General Dentistry – Chewing Motion

Doc-t February 10, 2015
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The normal chewing motion – in slow motion.

This horse has an injury to his head (a bullet) that affects the movement of the jaw and subsequently has caused an abnormal wear pattern of the incisors.

Muscle atrophy of the right masseter muscle (cheek) from trauma to the head and the destruction of the nerve to innervate this area. The right side is now scared and preventing the jaw from opening fully. This decreased jaw motion prevents this horse from chewing properly. Note the normal muscling of the left cheek while the right cheek muscle is gone leaving the flat jaw bone. Floating does not improve the chewing motion significantly.

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Chewing motion horse 2 – 15 yr old TB with loss of right masseter muscle for over 10 years and atrophy of the left masseter muscle. See movie. Jaw has a limited range of opening, is painful to open wide, and is maxed in the picture of the opened mouth. Her right arcades are always sharper. Her left arcade is sheared with an acute occlusal angle, and tarter accumulates along the upper left arcade.
Chewing motion horse 2 – 15 yr old TB with loss of right masseter muscle for over 10 years and atrophy of the left masseter muscle. See movie. Jaw has a limited range of opening, is painful to open wide, and is maxed in the picture of the opened mouth. Her right arcades are always sharper. Her left arcade is sheared with an acute occlusal angle, and tarter accumulates along the upper left arcade.
Chewing motion horse 2 – 15 yr old TB with loss of right masseter muscle for over 10 years and atrophy of the left masseter muscle. See movie. Jaw has a limited range of opening, is painful to open wide, and is maxed in the picture of the opened mouth. Her right arcades are always sharper. Her left arcade is sheared with an acute occlusal angle, and tarter accumulates along the upper left arcade.
Chewing motion horse 2 – 15 yr old TB with loss of right masseter muscle for over 10 years and atrophy of the left masseter muscle. See movie. Jaw has a limited range of opening, is painful to open wide, and is maxed in the picture of the opened mouth. Her right arcades are always sharper. Her left arcade is sheared with an acute occlusal angle, and tarter accumulates along the upper left arcade.
Chewing motion horse 2 – 15 yr old TB with loss of right masseter muscle for over 10 years and atrophy of the left masseter muscle. See movie. Jaw has a limited range of opening, is painful to open wide, and is maxed in the picture of the opened mouth. Her right arcades are always sharper. Her left arcade is sheared with an acute occlusal angle, and tarter accumulates along the upper left arcade.
Chewing motion horse 2 – 15 yr old TB with loss of right masseter muscle for over 10 years and atrophy of the left masseter muscle. See movie. Jaw has a limited range of opening, is painful to open wide, and is maxed in the picture of the opened mouth. Her right arcades are always sharper. Her left arcade is sheared with an acute occlusal angle, and tarter accumulates along the upper left arcade.
Chewing motion horse 2 – 15 yr old TB with loss of right masseter muscle for over 10 years and atrophy of the left masseter muscle. See movie. Jaw has a limited range of opening, is painful to open wide, and is maxed in the picture of the opened mouth. Her right arcades are always sharper. Her left arcade is sheared with an acute occlusal angle, and tarter accumulates along the upper left arcade.
Chewing motion horse 2 – 15 yr old TB with loss of right masseter muscle for over 10 years and atrophy of the left masseter muscle. See movie. Jaw has a limited range of opening, is painful to open wide, and is maxed in the picture of the opened mouth. Her right arcades are always sharper. Her left arcade is sheared with an acute occlusal angle, and tarter accumulates along the upper left arcade.
Chewing motion horse 2 – 15 yr old TB with loss of right masseter muscle for over 10 years and atrophy of the left masseter muscle. See movie. Jaw has a limited range of opening, is painful to open wide, and is maxed in the picture of the opened mouth. Her right arcades are always sharper. Her left arcade is sheared with an acute occlusal angle, and tarter accumulates along the upper left arcade.
Chewing motion horse 1 – R masseter muscle atrophied and horse unable to open the mouth
Chewing motion horse 1 – R masseter muscle atrophied and horse unable to open the mouth
Chewing motion horse 1 – This is as far as he can open his mouth comfortably. R masseter muscle atrophy
Chewing motion horse 1 – R masseter muscle atrophied and horse unable to open the mouth
The atrophied right cheek muscle and the limited ability to open the mouth (see previous images) has caused the incisors to wear unevenly. The condition of the cheek teeth are unknown as even with potent pain medication, the mouth opens only wide enough to insert the float but not wide enough to examine with fingers or visually.
Chewing motion horse 1 – Long, thick stem hay being left by a horse with very sharp teeth. In this case it is caused by a horse with a diminished chewing pattern due to muscle atrophy of the right masseter muscle.
Categories: Teeth and Oral Cavity System

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