Estimation of occlusal vertical dimension using cephalometric angular reconstruction.

AIM: To propose a new technique, based on cephalometrics for determining the vertical dimension of occlusion (VDO). METHODS AND MATERIAL: Thirty-five participants in the age range of 20. ­: 22 years who met the inclusion criteria were recruited. Lateral cephalograms were obtained and tracing done. Five reference landmarks, Nasion (N), Anterior Nasal Spine (ANS), Porion (P), Gonion (G) and Gnathion (Gn) were marked and joined to form four angles, N-ANS-Gn, N-ANS-G, P-G-Gn and P-G-ANS; distance between ANS and Gn was considered as VDO in cephalogram (VDO-Ceph). The angles N-ANS-Gn and N-ANS-G; P-G-Gn, and P-G-ANS were correlated; two simple linear regression models were developed to predict N-ANS-Gn and P-G-Gn, using N-ANS-G and P-G-ANS, as independent variables. Using the formulae, the predicted angles, N-ANS-Gn and P-G-Gn were drawn and intersection marked as 'reconstructed point Gn'. The predicted VDO-Ceph values (distance between ANS and reconstructed Gn) were measured and correlated with actual values. RESULTS: The angles N-ANS-Gn and P-G-Gn had a statistically significant positive correlation with N-ANS-G (r = 0.77, P < 0.001) and P-G-ANS (r = 0.83, P < 0.001), respectively. Using simple linear regression analysis, the following formulae were obtained: N-ANS-Gn (in degrees) = 1.271 N-ANS-G (in degrees) + 24.83 and P-G-Gn (in degrees) = 0.987 P-G-ANS (in degrees) + 35.93. The predicted and actual VDO-Ceph values showed no statistical significance difference (P = 0.92). CONCLUSION: By tracing four cephalometric landmarks, N, ANS, P, G; and using the angular reconstruction, it is possible to predict the location of Gn. Hence, during prosthetic replacement of lost teeth, this can be employed for the estimation of lost dimensions.