Dr Tatjana Savic-Stankovic BDS, MSc, my colleague and friend from the University of Belgrade School of Dentistry, completed an extensive study for her MSc thesis on tooth-bleaching agents.
Dr Savic-Stankovic defended her MSc thesis in a viva but also presented the highlights of her research at the School of Dentistry Anniversary in June 2009.
Click on the image to enlarge the poster. Since the poster is in Serbian, the abstract in English is given below. Copyright belongs to Dr Savic-Stankovic. For further contact, please use the email address
savic.t@nadlanu.com
The effect of different concentrations of bleaching agents on enamel properties in vitro and clinical efficiency of the „walking bleach“ technique
Dr Tatjana Savic-Stankovic BDS, MSc
Introduction. Bleaching results in slow transformation of organic substances into chemical intermediary products which are lighter than the original. Bleaching efficiency is related to the cause of tooth discoloration.
Aims. To evaluate changes in enamel microhardness and morphological aspects of enamel after treatment with different concentrations of bleaching agents. The aim of the clinical study was to evaluate the bleaching efficiency with regard to the cause of discoloration: trauma, necrosis, endo-sealer or unknown.
Materials and Methods. Twenty freshly extracted sound human molars were treated with 10%, 20% and 35% carbamide peroxide and 38% hydrogen peroxide (Opalescence gel, Ultradent. Pro.) in clinically recommended intervals. Knoop microhardness measurements were performed at baseline and 8 hours, 21 days and 3 weeks post-treatment. SEM was used to evaluate morphological changes in enamel post-treatment.
Forty non-vital central incisors were bleached using sodium perborate and hydrogen peroxide mixture which was changed weekly. Based on patients' dental history and clinical examination, discolored teeth were allocated to four groups depending on the cause of discoloration: trauma, necrosis, endo-sealer and unknown. Aesthetic results of the applied “walking bleach” technique were evaluated before and after treatment using the standardized colour-coded key for colour comparison.
Results. No statistically significant differences and no changes in enamel surface morphology were observed between 10% and 20 % carbamide peroxide groups. A significant decrease in enamel microhardness was found in 35% carbamide peroxide and 38% hydrogen peroxide groups. Mild and moderate changes in enamel surface morphology were observed in the group treated with 35% carbamide peroxide whilst substantial changes were found in the group treated with 38% hydrogen peroxide.
The shortest treatment (15.7 days) and greatest number of shades before and after bleaching were found in patients whose aetiological factor for discoloration was „trauma”. Bleaching efficiency decreased with age. No correlation was found between bleaching efficiency and the initial shade.
Conclusions. Increasing concentrations of tooth-bleaching agents resulted in lower enamel microhardness values and more profound changes in enamel surface morphology. The cause of tooth discoloration had a significant effect on the clinical efficiency of the "walking bleach" technique.
Keywords: dental materials, tooth bleaching, tooth whitening, carbamide peroxide, hydrogen peroxide, enamel, clinical trial, walking bleach
The study "Surface characterisation of resin-based composite materials using atomic force microscopy" was successfully presented by Ana Ergic and Dejan Nedeljkovic at the IADR-CED conference in Munich. Click on the image to enlarge the poster. Ana and Dejan are my former students who were involved in this study as part of their student research project. They have recently graduated at the University of Belgrade School of Dentistry.
