Transmission of Curing Light through Moist, Air-Dried, and EDTA Treated Dentine and Enamel

Abstract

Objective. This study measured light transmission through enamel and dentin and the effect of exposed dentinal tubules to light propagation. Methods. Light attenuation through enamel and dentin layers of various thicknesses (1 mm, 2 mm, 3 mm, and 4 mm) was measured using specimens that were (1) moist and (2) air-dried (n = 5). Measurements were repeated after the specimens were treated with EDTA. Specimens were transilluminated with a light curing unit (maximum power output 1869 mW/cm2), and the mean irradiance power of transmitting light was measured. The transmission of light through teeth was studied using 10 extracted intact human incisors and premolars. Results. Transmitted light irradiance through 1 mm thick moist discs was 500 mW/cm2 for enamel and 398 mW/cm2 for dentin (p < 0.05). The increase of the specimen thickness decreased light transmission in all groups (p < 0.005), and moist specimens attenuated light less than air-dried specimens in all thicknesses (p < 0.05). EDTA treatment increased light transmission from 398 mW/cm2 to 439 mW/cm2 (1 mm dentin specimen thickness) (p < 0.05). Light transmission through intact premolar was 6.2 mW/cm2 (average thickness 8.2 mm) and through incisor was 37.6 mW/cm2 (average thickness 5.6 mm). Conclusion. Light transmission through enamel is greater than that through dentin, probably reflecting differences in refractive indices and extinction coefficients. Light transmission through enamel, dentin, and extracted teeth seemed to follow Beer-Lambert's law.

Assessment of the depth of cure of resin composite restoration by using Trans-tooth curing technique with different light curing intensities

“…This result is in corroborates with the finding of Rueggeberg et al (8) . It was obvious that, high intensity group with 1mm tooth structure thickness reported highest depth of cure as compared to the other group due to decreasing the distance between the light curing tip and resin composite restoration so reduce the amount of light scattering and energy attenuation when the light passes through enamel and dentin producing so could guarantee adequate depth of cure (15) . Also, this was in agreement with (17) whom stated that, the resin composite has the property of dispersing the light of the light curing unit, so when the light passes through the bulk of the resin composite, light intensity is attenuated due to the light being scattered by filler particles and the resin matrix.…”

“…light transmission is considerably influenced when there is dentin or enamel between the light source and a light irradiance power detector. This issue has relevance when light curing adhesives and resin composites are cured through dentin and enamel (15) . Therefore, two different tooth structure plate thickness were prepared in class III cavities to assess the effect of thickness of enamel and dentin on the degree of curing of resin composite restoration with different two light intensities.…”

“…Light transmission through dentin and enamel is not well known. It has not been reported in the literature whether the thickness of hard tissues of the tooth would affect the depth of cure of resin composite restorations when the light of curing unite passes through them (15) If the restoration does not receive sufficient energy, various problems may arise, e.g., reduced degree of conversion, increased cytotoxicity, reduced hardness, increased pigmentation, increased wear, increased marginal breakdown and weak bond among the tooth, adhesive and the restoration (16) . Also If the less polymerized resin composite comes into contact with the pulp tissue, the remaining monomer can result in post restorative sensitivity, because of its toxicity.…”

Light-curing of orthodontic bracket adhesive by transillumination through dentine and enamel

“…The results of Oesterle and Shellhart [9] showed that transillumination through extracted maxillary incisors resulted in sufficiently high bond strengths of brackets, particularly when the curing time was 50 s. From the clinical point of view, the optimal bond strength has been considered to be at least 5.9 MPa [11], whereas the risk for enamel fractures increases when the bond strength is higher than 9.7 MPa [12]. Heravi et al [10] on the other hand, found that light curing through premolars resulted in bond strengths below clinically acceptable values even if curing time was increased to 80 s. In a previous study we studied the light propagation through the dental hard tissues and showed that light penetrates enamel better than dentin, and that penetration of light is enhanced if enamel and dentin are moisturized [6].…”

“…However, convexity of the labial tooth surface and the bracket material hinder or obstruct direct light propagation resulting in incomplete polymerization of the adhesive at the center of the bracket. We have shown previously that polymerization of the adhesive under a metal bracket can be enhanced by adding light transmitting glass fibers in the resin interface [5,6].…”