Force Values and Rate of Movement in Closure of Space Between Maxillary Central Incisors

Abstract

A study was conducted to determine the rate of tooth movement, pain response and tooth mobility when closing the space between the maxillary central incisors. Twenty children age 8 to 18 were selected who had a minimum of two millimeters space between the maxillary centrals. The forces used were 10, 20, 50, 75, 125, and 200 grams. It was found that there was a fast initial movement followed by a latent period of varying lengths of time. In most instances the lag period is from seven to ten days, but in three cases it was as high as eighteen to twenty-five days. The five patients in the 50 gram group had the shortest latent period. The three patients with the extended latent periods happened to be the three oldest patients in the sample. That is, they were from 16 ½ to 18 years of age, while the average age for the entire sample was about 11 years. After the latent period, the rate of movement in the 10 and 20 gram groups was slower than the rate of movement with higher force. When the higher forces in the 125 and 200 gram range were used, the rate did not continue to increase but was comparable to the rates in the 50 and 75 gram groups. What was noticed in the higher range of force was an increase in the amount of pain and mobility. From these observations it was felt that for tipping of the maxillary centrals the optimal range of force to be used would be 50 to 100 grams. At these forces the rate of tooth movement was rapid and the patient’s response to pain was at a minimum.