Dentitions Measurements
There is a certain numerical relationship between the size of the teeth and the size and shape of the dentition.
In physiological occlusion, the numerical ratio of the size of the permanent incisors of the upper and lower jaws is called the Tonn index (Tonn) which is normally 1.33.
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Dolgopolova Z.I. (1973) studied the ratio of the sums of the crowns width of the deciduous upper and lower incisors in physiological occlusion using the Tonn method and confirmed their correlation. The Dolgopolova index is 1.30.
Bolton Anthropometric Measurement
The mesiodistal dimensions of the 12 lower jaw teeth (from the first molar on one side to the first molar on the opposite side) are summed up and divided by the sum of the mesiodis-tal dimensions of the 12 upper jaw teeth. The resulting ratio expressed as a percentage is called «overall». The normal value is 91.3%.
In the same way, the ratio of the mesiodistal dimensions of the front teeth (from the canine on one side to the canine on the opposite side) is determined. In doing so, an «anterior» ratio is obtained. The normal value is 77.2%.
The proposed technique allows the doctor to determine in which area the teeth should be extracted when treating an occlusion anomaly accompanied by crowding in the anterior region. If the overall ratio in mesial occlusion is greater than 91.3% and the anterior ratio is less than normal or equal to 77.2%, then it is necessary to reduce the lower dentition in its lateral parts. If the overall ratio is less than normal or equal to 91.3% and the anterior ratio is greater than 77.2%, the lower dentition in the anterior section should be reduced. Conversely, if in distal occlusion the overall ratio is less than 91.3% and the anterior ratio is greater than or equal to 77.2%, then the upper dentition should be reduced in the lateral sections. If the overall ratio is greater than or equal to 91.3% and the anterior ratio is less than 77.2%, the upper dentition in the anterior section should be reduced