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Tighten your dentistry knowledge (Proceedings)

May 01, 2011

Skeletal anatomy

Skull types

There are 3 common head shapes in the dog and cat.

     • Mesocephalic or mesaticephalic - the most common head shape. Cephalic means head. Meso or mesati means medium. Typical mesocephalics are poodles, corgis, Labrador retrievers, and domestic shorthair cats.
     • Brachycephalic - brachy means short. Brachycephalic animals have a short and wide skull. This commonly results in crowded and rotated premolars. Typical brachycephalic animals are boxers, pugs, bulldogs, and Persian cats.
     • Dolichocephalic - dolicho means long and straight. These animals have long, narrow heads with an extremely long and thin mandible. Typical dolichocephalic animals are greyhounds, borzois, and sealpoint Siamese cats.

Maxillary

     • Incisive Bone: The rostral part of the maxilla. Within the body of the incisive bone are the six incisor teeth and the oval palatine fissures.
          o Dorsal aspect
               • Nasal aperture: This is composed of 2 symmetrical halves separated by the nasal septum
          o Ventral aspect
               • Incisivomaxillary suture: This articulates the incisive bone with the maxilla.
               • Incisive foramen : This is the opening to the incisivomaxillary canal
     • Maxillary Bone: The main body of the maxilla. Within the body of the maxilla are the premolars and molars.
          o Dorsal aspect
               • Infraorbital foramen: The most prominent feature of the dorsal maxilla. It is the opening to the cranial end of the infraorbital canal through which passes the infraorbital nerve, artery and vein.
               • Maxillary foramen: Opening to the caudal end of the infraorbital canal.
               • Pterygopalatine fossa: this is where the pterygoid and the palatine bones meet. Located in the rostral part of this fossa are two foramina.
                    √ Sphenopalatine foramen: This opens into the sphenopalatine canal which carrys the caudal nerves and vessels to the nasal cavity
                    √ Caudal palatine foramen: This is located ventral to the sphenopalatine foramen. This opens into the palatine canal which carries the anterior and posterior nerves and vessels to the hard and soft palate
               • Alveolar bone: This is the bone in which the tooth roots sit.
               • Alveolar jugum: The bony prominences on the buccal wall the alveolar bone
          o Ventral aspect
     • Interincisive suture: midline of the hard palate
     • Palatine sulcus: These are the bony troughs that sit on either side of the palatine suture. The major palatine nerves and vessels pass along this sulcus to supply the tissues of the hard palate
     • Major palatine foramen: This is located palatal to the upper fourth premolar
     • Minor palatine foramen: This is located palatal to the upper first molar
     • Interradicular septa: This is the bone that separates the roots of an individual tooth
     • Interalveolar septa: This is the bone that lies between teeth

Mandibular

The lower teeth are embedded in the mandible. The mandible is made up of symmetrical bilateral bones. The areas of the mandible are divided into three areas – the symphyseal, the body and the ramus.

     • Symphyseal Region: This contains the incisors and canine teeth
          o Mandibular symphysis: The strong fibrous joint that fuses the two bones of the mandible at the rostral aspect
          o Anterior mental foramen: These are located just below and between the first and second incisor.
     • The Body of the Mandible: This contains the premolars and molars.
          o Middle and posterior mental foramina: These are located on the buccal aspect of the mandible apical to the second premolar and third premolar respectively. The mental nerves run through the anterior, middle and posterior mental foramina innervating the lower lip and chin.
     • The Ramus of the Mandible is the perpendicular portion of the bone.
          o Coronoid process: Dorsal part of the ramus.
          o Condylar process: Helps form the TMJ. The neck and the head of the joint sit here.
          o Mandibular notch: Between the condylar and coronoid process
          o Angular process: A hooked eminence ventral to the condylar process. It serves as the attachment for the pterygoid muscle medially and the masseter muscle laterally.
          o Masseteric fossa: This is located on the buccal aspect of the ramus. It is a depression which serves as a point of insertion for the masseter muscle.
          o Mandibular foramen: This is located on the lingual aspect of the ramus. The inferior alveolar nerve passes through this foramen into the mandibular canal and innervates the mandibular teeth.