Introduction

Level bite is a condition in which the incisor teeth meet edge on edge. This is a traumatic form of bite that can cause attritional wearing down of the teeth into a closed bite (Wiggs & Lobprise 1997). Continued attrition will lead to dentin and possible pulp exposure (Bellows 2004). Anterior crossbite occurs when one or more upper incisors are displaced lingually to the lower incisors when the teeth are in occlusion (Harvey & Emily 1993). Treatment includes the use of orthodontic appliances and materials to correct the occlusal relationship (Legendre 1991), such as the use of maxillary expansion devices, brackets and arch bars or mandibular buttons and elastic chains or both appliances (Wiggs & Lobprise 1997). This study was designed to determine which optimum orthodontic care is required for efficient treatment in level bites and anterior crossbite in Rottweiler dogs.

Materials and Methods

Twelve Rottweiler dogs, 8 male and 4 female, 5 months to 5 years of age, were selected for this study. The dogs were examined by making a visual inspection of the malocclusion and each one had either level bite or anterior crossbite. Lower incisors were evaluated to know if there was interproximal space between them, mainly between third incisors and canine teeth. Upper incisors were also evaluated by observing the dental arch position. The animals were divided into three groups according to the need of a treatment: (G1) dogs with level bite and presence of space between lower incisors, (G2) level bite and absence of space to move incisors lingually, (G3) dogs with anterior crossbite. After fasting for 12-hours, dogs were tranquilized with acepromazine (0.05mg/kg/IM) and meperidine (1mg/kg/IM). Under general anesthesia using propofol induction (2mg/kg/IV), endotracheal intubation and maintenance with isoflurane in oxygen the orthodontic treatment was performed. Heart rate and blood pressure were continuously monitored by means of an electrocardiogram and a Doppler with pressure manometer respectively. The respiration rate was visually evaluated and the body temperature monitored and maintained by using a warm electric heating pad. In the G1 (n = 6) mandibular buttons and elastic chains were applied; G2 (n = 2) mandibular buttons with elastic chains and maxillary brackets and an arch bar were used; G3 (n = 4) a maxillary expansion device was applied. The animals were rechecked weekly for evaluation of tooth movement.

Results

The dogs adapted themselves very well to the treatment showing discomfort signs only within the first 24 hours. Most dogs obtained a harmonious occlusion only by using orthodontic appliances, however in five animals with small incisor crown, resin restoration had to be made to assure that upper and lower incisor edges overlapped slightly. From five animals with small incisor crown, two had level bite with space between the lower incisors (G1), one showed level bite without space between the lower incisors (G2) and two of them showed anterior crossbite (G3). Only one dog of the G2 had broken arch bar and it was necessary to replace the orthodontic device. The 5 to 18 months old dogs ended the treatment within 45 days approximately. The 2 to 5 years old dogs reached the final treatment within 5 months approximately. Prophylaxis was needed in all the animals after removing the appliance.

Discussion

In normal canine occlusion the upper incisors are just rostral to the lower incisors and the incisal tips of the lower incisors contact the cingula and cusps of the upper incisors (Emily & Penman 1994). Abnormal tooth alignment occurs from jaw length discrepancy, tooth malposition or a combination of both (Bellows 2004). A malocclusion could be due to genetic origin or caused by previous trauma (Tholen 1990). Because of the genetic aspect of this disorder, owners should be counseled about the hereditability of this abnormality (Wetering 2007). Anterior crossbite is common in domestic dogs and it occurs in a wide variety of head shapes and sizes (Harvey & Emily 1993). Veterinarians have an ethical and medical responsibility to provide animals with a healthy, comfortable, functional bite whenever possible (Wetering 2007). Abnormally positioned teeth may contribute to plaque and food accumulation, predisposing the dog to periodontal disease (Bellows 2004). The types of orthodontic treatment made use of in this study, although simple to apply, must have technique. The advantages of this appliance include minimal materials, ease of application, patient tolerance and minimal homecare requirements (Gengler 2004). Buttons and elastic chains can be used for multiple incisor movements in the maxilla or mandible, but can result in imbrication because it also produces mesial or distal movement of the adjacent anchor teeth (Wiggs & Lobprise 1997). This treatment was used when there was space between mandibular incisors teeth permitting lingual movement. Brackets and arch wears can be used attached to the maxillary canines with finger springs to push the abnormally placed teeth forward (Bellows 2004). This technique was used with buttons and elastic in the G2 for a lineup of lower incisors and to move upper teeth forward. A maxillary expansion device is a maxillary acrylic appliance with an expansion screw device (Bellows 2004). This study showed that dogs younger than two year responded more rapidly to the treatment. These findings agreed with the literature that suggests that young bone is less resistant to tooth movement and young animals typically accept placement of oral appliances easier than older ones (Wiggs & Lobprise 1997).

Conclusions

A correction of level bite and anterior crossbite is indicated as a preventive action to dentin and possible pulp exposure. The dogs adapted very well to the orthodontic treatment and the time needed for tooth movement is relatively short. As malocclusions can have a genetic factor, it is indicated to remove these animals of reproduction.

References

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3.  Harvey CE, Emily PP. 1993. Small Animal Dentistry. Mosby, St. Louis, p.266-296.

4.  Legendre LFJ. 1991. Anterior crossbite correction in a dog using a lingual bar, a labial bow, lingual buttons, and elastic threads. J. Vet. Dent. 8:21-25.

5.  Emily P, Penman S. 1994. Small Animal Dentistry. 2nd edition. Pergamon Press, New York, p.1-13.

6.  Tholen M. 1990. Orthodontics, p.232-240. In: Tholen M & Bojrab MJ. (Ed.) Small Animal Oral Medicine and Surgery. Lea & Febiger, Philadelphia.

7.  Wetering AV. 2007. Orthodontic correction of a base narrow mandibular canine tooth in a cat. J. Vet. Dent. 24:22-28.

8.  Gengler WR. 2004. Masel chain appliance for orthodontic treatment. J. Vet. Dent. 21:258-261.