Inhibition of Caries in Vital Teeth by CO₂-laser Treatment

Several well-controlled in-vitro laboratory studies have reported enhancement of caries resistance of dental enamel following short-pulsed 9.6 µm CO₂-laser irradiation. Objective: To prove in a short-term clinical study that the use of specific CO₂-laser irradiation conditions will significantly inhibit the formation of carious lesions around orthodontic brackets in vital teeth in human mouths. Methods: 24 subjects (average age 14.5 years) with premolars scheduled for extraction for orthodontic reasons were recruited; 12 each for a) a 4-week arm and b) a 12-week arm. Orthodontic brackets were placed on those premolars with a conventional composite resin (Transbond XT, 3M Unitek, REF 712-035) and a defined area next to the bracket was irradiated with a CO₂-laser, Pulse System, Inc (PSI) (Model #LPS-500, Los Alamos, New Mexico), wavelength 9.6µm, pulse duration 20µs, pulse repetition rate 20Hz, beam diameter 1100µm, average fluence 4.1±0.3J/cm², 20 laser pulses per spot. An adjacent non-irradiated area was selected as the control surface. Premolars were extracted after 4 and 12 weeks respectively for a quantitative assessment of demineralization by cross sectional microhardness testing. Results: Mean relative mineral loss ΔZ (vol% x µm) for the laser treated enamel was 402±84 (Standard Error SE) after 4-weeks with the control area significantly more demineralized (ΔZ 737±130(SE); P=0.04, t-test). The difference between irradiated and control areas was even larger after 12-weeks (laser treated mean ΔZ 135±98 (SE); control mean ΔZ 1067±53; P=0.002). The laser treatment produced a 46% demineralization inhibition after 4 weeks and a marked 87% inhibition for the 12 week arm. Conclusion: This study shows, for the first time in-vivo, that the specific CO₂ pulsed laser irradiation can be used successfully for the inhibition of dental caries in enamel in human mouths. Supported by NIH/NIDCR grant DE09958.