In Vitro Analysis of Quality of Dental Adhesive Bond Systems Applied in Various Conditions

The Effect of Radiotherapy on the Marginal Adaptation of Class II Direct Resin Composite Restorations: A Micro-computed Tomography Analysis

This laboratory study was designed to evaluate the marginal adaptation of Class II mesio-occluso-distal (MOD) restorations at the cervical region with micro-computed tomography (micro-CT). Two groups of restorations were compared: 1) those that had been exposed to radiotherapy before restoration was performed using a universal adhesive in etch-and-rinse and self-etch modes; and 2) those that had previously been restored using a universal adhesive in etch-and-rinse and self-etch modes and had subsequently undergone radiotherapy. Sixty intact human molars were randomly divided into groups according to irradiation status: no radiotherapy (control group); radiotherapy followed by restoration (radiotherapy-first group); and restoration followed by radiotherapy (restoration-first group). These three groups were then subdivided into two groups each on the basis of adhesive application type (etch-and-rinse and self-etch modes), for a total of six groups (n=10/group). Standardized Class II MOD cavities were prepared. A universal adhesive (Clearfil Universal Bond Quick, Kuraray, Okayama, Japan) was applied. The teeth were restored with resin composite (Estelite Posterior Quick, Tokuyama, Tokyo, Japan). The radiotherapy protocol was conducted with 60 gray (Gy) at 2 Gy/day, five days a week for six weeks. Adhesive defects were analyzed in distal and mesial views and evaluated with micro-CT (SkyScan 1174v2, Kontich, Antwerp, Belgium) on the basis of the volume of black spaces between the cavity walls and the restorative materials (mm3). The data were analyzed using the Kruskal-Wallis, Mann Whitney U and Wilcoxon tests (p<0.05). The radiotherapy protocol did not affect the marginal adaptation of the universal adhesive at the cervical regions. Regarding the application modes, for the radiotherapy-first group, the self-etch mode caused significantly higher adhesive defects than the etch-and-rinse mode at the dentin margin. For the no-radiotherapy group, the adhesive defects at the dentin margin were significantly higher than at the enamel margin with the application of the etch-and-rinse mode.

Assessment of Wettability and Contact Angle of Bonding Agent with Enamel Surface Etched by Five Commercially Available Etchants: An In Vitro Study

Background

The quantity and quality of the etching pattern produced by acids play a significant role in the wettability and contact angle of the adhesive with the enamel surface in orthodontics. The better the etch pattern, the more the surface energy of the enamel, better the penetration of the adhesive, which ultimately results in better bond strength. The present study aimed to evaluate the contact angle of the bonding agent with the enamel surface etched by five commercially available etchants and check if any difference existed between the five.

Materials and Methods

Twenty-five human maxillary and mandibular central incisors and premolars extracted for orthodontic or dental purposes were used in this study as samples. The teeth were allocated into five groups based upon the etchant used to etch the enamel surface. After the samples were etched, a hard tissue microtome was used to create thin slices of the enamel surface. The samples were then exposed to bonding agent Ormco Enlight. The bonding agent was released in the form of droplets onto the enamel slices mounted on a contact angle goniometer. The contact angle values were tabulated, and statistical analysis using the one-way ANOVA test was carried out.

Results

The contact angle measurements of the etchant group, DPI, were the lowest, while D-tech has the highest contact angle values. However, statistical analysis revealed no statistically significant difference between the contact angle measurements of the five groups included in the study.

Conclusion

No statistically significant difference existed between the five etchant groups included in the study. However, commercially available etchant DPI showed lesser contact angle and thus better wettability in comparison to other groups. Further elemental analysis and surface analysis are required to validate these results.

Bonding Performance of a Hydrophilic Amide Monomer Containing Adhesive to Occlusal and Cervical Dentin

This study aimed to evaluate the bonding performance of a new one-step self-etching adhesive system containing a novel hydrophilic amide monomer. Clearfil Universal Bond Quick (CUB) and Clearfil Megabond 2 (CMB) were used as the one-step and two-step adhesive systems, respectively. Flat dentin surfaces of human premolars were exposed using #600 SiC (silicon carbide) and bonded with the respective adhesives of each system. The teeth were sectioned to obtain beams (1 mm × 1 mm) after 24 h of water storage. The mean bond strength and standard deviations (MPa) on an occlusal surface were as follows: CUB: 45.9 ± 19.7 and CMB: 67.9 ± 25.3. The values for cervical ones were CUB: 56.0 ± 20.3 and CMB: 67.6 ± 16.0, respectively. In both conditions, the microtensile bond strength (μTBS) value was lower than that of CMB. As seen during the microscopic observation, no adhesive failure was observed after μTBS testing because CUB formed a firm and tight adhesive interface.