Head trauma commonly involves damage to the dentition, including fractures of the tooth crown and/or root, fractures of the alveolar bone, and tooth displacement-type injuries. Appropriate treatment can substantially improve the prognosis for continued function of the involved teeth.
Thorough assessment of history can provide many clues to guide appropriate treatment. Dental trauma patients without appropriate history should be evaluated for associated cranial disease. Complete examination of dental structures and treatment of dental injuries always involves general anesthesia, so particular attention should be paid to the neurologic status of the patient prior to the use of anesthetic agents. The maxilla and mandible should be assessed for fractures, the TMJ joints should be palpated to the extent the patient will allow, and soft tissues should be carefully examined for lacerations and the presence of foreign bodies.
Displacement injuries include concussion, subluxation, luxation, and avulsion.
Treatment must take into account possible damage to the neurovascular supply entering the apical area of the tooth, as well as damage to the attachment apparatus holding the tooth in place (cementum, periodontal ligament, alveolar bone, attached gingiva). Damage to the neurovascular supply may lead to necrosis of the pulp, eventual infection, root resorption, and/or calcification of the root canal. Damage to the root cementum can lead to areas of root resorption secondary to invasion of the external root surface by osteoclast-like cells. These areas may heal spontaneously or may lead to resorption of the root and gradual replacement with bone. If the periodontal ligament is lost, the tooth can become connected directly to bone, which is termed dentoalveolar ankylosis. This can predispose the tooth to future fracture. Successful treatment of displacement injuries depends on a number of prognostic factors, including age of the patient, periodontal status of the tooth, the severity of the injury, the time elapsed between injury and treatment, the extent of bony and soft tissue injury, the degree of contamination, the type of displacement in jury, cooperation of the patient, and willingness of the owner to provide the needed aftercare.
The types of displacement injury are defined as follows:
Concussion: Concussive injuries result in no appreciable laxity, bleeding, or distinct radiographic signs. In response to injury, pulp tissue can swell or bleed like any other soft tissue. This is significant because the root canal system is a “closed space,” with minimal ability to release excess pressure. When a concussive injury is suspected, treatment with anti-inflammatory drugs may be indicated. These teeth should be monitored closely for color change, which usually indicates that the tooth has died.
Subluxation: The tooth is slightly mobile, but is not displaced from the alveolus. Radiographic signs are typically lacking. Treatment for subluxation is the same as for concussion.
Luxation: The tooth is mobile, is still within the alveolus, but is displaced from its normal position.
Avulsion is the most severe form of displacement injury, referring to complete displacement of the tooth from the alveolus. Avulsion injuries have the worst prognosis all displacement injuries. This is due to the complete loss of blood supply, as well as damage to the periodontal cells on the root surface. Surprisingly, immature avulsed teeth (with an incompletely formed apical area of the root) do have some chance of regaining their blood supply if replanted immediately. Mature teeth with a closed apex will always remain non-vital and require root canal therapy if re-planted. Re-implantation of an avulsed tooth should be considered in working dogs, in a show dog that might be disqualified if missing a tooth, or if an owner prefers to maintain the tooth.
Successful re-plantation requires attention to several factors. Most critical is the time that the tooth is allowed to dry outside the mouth. Once the periodontal ligament cells have died, there is no chance for normal attachment to occur. If the tooth cannot be replanted immediately, it should be placed in a transport media that will help support vitality of these cells. If no specific tooth transport media is readily available, milk will suffice for a few hours. The alveolar socket and the tooth should be rinsed with saline to remove all foreign material, with care taken to avoid removal of any soft tissues present on the root and alveolar socket surfaces. The tooth is then placed into the alveolus in a normal position, ensuring no abnormal contact with other teeth when the jaws are in complete occlusion. Lacerated soft tissues are sutured as necessary. If no alveolar bone fracture is present, a semi-rigid splint is placed for 7-10 days which will allow some physiologic movement of the tooth. If the alveolus is fractured, a rigid splint is placed in a similar fashion as that used for a luxated tooth. Almost all avulsed teeth will require root canal therapy, especially if avulsed for longer than 1 hour before re-plantation, or if the tooth has closed root apices.
In the case presented here, a 6 ½ year-old mix breed dog presented with an avulsed left upper canine tooth secondary to a fight. The tooth was found in a mud puddle (really) shortly after the incident, was rinsed thoroughly and was placed into milk within 10 minutes of becoming displaced. The patient presented shortly after the injury. Under anesthesia, the avulsion site was radiographed, and the entire alveolus was noted to be intact. The tooth was rinsed gently in saline and then replaced into the alveolus. The soft tissues were then sutured, taking care to maintain a normal anatomic position of the re-planted tooth. A wire and acrylic splint incorporating the avulsed tooth was then fashioned, running from the left upper second incisor to the left upper second premolar. Normally the splint would have run from the affected tooth to the contralateral canine tooth, but in this patient the right maxillary canine tooth was missing and the splint location was adjusted accordingly.
The splint was removed three weeks later, and the tooth was treated with root canal therapy at that time. Near-normal stability was present at the time of splint removal and the root canal procedure went well.
In this patient, several factors contributed to the successful outcome. Rinsing the debris off the tooth, placing the tooth into an appropriate transport medium and rapid replacement of the tooth into the alveolus all helped preserve the vitality of the periodontal ligament cells.