Implant assessment
Introduction
• Endosteal – placed in the bone. These are manufactured in a variety of shapes – screw, smooth-sided or plate-form, and essentially replace the roots of one or more teeth
• Subperiosteal – placed on the bone, under the periosteum and secured in place with screws.
This chapter concentrates on endosteal dental implants which are more commonly used, particularly since P. I. Brånemark’s clinical research on the concept of osseointegration which he defined as a direct connection between living bone and a load carrying endosseous implant at the light microscopic level. There are many different endosteal implant systems available, and it is beyond the scope of this book to discuss all the systems and their various advantages and disadvantages. The Brånemark system, described here, is probably the best known and has been researched over the longest period demonstrating acceptable 20-year success rates. Most currently used implant systems can be viewed as design modifications to this basic concept.
The Brånemark system
Treatment usually involves either a two-stage or a one-stage (non-submerged) surgical procedure followed by the restorative phase. Initially, in the two-stage technique the fixture is placed in vital bone ensuring a precision fit. The cover screw is screwed into the top of the fixture to prevent downgrowth of soft and hard tissue into the internal threaded area. The fixture is then left buried beneath the mucosa for 3–6 months. (It is important during this initial healing period to avoid loading the fixture although early loading protocols are being used in certain clinical circumstances.) The fixture is then surgically uncovered, the cover screw removed and the abutment (the transmucosal component) connected to the fixture by the abutment screw. An hexagonal anti-rotation device is incorporated into the top of the fixture. The gold cylinder, an integral part of the final restorative prosthesis, is finally connected to the abutment by the gold screw. A standard Brånemark implant is illustrated in Fig. 23.1.
Main indications
Replacement of missing teeth in patients with:
• Healthy dentitions which have suffered tooth loss because of trauma
• Developmentally missing teeth
• Remaining teeth not suitable as bridge abutments
• Severe ridge resorption making the wearing of dentures difficult
• Cleft palate and insufficient remaining teeth to support a denture/obturator
Treatment planning considerations
Clinical examination
• The patient’s age, general health and motivation
• The condition and position of the remaining teeth (if present), including their occlusion
• The status of the periodontal tissues and the level of oral hygiene
• The condition – quality and quantity – of the edentulous mandibular or maxillary alveolar bone