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Article

Comparison of Marginal and Internal Fit of CAD/CAM Ceramic Inlay Restorations Fabricated Through Model Scanner, Intraoral Scanner, and CBCT Scans

by
Ayben Şentürk
1,*,
Bora Akat
1,
Mert Ocak
2,
Mehmet Ali Kılıçarslan
1 and
Kaan Orhan
3
1
Prosthetic Dentistry, Faculty of Dentistry, Ankara University, 06100 Ankara, Turkey
2
Department of Basic Medical Science—Anatomy, Faculty of Dentistry, Ankara University, 06100 Ankara, Turkey
3
Oral and Maxillofacial Radiology, Faculty of Dentistry, Ankara University, 06100 Ankara, Turkey
*
Author to whom correspondence should be addressed.
Appl. Sci. 2025, 15(9), 4626; https://doi.org/10.3390/app15094626
Submission received: 21 March 2025 / Revised: 19 April 2025 / Accepted: 22 April 2025 / Published: 22 April 2025
Browse Figure
Versions Notes

Abstract

:
Background and Objectives: CBCT images have been successfully used for CAD/CAM crown restorations; however, their use for ceramic inlay restorations remains unclear. This study aimed to evaluate the marginal and internal fit of CAD/CAM ceramic inlay restorations fabricated using intraoral scanner, model scanner, and CBCT data. Materials and Methods: Inlay preparations were performed on 11 mandibular molar typodont teeth. The teeth were scanned using an intraoral scanner, an extraoral scanner, and CBCT (0.075 mm voxel size). CBCT-generated DICOM data were converted to STL format with dedicated software. All scan data were transferred to CAD software, and a total of 33 restorations were designed. Feldspathic ceramic blocks were used for milling. Micro-CT was employed to measure marginal and internal gaps, with 60 measurement points taken from three cross-sections per sample. Data were analyzed using ANOVA and Bonferroni tests (p < 0.05). Results: CBCT exhibited greater marginal and internal gap dimensions (mean: 169.27 ± 38.64 μm), which were approximately 60–70 μm higher than those of the intraoral (97.00 ± 10.1 μm) and model scanner groups (109.67 ± 9.72 μm), exceeding clinically acceptable limits (≤120 μm) (p < 0.05). Intraoral and model scanners showed similar, clinically acceptable results. Conclusions: CBCT was less accurate for inlay restorations, likely due to their complex geometry. Nevertheless, fabrication was possible, and further research may improve its clinical applicability.

1. Introduction

The use of computer-aided design and manufacturing (CAD-CAM) systems has become increasingly common in prosthetic dentistry. The process of capturing digital impressions and generating three-dimensional virtual models is routinely applied to various prosthetic materials provided as prefabricated blocks [1]. A digital model can be obtained using either intraoral scanners or model scanners [2,3]. Intraoral scanners are fully digital systems that offer numerous advantages, allowing for precise scans. However, due to their high cost, they may not always be accessible in clinics, and their use can sometimes be challenging within the oral cavity. Model scanners are another well-known method of obtaining digital models, but they involve the inconvenient step of creating a stone model from a traditional impression. The traditional impression process can induce a gag reflex in patients, the sterilization of the impression material is difficult, distortion of the impression may occur, and there are many complex steps involved in the traditional impression process, all of which make the use of model scanners challenging [1,2,3,4,5]. Additionally, a significant limitation of both optical scanning methods is the loss of detail in areas where light cannot reach, such as between adjacent teeth and undercut areas [6].
CBCT, which provides essential 3D diagnostic information to dentists, has recently started to be used for prosthetic applications, in addition to procedures like producing surgical stents for implant placement. It is also considered an alternative method to intraoral and model scanners. Studies have indicated that although data scanned with CBCT are not as accurate as those obtained with intraoral and model scanners, they still provide clinically acceptable levels of accuracy [1,2,4,7]. CBCT data are in the Digital Imaging and Communications in Medicine (DICOM) format and therefore need to be converted to Standard Triangulation Language (STL) format to be used with other digital systems such as CAD/CAM systems, which operate in STL format. To overcome this issue, software that converts DICOM data to STL data is used. This allows DICOM data converted to STL format to be used in CAD/CAM systems, which is particularly useful in prosthetic dentistry. The accuracy of STL data obtained from CBCT depends on the quality of the DICOM data and the conversion software [8].
The ability to reproduce an accurate impression of the prepared teeth and the surrounding tissues is pivotal in the prosthetic workflow [9]. The impression transfers the intraoral situation, and the accuracy of this transfer influences the marginal and internal fit of the restorations, an important factor in the longevity of the final restoration [10]. Poor marginal fit can lead to microleakage, secondary caries, dissolution of the luting cement, and gingival inflammation [4,11]. Additionally, inadequate internal fit may lead to increased cement thickness, influence occlusion, compromise retention, weaken the fracture resistance of restorations, and consequently contribute to poor marginal fit. Marginal and internal adaptation play a critical role in inlay restorations, since their margins are subjected to physical, mechanical, and thermal loads [11,12,13]. Marginal fit is generally defined as a straight-line contact or a gap-less transition between the preparation and the margin of the restoration. Several studies have shown different values for clinically acceptable marginal fit; nonetheless, a universally accepted standard has yet to be established [14]. In addition to studies indicating that gaps smaller than 120 µm are clinically acceptable [15], there are studies suggesting that an ideal margin gap is between 50 and 100 µm [16]. Furthermore, there are studies indicating that the marginal gap for CAD-CAM restorations should be in the range of 58–200 μm [17].
Studies have been conducted on the production of prosthetic restorations using CBCT data, such as crown restorations and implant-supported acrylic resin interim crowns, showing clinically acceptable results. However, no studies have been found regarding the use of CBCT data for more complex restorations that require more precise scanning, such as inlay restorations. The limited number of studies using CBCT for inlay restorations may be attributed to the inherent complexity of inlay cavity designs, which require higher scanning precision than that typically achieved by CBCT. As a result, previous research has predominantly focused on simpler restorations, such as crowns, which are more compatible with the current resolution capabilities of CBCT.
Class II inlay cavities with a proximal box have a notably more complex configuration than Class I and supragingival crowns [9,18]. These designs, which complicate clinical steps such as cavity preparation and optical scanning, can become even more challenging when obtained using CBCT scanning data. Inlay restorations, particularly those with Class II preparations, pose greater challenges in terms of marginal and internal adaptation compared to full-coverage crowns [18]. Their internal geometries often include deep boxes and undercuts, which complicate the scanning and milling processes, potentially leading to reduced accuracy in adaptation.
Although CBCT is commonly used for diagnostic and surgical planning purposes, its potential integration into the prosthetic workflow could be advantageous, particularly in cases where patients have already undergone CBCT imaging for other clinical reasons. In such scenarios, utilizing existing CBCT data for inlay restoration fabrication could eliminate the need for additional impression procedures, thereby reducing patient discomfort, clinical time, and associated costs. Therefore, investigating the clinical relevance and applicability of CBCT for inlay restorations may expand its utility beyond diagnostics into restorative dentistry. The purpose of this study is to evaluate whether CBCT, commonly used for diagnostic purposes, can serve as a viable alternative to intraoral and model scanners in the fabrication of ceramic inlay restorations. To this end, the marginal and internal fit of CAD/CAM ceramic inlays produced from CBCT, intraoral, and model scanner data were compared using micro-CT. The null hypothesis was that there would be no significant difference among the three methods in terms of marginal and internal fit.

2. Materials and Methods

The sample size was determined based on previous studies evaluating marginal and internal fit using micro-CT, which typically employed 8 to 12 specimens per group to yield statistically meaningful results due to the high spatial resolution and reproducibility of the method [11,14,19]. Accordingly, a total of 11 mandibular molar typodonts (with enamel, dentin, and pulp layers) (Frasaco, Tettnang, Germany) were used for inlay cavity preparation. Mandibular molars were selected due to their wide occlusal surfaces and complex morphology, which make them ideal for assessing marginal and internal fit in inlay restorations. All typodont teeth were of the same brand and model to ensure standardization in terms of size and anatomy. A special bur set was used for mesio-occlusal inlay cavity preparation (Intensiv, Niigata, Japan). The following geometrical parameters for the inlay cavity were kept: 3 mm isthmus width, 1.5 mm axial depth, 2.5 mm occlusal depth, 1 mm rounded shoulder margin in the axio-gingival angle, and a 6–10-degree tapered angle. All inlay cavities were performed by the same operator using a phantom model to ensure standardization of the preparations.
The inlay preparation was scanned with an intraoral scanner (CEREC Omnicam system, Sirona Dental Systems GmbH, Bensheim, Germany), a model scanner (inEOS X5, Sirona Dental Systems GmbH, Bensheim, Germany), and CBCT (Planmeca Promax 3D Max Machine, Helsinki, Finland). CBCT scans were performed 0.075 mm voxel size. In order to standardize the imaging technique, all scans were taken at 90 kVp, 12 mA, and 50 mm × 40 mm FOV size. Prior to the main study, all scanning devices were calibrated and checked according to the manufacturers’ guidelines. The intraoral scanner (CEREC Omnicam; Sirona Dental Systems GmbH, Bensheim, Germany), model scanner (inEOS X5; Sirona Dental Systems GmbH, Bensheim, Germany), and CBCT unit (Planmeca Promax 3D Max; Planmeca Oy, Helsinki, Finland) underwent routine quality control, including internal calibration and software-based diagnostic checks. In addition, test scans were performed to ensure consistent output and proper device performance before data collection. The DICOM data acquired from CBCT were converted to STL format through a specialized 3D mesh processing software system (Planmeca Romexis version 6.2, Helsinki, Finland), which can be used in most CAD software (Planmeca Romexis version 6.2, Planmeca Oy, Helsinki, Finland; available at: https://www.planmeca.com/dental-software/romexis-viewer/, https://www.planmeca.com/dental-software/downloads/, accessed on 20 February 2024). The 3D STL images obtained from the intraoral scanner, laboratory scanner, and CBCT scans were transferred to a CAD software (Cerec CAD System, Sirona Dental Systems GmbH, Bensheim, Germany), and inlay restorations for mandibular molars were designed. No manual corrections were made during the design phase except for minor corrections in the margin drawing to avoid operator-related errors. The cement space was set to 20 μm in the marginal area and 80 μm in the remaining areas inside the inlay restoration.
After the design of a total of 33 inlay restorations was completed, the restorations were milled from feldspathic ceramic blocks (CEREC Blocs; Sirona Dental Systems GmbH, Bensheim, Germany) using a 4-axis milling unit (CEREC InLab MC XL; Sirona Dental Systems), following the manufacturer’s standard milling protocol. All inlay restorations were milled by a single experienced operator using the same milling unit. The milling device was calibrated before each session in accordance with the manufacturer’s instructions to ensure operational accuracy and consistency. The restorations were not randomly assigned but followed a fixed and consistent sequence for all typodont teeth to ensure standardization. Each tooth received one inlay restoration per group (CBCT, intraoral scanner, model scanner), enabling within-sample comparisons and eliminating anatomical variability. Inlay restorations were not adjusted after they were milled. Inlay restorations were not cemented to teeth because measurements would be made by placing differently manufactured restorations on the same prepared tooth; easily removable transparent paraffin was used to fix the restorations.
Marginal gap and internal adaptation values were measured using micro-CT, a non-destructive method. The Skyscan 1275 (Skycan, Kontich, Belgium) device, equipped with high-resolution scanning capacity, was utilized for micro-CT scans. Scanning parameters were set as follows: 125 kVp, 80 mA, 20 μm/pixel, and a rotation step of 0.2. To prevent radiological artifacts during scans, a 1 mm thick aluminum filter was used. Subsequently, each scanned sample was individually reconstructed using Skycan’s NRecon (version 1.7.4.6 Skycan, Kontich, Belgium) software. This software also facilitated the elimination of other potential radiological artifacts that could arise during scanning.
Two-dimensional (2D) axial projections were obtained from the reconstruction samples. These 2D axial projections were then transferred to CTan (version 1.23.0.2 Skycan, Kontich, Belgium) software for mathematical analysis. Substance volumes, to be included in the Region of Interest (ROI) based on adaptive interpolation of the substructures in contact with inlays, were determined using gray-color values within the ROIs. The substance quantities in the ROIs indicated the solid volume and the gap size, which were subsequently subjected to statistical comparison. DataViewer software (version 1.7.0.1 Skycan, Kontich, Belgium) was utilized for preparing 2D measurements. This software enabled examination of axially reconstructed images in transversal, coronal, and sagittal 2D views. Thereafter, these images were again uploaded into the CTan program, and 2D linear measurements were performed. To ensure measurement reliability, 20% of the restorations (n = 7) were randomly selected and re-analyzed by the same operator after a two-week interval using identical micro-CT and analysis protocols. The intraclass correlation coefficient (ICC) was calculated for the repeated measurements and yielded a value of 0.92, indicating excellent intra-observer agreement.

2.1. Linear Measurements

In the buccolingual direction, five vertical cuts were made. From each slice, 2 occlusal marginal gap (OMG), 2 axial internal gap (AIG), and 1 occlusal internal gap (OIG) measurements were recorded from each slice, for a total of 25 measurements. In the mesio-distal direction, 5 vertical cuts were also made. One gingival marginal gap (GMG), two axial internal gap (AIG) and two occlusal internal gap (OIG) measurements were recorded from each slice, for a total of twenty-five measurements. In the transverse section, 5 transverse cuts were made, and 2 points of measurements were recorded from each slice, 2 proximal marginal gaps (PMGs), for a total of 10 measurements (Figure 1). Outcomes from these three distinct cuts were averaged for each measurement point.
The OMG, AIG, GMG, OIG, and PMG were evaluated at 60 points for each inlay. OMG, GMG, and PMG values were used for the evaluation of marginal adaptation. AIG and OIG values were used for the evaluation of internal adaptation. The same operator performed all micro-CT measurements. For the measurement points, the points from the study by Alajaji et al. were used as a basis and modified [19].

2.2. Statistical Analysis

The obtained data were analyzed using the IBM SPSS Statistics V25 software package (SPSS Inc., Chicago, IL, USA). One-way ANOVA was used to statistically compare the data. According to the assumption of homogeneity of variance, the Bonferroni multiple comparison test was used (p = 0.05). Bonferroni correction was applied to control for Type I errors across multiple pairwise comparisons. As five marginal and internal gap parameters (OMG, GMG, PMG, AIG, and OIG) were analyzed across three groups, this correction accounted for the increased number of hypotheses tested.

3. Results

Table 1 presents the descriptive statistical analysis for the OMG, GMG, and PMG measurement points. Pairwise comparisons of the marginal and internal gap values among the three scanning methods, including confidence intervals and effect sizes (Cohen’s d), are presented in Table 2. Table 3 shows the analysis for the AIG and OIG measurement points. Both tables present the mean, standard deviation, upper bound, and lower bound values for all groups.
According to the ANOVA test results, statistically significant differences were identified among the groups. The Bonferroni multiple comparison test results indicated no statistically significant difference between the intraoral scanner group (94.09 μm ± 86.45 μm) and the model scanner group (99.18 μm ± 24.67 μm) for the OMG, GMG, and PMG measurement points (p > 0.05). In contrast, the CBCT group (166.72 μm ± 49.86 μm) exhibited significantly greater marginal gap dimensions compared to the other groups, and this difference was statistically significant (p < 0.05). Similarly, for the AIG and OIG measurement points, no statistically significant difference was found between the intraoral scanner group (219.45 μm ± 51.48 μm) and the model scanner group (167.72 μm ± 21.43 μm) (p > 0.05), whereas the CBCT group (219.45 μm ± 51.48 μm) showed significantly higher results (p < 0.05).
The average values of the OMG, PMG, and GMG measurement points were used to assess marginal fit, while the average values of the AIG and OIG measurement points were used to evaluate internal fit. For both marginal fit and internal fit, the mean, standard deviation, and upper and lower bound values are shown in Table 4. According to the Bonferroni test results, the CBCT group (169.27 μm ± 38.64 μm) demonstrated greater marginal and internal gap dimensions compared to the intraoral scanner group (97.00 μm ± 10.12 μm) and the model scanner group (109.67 μm ± 9.72 μm), and these differences were statistically significant (p < 0.05).

4. Discussion

The results of this study suggest the rejection of the null hypothesis. Significant differences were found among the marginal and internal gaps of ceramic inlay restorations fabricated through data obtained from CBCT scans, intraoral scanners, and model scanners (p < 0.05). The marginal and internal gaps of inlay restorations fabricated with data obtained from CBCT scans were significantly higher than those of inlay restorations fabricated with data obtained from intraoral and model scanners (p < 0.05). Therefore, the null hypothesis was rejected.
Previous studies have indicated that CBCT might be an alternative impression-taking method for implant-supported restorations [3,20]. Other studies have also reported that data obtained from CBCT can be used for crown restorations [1,2,7]. In this study, inlay restoration cavities were scanned by CBCT. The obtained DICOM data were converted to STL format, and the inlay restorations were designed and fabricated.
Studies have reported that marginal and internal fit are very important for prosthetic restorations. Poor marginal and internal fit can lead to issues such as secondary caries, microleakage, and reduced fracture resistance [4,11,12,21,22]. Moreover, restorations with excessive gaps may compromise long-term durability and necessitate additional clinical adjustments, such as chairside corrections or remakes, thereby increasing treatment time and cost. In this study, the inlay restorations fabricated with CBCT data exhibited significantly greater marginal and internal gap dimensions compared to those produced with intraoral and model scanners. Although some studies have indicated that a clinically acceptable marginal gap for CAD-CAM restorations is between 58 and 200 µm [17], most studies have emphasized that the marginal gap should be below 120 µm [4,12,15,23]. Accordingly, in the present study, 120 µm was adopted as the primary reference value to assess clinical acceptability. The marginal gap values of ceramic inlay restorations fabricated with intraoral and model scanner data were measured to be an average of 97.00 ± 10.12 µm for intraoral scanners and 109.67 ± 9.72 µm for model scanners. For inlays fabricated with data obtained from CBCT, the average marginal gap value was 169.27 ± 38.64 µm. The marginal gap values for intraoral and model scanners are below the clinically acceptable value of 120 µm. However, for the CBCT group, the average values are above the clinically acceptable limit of 120 µm. It should be noted, though, that these values are still below the 200 µm threshold mentioned in some studies. Nevertheless, gap values exceeding 120 µm may compromise the seal and structural integrity of the restoration under functional loading, potentially reducing clinical longevity [17].
For internal adaptation, while some studies have indicated that an ideal range is between 70 and 120 µm [24], there are also studies that suggest values between 50 and 100 µm could result in the most favorable resin cement performance [25,26]. In this study, the internal gap values (CBCT group: 224.64 ± 49.98 µm; intraoral scanner group: 124.55 ± 26.51 µm; model scanner group: 153.73 ± 19.02 µm) are above the clinically ideal gap values for all groups. Notably, axial internal gap (AIG) measurements showed higher values than occlusal internal gap (OIG) values. Therefore, it is suggested that the more retentive axial regions could affect the internal fit. Studies investigating the effect of cavity preparation on fit have similarly shown that non-retentive preparations have better adaptation [12,27].
CBCT is used in many areas of dentistry, but its application in tooth-supported restorations is relatively recent and more limited. Şeker et al. [7] evaluated the marginal fit of crown restorations fabricated from CBCT data. They reported that restorations produced from images obtained at three different voxel sizes (0.125 mm, 0.20 mm, and 0.30 mm) exhibited clinically acceptable marginal gap values. Similarly, Kim et al. [2] highlighted that interim crowns produced from CBCT data were within clinically acceptable marginal gap ranges. Kale et al. [1] also stated that monolithic zirconia crowns produced with CBCT data exhibited marginal gap values below 120 µm. The fabrication of restorations with CBCT data in the literature is limited to crowns, and no articles have been found regarding its use in inlay restorations. In this study, however, both the marginal and internal fits of inlay restorations fabricated with data obtained from CBCT scans (0.075 mm) were evaluated. For inlay restorations, CBCT did not show as successful gap values as intraoral and model scanners; the marginal gap range of inlay restorations produced from CBCT was found to be above the acceptable limits. Ashraf et al. [9] reported that intracoronal restorations showed less trueness and precision compared to extracoronal restorations. Similarly, Merrill et al. [28] in their study examining the effect of restoration type on marginal fit, emphasized that crown restorations tend to have less marginal gap compared to inlay and onlay restorations [28]. The high marginal and internal gap values of CBCT, which have shown successful results in crown studies, in this study could be attributed to the complex geometry of inlays, which are a type of intracoronal restoration.
The voxel size also affects accuracy by influencing the spatial resolution of orthogonal slices: the smaller the voxel size, the better the accuracy [29]. Şeker et al. stated that voxel size had a significant effect on the marginal integrity of CAD/CAM-fabricated crowns on virtual three-dimensional tooth models derived from CBCT imagings [7]. In this study, considering the positive effect of smaller voxel size on accuracy, a voxel size of 0.075 mm, which has not been used in previous studies for crowns or inlays restorations, was chosen.
The capability of the software program to convert DICOM data obtained from CBCT into STL format may also have influenced the marginal and internal fit of the inlay restorations [2]. Szymor et al. [30] stated that the accuracy of segmentation is the primary factor affecting the precision of models. In this study, Planmeca Romexis version 6.2 was used as the conversion software. The program is the native software of the CBCT device and has very high precision.
One of the key limitations of this study is the lack of direct validation of the STL files generated from CBCT DICOM data using a known gold standard, such as micro-CT-derived STL models. Although a high-precision, device-native software (Planmeca Romexis 6.2) was used to optimize segmentation, potential inaccuracies introduced during the DICOM-to-STL conversion process—such as those arising from thresholding, interpolation, or smoothing algorithms—cannot be entirely ruled out. While micro-CT was employed for non-destructive evaluation of marginal and internal fit, a voxel-wise or mesh-based comparison between CBCT- and micro-CT-derived STL files was not performed. Furthermore, common CBCT-related artifacts, including beam hardening, scatter, and minor phantom motion, may have affected segmentation quality and dimensional accuracy, particularly around complex inlay geometries. Although the use of standardized phantom models minimized patient-related variability, future studies incorporating quantitative mesh-to-mesh deviation mapping and voxel alignment techniques are recommended to rigorously assess the accuracy of CBCT-based digital models.
The micro-CT method was used to evaluate the marginal and internal fit of inlay restorations. This non-destructive method, which allows for repeated measurements, is considered one of the best and recommended methods for evaluating marginal and internal fit [11,31,32,33]. In the fit analysis of restorations, 50 measurements per specimen are recommended to obtain clinically significant information about the marginal gap size, regardless of the systematic or random approaches of the measurement sites. Depending on the required level of precision, at least 20 to 25 measurements per crown are acceptable [34]. In this study, 60 measurements were taken for each inlay restoration. This number is quite substantial in terms of providing clinically significant information.
In this study, no adjustments were made to the marginal and internal regions of inlay restorations to ensure standardization. However, it should be noted that in clinical reality, restorations are often adjusted post-milling through chairside modifications to optimize fit. If minor adjustments had been made to the internal surfaces of inlay restorations after milling, as is commonly performed in laboratory and clinical conditions, the marginal gap values could have been reduced. On the other hand, in this study, three different inlay restorations prepared for each preparation sample were not cemented; instead, they were secured to the tooth with paraffin bands for micro-CT analyses. This approach allowed for the control of tooth preparation variables among the groups and eliminated possible cementation errors. Although this non-cemented protocol is widely accepted in micro-CT studies to allow standardized and repeatable measurements, it does not replicate the clinical fit achieved under actual cementation pressure. Additionally, research has reported that the marginal gap is greater in cemented restorations compared to non-cemented restorations [34,35,36]. In this study, where the cementation process was not performed, this information should not be overlooked when evaluating the marginal and internal gap values.
The use of typodont teeth is one of the limitations of this study. Typodont teeth have been used in many marginal fit studies [11,14,19,37]. Ayad et al., in their study on crown preparation, indicated that there were similar results between typodont teeth and extracted natural teeth; they showed that the type of tooth used did not affect the results. However, it should be considered that extracted natural teeth may better reflect real intraoral conditions and could influence scanning accuracy. While this sample size aligns with established protocols in similar in vitro studies, we acknowledge its limitations regarding broad generalizability, and suggest that future research incorporate larger sample sizes with power analysis to confirm these findings.
In addition, the quantitative differences between inlays and crowns fabricated with CBCT data were likely influenced by the distinct internal geometry of inlays, which often feature deep boxes and sharp internal angles [9,18]. These features complicate both scanning and milling, especially when using brittle ceramic materials. Milling burs may be unable to precisely reproduce intricate details, and the milling process itself can induce micro-fractures or dimensional inaccuracies in feldspathic ceramics [38]. These factors may contribute to the higher marginal and internal gap values observed in inlay restorations in this study compared to crowns.
Crown restorations produced with data obtained from CBCT scans have shown successful results. Particularly, using CBCT images for prosthetic restorations in patients who already require CBCT imaging seems quite reasonable in light of the research conducted. However, inlay restorations have a much more complex geometry compared to crown restorations. Therefore, it is believed that the inadequacy of CBCT in this study is due to the complex geometry of inlay restorations. Although high marginal and internal values were measured in inlays produced with data obtained from CBCT, production could still be achieved with scanning data. It is believed that with further studies and advancements in technology, CBCT data can be used more successfully to produce inlay restorations. Future studies should focus on improving the accuracy of CBCT-based workflows for inlay restorations by optimizing scanning parameters, evaluating alternative ceramic materials and milling strategies, and validating STL data through micro-CT or other reference standards.

5. Conclusions

The following conclusions were drawn from this in vitro study:
(1)
Intraoral and model scanners showed similar results in terms of marginal and internal fit, while CBCT demonstrated higher marginal and internal gap values.
(2)
For the marginal gap, intraoral and model scanners showed clinically acceptable values; however, CBCT exceeded the clinically acceptable limits.
Although inlay restorations fabricated using CBCT data were not found to be sufficiently accurate in this study, the ability to fabricate them from CBCT data suggests feasibility. Given that CBCT imaging is frequently acquired for diagnostic or surgical planning purposes, exploring its application in inlay restoration fabrication may repurpose existing data and reduce patient visits, clinical steps, and treatment costs—offering a practical alternative in specific clinical situations. Studies aiming to optimize accuracy and validate its clinical applicability are encouraged.

Author Contributions

A.Ş., K.O. and M.A.K. conceived and designed the study. A.Ş. completed the preparations. B.A. scanned prepared teeth using intraoral and model scanner. K.O. performed CBCT scans and converted DICOM data to STL. M.O. and K.O. performed micro-CT scans and made measurements. A.Ş., B.A. and M.A.K. designed inlay restorations and milled using MCXL. A.Ş., M.O. and M.A.K. wrote and reviewed the manuscript. K.O. edited the manuscript. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

Conflicts of Interest

The authors declare no conflicts of interest.

Abbreviations

The following abbreviations are used in this manuscript:
CBCTCone Beam Computed Tomography
Micro-CTMicro-Computed Tomography

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Applsci 15 04626 g001
Figure 1. Marginal and internal gap evaluation (5 equal slices for each section and measurement points): (A) Bucco-lingual sections (OMG, AIG, OIG); (B) Mesio-distal sections (OIG, AIG, GMG); (C) Transverse sections (PMG).
Figure 1. Marginal and internal gap evaluation (5 equal slices for each section and measurement points): (A) Bucco-lingual sections (OMG, AIG, OIG); (B) Mesio-distal sections (OIG, AIG, GMG); (C) Transverse sections (PMG).
Applsci 15 04626 g001
Table 1. Descriptive statistics of occlusal marginal gap (OMG), gingival marginal gap (GMG), and proximal marginal gap (PMG).
Table 1. Descriptive statistics of occlusal marginal gap (OMG), gingival marginal gap (GMG), and proximal marginal gap (PMG).
OMGGMGPMG
GroupNMean ± SD (μm)95% CIM (μm)Mean ± SD (μm)95% CIM (μm)Mean ± SD (μm)95% CIM (μm)
LBUB LBUB LBUB
CBCT11166.72 ± 49.86 a133.22200.22177.27 ± 52.79 a141.8212.73168.09 ± 41.43 a140.25195.92
Intraoral Scanner1194.09 ± 86.45 b86.45101.72105.45 ± 30.77 b84.77126.1395.72 ± 12.44 b87.36104.08
Model Scanner1199.18 ± 24.67 b82.67115.68128.18 ± 16.62 b117.01139.35102.36 ± 14.12 b92.87111.85
The mean difference is significant at the 0.05 level. Groups with the same letters do not exhibit a statistically significant difference. SD: Standard deviation; CIM: Confidence Interval for Mean; LB: Lower bound; UB: Upper bound.
Table 2. Pairwise comparisons with 95% confidence intervals and effect sizes.
Table 2. Pairwise comparisons with 95% confidence intervals and effect sizes.
ComparisonMean Difference (µm)95% CICohen’s d
CBCT vs. IOS (Marginal)72.27[64.85, 79.68]2.17
CBCT vs. Model (Marginal)59.6[52.18, 67.01]2.0
IOS vs. Model (Marginal)−12.67[−20.08, −5.25]−0.55
CBCT vs. IOS (Internal)100.09[87.96, 112.22]2.52
CBCT vs. Model (Internal)70.91[58.79, 83.03]2.01
IOS vs. Model (Internal)−29.18[−41.30, −17.06]−0.81
CBCT = Cone Beam Computed Tomography; IOS = Intraoral Scanner; CI = Confidence Interval; µm = Micrometer; Cohen’s d = Standardized measure of effect size.
Table 3. Two-way ANOVA results for the comparison of wear values.
Table 3. Two-way ANOVA results for the comparison of wear values.
AIGOIG
GroupNMean ± SD (μm)95% CIM (μm)Mean ± SD (μm)95% CIM (μm)
LBUB LBUB
CBCT11219.45 ± 51.48 a184.86254.03235.45 ± 62.74 a193.3277.6
Intraoral Scanner11140.45 ± 31.63 b119.2161.793 ± 29.89 b72.91113.08
Model Scanner11167.72 ± 21.43 b153.32182.13125.90 ± 39.67 b99.25152.56
The mean difference is significant at the 0.05 level. Groups with the same letters do not exhibit a statistically significant difference. SD: Standard deviation; CIM: Confidence Interval for Mean; LB: Lower bound; UB: Upper bound.
Table 4. Descriptive statistics of marginal fit and internal fit.
Table 4. Descriptive statistics of marginal fit and internal fit.
Marginal FitInternal Fit
GroupNMean ± SD (μm)95% CIM (μm)Mean ± SD (μm)95% CIM (μm)
LBUB LBUB
CBCT11169.27 ± 38.64 a143.31195.24224.64 ± 49.98 a191.06258.22
Intraoral Scanner1197.00 ± 10.12 b90.20103.80124.55 ± 26.51 b106.73142.36
Model Scanner11109.67 ± 9.72 b102.15117.18153.73 ± 19.02 b140.94166.51
The mean difference is significant at the 0.05 level. Groups with the same letters do not exhibit a statistically significant difference. SD: Standard deviation; CIM: Confidence Interval for Mean; LB: Lower bound; UB: Upper bound.
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MDPI and ACS Style

Şentürk, A.; Akat, B.; Ocak, M.; Kılıçarslan, M.A.; Orhan, K. Comparison of Marginal and Internal Fit of CAD/CAM Ceramic Inlay Restorations Fabricated Through Model Scanner, Intraoral Scanner, and CBCT Scans. Appl. Sci. 2025, 15, 4626. https://doi.org/10.3390/app15094626

AMA Style

Şentürk A, Akat B, Ocak M, Kılıçarslan MA, Orhan K. Comparison of Marginal and Internal Fit of CAD/CAM Ceramic Inlay Restorations Fabricated Through Model Scanner, Intraoral Scanner, and CBCT Scans. Applied Sciences. 2025; 15(9):4626. https://doi.org/10.3390/app15094626

Chicago/Turabian Style

Şentürk, Ayben, Bora Akat, Mert Ocak, Mehmet Ali Kılıçarslan, and Kaan Orhan. 2025. "Comparison of Marginal and Internal Fit of CAD/CAM Ceramic Inlay Restorations Fabricated Through Model Scanner, Intraoral Scanner, and CBCT Scans" Applied Sciences 15, no. 9: 4626. https://doi.org/10.3390/app15094626

APA Style

Şentürk, A., Akat, B., Ocak, M., Kılıçarslan, M. A., & Orhan, K. (2025). Comparison of Marginal and Internal Fit of CAD/CAM Ceramic Inlay Restorations Fabricated Through Model Scanner, Intraoral Scanner, and CBCT Scans. Applied Sciences, 15(9), 4626. https://doi.org/10.3390/app15094626

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