The Journal of Adhesive Dentistry, 02/2009

Purpose: Proximal carious lesions comprise a constant clinical problem. The aim of this investigation was to test the safety and clinical effect of a new treatment for proximal caries. Materials and Methods: In 50 patients with two proximal initial lesions (D1-3 without cavitation, bitewing radiograph), orthodontic rubber rings were applied to gain access to the interproximal space. One of the lesions was sealed with a thin polyurethane-dimethacrylate foil using a bonding agent; the other lesion received oral home care with dental floss and fluoridated toothpaste, and was left as control. Results: In clinical follow-ups after 6 and 12 months and radiographic evaluation after two years, clinical retention of proximal tape and the underlying sealant, marginal adaptation, discoloration, tooth vitality, proximal plaque, and gingivitis were checked. In addition, carious lesions were assessed clinically and radiographically. The sealants showed good retention, marginal adaptation, and color. After two years, vitality of all teeth was still positive and no relevant differences in plaque accumulation or gingival status were found between sealed and control teeth. Nine sealed lesions showed caries regression and 2 progression. In contrast, only 4 control lesions regressed and also 2 showed progression. The loss of tape had no significant influence on the lesion progression, indicating the effect of the underlying bond. All other sealants and control lesions were stable, indicating an arrest of the lesion. Conclusion: Sealing initial proximal lesions showed no clinical problems and mostly arrest of initial carious lesions on bitewing radiographs. Keywords: proximal surfaces, sealant, clinical, radiographic

Purpose: To evaluate the antibacterial activity of three adhesive systems - Prime & Bond 2.1 (PB), Clearfil SE Bond (CS) and One Up Bond F (OU) - on Streptococcus mutans in vitro. Materials and Methods: Adherence and agar disk-diffusion tests were performed. For the adherence testing, 40 human enamel specimens (4 mm2) were sterilized and the adhesive sytems were applied (n = 10). The control group did not receive the application of any adhesive system. Specimens were immersed in brain heart infusion broth (BHI) inoculated with S. mutans standardized suspension (106 cells/ml) for 48 h at 37°C and 5% CO2. The number of S. mutans cells adhered to each specimen was evaluated by the plating method on BHI agar. For agar disk-diffusion testing, adhesive disks and disks soaked in distilled water (negative control) or 0.2% chlorexidine (positive control) were incubated with S. mutans for 48 h. The diameters of the zones of bacterial inhibition were measured. Adherence data were transformed in logarithms of base 10 (log10). Data were submitted to Kruskal-Wallis and Student-Neuman- Keuls tests at the 5% level of significance. Results: The results of the adherence test showed that One Up Bond F (OU) and Clearfil SE Bond (CS) did not differ significantly from one another, but allowed significantly less adherence than Prime & Bond 2.1 (PB) and control [mean log10 (standard deviation) values: PB 6.10 (0.19); CS primer 4.55 (0.98); OU 4.65 (0.54); control group 6.34 (0.27)]. The disk-diffusion test showed no significant difference between OU (diameter in mm: 3.02 ± 0.13) and CS (3.0 ± 0.12), but both were significantly more effective in inhibiting bacterial growth than PB (1.0 ± 0.10). Conclusion: The self-etching systems Clearfil SE Bond and One Up Bond F presented a greater inhibitory effect against S. mutans, also in terms of adherence, than did the conventional system, Prime & Bond 2.1. Keywords: Streptococcus mutans, adhesive systems, enamel

Purpose: In recent years, an increase of occupational respiratory diseases, such as asthma caused by methacrylates, has been observed in dental personnel. In this study, the exposure of dental personnel to various volatile methacrylates was investigated. Materials and Methods: The air levels of methacrylates were measured during filling treatment while bonding agents were used in 4 dental practices in Munich, Germany. Short-term air sampling (15 min) was performed using solid phase microextraction (SPME). The SPME fibers were coated with carbowax/divinyl benzene to enrich the analytes. For analysis, the analytes were thermically desorbed from the fiber and subsequently analyzed directly by gas chromatography/ mass spectrometry. Results: The methacrylates methyl methacrylate (MMA), 2-hydroxyethyl methacrylate (HEMA), ethylene glycol dimethacrylate (EGDMA), and triethylene glycol dimethacrylate (TEG-DMA) were identified in the air of dental practices. The exposure levels of the four methacrylates varied during the filling treatments. The maximum concentrations found were 0.4 mg/m3 for MMA, 45 µg/m3 for HEMA, 13 µg/m3 for EGDMA, and 45 µg/m3 for TEG-DMA. The detection of TEG-DMA correlated with the application of bonding agents during performance of dental fillings. Conclusion: Exposure levels of different methacrylates were observed at all investigated dental practices. The maximum levels of MMA measured in this study were at least 200 times lower than the toxicologically relevant maximum allowable concentrations defined in various countries. Nevertheless, the exposure levels of methacrylates should be kept as low as possible due to the allergenic potential of some methacrylates. Keywords: methacrylates, bonding agents, air monitoring, dental practices, respiratory diseases

Purpose: To evaluate the effects of multiple adhesive layers of three etch-and-rinse adhesives on both adhesive thickness and microtensile bond strength (µTBS). Materials and Methods: Midcoronal occlusal dentin of 36 extracted human molars was used. Teeth were randomly assigned to 3 groups (EB, XP, PQ) according to the adhesive system to be used: PQ1 (Ultradent) (PQ), EnaBond (Micerium) (EB), or XP Bond (Dentsply/DeTrey) (XP). Specimens from each group were further divided into three subgroups according to the number of adhesive coatings (1, 2, or 3). In all subgroups, each adhesive layer was light cured before application of each additional layer. After bonding procedures, composite crowns were incrementally built up. Specimens were sectioned perpendicular to the adhesive interface to produce multiple beams, approximately 1 mm2 in area. Beams were tested under tension at a crosshead speed of 0.5 mm/min until failure. Adhesive thicknesses and failure modes were evaluated with SEM. The µTBS data and mean adhesive thickness were analyzed by two-way ANOVA and multiple-comparison Tukey's test (α = 0.05). Results: The mean bond strength (in MPa (SD)) of group EB gradually increased from 1 to 3 consecutive coatings (27.02 (9.38) to 44.32 (4.93), respectively) (p 0.05). The highest mean bond strengths for the PQ (46.66 (12.95)) and XP groups (40.55 (5.69)) were obtained applying two adhesive coatings. The mean thickness of the adhesive layer (in µm (SD)) significantly increased with the number of coatings (p 0.05), ranging from 29.45 (1.42) to 77.64 (1.10) for PQ, from 5.12 (0.68) to 37.75 (0.92) for EB, and from 12.64 (0.68) to 37.92 (0.71) for the XP group. Failure modes for EB specimens were mainly classified as adhesive failure between adhesive and dentin. The XP3 and PQ3 subgroups showed a greater number of total cohesive failure in adhesive. Conclusion: Multiple adhesive coats significantly affected bond strength to dentin. An excess of adhesive layer thickness can negatively influence the strength and the quality of adhesion. Keywords: dentin adhesive, adhesive layer, microtensile bond strength, SEM

Purpose: The aim of this in vitro study was to evaluate the microtensile bond strength (µTBS) and hybrid layer morphology of different adhesive systems, either followed by treatment with Nd:YAG laser irradiation or not. Previous studies have shown the effects of Nd:YAG laser irradiation on the dentin surface at restoration margins, but there are few reports about the significance of the irradiation on the hybrid layer. Materials and Methods: The flattened coronal and root dentin samples of 24 bovine teeth were randomly divided into 8 groups, according to the adhesive system used - Scotchbond Multi Purpose (SBMP) or Clearfil SE Bond (CSEB) - and were either irradiated with Nd:YAG or not, with different parameters: 0.8 W/10 Hz, 0.8 W/20 Hz, 1.2 W/10 Hz, 1.2 W/20 Hz. The left sides of specimens were the control groups, and right sides were irradiated. A composite crown was built over bonded surfaces and stored in water (24 h at 37°C). Specimens were sectioned vertically into slabs that were subjected to µTBS testing and observed by SEM. Results: Control groups (27.81 ± 1.38) showed statistically higher values than lased groups (21.37 ± 0.99), and CSEB control group values (31.26 ± 15.71) were statistically higher than those of SBMP (24.3 ± 10.66). There were no significant differences between CSEB (20.34 ± 10.01) and SBMP (22.43 ± 9.82) lased groups. Among parameters tested, 0.8 W/10 Hz showed the highest value (25.54 ± 11.74). Nd:YAG laser irradiation caused dentin to melt under the adhesive layer of both adhesive systems tested. Conclusion: With the parameters used in this study, Nd:YAG laser irradiation of the hybrid layer promoted morphological changes in dentin and negatively influenced the bond strength of both adhesive systems. Keywords: adhesion, dentin, microtensile bond strength, Nd:YAG laser, scanning electron microscopy

Purpose: The purpose of this in-vitro study was to evaluate the resin bond strength to pre-etched lithium disilicate ceramic using different cleaning methods after two contamination modes (saliva or saliva and silicone). Materials and Methods: Plexiglas tubes filled with composite resin (MultiCore Flow) were bonded to etched and silanized ceramic disks made of lithium disilicate ceramic (IPS e.max Press) using a luting resin (Multilink Automix). Either etched or unetched ceramic surfaces were contaminated with saliva or with saliva followed by a disclosing silicone. Groups of 16 specimens each were bonded after pretreatment using 4 surface cleaning agents (37% phosphoric acid, 5% hydrofluoric acid, 96% isopropanol, air polishing device with sodium bicarbonate) in different combinations. Before measuring tensile bond strength, specimens were stored for 3 or 150 days with thermocycling. Results: After 150 days of storage, etching of saliva-contaminated surfaces with 5% hydrofluoric acid and/or 37% phosphoric acid provided statistically significantly higher bond strengths (37.9 to 49.5 MPa) than the other cleaning methods (1.7 to 15.5 MPa). After saliva and silicone contamination, etching with 5% hydrofluoric acid provided statistically significantly higher bond strengths (44.5 to 50.3 MPa) than all other cleaning methods (0.3 to 13.5 MPa). Conclusion: Ceramic cleaning methods after try-in procedures have a significant influence on the resin bond strength and are dependent on the type of contamination. Re-etching lithium disilicate ceramic with 5% hydrofluoric acid is most effective in removing contamination with saliva and/or a silicone disclosing medium. Keywords: lithium disilicate ceramic, cleaning, contamination, tensile bond strength

Purpose: To investigate the influence of the remaining dentin thickness after cavity preparation, calcium hydroxide lining, and two restorative systems on the occurrence of postoperative pain or hypersensitivity. Materials and Methods: One hundred twenty-three fillings were placed in 123 healthy patients. The remaining dentin thickness after caries excavation was measured with the Prepometer device at the deepest area of the cavity. The cavities were allocated to three different groups (shallow, medium, and deep) on the basis of the Prepometer results. The decision to use a calcium hydroxide liner or not was made by tossing a coin. Cavities which were to be later treated with an indirect restoration were restored with a buildup material. The other cavities were treated with a hybrid composite. After 6 months, the patients were re-examined and interviewed concerning postoperative pain incidents or hypersensitivity. A logistic regression was performed for the statistical analysis. Results: Logistic regression showed no statistically significant influence of any of the three different variables "cavity depth", "calcium hydroxide liner" and "restorative material" on the occurrence of pain or hypersensitivity. Conclusion: The occurrence of pain or hypersensitivity does not depend on the remaining dentin thickness, calcium hydroxide lining, or the restorative system used in the present study. Keywords: dentin thickness, calcium hydroxide liner, postoperative pain, hypersensitivity, composite, adhesive

Purpose: To study the durability of a recently developed low-shrinkage resin composite, suggested to counter the stress formation in direct resin composite restorations. Materials and Methods: Each of 50 patients received one or two pair(s) of Class II restorations. The first restoration in the pair was a low-shrinkage resin composite (InTen-S) and the second a hybrid resin composite restoration (Point 4). Both restorations were placed with an etch-and-rinse bonding system and an oblique layering technique. A total of 106 restorations, 33 premolar and 73 molars, were placed. The restorations were evaluated annually. Results: At 5 years, 97 restorations were evaluated. Two participants reported slight postoperative sensitivity symptoms for a few weeks after placement. Twelve non acceptable restorations were observed during the 5 years, five InTen-S (10.4%) and 7 Point 4 (14.3%) (not significant). Secondary caries was the main reason for failure (8) followed by composite fracture (2) and tooth fracture (2). Conclusion: The low-shrinkage resin composite showed good durability, but not significantly better than the control resin composite in Class II cavities. Most failures occurred at the last part of the study. Secondary caries was the main reason for failure. Keywords: clinical trial, composite restoration, posterior, resin, polymerization shrinkage

Purpose: To evaluate the 2-year clinical performance of three self-etching adhesives and one etch-and-rinse adhesive (control) in posterior composite restorations. Materials and Methods: Upon approval by the Institutional Review Board, 121 restorations were inserted in 38 subjects. The adhesives were applied as per manufacturers' instructions. Preparations were restored with a nanofilled composite resin (Filtek Supreme, 3M ESPE) and evaluated at baseline, 6 months, 1 year, and 2 years. Statistical analyses included the McNemar and the Mann-Whitney non-parametric tests (p 0.05). Results: At 2 years, 91 out of 121 restorations were evaluated using the USPHS modified criteria. The number of alpha ratings decreased significantly from baseline to 2 years for Adper Prompt L-Pop, Clearfil S3 Bond, and iBond in the categories color match, marginal staining, and marginal adaptation. For One-Step Plus, only marginal staining was significantly worse at 2 years than at baseline. Postoperative sensitivity to air improved significantly for One-Step Plus at 2 years, but this improvement was already detected at 1 year. When the 2-year evaluation criteria were pooled by pairs of adhesives, One-Step Plus resulted in a significantly greater number of alfa ratings for marginal adaptation than the other three adhesives. On the other hand, iBond resulted in a significantly lower number of alfa ratings than any of the other 3 adhesives for color match and marginal staining. Adper Prompt L-Pop, Clearfil S3 Bond, and One-Step Plus resulted in a statistically similar number of alfa ratings for marginal staining and color match. There were no significant differences in any of the evaluation criteria between Clearfil S3 Bond and Adper Prompt L-Pop. Conclusion: Only One-Step Plus, the etch-and-rinse adhesive, resulted in good marginal adaptation at 2 years. One of the self-etching adhesives, iBond, resulted in unacceptable clinical performance. Keywords: clinical trial, dental bonding, self-etching