IS NOT YOUR TOOTHBRUSH NOR YOUR BRUSHING TECHNIQUE!

When you bend a stick too much, the stick breaks from the stress. When you grind on a tooth too much, the tooth flexes, bends and the area where the tooth bends chips off and dissolves leaving a notch. The notch is at the bottom front of the dental crown near the gums and is called a dental abfraction. 

The anatomy of the maxillary bones is the first and main predisposing factor for gum recession, clenching and grinding a tooth towards the thinner part of the bone plate will cause the plate to reabsorb, leading to receding gums and triggering the notch formation.

Years ago dentists and hygienists believed that the primary cause of a dental abfraction was brushing hard but many patients who do not brush also have these tooth notches. Once the abfraction lesion is there the TOOTHPASTE used will in most cases, increase the size of the tooth notches, particularly with soft brushes, since they have a lot more bristles than a medium or a hard brush. 

The most common teeth to suffer with a dental abfraction is the bicuspid teeth, especially the upper bicuspids but the notches can also be found on cuspids ( vampire teeth ) and molars. The notch is below the dental crown on the root surface and is formed because the minerals that form the dental root have dissolved due to the grinding pressures. This exposes the tooth nerve and often causes tooth sensitivity to hot and cold. Desensitizing toothpastes, preferably natural, do help reduce the sensitivity from dental abfractions, but the real cause is from bruxism (tooth grinding and clenching). 

Some dentists attempt to fill the dental abfraction notches with white dental fillings, but because the tooth still flexes and bends, these white filling often pop out of the notch leaving a bigger hole than the original notch. We recommend that patients first get grinding guards or get minor occlusal adjustments before attempting to fill their tooth notches.

If a tooth has an abfraction, the occlusal loading on the tooth can be tested in centric occlusion and in excursive movements with occlusal marking paper. There is a good chance that the tooth with abfraction will have a heavy marking on one of the inclines of a cusp. This damaging lateral force produces stress lines in the tooth and results in tooth break down.

If the patient does not have heavy markings on the inclines, then he may have abnormal activity of the tongue. A ‘normal swallow’ is a swallow that is initiated with the tip of the tongue starting in the area of the maxillary anterior papilla, that continues with a peristaltic like action, pressing up against the roof of the maxilla, forcing the bolus posteriorly and finally down the throat. The tip of the tongue remains in the area of the anterior papilla during the entire swallow. Any other swallow is considered to be the result of abnormal tongue activity. The tongue should not press with any force into, against or between any teeth during the swallow.

We examine the area of abfraction with the patient’s teeth together and lips slightly parted to see whether the tongue is pushing into the tooth, or if salivary bubbles are visible coming between the interproximal spaces. Tongue thrusting can be the result of large tongues or obstructed airways.

When lateral tongue forces traumatize the teeth or if the key requirements of occlusion are not met, a series of deleterious events can occur

• Abfractions
• Sensitive teeth
• Loosening of teeth
• Excessive wear of teeth
• Change in alignment of teeth
• Bone breakdown and bone loss
• Broken or destroyed restorations
• Non-bacterial, non- plaque related gingival recession
• Opening of contacts.

 If during lateral excursions there is cuspid rise, the loadingforces of the excursive movement will be directed into the cuspid. Abfractions are frequently found in cases where malaligned cuspids cause initial lateral guidance forces to be exerted on the lingual incline of the buccal cusp of the maxillary bicuspid. Abfractions are also found in patients with slight anterior open bites. Here also, the guidance is coming from the bicuspids, rather than the cuspid.

The common clinical occurrence of class V restoration failure is often blamed on inadequate moisture control. Study by Rees J S and PH Jacobson shows that the presence of a class I restoration, especially an amalgam restoration on the same tooth can influence the prognosis of a class V restoration, They found that the presence of an occlusal restoration increased cuspal movements, which in turn increased the shear forces around the buccal class V cavity.

Lastly, it is important to remember that your cavity preparation and restoration of a class I cavity may cause an abfraction. It is well established that cavity preparation weakens a tooth, resulting in more cuspal movement under occlusal load. In a study by Rees J, under an eccentric 100 N occlusal load, a premolar with an occlusal amalgam restoration showed peak tensile and shear stresses in the buccal cervical region that were in excess of the known failure stress for enamel. Increases in the cavity depth of the occlusal amalgam restorations were found to increase cervical stress more than increases in cavity width.

Here is the last word, the weakening effect of an occlusal cavity preparation may contribute to the development of non carious cervical tooth loss.

Ref: 1. Rees JS & PH Jacobsen J Dent 26(4):361-7,1998

2. Rees JS Eur J Oral Sci 106(6): 1028-32,1998