[Enamel wear from ceramic and stainless steel orthodontic brackets]. / Apotrise adamantines apo keramika kai metallika orthodontika agkistra.

The purpose of this investigation was to examine the potential enamel wear upon contact with ceramic and stainless steel orthodontic brackets of the same company into an artificial mouth, which is a simulated oral environment. Two groups of ten lower premolars were bonded with ceramic and stainless steel brackets. The same number of upper premolars were used and each upper premolar was brought in contact with the opposing bracket and subjected to a lateral type of movement, like a mastication movement, by the artificial mouth. A constant load of approximately two pounds was used for the masticatory force, the rate of chewing was one cycle per second and the teeth were subjected to 2.5 and 10 masticatory cycles. The before and after occlusal surfaces of the upper premolars were compared using a computerized profiling system and the enamel volume loss was calculated. Qualitative changes, such as rate of enamel wear, were examined visually using SEM and computer graphics. Abrasion scores (mean +/- SD) in mm3 were 0.0142 +/- 0.020 for the metal and 0.2433 +/- 0.150 for the ceramic brackets and were significantly different at p less than 0.05. Ceramic brackets caused significantly greater enamel abrasion than stainless steel brackets.

Current concepts in education and research in orthodontics.

The science of dentistry is quickly advancing toward the 21st century. The constant innovations in dental material development, along with the ever-new concepts that are emerging in basic science and clinical research, are helping dentists to design methods of practice that have a more biologic and preventive substrate and a less restorative aim. As a result, all specialties of dentistry are undergoing constant changes in an effort to conform and manage the need of an educated, modern society. This report highlights some current concepts in orthodontic education and clinical research that are shaping the way that the specialty of orthodontics is taught and practiced.

Bond strength of ceramic brackets under shear stress: an in vitro report.

The shear bond strength and the potential enamel damage on debonding of various currently available ceramic and stainless steel brackets were examined in vitro using extracted premolar teeth. The brackets were divided into two groups, one bonded with a new light-cured orthodontic adhesive and the other with a conventional chemically cured system. An Instron Universal testing machine was used to apply the shear stress. Mean, standard deviation, and extreme values were calculated for each group. Statistical analysis showed that the mean shear bond strength of the silane chemical bond provided by some ceramic brackets is significantly higher (p less than 0.05) than the mean of the mechanical bond of other ceramic and stainless steel brackets. There was no statistically significant difference between the mean shear bond strength of the two adhesives used. Mechanical bonds failed primarily within the adhesive itself, whereas chemical bonds failed predominantly at the adhesive-bracket interface. Single-crystal ceramic brackets tend to be more brittle than the polycrystalline ones. Strong chemical bonds can potentially lead to enamel failure on debonding.