There are two complexes of risk factors:
1. risk factors controllable by dentists
Risk factors for longitudinal fractures that can be controlled by dentists in principle concern fillings, crowns and dental prostheses.
- Tooth loss without dental prosthesis, because the remaining teeth are subjected to higher loads,
occlusal surfaces not exactly adapted to fillings, crowns and dentures
- inadequate load due to dental prosthesis
- superhard, ceramic or non-precious metal functional surfaces on dental prostheses
Longitudinal root fractures were preceded by root canal treatment in about 90% of cases. Risk factors in root canal treatment and the subsequent treatment of root canal treated teeth are : (according to Tang W,et al as before)
- unnecessary loss of substance and weakening of the tooth when opening the canal accesses.
- inadequate exploration of the fine structures of the canal anatomy.
- Ignorance, carelessness and haste in the preparation of the root canal (type of instrument, degree of wear of instruments, exact determination of the preparation length, precision and caution in guiding the instruments, avoidance of unnecessary pressure on the canal wall, insufficient removal of drill chips during preparation, etc.).
- Collateral damage during rinsing of the root canal.
- Collateral damage during root canal filling.
- Tilting and jamming of all types of instruments in the root canal
- many criteria for pen selection.
- Precision and dimension of the pen preparation.
- Material selection and procedure for gluing or cementing root posts.
- Planning and precision of the execution of build-up fillings (anchoring, load-bearing capacity, bond with the tooth substance).
- The artificial crown does not sufficiently enclose the root at risk of fracture.
- Missing a necessary crown extension.
- Failure to protect the fragile tooth in time with a crown.
- inadequate static and caudal dynamic planning of the crown preparation.
- the crown does not fit perfectly at the edge and at the occlusal surface.
- lack of cleanliness, tightness and stability of the cementation.
2 Despite all due care, uncontrollable risk factors remain:
- Regional differences in chewing and eating habits
- Teeth grinding and pressing
How stable is a tooth after root canal treatment?
Stability depends on the size of the defect and the type of restoration after root canal treatment. Stress tests on removed teeth show the following values – assuming professional treatment.
|Load capacity in percent healthy tooth100Only filling, no root treatmentga) plastic or ceramic root canal treatmentin adhesive techniquesmall filling100medium filling80-100large filling70-80b) amalgam, gold or temporary small filling80-90medium filling70-90large filling50-80root treatment followedda) plastic or ceramic root canal treatmentin adhesive techniquesmall filling70-90medium filling50-70large filling30-50b) amalgam filling, Gold inlay or temporary fillingsmall filling50-70medium filling30-50large filling10-20c) Crown in optimal design with bonded build-up medium substance defect100-200large substance defect with root post80-120d) Crown with root post in faulty design5-50|
Improper handling may result in immediate fracture or extremely reduced stability.
Which teeth are affected?
The big cheek-teeth in the lower jaw and the small cheek-teeth in the upper jaw are particularly frakturgefährdet. Anatomical weak points and chewing force distribution play a role. About 50% of all fractures affect these teeth.
What types of cracks are there?
Enamel cracks extend from the surface to the surface of the dentin, where crack growth is almost always stopped by the structure of the dentin. They do not cause pain and do not require treatment.
Fractured cusps occur with the loss of a cusp. They run through enamel and dentin, deep fractures also through the pulp. The fracture surface is sensitive to hot-cold-sweet. Depending on size and load, a glued filling, a partial crown or a crown may be necessary.
Enamel dentin cracks (also called “infractures” or “cracks”) extend from the surface to deep into the dentin bone. When chewing, the parts of the fracture surface move slightly against each other, causing pain. Enamel dentin cracks are often difficult to detect. After some time germs penetrate from the oral cavity. If left untreated, enamel dentin cracks lead to inflammation of the pulp and fracture of the tooth, i.e. to tooth loss. A quickly fabricated crown protects the tooth from this. More: See download longitudinal cracks / enamel dentin cracks
Crown root fractures begin at the occlusal surface and end more or less deep in the root. The fragment hangs on the gums. The affected tooth hurts when chewing and on cold. Deep fractures mean tooth loss. If the fractures are less deep, a crown can be used after the fracture surface has been exposed with a crown extension or orthodontically by lengthening the tooth. More See download / Longitudinal cracks / Crown root fractures
Split teeth are completely broken lengthwise. They hurt when chewing and sometimes on cold.
root longitudinal fracture
1. partial cracks begin at the root canal wall and end somewhere inside the root wall. They can grow to complete cracks under load. Very little is known about details of crack growth.
2. complete cracks penetrate the entire wall of the root. They usually only become apparent after several weeks or even months due to symptoms.
(nach Tang W, Wu Y, Smales RJ. Identifying and reducing risks for potential fractures in endodontically treated teeth. J Endod. 2010;36(4):609-17)
(siehe dazu Ferrari M1, Cagidiaco MC, Grandini S, De Sanctis M, Goracci C. Post placement affects survival of endodontically treated premolars. J Dent Res. 2007 Aug;86(8):729-34.Mancebo JC, Jiménez-Castellanos E, Cañadas D.: Effect of tooth type and ferrule on the survival of pulpless teeth restored with fiber posts: a 3-year clinical study. Am J Dent. 2010 Dec;23(6):351-6.)