed meshwork framework and cured. The tray was placed intraorally to verify peripheral extensions, which were refined with modeling compound and selectively trimmed to accommodate impression material. Zinc oxide eugenol (ZOE) impression material was applied to the fitting surface and the tray was seated. Occlusal rests and indirect retainers were fully seated during the impression. According to the technique of producing the altered cast, patients were classified into two equal groups.\u003c/p\u003e\u003cp\u003e\u003cb\u003eGroup I: Digital altered cast construction\u003c/b\u003e [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]\u003c/p\u003e\u003cp\u003eThe fitting surface of the impression was scanned extra-orally Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eA. Then, STL file of the altered impression scan was selected then clicked on \"Invert the normal\" This command turned the fitting surface of impression into active surface Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eB. The original scan used to create the RPD framework was opened in the IOS software, and the distal extension denture base area was erased to accommodate the altered cast impression. The impression was seated intraorally, and IOS was used to scan the labial, buccal, and distal areas with the framework in place. Scanning continued until the dentition and impression material aligned in the software Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eC. Full arch scan with framework and the framework with the altered impression scan were imported into Meshmixer (Autodesk). Once both models were loaded, the align tool was used to match them accurately through selected common landmarks like teeth, clasps, and rest. After confirming the alignment, the digital altered cast was virtually merged with the tooth cast Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eD and fabricated using additive manufacturing (AM). After 3D printing of digital altered cast, it was duplicated into stone cast to continue the rest of RPD construction steps.\u003c/p\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eGroup II: Conventional altered cast construction\u003c/b\u003e [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]\u003c/p\u003e\u003cp\u003eEdentulous ridges were removed from the duplicated master cast 1 mm distal to the abutments using a jeweler\u0026rsquo;s saw, and the cut surfaces were roughened with a bur to ensure stone adhesion. The altered impression was seated on the cast, and the framework was checked for proper fit; sticky wax was applied to stabilize framework Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eA, B. A line was marked 2 mm below the impression border, along which beading wax was applied. The cast was then boxed with wax to a height of 13 mm above the highest point of the impression, and all edges were sealed to prevent stone leakage Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eC. The boxed impression was filled with dental stone and left to set. After setting, all boxing materials and the impression were removed to retrieve the altered cast Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eD.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eJaw relation of maxillary complete denture opposes class I removable partial denture for both groups was done. Try in of dentures was done to evaluate vertical dimension, esthetics and phonetics. Flasking of waxed denture to produce final prosthesis. Compression mold technique was used to produce mandibular class I RPD and maxillary complete denture. The flask is heated to 70\u0026deg;C for 7 hours then 100\u0026deg;C for 3 hours (The total 10 hours). Once the finished denture has been delivered. All the following were checked, fit of denture base, denture stability, retention, soft tissue adaptation, abutment tooth adaptation, vertical dimension of occlusion, esthetics and phonetics \u003cb\u003eFig .\u003c/b\u003e5A, B.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003eRadiographic evaluation\u003c/h2\u003e\u003cp\u003eThe alveolar bone height changes of abutment teeth and residual ridge was measured using CBCT at following periods: (T0) at RPD insertion, (T6) six months after RPD insertion and (T12) twelve months after RPD insertion. CBCT images were obtained using the CBCT machine (Carestream CS 8100 3D CBCT, Carestream Dental) at 90 kVp and 3.2 mA. Alveolar bone resorption was assessed using Real Guide software (3Diemme). CBCT image fusion was performed to establish a consistent reference point (the abutment apex) using a horizontal line tangential to the apex and perpendicular to the long axis. Coronal views were used to measure mesial and distal bone heights, while sagittal views assessed buccal and lingual heights. Vertical lines parallel to the abutment\u0026rsquo;s long axis were used to measure the distance from the crestal bone to the apex in all directions. Measurements were performed twice by the same calibrated examiner, two weeks apart, to evaluate reproducibility [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e] Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eCBCT scans adjusted to capture the entire mandibular residual ridge and analyzed using Real Guide software. Images were aligned to a standardized reference plane, with a horizontal line tangential to the superior border of the mandibular canal. Vertical lines were drawn perpendicular to this plane at measurement sites. Alveolar bone height was measured as the vertical distance from the alveolar crest to the superior border of the mandibular canal at 10, 20, and 30 mm from the last abutment tooth Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e. Measurements were performed twice by the same calibrated examiner, two weeks apart, and intra-examiner reliability was confirmed using the Intraclass Correlation Coefficient (ICC) [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003eMeasurements of alveolar bone height changes\u003c/h3\u003e\n\u003cp\u003e\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003eAlveolar bone height changes were calculated as follows: T1\u0026thinsp;=\u0026thinsp;T0\u0026ndash;T6 (first 6 months), T2\u0026thinsp;=\u0026thinsp;T6\u0026ndash;T12 (second 6 months), and T3\u0026thinsp;=\u0026thinsp;T0\u0026ndash;T12 (total 12 moths).\u003c/p\u003e\u003c/div\u003e\u003c/p\u003e\n\u003ch3\u003eStatistical methods\u003c/h3\u003e\n\u003cp\u003eStatistical analysis. The data was analyzed using the IBM SPSS software program version 20.0 (Armonk, NY: IBM Corp). The data distribution's normality was assessed using the Shapiro-Wilk test. The parametric data (quantitative data) was presented as a mean, and standard deviation. A significant level of 5% was utilized. For normally distributed quantitative variables, an independent \u003cem\u003et\u003c/em\u003e-test was utilized to evaluate and compare abutment bone changes and residual ridge bone changes between the two independent groups (digital and conventional) to determine the significance of the differences. For within-group comparison of bone changes at different times, after 1st 6 months, 2nd 6 months, and total 12 months of denture insertion, a repeated ANOVA test was utilized, followed by a paired \u003cem\u003et\u003c/em\u003e-test to determine significant differences between each pair. A \u003cem\u003eP\u003c/em\u003e value of less than .05 was considered statistically significant.\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003eTwelve males and ten females, ages 50 to 65, were recruited as the research subjects. Two sets of patients were randomly selected. All subjects attended regular appointments without any dropouts because of the motivation during the brief evaluation period. The subject enrolled in the groups of the study as the following: \u003cstrong\u003eGroup I\u003c/strong\u003e: Digitally fabricated altered cast includes 11 patients [6 male (54.5%) and 5 females (45.5%)]. \u003cstrong\u003eGroup II\u003c/strong\u003e: Conventionally fabricated altered cast: includes 11 patients [5 male (45.5%) and 6 females (54.5%)]. There was no statistically significant difference between groups regarding sex (Mann-Whitney Test, \u003cem\u003eP\u003c/em\u003e\u0026thinsp;=\u0026thinsp;.677), age (independent \u003cem\u003et\u003c/em\u003e-test, \u003cem\u003eP\u003c/em\u003e\u0026thinsp;=\u0026thinsp;.954). There was no statistically significant difference between the two groups regarding crown root ratio of the abutment teeth (independent \u003cem\u003et\u003c/em\u003e-test, \u003cem\u003eP\u003c/em\u003e\u0026thinsp;=\u0026thinsp;.631), residual ridge size category (Mann-Whitney Test, \u003cem\u003eP\u003c/em\u003e\u0026thinsp;=\u0026thinsp;.672), and thickness of the mucosa (independent T-test, \u003cem\u003eP\u003c/em\u003e\u0026thinsp;=\u0026thinsp;.753).\u003c/p\u003e\n\u003cp\u003eAnalytical analysis, between groups comparisons, comparing alveolar bone resorption around abutment teeth between the two study groups, using independent t-test, revealed that no statistically significant difference between the bone resorption around abutment teeth in the two groups at the intervals T1, T2 and T3 of RPD insertion where (\u003cem\u003eP\u003c/em\u003e value\u0026thinsp;=\u0026thinsp;.837, .423, .550) respectively. Comparing the residual alveolar ridge bone resorption between two study groups, using independent t-test, revealed that no statistically significant difference between the bone resorption of residual alveolar ridge in the two groups after the intervals T1, T2 and T3 of RPD insertion where (\u003cem\u003eP\u003c/em\u003e value\u0026thinsp;=\u0026thinsp;.850, .649, .949) respectively Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e\n\u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n \u003cdiv align=\"left\" class=\"colspec\"\u003e\u003cbr\u003e\u003c/div\u003e\n \u003cdiv align=\"left\" class=\"colspec\"\u003e\u003cbr\u003e\u003c/div\u003e\n \u003ctable id=\"Tab1\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eComparison between means of crestal alveolar bone resorption around abutment teeth and residual alveolar ridge in the two groups.\u0026nbsp;\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eGroup I (Digital)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eGroup II (Conventional)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eIndependent t-test\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eP\u003c/em\u003e value\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" rowspan=\"3\"\u003e\n \u003cp\u003e\u003cstrong\u003eAbutment bone loss\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eT1 (1st 6 months)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.173\u0026thinsp;\u0026plusmn;\u0026thinsp;0.011\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.175\u0026thinsp;\u0026plusmn;\u0026thinsp;0.022\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.837\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eT2 (2nd 6 months)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.258\u0026thinsp;\u0026plusmn;\u0026thinsp;0.014\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.265\u0026thinsp;\u0026plusmn;\u0026thinsp;0.026\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.423\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eT3 (12 months)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.431\u0026thinsp;\u0026plusmn;\u0026thinsp;0.019\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.441\u0026thinsp;\u0026plusmn;\u0026thinsp;0.044\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.550\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" rowspan=\"3\"\u003e\n \u003cp\u003e\u003cstrong\u003eRidge bone loss\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eT1 (1st 6 months)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.398\u0026thinsp;\u0026plusmn;\u0026thinsp;0.043\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.401\u0026thinsp;\u0026plusmn;\u0026thinsp;0.041\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.850\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eT2 (2nd 6 months)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.512\u0026thinsp;\u0026plusmn;\u0026thinsp;0.027\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.508\u0026thinsp;\u0026plusmn;\u0026thinsp;0.023\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.649\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eT3 (12 months)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.911\u0026thinsp;\u0026plusmn;\u0026thinsp;0.052\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.909\u0026thinsp;\u0026plusmn;\u0026thinsp;0.049\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.949\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eWithin each group comparison, alveolar bone resorption around abutment teeth at T1 and T2 revealed significant difference within time intervals. Within each group comparison, of the residual alveolar ridge bone resorption at T1 and T2 revealed significant difference within time intervals\u0026nbsp;\u003cstrong\u003eTable\u0026nbsp;2\u003c/strong\u003e.\u003c/p\u003e\n\u003cp\u003e\u003c/p\u003e\n\u003cdiv align=\"left\" class=\"colspec\"\u003eTable 2\u003c/div\u003e\n\u003ctable id=\"Taba\" border=\"1\"\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\" rowspan=\"3\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003cth align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003eGroup I (Digital)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003eGroup II (Conventional)\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eAbutment bone loss\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eRidge bone loss\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eAbutment bone loss\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eRidge bone loss\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eT1 (1st 6 months)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.173\u0026thinsp;\u0026plusmn;\u0026thinsp;0.011\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.398\u0026thinsp;\u0026plusmn;\u0026thinsp;0.043\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.175\u0026thinsp;\u0026plusmn;\u0026thinsp;0.022\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.401\u0026thinsp;\u0026plusmn;\u0026thinsp;0.041\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eT2 (2nd 6 months)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.258\u0026thinsp;\u0026plusmn;\u0026thinsp;0.014\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.512\u0026thinsp;\u0026plusmn;\u0026thinsp;0.027\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.265\u0026thinsp;\u0026plusmn;\u0026thinsp;0.026\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.508\u0026thinsp;\u0026plusmn;\u0026thinsp;0.023\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003epaired t-test\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eP value\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eP\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.001*\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eP\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.001*\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eP\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.001*\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eP\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.001*\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003c/p\u003e\n\u003cp\u003e\u003c/p\u003e\n\u003cp\u003eP: difference between T1 \u0026amp; T2\u003c/p\u003e\n\u003cp\u003e\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe present study compared alveolar bone resorption around abutments and in residual ridges associated with mandibular class I removable partial dentures (RPDs) fabricated using digitally and conventionally altered cast techniques. Both techniques utilized IOS, and frameworks fabricated by selective laser melting (SLM). The results demonstrated no statistically significant differences in bone resorption between the two groups at 6 and 12 months post-insertion. Therefore, the null hypothesis that no difference would be found between digital and conventional altered cast technique regarding the preservation of abutment teeth and residual ridge alveolar bone were accepted.\u003c/p\u003e\u003cp\u003eFree-end saddle RPDs rely on both abutment teeth and the residual ridge for support, which respond differently to chewing forces. This mismatch leads to uneven force distribution, increasing the risk of abutment tooth mobility, crestal bone loss, and residual ridge resorption [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. The altered cast impression technique reduces vertical movement of denture bases, which has significant benefits for alveolar bone health. Through lowering stresses on abutments, less periodontal damage, and reduce bone loss. It improves force distribution and denture fit, minimizing pressure and trauma to the residual ridge, which helps slow bone resorption and preserve ridge shape [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. The radiographic evaluation of alveolar bone level and density is capable of predicting the potential longevity of RPD abutment teeth. Earlier diagnosis of at-risk teeth facilitates enhanced treatment planning and perhaps superior outcomes [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThe application of CAD/CAM technology in production of RPDs presents several advantages, such as enhanced fitting accuracy, accelerated fabrication, a reduction in the number of laboratory steps, and a decrease in potential sources of error. This fabrication method offers the advantage of preserving digital data and images of the individual\u0026rsquo;s dentures, facilitating future replacements, particularly for elderly individuals or those with Alzheimer\u0026rsquo;s who may frequently misplace their dentures [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. The crown root ratio (CRR) of the abutment teeth was at most 1:2 to be suitable as an abutment for the removable partial denture (RPD). A high CRR suggests an increased probability of losing bone support, which result in reduced resistance to masticatory loads and lateral forces exerted by the RPD. This study included patients with good abutment teeth with at most CRR 1:2 [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. Using 0-degree built orientation during SLM of the RPD framework resulted in optimal framework adaptation. That\u0026rsquo;s why 0 degree-built ordination was used to construct Co-Cr frameworks of this study [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eNo statistically significant differences were found between the two groups in terms of bone resorption around abutments at any time interval. Similarly, no significant differences were observed between the groups in residual alveolar ridge resorption at corresponding time intervals. These findings indicated that both digital and conventional altered cast techniques offer comparable outcomes in preserving bone levels within the first year following RPD insertion [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. The modified cast technique captures the edentulous ridge in a functional position, resulting in a denture base that conforms closely to the mucosa. This adaptation promotes a more even distribution of occlusal stresses. Research has shown that dentures created with the modified cast procedure provide enhanced stability and support, essential for maintaining the integrity of the residual ridge over time [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eIn the management of mandibular Kennedy Class I cases, the application of the broad stress distribution (BSD) philosophy significantly reduced alveolar bone resorption, with an average bone loss of 0.19 mm observed radiographically compared to 0.72 mm in cases without load distribution, while the altered cast technique demonstrated bone loss of 0.17 mm around abutment teeth which considered comparable outcome to broad stress distribution (BSD) philosophy [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThe comparable outcomes between the two fabrication methods provide valuable clinical insight. With the advent of digital workflows in prosthodontics, the use of digitally altered casts can offer practical advantages, such as reduced clinical and laboratory time, better reproducibility, and enhanced comfort [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. Digital altered cast technique may be considered a viable and efficient alternative for RPD fabrication [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eDespite the lack of intergroup differences, both groups exhibited statistically significant increases in bone resorption over time. Clinical investigations indicate that RPDs fabricated using the modified cast approach exhibit reduced mobility and enhanced periodontal health of abutment teeth in comparison to those produced with standard procedures [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e, \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. Abutment teeth with direct retainers, especially in distal positions, showed the greatest decline in periodontal health. This highlights the need for careful abutment selection and consistent periodontal maintenance to minimize long-term bone loss around these teeth in RPD wearers [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThe increased bone loss around abutments through time may be related to the impact of RPD on the periodontal health of abutment teeth. This consistent with a study revealed that removable partial dentures (RPDs) can adversely result in higher plaque formation, bleeding during probing, and greater probing depth which can lead to increased bone loss over time. Nonetheless, via carefully planned prosthetic interventions and proper oral and denture hygiene management, periodontal infections can be averted [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Removable partial dentures (RPDs) contribute to alveolar bone resorption, especially in abutment teeth, with an average bone loss of .38 mm observed over a short period of six months, whereas the use of the altered cast technique resulted in a reduced bone loss of only .17 mm around abutment teeth [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. long-term RPD use contributes to progressive alveolar bone resorption, with the severity influenced by denture design, duration of wear, and anatomical location [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. This highlights the necessity for appropriate denture design, consistent monitoring, and ongoing care to avoid long-term bone loss in RPD users. However, it's essential to consider the limitations of this study, including the relatively short follow-up period and sample size. Future researches with extended observation periods and larger cohorts are necessary to validate these findings and assess the long-term implications of digital fabrication techniques in RPDs.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eDespite the limitations of this comparative clinical study, the following conclusions can be drawn:\u003c/p\u003e\u003cp\u003eBoth digital and conventional altered cast impression techniques, when used for fabricating distally extended RPDs with digitally constructed metal frameworks, showed similar effectiveness in maintaining alveolar bone height around abutment teeth and residual ridges over a one-year observation period. Moreover, The accuracy of digital impressions used for fabricating distally extended RPDs with digitally constructed metal frameworks presents a viable alternative to traditional methods, effectively preserving bone integrity.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003eCD Complete Denture\u003c/p\u003e\u003cp\u003eRPD Removable Partial Denture\u003c/p\u003e\u003cp\u003eCBCT Cone-Beam Computed Tomography\u003c/p\u003e\u003cp\u003eCAD/CAM Computer-Aided Design/Computer-Aided Manufacturing\u003c/p\u003e\u003cp\u003eSPSS Statistical Package for the Social Sciences\u003c/p\u003e\u003cp\u003eCONSORT Consolidated Standards of Reporting Trials\u003c/p\u003e\u003cp\u003eCI Confidence Interval\u003c/p\u003e\u003cp\u003e\u003cem\u003eP\u003c/em\u003e value \u003cem\u003eP\u003c/em\u003e – Probability value\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cstrong\u003ePatient consent\u003c/strong\u003e\u003c/p\u003e\u003cp\u003eInformed patient consent was provided.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\u003cp\u003e Approval to conduct this study was given by the Institution Ethics Committee, the Faculty of Dentistry, Mansoura University, Egypt (Approval No: A0203023 RP), and the trial was registered on ClinicalTrials.gov (Identifier: NCT05899712; registration date: September 6, 2023). Participants’ agreements were taken by signing the informed consent to undergo\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003ch2\u003eConsent for publication\u003c/h2\u003e\u003cp\u003eNot Applicable.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003ch2\u003eFunding\u003c/h2\u003e\u003cp\u003eOpen access funding provided by The Science, Technology \u0026amp; Innovation\u003c/p\u003e\u003cp\u003eFunding Authority (STDF) in cooperation with The Egyptian Knowledge Bank\u003c/p\u003e\u003cp\u003e(EKB).\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eASA: Conceptualization, methodology, and manuscript writing. MAA: DataCollection. AZH: Data curation, supervision, and writing draft preparation. MFM:Supervision, writing, reviewing, and editing. All authors read and approvedthe final manuscript.\u003c/p\u003e\u003ch2\u003eAcknowledgements\u003c/h2\u003e\u003cp\u003eThe authors thank all patients for their participation in this study.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eThe datasets used in the current study are available from the corresponding author upon request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eOh KC, Jeon J, Kim JH. Fabrication of a removable partial denture combining conventional and digital techniques. 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J Int Acad Periodontol. 2020;22(2):10\u0026ndash;7.\u003c/span\u003e\u003c/li\u003e\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":"Digital altered cast, Conventional altered cast, Distal extension RPD, Alveolar bone height, Abutment teeth, Residual ridge resorption, CBCT","lastPublishedDoi":"10.21203/rs.3.rs-7739601/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7739601/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eBackground \u003c/strong\u003eConventional altered cast technique for distal extension removable partial dentures (RPDs) involve multiple clinical and laboratory steps. To overcome the limitations of conventional method and enhance bone support and load distribution, digital workflows have been introduced in RPD fabrication.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods\u003c/strong\u003e Twenty-two patients (n=22) of age ranging from 50 to 60 years were included in this parallel clinical study. Each patient received a maxillary complete denture and a mandibular bilateral distally extended RPD made with digitally constructed frameworks. Patients were randomly and equally divided into two groups (n=11) based on the altered cast method used: \u003cstrong\u003eGroup I\u003c/strong\u003e: Digitally fabricated altered cast and \u003cstrong\u003eGroup II\u003c/strong\u003e: Conventionally fabricated altered cast. Alveolar bone height changes of the residual ridge and around abutment teeth were assessed using CBCT at three intervals: 1\u003csup\u003est\u003c/sup\u003e 6 months (T1), 2\u003csup\u003end\u003c/sup\u003e 6 months (T2) and 12 months (T3) post-insertion. Data were collected and statistically analyzed using SPSS software version 25.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults\u003c/strong\u003e There was no statistically significant difference in bone resorption around abutment teeth in two groups at T1, T2 and T3 intervals after RPD insertion where (\u003cem\u003eP\u003c/em\u003e value= .837, .423, .550) respectively. There was no statistically significant difference in bone resorption of residual alveolar ridge in two groups at T1, T2 and T3 intervals after RPD insertion where (\u003cem\u003eP\u003c/em\u003e value= .850, .649, .949) respectively. Within each group the comparison of alveolar bone height changes around abutment teeth and of residual ridge revealed significant difference between time intervals.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusion \u003c/strong\u003eBoth digital and conventional altered cast techniques utilizing digitally constructed metal frameworks demonstrated comparable effectiveness of maintaining alveolar bone height of residual ridges and around abutment teeth of distally extended RPDs.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eClinical trial registry number (No.\u003c/strong\u003eNCT05899712) (06/09/ 2023)\u003c/p\u003e","manuscriptTitle":"Digital Versus Conventional Altered Cast Techniques For Constructing Mandibular Distal Extension Removable Partial Dentures Using Digitally Fabricated Frameworks: A clinical comparative parallel study of alveolar bone height changes","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-11-11 10:11:10","doi":"10.21203/rs.3.rs-7739601/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":"033dcda0-14d2-4828-abb8-be031e7252cf","owner":[],"postedDate":"November 11th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-04-08T07:42:08+00:00","versionOfRecord":[],"versionCreatedAt":"2025-11-11 10:11:10","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7739601","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7739601","identity":"rs-7739601","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}