Influence of ceramic primers on microshear bond strength to zirconia

This study aimed to investigate the effect of two ceramic primers on the microshear bond strength (µSBS) of yttria-stabilized zirconia (Y-TZP) to two types of self-adhesive resin cement and one BisGMA-based resin cement. Zirconia specimens were sandblasted with 27-µm aluminum oxide and composite cylinders were cemented with resin cement with or without the prior use of ceramic primers. Nine groups (n=12) were randomly distributed according to the cement (self-adhesive RelyX U200/3M ESPE, self-adhesive Maxcem Elite/Kerr, and BisGMA-based dual-cure RelyX ARC/3M ESPE) and ceramic primer (Z-Primer Plus/Bisco and Porcelain Liner M/Sun Medical Co.). After luting, the specimens were stored in distilled water at 37°C for 24 hours and then submitted to the µSBS test. The data were analyzed with two-way ANOVA followed by the Scheffe post hoc test (p<0.05). There were significant differences between RelyX U200 and other groups. There were also significant differences between the RelyX U200 group without ceramic primer and other groups without ceramic primers (p<0.05). Self-adhesive resin cement (RelyX U200 and MaxCem) presented higher microshear bond strength (6.17 and 2.32 MPa) than the conventional resin cement (RelyX ARC) when a porcelain primer was not used (0.43 MPa). When using Porcelain Liner M, the results of RelyX ARC (2.94 MPa) were equivalent to the results of self-adhesive cement (3.93 and 2.11 MPa). When using Z-Prime Plus, the results of MaxCem (5.36 MPa) were lower than those of RelyX U200 (9.59 MPa) but equivalent to those of RelyX ARC (6.07 MPa). When using the RelyX ARC, the use of both ceramic primers improved bond strength to zirconia. When using self-adhesive resin cement, Z-Prime Plus improved microshear bond strength values. It can be concluded that, after 24 hours, the highest µSBS results were obtained when using Z-Prime Plus and RelyX U200 self-adhesive cement.

Influence of the apical limit of instrumentation and photodynamic therapy on the postoperative pain of lower molars with asymptomatic apical periodontitis.

INTRODUCTION: The aim of present study was to evaluate the influence of apical limit of instrumentation and PDT on the postoperative pain of lower molars with asymptomatic apical periodontitis. METHODS: Forty patients were included in the present study and were divided into 4 groups (n=10), according to apical limit of instrumentation and use of PDT: instrumentation at 0.0 measurement; instrumentation at 0.0 measurement+PDT; instrumentation 1mm beyond 0.0 measurement; instrumentation 1mm beyond 0.0 measurement+PDT. In the PDT, the root canals were filled with 0.01% methylene blue, remaining for 5 min. The low-intensity laser was used with 100 mW, 660-690 nm wavelength), using intra-canal fibre. Root canals were irradiated for 90 s, delivering total dose of 9 J and energy density of 320 J/cm2. After root canal preparation and PDT protocols, root canals were filled with gutta-percha and AH Plus endodontic sealer, being sealed with composite resin.The evaluation of postoperative pain was performed by visual analog scale after 24, 48, 72 hours and 7 days. Data were analysed by specific statistical tests, at level of 5%. RESULTS: No statistical significant difference was observed among experimental groups in all evaluation periods, as well as in the intragroup analysis over time, regarding postoperative pain and analgesic medication consumption (p>0.05). CONCLUSIONS: Apical limit of instrumentation and PDT have no influence on the postoperative pain of lower molars with asymptomatic apical periodontitis.

Association of calcium hypochlorite, reciprocating instrumentation and photodynamic therapy: Antimicrobial analysis and effects on root dentin structure.

INTRODUCTION: This study aimed to evaluate the antimicrobial action of calcium hypochlorite(Ca[OCl]2) and sodium hypochlorite (NaOCl) with reciprocating instrumentation and photodynamic therapy(PDT), and its influence on root dentin structure. METHODS: One hundred and ten human teeth were used to antimicrobial evaluation, inoculated with Enterococcus faecalis and divided into 11 groups (n = 10): G1 - distilled water(control); G2-1 % NaOCl; G3-5.25 % NaOCl; G4-1 % Ca(OCl)2; G5-5.25 % Ca(OCl)2; G6-PDT; G7-distilled water + PDT; G8-1 % NaOCl + PDT; G9-5.25 % NaOCl + PDT; G10-1 % Ca(OCl)2+PDT; G11-5.25 % Ca(OCl)2+PDT. In all groups, except G6, the root canals were instrumented with #R50 Reciproc file in the working length in association with tested chemical auxiliary substance. The counting of colony forming units (CFUs) was performed to calculate the bacterial percentage reduction of each group. Following, 55 bovine teeth were used to microhardness evaluation and divided into the same 11 groups (n = 5), with no instrumentation and immersion in the tested protocols. The modification of root dentin microhardness was evaluated by using the Vicker tester. Finally, 33 bovine teeth were used to organic components evaluation and divided into the same 11 groups (n = 3), with no instrumentation and immersion in the tested protocols. The modification of organic components of root dentin was evaluated by light microscopy. Specific statistical analysis was performed for each evaluation. RESULTS: The higher bacterial reduction was observed in groups 3,4,5,8,9,10 and 11, with no statistical difference between them (p > 0.05). The higher microhardness reduction was observed in groups 8,9,10 e 11, with no statistical difference between them (p > 0.05). The highest modification on organic components was observed in groups 3,5,9 and 11, with no statistical difference between them (p > 0.05). CONCLUSIONS: The association of Ca(OCl)2, reciprocating instrumentation and PDT promotes effective antimicrobial action. Moreover, lower modification was induced in microhardness and organic components of root dentin, by using Ca(OCl)2 in low concentration associated to PDT.