Abstract:

BACKGROUND
The whitening of dark-shaded teeth is widely considered desirable and can be achieved with a simple therapeutic procedure that reduces or eliminates dental discoloration and also acts as a preservative treatment to maintain tooth integrity, with few side effects.
New industry is developing a variety of bleaching systems based on different concentrations of the bleaching agent and the use of light or heat to enhance or accelerate the effect.
Higher concentrations of the bleaching agent increase tooth bleaching capacity but it is necesary to take care on sensitivity and the damage of soft tissues.
The application of this technique can represent a very useful and effective tool for improving tooth whitening for postgraduate students.

OBJECTIVES
To check the effectiveness and precision of a teeth bleaching system with or without light and the postgraduate students capacity for its application in the postgraduate programm through a study that is the subject of a research project within the Teaching Innovation programm, at a first level performed by a group of teachers and in a second level by postgraduate students.

MATERIAL AND METHOD
21 pacients patients aged between 18 and 38 years were selected with intact upper-anterior teeth from one canine to the canine on the contralateral hemi-arch and had tooth shade A2 or darker among the patients involved in the Esthetic Dentistry Master in the Faculty of Odontology at the Complutense University of Madrid.
A divided mouth model was used for the study, treating both hemi-arches with hydrogen peroxide but light-activating only one of them. The bleaching agent was Quick White 35% hydrogen peroxide (DMDS House, Canterbury, UK) with photoinitiators. A Luma Cool diode lamp (Lumalite, Inc. Spring Valley, California USA) was used for the light-activation.
A group of 12 postgraduate students applied the treatment. They first observed the initial numerical shade values. Soft tissues were protected and the hydrogen peroxide gel was then applied in 2-mm thick layers to the vestibular surface of a randomly selected hemi-arch. Light was applied for 10 min and the gel was then removed. The entire procedure was then repeated on the same hemi-arch. Hydrogen peroxide was then applied to the contralateral hemi-arch without light for 10 min, removed and then reapplied for a further 10 min. After the bleaching procedure, the shade of the treated teeth was scored again.
Statistical Analysis: The Wilcoxon signed ranks test was used to compare differences in tooth shade values between before and after the bleaching and to compare mean post-treatment values between test and control hemi-arches. The S.A.S. (9.1) software package was used for the statistical analyses.

RESULTS AND CONCLUSIONS
Both light-treated and non-light treated groups showed significant differences between pre-treatment and post-treatment scores for all tooth types studied.
The overall mean whitening in shade was 2.4 units for the side treated without light and 2.9 units for the side treated with light-activation.
There were no soft tissue damage and no pacient refered sensitivity with or without light.
Both are techniques to be applied successfully and safety by postgraduate students.

Keywords:

whitening, diode light, hydrogen peroxide, power bleaching, innovation, research projects, dental.