PROGNOSIS OF RETENTION AND ABNORMAL POSITION OF CANINES
Authors: Doroshenko S.I. , Kaniura O.A. , Storozhenko K.V. , Irkha S.V. , Marchenko D.O. , Demianchuk Kh.M. 
Published: September 2020

Canines play an important role in the act of chewing and especially in the aesthetics of the face when you smile. They also serve as a guide to the movements of the mandible “canine management” and they are more resistant to carious lesions.

Germination of the canine embryos, unlike other teeth, occurs closer to the base of the jaw, so they erupt later than all front teeth, encountering a number of barriers and, above all, lack of space in the dental arch or its absence in case of early loss of temporary teeth.

Given that the canines erupt after the incisors and the first premolars, it is possible to prevent their retention and abnormal eruption in the dental arch. This can be done by timely detection of changes in their main inclination, both to the base of the jaw and relative to the inclination of the erupted teeth, especially lateral incisors, the roots of which serve as a guide axis for canine eruption.

The aim of the research was to increase the effectiveness of treatment of retention and abnormal eruption of canines by developing a method for their prediction and timely detection.

During the research, 52 patients aged from 7 to 25 years, were divided into four age groups, and they were examined and admitted for orthodontic treatment: I group – 12 patients (23,1%) aged from 7 to 9 years, - with early variable occlusion; II group – 16 patients (30,7%) aged from 10 to 12 years, - at the final stage of variable occlusion; III group – 12 patients (23,1%) aged from 13 to 15 years, - with early permanent occlusion; IV group – 12 patients (23,1%) aged from 16 to 25 years, - with a permanent bite.

All patients did not have acute occlusal abnormalities.

The following research methods were used during the examination: clinical (presence of abnormal position of the canines in parents and close relatives); anthropometric (measurements on diagnostic models); radiological, mainly orthopantomography (measurement of the axial inclination of the canines relative to the base of the jaw and adjacent teeth) and static research methods.

Research in all four groups determined that the inclining of the upper canines to the base of the jaw, averaged on the Maxilla – 86,4° (right side – 86,7°, left side – 86,2° with a difference – 0,5°), and on Mandible – 100,75° (right side – 100,7°, left side – 100,8° with the difference – 0.1°). Axial inclinations of the upper lateral incisors averaged 99,1° (right side – 95,8°, left side – 102,5° with the difference – 6,7°), and lower lateral incisors – 100,65° (right side – 100,7°, left side – 100,8° with the difference – 0,1°). The difference in the inclinations of the canines and lateral incisors on the Maxilla averaged 11,6° (right side – 9,5°, left side – 13,7° with the difference 4,2°) and on the Mandible – 8,9° (right side – 8,6°, left side – 9,3° with the difference – 0.7°). As for these indicators in patients of each of the four age groups, they varied significantly.

Conducted research has detected that the most objective indicator in the eruption of abnormal eruption of canines is the significant difference in their inclinations with lateral incisors, which serve as the guiding axis of eruption.

In patients from the I group, the difference in inclinations and lateral incisors was on the Maxilla on the right – 9,3°, on the left – 16,0°; and on the Mandible – right side 11,8°, left side 12,2°. In patients from the II group the difference in inclinations and lateral incisors was on the Maxilla on the right side – 13,8°, on the left side – 18,1°; and on the Mandible – right side 7,1°, left side 10,5°, in accordance. In the III group on the Maxilla from the left side – 10,6° and right side – 8,6°; and on the Mandible – 9,6° and 11,1°, in accordance. The difference in inclinations of these teeth was on the Maxilla – right side 4,3°, left side 12,3°; and on the Mandible – 6,0° and 3,3°, in accordance.

On this basis, we proposed a method for predicting abnormal eruption of the canines using the constructed “canine triangle” on the orthopantomogram formed by the intersection of the axial inclinations of the canines and lateral incisors (ւВ) with the plane of the base of the jaw, on which the segment (a) is the base of the triangle.

The more difference between the inclinations of the canines and lateral incisors ( > 10°), that is the larger the value (ւВ), the longer the size of the base (a) of the triangle, which indicates the difficulty of eruption of the canines in the future (outside the dentition or retention).

Timely detection of a significant difference in the inclinations of canines and lateral incisors can prevent abnormal eruption and retention of canines by adjusting their inclinations with lateral incisors and eliminating the lack of space in the early stages of formation of the dental apparatus.