Shear Bond Strength of Three Composite Resins to Fluorosed and Sound Dentine: In Vitro Study

Bonding to Fluorosed Teeth: A Review of the Literature

Excessive fluoride availability during tooth formation can cause structural alterations in enamel and dentin. These alterations may negatively impact the adhesion of various dental materials to teeth with dental fluorosis. The aim of this review of literature is to identify updates in bonding to fluorosed teeth and summarize relevant recommendations. Findings from the available literature suggest that bonding procedures may be carried out reliably on most fluorosed teeth with consideration to the severity of fluorosis and the employment of additional bond-enhancing measures for the severely involved teeth.

Effects of dimethyl sulfoxide pretreatment on the bonding properties of fluorotic dentin of different severity: An in vitro study

STATEMENT OF PROBLEM

Bonding to fluorotic dentin is weaker than to sound dentin, but methods to improve bonding have not been well addressed.

PURPOSE

The purpose of this in vitro study was to investigate the effects of dimethyl sulfoxide (DMSO) pretreatment on the bond strength and resin-dentin surface of fluorotic dentin of different severity.

MATERIAL AND METHODS

Phosphoric acid-etched dentin specimens exhibiting mild fluorosis (ML-F), moderate fluorosis (MD-F), and severe fluorosis (SE-F) were randomly bonded with Single Bond 2 (SB2) pretreated with 50% DMSO (experimental groups) or deionized water (control groups). The bonded teeth were sectioned for microshear bond strength (μSBS) testing immediately or after aging, for micromorphology observation of the bonding interface under a scanning electron microscope, and for resin tags and microleakage evaluation under a confocal laser scanning microscope. The degree of conversion of the adhesive resin was calculated by Fourier transform infrared spectroscopy. According to varying bonding steps, the mineralized dentin powders of ML-F, MD-F, and SE-F were randomly divided into 4 subgroups (blank, PA, PA+SB2, and PA+DMSO+SB2) and incubated in artificial saliva to examine the level of enzymatic degradation product of type I collagen. Data were analyzed by using ANOVA and the Tukey test (α=.05).

RESULTS

Dental fluorosis and thermocycling had negative effects on μSBS (P<.001), while DMSO pretreatment preserved or even improved μSBS (P<.001). DMSO had no influence on the degree of conversion (P=.618). Significant effects were found for bonding steps (P<.001), but not that of dental fluorosis (P=.131) on the enzymatic degradation product of type I collagen. Images showed sparser and more expanded collagen fibril meshwork, deeper resin penetration, and less microleakage in the experimental groups.

CONCLUSIONS

DMSO pretreatment provided increased and durable dentin bonding to fluorotic dentin probably by dispersing collagen fibrils into a sparser network and inhibiting the degradation of type I collagen.

Siloranes-Suitability of a Novel Adhesive for Orthodontic Bracket Bonding

Recently, an epoxy-based resin-Filtek Silorane-has been proposed for restorative fillings. It was the aim of the investigation to evaluate the suitability of this novel resin for orthodontic bracket bonding on unground enamel. Shear bond strength was measured for two adhesives-Filtek Silorane, Transbond XT-in combination with steel, ceramic and polymer brackets. For Filtek Silorane etching was performed with the Silorane self-etching primer, as well as phosphoric acid. The Transbond XT samples were etched with phosphoric acid only and served as the control group. All samples were thermo-cycled (1000×, 5-55 °C). Shear testing was carried out with an Instron 3344. In addition, ARI scores were evaluated. The Shear bond strength showed a weak adhesion of Filtek Silorane to unprepared enamel, either with the self-etching primer or the conventional etching (0.87-4.28 MPa). The Shear bond strength of the control group was significantly higher (7.6-16.5 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. The novel epoxy-based resin Filtek Silorane is not appropriate for bracket bonding to unprepared enamel.