Differences in histochemical characteristics of gingival collagen after ER:YAG laser periodontal plastic surgery

The aim of this study is to evaluate gingival collagen for the effect of treatment with the Erbium:YAG Kesler handpiece. The handpiece is designed for gingival resurfacing in cases of hypertrophic gingiva and gingival pigmentation.

Lasers represent recent technological advances that afford new options for the treatment of periodontal diseases. However, lasers used for esthetic gingival soft tissue resurfacing require careful histopathological evaluation of the effects on tissue. In particular, it is important to determine the effect of laser irradiation on connective tissue, especially the collagen fibers. To date, no stage-wise clinical or histological studies have been performed addressing this issue.

Ten patients underwent irradiation with the following parameters: energy per pulse, 500 mJ; repetition rate, 10 pps; spot size, 3 mm. Gingival biopsy specimens were derived from 6 patients with hypertrophic gingiva and 4 with gingival pigmentation. The patients were examined before laser treatment and at 7 and 14 days after laser treatment. The tissues were fixed in tymph node revealing solution (LNRS), embedded in paraffin, sectioned at 5 microm, and stained with hematoxylin & eosin. The status of collagen in the treatment site was examined under polarized light after picrosirius red (PSR) staining. PSR is a collagen stain that differentiates collagen fiber density or size by means of a spectrum of color changes under polarized light. The major colors are red, orange, yellow, and green.

We found a significant difference in the properties of collagen fibers at the first week and at 14 days post-treatment. In the normal gingiva, the predominant polarization colors were in the red-orange range, signifying tightly packed, mature collagen. During the first postoperative week, collagen fibers exhibited polarization colors in the green to green-yellow range, implying loosely packed collagen fibers. After 2 weeks, collagen fibers reacquired their preoperative PSR characteristics.

We conclude that sequential series of changes accompany photothermal treatment of the gingiva. The occurrence of this sequence in all successful outcome cases may suggest the importance of these temporally sequenced changes in collagen during gum healing. In any event, the status of PSR staining of gum collagen provides a useful adjunct in the assessment of gingival health.