Effect of platform switching on peri-implant bone: A 3D finite element analysis.

STATEMENT OF PROBLEM: A consensus regarding the effects of platform switching on peri-implant marginal bone levels is lacking. Finite element studies have reported contradictory results. PURPOSE: The purpose of this finite element analysis study was to evaluate stress distribution in platform-switched (PS) and platform-matched (PM) implants and their surrounding bone. MATERIAL AND METHODS: An implant (4.5×11 mm) was modeled and screwed into a human mandibular bone block using a computer-aided design (CAD) software program. Two separate models were generated: (1) PM, 4.5-mm implant with 4.5-mm-wide abutment and (2) PS, 4.5-mm implant with 3.5-mm-wide abutment. Implant components were modeled with linear isotropic properties and bones with anisotropic properties. Vertical (200 to 800 N) and oblique (50 to 150 N) forces were applied to each model to simulate occlusal loads. Linear elastic analysis was performed using ANSYS Workbench 16. von Mises equivalent stresses in the implant assemblies and peri-implant bone were calculated and compared with independent samples t test (α=.05). RESULTS: von Mises equivalent stress values under simulated axial and nonaxial occlusal loads were lower for PM than for PS implant assemblies. However, the differences were not statistically significant. Stress within the peri-implant bone was significantly higher for the PM group than for the PS group (P<.001). CONCLUSIONS: Platform switching decreased stress within peri-implant bone and may help limit marginal bone resorption.

Ceramic Fracture in Metal-Ceramic Restorations: The Aetiology.

All dental restorations are liable to failure during function. Failure could be biologic, aesthetic, mechanical or a combination. Ceramic restorations in particular, including metal-ceramics, are prone to mechanical fracture, especially the fracture of veneering porcelain. Fracture of a metal-ceramic restoration jeopardizes function as well as aesthetics. It is equally onerous to manage for both patient and dentist. Optimal management of such cases requires a detailed knowledge of the aetiology behind this phenomenon. The current paper aims to highlight possible causative factors involved in the mechanical failures of metal-ceramic restorations. Clinical relevance: Ceramic fracture in metal-ceramic crowns and fixed partial dentures is routinely encountered in dental clinics. Knowledge of the aetiology is required to diagnose and manage such cases accurately as well as to avoid these errors in future.

Antibacterial activities of Diospyros blancoi, Phoenix dactylifera and Morus nigra against dental caries causing pathogens: An in vitro study.

The study was undertaken to determine the in-vitro antibacterial potential of Diospyrosblancoi, Phoenix dactylifera and Morusnigra leaf extracts in hexane, chloroform, methanol, ethyl-acetate and aqueous extracts against dental caries causing bacteria. Disc diffusion assay was used to determine the antibacterial efficacy; the extracts were further separated using Thin Layer Chromatography and the anti-biofilm activity of the extracts was also determined. The preliminary phytochemical screening of the extracts revealed the presences of flavonoids, saponins, alkaloids and tannins because of which the extracts showed strong antibacterial activity against the selected pathogens. The ethyl-acetate extracts showed maximum inhibitory effect on biofilm formation by S. mutans.96% inhibition was observed in methanol extract of Diospyrosblancoi, and 95% in ethyl acetate extract. The results evidenced that the plants inhibit the growth of oral bacteria responsible for dental caries with their abundance source of secondary metabolites and can be used as an alternative treatment for caries, thus minimizing the antibiotics used to treat the disease in local medicine.

An Analysis of Maxillary Anterior Teeth Crown Width-Height Ratios: A Photographic, Three-Dimensional, and Standardized Plaster Model's Study.

OBJECTIVE: To analyze the width and height ratios of maxillary anterior teeth at different crown levels through photographs, 3D, and plaster dental model techniques in a subset of the Pakistani population. Material and Methods. This clinical study consisted of 230 participants. The maxillary impression, standardized photographs, and models were constructed for crown width and height analysis. The SPSS version 25 was used for statistical analysis. Descriptive statistics were carried out for mean, standard deviation, and percentage calculation of teeth width and height, gender, and age of participants. Paired t-test analysis was carried out to compare the dependent variables (teeth size, width, and height ratios) with independent variables (techniques applied, side disparity). A p value of ≤ 0.05 was considered statistically significant. RESULTS: The mean width and height of maxillary anterior teeth obtained through photographs, 3D, and plater models were statistically different. The 3D dental model analysis showed reliable and accurate results. The mean width and height ratio of teeth were different on both sides of the arch. There was a significant difference (p = 0.001) in crown width-height ratios at different crown levels. CONCLUSION: The width and height ratios in the studied population were different at various crown levels. The dimensions of teeth varied from the incisal to the cervical part of the crown. Hence, rather than relying on a single, fixed ratio of 78% to 80% suggested by researchers for anterior teeth, the clinician should adopt different crown width-height ratios to restore teeth with the optimum esthetic outcome.

The Analysis of Facio-Dental Proportions to Determine the Width of Maxillary Anterior Teeth: A Clinical Study.

The present study aimed to analyze mid horizontal facial third proportions, those being the interpupillary, inner intercanthal, and bizygomatic distance modified with golden proportion, The Preston proportion, golden percentage and 70% recurring esthetic dental proportion were used for determining maxillary anterior teeth width. A total of 230 participants took part in this study. The front dental and facial photographs along dental stone cast which were converted to three-dimensional (3D) models were used for evaluation. The mid horizontal facial third proportions showed no significant relationship with maxillary anterior teeth width without modification with dental proportions. Whereas, with modification, no statistically significant difference was found between inner-intercanthal distance by golden percentage and width of central incisors. The bizygomatic distance was greater than intercanine distance. While the interpupillary distance by golden proportion was found to be consistent with intercanine distance in female participants. The modified anterior teeth width was significantly different from measured values, when determined by using the three mid facial proportions with Preston and 70% recurring esthetic dental (RED) proportion. Furthermore, the measured width of maxillary anterior teeth showed no difference when plaster dental casts widths were compared with 3D models. The interpupillary, inner-intercanthal, and bizygomatic distance should not be directly used to determine maxillary anterior teeth width. While maxillary anterior teeth width can be determined by modifying the inner inter-canthal distance with golden percentage and interpupillary distance with golden proportion. Moreover, the midfacial third proportions modified with Preston and 70% recurrent esthetic dental proportion were found to be unreliable for the determination of maxillary anterior teeth widths.

COVID-19 Era: Challenges and Solutions in Dental Education.

Coronavirus infecious disease 2019 (COVID-19) pandemic has brought a myriad of challenges to the dental education. Amidst the quarantine and lockdown measures, face-to-face education is disrupted around the globe. Dental educators have come up with innovative solutions to resume dental education remotely. Different online platforms are being utilised for didactic teaching and learning as well as for students 2019; assessment and examination. Clinical learning has also shifted to virtual learning. Manikins and virtual reality/augmented reality (VR/AR)-based simulation devices along with haptic technology can be very helpful for skills training. However, some sorts of blended learning and virtual curriculum may be incorporated in dental education in the future. For this narrative review, a thorough in-depth review of the available literature, relevant to our field, was carried out. In this article, impact of COVID-19 on dental education has been discussed along with some solutions to these challenges. Key Words: COVID-19, Dental education, E-learning, Virtual/augmented reality.

Platform-Switching to Preserve Peri-Implant Bone: A Meta-Analysis.

The objective of this meta-analysis was to determine the literature-based evidence if platform-switching has an effect in preventing marginal bone loss around prosthodontic implants following their functional loading in comparison to conventional platform-matching. A systematic literature search was performed on PubMed, Science Direct, Google Scholar for Literature from 1950 to January 2015, human randomized clinical trials (RCTs) and prospective clinical controlled cohort studies (PCCS) reporting marginal bone loss around platform-switched and matched implants. Six RCTs with a low risk of bias revealed a significantly less mean marginal bone loss (0.57 mm [CI 95% 0.30; 0.84]) around platform-switched implants in comparison to platform-matched implants [1.14 mm (CI 95% 0.69; 1.6, p &lt; 0.001)]. The meta-analysis revealed a significantly less peri-implant marginal bone loss with platform-switched implants as compared to platform-matched implants. The qualitative analysis depicts a trend favouring the platform-switching technique over platform- matching technique to prevent marginal bone loss. However, owing to the heterogeneity of the included studies, their results necessitate cautious interpretation.

Chemical and morphological characteristics of mineral trioxide aggregate and Portland cements.

The purpose of this study was to investigate the chemical composition and particle morphology of white mineral trioxide aggregate (WMTA) and two white Portland cements (CEM 1 and CEM 2). Compositional analysis was performed by energy dispersive X-ray spectroscopy, X-ray fluorescence spectrometry and X-ray diffraction whereas, morphological characteristics were analyzed by scanning electron microscope and Laser scattering particle size distribution analyzer. The elemental composition of WMTA, CEM 1 and CEM 2 were similar except for the presence of higher amounts of bismuth in WMTA. Calcium oxide and silicon oxide constitute the major portion of the three materials whereas, tricalcium silicate was detected as the major mineral phase. The particle size distribution and morphology of WMTA was finer compared to CEM 1 and CEM 2. The three tested materials had relatively similar chemical composition and irregular particle morphologies.