This paper reviews studies on the basic principles of biostimulation of wound healing by various low-energy lasers. It looks at the mechanism of action of biostimulation as well as the laser's effect on cell proliferation, collagen synthesis, and would healing.

The purpose of this study was to compare the in vivo osseous healing response of 4 commercially-available synthetic bone grafting materials; hydroxylapatite (HA), calcium sulfate (CaSO4) plus autogenous bone, or a bioactive glass ceramic: with particle size of 300-360 microm (BG1) or 90 to 710 microm (BG2). 4 osteotomy sites were prepared in each tibia of 10 adult male rabbits. One unfilled osteotomy site served as negative control (NC) and another site filled with autogenous bone was the positive control (PC). All animals received BG1 in 2 sites and BG2 in 2 sites. 5 animals received HA and five CaSO4 plus autogenous bone in the remaining 2 sites. Animals were sacrificed at 28 days post-surgery, histologic sections obtained and the % surface area of new bone formation for each material was determined by computerized image analysis. All graft sites showed evidence of bone formation, i.e., (NC) 41.95%; (PC) 50.41%; (BG1) 41.82%; (BG2) 40.36%; (HA) 41.83% and (CaSO4) 58.83%. Statistical analysis using an ANOVA with repeated measures on the materials common to all animals (excluding HA and CaSO4 groups) showed significant differences between materials in surface area of bone, with positive controls better than negative controls, and BG1 and BG2 not significantly different from the negative control. These results indicate that synthetic graft materials can support new bone formation in surgically prepared defects. The utility of a rabbit model for studying physiologic osseous turnover and healing is questioned for studies of slowly resorbing synthetic graft materials.

The purpose of this investigation was to determine the ability of human gingival fibroblasts, in vitro, to migrate along a chemotactic gradient over 3 different guided tissue regeneration barrier materials; i.e., polytetrafluoroethylene, polylactic acid, and sterile calcium sulfate. Forty petri dishes were divided into 4 equal groups. In each group of 10 dishes, a different barrier material served as the fibroblast substrate with the polystyrene floor of one group of Petri dishes serving as the control. The under agarose technique of measuring cell migration was employed using platelet derived growth factor-BB homodimer as the chemoattractant and Hanks balanced salt solution to test random migration. In addition, fibroblasts were directly cultured on triplicate sets of barrier materials and the control surface for 24 hours and examined by scanning electron microscopy. Comparative analysis of the fibroblast migration data showed the mean migration distance (adjusted for random migration) for controls to be significantly greater than any of the three barrier materials. Further, mean migration distance over calcium sulfate was significantly greater when compared to that of the polylactic acid barrier group. All other comparisons between groups were not statistically significant. Scanning electron microscopic examination fibroblasts cultured directly on barrier membranes and compared to controls indicated that the calcium sulfate substrate appeared to facilitate cell attachment and spreading whereas cells on polytetrafluoroethylene and polylactic acid barriers exhibited a morphology not conducive to migration or, in many cases, cell health. Based on these limited in vitro results and, given the 3 barrier materials considered, it would appear that calcium sulfate offers the greater potential for guided tissue regeneration in surgical sites where primary wound closure cannot be obtained.

In this study 50 patients with diabetes mellitus had gingival crevicular blood from periodontal probing collected in small plastic pipettes. The pipettes transferred the crevicular blood to a non‐wipe glucose self‐monitoring instrument. At the same time, fingerstick capillary blood measurements were analyzed in the same glucose self‐monitoring instrument, and venous blood was collected for measurement in a laboratory glucose analyzer. Each laboratory measurement was corrected from a serum glucose value to a whole blood glucose value by a function of the patient's hematocrit. This corrected glucose value allowed direct comparison of the laboratory measurement to the intraoral and finger‐stick whole blood measurements. The patient blood glucose concentrations ranged from 59 mg/dl to 366 mg/dl. The gingival crevicular blood exhibited a correlation of r = 0.975 (P <.0001) to the corrected laboratory standard measurement, with a mean prediction error (bias) of −4.11 mg/dl and a root mean square error (precision) of 17.43 mg/dl. The finger‐stick blood had a correlation of r = 0.983 (P <.0001) to the corrected laboratory standard, with a mean prediction error of 4.65 mg/dl and a root mean square error of 14.48 mg/dl. The American Diabetic Association recommends that the prediction error of blood glucose monitoring devices fall within 15% of the laboratory standard. Using this criterion 92% of the gingival crevicular measurements and 90% of the fingerpuncture measurements fell within 15% of the laboratory value. The results suggest that gingival crevicular blood collected by a small plastic pipette and measured in a nonwipe glucose self‐monitor is feasible for in‐office blood glucose testing with measurements comparable to those obtained using the finger‐puncture method. J Periodontol 1993;64:666–672.

The purpose of this study was to evaluate the effects of Nd:YAG laser treatment on root surfaces in vitro when used alone or in combination with conventional scaling and root planing. The study population consisted of 18 unerupted third molars, each with a 3 mm diameter treatment site outlined on the root surface. Three specimens were randomly assigned to each of 6 different treatment groups: 1) untreated control; 2) root planed only; 3) laser treated only using 1.25 W of energy; 4) laser treated only using 1.50 W of energy; 5) laser treated with 1.25 W of energy followed by root planing; and 6) laser treated with 1.50 W of energy followed by root planing. Following their respective treatment, all specimens were prepared for evaluation by scanning electron microscopy. Specimens from Group 2, root planed only, exhibited a smear layer of scale-like texture with parallel instrument tracks resulting from curet use. Specimens treated by laser only, Groups 3 and 4, featured various surface changes not observed in controls such as charring and carbonization of the cementum surface, randomly distributed pitting and crater formation, and melting of the root mineral phase with subsequent resolidification as porous globules. Those specimens treated by laser followed by root planing, Groups 5 and 6, exhibited surface characteristics similar to those noted in Group 2 specimens. Further, there were areas of exposed dentinal tubules resulting from a "peeling" of the cementum layer. The results of this in vitro study suggest that laser use during root preparation, even at relatively low energy levels, will result in physical changes to the root surface.(ABSTRACT TRUNCATED AT 250 WORDS)

In this animal model, laser-induced osteotomy defects, when compared to those prepared by rotary bur, exhibited a delayed healing response that appeared to be related to the presence of residual char in the osseous defect.

The Nd:YAG and CO2 lasers have been shown to be bactericidal at relative low energy densities. However, at energy densities exceeding 120 J/cm2 (CO2) and 200 J/cm2 (Nd:YAG), laser irradiation also causes irreparable root surface damage. The purpose of this study was to determine, in vitro, the energy density threshold at which microbial ablation could be achieved while inflicting the least amount of damage to the root surfaces of human teeth. Pairs of Escherichia coli colonies cultured on broth agar were treated with a CO2 laser using a pulsed waveform at approximate energy densities ranging from 3 to 110 J/cm2. One of each colony-pair was then examined by scanning electron microscopy (SEM) and the other subcultured for viable microbes. Roots of extracted teeth were lightly scaled and treated by CO2 laser, again with pulsed beam using approximate energy densities of 3 to 110 J/cm2: and examined by SEM. Regardless of the level of energy density, residual bacteria could be subcultured from all laser treated microbial colonies. The inability of the laser to completely obliterate microbial colonies was likely due to: depth of energy penetration, difficulty in precisely overlapping beam focal spots, irregular beam profile, and presence of microbes at the periphery of the beam focal spot. The threshold energy density for bacterial obliteration was determined to be 11 J/cm2 and that for root damage was 41 J/cm2. Root damage was evident by charring, crater formation, melt-down and resolidification surface mineral, and increasing surface porosity. The results of this in vitro study indicate that when used at an energy density between 11 and 41 J/cm2 the CO2 laser may destroy microbial colonies without inflicting undue damage to the tooth root surface.

The purpose of this in vitro study was to evaluate the effects of the Nd:YAG laser either alone or in combination with root planning or air-powder abrasive treatment on fibroblast attachment to non-diseased root surfaces. 28, 4 x 4 mm root specimens and four disc-shaped root specimens 6 mm in diameter were obtained from unerupted 3rd molars. The root segments were randomly assigned to 4 treatment groups: (1) control; (2) laser-only treated; (3) laser treated followed by root planning; (4) laser treated followed by air-powder abrasive treatment. Laser-treated root specimens were exposed for 1 min with the Nd:YAG laser calibrated at an energy setting of 75 mJ at 20 pulses/s using a 320 microns contact fiber. The contact fiber was held parallel to the root segments and the root segments were kept moist with distilled water. Following the prescribed treatments, the root specimens were incubated with fibroblast cultures and then prepared for SEM examination. Results of cell counts of fibroblasts attached to specimens within each treatment group yielded the following means and standard deviations: control groups, 181.64 +/- 44.74; lased only, 78.57 +/- 21.35; lased and root planed 125.35 +/- 26.13; and lased followed by an air-powder abrasive, 177.28 +/- 55.71. Application of ANOVA followed by the Dunn Multiple Comparison test revealed significant differences (p < 0.01) in the number of attached cells between the control and laser-only treated groups; and between the laser-only and laser/air-powder abrasive treated groups.(ABSTRACT TRUNCATED AT 250 WORDS)