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 cav ity preparation affected the retention of crowns in anterior teeth and then to determine whether this retention can be regained by amalgam o r 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 measur ed with a tensile testing machine. Retention values for all stages wer e 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 c ent 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 analys is 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 ca vities reduced the retention of the crowns, and subsequent restoration with amalgam or a post can regain the retention. Post-retained restor ations showed the highest retention when compared with the amalgam res torations, but the high standard deviation in the post group indicates that the amount of retention to be gained may be clinically unpredict able.