There is a wide variety of orthodontic appliances used for different situations to move teeth. The device shown in figure 183 was developed to spread the 307 and 309 to create room for the eruption of a trapped 308.
It is basically a metal spring positioned in a plastic cylinder with a washer and stud on each end to maintain placement between the teeth. The tension produced by the spring is adjustable, depending on the compression of the spring in regard to the space provided between the teeth. The tension is continuous and will move teeth gradually in a short period of time. In this case, adequate room for eruption of the 308 was obtained in a few weeks. Because tension is only placed on the proximal crown, the teeth are actually being tipped as can be verified by the steps produced on the occlusal surface(Fig. 182).
This is an ideal situation for providing space for a trapped cheek tooth where only increased space is required above the gum line. This horse is 5 years of age which means that this tooth has been trapped since he was 3 1/2. Unfortunately, this tooth did not erupt after the necessary space was provided at the crown level by the orthodontic device.
Weekly exams over a 3-month period showed no signs of any eruption of this tooth. Radiographs show that there are disturbing root changes consisting of distortion and blunting that may be hindering the eruption of this 308. A decision was made to surgically remove that distal potion of the root, followed by a root canal. An apicoectomy was performed on the 308 by removing a section of bone from the lateral mandible to expose the root. The skin and periosteum were elevated away from the bone, which created a proximal flap that would be sutured back into place after the apicoectomy and root canal were completed. The distal portion of the root was cut off just above the distorted area with a diamond cut off wheel. The cut was angled to allow better exposure of the pulp chambers for the root canal. Post surgical x-rays show the portion of root removed and the composite placed in the pulp cavities.
This surgical procedure was performed with the horse standing, using sedation and local anesthesia. This horse was difficult to handle and was reluctant to be caught prior to the surgery. He noticeably had an immediate change in disposition, which indicates relief of pain. The distorted root was caused by pressure from the inability of normal eruption to occur, which creates inflammation and pain. In my experience, most trapped premolars eventually abscess and form a drain tract through the distal mandible below the root if they are not extracted. Figures 185, 186, 187
The spring type orthodontic device was replaced immediately after the completion of the apicoectomy and root canal, to ensure space for eruption of the 308. Followup exams and radiographs show that the 308 is indeed erupting, but slowly. Normal eruption time would be approximately 6 months for a premolar to be in wear after erupting through the gum line. The 308 in this case erupted in wear in approximately 9 months post surgery. The orthodontic device was removed 3 months post surgery. This is an experimental procedure, but it does show promise as an alternative to extraction of trapped premolars. Early detection of a problematic eruption of a premolar would increase the chances for success and may only require an orthodontic device to provide the space necessary for eruption. Relief cuts on the crowns of the adjacent teeth are also an option that has been successful in certain cases if performed early enough. I prefer not to extract these premolars on young horses if at all possible, because of the disruption of the integrity of the arcade, however, extraction is still a reasonable treatment for this problem if no other options are available. Figures 188, 189