SEM Evaluation of Enamel Surface Changes and Enamel Microhardness around Orthodontic Brackets after Application of CO2 Laser, Er,Cr:YSGG Laser and Fluoride Varnish: An In vivo Study

Abstract

Introduction: One of the most undesirable consequences of orthodontic treatment is occurrence of enamel demineralization around orthodontic brackets. Numerous in vitro studies have reported the prevention of enamel demineralization by surface treatment with lasers and fluoride varnish.

Aim: To evaluate the changes on the enamel surface and microhardness around orthodontic brackets after surface treatment by CO₂ laser, Er, Cr:YSGG laser and fluoride varnish in vivo.

Materials and methods: A double blind interventional study was carried out on 100 premolars which were equally divided into five groups, out of which one was the control group (Group 0). The intervention groups (Group I to IV) comprised of patients requiring fixed orthodontic treatment with all 4 first premolars extraction. Brackets were bonded on all 80 premolars which were to be extracted. Enamel surface treatment of Groups I, II and III was done by CO₂ laser, Er, Cr:YSGG laser and 5% sodium fluoride varnish respectively and Group IV did not receive any surface treatment. A modified T-loop was ligated to the bracket and after two months, the premolars were extracted. Surface changes were evaluated by Scanning Electron Microscopic (SEM) and microhardness testing. Comparison of mean microhardness between all the groups was assessed using post-hoc test with Bonferroni correction.

Results: Group I showed a melted enamel appearance with fine cracks and fissures while Group II showed a glossy, homogenous enamel surface with well coalesced enamel rods. Group III showed slight areas of erosions and Group IV presented areas of stripped enamel. Significant difference was observed between the mean microhardness (VHN) of Group I, Group II, Group III, Group IV and Group 0 with p<0.001. A significant difference of p<0.001 was observed while comparing Group I vs II,III,IV,0 and Group II vs III,IV,0. However, difference while comparing Group III vs IV was p=0.005 and difference between the mean microhardness of Group 0 vs Group III was non significant.

Conclusion: Surface treatment with Er,Cr:YSGG laser causes a positive alteration of the enamel surface increasing its ability to resist demineralization with optimum microhardness as compared to CO₂ laser and sodium fluoride varnish.

Keywords: Dental enamel; Sodium fluoride; Surface treatment.

[Table/Fig-1]:

T loop engaged using an elastomeric ligature to increase plaque accumulation.

[Table/Fig-2]:

SEM photograph of Group 0 (control) exhibited circumferentially arranged enamel rods filled with inter rod material on the surface (magnification 2000X).

[Table/Fig-3]:

SEM photograph of Group I (CO₂ laser) showed a melted enamel appearance with fine cracks and fissures (magnification 2000X).

[Table/Fig-4]:

SEM photograph of Group II (Er,Cr:YSGG laser) showed a smooth, homogenous enamel surface with well coalesced enamel rods (magnification 2000X).

[Table/Fig-5]:

SEM photograph of Group III (5% Sodium fluoride varnish) showed areas of slight erosions near the bracket tooth interface. (at magnification 2000X).

[Table/Fig-6]:

SEM photograph of Group IV (no surface treatment) presented areas of stripped enamel revealing the enamel rods which were exposed vividly. Enhanced enamel porosities with loss of prismatic structure were appreciated (at magnification 2000X) (marked with red arrow).