This study was performed in 15 horses of different breeds, aged between 5 and 19 years. Horses with low grade dental pathology were accepted, horses with moderate or severe pathological changes were excluded form the study.
The study was conducted in two stages. In stage 1 the chewing pattern of each horse was recorded. In a second step it was intended to examine whether the effects of routine dental treatment could be detected using the system described below. Each horse was measured 6 times, 3 times before and 3 times after dental treatment. Ten spheric marker balls of 1-2 cm diameter were glued to the skin at defined anatomical landmarks (marker 1: midline on frontal bone, marker 2: midline on nasal bone, level of incisura nasoincisiva, marker 3: right temporal bone dorsal to temporo-mandibular joint, marker 4: left temporal bone dorsal to temporo-mandibular joint, marker 5: ros-tral edge of right facial crest, marker 6: rostral edge of left facial crest, marker 7: 1 cm rostral to the right incisura vasorum, marker 8: 1 cm rostral to the left incisura vasorum, marker 9: caudal edge of the sutura intermandibularis, marker 10: fixed to marker 1). The horses were fed from the ground with hay of standardised quality. Masticatory movements were recorded with 6 high speed infrared cameras (Motion Analysis System Corp. ®, 120 Hz), placed in a circle around the horses feeding place. All recordings were performed under standardised conditions.
Comparison of the results of three consecutive measurements performed prior to dental correction revealed excellent reproducibility which was of the utmost importance for the further progress of the study.
The individual horse responded not uniformely to therapy. The rostro-caudal man-dibular movement (X-axis) decreased in 13 horses, an increased range of motion could be found in two cases, in one horse the motion range did not change. These changes were not significant. The results of the Y-axis (lateral jaw movement) were different. Lateral mandibular motion increased in 11 animals, of which 7 had significant changes. Four horses showed a decreased lateral mandibular excursion after dental treatment, which was found to be significantly different after routine dental treatment in only one case. The maximal opening of the mouth (Z-axis) revealed a significant decrease in 9 horses and an increased range of motion along the Z-axis in the remaining six horses with a significant difference in one animal.
Based on these findings it can be concluded that the alteration of masticatory move-ments should not be compared to a standardised chewing cycle but have to be evaluated for each horse individually before and after dental treatment.
The shapes of the chewing cycles in all three planes were similar to the results of previous studies. Repeated measurements showed that the direction of the chewing cycle shifted from clockwise to counter-clockwise, or the other way round, between different measurments but never during one single session. The mean duration of the masticatory cycle before dental treatment was 0,7 sec. (SD 0,04) and after dental treatment 0,69 sec. (SD 0,04). There were no significant changes (p = 0,115).
The described method proved its excellent reproducibility. Furthermore measure-ments are easy and quick to perform and non invasive. Therefore this method can be recommended for the recording of equine masticatory movements. Further studies will reveal whether or not this method has the potential to be implemented as a clini-cal routine diagnostic method.
Horse / masticatory movement / kinematic system / routine dental treatment