Fiber-reinforced composite (FRC) materials were introduced to dentistry more than five decades ago . Following extensive research and product development, it took more than twenty-five years until FRCs were first indicated as a reconstruction material for fixed dental prostheses (FPDs) . Early FRC FPDs were used in the design of full coverage crown retainers but the rationale for using indirect crown-retained FRC FPDs were questioned when it became evident that the longevity of the FRC FDPs was not as favourable as porcelain-fused-to-metal FDPs . Preserving dental hard tissue during the preparation of abutments became essential and progress in adhesive and FRC technology enabled the development of the concept of minimally invasive FDP’s using FRC materials that could be utilized in the lab or at chairside. Glass FRCs fulfilled this requirement and active research on direct surface- or intra-coronally-retained FRC FDPs commenced . Nearly twenty-five years after the beginning of effective FRC FDP research, some conclusions could be drawn on the rationale for indicating FRC FPDs and some statements could be made on possible risk factors that may affect the longevity of the treatment outcome with such reconstructions. In this regard, a consensus meeting on the current status FRC FDPs was held in Leuven, Belgium, September 23rd, 2016.
Longevity of the FRC FDPs has been evaluated in a limited number of clinical studies in which various FDP designs, material combinations and cementing systems were employed. The majority of the available studies were often criticized due to the heterogeneous nature of FDPs being evaluated. A systematic review, including studies with a suboptimal clinical study design, demonstrated only moderate success for indirect FRC FDPs . However, once the FRCs started to be used in conjunction with the direct technique, more encouraging clinical results have been reported , although only short or mid-term follow-up results are available. Depending on the expectations of longevity of an FDP, it is now evident, from the present clinical experience with direct FRC FDPs, that such reconstructions could be considered as definite prosthodontics solutions with survival time of at least five to six years. The use of FRC materials expanded from direct, semi-direct or indirect FRC FDPs to other indications in periodontology, orthodontics, conservative dentistry and fixed prosthodontics. Since the introduction of resin-bonded direct FDPs there has been a diminishing border between conventional fixed prosthodontics (indirect restorative dentistry) and conservative dentistry (direct restorative dentistry).
When benefits of FRC FDPs were discussed, the dentists proposed four principal arguments:
FRC materials allows for following the Dynamic Treatment Concept (life-long dental treatment starting with the least invasive treatment preserving the maximum amount of tooth substance that would save the dental hard tissues for possible prospective treatments even years after the first intervention),
profitable and affordable treatment options and
high patient satisfaction.
From the patient perspective, the most significant reasons for selecting FRC FDPs seems to be:
the possibility of receiving the FDP in a single-visit,
being less expensive and painless treatment and
the possibility of avoiding removable devices.
Apparently, many reasons of these kinds are relevant for specific groups of patients but some of them are valid arguments regardless of the patient background or the country where treatment is provided. However, it was emphasized that decision making regarding the type of dental treatment and dental material selection is largely affected by the regulations of the national health insurance systems, and not neccessarily on the appropriateness of treatment or subjective demands of the patients.
Some risk factors could be identified that could decrease the longevity of FRC FDPs. These include material type, FDP design, oral environment and oral hygiene. The decreased treatment expenses could essentially increase the indication of FRC FDPs in patients with less attention to and awareness of their oral hygiene. Consequently, such factors could affect the treatment outcome of any dental treatment in patients with increased risk for caries and periodontal diseases. In addition, occlusion and especially limited vertical space seems to represent major risk factor for damage in FRC FDPs. Essentially, without adequate inter-occlusal space, optimum framework design and dimensions of FRC FDPs could not be accomplished. Minimal requirements for the inter-occlusal space are 4.0 mm for pontic, 2.5 mm for the connector area (vertically in the posterior and palato/linguo-buccally in the anterior region) and 2.0 mm for the occlusal surface of the abutment. Furthermore, increased mobility of abutment teeth appears to increase the risk for debonding of intracoronal retainers and periodontal splints. If increased mobility of abutments is noted, additional surface bonding wings or crown retainers with the cantilever FDP design should be considered.
Increased patient and societal expectations for fixed reconstructions have increased the demand for developing treatment alternatives for partially edentulous patients. Significant improvements in adhesive techniques and mechanical properties of resin composites using FRC materials have increased the indication of adhesive FRC FDPs in larger number of patients. Nevertheless, understanding and managing the risk factors dictate the successful use of direct or indirect FRC FDP treatment modalities. Based on the present knowledge and experience, with sufficient inter-occlusal space, correct framework design and precise application of adhesive techniques, FRC FDPs could provide fixed prosthodontic solutions, with expected survival time of at least five to six years, high patient satisfaction, and postpone other invasive and costly treatments.