Development and validation of a robotic system for milling individualized jawbone cavities in oral and maxillofacial surgery.

OBJECTIVES: This study aimed to develop and validate a robotic system capable of performing accurate and minimally invasive jawbone milling procedures in oral and maxillofacial surgery. METHODS: The robotic hardware system mainly includes a UR5E arm (Universal Robots, Denmark) and the binocular positioning system (FusionTrack 250, Atracsys LLC, Switzerland). The robotic software (Dental Navi 3.0.0, Yakebot Technology Ltd., China) is capable of generating cutting tool paths based on three-dimensional shape description files, typically in the stereolithography format, and selected cutting tool parameters, as well as designing surgical accessories. Fully impacted supernumerary tooth models in the maxilla were fabricated using software and three-dimensional printing. Following the planning of a customized cavity to fully expose the tooth, maxillary bone milling was performed on both the robot and static guide groups (n = 8). After milling, all models underwent scanning for assessment. RESULTS: In the experiment with fully buried supernumerary tooth models in the maxilla, the root mean square, translation error, over-removal rate, and maximum distance were significantly smaller in the robot group compared to the static guide group. Moreover, the overlap ratio and Dice coefficient were significantly greater in the robot group. No statistically significant differences were observed between the two groups in terms of the rotation error (P = 0.80) or under-removal rate (P = 0.92). CONCLUSIONS: This study has developed a robotic system for milling individualized jawbone cavities in oral and maxillofacial surgery, and its accuracy has been preliminarily verified to meet clinical requirements. CLINICAL SIGNIFICANCE: The robotic system can achieve precise, minimally invasive, individualized jawbone milling in a variety of oral and maxillofacial surgeries, including tooth autotransplantation, surgical reshaping for zygomatic fibrous dysplasia, removal of fully impacted supernumerary or impacted teeth, and endodontic microsurgery, among other relevant clinical applications.

Evaluation Methods and Influencing Factors on Accuracy for Static Virtual Articulation Obtained by Intraoral Scanners: A Critical Review of the Literature.

OBJECTIVE: Digital technology in dentistry has advanced rapidly in recent years, and as a result, the identification of static virtual articulation as a crucial stage in the digital process has attracted increasing attention. The use of intraoral scanners (IOSs) has made the acquisition of occlusal records more efficient. The purpose of this article is to review information on evaluation methods and influencing factors on the accuracy of static virtual articulation obtained by intraoral scanners. OVERVIEW: An electronic search of the published literature was performed up to November 2023 using five databases: PubMed, Cochrane, Embase, Web of Science, and Scopus. The inclusion criteria were defined as relevant clinical or in vitro English studies on the accuracy of the occlusal relationship obtained using intraoral scanners. Therefore, a total of 30 articles were selected, reviewed, and discussed. Based on the results of the literature review, three methods have been used to evaluate the accuracy of virtual interocclusal records, including distance measurement (10 studies), occlusal contact analysis (13 studies), and deviation analysis after superimposing casts (8 studies). However, direct comparisons between these studies are challenging due to the different methods employed. Factors that were found to potentially impact accuracies, such as the range of vestibular scans, the number and position of virtual interocclusal records (VIRs), the location and extension of edentulous areas, alignment methods, and evaluation software programs have been extensively studied, but the extent to which these factors affect accuracy remains uncertain and varies depending on the specific circumstances. CONCLUSIONS: A combination of multiple evaluation methods for a more rigid assessment of virtual interocclusal records may be a better approach. Attention should be given to the factors that may influence the accuracy of virtual interocclusal records. Future research should focus on optimizing these factors to improve the clinical applicability of virtual interocclusal records. CLINICAL SIGNIFICANCE: In restorative dentistry, virtual interocclusal records obtained with intraoral scanners have been successfully used with acceptable accuracy, although they present some issues. Understanding the evaluation methods for virtual interocclusal records and the factors that may affect the accuracy of VIRs may lead to better use in clinical practice.

Factors affecting accuracy in the additive manufacturing of interim dental prostheses: A systematic review.

STATEMENT OF PROBLEM: A systematic review of the effect of different factors on the accuracy of additively manufactured (AM) interim dental prostheses is lacking. PURPOSE: The purpose of this systematic review was to identify potential factors that may affect the accuracy of AM interim dental prostheses. MATERIAL AND METHODS: The review adhered to the guidelines outlined in the preferred reporting items for systematic reviews and meta-analyses (PRISMA) statement. The protocol was registered in the international prospective database of systematic reviews (PROSPERO) (CRD42024521564). The risk of bias in the included studies was assessed by using the Joanna Briggs Institute (JBI) checklist. Two reviewers performed an electronic search on the Web of Science, Scopus, PubMed, and Embase databases for articles published up to the end of 2023. RESULTS: The electronic search resulted in 406 studies. After removing duplicates, 205 studies remained. Thirty-one studies (30 in vitro and 1 in vivo) were included and categorized into 6 types: AM material (type and composition), prosthetic factor (tooth type, restoration size, finish line, abutment taper), AM system (technique and printer), AM parameters (layer thickness, printing orientation), postprocessing (rinsing, postpolymerization), and aging. CONCLUSIONS: The accuracy of AM interim dental prostheses is affected by factors that include the AM material, prosthetic factors, the AM system, the AM parameters, postprocessing, and aging.

A digital workflow for fabricating a mandibular guide plane prosthesis for patients about to undergo hemimandibulectomy: A dental technique.

Patients who undergo hemimandibulectomy have multiple functional impairments, and early initiation of guidance therapy has been associated with an improved definitive occlusal relationship. This article describes a digital workflow to determine the angle and form the shape of the flange of the mandibular guide plane prosthesis (MGPP), and to create an MGPP before mandibular resection surgery. A virtual articulator was used to achieve the movements of the maxilla relative to the mandible, and the shape of the MGPP was adjusted by dynamic occlusion. The MGPP and mandibular case were printed using a digital light processing (DLP) printer. This technique avoids intraoral procedures such as making impression and tooth preparation when mouth opening is limited after surgery and enables early functional training.

A new method to orient a 3-dimensional facial model to natural head position: A preliminary report on accuracy and reproducibility.

OBJECTIVES: To establish and validate a novel method to orient a 3-dimensional (3D) facial model to natural head position (NHP) in a stereophotogrammetric system using a 2-dimensional frontal full-face photograph of NHP. MATERIAL AND METHODS: Specific technique procedure was reported for our method, and in vitro model experiment was performed for accuracy test. A preliminary volunteer study was then planned for reproducibility test. RESULTS: The accuracy on a 3D-printed test model was within 0.15°. Within an observational cohort of 22 dental students, the angular deviations of different maxillofacial regions (e.g., central forehead, left and right zygomatic regions, apex of nose and mental region) were no more than 2° between the 3D NHP models acquired with a shorter time-interval (1 h from baseline) or a longer time-interval (7 days from baseline), which were all considered clinically insignificant. In addition, the angular deviations were significantly larger with a 7d-interval than with a 1h-interval, indicting a decline in 3D NHP reproducibility over short time duration. CONCLUSION: The current method may represent a clinically useful protocol for recording and transferring 3D NHP in stereophotogrammetry. CLINICAL RELEVANCE: It may provide reliable and meaningful reference information for evaluating craniofacial morphology, and be of clinical use in the diagnosis, treatment and follow-ups of patients with aesthetic or deformed craniofacial problems.

Fit comparison of interim crowns manufactured with open and proprietary 3D printing modes versus milling technology: An in vitro study.

OBJECTIVES: This study aimed to assess the fit of interim crowns produced using DLP-based 3D printing with different manufacturing workflows-open and proprietary-versus milling technology. METHODS: A total of 120 crowns were evaluated using the replica technique. The control group (Mill, n = 30) was manufactured via subtractive technology. Experimental groups were printed using a DLP printer (SprintRay Pro95). In the proprietary mode (SR100, n = 30), manufacturer resin was used with a 100-µm layer thickness (LT) and a splashing cleaning postprocessing. In the open mode, validated resin was used. Group B100 (n = 30) had a 100-µm LT, and group B50 (n = 30) had a 50-µm followed by postprocessing in an ultrasonic bath with full immersion in isopropyl alcohol. Kruskal-Wallis tests with Bonferroni correction was applied after normal analysis (α = 0.05). RESULTS: Group B50 exhibited the best overall fit (123.87 ± 67.42 µm), which was comparable to the gold standard Milling group, which demonstrated the lowest marginal fit (p = 0.760). SR100 showed significantly poorer performance compared to Mill, B50, and B100 (p < 0.001). CONCLUSIONS: 3D printed and milled interim crowns generally demonstrated clinically acceptable fit, with the exception of the SR100 group. Postprocessing notably influenced crown fit, with the open mode with total immersion in isopropyl alcohol being superior. CLINICAL SIGNIFICANCE: The present study demonstrates that the selection of an optimal manufacturing and postprocessing workflow results in superior fit for interim crowns. This enables dental professionals to evaluate protocols and ensure reliable outcomes with improved clinical outcomes in interim crown fabrication.

Polyetheretherketone split post and core for restoration of multirooted molar with insufficient dental tissue remnants by digital techniques: a case report and 3-year follow up.

BACKGROUND: Multi-rooted teeth with extensive dental defects often face challenges in stability and biomechanical failure. High-performance polymer PEEK materials, with properties closer to dentin, show promise in reducing stress concentration and preserving tooth structure. This report aimed to explore the use of a highly retentive polyetheretherketone (PEEK) for manufacturing custom-made split post and core for the restoration of grossly destroyed endodontically treated molars. CLINICAL CONSIDERATIONS: A 40-year-old female patient presented with complaints of loss of tooth substance in the posterior mandibular tooth. This case involved the digital design and fabrication of PEEK split post and core to restore multirooted molar with insufficient dental tissue remnants. The restorations were evaluated over a 3-year follow-up using the World Federation criteria (FDI). The restoration was clinically evaluated through intraoral examination, radiographic assessment, and subjective patient satisfaction, and was deemed clinically good according to FDI criteria. CONCLUSION: The outstanding mechanical properties of PEEK, coupled with the structure of the split post, provide an effective treatment option for weakened multirooted teeth. Simultaneously, the restoration configuration effectively addressed the challenge of varying postinsertion directions, and the interlocking mechanism between the primary and auxiliary posts enhanced the stability of the post and core.

Fully integrated additive manufacturing of an obturator prosthesis for an edentulous patient with a maxillectomy defect.

Maxillary defects pose challenges for prosthodontists, especially when patients have no remaining teeth. This clinical report describes rehabilitation with a complete denture obturator fabricated in 2 visits for an edentulous patient after a maxillectomy. The obturator base and artificial teeth were digitally designed and merged into a 1-piece prosthesis. Following a virtual reduction, the integrated prosthesis and a gingival veneer were calculated and then printed and bonded together to complete the fabrication. Balanced occlusion was achieved with the assistance of a digital occlusion analyzer at the insertion visit. This approach avoided base-tooth assembly deviations and provided a prosthesis with good patient-reported outcomes at the 6-month follow-up.

In vivo evaluation of T-Scan in quantifying occlusal contact.

BACKGROUND: The T-scan system has been used previously to analyse occlusion, but the quantitative analysis of occlusal contact by T-Scan system has yet to be reported. OBJECTIVES: To evaluate the reliability and validity of T-Scan system for quantitatively measuring occlusal contact area and occlusal contact number. METHODS: Twenty-two individuals with normal occlusion, 11 men and 11 women, were recruited for the study. Two occlusal analysis methods, including silicone transmission analysis method (STA) and T-Scan occlusion analysis method (TSO), were used to make quantitative analysis to measure occlusal contact area (OCA) and occlusal contact number (OCN). A test-retest check was performed with an interval of 2 weeks. The values of intraclass correlation coefficients (ICC) between test-retest of each method were calculated for reliability evaluation. Pearson correlations analysis, paired t-tests, regression analysis and Bland-Altman analysis were performed for validity evaluation. RESULTS: The ICC values of STA were greater than those of TSO for OCA while for OCN, ICC values of TSO were greater than STA. The higher OCA and OCN values were found in TSO compared with STA. Pearson's correlation coefficient indicated strong relations between TSO and STA (0.730-0.812) for OCA, while good relations between then (0.569-0.583) for OCN. Paired t-test showed a significant difference between the OCA and OCN values between TSO and STA. Bland-Altman analysis showed good agreement between OCA and OCN values of TSO and STA both in men and women. Regression analysis identified a linear correlation between OCA values obtained from these two methods. CONCLUSIONS: T-Scan method showed strong reliability for measuring OCA and OCN quantitatively. Strong correlations were found between OCA values from TSO and STA method, but the validity of TSO for measuring OCN needs to be promoted. CLINICAL SIGNIFICANCE: T-Scan system demonstrates good potential in quantitative analysis of occlusion, which will expand its clinical application.

Fully automatic AI segmentation of oral surgery-related tissues based on cone beam computed tomography images.

Accurate segmentation of oral surgery-related tissues from cone beam computed tomography (CBCT) images can significantly accelerate treatment planning and improve surgical accuracy. In this paper, we propose a fully automated tissue segmentation system for dental implant surgery. Specifically, we propose an image preprocessing method based on data distribution histograms, which can adaptively process CBCT images with different parameters. Based on this, we use the bone segmentation network to obtain the segmentation results of alveolar bone, teeth, and maxillary sinus. We use the tooth and mandibular regions as the ROI regions of tooth segmentation and mandibular nerve tube segmentation to achieve the corresponding tasks. The tooth segmentation results can obtain the order information of the dentition. The corresponding experimental results show that our method can achieve higher segmentation accuracy and efficiency compared to existing methods. Its average Dice scores on the tooth, alveolar bone, maxillary sinus, and mandibular canal segmentation tasks were 96.5%, 95.4%, 93.6%, and 94.8%, respectively. These results demonstrate that it can accelerate the development of digital dentistry.

Evaluation of the accuracy of seven intraoral scanners for the full dentate and partially edentulous complete-arch mandibular casts: An in vitro comparison.

Statement of problem: Intraoral scanners (IOSs) are widely used in dentistry, providing high accuracy in short-range scanning. Nevertheless, when scanning the full dental arch, it remains a challenge. Furthermore, there is a lack of studies reporting the differences in scan accuracy between dental arches with large-span mucosal areas and fully dentate casts or optimal IOS selection for different dental statuses. Purpose: This study aimed to evaluate the accuracy and scanning time of different IOSs for full dentate (FD) and partially edentulous (PE) casts with missing teeth in the #34-#44 range and to determine the IOSs with the optimal clinical adaptability and scanning accuracy for different complete-arch casts. Material and methods: Reference scans of two complete-arch (FD and PE) casts were obtained using a laboratory scanner (Ceramill Map 600). Subsequently, the same casts were scanned ten times each by seven IOSs (3Shape Trios 3, CS3600, Planmeca Emerald, iTero Element 5D, Medit i500, BAMBOO B1, and Shining Aoralscan 3), and the scanning time was recorded. The test data were superimposed on the reference scans for the selected areas, and three-dimensional deviations between the reference and test casts (trueness), and between test casts (precision) were determined using reverse engineering software (Geomagic Wrap). The dataset was analyzed using a two-factor analysis of variance with post-hoc Bonferroni tests. Results: Two-factor analysis of variance revealed significant differences in accuracy and scanning time for different casts (P < 0.001) and IOSs (P < 0.001). For the FD cast, the i500 (0.35 ± 0.11 mm trueness) and CS3600 (0.23 ± 0.12 mm precision) performed worse than the remaining scanners. For the PE cast, the BAMBOO B1(0.89 ± 0.58 mm trueness; 0.88 ± 0.48 mm precision) performed worse than the remaining scanners. There were no differences in the accuracy of scanning between the Element 5D and Emerald for both cast types. However, the scanning time differed significantly between the different IOSs (P < 0.001). Regardless of the cast type, the fastest and slowest scans were performed by the Trios3 and CS3600 scanners respectively. Conclusions: The accuracy and scanning time differed between the different IOSs and types of complete-arch casts.

A simplified digital workflow for the rapid design and fabrication of interim fixed prostheses using an open-access software program.

A digital workflow for the rapid design and fabrication of interim fixed prostheses using an open-access software program and 3-dimensional printing technology is described. After obtaining intraoral scanning data, the prostheses are designed by offset, margin sculpting, and a Boolean operation. Then, the prostheses are finalized and manufactured additively. The use of the open-access software program and simplified design steps enhances the manufacturing efficiency and accessibility of computer-aided design and computer-aided manufacturing of interim restorations.

A digital workflow for designing and manufacturing metal frameworks and removable partial dentures: A novel dental technique.

The purpose of this technical report is to demonstrate a fully digital workflow for designing and fabricating metal frameworks and removable partial dentures. After obtaining a digital cast of the dental arch with bilateral distal extension defect, computer-aided design software and 3D printing technology are used for the design and fabrication of the removable partial denture frameworks, denture teeth, and denture bases, instead of the traditional workflow. The assembly of the three components is facilitated through a meticulously structured framework. The technology, which prints metal frameworks, denture bases, and denture teeth through different processes with different materials, achieves full 3D printing technology for making removable partial dentures.

The evolution of robotics: research and application progress of dental implant robotic systems.

The use of robots to augment human capabilities and assist in work has long been an aspiration. Robotics has been developing since the 1960s when the first industrial robot was introduced. As technology has advanced, robotic-assisted surgery has shown numerous advantages, including more precision, efficiency, minimal invasiveness, and safety than is possible with conventional techniques, which are research hotspots and cutting-edge trends. This article reviewed the history of medical robot development and seminal research papers about current research progress. Taking the autonomous dental implant robotic system as an example, the advantages and prospects of medical robotic systems would be discussed which would provide a reference for future research.

Coordinate-based data analysis of the accuracy of five intraoral scanners for scanning completely dentate and partially edentulous mandibular arches.

STATEMENT OF PROBLEM: Current methods for assessing the accuracy of intraoral scanners (IOSs) that reduce errors and provide comprehensive data compared with previous methods are lacking. PURPOSE: The purpose of this in vitro study was to present a coordinate-based data analysis method to compare the accuracy of 5 IOSs for scanning completely dentate and partially edentulous casts. MATERIAL AND METHODS: Reference scans of 2 complete arch casts (completely and partially dentate) were digitized using a high-precision laboratory scanner (Ceramill Map 600). Each cast was scanned 10 times each using 5 IOSs (3Shape TRIOS 3, Planmeca Emerald, iTero Element 5D, Medit i500, and Shining Aoralscan 3). The dataset of all 10 test groups was analyzed by using a reverse engineering software program (Geomagic Wrap). Each test cast was aligned with the reference cast by 3-dimensional (3D) superimposition to determine the translation and rotation along the x-, y-, and z-axes. The dataset was analyzed using the Kruskal-Wallis and post hoc Bonferroni tests (α=.05). RESULTS: Significant differences were observed in all parameters among all scanners when scanning the same cast (P<.05). Significant differences were observed in at least 1 parameter for all scanners, except Element 5D after scanning different casts using the same scanner. Deviations in the test data generally relocated toward the mesial, buccal, and apical sides, and the casts were almost always rotated clockwise around the y-axis and counterclockwise around the z-axis. For the completely dentate cast, among all IOSs, Element 5D demonstrated the highest accuracy in most of the measured parameters, specifically in the y-axis translation (0.06[0.07] mm), z-axis translation (0.08[0.05] mm), and y-axis rotation (0.21[0.16] degree) (P<.05). For the partially edentulous cast, Element 5D displayed higher accuracy in most of the measured parameters, including the x-axis translation (0.11[0.14] mm) and z-axis rotation (0.12[0.18] degree) (P<.05). Emerald also displayed higher accuracy in most of the measured parameters, including the y-axis translation (0.05[0.08] mm) and y-axis rotation (0.14[0.12] degree) (P<.05). Element 5D exhibited no difference in the scanning accuracy between the 2 types of casts (P>.05). CONCLUSIONS: Element 5D offered a high level of accuracy and was an appropriate scanner for both situations. The method presented in this study provides a good assessment of accuracy deviations in complete arch scans using 3D coordinate-based data analysis.

Clinical evaluation of autonomous robotic-assisted full-arch implant surgery: A 1-year prospective clinical study.

OBJECTIVES: This prospective clinical study aimed to evaluate the accuracy and 1-year clinical follow-up performance of dental implant placement with an autonomous dental implant robot (ADIR) system in full-arch implant surgery. MATERIALS AND METHODS: Twelve patients with edentulous arches or final dentition received 102 implants using the ADIR system. Global platform deviation, global apex deviation, and global angular deviation between the planned and actual implants were calculated after surgery. Data were statistically analyzed for factors including jaws, implant positions, patient sequences, implant systems, and implant length. Surgery duration was recorded. Patients were followed for 3 months and 1 year after surgery. Periodontal parameters, buccal bone thickness (BBT), and facial vertical bone wall peak (IP-FC) were recorded. RESULTS: Among the 102 implants, the mean (SD) global platform deviation, global apex deviation, and global angular deviation were 0.53 (0.19) mm, 0.58 (0.17) mm, and 1.83 (0.82)°, respectively. The deviation differences between the mandible and maxilla did not show statistical significance (p > .05). No statistically significant differences were found for the jaws, implant positions, patient sequences, implant systems, and implant length to the deviations (p > .05). The periodontal parameters, the BBT, and IP-FC remained stable during 1-year follow-up. CONCLUSION: The ADIR system showed excellent positional accuracy. The 1-year follow-up after full-arch implant surgery indicated that the ADIR system could achieve promising clinical performance. Additional clinical evidence is requisite to furnish guidelines for the implementation of the ADIR system in full-arch implant surgery.

Endodontic Microsurgery With an Autonomous Robotic System: A Clinical Report.

INTRODUCTION: Endodontic microsurgery (EMS) requires minimally invasive osteotomy and accurate root-end resection, which can be challenging in many instances. Evidence suggests that autonomous robotic systems can significantly enhance the precision of dental implantation. The aim of this case report is to introduce a novel EMS technique that employs robot-guided osteotomy and root resection procedures. METHODS: A 59-year-old man was diagnosed with previously treated, symptomatic apical periodontitis in the mandibular left first molar. Patient data were used to integrate a digital model into preoperative planning software to design the surgical plan. The robotic system utilizes spatial alignment techniques for registration, guiding the robotic arm to autonomously perform a 3-mm osteotomy and root-end resection, based on the surgical plan. After completing the resection, the clinician confirmed the absence of cracks or root fractures and subsequently performed root-end preparation and filling under a microscope. RESULTS: To the best of our knowledge, this case marks the first use of autonomous robotic assistance in EMS. CONCLUSIONS: Utilizing an autonomous robotic system could enable precise apicoectomy in patients with intact cortical plates, thus facilitating successful EMS procedures. This has the potential to minimize errors caused by operator inexperience and mitigate the risks associated with excessive bone removal.

Correlation between intraosseous thermal change and drilling impulse data during osteotomy within autonomous dental implant robotic system: An in vitro study.

OBJECTIVES: This study aims at examining the correlation of intraosseous temperature change with drilling impulse data during osteotomy and establishing real-time temperature prediction models. MATERIALS AND METHODS: A combination of in vitro bovine rib model and Autonomous Dental Implant Robotic System (ADIR) was set up, in which intraosseous temperature and drilling impulse data were measured using an infrared camera and a six-axis force/torque sensor respectively. A total of 800 drills with different parameters (e.g., drill diameter, drill wear, drilling speed, and thickness of cortical bone) were experimented, along with an independent test set of 200 drills. Pearson correlation analysis was done for linear relationship. Four machining learning (ML) algorithms (e.g., support vector regression [SVR], ridge regression [RR], extreme gradient boosting [XGboost], and artificial neural network [ANN]) were run for building prediction models. RESULTS: By incorporating different parameters, it was found that lower drilling speed, smaller drill diameter, more severe wear, and thicker cortical bone were associated with higher intraosseous temperature changes and longer time exposure and were accompanied with alterations in drilling impulse data. Pearson correlation analysis further identified highly linear correlation between drilling impulse data and thermal changes. Finally, four ML prediction models were established, among which XGboost model showed the best performance with the minimum error measurements in test set. CONCLUSION: The proof-of-concept study highlighted close correlation of drilling impulse data with intraosseous temperature change during osteotomy. The ML prediction models may inspire future improvement on prevention of thermal bone injury and intelligent design of robot-assisted implant surgery.

Accuracy of implant placement using CAD-CAM tooth-supported surgical guides for an auricular prosthesis in vitro.

PURPOSE: To evaluate the accuracy of tooth-supported surgical guides used to place implants in auricular prostheses. The accuracy (trueness and precision) of the implant positions was evaluated, and the difference between the surgical guide with and without retention of the external auditory canal (EAC) was compared. MATERIALS AND METHODS: This study simulated implant placement in vitro for the treatment of right auricle malformation. Surgical guides and other casts were fabricated using additive manufacturing technology. The casts were divided into 2 groups according to the surgical guide, with 10 bone blocks in each group (with or without the EAC plug (Guides 1 and 2)). Three implant positions (Implants 1-3) were prepared for each bone block using surgical guides. Implant positions were registered using light-body silicone impressions combined with optical surface scans to measure the coronal, apical, depth, and angular deviations. Four deviations of trueness and precision were reported as the mean ± standard deviation, which was analyzed by Student's t-test. RESULTS: Each group of 10 bone blocks with 30 implant positions was successfully prepared and digitally reproduced as implants. The accuracies of implant position with surgical guides were acceptable when compared with the preoperatively planned implant positions. Compared with the Guide 2 group, there was a significant difference in the apical, depth, and angular deviations of Guide 1 group in terms of precision (p = 0.001). There was a significant difference in the depth deviation of Implant 1 (p = 0.028) and apical deviation of Implant 2 (p < 0.001) compared two groups in terms of trueness. In terms of precision, there was a significant difference in the coronal (p = 0.002), apical (p = 0.001), and depth (p < 0.001) deviation of Implant 1; apical (p = 0.036) and angular (p < 0.001) deviation of Implant 2 also existed significant difference; the coronal deviation of Implant 3 (p = 0.018) also existed significant difference. Moreover, the group with the EAC plug showed lower deviation in precision and a smaller volume in the 95% confidence ellipsoid. CONCLUSION: Both types of tooth-supported surgical guides can provide acceptable accuracy. A surgical guide with an EAC plug was considered to be more precise.

A digital and cast-free workflow for fabricating a definitive hollow obturator prosthesis for a maxillectomy defect: A dental technique.

This article presents a novel digital and cast-free workflow for fabricating a definitive hollow obturator prosthesis. A digital altered cast is made after the framework-fitting appointment to maximize support. The framework, hollow obturator base, and teeth are digitally designed, additively manufactured, and then assembled precisely without a cast. This method simplifies the laboratory process, reduces human errors, and provides a prosthesis with high accuracy and good fit.