In vitro comparison of endodontic posts in structurally compromised roots of maxillary incisors.

STATEMENT OF PROBLEM: The structurally compromised root remains a restorative challenge to the general dental practitioner.

PURPOSE: The purpose of this in vitro study was to investigate the fracture resistance of maxillary incisors with structurally compromised root canals, using 4 different post and core systems. A compromised root canal for the purpose of this study is defined as a flared canal resulting from destructive causes such as dental caries, tooth crown fractures, previous failing restorations or endodontic filing procedures.

MATERIAL AND METHODS: The crowns of 100 maxillary incisors were sectioned horizontally and 2mm incisally from the cement-enamel junction and randomly divided into 4 groups (n = 25 teeth) as follows: group MC: cast post and core (base metal, Ni-Cr); group GF: glass-fiber post and composite resin core; group CF: carbon fiber post with composite resin core and group Ti: prefabricated parallel-sided titanium post and composite resin core. All specimens were prepared with enlarged and flared root canals, representative of structurally compromised teeth, with composite resin filling the circumferential space between the post and roots of all specimens except the cast post and core. The specimens were subjected to an increasing palatal force at an angle of 130 degrees to the long axis of the tooth until fracture occurred. Loading forces were applied and measured using a universal testing device (model 1446, Zwick, Ulm, Germany).

RESULTS: Results showed cast post and cores had significantly higher fracture loads than the resin reinforced groups (P< .05). The difference in fracture resistance between the three resin reinforced groups (fiber posts and titanium posts) was found not to be significant (P > .05).

CONCLUSIONS: Maxillary incisors with compromised roots restored with cast posts, had fracture strength values more than twice that of the fiber post groups, but all the fractures resulted in unrestorable roots. With the prefabricated posts where resin filled the space between the post and the flared root walls, 60 to 80% of the failures resulted in non-restorable root fractures.

CLINICAL IMPLICATIONS: Within the limitations of this study, cast posts and cores provide the highest fracture resistance but resulted in not restorable fractures. Using the composite resin reinforcement technique to restore flared canals, none of the prefabricated posts used in this study appear to be superior to the others. The final clinical decision when restoring compromised canals should consider all patient-, dental- and material related variables for a more predictable outcome.