The mylohyoid ridge and endoalveolar crest: an anatomical and clinical study with reference to preprosthetic surgery

Abstract

This research report is presented in five main sections. The first section provides a general review of the growth and development of the mandible and the soft tissues of the oral cavity leading on to a discussion of the edentulous state, including the changes that occur in the alveolar bone following tooth loss. Some of the newer approaches aimed at stimulating new bone growth are also mentioned. The more insidious changes that occur in the mouth following loss of teeth are described, including the changing behaviour of the tongue and the alteration of chewing patterns. The aims of this section are to highlight the need to appreciate the relationships between form and function, including the changing relationships of the various oral structures resulting from alterations to their form. The second section provides a detailed review of the various surgical methods used to reduce discomfort from a prosthesis in the edentulous mandible. These include relative and absolute augmentation, lingual and labial sulcoplasty, the associated grafting of various tissues including the use of hydroxyapatite, and surgery of the mylohyoid ridge. The author's preferred method of mylohyoid ridge surgery is described and its advantages discussed. This section summarises the various approaches available to enable the construction of a comfortable denture in the badly damaged edentulous mandible. lt indicates the advantages and disadvantages of these procedures and compares them with the relatively simple procedure preferred by the author which formed the basis of the clinical research included in this research report. The third section of the report comprises an analysis of the results after treatment of 521 patients who were referred to the author for the construction of new dentures. All of these patients were edentulous and suffered pain and discomfort. They were divided into 3 groups according to the treatment they received. The outcomes of treatments were compared, including the influence of age and gender. The results showed that those patients who had undergone surgery to modify the mylohyoid ridge prior to construction of prostheses showed a more satisfactory treatment response than either those who were considered not to need surgery, or those on whom surgery was considered necessary but not carried out. The fourth section of the report deals with the anatomy of the inner aspect of the mandible in the mylohyoid region. During surgical procedures the author became aware that not all of the bony exostoses in this region constituted the mylohyoid ridge. Another closely associated, but quite distinct crest of bone was discovered. Due to the paucity of literature reports regarding this area, a series of investigations involving collections of human and animal skulls, and the dissection of preserved cadavers and postmortem specimens were carried out. These investigations revealed that a crest of bone, termed the endoalveolar crest, was present just above the mylohyoid ridge. lt is described and its diversity of expression in humans and primates illustrated. The fifth section provides a summary of the main findings of the study, including conclusions.