Effect of HEMA Phosphate as an Alternative to Phosphoric Acid for Dentin Treatment Prior to Hybridization with Etch-and-Rinse Adhesive Systems.

PURPOSE: To evaluate the effect of dentin treatment using HEMA phosphate (HEMA-P) on the microtensile bond strength (µTBS) and nanoleakage of an etch-and-rinse adhesive system. MATERIALS AND METHODS: The occlusal surfaces of human molars were wet ground until superficial dentin was exposed. The specimens were then assigned to two groups according to dentin treatment: PA: 37% H3PO4 for 15 s; or HP: HEMA-P for 15 s. Adper Single Bond 2 was applied to the treated dentin surfaces and resin composite buildups were incrementally constructed over them. After 24-h storage in artificial saliva at 37°C, the bonded teeth were cut into resin-dentin sticks with a cross-sectional area of 1 mm², which were submitted to µTBS testing immediately or after 3 months of storage in artificial saliva at 37°C. Nanoleakage was assessed using SEM/EDS, and the interaction between dentin and H3PO4 or HEMA-P was evaluated by combining micro-Raman and FT-IR spectroscopy. The data were analyzed using two-way ANOVA and Tukey's HSD post-hoc test (α = 0.05). RESULTS: HP presented significantly higher µTBS than PA at both times (p < 0.05). Both treatments maintained µTBS stability after 3 months of artificial saliva storage (p > 0.005). At both times, PA presented higher nanoleakage than HP (p < 0.05). CONCLUSIONS: Both dentin treatments maintained µTBS stability after 3 months of artificial saliva storage. The use of HEMA-P was associated with less nanoleakage than was traditional phosphoric-acid etching.

Stability of the bond between two resin cements and an yttria-stabilized zirconia ceramic after six months of aging in water.

STATEMENT OF THE PROBLEM: The behavior of the luting cement and the cementation protocol are essential in the clinical success of ceramic restorations. PURPOSE: The purpose of this study was to evaluate the bond stability of 2 resin cements and a yttria-stabilized tetragonal polycrystalline zirconia (Y-TZP) ceramic submitted to 2 surface treatments. MATERIAL AND METHODS: Sixty plates of a Y-TZP ceramic were assigned to 3 groups according to the surface treatments: control, as sintered surface; methacryloxydecyl dihydrogen phosphate (MDP), coated with an MDP-based primer, and tribochemical silica-coating (TSC), coated with tribochemical silica. The plates of each group were further divided into 2 subgroups according to the resin cement as follows: RelyX adhesive resin cement (conventional) and RelyX Unicem (self-adhesive). Cylinders of resin cements (∅=0.75 mm × 0.5 mm in height) were built up on the ceramic surfaces, and the plates stored in distilled water at 37°C for either 24 hours or 6 months before being submitted to a microshear bond strength test. The data were submitted to 3-way ANOVA and the Tukey honestly significant difference test (α=.05). RESULTS: Three-way ANOVA showed statistical significance for the 3 independent factors: resin cement, surface treatment, and period of water immersion (P<.001). Unicem presented the highest microshear bond strength after 24 hours (MDP, 37.4 ±2.3 and TSC, 36.2 ±2.1 MPa). Except for RelyX adhesive resin cement applied on ceramic surfaces treated with TSC, the microshear bond strength of all the other groups decreased after 6 months of aging in water. The microshear bond strength decreased most in the control groups (-81.5% for ARC and -93.1% for Unicem). In the group treated with TSC, the microshear bond strength for Unicem decreased by 54.8% and in that treated with MDP-based primer by -42.5%. In the group treated with MDP-based primer, the microshear bond strength for RelyX ARC decreased by -52.8%. CONCLUSIONS: Irrespective of surface treatments, self-adhesive resin cement was not able to maintain the bond to Y-TZP ceramic after 6 months of aging in water.

Evaluation of self-adhesive resin cement bond strength to yttria-stabilized zirconia ceramic (Y-TZP) using four surface treatments.

PURPOSE: To evaluate the influence of four surface treatments on the bond strength of a self-adhesive resin cement to an yttria-stabilized zirconia (Y-TZP) ceramic material (Lava Frame zirconia). MATERIALS AND METHODS: Forty plates (8 x 6 x 1 mm) of a Y-TZP ceramic restorative material were randomly assigned to four groups (n = 10) according to the surface treatments: control, no treatment; airborne-particle abrasion with 50-µm Al2O3; coating with an MDP-based primer; conditioning with Rocatec System. The ceramic plates treated with each of the four methods were further divided into 2 subgroups according to the resin cement tested: RelyXTM ARC (ARC, conventional) and RelyXTM Unicem (Ucem, self-adhesive). The resin cements were put into PVC tubes (diameter 0.75 mm, 0.5 mm height) placed on the ceramic plate surfaces. After water storage at 37°C for 24 h, the specimens were submitted to a microshear bond strength (µSBS) test at a crosshead speed of 1.0 mm/min. RESULTS: The surface treatments significantly influenced the µSBS (p < 0.05). For the four surface treatments, UCem presented significantly higher µSBS than ARC (p < 0.05). For both resin cements, the best result was produced by the MDP-based primer: ARC 15.9 ± 5.0 MPa and UCem 36.2 ± 2.1 MPa. The highest µSBS values were presented by UCem on ceramic plates treated with the MDP-based primer (36.2 ± 2.1 MPa) and Rocatec system (37.4 ± 2.3 MPa). CONCLUSION: Irrespective of the surface treatment, the self-adhesive resin cement performed better in terms of bond strength to yttria-stabilized zirconia ceramic than did conventional resin cement.

Effect of intra-oral aging on t→m phase transformation, microstructure, and mechanical properties of Y-TZP dental ceramics.

The aim of the present study was to evaluate the influence of intra-oral aging on the tetragonal-to-monoclinic (t→m) phase transformation of two Y-TZP dental ceramics - Lava Frame (Frame) and Lava Plus (Plus) - and determine the impact of this response on their microstructures and mechanical properties: flexural strength, Young's modulus, microhardness and fracture toughness. Standardized ceramic specimens were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). After the baseline analysis, the specimens were attached to personalized intra-oral resin appliances and exposed to the oral cavity of 20 subjects for 60 days and then analyzed again. Specimens produced for mechanical properties evaluation were also analyzed before and after the 60-day intra-oral aging. The data were analyzed using two-way ANOVA and Tukey HSD's post hoc test (α=0.05). Weibull analysis was used to evaluate the strength reliability. Both Y-TZP ceramics suffered t→m phase transformation after 60-day intra-oral aging (Plus=4.7%/Frame=7.7%). SEM and AFM analyses showed dislodgement of ZrO2 grains and a significant increase in roughness after intra-oral aging for both ceramics. Both Y-TZP ceramics suffered a decrease on flexural strength, Young's modulus and fracture toughness after intra-oral aging (p<0.05). Only Plus presented a decrease of microhardness after intra-oral aging (p<0.05). Intra-oral aging for 60 days produced t→m phase transformation, changed the microstructure and decreased the mechanical properties of two Y-TZP dental ceramics.

Characterization of an experimental resin composite organic matrix based on a tri-functional methacrylate monomer.

This study evaluated the potential of a tri-functional monomer (trimethylolpropane trimethacrylate -TMPTMA) for inclusion in a dental composite organic matrix. Initially, four ternary matrixes with different concentrations (wt%) of bi-functional monomers [BisGMA (G), Bis-EMA (E) and TEGDMA (T)] were analyzed: GET523, GET532, EGT523 and EGT532 (the numbers (n) represent n×10 wt% of each monomer). The following properties were evaluated: degree of conversion, flexural strength, elastic modulus, hardness, absorption, solubility, diffusion coefficient of water and crosslink density. Based on the best overall results obtained for EGT532, all properties were re-evaluated in a matrix where TEGDMA (T) was replaced by a tri-functional monomer, TMPTMA (A)-EGA532. EGA532 presented the best results for flexural strength, hardness, absorption and crosslink density. EGT523, EGT532 and EGA532 presented the lowest diffusion coefficients of water. The overall results indicated that TMPTMA could be useful in formulating organic matrixes suitable for dental restorative composites.

Influence of Organic Acids from the Oral Biofilm on the Bond Strength of Self-Etch Adhesives to Dentin.

The aim of this study was to evaluate the microtensile bond strength of self-etch adhesive systems to dentin after storage in acids from oral biofilm. Three adhesive systems were used in the study: a two-step self-etch adhesive for use with a silorane-based resin composite (Filtek P90 adhesive system - P90), a two-step self-etch adhesive (Clearfil SE Bond - CSE) and a one-step self-etch adhesive (Adper Easy One - AEO). The bond strength of these products was evaluated by bonding resin composite (Filtek Z350 for CSE and AEO; and Filtek P90 for P90) to 90 bovine dentin tooth fragments, according to the manufacturer's instructions. After 24 h of water storage at 37 °C, the specimens were sectioned into beams (1 mm2) divided and stored in distilled water, lactic acid and propionic acid, for 7 and 30 days. After storage, the specimens were tested for microtensile bond strength. Data were analyzed by three-way ANOVA and Tukey´s test (α=0.05). CSE presented the highest microtensile bond strength after storage in distilled water for 7 and 30 days. The microtensile bond strength of all adhesive systems was lower after storage in lactic acid and propionic acid than after water storage. Significant difference was not found between storage times.

Influence of Organic Acids from the Oral Biofilm on the Bond Strength of Self-Etch Adhesives to Dentin

Abstract: The aim of this study was to evaluate the microtensile bond strength of self-etch adhesive systems to dentin after storage in acids from oral biofilm. Three adhesive systems were used in the study: a two-step self-etch adhesive for use with a silorane-based resin composite (Filtek P90 adhesive system - P90), a two-step self-etch adhesive (Clearfil SE Bond - CSE) and a one-step self-etch adhesive (Adper Easy One - AEO). The bond strength of these products was evaluated by bonding resin composite (Filtek Z350 for CSE and AEO; and Filtek P90 for P90) to 90 bovine dentin tooth fragments, according to the manufacturer's instructions. After 24 h of water storage at 37 °C, the specimens were sectioned into beams (1 mm2) divided and stored in distilled water, lactic acid and propionic acid, for 7 and 30 days. After storage, the specimens were tested for microtensile bond strength. Data were analyzed by three-way ANOVA and Tukey´s test (α=0.05). CSE presented the highest microtensile bond strength after storage in distilled water for 7 and 30 days. The microtensile bond strength of all adhesive systems was lower after storage in lactic acid and propionic acid than after water storage. Significant difference was not found between storage times.

Resumo: O objetivo deste trabalho foi avaliar a resistência de união de sistemas adesivos autocondicionantes após estocagem em ácidos presentes no biofilme oral. Foram utilizados três sistemas adesivos: um autocondicionante de dois frascos indicado para uso com a resina composta à base de silorano (P90 System Adhesive- P90), um autocondicionante de dois frascos (Clearfil SE Bond - CSE) e um autocondicionante de frasco único (AdperEasyOne - AEO). Para avaliação da resistência de união à dentina, 90 fragmentos de dentes bovinos foram restaurados de acordo com as recomendações dos fabricantes. Após a confecção de blocos de resina composta (Filtek Z350 para os sistemas adesivos AEO e CSE; Filtek P90 para o sistema adesivo P90) e estocagem em água destilada por 24 h a 37 °C, os fragmentos foram seccionados para a obtenção de palitos (1 mm2) que foram divididos e estocados nos três diferentes meios de imersão (água destilada, ácido lático e ácido propiônico) por períodos de 7 dias e 30 dias (n=5). Em seguida, foi realizado o ensaio de resistência à microtração. Os dados foram submetidos à Análise de Variância (3 fatores) e ao Teste de Tukey (α=0,05). O sistema adesivo CSE apresentou maior resistência de união após imersão em água por 7 ou 30 dias. A resistência de união de todos os sistemas adesivos foi menor após imersão em ácido lático e propiônico do que após imersão em água. Não foi observada diferença significativa entre os tempos de imersão.

Fechamento de diastema com coroas de alumina densamente sinterizadas / Diastema closure with densely sintered alumina crowns

O objetivo deste trabalho é apresentar um caso de fechamento de diastema com coroas de alumina densamente sinterizadas através da utilização do Sistema Procera®, mostrando as etapas de confecção e requisitos técnicos para o sucesso dos casos. O caso apresentado seguiu o seguinte protocolo clínico: enceramento diagnóstico, confecção de preparo comtérmino em chanfro e desgaste de 1,5mm nas paredes axiais e 2,0mm de desgaste incisal, confecção de restaurações provisórias, moldagem com técnica de duplo fio de afastamento, enceramento das subestruturas para duplo escaneamento, aplicação cerâmica e cimentação por meio de cimento resinoso. Os resultados obtidos foram julgados como bastante satisfatórios pela paciente e pelo profissional responsável sob os pontos de vista estéticos e biológicos.