[Investigation of the relationship between the posterior edge of the base of complete lower dentures and the mandibular tuberculum].
Surveying the data published in the literature one can establish that opinions of authors differ concerning the appropriate relationship between complete lower dentures and the tuberculum alveolare mandibulae (TAM). Some authors claim that, following extensional principles, the base of complete lower dentures must fully cover the TAM. Others think that it is enough if the base covers half of the TAM; yet others recommend that the base should merely extend as far as the mesial edge of the TAM. In the present investigations, we tried to find out what the relationship was between complete lower dentures prepared in everyday practice and the TAM. Dentists of the Clinic of Prosthetic Dentistry examined 8346 patients in eight different regions of Hungary over a period of three years. In the present analysis, we discuss the data of subjects wearing a complete lower denture. In the populations concerned, 669 subjects met these criteria. With respect to the relationship between the base and the TAM, we distinguished three groups. The first group was made up by cases where the base extended as far as the mesial edge of the TAM, the second group included subjects whose base reached the medial line of the TAM, whereas the third group comprised patients in whose case the base fully covered the TAM. The relationship between the base and the TAM was examined intraorally, by ocular inspection. The data were analysed with regard to gender and laterality, by the help of the SPSS software package and the chi 2 test. The investigations showed that, in everyday practice, an overwhelming majority (77.10%) of complete lower dentures had a base extending to the mesial edge of the TAM, and it was in a mere 3.9% of cases that the base covered (some of) the TAM. Cases where the edge of the base did not reach the TAM (19.01%) were taken as cases where the dentist disregarded the significance of the relationship between the base and the TAM. The tuberculum alveolare mandibulae is a structure made up by dense fibrous connective tissue that, in most cases, may get displaced over its base and is not pressure resistant, not able to provide a value-like seal and, therefore, not suitables for the extension of the base. Our results suggest that practising dentists have noticed this; furthermore, they have probably also noticed that whenever the base extends as far as the mesial edge of the TAM, leaning against it as it were, it effectively prevents the denture from shifting backwards, i.e. is an obstacle to its anteroposterior displacement.