Influence of light transmittance and background reflectance on the light curing of adhesives used to bond esthetic brackets

Influence of the Bracket Material on the Post-Cure Degree of Conversion of Resin-Based Orthodontic Adhesive Systems

The aim of this study was to examine the influence of the orthodontic bracket material on the short-term and long-term post-cure development of the degree of conversion (DC) of resin-based orthodontic adhesive systems. Five commercially available materials characterized by different compositions and curing modes (light-curable or dual-curable) were tested under three different light curing conditions: without brackets (control group, CO), and in the presence of metal brackets (MB group) or ceramic brackets (CB group). Fourier-transform infrared spectroscopy was used to determine the post-cure DC development, both after "short-term" periods (2, 6, and 10 min) and "long-term" periods (1, 7, and 28 days). The short-term DC values ranged from 43.9% to 76.1%, and the long-term DC values were higher and ranged from 54.3% to 85.3%. The MB group demonstrated significantly lower short-term DC values compared to the CO and the CB groups, while the CB group had statistically similar or slightly lower DC values compared to the CO group. Long-term DC values in the MB and the CB groups were statistically lower or similar compared to the CO group, which depended on the post-cure time. The results indicated that the post-cure DC development was highly material-dependent and affected by the presence of different types of bracket material.

Review of translucency determinations and applications to dental materials

STATEMENT OF PROBLEM

There are several ways to measure the translucency of materials, as various basic colorimetric concepts have been used to describe the translucency of natural and esthetic dental materials. There are currently no guidelines regarding which method to use to describe the translucency of these materials.

PURPOSES OF STUDY

Two initial purposes of this study are to review the initial developments of the major translucency measurement methods first in the color science literature and then in the dentistry literature, and to review in the dentistry literature the recent uses of the various translucency measurement methods in light of the objectives of the presented research.

MATERIAL AND METHODS

A major color science textbook was reviewed to obtain the background information and selected references regarding the original methods of opacity measurement and the original references regarding the development and use of a translucency parameter were also reviewed. Then the recent dentistry literature was reviewed to describe the uses of the various methods of opacity or translucency determinations for various dental materials.

RESULTS

The three major methods of translucency measurement were found to be contrast ratio, transmittance, and translucency parameter, with the contrast ratio and transmittance methods each having the possibility of being either luminous or spectral. Translucency measurements were mainly used to describe dental resin composites and dental ceramic materials, but prosthetic elastomers, fiber posts, orthodontic brackets, natural tooth dentine and enamel, and combinations of materials were also studied using at least one of these methods.

CONCLUSIONS

The more-developed use of models that relate the thickness of the translucent materials to the translucency measurement of interest is encouraged. Also, care must be taken when comparing previously generated translucency measurements with any newly generated data because technical details of the thickness and the backings used in previous research must be matched or adjustments must be made to make any newly generated data comparable with published values.

CLINICAL SIGNIFICANCE

The method of specifying the translucency of esthetic dental materials may be based on clinical appearance requirements of the patient, on technical demands of optimizing the setting of underlying material, or on both. The method or methods used to describe translucency may provide clinically relevant information in order for the clinician to select the optimum material to satisfy these requirements.