Abstract
The main movement of the temporomandibular joint of dogs and cats is in vertical dimensions (opening and closing the mouth). An objective evaluation of the vertical mandibular range of motion (vmROM) may favor early diagnosis of a number of conditions affecting the joint mobility. vmROM, corresponding to the maximum interincisal opening, was measured in 260 dogs and 127 cats anesthetized between June 2011 and April 2015 because of oral or maxillofacial problems and procedures. Animals with a known history of or having current diseases considered to hamper mandibular extension were excluded from the study. Dogs were divided into four subgroups, based on body weight: subgroup 1 (≤5.0 kg, 51 dogs), subgroup 2 (5.1–10.0 kg, 56 dogs), subgroup 3 (10.1–25 kg, 66 dogs), and subgroup 4 (>25.1 kg, 87 dogs). The mean vmROM of all dogs was 107 ± 30 mm (median 109, range 40–180); in subgroup 1 was 67 ± 15 mm (median 67, range 40–100), in subgroup 2 was 93 ± 15 mm (median 93, range 53–128), in subgroup 3 was 115 ± 19 mm (median 116, range 59–154), and in subgroup 4 was 134 ± 19 mm (median 135, range 93–180). The mean vmROM of the cats was 62 ± 8 mm (median 63, range 41–84). Correlations between vmROM, age, sex, and body weight were evaluated. In dogs, vmROM did not correlate with age, and in cats a weak positive correlation was found. vmROM and body weight were positively correlated in both populations, except dog subgroup 2. Overall, mean vmROM and body weight were significantly higher in male than in female, both in dogs and in cats. However, vmROM did not differ between sexes in any of the canine subgroups, and only in subgroup 4 male dogs were significantly heavier than females. Evaluation of vmROM should be incorporated into every diagnostic examination as it may be valuable in showing changes over time for every single patient.
Highlights
The temporomandibular joint (TMJ) is a synovial condylarthrosis composed by the mandibular head of the condylar process and the mandibular fossa of the squamous part of the temporal bone
Because of the shape and angulation of the condylar process of the mandible, in dogs and cats, the main mandibular movement is in vertical dimensions, with little lateral range of motion (ROM) [3, 4]
Data collected for each animal included signalment and measurements of vertical mandibular range of motion
Summary
The temporomandibular joint (TMJ) is a synovial condylarthrosis composed by the mandibular head of the condylar process and the mandibular fossa of the squamous part of the temporal bone. Joint mobility is favored by the action of the masticatory muscles, including the masseter, the temporal, the medial and lateral pterygoid, and the digastricus muscles. They all originate from the skull, attach to the caudoventral region of the mandible and, except the digastricus muscle, act adducting or raising the mandible, closing the mouth. Because of the shape and angulation of the condylar process of the mandible, in dogs and cats, the main mandibular movement is in vertical dimensions (opening and closing the mouth), with little lateral range of motion (ROM) [3, 4]
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