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ePaper created 2017-05-10, 16:12:25 | version 1.38.0
| case report restoration of the edentulous maxilla Treatment options for the edentulous arch Author: Dr Mark Montana, USA Fig. 1 Fig. 2 Fig. 1: Pre-treatment radiograph Introduction The implant-retained overdenture showing five implants clustered in the anterior mandible. Fig. 2: Clinical image of patient. Note the wear of the metal abutments due to disengagement of the nylon retention inserts as a result of fulcrum during function. 10 CAD/CAM 2 2017 Historically, when a patient’s dental condition reached a state of total tooth loss, treatment was limited to a complete denture with no hope of improving that status. The greatest challenge, particularly when working with a lower jaw, was providing a denture with reasonable stability and retention.1 Success was greatly dependent upon the skill of the practitioner but also on the neuro- muscular ability of the patient, their supporting structures and a philosophical attitude toward their condition.2 Treatment for patients suffering complete edentulism has been revolutionised by the ongoing success of dental implants so that the standard of care for the mandible is an implant overdenture. The spectrum of prosthetic modalities devel- oped since the acceptance of endosseous im- plants to the dental market ranges from the very simple to the astoundingly complex. Once di- rected by specialists, this field of study has evolved into a mainstay of the general practice, and so favour of expeditious and reproducible methods has gained dominance over complex therapies. Implant overdentures and fixed hy- brid prostheses are choices typically offered by the dentist based upon a patient’s financial abil- ity. While both are generally successful, the overdenture and the hybrid prosthesis are not without pitfalls. The implant-retained overdenture is described as a prosthesis that covers, and is supported by, the natural tissues retained by the dental implant; the design is considered implant-assisted rather than supported.3 Placement of two to five implants is com- monly found for the edentulous mandible with em- phasis on creating a large anteroposterior (AP) spread between the endosseous pillars. If more than two im- plants are clustered in a small AP range, the prosthe- sis cannot move freely about a single axis of rotation and the denture may dislodge during function. By creating the fulcrum on the most posterior overdenture abutments, the denture will pivot in function resulting in disengagement from the at- tachment mechanism and cause premature wear of the retentive components. Therefore, an increase in the number of implants beyond two does not nec- essarily provide a linear increase in retention and stability. In fact, the opposite may be true. Because support is provided by the mandible itself, resorp- tion of the supporting structure will result in in- creased tipping of the denture during function, re- sulting in dislodgement. Therefore, the dentist and patient must be cognisant of the need for relining of the prosthesis periodically to assure optimal perfor- mance.4–7 Recommendation is, therefore, placement of two implants in the anterior mandible to allow one axis