Key Points
Mixed dentition
- Cross-bites with displacement may be treated in the mixed dentition.
- Treatment of increased overjet can become lengthy if started early.
- Persistent digit-sucking habits usually resolve when appliance treatment is started.
- Upper incisor spacing usually reduces as the permanent canines erupt.
- An upper mid-line diastema may be a sign of an anomaly of tooth size or number.
14.5 ANOMALIES OF ERUPTION⎯THE ECTOPIC MAXILLARY CANINE
14.5.0 Introduction
The path of eruption of any tooth can become disturbed. Sometimes the reason is
obvious, such as a supernumerary tooth impeding an upper incisor (see 939HSection
14.6.1), but often it is obscure. In clinical orthodontics, the most common problem of
aberrant eruption is the impacted maxillary canine, which is second only to the third
molar in the frequency of impaction.
14.5.1 Prevalence of impacted maxillary canines
Ectopic maxillary canines occur in about 2% of the population, of which about 85%
of canines are palatal and 15% buccal to the line of the upper arch. The risk of
impaction of the upper canine is greater where the lateral incisor is diminutive or
absent⎯the lateral incisor root is known to guide the erupting canine. An impacted
canine can sometimes resorb adjacent incisor roots, and this risk may be as high as
12%. Incisor resorption is sometimes quite dramatic (940HFig. 14.17).
941H
Fig. 14.17 An |3 causing root resorption
of |12.14.5.2 Clinical assessment
During the mixed dentition stage the normal path of eruption of the maxillary canines
is slightly buccal to the line of the arch, and from about 10 years of age the crowns
should be palpable as bulges on the buccal aspect of the alveolus.
If not, an abnormal path of eruption should be suspected, particularly where eruption
of one canine is very delayed compared with the other side. Unerupted maxillary
canines should be palpated routinely on all children from the age of 10 years until
eruption.