Experimental craniosynostosis in growing rabbits. The role of the periosteum.

Reports on the role of the periosteum in premature sutural synostosis have been contradictory. The present study summarizes a series of six experiments designed to clarify these previously conflicting findings. Twenty-five male New Zealand White rabbits were divided into six experimental groups. In four of the groups, methyl-2-cyanoacrylate was used to glue the frontal and parietal bones together and temporarily immobilize the coronal suture. In the other two groups, the sutures were not immobilized. Polyethylene was used to separate the cyanoacrylate from the periosteum in two of the groups. The experiments were performed at 5 weeks of age, and the animals were killed at either 30, 45, or 180 days postoperatively. Metallic implants were placed in the frontal and parietal bones for monitoring growth and/or sutural immobilization. Sutural fusion was confirmed radiographically or histologically. Based upon the findings it seems that mechanical immobilization of a suture does not induce fusion of that suture in rabbits. Furthermore, it appears that the mere application of methyl-2-cyanoacrylate to the periosteum overlying a suture will consistently cause the formation of a bony bridge in growing rabbits but not in nongrowing animals. The adhesive does not consistently induce synostosis if the periosteum is excised.

Orthodontic extrusion of premolar teeth: an improved technique.

Traditional methods of tooth restoration may be impossible because of insufficient crown length. This article describes a method to orthodontically extrude "nonrestorable" premolar teeth. More than 100 patients who required premolar extrusion before prosthetic restoration have been treated with this procedure. Clinical records of a typical patient are shown to demonstrate the effects of the application of this technique, and a method of bracket placement on a severely broken down "nonrestorable" tooth is described. The advantages of the technique recommended in this article are described.

Gingival contour and clinical crown length: their effect on the esthetic appearance of maxillary anterior teeth.

Fractured, congenitally missing, or avulsed maxillary incisors can often jeopardize the esthetic appearance of the remaining maxillary anterior teeth after orthodontic treatment. In many cases the unesthetic appearance is related to the irregular clinical crown lengths of either the fractured teeth or those that have been substituted for the missing teeth. The results of five cases with either fractured or traumatically avulsed central incisors are reported. Selective tooth intrusion and restorative techniques were used during the finishing stages of orthodontic treatment to improve the final esthetic result. The advantages and disadvantages of the intrusion technique are discussed.