[Statistical analysis of functional interrelations between anterior guidance and posterior determinants]

During the last decade, the concept of an effective, even steep anterior guidance did evolve toward the description of a "kinder" or "softer" anterior guidance which, while ensuring the disclusion of the posterior teeth, leaves some anterior functional freedom. It then becomes necessary to determine more precisely the criteria for diagnosis, orthodontic treatment, prosthetic restoration of anterior functional surfaces. In order to reveal some functional agreement between an anterior and posterior guidance, the analysis of the functional morphology of antero-maxillar teeth in relation to their skeletal context was proposed, in a study of 33 cases, so as to correlate the condylar steepness measured by axiography. It should be noted that a decreasing gradient exists between the mean respective values of the functional slopes of the central incisors (S1 = 64.3 degrees), and lateral incisors (SF1 = 53.5 degrees) and the canine (Cf = 51.8 degrees). Although the cingular surface S1 does not appear to have any influence on the posterior guiding factor (r = 0.1), in fact the anterior functional surface which is stategic in mastication, is located on the occlusal surface of the palatol side (S2) of the antero-maxillary teeth. The correlation is significant (r = 0.325) when the anterior guidance (incisives and canines) is associated to the mean condylar value more than being correlated to the mean functional value of the central incisor alone. It thus appears logical that the functional modeling of the articular cavities be influenced by the overall anterior guidance and not by the single central incisor. It has also been possible to emphasise the influence of the orientation of the occlusal plane in the anterior functional relationship (r = 0.547); thus, the anterior guidance appears to have to be assessed over a "relative overall analysis": overall: meaning the overall anterior guidance, i.e. the six anterior maxillary teeth; relative: meaning measured in relation to the occlusal plane. This concept of relative overall analysis of the anterior guidance, developed using a simple computerised program, will allow the diagnosis and anterior prosthetic or orthodontic restoration to be facilitated.