MATERIALS AND METHODS: Three different makes of ceramic brackets, Pure Sapphire(M), Clarity™ ADVANCED(P) and Dual Ceramic(P) were used. Eighteen specimens of each make were prepared and allocated to three groups (n = 6). MARC(®)-resin calibrator was used to determine the light curing unit (LCU) tip irradiance (mW/cm(2)) and TLE (J/cm(2)) transmitted through the ceramic brackets, and through ceramic bracket plus Transbond™ XT Light Cure Adhesive, for 5, 10 and 20 s. Vickers-hardness values at the bottom of the cured adhesive were determined. Statistical analysis used one-way analysis of variance (ANOVA); P = 0.05.
RESULTS: TLE transmission rose significantly among all samples with increasing exposure durations. TLE reaching the adhesive- enamel interface was less than 10 J/cm(2), and through monocrystalline and polycrystalline ceramic brackets was significantly different (P
METHODS: Six makes, three each monocrystalline (M) and polycrystalline (P) were used; PureSapphire (M), SPA Aesthetic (M), Ghost (M), Mist (P), Reflections (P), and Dual Ceramic (P). The Ortholux™ Light Curing Unit (LCU) was used to cure the orthodontic adhesive Transbond™XT. The LCU's tip irradiance was measured and TLE transmitted through the ceramic bracket was obtained, then adhesive added to the bracket, and transmitted TLE measured through bracket-plus-adhesive samples. The LCU was set at five seconds as recommended for curing adhesive through ceramic brackets.
RESULTS: Mean tip irradiance was 1859.2±16.2mW/cm2. The TLE transmitted through brackets alone ranged 1.7 to 3.9J/cm2, in the descending order: Ghost>Pure Sapphire>Reflections>Mist>SPA Aesthetics>Dual Ceramic. The TLE transmitted through bracket-plus-adhesive samples ranged 1.6 to 3.7J/cm2, in the descending order: Ghost>Mist>Reflections>Pure Sapphire>SPA Aesthetics>Dual Ceramic. TLE was reduced with the addition of adhesive (range -0.1 to -0.7J/cm2). There was a significant difference for Pure Sapphire, Reflections, and Mist (P<0.05), but not for SPA Aesthetics, Ghost, and Dual Ceramic. There was no overall significant difference between the monocrystalline and polycrystalline makes. The two best makes were of the monocrystalline type, concerning TLE transmission, but with the exception of polycrystalline Dual Ceramic; the next worst make was a monocrystalline bracket, SPA Aesthetics.
CONCLUSION: Light energy attenuation through ceramic orthodontic brackets is make-dependent, with no overall difference between monocrystalline and polycrystalline brackets. Light energy is further attenuated with the addition of resin-based orthodontic adhesive.