Association of Body Mass Index and Chronology of Tooth Eruption in Children visiting a Dental Hospital in UAE: A Cross-sectional Study.

The objective of this research was to investigate the relationship between body mass index (BMI) and the mean age at which permanent teeth erupt in school-going children. Materials and Method: This cross-sectional study at RAK College of Dental Sciences, UAE, involved 89 children aged 6-14 years. Erupted teeth in the mouth were included. Statistical analysis, including t-tests, ANOVA, and Kruskal-Wallis, was conducted using SPSS version 29, with a significance threshold set at p < 0.05. Results: Out of 89 children (41 girls and 48 boys) in the study, 56.17 % had normal weight, 20.22 % were overweight, 17.97 % were underweight, and 5.6 % were obese. Female children generally experienced earlier permanent tooth eruption than males. Additionally, there was an observed trend of earlier tooth eruption with increasing weight or BMI. Underweight children notably displayed a delayed mean age of tooth eruption. Conclusion: This study demonstrates a notable correlation between BMI and the mean age at which permanent teeth erupt in school-going children aged 6 to 14 years who visited our dental hospital. To establish a more precise understanding of the connection between BMI and dental development, we recommend conducting further longitudinal studies involving multiple centers. Clinical Significance: Monitoring a child's BMI is crucial for assessing dental health and planning tailored treatment for those aged 6 to 14. Understanding the BMI's connection to permanent tooth eruption timing allows dental professionals to identify trends in early or delayed development. This enables them to customize treatment strategies, promoting a precise and personalized approach for better oral health outcomes in this age group.

New adhesive protocol improves shear bond strength of Polyetherketoneketone (PEKK).

OBJECTIVE: Inert surface of Polyetherketoneketone (PEKK) jeopardizes resin bonding. This study aimed to present a new adhesive protocol to improve PEKK bonding. METHODS: A total of 360 PEKK blocks were milled, polished (maximum roughness of 0.20 µm), and randomly assigned to groups. The new protocol was applied (n = 36) and compared to conventional treatments (no treatment; sandblasting (110-µm Al2O3 and silica); no adhesive; Visiolink (Bredent); and PEKKbond (AnaxDent)) (n = 36). For the new protocol, the surface was blasted (110 µm Al2O3 and 96% isopropyl alcohol at 60 psi), followed by 96% isopropyl alcohol washing, and air drying. PEKKbond was applied (dried for 3 min at 77 °C), followed by Visiolink (dried for 3 min at 60 °C); both light-cured for 3 min (800 mW/cm2). Preopaque (GC Europe) and Opaque (AnaxDent) were applied and light-cured (5 min). Morphological topography was analyzed, and flowable gingiva-colored composite (AnaxGum, AnaxDent) was bonded. All specimens were aged for 24 h and thermocycled (5000 cycles, 5-55 °C). Shear bond strength (SBS) was measured (MPa) and data were analyzed by two-way ANOVA, Tukey, and Weibull moduli estimation (α = 0.05). RESULTS: The highest SBS values were found in the new protocol (p < 0.05), regardless of aging. Thermocycling reduced SBS (p < 0.05), while Al2O3 and PEKKbond produced higher SBS values than silica and Visiolink, respectively (p < 0.05). SIGNIFICANCE: The new protocol strongly improves PEKK adhesiveness, and this can reflect in the longevity of prostheses.

Clinical longevity of metallic versus fiberglass intraradicular posts: a systematic review / Longevidade clínica de pinos intraradiculares metálicos versus de fibra de vidro: uma revisão sistemática

Objective: This systematic review aims to compare the clinical longevity of metallic and fiberglass intraradicular posts in teeth with severely compromised crowns, utilizing randomized clinical trials and case reports published in the last eleven years. Material and Methods: The research was conducted on PubMed, Medline, Lilacs, and BBO databases using the first search strategy with the descriptors 'dental posts,' 'longevity,' 'fiberglass-reinforced posts' or 'metallic posts.' The second search strategy involved analyzing the references of articles identified by the first search. Both studies were carried out with stringent inclusion and exclusion criteria. Results: No statistically significant and clinically relevant differences in longevity were observed between metallic and fiberglass posts. Conclusion: The clinical success and durability of the restorative procedure using intraradicular posts primarily depend on the remaining amount around the post (ferrule), the type and position of the tooth in the arch (impacting the masticatory forces exerted on the restored tooth), and the correct application of the cementation technique. It is noteworthy that fiberglass posts offer substantial advantages by presenting a modulus of elasticity similar to dental structure, ensuring a more homogeneous distribution of masticatory forces and reducing the risk of fractures. These findings have practical implications for material selection in restorative procedures involving intraradicular posts.(AU)

Objetivo: Esta revisão sistemática visa comparar a longevidade clínica de pinos intrarradiculares metálicos e de fibra de vidro em dentes com coroas severamente comprometidas, através de estudos clínicos randomizados e relatos de casos, publicados nos últimos onze anos. Material e Métodos: A pesquisa foi conduzida nas bases de dados PubMed, Medline, Lilacs e BBO, utilizando a primeira estratégia de busca com os s 'pinos dentais' e 'longevidade' e 'pinos reforçados com fibra de vidro' ou 'pinos metálicos'. A segunda estratégia de busca consistiu na análise das referências dos artigos identificados pela primeira estratégia. Ambos os estudos foram delineados com critérios rigorosos de inclusão e exclusão. Resultados: Não se constataram diferenças estatisticamente significativas e clinicamente relevantes na longevidade entre pinos metálicos e de fibra de vidro. Conclusão: O êxito clínico e a durabilidade do procedimento restaurador empregando pinos intrarradiculares dependem primordialmente da quantidade de remanescente ao redor do pino (férula), do tipo e posição do dente na arcada (o que impacta nas forças mastigatórias exercidas sobre o dente restaurado) e da aplicação correta da técnica de cimentação.Destaca-se que o pino de fibra de vidro oferece vantagens substanciais ao apresentar módulo de elasticidade similar à estrutura dentária, assegurando uma distribuição mais homogênea das forças mastigatórias e reduzindo o risco de fraturas (AU)

Physical analysis of an acrylic resin modified by metal and ceramic nanoparticles.

BACKGROUND: Nanoparticles (NPs) have gained significant attention in various fields due to their unique properties and potential applications. Polymethyl methacrylate (PMMA) is an acrylic resin widely used in dentistry and medicine. However, the effect of different types of NP fillers on the physical properties of PMMA-based resins has not been thoroughly explored in the literature. OBJECTIVES: The present study aimed to evaluate the effects of 3 different types of NP fillers on the physical properties of an experimental PMMA-based resin as a function of the NP content and concentration. MATERIAL AND METHODS: Ten groups (n = 10) were designed. The specimens were composed of an acrylic resin, silicon dioxide (SiO2), cerium dioxide (CeO2), and titanium dioxide (TiO2) at the following ratios (wt%): group 1 (G1) - control; group 2 (G2) - 0.5% SiO2; group 3 (G3) - 1% SiO2; group 4 (G4) - 3% SiO2; group 5 (G5) - 0.5% CeO2; group 6 (G6) - 1% CeO2; group 7 (G7) - 3% CeO2; group 8 (G8) - 0.5% TiO2; group 9 (G9) - 1% TiO2; and group 10 (G10) - 3% TiO2. Transmission electron microscopy (TEM) was used to assess the quality of NP dispersion. Thermal stability was assessed with thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The effects of the abovementioned NPs on the properties of the resin were evaluated using the Archimedes principle for density, the Vickers hardness (VH) test and the impact strength (IS) test. Data analysis employed the oneand two-way analysis of variance (ANOVA), followed by Duncan's post hoc test at a significance level of 0.05. RESULTS: Transmission electron microscopy showed partial NP dispersion. All types of NPs enhanced the mechanical properties of the acrylic resin except for IS, which was similar to that of the control group. Among the types of NPs, irrespective of the weight percentage, CeO2 showed higher thermal stability and higher IS for 0.5 wt% and 1 wt% as compared to other groups, as well as the highest values of density at 0.5 wt%, 1 wt% and 3 wt%. Titanium oxide at 1 wt% presented a higher VH as compared to other groups. The fracture pattern was the same for all groups. CONCLUSIONS: Incorporating the tested NPs into the acrylic resin resulted in enhanced physical properties, primarily attributed to a lower NP content.

Bond Strength and Surface Roughness of Two Ceramics After Metal Bracket Debonding.

Objective: The aims of this study were to compare the bond strength between metallic brackets and two different glass ceramics and to evaluate the ceramic surface roughness after different finishing protocols. Methods: The surface roughness of lithium disilicate and resin matrix ceramic samples was measured (initial). All samples were treated with hydrofluoric acid and silane and bonded to metallic brackets with orthodontic cement adhesive. Shear bond strength tests were performed using a universal testing machine (n=12). The surface roughness was measured again (intermediate, n=6) after removing the remaining cement adhesive from the ceramic surfaces with a diamond or 24-blade bur after polishing the ceramic surfaces (final, n=6). Results: The resin matrix ceramic had the highest bond strength. The rotatory instrument used for the removal of cement adhesive did not affect the surface roughness of the resin matrix ceramic or lithium disilicate (p=0.985 and p=0.504, respectively), but did affect the evaluation time (p<0.001) for both restorative materials. The intermediate roughness was the highest. For the resin matrix ceramic, polishing promoted a final surface roughness similar to the initial condition; however, changes in the surface shape of this ceramic could be visibly observed when using a 24-blade bur. Conclusion: The bond strength of metallic brackets bonded on resin-matrix ceramics is higher than bonding on lithium disilicate. The use of diamond burs for the removal of the remaining adhesive from the resin matrix ceramics is highly recommended.

Post-fatigue fracture load, stress concentration and mechanical properties of feldspathic, leucite- and lithium disilicate-reinforced glass ceramics.

Objective: To evaluate the mechanical properties of different CAD/CAM ceramic systems and the post-fatigue fracture and stress distribution when used as cemented crowns. Materials and methods: Sixty (60) CAD/CAM monolithic crowns were milled using three different ceramic materials (FD - Feldspathic [Vita Mark II]), LE - Leucite-based ceramic [IPS Empress CAD] and LD - Lithium Disilicate [IPS e.max CAD]) and adhesively cemented on resin composite dyes. Specimens were stored in distillated water (37 °C) for 7 days. After, half of the crowns were submitted to immediate fracture load test while the other half was submitted to fatigue cycling. The average cement layer of approximately 80 µm was assessed using scanning electron microscopy (SEM). The average thickness was used in the three-dimensional (3D) Finite Element Analysis (FEA). For each ceramic material, the density, Poisson ratio, shear modulus, Young modulus, fracture toughness, and true hardness were assessed (n = 3). The data was used to assess the Maximum Principal Stress throughout 3D-FEA according to each material during load to fail and post-fatigue. Data were submitted to two-way ANOVA and Tukey test (α = 0.05). Results: LD showed the highest compression load, density, shear modulus, Young modulus, fracture toughness and true hardness values. While LE presented the lowest mechanical properties values. There is no difference in the Poisson ratio between the evaluated ceramics. Conclusion: LD was susceptible to aging process but presented stronger physicomechanical properties, showing the highest post-fatigue fracture load and highest stress magnitude.

Effect of the Combination of Restorative Material and the Etching Protocol in Enamel Microleakage in Class II Cavities after Thermocycling.

This study is aimed at evaluating the marginal microleakage of bulk-fill class II restorations after thermocycling. Thirty-two human third molars received class II cavities prepared on mesial and distal faces. The cavities were bonded according to the adhesive protocol (total or self-etching). The cavities were then restored with composite and divided into 8 groups based on the composite combination: layering technique with Filtek Z350XT (G1 and G5), first layer with Filtek Z350 XT Flowable Restorative and then Filtek Z350XT (G2 and G6), bulk-fill technique with Filtek One Bulk Fill (G3 and G7), and first layer with Filtek One Bulk Fill Flow and Filtek Z350 XT (G4 and G8). The restorations were then subjected to thermocycling (2000 cycles, 5°C and 55°C, dwell time of 30 s). After aging, the restored teeth were immersed in methylene blue for 48 hours. The restorations (n = 32) were sectioned in the middle (two sections). The microleakage results were analyzed by two-way ANOVA followed by Tukey's post hoc test (α = 0.05). The groups did not differ statistically from each other in terms of marginal microleakage (p = 0.295). It can be concluded that there is no difference in the percentage of microleakage between conventional and bulk-fill resins on both consistencies, as well as there is also no statistically significant difference when the adhesive system is used in a conventional or self-etching mode.

Effect of different fabrication methods of occlusal devices on periradicular stress distribution: A photoelastic analysis.

STATEMENT OF PROBLEM: Investigations on the effectiveness of new methods for optimizing the fabrication of oral devices are lacking. PURPOSE: The purpose of this in vitro study was to evaluate stress distribution with photoelastic analysis in the periradicular area of teeth supporting occlusal devices fabricated by 5 different processes. MATERIAL AND METHODS: The occlusal devices were fabricated by vacuum thermoforming, heat-polymerized acrylic resin, chemical polymerized acrylic resin, 3-dimensional printing, and milling (computer-aided manufacturing). The devices were evaluated regarding initial fit, number of adjustments for passive fit, and stress distribution under 100-N and 400-N loads in the periradicular locations of posterior teeth. RESULTS: The 3-dimensional printing device did not require any adjustment for initial adaptation to the photoelastic model and presented a little friction with the model. The heat-polymerized acrylic resin device did not seat initially, requiring more sites of adjustment until passive adaptation. At 100-N and 400-N loads, the use of the computer-aided manufacturing occlusal device resulted in the lowest stresses in periradicular areas (0.744 and 1.583, respectively), and the 3-dimensional printing occlusal device produced the highest stresses with a 400-N load application (2.427). The lowest mean of fringe pattern was observed for the computer-aided manufacturing device, and the highest mean of fringe pattern was observed for the vacuum thermoforming device. CONCLUSIONS: The computer-aided design and computer-aided manufacturing milled occlusal device presented the best initial adaptation and transferred lower stresses to the periradicular areas than the other evaluated devices.

Linear dimensional change of edentulous models made of high-density laboratory silicones at different storage times / Alteração dimensional linear de modelos edêntulos fabricados com silicones laboratoriais de alta densidade em diferentes tempos de armazenagem

ABSTRACT Objective: To evaluate the dimensional change of edentulous models made of high density laboratory silicones at different storagetimes. Methods: A metallic master model simulating an edentulous maxilla was used. The model had projections of 1.8 cm located in the regions of canines (A and B) and molars (C and D) allowing the linear measurement of distances AB, BC, CD, DA, AC and BD. A laboratory silicone mold was made for duplication of master model in the following materials (n = 10): G1: Zetalabor 85, G2: Titanium 95, G3: Platinum 95 and G4: Gypsum type III (control). The samples were photographed and measured using a software (Image J) at times T1 (baseline) and T2 (after one week of models fabrication). The data were statistically analyzed using Kruskal- Wallis and Dun non-parametric tests (α = 0.05). Results: The storage time influenced the behavior of the materials evaluated. All groups presented dimensional changes in both times and the group Tit95 presented the best results. Only Zet85 group showed a different behavior related to the region of the model. Conclusions: The high density laboratory silicones showed satisfactory results when compared to the gypsum group. Tit95 was the most stable material and it can be recommended as an edentulous model for total protheses.

RESUMO Objetivo: Avaliar a alteração dimensional de modelos edêntulos fabricados em silicone laboratorial de alta densidade em diferentes tempos de armazenagem. Métodos: Um modelo mestre metálico simulando uma maxila edêntula foi utilizado. O modelo possuía projeções oclusais de 1,8 cm localizadas nas regiões de caninos (A e B) e molares (C e D), permitindo a mensuração das distâncias lineares AB, BC, CD, DA, AC e BD. Um molde foi fabricado em silicone laboratorial para duplicação do modelo mestre com os seguintes materiais (n = 10): G1: Zetalabor 85, G2: Titanium 95, G3: Platinum 95 e G4: Gesso tipo III (controle). As amostras foram fotografadas e mensuradas com auxílio de um software (Image J) nos tempos T1 (baseline) e T2 (após uma semana de confecção). Os dados obtidos foram avaliados estatisticamente utilizando os testes não paramétricos de Kruskal- Wallis e Dunn (α = 0.05). Resultados: O tempo de armazenagem influenciou o comportamento dos materiais avaliados. Todos os grupos apresentaram alterações dimensionais em ambos os temos de avaliação e o G2 apresentou os melhores resultados. Apenas o grupo G1 mostrou alteração dimensional dependente da região mensurada. Conclusão: Silicones laboratoriais de alta densidade mostraram resultados satisfatórias de alteração dimensional quando comparados ao gesso tipo III. O material Titanium 95foi o mais estável e pode ser recomendado como alternativa para a confecção de modelos edêntulos.

Bond strength of self-adhesive resin cement to dentin using different adhesion protocols.

BACKGROUND: The treatment of dentin before the use of self-adhesive cements is still a crucial point to achieve the best bond strength values. The objective of this study was to evaluate the bond strength between dentin and composite resin using different adhesion strategies with self-adhesive resin cement. MATERIAL AND METHODS: Forty healthy third human molars were randomly divided into 4 groups (n = 10): CA (control); application of self-adhesive cement (Rely X U200, 3M ESPE), AD + CA: only application of conventional adhesive (Adper Single Bond 2, 3M ESPE) + self-adhesive cement, AC + AD + CA; conditioning with 37% phosphoric acid for 15 seconds + application of conventional adhesive + self-adhesive cement and AC + CA; conditioning with 37% phosphoric acid for 15s + self-adhesive cement. Blocks made of composite resin (Z250 XT, 3M ESPE) were cemented over dentin. The samples were stored for 24h in distilled water at 37ºC and then were sectioned on a metallographic cutter to obtain tooth picks with approximately 1.0 mm2 in cross section. A universal testing machine was used with a speed of 0.5 mm/min to test the microtensile bond strength,. The fracture patterns were classified as adhesive, cohesive and mixed failures. The data (MPa) were analyzed statistically by One-way ANOVA and Holm-Sidak test (α=5%). RESULTS: The AC + AD + CA and AC + CA groups had the highest averages, while the CA and AD + CA groups had the lowest bond strength values. Adhesive failure was prevalent in all groups. CONCLUSIONS: Conditioning with 37% phosphoric acid for 15s increases the adhesion of the self-adhesive resin cement to the dentin, regardless of the use of dental adhesive system. Key words:Resin cement, microtensile bond strength, acid conditioning.

Mechanical Properties of Experimental Composites with Different Photoinitiator.

OBJECTIVE: The effect of different photoinitiators on mechanical properties of experimental composites was evaluated. MATERIALS AND METHODS: Resin composites were formulated by using a blend of bisphenol A-glycidyl and triethylene glycol (50/50 wt%) dimethacrylate monomers, and 65 wt% of barium aluminium silicate and silica filler particles. Photoinitiators used were 0.2% camphorquinone (CQ) and 0.8% co-initiator (DMAEMA); 0.2% phenyl-propanedione and 0.8% DMAEMA; 0.1% CQ + 0.1% phenyl propanedione and 0.8% DMAEMA; 0.42% mono(acyl)phosphine oxide (MAPO); and 0.5% bis(acyl)phosphine oxide (BAPO). Specimens (n = 10) were light cured by using a multiple-emission peak light-emitting diode for 20 seconds at 1,200 mW/cm2 of irradiance and Knoop hardness and plasticization, depth of cure, flexural strength, and elastic modulus were evaluated. Data were statiscally analyzed at significance level of α = 5%. RESULTS: Experimental composites containing MAPO and BAPO photoinitiators showed the highest values of flexural strength, elastic modulus, top surface hardness, and lower hardness reduction caused by alcohol compared with CQ. Composites containing CQ and PPD showed similar results, except for depth of cure and hardness of bottom surface. CONCLUSION: BAPO and MAPO showed higher flexural strength, elastic modulus, hardness on top surface, and lower polymer plasticization to CQ.

Improving the bonding stability between resin cements and zirconia-based ceramic using different surface treatments.

PURPOSE: To evaluate the effects of airborne-particle abrasion with alumina particles or silicamodified alumina particles on the bond strength between zirconia and conventional MDP-based (Ph; Panavia F 2.0, Kuraray) or self-adhesive (SA; RelyX U200, 3M ESPE) resin cements. MATERIALS AND METHODS: Five surface treatments were evaluated: C = no surface treatment; AB = airborne-particle abrasion with alumina particles (BIO-ART Dental Supplies and Equipment); ABP = AB combined with MDP-based primer (Alloy Primer, Kuraray); SS = airborne-particle abrasion with silica-modified alumina particles (CoJet, 3M ESPE) combined with silane (RelyX Ceramic Primer, 3M ESPE); and SSP = SS combined with MDP-based primer. The surface roughness (Ra) of the airborne particle-abraded samples (n = 5) was measured by a contact profilometer (Mitutoyo Surftest SJ-401, Mitutoyo). Cylinders of the resin cements tested were bonded to the surface-treated zirconia. The microshear test was performed by the application of a load with a wire loop parallel to the adhesive interface until debonding of the resin cement cylinders. The microshear bond strength (µSBS) of the samples was measured before and after being subjected to thermocycling (TC; 5°C to 55°C, 60 seconds dwell time for 3,000 cycles; MSCT, Marcelo Nucci). One-way (Ra) and two-way (µSBS) analysis of variance followed by Tukey post hoc test (α = .05) were used. RESULTS: The SS (Ph: 12.6 MPa; Ph-TC: 6.37 MPa; SA: 11.8 MPa; SA-TC: 9.37) and SSP (Ph: 10.4 MPa; Ph-TC: 5.82 MPa; SA: 10.4 MPa; SA-TC: 10.0) surface treatments produced the highest surface roughness values (P < .001). The SS samples achieved the highest immediate bond strength for both resin cements. However, after TC, SA resin cement associated with any surface treatment produced the highest bond strength values. CONCLUSION: The self-adhesive resin cement promoted higher and more stable bond strength values when associated with a surface roughening method.

Adhesive systems applied to dentin substrate under electric current: systematic review.

OBJECTIVES: The purpose of this systematic review was to collect and discuss the technique of adhesive systems application on dentin substrate under electric current. MATERIALS AND METHODS: The first search strategy was based on data available at PubMed, LILACS, Scielo, Scopus, and Cochrane Library, using a combination of descriptors such as "dentin bond agents OR adhesive system AND electric current OR electrobond" or "dentin bonding agents OR dentin bonding agent application OR adhesive system AND electric current OR electrobond", with no limit regarding the publication year. The second search strategy was based on the articles' references found previously. An additional search strategy was applied that concerned the proposed theme in the SBU-UNICAMP (Unicamp's Library System Institutional Repository). RESULTS: Twelve studies published between 2006 and 2020 were found. The analyses of the selected studies showed that the use of electric current during adhesive systems application on dentin, whether conventional or self-conditioning, increases resinous monomer infiltration in the dentin substrate, which improves the hybridization processes and the bond strength of the restorative material to dentin. CONCLUSIONS: Despite the favorable results related to the use of this technique, there is still no specific protocol for the application of adhesive systems under electric current.

Effect of Cement Layer Thickness on the Immediate and Long-Term Bond Strength and Residual Stress between Lithium Disilicate Glass-Ceramic and Human Dentin.

This study tested whether three different cement layer thicknesses (60, 120 and 180 µm) would provide the same bonding capacity between adhesively luted lithium disilicate and human dentin. Ceramic blocks were cut to 20 blocks with a low-speed diamond saw under cooling water and were then cemented to human flat dentin with an adhesive protocol. The assembly was sectioned into 1 mm2 cross-section beams composed of ceramic/cement/dentin. Cement layer thickness was measured, and three groups were formed. Half of the samples were immediately tested to evaluate the short-term bond strength and the other half were submitted to an aging simulation. The microtensile test was performed in a universal testing machine, and the bond strength (MPa) was calculated. The fractured specimens were examined under stereomicroscopy. Applying the finite element method, the residual stress of polymerization shrinkage according to cement layer thickness was also calculated using first principal stress as analysis criteria. Kruskal-Wallis tests showed that the ''cement layer thickness'' factor significantly influenced the bond strength results for the aged samples (p = 0.028); however, no statistically significant difference was found between the immediately tested groups (p = 0.569). The higher the cement layer thickness, the higher the residual stress generated at the adhesive interface due to cement polymerization shrinkage. In conclusion, the cement layer thickness does not affect the immediate bond strength in lithium disilicate restorations; however, thinner cement layers are most stable in the short term, showing constant bond strength and lower residual stress.

Dimensional Accuracy Comparison of Physical Models Generated by Digital Impression/3D-Printing or Analog Impression/Plaster Methods

ABSTRACT: This study aimed to compare the trueness and precision of physical models manufactured chairside (intraoral scanner and 3D printed) or by plaster models obtained using impression with alginate or addition silicone. A full- arch stainless steel die was impressed to obtain ten physical models for each group. The models were measured in a stereomicroscope, considering four linear distances. To assess the precision accuracy, an analysis of the measurement variability was carried out, identified by the coefficients of variation and by the Levene's test to compare the groups. To analyze trueness, the data average was subtracted from the database and compared considering alpha as 5 %. Considering precision, the higher dispersion of data occurred in the models obtained with silicone impression. And for trueness, Kruskal Wallis and Dunn tests results did not indicate differences between the groups in the anteroposterior linear distances (p> 0.05). Only in anterior transverse distance obtained through TRIOS (0.31 mm), it presented lower accuracy compared to the models from silicone impression (0.13 mm); however, at transverse posterior distance, the models from silicone impression showed the lowest accuracy (p 0.05). The physical dental models obtained by digital and analog workflows showed acceptable dimensional accuracy expressed by high precision and trueness. There is no difference between the evaluated intraoral scanner systems and the impression materials for the full-arch impression.

RESUMEN: Este estudio tuvo como objetivo comparar la veracidad y precisión de modelos físicos fabricados en la clínica dental (escáner intraoral e impreso en 3D) o por modelos de yeso obtenidos mediante impresión con alginato o silicona de adición. Una matriz de acero inoxidable de arco completo fue impresa para obtener diez modelos físicos para cada grupo. Los modelos se midieron en un estereomicroscopio, considerando cuatro distancias lineales. Se realizó un análisis de la variabilidad de la medida para evaluar la precisión, identificada por los coeficientes de variación y por la prueba de Levene para comparar los grupos. Para analizar la veracidad, el promedio de los datos se restó de la base de datos y se comparó considerando alfa como 5 %. Considerando la precisión, la mayor dispersión de datos ocurrió en los modelos obtenidos con impresión de silicona. Y para la veracidad, los resultados de las pruebas de Kruskal Wallis y Dunn no indicaron diferencias entre los grupos en las distancias lineales anteroposteriores (p> 0,05). Solo en la distancia transversal anterior obtenida mediante TRIOS (0,31 mm) presentó menor precisión en comparación con los modelos de impresión de silicona (0,13 mm); sin embargo, la distancia transversal posterior, los modelos de impresión de silicona mostraron la menor precisión (p 0,05). Los modelos dentales físicos obtenidos mediante flujos de trabajo digitales y analógicos mostraron una precisión dimensional aceptable expresada por alta precisión y veracidad. No se observó diferencia entre los sistemas de escáner intraoral evaluados y los materiales de impresión para la impresión de arco completa.

Stress Concentration of Endodontically Treated Molars Restored with Transfixed Glass Fiber Post: 3D-Finite Element Analysis.

The loss of dental structure caused by endodontic treatment is responsible for a decrease in tooth resistance, which increases susceptibility to fracture. Therefore, it is important that minimally invasive treatments be performed to preserve the dental structure and increase the resistance to fracture of endodontically treated posterior teeth. To evaluate under axial loads, using the finite element method, the stress distribution in endodontically treated molars restored with both transfixed or vertical glass fiber posts (GFP) and resin composite. An endodontically treated molar 3D-model was analyzed using finite element analyses under four different conditions, class II resin composite (G1, control model), vertical glass fiber post (G2), transfixed glass fiber posts (G3) and vertical and transfixed glass fiber posts (G4). Ideal contacts were considered between restoration/resin composite and resin composite/tooth. An axial load (300 N) was applied to the occlusal surface. The resulting tensile stresses were calculated for the enamel and dentin tissue from five different viewports (occlusal, buccal, palatal, mesial and distal views). According to the stress maps, similar stress trends were observed, regardless of the glass fiber post treatment. In addition, for the G1 model (without GFP), a high-stress magnitude can be noticed in the proximal faces of enamel (7.7 to 14 MPa) and dentin (2.1 to 3.3 MPa) tissue. The use of transfixed glass fiber post is not indicated to reduce the stresses, under axial loads, in both enamel and dentin tissue in endodontically treated molar with a class II cavity.

Tooth Discoloration Using Calcium Silicate-Based Cements For Simulated Revascularization in Vitro.

The endodontic revascularization may be an alternative treatment for necrotic immature teeth, however, several treatment steps may cause tooth discoloration. This study evaluated the use of three calcium silicate-based cements with different radiopacifying agents on the color alteration (∆E) of extracted premolars after simulation of revascularization. Forty single rooted extracted premolars were shaped with #1-6 gates Glidden drills, rinsed with sodium hypochlorite, and filled with fresh human blood. Three calcium silicate-based cements with different radiopacifying agents (bismuth oxide - CSBi, calcium tungstate - CSW, and zirconium oxide - CSZr) were applied over the blood clot (n=10). The control group received the application of a temporary zinc oxide-based cement (TFZn) (n=10). ∆E was measured with a spectrophotometer, using the L*a*b* color system of the International Commission on Illumination (CIELab), in different times: prior to the preparation of the access cavity (t0); right after treatment (t1); and after one (t2), two (t3), three (t4) and four (t5) months. The tooth site for color evaluation was standardized by silicon matrix, the color reading was performed 3 times per tooth, and the teeth were stored in 37º water between evaluations. ∆E, whiteness (WID index) and yellowness (b*) were evaluated. Data were subjected to one-way ANOVA and repeated measures ANOVA, followed by Tukey's post hoc test (α=0.05). All groups were similar in ∆E1 (t0-t1). The ∆E was the lowest and constant in the control group. In all evaluation times, CSBi presented the highest ∆E (p<0.01). CSW and CSZr were similar in all evaluated times and presented intermediate ∆E values. WID index from CSBi and CSW presented more distancing from 'white' reference. CSBi presented the greatest decrease in yellowness (b* value). The cement containing bismuth oxide presented the highest color alteration values. All tested calcium silicate-based cements presented clinically perceptible discoloration. Calcium tungstate and zirconium oxide may be used as alternative radiopacifiers to decrease tooth discoloration after endodontic tooth revascularization.

Resin composite adhesion to dentin using different curing lights and adhesive systems applied under electric current.

OBJECTIVES: To evaluate the effect of electric current application on the resin composite-tooth bond strength and hybrid layer of three adhesive systems light-cured by two light-curing units (LCUs). MATERIALS AND METHODS: Human molar teeth were distributed into 12 groups (n=6). Three adhesive systems were used: two-step etch-and-rinse (SB2; Adper Single Bond 2, 3M ESPE); two-step self-etch (CSE; Clearfil SE Bond, Kuraray); and one-step self-etch (SBU; Single Bond Universal, 3M ESPE) applied with (50µA) and without (control; conventional application) electric current, and light-cured with different LCUs. Resin composite blocks (Filtek Z350XT, 3M ESPE) were produced and cut into sticks (~1mm2) for microtensile bond strength (µTBS). Fracture patterns were analyzed on stereomicroscope and classified as cohesive-dentin, cohesive-resin, adhesive, or mixed. Specimens were prepared for scanning electron microscope observation. The hybrid layer analysis was carried out using a confocal laser scanning microscopy (n=2). Data were submitted to three-way ANOVA followed by Tukey's post hoc test (α=0.05). RESULTS: The electric current increased the µTBS for all adhesive systems light-cured with single-emission peak and multiple-emission peak LCUs. Both LCUs presented similar µTBS values. CSE applied under electric current showed the highest µTBS mean values. The adhesive failure pattern was more frequently observed in all groups. The electric current formed long resin tags for all adhesive systems. CONCLUSIONS: The adhesive systems applied under electric current increased the bond strength using single-emission peak and multiple-emission peak LCUs. CLINICAL RELEVANCE: Electric current at 50µA applied throughout the dentin is a safe mode and results in better impregnation of the adhesive systems.

Tooth discoloration using calcium silicate-based cements for simulated revascularization in vitro

Abstract The endodontic revascularization may be an alternative treatment for necrotic immature teeth, however, several treatment steps may cause tooth discoloration. This study evaluated the use of three calcium silicate-based cements with different radiopacifying agents on the color alteration (∆E) of extracted premolars after simulation of revascularization. Forty single rooted extracted premolars were shaped with #1-6 gates Glidden drills, rinsed with sodium hypochlorite, and filled with fresh human blood. Three calcium silicate-based cements with different radiopacifying agents (bismuth oxide - CSBi, calcium tungstate - CSW, and zirconium oxide - CSZr) were applied over the blood clot (n=10). The control group received the application of a temporary zinc oxide-based cement (TFZn) (n=10). ∆E was measured with a spectrophotometer, using the L*a*b* color system of the International Commission on Illumination (CIELab), in different times: prior to the preparation of the access cavity (t0); right after treatment (t1); and after one (t2), two (t3), three (t4) and four (t5) months. The tooth site for color evaluation was standardized by silicon matrix, the color reading was performed 3 times per tooth, and the teeth were stored in 37º water between evaluations. ∆E, whiteness (WID index) and yellowness (b*) were evaluated. Data were subjected to one-way ANOVA and repeated measures ANOVA, followed by Tukey's post hoc test (α=0.05). All groups were similar in ∆E1 (t0-t1). The ∆E was the lowest and constant in the control group. In all evaluation times, CSBi presented the highest ∆E (p<0.01). CSW and CSZr were similar in all evaluated times and presented intermediate ∆E values. WID index from CSBi and CSW presented more distancing from 'white' reference. CSBi presented the greatest decrease in yellowness (b* value). The cement containing bismuth oxide presented the highest color alteration values. All tested calcium silicate-based cements presented clinically perceptible discoloration. Calcium tungstate and zirconium oxide may be used as alternative radiopacifiers to decrease tooth discoloration after endodontic tooth revascularization.

Resumo A revascularização endodôntica pode ser um tratamento alternativo para dentes imaturos necrosados, porém, várias etapas do tratamento podem causar alteração de cor dental. Este estudo avaliou o uso de três cimentos a base de silicato de cálcio com diferentes agentes radiopacificadores na alteração de cor (∆E) de pré-molares extraídos após a simulação de revascularização. Quarenta pré-molares unirradiculares extraídos foram conformados com brocas gates glidden #1-6, irrigados com hipoclorito de sódio, e preenchidos com sangue humano fresco. Três cimentos a base de silicato de cálcio com diferentes agentes radiopacificadores (óxido de bismuto - CSBi, tungstato de cálcio - CSW, e óxido de zircônio - CSZr) foram aplicados sobre o coágulo sanguíneo (n=10). O grupo controle recebeu a aplicação de um cimento temporário a base de óxido de zinco (TFZn) (n=10). ∆E foi medida com um espectrofotômetro, utilizando o sistema de cor L*a*b* da International Commission on Illumination (CIELab), em tempos diferentes: previamente ao preparo da cavidade de acesso (t0); logo após o tratamento (t1); e após um (t2), dois (t3), três (t4) e quatro (t5) meses. O local do dente para a avaliação de cor foi padronizado por uma matriz de silicone, a leitura da cor foi realizada 3 vezes por dente, e os dentes foram armazenados em água a 37ºC entre as avaliações. ∆E, 'clareamento' (índice WID) e tom amarelado (b*) foram avaliados. Os dados foram submetidos ao teste de ANOVA um fator e teste ANOVA de medidas repetidas, seguidos pelo teste post hoc de Tukey (α=0,05). Todos os grupos foram semelhantes em ∆E1 (t0-t1). A ∆E foi menor e constante no grupo controle. Em todos os tempos de avaliação, CSBi apresentou os maiores valores de ∆E (p<0.01). CSW e CSZr foram semelhantes em todos os tempos avaliados e apresentaram valores intermediários de ∆E. O índice WID de CSBi e CSW se distanciaram mais da referência 'branco'. CSBi apresentou maior diminuição no tom amarelado (valor de b*) os outros grupos. O cimento contendo óxido de bismuto apresentou os maiores valores de alteração de cor. Todos os cimentos testados apresentaram alteração de cor clinicamente perceptível. O tungstato de cálcio e óxido de zircônio podem ser usados como radiopacificares alternativos para a diminuição da alteração de cor dental após o processo de revascularização endodontica.

Mechanical performance of experimental acrylic resins modified by nanoparticles after chemical and mechanical degradation.

BACKGROUND: Different materials have been incorporated into the polymethylmethacrylate matrix to improve its performance. The aim of this study was to evaluate the degree of conversion (DC), the flexural strength (FS), the elasticity modulus (EM), and the effect of exposure to food-simulating liquids prior to brushing simulation on the gloss loss (GL) of experimental acrylic resins modified by nanoparticles. MATERIAL AND METHODS: Three different types of nanoparticles; silicon oxide (SiO2), cerium oxide (CeO2) and titanium oxide (TiO2) were added to a poly (methylmethacrylate) matrix, in proportions of 0.5wt%, 1wt% and 3wt% each, forming nine experimental groups. The acrylic resin was also tested as a control group. DC was investigated using Fourier transform infrared spectroscopy (FTIR). A three-point bending test was used for FS and EM. GL after chemical degradation and simulated brushing was evaluated using a glossmeter. Data were submitted to one and two-way ANOVA followed by Duncan's post hoc test (α=0.05). RESULTS: All nanoparticle-modified groups showed higher values of DC. Ce1% showed higher values of FS and EM. All other groups showed similar or lower physical-mechanical properties (FS, EM, GL). Regarding type and wt%, CeO2 and TiO2 groups had better performances and were similar to each other. CONCLUSIONS: Incorporating metal nanoparticles, especially CeO2, could improve the physical properties of the dental materials. Key words:Polymethylmetacrylate, degree of conversion, flexural strength, elasticity modulus, gloss loss.