The International Journal of Prosthodontics, 02/1993

The so-called concept of osseointegration demands both histomorphometric as well as clinical descriptions and definitions. The understanding of both of these aspects is still evolving and impacts significantly on the ongoing clinical determinants of success. This paper reviews some of the current clinical concerns regarding the clinical evaluation of osseointegrated implants.

Although the biologic principles underlying successful clinical implants are still not completely understood, it is clear that both physical and chemical attributes of the material may influence the clinical outcome. Knowledge of the stresses and strains in an implant system and superstructure is still incomplete, but micromotion at the interface must be avoided for bone fixation. The composition and topography of the implant surface influence the cellular events at the bone-biomaterial interface. These surface parameters require definition to interpret the tissue response to a particular material. Hydroxyapatite-coated surfaces are an example of a variable implant modality that has resulted in variable clinical performance. The clinician should consider all the available information on material and design before embarking on extensive clinical trial.

With the introduction of osseointegration by Dr P.-I. Brånemark, reconstruction of advanced residual ridge resorption has become a successful procedure in patients for whom previous methods had been disappointing. For reconstruction of the maxillae an onlay, nasal and/or antral inlay, labial and/or buccal onlay, or interpositional bone graft with osseointegrated implants used to provide support for both the graft and the prosthesis can be used. The maxillary and mandibular onlay bone grafts and the nasal and/or antral inlay bone grafts are discussed.

Osseointegrated implants have been in widespread use for more than 10 years. During this time, the design and use of implant-supported and implant-retained dental restorations have undergone steady change. This paper discusses this evolution and defines current trends in this exciting new discipline.

Osteopromotion to enhance the formation of bone approximating implant surfaces can be obtained using bone regeneration techniques with polytetrafluoroethylene membranes. Treatment of dehiscences and other deficiencies of bone volume allows implants to be successfully placed in regions previously thought to be unsuitable. Bone regeneration is possible in peri-implant osteitis defects if appropriate surgical techniques are used.

In the last decade, the success of osseointegration has encouraged dentists internationally to use titanium implants to assist in the replacement of tissue, ranging from a single tooth to facial prostheses. Investigations have focused on more sophisticated treatment planning, improved clinical procedures, selection of better materials, development of superior components, and reduced treatment time. The introduction of procedures from other industries has brought a new level of standardization and quality control to the fabrication of prostheses.

The evolution of criteria for success of dental implants reflects the evolution of knowledge of implant performance and biologic reactions to them. Most criteria are written in the interest of predictability of performance of an implant system. This approach is valuable to the clinician in selecting implants for patients, but the criteria for bone level changes may be unnecessarily stringent for monitoring performance in an individual patient. Some experience and difficulties related to radiographic monitoring are reviewed. The need for tempering the application of marginal bone criteria to clinical applications is illustrated by longitudinal data on marginal bone height changes.

Forty-six female patients participated in a survey study to assess the relative health status impact of implant-retained oral prostheses and conventional complete dentures. They completed a structured questionnaire based on three valid and reliable treatment outcome measures: the Dental Functional Status Index (DFSI), the Rand Mental Health Index (MHI), and elements of the Sickness Impact Profile (SIP). The implant patients were associated with significantly better characteristics in areas of oral mechanical ability, signs and symptoms, and eating. A favorable tendency emerged with respect to communication, self-care, psychosocial functioning, and role performance. The data demonstrated that for some patients there are clinically important, pervasive advantages of implant therapy, in terms of improved physical, psychologic, and social functioning. The results supported the usefulness of self-report, dentopsychosocial indicators to assist in defining treatment needs, evaluating quality and consequence of care, and addressing cost-benefit issues.

The maxillofacial patient faces many challenges that go beyond those of edentulism. These obstacles leave the patient handicapped and socially vulnerable. One of the greatest of these difficulties is retention of the craniofacial prosthesis. Ingenious strategies based on experience have provided limited success. For selected patients, however, the osseointegrated implant has largely eliminated this vexing technical predicament, thus freeing the patient to enjoy a more normal lifestyle. The treatment indications for this service, the remaining unresolved patient problems, the new planning criteria, and the requirement to document success all point to the need for well-validated instruments to measure the effectiveness of this newly augmented service.

Immediate implants are implants placed into a prepared extraction socket following tooth removal. Short-term animal and human studies have shown these implants to be comparable to implants placed into healed bone. The advantages of the procedure include fewer surgical sessions, elimination of the waiting period for socket healing, shortened edentulous time period, reduced overall cost, as well as preservation of bone height and width. Although immediate implantation is more demanding both surgically and prosthetically compared to the conventional placement technique, the advantages make it very appealing to patients who are in need of both extractions and implant therapy.

A variety of imaging modalities are available for the preoperative evaluation of potential implant sites. The pantomograph provides initial screening information. Cephalometric films are most useful in analyzing the incisor regions. Tomography can provide cross-sectional views of segments at a relatively low patient radiation dose. Computed tomography is a superior method when the analysis of complete arches is required. Experimental designs of postoperative radiologic evaluation of small changes in bone height require reproducible image geometry and the evaluation of intraobserver error.

For many years the technique of osseointegration in the anterior part of the mouth has been used with predictable success to treat completely edentulous arches. This prospective study was begun in the mid-1980s to adapt this technique to the partially edentulous situation in this same anterior region of both the maxillae and mandible. Ninety-four implants were placed into 34 edentulous areas in 30 partially edentulous patients. Forty-seven (94%) of the 50 implants placed into maxillae and 39 (88.6%) of the 44 placed into mandibles remain in function after periods of loading ranging from 2 to 8 years (mean 4.7 years). This average success rate of 91.5% was sufficient to ensure a 100% resolution of the selected patients' maladaptive prosthodontic experiences. These results suggest that past experiences with osseointegration in the anterior of the completely edentulous mouth can be replicated in patients with anterior partial edentulism.

While considerable data have been published on the use of the osseointegration technique in the anterior region of the edentulous mouth, there remains scant information on its success in the posterior areas of either the maxillae or mandible. This prospective study was begun in the mid-1980s to test the effectiveness of this technique in the treatment of partially edentulous posterior areas of the maxillae and mandible, and in situations where the implant-supported prosthesis carries a significant portion of the total occlusal load. One hundred five implants were placed into 46 edentulous areas in 35 patients. After periods of loaded service ranging from 2.6 to 7.4 years (mean 5.2 years), of the 41 implants placed in maxillae, 40 (97.6%) remain in function, and of the 64 placed in mandibles, 59 (92.2%) remain in function. The overall implant survival rate of 94.3% suggests that partially edentulous areas in the posterior zones of either arch can be treated prosthodontically using osseointegrated implants with predictable success.

A series of studies was begun in the mid-1980s in an effort to test the versatility of the osseointegration technique. One of these studies specifically tests the efficacy of single-implant support for crowns to replace missing single teeth. Thirty-two patients with 40 single-tooth spaces were treated with 40 implants, placed between 8 August 1985 and 21 June 1990. Twenty-eight were placed in the maxillae (27 in the anterior and 1 in the posterior zone). Twelve implants were placed in the mandible (all in the posterior zone). After loaded service periods ranging from 1.4 to 6.6 years (mean 2.9 years), all implants remain in function and have ensured successful prosthodontic treatment. These results suggest that the osseointegration technique can be adapted for use in patients with a missing single tooth with predictable good success.

Two groups of elderly edentulous patients with implant-supported mandibular overdentures were compared. There were 25 patients with an average age of 62.2 years and 34 patients with an average age of 68.9 years treated in Toronto and in Bern, respectively. A high incidence of compromised general health was found in both groups. All patients had been treated in the years 1984 through early 1987 and had worn their implant-supported overdentures for the previous 5 years. Regular monitoring of the patients was done by two investigators using periodontal and radiographic parameters. Two different implant systems were used: Brånemark fixtures in Toronto and ITI implants in Bern. Most overdentures were retained by only two implants in both groups. The 5-year longitudinal data show a similar high success rate (> 90%) for both patient groups.

Periodontal prostheses have resolved many problems for patients with advanced loss of the periodontium and multiple missing teeth. However, the success of osseointegrated implants has had a dramatic effect on the process of periodontal treatment planning. It has reduced the need to use teeth that are at great risk as abutments. It has also reduced the need for laboratory heroics with extensive units of fixed partial dentures by allowing problems to be addressed individually and then collated into a total treatment plan for the partially dentate patient. This paper addresses those issues and the role of osseointegration in periodontics.