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Fundamentals of Esthetic Implant Dentistry
Conventional Fixed Bridges Conventional fixed bridges have long been considered the most ideal treatment modality for restoring natural dentition. They have exhibited clinically proven high success rates with their excellent esthetics and long-term functional serviceability, even if the structure of the remaining natural teeth was compromised (Meyenberg 1995). However, in spite of their outstanding clinical performance, there is a significant variation in their success rates, documented in the literature as ranging from 97 to 80% (Palmquist and Swartz 1993, Schwartz et al. 1970). These variations are probably due to differences in clinical performance, precision of the bridge fabrication, and the type of metal alloy used. Conventional singletooth replacement with fixed partial dentures involves several biological and technical risks, such as endodontic complications, secondary caries, difficult access for plaque control resulting in periodontal complications, loss of retention, and fractures of abutment teeth. The main reason for failure of conventional bridges is attributed to endodontic failure of the abutment teeth after an unknown period of time (Meyenberg and Imoberdof 1997). The extensive destruction of the abutment teeth through tooth preparation for conventional bridges is now considered to be a clinical drawback, especially when the teeth are sound. The immense loss of tooth structure during tooth preparation can be the actual reason for unsatisfactory results that result from this treatment option. With the evolution of dental implants, there is greater emphasis on the preservation of natural teeth that would normally be used to serve as abutments for a fixed bridge. In other words, dental implants have led to increased preservation of remaining natural teeth. Dental implants are used to replace missing teeth without resorting to including adjacent abutment teeth that are in relatively good condition. Using general standards in the literature, the average lifetime of a fixed bridge is 8.3 years to 10.3 years (Koth 1982, Silness 1970). This might raise the question of how many restorations a young patient might require over a lifetime. Alternatively, if the teeth adjacent to an edentulous space have either severe attrition or a gross restoration, dental implants may not be the preferred treatment option. In this case, it is better to consider protecting and splinting these compromised teeth within a bridge framework. Thus, the condition and number of the remaining dentition, parafunctional habits, type of occlusion, and leverage are all factors that help determine the appropriateness of this treatment modality.
Adhesive Bridges Adhesive bridges, which eliminate the need for substantial destruction of natural abutments, are another
option. Adhesive bridges were originally introduced by Rochette (1986) to be used as periodontal splints. However, adhesive bridges require greater clinical skills than do conventional bridges, and there is the possibility of recurrent dental caries occurring around the bridge margins and line angles. Debonding of adhesive bridges, which leads to loosening of the bridge, tends to occur at a frequency rate as high as 25% to 31% (Hussey et al. 1991, Williams 1989). The debonding tendency is considered to be the major complication of this type of bridge, which limits its regular daily use. Resin-bonded restorations have shown a wide range of clinical results, as cited in the literature, from a failure rate of 54% in 11 months (when used in the absence of mechanical retentive methods) to a success rate of 92.9% in 127 cases (with a mean longevity of five years) (Hansson 1994, Barrack and Bretz 1993). Resin-bonded bridges are only suggested for patients seeking a temporary, inexpensive esthetic solution for a particular period of time. The specific nature of this treatment option should be explicitly explained.
Dental Implants Unlike the previous treatment alternatives, dental implants have been exhaustively investigated under controlled parameters as treatment options, especially for completely edentulous patients (Priest 1996, Haas et al. 1995, Jemt et al. 1990). Since the late 1980s, continuous research and sophisticated statistical analyses have shown dental implants to be a predictable treatment option for dental restoration in totally and partially edentulous patients. The scope of dental implants was later expanded to include the treatment of missing single teeth. This treatment has shown consistent success rates ranging from 91% to 97.4% over a three- to six-year period (Haas et al. 1995, Jemt et al. 1990). However, a few complications were encountered with this treatment modality; screw loosening has been reported most often in single-tooth implant-supported restorations (Schwarz 2000). This drawback has been overcome greatly by the introduction of new implant-abutment connections that provide greater surface areas, stability against lateral displacement, and a predictable retention. Implant dentistry has dramatically changed the conventional routine of restorative dentistry. It has inspired many clinicians who, in turn, have contributed to improving the clinical esthetic outcome of this treatment modality. New soft and hard tissue augmentation procedures were developed to optimize the long-term esthetic outcome of dental implants (Grunder et al. 1996). In partially edentulous patients, dental implants offer the advantage of eliminating the natural abutment preparation. These procedures are considered to be the