Recent Advances in Material and Geometrical Modelling in Dental Applications

This article touched, in brief, the recent advances in dental materials and geometric modelling in dental applications. Most common categories of dental materials as metallic alloys, composites, ceramics and nanomaterials were briefly demonstrated. Nanotechnology improved the quality of dental biomaterials. This new technology improves many existing materials properties, also, to introduce new materials with superior properties that covered a wide range of applications in dentistry. Geometric modelling was discussed as a concept and examples within this article. The geometric modelling with engineering Computer-Aided-Design (CAD) system(s) is highly satisfactory for further analysis or Computer-Aided-Manufacturing (CAM) processes. The geometric modelling extracted from Computed-Tomography (CT) images (or its similar techniques) for the sake of CAM also reached a sufficient level of accuracy, while, obtaining efficient solid modelling without huge efforts on body surfaces, faces, and gaps healing is still doubtable. This article is merely a compilation of knowledge learned from lectures, workshops, books, and journal articles, articles from the internet, dental forum, and scientific groups' discussions

A finite element study on stress distribution of two different attachment designs under implant supported overdenture

Objective: This study aimed to evaluate stress patterns generated within implant-supported mandibular overdentures retained by two different attachment types: ball and socket and locator attachments. Materials and methods: Commercial CAD/CAM and finite element analysis software packages were utilized to construct two 3D finite element models for the two attachment types. Unilateral masticatory compressive loads of 50, 100, and 150 N were applied vertically to the overdentures, parallel to the longitudinal axes of the implants. Loads were directed toward the central fossa in the molar region of each overdenture, that linear static analysis was carried out to find the generated stresses and deformation on each part of the studied model. Results: According to FEA results the ball attachment neck is highly stressed in comparison to the locator one. On the other hand mucosa and cortical bone received less stresses under ball and socket attachment. Conclusions: Locator and ball and socket attachments induce equivalent stresses on bone surrounding implants. Locator attachment performance was superior to that of the ball and socket attachment in the implants, nylon caps, and overdenture. Locator attachments are highly recommended and can increase the interval between successive maintenance sessions. Keywords: Ball and socket attachment, Locator attachment, Finite element analysis, Implant supported overdentur

A finite element study on the mechanical behavior of reciprocating endodontic files

evaluate the mechanical behavior of reciprocating endodontic files, comparing nickeltitanium (NiTi) and stainless steel 316L (St.St. 316L) as manufacturing material for such instruments. Methods: A three-dimensional finite element model was designed for this study. The simplified instrument model geometry was created on commercial CAD/CAM software. Real strain stress curves of St.St. 316L and NiTi were used in the analysis. Non-linear static analysis was performed to simulate the instrument inside root canal at an angle of 45° in the apical portion, and subjected to torsion of 0.3 N.cm. Results: Non-linear NiTi material showed super elasticity and high functionality in such applications. Very high levels of stress appeared in the file at 3 mm from the tip close to yield point. Conclusions: St. St. 316L is not suitable for manufacturing reciprocating instruments. Modeling of the instrument with equivalent circular cross-sectional area did not affect results quality. Reciprocating instruments have short lifespan, thus manufacturers recommend using one file per tooth. Reciprocating instruments are recommended for less experienced dentist

The Effect of Surface Treatments on the Shear Bond Strength of Indirect Esthetic Restorative Materials to Dentin

AIM: The purpose of this research was to evaluate the influence of air abrasion, hydrofluoric acid, and combination of air abrasion and hydrofluoric acid on the shear bond strength between dentin and CEREC, VITA VM7, and E-max. MATERIAL AND METHODS: Ninety extracted human lower molars were used. The teeth were divided into three groups (n = 30) according to the surface treatment (air abrasion, hydrofluoric acid, and air abrasion + hydrofluoric acid). Each group was then subdivided into three subgroups (n = 10) according to the ceramic material (CEREC, E-max, and VITA VM7). Shear bond strength was determined by the compressive mode of force applied at the ceramic-tooth interface. The collected data were analysed using two-way analysis of variance (ANOVA), and Tukey’s post-hoc test statistical significance was set at P < 0.05. RESULTS: The highest mean shear bond strength value was recorded with the CEREC group treated by hydrofluoric acid (8.01MPa). While the least mean shear bond strength was recorded with the Cerec group but when treated by air abrasion alone, it was 4.33MPa. CONCLUSION: Hydrofluoric acid etching for various types of ceramic restoration improved the bond strength to dentin

Determinants of COVID-19 Vaccine Acceptance among Dental Professionals: A Multi-Country Survey

Purpose: This study sought to investigate the acceptance rate and associated factors of COVID-19 vaccines among dentists and dental students in seven countries. Material and Methods: A structured questionnaire prepared and guided by the report of the SAGE Working Group on Vaccine Hesitancy was distributed among groups of dentists and dental students in seven countries across four continents. Results: A total of 1527 subjects (850 dentists and 677 dental students) participated in this survey. Although 72.5% of the respondents reported their intention to accept COVID-19 vaccines (dentists: 74.4%, dental students: 70.2%), there was a significant difference in agreement between dentists/dental students across countries; generally, respondents in upper-middle-, and high-income countries (UM-HICs) showed significantly higher acceptance rates compared to those in low- and lower-middle income countries (L-LMICs). Potential predictors of higher vaccine acceptance included being a dentist, being free of comorbidity, being well-informed about COVID-19 vaccines, having better knowledge about COVID-19 complications, having anxiety about COVID-19 infection, having no concerns about the side effects of the produced vaccines and being a resident of an UM-HIC. Conclusion: The results of our survey indicate a relatively good acceptance rate of COVID-19 among the surveyed dentists and dental students. However, dentists and dental students in L-LMICs showed significantly lower vaccine acceptance rates and trust in COVID-19 vaccines compared to their counterparts in UM-HICs. Our results provide important information to policymakers, highlighting the need for implementation of country-specific vaccine promotion strategies, with special focus on L-LMICs