THE ACCURACY OF INTRAORAL SCAN IN OBTAINING DIGITAL IMPRESSIONS OF EDENTULOUS ARCHES: A SYSTEMATIC REVIEW.

OBJECTIVES: Accuracy is a crucial factor when assessing the quality of digital impressions. This systematic review aims to assess the accuracy of intraoral scan (IOS) in obtaining digital impressions of edentulous jaws. METHODS: This systematic review adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) and was registered in the International Prospective Register of Systematic Reviews (PROSPERO ID: CRD42022382983). A thorough retrieval of 7 electronic databases was undertaken, encompassing MEDLINE (PubMed), Web of Science, EMBASE, Scopus, Cochrane Library, Virtual Health Library, and Open gray, through September 11, 2023. A snowball search was performed by tracing the reference lists of the included studies. The Population, Intervention, Comparison, and Outcome (PICO) question of this systematic review was: "What is the accuracy of intraoral scan in obtaining digital impressions of edentulous arches?" The Modified Methodological Index for Nonrandomized Studies (MINORS) was employed to assess the risk of bias. RESULTS: Among the studies retrieved from databases and manual search, a total of 25 studies were selected for inclusion in this systematic review, including 9 in vivo and 16 in vitro studies. Twenty-one of the included studies utilized the 3D deviation analysis method, while 4 studies employed the linear or angular deviation analysis method. The accuracy results of in vitro studies indicated a trueness range of 20-600 µm and a precision range of 2-700 µm. Results of in vivo studies indicated a trueness range of 40-1380 µm, while the precision results were not reported. CONCLUSION: According to the results of this study, direct digital impressions by IOS cannot replace the conventional impressions of completely edentulous arches in vivo. Edentulous digital impressions by IOS demonstrated poor accuracy in peripheral areas with mobile tissues, such as the soft palate, vestibular sulcus, and sublingual area.

Establishment of a 3D esthetic analysis workflow on 3D virtual patient and preliminary evaluation.

BACKGROUND: In esthetic dentistry, a thorough esthetic analysis holds significant role in both diagnosing diseases and designing treatment plans. This study established a 3D esthetic analysis workflow based on 3D facial and dental models, and aimed to provide an imperative foundation for the artificial intelligent 3D analysis in future esthetic dentistry. METHODS: The established 3D esthetic analysis workflow includes the following steps: 1) key point detection, 2) coordinate system redetermination and 3) esthetic parameter calculation. The accuracy and reproducibility of this established workflow were evaluated by a self-controlled experiment (n = 15) in which 2D esthetic analysis and direct measurement were taken as control. Measurement differences between 3D and 2D analysis were evaluated with paired t-tests. RESULTS: 3D esthetic analysis demonstrated high consistency and reliability (0.973 < ICC < 1.000). Compared with 2D measurements, the results from 3D esthetic measurements were closer to direct measurements regarding tooth-related esthetic parameters (P<0.05). CONCLUSIONS: The 3D esthetic analysis workflow established for 3D virtual patients demonstrated a high level of consistency and reliability, better than 2D measurements in the precision of tooth-related parameter analysis. These findings indicate a highly promising outlook for achieving an objective, precise, and efficient esthetic analysis in the future, which is expected to result in a more streamlined and user-friendly digital design process. This study was registered with the Ethics Committee of Peking University School of Stomatology in September 2021 with the registration number PKUSSIRB-202168136.

Wearing individualized 3D printed oral stent to protect normal tissues in patients with nasopharyngeal carcinoma during radiotherapy.

PURPOSE: To demonstrate a new individualized 3D printed oral stent in radiotherapy of nasopharyngeal carcinoma (NPC) patients and carry out a comparative analysis combining with clinical case. MATERIAL AND METHODS: Thirty NPC patients treated in our institution from September 2021 to October 2022 were prospectively enrolled. An individualized 3D printed oral stent was designed for each patient, and one set of computed tomography (CT) slices were obtained with /without wearing the oral stent, respectively. After delineation of target volumes and organs at risk (OARs) on the two CT slices, we finished two treatment plans by using the same target objectives, critical constraints and plan setup for each patient. Finally, the dose distribution and other dosimetric parameters of target volumes and OARs between the two plans were compared. RESULTS: Tongue volume and tongue length outside of mouth was 10.4 ± 2.5 cm3 and 2.8 ± 0.6 cm, respectively, distance between dorsal surface of oral tongue and plate increased from 0.3 ± 0.3 cm to 2.2 ± 0.5 cm by wearing the oral stent. For the target volume, there was no significant difference. However, Dmax of tongue, tongue tip and periglottis decreased significantly from 6352.6 ± 259.9 cGy to 5994.9 ± 478.9 cGy, 3499.8 ± 250.6 cGy to 3357.7 ± 158.0 cGy and 6345.5 ± 171.0 cGy to 6133.4 ± 263.3 cGy, respectively (p = 0.000); Dmean of tongue, tongue tip and periglottis decreased significantly from 3714.7 ± 204.2 cGy to 3169.7 ± 200.9 cGy, 3060.8 ± 216.2 cGy to 2509.6 ± 196.7 cGy and 3853.3 ± 224.9 cGy to 3079.3 ± 222.0 cGy, respectively (p = 0.000). CONCLUSION: The individualized 3D printed oral stent can reduce the dose of oral tissues and organs, so as to reduce the oral adverse reactions and improve the compliance of patients and the quality of their life. The technique can be used in radiotherapy of NPC patients.

Preliminary application and evaluation of digital step-by-step tooth-preparation templates.

STATEMENT OF PROBLEM: Tooth preparation is a fundamental technique, and inaccurate preparation may lead to excessive irreversible tooth removal or insufficient restorative space. The conventional process depends mostly on operator experience, and variable quality is inevitable. Whether a tooth preparation template would be beneficial, especially for inexperienced dentists, is unclear. PURPOSE: The purpose of this preliminary study was to evaluate the application of new digitally designed step-by-step templates to guide tooth preparation. MATERIAL AND METHODS: A laboratory scanner was used to obtain digital scans of dental casts. A 3-dimensional reverse engineering software program was used for the step-by-step digital design. The data for a series of guide templates were imported into a computer-aided manufacturing (CAM) machine for milling. Ten experts and 10 inexperienced dentists prepared teeth on a dentoform in a mannequin head. They were instructed to complete the preparation within 20 minutes both with and without the step-by-step template. The prepared crowns were subsequently scanned with an intraoral scanner, the scans were imported into a preparation evaluation software program, and various indexes were scored. The t test was used to analyze the differences between the 2 methods of tooth preparation in each group (α=.05). RESULTS: No significant differences were found in total scores with and without the guide templates in the expert group (P=.256), but the scores in the inexperienced group differed significantly between the 2 preparation methods (P<.001). In undercut comparisons, the 2 methods of preparation did not differ significantly in the expert (P=.912) or inexperienced groups (P=.601). However, the scores for taper and occlusal reduction were significantly higher in the inexperienced group when using the guide template (P<.001). CONCLUSIONS: The new digitally designed step-by-step tooth preparation guide template significantly improved the efficiency and quality of tooth preparation for inexperienced dentists when preparing multiple teeth.

The accuracies of three intraoral scanners with regard to shade determination: An in vitro study.

PURPOSE: To compare the accuracies of three intraoral scanners for shade determination function in vitro, and to preliminarily investigate the shade-matching characteristics of the three intraoral scanners. MATERIALS AND METHODS: The shade of the middle third region of each shade tab on the Vita Classical A1-D4 shade guide (VC) was measured with a spectrophotometer (Vita Easyshade V, VE) and three intraoral scanners, including CEREC Omnicam (OM), 3Shape TRIOS 3 (T3), and TRIOS 4 (T4). A conversion table between VC values and CIELAB values was established from the database of VE to analyze the trueness. The reproducibility of the instruments was then compared by repeating the measurements five times. RESULTS: The mean color difference for each instrument was highest in the OM, followed by the T4, and lowest in the T3 and VE, respectively. The L* and a* value for OM, and the b* value for T4, were significantly different from those for VE (p <0.05). The reproducibility of the instrument was highest in the VE (Fleiss' kappa: 0.95), followed by the T3 (Fleiss' kappa: 0.89), T4 (Fleiss' kappa: 0.87), and OM (Fleiss' kappa: 0.78). CONCLUSIONS: Of the three intraoral scanners, the trueness was best on the T3. The reproducibility of all the instruments was excellent.

Comparison of the dimensional and morphological accuracy of three-dimensional digital dental casts digitized using different methods.

The purpose of this study was to compare the accuracy of digital dental casts from plaster cast scanning (PCS), impression scanning (IPS), intraoral scanning (IOS), and cone-beam computed tomography (CBCT) scanning (CCS) methods. The maxillary and mandibular dental casts of 15 patients who needed CBCT scans for oral examination or treatment were digitized via four methods. 12 linear distance measurements of all digital dental casts were selected and acquired with software and compared to those of the reference plaster cast to evaluate the dimensional accuracy. Three-dimensional deviation analysis of the IPS, IOS and CCS groups with respect to the reference PCS group was performed to evaluate the morphological accuracy. The discrepancy in linear distances between the digital dental casts and reference plaster casts was statistically significant (p < 0.01). The dimensional accuracies of the PCS (0.06 ± 0.12 mm) and IPS (0.03 ± 0.05 mm) casts were better than those of the IOS (0.37 ± 0.30 mm) and CCS (0.54 ± 0.40 mm) casts. The one-sample t test showed that there were statistically significant differences between the discrepancies in 8 of the linear distances for the PCS group and 9 of the linear distances for the IPS group between the digital dental casts and reference plaster casts, with an ideal error of 0.00 (p < 0.05). The sequence of morphological accuracy from good to poor was maxillary and mandibular IPS, mandibular IOS; maxillary IOS; and maxillary and mandibular CCS. The accuracy of the digital dental casts from the PCS and IPS methods was greater than that of IOS and CCS methods. Although accuracy of the digital dental cast from IOS was low, it satisfied the clinical requirements for fixed restorations in small units. The accuracy of the digital dental cast from CCS was poorest and could only be used for procedures with lower accuracy requirements.

Investigation on the application of teaching technology of virtual simulation in undergraduate schools of stomatology in China / 口腔疾病防治

Objective@#To investigate the current situation of using virtual simulation technology in undergraduate schools of stomatology in China, analyze the problems and put forward corresponding improvement suggestions. @*Methods@# A questionnaire survey was conducted among 672 teachers and 3 849 students in undergraduate schools of stomatology in China. @*Results @#25.81% of all participants had took part in dental virtual simulation courses, and 37.80% of the participants from “Double First-Class” universities had participated in dental virtual simulation courses. 92.12% of the virtual simulation courses were established for undergraduates. "Traditional course + virtual simulation model demonstration" is the main teaching form of virtual simulation courses. Most of the participants were satisfied with the virtual simulation courses offered by their schools. At present, there are also some deficiencies in the virtual simulation courses, such as lack of teaching resources, insufficient interaction and simulation.@*Conclusion@#There is difference in the application of virtual simulation technology in undergraduate schools of stomatology in China. The virtual simulation technology is more widely used in "Double First-Class" universities than in ordinary universities. Undergraduates are the main teaching objects of virtual simulation courses. Stomatological schools in China should pay attention to the development and utilization of virtual simulation curriculum resources by cooperation, enrich the form of virtual simulation courses and strengthen the promotion and application of virtual simulation technology in stomatological education.

Evaluation of the marginal adaptation and gingival status of full-crown restorations using an intraoral camera.

OBJECTIVE: The purpose of this study was to compare the usefulness of intraoral photographs, acquired with a household intraoral camera operating in conventional, calibrated, and polarized modes, with clinical examinations for assessing the marginal adaptation and gingival status of full-crown restorations. METHODS: Clinical examinations were performed by a prosthodontist who classified the marginal adaptation of full-crown restorations according to FDI World Dental Federation criteria, and a periodontal expert who classified gingival status according to the Modified Gingival Index (MGI). The margins and gingival status of the conventional, calibration, and polarization groups of full-crown restorations were independently assessed by three evaluators who obtained photographs using an intraoral camera. Cases where at least two of three assessors were in agreement were analyzed using Cohen's kappa coefficient and the chi-square test, and the sensitivity and specificity were calculated. RESULTS: The conventional, calibration, and polarization groups differed significantly in marginal and gingival status of full-crown restorations. In the calibration group, there was good agreement between the camera-based and oral clinical examinations in terms of the gingival status of full-crown restorations (kappa = 0.945), with 100% sensitivity and 91.67% specificity; this was also the case in the polarization group with respect to the margins of full-crown restorations (kappa = 0.917, sensitivity = 97.22%, specificity = 94.44%). CONCLUSIONS: An intraoral camera with black and white calibrated images is useful to assess the gingival status of full-crown restorations. Polarization mode can be used to assess the marginal adaptation of full-crown restorations. The camera is a feasible and valid diagnostic aid.

Quality of life in patients with cancer-related Brown IIb maxillary defect: A comparison between conventional obturation rehabilitation and submental flap reconstruction.

OBJECTIVES: The purpose of this retrospective study was to compare the differences in quality of life (QOL) outcomes between the conventional obturator prostheses (COP) and the pedicled submental artery island flap (SAIF) in the reconstruction of Brown IIb maxillary defects. MATERIALS AND METHODS: The QOL of 116 eligible patients who had a lapse ≥ 12 months after the cancer-related maxilla ablation was evaluated by the University of Washington quality of life scale (UW-QOL), Performance Status Scale for Head and Neck (PSS-HN), and Obturator Functioning Scale (OFS). RESULTS: Patients in the SAIF group reported statistically and clinically significant higher overall QOL scores but lower chewing scores in the UW-QOL scale when compared with those in the COP group (P < 0.05). Clinically significantly higher scores were also observed in the recreation and anxiety domains in the UW-QOL scale for the SAIF group, but there was no statistical significances. The COP group reported more complaints about the nasal leakage when swallowing and the shape of the upper lip, and had a stronger willingness to avoid family or social events in the OFS (P < 0.05). CONCLUSIONS: For patients with Brown IIb defects, SAIF reconstruction can achieve reduced nasal leakage when swallowing, improved upper-lip contour, increased social activity, and superior overall QOL than COP. The inferior chewing function in the SAIF group indicated the need for dental rehabilitation with a conventional denture or osseointegrated implants.

Influence of Maxillary Anterior Tooth Restoration Labial Thickness on Labial Soft Tissue in Young Asian People.

PURPOSE: To determine whether a significant dimensional difference in labial soft tissue could be produced by maxillary anterior tooth restorations with diverse labial thicknesses. MATERIALS AND METHODS: Changes in the contour of the lips in each participant produced by provisional restorations with different labial thicknesses (1-4 mm) compared to baseline (0 mm) were assessed using 3D software and using a visual analog scale by a group of prosthodontists and a group of laypeople. RESULTS: Significant enhancements in 3D deviation compared to baseline were present when the participants were wearing the labial provisional restorations. Negative correlations for labial thickness with nasolabial angle and distance from upper lip to E-plane measurements were found. However, the changes were most pronounced for the prosthodontist and laypeople groups when the labial veneer thickness was 2 mm or more. CONCLUSION: Prosthodontists and laypeople hardly recognized the lip profile changes when labial provisional restorations were below 2 mm. Therefore, restorations with limited labial thickness had a weak esthetic impact on lip morphology.

Comparison of four CAD-CAM guides for preparing guiding planes of removable partial dentures.

BACKGROUND AND OBJECTIVE: To evaluate the effect of guiding structure and 3D-printing material of CAD-CAM guides on the accuracy of guiding planes preparation. METHODS: Four types of computer-aided design and computer-aided manufacturing (CAD-CAM) guides for preparing guiding planes of removable partial denture (RPD) were designed in two types of guiding structures (triple-constraint and single-plane constraint) and were 3D printed using resin and cobalt-chromium (Co-Cr) alloy. Guiding plane preparation of identical resin casts was performed using CAD-CAM guides (resin template, metal template, resin guided device, and metal guide device) in four test groups and by freehand in the control group (n = 22 per group). All prepared casts were then scanned (Test) and aligned to the reference cast with designed guiding planes. 3D compare analysis was performed and root-mean-square (RMS) values were calculated for assessing the 3D trueness and 3D precision of guiding plane preparation. The angle between the prepared guiding plane (Test) and the designed path of placement of RPD (Reference) was measured for evaluating the direction trueness. RESULTS: RMS values of the metal template group for 3D trueness (39.7 ± 14.6 µm) and 3D precision (28.6 ± 6.8 µm) were significantly lower than that of other groups (p < .05). For direction trueness, the metal template group showed the least angle deviation (1.09 ± 0.56°), and the freehand group demonstrated the largest angle deviation (7.03 ± 2.83°). CONCLUSIONS: The Co-Cr alloy guides with triple-constraint guiding structure can assist to prepare accurate guiding planes of RPD.

Preparing guiding planes for removable partial dentures: an in vitro comparison between assisted CAD-CAM template procedure and freehand preparation.

OBJECTIVES: To compare the trueness of computer-aided design and computer-aided manufacturing (CAD-CAM) assisted procedure and freehand procedure for preparing guiding planes for removable partial dentures (RPDs). METHODS: Forty identical mandibular resin casts were divided into two groups in which the guiding planes of two abutment teeth were prepared freehand (control group, n = 20) and using rigidly constrained templates (test group, n = 20). The template was designed on a digital cast of virtually prepared guiding planes and fabricated by selective laser melting using cobalt-chromium alloy. To assess the 3D trueness, all prepared guiding planes (Test data) were digitized using a laboratory scanner and compared to the virtually designed guiding planes (Reference data). The angle deviation between the Test data and the designed direction of the path of placement was measured for assessing the direction trueness of guiding plane preparation. RESULTS: The 3D trueness of guiding plane preparation was significantly better in the Test group (48.4 ± 12.9 µm) than in the Control group (128.5 ± 37.6 µm, p < 0.01). The direction trueness of guiding plane preparation was also significantly better in the Test group (1.20 ± 0.55°) than in the Control group (7.68 ± 3.00°, p < 0.01). CONCLUSIONS: The CAD-CAM template assisted procedure can significantly improve tooth preparation of the guiding planes compared to the freehand preparation. The CAD-CAM template could help clinicians prepare parallel guiding planes in a predictable manner.

Comparison of the accuracy (trueness and precision) of virtual dentofacial patients digitized by three different methods based on 3D facial and dental images.

STATEMENT OF PROBLEM: The accuracy of virtual dentofacial patients has been explored, but the accuracy of virtual patients established by using a straightforward and reliable method and the accuracy of different virtual patients are unclear. PURPOSE: The purpose of this clinical study was to compare the accuracy of virtual dentofacial patients digitized by using registered-block impression, exposed anterior teeth, and cone beam computed tomography (CBCT) reconstruction methods based on 3-dimensional (3D) facial and dental images. MATERIAL AND METHODS: From the 15 selected participants who needed CBCT scanning, 3 kinds of virtual dentofacial patients were established by using 3 registration methods based on digital dental casts: 3D facial images, CBCT data, and registered-block impression. Compared with actual measurement, 25 linear distances of all virtual dentofacial patients were selected and measured by using a software program, and 3 separate measurements were calculated by the same person. The 1-way analysis of variance (ANOVA) was used to compare the deviations among 3 kinds of virtual dentofacial patients (trueness) and the deviations within groups (precision). The 1-sample t test was used to compare the difference between the deviation and the ideal error of 0.00 (α=.05). RESULTS: Compared with the actual measurement, the trueness of the average deviations for registered-block impression (1.02 ±1.24 mm) was better than that of exposed anterior teeth (2.35 ±1.71 mm) and CBCT reconstruction (2.86 ±1.61 mm). The precision of the average deviations for registered-block impression (1.29 ±1.43 mm) was better than that of exposed anterior teeth (2.00 ±1.72 mm) and CBCT reconstruction (2.12 ±1.94 mm). Significant differences in trueness and precision were found among the 3 groups of virtual dentofacial patients (P<.01). Significant differences among the deviations of all linear distances and the ideal error of 0.00 were observed for all groups of virtual dentofacial patients (P<.05). CONCLUSIONS: The accuracy of registered-block impression was better than that of the exposed anterior teeth and CBCT reconstruction. The accuracy of exposed anterior teeth was lower than that of the other methods but could satisfy the requirements of clinical diagnostics and scientific methods. The accuracy of CBCT reconstruction was poor and could only be used for special situations that permitted low accuracy.

Biometry of width between labial transitional line angles in anterior teeth: an observational study.

PURPOSE: The maximum width between the mesial and distal labial transitional line angles, described as "esthetic width" herein, could significantly influence the visual perception of the teeth and smile. This study aimed to conduct biometric research on esthetic width and to explore whether regular distribution exists in the esthetic width of human teeth. MATERIALS AND METHODS: A total of 4,264 maxillary and mandibular anterior teeth were measured using the Geomagic studio software program. The proportions of maxillary to mandibular homonymous teeth and proportions between the adjacent teeth were calculated. Bilateral symmetry and the correlation between the esthetic and mesiodistal widths were both accounted for during the measurement procedures. RESULTS: The mean esthetic widths were 6.773 ± 0.518 mm and 4.329 ± 0.331 mm for maxillary and mandibular central incisors, respectively, 5.451 ± 0.487 mm and 5.008 ± 0.351 mm for maxillary and mandibular lateral incisors, respectively, and 3.340 ± 0.353 mm and 5.958 ± 0.415 mm for maxillary and mandibular canines, respectively. Except for the mandibular canines, no significant difference in esthetic width was found among homonymous teeth from the same jaw. A high linear correlation was found between the esthetic and mesiodistal widths of the same tooth, except for the maxillary canines. Esthetic width proportions among different tooth categories showed some regular patterns, which were similar to those of the mesiodistal width. CONCLUSION: Esthetic width is regularly distributed among the teeth in the Chinese population. This could provide an important reference for anterior dental restorations and dimension recovery in esthetic reconstruction of anterior teeth.

Mixed Reality and Haptic-Based Dental Simulator for Tooth Preparation: Research, Development, and Preliminary Evaluation.

BACKGROUND: Virtual reality (VR) dental simulators are currently used in preclinical skills training. However, with the development of extended reality technologies, the use of mixed reality (MR) has shown significant advantages over VR. OBJECTIVE: This study aimed to describe the research and development of a newly developed MR and haptic-based dental simulator for tooth preparation and to conduct a preliminary evaluation of its face validity. METHODS: A prototype of the MR dental simulator for tooth preparation was developed by integrating a head-mounted display (HMD), special force feedback handles, a foot pedal, computer hardware, and software program. We recruited 34 participants and divided them into the Novice group (n=17) and Skilled group (n=17) based on their clinical experience. All participants prepared a maxillary right central incisor for an all-ceramic crown in the dental simulator, completed a questionnaire afterward about their simulation experience, and evaluated hardware and software aspects of the dental simulator. RESULTS: Of the participants, 74% (25/34) were satisfied with the overall experience of using the Unidental MR Simulator. Approximately 90% (31/34, 91%) agreed that it could stimulate their interest in learning, and 82% (28/34) were willing to use it for skills training in the future. Differences between the 2 study groups in their experience with the HMD (resolution: P=.95; wearing comfort: P=.10), dental instruments (P=.95), force feedback of the tooth (P=.08), simulation of the tooth preparation process (P=.79), overall experience with the simulation (P=.47), and attitude toward the simulator (improves skills: P=.47; suitable for learning: P=.36; willing to use: P=.89; inspiring for learning: P=.63) were not significant. The Novice group was more satisfied with the simulator's ease of use (P=.04). There were significant positive correlations between the overall experience with the simulation and the HMD's resolution (P=.03) and simulation of the preparation process (P=.001). CONCLUSIONS: The newly developed Unidental MR Simulator for tooth preparation has good face validity. It can achieve a higher degree of resemblance to the real clinical treatment environment by improving the positional adjustment of the simulated patients, for a better training experience in dental skills.

The accuracy of a novel 3D digital evaluation method of intraoral fitness for removable partial dentures.

With the development of three-dimensional (3D) scanning and measurement technologies, the internal adaptation of restorations was measured by the 3D analysis method. The purpose of this study was to explore a novel 3D digital evaluation method to assess the intraoral fitness of removable partial dentures (RPDs) and evaluate the accuracy of this novel digital method in vitro. A 3D digital method to evaluate the clinical fitness of RPD was introduced. A standard stone cast of a partially edentulous mandible simulating the oral tissues and a corresponding RPD were used to evaluate the accuracy of this novel digital method (3D analysis on duplicated polyether cast) and another reported 3D digital evaluation method (3D analysis on RPD directly) for intraoral fitness of RPD in vitro. 12 polyvinyl siloxane (PVS) replica specimens were fabricated in each method in vitro, and the thicknesses of these PVS replicas were measured by 3D analysis on duplicated polyether cast (named Polyether group), 3D analysis on RPD directly (named Denture group), and 3D analysis on the stone cast (named Stone group), respectively. The thicknesses of PVS replicas were compared with analyses of variance (ANOVA) to evaluate the accuracy of these methods (α = 0.05). The accuracy based on the mean thickness of the PVS replicas of Polyether group were better than that of Denture group (P < 0.05) and had no statistical difference with that of Stone group (P > 0.05). 3D analysis on duplicated polyether cast has comparable trueness and precision to 3D analysis on the stone cast and is feasible for evaluating clinical fitness of RPD.

Interdisciplinary 3D digital treatment simulation before complex esthetic rehabilitation of orthodontic, orthognathic and prosthetic treatment: workflow establishment and primary evaluation.

BACKGROUND: An interdisciplinary treatment simulation and smile design before a complex esthetic rehabilitation is important for clinicians' decision-making and patient motivation. Meanwhile, intervention and interaction are necessary for dental specialists in these complex rehabilitations. However, it is difficult to visualize an interdisciplinary treatment plan by using the conventional method, especially when orthognathic surgery is involved, thus hindering communication between dental specialists. This research aims to establish a 3D digital workflow of interdisciplinary treatment simulation to solve this problem. METHODS: An interdisciplinary 3D digital workflow of simulated treatment plan for complex esthetic rehabilitation was established. Eleven patients were enrolled and illustrated with their treatment plans using 3D treatment simulation, as well as 2D digital smile design (DSD) plus wax-up. Visual analogue scales (VAS) were used to rate the intuitiveness, understanding, and satisfaction or help between the two methods by patients and dental specialists. RESULTS: According to the ratings from the patients, 3D treatment simulation showed obvious advantages in the aspects of intuitiveness (9.7 ± 0.5 vs 6.4 ± 1.4) and treatment understanding (9.1 ± 0.8 vs 6.6 ± 1.5), and the satisfaction rates were also higher (9.0 ± 0.6 vs 7.1 ± 1.8). Dental specialists regarded the 3D digital plans as more intuitive (8.9 ± 0.8 vs 5.9 ± 1.0) and useful to understand the plans from the other specialists (8.9 ± 0.7 vs 6.1 ± 1.0) and helpful to their own treatment plans (8.7 ± 0.9 vs 5.9 ± 1.4). CONCLUSIONS: The interdisciplinary 3D digital treatment simulation helps both patients and dental specialists to improve treatment understanding, and facilitates dental specialists for decision-making before complex esthetic rehabilitation. TRIAL REGISTRATION: This study was registered in the National Clinical Trials Registry under the identification number MR-11-20-002862. This is an observational study in which we did not assign the intervention.

Evaluation of accuracy and characteristics of tooth-color matching by intraoral scanners based on Munsell color system: an in vivo study.

To compare the accuracy of visual and instrumental methods for tooth-color matching based on three attributes in the Munsell color system and to investigate the characteristics of intraoral scanners for tooth-color matching. Shades of the cervical, middle, and incisal third region of 130 maxillary anterior teeth were matched visually by an experienced prosthodontist (EP) using Vita classical A1-D4 (VC) and Vita System 3D-Master (V3D) shade guides, and digitally by a spectrophotometer (Vita Easyshade V, VE) and two intraoral scanners (3Shape TRIOS 3, T3; TRIOS 4, T4). VE was used as a reference. The reproducibility of the three test groups was examined by repeating the measurements in triplicate. The overall trueness of the three test groups (from high to low) was T3 > EP > T4 for VC values (p < 0.01), and T3, EP > T4 (p < 0.01) for V3D. The trueness of T3 in incisal regions was lower than cervical and middle regions. When hue or lightness was correct, the mismatched chroma in test groups was smaller than VE (p < 0.01). The repeatability of EP was the poorest (p < 0.01). The color-matching trueness of T3 was higher than EP and T4. The reproducibility of intraoral scanners was better than visual methodology.

Three-dimensional digital evaluation of thickness accuracy of mock-ups fabricated by silicone matrices: An in vitro study.

PURPOSE: Although mock-ups have been widely used in dental esthetic rehabilitation, their accuracy has not been quantitatively evaluated, and the methods of fabricating mock-ups are various. This in vitro study investigated the thickness accuracy of mock-ups fabricated with different silicone matrices. METHODS: Mock-ups of maxillary anterior teeth were respectively fabricated by 72 silicone matrices that were equally divided into four groups (n=18 for each group) according to two variables of the silicone matrices: labial margin position (equigingival or cover labial gingiva for 1-2 mm) and palatal notches (with or without notches on the palatal side of silicone matrices). The thickness accuracy of the mock-ups was analyzed using 3D scanning and 3D deviation analysis techniques compared with diagnostic waxing. The thickness change ratios of the mock-ups were compared using a two-way analysis of variance (ANOVA). One-way ANOVA and Kruskal-Wallis tests were used to compare differences in thickness change ratios between different teeth in each group. RESULTS: The thickness accuracy of the mock-ups was significantly affected by the labial margin position and the palatal notches of the silicone matrices, respectively, in the labial area and the incisal area. The most accurate mock-ups were made using silicone matrices with equigingival labial margins and palatal notches. The thickness accuracy of the mock-ups was also inconsistent on different teeth. CONCLUSION: The mock-ups fabricated by silicone matrices were thicker than the diagnostic waxing. The application of silicone matrices to equigingival labial margins and palatal notches was beneficial to the thickness accuracy of mock-ups.

Baseline selection for evaluation of peri-implant soft tissue changes: a clinical trial.

BACKGROUND: To select the optimal baseline for evaluation of peri-implant soft tissue changes among 1, 2, and 3 weeks after definitive crown insertion. METHODS: A total of 22 individuals who required implant restoration were recruited to this study. Each participant received a screw-retained conventional implant restoration. Peri-implant soft tissue was captured by an intraoral scanner and analyzed by 3D analysis software. Soft tissue changes [mucosal margin (MM) and soft tissue thickness (STT)] on the buccal side of implant sites were evaluated at 1, 2, and 3 weeks after definitive crown insertion. One-way analysis of variance (ANOVA) for repeated measurement and Tukey's test were used to analyze significant differences between the 3 time points (α=0.05). RESULTS: An increased volume of peri-implant soft tissue was observed shortly after definitive crown insertion. Based on the findings of peri-implant soft tissue changes, significant differences were observed between weeks 1 and 2 (P<0.01), and weeks 1 and 3 (P<0.01), while there was no significant difference between weeks 2 and 3 (P>0.05). CONCLUSIONS: Minimal peri-implant soft tissue changes occurred in this study. The time point of 2 weeks after definitive crown insertion was preliminarily selected as the baseline. The small sample size and few time points must be taken into consideration when interpreting these findings. TRIAL REGISTRATION: This study was retrospectively registered in the Chinese Clinical Trial Registry (Registration number: ChiCTR2000037954; Date of registration: 6 September 2020).