One-year evaluation of two hybrid composites placed in a randomized-controlled clinical trial
Introduction
Amalgam, which was the filling material of choice for direct posterior restorations for more than 100 years, is increasingly being replaced in favor of composite restorations. This tendency can be explained by growing concern in populations over possible mercury intoxication from amalgam and the rising demand for tooth-colored restorations [1], [2], [3], [4], [5], [6]. Furthermore, composite filling materials, in contrast to amalgam, meet the criteria to allow for the use of “minimal invasive technique” in dentistry and to maintain a maximum of tooth tissue [7].
The patient demand for white filling materials is rising, and furthermore, composite materials such as packable resin-based composites and “bulk-fill” materials are being promoted as an alternative to amalgam in respect to their handling procedures [8], [9], [10].
The longevity of a dental restoration is influenced by material-, dentist- and patient-related factors. Patient-related factors include oral hygiene amongst others (dietary habits, preventive measures, compliance in recall, oral environment and systemic diseases, tooth-related factors, cooperation and parafunctional habits) [6]. There are numerous studies in which dental students have served partly or solely as a patient population [3], [5], [11], [12], [13], [14].
As a matter of fact, the performance of restorations in dental students can greatly vary from that of socially deprived patients. The different dental awareness of oral hygiene and caries prevention is a possible reason [15]. In 1997, Roulet stated that “trial patients are very carefully selected, especially for good compliance” [1]. In recently published recommendations for conducting clinical trials, the authors call for study groups that represent a cross-section of the population [15]. According to Opdam et al., cross-sectional studies represent more daily practice, but they do not offer data on survival or failure rates [16]. Controlled longitudinal clinical studies do provide this information [6]. In most conducted clinical trials, the restorations are performed by experienced university dentists on selected patients, who are motivated to maintain good oral hygiene. Practice-settings can differ from that in controlled, clinical trials. Typically, university dentists dedicate more time to the placement of a composite filling compared with practice-settings. [16], [17].
Several clinical trials published during the last several years only provide so-called short-term results (0–5 years) [6], [18], [19]. Long-term clinical trials are clearly needed, particularly when considering that failures in restorations should be subdivided into early (after weeks or months) and late failures (after several years of clinical function) [6], [15]. Failures during the treatment procedures can be held primarily responsible for the early failures, whereas late failures are a result of tooth and/or restoration fracture, secondary caries and wear [6].
Furthermore, long-term data are necessary to evaluate the long-term costs of a restorative treatment. The longevity of a restoration can be regarded as an indicator of the success of a treatment procedure [20].
The failure rate among 17 clinical studies between 1996 and 2002 varied greatly from 0% to 45%. Studies lasting longer than 10 years had the highest failure rates. It could be demonstrated that short-term studies provided more favorable results, in addition to having smaller study populations [18].
According to van Dijken and Lindberg, the longevity of a restoration is predominantly dependent on the dentist's qualification and the stress the oral cavity is exposed to [21].
The shortcomings of all of these studies (small study population, short-term results, selection of the study population in favor of oral hygiene) served as a basis for this present study.
The aim of this study is to assess the long-term performance of two direct composite resins for posterior restorations placed in a randomized-controlled clinical trial (over 10 years). This feasibility study demonstrates if treatment of a high number of participants is feasible in the routine clinical student course. This study also examines if the failure rate of these composites will differ more than 10% after 10 years of clinical service using modified US Public Health Service (USPHS) scoring system [22]. This study provides the results after one year of clinical service.
Section snippets
Study design, patient selection and description of the study population
The null hypothesis reflects that no difference will be determined between the restorations of Class I/II (including cuspal coverage) after an observation period of 10 years using two different composite materials (Table 1).
The primary outcome of this study is the clinical service of restorations of Class I/II defects (occurrence of failure: yes/no). The following is recorded: restoration failure; if dentin or base was exposed; if contact point was missing (present periodontal inflammation);
The results of the baseline evaluation (T0)
At baseline, the mean age of the patients was 33.96 (SD: 11.23) years. 456 patients received a total of 1805 fillings during one year. Treatment groups and gender specification are depicted in Table 3.
A detailed analysis of all the fillings according to the variable “tooth position” reveals that in both the upper and lower jaw, molars were the most treated teeth: 46 in the group “Ceram X” (8.17%, n = 72) and 16 in the group “Tetric Ceram” (8.23%, n = 76). The number of fillings in premolars (PM)
Discussion
This longitudinal, randomized-controlled clinical study investigates the longevity of two composite materials (Ceram X and Tetric Ceram) using modified USPHS criteria. During one year, patients visiting the Department of Restorative Dentistry at the University of Dentistry of Vienna were offered participation in this study, providing that Class I or II restoration in their posterior teeth were indicated (n = 456). No patient was excluded because of high caries risk, poor oral hygiene or
Conclusion
Within the limitations of this study, it can be concluded that in a group of Class I/II and cuspal-coverage restorations, there was no significant difference in the failure rates between an ormocer-based nanohybrid (Ceram X) and a bis-GMA-based microhybrid (Tetric Ceram) restorative system after one year. A root canal treatment at baseline had no negative influence on the failure rate. A longer observation period is indicated to obtain clear evidence of the long-term performance of these
Acknowledgments
The authors would like to thank the Dentsply DeTrey GmbH for sponsoring the study (investigation number: 14.1058) and Dr. Andreas Grützner, Dentsply DeTrey GmbH, for his valuable contributions to the study design.
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