The Journal of Adhesive Dentistry, 01/2013

Purpose: To evaluate the suitability of a novel epoxy-based resin, Filtek Silorane, for orthodontic bracket bonding on unprepared enamel. Materials and Methods: Shear forces to bovine enamel were measured for Filtek Silorane and Transbond XT in combination with steel, ceramic, and polymer brackets. For Filtek Silorane, etching was performed with the Silorane self-etching primer alone or an additional previous application of phosphoric acid. Transbond XT (conventional methacrylate) was used for the control group and the enamel was previously etched with 35% phosphoric acid. All samples were thermocycled (1000X, 5°to 55° C). Shear bond testing was done with an Instron 3344 at a crosshead speed of 1 mm/min. In addition, adhesive remnant index (ARI) scores were evaluated. Results: The shear forces showed a weak adhesion of Filtek Silorane to unprepared enamel both with the selfetching primer and conventional etching (0.87 to 4.28 MPa). The shear forces of the control group were significantly higher (7.6 to 16.5 MPa). The ARI scores showed a clear failure at the enamel/adhesive interface for all Filtek Silorane samples. For the combination of Transbond XT and different brackets, the failure was found at the adhesive/bracket interface. Conclusion: The novel epoxy-based resin Filtek Silorane is not appropriate for bonding of brackets to unprepared enamel. Keywords: shear force, silorane, adhesive, bonding

Purpose: To evaluate the association between chlorhexidine application and the bond strength of an adhesive system to dentin and to assess the association among eight other variables. Materials and Methods: Laboratory studies evaluating the use of chlorhexidine on dentin that verified the immediate and longitudinal bond strength were included. The terms were selected according to the Medical Subject Headings (MeSH) for PubMed and adapted for the other databases accordingly. Systematic searches were conducted in 3 electronic databases in December 2010: PubMed, EMBASE, and LILACS. Languages were limited to English, Spanish, and Portuguese. Results: All longitudinal bond strength studies were analyzed in accordance with the inclusion/exclusion criteria, totaling 16 articles. A meta-regression analysis was performed with articles containing complete mean bond strength data (n = 14 articles). Conclusion: Our results showed that the association between the concentration of chlorhexidine and the bond strength is, apparently, not linear. Therefore, future large-scale studies should be developed to investigate the association between the chlorhexidine concentration and hybrid layer preservation. Keywords: adhesive, dentin, matrix metalloproteinases

Purpose: To evaluate in vitro the influence of dynamic loading applied to a glass-fiber-reinforced hybrid composite resin on its flexural strength in a moist, simulated oral environment. Materials and Methods: Three-point flexural strength specimens were subjected to cyclic loading in water at 37°C and 55°C to investigate the influence of immersion temperature on impact fatigue properties. Specimens were subjected to cyclic impact loading at 1 Hz for up to 5 × 105 cycles to obtain the number of cycles to failure, the number of unbroken specimens after 5 × 105 cycles, and the residual flexural strength of unbroken specimens. Maximum loads of 100, 200, and 300 N were chosen for both the non-reinforced and the glass-fiberreinforced hybrid composite resins. Results: The mean residual flexural strength for 100 N impact loading at temperatures of 37°C and 55°C was 634 and 636 MPa, respectively. All specimens fractured at fewer than 5 × 105 cycles for loads of 200 and 300 N. Conclusion: Reduced numbers of cycles to fracture and lower fatigue values were observed as both the maximum load and immersion temperature increased. Keywords: glass fiber, hybrid composite resin, cyclic impact loading, water temperature, bending strength

Purpose: To evaluate the influence of different adhesive strategies (etch-and-rinse and self-etching adhesives) and type of field isolation (absolute or relative) on the clinical performance of restorations of noncervical carious lesions (NCCLs). Materials and Methods: One hundred forty NCCLs were selected from 38 patients, according to previously established inclusion/exclusion criteria, and assigned to one of four groups (n = 35): etch-and-rinse/rubber-dam (ERR), etch-and-rinse/cotton roll (ERC), self-etching/rubber-dam (SER) and self-etching/cotton roll (SEC). The adhesive systems used were: Adper Single Bond 2 (3M ESPE) and Adper SE Plus (3M ESPE), with restorations made using a composite resin (Z350, 3M ESPE). Using the USPHS modified criteria, 140 restorations were evaluated by two calibrated examiners at 5 different times: immediately after placement, at 7 days, and 2, 6, and 12 months. In order to evaluate the presence of gingival recession after the use of the #212 rubber-dam clamp, the clinical crowns of the teeth from groups ERR and SER were measured at six different periods (baseline, immediately, and at 7 days, 2, 6, and 12 months). Data were subjected to McNemar's, chi-square, and Student's t-tests. Results: Both adhesive strategies reduced tooth sensitivity beyond the second period of evaluation (7 days); tooth sensitivity disappeared after the third period of evaluation (2 months). There were no statistically significant differences between the adhesive techniques or isolation techniques, except for a Bravo score for marginal discoloration in group SEC at 6 months, which was significantly different from the other groups. The rubber-dam isolation technique was more uncomfortable for the patient and resulted in short-term gingival recession. Conclusion: No significant differences were found between the types of isolation or adhesive strategy in this clinical evaluation, with the exception of 2 restorations in group SEC that showed marginal discoloration, possibly due to inadequate enamel etching by the self-etching adhesive. Class V restorations perform equally well placed with or without rubber-dam. Keywords: rubber-dam, clinical study, Class V restorations, bonding agents

Purpose: To evaluate the Knoop hardness (KH) and the bond strength (BS) at the tooth/restoration interface of conventional methacrylate- (Filtek Supreme) and silorane-based (Filtek P90) composites photoactivated by different methods using an LED Freelight 2. Materials and Methods: Bond strength was tested in a universal testing machine by the "push-out" test in restored cavities measuring 2 × 1.5 × 2 mm with a C-factor of 2.2, prepared in 60 bovine teeth. To restore the cavities, the respective adhesive system of each composite was used (Single Bond 2 and P90 system adhesives). The composites were photoactivated by 3 different methods: continuous light: 40 s at 1000 mW/cm2; soft-start: 10 s at 150 mW/cm2 + 38 s at 1000 mW/cm2; pulse delay: 5 s at 150 mW/cm2, followed by a 3-min wait (without photoactivation) and 39 s at 1000 mW/cm2. Before the push-out test was performed, the KH was analyzed at the top and bottom of the restorations. Data were statistically anaylzed using ANOVA and Tukey's test. Results: The photoactivation methods produced no differences in BS or KH in the same composite, while Filtek P90 (28.0 MPa) showed higher BS values than Filtek Supreme (22.3 MPa) and a lower KH. Conclusion: The composite Filtek P90 was capable of increasing bond strength, but presented lower Knoop hardness. Keywords: resin composite, photoactivation, bond strength, silorane, methacrylate

Purpose: To evaluate the effects of the temperature of air used for solvent evaporation on water sorption, solubility, and ultimate tensile strength (UTS) of simplified etch-and-rinse adhesives. Materials and Methods: Four commercial simplified etch-and-rinse adhesives (Adper Single Bond 2 [SB]; Te Econom [TE]; XP Bond [XP] and Ambar [AM]) were selected. Disk-shaped specimens were prepared by dispensing the uncured resin into a mold (5.8 mm x 0.8 mm). Solvent evaporation was performed using a warm (60°C) or cold (20°C) air stream for 40 s. After desiccation, the cured specimens were weighed and then stored in distilled water for evaluation of the water diffusion kinetics over a 28-day period. For the UTS measurement, hourglass-shaped specimens of adhesives were prepared and tested in tension. The data from each test were evaluated with two-way ANOVA and Tukey's test at a confidence level of 95%. Results: Water sorption and solubility varied significantly between materials, but no significant difference was observed between warm and cold conditions (p > 0.05). TE and AM showed the lowest water sorption and solubility (p < 0.05). For SB, TE, and XP, the use of a warm air stream resulted in higher ultimate tensile strength (p < 0.05) in both experimental conditions. Conclusions: The water sorption and solubility of the materials seem to be more influenced by their composition than by the temperature used for solvent evaporation. For some adhesives, the use of a warm air stream can yield higher ultimate tensile strength. Keywords: adhesives systems, water sorption, solubility, adhesive strength, warm air

Purpose: To compare contraction stresses in direct and indirect composite restorations using crack analysis. Materials and Methods: Glass disks with a central cylindrical hole were prepared. Initial cracks were made in the glass using a Vickers indenter at various distances from the edge of the hole. The indentation crack lengths were measured parallel to the tangent of the edge of the hole. Silanized holes were directly or indirectly filled with a resin composite. The composite was either self-curing and light curing or only self-curing. Various thicknesses of composite cement were applied to the indirect restorations. The crack lengths were re-measured 15 and 30 min after they were filled. The contraction stresses were calculated from the crack lengths and fracture toughness of the glass. Elastic moduli of light-cured and self-cured composite samples were measured using a nanoindentation method 15 and 30 min after curing. Results: The stress could not be calculated for the light-cured direct composite and light-cured indirect composite restorations with thicker cement, due to glass failure caused by the contraction stress. Glass failure did not occur in the indirect composite restoration with thinner cement or in the self-cured direct composite restoration. The stress in the glass was lower for greater distances or shorter times. Factors of indentation-hole distance and restorative procedure significantly affected the stress. The measuring time and the type of curing had significant influence on the elastic modulus. Conclusion: Light-cured indirect composite restorations with a cement thickness < 200 µm generated less contraction stress than did light-cured direct composite restorations. The lowest contraction stress was developed in the self-cured direct composite restoration. Keywords: polymerization, shrinkage, resin composite

Purpose: To investigate the bond strength of low-fusing porcelain to commercially pure titanium (Ti) that was laser irradiated with different levels of energy and sandblasted. Materials and Methods: A total of 30 titanium rods (10 mm in length and 12 mm in diameter) were prepared. The rods were divided into three groups (n = 10) according to surface treatments: SB: sandblasted; L1: Nd:YAG laser irradiated at 100 mJ, 10 Hz, and 1 W; L2: Nd:YAG laser irradiated at 200 mJ, 10 Hz, and 2 W. After surface treatment, low-fusing porcelain was applied onto the titanium specimens according to the manufacturer's instructions, and these specimens were stored in distilled water at 37°C for 24 h. The shear bond strength test was performed at a crosshead speed of 1 mm/min. In addition, Kruskal-Wallis and Mann-Whitney U-tests were used to compare the bond strength results (α = 0.05). SEM and EDS analysis were also performed for one specimen of each group after the shear bond strength test to evaluate the nature of the fracture surface. Results: Group L2 produced the highest shear bond strength among the groups. There was a statistically significant difference in shear bond strength between groups L1 and L2 (p < 0.001). Nevertheless, no significant difference was found between groups SB and L1. EDS analysis revealed that laser treatment reduced presence of oxygen on the surface of Ti. In contrast to the sandblasted specimens, laser-irradiated specimens showed predominantly adhesive failure. Conclusion: Laser treatment may be an alternative method to sandblasting for enhancing the bond strength of low-fusing porcelain to commercially pure titanium. Keywords: Nd:YAG, sandblasting, titanium, ceramic, shear bond strength, low-fusing porcelain

Purpose: To evaluate the effect of different chemical surface treatments on the adhesion of self-adhesive resin cements to commercially pure titanium (cp Ti) by means of strain energy release rate (G-value, J/m2). Materials and Methods: Machined cp Ti plates grade II were prepared and divided into ten groups in each test according to the surface treatment used; Gr 1: control, machined; Gr 2: sandblasted; Gr 3: methylene chloride (CH2Cl2) for 5 min; Gr 4: CH2Cl2 for 10 min; Gr 5: 10% hydrogen peroxide (H2O2) for 5 min; Gr 6: 10% H2O2 for 10 min; Gr 7: 30% H2O2 for 5 min; Gr 8: 30% H2O2 for 10 min; Gr 9: 9% hydrofluoric acid (HF) for 5 min; Gr 10: 9% HF for 10 min. For bond strength testing, each group was further divided into two subgroups according to the type of resin cement used (G-CEM and Rely × Unicem). Surface roughness examination and SEM analysis of treated cp Ti surfaces were carried out. Data were analyzed using ANOVA and Tukey's test. Statistical significance was set at the 0.05 probability level. Results: The cp Ti/G-CEM and cp Ti/Rely × Unicem (9% HF for 5 or 10 min) groups showed the highest G-values (13.7 ± 2.2, 13.8 ± 2.1, 11.6 ± 1.6 and 11.8 ± 1.2, respectively) among their groups. The sandblasted group showed the highest surface roughness value (3.4 ± 0.2 µm) when compared with other treated groups. Conclusion: Adhesion between resin cements and cp Ti can be improved by the use of certain chemical baths as surface treatments of titanium prior to cementation as alternative techniques to sandblasting treatment. Keywords: titanium, resin cements, adhesion, hydrofluoric acid, methylene chloride, hydrogen peroxide, surface roughness

Purpose: To evaluate under controlled clinical conditions the outcomes of cast-metal slot-retained resin-bonded fixed dental prostheses (RBFDPs) in which resin composite interlocked the restoration retainers in place after cementation in cases with single missing first molars, and to collect survival data on this esthetic RBFDP design combined with an economical metal fit-surface treatment method and resin luting system. Materials and Methods: Forty-one tub-shaped inlay-retained RBFDPs were clinically observed for up to 7.7 years in 35 recipients of both genders between 18 and 52 years of age. Clinical examinations were performed at baseline and 6 and 12 months after restoration placement, and thereafter at regular 1-year intervals. Modified US Public Health Service (USPHS) parameters, sulcus bleeding index, Silness-Löe plaque index, pocket depths, tooth mobility, pulp vitality, and periapical radiographs regarding the abutment teeth were assessed at these follow-up appointments. The Kaplan-Meier survival estimation method was performed to detect the overall and functional survival rates and mean survival times of the RBFDPs at the end of the study. The Breslow (Generalized Wilcoxon) test was used to evaluate the influence of restoration location and age and gender of the patient regarding the overall survival probability at the end of the follow-up (α = 0.05). Results: At the end of the study, 34 RBFDPs (83%) were still functioning with a mean follow-up of 6.3 years. According to the Kaplan-Meier survival curve, the overall and functional survival probabilities were calculated as 76% and 83%, with mean survival times of 6.8 years and 7.2 years, respectively. All clinical parameters monitored throughout the follow-up period predominantly revealed clinically acceptable results. Breslow test statistics presented nonsignificant differences with better results for the RBFDPs placed in the mandible of female recipients younger than 30 years of age. The most common failure noted with the RBFDPs was fracture of the occlusal veneering composite restoration over the retainer of a single abutment, leading to a predisposition of the restoration to partial debonding. Conclusion: Within the limitations of this prospective cohort study, it can be concluded that cast-metal slot-retained RBFDPs utilizing the interlocking mechanism of a resin composite to obtain additional retention from the abutment cavities show acceptable clinical success rates, and can be considered a minimally invasive, economical, and time-saving treatment alternative for the prosthetic rehabilitation of single missing first molars. Keywords: Resin-bonded FDPs, cast-metal RBFDPs, slot-retained RBFDPs, inlay-retained RBFDPs, posterior RBFDPs

Purpose: To evaluate the clinical performance of polyethylene fiber for anterior primary teeth restorations in children after 2.5 years, according to modified Ryge criteria. Materials and Methods: Fifty-five maxillary incisors with extensive caries in 24 Iranian patients (mean age 4.2 years) were restored. All teeth were treated endodontically. First, 4-mm layer of paste at the entrance of canal was removed, and a thin base layer of polycarboxylate cement was placed at the bottom of the prepared canal. All tooth surfaces were etched, rinsed and dried, and the dentin adhesive Single Bond (3M ESPE, St Paul, MN, USA) was applied. The teeth received intracanal fiber-reinforced resin (Ribbond Triaxial, Seattle, WA, USA) fixed with a flowable composite and the crowns were reconstructed with microhybrid composite resin (Z250, 3M). All restorations were evaluated every 6 months for 30 months by 2 independent evaluators. Statistical analysis was done with McNemar's test. Results: The surface textures for most of the restorations were judged as excellent. There was no evidence of significant changes in marginal integrity. Most restored incisors (81%) received an Alpha rating for retention. The baseline and recall retention scores differed significantly (p=0.002). Conclusion: Polyethylene fiber posts associated with extensive composite restoration showed excellent clinical performance after 2.5 years in primary anterior teeth after pulp therapy. Keywords: primary anterior teeth, composite resin restoration, polyethylene fiber