On the reliability of the holographic method for measurement of soft tissue modifications during periodontal therapy

Holographic evaluations count among recent measurement tools in orthodontics and prosthodontics. This research introduces holography as an assessment method of 3D variations of gingival retractions. The retraction of gingiva on frontal regions of 5 patients with periodontitis was measured in six points and was evaluated by holographic methods using a He-Ne laser device (1mV, Superlum, Carrigtwohill, Ireland) inside a holographic bank of 200 x 100cm. Impressions were taken during first visit and cast models were manufactured. Six months after the end of periodontal treatment, clinical measurements were repeated and the hologram of the first model was superimposed on a final model cast, by using reference points, while maintaining the optical geometric perimeters. The retractions were evaluated 3D in every point using a dedicated software (Sigma Scan Pro,Systat Software, SanJose, CA, USA). The Wilcoxon test was used to compare the mean recession changes between baseline and six months after treatment, and between values in vivo and the values on hologram. No statistically significant differences between values in vivo and on the hologram were found. In conclusion, holography provides a valuable tool for assessing gingival retractions on virtual models. The data can be stored, reproduced, transmitted and compared at a later time point with accuracy.