The effects of the spring-loaded posterior bite-block on the maxillo-facial morphology.

The purpose of this study was to determine the effects of the spring-loaded bilateral posterior occlusal bite-block on the maxillo-facial morphology, with emphasis on the response of the facial structures to the progressively increased vertical dimension. Our sample consisted of two groups: eleven open-bite subjects having a mean age of 10.30 years, treated with spring-loaded posterior bite-blocks over a mean period of 0.49 +/- 0.08 years (6 months); and twelve open bite subjects with a mean age of 9.84 years, treated by means of passive posterior bite-block and vertical chin-cap for a mean period of 0.67 +/- 0.03 years (8 months). The average daily use of the appliances was 16 hours. The study was carried out on lateral head films taken prior to and after treatment, which was concluded when an overbite of 1-1.5 mm was achieved. The results did not reflect any statistically significant difference between the groups when considering the changes in the horizontal growth pattern of the mandible, the decrease of the lower and the total anterior facial heights, or the overbite achieved by the two types of posterior bite-blocks. The artificial increase of the vertical dimension contributed to a statistically significant increase in the ramal inclination in both groups, though greater in the spring-loaded posterior bite-block group.