André Luis Faria-e-Silva

Fiber post etching with hydrogen peroxide: effect of concentration and application time.

INTRODUCTION Etching is necessary to expose the fibers and enable both mechanical and chemical bonding of the resin core to the fiber post. This study evaluated the effect of concentration and application time of hydrogen peroxide on the surface topography and bond strength of glass fiber posts to resin cores. METHODS Fiber posts were etched with 24% or 50% hydrogen peroxide for 1, 5, or 10 min (n = 10). Posts without any treatment were used as a control. After etching, the posts were silanated and adhesive resin was applied. The posts were positioned into a mold to allow a self-cured resin core to be inserted. The post/resin assembly was serially sectioned into five beams that were subjected to a tensile bond strength test. Data were subjected to two-way ANOVA and Tukey test (α = 0.05). The surface topography was analyzed using scanning electronic microscopy. RESULTS Non-etched post presents a relatively smooth surface without fiber exposure. Application of hydrogen peroxide increased the surface roughness and exposed the fibers. All experimental conditions yielded similar bond strength values that were higher than those obtained in the control group. CONCLUSION Both 24% and 50% hydrogen peroxide exposure increased the bond strength of resin to the posts, irrespective of the application time.

EFFECT OF RELINING ON FIBER POST RETENTION TO ROOT CANAL

One of the clinically relevant problems dentists face when restoring endodontically treated teeth is the mismatch between fiber post and post space diameters, which results in an excessively thick resin cement layer. Fiber post relining appears as a solution for this problem. Objectives: The aim of this study was to evaluate the effect of fiber post relining with composite resin on push-out bond strength. Material and Methods: Twenty bovine incisors were selected to assess post retention. The crowns were removed below the cementoenamel junction and the root canals were treated endodontically and flared with diamond burs. The roots were allocated into two groups (n=10): G1: fiber posts without relining and G2: fiber posts relined with composite resin. The posts were cemented with a dual-cured resin cement and the specimens were sectioned transversally. Three 1.5-mm thick slabs were obtained per root and identified as cervical, medium and apical thirds. The push-out test was performed at a crosshead speed of 0.5 mm/min until post dislodgement occurred. The failure mode of fractured specimens was analyzed under scanning electron microscopy. Data were analyzed by split-plot ANOVA and post-hoc Tukeys test at a pre-set alpha of 0.05. Results: Relined fiber posts presented higher retention values than non-relined post in all thirds. No statistically significant differences (p>0.05) were found among thirds for relined posts. All failures occurred at the interface between resin cement and root dentin. Conclusions: Relining with composite resin seems to be an effective method to improve the retention of fiber posts to flared root canals.

Do Metal Post–retained Restorations Result in More Root Fractures than Fiber Post–retained Restorations? A Systematic Review and Meta-analysis

INTRODUCTION Teeth requiring endodontic treatment commonly have compromised a coronal tooth structure that often requires the use of an intraradicular post to retain the coronal restoration. Although usually successful, catastrophic failures requiring extraction have been reported in the literature. The aim of this systematic review was to analyze clinical trials and cohort studies that evaluated the incidence rate of root fractures in post-retained restorations. The hypothesis was that the incidence rate related to the use of metal posts was higher than that of fiber posts. METHODS A MEDLINE search for clinical studies reporting the incidence of root fractures of restorations retained with fiber posts or metal posts of endodontically treated teeth with a more than 5-year follow-up was conducted from inception to January 2014. Seven randomized clinical trials and 7 cohort studies were included. RESULTS The pooled survival rate was 90% (95% confidence interval, 85.5-93.3) for metal-based posts and 83.9% (95% confidence interval, 67.6-92.8) for fiber-reinforced posts. The overall incidence rate of root fractures (catastrophic failures) was similar between metal and fiber posts. Prefabricated metal posts and carbon fiber posts had a 2-fold increase in the incidence rate of root fractures compared with cast metal posts and glass fiber posts, respectively. CONCLUSIONS The results of this study did not show significant differences for root fracture incidence between metal- and fiber posts. However, the studies included in this review presented a high risk of bias, and further well-designed clinical studies are required to confirm these findings.

Effect of Immediate or Delayed Light Activation on Curing Kinetics and Shrinkage Stress of Dual-Cure Resin Cements

OBJECTIVES This study evaluated the effect of light activation (absence, immediate, or delayed) on conversion kinetics and polymerization stress of three commercial dual-cured resin cements (Enforce, RelyX ARC, and Panavia F). METHODS Degree of conversion (DC) was monitored for 30 minutes using real-time near–Fourier transform infrared spectroscopy. The cement was mixed, placed on the spectrometer sample holder, and light activated either immediately or after five minutes (delayed light activation). When no light activation was performed, the materials were protected from light exposure (control). DC was evaluated at five and 30 minutes postmixture. Maximum rates of polymerization (Rp(max)) were obtained from the first derivative of the DC vs time curve. Polymerization stress was monitored for 30 minutes in 1-mm-thick specimens inserted between two cylinders attached to a universal testing machine. Data were submitted to analysis of variance/Tukey tests (α=0.05). RESULTS Immediate light activation promoted the highest DC at five minutes. At 30 minutes, only RelyX ARC did not present a significant difference in DC between activation modes. Enforce and Panavia F presented higher Rp(max) for immediate and delayed light-activation, respectively. RelyX ARC showed similar Rp(max) for all activation modes. The absence of light activation resulted in the lowest stress followed by delayed light activation, while immediate light activation led to the highest values. RelyX ARC showed higher stress than Enforce, while the stress of Panavia F was similar to that of the others. CONCLUSION Delayed light activation reduced the polymerization stress of the resin cements tested without jeopardizing DC.

Hardness and microshear bond strength to enamel and dentin of permanent teeth with hypocalcified amelogenesis imperfecta

BACKGROUND Adhesive procedures are often required to restore teeth affected by hypocalcified amelogenesis imperfecta (HAI). AIM To evaluate the hardness of enamel/dentin of teeth affected by HAI and the bond strength to these substrates, as well the influence of 5% NaOCl on bond strength. DESIGN Permanent molars presenting HAI and sound third molars were used. Enamel surfaces were wet-flattened and Knoop hardness was assessed. The two-step, etch-and-rinse adhesive Single Bond 2 (3M ESPE) was applied and resin cylinders bonded to the surfaces and submitted to microshear testing. The subjacent medium dentin was then exposed by wet-grinding. Hardness readings and microshear testing were carried out again. The relationship between hardness and bond strength was assessed by nonlinear regression analysis. RESULTS Hardness of normal enamel was higher than hardness of enamel affected by HAI, whereas dentin hardness did not differ from normal to HAI-affected teeth. Enamel and dentin hardness were similar for teeth affected by HAI. Higher bond strengths were obtained to the normal tooth tissues. Dentin bond strength was higher than enamel bond strength. NaOCl exposure did not influence bond strengths. A positive linear relationship between enamel hardness and bond strength was observed. CONCLUSION HAI imposes challenges to bonding to enamel and dentin.

Nonsurgical endodontic management using MTA for perforative defect of internal root resorption: report of a long term follow-up

Internal root resorption is an uncommon lesion following a dental injury. The use of mineral trioxide aggregate (MTA) is a conservative approach to repair lesions with periodontal communication. This case report presents a long-term follow-up of a nonsurgical endodontic management using MTA for perforative defect of internal root resorption. During the endodontic treatment, the granulation tissue was removed and the root canal prepared. Calcium hydroxide was placed as a temporary dressing for 30 days. After this period, the root canal space and the perforation defect were filled with MTA. The clinical findings and periapical radiographs indicated success of treatment until 2 years of follow-up. However, the radiograph after 8 years showed an extensive radiolucent area in the middle third of the root with separation of the apical and coronal root segments. These findings were observed more accurately by using cone-beam computerized tomography.

Adhesion strategy and early bond strengths of glass-fiber posts luted into root canals

This study investigated the effect of coinitiator solutions and self-adhesive resin cement on the early retention of glass-fiber posts. Cylindrical glass-fiber posts were luted into 40 incisor roots with different adhesion strategies (n = 10): SB2, Single Bond 2 + conventional resin cement (RelyX ARC); AP, Scotchbond Multipurpose Plus (SBMP) activator + primer + ARC; APC, SBMP activator + primer + catalyst + ARC; and UNI, self-adhesive cement (RelyX Unicem). Pull-out bond strength results at 10 min after cementation showed APC > UNI > SB2 = AP (P < 0.05). The adhesion strategy significantly affected early bonding to root canals.

Bond strength of self-adhesive resin cements to composite submitted to different surface pretreatments

Objectives Extensively destroyed teeth are commonly restored with composite resin before cavity preparation for indirect restorations. The longevity of the restoration can be related to the proper bonding of the resin cement to the composite. This study aimed to evaluate the microshear bond strength of two self-adhesive resin cements to composite resin. Materials and Methods Composite discs were subject to one of six different surface pretreatments: none (control), 35% phosphoric acid etching for 30 seconds (PA), application of silane (silane), PA + silane, PA + adhesive, or PA + silane + adhesive (n = 6). A silicone mold containing a cylindrical orifice (1 mm2 diameter) was placed over the composite resin. RelyX Unicem (3M ESPE) or BisCem (Bisco Inc.) self-adhesive resin cement was inserted into the orifices and light-cured. Self-adhesive cement cylinders were submitted to shear loading. Data were analyzed by two-way ANOVA and Tukeys test (p < 0.05). Results Independent of the cement used, the PA + Silane + Adhesive group showed higher microshear bond strength than those of the PA and PA + Silane groups. There was no difference among the other treatments. Unicem presented higher bond strength than BisCem for all experimental conditions. Conclusions Pretreatments of the composite resin surface might have an effect on the bond strength of self-adhesive resin cements to this substrate.

Dentin deproteinization effect on bond strength of self-adhesive resin cements

This study examined the effect of deproteinization on the bond strength between self-adhesive resin cements and dentin surfaces that were untreated (control), acid-etched, or acid-etched and subjected to a post-etch deproteinization treatment. Cylinders of RelyX Unicem or BisCem (n = 6) cement were build-up on the dentin surfaces and tested to determine shear strength. The results were analyzed using two-way ANOVA and Tukeys test (5%). While neither dentin pretreatment improved the bond strength for RelyX Unicem, deproteinization treatments resulted in greater bond strength in BisCem specimens while acid etching alone did not improve the performance of the material.

Solvent content and dentin bond strengths using water-wet, ethanol-wet and deproteinization bonding techniques

Abstract Objectives. To evaluate the impact of solvent content in two-step, etch-and-rinse adhesives on the dentin bond strengths obtained via water-wet, ethanol-wet or deproteinization techniques. Materials and methods. A model photocurable Bis-GMA/HEMA blend was diluted in ethanol (7.5, 15 or 30 mass%) or acetone (15, 30 or 60 mass%) (low, medium or high solvent content, respectively). Viscosity of the solutions was measured with an oscillatory viscometer and data analyzed using ANOVA on Ranks (5%). Dentin bond strengths were evaluated using microshear bond test. After acid-etching and rinsing, the dentin was kept wet (water-wet), treated with ascending ethanol concentrations (ethanol-wet) or with 10% NaOCl solution (deproteinization). Composite cylinders built-up on the surfaces for the microshear test. Data from each bonding technique were submitted to two-way ANOVA and Fishers LSD method (5%). Failure modes were classified under magnification and data analyzed using chi-square tests (5%). Results. Viscosity of ethanol-based agents was remarkably higher than acetone solutions. For the water-wet technique, lower bond strength was observed for the low compared with medium and high ethanol contents. For the ethanol-wet technique, the bond strength for both solvents types was low < medium = high solvent content. For the deproteinization technique, no significant differences were observed among groups. Significant differences in failure modes were observed between the bonding techniques. The ethanol-wet technique had more adhesive failures, whereas the other techniques showed a predominance of mixed failures. Conclusions. The solvent content may interfere with the dentin bond strengths for the conventional and ethanol bonding techniques.