From the beginning--oral anatomy and physiology (Proceedings)

The implementation of veterinary dentistry is increasing in both private and specialty practices. More responsibility is being delegated to the technician, and the expansion of this service relies heavily on a well trained and informed staff. We must remember it is the veterinarian's role to make a diagnosis and prescribe treatment, but it is the technician's role to carry out these orders with competence. You, as the technician, must earn that trust by having a good understanding of dentistry.

Occlusion

The patient's occlusion is primarily determined by his or her genetics and is defined as the normal position of the teeth (coming together in harmony) when the patient closes his/her jaws. When evaluating occlusion, one should rely not on the positioning of the incisors, but of the canines and pre-molars, whose relations will often give a better indication to any malocclusion, if present. A patient's head shape will affect the positioning of the teeth, and malocclusions will occur in any of the three head shape categories (dolicocephalic, mesocephalic and brachycephalic), with brachycephalics being the most commonly affected. A normal occlusion is one with a scissor bite and an interdigitation of the canines and pre-molars, also known as the pinking shear effect.

·            Scissor bite- the normal relationship of the maxillary incisors overlapping the mandibular incisors, whose incisal edges rest on or near the cingulum on the lingual surface of the maxillary incisors.

·            Interdigitation- where the tips of the pre-molars oppose the interdental space of the opposite arcade.

Types of malocclusions

·            Malocclusion- abnormal tooth positioning. These can be painful/ uncomfortable and cause severe oral pathology.

·            Prognathism- having a longer or protruding jaw.

·            Brachygnathism- having a short jaw.

·            Anterior crossbite/ Rostral crossbite (RXB)- reverse scissor occlusion of one, several or all of the incisors.

·            Posterior crossbite/Caudal Crossbite (CXB)- an abnormal relationship of the carnassial teeth, where the normal buccolingual relationship is reversed.

·            Wry bite- a deviation from the mid-line to the left or right.

Classes of Malocclusions: New Vocabulary

·            Neutroclusion (Class 1 malocclusion; MAL/1): A normal rostral-caudal relationship of the maxillary and mandibular dental arches, with mal-position of one or more individual teeth. This is related to rostral and caudal crossbite

·            Mandibular distoclusion (Class 2 malocclusion; MAL/2): An abnormal rostral-caudal relationship between the dental arches in which the mandibular arch occludes caudal to its normal position relative to the maxillary arch. (mandible is either too short or the maxilla is too long).

·            Mandibular mesioclusion (Class 3 malocclusion; MAL/3): An abnormal rostral-caudal relationship between the dental arches in which the mandibular arch occludes rostral to its normal position relative to the maxillary arch (maxilla is too short or mandible is too long.).

General anatomy

·            Maxillary-pertaining to the upper arch, this consists of many bones.

·            Mandible-lower jaw, there are 2: the left and right mandible.

·            Mandibular symphysis-the point at which the mandibular processes fuse, forming the mandible.

Oral Anatomy

Basic knowledge of dentition is a must for the technician to effectively communicate with the Veterinarian.

           Tooth development

·            Initiation stage- the interaction between mesenchymal tissue and ectodermal tissue.

·            Bud stage- the dental lamina will proliferate into the mesenchyme to form buds which teeth will develop from.

·            Cap stage- during this stage there are three structures that develop: the enamel organ (ectodermal cells that produce enamel, this will determine the shape of the tooth), the dental papilla (mesenchymal tissue which will form dentin and pulp), and the dental sac (which will develop the periodontium). These are collectively known as the tooth germ.

·            Bell stage- this is where the enamel organ is differentiated into 4 distinct layers and separated from the dental papilla, which differentiates into two layers.  This is then followed by the dental sac at a later time, which develops the gingival tissue, alveolus, periodontal ligament and cementum.           

Tooth anatomy

·            Enamel-this is the very hard outer layer of the tooth crown that is composed of 96% mineral (calcium hydroxyapatite), 2% protein (enamelin), and 2% water.

·            Dentine (dentin)-Hard connective tissue forming the main bulk of most teeth; 70% mineral (calcium hydroxyapatite), 18% organic (mainly collagen), and 12% water.

·            Pulp-soft tissue within the tooth composed of odontoblasts, nerves, blood vessels, lymphatics and connective tissue.

·            Cementum- bone–like connective tissue usually covering the surface of tooth roots, 65% mineral (calcium hydroxyapatite), 23% organic (mainly collagen), and 12% water. Acts as an anchor for the periodontal ligament.

·            Periodontal Ligament-connective tissue connecting the tooth to the alveolar bone.

·            Gingiva-connective tissue cuff around each tooth (Gums).

·            Alveolar bone-bone forming the sockets for the teeth.

·            Furcation-the area where two or more roots branch from the crown.

·            Apical Delta- The canal openings at the apex of the root that allows access of nerves and blood vessels.

Periodontal structure

·            Alveolar mucosa- this is located apical to the mucogingival line and is loosely attached to the underlying alveolar bone.

·            Mucogingival junction- the border between the alveolar mucosa and the attached gingiva.

·            Attached gingiva- the soft tissue that extends from the free margin of the gingiva to the mucogingival line, minus the depth of the gingival sulcus.

·            Gingival sulcus- the normal space between the free gingiva and the tooth.

·            Gingival margin- the most coronal unattached edge of the gingiva.

·            Free gingiva- the most coronal portion of the gingiva not directly attached to the tooth.

·            Epithelial attachment- the epithelium which attaches the gingiva.

Root structure

 A good knowledge of the root structure of the dog and cat is important when extractions are performed.  This insures that all roots are recovered to prevent complications.

In the dog, the incisors, canines, first pre-molars and mandibular  third molars are single rooted teeth. The maxillary 2nd and 3rd pre-molar and mandibular 2nd,3rd,4th pre-molar, 1st and 2nd molars have two roots. The maxillary 4th pre-molar and 1st, 2nd molar have 3 roots.

The root structure in the cat has similarities.  The incisors, canines, and 2nd pre-molars and 1st maxillary molars are single rooted teeth. The maxillary 3rd pre-molar and mandibular 3rd  and 4th pre-molar and 1st molar have 2 roots. The only 3 rooted teeth are the maxillary 4th pre-molars.

Positional terminology

·            Labial/Vestibular-the surface of the tooth adjacent to the lips

·            Buccal/Vestibular- the surface of the tooth adjacent to the cheeks

·            Palatal- the surface of tooth adjacent to the palate or roof of the mouth (can use lingual).

·            Lingual- the surface of the tooth adjacent to the tongue.

·            Mesial-the surface of the tooth closest to the median line of the head.

·            Distal- the surface of the tooth farthest away from the median line of the head.

·            Coronal- towards the crown

·            Rostral- closer to or towards the nose or rostrum

·            Caudal- closer to or towards the tail (Anterior and Posterior are terms used in human dentistry).

·            Apical- towards the apex or root tip.

·            Interdental space-the space between adjacent teeth.

·            Interproximal space- the space between adjoining teeth.

Dog Cat Dental formula Dental formula Puppy 2x(3/3i,1/1c,3/3p)=28  Kitten 2x(3/3i,1/1c,3/2p)=28 Adult  2x(3/3I,1/1C,4/4P,2/3M)=42 Cat 2x(3/3I,1/1C,3/2P,1/1M)=30     Eruption schedule Eruption schedule Birth= 0 teeth 2-3 weeks= primary incisors 3-4-weeks= primary incisors  3-4 weeks= primary canines 3 weeks= primary canines 3-6 weeks= primary pre-molars 4-12 weeks= primary pre-molars  3-4 months= secondary incisors 3-5 months secondary incisors 4-5 months= secondary canines 4-6 months secondary canines and pre-molars  4-6 months= secondary pre-molars 5-7 months= molars  4-5 months= molars

Reference

American Veterinary Dental College, www.avdc.org

Veterinary Dentistry for the Technician & Office Staff, Holmstrom, S., Suanders Company, 2000.