Paedodontics

Introduction

The dentition of young animals is often overlooked, as the most prevalent dental problem seen in general practice is periodontal disease, which is rarely found in immature animals. However, deciduous and early permanent dentitions have unique conditions, and dealing with them correctly is essential.

Tooth Development

Development of the gastrointestinal tract begins early in embryonic formation. It is initially a blind tract, being closed at both ends. At around day 23 of gestation, the paired maxillary and mandibular processes are present, the latter growing forwards to form the mandible and merging at the mandibular symphysis. The maxillary processes form most of the maxilla, incisal and palatine bones of the roof of the mouth.

Initial development of the dental structures occur during embryonic formation. Tooth development begins at day 25, when the dental lamina, a thickening of the oral stratified squarmous epithelium, forms a U shape which ultimately becomes the upper and lower dental arcades. The oral epithelium, dental lamina and enamel organ (which forms each tooth), originates from the embryonic germ cells known as ectoderm. The animal’s skin also arises from the ectoderm, thus the skin and teeth are related. This is witnessed in the Chinese Crested breed dog, as a condition termed ectodermal hypoplasia, which results in alopecia and anodontia. The dental papilla (which forms the dental pulp tissue) originates from the embryonic germ cells known as mesoderm.

The development of the tooth germ. Diagramatic representation of a section through the maxillary incisor region. Adapted from Avery LB, Developmental Anatomy, A textbook and Laboratory Manual of Embryology, 1947, 5th ed. Philadelphia, WB Saunders.

Puppies and kittens are born without teeth, and rely on a milk diet supplied by their mother. The deciduous teeth form during gestation, with the enamel organ developing through a series of stages known as the bud, cap and bell. The initial stage, known as the bud stage, commences at day 24 of gestation, and is the initial budding off from the dental lamina at the areas corresponding to the deciduous teeth. The bud develops a concavity, marking the cap stage, which occurs at day 28 of gestation and is composed of three parts, the outer enamel epithelium, the inner enamel epithelium and the stellate reticulum. The bell stage starts at day 33 of gestation and occurs as a fourth layer, the stratum intermedium, between the inner epithelium layer and the stellate reticulum.

Each layer has a specific function:

• The outer enamel epithelium – acts as a protective layer for the entire organ.
• The inner enamel epithelium – forms the enamel of the tooth crown
• The stellate reticulum – acts to protect the inner enamel epithelium and allows fluids to percolate into the stratum intermedium.
• The stratum intermedium – converts the fluids to usable nourishment for the inner enamel epithelium.

The dental lamina buds that form the deciduous teeth develop lingual extensions that proceed through the same bud, cap, bell process to form the permanent teeth. Based on this observation, whenever a deciduous tooth is absent, by definition, the permanent counterpart will also be absent.

The stages of tooth development from root formation of the tooth bud to function of the erupted tooth. Adapted from Avery LB, Developmental Anatomy, A textbook and Laboratory Manual of Embryology, 1947, 5th ed. Philadelphia, WB Saunders.

During the late bud stage, mesenchymal cells begin to develop adjacent to the inner enamel epithelium, which form the dental papilla and dental sac. The dental papilla forms the dental pulp. The dental sac is composed of several layers of flatterned mesenchymal cells, which give rise to the cementum, periodontal ligament, and some alveolar bone. During the bell stage, the inner enamel epithelium cells lengthen and become known as pre-ameloblasts. The peripheral cells of the dental papilla bordering the pre-ameloblasts transform into cuboidal cells known as odontoblasts. As the newly formed odontoblasts moves toward the centre of the dental papilla and away from the pre-ameloblast, they form a mucopolysaccaride matrix, which mineralizes to form dentine. The movement changes the nutritional supply and polarity in the pre-ameloblast, forming a new cell termed an ameloblast, which is now able to form a mineralized mucopolysaccide material termed enamel. As enamel is formed, the ameloblasts begin to compress the two middle layers, the stratum intermedium and the stellate reticulum, which are eventually lost. The final function of the ameloblast is for a cuticle on top of the enamel, which serves to protect the tooth after it erupts. It is eventually worn away by abrasion once the tooth erupts into the mouth. Once the cuticle is formed, the ameloblasts come in contact the outer enamel organ which form the reduced enamel epithelium, which produces an adhesive material, known as secondary enamel epithelium or epithelial attachment, the function is to hold the gingival and tooth together at the base of the gingival sulcus.

Mesodermal tissues from the dental papilla form the pulp, which consists of blood vessels, lymphatic tissue, nerves, fibroblasts, collagen fibres, undifferented mesenchymal cells and odontoblasts. The nerves are primarily sensory and transmit only the sensation of pain.

Root formation begins after the general form of the crown has developed but before it completely calcifies. Crown calcification occurs in the deciduous teeth two weeks prior to birth and is complete one week after birth, thus the tetracycline antibiotics and other calcium-trophic ions, which affect the calcium structures such as teeth and bones, may result in teeth abnormalities, such as discolouration or dysplasis. At the junction of the outer enamel epithelium and the inner enamel epithelium, the stellate reticulum and stratum intermedium, the enamel organ is missing and this is termed the epithelial root sheath or Hertwigs epithelial root sheath. Once the crown is developed the root sheath begins to develop forming the root, which continues deep into the tissue. As the root is formed, the crown moves towards the gingival and eventually emerges and erupts through the gingival tissue, entering the oral cavity.

Cementum forms at the neck of the tooth forming the cemento-enamel junction. Cementoblasts secrete cementum as they move away from the junction. The periodontal ligament is derived from the mesenchymal cells of the dental sac. The formation of the periodontal ligament occurs after the cementum has been initiated.

At two to three weeks of age the first teeth, called the temporary teeth (or deciduous teeth) erupt through the gingiva. By four weeks of age the puppy will have 28 teeth and the kitten should have 26 deciduous teeth.

In the puppy these teeth include three incisors, one canine and three pre-molar teeth in each of the four jaws. In the kitten, the maxilla house three incisors, one canine and three pre-molars, whereas, the mandibles house three incisors, one canine and two pre-molars. The deciduous dental formulae are: 2x (Id33, Cd11, Pd33) = 28 and 2x (Id33, Cd11, Pd 32) = 26 for puppies and kittens respectively. Using the Modified Triadan system: 501, 502, 503, 504, 506, 507, 508, 601, 602, 603, 604, 606, 607, 608, 701, 702, 703, 704, 706, 707, 708, 801, 802, 803, 804, 806, 807, 808 in the puppy and 501, 502, 503, 504, 506, 507, 508, 601, 602, 603, 604, 606, 607, 608, 701, 702, 703, 704, 707, 708, 801, 802, 803, 804, 807, 808 in the kitten. The temporary teeth are shed and the first permanent teeth (or adult teeth) erupt through the gums at about fourteen weeks of age. Shedding of the deciduous teeth is a complex and incompletely understood process. It is understood that as the root of the permanent tooth begins to develop, the crown makes contact with the deciduous tooth root structure. The pressure of the crown on the root stimulates the resorptive process of the root of the deciduous tooth. Once sufficient root is resorbed and support lost, the deciduous tooth is shed.

By the end of the seventh month, all the permanent teeth should be present. The adult cat and dog should have 30 and 42 teeth respectively. In the cat, each right and left maxilla have three incisors, one canine, three pre-molars and one molar teeth, whereas each mandible has three incisors, one canine, two pre-molars and one molar teeth. In the dog, each right and left maxilla have three incisors, one canine, four pre-molars and two molar teeth, whereas each mandible has three incisors, one canine, four pre-molars and three molar teeth. The permanent dental formulae are 2x (I33, C11, P44, M23) = 42 and 2x (I33, C11, P32, M11) = 30 for adult dogs and cats respectively. Using the Modified Triadan system: 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 201, 202, 203, 204, 205, 206, 207, 208, 209, 210, 301, 302, 303, 304, 305, 306, 307, 308, 309, 310, 311, 401, 402, 403, 404, 405, 406, 407, 408, 409, 410, 411 in the dog and 101, 102, 103, 104, 106, 107, 108, 109, 201, 202, 203, 204, 206, 207, 208, 209, 301, 302, 303, 304, 307, 308, 309, 401, 402, 403, 404, 407, 408, 409 in the cat.

Deciduous and permanent teeth eruption dates

Deciduous

Incisor:

• First: 2 – 4 weeks
• Second: 2 – 5 weeks
• Third: 2 – 5 weeks

Canine:

• 3 – 6 weeks

Pre-molar:

• First: 3 – 7 weeks
• Second: 3 – 6 weeks
• Third: 3 – 6 weeks

Permanent

Incisor:

• First: 3 – 5 months
• Second: 4 – 5 months
• Third: 4 – 5 months

Canine:

• 4 – 7 months

Pre-molar:

• First: 4 – 5 months
• Second: 5 – 6 months
• Third: 5 – 6 months
• Fourth: 4 – 6 months

Molar:

• First: 5 – 6 months
• Second: 5 – 7 months
• Third: 6 – 7 months

Deciduous incisor and canine teeth of a puppy. Note the six maxillary and six mandibular incisor teeth and the four canine teeth (maxillary left and right, and mandibular left and right).

Left maxilla showing deciduous canine (red circle) and three pre-molar (blue circle) teeth in a puppy.

Left mandible showing deciduous canine (red circle) and pre-molar (blue circle) teeth in a puppy.

Scissor bite in a puppy. Note the mandibular deciduous canine tooth is positioned equal distance between the maxillary deciduous third incisor and canine teeth.

Radiograph of the rostral maxilla in a puppy showing a complete set of deciduous incisors, left and right canine teeth, as well as the permanent tooth buds of the incisor, canine and first premolar teeth.

Radiograph of the rostral maxilla in a puppy showing a complete set of deciduous incisors (red circle), left and right canine teeth (blue circle), as well as the permanent tooth buds of the incisor (black circles), canine (yellow circles) and first premolar (green circles) teeth.

Radiograph of the rostral mandibles in a puppy showing a complete set of deciduous incisors, left and right canine and premolar teeth as well as the permanent tooth buds of the incisor, canine teeth.

Radiograph of the rostral mandibles in a puppy showing a complete set of deciduous incisors (red circle), left and right canine (blue circle) and premolar teeth (green circles) as well as the permanent tooth buds of the incisor (black circles), canine (yellow circles) teeth.

Radiograph of the maxilla in a puppy showing deciduous canine, three premolar teeth, as well as the permanent tooth buds of the canine and premolar and molar teeth.

Radiograph of the maxilla in a puppy showing deciduous canine (red circle), three premolar teeth (blue circles), as well as the permanent tooth buds of the canine (yellow circle) and premolar (black circles) and molar (green circles) teeth.

View of the right side of a puppy’s mouth, showing a scissor bite, demonstrating the incisor, canine, premolar and molar teeth relationship.

View of the front of a puppy’s mouth, showing a scissor bite, demonstrating the incisor and canine teeth relationship.

Causal factors

During the development of both deciduous and permanent teeth, various factors can greatly alter normal crown and root formation. Systemic and local inflammation or infection, sometimes accompanied with fever, at the time of tooth bud maturation can commonly alter the appearance and structure of the enamel and root.

Trauma, whether accidental or iatrogenic, during extraction of deciduous teeth, can also cause significant pathology. The position of the permanent tooth bud lingual to most of the deciduous teeth, except the maxillary canines, which are mesial, makes it extremely susceptible to stimuli from its predecessor.

Conditions and pathology of deciduous teeth

Missing Deciduous Teeth

Missing deciduous teeth in itself does not always present a serious physical problem, but may be an indication of missing permanent analogs or a dentiguous cyst. By eight to twelve weeks of age, radiographs can be taken to confirm the presence or absence of permanent tooth buds. A single missing tooth typically does not indicate a major abnormality, but multiple missing teeth, especially bilaterally, increase the probability of genetic predisposition.

By eight weeks of age, all of the deciduous teeth should have erupted into the mouth. If a tooth is missing, it may be impacted under the fibrous gingival or alveolar bone; it may be unable to erupt due to overcrowding and lack of space; or it may be absent. Impaction of the deciduous tooth may also lead to impaction of the permanent tooth.

Treatment involves radiography to determine whether the tooth is impacted or absent, to document the size, shape and location of the tooth. If the tooth is impacted beneath fibrous gingival or bone, a window of gingiva can be resected using a biopsy punch, or alveolar bone removed using a high speed bur respectively, in order to clear a path for the tooth to erupt. This should be performed between 8 and twelve weeks of age.

Failure to detect and extract an unerupted tooth often leads to the formation of a dentigerous cyst. These cysts although benign, are destructive of bone as they expand, which leads to loss and movement of adjacent teeth. Treatment involves removal of the unerupted tooth and the secretory epithelial lining of the cyst before closure of the incision.

The view of a 10 week old puppy showing missing deciduous incisors. Note there are four incisors in the maxilla and five incisors in the mandible. The puppy is missing the lateral maxillary incisors bilaterally (indicated by red dot) and the right mandibular second incisor (indicated by red dot).

Radiograph of dog in previous picture, maxilla showing presence of only four deciduous incisor teeth and four permanent tooth buds.

Radiograph of dog in previous picture, maxilla showing presence of only four deciduous incisor teeth (red dots) and four permanent tooth buds (blue dots).

Fractured Deciduous Teeth

The deciduous teeth have very thin walls and can be fractured during play or trauma. Fractured deciduous teeth should generally be extracted, as endodontic therapy is typically unwarranted, and any potential source of infection to nearby permanent tooth buds and alveolar bone should be removed. Infection may gain access through the open pulp canal. The root of the deciduous tooth can easily fracture on extraction, so care must be taken. If endodontic treatment is necessary in deciduous teeth, it is relatively simple, using zinc oxide and eugenol, as a filler (or calcium hydroxide if resorption has started) with a composite restorative closure.

A puppy with a complicated crown fracture (CCF) of the maxillary right deciduous canine tooth (504).

The radiograph from the previous picture of the puppy with the CCF 504. The thin large pulp canal of 504 is seen with an absent crown cusp on the left (blue circle). Whilst the developing and erupting permanent adult canine tooth (104) is seen on the right side adjacent to 504 (red circle).

Malocclusions

Deciduous teeth may also be extracted in cases of early malocclusions. If the primary dentition shows abnormal positioning, such as base narrow canines, retention of these canine teeth may not only cause a detrimental interlock of teeth into the hard palate, resulting in ulceration and interfering with mandibular growth, but they may also influence their permanent counterparts to erupt even further lingually, except the maxillary canines which erupt mesially. The growth and maturation for each jaw quadrant (upper and lower mandibulae and maxillae) is under separate genetic control and is therefore relatively independent of each other. Therefore, slight variations in growth may also cause a malevolent interlock of deciduous incisors and canines, again potentially influencing jaw growth, in an otherwise genetically normal individual. In these cases, selective extractions of deciduous teeth may be attempted, realizing that extractions of this kind will not be effective if malocclusions are of genetic origin. One simple rule is to extract the canines and incisors of the shorter jaw to prevent further interference. It should be remembered, however, that interlocks are occasionally advantageous, especially when the lower canines are tight against the upper lateral incisors in an animal experiencing a mandibular growth spurt. In such a case, the only beneficial extractions would be of the upper central and intermediate incisors.

An excellent review article by Hennet and Harvey on craniofacial development in the dog, Craniofacial development and growth in the dog, J Vet Dent 1992; 9 (2): 11, details the complex interactions between genetics and function, soft tissues, and hard tissues in the development and growth of the maxilla and mandible. Among the salient points was that up to day 50, the increase in the mandible length occurs as a result of rostral bone, and after day 50, between the 3rd and 6th month, almost all the mandible length occurs caudal to the first molar tooth.

A puppy with a Class 2 brachygnathic jaw (or overshot) showing a longer maxilla and a shorter mandible. Demonstrated by observing the position of the mandibular deciduous canine tooth positioned caudal to the maxillary deciduous canine tooth.

Interceptive Orthodontics

The practice of interceptive orthodontics involves the extraction of deciduous teeth prior to the eruption of their permanent counterparts. It should ideally be performed between six to eight weeks of age (no later than 12 weeks), after which time the permanent teeth eruptions are imminent, and often take the abnormal place of their predecessors. The extraction of the deciduous tooth removes all opportunity of physical eruption into a malocclusion, thus allowing the permanent tooth to adopt normal occlusion. The actual process of exodontias should be carried out with extreme caution in minimize potential damage to the permanent tooth bud under the gingival surface. Infiltration of a local anaesthesia with vasoconstrictor (adrenaline 1:100,000) will help with local discomfort and decrease haemorrhage, as the forming enamel can be discoloured by the pigments in the blood. Elevation of the tooth should be done gently with gradual forces. Extreme gouging and rotation should be avoided to prevent fracture of the delicate deciduous roots. If the crown breaks off, attempts should be made to completely retrieve the remaining roots, but again with care. If necessary, a moderate gingival flap and alveloplasty may be performed to expose the root tip. If infection is present, oral antibiotics should be continued post-operatively. Whenever attempting extractions, the owner should be notified that changes may occur to the permanent tooth, no matter how carefully the procedure is done. These changes may range from very mild enamel pitting, to more severe enamel and root dysplasias, and even malpositioned or unerupted teeth. The most commonly teeth that are involved in interceptive orthodontics are the mandibular canine teeth, especially in breeds predisposed to linguo-version such as the Staffordshire Bull Terrier.

Persistent Deciduous Teeth

One area where primary exodontia is the only choice is in cases of persistent deciduous teeth. By the time the pet is 4 months of age, some of the permanent teeth should be erupting. The rule is that if the permanent tooth crown is visible above the gum line, the primary tooth should be gone. If the primary tooth is present, it should be removed as soon as possible. Leaving it in place until 6 months to be performed at speying or castration is inappropriate because it forces the permanent tooth to erupt into an abnormal location. If the permanent counterpart has not erupted, the mouth should be radiographed, and if the permanent tooth bud is absent, the deciduous tooth should be left. Exfoliation can be influenced by many factors, such as nutrition, inflammation, trauma, endocrine disorders such as hypothyroidism and ankylosis of the tooth to alveolar bone. Once the adult tooth starts eruption, unless its way is unimpeded, it will be deflected away from its normal position, lingually for most teeth, except for the maxillary canine, which are displaced rostrally. This may result in the lower canine tooth being displaced labially. While the deciduous crown may be ready to exfoliate in some cases, if any root structure remains, it should be completely remove. Retained deciduous teeth may commonly cause malocclusion such as base narrow canines, where the lower canine teeth erupt lingually to the deciduous teeth, or anterior cross bite, where one or more of the maxillary incisors lean lingually to the mandibular incisors (linguoversion). While specific dental malocclusions caused by retained deciduous teeth have not been proven to be genetic, as are jaw length discrepancies, any orthodontic adjustment should be thoroughly discussed, including breeding counselling.

A kitten with a retained deciduous maxillary left canine tooth (604). Note both the deciduous and permanent canine teeth are present.

Radiograph of the previous kitten demonstrating the persistent deciduous left canine tooth (604) caudal [right on picture] to the permanent canine tooth (204)[left on picture].

Development and Genetic Defects

Other developmental and genetic defects in young animals may be seen associated with the soft tissues and bony structures of the head. Primary cleft (rostral to the incisive foramen and including the lips) and secondary cleft (hard palate caudal to the incisive foramen and the soft palate) defects can lead to serious complications if not managed correctly.

Defects of the primary palate usually cause no problems with nursing or respiration and are largely cosmetic in nature. Surgery can be performed to correct these if the client desires and can be delayed until the pet is mature. Standard surgery texts include techniques on these.

Defects of the secondary palate are more serious, are almost always midline and usually result in communication between the mouth and nasal cavities. During nursing, milk flows into the nasal passages leading to sneezing, gagging or aspiration pneumonia. Prognosis is guarded unless surgical correction is performed.

Conditions and pathology of immature permanent teeth

Missing permanent teeth

Missing permanent teeth can be a common problem in certain breeds. The teeth are formed from the ectodermal tissue, which also forms the skin. Thus, in Chinese Crested breed dogs with ectodermal dysplasia, a condition that produces alopecia, also results in anodontia of many premolar and molar teeth in both maxilla and the mandible. The first premolar in German Shepherds and the second and third premolars in smaller breeds may be missing. In the German Shepherd dog, as well as many other breeds, absent teeth can be a problem if the owner wishes to show and breed the animal. When a tooth is absent on examination, a radiograph should be taken to confirm the presence or absence of the permanent tooth bud.

Treatment may involve replacement of the tooth using an implant, a titanium root, which is placed into a pre-drilled hole in the bone, allowed to ankylose to the bone, and then a crown cemented to the implant.

A Chinese Crested breed dog showing missing permanent premolar teeth. This dog is missing the right third and fourth permanent maxillary premolar and the right first, third and fourth permanent mandibular premolar teeth.

A German Shepherd breed dog missing the left mandibular permanent first premolar tooth.

Radiographs of the dog above. The first radiograph shows the absence of the right permanent mandibular first premolar tooth. The second radiograph was taken of the left side mandible from the same dog. Note the presence of the permanent first premolar tooth.

Impacted permanent teeth

Missing permanent teeth may be an indication of an impacted tooth. By six months of age, radiographs can be taken to confirm the presence or absence of the impacted permanent tooth. A single missing tooth typically does not indicate a major abnormality, but multiple missing teeth, especially bilaterally, increase the probability of genetic predisposition.

If a tooth is missing, it may be impacted under the fibrous gingival or alveolar bone; it may be unable to erupt due to overcrowding and lack of space; or it may be absent. Treatment involves radiography to determine whether the tooth is impacted or absent, to document the size, shape and location of the tooth. If the tooth is impacted beneath fibrous gingival or bone, a window of gingiva can be resected using a biopsy punch, or alveolar bone removed using a high speed bur respectively, in order to clear a path for the tooth to erupt.

A Beagle breed dog showing a missing permanent right maxillary third incisor tooth.

A radiograph of the dog above, showing the presence, but impacted permanent right maxillary third incisor tooth.

Dentigerous Cyst

A dentigerous cyst is a cavity lined by non-keratinised stratified squamous epithelial cells derived from reduced enamel epithelium of the tooth forming organ. The cyst is an odontogenic cyst associated with the crown of an unerupted permanent tooth. Clinically the permanent tooth is missing. Radiographically, the appearance is of a well demarcated radiolucent lesion with a radio-opaque denticle within the cystic lining. FNA aspirates straw coloured fluid. Histology confirms the diagnosis. Surgery is required to excise the cyst lining along with the extraction of the assosciated tooth. In case of a large cyst marsupialization is done.

Missing 305 and intrinsic staining of 304.

A routine radiograph was taken prior to root canal procedure of the 304 and missing 305 and a dentigerous cyst was confirmed.

Retained deciduous and absent permanent teeth

Sometimes, a deciduous tooth may be retained with no evidence of a permanent tooth erupting. Before extraction of the deciduous tooth, a radiograph must be taken to confirm the presence or absence of a permanent tooth bud.

Orthodontics / Malocclusions

Many stimuli can have some influence on the eventual placement of the permanent dentition. If the teeth are in abnormal positions, orthodontic evaluation is usually initiated when the animal is still very young. The timing for orthodontic therapy is very important. Specifics of orthodontics will not be discussed here, but some general guidelines are important to follow when dealing with immature dentitions. Unless severe trauma is present, orthodontic movement generally should not be attempted until the patient is at least nine months of age (sometimes later), due to the underdevelopment of the root and apex, as well as incomplete coronal height. Any forces applied should be relatively light to avoid excess trauma.

A puppy with an rostral cross bite. Note the presence of all permanent incisor teeth, but the maxillary left and right first incisor teeth are positioned lingual to the lower arcade.

A puppy with a rostrally deviated permanent left canine tooth. Note the diastema between the canine and the third incisor is absent.

A puppy with a posterior cross bite. Note the position of the permanent mandibular first molar tooth is lateral to the maxillary fourth premolar tooth.

A puppy with a wry bite. The position of the mandible is twisted to the left.

Abnormalities in the shape of teeth

Developmental abnormalities in the shape of the tooth are rare and usually of little clinical importance. Dens in dente is a rare condition when, during tooth development, the enamel organ enters the dental papilla, resulting in an area of enamel within the dentine. This exposes the pulp to bacterial infection, which may result in periapical abscessation or suborbital swelling. Treatment involves extraction of the affected tooth.

Fractures

Canal exposure in immature permanent teeth can respond to treatment, if handled correctly. Due to the large canal size and excellent blood supply, vital pulpotomy procedures (apexogenesis) can be attempted as late as two weeks post-exposure. If there is any chance to preserve pulp vitality to encourage continued maturation of the open apex and thin dentinal walls it should be tried. If the pulp is completely non-vital, however, apexification with canal debridement and calcium hydroxide placement may help stimulate a hard tissue closure of the apex.

A puppy with a fractured maxillary permanent canine tooth showing an oblique fracture and pulp exposure.

Enamel defects

As the permanent teeth erupt, certain enamel changes may become evident. The crown of each tooth should be completely covered in an even thickness of enamel with no wear, tear, cracks, crazes, defects or fissures. A chalky white appearance to the enamel may indicate hypocalcification, while others may exhibit enamel dysplasias, a severe generalised enamel defect. In general, any febrile or systemically debilitating disease during the developmental stages may cause lack of proper mineralization (hypocalcification) of the enamel. Distemper teeth are commonly mislabeled as enamel hypoplasia, but this is wrong, as they should be termed enamel hypomineralisation. Hypoplasia means thin enamel but normal mineralization, whereas hypomineralisation means poorly mineralized enamel that may discolour, decay, be soft and have rapid attrition. It should be noted that some cases of enamel dysplasia may be accompanied by some degree of root dysplasia, possibly even total absence, so radiographs should always be taken. Gently scrubbing to remove the diseased enamel, accompanied by smoothing of the surfaces, polishing and fluoride treatment can help the overall appearance to a degree. Full crown restorations (crowns) are occasionally attempted in individual teeth, are less practical in generalized situations. The owners should be encouraged to maintain good dental hygiene, including weekly stannous fluoride applications, or brushing with animal toothpaste, but they should also be informed that the remaining enamel may eventually experience some changes as well.

Enamel hypomineralisation of the mandibular canine tooth. Note the discolouration of the dentine and enamel at the edges of the enamel loss.

Severe enamel dysplasia showing shelves of enamel.

Enamel hypomineralisation, showing a lack of enamel formation from the gingival margin to the cusp. Note a thin layer of enamel at the crown tip. This condition has been seen in the Akita breed.

Odontomas

Odontomas are a benign oral tumour composed of dental tissues. Compound odontomas are characterized by the presence of a few dozen denticles (which appear like small teeth) comprising all the dental tissues: pulp, dentin, cementum and enamel, in a normal relationship. They are diagnosed by radiography by the presence of denticles surrounding a permanent tooth. Complex odontomas are characterized by a deranged architecture of the dental tissues such that the radiograph shows an amorphous mass of dental density. Treatment involves surgical removal of all the denticles and the associated teeth, and the vascular stroma from which they are growing. The prognosis is excellent.

Papilloma Virus

The papilla virus causes pathology in the puppy’s mouth, both on the tongue, lips, mucosa and occasionally the gingival tissues. The papilloma lesion produces a wart like lesion, small 1-5mm diameter, soft, raised, grey – white in color and usually is found on examination during vaccination check-up. Often they are found by owners, as the dog causes the lesion to haemorrhage or is associated with halitosis. The lesion usually occurs in young animals under 2 years of age, are self-limiting. They occasionally are a precursor for squarmous cell carcinoma tumours though, thus I advise clients it is ideal to surgically remove them, take an incisional biopsy and get histopathology performed.

A puppy with oral papilloma virus lesions on the buccal mucosa of the lip.

A puppy with an oral papilla lesion on the rostral portion of the mandible.

Intrinsic Staining

The teeth are formed from calcium ions and are therefore prone to discolouration from products, which bind the 2+ ions. The permanent crown forms between eight and thirteen weeks of age, so it is therefore important not to prescribe these drugs during tooth development at this age. One such product, which may result in tooth staining, are the family of tetracycline antibiotics. Tetracycline produces a dark brown discolouration of the dentine and enamel, oxytetracycline produces an orange colour, whilst doxycycline produces a yellow discolouration.

A puppy with yellow intrinsic stained teeth following treatment with doxycycline during tooth development between eight and thirteen weeks of age.

Supernumerary Teeth, Crowding and Rotation

Extra teeth are common in many breeds are radiographs should be performed. The radiograph will determine whether two completely separate teeth are present, or whether they share the two crowns share a common root, termed ‘bigeminy’. As well as crowding, supernumerary teeth may lead to malocclusions and rotation. Crowding and rotation leads to food impaction, bacterial accumulation, gingival inflammation and potentially periodontal disease. The suggestive treatment is to extract the supernumerary tooth or the less significant tooth to improve the prognosis and decrease the disease.

Supernumerary permanent maxillary incisor teeth. Note the puppy has eight incisor teeth.

Conclusion

Paediatric dentistry is the diagnosis and treatment of developmental, genetic and iatrogenic factors that may lead to missing teeth, tooth fractures, root or enamel dysplasia and dental malocclusions. While in some individuals, teeth may experience unusual juvenile syndromes, periodontal disease is typically not a problem in young animals. When the young animal has emphasis placed on accurate diagnosis and treatment of early dental pathology, current dental conditions and any future problems can be avoided throughout the pet’s life.

References

• Small Animal Dentistry, ed. Harvey CE & Emily PP. 2nd ed. Mosby, Baltimore
• Veterinary Dentistry, ed. Wiggs RB & Lobprise HB. Lippincott-Raven, Philadlephia
• Veterinary Clinics of North America. Small Animal Practice., ed. Holmstrom, SE, Saunders, Philadelphia
• Hennet PR, Harvey CE, Craniofacial development and growth in the dog, J Vet Dent 1992; 9 (2): 11
• Clarke DE, Lobprise HB, Some aspects of clinical paedodontics in dogs and cats. Aust Vet Prac 1994, 24:203.