Jaime Portugal

Grau de Conversão de Resinas Compostas. Influência do Método de Fotopolimerização.

Objectives: To evaluate the degree of conversion of four composite resins and to determine the influence of two polymerization methods. Methods: Forty 2mm thick composite disks were assigned to 8 experimental groups (n=5) accor- ding to several possible combinations between the polymerization methods (QTH curing unit (400mW/cm 2 ) / 40s and a LED curing unit (800mW/cm 2 ) / 20s) and the composites (Suprafil (R&S), Natural Elegance (Henry Schein Inc.), Proclinic Composite PM (Madespa SA) and FiltekTM Z250 (3M ESPE)) tested. Specimens were polymerized exposing the light only to the top surface. Human enamel was used below the disks, as a reflection material. After dry storage in the dark for 24h, Vickers microhardness measurements were performed for each specimen on the top and bottom surfaces. Microhardness ratio was calculated for each specimen. A minimum of 0.80 was considered as a correct polymerization. Data were analy- zed with ANOVA and t-Teste. Results: Microhardness ratio ranged between 0.79 and 0.98. To QTH specimens, Z250 showed statistically (p<0,05) higher ratios than the others composites. To LED specimens, there were no statistically (p≥0.05) differen- ces between composites with the exception of Suprafil who has shown a lower ratio. Conclusions: Despite the fact that Z250 showed an higher microhardness ratio, all the experimental groups reached an adequate polymerization, excepted for the group Proclinic/QTH (0.79). Using the LED curing unit may reduce the working time.

Effect of saliva contamination and artificial aging on different primer/cement systems bonded to zirconia

Statement of problem. Saliva contamination has been shown to decrease bonding to zirconia. Adopting a less contamination‐sensitive cement system may be an alternative to decontamination. Purpose. The purpose of this in vitro study was to assess the ability of different primer/cement systems to promote a durable bond to zirconia after saliva contamination. Material and methods. Zirconia blocks (Lava Plus) (N=320) were airborne‐particle abraded (50 &mgr;m Al2O3) and divided into 32 experimental groups (n=10) according to the variables in the study: saliva contamination; primer/cement system (Panavia SA [PSA]; RelyX Unicem 2 [RU2]; Bifix SE [BSE]; Panavia F2.0 [PF2]; Scotchbond Universal + RelyX Ultimate [SBU+RXU]; Futurabond M+ + Bifix QM [FBM+BQM]; All‐Bond Universal + Duo‐link [ABU+DL]; Z‐Prime Plus + Duo‐link [ZPP+DL]; and aging period (72 hours; 30 days with 10 000 thermocycles at 5°C to 55°C). After half of the blocks had been contaminated with fresh human saliva for 10 minutes, rinsed with water, and air‐dried, each primer/cement was applied. Polymerized composite resin disks were then placed over the cement, and the resin cement was light‐polymerized for 20 seconds each at 2 opposite margins. After the aging time, the specimens were tested in shear (1 mm/min). The failure mode was classified as adhesive, cohesive, or mixed. Statistical analysis of the shear bond strength (SBS) data was performed with ANOVA followed by Tukey honest significant difference post hoc tests. Chi‐square tests were used to analyze the failure mode data (&agr;=.05). Results. The mean SBS ranged between 4.2 and 34.5 MPa. Shear bond strength was influenced (P<.001) by all the factors studied (cement system, saliva contamination, aging time). SBU+RXU and FBM+BQM showed a higher mean SBS than those of the other experimental groups (P<.05) and were the only groups not affected by saliva contamination (P>.05). Failure was predominantly classified as adhesive. Conclusions. In general, saliva contamination and aging decreased bonding efficacy. Two systems, combining an application of a universal adhesive and a resin cement (SBU+RXU and FBM+BQM) were not affected by saliva contamination.

Adhesion of dental sealants to enamel with self-etching adhesives in salivary contamination conditions: Influence of the light curing protocol

Purpose: To evaluate the influence of the light curing protocol in the shear bond strength of a sealant to enamel treated with two self-etching adhesive systems, in salivary contamination conditions. Materials and Methods: The dental sealant (Delton, Dentsply) was applied, after saliva contamination, onto the vestibular enamel of sixty human incisors treated with Xeno III (Dentsply) or Prompt-L-Pop (3M/Espe). These two groups were further divided into two subgroups (n = 15) according to the curing time: 1) the adhesive system was cured with the sealant (co-polymerization), and 2) adhesive and sealant were light cured independently (independent polymerization). After the adhesive procedures, specimens were stored in water (37 °C-24 h) and thermal-cycled. Shear bond strength tests were done in an universal testing machine. Data was analyzed with two-way ANOVA. Results: There were no statistical differences (p = 0.267) between the adhesive systems tested. The co-polymerization groups (33.3 ± 9.4 MPa) yielded statistically higher shear bond strength values than the independent polymerization groups (28.2 ± 4.7 MPa). Even with saliva contamination, the self-etching adhesive systems used yielded high shear bond strength values. Conclusions: In the conditions tested, the co-polymerization of the adhesive systems with the sealant led to higher bond strength values to enamel than the independent polymerization.

# 44. Resistência adesiva ao ProRoot® MTA e BIODENTINE™ com diferentes estratégias adesivas

Poster apresentado no XXXV Congresso Anual da Sociedade Portuguesa de Estomatologia e Medicina Dentaria (SPEMD), 9-10 Outubro 2015, Centro de Congressos do Lagoas Park, Oeiras, Lisboa.