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Scientific article
English

Kinetics of light-cure bracket bonding: power density vs exposure duration

Contributors

Mavropoulos, Anestis; Cattani-Lorente, Maria Angeles; Krejci, Ivo; Staudt, Christine Bettina

Published in

American journal of orthodontics and dentofacial orthopedics, vol. 134, no. 4, p. 543-547

Publication date

2008

Abstract

INTRODUCTION: Recent technologic advances make it possible to increase the light power density to reduce the necessary exposure duration. The kinetics of polymerization are complex. The special case of indirectly curing the thin layler of composite below the metallic bracket base further increases this complexity. It was hypothesized that the concept of "total energy,"--the reciprocity between power density and exposure duration--does not hold for orthodontic light-cure bracket bonding. METHODS: Stainless steel brackets were bonded on deciduous bovine incisors with a standard light-cured composite. A calibrated, powerful halogen lamp allowed for modification of power density from 300 to 3000 mW/cm2. Metallic brackets were bonded in 8 groups of 20 incisors each with various combinations of power densities and exposure durations to obtain 3 levels of energy density (6000, 12000, and 24000 mJ/cm2). Another group of 20 incisors served as the positive control with a conventional powerful halogen lamp (1000 mW/cm2) for 40 seconds. After storage for 24 hours at 37 degrees C in water, the bracket shear bond strength (SBS) and the adhesive remnant index (ARI) were measured. RESULTS: It was confirmed that bracket SBS mainly depends on the energy density of the light cure. All groups with an energy density of 6000 mJ/cm2 had significantly lower SBS than the groups with higher energy densities (P <0.01). The dependence of SBS on exposure duration for the same energy density followed an exponential model of nonlinear regression (r2 = 0.98). CONCLUSIONS: The concept of "total energy" does not hold for orthodontic light-cure bracket bonding. An exposure time of less than 4 seconds, irrespective of the power density, cannot guarantee sufficient bracket bond strength. There seems to be an advantage of power density over exposure duration in the context of metallic bracket bonding. These results show that, for an efficient light-cure bracket bonding, there is an absolute lower limit of exposure duration (4 seconds) and an upper limit of useful power density (3000 mW/cm2).

Keywords

  • Analysis of Variance
  • Animals
  • Cattle
  • Dental Bonding
  • Dental Stress Analysis
  • Kinetics
  • Light
  • Orthodontic Brackets
  • Phase Transition
  • Regression Analysis
  • Resin Cements/radiation effects
  • Shear Strength
  • Stainless Steel

UNIGE affiliation entities

UNIGE research groups

Citation (ISO format)

MAVROPOULOS, Anestis et al. Kinetics of light-cure bracket bonding: power density vs exposure duration. In: American journal of orthodontics and dentofacial orthopedics, 2008, vol. 134, n° 4, p. 543–547. doi: 10.1016/j.ajodo.2006.09.068

Main files (1)

Article (Accepted version)

Identifiers

Journal ISSN

0889-5406
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Technical informations

Creation

07/04/2009 08:50:00

First validation

07/04/2009 08:50:00

Update

14/03/2023 15:04:23

Status update

14/03/2023 15:04:23

Last indexation

29/10/2024 11:28:14
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