Periostomy and growth of the mandibular condyle in the rat

It has been shown that a release of periosteal tension may augment the growth of a long bone; however, similar experiments in the mandible have produced equivocal results. For further definition of the role of periosteal tension in the growth of the mandibular condyle, 80 young female Sprague-Dawley rats were randomly assigned to four equal groups: (1) sham, (2) condylotomy, (3) narrow periostomy, and (4) wide periostomy. All procedures were performed unilaterally. Lateral cephalograms, transcranial condylar radiographs, and metallic implants made possible the measurement of the actual increment of condylar growth over three post-operative periods: 0 to 14 days, 14 to 28 days, and 0 to 28 days. Analysis of covariance was performed (weight gain as the covariate) and, where overall significance was found, Turkey's HSD test was used for determination of individual group differences. Conservative, circumferential periostomy of the condylar neck as well as condylotomy failed to alter the condylar growth rate, whereas removal of a wide band of periosteum led to a small decrease. These findings suggest that, at least in the rat, periosteal tension plays only a minor role-if any-in the control of condylar/mandibular growth. Furthermore, a subsequent increase or decrease in condylar growth, in experiments that use a condylotomy model, cannot be attributed solely to a disturbance in periosteal integrity caused by the condylotomy.