Effect of retained fractured instruments on tooth resistance to vertical fracture with or without attempt at removal.
OBJECTIVE
To investigate the effect of retained fractured endodontic instruments on root strength and to evaluate the effectiveness of several root filling materials in reinforcing roots that had undergone unsuccessful attempt at removal of fractured instruments.


METHODS
Seventy five mandibular premolar roots were divided into five groups. In group A (control), canals were prepared to a size F5-ProTaper instrument and filled with gutta-percha and TubliSeal sealer fragments. In the experimental groups (B, C, D and E), 4 mm of F5-ProTaper instruments were fractured in the apical one-third of the canal and then treated as follows: in group B, the fragments were left in situ without attempt at removal, and canals were filled with gutta-percha and TubliSeal sealer (GP No Removal). In groups C, D and E, an attempt at removal of the fragment was simulated by preparing a staging platform coronal to the fragment using modified Gates Glidden burs (No 2-5). Canals in group C were filled with gutta-percha and TubliSeal sealer (GP Removal), group D filled with Resilon (Resilon Removal) and group E with mineral trioxide aggregate (MTA Removal). Roots then underwent vertical fracture. Data were analysed using the one-way anova at P<0.05.


RESULTS
Roots in the GP Removal group had significantly lower values for mean force for fracture (404.9 N). There was no significant difference between the control group and GP No Removal (765.2 and 707.8, respectively). Resilon Removal and MTA Removal groups (577.3 and 566.6 N) were not significantly different from the GP No Removal group.


CONCLUSIONS
Leaving fractured instruments in the apical one-third of the canal does not appear to affect the resistance of the root to vertical fracture; Resilon and MTA appear to compensate for root dentine loss that occurred as a consequence of attempts at retrieval of fractured instruments when used as canal filling materials.
Madarati
A A
AA
School of Dentistry, The University of Manchester, Manchester, UK. ahmad.madarati@hotmail.co.uk
Qualtrough
A J E
AJ
Watts
D C
DC
D017607:Aluminum Compounds / Q000737:chemistry / Q000627:therapeutic use; D017610:Calcium Compounds / Q000737:chemistry / Q000627:therapeutic use; D003786:Dental Pulp Cavity / Q000473:pathology; D003799:Dental Stress Analysis / Q000295:instrumentation; D003804:Dentin / Q000473:pathology; D004338:Drug Combinations; D004868:Equipment Failure; D005547:Foreign Bodies / Q000150:complications* / Q000628:therapy; D006171:Gutta-Percha / Q000737:chemistry / Q000627:therapeutic use; D006801:Humans; D006813:Humidity; D008422:Materials Testing; D010087:Oxides / Q000737:chemistry / Q000627:therapeutic use; D012387:Root Canal Filling Materials / Q000737:chemistry / Q000627:therapeutic use; D018915:Root Canal Preparation / Q000009:adverse effects / Q000295:instrumentation*; D017640:Silicates / Q000737:chemistry / Q000627:therapeutic use; D013314:Stress, Mechanical; D013696:Temperature; D013997:Time Factors; D019227:Tooth Apex / Q000473:pathology; D014082:Tooth Fractures / Q000209:etiology*; D014092:Tooth Root / Q000293:injuries*; D015035:Zinc Oxide-Eugenol Cement / Q000737:chemistry / Q000627:therapeutic use
D017607:Aluminum Compounds; D017610:Calcium Compounds; D004338:Drug Combinations; D010087:Oxides; D012387:Root Canal Filling Materials; D017640:Silicates; D015035:Zinc Oxide-Eugenol Cement; C086631:mineral trioxide aggregate; C486892:resilon sealer; C048769:tubliseal; D006171:Gutta-Percha