An in vitro study of the effect endodontic access preparation and amalgam restoration have upon incisor crown retention

In Vitro Comparison of Porcelain Fused to Metal Crown Retention after Endodontic Access and Subsequent Restoration: Composite, Amalgam, Amalgam with Composite Veneer, and Fiber Post with Composite

INTRODUCTION

The aim of this study was to evaluate the effect of different access opening restorative materials on crown retention.

METHODS

Thirty-eight extracted molars were mounted in resin and prepared for porcelain fused to metal (PFM) crowns. The crowns were fabricated and cemented with zinc phosphate, and the force to displace it was measured with a tensile-testing machine before and after endodontic access preparations. The endodontic access area, crown preparation axial wall, and preparation surface area were measured for comparison. The crowns were then recemented, and access openings were restored with either amalgam or composite before displacement force was remeasured. The restorative material was removed from each access opening; access area was measured and restored again (amalgam with composite or fiber post with composite) for displacement force to be remeasured. Paired t test was used to compare the means of displacement between groups. One-way analysis of variance was used to compare the mean outcome measure within the groups.

RESULTS

Statistical analyses showed retention after unfilled access was significantly lower than intact crowns. Amalgam, composite, amalgam + composite, and fiber post + composite increased retention beyond the original value. There was no statistical difference among the different restorative protocols. Qualitative results indicate that the restorative material remains in the crown after displacement regardless of the material used to restore the access.

CONCLUSIONS

The results from this study suggest that an endodontic access cavity decreases retention of a PFM crown. However, subsequent restoration with amalgam, composite, amalgam + composite, or post + composite may increase the original retention of the crown.

The effect of endodontic access on all-ceramic crowns: A systematic review of in vitro studies

OBJECTIVES

The aim of this systematic review was to identify from in vitro studies the effect of endodontic access on the fracture resistance and damage around the access cavity of all-ceramic crowns.

DATA

The articles identified were screened by two reviewers according to inclusion and exclusion criteria. The reference lists of articles advanced to second round screening were hand searched to identify additional potential articles. The risk of bias for the articles was independently performed by two reviewers.

SOURCES

An electronic search was conducted on PubMed/Medline, Web of Science, Scopus and Embase databases with no limitations.

STUDY SELECTION

383 articles were identified, of which, eight met the inclusion criteria and formed the basis of this systematic review. Factors investigated in the selected articles included the, presence of microcracks at the access cavity, repair protocol, ceramic type, crown fabrication method, luting agent and grit size of the diamond bur. The risk of bias was deemed to be high for three, medium for two and low for three of the reviewed studies. The high level of heterogeneity across the studies precluded meta-analyses.

CONCLUSION

Based on the currently available scientific evidence, a 'best practice' protocol with regard to improving the fracture resistance of endodontically accessed and repaired all-ceramic crowns cannot be conclusively identified. However, some key factors which potentially impact on the fracture resistance of endodontically accessed and repaired all-ceramic crowns have been isolated. Cautious clinical interpretation of these factors is concluded for the maintenance of the crown as a permanent restoration.

CLINICAL SIGNIFICANCE

Key factors which impact on the fracture resistance of endodontically accessed and repaired all-ceramic crowns have been isolated from in vitro studies. Cautious clinical interpretation of these factors is advised for the maintenance of the crown as a permanent restoration.

Fate of vital pulps beneath a metal-ceramic crown or a bridge retainer

AIM

To investigate the incidence of and factors associated with pulpal necrosis in vital teeth restored with metal-ceramic crowns (CMCs) or crowned as part of a fixed-fixed bridge.

METHODOLOGY

Patients who had a CMC or bridge retainer (BR) placed on a tooth with no previous history of root canal treatment from 1981 to 1989 were retrieved from computer records. The collated patients were randomly selected and their clinical records examined. Those who satisfied the inclusion criteria were contacted and offered a review. After clinical examination, long-cone paralleling periapical radiographs were taken of the selected teeth, which were then assessed by two precalibrated operators to ascertain the pulpal status. Factors that might contribute to loss of pulp vitality and the tooth type were also recorded. The collected data were analysed statistically using the chi-square test and subject to Bonferroni adjustment where indicated.

RESULTS

The numbers of preoperatively vital teeth in the CMC and BR groups were 122 and 77, and the mean observation periods were 169 +/- 25 (SD) and 187 +/- 23 months, respectively. In the CMC group, 19 failed cases (15.6%) were due to an endodontic reason; total number of failures was 34. In the BR group, 25 (32.5%) showed signs of pulpal necrosis; a significant association with maxillary anterior teeth was noted. The survival rates for pulp vitality were 84.4% (CMC) and 70.8% (BR) after 10 years, and 81.2% (SC) and 66.2% (BR) after 15 years. The difference between the two groups was significant.

CONCLUSION

The survival of the vital pulp in teeth restored with a single-unit CMC was significantly higher than those serving as an abutment of a fixed-fixed bridge. Maxillary anterior teeth used as bridge abutments had a higher rate of pulpal necrosis than any other tooth types.

The effect of endodontic access cavity preparation and subsequent restorative procedures on molar crown retention

Preparation of an endodontic access cavity through a full crown may affect its retention. This study was undertaken to investigate the effects on molar crown retention of endodontic access cavities and their subsequent restoration. Thirty human molars were mounted in resin, crown preparations were cut and their surface areas were determined. Vented metal copings were cemented with zinc phosphate and the forces required to displace each coping were measured using a tensile-testing machine. The copings were recemented, access cavities were cut and their surface areas determined prior to the displacement forces being re-measured. The copings were recemented, assigned to two groups, and the access cavities were restored--Group 1 with amalgam; Group 2 with glass ionomer (GIC). Displacement forces were re-measured and the copings were recemented. The occlusal margins of the access cavities were bevelled and restored again prior to displacement forces being remeasured. Mean displacement forces were - Group 1: Original (kg force), 37.86 +/- 3.97; After access cavity, 29.28 +/- 3.22; Amalgam, 50.21 +/- 4.71; Amalgam + bevel, 46.45 +/- 6.21. Group 2: Original, 42.77 +/- 4.49; After access cavity, 39.25 +/- 5.91; GIC, 48.11 +/- 3.55; GIC + bevel, 39.63 +/- 5.31. Statistical analyses with paired t tests showed that retentive values with access cavities were significantly lower than with intact crowns. Amalgam or GIC restorations increased retention beyond original values, significantly with amalgam. Bevelled occlusal margins decreased retention of crowns with restored access cavities but this was not significantly different from the original values. A significant relationship existed between total surface areas of the crown preparations, areas of the occlusal tables, and retentive values for crowns without access cavities. The access cavity area, as a proportion of the total area of the preparation, was related to the decrease in retention.

The effect of endodontic access cavity preparation and subsequent restorative procedures on incisor crown retention

Endodontic treatment often will require access through existing crowns. This study was undertaken to determine whether endodontic access cavity preparation affected the retention of crowns in anterior teeth and then to determine whether this retention can be regained by amalgam or post-retained amalgam restorations. Twenty extracted human incisors were mounted in acrylic blocks and prepared for crowns. Metal copings were fabricated and cemented with zinc phosphate cement and the forces required to displace the copings after various procedures were measured with a tensile testing machine. Retention values for all stages were compared with the initial retentive value for each coping without an access cavity which was set at 100 per cent. Group one specimens had the following means: copings with access cavity, 85.64 +/- 28.65 per cent of the initial values; amalgam flush with lingual dentine, 95.81 +/- 36.2 per cent; amalgam flush with coping, 114.89 +/- 34.5 per cent. Group two means were: copings with access cavity, 89.95 +/- 21.42 per cent; posts and amalgam, 177.37 +/- 77.5 per cent. Statistical analysis with the two sample t test showed that retention with post-retained amalgam restorations showed significantly higher values when compared with access cavities without restorations (p < 0.05). Retention values for post-retained restorations were significantly different from those just using amalgam. This study demonstrated that endodontic access cavities reduced the retention of the crowns, and subsequent restoration with amalgam or a post can regain the retention.(ABSTRACT TRUNCATED AT 250 WORDS)