Influência de diferentes fotoiniciadores na resistência de união na dentina bovina / Influence of different photoinitiators on the bond strength in bovine dentin

em polímeros, resulta em propriedades mecânicas satisfatórias para a adesão. Alterações na formulação dos materiais resinosos têm sido propostas com intuito de solucionar os problemas relacionados à polimerização desses sistemas, desta forma, fotoiniciadores diferentes da canforoquinona e que relatam maior grau de conversão têm sido utilizados. No entanto, o uso inadvertido de sistemas adesivos associados a compósitos odontológicos com diferentes sistemas de fotoiniciadores pode ocasionar uma redução na eficicácia da polimerização e, como consequência, da resistência adesiva. O objetivo deste estudo in vitro foi avaliar a influência dos fotoiniciadores na resistência à microtração de sistemas adesivos e resinas compostas na dentina bovina. Quarenta fragmentos dentais, com superfícies em dentina planificadas e lisas, obtidos da face vestibular coronária de incisivos bovinos hígidos, foram distribuídos aleatoriamente em 4 grupos experimentais (n=10) de acordo com os diferentes sistemas adesivos e resinas compostas utilizados: Grupo AAPS + VAPS (Ambar APS + Vittra APS); Grupo AAPS + O (Ambar APS + Opallis); Grupo A + VAPS (Ambar + Vittra APS); Grupo A + O (Ambar + Opallis). Após restauração com compósito, as amostras foram seccionadas para obtenção de palitos que foram submetidos ao teste de microtração (1,0 mm/min). Os dados obtidos foram submetidos à análise estatística. O teste de Kruskal-Wallis revelou não haver diferenças significativas entre os grupos (p<0,05). Valores em MPa foram: AAPS + VAPS - 19,56 MPa; AAPS + O - 19,77 MPa; A + VAPS - 17,78 MPa; A + O - 22,44 MPa. O resultado do teste de Mann-Whitney mostrou não haver diferenças significativas em função do adesivo (Ambar Universal- 19,11 MPa, Ambar APS Universal- 21,70 MPa) e da resina composta utilizada (Vittra APS- 18,75 MPa, Opallis- 23,75 MPa). Concluiu-se que a utilização de diferentes fotoiniciadores na composição dos sistemas adesivos e compósitos restauradores não influenciou seus valores de resistência adesiva devido à padronização dos fatores que influenciam o padrão de polimerização dos mesmos. (AU)

An effective polymerization of the composite resin provides a higher monomer degree conversion into polymers, resulting in satisfactory mechanical properties for adhesion. Changes in the formulation of resinous materials have been proposed with the aim to solve the problems related to the polymerization of these systems. Thus, different photoinitiators from camphorquinone and that report higher degree of conversion have been used. However, the inadvertent use of adhesive systems associated with dental composites with different photoinitiators systems can lead to a reduction in the efficiency of the cure and, consequently, of the adhesive resistance. The objective of this in vitro was to evaluate the influence of photoinitiators on the microtensile strength of adhesive systems and composite resins to bovine dentin. Forty dental fragments with smooth and straightened dentin surfaces obtained from the coronary vestibular surface of healthy bovine incisors were randomly divided into 4 experimental groups (n = 10) according to the different adhesive systems and composite resins used: Group: AAPS + VAPS (Ambar APS + Vittra APS); Group: AAPS + O (Ambar APS + Opallis); Group: A + VAPS (Ambar + Vittra APS); Group: A + O (Ambar + Opallis). After composite restoration, the samples were sectioned to obtain sticks that were submitted to the microtensile test (1.0mm/min). The data were submitted to statistical analysis. The Kruskal-Wallis test revealed no significant diferences between groups (p<0.05). Values in MPa were: AAPS + VAPS - 19,56 MPa; AAPS + O - 19,77 MPa; A + VAPS - 17,78 MPa; A + O - 22,44 MPa. The result of the Mann-Whitney test showed no significant statistical difference as a function of adhesives (Ambar Universal- 19.11 MPa, Ambar Universal APS - 21,70 MPa) and the composite resin used (Vittra APS - 18.75 MPa, Opallis - 23.75 MPa). It was concluded that the use of different photoinitiators in the composition of adhesive systems and restorative composites did not influence their adhesive strength values due the standardization of the factors that influence the curing pattern of the adhesive systems. (AU)

Longitudinal Evaluation of Bond Strength to Enamel of Dental Adhesive Systems Associated with Nd:YAG Laser.

OBJECTIVES: This study evaluated the durability of bond strength to enamel using total-etch (Single Bond/SB) and self-etch (Clearfil SE Bond/CSEB) adhesives associated with neodymium:yttrium-aluminu-garnet (Nd:YAG) laser irradiation through the uncured adhesives. METHODS: Bovine incisors were worn to expose an area of enamel and were divided into four groups: group 1 (control) SB + polymerization; group 2 (control) CSEB + polymerization; group 3 (laser) - SB + Nd:YAG laser (174.16 J/cm(2)) + polymerization; and group 4 (laser) CSEB + Nd:YAG (174.16 J/cm(2)) + polymerization. Blocks of composite were fabricated and stored for 24 hours or 12 months, sectioned into beams, and submitted to microtensile tests. Results were analyzed by three-way analysis of variance (ANOVA) (adhesive, technique, and storage time) and Tukey tests. RESULTS: ANOVA revealed significant differences for adhesive × technique and technique × storage time (p<0.05). The mean values (MPa) for interaction adhesive × technique (standard deviation) were as follows: SB/control = 35.78 (6.04)a; SB/laser = 26.40 (7.25)b, CSEB/control = 26.32 (5.71)b, CSEB/laser = 23.90 (7.49)b. For interaction technique × storage time the mean values were as follows: control/24 hours = 32.58 (6.49)a; control/12 months = 29.52 (8.38)a; laser/24 hours = 29.37 (5.71)a; laser/12 months = 20.92 (6.5)b. Groups with the same letters showed no statistically significant differences. CONCLUSION: Scanning electron microscope analysis showed evident areas of micromorphological alterations in lased samples after 12 months of water storage. Nd:YAG laser irradiation of enamel through unpolymerized total-etch adhesive significantly reduced bond strength compared with the control. Bond strength decreased when enamel samples irradiated with Nd:YAG laser through unpolymerized adhesives were stored in water for 12 months.

Effect of light-emitting diode and halogen light curing on the micro-hardness of dental composite and resin-modified glass ionomer cement: an in vitro study.

AIMS: This in vitro study was conducted to evaluate and compare the micro-hardness of composite resin and resin-modified glass ionomer cement using light-emitting diode (LED) and halogen curing and also to inter-compare the effect of LED and halogen curing. MATERIALS AND METHODS: The study sample comprised of 4 stainless steel plates with a thickness of 2 mm. For these stainless steel plates, holes were made to a diameter of 3 mm. The samples were divided into 4 groups of 8 each and labeled as group I, group II, group III, group IV, thus making provision for the two different modes of light exposure. In each group, the hole was restored with its respective restorative material and cured with light-curing unit according to manufacturer instructions. The results were statistically analyzed using Mann-Whitney test. RESULTS AND CONCLUSION: It was concluded that the curing efficacy of the LED lamp was comparable to that of conventional halogen lamp, even with a 50% reduction in cure time, and resin composite (Filtek Z-250) presented the highest hardness values, whereas complete hardening of resin-modified glass ionomer cement (RMGIC) (Vitremer) was observed because of its self-curing system even after the removal of light source.

Depth of cure of resin composites: is the ISO 4049 method suitable for bulk fill materials?

OBJECTIVES: To evaluate if depth of cure D(ISO) determined by the ISO 4049 method is accurately reflected with bulk fill materials when compared to depth of cure D(new) determined by Vickers microhardness profiles. METHODS: D(ISO) was determined according to "ISO 4049; Depth of cure" and resin composite specimens (n=6 per group) were prepared of two control materials (Filtek Supreme Plus, Filtek Silorane) and four bulk fill materials (Surefil SDR, Venus Bulk Fill, Quixfil, Tetric EvoCeram Bulk Fill) and light-cured for either 10s or 20s. For D(new), a mold was filled with one of the six resin composites and light-cured for either 10 s or 20 s (n=22 per group). The mold was placed under a microhardness indentation device and hardness measurements (Vickers hardness, VHN) were made at defined distances, beginning at the resin composite that had been closest to the light-curing unit (i.e. at the "top") and proceeding toward the uncured resin composite (i.e. toward the "bottom"). On the basis of the VHN measurements, Vickers hardness profiles were generated for each group. RESULTS: D(ISO) varied between 1.76 and 6.49 mm with the bulk fill materials showing the highest D(ISO). D(new) varied between 0.2 and 4.0 mm. D(new) was smaller than D(ISO) for all resin composites except Filtek Silorane. CONCLUSIONS: For bulk fill materials the ISO 4049 method overestimated depth of cure compared to depth of cure determined by Vickers hardness profiles.