AIM: Evaluation of the push-out bond strength (PBS) of zirconia post-bonded to radicular dentin after using different final irrigants (MTAD, Malachite green (MG), Ti-sapphire laser and Salvadora persica (S.persica). MATERIAL AND METHOD: Forty human permanent single-rooted were decoronated above the cement-enamel junction. An experienced endodontist performed all the root canal instrumentation using ProTaper universal rotary files. Canals were irrigated using 5.25% NaOCl solution followed by EDTA as a final sterilant. Obturation with gutta-percha using AH Plus sealer was performed. Post-space preparation was completed using Gates Glidden and specimens were randomly assigned to four groups based on the final disinfectant received (n=10). Group 1: 5.25% NaOCl + MTAD, group 2: 5.25% NaOCl + MG, group 3: 5.25% NaOCl +Ti-sapphire laser, and group 4: 5.25% NaOCl + S. persica. The chemically polymerized resin was used to lute zirconia posts. PBS and failure mode analysis were performed using a universal testing machine and stereomicroscope at 40X magnification. Data were compared between the two groups with 95% CI using one-way analysis of variance (ANOVA) with the Tukey post hoc test. p=0.05. RESULTS: Group4(5.25% NaOCl+ S.persica) specimens demonstrated the maximum (8.94±0.14 MPa) bond strength. Conversely, the apical third of Group 2 (5.25% NaOCl+ MG) (2.87±0.15 MPa) samples revealed the minimum bond strength scores. Intergroup comparison exposed that Group 1 (1.3% NaOCl+ MTAD), Group 3 (5.25% NaOCl+Ti-sapphire laser), and Group 4 (5.25% NaOCl+ S. persica) at all three-thirds unveiled no significant difference in PBS (p<0.05). CONCLUSION: Ti-sapphire laser and Salvedora Persica possess the potential to be used as a final root canal irrigant to improve the push-out bond strength of zirconia post-to-root dentin.
Photochemotherapy , Root Canal Filling Materials , Humans , Epoxy Resins , Aluminum Oxide , Edetic Acid , Photochemotherapy/methods , Photosensitizing Agents , Titanium , Lasers , Dentin , Root Canal Irrigants , Materials Testing , Dental Pulp Cavity , Root Canal Preparation
OBJECTIVE: The objective of this study was to compare types of veneer preparations and their combination with three materials. MATERIALS AND METHODS: Two finite element models were specially prepared used representing window and wrap around preparation for veneers. The "central incisor" tooth geometry was acquired using a laser scanner, and then its surface was adjusted to form a solid model prior to the removal of each preparation separately. Three materials (Lava Ultimate, IPS e-max, and Celtra) were tested in combination with the preparation type. Bone geometry was simplified as two coaxial cylinders in all models. Each model was subjected to two loading conditions of occlusion (edge-to-edge bite and normal bite). STATISTICAL ANALYSIS AND RESULTS: It was observed that cortical, cancellous bone, and periodontal ligament are insensitive to preparation or materials. Their stresses and deformation were within physiological limits. Significant changes appeared on the central incisor tooth structure, cement layer, and veneer layer stresses and deformations under loading cases. CONCLUSIONS: Edge-to-edge bite stresses are severe with window-type preparation, and normal bite did not show any critical values on tooth structure, cement layer, or veneer layer. Veneer layer finish line and its contact with the cement layer and tooth structure play a role in the loading transfer mechanism. Preparation type alters the values of stresses on tooth structure, cement, and veneer layers. With window preparation, extreme stresses appear at finish line, while stresses appear under the loading site with wrap around preparation. Veneer and cement layers withstand the load energy with wrap around preparation and reduce tooth structure stresses. Thus, the lifetime of veneer and cement layers might be longer with window preparation.
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.
OBJECTIVE: To study the effect of using different cement types under pediatric stainless-steel crown (SSC) around mandibular second primary molar using three-dimensional (3D) finite element analysis. MATERIALS AND METHODS: A 3D finite element model was built for pediatric mandibular molar by laser scanning of natural extracted tooth. Four types of cement (zinc phosphate, glass ionomer, resin-modified glass ionomer, and resin) of 200 µm layers thickness were tested under a stainless-steel crown of 130-µm thickness. Twelve case studies were reported within this research, as the applied load of 330 N was tested with three angulations: vertical, oblique at 45°, and laterally. RESULTS: Linear static stress analysis was performed. The resultant stresses and deformations' distribution patterns did not change with cement type, while the values were altered. All deformations and stresses were found within the normal range. CONCLUSIONS: Analysis results indicated that using stiffer cement material increases tooth structure stresses and reduces crown body stresses and deformations, while bone was nearly insensitive to cement type.
OBJECTIVE: The objective of this study was to determine the effect of Cosmopost's two different surface treatments (sandblasting and silica coating) on persistence to various core materials using push-out test set-up. MATERIAL AND METHODS: A total of 30 Cosmoposts was used in this study. Cosmoposts were divided into three groups (10 samples each) according to the post-surface treatment received. Every category was additionally subdivided into two subgroups according to the type of core material (n = 5 samples). A specially designed copper mold was used for construction of different core materials with standardized dimensions around the posts, in such a way to ensure that the posts will be centralized. Surface roughness was estimated for all Cosmoposts, following different surface treatments using SEM. Cylindrical cores were fabricated of either composite resin or heat-pressed zirconia-containing glass-ceramic (IPS Empress Cosmo, Ivoclar Vivadent). Following the construction of different Core materials, samples were subjected to push-out test set-up to Evaluate the impact of various treatments on post/core bond strength. Data were collected, tabulated and statistically analyzed. SEM was performed on Cosmoposts following debonding of different post/core samples to determine their mode of failure. RESULTS: Results of push-out bond strength revealed that core material, surface treatment and the interaction between the two variables using Two-way ANOVA had a statistically significant effect on mean push-out bond strength. Regarding the effect of type of core material on Push-out bond strength, results showed that IPS Empress Cores showed statistically significant higher mean push-out bond strength to Cosmopost (36.4±9.7MPa) than composite cores (15.8±2.5 MPa). CONCLUSION: Within the limitations of this study, direct heat-pressed ceramic core was more beneficial for zirconia post buildups, than Composite Cores, since they provided higher bond strength. Thanks to a double improvement: increase in fracture resistance and retentive capacity to post. Also, Tribochemical Silicacoating technique was proved to be more effective in Cosmopost treatments than sandblasting technique.
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.
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.
In the present study, GTX and ProTaper as continuous rotating endodontic files were numerically compared with WaveOne reciprocating file using finite element analysis, aiming at having a low cost, accurate/trustworthy comparison as well as finding out the effect of instrument design and manufacturing material on its lifespan. Two 3D finite element models were especially prepared for this comparison. Commercial engineering CAD/CAM package was used to model full detailed flute geometries of the instruments. Multi-linear materials were defined in analysis by using real strain-stress data of NiTi and M-Wire. Non-linear static analysis was performed to simulate the instrument inside root canal at a 45° angle in the apical portion and subjected to 0.3 N.cm torsion. The three simulations in this study showed that M-Wire is slightly more resistant to failure than conventional NiTi. On the other hand, both materials are fairly similar in case of severe locking conditions. For the same instrument geometry, M-Wire instruments may have longer lifespan than the conventional NiTi ones. In case of severe locking conditions both materials will fail similarly. Larger cross sectional area (function of instrument taper) resisted better to failure than the smaller ones, while the cross sectional shape and its cutting angles could affect instrument cutting efficiency.
Dental Instruments , Nickel/chemistry , Titanium/chemistry , Finite Element Analysis
Abstract In the present study, GTX and ProTaper as continuous rotating endodontic files were numerically compared with WaveOne reciprocating file using finite element analysis, aiming at having a low cost, accurate/trustworthy comparison as well as finding out the effect of instrument design and manufacturing material on its lifespan. Two 3D finite element models were especially prepared for this comparison. Commercial engineering CAD/CAM package was used to model full detailed flute geometries of the instruments. Multi-linear materials were defined in analysis by using real strain-stress data of NiTi and M-Wire. Non-linear static analysis was performed to simulate the instrument inside root canal at a 45° angle in the apical portion and subjected to 0.3 N.cm torsion. The three simulations in this study showed that M-Wire is slightly more resistant to failure than conventional NiTi. On the other hand, both materials are fairly similar in case of severe locking conditions. For the same instrument geometry, M-Wire instruments may have longer lifespan than the conventional NiTi ones. In case of severe locking conditions both materials will fail similarly. Larger cross sectional area (function of instrument taper) resisted better to failure than the smaller ones, while the cross sectional shape and its cutting angles could affect instrument cutting efficiency.
Resumo As limas rotativas GTX e ProTaper foram comparadas numericamente com as limas reciprocatórias WaveOne pela análise de elementos finitos, com o objetivo de baixar custos, comparação fiel e exata, além de pesquisar o efeito do projeto das limas e de seu material sobre a durabilidade. Dois modelos tridimensionais de análise de elementos finitos foram especialmente elaborados para esta comparação. Utilizou-se um sistema de engenharia CAD/CAM comercial para construir o modelo totalmente detalhado da geometria das estrias das limas. Materiais multi-lineares foram definidos na análise usando dados reais de deformação por estresse de NiTi e M-Wire. Procedeu-se à análise estática não linear para simular a ação do instrumento dentro do canal radicular em ângulo de 45° na região apical, submetido a uma torsão de 0.3 N.cm. As três simulações realizadas no presente estudo demonstraram que o M-Wire é um pouco mais resistente a falhas que o NiTi convencional. Por outro lado, ambos os materiais são bastante similares em condições de travamento severo. No caso da geometria das limas, os instrumentos de M-Wire podem ter vida útil mais longa que os de NiTi convencional. Em condições de travamento severo, ambos os materiais terão falhas similares. Maior área transversal (em função da conicidade do instrumento) resiste melhor a falhas que as áreas transversais menores, ao passo que a geometria da área transversal e seus ângulos de corte podem afetar a eficiência de corte das limas.
Dental Instruments , Nickel/chemistry , Titanium/chemistry , Finite Element Analysis
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.
BACKGROUND: The purpose of this study was to evaluate clinically and radiographically median lingualized occlusion in implant-retained mandibular complete overdenture. MATERIALS AND METHODS: Ten completely edentulous male patients were participated in this study. Each patient received two implants in the intraforaminal area of the edentulous mandible that were left unloaded for 4 months. Patients were received conventional maxillary complete denture and implant mandibular overdenture with ball and socket attachment. The posterior teeth were set according to median lingualized occlusion scheme. All patients were evaluated clinically and radiographically immediately after denture insertion, 6 and 12 months of overdenture insertion. RESULTS: The results revealed significant differences in probing depth, gingival index, plaque index, and marginal bone height between the different follow-up periods. With the limitation of this study, and according to the results of the mean marginal bone loss and the other peri-implant parameters after 1 year of loading. CONCLUSION: The implant retained overdenture with the median lingualized occlusal scheme may be recognized as being acceptable according to the general implant success rates and criteria.
To evaluate the mechanical behavior of reciprocating endodontic files, comparing nickel-titanium 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...
Humans , Endodontics/instrumentation , Nickel , Stainless Steel , Titanium
