Reopening of a school of dentistry in the era of COVID-19 pandemic, "Step-by-step" approach.

INTRODUCTION: The COVID-19 pandemic has a great impact on all aspects of higher education worldwide. In Iran, after several months of lockdown, all dental schools coped with the challenge of "reopening." School of Dentistry of Tehran University of Medical Sciences (TUMS) planned to facilitate the process of reopening using a "step-by-step" approach. The aim of this study was sharing our experiences of reopening of the school during the pandemic. METHODS: TUMS School of Dentistry planned a "step-by-step" approach of reopening of school to both provide infrastructure of online education for theoretical credits and reassure all staff and students about infection control for practical courses. Also, a two-section survey on students' satisfaction with a variety of aspects of reopening process and the clinical performance of students in different clinical courses was conducted. RESULTS: Findings showed 65.1% of the students, attended the survey, were satisfied with reopening of the school. Also, 86.4% were satisfied with the new online method of education for theoretical courses. Regarding personal protective equipment (PPE) provided for the students, 22.9% and 56.5% of them were satisfied and moderately satisfied, respectively. Additionally, 78.2% of the students were satisfied with the newly developed online assessment method. CONCLUSION: Although reopening of schools during COVID-19 pandemic seems enigmatic for all authorities and students, the "step-by-step" plan designed by TUMS School of dentistry including emotional and infrastructural prerequisites might be a reliable method for all people, who are in charge of management of dental school in uncertain crisis.

Marginal and internal adaptation of single crowns and fixed dental prostheses by using digital and conventional workflows: A systematic review and meta-analysis.

STATEMENT OF PROBLEM: Digital and conventional options for definitive impressions and for the fabrication of fixed dental prostheses (FDPs) have been compared in previous studies. However, a comprehensive review with concluding data that determined which method provided the minimal internal and marginal adaptation is lacking. PURPOSE: The purpose of this systematic review and meta-analysis of in vivo and in vitro studies was to compare the marginal and internal adaptation of complete-coverage single-unit crowns and multiunit FDPs resulting from digital and conventional impression and fabrication methods. MATERIAL AND METHODS: The review protocol was registered in International Prospective Register of Systematic Reviews (PROSPERO) and followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. PubMed, Cochrane Trials, Scopus, and Open Grey databases were used to identify relevant articles. Based on fixed prostheses impression and fabrication methods, groups from each study were categorized into 4 groups: conventional impression and fabrication (CC), conventional impression and digital fabrication (CD), digital scanning and conventional fabrication (DC), and digital scanning and fabrication (DD). The risk of bias was assessed by using the Cochrane Collaboration tool for clinical trials and the modified Methodological Index for Non-Randomized Studies (MINORS) for in vitro studies. Heterogeneity was evaluated among studies, and meta-analysis was performed with random-effect models (α=.05). Subgroup analysis was conducted when possible. RESULTS: Eight clinical trials and 21 in vitro studies were eligible for analysis. There was no significant difference between the CD and DD clinical groups for marginal adaptation (P=.149); However, the DD group had significantly less internal discrepancy than the CD group (P=.009). The in vitro studies found no significant difference in marginal adaptation among the CC-CD, CC-DC, and CC-DD pairs (P=.437, P=.387, P=.587), but in the comparison CD versus DD group, a significantly better marginal adaptation was observed for the DD group (P=.001). All the compared in vitro groups were similar in terms of internal adaptation. CONCLUSIONS: Impression and fabrication techniques may affect the accuracy of fit of complete-coverage fixed restorations. A completely digital workflow yielded restorations with comparable or better marginal adaptation than the other methods.

In Vivo and In Vitro Comparison of Internal and Marginal Fit of Digital and Conventional Impressions for Full-Coverage Fixed Restorations: A Systematic Review and Meta-analysis.

PURPOSE: This study aims to evaluate digital and conventional impressions for full-coverage restorations in terms of marginal and internal discrepancies. STUDY SELECTION: The analysis included in vivo and in vitro studies reporting the marginal or internal gap of full-coverage restorations that provide both the conventional and digital impression. The PubMed, Cochrane Trials, and Scopus databases were searched. The quality of clinical trials was rated using Cochrane Collaboration's tool, and the quality of the evidence was evaluated using the Grading of Recommendations, Assessment, Development, and Evaluation tool. Heterogeneity among the studies was evaluated, and a meta-analysis with subgroup analysis was conducted whenever it was possible. RESULTS: Thirty-three articles (8 prospective clinical trials and 26 in vitro studies) were selected to extract data after applying the predefined selection criteria. The standard mean difference (SMD) of the meta-analysis for marginal adaptation was -0.76 (95% confidence interval: -1.23 to -0.29) and -0.59 (95% confidence interval: -0.93 to -0.24) for in vitro and in vivo studies, respectively, indicating digital impressions provided significantly less marginal gap than conventional impressions in in vitro studies (P = .002). The impression technique did not significantly influence the internal adaptation. CONCLUSIONS: Differences in marginal adaptation between the digital and conventional groups are not significant for in vivo studies, but for in vitro studies, the digital impression resulted in better marginal adaptation. Based on the Grading of Recommendations, Assessment, Development, and Evaluation approach for marginal adaptation, clinical studies were classified as high confidence and in vitro studies were graded moderate because of the inconsistency. Furthermore, high-quality studies are needed to confirm our results (the International Prospective Register of Systematic Reviews; CRD42017077925).

Prosthetic rehabilitation of an edentulous patient with microstomia using digital and conventional methods: A case report.

This study describes prosthetic rehabilitation an edentulous patient with microstomia. Maxillary preliminary and definitive impression were made by intraoral scanning and custom 2-piece impression tray respectively to fabricate conventional denture.

Comparison of the marginal and internal fit of PMMA interim crowns printed with different layer thicknesses in 3D-printing technique.

OBJECTIVE: The aim of this in vitro study was to compare the effect of printing layer thickness on the marginal and internal fit of interim crowns. MATERIAL AND METHODS: A maxillary first molar model was prepared for ceramic restoration. Thirty-six crowns were printed with three different layer thicknesses using a digital light processing-based three-dimensional printer (25, 50, and 100 µm [LT 25, LT 50, and LT 100]). The marginal and internal gaps of the crowns were measured with replica technique. An analysis of variance was conducted to determine if there were significant differences between the groups (ɑ = .05). RESULTS: The marginal gap of LT 100 group was significantly higher than that LT 25 (p = .002) and LT 50 groups (p ≤ .001). The LT 25 group has significantly larger axial gaps than LT 50 group (p = .013); however, there were no statistically significant differences between other groups. The LT 50 group showed the smallest axio-occlusal gap. The mean occlusal gap differed significantly by printing layer thickness (p ≤ .001), with the largest gap occurring for LT 100. CONCLUSIONS: Provisional crowns printed with 50 µm layer thickness provided the best marginal and internal fit. CLINICAL SIGNIFICANCE: It is recommended that provisional crowns be printed with a 50 µm layer thickness to ensure optimal marginal and internal fit.

Comparison of marginal and internal adaptation of provisional polymethyl methacrylate restorations fabricated by two three-dimensional printers: An in vitro study.

Background: Chairside fabrication of provisional restorations using three-dimensional (3D) printers is rising in digital dentistry. The purpose of this research was to compare the marginal and internal adaptation of provisional polymethyl methacrylate (PMMA) restorations fabricated by two different 3D printers. Materials and Methods: In this in vitro investigation, an intact maxillary 1st molar acrylic model was first digitalized by a laboratory scanner. It was then prepared for an all-ceramic restoration and scanned again by the same scanner. The final restoration was designed in Exocad according to the scan files with a 50 µm cement gap. PMMA restorations were printed by two 3D printers; Group 1: Asiga (n = 10) and Group 2: Digident (n = 10). The replica technique was used to assess the marginal and internal fit of the restorations, and one-way ANOVA was used to analyze the data. P <0.05 was regarded as statistically significant. Results: The mean marginal gap of crowns in Group 1 was significantly lower than that of Group 2 (75 vs. 195 µm, P = 0.001). Regarding internal adaptation, no significant difference was found between the axial gap values in both groups (P > 0.05). The mean occluso-axial gap (90 vs. 140 µm, P = 0.026) and the mean occlusal gap (116 vs. 300 µm, P = 0.001) of crowns in Group 1 were significantly smaller compared to the equivalent values in Group 2. Conclusion: Provisional PMMA crowns fabricated by the Asiga printer showed significantly higher marginal and internal adaptation than those manufactured by Digident at all points except for the axial surface.

Effect of Clinical Rotation Timing on Learning Quality of Dental Students.

Objective: Dental educational curricula are under constant modification and improvement. However, designing a comprehensive, efficient, and flexible curriculum is still challenging for the authorities. An efficient curriculum should obviate the educational needs of students and promote their knowledge and expertise for future practice. Time planning of clinical rotations is highly important for optimization of the learning process. This study aimed to compare the efficacy of two different timing models of clinical rotations, namely four versus two rotations in each semester. Materials and Methods: A total of 74 dental students and 54 faculty members of Tehran University of Medical Science that experienced both rotation models for two consecutive years (2018 and 2019) participated in this study. A questionnaire was designed to assess different aspects of the two timing-models. Results: A one-sample t-test indicated that students' and faculty members' mean perception were significantly better regarding the two-rotation program. Conclusion: This study indicated that changing the time planning of educational rotations can affect different aspects of education.

Rehabilitation of a deep bite patient with worn dentition using minimally invasive approach: A 3-year follow-up.

Full mouth rehabilitation of severely worn teeth represents a challenging situation for dental clinicians. This case report describes the minimally invasive interdisciplinary approach for treatment of severely worn dentition with a loss of vertical dimension of occlusion. After 3 years of follow-up, no complication was observed.

The Effect of Sandblasting on Bond Strength of Soft Liners to Denture Base Resins: A Systematic Review and Meta-Analysis of In Vitro Studies.

OBJECTIVES: This study aimed to evaluate the effect of sandblasting on the bond strength of denture base resin to soft liners. MATERIALS AND METHODS: This report follows the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. PubMed, Embase, Cochrane, Scopus, and OpenGrey databases were searched for in vitro studies that compared sandblasting with no treatment in terms of the tensile, shear, and peel bond strength of resilient lining materials (acrylic-based or silicone-based) to polymethyl methacrylate denture base resin. Based on the outcome, the analysis was carried out in three groups of tensile, shear, and peel bond strength. Subgroup analysis was done for the effect of size of particles on sandblasting, blasting pressure, and type of soft liner whenever possible. Heterogeneity was evaluated among the studies, and meta-analysis was performed with random effect models (p < .05). RESULTS: After screening, 16 articles met the inclusion criteria for meta-analyses. No treatment showed significantly higher tensile (p < 0.001) or peel (p=0.04) bond strength, although shear bond strength of sandblasted resin was significantly better (p=0.008). Results of subgroup analyses of particle size favored the control group in 50 µ Al2O3 particle size (p < 0.001). In analyses of blasting pressure, the control group had significantly better tensile bond strength than specimens with blasting pressure ≤1 bar (p < 0.001) while specimens with blasting pressure beyond 1 bar showed significantly more tensile strength than control group (p=0.03). In silicon-based liners, groups without any surface treatment had significantly higher tensile bond strength (p < 0.001). CONCLUSION: According to the in vitro studies, sandblasting would not lead to significant increase in bond strength of soft liner to the denture base resin.

Comparative Evaluation of the Internal and Marginal Adaptations of CAD/CAM Endocrowns and Crowns Fabricated from Three Different Materials.

PURPOSE: To evaluate and compare the internal and marginal adaptations of chairside CAD/CAM (CEREC) endocrowns and crowns fabricated from lithium disilicate glass-ceramic (IPS e.max CAD), zirconia-reinforced lithium silicate glass-ceramic (VITA Suprinity), and hybrid ceramic (VITA Enamic). MATERIALS AND METHODS: Dental models of the two first maxillary molars were selected. One was prepared for an endocrown, and the other for a standard all-ceramic crown. A total of 72 CAD/CAM restorations, including 36 endocrowns and 36 crowns made of IPS e.max CAD, VITA Suprinity, and VITA Enamic (n = 12 each), were fabricated. Discrepancies were measured in the buccal, mesial, lingual, and distal aspects of three sites (marginal, mid-axial wall, and occlusal/floor) using the noncontact ATOS scanner. Statistical analysis was performed using MANOVA and between-subject effects tests (α = .05). RESULTS: Mesial axial wall discrepancy was significantly lower in endocrowns compared to occlusal discrepancy in crowns, while distal axial wall discrepancy was significantly higher. Moreover, floor discrepancy was found to be significantly lower in endocrowns compared to crowns. However, type of material had no significant effect on any kind of discrepancy. CONCLUSION: The marginal and internal adaptation values were within a clinically acceptable range for both kinds of restoration and all three materials. However, restoration type (crown vs endocrown) was significantly different in the mesial and distal axial wall and occlusal/floor discrepancies, regardless of restoration material.

Dental care management during the COVID-19 outbreak.

AIM: The level of preparedness of the healthcare system plays an important role in management of coronavirus disease 2019 (COVID-19). This study attempted to devise a comprehensive protocol regarding dental care during the COVID-19 outbreak. METHODS AND RESULT: Embase, PubMed, and Google Scholar were searched until March 2020 for relevant papers. Sixteen English papers were enrolled to answer questions about procedures that are allowed to perform during the COVID-19 outbreak, patients who are in priority to receive dental care services, the conditions and necessities for patient admission, waiting room and operatory room, and personal protective equipment (PPE) that is necessary for dental clinicians and the office staff. CONCLUSION: Dental treatment should be limited to patients with urgent or emergency situation. By screening questionnaires for COVID-19, patients are divided into three groups of (a) apparently healthy, (b) suspected for COVID-19, and (c) confirmed for COVID-19. Separate waiting and operating rooms should be assigned to each group of patients to minimize the risk of disease transmission. All groups should be treated with the same protective measures with regard to PPE for the dental clinicians and staff.

How adjustment could affect internal and marginal adaptation of CAD/CAM crowns made with different materials.

PURPOSE: Recently introduced hybrid and reinforced glass ceramic computer-aided design/computer-aided manufacturing (CAD/CAM) materials have been used for full-coverage restorations. However; the effect of adjustment and type of materials on internal and marginal adaptation are unknown. This study aimed to evaluate and compare the marginal and internal adaptations of crowns made of three different CAD/CAM materials before and after adjustment. MATERIALS AND METHODS: One acrylic resin maxillary first molar was prepared and served as the master die. Thirty-six restorations were fabricated using CAD/CAM system (CEREC Omnicam, MCXL) with three materials including lithium disilicate (IPS e.max CAD), zirconia-reinforced lithium silicate (Suprinity), and hybrid ceramic (Enamic). Internal and marginal adaptations were evaluated with the reference point matching technique before and after adjustment. The data were analyzed using mixed ANOVA considering α=.05 as the significance level. RESULTS: The effect of adjustment and its interaction with the restoration material were significant for marginal, absolute marginal, and occlusal discrepancies (P<.05). Before adjustment, Suprinity had lower marginal discrepancies than IPS e.max CAD (P=.18) and Enamic (P=.021); though no significant differences existed after adjustment. CONCLUSION: Within the limitations of this study, crowns fabricated from IPS e.max CAD and Suprinity resulted in slightly better adaptation compared with Enamic crowns before adjustment. However, marginal, axial, and occlusal discrepancies were similar among all materials after the adjustment.

Comparison of three-dimensional digital technique with two-dimensional replica method for measuring marginal and internal fit of full coverage restorations.

PURPOSE: This study compared digital (reference point matching) and replica methods for measuring marginal and internal fit of full coverage restorations. MATERIALS AND METHODS: A maxillary left first molar typodent was fixed on to an aluminum base and prepared to receive all-ceramic full coverage restoration. The model was scanned with an intraoral scanner (CEREC Omnicam, Sirona, York, PA, USA). Twelve crowns were fabricated from lithium disilicate blocks (IPS emax CAD, Ivoclar Vivadent) and then crystalized. Marginal and internal fit of each restoration was measured by two examiners using replica and a new digital three-dimensional technique. Reliability between the two methods and two examiners was assessed by correlation and Cronbach's Alpha coefficient (P<.05). A Bland-Altman assessment for agreement was used to compare the two methods. RESULTS: Bland-Altman assessment showed that the mean of difference for marginal, absolute marginal, and axial gap was respectively -1.04 µm, -41.9 µm, and -29.53 µm with limit of agreement (LOA) between -37.26 to 35.18 µm for marginal, -105.85 to 22.05 µm for absolute marginal and -80.52 to 22.02 µm for axial gap. Positive correlation for repeatability (P<.05) in determining marginal and internal gaps by the two examiners in both techniques was revealed. Reliability of both techniques in all sites of measurements was at least good (0.8 ≤ α < 0.9). CONCLUSION: Both measuring techniques appeared highly reliable for evaluating fit of fixed dental restorations, while reference point matching provided higher values in axial and absolute marginal gap assessment.

Implant-Retained Nasal Prosthesis with Bar and Clip for a Patient with Total Rhinectomy: A Clinical Report.

The present clinical report describes the fabrication of an implant -retained prosthesis with bar and clip retention for a patient with total rhinectomy due to basal cell carcinoma (BCC). The nasal prosthesis was retained on the face by a reverse Y-shaped bar with horizontal and vertical extensions, resulting in favorable retention and function.

Three-Dimensional Accuracy of Digital Impression versus Conventional Method: Effect of Implant Angulation and Connection Type.

PURPOSE: The aim of this in vitro study was to compare the accuracy of different implant impression techniques of the maxillary full arch with tilted implants of two connection types. MATERIALS AND METHODS: Two maxillary edentulous acrylic resin models with two different implant connections (internal or external) served as a reference model. Each model had two anterior straight and two posterior angulated implants. Ninety impressions were made using an intraoral scanner (Trios 3Shape) with scan bodies for digital impression (groups DII and DIE), a custom open tray with additional silicone for the conventional direct group (groups CDI and CDE), and a custom closed tray with additional silicone for the conventional indirect group (groups CII and CIE) from both internal and external models, respectively. A coordinate-measuring machine (CMM) was used to measure linear and angular displacement for conventional specimens. For digital groups, an optical CMM was used to scan the reference model. STL data sets from the digital specimen were superimposed on STL reference data sets to assess angular and linear deviations. Data were analyzed with three-way ANOVA and t-test at α=0.05. RESULTS: There were significant angular and linear distortion differences among three impression groups (P < 0.001), angular distortion differences between internal and external connections (P < 0.001), and between straight and tilted implants for either linear (P < 0.001) or angular (P=0.002) distortion. The type of the connection and implant angle did not have any effect on linear and angular distortion of the digital technique (p > 0.05). Minimum angular and linear distortion was seen for tilted implants in DII and DIE groups (0.36° ± 0.37 and 0.16 ± 0.1 mm). CONCLUSION: Impression techniques (digital versus conventional) affected the transfer accuracy. Digital techniques demonstrated superior outcome in comparison with conventional methods, and the direct technique was better than the indirect conventional technique. Connection type and implant angulation were other factors that influenced accuracy. However, when digital impression was applied, accuracy was not affected by the type of connection and angulation.