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Dental Implants: Benefit and Risk

National Institutes of Health
Consensus Development Conference Statement
June 13-14, 1978

This statement is more than five years old and is provided solely for historical purposes. Due to the cumulative nature of medical research, new knowledge has inevitably accumulated in this subject area in the time since the statement was initially prepared. Thus some of the material is likely to be out of date, and at worst simply wrong. For reliable, current information on this and other health topics, we recommend consulting the National Institutes of Health's MedlinePlus

This statement was originally published as: Dental Implants: Benefit and Risk. NIH Consens Statement 1978 Jun 13-14;1(3):13-19

For making bibliographic reference to the statement in the electronic form displayed here, it is recommended that the following format be used: Dental Implants: Benefit and Risk. NIH Consens Statement Online 1978 Jun 13-14 [cited year month day];1(3):13-19.


Guidelines for the use of dental implants were issued at the Harvard-National Institutes of Health-National Institute of Dental Research Consensus Development and Technology Assessment Conference held June 13-14, 1978, in Boston. Official statements and full proceedings will be published and available in early 1979. Dr. Paul Schnitman and Dr. Leonard Shulman, co-directors of the Harvard Tooth Implant-Transplant Research Unit at the School of Dental Medicine, organized, convened, and moderated the conference and have prepared this summary of the conference's objectives and recommendations.

Much information regarding the safety and effectiveness of dental implants is controversial, presently existing as the result of individual experience and opinion rather than scientific fact. Although implant authors are prolific, extremes of success and failure are commonplace and these conflicting reports are difficult to interpret. Essentially, common criteria have not been used by implant authors to judge success and failure. Generally, conclusions have been based only on whether implant devices are or are not in place and whether or not they are symptomatic. Little attention has been given to data relating to true efficacy, e.g., is the implant standing on its own and truly helping the patient, or is it being held in place by the bridge it was designed to support? Is the patient left measurably worse off then before the procedure? Would the benefit/risk ratio of conventional dentistry have been better than that of implantation?

Clinically, thousands of patients have been treated with dental implants for years and there is no question that many have received long-term benefits. Some implants, on the other hand, fail in patients within six months; some have resulted in extensive bone loss and produced irreversible defects and complications.

Problems related to implant use frequently stem from poor patient selection. Insufficiently informed patients, and the unrestricted use of implants inadequately tested. These implant problems have led to a large body of unhappy patients and disappointed dentists.

In response to the concern of both the public and the profession, the American Dental Association and the Food and Drug Administration have taken steps to assure that these devices be reasonably safe and effective. The ADA has developed an implant registry to establish uniform case reports in the hope that in three to five years reasonably reliable information on safety and efficacy will be available. The FDA has now projected standards, classifications and limitations on all medical devices, including dental implants.

The purpose of this conference was to provide the dental consumer, practitioner, and researcher with a balanced and realistic appraisal of the four most commonly used implants in current clinical practice; the subperiosteal; staple/transosteal; vitreous carbon; and blade.

The NIH has developed, in the past year, the concept of technology assessment/consensus development, and the first such conference was held in 1977 to assess mammography as a screening and diagnostic technique for breast cancer. The decision of the medical field to modify its guidelines for mammography was a major outcome of the proceedings.

The NIH Office of the Medical Applications of Research (OMAR) has scheduled 20 consensus development meetings. This conference "Dental Implants: Benefit and Risk" was the third consensus conference and sought technical consensus on definitions of success, benefit and risk, and guidelines for use of the major dental implant types now available.

Paul Goldhaber, D.D.S., Dean of the Harvard School of Dental Medicine; Seymour Perry, M.D., Director of OMAR; David Scott, D.D.S., Director of NIDR; and David Link, Director of the Bureau of Medical Devices, Food and Drug Administration, outlined the importance and relevance of the conference to the field of dentistry, NIH, NIDR, and FDA.

In welcoming the group to Harvard. Dean Goldhaber said this conference was the first of what he hoped would be a series of real evaluations of what we do in the dental profession. He further quoted from an article by Frazier and Hiatt (Evaluation of medical priorities. Science, 200:875-878, 1978): "The term efficacy should be used to describe the net benefits and risks of an intervention. Both society and the individual have a stake in the measurement of efficacy with fair representation of the available information on risks and benefits to the individual that results from the intervention. Also, that as the largest single source of financial support for health care, society has a growing interest in the cost effectiveness of medical interventions."

Dr. Perry defined consensus as "general agreement, the judgment of most of those concerned." He went on to say NIH views technical consensus as a process whereby the research community, with participation by the practicing community, and others as appropriate, assess a technology to make sure it has been validated for safety and efficacy. He noted that there are three critical elements: 1) all viewpoints must be heard in broad, open participation with careful balancing of the biases to achieve consensus on the gaps as well as the advances in knowledge, 2) presentation of the facts necessary to show the biases, the degree of agreement, and the shades of various opinions, 3) recommendations must not be "written in concrete" or used to dictate the practice of dentistry or medicine; they should reflect only the best opinions of those who are in the best position to know.

Dr. Scott told conferees, "Considering the widespread use of implants as a technology already in practice, and the need for information on the part of the profession and public, the only alternative to rapid assessment is to take a retrospective look at the scientific basis for the procedure, the clinical evidence of its safety and efficacy, the existing evidence of its impact, and in so far as possible, consider its implications prospectively. We at NIDR constantly strive to keep ourselves and the research community abreast of the status of technical development at any or all phases of the research continuum and we depend on assessment of the state of the art for the generation of this information."

David Link, Director of the Bureau of Medical Devices for the FDA told conferees that FDA must strike a fine balance between ensuring that products are reasonably and acceptably safe and effective, while not having so stringent a policy that good new products are abandoned or not developed. He went on to explain the medical device amendment of 1976 and the placement of endosseous dental implants into a preclearance category, stating, "Don't jump to the conclusion that this is going to be the disappearance of dental implants. By no means. Those that are already on the market when regulation takes effect will have at least two and a half years in which to prove themselves to the satisfaction of the agency that they are indeed safe and effective."

He further remarked, "This type of conference is very useful to FDA because it sets the stage and draws out of the profession the best consensus as to what is good, what is bad, and the kinds of concern that should be raised about these products."

This conference was designed as a retrospective study to review clinical data on subperiosteal, staple/transosteal, vitreous carbon, and blade implants.

Participants, chosen by committee (Robert James, D.D.S.; Jerome Klawitter, Ph.D.; and Marvin Weiss, D.D.S.) were 46 of the major clinicians, researchers, academicians, and manufacturers in the field.

For each implant type a session was planned with a complete review of the literature, a speaker for the benefits, a speaker for the risks, and a speaker who would objectively review both sides and comment. The literature reviewer, two speakers, and the discussant for each implant type were Joseph Natiella, Roy Bodine, Norman Goldberg, and Louis Boucher on the subperiosteal implant; James Hayward, Irwin Small, Norman Cranin, and Daniel Laskin on the transosteal/staple implant; Robert James, Roland Meffert, Gene McCoy, and Joseph Natiella on the vitreous carbon implant; and Krishan Kapur, Leonard Linkow, Jack Armitage, and again, Krishan Kapur, on the blade implant. Extensive discussion by the entire group followed the formal presentation of each session.

In preparation for the conference, the organizers and conference statistician, Gary Koch, Ph.D., of the University of North Carolina, converted for uniform presentation all the data from approximately 1,200 implants. All participating clinicians submitting data for use in the conference were asked to enter information on forms provided by the conference organizers. Patients included in the sample were not judgmentally preselected, but were every patient for whom implants were inserted by a given investigator during a specific time period, e.g., 1971-1976.

The research design was homogeneous with respect to the following variables: 1) implant design (subperiosteal, staple/transosteal, vitreous carbon, blade); 2) implant type (free end, full arch, single free standing interdental); 3) number of natural abutments and pontics; 4) site (maxillary, mandibular, anterior, posterior); 5) opposing dentition (fixed or movable); and 6) changes in insertion technique.

Time periods for analysis were: subperiosteal--annually for 5 years and at 10 years; staple/transosteal--annually for 5 years; vitreous carbon--annually for 5 years; and blade--annually for 5; years and at 10 years. Analysis at these time periods was expressed in terms of 1) annual percent survival by life table method (Cutter, S.M. and Ederer, F. Maximum utilization of the life table method in analyzing survival Journal of Chronic Diseases 6, 699-712 December 1958), 2) the quality of survival (mobility, radiographs, gingival health, and pocket depth), and 3) the percent complications.

The standardized criteria for expressing survival quality were: mobility (total buccolingual movement in .5mm intervals); radiographs (standard photographs with three or four grades specific for each implant type); gingival health (standard photographs, four grades); and pocket depth (deepest pocket in millimeters).

All data for conference consideration were presented in uniform individual tables for each application of each implant type. Fifty-six such analyses were prepared, presented, and discussed. The conference table included the specific analysis, the insertion technique, the number of implants inserted, the number with usable data, the number lost to follow-up, the number of failures, and the number of patients left worse off.

Following the formal presentations and full group discussion of data, all participants were distributed into eight workshop panels to develop recommendation statements to be brought before the entire body for the determination of consensus. Since there was insufficient time to allow for more than one vote on each recommendation or for revised recommendations, drafting of the recommendations themselves had to be made with achievable consensus in mind: what was going to be acceptable to the group. Therefore, the membership of each workshop was balanced with respect to expertise and poles of opinion. Panels dealt with: definition of success, interpretation of survival statistics, guidelines for current use (two groups), complications and removal criteria, required patient information, evaluation criteria, and future directions.

Recommendations were brought to the entire body by workshop panels. Every recommendation except for one received general agreement, as indicated by overwhelming majority endorsement.  

Definition of Success

Panel 1

To be considered successful, the dental implant should provide functional service for five years in 75% of the cases.

Subjective criteria for success include: 1) adequate function, 2) absence of discomfort, 3) improved aesthetics, and 4) improved emotional and psychological attitude.

Objective criteria include: 1) bone loss no greater than one-third of the vertical height of the implant, 2) good occlusal balance and vertical dimension, 3) gingival inflammation amenable to treatment, 4) mobility of less than 1 mm in any direction, 5) absence of symptoms and infection, 6) absence of damage to adjacent teeth, 7) absence of parathesia or anesthesia or violation of the mandibular canal, maxillary sinus or floor of the nasal passage, and 8) healthy collagenous tissue without polymorphonuclear infiltration.  

The Interpretation of Survival Statistics

Panel 2

The data were considered statistically reliable when the number of implants was moderately large (40) for either a single or set of investigators; and statistically valid when representative of the general population. Strictly speaking, none of the data were considered statistically valid because the information was either self-reported, without panel review, or presented conflicting results. Therefore, it was agreed to append a warning to all data.


To have a sound statistical basis, conference data should be validated in new clinical trials with panel review, tighter patient selection, and uniform data collection and evaluation criteria.

Accordingly, to be the subject of a consensus vote or to be "quotable," data had to be of sufficient sample size and without conflicting results from different investigators. Accepting the cautionary qualifications on the data as noted with recommendation above, and eliminating results that were not considered quotable, there was consensus on the following statements on statistics:

Consensus: Subperiosteal Implants

Summary statistics cannot be quoted for subperiosteal implants except for mandibular implants opposing a complete denture.

For the mandibular opposing a complete denture, there are conflicting results (which may be a consequence of differences in patient population, evaluation criteria, or other factors). The reports from five investigators concerning approximately 200 patients show that 5-year survival may be as high as 90% and 10-year survival as high as 65%. The experience of another investigator with 94 patients showed that 5-year survival may be as low as 46% and 10-year survival may be as low as 39%.

Consensus: Staple Implants

A 5-year survival rate of 95 �3 percent for Type 7 staple implants (43 patients) is considered statistically reliable. However, there is concern relative to validity because this estimate is based on the self-reported data of primarily one investigator. For this reason, such estimates would need further support through the experience of other investigators and the introduction of Panel review data collection/evaluation methods.

Consensus: Transosteal Implants

It is not possible to quote survival ranges for transosteal implants at this time because of the relatively small sample sizes for the specific subgroups which were considered and the variation that was exhibited in the reported experiences among them.

Consensus: Vitreous Carbon Implants

A 3-year survival rate of approximately 55% or a range of 50% to 60% is consistent with the reported experience for the 133 vitreous carbon single interdental implants as reported by two investigators. Other aspects of survival analysis pertaining to this type of implant are not considered quotable because of insufficient sample size or conflicting results.

Consensus: Blade Implants

For blade implants in the free end application which primarily involve bridges or one pontic and two or more natural abutments, there are conflicting results concerning survival. This may be a consequence of differences in patient population, evaluation criteria, or other factors. With this consideration in mind, the reports of two investigators (but primarily of one) concerning a combined series of approximately 200 implants suggests a 5-year survival rate may be as high as 90%. However, the experience of two other investigators with a combined series of approximately 70 implants suggests that a 5-year survival rate may be as low as 65%.

For free end blade implants supporting 3 unit bridges of one pontic and one natural abutment or bridges containing 2 pontics and more than 2 natural abutments, no specific survival estimates can be quoted because of insufficient sample size or conflicting results.

For full arch blade implants (no natural teeth remain), a 5-year survival rate of 75 �5 percent for 89 patients is statistically reliable. However, there is concern relative to its underlying validity because it is based on the self-reported data of one investigator. For this reason, such estimates would need further support through the experience of other investigators and the introduction of panel review and uniform collection evaluation methods.  

Guidelines for Current Use

Consensus: Preamble

The placement of an implant device in any of the following categories assumes that the operator will be trained and competent and will use good judgment and ethical conduct in the use of such devices. Under these circumstances, the following four categories are adopted: 1) UNRESTRICTED--(adequate data for a favorable 5-year prognosis); 2) USE WITH GUIDELINES--(reason for a specific restricted application even though there may be adequate data for a 5-year prognosis); 3) CLINICAL TRIAL--(insufficient data to provide the basis for prognosis); 4) HUMAN APPLICATION CONTRAINDICATED.  

Subperiosteal and Staple/Transosteal

Panel 3

Consensus: Subperiosteal Implants

Subperiosteal implants are recommended for USE WITH GUIDELINES in mature (50 to 70) adult patients when conventional methods cannot be used successfully and who have acceptable general and oral health. The benefit:risk ratio may be improved when the implant is used: 1) in the mandible versus the maxilla, 2) on basal bone and 3) against a full upper denture.

No Consensus: Staple Implants

There was no endorsement of the workshop panel's recommendation of the mandibular staple for USE WITH GUIDELINES in adult patients unable to function with conventional dental prostheses with acceptable general and oral health. The mandible must have at least 9mm of true bone height in the para-aymphyseal area. The recommended surgical technique, instrumentation and prosthodontic management, must be adhered to. The benefit/risk ratio may be improved when the opposing dentition is a complete denture.

A follow-up questionnaire as to why half of the body did not agree with the category USE WITH GUIDELINES revealed a basic concern with safety and efficacy since the panel recommendation was based on the report of only a single investigator.

Consensus: Transosteal Implants

CLINICAL TRIALS are recommended for all applications of transosteal implants. The basis is insufficient data. Guidelines in clinical trial should be those of the present investigator: a minimum of 25 mm of available bone from alveolar bone crest to inferior border and avoidance of neurologic structures.  

Vitreous Carbon and Blade

Panel 4

Consensus: Vitreous Carbon Implants

CLINICAL TRIALS are recommended for all applications of the vitreous carbon implant: both free end and single interdental applications, whether splinted or free standing.

Consensus: Blade Implants

Blade implants are recommended for USE WITH GUIDELINES in free end and interdental application as partial support for fixed prosthesis: 1) when conventional methods cannot be used successfully, 2) to replace adult dentition, 3) when there is adequate bone, 4) when there is adequate intermaxillary space, and 5) when the treatment plan favors a fixed prosthesis.  

Complications and Removal Criteria

Panel 5

Eleven criteria incorporating reported implant complications are recommended as guidelines for removing an implant: 1) chronic pain; 2) significant movement; 3) infection; 4) significant and/or progressive loss of supportive bone; 5) intolerable dysthesia (anesthesia or parasthesia); 6) oro-antral or oro-nasal fistulae; 7) bone fracture; 8) psychological or other significant medical problems; 9) uncorrectable implant breakdown; 10) possible irreversible damage to adjacent teeth: and 11) cosmetic problems.  

Required Patient Information

Panel 6

The conference endorsed in principle a thorough statement of informed consent. Answers to the following questions formed the basis for the statement:

  • Why is the procedure necessary?
  • What are its benefits, what is the likelihood of their occurring in full, and how long can they be expected to last?
  • What implant procedures will be performed, what risks might be expected and what are the guidelines for implant removal? (See Complications and Removal Criteria above).
  • What alternative forms of treatment are available and why is the dentist recommending this course of treatment as opposed to alternative methods?
  • What would happen if treatment is not received?

Evaluation Criteria

Panel 7

The assessment of implant status includes the criteria of mobility, radiographs, gingival health, and pocket depth as standardized below:

  1. Mobility--To be measured in millimeter intervals for the subperiosteal, staple/transosteal and in .5 millimeter intervals for the vitreous carbon and blade.
  2. Radiographs--Further investigations of standardized radiographic techniques and criteria are recommended for all implants. The present recommended standards are:
    1. Subperiosteal. Radiolucency under any abutment or major strut and for implant sinking.
      • Grade 1: 0 mm.
      • Grade 2: <1 mm.
      • Grade 3: less than or equal to 2 mm.
      • Grade 4: less than or equal to 3 mm.
      • Grade 5: >3 mm.
    2. Staple/Transosteal. Radiolucency along transosteal and retentive pins.
      • Grade 1: none.
      • Grade 2: <1/2 transosteal.
      • Grade 3: >1/2 transosteal.
      • Grade 4: complete transosteal and retentive pins.
    3. Vitreous Carbon. Bone adaptation.
      • Grade 1: complete.
      • Grade 2: >1/2 vertical height.
      • Grade 3: <1/2 vertical height.
    4. Blade. Radiolucency.
      • Grade 1: None.
      • Grade 2: to neck.
      • Grade 3: to shoulder.
      • Grade 4: beyond shoulder.
  3. Gingival Health--For all implants.
    • Grade 1: No inflammation
    • Grade 2: mild inflammation (slight color change, edema, and no bleeding or probing).
    • Grade 3: moderate inflammation (redness, edema, glazing, bleeding on probing).
    • Grade 4: severe inflammation (marked redness and edema, ulceration, and spontaneous bleeding).
  4. Probing--pocket depth in millimeters is recommended on four sides for the vitreous carbon and blade and contraindicated for the subpenosteal and staple/transosteal implants.

Future Directions

Panel 8

This panel proposed the following approaches for the future:

Determine the implant types and materials in current use.

Utilize suitable data collection methods to continue to analyze the efficacy of all such implants.

Longitudinal and controlled prospective clinical studies are advised.

Support in vivo and in vitro animal studies that will further define the requirements of interface for all permucosal implants.

Formulate an educational minimum for the performance of implant procedures.

Encourage university and private sector interaction in the areas of implant research and education.  

Conference Sponsors

National Institute of Dental Research

Office of Medical Applications of Research, NIH

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