[Five year survival of posterior adhesive bridges. Influence of bonding systems and tooth preparation]. / Vijfjaarsoverleving van adhesiefbruggen in de zijdelingse delen. De invloed van hechtsysteem en preparatievorm.

The present study reports the final analysis of a randomized controlled clinical trial in which different designs of posterior resin-bonded bridges were evaluated for a period of at least 5 years. The operational hypothesis was that the bonding system and the preparation design used in posterior resin-bonded bridges have an influence on the survival and clinical functioning of these restorations. Survival in this study was defined at two levels: (1) 'primary' survival (survival without any debonding), and (2) 'functional' survival (survival including loss of retention on one occasion and successful rebonding of the original resin-bonded bridge without further debonding). Preparation of grooves in abutment teeth for posterior resin-bonded bridges appeared to be beneficial to their chance of survival. Resin-bonded bridges placed in the maxilla have a better prognosis than those made in the mandible. The bonding systems used in this study (etching/Clearfil F2, sand blasting/Panavia EX and silica-coating/Microfill Pontic C) appear to have no influence on the chance of failure with regards to the 'primary' survival. In rebonded posterior resin-bonded bridges, the bonding system silica coating/Microfill Pontic C was more retentive than the other systems tested.

Risk factors and multiple failures in posterior resin-bonded bridges in a 5-year multi-practice clinical trial.

OBJECTIVES: A randomized controlled clinical trial was undertaken, to study the influence of some patient- and operator-dependent variables on the survival of posterior resin-bonded bridges (PRBBs) and to assess the survival of replacement' PRBBs. This report contains some of the results of the 5-year analysis. METHODS: Survival was defined at three levels: (1) complete survival (without any debonding), (2) functional survival (i.e. survival after one loss of retention) and (3) replacement survival (survival of 'replacement' PRBBs, inserted after rebonded bridges suffered a second dislodgement). Potential risk factors were analysed with Cox's proportional hazards model and differences were tested for significance with the Breslow test. Observed effects are expressed as conditional-relative-risk (CRR). Survival of 'replacement' PRBBs was assessed with the Kaplan-Meier method. RESULTS: Factors showing significant influences on complete survival were: 'location' (highest risk for mandibular PRBBs: CRR = 2.2), 'aetiology' (higher risk in treatment of aplasia: CRR = 2.9), and 'time of existence' (open spaces existing less than 2 years before insertion of PRBB: CRR: 2.0). The factor 'large open spaces in the mandible' was a risk for both complete and functional survival (CCR values 3.1 and 3.5, respectively). The survival of mandibular and maxillary 'replacement' PRBBs after 5 years was 19 +/- 7% and 31 +/- 18%, respectively. CONCLUSIONS: Risk factors for PRBBs were: 'location', 'aetiology', 'time of existence', 'isolation method' and 'large open spaces in the mandible'. Mandibular 'replacement' PRBBs showed such an unacceptably low survival rate that fabrication is not recommended.

A five-year multi-practice clinical study on posterior resin-bonded bridges.

Previous clinical observations have revealed that resin-bonded bridges for posterior tooth replacements are less retentive than anterior resin-bonded bridges. Improved bonding procedures and preparation designs, however, may have a positive effect on the functional durability of these restorations. The present study reports the final analysis of a randomized controlled clinical trial in which different designs of posterior resin-bonded bridges were evaluated for a period of at least 5 years. The operational hypothesis was that the bonding system and the preparation design used in posterior resin-bonded bridges have an influence on the survival and clinical functioning of these restorations. Survival in this study was defined at two levels: (1) 'complete' survival (survival without any debonding), and (2) 'functional' survival (survival including loss of retention on one occasion and successful rebonding of the original RBB without further debonding). With regard to 'complete' survival, no significant differences were found between the bonding systems used for adherence of the restorations to abutment teeth (etching/Clearfil F2, sandblasting/Panavia EX, and silica-coating/Microfill Pontic C). The variable 'preparation form' (conventional preparation form vs. modified preparation form) for complete survival was statistically in favor of the modified preparation form (62% vs. 46%), but did not influence the functional survival. With regard to 'functional' survival, the combination of silica coating and Microfill Pontic C was more retentive than the other bonding systems (90% survival vs. 72% and 75%, p < 0.01). Factor location was found to be highly significant for both survival levels [Cox's PH model, p = 0.0002 (Cox, 1972)]: The five-year 'complete' survival rates were 65% for maxillary restorations and 40% for mandibular restorations, while the five-year 'functional' survival rates were 89% and 68%, respectively. It is concluded that preparation of grooves in abutment teeth for posterior resin-bonded bridges is beneficial to their chance of survival. Resin-bonded bridges placed in the maxilla have a better prognosis than those made in the mandible. The bonding systems used in this study appear to have no influence on the chance of failure. In rebonded posterior resin-bonded bridges, the bonding system silica-coating/Microfill Pontic C was more retentive than the other systems tested.

A multicentered clinical study on posterior resin-bonded bridges: the 'Manchester trial'.

This study was designed to investigate and identify factors relevant to the success and failure of posterior resin-bonded bridges (PRBBs) related to the patient, technique, operator and bridge design. It was a long-term controlled clinical trial and formed part of a multicentered study on PRBBs. Data are presented 2.5 years from the start of the study. Following a strict protocol for case selection, 54 posterior, resin-bonded, fixed-fixed, three unit bridges were placed in 45 patients. Twenty-four patients with 27 PRBBs attended for 2.5-year recall. Treatment variables were limited to one of two operators and either a conventional tooth preparation or a more extensive modified preparation was performed. The allocation of treatment modalities was performed using a computer program to balance patient variables such as age, gender, location of bridge, restoration of abutment teeth. All bridges were produced in one laboratory, treated to produce a silicate-coating bond and placed using Microfill Pontic C (Kulzer, Wehrheim, Germany). Data relating to the patients, the open spaces, bridge preparation, bridge placement and subsequent annual evaluation were recorded. The survival of PRBBs in the maxilla was 77% and in the mandible 47%.

A multi-practice clinical study on posterior resin-bonded bridges: a 2.5-year interim report.

A clinical trial of 201 posterior resin-bonded bridges (PRBBs) was conducted partially in a University clinic and partially in general dental practices, for study of the influence of some experimental variables on the survival of these restorations. This report contains the results of an interim analysis which was done after 2.5 years' follow-up. No significant differences were found among the bonding systems used to adhere the PRBBs (Clearfil F2/etching, Panavia EX/sandblasting, and Microfill Pontic C/silicate-coating), or among the different preparation forms. PRBBs made in general dental practices were as retentive as those made in the University clinic. The "location" factor was found to be highly significant (p = 0.0001). The survival rates were 81% for maxillary PRBBs and 56% for mandibular PRBBs.

A meta-analysis of two different trials on posterior resin-bonded bridges.

In a meta-analysis the results of two different trials on posterior resin-bonded bridges (PRBBs) were combined. The common experimental variable 'preparation form' and the variable 'location' were combined for this analysis. The meta-analysis showed a highly significant effect for the variable 'location' (P < 0.001). Although the experimental variable 'preparation form' had no significant influence in the separate trials, the combined study revealed a significant effect for this variable on the retention of PRBBs (P = 0.03).

The influence of polymerization shrinkage of resin cements on bonding to metal.

During the setting of a resin composite cement (RCC) used as an adhesive between a resin-bonded bridge and tooth structure, the adhesion may be disrupted by the development of shrinkage stress. The aim of this study was to investigate the influence of the shrinkage stress of three different RCCs on their adhesive and cohesive qualities when bonded to metal surfaces in a rigid set-up. Two opposing parallel NiCr discs (Wiron 77) were mounted in a tensilometer at a mutual distance of 200 microns and cemented with Panavia Ex, Clearfil F2, or Microfill Pontic C. The alloy surfaces were treated by either electrolytic etching, sand-blasting, silane-coating, or tin-plating. During setting, the discs were kept at their original mutual distance to simulate the extreme clinical situation of "complete" rigidity, where the casting and the tooth cannot move toward each other. The developing shrinkage stress was recorded continuously. During setting, the adhesive strength of the RCCs to silane-coated surfaces was always higher than their early cohesive strength. Electrolytically-etched surfaces as well as sand-blasted surfaces showed, in almost all cases, adhesive failure. The tin-plated samples showed mainly adhesive failure at the metal/resin interface. The highest bond strength values were found for silane-coated surfaces in combination with Clearfil F2.

Treatment times for posterior resin-bonded bridges.

In a longitudinal clinical trial the treatment times needed for the fabrication of Posterior Resin-Bonded Bridges (PRBB's) were recorded and analyzed. From a total of 200 PRBB's with different designs and retention systems, 152 were selected for this analysis. The selected bridges were made by 12 operators: 3 university staff members and 9 general practitioners. The mean treatment time for PRBB's was 80 min. When posterior composite restorations were made in the abutment teeth, the mean treatment time increased by 25% up to 100 min. From the factors which were considered to influence the treatment time, a significant effect was found for "restorations", "operator" and "experience of the operator". The other factors considered, such as "tooth preparation", "retention system", "isolation method", "occlusion", and "location", showed no detectable effect on the treatment time. The results of this study are considered to be useful in further cost-benefit analyses.