Patient Satisfaction and Masticatory Function

At a conference in Toronto in 1998, a critical review of literature on the patient-based outcomes of implant therapy surprised the audience. What every prosthodontist considered evident—the great benefits of implant-supported prostheses—was questioned because most studies had design flaws that threatened their internal validity.⁶ The reviewer noted that, from a strictly scientific point of view, the studies conducted up to 1998 provided relatively little scientific evidence that implant therapy is of substantially more benefit to edentulous patients than alternative forms of treatment. It was concluded that further research was needed using randomized controlled trial (RCT) designs. Outcome measures need to be more carefully selected so as to reflect patients’ concerns. More recent studies have addressed patient satisfaction and verified that patients with implant overdentures had higher satisfaction scores than complete denture wearers, even in comparison with those who had preprosthetic surgery to enlarge the denture-bearing area.⁷ In one of the recent studies using patient-based assessments (eg, O ral Health Impact Profile, or OHIP), it was found that patients who chose complete dentures when implant overdentures also were available reported significant improvement after treatment, as did those who received implant treatment. Both groups reported much greater improvement compared to the patients who requested implants but received complete dentures. ⁸ During the past few years, a series of RCTs have shown higher satisfaction and oral health-related quality of life among patients with implant overdentures than among those with conventional dentures (see chapter 5).

Figs 14-1 a and 14-1b Single midline implant to retain a mandibular overdenture. (Reprinted from Krennmair and Ulm¹⁶ with permission.)

Cross-over studies have been conducted for comparison of fixed ve rsus removable implant-supported prostheses. The removable design was selected (by half of the patients) for ease of cleaning, among other reasons, whereas the fixed prosthesis was chosen because it provided better stability and ability to chew.⁹ There was no difference in general satisfaction between the fixed and removable treatments, but patients found the fixed prosthesis to be better for chewing harder foods.¹⁰ Improvements in bite force and chewing efficiency following implant treatment in edentulous patients has been demonstrated for many years,¹¹ and similar results for mandibular implant overdentures have been presented.¹²

Number of Implants

The theory that more implants will better support a heavy functional load may be true from a theoretical biomechanical point of view, and it explains the early uncertainty about how many implants to use for supporting or retaining an overdenture. However, numerous clinical prospective studies up to 12 years have proven that two mandibular intraforaminal implants, splinted or unsplinted, retaining an overdenture provide successful treatment for edentulous mandibles.^5,13,14

A few studies have compared mandibular overdentures supported by two, three, or four implants. Results indicate that two implants are sufficient, in general, and this seems to be the most common choice today. The recommendations to use more than two implants in special situations⁵ appear to be based on speculation rather than on results of controlled clinical studies. Such studies would be desirable to provide a better basis for decision making. However, there is consensus that, for the great majority of edentulous patients, two intraforaminal implants are sufficient for a successful mandibular implant overdenture.

The possibility of reducing the number of implants to one has been tested in a 5-year prospective study of 21 elderly patients.¹⁵ None of the implants was lost during the follow-up period and “remarkable improvement of oral comfort and function was evidenced with the overdenture treatment.” Similar success was reported in a more recent investigation with fewer patients and a shorter observation period (Figs 14-1a and 14-1b).¹⁶ The authors of both studies emphasized the benefit of their method, especially for geriatric patients with severe denture problems, because it is relatively inexpensive and is a surgically and prosthodontically simple way of retaining a complete denture. In spite of these successful results, the method with only one implant does not seem to have become more widely accepted. However, this alternative deserves to be investigated using an RCT that compares the outcome of complete dentures to mandibular overdentures anchored to one implant.