Department of Odontology
Division of Periodontology

The importance of the length of coherence in laser therapy of gingival inflammation.


In a previous study we were able to show that irradiation with a therapeutic laser had a beneficial effect on gingival inflammation. The aim of the present study is to investigate whether or not the length of coherence has an importance in photomedicine.

Material and Methods Twenty patients with moderate periodontitis were selected. After oral hygiene instructions, scaling and root planing (SRP), one side of the upper jaw was randomly selected for HeNe (632,8 nm, 3 mW) or InGaAlP (650 nm, 3 mW) laser irradiation. One week after SRP, the following parameters were measured: pocket depth, gingival index, plaque index, gingival crevicular fluid volume, matrix metalloproteinase (MMP)-8, interleukin (IL)-8 and Subgingival micro flora. The irradiation (180 s per point, energy 0.54 J) was then performed once a week for 6 weeks.


All clinical parameters had improved significantly in both groups. A more pronounced decrease of clinical inflammation was observed after HeNe treatment. MMP-8 levels were considerably reduced on the HeNe side, while there was no difference for IL-8 or micro flora. Coherence length appears to be an important factor in laser phototherapy.

The HeNe laser (long coherence) had a significant better effect on the gingival inflammation compare to the diode laser (short coherence).