Evaluation of the accuracy of different intraoral scanning techniques under rubber-dam isolation: An invitro study

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Kamel, Waleed El Mahy, Mona Ghoneim, Rania Afifi This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7466317/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: The application of rubber dam during intraoral scanning provides the ideal conditions for scanning including operative field clarity, moisture reduction, gingival retraction, and isolation from saliva, blood, and tongue. Aim of the study: The purpose of this study was to evaluate the accuracy of intraoral scanning under rubber dam isolation using cut and lock techniques. Materials and methods: A lower first molar in mandibular typodont was prepared for indirect onlay restoration. The reference typodont was then digitized as a reference model using a desktop scanner (MD-1D0410, Medit, South Korea) to obtain a reference standard tessellation language (STL). Thirty digital scanning procedures were performed on the reference model using IOS (i7oo wireless, Medit, South Korea) with three different scanning techniques as follows: Group I: scans were done for the full arch without rubber dam (No-RD) and 10 STL G1 files were exported (control group), G roup II: scans were done under RD with cut technique (RD-C), where a digital scan was done for the full arch of the typodont first. Then, the prepared area was cut using the software tool and then rescanned again after applying the rubber dam. The procedure was repeated till 10 STL G2 files were exported. Group III: scans were done under rubber dam isolation using lock technique (RD-L), where a digital scan was done for the prepared area first under rubber dam with at least one tooth distal and one tooth mesial to the prepared tooth. Then the prepared area was locked and then a complete arch scan was completed after removal of the rubber dam and repeated till 10 STL G3 files were exported.The digital scans were imported to a reverse engineering software program (Geomagic Control X; 3D Systems) to calculate the 3D deviation and assess scanning accuracy using the root mean square (RMS) error, calculated in terms of two regions of interest, one including the full arch dentition (Dentition Area-DA) extending from the distal of the right second molar till the distal of the left second molar, and another area of the onlay preparation surface (Preparation Area-PA). Results: For DA trueness, Group I, with a mean of 60.58 ± 13.19 µm, showed significantly lower error values than both Group II (90.00 ± 13.86 µm) and Group III (84.08 ± 10.99 µm). However, no significant difference was found between Group II and Group III (p = 0.982). When examining DA precision, Group I (57.68 ± 13.60 µm) again demonstrated significantly lower error values compared to Group II (89.71 ± 12.15 µm) and Group III (79.53 ± 10.85 µm). For PA measurements, Group I (43.45 ± 16.45 µm) showed better trueness than Group II (58.33 ± 18.88 µm) and Group III (53.43 ± 19.74 µm), but no significant difference was observed among the groups (p = 0.251). Also, Group I exhibited higher precision (41.24 ± 17.42 µm) compared to Group II (64.35 ± 18.40 µm), with a p value of 0.017, while no significant difference was found between Group II and Group III (p = 0.704). Conclusion: Rubber dam isolation was shown to negatively influence the overall accuracy of intraoral scanning when compared to scans without isolation. However, both the cut and lock techniques produced results within clinically acceptable thresholds, with the lock technique demonstrating superior reliability over the cut technique, particularly in single indirect restorations. These findings suggest that while optimal accuracy is achieved without rubber dam isolation, the lock technique provides a clinically viable alternative when isolation is required. Clinical Implications : In cases which require rubber dam isolation, scanning using the lock technique provides greater accuracy and reliability than the commonly used cut technique. Although full-arch scans without isolation remain the most accurate, the lock technique yields clinically acceptable results for single-tooth restorations, offering clinicians a practical and predictable alternative in situations where isolation is essential. Intra oral scanning Digital Techniques Accuracy Rubber dam Cut technique Lock technique Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Introduction The adoption of digital systems in dentistry is on the rise. Among the latest developments in computer-aided design and manufacturing (CAD/CAM) is the successful integration of intraoral scanning into dental practice. ( 1 ) Intraoral scanners (IOS) offer a reliable and clinically approved method for producing indirect partial coverage restoration, crowns and short-span fixed partial dentures. ( 2 ) The light scanning process is based on capturing the reflected light that has been previously emitted on the tooth surface. The performance of IOS is influenced by different factors, such as scanner technology, ( 3 ) ambient light, ( 4 , 5 ) software algorithm, ( 6 , 7 ) operator experience, ( 3 , 8 ) scanning sequence, ( 9 ) scanning span (partial arch or complete arch), ( 10 ) moisture, ( 11 , 12 ) scanning distance, angulation and surface characteristics ( 13 ) and scanning protocol. ( 14 ) Cervical fluids, saliva, and blood, particularly present during deep margin preparations, can impair the scan accuracy. ( 11 , 12 ) Moreover, movement of the tongue can wet the scanning surface. Also, the movement of the mucosa can interfere with the scanner's image stitching process. All this, coupled with a lack of distinct and stable intraoral features for secure stitching, can distort the final scan. ( 12 ) Reducing these problems is thought to improve the accuracy of digital scans, and complete isolation using rubber dam (RD) can decrease the impact of these factors. Rubber dams are commonly employed in dental restorations. ( 15 ) Adhesive dentistry has led to an increased use of dental dam in many dental procedures, such as immediate dentin sealing, build-up, and direct or indirect restoration performance, in which the use of the RD is considered essential. ( 16 ) In some situations, especially in onlays or overlays with deep margins, a RD needs to be placed to optimize the cavity before tooth preparation ( 16 , 17 ) or to elevate a deep margin. ( 18 ) In these cases, scanning the preparation without removing the RD would be more convenient and practical. The possibility of scanning with the RD in place has been previously described in the literature using Cut tool in the IOS. ( 19 – 21 ) In which, a preoperative scan is taken with the opposing arch together with the bite registration. Then the ‘Cut’ feature in the software of the IOS is used to cut off the preparation area which will then be rescanned with the RD in place after the preparation is performed, relying on the neighboring teeth as a reference. ( 21 ) Cut off and rescanning is a common procedure performed to capture unscanned areas of an intraoral digital scan to allow the completion of the 3D mesh geometry of the scanned surfaces. However, a recent in vitro investigation has reported that this procedure might decrease the accuracy of IOSs. ( 22 , 23 ) The IOS software program provides further functional tools that aim to facilitate the digitalization procedures of different clinical interventions. One of the available options is to Block the preexisting scan, which allows for rescanning of a particular section of the digital scan without affecting the blocked original mesh in any way. ( 24 ) Revilla-León et al. (2023) ( 24 ) , in a clinical study stated that blocking the preexisting intraoral digital mesh can prevent further modification with the rescanning procedures, to maximize scanning accuracy. A proposed technique “Lock technique” was designed, in which the lock feature could be used instead in RD scanning by making the definitive scan for the prepared area under RD first then lock it, and continue scanning the remaining arch, opposing arch and the bite. Although some studies reported the use of RD during scanning, no studies have been conducted to evaluate the scanning accuracy of different techniques under rubber dam isolation. Therefore, the purpose of the present in-vitro study is to evaluate and compare the accuracy of the digital impression with different scanning techniques under rubber dam isolation. The null hypothesis is that there is no significant difference in scanning accuracy between the different scanning techniques. Material and methods The research protocol was approved by the Institutional Review Board (IRB) committee of the Faculty of Dentistry, Alexandria University (IRB2021- 0488-CD-EXP). The study was conducted at the lab of Conservative Dentistry Department at the Faculty of Dentistry, Alexandria University. A mandibular typodont set (NISSIM Type 2; Nissim, Kyoto, Japan) was used. The first left molar was prepared for indirect onlay following these criteria (Fig.1): Walls were flared at 6-12º to the tooth’s long axis, ensuring a 2mm depth of the pulpal floor, while maintaining a minimum isthmus width of 2 mm, and round internal angles to minimize stress. The cusp was reduced by 2mm creating butt joint margins without beveling. Proximal boxes were prepared above the cemento-enamel junction with a butt joint gingival floor. (25) The reference typodont was then digitized as a reference model using a desktop scanner (MD-1D0410, Medit, South Korea) to obtain a reference standard tessellation language (STL) file (Fig.2). The scanner had been previously calibrated following the manufacturer’s instructions. Sample size calculation Sample size was estimated assuming 5% alpha error and 80% study power. The mean ± SD trueness was 15 ± 6 μm for standard scanning and 26 ± 9 μm for the cutting off rescanning procedure (22) . Based on difference between independent means, sample size was calculated to be 9 samples per group, yielding an effect size of 1.438. This was increased to 10 per group to make up for processing errors. Total sample = Number per group x Number of groups = 10 x 3 = 30 samples. Thirty digital scanning procedures were performed on the reference model using IOS (i7oo wireless, Medit, Korea) with three different scanning techniques as follows (Fig.3): - G roup I scanning without rubber dam (No-RD) , 10 scans were done for the full arch without rubber dam and 10 STL G1 files were exported. -Group II scanning under RD with cut technique (RD-C) , where a digital scan was done for the full arch of the typodont first with the same protocol for group I. Then, the prepared area was cut using the software tool and then rescanned again after applying the rubber dam (Isodam, Hedy, Medicom, Canada). The procedure was repeated till 10 STL G2 files were exported. -Group III scanning under RD with lock technique (RD-L) , a digital scan was done for the prepared area first under rubber dam with at least one tooth distal and one tooth mesial to the prepared tooth. Then the prepared area was locked and then a complete arch scan was completed after removal of the rubber dam. The procedure was repeated till 10 STL G3 files were exported. The scanning protocol (26) : The occlusal-first scanning protocol was executed using the following approach: the process started by scanning the occlusal surface of the mandibular left second molar and continued systematically across the arch to the opposite side, capturing all occlusal surfaces. For posterior teeth, the scanner tip was kept nearly parallel to the occlusal plane to ensure proper data acquisition. In the anterior region, the tip was slightly tilted toward the facial aspect to include the incisal edges and portions of both facial and lingual surfaces. After completing the occlusal sequence, the scanner was rotated toward the lingual aspect, and the lingual surfaces were recorded from the mandibular right second molar to the left second molar. Finally, the tip was angled buccally to capture the buccal surfaces of all teeth. To enhance the accuracy of the digital model and facilitate reliable superimposition, the buccal and lingual scans were performed with extensive overlap relative to the initial occlusal scan. Standardization: The IOS was calibrated following the manufacturer’s recommendations before starting each experimental group. Digital scanning was performed by a prosthodontist (H.M.) with 5 years of experience using intraoral scanners and who was calibrated before the procedure. To avoid user fatigue from scanning, the operator took 15 minutes break after every 10 scans. The digital scans were captured in a room with a dental unit but without windows and with the unit light turned off. The ambient light illuminance was checked regularly and maintained at 1000 lux as measured by using a light meter (LX1330B Light Meter; Dr Meter Digital Illuminance, Shenzhen, China). (27) The intraoral digital scans were trimmed 4 mm apical to the gingival margins of the mandibular teeth by using the cut tool of the IOS software. Ten successful scans for each group were generated with a total of 30 scans. All the scans were exported and saved in the standard tessellation language (STL) file format. The files were then imported into a reverse engineering software program (Geomagic Control X; 3D Systems) to assess scanning accuracy. The reference and experimental files were aligned using the iterative closest point best-fit matching algorithm. (28, 29) Accuracy has been defined as the combination of precision and trueness in the International Organization for Standardization (ISO) 5725–1 standard. (30) Trueness is related to the ability to replicate a dental arch as closely as possible to its true dimensions, without distortion or deformation, while precision indicates the degree of identical images acquired by repeated digital scanning under the same conditions. (30) The root-mean-square deviation (RMSD) was utilized to quantify the differences between scans, providing a single numerical value that represents the three-dimensional congruency of two superimposed meshes. This metric reflects the extent to which two distinct 3D images diverge from each other. Lower RMSD values correspond to greater agreement and higher spatial accuracy between the superimposed images. (31-33) The discrepancy calculations for each group were used to analyze the data. Trueness was calculated from the average RMS error discrepancy between the reference file and experimental scans, while precision was calculated from the RMS error variation per each group or standard deviation. (13, 30) On the reference scan, only the teeth were selected and isolated from the gingiva as a comparison area for consistent analysis. Once the scans were successfully superimposed, RMSD values between the reference scan and the superimposed intraoral scans were calculated in terms of two regions of interest, one including the full arch dentition (Dentition Area- DA ) extending from the distal of the right second molar till the distal of the left second molar, and another area of the onlay preparation surface (Preparation Area- PA ) (Fig. 4A) with total of 20 comparisons for each group. The discrepancies identified by the software program between each mesh pair comparison were demonstrated through a color-coded map that indicated the directionality of the deviation with a threshold of 100 μm on a color graded scale. Inward deviations were represented with cool shade colors, outward deviations were represented with warm shade colors, and minimal deviations were colored green (±20 μm) (Fig. 4B). Fig 5 demonstrates the flowchart of the whole experimental procedure Blinding The statistician was blinded to the different scanning groups tested. Intra and inter-operator reliability The reliability of the operator in performing digital measurements was assessed using the Intraclass Correlation Coefficient (ICC). The principal operator and another operator measured the deviation from the reference standard twice on two separate occasions using the same models under identical conditions. The ICC value was 0.920 and 0.90 respectively, indicating excellent intra-operator and inter-operator reliability. Statistical analysis Normality of precision and trueness values were assessed using Shapiro Wilk test and Q-Q plots. Normal distribution was confirmed for both variables; thus, values were presented using mainly mean and standard deviation in addition to median, minimum and maximum values. Trueness and precision were compared among groups using Repeated Measure Analysis of Variance (ANOVA) followed by post hoc test with Bonferroni correction. Data was analyzed using IBM SPSS version 23, Armonk, NY, USA. Results Table 1 Comparison of trueness (µm) and precision (µm) among the study groups Group I (n = 10) Group II (n = 10) Group III (n = 10) p value Mean ± SD Trueness Dentition Area (DA) 60.58 ± 13.19 a 90.00 ± 13.86 b 84.08 ± 10.99 b < 0.001* Preparation Area (PA) 43.45 ± 16.45 58.33 ± 18.88 53.43 ± 19.74 0.251 Precision Dentition Area (DA) 57.68 ± 13.60 a 89.71 ± 12.15 b 79.53 ± 10.85 b < 0.001* Preparation Area (PA) 41.24 ± 17.42 a 64.35 ± 18.40 b 55.18 ± 15.04 ab 0.017* *Statistically significant difference at p value < 0.05, different superscript lowercase letters denote statistical significance difference between groups Table 2 Pairwise comparison regrading trueness (µm) and precision (µm) between groups Groups Compared to Dentition Area (DA) Preparation Area (PA) Mean Difference P value Mean Difference P value Trueness Group I Group II -29.42 0.009* -14.88 0.383 Group III -23.50 0.009* -9.98 0.811 Group II Group III 5.92 0.982 4.90 1.00 Precision Group I Group II -32.03 0.005* -23.11 0.022* Group III -21.85 0.013* -13.94 0.329 Group II Group III 10.18 0.360 9.17 0.704 *Statistically significant difference at p value < 0.05 The trueness and precision values obtained from the tested groups are presented in Table (1). The analysis of trueness across the three study groups revealed significant differences in DA trueness values (p < 0.001). Using Repeated Measures ANOVA, it was found that the NO-RD group demonstrated a mean trueness of (60.58 ± 13.19 µm), which was significantly lower than that of the RD-C group (90.00 ± 13.86 µm) and the RD-L group (84.08 ± 10.99 µm), with p-values of (0.009) for both, indicating superior accuracy in the NO-RD group. Although the RD-L group exhibited better trueness values compared to the RD-C group, this difference was not statistically significant (p = 0.982). When examining DA precision, Group I (57.68 ± 13.60 µm) again demonstrated significantly better values compared to Group II (89.71 ± 12.15 µm) and Group III (79.53 ± 10.85 µm). For PA measurements, Group I (43.45 ± 16.45 µm) showed better trueness than Group II (58.33 ± 18.88 µm) and Group III (53.43 ± 19.74 µm), but no significant difference was observed among the groups (p = 0.251). Also, Group I exhibited significantly lower error precision values (41.24 ± 17.42 µm) compared to Group II (64.35 ± 18.40 µm) and Group III (55.18 ± 15.04 µm), with a p-value of 0.017, while no significant difference was found between Group I and Group III (p = 0.329) or Group II and Group III (p = 0.704). Pairwise comparisons using the Bonferroni correction confirmed these results and are presented in Table (2). Discussion The objective of the present study was to assess the accuracy of different intraoral scanning techniques under rubber dam isolation, comparing the cut technique and the lock technique to scanning without RD isolation as a control group. The null hypothesis was rejected as the findings indicate that there was significant difference among the different scanning techniques. While digital scanning under rubber dam isolation has been previously investigated, existing literature predominantly comprises clinical case reports and observational studies. Based on our knowledge, the present study is the first to systematically evaluate digital scanning accuracy under rubber dam isolation using two distinct scanning techniques. From a clinical perspective, the ability to scan under rubber dam isolation is advantageous in scenarios such as cavity optimization, deep margin elevation, or adhesive procedures where contamination control is critical. Therefore, onlay cavity preparation was tested in the present study. Consistent with previous investigations, ( 22 , 24 ) the control group (No-RD) demonstrated the highest accuracy for both trueness and precision across the full dentition. This confirms that intraoral scanning without rubber dam isolation remains the most accurate method for achieving optimal digital scans. The superior accuracy can be attributed to the absence of interfering materials and the elimination of potential stitching errors introduced by rescanning procedures. In the Cut technique performed in Group II, cutting and rescanning of the prepared area could have introduced additional alignment errors, resulting in significantly higher deviation values. These findings align with previous studies ( 34 , 35 ) reporting that rescanning procedures decrease the accuracy of intraoral scans due to mesh distortion and stitching discrepancies. Interestingly, the lock technique yielded accuracy values closer to the control group, particularly at the preparation level. Locking the scan data prevented subsequent modifications to the already captured area, thus reducing alignment errors and enhancing the stability of the final dataset. Although not equivalent to the accuracy achieved without isolation, the lock technique represents a more reliable option than the cut technique when a rubber dam is necessary. On the contrary, upon comparing the preparation area, the difference in trueness between the three groups was not significant. Moreover, there was a significant difference in precision only between (No-RD) and (RD-C). Hence, it can be suggested based on the findings that, while full-arch scans are most accurate without isolation, single-tooth or localized scans can be performed under rubber dam without jeopardizing clinical outcomes-provided the lock technique is used. Although no definitive consensus exists regarding the exact maximum value for clinically acceptable marginal discrepancy, ( 36 , 37 ) many authors agree on a threshold of approximately 120 µm as an acceptable standard. ( 38 – 41 ) The misfit of restorations can therefore be considered a reliable reference for assessing the clinical accuracy of intraoral scanners. ( 42 ) In light of this benchmark, the RMS errors recorded across all three groups in this study fell within clinically acceptable limits, supporting the feasibility of performing digital scans under rubber dam isolation. In comparison with other studies, the research conducted by Gómez-Polo et al. (2021) ( 22 ) indicated that the influence of rescanning mesh holes and stitching procedures adversely affects complete-arch scanning accuracy, diminishing both trueness and precision. This aligns with the current study’s results which showed that the scans in (No-RD) group, that were done without cutting and rescanning, demonstrated significantly lower deviation (higher accuracy) compared to the other two groups. In addition, a recent clinical trial by Espona et al. (2024) ( 43 ) , which evaluated optical impressions for overlay restorations with rubber dam further supports the notion that isolation materials impact scanning accuracy. However, their results showed no significant clinical differences between overlay restorations made from a scan with a rubber dam and without. They demonstrated that scanning with the RD in place may be a reliable clinical option for overlay restorations and optimizing scanning protocols can help mitigate some of these issues. The findings of the current study are also in agreement with Revilla-León et al. (2023) ( 24 ) , who examined the effects of cutting off and rescanning with and without blocking on intraoral scanning accuracy. Their study revealed that rescanning, especially after cutting off portions of the initial scan, introduces significant alignment errors. They noticed that the allowance of further modification of the preexisting intraoral digital scan (no blocking) significantly decreased the trueness and precision values of the IOS tested. This is in line with our observation that (RD-C) group, which involved rescanning after cutting off the initial scan, exhibited the highest RMS error, while (RD-L) group showed more accurate values. It is noteworthy to mention that the RMS deviation range in their study is less than the present study. This could be attributed to only performing a half arch scan and not a full arch scan like in the current study. In addition, they used different scanners with different scanning technologies that might have affected the results. Moreover, Reich et al. (2021) ( 23 ) explored the impact of "cut-out-rescan" procedures on digital scan accuracy. They concluded that “Cut out-rescan” procedures do not have a statistically significant influence on the accuracy of complete-arch digital scans. Obviously, their results contradict with our findings and this could be explained by using a different intra oral scanner and without applying rubber dam in any group. To add, their cut-out area has a free end extending from the left lateral incisor till the left end of the arch, which was different from the current study’s cut-out areas which were in the middle posteriorly. These findings underscore the critical role of scanning protocols and isolation methods in determining the accuracy of digital impressions, particularly in clinical scenarios involving rubber dam isolation. Although the lock technique presents an improvement over the cut technique, both methods fall short of the accuracy achieved without rubber dam isolation, suggesting that further refinements in digital impression technology and protocols are warranted. The present study's limitations include its in vitro design, which may not fully replicate the complexities of intraoral environments, where patient movement, saliva, and soft tissue dynamics could further influence accuracy. Additionally, the study focused on a single IOS model, and results may vary with different scanner technologies or software versions. This restricts the generalizability of the results across different technologies. Future research should include in vivo investigations and explore the performance of various IOS models under different clinical conditions. Moreover, investigating the impact of operator experience and environmental factors on scanning accuracy could provide further insights into optimizing digital impression techniques. Long-term clinical outcome studies comparing restorations fabricated from scans with and without rubber dam isolation would further validate the clinical significance of these findings. Conclusions Although rubber dam placement reduces accuracy compared to scans without isolation, the deviations observed remain well within the limits considered clinically acceptable. Importantly, the lock technique proved to be more accurate and consistent than the cut technique, particularly for the preparation area of a single indirect restoration, making it a more suitable approach when scanning under isolation is unavoidable. Clinically, these results highlight that practitioners can safely utilize the lock technique to capture digital impressions in scenarios demanding rubber dam use, without compromising restoration fit. Nevertheless, full-arch accuracy remains superior when scanning is performed without isolation. Declarations Ethics approval and consent to participate The study was approved by the institutional review board at the Faculty of Dentistry, Alexandria University (IRB2021- 0488-CD-EXP). All procedures were done in compliance with the Declaration of Helsinki. Consent for publication No consent was needed for publication Availability of supporting data The datasets used and/or analyzed during the current study are available in the manuscript. Competing interests The authors declare that they have no competing interest. Funding: This study received no external fund from any institute or authority. Clinical trial number : not applicable. Authors’ contribution: HK: Conceptualization, performing all methodology procedures, perform all work done on software, data curation, writing and original draft preparation, visualization, and investigation. WM: Supervision of the experimental procedures, conceptualization, validation, reviewing, and editing, help in results analysis and interpretation. MG: Supervision, conceptualization, validation, reviewing, discussion of knowledge gap to reach specific aims of the study, help in results analysis and interpretation, drawing conclusions out of the results. RA: Supervision, conceptualization, reviewing, help in results analysis and interpretation, calibration of the investigator, as well as doing the inter-examiner reliability. All authors reviewed the manuscript Acknowledgements: Not applicable. References Passos L, Meiga S, Brigagão V, Neumann M, Street A. 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Influence of rescanning mesh holes on the accuracy of an intraoral scanner: An in vivo study. J Dent. 2021;115:103851. Holmes JR, Bayne SC, Holland GA, Sulik WD. Considerations in measurement of marginal fit. J Prosthet Dent. 1989;62(4):405–8. Rinke S, Fornefett D, Gersdorff N, Lange K, Roediger M. Multifactorial analysis of the impact of different manufacturing processes on the marginal fit of zirconia copings. Dent Mater J. 2012;31(4):601–9. Jw M. The estimation of cement film thickness by an in vivo technique. Br dent j. 1971;131:107–11. Martínez-Rus F, Suárez MJ, Rivera B, Pradíes G. Evaluation of the absolute marginal discrepancy of zirconia-based ceramic copings. J Prosthet Dent. 2011;105(2):108–14. Diker B, Tak Ö. Comparing the accuracy of six intraoral scanners on prepared teeth and effect of scanning sequence. J Adv Prosthodont. 2020;12(5):299. Medina-Sotomayor P, Pascual-Moscardo A, Camps I. Accuracy of 4 digital scanning systems on prepared teeth digitally isolated from a complete dental arch. J Prosthet Dent. 2019;121(5):811–20. Vitai V, Németh A, Solyom E, Czumbel LM, Szabó B, Fazekas R, et al. Evaluation of the accuracy of intraoral scanners for complete-arch scanning: a systematic review and network meta-analysis. J Dent. 2023;137:104636. Espona J, Roig E, Ali A, Vidal C, Garcia-Font M, Roig M, et al. Optical impressions assessment for overlay restorations with rubber dam: A clinical trial. J Dent. 2024;143:104825. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7466317","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":516182056,"identity":"d817597a-5754-4613-ab1d-00152d738c09","order_by":0,"name":"Hossam M. 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07:39:04","extension":"html","order_by":19,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":118368,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-7466317/v1/4ef25beb29769f370c16a173.html"},{"id":91959338,"identity":"3e477ee5-0d6a-4b6d-b9c6-28ad57fc34e9","added_by":"auto","created_at":"2025-09-23 07:38:59","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":326603,"visible":true,"origin":"","legend":"\u003cp\u003eDiagram of the onlay cavity preparation\u003c/p\u003e","description":"","filename":"Fig.1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7466317/v1/56108de0af8df87e43bfa67e.jpg"},{"id":91959368,"identity":"96c75e32-1641-4c69-8cfc-6a2bca7a3db7","added_by":"auto","created_at":"2025-09-23 07:39:02","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":451203,"visible":true,"origin":"","legend":"\u003cp\u003eDigitizing the reference typodont to create a reference STL file.\u003c/p\u003e","description":"","filename":"Fig.2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7466317/v1/ec8cbaa845c44fb3e7078fec.jpg"},{"id":91959373,"identity":"c8bd949d-05e5-44ee-84c7-243a1e8c0dc9","added_by":"auto","created_at":"2025-09-23 07:39:03","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":459699,"visible":true,"origin":"","legend":"\u003cp\u003eDifferent scanning techniques, Gp1: scanning without rubber dam. Gp 2A: scanning the arch first. Gp 2B: cut the prepared area. Gp 2C: rescan the prepared area after applying the rubber dam. Gp 3A: scanning the prepared area first with the rubber dam placed. Gp 3B: lock the data. Gp 3C: scan the rest of the arch after removing the rubber dam.\u003c/p\u003e","description":"","filename":"Fig.3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7466317/v1/5e4826938b993897103a6ba5.jpg"},{"id":91959389,"identity":"0677b893-807e-42c7-bcd3-e98ddc92c79d","added_by":"auto","created_at":"2025-09-23 07:39:04","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":507156,"visible":true,"origin":"","legend":"\u003cp\u003eRoot mean square deviation calculation in Geomagic software. A, identification of the areas of interest, yellow represents dentition area and red represents preparation area. B, color map demonstrating the discrepancies between the meshes.\u003c/p\u003e","description":"","filename":"Fig.4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7466317/v1/f09336971435240ec4dd706a.jpg"},{"id":91960422,"identity":"ed19e060-1a01-4e7e-9b28-36257f63caae","added_by":"auto","created_at":"2025-09-23 07:46:58","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":818023,"visible":true,"origin":"","legend":"\u003cp\u003eFlow chart of the procedures.\u003c/p\u003e","description":"","filename":"Fig.5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7466317/v1/37e53d4a15377bb518f45671.jpg"},{"id":99308494,"identity":"16beba73-6b90-4a34-aa5f-e1f3de40b945","added_by":"auto","created_at":"2025-12-31 16:08:42","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3281733,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7466317/v1/3b386146-4bf2-49af-b03a-009b04eddbf2.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Evaluation of the accuracy of different intraoral scanning techniques under rubber-dam isolation: An invitro study","fulltext":[{"header":"Introduction","content":"\u003cp\u003eThe adoption of digital systems in dentistry is on the rise. Among the latest developments in computer-aided design and manufacturing (CAD/CAM) is the successful integration of intraoral scanning into dental practice.\u003csup\u003e(\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e)\u003c/sup\u003e Intraoral scanners (IOS) offer a reliable and clinically approved method for producing indirect partial coverage restoration, crowns and short-span fixed partial dentures.\u003csup\u003e(\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e)\u003c/sup\u003e\u003c/p\u003e\u003cp\u003eThe light scanning process is based on capturing the reflected light that has been previously emitted on the tooth surface. The performance of IOS is influenced by different factors, such as scanner technology,\u003csup\u003e(\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e)\u003c/sup\u003e ambient light,\u003csup\u003e(\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e)\u003c/sup\u003e software algorithm,\u003csup\u003e(\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e)\u003c/sup\u003e operator experience,\u003csup\u003e(\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e)\u003c/sup\u003e scanning sequence,\u003csup\u003e(\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e)\u003c/sup\u003e scanning span (partial arch or complete arch),\u003csup\u003e(\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e)\u003c/sup\u003e moisture,\u003csup\u003e(\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e)\u003c/sup\u003e scanning distance, angulation and surface characteristics\u003csup\u003e(\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e)\u003c/sup\u003e and scanning protocol.\u003csup\u003e(\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e)\u003c/sup\u003e\u003c/p\u003e\u003cp\u003eCervical fluids, saliva, and blood, particularly present during deep margin preparations, can impair the scan accuracy.\u003csup\u003e(\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e)\u003c/sup\u003e Moreover, movement of the tongue can wet the scanning surface. Also, the movement of the mucosa can interfere with the scanner's image stitching process. All this, coupled with a lack of distinct and stable intraoral features for secure stitching, can distort the final scan.\u003csup\u003e(\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e)\u003c/sup\u003e Reducing these problems is thought to improve the accuracy of digital scans, and complete isolation using rubber dam (RD) can decrease the impact of these factors.\u003c/p\u003e\u003cp\u003eRubber dams are commonly employed in dental restorations.\u003csup\u003e(\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e)\u003c/sup\u003e Adhesive dentistry has led to an increased use of dental dam in many dental procedures, such as immediate dentin sealing, build-up, and direct or indirect restoration performance, in which the use of the RD is considered essential.\u003csup\u003e(\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e)\u003c/sup\u003e In some situations, especially in onlays or overlays with deep margins, a RD needs to be placed to optimize the cavity before tooth preparation\u003csup\u003e(\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e)\u003c/sup\u003e or to elevate a deep margin.\u003csup\u003e(\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e)\u003c/sup\u003e In these cases, scanning the preparation without removing the RD would be more convenient and practical.\u003c/p\u003e\u003cp\u003eThe possibility of scanning with the RD in place has been previously described in the literature using Cut tool in the IOS.\u003csup\u003e(\u003cspan additionalcitationids=\"CR20\" citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e)\u003c/sup\u003e In which, a preoperative scan is taken with the opposing arch together with the bite registration. Then the \u0026lsquo;Cut\u0026rsquo; feature in the software of the IOS is used to cut off the preparation area which will then be rescanned with the RD in place after the preparation is performed, relying on the neighboring teeth as a reference.\u003csup\u003e(\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e)\u003c/sup\u003e\u003c/p\u003e\u003cp\u003eCut off and rescanning is a common procedure performed to capture unscanned areas of an intraoral digital scan to allow the completion of the 3D mesh geometry of the scanned surfaces. However, a recent in vitro investigation has reported that this procedure might decrease the accuracy of IOSs.\u003csup\u003e(\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e)\u003c/sup\u003e\u003c/p\u003e\u003cp\u003eThe IOS software program provides further functional tools that aim to facilitate the digitalization procedures of different clinical interventions. One of the available options is to \u003cb\u003eBlock\u003c/b\u003e the preexisting scan, which allows for rescanning of a particular section of the digital scan without affecting the blocked original mesh in any way.\u003csup\u003e(\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e)\u003c/sup\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eRevilla-Le\u0026oacute;n et al. (2023)\u003c/b\u003e\u003csup\u003e(\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e)\u003c/sup\u003e, in a clinical study stated that blocking the preexisting intraoral digital mesh can prevent further modification with the rescanning procedures, to maximize scanning accuracy. A proposed technique \u0026ldquo;Lock technique\u0026rdquo; was designed, in which the lock feature could be used instead in RD scanning by making the definitive scan for the prepared area under RD first then lock it, and continue scanning the remaining arch, opposing arch and the bite.\u003c/p\u003e\u003cp\u003eAlthough some studies reported the use of RD during scanning, no studies have been conducted to evaluate the scanning accuracy of different techniques under rubber dam isolation. Therefore, the purpose of the present in-vitro study is to evaluate and compare the accuracy of the digital impression with different scanning techniques under rubber dam isolation. The null hypothesis is that there is no significant difference in scanning accuracy between the different scanning techniques.\u003c/p\u003e"},{"header":"Material and methods","content":"\u003cp\u003eThe research protocol was approved by the Institutional Review Board (IRB) committee of the Faculty of Dentistry, Alexandria University (IRB2021- 0488-CD-EXP). The study was conducted at the lab of Conservative Dentistry Department at the Faculty of Dentistry, Alexandria University.\u003c/p\u003e\n\u003cp\u003eA mandibular typodont set (NISSIM Type 2; Nissim, Kyoto, Japan) was used. \u0026nbsp;The first left molar was prepared for indirect onlay following these criteria (Fig.1): Walls were flared at 6-12º to the tooth’s long axis, ensuring a 2mm depth of the pulpal floor, while maintaining a minimum isthmus width of 2 mm, and round internal angles to minimize stress. The cusp was reduced by 2mm creating butt joint margins without beveling. Proximal boxes were prepared above the cemento-enamel junction with a butt joint gingival floor.\u003csup\u003e(25)\u003c/sup\u003e\u003c/p\u003e\n\u003cp\u003eThe reference typodont was then digitized as a reference model using a desktop scanner (MD-1D0410, Medit, South Korea) to obtain a reference standard tessellation language (STL) file (Fig.2). The scanner had been previously calibrated following the manufacturer’s instructions.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSample size calculation\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eSample size was estimated assuming 5% alpha error and 80% study power. The mean ± SD trueness was 15 ± 6 μm for standard scanning and 26 ± 9 μm for the cutting off rescanning procedure\u003csup\u003e(22)\u003c/sup\u003e. Based on difference between independent means, sample size was calculated to be 9 samples per group, yielding an effect size of 1.438. This was increased to 10 per group to make up for processing errors. Total sample = Number per group x Number of groups = 10 x 3 = 30 samples.\u003c/p\u003e\n\u003cp\u003eThirty digital scanning procedures were performed on the reference model using IOS (i7oo wireless, Medit, Korea) with three different scanning techniques as follows (Fig.3):\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e-\u003c/strong\u003eG\u003cstrong\u003eroup I\u003c/strong\u003e scanning without rubber dam \u003cstrong\u003e(No-RD)\u003c/strong\u003e, 10 scans were done for the full arch without rubber dam and 10 STL\u003csub\u003eG1\u003c/sub\u003e files were exported.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e-Group II\u003c/strong\u003e scanning under RD with cut technique \u003cstrong\u003e(RD-C)\u003c/strong\u003e, where a digital scan was done for the full arch of the typodont first with the same protocol for group I. Then, the prepared area was cut using the software tool and then rescanned again after applying the rubber dam (Isodam, Hedy, Medicom, Canada). The procedure was repeated till 10 STL\u003csub\u003eG2\u0026nbsp;\u003c/sub\u003efiles were exported.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e-Group III\u003c/strong\u003e scanning under RD with lock technique \u003cstrong\u003e(RD-L)\u003c/strong\u003e, a digital scan was done for the prepared area first under rubber dam with at least one tooth distal and one tooth mesial to the prepared tooth. Then the prepared area was locked and then a complete arch scan was completed after removal of the rubber dam. The procedure was repeated till 10 STL\u003csub\u003eG3\u0026nbsp;\u003c/sub\u003efiles were exported. \u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eThe scanning protocol\u003c/em\u003e\u003csup\u003e(26)\u003c/sup\u003e:\u003c/p\u003e\n\u003cp\u003eThe occlusal-first scanning protocol was executed using the following approach: the process started by scanning the occlusal surface of the mandibular left second molar and continued systematically across the arch to the opposite side, capturing all occlusal surfaces. For posterior teeth, the scanner tip was kept nearly parallel to the occlusal plane to ensure proper data acquisition. In the anterior region, the tip was slightly tilted toward the facial aspect to include the incisal edges and portions of both facial and lingual surfaces.\u003c/p\u003e\n\u003cp\u003eAfter completing the occlusal sequence, the scanner was rotated toward the lingual aspect, and the lingual surfaces were recorded from the mandibular right second molar to the left second molar. Finally, the tip was angled buccally to capture the buccal surfaces of all teeth.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eTo enhance the accuracy of the digital model and facilitate reliable superimposition, the buccal and lingual scans were performed with extensive overlap relative to the initial\u0026nbsp;occlusal\u0026nbsp;scan.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eStandardization:\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe IOS was calibrated following the manufacturer’s recommendations before starting each experimental group. Digital scanning was performed by a prosthodontist (H.M.) with 5 years of experience using intraoral scanners and who was calibrated before the procedure. To avoid user fatigue from scanning, the operator took 15 minutes break after every 10 scans.\u003c/p\u003e\n\u003cp\u003eThe digital scans were captured in a room with a dental unit but without windows and with the unit light turned off. The ambient light illuminance was checked regularly and maintained at 1000 lux as measured by using a light meter (LX1330B Light Meter; Dr Meter Digital Illuminance,\u0026nbsp;Shenzhen, China).\u003csup\u003e(27)\u003c/sup\u003e\u003c/p\u003e\n\u003cp\u003eThe intraoral digital scans were trimmed 4 mm apical to the gingival margins of the mandibular teeth by using the cut tool of the IOS software. Ten successful scans for each group were generated with a total of 30 scans. All the scans were exported and saved in the standard tessellation language (STL) file format.\u003c/p\u003e\n\u003cp\u003eThe files were then imported into a reverse engineering software program (Geomagic Control X; 3D Systems) to assess scanning accuracy. The reference and experimental files were aligned using the iterative closest point best-fit matching algorithm.\u003csup\u003e(28, 29)\u003c/sup\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAccuracy has been defined as the combination of precision and trueness in the International Organization for Standardization (ISO) 5725–1 standard.\u003csup\u003e(30)\u003c/sup\u003e Trueness is related to the ability to replicate a dental arch as closely as possible to its true dimensions, without distortion or deformation, while precision indicates the degree of identical images acquired by repeated digital scanning under the same conditions.\u003csup\u003e(30)\u003c/sup\u003e\u003c/p\u003e\n\u003cp\u003eThe root-mean-square deviation (RMSD) was utilized to quantify the differences between scans, providing a single numerical value that represents the three-dimensional congruency of two superimposed meshes. This metric reflects the extent to which two distinct 3D images diverge from each other. Lower RMSD values correspond to greater agreement and higher spatial accuracy between the superimposed\u0026nbsp;images.\u003csup\u003e(31-33)\u003c/sup\u003e\u003c/p\u003e\n\u003cp\u003eThe discrepancy calculations for each group were used to analyze the data. Trueness was calculated from the average RMS error discrepancy between the reference file and experimental scans, while precision was calculated from the RMS error variation per each group or standard deviation.\u003csup\u003e(13, 30)\u003c/sup\u003e\u003c/p\u003e\n\u003cp\u003eOn the reference scan, only the teeth were selected and isolated from the gingiva as a comparison area for consistent analysis. Once the scans were successfully superimposed, RMSD values between the reference scan and the superimposed intraoral scans were calculated in terms of two regions of interest, one including the full arch dentition (Dentition Area-\u003cstrong\u003eDA\u003c/strong\u003e) extending from the distal of the right second molar till the distal of the left second molar, and another area of the onlay preparation surface (Preparation Area-\u003cstrong\u003ePA\u003c/strong\u003e) (Fig. 4A) with total of 20 comparisons for each group.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe discrepancies identified by the software program between each mesh pair comparison were demonstrated through a color-coded map that indicated the directionality of the deviation with a threshold of 100 μm on a color graded scale. Inward deviations were represented with cool shade colors, outward deviations were represented with warm shade colors, and minimal deviations were colored green (±20 μm) (Fig. 4B). Fig 5 demonstrates the flowchart of the whole experimental procedure\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eBlinding\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe statistician was blinded to the different scanning groups tested.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eIntra and inter-operator reliability\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe reliability of the operator in performing digital measurements was assessed using the Intraclass Correlation Coefficient (ICC). The principal operator and another operator measured the deviation from the reference standard twice on two separate occasions using the same models under identical conditions. The ICC value was 0.920 and 0.90 respectively, indicating excellent intra-operator\u0026nbsp;and inter-operator reliability.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eStatistical analysis\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNormality of precision and trueness values were assessed using Shapiro Wilk test and Q-Q plots. Normal distribution was confirmed for both variables; thus, values were presented using mainly mean and standard deviation in addition to median, minimum and maximum values. Trueness and precision were compared among groups using \u003cstrong\u003e\u003cem\u003eRepeated Measure Analysis of Variance (ANOVA)\u003c/em\u003e\u003c/strong\u003e followed by post hoc test with Bonferroni correction. Data was analyzed using IBM SPSS version 23, Armonk, NY, USA.\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eComparison of trueness (\u0026micro;m) and precision (\u0026micro;m) among the study groups\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"6\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eGroup I\u003c/p\u003e\u003cp\u003e(n\u0026thinsp;=\u0026thinsp;10)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eGroup II\u003c/p\u003e\u003cp\u003e(n\u0026thinsp;=\u0026thinsp;10)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eGroup III\u003c/p\u003e\u003cp\u003e(n\u0026thinsp;=\u0026thinsp;10)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003e\u003cem\u003ep\u003c/em\u003e value\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"3\" nameend=\"c5\" namest=\"c3\"\u003e\u003cp\u003eMean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eTrueness\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eDentition Area (DA)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e60.58\u0026thinsp;\u0026plusmn;\u0026thinsp;13.19\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e90.00\u0026thinsp;\u0026plusmn;\u0026thinsp;13.86\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e84.08\u0026thinsp;\u0026plusmn;\u0026thinsp;10.99\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001*\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003ePreparation Area (PA)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e43.45\u0026thinsp;\u0026plusmn;\u0026thinsp;16.45\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e58.33\u0026thinsp;\u0026plusmn;\u0026thinsp;18.88\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e53.43\u0026thinsp;\u0026plusmn;\u0026thinsp;19.74\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.251\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003ePrecision\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eDentition Area (DA)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e57.68\u0026thinsp;\u0026plusmn;\u0026thinsp;13.60\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e89.71\u0026thinsp;\u0026plusmn;\u0026thinsp;12.15\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e79.53\u0026thinsp;\u0026plusmn;\u0026thinsp;10.85\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001*\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003ePreparation Area (PA)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e41.24\u0026thinsp;\u0026plusmn;\u0026thinsp;17.42\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e64.35\u0026thinsp;\u0026plusmn;\u0026thinsp;18.40\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e55.18\u0026thinsp;\u0026plusmn;\u0026thinsp;15.04\u003csup\u003eab\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e0.017*\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"6\"\u003e*Statistically significant difference at \u003cem\u003ep\u003c/em\u003e value\u0026thinsp;\u0026lt;\u0026thinsp;0.05, different superscript lowercase letters denote statistical significance difference between groups\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003e\u003cb\u003ePairwise comparison regrading trueness (\u0026micro;m) and precision (\u0026micro;m) between groups\u003c/b\u003e\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"7\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eGroups\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eCompared to\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e\u003cp\u003eDentition Area (DA)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e\u003cp\u003ePreparation Area (PA)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eMean Difference\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eP value\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eMean Difference\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003eP value\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e\u003cp\u003eTrueness\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eGroup I\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eGroup II\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-29.42\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.009*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e-14.88\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0.383\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eGroup III\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-23.50\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.009*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e-9.98\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0.811\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eGroup II\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eGroup III\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e5.92\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.982\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e4.90\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e1.00\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e\u003cp\u003ePrecision\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eGroup I\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eGroup II\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-32.03\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.005*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e-23.11\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0.022*\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eGroup III\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-21.85\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.013*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e-13.94\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0.329\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eGroup II\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eGroup III\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e10.18\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.360\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e9.17\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0.704\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"7\"\u003e*Statistically significant difference at \u003cem\u003ep\u003c/em\u003e value\u0026thinsp;\u0026lt;\u0026thinsp;0.05\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eThe trueness and precision values obtained from the tested groups are presented in Table\u0026nbsp;(1). The analysis of trueness across the three study groups revealed significant differences in DA trueness values (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). Using Repeated Measures ANOVA, it was found that the NO-RD group demonstrated a mean trueness of (60.58\u0026thinsp;\u0026plusmn;\u0026thinsp;13.19 \u0026micro;m), which was significantly lower than that of the RD-C group (90.00\u0026thinsp;\u0026plusmn;\u0026thinsp;13.86 \u0026micro;m) and the RD-L group (84.08\u0026thinsp;\u0026plusmn;\u0026thinsp;10.99 \u0026micro;m), with p-values of (0.009) for both, indicating superior accuracy in the NO-RD group. Although the RD-L group exhibited better trueness values compared to the RD-C group, this difference was not statistically significant (p\u0026thinsp;=\u0026thinsp;0.982). When examining DA precision, Group I (57.68\u0026thinsp;\u0026plusmn;\u0026thinsp;13.60 \u0026micro;m) again demonstrated significantly better values compared to Group II (89.71\u0026thinsp;\u0026plusmn;\u0026thinsp;12.15 \u0026micro;m) and Group III (79.53\u0026thinsp;\u0026plusmn;\u0026thinsp;10.85 \u0026micro;m).\u003c/p\u003e\u003cp\u003eFor PA measurements, Group I (43.45\u0026thinsp;\u0026plusmn;\u0026thinsp;16.45 \u0026micro;m) showed better trueness than Group II (58.33\u0026thinsp;\u0026plusmn;\u0026thinsp;18.88 \u0026micro;m) and Group III (53.43\u0026thinsp;\u0026plusmn;\u0026thinsp;19.74 \u0026micro;m), but no significant difference was observed among the groups (p\u0026thinsp;=\u0026thinsp;0.251). Also, Group I exhibited significantly lower error precision values (41.24\u0026thinsp;\u0026plusmn;\u0026thinsp;17.42 \u0026micro;m) compared to Group II (64.35\u0026thinsp;\u0026plusmn;\u0026thinsp;18.40 \u0026micro;m) and Group III (55.18\u0026thinsp;\u0026plusmn;\u0026thinsp;15.04 \u0026micro;m), with a p-value of 0.017, while no significant difference was found between Group I and Group III (p\u0026thinsp;=\u0026thinsp;0.329) or Group II and Group III (p\u0026thinsp;=\u0026thinsp;0.704). Pairwise comparisons using the Bonferroni correction confirmed these results and are presented in Table\u0026nbsp;(2).\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe objective of the present study was to assess the accuracy of different intraoral scanning techniques under rubber dam isolation, comparing the cut technique and the lock technique to scanning without RD isolation as a control group. The null hypothesis was rejected as the findings indicate that there was significant difference among the different scanning techniques.\u003c/p\u003e\u003cp\u003eWhile digital scanning under rubber dam isolation has been previously investigated, existing literature predominantly comprises clinical case reports and observational studies. Based on our knowledge, the present study is the first to systematically evaluate digital scanning accuracy under rubber dam isolation using two distinct scanning techniques.\u003c/p\u003e\u003cp\u003eFrom a clinical perspective, the ability to scan under rubber dam isolation is advantageous in scenarios such as cavity optimization, deep margin elevation, or adhesive procedures where contamination control is critical. Therefore, onlay cavity preparation was tested in the present study.\u003c/p\u003e\u003cp\u003eConsistent with previous investigations,\u003csup\u003e(\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e)\u003c/sup\u003e the control group (No-RD) demonstrated the highest accuracy for both trueness and precision across the full dentition. This confirms that intraoral scanning without rubber dam isolation remains the most accurate method for achieving optimal digital scans. The superior accuracy can be attributed to the absence of interfering materials and the elimination of potential stitching errors introduced by rescanning procedures. In the Cut technique performed in Group II, cutting and rescanning of the prepared area could have introduced additional alignment errors, resulting in significantly higher deviation values. These findings align with previous studies \u003csup\u003e(\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e, \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e)\u003c/sup\u003e reporting that rescanning procedures decrease the accuracy of intraoral scans due to mesh distortion and stitching discrepancies. Interestingly, the lock technique yielded accuracy values closer to the control group, particularly at the preparation level. Locking the scan data prevented subsequent modifications to the already captured area, thus reducing alignment errors and enhancing the stability of the final dataset. Although not equivalent to the accuracy achieved without isolation, the lock technique represents a more reliable option than the cut technique when a rubber dam is necessary.\u003c/p\u003e\u003cp\u003eOn the contrary, upon comparing the preparation area, the difference in trueness between the three groups was not significant. Moreover, there was a significant difference in precision only between (No-RD) and (RD-C). Hence, it can be suggested based on the findings that, while full-arch scans are most accurate without isolation, single-tooth or localized scans can be performed under rubber dam without jeopardizing clinical outcomes-provided the lock technique is used.\u003c/p\u003e\u003cp\u003eAlthough no definitive consensus exists regarding the exact maximum value for clinically acceptable marginal discrepancy, \u003csup\u003e(\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e, \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e)\u003c/sup\u003e many authors agree on a threshold of approximately 120 \u0026micro;m as an acceptable standard. \u003csup\u003e(\u003cspan additionalcitationids=\"CR39 CR40\" citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e)\u003c/sup\u003e The misfit of restorations can therefore be considered a reliable reference for assessing the clinical accuracy of intraoral scanners. \u003csup\u003e(\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e)\u003c/sup\u003e In light of this benchmark, the RMS errors recorded across all three groups in this study fell within clinically acceptable limits, supporting the feasibility of performing digital scans under rubber dam isolation.\u003c/p\u003e\u003cp\u003eIn comparison with other studies, the research conducted by G\u0026oacute;mez-Polo et al. (2021)\u003csup\u003e(\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e)\u003c/sup\u003eindicated that the influence of rescanning mesh holes and stitching procedures adversely affects complete-arch scanning accuracy, diminishing both trueness and precision. This aligns with the current study\u0026rsquo;s results which showed that the scans in (No-RD) group, that were done without cutting and rescanning, demonstrated significantly lower deviation (higher accuracy) compared to the other two groups.\u003c/p\u003e\u003cp\u003eIn addition, a recent clinical trial by \u003cb\u003eEspona et al. (2024)\u003c/b\u003e\u003csup\u003e(\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e)\u003c/sup\u003e, which evaluated optical impressions for overlay restorations with rubber dam further supports the notion that isolation materials impact scanning accuracy. However, their results showed no significant clinical differences between overlay restorations made from a scan with a rubber dam and without. They demonstrated that scanning with the RD in place may be a reliable clinical option for overlay restorations and optimizing scanning protocols can help mitigate some of these issues.\u003c/p\u003e\u003cp\u003eThe findings of the current study are also in agreement with \u003cb\u003eRevilla-Le\u0026oacute;n et al. (2023)\u003c/b\u003e\u003csup\u003e(\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e)\u003c/sup\u003e, who examined the effects of cutting off and rescanning with and without blocking on intraoral scanning accuracy. Their study revealed that rescanning, especially after cutting off portions of the initial scan, introduces significant alignment errors. They noticed that the allowance of further modification of the preexisting intraoral digital scan (no blocking) significantly decreased the trueness and precision values of the IOS tested. This is in line with our observation that (RD-C) group, which involved rescanning after cutting off the initial scan, exhibited the highest RMS error, while (RD-L) group showed more accurate values. It is noteworthy to mention that the RMS deviation range in their study is less than the present study. This could be attributed to only performing a half arch scan and not a full arch scan like in the current study. In addition, they used different scanners with different scanning technologies that might have affected the results.\u003c/p\u003e\u003cp\u003eMoreover, \u003cb\u003eReich et al. (2021)\u003c/b\u003e\u003csup\u003e(\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e)\u003c/sup\u003e explored the impact of \"cut-out-rescan\" procedures on digital scan accuracy. They concluded that \u0026ldquo;Cut out-rescan\u0026rdquo; procedures do not have a statistically significant influence on the accuracy of complete-arch digital scans. Obviously, their results contradict with our findings and this could be explained by using a different intra oral scanner and without applying rubber dam in any group. To add, their cut-out area has a free end extending from the left lateral incisor till the left end of the arch, which was different from the current study\u0026rsquo;s cut-out areas which were in the middle posteriorly.\u003c/p\u003e\u003cp\u003eThese findings underscore the critical role of scanning protocols and isolation methods in determining the accuracy of digital impressions, particularly in clinical scenarios involving rubber dam isolation. Although the lock technique presents an improvement over the cut technique, both methods fall short of the accuracy achieved without rubber dam isolation, suggesting that further refinements in digital impression technology and protocols are warranted.\u003c/p\u003e\u003cp\u003eThe present study's limitations include its in vitro design, which may not fully replicate the complexities of intraoral environments, where patient movement, saliva, and soft tissue dynamics could further influence accuracy. Additionally, the study focused on a single IOS model, and results may vary with different scanner technologies or software versions. This restricts the generalizability of the results across different technologies.\u003c/p\u003e\u003cp\u003eFuture research should include in vivo investigations and explore the performance of various IOS models under different clinical conditions. Moreover, investigating the impact of operator experience and environmental factors on scanning accuracy could provide further insights into optimizing digital impression techniques. Long-term clinical outcome studies comparing restorations fabricated from scans with and without rubber dam isolation would further validate the clinical significance of these findings.\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eAlthough rubber dam placement reduces accuracy compared to scans without isolation, the deviations observed remain well within the limits considered clinically acceptable. Importantly, the lock technique proved to be more accurate and consistent than the cut technique, particularly for the preparation area of a single indirect restoration, making it a more suitable approach when scanning under isolation is unavoidable. Clinically, these results highlight that practitioners can safely utilize the lock technique to capture digital impressions in scenarios demanding rubber dam use, without compromising restoration fit. Nevertheless, full-arch accuracy remains superior when scanning is performed without isolation.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe study was approved by the institutional review board at the Faculty of Dentistry, Alexandria University\u0026nbsp;(IRB2021- 0488-CD-EXP). All procedures were done in compliance with the Declaration of Helsinki.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNo consent was needed for publication\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of supporting data\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets used and/or analyzed during the current study are available in the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no competing interest.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study received no external fund from any institute or authority.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eClinical trial number\u003c/strong\u003e: not applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors’ contribution:\u0026nbsp; \u0026nbsp;\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eHK:\u003c/strong\u003e Conceptualization, performing all methodology procedures, perform all work done on software, data curation, writing and original draft preparation, visualization, and investigation. \u003cstrong\u003eWM:\u0026nbsp;\u003c/strong\u003eSupervision of the experimental procedures, conceptualization, validation, reviewing, and editing,\u0026nbsp;help in results analysis and interpretation.\u0026nbsp;\u003cstrong\u003eMG:\u0026nbsp;\u003c/strong\u003eSupervision, conceptualization, validation, reviewing,\u0026nbsp;discussion of knowledge gap to reach specific aims of the study, help in results analysis and interpretation, drawing conclusions out of the results.\u0026nbsp;\u003cstrong\u003eRA:\u0026nbsp;\u003c/strong\u003eSupervision, conceptualization, reviewing,\u0026nbsp;help in results analysis and interpretation, calibration of the investigator, as well as doing the inter-examiner reliability. All authors reviewed the manuscript\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003ePassos L, Meiga S, Brigag\u0026atilde;o V, Neumann M, Street A. Digital impressions\u0026rsquo; accuracy through cut-out-rescan and data exchange by over scanning techniques in complete arches of two intraoral scanners and CAD/CAM software. J Prosthodontic Res. 2022;66(3):509\u0026ndash;13.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eAhlholm P, Sipil\u0026auml; K, Vallittu P, Jakonen M, Kotiranta U. Digital versus conventional impressions in fixed prosthodontics: a review. J Prosthodont. 2018;27(1):35\u0026ndash;41.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003ePark J-M, Kim RJ-Y, Lee K-W. Comparative reproducibility analysis of 6 intraoral scanners used on complex intracoronal preparations. 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Evidence-based concepts and procedures for bonded inlays and onlays. Part III. A case series with long-term clinical results and follow-up. Int J Esthet Dent. 2019;14:2\u0026ndash;17.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eFalacho RI, Melo EA, Marques JA, Ramos JC, Guerra F, Blatz MB. Clinical in-situ evaluation of the effect of rubber dam isolation on bond strength to enamel. J Esthetic Restor Dentistry. 2023;35(1):48\u0026ndash;55.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMagne P, Spreafico RC. Deep margin elevation: a paradigm shift. Am J Esthet Dent. 2012;2(2):86\u0026ndash;96.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eCaponi LQ, Flor E, Ortega-Mart\u0026iacute;nez J, Figueras‐Alvarez O. Protocol for indirect restoration intraoral scanning under dental dam isolation: a dental technique. J Prosthodont. 2021;30(8):725\u0026ndash;8.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eHenarejos-Domingo V, Clavijo V, Blasi \u0026Aacute;, Madeira S, Roig M. Digital scanning under rubber dam: An innovative method for making definitive impressions in fixed prosthodontics. J Esthetic Restor Dentistry. 2021;33(7).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eJurado CA, Lederman R, Cohen J, Tsujimoto A. Intraoral scanning with rubber dam isolation in place for fabrication of a chairside computer-assisted design and computer-assisted manufacture ceramic restoration. J Contemp Dent Pract. 2021;22(8):943\u0026ndash;46.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eG\u0026oacute;mez-Polo M, Piedra-Casc\u0026oacute;n W, Methani MM, Quesada-Olmo N, Farjas-Abadia M, Revilla-Le\u0026oacute;n M. Influence of rescanning mesh holes and stitching procedures on the complete-arch scanning accuracy of an intraoral scanner: An in vitro study. J Dent. 2021;110:103690.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eReich S, Yatmaz B, Raith S. Do cut out-rescan procedures have an impact on the accuracy of intraoral digital scans? J Prosthet Dent. 2021;125(1):89\u0026ndash;94.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eRevilla-Le\u0026oacute;n M, Sicilia E, Agust\u0026iacute;n-Panadero R, G\u0026oacute;mez-Polo M, Kois JC. Clinical evaluation of the effects of cutting off, overlapping, and rescanning procedures on intraoral scanning accuracy. J Prosthet Dent. 2023;130(5):746\u0026ndash;54.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSouza J, Fuentes MV, Baena E, Ceballos L. One-year clinical performance of lithium disilicate versus resin composite CAD/CAM onlays. Odontology. 2021;109(1):259\u0026ndash;70.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eAn H, Langas EE, Gill AS. Effect of scanning speed, scanning pattern, and tip size on the accuracy of intraoral digital scans. J Prosthet Dent. 2024;131(6):1160\u0026ndash;7.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eOchoa-L\u0026oacute;pez G, Revilla-Le\u0026oacute;n M, G\u0026oacute;mez-Polo M. Influence of the ambient color lighting on the accuracy of complete arch implant scans recorded by using two intraoral scanners. J Prosthet Dent. 2025;133(2):552\u0026ndash;9.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eRevilla-Le\u0026oacute;n M, Gohil A, Barmak AB, Zandinejad A, Raigrodski AJ. Alonso P\u0026eacute;rez‐Barquero J. Best‐fit algorithm influences on virtual casts\u0026rsquo; alignment discrepancies. J Prosthodont. 2023;32(4):331\u0026ndash;9.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eRevilla-Le\u0026oacute;n M, P\u0026eacute;rez-Barquero JA, Barmak BA, Agust\u0026iacute;n-Panadero R, Fern\u0026aacute;ndez-Estevan L, Att W. Facial scanning accuracy depending on the alignment algorithm and digitized surface area location: an in vitro study. J Dent. 2021;110:103680.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eISO I. 5725-1: 1994, Accuracy (trueness and precision) of measurement methods and results-Part 1: General principles and definitions. International Organization for Standardization, Geneva. 1994:2.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eEnder A, Mehl A. Full arch scans: conventional versus digital impressions\u0026ndash;an in-vitro study. Int J Comput Dent. 2011;14(1):11\u0026ndash;21.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSchaefer O, Watts DC, Sigusch BW, Kuepper H, Guentsch A. Marginal and internal fit of pressed lithium disilicate partial crowns in vitro: a three-dimensional analysis of accuracy and reproducibility. Dent Mater. 2012;28(3):320\u0026ndash;6.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eCho S-H, Schaefer O, Thompson GA, Guentsch A. Comparison of accuracy and reproducibility of casts made by digital and conventional methods. J Prosthet Dent. 2015;113(4):310\u0026ndash;5.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eGuo J, Lu Y, Li R, Zhou K, Ge R, Zhao D, et al. Influence of repeated cut-off and rescanning on the trueness of the intraoral digital scans. J Dent. 2024;150:105153.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eRevilla-Le\u0026oacute;n M, Quesada-Olmo N, G\u0026oacute;mez-Polo M, Sicilia E, Farjas-Abadia M, Kois JC. Influence of rescanning mesh holes on the accuracy of an intraoral scanner: An in vivo study. J Dent. 2021;115:103851.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eHolmes JR, Bayne SC, Holland GA, Sulik WD. Considerations in measurement of marginal fit. J Prosthet Dent. 1989;62(4):405\u0026ndash;8.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eRinke S, Fornefett D, Gersdorff N, Lange K, Roediger M. Multifactorial analysis of the impact of different manufacturing processes on the marginal fit of zirconia copings. Dent Mater J. 2012;31(4):601\u0026ndash;9.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eJw M. The estimation of cement film thickness by an in vivo technique. Br dent j. 1971;131:107\u0026ndash;11.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMart\u0026iacute;nez-Rus F, Su\u0026aacute;rez MJ, Rivera B, Prad\u0026iacute;es G. Evaluation of the absolute marginal discrepancy of zirconia-based ceramic copings. J Prosthet Dent. 2011;105(2):108\u0026ndash;14.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eDiker B, Tak \u0026Ouml;. Comparing the accuracy of six intraoral scanners on prepared teeth and effect of scanning sequence. J Adv Prosthodont. 2020;12(5):299.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMedina-Sotomayor P, Pascual-Moscardo A, Camps I. Accuracy of 4 digital scanning systems on prepared teeth digitally isolated from a complete dental arch. J Prosthet Dent. 2019;121(5):811\u0026ndash;20.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eVitai V, N\u0026eacute;meth A, Solyom E, Czumbel LM, Szab\u0026oacute; B, Fazekas R, et al. Evaluation of the accuracy of intraoral scanners for complete-arch scanning: a systematic review and network meta-analysis. J Dent. 2023;137:104636.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eEspona J, Roig E, Ali A, Vidal C, Garcia-Font M, Roig M, et al. Optical impressions assessment for overlay restorations with rubber dam: A clinical trial. J Dent. 2024;143:104825.\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":"Intra oral scanning, Digital, Techniques, Accuracy, Rubber dam, Cut technique, Lock technique","lastPublishedDoi":"10.21203/rs.3.rs-7466317/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7466317/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eBackground: \u003c/strong\u003eThe\u003cstrong\u003e \u003c/strong\u003eapplication of rubber dam during intraoral scanning provides the ideal conditions for scanning including operative field clarity, moisture reduction, gingival retraction, and isolation from saliva, blood, and tongue.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAim of the study: \u003c/strong\u003eThe purpose of this study was to evaluate the accuracy of intraoral scanning under rubber dam isolation using cut and lock techniques.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMaterials and methods: \u003c/strong\u003eA lower first molar in mandibular typodont was prepared for indirect onlay restoration. The reference typodont was then digitized as a reference model using a desktop scanner (MD-1D0410, Medit, South Korea) to obtain a reference standard tessellation language (STL). Thirty digital scanning procedures were performed on the reference model using IOS (i7oo wireless, Medit, South Korea) with three different scanning techniques as follows: \u003cstrong\u003eGroup I:\u003c/strong\u003e scans were done for the full arch without rubber dam (No-RD) and 10 STL\u003csub\u003eG1\u003c/sub\u003e files were exported (control group), G\u003cstrong\u003eroup II:\u003c/strong\u003e scans were done under RD with cut technique (RD-C), where a digital scan was done for the full arch of the typodont first. Then, the prepared area was cut using the software tool and then rescanned again after applying the rubber dam. The procedure was repeated till 10 STL\u003csub\u003eG2 \u003c/sub\u003efiles were exported. \u003cstrong\u003eGroup III:\u003c/strong\u003e scans were done under rubber dam isolation using lock technique (RD-L), where a digital scan was done for the prepared area first under rubber dam with at least one tooth distal and one tooth mesial to the prepared tooth. Then the prepared area was locked and then a complete arch scan was completed after removal of the rubber dam and repeated till 10 STL\u003csub\u003eG3 \u003c/sub\u003efiles were exported.The digital scans were imported to a reverse engineering software program (Geomagic Control X; 3D Systems) to calculate the 3D deviation and assess scanning accuracy using the root mean square (RMS) error, calculated in terms of two regions of interest, one including the full arch dentition (Dentition Area-DA) extending from the distal of the right second molar till the distal of the left second molar, and another area of the onlay preparation surface (Preparation Area-PA).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults:\u003c/strong\u003e For DA trueness, Group I, with a mean of 60.58 ± 13.19 µm, showed significantly lower error values than both Group II (90.00 ± 13.86 µm) and Group III (84.08 ± 10.99 µm). However, no significant difference was found between Group II and Group III (p = 0.982). When examining DA precision, Group I (57.68 ± 13.60 µm) again demonstrated significantly lower error values compared to Group II (89.71 ± 12.15 µm) and Group III (79.53 ± 10.85 µm). For PA measurements, Group I (43.45 ± 16.45 µm) showed better trueness than Group II (58.33 ± 18.88 µm) and Group III (53.43 ± 19.74 µm), but no significant difference was observed among the groups (p = 0.251). Also, Group I exhibited higher precision (41.24 ± 17.42 µm) compared to Group II (64.35 ± 18.40 µm), with a p value of 0.017, while no significant difference was found between Group II and Group III (p = 0.704). \u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusion: \u003c/strong\u003eRubber dam isolation was shown to negatively influence the overall accuracy of intraoral scanning when compared to scans without isolation. However, both the cut and lock techniques produced results within clinically acceptable thresholds, with the lock technique demonstrating superior reliability over the cut technique, particularly in single indirect restorations. These findings suggest that while optimal accuracy is achieved without rubber dam isolation, the lock technique provides a clinically viable alternative when isolation is required.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eClinical Implications\u003c/strong\u003e: In cases which require rubber dam isolation, scanning using the lock technique provides greater accuracy and reliability than the commonly used cut technique. Although full-arch scans without isolation remain the most accurate, the lock technique yields clinically acceptable results for single-tooth restorations, offering clinicians a practical and predictable alternative in situations where isolation is essential.\u003c/p\u003e","manuscriptTitle":"Evaluation of the accuracy of different intraoral scanning techniques under rubber-dam isolation: An invitro study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-09-23 07:38:29","doi":"10.21203/rs.3.rs-7466317/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":"e3e2d26f-1600-46e8-91f2-4a829f2097da","owner":[],"postedDate":"September 23rd, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-12-23T08:11:02+00:00","versionOfRecord":[],"versionCreatedAt":"2025-09-23 07:38:29","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7466317","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7466317","identity":"rs-7466317","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}