The influence of temporary cements on dental adhesive systems for luting cementation.

OBJECTIVE: This study tested the hypothesis that bond strength of total- and self-etching adhesive systems to dentine is not affected by the presence of remnants from either eugenol-containing (EC) or eugenol-free (EF) temporary cements after standardized cleaning procedures. METHODS: Thirty non-carious human third molars were polished flat to expose dentine surfaces. Provisional acrylic plates were fabricated and cemented either with EC, EF or no temporary cements. All specimens were incubated for 7 days in water at 37°C. The restorations were then taken out and the remnants of temporary cements were mechanically removed with a dental instrument. The dentine surfaces were cleaned with pumice and treated with either total-etching (TE) or self-etching (SE) dental adhesive systems. Atomic force microscopy was used to examine the presence of remnants of temporary cements before and after dentine cleaning procedures. Composite resin build-ups were fabricated and cemented to the bonded dentine surfaces with a resin luting cement. The specimens were then sectioned to obtain 0.9mm(2) beams for microtensile bond strength testing. Fractographic analysis was performed by optical and scanning electron microscopy. RESULTS: ANOVA showed lower mean microtensile bond strength in groups of specimens treated with EC temporary cement than in groups treated with either no cement or an EF cement (p<0.05). Mean microtensile bond strength was lower in groups employing the SE rather than the TE adhesive system (p<0.001). SE samples were also more likely to fail during initial processing of the samples. There was no evidence of interaction between cement and adhesive system effects on tensile strength. Fractographic analysis indicated different primary failure modes for SE and TE bonding systems, at the dentine-adhesive interface and at the resin cement-resin composite interface, respectively. CONCLUSION: The use of eugenol-containing temporary cements prior to indirect bonding restorations reduce, to a statistically similar extent, the bond strength of both total- and self-etching adhesive systems to dentine.

Histomorphologic and bone-to-implant contact evaluation of dual acid-etched and bioceramic grit-blasted implant surfaces: an experimental study in dogs.

PURPOSE: The objective of this study was to histologically evaluate a bioceramic grit-blasted and acid-etched surface (presenting calcium and phosphorous incorporation within the surface and its oxide) versus a dual acid-etched (no calcium and phosphorous, control) moderately rough implant surface in a dog tibia model. MATERIALS AND METHODS: Implants 3 x 10 mm were placed bilaterally along the proximal tibia of 6 Doberman dogs and remained for 2 and 4 weeks in vivo. After the dogs were euthanized, the implants were nondecalcified processed to approximately 30-microm-thick plates. Transmitted light optical microscopy was used to evaluate healing patterns and bone-to-implant contact. Statistical analysis was performed by 1-way analysis of variance at the 95% level of significance and by Tukey post hoc tests. RESULTS: At 2 weeks, histologic evaluation showed woven bone formation throughout the perimeter of both implant surfaces. However, replacement of woven bone by lamellar bone was only observed around the test surface at 4 weeks in vivo. No significant differences in bone-to-implant contact were observed for the different groups (P > .27). CONCLUSION: Despite nonsignificant differences between bone-to-implant contact for the different surfaces and times in vivo, higher degrees of bone organization were observed for the test implants. Biomechanical testing is warranted to verify potential differences in biomechanical fixation effectiveness between surfaces.

Reliability of one-piece ceramic implant.

UNLABELLED: The fundamental aspects of damage initiation and accumulation in one-piece zirconium oxide endosseous dental implants remain to be investigated. AIMS: This study tested the null hypothesis that there is no influence on mouth-motion fatigue reliability and failure modes between as-received and after full crown preparation on one-piece ceramic implants. METHODS: Forty-eight one-piece Y-TZP ceramic implants (Nobel Biocare, Goteborg, Sweden) were utilized. All specimens were embedded in acrylic resin exposing the first two threads at 30 degrees angulation with respect to the vertical axis (as per ISO specification 14801). Full crown preparations were performed following prosthodontic guidelines for half of the specimens. As-received and prepared specimens were distributed among three step-stress profiles based on the specimens ultimate fracture strength. Specimens were step-stress fatigued until failure or survival. A master Weibull curve was generated from the data and the reliability for completion of a mission of 50,000 cycles at 600 N load calculated. RESULTS: No differences between the groups' reliability was observed. Failure mode for both groups was similar, where cracks initiated mainly at the tensile bending side of the second thread's internal diameter. The low Weibull modulus (<1) indicates that fatigue (<150,000 cycles) did not influence failure. Failure depended upon the applied load. CONCLUSION: Crown preparation did not influence the reliability of the one-piece ceramic implant. The null hypothesis was accepted. Fatigue did not influence the life time of ceramic implants at loads under 600 N.

Bond angle effects on microtensile bonds: laboratory and FEA comparison.

OBJECTIVE: To test the hypothesis that there is a reduction in bond strength when a microtensile load is applied to adhesive junctions prepared at 10, 20 and 30 degrees to the usual perpendicular interface. To evaluate the effect of bond angle and adhesive layer thickness on stress levels within the adhesive joint utilizing FEA. METHODS: Twenty-four non-carious third molars were selected, occlusal enamel removed and polished perpendicular to the long axis of the tooth. The Clearfil SE Bond and Single Bond were applied on the dentin. A 4 mm resin restoration, Z 100, was built up. The teeth were sectioned at 10 degrees, 20 degrees and 30 degrees to the bonding interface (n = 3). The control (n = 3) group had all cuts parallel to the tooth longitudinal axis (0 degrees bond angle). The bond values were calculated in MPa and Two-Way ANOVA and Tukey test applied. FEA was performed (1 mm/side square specimens) to obtain the maximum principal stress (MPS) in the microtensile-model for each bond angle and for varying adhesive thickness from 20 microm to 200 microm for each group. RESULTS: The bond strength results diminish as the angle on the interface increased (P<0.05) for Clearfil SE Bond between 0 (control) and 30 degrees, and for Single Bond between 0 (control) and 10, 20, and 30 degrees. The hypothesis can be fully accepted for Single Bond and partially accepted for Clearfil SE Bond. For the FEA, there was a trend toward decreasing MPS as the bond angle increased, while the MPS for each angled group increased with adhesive layer thickness. SIGNIFICANCE: The MPS results for angled interfaces, exhibited the same trend as the lab values. FEA results indicated an MPS increase with increased adhesive thickness.

Microtensile bond strength of several adhesive systems to different dentin depths.

PURPOSE: To determine the bond strength of five adhesives systems to either superficial or deep dentin. METHODS: Extracted human third molars had their crowns transversally sectioned either next to the occlusal DEJ or next to the pulp, to expose flat, superficial or deep dentin surfaces. The surfaces were bonded with: 1) three two-step, total-etch, self-priming adhesives (Single Bond, Prime&Bond NT, and Excite), 2) a two-step, self-etching primer (Clearfil SE Bond), and 3) a single-step, self-etching all-in-one adhesive (Etch & Prime 3.0) according to manufacturers' directions. Composite build-ups were constructed incrementally with Z250. After storage for 24 hours in water at 37 degrees C, the teeth were sectioned to obtain several bonded beams of 1.0 mm2 cross-sectional area. Each beam was tested in tension in an Instron machine at 0.5 mm/minute. Results were analyzed by two-way ANOVA and post-hoc multiple comparisons (P = 0.05). Bonded interfaces were also examined by TEM. Nanoleakage was examined using a silver-staining technique. RESULTS: Single Bond, Prime&Bond NT and Clearfil SE Bond performed equally when were bonded to superficial dentin; the lowest value was obtained with Etch & Prime 3.0. On deep dentin, the highest bond strengths were attained with Clearfil SE Bond and Prime & Bond NT. The bond strengths of Prime & Bond NT and Excite were significantly higher to deep than to superficial dentin and the rest of the adhesives showed similar bond strength to both dentin depths. Nanoleakage was manifested to variable extent within all hybrid layers examined.