Accuracy of edentulous full-arch implant impression: An in vitro comparison between conventional impression, intraoral scan with and without splinting, and photogrammetry.

OBJECTIVES: The purpose of this in vitro study was to compare the trueness and precision of complete arch implant impressions using conventional impression, intraoral scanning with and without splinting, and stereophotogrammetry. MATERIALS AND METHODS: An edentulous model with six implants was used in this study. Four implant impression techniques were compared: the conventional impression (CI), intraoral scanning (IOS) without splinting, intraoral scanning with splinting (MIOS), and stereophotogrammetry (SPG). An industrial blue light scanner was used to generate the baseline scan from the model. The CI was captured with a laboratory scanner. The reference best-fit method was then applied in the computer-aided design (CAD) software to compute the three-dimensional, angular, and linear discrepancies among the four impression techniques. The root mean square (RMS) 3D discrepancies in trueness and precision between the four impression groups were analyzed with a Kruskal-Wallis test. Trueness and precision between single analogs were assessed using generalized estimating equations. RESULTS: Significant differences in the overall trueness (p = .017) and precision (p < .001) were observed across four impression groups. The SPG group exhibited significantly smaller RMS 3D deviations than the CI, IOS, and MIOS groups (p < .05), with no significant difference detected among the latter three groups (p > .05). CONCLUSIONS: Stereophotogrammetry showed superior trueness and precision, meeting misfit thresholds for implant-supported complete arch prostheses. Intraoral scanning, while accurate like conventional impressions, exhibited cross-arch angular and linear deviations. Adding a splint to the scan body did not improve intraoral scanning accuracy.

Accuracy of open-sleeved vs. closed-sleeved static computer-assisted implant systems in immediate maxillary molar implant placement: An in vitro study.

OBJECTIVES: The objective of this study is (1) to compare the accuracy of an open-sleeved static computer-assisted implant system (sCAIS) with a closed-sleeve sCAIS and free-hand approach in immediate implant placement (IIP) of maxillary molar sites and (2) to investigate the influence of socket morphology on these approaches. MATERIALS AND METHODS: Ninety partially edentulous duplicated maxillary models simulating three different molar sockets (type A, B, and C based on Smith and Tarnow's classification) were investigated. Three modalities, including sCAIS with open-sleeves, sCAIS with closed-sleeves, and free-hand approach, were applied separately to 30 models with 120 sockets. A customized Python script automatically measured the deviations between the virtual and actual implant positions for all 360 implants. RESULTS: The 3D deviations of sCAIS were significantly influenced by the socket and sleeve types. Both guided groups exhibited significantly less deviation than the free-hand approach. Type A and C sockets resulted in better implant positions than type B socket sites. In type B sockets, the open-sleeve group achieved significantly less deviation compared to the closed-sleeve group, with respect to apical global (1.34 ± 0.53 vs. 1.84 ± 0.59 mm), coronal horizontal (0.68 ± 0.36 vs. 0.93 ± 0.34 mm), apical horizontal (1.21 ± 0.59 vs. 1.74 ± 0.63 mm), and angular (3.30 ± 1.41 vs. 4.41 ± 1.96°) deviations. CONCLUSIONS: Guided implant surgery significantly reduces deviations during molar IIP compared to free-hand procedures. Furthermore, the use of open-sleeve sCAIS appears to be more effective in minimizing deviations in type B sockets when compared with the closed-sleeve guided system.

Recommendations for successful virtual patient-assisted esthetic implant rehabilitation: A guide for optimal function and clinical efficiency.

OBJECTIVE: Complete arch implant rehabilitation necessitates meticulous treatment planning and high-level collaboration between surgical and prosthetic dental teams. Emerging virtual technologies hold considerable promise in streamlining this process. The aim of this article is to extend recommendations to clinicians venturing into the virtual patient-assisted esthetic implant rehabilitation workflow. OVERVIEW: This article summarizes recommendations for virtual patient-assisted esthetic implant rehabilitation in the following five aspects: three-dimensional data handling and superimposition, occlusion and virtual articulator integration in creating virtual patients, streamlined face- and prosthetic-driven surgical planning, reuse of presurgical data ("Copy & Paste"), and final impression for passive fitting of final restoration. To illustrate these principles, a case with complete-mouth implant rehabilitation completed within six visits using this virtual patient workflow is presented. CONCLUSION: The virtual patient workflow serves as an invaluable tool to perform treatment planning, enhance efficiency, and ensure predictable outcomes in esthetic complete arch implant rehabilitation. CLINICAL SIGNIFICANCE: Virtual workflows are increasingly prevalent in esthetic implant rehabilitation. Nevertheless, these workflows necessitate a distinct set of knowledge and tools divergent from conventional dentistry practices. This article offers guidelines and recommendations for dental clinicians who are new to this field.

Superimposing digital arch scans onto cone beam computed tomography scans with metallic artifacts by applying a radiopaque occlusal registration material: A chairside dental technique.

Precise alignment between digital arch scans and cone beam computed tomography (CBCT) scans is a crucial step in computer-aided implant planning and placement. However, clinicians frequently encounter challenges during this process when imaging patients with existing metal restorations or orthodontic devices, as these can introduce metallic artifacts on CBCT scans that lead to alignment deviations. The presented technique describes a straightforward approach using a radiopaque occlusal registration material as a radiographic marker to facilitate the alignment between digital arch scans and CBCT scans with metallic artifacts. This technique simplifies the clinical workflow by eliminating the need for additional radiographic templates or specialized devices, offering a cost-effective option for clinicians.

Digital cross-mounting of intraoral scan casts from a virtual articulator to a mechanical articulator by using a custom transfer plate: A dental technique.

With the development of digital dental technologies, a complete digital workflow without using physical casts has become possible. However, for certain clinical and dental laboratory procedures, especially in complex rehabilitation treatments, physically mounted casts in an ideal location in a mechanical articulator are still necessary for treatment planning and restoration fabrication. This technique report describes a digital approach to fabricating a custom transfer plate to cross mount intraoral scan casts from a virtual articulator to the corresponding mechanical articulator. This technique eliminates the need for conventional physical facebow transfer processes and offers a straightforward approach to integrating virtual procedures with analog workflows.

The 4D virtual patient: A proof of concept in digital dentistry.

This dental technique article updates the 3-dimensional (3D) virtual patient digital workflow by introducing the space-time information acquired with jaw tracking motion. The direct digital procedure involved scanning the interim prostheses, creating virtual casts, and transferring the digital facebow, virtual articulation, and jaw-tracking motion. All 3D files and records from the intraoral scanner, cone beam computed tomography, extraoral scanner, and jaw tracking motion were superimposed using existing teeth as the connecting link in all data sets and adopting the best-fit alignment. The main advantages of the technique were creating a 4-dimensional virtual patient and standardizing the introduction of clinical space-time information (the fourth dimension) beyond the static condition.

Influence of apical finish line location of tooth preparations on the scanning accuracy of intraoral scanners with various focal lengths and scanning technologies.

STATEMENT OF PROBLEM: Limited studies have reported the influence of finish line location on the accuracy of intraoral scanners (IOSs). Focal length is a hardware characteristic of IOSs. Whether there is a relationship between scanning accuracy of tooth preparations with the finish located at different apical positions and focal length and IOS technology or system remains uncertain. PURPOSE: The purpose of the present in vitro study was to assess the influence of the apical finish line location of tooth preparations on the accuracy of 4 IOSs with various focal lengths and scanning technologies. MATERIAL AND METHODS: A maxillary typodont with a crown preparation on the left first molar was digitized (T710). Afterwards, a removable die was created on the prepared first molar of the virtual cast and duplicated to create 4 dies with different apical finish line locations: 2- or 1-mm supragingival, 0-mm or equigingival, and -0.5-mm or intracrevicular. The cast and die designs were additively fabricated (Asiga Pro 4K with Keystone Model Ultra). Each die was independently scanned by using the same laboratory scanner (reference scans). Four groups were created: TRIOS 5, i700, iTero, and Primescan. Four subgroups were developed depending on the apical position of the finish line (n=15). In each subgroup, the cast was assembled by positioning the corresponding die into the cast. The cast was then scanned by using the corresponding IOS. The reference scans were used as a control to compute the root mean square (RMS) error discrepancies with each experimental scan on the preparation and margin of the preparation areas. Two-way ANOVA and pairwise comparisons were used to analyze trueness (α=.05). The Levene and pairwise comparisons using the Wilcoxon Rank sum test were used to analyze precision (α=.05). RESULTS: Trueness discrepancies in the preparation area were found among the groups (P=.010) and subgroups (P<.001), with a significant interaction between group×subgroup (P<.001). The -0.5 mm location obtained significantly worse trueness in the preparation area. The TRIOS 5 and i700 obtained the best trueness in the preparation area. Trueness discrepancies in the margin area were found among the groups (P=.002) and subgroups (P<.001), with a significant interaction between group×subgroup (P=.004). The -0.5 mm location obtained the worst trueness in the margin area. The i700 and Primescan obtained the best trueness in the margin area. Precision discrepancies were found in the preparation area (P<.001). The TRIOS 5 obtained the best precision in the preparation area (P=.001). Precision discrepancies in the margin area were obtained (P<.001). The 1-mm subgroup obtained the best precision (P=.001). CONCLUSIONS: The apical position of the finish line of the tooth preparation tested affected the trueness and precision of the IOSs tested.

Intraoral scanner-based virtual facebow transferring: A chairside dental technique.

Accurately mounting dental casts on an articulator is an essential step in prosthetic treatments. In digital dentistry, virtual articulator mounting procedures rely on virtual facebow records. However, virtual facebow records usually require devices like face scanners or jaw motion tracking systems that are not commonly available in most dental practices. The present technique report describes a straightforward intraoral scanner-based virtual facebow transfer approach. In this technique, a reference facebow joint support was first scanned and aligned with a virtual articulator. Then, a patient's facebow joint support and bite fork assembly were scanned chairside with an intraoral scanner and aligned with the virtual articulator by matching common features with the reference facebow joint support. After aligning the patient's intraoral scans with the patient's bite fork scan that was already superimposed on the virtual articulator, a virtual mounting process was achieved. Once the corresponding reference facebow joint supports have been generated, this technique can be easily implemented with most facebow systems and be seamlessly integrated into daily clinical practice as only an intraoral scanner and a conventional facebow were required.

Cationic Gelatin Cross-Linked with Transglutaminase and Its Electrospinning in Aqueous Solution.

Gelatin (GE) is a renewable biopolymer with abundant active groups that are beneficial for manufacturing functional biomaterials via GE modification. An antibacterial fibrous GE film was prepared by electrospinning the modified GE in an aqueous solution. The original GE was modified by reacting it with N,N-dimethyl epoxypropyl octadecyl ammonium chloride (QAS), and then it was cross-linked with transglutaminase (TGase). FTIR analysis illustrated that QAS was grafted onto GE through the epoxy ring-opening reaction, and the modification did not influence the main GE skeleton structure. The investigation of the solution properties showed that the grafted cationic QAS group was the main factor that decreased the surface tension of the solution, increased the electrical conductivity of the solution, and endowed GE with antibacterial activity. TGase cross-linking clearly influenced the rheological properties such that the flow pattern of the spinning solution varied from Newton-type to shear thinning, and the aqueous solution of GE-QAS-TGs transformed from liquid-like to solid-like and even induced gelatinization with increasing TGase content. A satisfactory fibrous morphology of 200-500 nm diameter was obtained using a homemade instrument under the optimized electrospinning conditions of a temperature of 35 °C, a distance between electrodes of 12 cm, and a voltage of 15 kV. The study of film properties showed that the antibacterial activity of the fibrous GE film depended only on the grafted quaternary ammonium, whereas the thermostability, wettability, and permeability were greatly influenced by both the TGase cross-linking and film-forming methods. Cytotoxicity was tested using the CCK-8 and live/dead kit staining methods in vitro, which showed that the modified GE had good biocompatibility.

Effects of crown contour on artificial biofilm removal efficacy with interdental cleaning aids: An in vitro study.

OBJECTIVES: To evaluate the efficacy of various interdental cleaning aids for artificial biofilm removal on different implant-supported crown designs. METHODS: Mandibular models with missing first molar were fabricated and installed with single implant analogs and loaded with crowns of different designs (concave, straight, and convex). Artificial biofilm was made with occlusion spray. Thirty volunteers (periodontists, dental hygienists, and laypersons) were asked to clean the interproximal areas. The crowns were unscrewed and photographed in a standardized setting. The outcome was measured by the cleaning ratio which represents the cleaned surfaces in relation to the area of the tested surface. RESULTS: A significant difference in favor of concave crown (p < .001) on the basal surface was cleaned by all tools, except the water flosser. There was evidence of an overall effect of "cleaning tool," "surface," and "crown design" (p < .0001) except for the "participant" factor. The mean cleaning ratio for each cleaning tool and overall combined surfaces were (in%): dental floss: 43.02 ± 23.93, superfloss: 42.51 ± 25.92, electric interspace brush: 36.21 ± 18.78, interdental brush: 29.10 ± 15.95, and electric water flosser: 9.72 ± 8.14. Dental floss and superfloss were significantly better (p < .05) than other tools in removing plaque. CONCLUSIONS: Concave crown contour had the greatest artificial biofilm removal, followed by straight and convex crowns at the basal surface. Dental floss and superfloss were the most effective interdental cleaning devices for artificial biofilm removal. None of the tested cleaning devices were able to completely remove the artificial biofilm from the interproximal/basal surfaces.

A fully digital workflow to register maxillomandibular relation using a jaw motion tracer for fixed prosthetic rehabilitation: A technical report.

OBJECTIVE: This technique aimed to describe a fully digital workflow to register maxillomandibular relation for fixed prosthetic rehabilitation. CLINICAL CONSIDERATIONS: Mandibular kinematics could be reproduced in a four-dimensional (4D) virtual patient based on the intraoral scan, facial scan, cone beam computed tomography, and jaw motion trajectory, which helped record centric relation and determine a proper occlusal vertical dimension in a virtual environment. The therapeutic position could be exported directly to the dental computer-aided design software for digital waxing design with a facial scan. The 4D virtual patient was also used to verify the functional and esthetic outcomes of provisional restorations. CONCLUSIONS: This novel approach digitized the process of determination, delivery, and double-check of maxillomandibular relation, thus contributing to the establishment of a completely digital workflow for fixed prosthetic rehabilitation. CLINICAL SIGNIFICANCE: Registration of maxillomandibular relation, including centric relation and occlusal vertical dimension is critical to the success of prosthetic rehabilitation. Traditional procedures are complex and time-consuming, and heavily rely on the clinical experience of dentists. A fully digital approach to creating a 4D virtual patient and registering the maxillomandibular relation is established, which guides to determine a proper occlusal vertical dimension in centric relation. Digital delivery and double-check can simplify the conventional procedure and ensure that the determined maxillomandibular relation is reliable.

Face oriented digital workflow for transferring intraoral and extraoral data of edentulous arch rehabilitated with multiple implants: A clinical technique.

A modified scan body system is described to preserve the occlusal vertical dimension and obtain intraoral and extraoral records to transfer to the dental laboratory technician for a complete arch fixed implant-supported prosthesis. This technique helps to effectively manage the orientation and articulation of the maxillary implants for 3-dimensional smile design.

Prosthetic articulator-based implant rehabilitation virtual patient: A technique bridging implant surgery and reconstructive dentistry.

This technique report describes a fully digital workflow to create a prosthetic articulator-based implant rehabilitation (PAIR) virtual patient for complete-arch or complete-mouth implant rehabilitation. This workflow uses a custom gothic arch tracer during the cone beam computed tomography (CBCT) scan and a 3-dimensional virtual facebow when superimposing data. The PAIR virtual patient possesses reliable centric relation and vertical dimension of occlusion and is compatible with virtual articulators. Computer-aided implant planning and a digital prosthetic design can be seamlessly integrated by using this virtual patient.

Digitally Guided Lateral Sinus Floor Elevation With Simultaneous Implant Placement: 3 Case Reports With Technical Considerations.

A sinus floor elevation via lateral window (LSFE) is one of the most widely used bone augmentation procedures for implant therapy in the posterior area of the maxilla. Locating and preparing a correct opening window on the lateral sinus wall is a key step of this procedure. Conventionally, the surgeon designs and locates the window after the flap is reflected based on the information obtained from cone-beam computed tomography (CBCT) images or other diagnostic aids. Nevertheless, in spite of the advancements in CBCT imaging, clinicians may still experience hardships in situating and procuring meticulous access to the maxillary sinus by using CBCT alone. Therefore, in cases requiring an LSFE simultaneous to implant placement, a maxillary sinus surgical guide has been tested and reported to be the amiable method to be utilized as a conjunct to prevent unpredictable consequences according to its application in implying both the direction for the implant and the location of the lateral window. This article presents 3 clinical cases with a fully digital approach to guide the opening of the lateral wall of the maxillary sinus as well as the simultaneous placement of a single implant in an ideal 3D position. Based on the CBCT images and intraoral scan, a surgical guide was fabricated based on 3D software. During surgery, this teeth-supported template can be placed intraorally, guiding sinus window opening preparation. This technique makes the sinus window opening procedure simple and predictable, reduces surgical time and the risk of complications, and allows the placement of the implant in the ideal 3D position.

Digitally-Guided Lateral Sinus Floor Elevation with Simultaneous Implant Placement: Three Case Reports with Technical Considerations.

INTRODUCTION: A sinus floor elevation via lateral window (LSFE) is one of the most widely used bone augmentation procedures for implant therapy in the posterior area of the maxilla.  Locating and preparing a correct opening window on the lateral sinus wall is a key step of this procedure. Conventionally, the surgeon design and locate the window after the flap is reflected based upon the information obtained from cone-beam computed tomography (CBCT) images or other diagnostic aids. Nevertheless, in spite of the advancements in CBCT imaging, clinicians may still experience hardship in situating and procuring meticulous access to the maxillary sinus by using CBCT alone. Therefore, in cases requiring a LSFE simultaneous to implant placement, a maxillary sinus surgical guide (MSSG) has been tested and reported to be the amiable method to be utilized as a conjunct, to prevent unpredictable consequences according to its application in implying both the direction for the implant and the location of the lateral window. CASE SERIES: This article presents 3 clinical cases with a fully digital approach to guide the opening of the lateral wall of the maxillary sinus, as well as the simultaneous placement of a single implant in an ideal 3D position. Based on the CBCT images and intraoral scan, a surgical guide was fabricated base on 3D software. During the surgery, this teeth-supported template can be placed intraorally, guiding sinus window opening preparation. CONCLUSION: This technique makes the sinus window opening procedure simple and predictable, reduces surgical time as well as the risk of complications, and allows the placement of the implant in the ideal 3D position.

Virtual occlusal records acquired by using intraoral scanners: A review of factors that influence maxillo-mandibular relationship accuracy.

PURPOSE: This review aims to provide a comprehensive summary of how much progress has been made in the field of virtual occlusal records (VOR) obtained with intraoral scanners (IOSs), their accuracy, and what factors influence their accuracy. MATERIALS AND METHODS: An electronic search was performed in MEDLINE via PubMed and Scopus databases in February 2023. Eligible articles were clinical or in vitro studies evaluating the accuracy of virtual occlusal records with intraoral scanners in completely dentate and partially edentulous arches. RESULTS: Virtual occlusal records have shown promising results in terms of accuracy, with some studies reporting a high level of agreement with traditional methods. Key factors influencing the accuracy of VOR through intraoral scanners were identified which encompass multiple parameters such as scanner brands, imaging technology, scan quality, best-fit alignment, software algorithms, intermesh penetrations, and the number of sections and dimensions of the virtual occlusal record. In partially edentate areas, the lack of landmarks in the edentulous area compromises the accuracy of VOR, thus limiting the use of IOS in patients with missing teeth. CONCLUSION: Understanding and recognizing these influencing factors will increase the predictability and reliability of dental treatments completed by using digital workflows.  However, certain challenges need to be addressed which can influence its accuracy and limit its use in daily practice. Future research should focus on improving these factors to enhance the clinical applicability of virtual occlusal records.

Open-sleeve templates for computer-assisted implant surgery at healed or extraction sockets: An in vitro comparison to closed-sleeve guided system and free-hand approach.

OBJECTIVE: A buccal opening guide provides better view and better irrigation. The aim of this study was to investigate the accuracy of this open-sleeve system. MATERIAL AND METHODS: Thirty duplicated maxillary models, each with six extraction sockets and four healed sites, were used. Based on the same digital plan, three modalities, sCAIS with open-sleeves, closed-sleeves, and free-hand approach, were used to place implants. The global, horizontal, depth, and angular deviations between the virtual and actual implant positions were measured. RESULTS: Both sCAIS groups exhibited better accuracy than the free-hand group in two clinical scenarios. At healed sites, the closed-sleeve group showed a significantly fewer error than the open-sleeve group in global apical (0.68 ± 0.33 vs. 0.96 ± 0.49 mm), horizontal coronal (0.28 ± 0.15 vs. 0.44 ± 0.25 mm), horizontal apical (0.64 ± 0.32 vs. 0.94 ± 0.48 mm), and angular deviations (1.83 ± 0.95 vs. 2.86 ± 1.46°). For extraction sockets, the open-sleeve group exhibited fewer deviations than the closed-sleeve group in terms of global (coronal: 0.77 ± 0.29 vs. 0.91 ± 0.22 mm; apical: 1.08 ± 0.49 vs. 1.37 ± 0.52 mm) and horizontal (coronal: 0.60 ± 0.24 vs. 0.86 ± 0.20 mm; apical: 0.95 ± 0.50 vs. 1.32 ± 0.51 mm) deviations. However, the closed-sleeve group was more accurate in the depth control (0.26 ± 0.20 vs. 0.40 ± 0.31 mm). CONCLUSION: In this in vitro investigation, open-sleeve sCAIS proved better accuracy than free-hand surgery for both delayed and immediate implant placement. Compared with a closed-sleeve sCAIS system, open sleeve have the potential of providing better outcomes in extraction sockets but not in healed sites.

Does guided level (fully or partially) influence implant placement accuracy at post-extraction sockets and healed sites? An in vitro study.

OBJECTIVES: The aim of this study is to evaluate the effect of guide level on the accuracy of static computer-aided implant surgery (sCAIS) at post-extraction sockets and healed sites. MATERIALS AND METHODS: A total of 30 duplicate dental models, with 300 potential implant sites, were used. All the models were equally randomized into three groups: fully guided (FG, n = 100), partially guided (PG, n = 100), and free handed (FH, n = 100) surgeries. After implant placement, the mean global, horizontal, depth, and angular deviations between the virtually planned and actual implant positions were measured automatically by a Python script within software Blender. RESULTS: Both FG and PG surgeries showed significantly higher accuracy than FH surgery at post-extraction sockets and healed sites. In both sCAIS groups, there were nearly 50% more deviations from implants placed at sockets than those from delayed placement. For the immediate implant placement, the accuracy of sCAIS was significantly affected by the level of guidance. The FG group exhibited lower deviations than the PG group, with a significant difference in coronal global and horizontal deviations (p < .05). For the healed sites, two guided groups exhibited similar outcomes (p > .05). CONCLUSIONS: sCAISs provide more accuracy than the free-handed approach in position transferring from planning to a model simulation. Full guidance can significantly increase the accuracy, especially at post-extraction sites. CLINICAL RELEVANCE: Guided protocols showed significantly higher accuracy than free-handed surgery regardless of implantation timing, but both had nearly 50% more deviations in immediate implant placement.

A three-dimensionally printed template for locating the screw channel in a cement-retained implant-supported crown: A digital workflow.

Locating the screw channel in a cement-retained implant-supported crown is challenging. This article describes a fully digital workflow for fabricating a 3D-printed template which can accurately guide the dentist to find the screw channel. A definitive implant cast from the patient and an implant planning software program are used in the workflow. This technique provides precise guidance for finding the location and angulation of the abutment screw access hole.

Accuracy of three digital waxing-guided trial restoration protocols for controlling the depths of tooth preparation for ceramic veneers.

STATEMENT OF PROBLEM: The accuracy of digital waxing-guided trial restoration protocols that have been implemented with ceramic veneers has not been reported. PURPOSE: The purpose of this in vitro study was to evaluate the accuracy of 3 digital trial restorations fabricated from digital waxing for ceramic veneers. MATERIAL AND METHODS: A uniform 0.3-mm digital waxing added to the facial surface of 30 maxillary central typodont incisors was created in a software program. The trial restorations were fabricated on typodont teeth with autopolymerizing acrylic resin by using a silicone index based on 3-dimensionally printed casts designed from the digital waxing. The 30 maxillary central incisors were divided into 3 groups: the depth cutter (0.5 mm, Komet) (DC) group, the round bur (1.5 mm, Diatech) (RB) group, and the specially designed calibrated depth bur (laser mark of 0.5 mm, Gaofeng) (CD) group. The 3 groups were randomly prepared with a random number table by 2 experienced prosthodontists aiming to produce an even facial clearance of 0.5 mm. The dimensional differences in the standard tessellation language (STL) files between the surfaces of the original teeth, digital waxing, trial restorations, and prepared teeth in the software program were measured and analyzed at the same 9 points on the labial surface. One-way ANOVA with a post hoc test was used to identify significant discrepancies between trial restorations and waxing and differences in the reduction depth of typodont teeth (RDT) and the reduction depth (RD) among the 3 techniques (α=.05). The mean relative differences (MRDs) were calculated to determine the accuracy (%). RESULTS: The thickness of the trial restorations was significantly greater than that of the digital waxings, with a discrepancy of 0.20 ±0.14 mm, especially at the cervical site. With the use of a trial restoration, the RDTs of the middle (-0.01 ±0.11 mm) and cervical locations (0.09 ±0.20 mm) showed significantly smaller preparation depths than did the other locations. Significant differences in RD were found among the 3 guided techniques (P<.05). Group DC presented the most accurate result of 0.51 ±0.08 mm with an MRD of 2%, whereas the results of 0.57 ±0.10 mm with an MRD of 14% and 0.60 ±0.11 mm with an MRD of 20% were obtained from group RB and group DC, respectively. CONCLUSIONS: The trial restoration was significantly thicker than its corresponding waxing. The DC technique presented the most accurate reduction result among the 3 protocols examined.