Accuracy of 3 Intraoral and 1 Extraoral Digital Scanning Systems for Multiple Laminate Veneer Preparations: An In Vitro Study

Introduction

Digital impression systems have revolutionized restorative dentistry by eliminating many limitations of conventional impressions, including selection of tray, type of impression material, type of impression technique, time consumption, impression disinfection, dimensional inaccuracies, and storage challenges [1,2]. The unavoidable expansion characteristics of die stones during initial setting, as well as in dental stones used for base fabrication of the working die, prevent precise reproduction of tooth positions in the final working model. Intraoral scanning technology bypasses the conventional procedures by generating virtual 3D representations, and extraoral laboratory scanning procedures where dental casts undergo scanning processes to create digital impression models [3]. Although scanning accuracy has evolved, it remains difficult to reproduce an object with 100% accuracy as a result of the machines’ errors in data reproduction [4,5]. Errors can occur due to the confined nature of the oral environment, quality of the production machine, size of the image captured, and file transfer method from the intraoral scanners (IOS) to the production machine [6]. Extraoral scanners execute the scanning procedure through single-sensor position imaging that encompasses the whole structure, producing integrated digital models while accommodating data gathered from the inaccessible zones [7,8]. However, achieving optimal accuracy remains critical, particularly for esthetic laminate veneers where marginal adaptation directly influences clinical success and restoration longevity [9,10]. The veneer should fit as precisely as possible against the tooth to minimize the bonding cement thickness and reduce potential contact with the oral environment [11].

Recent studies have evaluated digital scanning accuracy for fit of the full-coverage restorations, with conflicting results. While Zarauz et al [12] reported superior accuracy with intraoral digital scanning compared to conventional impressions for crown fabrication, Nagy et al found that indirect digital methods outperformed direct intraoral scanning [13]. Kwong et al [14] and Sakornwimon et al found no significant differences between 2 intraoral scanners for marginal gap measurements in lithium disilicate crowns [15]. Despite these investigations, a critical gap exists in the literature: no studies have systematically compared multiple intraoral scanners and extraoral benchtop scanner for multiple laminate veneer preparations.

The tooth preparation for laminate veneers presents unique challenges compared to full-coverage restorations as it involves minimal tooth reduction with delicate finish lines, multiple measurement points including proximal surfaces and incisal edges, and aesthetic demands requiring exceptional marginal adaptation. The scanning accuracy required for these thin restorations can differ substantially from those established for crowns. Most prior investigations have focused on single-tooth preparation or limited reference points, failing to account for the complex interplay of multiple preparation geometries [16–18]. To address this gap, the present in vitro study was aimed to evaluate and compare the accuracy of 3 commercially available intraoral scanners (Trios intraoral scanner, Medit i700 intraoral scanner, and iTero intraoral scanner) and 1 extraoral benchtop scanner (3Shape) for multiple tooth preparations at 6 standardized reference points across diverse anatomical surfaces and preparation geometries for all-ceramic laminate veneers. The null hypothesis was that there would be no significant differences in linear deviations among the 4 scanning systems at the measured reference points.

Material and Methods

MASTER MODEL PREPARATION:

A maxillary dentulous typodont model (Frasaco, Germany) was chosen for its standardized tooth morphology and dimensions [19]. Three anterior teeth (#11, #12, and #13), corresponding to the right central incisor, lateral incisor, and canine were prepared by a single experienced prosthodontist to minimize operator variability for laminate veneer preparations [20,21]. Prior to the study, the operator underwent calibration sessions which included verification of preparation depths and finish-line configurations using digital measurement tools until 3 consecutive preparations met the predetermined specifications (±0.05 mm tolerance). The middle and incisal third of the facial surfaces were reduced by 0.6 mm, and a chamfer finish-line with a depth of 0.4 mm was prepared for each tooth [22]. Two millimeters of incisal reduction with incisal overlap preparation design was performed. Interproximal surfaces were prepared without breaking the contact points to simulate a clinical scenario [23]. The preparation depths were verified using a putty index (Exaflex, GC, Japan) to confirm the tooth reduction at multiple points [24].

REFERENCE POINTS ESTABLISHMENT:

Six reference points were established on each prepared tooth to allow for standardized measurements for linear dimensional deviations between the master model and the digital scans [25,26]. These reference points were located at:

DIGITAL IMPRESSION PROCEDURES:

The prepared maxillary typodont model was first scanned using a high-precision industrial-grade reference scanner (ATOS Core 80, Germany) to establish the reference STL (Standard Tessellation Language) file for all comparative analyses [27].

INTRAORAL SCANNING: Three different intraoral scanners – the Trios intraoral scanner (3Shape, Copenhagen, Denmark), Medit i700 intraoral scanner (Medit Corp., Seoul, South Korea), and iTero intraoral scanner (Align Technology, CA, USA) – were used to make the digital impressions of the prepared typodont master model (Figure 1). Each scanner created 10 digital impressions under standardized conditions with 30-min intervals between scans to prevent operator fatigue [28,29]. Each scan represented an independent acquisition, not re-analysis of the same file. Thirty scans were obtained to ensure adequate statistical power for comparative analysis and to assess the precision and repeatability of each scanner, established in previous studies [26–28].

EXTRAORAL SCANNING: A polyvinyl siloxane impression (Elite HD+, Zhermack, Italy) was made and poured with Type IV dental stone (GC Corporation, Japan) following the manufacturer’s specifications [30]. After setting for 60 min, the cast was removed and dried for 24 h before scanning [31]. The stone cast was then scanned 10 times using the 3Shape extraoral benchtop scanner (3Shape, Copenhagen, Denmark) following the manufacturer’s protocols [32].

RANDOMIZATION AND BLINDING PROTOCOL:

The sequence of scanner usage was randomized using a computer-generated randomization list. The order of scanner systems was randomly assigned to prevent sequence effects. All STL files were coded with alphanumeric identifiers by an independent researcher not involved in scanning or measurement procedures. The principal investigator performing deviation measurements was blinded to scanner identity until final statistical analysis.

OPERATOR STANDARDIZATION AND BIAS CONTROL: All intraoral and extraoral benchtop scans were performed by a single operator with at least 2 years of experience. To control the operator bias and ensure reproducibility, the operator completed 5 practice sessions to ensure the standardized scanning protocol. A mandatory 30-min interval was maintained between consecutive scans to prevent operator fatigue [33]. All scans followed an identical predetermined path: starting from the right posterior region, proceeding through the anterior region, and ending at the left posterior region of the maxillary arch [34–36]. The typodont model was fixed in a stable position using a custom-fabricated mounting jig to ensure consistent scanner-to-object positioning and distance.

DATA PROCESSING AND ANALYSIS:

The subsequent data analysis was performed using specialized software (Medit Clinics, Medit Corp., South Korea) after successful data importation [35]. The 6 reference points were identified on each scan of the 3 prepared teeth (Figure 2). For superimposition of the scan data, a best-fit alignment algorithm was applied using Medit Clinics software. The software automatically aligned the STL files of each scan with the reference scan of the master model by minimizing the distance between the corresponding surfaces [32]. The linear deviations were calculated at each reference point and converted to absolute values (magnitude of difference) before statistical analysis to assess trueness, representing the magnitude of discrepancy between each scan and the master model regardless of directional bias (over- or under-capture). All deviation measurements were screened for outliers using boxplot visualization and the interquartile range method. No systematic outliers were identified that would warrant exclusion, and all measured values were retained for analysis to preserve the full range of scanner performance variability. The observed variability in standard deviations reflected genuine variation in scanner precision across the 10 repeated measurements at each reference point.

STATISTICAL ANALYSIS:

Statistical analysis was performed using SPSS for Windows version 29.0 (IBM Corp., Somers, NY, USA). Mean and standard deviation values (μm) were calculated at 6 reference points across teeth #11, #12, and #13 for 3 intraoral scanners and 1 extraoral benchtop scanner. Data normality was confirmed using the Shapiro-Wilk test (P>0.05), and homogeneity of variance was verified with Levene’s test (P>0.05). Absolute deviation values were analyzed to represent trueness independent of directional bias. The statistical unit of analysis was defined as the individual surface-level deviation measurement. Each scanner performed 10 independent scans at 30-min intervals with repositioning to ensure independence of digital acquisitions [37,38]. Intraclass correlation coefficients (ICCs) confirmed that between-scan variability exceeded measurement error. For each of the 18 tooth–surface combinations (3 teeth×6 surfaces), one-way ANOVA was initially conducted with 10 measurements per scanner (n=40 per comparison). F-statistics and Bonferroni-adjusted post hoc tests were tabulated and reported (Table 1). To explicitly account for the hierarchical clustering inherent in the study (scanner → replicate → tooth → surface), a confirmatory linear mixed-effects (LME) model was constructed. “Scanner” was treated as a fixed effect, while “tooth” was modeled as a random intercept to account for within-tooth correlation arising from repeated scanning of the same physical preparation (Table 2). Because the same 3 typodont teeth were repeatedly scanned across scanners, observations were not statistically independent; therefore, tooth-level clustering was accounted for using random intercepts. Restricted maximum likelihood (REML) estimation was applied. The LME model directly addressed within-tooth correlation that cannot be captured by one-way ANOVA alone, and constituted the basis for all scanner comparison inferences reported in the study. Estimated marginal means with Bonferroni correction were used for pairwise scanner comparisons. Statistical significance was set at P<0.05 [39]. ANOVA results were presented for descriptive transparency (Table 1) to facilitate surface-by-surface comparison and to confirm consistency with the mixed-effects findings; the direction and statistical significance of all scanner group differences were identical with both analytical approaches, supporting the robustness of the reported conclusions.

Results

The mean of linear deviations at 6 reference points for teeth #11, #12, and #13 was calculated for the 3 intraoral scanners (Trios intraoral scanner, Medit i700 intraoral scanner, iTero intraoral scanner) and the extraoral benchtop scanner (3Shape). The results of linear mixed-effects (LME) were consistent with one-way ANOVA across all tooth–surface combinations, confirming that within-tooth correlation did not alter the direction or significance of scanner group differences (Tables 1, 2).

For the center of buccal chamfer finish-line, the results of the study revealed a significant effect (Table 1) among all 4 scanners across teeth #11, #12, and #13 (P<0.001; F value 12.96 for central incisors; 57.81 for lateral incisors and 41.26 for canines, Table 1). The Trios intraoral scanner consistently showed the lowest mean deviations across all 3 teeth (5.70 μm to 12.604μm). The iTero intraoral scanner demonstrated significantly higher deviations (47.00 μm to 63.80 μm) compared to other scanners for all tooth positions (Figure 3). The Medit i700 intraoral scanner (24.00 μm to 26.80 μm) and 3Shape extraoral benchtop scanner (23.30 μm to 28.70 μm) showed statistically similar intermediate performance, with no significant differences (P =0.974; Table 2) between them at any tooth position. The pairwise comparisons among the 4 scanners for central incisors and canines were 3 >4 >2 >1 and 3 >2 >4 >1 for lateral incisors (Table 1). The linear mixed-effects model confirmed these findings (Table 2), with scanner type as a significant fixed effect (P<0.001) after accounting for within-tooth correlation. The pairwise ranking of scanner performance was unchanged relative to ANOVA.

The mean deviations at the incisal edge (mid-point) showed significant inter-scanner-dependent performance variations (P<0.001; F value=52.35 for central incisors; 31.93 for lateral incisors and 19.41 for canines, Table 1). The Trios intraoral scanner showed the lowest mean deviations (5.20 μm to 18.00 μm), followed by the Medit i700 intraoral scanner (22.50 μm to 32.30 μm), while the iTero intraoral scanner (37.30 μm to 51.70 μm) and 3Shape extraoral benchtop scanner (44.20 μm to 57.80 μm) had substantially higher mean deviations (Figure 4). The Bonferroni-adjusted pairwise comparison (Table 1) confirmed that the iTero intraoral scanner and 3Shape extraoral benchtop scanner performed similarly and were significantly less accurate than the Medit i700 intraoral scanner and Trios intraoral scanner across all 3 tooth positions: the ranking pattern for central incisors was 3 >4 >2 >1 and for lateral incisors and canines it was 4 >3 >2 >1. The linear mixed-effects model confirmed these findings (Table 2), with scanner type as a significant fixed effect (P=0.021) after accounting for within-tooth correlation; the pairwise ranking of scanner performance was unchanged relative to ANOVA. Notably, the 3Shape extraoral benchtop scanner performed better than the iTero intraoral scanner at central incisor incisal position but demonstrated higher deviations at lateral incisor and canine positions (Table 1). The 3Shape benchtop extraoral scanner’s poor performance in this region likely reflects cumulative errors from impression-taking and cast fabrication processes, supporting the hypothesis that indirect digitization introduces systematic errors.

The mesial proximal surface (mid-point) accuracy assessment revealed the maximum pronounced inter-scanner differences (P<0.001; F value=92.99 for central incisors; 139.63 for lateral incisors and 179.8 for canines, Table 1) representing the most challenging area for all scanners. The Trios intraoral scanner showed the lowest mean deviations (10.80 μm to 13.70 μm), followed by the Medit i700 intraoral scanner (18.10 μm to 26.70 μm), while the iTero intraoral scanner (73.90 μm to 89.30 μm) and 3Shape extraoral benchtop scanner (58.70 μm to 79.60 μm) exhibited considerably higher mean deviations (Figure 5). The Bonferroni-adjusted pairwise comparison (Table 1) revealed ranking pattern for central incisors and lateral incisors as 3 >4 >2 >1, but for canines it was 4 >3 >2 >1, indicating the Trios intraoral scanner consistently outperformed all other scanners at this anatomically challenging location. Proximal surfaces on the mesial side had high absolute deviations with all scanners, with the iTero intraoral scanner and 3Shape extraoral benchtop scanner exceeding 80 μm. This is a critical clinical concern, as proximal adaptation is essential for preventing microleakage, secondary caries, and maintaining periodontal health, particularly for multiple anterior laminate veneers, for which proximal seal integrity determines long-term success.

The distal proximal surfaces (mid-point) demonstrated slightly smaller deviations compared to mesial surfaces for most scanners, potentially reflecting differences in optical access angles during the scanning process (P<0.001; F value=116.87 for central incisors; 160.78 for lateral incisors, and 68.8 for canines, Table 1). All 4 scanners had deviation patterns (Table 1) for distal proximal surfaces similar to those for mesial proximal surfaces (for central incisors and lateral incisors it was 3 >4 >2 >1 and for canines it was 4 >3 >2 >1). For canines, the 3Shape extraoral benchtop scanner (72.4 μm) showed the highest deviation, followed by the iTero intraoral scanner (56.8 μm), Medit i700 intraoral scanner (29.8 μm) and Trios intraoral scanner with lowest deviation (9.5 μm). This tooth-specific variation suggests that canine distal anatomy presents unique challenges for the 3Shape extraoral benchtop scanner workflows (Figures 6, 7). The consistent pattern of greater deviations at proximal surfaces for all scanners except the Trios intraoral scanner suggests that these areas present universal scanning challenges. However, the magnitude of difference indicates that scanner technology, specifically confocal microscopy versus parallel confocal imaging, significantly influences proximal surface capture accuracy.

The mid-buccal tooth surface, which is the most accessible scanning area, showed distinct patterns: P<0.001, F value=113.15 for central incisors; 197.13 for lateral incisors; and 153.53 for canines, Table 1). The Trios intraoral scanner showed the lowest mean deviations (7.80 μm to 13.40 μm), followed by the Medit i700 intraoral scanner (18.80 μm to 28.70 μm) and 3Shape extraoral benchtop scanner (19.20 μm to 20.50 μm), while the iTero intraoral scanner exhibited the highest mean deviations, ranging from 68.00 μm to 101.40 μm (Figure 8). Bonferroni-adjusted pairwise comparison showed the ranking pattern for central incisor and lateral incisors as 3 >2 >4 >1 and 3 >4 >2 >1for canines. The iTero intraoral scanner was significantly less accurate among all the scanners (Table 1). The mean deviation was significantly greater for all 3 teeth using the iTero intraoral scanner (68.0–101.4 μm), suggesting fundamental limitations in its parallel confocal imaging technology. The lack of significant difference between the Medit i700 intraoral scanner and 3Shape extraoral benchtop scanner at the canines (P=0.099 as stated by LME estimate, Table 2) indicates comparable performance in optimal scanning conditions. However, the iTero intraoral scanner’s increased deviation at central incisors (101.4 μm) versus canines (68.0 μm) suggests potential sensitivity to tooth morphology or preparation design.

The center of palatal chamfer finish-line measurements demonstrated scanner-dependent performance with notable differences (P<0.001; F value=75.2 for central incisors; 64.77 for lateral incisors, and 33.35 for canines, Table 1). The Trios intraoral scanner recorded the lowest mean deviations (4.50 μm to 14.70 μm), followed by the Medit i700 intraoral scanner (23.80 μm to 28.50 μm), while the iTero intraoral scanner (34.90 μm to 59.10 μm) and 3Shape extraoral benchtop scanner (36.90 μm to 56.90 μm) demonstrated higher mean deviations across all 3 teeth (Figure 9). For central and lateral incisors, pairwise comparison among the scanners was 3 > 4 > 2 > 1 but for canines it was 4 >3 >2>1 (Table 1). This variation indicates that performance of the iTero intraoral scanner and 3Shape extraoral benchtop scanner is influenced by tooth position and palatal anatomy (Figure 10). Interestingly, for canines, the iTero intraoral scanner outperformed the 3Shape extraoral benchtop scanner (34.9 μm vs 56.9 μm, P<0.001), suggesting that canine palatal anatomy is more amenable to the iTero’s intraoral scanner technology, or alternatively, that the 3Shape extraoral benchtop scanner faces specific challenges with canine cast reproduction. The linear mixed-effects model did not identify a statistically significant difference between these 2 scanners (estimate +1.3 μm; 95% CI: −4.7 to 7.3; P=0.670, Table 2), indicating that their overall performance at the palatal chamfer finish line is comparable when within-tooth correlation is accounted for.

Discussion

This in vitro study compared the precision of 3 different intraoral scanners (Trios intraoral scanner, Medit i700 intraoral scanner, and iTero intraoral scanner) and 3Shape extraoral benchtop scanner at 6 different positions of central incisors, lateral incisors, and canines, prepared for all-ceramic laminate veneers. The Trios intraoral scanner consistently showed the smallest mean deviations across all measurement points compared to the other scanners. This finding aligns with previous studies by Mangano et al [30] and Renne et al [31], that demonstrated better trueness and precision of the Trios intraoral scanner compared to other intraoral scanners. The trueness of the Trios intraoral scanner across all measurement points reflects fundamental differences in optical capture technology. Its confocal microscopy with structured light projection provides exceptional depth of field and detail reproduction, which is advantageous for the complex 3D geometry of veneer preparations [28,36]. The small deviations at margin areas (5.7–12.6 μ at the buccal chamfer finish line) suggest that confocal systems excel at capturing sharp transitional zones, which is directly relevant to the marginal seal quality in bonded restorations. The Medit i700 intraoral scanner showed intermediate accuracy, with larger mean deviations higher than Trios intraoral scanner but lower than with the iTero intraoral scanner and 3Shape extraoral benchtop scanner for most reference points. This finding was consistent with research by Kim et al [29], who demonstrated acceptable accuracy of the Medit i700 intraoral scanner for clinical applications. The 3D video technology with structured light used by the Medit i700 intraoral scanner provides good scanning efficiency but does not capture the fine details of preparation margins as accurately as confocal microscopy systems [40]. While its deviations exceeded those of the Trios intraoral scanner, it remained within clinically acceptable thresholds at most measurement points. For practitioners prioritizing workflow efficiency, the Medit i700 intraoral scanner may represent an optimal cost-benefit ratio, particularly given that cement thickness can compensate for minor discrepancies within acceptable limits [10,11]. The iTero intraoral scanner consistently showed the largest deviations, particularly at the buccal chamfer finish-line, mesial and distal proximal surfaces, mid-buccal tooth surface, and palatal chamfer finish line. These findings agree with those of Abduo and Elseyoufi [41], who reported that parallel confocal imaging systems used by iTero intraoral scanners have limitations in capturing certain geometric features, especially in areas with sharp angles or undercuts. While this technology works well on broad and easily accessible surfaces, it faces challenges in confined anatomical regions such as proximal tooth surfaces (56.8–90.7 μ). In these areas, limited access and overlapping structures prevent the scanner from capturing complete and accurate surface details. As a result, the scanner may miss critical data or rely on interpolation, leading to increased deviations in proximal measurements. The 3Shape extraoral benchtop scanner and iTero intraoral scanner demonstrated variable relative performance depending on anatomical location. At 13 of 18 tooth–surface combinations, the iTero intraoral scanner showed larger deviations than the 3Shape extraoral benchtop scanner (Table 1, pairwise rankings). However, at 5 specific locations (mid-point of incisal edge for #12 and #13; mesial and distal proximal surface for #13; and palatal chamfer finish-line for #13), the 3Shape extraoral benchtop scanner demonstrated less accurate performance than the iTero intraoral scanner (Table 1). This inconsistency suggests that both systems face anatomical-location-specific limitations, with the 3Shape extraoral benchtop scanner particularly challenged by canine palatal anatomy and the iTero intraoral scanner demonstrating more widespread accuracy deficits across multiple surfaces. Unlike direct intraoral capture, the 3Shape extraoral benchtop scanner has inaccuracies from impression-making, setting expansion of stone casts, and working cast preparation before digitization. Interestingly, the 3Shape extraoral benchtop scanner occasionally matched or surpassed intraoral systems at mid-buccal surfaces (19.2 μ to 20.5 μ for central and lateral incisors), suggesting that when physical models are used under ideal scanning conditions (eg, stable, dry, and well-illuminated surfaces), the 3Shape extraoral benchtop scanner can achieve high accuracy. This inconsistency indicates that 3Shape extraoral benchtop scanning accuracy is context-dependent and influenced by the preceding analog steps, making it less reliable for precision applications like laminate veneers.

The large deviations at proximal surfaces across all the scanning systems (ranging from 10.8 μ to 90.7 μ) expose a critical vulnerability in current digital impression technology. This pattern transcends individual scanner characteristics and instead reflects inherent limitations in optical access and light projection geometry when capturing interproximal zones. This systematic weakness carries profound clinical implications. Proximal marginal discrepancies are common sites for microleakage and secondary caries in laminate veneers [42]. The measured deviations at proximal surfaces varied systematically by anatomical location across all scanning systems. Clinicians must recognize that even with optimal scanning technique, proximal areas may require additional verification or adjustment during try-in procedures. According to McLean and von Fraunhofer [42], marginal gaps of up to 120 μm could be considered as being within the acceptable clinical limit. Based on this criterion, all intraoral scanners in the present study produced clinically acceptable results for the buccal chamfer finish line, with the Trios intraoral scanner demonstrating the smallest mean deviations across all measurement points. Our findings suggest that while digital impression technology has advanced significantly, not all scanning systems offer equal accuracy for laminate veneer preparations. Clinicians should select scanning protocols by assessing the specific factors such as tooth preparation protocols, the physical properties of restorative materials, and areas requiring optimal marginal integrity.

A potential concern with the repeated-measures in vitro design was that performing multiple independent scans of the same physical preparation may violate the strict independence assumption underlying one-way ANOVA. In the present study, this was addressed by implementing a linear mixed-effects model as the primary inferential framework (Table 2), with “scanner type” as a fixed effect and “tooth identity” as a random intercept, thereby explicitly partitioning between-tooth variability from scanner effects. “Scan replicate” was additionally modeled as a random factor nested within teeth. The estimated marginal means and pairwise rankings derived from this model were fully concordant with ANOVA findings across all 18 tooth–surface combinations, demonstrating that within-tooth correlation did not substantively influence the magnitude or significance of observed scanner differences. This consistency strengthened the reported conclusions and satisfied the statistical independence requirements for hierarchically structured repeated-measures data.

This research has several limitations, including its laboratory-based methodology, which cannot completely simulate the complexities encountered during clinical intraoral scanning procedures, including patient motion, saliva management, and restricted visibility. Furthermore, the study examined just a single preparation method, so findings may vary when different preparation approaches are used. Additionally, this study did not assess clinical outcomes, cement behavior, or patient-related factors. The focus was exclusively on the dimensional accuracy of digital impressions at the preparation level. Clinical performance of restorations fabricated from these digital impressions, including factors such as marginal integrity over time, cement thickness variation, and patient satisfaction, were beyond the scope of this investigation. Further research is needed to evaluate how accurately digital impression systems capture varying laminate preparation geometries, especially conservative approaches utilizing finish lines positioned above gingival tissues methods that continue to gain popularity among practitioners.

Conclusions

This in vitro study revealed significant differences among the digital scanning systems assessed for multiple anterior laminate veneer preparations. The Trios intraoral scanner consistently produced the smallest linear deviations at all reference points and tooth positions. The Medit i700 intraoral scanner exhibited intermediate accuracy, generally remaining within clinically acceptable thresholds. In contrast, the iTero intraoral scanner demonstrated larger deviations, especially at the proximal and finish-line regions, whereas the 3Shape extraoral benchtop scanner workflow showed variable accuracy, likely attributable to the additional analog steps. These findings suggest that scanner selection can substantially influence the trueness of digitally captured veneer preparations, particularly in anatomically complex areas such as proximal surfaces. However, the laboratory setting, reliance on a typodont model, and exclusive focus on dimensional deviation without clinical outcome assessment limit the direct applicability of these results to intraoral conditions. Further clinical research is necessary to evaluate how these differences affect long-term marginal integrity and restoration performance.