Laser irradiation of bone: III. Long-term healing following treatment by CO2 and Nd:YAG lasers.
BACKGROUND
Relative few reports exist concerning healing of laser created osteotomies over an extended period of time. The purpose of this study was to evaluate long-term healing, from 21 to 63 days, of osteotomy defects in the rat tibia created with the Nd:YAG and CO2 in the presence of a surface cooling spray of air/water.


METHODS
The experimental model consisted of 15 large Sprague-Dawley rats. Six treatment modalities were randomly distributed among 6 tibial recipient sites: 1) a negative control (no treatment); 2) a positive control (bur osteotomy); 3) CO2 laser at 5 W (860 J/cm2); 4) CO2 laser at 6 W (1,032 J/cm2); 5) Nd:YAG laser at 5 W (714 J/cm2); and 6) Nd:YAG laser at 7 W (1,000 J/cm2). All laser irradiation was delivered in the presence of a surface coolant consisting of air (15 psi) and sterile water. Five animals were sacrificed at each of 3 time intervals: 21, 35, and 63 days post-treatment. Multiple histologic sections from each treatment site were examined by light microscopy using hematoxylin and eosin Goldner's trichrome stains, and polarized light and evaluated for presence of a char layer, heat induced cracking, heat related alterations in cells or tissue matrix, and osseous regeneration.


RESULTS
Healing was severely delayed in all laser treated sites compared to positive control sites. Of the laser treated sites, those irradiated by CO2 laser at 5 W (780 J/cm2) exhibited the greater amount of bone regeneration. At best, however, only a small percentage of sections from any of the laser treated specimens showed evidence of bone regeneration within the ablation defect regardless of the post-treatment time interval.


CONCLUSIONS
Under the conditions of this study, the osseous healing response was severely delayed by CO2 and Nd:YAG laser irradiation of bone, even in the presence of a surface cooling spray of air/water.
McDavid
V G
VG
Department of Periodontics, School of Dentistry, University of Missouri-Kansas City, 64108, USA.
Cobb
C M
CM
Rapley
J W
JW
Glaros
A G
AG
Spencer
P
P
D000388:Air; D000538:Aluminum Silicates; D000704:Analysis of Variance; D000818:Animals; D001853:Bone Marrow / Q000473:pathology / Q000601:surgery; D001857:Bone Matrix / Q000473:pathology / Q000601:surgery; D001861:Bone Regeneration; D001842:Bone and Bones / Q000473:pathology / Q000601:surgery*; D002245:Carbon Dioxide; D004396:Coloring Agents; D005456:Fluorescent Dyes; D006358:Hot Temperature; D053685:Laser Therapy; D008137:Longitudinal Studies; D008297:Male; D008859:Microscopy, Polarization; D023421:Models, Animal; D009336:Necrosis; D009354:Neodymium; D010027:Osteotomy / Q000295:instrumentation / Q000379:methods; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D013977:Tibia / Q000473:pathology / Q000601:surgery; D014867:Water; D014945:Wound Healing; D015019:Yttrium
D000538:Aluminum Silicates; D004396:Coloring Agents; D005456:Fluorescent Dyes; D014867:Water; D002245:Carbon Dioxide; D009354:Neodymium; D015019:Yttrium