Anatomic Considerations to Harvest Subepithelial Connective Tissue Grafts from the Palate on the Three-Dimensional Reconstruction of Cone Beam Computed Tomography

Abstract

Objectives: Biotype conversion around both natural teeth and implants with subepithelial connective tissue graft (SCTG) has been advocated. The harvesting procedure should be carefully conducted to avoid violating the greater palatine neurovascular bundle (GPB). The GPB, which comprises the greater palatine artery, vein, and nerve, travels through the pterygopalatine fossa, passes through the pterygopalatine canal, and exits into the greater palatine foramen (GPF). This study assessed the accuracy of predicting the location of the GPF and measured the thickness of the palatal masticatory mucosa and the distance from the GPB in the posterior palatal area, using cone beam computerized tomography (CBCT). Methods: CBCT images of 21 patients (13 men and 8 women, 22~46y) were evaluated retrospectively. The inclusion criterion was complete dentition from the maxillary first premolar to the third molar (first premolar: P1, first molar: M1, second molar: M2, area between second molar and third molar: M2-M3, third molar: M3, distal area of third molar: M3D). The distance from the cemento-enamel junction (CEJ) of the P1 and M1 to the GPB (P1d and M1d, respectively) was defined as the safe zone of the palate. The perpendicular distance from the middle P1d and M1d to the palatine bone was defined as the thickness of the palate (P1t and M1t, respectively). Foramen of transversal diameter (FTD) is the transverse diameter of the GPF. The location of the GPF in relation to the tooth and the distance from the CEJ to GPF (M3d) was also determined. Results: The most frequent location of the GPF was M3 (59.5%), followed by M2-M3 (26.2%) and M3D (14.3%). The mean diameter of FTD was 3.4±0.7mm. The mean M3d was 14.6±1.4mm. P1d and M1d were 12.1±1.4mm and 13.3±1.4mm, respectively. P1t and M1t were 3.7±0.5mm and 3.6±0.8mm, respectively. No significant difference was observed between P1d and M1d, but significant difference was noted between P1t and M1t. Conclusion: The thickness of palatal masticatory mucosa increased from the first premolar but decreased at the first molar region. The results of this study can assist clinicians in planning the location for harvesting SCTG on the hard palate.