Evaluation of Enamel Loss with Polycrystalline Ceramic Bracket using two different Debonding Techniques

Introduction: Debonding of ceramic brackets requires a technique that will restore the enamel surface possibly to its pretreatment condition. Objective: To evaluate a comparative degree of enamel loss with various debonding techniques. Materials & Method: 30 extracted premolars were divided into three equal groups of 10 each on the basis of bonding material used. Six subgroups comprising of 5 teeth each were formed on the basis of debonding techniques. Debonded enamel surfaces were photographed under Scanning Electron Microscope to evaluate the enamel loss percentage and compared using oneway ANOVA. Result: Decreasing order of enamel surface loss was 63.1%, 56.3%, 45.4%, 43%, 31% and 30.5% for light cure–mechanical, light cure-electrothermal, self cure-mechanical, self cure-electrothermal, single composite-mechanical and single compositeelectrothermal combination respectively. Conclusion: Mechanical debonding leads to greater enamel loss than electrothermal debonding. Bonding with Light cure composite always leads to greater enamel loss irrespective of type of debonding technique. Bonding with single composite always leads to lesser enamel loss irrespective of debonding technique.


INTRODUCTION
Fixed orthodontic treatment is the most common and extensively used treatment option for various types of malocclusions. The term debonding refers to removal of orthodontic attachments and residual adhesive from the enamel surfaces that restore as closely as possible to its pre-treatment condition without inducing iatrogenic enamel damage. 3ring debonding it should be ensured that natural structure of the tooth remains intact or minimal tooth enamel loss shall occur.
This study facilitates in recognizing a bonding agent that will have sufficient bond strength throughout the treatment period, and when it is debonded, it shall cause minimal loss of tooth enamel.The study identifies a technique of debonding that will cause minimal tooth enamel loss.Debonding is required at the termination of active treatment.Great consideration should be given to debonding procedures and their effect on the enamel surface underlying the bonded attachments.
Primary consideration lies in the returning the enamel surface to as near as its original state as possible following the removal of bonded orthodontic attachments.
The purpose of the study was to microscopically examine the as possible to natural enamel surface.Thus the objective of this study was to identify a debonding technique that will cause minimal enamel loss and to evaluate a comparative degree of enamel loss with various debonding techniques.

MATERIALS AND METHOD
Thirty premolars (extracted for therapeutic purpose) were collected.Tooth that have any type of enamel loss, carious lesion, hypoplastic or fluorosed enamel, fractured or treated were not included in the study.Teeth were stored in storage medium containing 10% formalin solution.Prophylaxis of enamel surface was performed by using rubber cup (Microdont Soccoro, Brazil) and fine pumice powder (SS white) and rinsed with water at low speed for 10 second and dried with oil-free compressed air.[12][13] Bracket/enamel interface was cured with LED light curing unit at a distance of 5 mm for 10 second at the mesial surface and 10 sec at the distal surface. 13[3] Bracket removal was done using the debonding plier in such a way that the plier was placed at the base of the bracket, and a slight amount of squeezing pressure applied to the handles of plier until debonding occurred.The direction of applied force was occluso-gingival.In electrothermal debonding (ETD) of brackets from the tooth surface; electrical device (Figure 1) was used to generate heat and that heat is transferred to the bracket base by a blade of electrothermal device that is placed at the bracket slot at less than 160 o c. 12 When the heat is applied to the bracket, heat is transferred and deformed the adhesive bracket interface then the bracket could be easily lifted without excessive force to underlying enamel surface. 12Before removing excess adhesive and polishing the enamel surfaces, each specimen was assessed for enamel loss under the magnification with scanning electron microscope (SEM) for surface enamel loss. 10Before keeping the samples inside the sputter coater (Emitech sc-7620 Quaram technology) (Figure 2) for gold palladium coating sample was dried in incubator and dessicator (Figure 3).Enamel surface following debonding were examined under SEM (Figure 4); which were viewed in computer monitor (Figure 5).
Evaluation was done by measuring the surface area of enamel under the bracket then lost enamel surface was measured for each sample.Then mean was calculated for one subgroup then percentage loss of enamel was calculated and this percentage loss was compared and analyzed by ANOVA for intra-group and paired t-test for inter-group variation among all six subgroups.strength for orthodontics but it is very less as compared to the light cure however, it is easy to remove and lesser enamel damage is reported with single composites.

CONCLUSION
Maximum enamel loss occur during mechanical debonding using light cure composite bonding material and minimum enamel loss occur during electro thermal debonding using single composite bonding material.

DISCUSSION
Debonding of bracket always leads to enamel loss and it depends upon the type of bonding material and debonding technique used.Removal of ceramic brackets using mechanical debonding technique always leads to greater enamel loss than electro-thermal debonding.Following the etching; bonding is achieved mainly by the formation of resin tags, hence when we debond mechanically it leads to breakage of the resin tags along with the adjacent enamel structure, leading to more enamel loss compared to electrothermal debonding i.e. in which the heat delivered by the instrument weakens the resin tags and allow easy removal and less enamel damage.
Bonding with light cure composite causes greater enamel loss irrespective of type of debonding technique used. OJN enamel surface structure subjected to different debonding techniques using Scanning Electron Microscope (SEM) to identify a technique that restores the enamel surface as closely Orthodontic Journal of Nepal, Vol. 5, No. 1, June 2015

Figure
Figure 6a-Enamel surface after mechanical debonding using light Cure composite