Identifying and reducing risks for potential fractures in endodontically treated teeth.

By Tang W, Wu Y, Smales RJ.

Date: 09/2011
Journal: JOE

Purpose: to identify and reduce the risks for potential tooth fractures.

Materials and Methods:

– Literature retrieved from Pubmed and searching selected journals.

Most highlighted Results: 

-Prevalance and Incidence of Tooth Fractures:

• Extensive amalgam and resin composite restorations without cuspal overlays increase the long-term risks for tooth fracture in both vital and endodontically treated teeth. 

•Vertical root fractures occur mainly in endodontically treated molar teeth and are underdiagnosed clinically. ØEtiology of Tooth Fractures

Noncontrollable risk factors: 

•- Reduced mechanical properties of tooth structure. 

•The modulus of elasticity and the fracture toughness of teeth might be reduced.

•The tensile strength of dentin is far lower than the compressive strength. •Different coronal and radicular tooth forms ,sizes ,anatomical locations, and root numbers result in the teeth being subject to extremely variable functional and parafuctional occlusal forces.

Controllable risk factors: (iatrogenic risks)

•Immature teeth with incomplete root formation -> apexification and root reinforcement.

•Endodontic access cavity preparation. ->  existing large carious lesions and intracoronal tooth      preparations would decrease the fracture resistance of the teeth. Care when preparing access cavities through ceramic restorative materials to avoid brittle cracking.

Root canal preparation.:

•Tooth type, canal wall thickness and root canal diameter and cross-sectional shape, root canal preparation instruments and preparation methods, and the size of the master apical file might all be involved in the increased risk for tooth fracture during and subsequent to endodontic therapy.

Tooth type: In one study: the force required to fracture the instrumented premolars was 30% lower than that required to fracture their noninstrumented counterparts.

•overinstrumentation of root canals with excessive removal of dentin and the presence of noncircular canals and thin canal walls, increase the risk for root fracture.

Root canal irrigation:

• The prolonged use of high concentrations of EDTA and NaOCl canal irrigants, particularly in combination, might increase the risk for root fracture. The irrigants should be eliminated completely from the root canals before endodontic obturation and before using resin-based adhesives.

Root canal obturation:

• Stable adhesion to root canal dentin walls.

–elastic modulus similar to dentin. Care should be taken during lateral compaction of root filling materials to avoid fracture.

Post Space Preparation:

•posts do not usually strengthen roots and also lead to apical microleakage when insufficient root canal obturation seal remains.

•fiber-reinforced posts and resin-based luting cements resulted in fewer severe root fracture failures than occurred previously with rigid metal alloy posts.

Coronal Restoration:

•Permanent restoration has to be placed immediately. 

•well-constructed coronal restoration has a greater effect on endodontic success than the quality of the endodontic obturation.

Endodontically Treated Teeth as Abutments:

•The use of endodontically treated teeth to support a precision attachment RPD, a distal-extension base RPD, or a posterior cantilevered FPD cannot be considered to be highly predictable.

Clinical significance: 

Potential tooth fractures might be reduced by practitioners being aware during dental treatments of controllable and noncontrollable risks.