Can the hydrophilicity of functional monomers affect chemical interaction?

The number of carbon atoms and/or ester/polyether groups in spacer chains may influence the interaction of functional monomers with calcium and dentin. The present study assessed the chemical interaction and bond strength of 5 standard-synthesized phosphoric-acid ester functional monomers with different spacer chain characteristics, by atomic absorption spectroscopy (AAS), ATR-FTIR, thin-film x-ray diffraction (TF-XRD), scanning electron microscopy (SEM), and microtensile bond strength (µTBS). The tested functional monomers were 2-MEP (two-carbon spacer chain), 10-MDP (10-carbon), 12-MDDP (12-carbon), MTEP (more hydrophilic polyether spacer chain), and CAP-P (intermediate hydrophilicity ester spacer). The intensity of monomer-calcium salt formation measured by AAS differed in the order of 12-MDDP=10-MDP>CAP-P>MTEP>2-MEP. FTIR and SEM analyses of monomer-treated dentin surfaces showed resistance to rinsing for all monomer-dentin bonds, except with 2-MEP. TF-XRD confirmed the weaker interaction of 2-MEP. Highest µTBS was observed for 12-MDDP and 10-MDP. A shorter spacer chain (2-MEP) of phosphate functional monomers induced formation of unstable monomer-calcium salts, and lower chemical interaction and dentin bond strength. The presence of ester or ether groups within longer spacer carbon chains (CAP-P and MTEP) may affect the hydrophilicity, µTBS, and also the formation of monomer-calcium salts.

Two methods to simulate intrapulpal pressure: effects upon bonding performance of self-etch adhesives.

AIM: To evaluate the effects of two methods to simulate physiological pulpal pressure on the dentine bonding performance of two all-in-one adhesives and a two-step self-etch silorane-based adhesive by means of microtensile bond strength (µTBS) and nanoleakage surveys. METHODOLOGY: The self-etch adhesives [G-Bond Plus (GB), Adper Easy Bond (EB) and silorane adhesive (SIL)] were applied to flat deep dentine surfaces from extracted human molars. The restorations were constructed using resin composites Filtek Silorane or Filtek Z350 (3M ESPE). After 24 h using the two methods of simulated pulpal pressure or no pulpal pressure (control groups), the bonded teeth were cut into specimens and submitted to µTBS and silver uptake examination. Results were analysed with two-way anova and Tukey's test (P < 0.05). RESULTS: Both methods of simulated pulpal pressure led statistically similar µTBS for all adhesives. No difference between control and pulpal pressure groups was found for SIL and GB. EB led significant drop (P = 0.002) in bond strength under pulpal pressure. Silver impregnation was increased after both methods of simulated pulpal pressure for all adhesives, and it was similar between the simulated pulpal pressure methods. CONCLUSIONS: The innovative method to simulate pulpal pressure behaved similarly to the classic one and could be used as an alternative. The HEMA-free one-step and the two-step self-etch adhesives had acceptable resistance against pulpal pressure, unlike the HEMA-rich adhesive.

Effects of surface treatments, thermocycling, and cyclic loading on the bond strength of a resin cement bonded to a lithium disilicate glass ceramic.

SUMMARY Objectives : The aim of this present study was to investigate the effect of two surface treatments, fatigue and thermocycling, on the microtensile bond strength of a newly introduced lithium disilicate glass ceramic (IPS e.max Press, Ivoclar Vivadent) and a dual-cured resin cement. Methods : A total of 18 ceramic blocks (10 mm long × 7 mm wide × 3.0 mm thick) were fabricated and divided into six groups (n=3): groups 1, 2, and 3-air particle abraded for five seconds with 50-µm aluminum oxide particles; groups 4, 5, and 6-acid etched with 10% hydrofluoric acid for 20 seconds. A silane coupling agent was applied onto all specimens and allowed to dry for five seconds, and the ceramic blocks were bonded to a block of composite Tetric N-Ceram (Ivoclar Vivadent) with RelyX ARC (3M ESPE) resin cement and placed under a 500-g static load for two minutes. The cement excess was removed with a disposable microbrush, and four periods of light activation for 40 seconds each were performed at right angles using an LED curing unit (UltraLume LED 5, Ultradent) with a final 40 second light exposure from the top surface. All of the specimens were stored in distilled water at 37°C for 24 hours. Groups 2 and 5 were submitted to 3,000 thermal cycles between 5°C and 55°C, and groups 3 and 6 were submitted to a fatigue test of 100,000 cycles at 2 Hz. Specimens were sectioned perpendicular to the bonding area to obtain beams with a cross-sectional area of 1 mm(2) (30 beams per group) and submitted to a microtensile bond strength test in a testing machine (EZ Test) at a crosshead speed of 0.5 mm/min. Data were submitted to analysis of variance and Tukey post hoc test (p≤0.05). Results : The microtensile bond strength values (MPa) were 26.9 ± 6.9, 22.2 ± 7.8, and 21.2 ± 9.1 for groups 1-3 and 35.0 ± 9.6, 24.3 ± 8.9, and 23.9 ± 6.3 for groups 4-6. For the control group, fatigue testing and thermocycling produced a predominance of adhesive failures. Fatigue and thermocycling significantly decreased the microtensile bond strength for both ceramic surface treatments when compared with the control groups. Etching with 10% hydrofluoric acid significantly increased the microtensile bond strength for the control group.

Influence of the volume of composite and photoactivation method on push-out bond strength and Knoop hardness of a resin composite.

AIM: The aim of this paper was to evaluate the influence of modulated photoactivation methods and volume of composite on Knoop hardness (KHN) and push-out bond strength (PBS) of Filtek Z350 to root dentin. METHODS: Three volumes (small, medium and large) of composite were bulk inserted in cavities prepared in 90 premolars. The specimens were photoactivated with continuous light, pulse-delay, or soft-start methods and submitted to PBS and KHN tests. The failure pattern was evaluated in stereomicroscope after the bond strength test. The data were submitted to two-way ANOVA and Tukey's test (P<0.05). RESULTS: Modulated photoactivation methods showed a higher PBS than continuous method (P<0.05). Medium volume of composite showed higher PBS than small and large volumes when photoactivated with continuous method (P<0.05). Pulse-delay significantly increased KHN for medium and large volumes in comparison to continuous method (P<0.05). Medium volume of composite showed KHN significantly higher than small and large volumes (P<0.05). CONCLUSION: The volume of composite influenced the PBS and KHN of resin composites. Pulse-delay showed the highest bond strength to dentin, as well KHN similar to the conventional method. The analysis of the failure pattern showed predominance of adhesive failure.

Variations in caries diagnoses and treatment recommendations and their impacts on the costs of oral health care.

OBJECTIVE: To evaluate the reproducibility of caries detection and treatment planning among public health dentists and estimate the possible impact of their decisions on financial costs. RESEARCH DESIGN AND SETTINGS: Thirty nine dentists working in the public health service of Piracicaba, São Paulo, Brazil made a combined visual-radiographic caries examination of 40 occlusal surfaces of extracted permanent teeth mounted on two dental mannequins and proposed treatment plans for each tooth. Histological validation then evaluated the diagnoses validity and the suitability of the treatment plans. OUTCOME MEASURES: Inter-examiner agreement was calculated by Cohen's Kappa statistics. The sensitivity and specificity of caries detection and treatment decision were calculated. The costs of dental treatment plans for public health system were calculated from a Brazilian public health service fee scale. RESULTS: Inter-examiner agreement for caries detection was moderate (kappa = 0.42) while for treatment decisions it was fair (kappa = 0.29). The sensitivity and specificity were 0.69 and 0.65 for caries detection and 0.56 and 0.65 for treatment decision respectively. Dentists overestimated the presence and depth of carious lesions and there was a tendency to treat enamel lesions using invasive therapeutic procedures. Mean treatment cost across the two cases was 32US$ (range 9-65) while the histologically validated cost was 23US$. CONCLUSION: The variability in caries detection and treatment decision negatively affected the cost of the dental treatment.

Radiopacity of root filling materials using digital radiography.

AIM: To evaluate radiopacity of root filling materials using digital radiography. METHODOLOGY: The sealers tested were AH Plus, Endofill, EndoREZ and Epiphany. Gutta-percha (Dentsply Maillefer) and Resilon cones were also tested. Acrylic plates, containing six wells, measuring 1 mm in depth and 5 mm in diameter, were prepared for the test, and filled with the materials. The test samples were radiographed together with an aluminium stepwedge calibrated in millimetres, according to ANSI/ADA Specification 57. For the radiographic exposures, digital imaging plates and an X-ray machine at 70 kVp and 8 mA were used. The object-to-focus distance was 30 cm, and the exposure time, 0.2 s. After the laser optic reading process, the software determined the radiopacity of the standardized areas, using grey-scale values, calculating the average radiographic density for each material. RESULTS: The decreasing values of radiopacity of the studied materials, expressed in millimetres of aluminium equivalent, were: Resilon (13.0), AH Plus(TM) (11.2), gutta-percha (9.8), Epiphany (8.0), Endofill (6.9) and EndoREZ (6.6). CONCLUSION: All materials had radiopacity values above 3 mm of aluminium recommended by ANSI/ADA Specification 57.

Halogen and LED light curing of composite: temperature increase and Knoop hardness.

This study assessed the Knoop hardness and temperature increase provided by three light curing units when using (1) the manufacturers' recommended times of photo-activation and (2) standardizing total energy density. One halogen--XL2500 (3M/ESPE)--and two light-emitting diode (LED) curing units--Freelight (3M/ESPE) and Ultrablue IS (DMC)--were used. A type-K thermocouple registered the temperature change produced by the composite photo-activation in a mold. Twenty-four hours after the photo-activation procedures, the composite specimens were submitted to a hardness test. Both temperature increase and hardness data were submitted to ANOVA and Tukey's test (5% significance). Using the first set of photo-activation conditions, the halogen unit produced a statistically higher temperature increase than did both LED units, and the Freelight LED resulted in a lower hardness than did the other curing units. When applying the second set of photo-activation conditions, the two LED units produced statistically greater temperature increase than did the halogen unit, whereas there were no statistical differences in hardness among the curing units.

Efeito das técnicas de inserção de compósitos odontológicos sobre a infiltração marginal / Effect of techniques of composit resin on microleakage

O objetivo deste estudo foi avaliar o efeito de duas técnicas de inserção do compósito sobre o nível de infiltração marginal na interface dente/compósito restaurador. Foram preparadas 40 cavidades circulares medindo 4 mm de diamêtro por 3 mm de profundidade em dentes bovinos, que foram divididos em 4 grupos (n=10): Grupo 1 - Único encremento + P60; Grupo 2 - Único encremento + Definite; Grupo 3 - Três incrementos + P60 ; e Grupo 4 - Três incrementos + Definite. Todas as amostras foram armazenadas em água destilada a 37°C, por 24 horas e submetidas a 500 ciclos térmicos (5° e 55°) por 30 segundos em cada banho. Em seguida, os dentes foram imersos em solução de azul de metileno a 2 por cento, por 4 horas, e a microinfiltração avaliada. Os resultados submetidos ao teste estatístico de Kruskal-Wallis mostraram que a técnica de inserção em 3 incrementos para o Definite com 1 incremento; o P60 com 3 incrementos apresentou níveis de infiltração marginal estatisticamente menores em relação ao P60 e Definite, ambos com 1 incremento