Fracture Resistance of Upper Central Incisors with Different Endodontic Accesses Restored with Lithium Disilicate Partial Laminate Veneers

Abstract

Purpose: A treatment protocol involving the root canal treatment with conventional palatal access cavity and the partial veneer application may considerably reduce the fracture resistance of the teeth. On the other hand, labial access cavity within the partial veneer outlines followed with the partial veneer application may more successfully recover the lost fracture resistance of the endodontically treated teeth. In this regard, the present study aims to compare the fracture resistances of upper central incisors endodontically treated with palatal and labial accesses and restored with restorative resin composite and lithium disilicate partial veneers.

Materials and methods: Three groups consisting ten specimens each were prepared by using extracted sound human upper central incisors. Root canal treatments with palatal access, resin composite restoration of the access cavities and veneer restorations were applied to the first group (Group P). Root canal treatments with labial access, resin composite restoration of the access cavities and veneer restorations was applied to the second group (Group L). Veneer restorations were applied to the third group (Group C) without root canal treatment. Specimens were thermocycled and loaded to fracture in order to record their fracture resistances.

Results: The mean fracture resistance of Group C was observed to be significantly higher, compared to Groups P and L (P < 0.05). Fracture resistance of Group L was observed to be higher, compared to Group P, but the difference was not found statistically significant. Light microscope revealed that the specimens fractured in five different modes.

Conclusion: Although the mean fracture resistance of the teeth that endodontically treated with labial access cavity prior to the ceramic partial veneer application was higher in comparison with the teeth that endodontically treated with palatal access cavity prior to the ceramic partial veneer application, the difference was found statistically insignificant (P < 0.05).

Keywords: access cavity; fracture resistance; labial access; laminate veneer; palatal access; partial veneer.

Figure 1

A specimen tooth embedded in autopolymerizing acrylic cylinder with the help of the vertical positioner.

Figure 2

A specimen which is fixed in the housing of the special specimen holder, during fracture testing.

Figure 3

Bar graph presentation of the descriptive statistics.

Figure 4

Adhesive failure between the tooth and ceramic surfaces. No damage was detected in the tooth (A) or the porcelain (B).

Figure 5

Cohesive failure in which the tooth structure is not damaged (A), only the porcelain is fractured (B).

Figure 6

Cohesive failure in both the tooth (A) and the porcelain (B).

Figure 7

Cohesive failure in which the tooth structure is fractured (A) while the porcelain was not damaged (B).

Figure 8

Cervical fracture as cohesive failure mode. Fractured root fragment of the specimen tooth (A) and coronal region with intact PLV (B).