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The study was carried out in two age-matched groups of patients from two different periods of time. The aim of the study was to determine whether any craniofacial system alterations attributable to the influence of secular trend had occurred during a defined period of time. Four basic craniofacial variables, from which the craniofacial indices were derived, were measured. The findings were statistically processed by the basic parameter evaluation and testing of differences of arithmetical means of the same variables between the two study groups. The results showed the following alterations to have occurred during a 13-year period due to the secular trend effects: cranial indices decreased, mostly by a significant cranial length increase (g-op); and facial indices decreased, mostly by a facial height decrease (n-gn).

In this study, teleroentgenocephalograms of 34 subjects with at least 20 natural teeth were used. Correlation between the angle formed by linking the PORION-NASION-SPINA NASALIS ANTERIOR (PONANS angle) points and the angle made by Frankfort horizontal and occlusion plane was studied. The coefficient of correlation was 0.1263. It is considered that there is no correlation if the coefficient of correlation is less than 0.5. Thus, there was no correlation in the study sample, which is consistent with the results reported by Karkazis and Polyzois, but in disagreement with those published by Monteith. In our sample, the occlusion plane could not be oriented in the articulatory space or in toothless mouth by means of the method proposed by Monteith.