CT of Equine Teeth

La Dolce Vita ‘90 QH mare

Two most important dental diseases in horses are apical tooth infections and infundibular caries Pathogenesis of both is poorly understood

Infundibulum -cup or funnel shaped invagination of enamel from the occlusal surface of incisor and maxillary cheek teeth

Three main infundibular abnormalities infundibular caries infundibular cemental hypoplasia (central infundibular

cemental hypoplasia and junctional cemental hypoplasia)

difficult to differentiate hypoplasia vs caries clincally

Caries-disease of the calcified tissues of teeth, action of microorganisms on carbohydrates leads to demineralization, resulting in destruction of the enamel and dentine, and cavitation of the tooth

Rarely, can progress to involve the enamel which, if breached, will contaminate the dentine leading to pulpitis, necrosis and eventually an apical tooth infection if severe enough, could spread across the dentine to affect the

adjacent infundibulum Advanced infundibular caries may lead to midline

sagittal fractures, pulpal and thus apical infections upper first molar is most commonly involved in apical

infections (in horses ~8 years) and an extension of infundibular caries has recently been shown to cause 16% of maxillary apical infections

Cemental hypoplasia reported to occur in up to 65% of equine

maxillary cheek teeth pathogenesis unknown- vascular

disruption? may predispose to infundibular caries

33 clinically normal horses 3-30y

Equine vet. J. (2010)

Infundibular cemental hypoplasia was grossly observed in 22% of all infundibula previously reported to occur in 65% ▪ more subtle changes were likely detected in that

study▪ some abnormalities classified as miscellaneous

may have had low grade hypoplasia Found most commonly in younger horses

(29.2% in 3–5 y and 27.1% in 6–11 y) developmental defect

Many areas of hypoplastic cementum were situated apically, suggesting that loss of vascular supply from this aspect of infundibula may compromise cemental formation study also confirmed the presence of an apical blood

supply to infundibula in younger horses Consequences of such apically located defects may

not appear until later in life when they first become exposed occlusally and infected by oral bacteria

Did not find an obvious relationship between cemental hypoplasia and cemental caries possibly because once areas of cemental hypoplasia

communicate with the occlusal surface they become infected and so were carious at the time of examinations

Caries involving the full length of the infundibula were present in 8.2%, most commonly in horses 12–20 years old

Upper first molars were most commonly affected with extensive caries 30 times more common also the most common site of idiopathic fractures▪ supports the role of caries in the pathogenesis of these

fractures▪ however, idiopathic fractures were most commonly

observed in horses aged 9–10 years, whereas in this study complete infundibular caries were most common in older horses

The rostral infundibulae of this study had a higher prevalence and greater severity of lesions in comparison to the caudal infundibulae slightly different vascular supply in previous studies, cemental hypoplasia

also occurred most commonly rostrally

• A number of teeth 0–4 years post eruption had lesions visible at the occlusal surface of their infundibulae caries within these infundibulae were only

present superficially at the coronal aspect of the infundibulae

infundibulae of cheek teeth are open when they are erupting▪ allows for debris, food and bacteria to enter ▪ by 4–6 years post eruption this area of

infundibulae is lost by attrition and the apical infundibulae become exposed

Other findings A lot of findings classified as ‘other’ may have

actually represented cemental hypoplasia or caries (58%) of infundibula centrally located defect at site of former vasculature

with darker localized areas of caries or food staining when these were exposed occlusally

others had areas of more porous cementum that was dark if connected to the occlusal surface

Majority (88%) of infundibula were not completely filled with normal appearing cementum variations in cemental appearance may be normal

findings

CT

126 cheek teeth evaluated with CT Clinically normal horses 4-20 y 1mm slices

Graded infundibular lucencies

Increasing age was associated with decreases in: pulpar volume ▪ due to the deposition of regular secondary dentine on the

periphery of the pulp cavity the number of interpulpar communications between pulp

horns the distance the pulp extended apically within individual

roots the length of the reserve crown

The number of apical foramina per root increased with increasing age

The apical extension of the enamel around the roots decreased with age no enamel could be seen around the roots of teeth >15y

post eruption

1.5 yo

Equine vet. J. (2009)

Infundibulae High incidence of infundibular lesions 2 infundibulae, rostral and caudal

located within the central portion of the occlusal surface of all maxillary cheek teeth

Extension from the occlusal surface varied with age 0–2 y -the infundibulae extended up ~75% tooth length >14 y -the infundibulae extended up ~50% of the tooth

length Radiolucent area of the occlusal surface in the center of

all infundibulae on CT correlated with the infundibular cementum overlying the central vascular channel also visible on the occlusal surface as a small dark circular

area and in normal infundibulae no surface defect was associated with this area

this radiolucency did not extend apically in normal infundibulae

Only 10% of the infundibulae had no lesions on either grossly on the occlusal surface or CT examination

65% of infundibulae had lesions on gross occlusal examination alone, compared to 90% on CT examination

Equine vet. J. (2009)

Grade 1a Grade 2a Grade 3a

Grade 1b Grade 2b Grade 3b

Hypoplasia or caries In contrast to Henninger et. al, 2003,

which stated ‘Detection of hypoattenuation

representing gas was a sign indicative of severe tooth root infection and was always found in combination with infundibular necrosis and pulpitis. In CT images, cementum of inferior quality with encapsuled gas bubbles could be detected in a diseased tooth.’

•sectioning of teeth with grade 3 lesions (apical bulbous expansion)revealed obvious necrosis and/or food material within the apical depths of the infundibulae•proposed that grade 3 lesions are indicative of infundibular caries and unlikely to be the result of cemental hypoplasia

Equine vet. J. (2009)

Although a wide range of infundibular lesions observed, relatively few pulpar lesions were detected Implies that infundibular caries are not

the most common pathogenesis for apical pulpitis in horses