Efficiency of ceramic bracket debonding with the Er:YAG laser

Chung-Hwan Suh; Na-Young Chang; Jong-Moon Chae; Jin-Hyoung Cho; Sang-Cheol Kim; Kyung-Hwa Kang

doi:10.4041/kjod.2009.39.4.213

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Suh, Chang, Chae, Cho, Kim, and Kang: Efficiency of ceramic bracket debonding with the Er:YAG laser

Original Article

Korean Journal of Orthodontics

Korean Journal of Orthodontics 2009; 39(4): 213-224.

Published online: 31 August 2009

DOI: https://doi.org/10.4041/kjod.2009.39.4.213

Efficiency of ceramic bracket debonding with the Er:YAG laser

Chung-Hwan Suh, DDS, MSD, PhD^a, Na-Young Chang, DDS, MSD^a, Jong-Moon Chae, DDS, MSD, PhD^b, Jin-Hyoung Cho, DDS, MSD, PhD^b, Sang-Cheol Kim, DDS, MSD, PhD^c, Kyung-Hwa Kang, DDS, MSD, PhD^d

^aFellow, Department of Orthodontics, School of Dentistry, Wonkwang University, Korea.

^bAssistant Professor, Department of Orthodontics, School of Dentistry, Wonkwang University, Korea.

^cProfessor, Department of Orthodontics, School of Dentistry, Wonkwang University, Korea.

^dAssociate Professor, Department of Orthodontics, School of Dentistry, Wonkwang University, Korea.

Corresponding author: Kyung-Hwa Kang. Department of Orthodontics, School of Dentistry, Wonkwang University, 344-2, Shinyong-dong, Iksan 570-711, Korea. +82 63 850 6635; pigtail@wonkwang.ac.kr

Received 4 March 2009 Revised 25 May 2009 Accepted 30 May 2009

Abstract

Objective

The aim of this study was to find out whether Er:YAG laser can aid in debonding ceramic brackets, and to see what kind of method will be the most appropriate for debonding.

Methods

One hundred and ninety teeth, monocrystalline brackets (MISO™, HT, Ansan-Si, Korea), polycrystalline brackets (Transcend™ series 6000, 3M Untek, Monrovia, CA, USA) and the KEY Laser3 (KavoDental, Biberach, Germany) were used. Experimental groups were classified according to the type of ceramic brackets, and the amount of laser energy (0, 140, 300, 450, 600 mJ). After applying laser on the bracket at two points at 1 pulse each, the shear bond strength was measured. The effect of heat caused by laser was measured at the enamel beneath the bracket and pulp chamber. After measuring the shear bond strength, adhesive residue was evaluated and enamel surface was investigated using SEM.

Results

All ceramic bracket groups showed a significant decrease in shear bond strength as the laser energy increased. The greatest average temperature change was 3.78℃ on the enamel beneath the bracket and 0.9℃ on the pulp chamber. Through SEM, crater shape holes caused by the laser was seen on the enamel and adhesive surfaces.

Conclusions

If laser is applied on ceramic brackets for debonding, 300 - 450 mJ of laser energy will be safe and efficient for monocrystalline brackets (MISO™), and about 450 mJ for polycrystalline brackets (Transcend™ series 6000).

Keywords: Debonding, Er:YAG laser, Ceramic bracket

Figures and Tables

Fig. 1

A, Laser delivery device with laser focusing guide; B, lasing point (★); C, tooth cross-section. Thermocouple point (T) and lasing point (★). The lasing direction is perpendicular to the slot base.

Fig. 2

Shear bond strength values (MPa) at various amounts of laser energy on each type of bracket.

Fig. 3

Temperature change (℃) at various amounts of laser energy on each type of bracket. A, Monocrystalline bracket; B, polycrystalline bracket.

Fig. 4

Graph of residual adhesive ratings according to the adhesive remnant index (ARI). A, Monocrystalline bracket; B, polycrystalline bracket.

Fig. 5

SEM images of debonding remnant adhesives and tooth of 'Monocrystalline bracket' group. A-C, Group M300; D-F, group M450; G-I, group M600. A and D and G, Remnant adhesive surface on tooth, after laser debonding. Ablated volcano-like hollow was observed (arrow) (original magnification × 30, scale bar: 500 µm); B and E and H, low power SEM image of adhesive-enamel interface, a cross-section view (original magnification × 35, scale bar: 500 µm, e = enamel, r = remnant adhesive); C and F and I, higher magnification of the box shown in B & E & H in cross-sectional view. Ablated volcano-like hollow was also observed. Enamel damage about 10 - 30 µm (▴) (original magnification × 150, scale bar: 100 µm, e = enamel, r = remnant adhesive).

Fig. 6

SEM images of debonding remnant adhesives and tooth of 'Polycrystalline bracket' group. A-C, Group P450; D-F, group P600. A and D, Remnant adhesive surface on tooth, after laser debonding. Ablated volcano-like hollow was observed (arrow). Note that remnant adhesives on the tooth have partially exfoliated (original magnification × 30, scale bar: 500 µm); B and E, low power SEM image of adhesive-enamel interface, a cross-sectional view (original magnification × 35, scale bar: 500 µm, e = enamel, r = remnant adhesive); C and F, higher magnification of the box shown in B & E in cross-sectional view. Ablated volcano-like hollow was also observed. Enamel damage about 10 - 30 µm (▴) (original magnification × 150, scale bar: 100 µm, e = enamel, r = remnant adhesive).

Table 1

Control and experimental groups

CM, Control group of monocrystalline bracket; CP, control group of polycrystalline bracket.

Table 2

Comparison of shear bond strength values (MPa) at various amount of laser energy levels on each type of bracket

The same abbreviation as Table 1. SD, Standard deviation. ^*p < 0.001. Entries with the same superscripted letter were not significantly different at p < 0.001.

Table 3

Comparison of temperature change (℃) at various amount of laser energy levels on the monocrystalline bracket group

SD, Standard deviation; Max, maximum; T, average time to reach maximum temperature (second). ^*p < 0.05. Entries with the same superscripted letter were not significantly different at p < 0.05.

Table 4

Comparison of temperature change (℃) at various amount of laser energy levels on the polycrystalline bracket group

SD, Standard deviation; Max, maximum; T, average time to reach maximum temperature (second). ^*p < 0.05. Entries with the same superscripted letter were not significantly different at p < 0.05.

Table 5

Residual adhesive ratings of the monocrystalline and polycrystalline bracket groups according to the adhesive remnant index (ARI)

^*Adhesive remnant index scores were: 1, All adhesive remaining on the tooth; 2, more than 90% of the adhesive remaining on the tooth; 3, more than 10% but less than 90% of the adhesive remaining on the tooth; 4, less than 10% of the adhesive remaining on the tooth; 5, no adhesive remaining on the tooth. ^{a, b}: ARI score of group 'CP' was significantly different from group 'P600' (p < 0.05).

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