Materials and Methods: Sample included 40 edentulous patients, ranging in age between 41-84 years (20 male and 20 females). Record bases had anterior occlusal wax rims at the anterior region only in maxillary and mandibular. The mandibular posterior occlusal plane was determined on the master cast at both sides, in line with the convergence of the middle third with the upper third of retromolar pad, and the posterior wax height of mandibular was constructed according to this plane. Then, this plane in patient's mouth was modified to fit the lateral border of the tongue and the commissure of the lips. The determinants of the registration of the centric relationship were fixed to the posterior inferior mandibular occlusal wax rims, and the posterior wax rims of maxillary was made according to the posterior wax rims of mandibular. The relationship of the posterior maxillary occlusal plane to Ala-Tragus line was examined using a double-level ruler specially designed for this purpose. The data obtained was statistically analyzed using Student’s independent T-test, and Pearson correlation coefficients. The level of confidence was set at 95%.

Results: The results showed that there were no statistically significant differences in the mean angle values between mandibular occlusal plane and maxillary occlusal plane. There was a statistically significant effect of patient's age on maxillary occlusal plane in females (P=0.010), while there was no statistically significant effect of the patient’s age on maxillary occlusal plane in males and in the whole research sample (P=0.783, 0.064 respectively.

Conclusions: The mandibular occlusal plane can be used to determine the maxillary occlusal plane in complete dentures. The use of retromolar pad, the lateral borders of the tongue and the commissure of the lips as intraoral reference points to determine the occlusal plane is a reliable landmark. The impact of patient’s age must be taken into account while determining the occlusal plane in this technique.