The Journal of Adhesive Dentistry, 06/2010

Purpose: To determine the bond strength to unground enamel of all-in-one adhesives in comparison with an etch-andrinse system and to compare the reliability of microtensile and microshear methods in providing such measurements. Materials and Methods: The bonding procedure was performed on enamel of 64 extracted molars. The tested all-inone adhesives were: Bond Force (Tokuyama), AdheSE One (Ivoclar-Vivadent), and Xeno V (Dentsply). Prime&Bond NT (Dentsply) served as control. Microtensile specimens were obtained from 4 teeth per group. Twelve teeth per group were used for microshear testing. Microtensile specimens that failed prior to testing were included in statistical calculations; they were assigned the lowest value measured in the respective group. Failure modes were observed under light microscope and classified (cohesive within substrates, adhesive, mixed). Statistically significant differences in bond strength were assessed among the adhesives within each testing method and between microshear and microtensile data for each adhesive. Failure mode distributions were compared using the chi-square test. Results: All-in-one adhesives had similar microshear and microtensile bond strengths. In both testing methods, the etch-and-rinse system achieved the strongest bond. For all adhesives, significantly higher bond strengths were measured with the microshear test. In microtensile testing, specimens bonded with the etch-and-rinse adhesive exhibited a significantly different distribution of failure modes. The coefficients of variation were extremely high for microtensile bond strength data, particularly of all-in-one adhesives. Conclusion: The adhesive potential to intact enamel of recently introduced all-in-one adhesives was inferior to that of an etch-and-rinse system. When testing bond strength to enamel of all-in-one adhesives, microshear testing may be a more accurate method than microtensile. Keywords: all-in-one adhesives, unground enamel, microtensile, microshear, bond strength test

Purpose: The aim of this study was to evaluate the effect of dental conditioners in terms of dentin micromorphology and the thickness of the hybrid layer obtained by using the self-etching adhesive systems Adhe SE (AD), G Bond (GB), Adper Prompt L Pop (LP) and Tyrian (TY) and the etch-and-rinse Single Bond (SB). Materials and Methods: Dentin sticks from 50 third human molars were obtained by first cutting dentin disks out of crowns; the disks were subsequently sectioned into sticks. The sticks were assigned to experimental groups as follows: G1: phosphoric acid 37%, Single Bond (SB); G2: Adhe SE (AD); G3: G Bond (GB); G4: Adper Prompt L-Pop (LP); G5: Tyrian SPE (TY). Half the samples served to investigate the dentin micromorphology. To this end, the proprietary conditioner of the respective adhesive system was applied to these samples, and conditioner effects were examined with SEM. The other half of the samples was hybridized and restored with composite resin to investigate the thickness of the hybrid layer, which was also evaluated with SEM. Statistical analysis was performed with ANOVA, Tukey's, and the Kruskal-Wallis tests. Results: SEM observation showed significant differences of the hybrid layer thickness. LP presented the highest average thickness, 3.45 µm, while SB presented an average of 2.44 µm and AD an average of 1.43 µm. The averages of TY and SB did not show any statistically significant differences. The adhesive system GB presented the lowest average in hybrid layer, 0.37 µm. The micromorphological evaluation showed that the conditioners commonly removed the smear layer. Conclusion: All the micromorphological alterations and the hybrid layer thickness show that the adhesive systems studied performed distinct actions. Although there is no apparent correlation of the pH of the conditioners with the thickness of the hybrid layer, it is clear that more acidic conditioners promote more severe transformations in the dentin micromorphology. Keywords: adhesion, dentin bonding agent, dentin, surface modification

Purpose: To evaluate whether retention loss of Class V restorations can be simulated in the laboratory and to compare these results with those from clinical trials. Materials and Methods: Nonretentive v-shaped Class V cavities were prepared on the lingual and buccal side of extracted premolars, half in dentin and half in enamel. Different adhesive systems (AS) were used with the same composite resin (Tetric EvoCeram) and 12 restorations per group: 1-step self-etching AS (AdheSE One, Adper Prompt L-Pop, Futurabond N, Hybrid Bond, iBond, Xeno III, Xeno IV), 2-step self-etching AS (AdheSE), 2-step etch-and-rinse AS (Excite, Prime & Bond NT), 3-step etch-and-rinse AS (Syntac) as well as a conventional glass ionomer (Ketac Fil) with and without conditioner. The comparison groups were the composite without adhesive and a 2-step etch-and-rinse AS (Prime & Bond NT) without etching of enamel and dentin. The restored teeth were submitted to an aging process involving 18 months of water storage, three intermittent phases of thermocycling (TC 10,000 times), and two phases of thermomechanical loading (1 x 640,000 chewing cycles after 12 months, 1 x 1,200,000 chewing cycles after 18 months; 100 N sine-wave force profile, pressing with steel ball without lifting). Retention loss of the restorations was evaluated after every 1000 thermocycles and every 120,000 cycles of thermomechanical loading. The databases MEDLINE and IADR abstracts were used to search for clinical studies on retention loss involving the adhesive systems that were included in the present study. Results: Retention loss was only observed in the following groups: composite without adhesive (100% after first 1000 TC), glass ionomer without conditioner (8% after 6 months; 33% after 12 months, 100% after 18 months), adhesive without etching (17% after 6 months, 42% after 12 months). The laboratory results, however, matched with the clinical results only for three adhesive systems (Futurabond NR, Hybrid Bond, Xeno IV, 0% retention loss, 5 studies, observation period between 1.5 and 2 years). Conclusions: If the materials were applied according to the manufacturer's instructions, no retention loss was observed in the laboratory model. The laboratory model did not reflect the clinical findings. Keywords: Class V, retention loss, laboratory, water storage

Purpose: This study evaluated the effect of different aging methods on the repair bond strength and failure types of a microhybrid and a nanohybrid composite. Materials and Methods: Disk-shaped microhybrid (Quadrant Anterior Shine-QA) and nanohybrid (Tetric EvoCeram-TE) resin composite specimens (N = 192, n = 12/per group) were photopolymerized and randomly assigned to one of the three aging conditions: (1) immersion in deionized water (37°C, 2 months), (2) thermocycling (5000 times, 5 to 55 °C), (3) immersion in citric acid (pH: 3.0; 1 week). The control group was stored dry for 24 h at 37°C. After aging procedures, the specimens were silica coated (30 µm SiO2) (CoJet-Sand) using an intraoral air abrasion device, silanized (ESPESil) and an intermediate adhesive resin was applied (Visio-Bond, 3M ESPE). Resin composites, once of the same kind as the substrate (QA-QA, TE-TE) and once other than the substrate material (QA-TE, TE-QA) were adhered onto the conditioned substrates. Shear force was applied to the adhesive interface in a universal testing machine (cross-head speed: 1 mm/min). Results: A significant influence of the aging method was observed (p 0.05) but the composite type did not affect the repair bond strength (p = 0.755) (2-way ANOVA, Tukey's test). Interaction terms were significant (p 0.05). Thermocycling showed lower results (10 ± 2.6 to 14.4 ± 4.4 MPa) than those of other aging methods (12.7 ± 5.2 to 28 ± 5.3 MPa). Using the substrate and the adherend interchangeably (QA-TE, TE-QA) did not show significant differences in the control group, but the results were significant after aging (p = 0.007) (2-way ANOVA, Tukey's test). Interaction terms were not significant (p = 0.124). The incidence of score A (cohesive failures in the substrate) was not significant between the composite combinations in the control groups (exclusively 100%) and water-storage aged groups (92% to 100%) (p > 0.05) (chi-square). Citric acid aging yielded significantly less incidence of score A (8-75%) compared to the control group in all composite combinations (p 0.05). Conclusion: Both microhybrid and nanohybrid composites could be used either as a substrate or as relayering composites in early repairs. Aging factors may diminish the repair quality. Keywords: aging, microhybrid composite, nanohybrid composite, repair, silica coating, surface conditioning

Purpose: The purpose of the study was to compare the ratio of carbon-carbon double bonds (RDB) of two adhesive systems cured by five different light-curing units (LCUs) using micro-Raman spectroscopy. Materials and Methods: Ten samples of an etch-and-rinse (Excite), a two-step self-etching adhesive system (AdheSE) - ie, primer and bond mixed - and AdheSE Bond only were prepared and cured with one of the following LEDs: Elipar Freelight2; Bluephase; SmartLite; Coltolux, each for 10 s; or a conventional halogen Prismetics Lite for 10 s or 20 s. Micro-Raman spectra were obtained from uncured and cured samples of all three groups to calculate the RDB. Data were statistically analyzed using ANOVA. Results: The mean RDB values were 62% to 76% (Excite), 36% to 50% (AdheSE Primer+Bond) and 58% to 63% (AdheSE Bond). At 20 s, Prismetics Lite produced significantly higher RDB in Excite than the other LCUs and Prismetics Lite at 10 s (p 0.05). Prismetics Lite at 20 s and Elipar produced comparable RDB values of AdheSE Bond and AdheSE Primer+Bond (p > 0.05). Excite showed significantly higher RDB values than AdheSE (p 0.05) whilst AdheSE Bond showed significantly higher RDB than AdheSE Primer+Bond (p 0.05). Conclusion: The etch-and-rinse adhesive cured with the halogen LCU for 20 s gave higher conversion than LED LCUs or halogen for 10 s curing time. The highest intensity LED [Elipar] produced higher or comparable conversion compared to the lower intensity LED LCUs for the same curing time. The etch-and-rinse adhesive showed higher RDB than the self-etching adhesive system. The presence of the primer in the self-etching adhesive compromised polymerisation. Keywords: micro-Raman spectroscopy, adhesive systems, degree of conversion, light curing units

Purpose: To evaluate the dentin bond strength of a composite resin material after the removal of two experimental cements containing zeolite, bone hydroxyapatite and linoleic acid, and one conventional glass-ionomer cement intended as provisional cements. Materials and Methods: Forty extracted caries-free, erupted permanent third molars were used. Experimental provisional cements containing zeolite and bone hydroxyapatite (BHA) and one conventional glass-ionomer cement (GIC) were placed on the dentin surfaces and covered with tinfoil. Cement-covered dentin surfaces were stored in distilled water at 37°C ± 2°C for seven days. After this period, temporary cements were mechanically removed, dentin surfaces were rinsed in distilled water and dried with an air syringe before adhesive application. Dentin bonding agent was applied according to the manufacturer's instructions and the adhesion test was performed according to ISO TR 11405. Results: The following shear bond strengths for the composite material were obtained: no treatment applied (control, group 4): 17.30 ± 1.37 MPa; provisional cement containing BHA (group 2): 15.03 ± 3.44 MPa; GIC (group 3): 14.13 ± 2.85 MPa; provisional cement containing zeolite (group 1): 11.29 ± 2.71 MPa. The difference between groups 1 and 4 the control group was significant, where as the statistical analysis showed no significant difference between the control and BHA groups (ANOVA, Tukey's, p > 0.05). Conclusion: In clinical applications where the previous application of provisional cements is necessary, material choice may influence the bond strength of the subsequent composite resin restoration. Keywords: bone hydroxyapatite, linoleic acid, provisional cement, shear bond strength, zeolite

Purpose: The aim of this study was to evaluate the ability of bond strength tests to accurately measure the bond strength of fiber posts luted into root canals. Materials and Methods: The test methods studied were hourglass microtensile (HM), push-out (PS), modified pushout (MP), and pull-out (PL). The evaluated parameters were: bond strength values, reliability (using Weibull analysis), failure mode (using confocal microscopy), and stress distribution (using finite element analysis). Forty human intact single-rooted and endodontically treated teeth were divided into four groups. Each group was assigned one of the test methods. The samples in the HM and PS groups were 1.0 ± 0.1 mm thick; the HM samples were hourglass shaped and the PS samples were disk shaped. For the PL and MP groups, each 1-mm dentin slice was luted with a fiber post piece. Three-dimensional models of each group were made and stress was analyzed based on Von Mises criteria. Results: PL provided the highest values of bond strength, followed by MP, both of which also had greater amounts of adhesive failures. PS showed the highest frequency of cohesive failures. MP showed a more homogeneous stress distribution and a higher Weibull modulus. Conclusion: The specimen design directly influences the biomechanical behavior of bond strength tests. Keywords: bond strength, fiber post, root dentin, scanning confocal microscopy, finite element analysis

Purpose: To evaluate the effects of three luting resins and roughening of the dentinal walls on the long-term retention of tapered titanium dowels. Materials and Methods: Ninety-six single-rooted teeth were endodontically treated. All root specimens were divided into three groups (n = 32). Dowel spaces were then prepared with ISO 90 drills 10 mm deep. Corresponding prefabricated tapered titanium dowels were air abraded and luted with Panavia 21 (P21), Super Bond C&B (SB) or with Chemiace II (CH) according to the manufacturers' instructions. In the subgroups of each luting agent, the dentinal walls were either left in their original state as prepared by the drills (n = 16), or roughened with a handheld diamondcoated ISO 90 cutting instrument (n = 16). The bonded specimens were stored in water at 37°C for 3 days (n = 8) or 150 days with simulated aging conditions of 37,500 thermal cycles (5°C/55°C) and 300,000 mechanical loading cycles with 30 N (n = 8). Dowel retention in N was measured using a universal testing machine with a crosshead speed of 2 mm/min. Statistical analysis was performed with ANOVAs followed by Scheffé post-hoc tests. Results: The dowel retention with P21 and SB was significantly higher than that of CH (p = 0.05). Roughening the dentinal walls significantly increased the retention for all cements (p = 0.01). Storage for 150 days with thermal cycling and mechanical loading caused a significant decrease in dowel retention (p = 0.05). Conclusion: P21 and SB luting resins provided a durable retention of prefabricated titanium dowels in root canals, especially for root canals with roughened dentinal walls, as the combined result of sliding friction, micromechanical interlocking and adhesive dentin bonding. Keywords: retention, titanium dowels, luting resin