The gingival biotype: measurement of periodontal tissue dimensions in esthetic zone using a non-invasive digital method

Abstract

Objectives. The aim of this study was to measure and determine the relationship between labial alveolar bone and gingival thicknesses using a non-invasive and relatively accurate digital registration method. In addition, the correlation of different morphometric parameters with the thickness of the labial gingiva and alveolar bone at different apico-coronal levels was evaluated.

Methods. In 20 periodontally healthy subjects, cone-beam computed tomography (CB-CT) images and intraoral scanned files were obtained. Measurements of labial alveolar bone and gingival thickness at the central incisors, lateral incisors, and canines were performed at 0–5 mm points from the alveolar crest on the superimposed images. Clinical parameters including the crown width/crown length ratio (CW/CL), gingival width (GW), gingival scallop (SC), and transparency of the periodontal probe through the gingival sulcus (TRAN) were examined.

Results. The mean labial alveolar bone thicknesses at the central incisors, lateral incisors, and canines were 0.86, 0.83, and 0.9 mm, respectively. Likewise, the mean gingival thicknesses at the central incisors, lateral incisors, and canines were 0.92, 0.83, and 0.81 mm, respectively. Significant differences in gingival thickness were observed at the alveolar crest level (G0) between the central incisors and the canines (p=0.001), and between the central incisors and the lateral incisors (p=0.001). At the G1 level (gingival thickness at 1 mm inferior to the alveolar crest), there was also a difference between the central incisors and the canines (p=0.002), and between the central incisors and the lateral incisors (p=0.004). Gingival thickness at the alveolar crest level was positively correlated with the thickness of the alveolar bone plate (p<0.05). The correlation analyses revealed no significant correlation between the clinical parameters and the hard and soft tissue thicknesses.

Conclusions. Despite the morphologic variations of the periodontium, the gingival and labial alveolar bone thicknesses of the anterior maxillary teeth were found to be relatively thin (<1 mm) overall. An analysis of the mean thickness at each level showed that gingival thickness tended to increase and that alveolar bone thickness tended to decrease toward the root apex. With respect to the tooth types, a significant difference in gingival thickness at the alveolar crest level was observed. The gingival thickness at the alveolar crest level also revealed a positive correlation with labial alveolar bone thickness, although this correlation at identical depth levels was not significant. However, the measurement of gingival thickness at, or under the alveolar crest level, was not associated with the clinical parameters of the gingival features, such as the crown form and the gingival scallop, or the keratinized gingival width. Therefore, it is recommended that, in future studies, accurate measuring methods of the supracrestal gingival area should be developed, and the predictive potential of clinical parameters on tissue thickness should be verified.