Fall 2002 Presentation Summary:

"Tooth Wear in Children and Adults"

Presented by Dr. Doug Knight

Summarized by Dr. Bruce Hawley, Northern Region Editor

Dr. Doug Knight identified three varieties of dental wear: erosion (caused by chemical factors such as bulimia), abrasion (when a foreign object abrades the tooth surface) and attrition (from functional or parafunctional tooth-to-tooth contact).

He posed a pertinent question: Do children with heavy attrition experience heavy tooth wear as adults, and, if so, what are the occlusal characteristics and correlates?

Dr. Knight performed a study using a sample of 223 patients from the University of Washington post-retention sample, in which each patient initially had at least one primary tooth, a good final orthodontic result, and full records, including post-retention records at 10 years or greater.

Tooth wear was scored numerically with 0 being a normal tooth, 1 showing some incisal wear, 2 showing wear into the dentin, and 3 identifying extensive wear into the dentin (greater than 2mm).

In the mixed dentition, the four primary canines exhibited the most wear, with a greater amount seen in the mandible and in males.

Immediately following orthodontic treatment, the four central incisors showed the most wear, with more in the mandible than in the maxilla.

Anterior overbite was negatively correlated—the deeper the overbite, the less wear.

Attrition on the lower primary canines and primary first and second molars was the most predictive of wear in the adult (post-retention) dentition.

Therefore, wear of the primary teeth is not independent of wear on the permanent teeth, and there may be a common etiologic factor involved.

Wear on younger males is more significant as a predictor than older males or their female counterparts.

In addition, Class I occlusions tended to have less overall attrition.

Dr. Knight recommends recognizing wear early in the patient’s development, as it may become more significant later on. It may also influence the doctor’s choice of retention protocol—the patient may need a night guard during or following orthodontic treatment.

Managing Patients with Significant Incisal Edge Wear

Often restorative needs will create orthodontic needs. Incisal edges can either be adjusted or restored if there are significant discrepancies.

According to Dr. Knight, the black triangle problem can result from either a loss of root parallelism or a misplaced interproximal contact, and is sometimes complicated by tooth wear.

If the roots are not parallel, as identified from an x-ray, it can be managed in orthodontic finishing.

If the roots are parallel, it is more likely that the interdental contact point is too close to the incisal edge. The orthodontist might disk the interproximal enamel surfaces in order to bring the contact point gingivally, which in many cases reduces or eliminates the triangle.

To Trim the Incisal Edge or Restore It?

Take into account esthetic considerations along with the functional elements of the occlusion.

Esthetic considerations:

• width-to-length proportions of the teeth
• facial proportions
• smile line
• acial mobility

Functional considerations:

• vertical overbite
• speech patterns
• freeway space
• incisal guidance
• occlusal plane

There is a range of normality of upper anterior tooth width to length. The acceptable ratio is between 75–90% width-to-length.

While every patient is unique, Dr. Knight finds that a ratio below 65% indicates a tooth that is too long and narrow, while above 90% a tooth tends to be short and square.

To increase crown length, one can augment the incisal edge restoratively, move the gingival line through gingivectomy or sliding a gingival flap, or use a combination of methods.

To set a goal, the ratio of crown size can be determined mathematically. The corrective method may depend on the amount of attached gingiva and gingival pocket depth.

Delayed altered passive eruption patients tend to have deep pockets, whereas delayed altered active eruption patients do not.

When adding to incisal edge length, one can orthodontically increase or decrease the overbite prior to restoration.

For a tooth that is going to be restored during orthodontic treatment, a good sequence is to remove the archwire and bracket in the morning, see the dentist for the provisional restoration, and rebracket the tooth later the same day.

The advantage of a mid-treatment provisional is that the dentist and patient can plan ahead for the final restoration post-orthodontia, and the orthodontist can finish treatment without special allowances for positioning the tooth.

In summary, both the status of the periodontium and attrition must be part of the decision-making on crown lengthening.

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