COSMETIC & RESTORATIVE CARE |
COVER STORY
JADA Continuing Education
The implant-supported overdenture as an alternative to the complete mandibular denture
JAMES H. DOUNDOULAKIS, D.M.D., M.S.,
STEVEN E. ECKERT, D.D.S.,
CLARENCE C. LINDQUIST, D.D.S. and
MARJORIE K. JEFFCOAT, D.M.D.
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ABSTRACT
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Background. Approximately one-third of Americans older than 65 years of age are fully edentulous, requiring replacement of missing teeth. While the conventional denture may meet the needs of many patients, others require more retention, stability, function and esthetics, especially in the mandible. The implant-supported prosthesis is an alternative to the conventional removable denture.
Methods. This article describes the strengths of the implant-supported mandibular overdenture. The authors also outline the risks of this approach. They performed a review of recent literature to summarize the reported success rate of implants used to support a mandibular overdenture.
Results. The literature review indicates that implants placed in the anterior mandible (anterior to the foramen) have a success rate better than 95 percent. Patients have reported a high degree of satisfaction with the implant-supported overdenture.
Conclusions. The literature indicates that implant-supported overdentures in the mandible provide predictable results with improved stability, retention, function and patient satisfaction compared with conventional dentures. Implants placed in the anterior mandible have a success rate equal to or greater than 95 percent.
Clinical Implications. When planning treatment for patients with edentulous mandibles, clinicians should consider the implant-supported prosthesis.
The edentulous patient has not disappeared. While the prevalence of edentulism is less than what it was 20 years ago, about 33 percent of Americans older than 65 years of age were completely edentulous as of 2000.1,2 When all Americans older than 18 years of age are considered, approximately 10 percent are completely without teeth.1 There are disparities in the rate of edentulism among racial and ethnic groups, with Mexican-Americans least likely to lose all of their teeth.1 Edentulism is one of a few dental conditions for which state-specific data exist. These data reveal a wide variation in the percentages of the population aged 65 and older who have no teeth, from a low of 13.9 percent in Hawaii to a high of 47.9 percent in West Virginia.2
When planning treatment for patients with edentulous mandibles, clinicians should consider the implant-supported prosthesis.
The classical treatment plan for the edentulous patient is the complete removable maxillary and mandibular denture. This treatment is relatively inexpensive in comparison with fixed implant-supported prostheses, but it has several drawbacks (Box 1
). Like all dental restorative procedures, a complete removable denture requires extensive attention to detail if an excellent clinical result is to be achieved. Depending on the shape of the regional ridge, the denture may be unstable or inadequately retained, leaving the patient dissatisfied with the functional result.
The rate of residual ridge resorption in edentulous patients who do not have tooth replacements is highly variable and may be as much as several millimeters per year. This resorption can render the current prosthesis inadequate in terms of both function and esthetics and can lead to the necessity of fabricating a new denture. Over time, occlusion, esthetics and function may be compromised.
Perhaps one of the greatest drawbacks to the full denture is the misconception to which it gives rise, on the patient’s part, that dental care no longer is needed. Such patients deny themselves not only routine maintenance of their prostheses but also the advantages of cancer screening.
Today’s patients have high expectations for oral health; providing a traditional denture that eventually becomes an ill-fitting prosthesis does not help meet these expectations. The implant-supported denture is one solution to these problems.
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ADVANTAGES OF THE IMPLANT-SUPPORTED PROSTHESIS
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The implant-supported overdenture has many advantages. Although as few as two to four implants may be used for support (Box 2), it is beneficial to use more than two implants in the unlikely event that one of the implants fails to function during the patient’s life span. Implant placement surgery is relatively simple to perform and, in experienced hands, may take less than an hour. Many options are available for retention of the prosthesis, including magnets, clips, bars and balls (Figure 1). The resultant implant-supported denture (Figure 2) has good stability and retention, and patients who have received them have reported improved function and satisfaction.3
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Figure 2. The clinical results of the implant placement shown in Figure 1 : an implant-supported mandibular denture and a conventional maxillary denture.
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Another benefit of implant-supported prostheses is suggested by preliminary data indicating that after receiving implants, patients may eat a diet with more fiber (M.K. Jeffcoat, D.M.D., unpublished data, 2003). If this is proven, the implant-supported denture would make an important contribution to general health and well-being.
Other studies have measured the rate of residual ridge resorption in the five years after implant placement. The rate of resorption is decreased significantly from the rates seen with conventional dentures, and recent research has shown that the height of the posterior ridge increases with continued use of implant-supported prostheses.4 Although patients in studies are not directly comparable to the population as a whole, patients with implant-supported prostheses return for visits with the same practitioner at a very high rate.5 In one study, this rate exceeded 95 percent over seven years, permitting detection of two cancers in a study population of 120.5 A 2002 consensus statement developed by scientists and expert clinicians at a symposium on the efficacy of overdentures for the treatment of edentulous patients held at McGill University in Montreal, Quebec, Canada, lists a mandibular overdenture as the first choice in treating edentulous patients.6
Success rates.
Implants no longer are considered experimental. The table shows representative clinical trials over the past six years.3,5,7–13 We performed a library search for implant clinical trials in the anterior mandible reported in English; the table shows the primary author, size of study, study design and representative results of each study we found. (This article is not intended to provide extensive statistical meta-analysis.) Most of the trials were longitudinal studies of cohorts of patients treated according to the sample protocol. We evaluated data from these studies and found that they demonstrate a success rate above 95 percent in the anterior mandible. It is noteworthy that among the sources of support for these studies were many different implant manufacturers and the U.S. government. Furthermore, the success rate exceeds the rate prescribed for the ADA Seal of Acceptance by the ADA Council on Scientific Affairs.
Risks.
No surgical procedure, including the placement of implants, is without risk. The risks associated with implant placement are outlined in Box 3.14,15 Risks include postoperative bleeding, numbness if the mandibular nerve is disturbed, infection and lack of osseointegration. The risks can be minimized with proper training and experience. Case selection and diagnosis is the key to success with implant procedures, as with all dental procedures.
Other risk factors also may affect the outcome of the implant-supported prosthesis. Smoking is a risk factor for long-term implant success. Patients who smoke are more likely to experience infection and/or progressive alveolar bone loss, which ultimately may lead to implant loss. A smoking cessation plan including periodic assessment of cotinine levels may be ordered to track long-term exposure to tobacco.
Untreated periodontitis also is a risk factor for the failure of dental implants. Obviously, fully edentulous patients do not have periodontitis, but even after the extraction of a single tooth with periodontal disease, the site may harbor pathogenic bacteria that may lead to peri-implantitis.
Factors that may influence the healing or potential infection of the implant recipient site also may affect the outcome. Uncontrolled diabetes and use of drugs such as steroids need to be carefully considered in the treatment plan, and the clinician may need to adjust time to loading accordingly. Anatomy and bone quality also affect the outcome and ease of surgical placement of implants. Implants need adequate bone height and width for placement. If the native bone at the recipient site is inadequate to accept the implant, bone grafts—with or without guided bone regeneration—must be considered. Bone quality, which is related to density of the trabecular bone, usually is not a problem in the anterior mandible. Other segments of the alveolar bone, such as the posterior maxilla, are more likely to have lower bone density, which can limit implant stability and osseointegration.
With proper diagnosis and treatment planning, the limitations and risks of implant placement are manageable. Good communication between the surgical and restorative members of the team is a necessity. High-quality training and experience in implant surgery and restorative care are fundamental to delivering quality care.
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CONCLUSION
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The literature and clinical experience indicate that the implant-supported prosthesis provides predictable results with improved stability and function and a high degree of satisfaction as compared with conventional removable dentures. Clinical studies in the literature in which implants were used in the mandible anterior to the foramen indicate that the success rate for implants in the lower mandible is 95 percent or greater. These data indicate that implant-supported prostheses should be considered in planning treatment for the fully edentulous patient.
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FOOTNOTES
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Dr. Doundoulakis maintains a private practice in cosmetic dental rehabilitation in New York City. He also is section chief, Maxillofacial Prosthetics, and attending dentist, St. Luke’s-Roosevelt Hospital Center, New York City; and attending and assistant clinical professor, New York/Presbyterian, The University Hospitals of Columbia and Cornell, New York City. Address reprint requests to Dr. Doundoulakis at 3 E. 66th St., New York, N.Y. 10021, e-mail "cosmeticdental{at}att.net".
Dr. Eckert is an associate professor of dentistry, Mayo Medical School, Rochester, Minn.
Dr. Lindquist maintains a private practice in oral and maxillofacial surgery, Chevy Chase, Md., and Washington.
Dr. Jeffcoat is dean, University of Pennsylvania School of Dental Medicine, Philadelphia, and the editor of JADA.
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REFERENCES
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- U.S. Surgeon General. Oral health in America: A report of the surgeon general. Part two: What is the status of oral health in America? Rockville, Md.: U.S. Dept. of Health and Human Services, U.S. Public Health Service, Office of the Surgeon General; 2000. Available at: "www.nidcr.nih.gov/sgr/sgrohweb/part2.htm". Accessed Oct. 2, 2003.
- Tomar S. Total tooth loss among persons aged greater than or equal to 65 years: selected states, 1995–1997. MMWR Morb Mortal Wkly Rep 1997;48:206–10.
- Awad MA, Lund JP, Dufresne E, Feine JS. Comparing the efficacy of mandibular implant-retained overdentures and conventional dentures among middle-aged edentulous patients: satisfaction and functional assessment. Int J Prosth 2003;16:117–22.
- Reddy MS, Geurs NC, Wang IC, et al. Mandibular growth following implant restoration: does Wolff’s law apply to residual ridge resorption? Int J Periodontics Restorative Dent 2002;22(4):315–21.[Medline]
- Jeffcoat MK, McGlumphy EA, Reddy MS, Geurs NC, Proskin HM. A comparison of hydroxyapatite (HA)-coated threaded, HA-coated cylindric, and titanium threaded endosseous dental implants. Int J Oral Maxillfac Implants 2003;18:406–10.
- Thomason JM. The McGill Consensus Statement on Overdentures. Mandibular 2-implant overdentures as first choice standard of care for edentulous patients. Eur J Prosthodon Restor Dent 2002;10(3):95–6.
- Buser D, Mericske-Stern R, Bernard JP, et al. Long-term evaluation of non-submerged ITI implants, part 1:8-year life table analysis of a prospective multi-center study with 2359 implants. Clin Oral Implants Res 1997;8(3):161–72.[Medline]
- Tawse-Smith A, Perio C, Payne AG, Kumara R, Thomson WM. One-stage operative procedure using two different implant systems: a prospective study on implant overdentures in the edentulous mandible. Clin Implant Dent Relat Res 2001;3(4):185–93.[Medline]
- Meijer HJ, Geertman ME, Raghoebar GM, Kwakman JM. Implant-retained mandibular overdentures: 6-year results of a multicenter clinical trial on 3 different implant systems. J Oral Maxillofac Surg 2001; 59(11):1260–8.[Medline]
- Moberg LE, Kondell PA, Sagulin GB, Bolin A, Heimdahl A, Gynther GW. Branemark System and ITI Dental Implant System for treatment of mandibular edentulism: a comparative randomized study—3-year follow-up. Clin Oral Implants Res 2001;12:450–61.[Medline]
- Rodriguez AM, Orenstein IH, Morris HF, Ochi S. Survival of various implant-supported prosthesis designs following 36 months of clinical function. Ann Periodontol 2000;5(1):101–8.[Medline]
- Morris HF, Ochi S. Survival and stability (PTVs) of six implant designs from placement to 36 months. Ann Periodontol 2000;5(1):15–21.[Medline]
- Bergendal T, Engquist B. Implant-supported overdentures: a longitudinal prospective study. Int J Oral Maxillofac Implants 1998; 13:253–62.[Medline]
- Quirynen M, De Soete M, van Steenberghe D. Infectious risks for oral implants: a review of the literature. Clin Oral Implants Res 2002;13(1):1–19.[Medline]
- Tonetti MS. Determination of the success and failure of root-form osseointegrated dental implants. Adv Dental Res 1999:13:173–80.[Abstract/Free Full Text]
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An Eight-year Follow-up to a Randomized Clinical Trial of Aftercare and Cost-analysis with Three Types of Mandibular Implant-retained Overdentures
Journal of Dental Research,
March 1, 2007;
86(3):
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[Abstract]
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ADVANTAGES OF THE IMPLANT...
