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Treatment Planning for the Two-Implant Overdenture

Joseph R. Carpentieri, DDS  •  Dennis P. Tarnow, DDS

 

 A patient interview in which the clinician asks key questions and listens carefully to the answers provided is the critical first step to successful treatment of the edentulous patient. Only with appropriate treatment planning can patient-specific restorations (ie, the most appropriate treatment for each patient) be delivered (Figure 1).

 

PATIENT INTERVIEW AND EVALUATION  

The essential information that must be elicited from the patient evaluation for the two-implant overdenture:Does the patient want more retention of an existing denture? Or does he or she hope to replace the denture with a fixed restoration?It is important for the clinician to differentiate between patient wants and preferences. A want may or may not be related to the treatment, but a preference infers that through sufficient education, the patient has a full understanding of what the treatment and/or prosthesis does or does not include.

Sound treatment planning and decision-making is a balance among:

  • Patient preference: an “informed consent” of treatment choice;
  • Financial considerations: what the patient can afford; and
  • Clinical factors: what is clinically necessary and feasible based upon the patient’s medical and dental history and other presenting circumstances determined upon extensive clinical examination, study casts, and radiographic evaluation (ie, the quality, quantity, and shape of the residual bone) (Figure 2).

As in all implant therapies,the final two-implant overdenture will require some follow-up treatment and maintenance to ensure a predicable level of patient comfort and satisfaction. A thorough and clear review of potential maintenance requirements and their associated costs and time requirements should be provided before treatment begins.

THE CONVENTIONAL DENTURE

Traditionally, the prosthetic rehabilitation of edentulous patients has focused on the replacement of lost structures with removable prostheses. Although the obvious disfigurement of edentulism may be markedly improved by dentures,1 studies indicate that the function of clinically acceptable dentures is often poor and leads to overall negative treatment outcomes.2,3

For those patients treated with complete dentures, research also indicates that their most important priorities are comfort, stability, and the ability to chew, yet it has been reported that over 50% of mandibular denture patients have problems with stability and retention and their masticatory performance is markedly reduced (25% to 15% of that of adults with natural dentition).4 Overall, mandibular dentures cause many more problems than maxillary dentures, and their overall high level of patient dissatisfaction dictates that dental professionals consider a new paradigm for the management of such patients.

 

TWO-IMPLANT OVERDENTURE

The biotechnical achievement of osseointegration has been a significant breakthrough for edentulous people. Numerous studies have demonstrated that the mandibular two-implant overdenture is a simple and effective solution for the edentulous patient.5 Mandibular two-implant overdentures have shown to be superior to conventional dentures in randomized and non-randomized clinical trials ranging in duration from six months to ten years.6-10 This treatment has demonstrated a high level of implant success (97% to 100%), long-term prosthesis survival, and a consistent high level of patient satisfaction. It represents a much-needed treatment modality that is highly predictable, yet less invasive, less expensive, and less complex as compared to other implant options.

Restoration with a mandibular two-implant overdenture will provide patients with significantly overall better treatment outcomes than a conventional denture and should become the first choice standard of care for the edentulous patient. The two-implant overdenture specifically addresses the effects of edentulism in numerous ways.

 

1. Bone Loss

Progressive loss of tissue volume further debilitates these patients in terms of their disfigurement and their ability to bite and chew. The pathologic resorptive process may be significantly reduced with this treatment. Studies indicate the anterior mandibular bone beneath an implant overdenture may resorb as little as 0.1 mm annually (ie, 25% as much as is observed with conventional dentures) or remain at 0.5 mm after a five-year period.11 Additionally, increased function after treatment appears to result in load-related bone formation that minimizes the physiologic age-related mandibular bone mineral content loss.12

 

2. Nutrition

A randomized controlled clinical trial compared between-group pre- and posttreatment nutritional status in patients with mandibular two-implant overdentures and those with new conventional dentures.13 Evaluation of blood parameters found significant increases in concentrations of serum albumen, hemoglobin, B12, and carotene in patients treated with two-implant overdentures while no significant change was found in patients restored with conventional prosthesis. This and other clinical data suggest that providing edentulous people with even the least-complicated forms of implant prosthesis encourages and enables patients to modify their diets and improve their nutrition, which may  have considerable impact on their general health.

 

3. Quality of Life

Evidence utilizing questionnaires of sufficient sensitivity to provide reliable data (ie, oral health implant profiles, VAS measurements) suggests that quality of life ratings for oral health are higher for patients who receive two-implant overdentures than for those with new conventional dentures.14,15 This is of considerable importance, indicating that this simple implant rehabilitation may actually restore a patient’s quality of life that had been previously lost!

Therefore, the evidence currently available suggests that the restoration of the edentulous mandible with a conventional denture is no longer the most appropriate choice of treatment. There is overwhelming evidence that the mandibular two-implant overdenture will provide patients with a significantly overall better treatment outcome and should be the first-choice standard of care for edentulous people.

 

INDICATIONS FOR THE TWO-IMPLANT OVERDENTURE

The two-implant overdenture is indicated for all fully edentulous patients (Class I to Class IV) who are capable of undergoing a minor surgical procedure and the placement of two dental implants. Specifically this includes:

  • The maladaptive or unsatisfied denture patient who demands greater retention and oral comfort;
  • The middle-aged to elderly denture patient who desires a more stable mandibular denture; and
  • The partially edentulous patient with severely compromised dentition (ie, about to become edentulous) that cannot be successfully maintained to retain or support a prosthesis.

 

CONTRAINDICATIONS FOR THE TWO-IMPLANT OVERDENTURE

  • Insufficient available bone for implant placement (ie, less than 5 mm to 7 mm);
  • Psychological denture intolerance (ie, a conspicuous discrepancy between objective findings and subjective patient complaints); and
  • Medical conditions, which may include uncontrolled metabolic diseases (eg, uncontrolled diabetes mellitus).

Previous history of radiation to the intended area of implant placement and the use of immunosuppressives must be carefully evaluated on an individual basis. This treatment should also be used cautiously in patients sensitive to the bulk of a conventional denture and in younger patients, for whom a greater number of implants would be more ideal for anterior and posterior bone preservation. Neither increasing age nor osteoporosis has been shown to contraindicate successful osseointegration of dental implants.

(Continued from page 1 )

 

OVERDENTURE TERMINOLOGY

1) Implant-retained and supported (ie, rigid): These prosthesis require multiple implants and will function most similarly to a fixed partial denture. Although a patient can remove them for hygiene, when in place they will have no movement.

2) Combined implant-retained and soft tissue-supported (ie, nonrigid): These prostheses will require fewer implants and include both the mandibular two-implant unsplinted and bar overdentures. Although they are associated with a high level of patient satisfaction and are highly retentive, when in place they will have (by design) some rotation and therefore some movement. It is helpful to explain to patients how this prosthesis is expected to function.

 

GENERAL TREATMENT PLANNING CONSIDERATIONS

Implant overdentures are space sensitive. While they are often the treatment of choice for the severely atrophic jaw, they paradoxically require the most restorative space as compared to other fixed prostheses. Generally, bar overdentures require more space than do unsplinted overdentures. Therefore, an evaluation of available restorative space or the attainment of the necessary space is critical to avoid overcontoured lingual areas or a thinning of acrylic that will increase the incidence of denture fracture. Careful prosthetic and surgical planning is essential for the overdenture patient!

The treatment challenges will vary from the minimally resorbed mandible (ie, Class I), which may paradoxically be difficult in terms of a lack of available space within the profile of the denture. For these patients additional space may be attained in one of two ways:

1. Prosthetically--Fabrication of a new two-implant overdenture with an increased vertical dimension (if such freeway space exists); and/or

2. Surgically--By moderately reducing the residual ridge and then  the conversion of existing denture.

For the severely resorbed mandible (ie, Class IV), available space is not a concern. Less retention and stability is expected, however, due to an overall diminished residual ridge and therefore a smaller denture base.

The treatment is generally more straightforward when a patient presents in the fully edentulous state, meaning they have already experienced the wearing of a removable denture. It is more difficult when the patient will experience the transition from fixed to a removable prosthesis. The success of overdenture treatment is dependent on the classical principles of denture fabrication and the placement of implants should not be a substitute to these tenets. Ultimately, the form and contour of a two-implant overdenture must be similar to a conventional denture, and an adequate base extension and adaptation to the remaining structures are basic requirements.

 

RESTORATIVE OPTIONS

Appropriate treatment planning culminates in selection of an appropriate restorative design for the patient. It is critical to select a final restorative design for the two-implant overdenture before starting the case (ie, prior to implant surgery). Since the philosophical goal of the mandibular two-implant overdenture is to make implant therapy accessible and affordable for patients, a significant aspect of design selection is deciding whether to restore the patient with a new two-implant overdenture or to convert an existing denture to a two-implant overdenture (Figures 3 and 4). This decision may have a profound impact on treatment time, costs, and case acceptance.

Can I convert existing denture to a two-implant overdenture or do I need to fabricate a new two-implant overdenture? This is a critical question initially, and arriving at a decision involves a thorough understanding of many factors such as aesthetics (ie, extraoral, facial, intraoral), vertical dimension, and the patient’s subjective needs. An understanding of space requirements, however, will often be the determining factor. If indicated, the conversion strategy should help make this treatment accessible and affordable for most patients.

 

References:

  1. Feine JS, Carlsson GE. Implant Overdentures: The Standard of Care for Edentulous Patients. Carol Stream, IL: Quintessence Publishing, 2003.
  2. Berg E. The influence of some anamnestic, demographic, and clinical variables on patient acceptance of new complete dentures. Acta Odontol Scand 1984;42(2):119-127.
  3. Pietrokovski J, Harfin J, Mostavoy R, Levy F. Oral findings in elderly nursing home residents in selected countries: Quality of and satisfaction of complete dentures. J Prosthet Dent 1995;73(2):132-135.
  4. Redford M, Drury T, Kingman A, Brown LJ. Denture use and technical quality of dental prosthesis among persons 18-74 years of age: United States,1988-1991. J Dent Res 1996;75:714-725.
  5. Schmitt A, Zarb G. The notion of implant supported overdentures. J Prosthet Dent 1998;79(1):60-65.
  6. Boerrigter EM, Stegenga B, Raghoebar Boering G. Patient satisfaction and chewing ability with implant-retained overdentures: A comparison with new complete dentures with or without preprosthetic surgery. J Oral Maxillofac Surg 1995;53(10):1176-1173.
  7. Raghoebar GM, Meijer HJ, Stegenga B, et al. Effectiveness of three treatment modalities for the edentulous mandible. A five year randomized clinical trial. Clin Oral Implants Res 2000;11(3):195-201.
  8. Geertman ME, Boerrigter EM, Van’t Hof MA, et al. Two-center clinical trial of implant-retained overdentures versus complete dentures-chewing ability. Community Dent Oral Epidemiol 1996;24(1):79-84.
  9. Geertman ME, van Waas MA, Van’t Hof MA, Kalk W. Denture satisfaction in a comparative study of implant-retained overdentures: a randomized clinical trial. Int J Oral Maxillofac Implants 1996;11(2):194-200.
  10. Awad MA, Lund JP, Dufresne E, Feine J. Comparing the efficiency of mandibular implant-retained overdentures and conventional dentures among middle-aged edentulous patients. Satisfaction and functional assessment. Int J Prosthodont 2003;16:117-1220
  11. Jemt T, Chai J, Jarnett J, et al. A 5-year prospective multicenter follow-up report on overdentures supported by osseointegrated implants. Int J Oral Maxillofac Implants 1996;11(3):291-80.
  12. Von Wowern N, Gotfredsen K. Implant-supported overdentures, a prevention of bone loss in edentulous mandibles? A 5-year follow-up study. Clin Oral Implants Res 2001;12(1):19-25.
  13. Morais JA, Heydecke G, Pawliuk J, et al. The effects of mandibular two-implant overdentures on nutrition in elderly edentulous individuals. J Dent Res 2003;82(1):53-58.
  14. Awad MA, Locker D, Korner-Bitensky N, Feine J. Measuring the effect of intra-oral implant rehabilitation on heatlh-related quality of life in a randomized controlled clinical trial. J Dent Res 2000;79(9):1659-1663.
  15. Awad MA, Lund JP, Shapiro SH, et al. Oral health status and treatment satisfaction with mandibular implant overdentures and conventional dentures: A randomized clinical trial in a senior population. Int J Prosthodont 2003;16(4):390-396.

 

 

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