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Quality general dental care with an emphasis on natural esthetics, form and function. Experience with complex restorative, prosthetic and implant treatment.

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National Institutes of Health Consensus

Development Conference Statement

June 13-15, 1988

This statement was originally published as:

DENTAL IMPLANTS. NIH CONSENS STATMEMENT 1988 JUN 13-15;7(3):1-22.

For making bibliographic reference to the statement in the electronic form displayed here, it is recommended that the following format be used:

DENTAL IMPLANTS. NIH CONSENS STATMEMENT ONLINE 1988 JUN 13-15 [CITED YEAR MONTH DAY];7(3):1-22.

INTRODUCTION

The use of dental implants to provide support for replacement of missing teeth is becoming an important component of modern dentistry. As a result of advances in research on implant design, materials, and techniques the use of these devices has increased dramatically in the past few years and is expected to expand further in the future. Many types of implants are now available for application to different clinical cases, and an increasing number of dentists have become involved in this form of treatment. It has been estimated that the overall number of dental implants inserted in the United States increased fourfold from 1983 to 1987, and during that same period the number of practitioners who perform implant therapy increased tenfold. It is estimated that as many as 300,000 dental implants will be used in the United States by 1992. Growth in dental implant utilization also is evident in Europe and Japan.

The magnitude of the missing tooth problem (edentulism) in the United States' adult population remains considerable. Although there has been a tremendous reduction in coronal dental caries during the past several decades, this improvement is evident mainly in the younger segments of the population, with individuals over 35 years of age still showing a significant prevalence of full or partial edentulism. According to the 1985-1986 National Institute of Dental Research's (NIDR) national survey of oral health conducted on U.S. employed adults and seniors attending multipurpose senior centers, approximately 42 percent of Americans over 65 years of age and 4 percent of those 35 to 64 years of age are totally edentulous. Moreover, those over 65 years with teeth have lost an average of more than 10 of 28 teeth, and employed dentate persons ages 55 to 64 have lost an average of 9 of 28 teeth. Thus, there are many individuals in this country who could conceivably benefit from dental implant therapy.

Many individuals with edentulism can be treated with partial or complete traditional removable dentures or fixed bridges. However, these prostheses are not satisfactory for a significant number of individuals who have lost the tooth-bearing portions of the bone and simply cannot manage removable prostheses, or are medically compromised and cannot properly masticate food. Moreover, there is a strong suggestion that a substantial number of patients prefer implant- supported prostheses over soft tissue supported prostheses.

Research advances in dental implantology have led to the development of several different types of implants, and it is anticipated that continued research will lead to improved devices. At present, continued evaluation is necessary to determine that appropriate implant devices are available to meet the therapeutic demands of the different portions of the jawbones and the unique needs of patients.

In an effort to resolve some of the existing controversies and to deal with the gaps in knowledge in dental implantology, the NIDR in conjunction with the National Institutes of Health (NIH) Office of Medical Applications of Research and the Food and Drug Administration convened a consensus development conference on June 13-15, 1988. It also is evident that the tremendous interest in this field as well as many clinical case series studies also are responsible for the NIH convening this second Consensus Development Conference on Dental Implants within a 10-year period. A group of distinguished speakers presented current data on many aspects of implantology. The audience of approximately 750 included an illustrious group of clinicians, researchers, and educators, many of whom were responsible for the development and advancement of the field of dental implantology. Following 1-1/2 days of presentations by experts in the relevant fields and presentations by professional organizations involved in dental implantology, a consensus panel consisting of representatives from the fields of dental implantology, oral surgery, anatomy, bone biology, periodontology, materials and engineering, epidemiology, statistics, behavioral science, and the public considered the evidence and formulated a consensus statement responding to the following questions:

• What is the evidence that dental implants are effective for the long term?
• What are the indications and contraindications of various types of dental implants?
• What are the requirements for surgical, restorative, and periodontal management of patients with dental implants?
• What are the health risks of dental implants?
• What are the future directions for research on materials and designs of dental implants and on clinical Management?

WHAT IS THE EVIDENCE THAT IMPLANTS ARE EFFECTIVE FOR THE LONG TERM?

Criteria of success vary with different implant systems. Therefore, it is difficult to compare certain types of implants for which success criteria and indications may be different. Furthermore, for implants that are comparable, proper research designs for comparison (randomized, controlled trials) have not been used. Thus, the panel could only conclude that there is evidence from a number of case series studies that when specific types of dental implants are inserted by clinicians experienced with the respective techniques, a large proportion of implants remains in place for periods of 10 years or more.

However, it is difficult to make definitive statements on the long-term effectiveness of dental implants from these case series studies because of unreported information and the lack of uniform application of proper research designs. Although the ideal research design for documenting the effectiveness of new treatment techniques should be a randomized, controlled clinical trial, case series studies are capable of providing limited evidence when proper methods are used. Future case series studies should conform to the following principles:

• A prospective statement of study aims, with clear definitions of success and failure for all measures.
• A description of the study populations and criteria for patient selection.
• Standardization to the extent possible of treatment outcome measures, with presentation of data on reliability. Use of independent examiners is desirable
• Adequate sample size adjusted for the expected attrition over the length of the study.
• Concise reporting of reasons for attrition.
• Reporting of all failures from time of insertion of the implants.
• Documentation and followup of each failure.
• Use of standardized reporting methods, including life tables.
• Limiting extrapolation of results to populations similar to that of the study under similar experimental conditions.

The case series studies available generally did not follow these principles. In addition, little data were available on traditional treatment outcome measures such as patient satisfaction, esthetics, comfort, lack of physical and psychological symptoms, phonetics, and masticatory efficiency.

The evidence that dental implants are effective in providing total support for restorations is based on several case series studies with a duration of 10 years or more and several others that lasted for more than 5 years. The evidence that implants are effective in the long term in partially tooth-supported restorations is based on fewer studies that have been conducted for periods of up to 10 years. Because of the lack of randomized trials to compare different implant systems and the lack of uniformity in defining success, it is not possible to make judgments on the comparative merits of different implant systems. Additional knowledge about the biology of hard and soft tissues coupled with technological advances in the construction and insertion of various implants will likely result in a trend toward improved long-term success rates. This expectation is evident in the historical learning curve apparent when survival rates of specific implant systems are monitored. For example, in the case of endosseous implants, available long-term data are derived from studies in which many factors now known to affect implant survival were not properly appreciated when the longitudinal studies were begun. Included among these factors were bone preparation procedures that failed to stay within certain thermal limits now known to be critical for bone cell survival. Furthermore, the insertion of implants in a one-stage procedure may not have ensured absence of functional forces during the critical early stages of wound healing. These techniques may explain in part the early failure of some implants and the frequent fibrous adaptation of bone to some implants. Although it is not clear that the fibrous tissue interface compromises the long- term success rate of endosseous blade implants, the best reported long- term survival rates for root-form implants have been achieved with systems that have bone at the interface.

No reliable data are available on the effect of variations in restorative techniques on the long-term success rate of implants nor are data available on the long-term use of implants in edentulous children.

WHAT ARE THE INDICATIONS AND CONTRAINDICATIONS OF VARIOUS TYPES OF DENTAL IMPLANTS?

Dental implants may be classified by type as endosseous, subperiosteal, transosteal, intramucosal, endodontic, and bone substitutes. The data that were presented at this conference were confined to the first three types. These are the only ones for which indications and contraindications have been promulgated in this statement. These implant types are subdivided as follows:

• Endosseous:
• Root form.
• Blade (plate) form.
• Ramus frame.
• Subperiosteal:
• Complete.
• Unilateral.
• Circumferential.
• Transosteal:
• Staple.
• Single pin.
• Multiple pin

For long-term successful performance of all dental implant types the following general factors should be considered:

• Biomaterials.
• Biomechanics.
• Dental evaluation.
• Medical evaluation.
• Surgical requirements.
• Healing processes.
• Prosthodontics.
• Postinsertion maintenance.

All practitioners involved in patient care should be knowledgeable regarding these factors and their interrelationships. Standards of dental practice would suggest the following general contraindications for the above three categories of dental implants:

• Debilitating or uncontrolled disease.
• Pregnancy.
• Lack of adequate training of practitioner.
• Conditions, diseases, or treatment that severely compromise healing, e.g., including radiation therapy.
• Poor patient motivation.
• Psychiatric disorders that interfere with patient understanding and compliance with necessary procedures.
• Unrealistic patient expectations.
• Unattainable prosthodontic reconstruction.
• Inability of patient to manage oral hygiene.
• Patient hypersensitivity to specific components of the implant.

With regard to indications for a specific implant type, the bone available to support the implant is the primary factor after prosthodontic diagnosis and treatment plan. This bone is measured in width, height, length, anatomical contour, and density. These physiological and anatomical factors may be altered by either osteoplasty or augmentation of the bone. In addition, other factors affecting indications for implant type are the degree and location of the edentulism of the patient. Indications for each implant type are specified below:

• ENDOSSEOUS, root form:
• Adequate bone to support the implant with width and height being the primary dimensions of concern.
• Maxillary and mandibular arch locations.
• Completely or partially edentulous patients.
• ENDOSSEOUS, blade (plate) form:
• Adequate bone to support the implant with width and length being the primary dimensions of concern.
• Maxillary and mandibular arch locations.
• Completely or partially edentulous patients.
• ENDOSSEOUS, ramus frame:
• Adequate anterior bone to support the implant with width and height being the primary dimensions of concern.
• Mandibular arch location.
• Completely edentulous patients.
• SUBPERIOSTEAL, complete, unilateral, circumferential:
• Atrophy of bone but with adequate bone to support the implant.
• Maxillary and mandibular arch locations.
• Completely and partially edentulous patients.
• Stable bone for support.
• TRANSOSTEAL, staple, single pin, multiple pin:
• Adequate anterior bone to support the implant with width and height being the primary dimensions of concern.
• Anterior mandibular arch location.
• Completely and partially edentulous patients.

WHAT ARE THE REQUIREMENTS FOR SURGICAL, RESTORATIVE, AND PERIODONTAL MANAGEMENT OF PATIENTS WITH DENTAL IMPLANTS?

Implant treatment is delivered in several ways: (1) by multidisciplinary teams of dentists in which an oral surgeon or periodontist performs the surgical component of the implant and a prosthodontist performs the prosthetic component; (2) by individual implantologists with extensive training in both the surgical and prosthetic components who perform all aspects of the procedure; and (3) by general dentists who may perform both components or the prosthetic component only and whose training in implant techniques may vary widely.

Unfortunately, there are no data available to the panel that address the surgical, restorative, and periodontal requirements for the individuals managing the implant patient.

Minimal training has not been precisely defined, but the panel recommends that the individual that assumes the surgical treatment phase be well prepared in accepted surgical methodologies. In as much as the restorative procedures employed in implantology differ from those in traditional restorative dentistry procedures, the panel recommends instruction in the restorative phase of implantology. These programs also should include expertise in short- and long-term tissue maintenance addressing gingival status as well as radiographic evaluation of tissue support.

Patient selection should be restricted to those patients who show a need and motivation for the implant procedures. The evaluation of the recipient should include a survey of adequate bone structure, medical history, and, where indicated, medical laboratory studies and consultation with the patient's physician. The use of computerized tomography for evaluation of maxillary and mandibular anatomy is suggested when more accurate information regarding implant placement is needed. The patient's dental evaluation also should include a psychosocial appraisal of his or her suitability for implant procedures when psychological symptoms are present.

The panel supports a multidisciplinary approach, and we recommend a preimplant consultation involving the professional participants with the patient. Postimplant procedures should include communication, monitoring, and collection of recorded data by the professional. We recommend that the patient be thoroughly instructed in maintenance therapy with the understanding that the patient serves as a cotherapist.

There is a lack of data detailing the minimum requirements for an adequate maintenance program. The proper recall interval, methods of plaque and calculus removal, and use of antimicrobial agents are critical variables that need further evaluation.

WHAT ARE THE HEALTH RISKS OF DENTAL IMPLANTS?

There are at least three areas in which the assessment of patient risk should be considered, including risks associated with the surgery and/or anesthesia, psychological risks, and medical risks. Risks associated with the surgical procedure may include inadvertent perforation of the nasal sinus, local and systemic infection, and nerve injury. Before surgery a medical history should be taken to evaluate the history of the presenting problem and chief complaints. A review of the current status of the patient's organ systems should be made.

Children need special consideration, given long-term morbidity concerns, requirements of growth, manual dexterity, and coping skills.

Psychological stressors and motivational factors have been shown to influence patient response to surgery and long-term compliance with oral hygiene maintenance. These stressors include both familial and social environmental factors such as job satisfaction, financial status, and health concerns. Specific mental conditions may require psychological intervention to assist with patient cooperation and outcome satisfaction. Individuals with excessive neurotic concerns, depression, anxiety, and specific medical fears or previous negative medical or dental experiences should be appropriately evaluated. Relative contraindications include individuals with psychotic symptomatology, especially requiring psychotropic medication, and somatization disorders or chronic pain complaints where medical symptoms are exhibited in the absence of organic evidence. Tobacco use, alcohol, or drug dependency may interfere with good nutrition or compliance requirements.

Temporary conditions that may result from implant placement may include pain and swelling, speech problems, and gingivitis. Long-term problems may include nerve injury, local bone loss exacerbation, hyperplasias, local or systemic bacterial infection, and infectious endocarditis in susceptible individuals, including those with body part replacement. Existing natural dentition may be compromised.

Factors related to prediction of health risks need to be continuously assessed before the surgical decision, after implantation, during the temporary waiting period, following the loading period, and at 6-month intervals throughout the followup period. Reliable and valid standardized measurements sensitive to both psychological and physical factors should be used in clinical prospective studies to enhance comparison across studies.

WHAT ARE THE FUTURE DIRECTIONS FOR RESEARCH ON MATERIALS AND DESIGNS OF DENTAL IMPLANTS AND ON CLINICAL MANAGEMENT?

Materials and Designs

Dental implants have many compositions and surface textures. Manufacturing processing techniques affect these surfaces in subtle ways. To better control clinical protocols, characterization of these surfaces is essential. Ion release from the implant may influence biocompatibility (bioacceptance). To achieve a more complete understanding of tissue response to the implant, basic experiments in host-implant physiology and biology must be continued. Dynamic studies in laboratory animals also should be completed. Other matters that warrant further study are the influence of surface preparation on wettability or bonding of tissues to the implant and the effect of galvanic couples resulting in corrosion. Studies must document the possible release of constituents of implant materials at the trace and subtrace level into other tissues to determine their significance with respect to toxicity, mutagenicity, or carcinogenicity.

Basic research should be emphasized to develop materials and methodology to allow for predictable bone augmentation. The implant- host interface should be studied to characterize wound repair and tissue adaptation in the peri-implant region.

Among the factors involved in the design of an implant are the force components produced during loading, the dynamic nature of loading, and the mechanical and structural properties of the prosthesis of stress transfer to tissues. Unfortunately, accurate data on such parameters are incomplete. Such information is essential for efficient design of implants.

Clinical Management

Randomized, controlled, prospective multicenter clinical studies should be initiated. These studies should investigate the role of several factors on the long-term effectiveness of dental implants. These factors include, in addition to implant characteristics, the operator's skills in implant placement, tissue management, various patient characteristics, including the intraoral location of the implant, and occlusal and prosthetic considerations. The panel feels that one important method of accumulating accurate data on implant performance is to establish a National Dental Implant Registry, which will standardize reporting forms to collect information on this activity in the United States. A rating scale based upon function and discomfort should be developed for evaluation of all implant procedures. In this way, the causative factors involved in success and failure of implants can be more accurately identified. Consideration also should be given to the establishment of centers for training, treatment, and research in dental implantology.

To ensure continued safety evaluation of dental implants, long-term prospective studies should specifically address failures due to medical or psychological complications that led to premature removal of the implant. When failures occur in either implants or an existing dentition, a failure analysis should be performed and reported. All patient data should be recorded, including age, education, socioeconomic level, number of previous implants, nutritional status, periodontal status, acute or chronic coexisting diseases, and pharmacologic use.

Patient Considerations

Considering that edentulousness is frequently the result of the patient's high susceptibility to destructive forms of periodontal disease, the relationship of implant success rates to the patient's relative susceptibility to periodontitis should be studied. Also, data are needed on both the acute and chronic or long-term morbidity that may result from various types of implants.

The public is entitled to educational materials that enable informed participation in implant treatment decisions, and the panel recommends that these materials be developed.

CONCLUSION

During the 10 years since the first Consensus Development Conference on Dental Implants, a great deal of activity in the field has occurred with the development of better materials and newer techniques that have resulted in improved implant-bone interface. This conference examined case series studies, and the panel concluded that a large proportion of endosseous, subperiosteal, and transosteal implants have remained in place for more than 10 years. The indications and contraindications of various types of dental implants have been described. The complexity of the surgical, restorative, and periodontal procedures used to successfully insert and maintain dental implants demonstrates the need for a multidisciplinary approach in this field.

Long-term studies that concurrently compare various types of implants are needed to provide information beyond mere survival rates. Functional success of various implants should include such criteria as the ability to support fixed or removable prostheses in the absence of discomfort, the presence of satisfactory esthetics, and clinical and radiographic evidence of tissue health. A suggestion for the establishment of a National Dental Implant Registry was proposed with the objective of collecting data and documentation on various procedures being conducted in the United States. Future studies in materials and techniques were proposed.

Implant Cosmetic Dental Center™