Equine Periodontal Disease: Evidence and Opinion
Author(s):
S.S. Galloway
In: AAEP Focus Meeting - Focus on Dentistry - Charlotte, 2013 by American Association of Equine Practitioners
Updated:
AUG 06, 2013
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Take Home Message—The periodontium is the attachment apparatus of the tooth. It is responsible for hypsodontic tooth eruption and for the distribution of masticatory forces from the teeth into the supporting bone. Periodontal disease is the leading cause of tooth loss in horses. Since the periodontal procedures currently being performed on horses lack scientific validation, practitioners must understand the pathophysiology of periodontal disease and the principles of periodontal treatment before making treatment decisions. Prevention, early recognition, and early treatment are the basis of successful equine periodontics.
I. Introduction
The periodontium is the attachment apparatus of the tooth consisting of the gingiva, alveolar bone, periodontal ligament (PDL), and the cementum. The periodontium is responsible for distributing masticatory forces from the teeth into the supporting bone as well as for the orthodontic movement of teeth, which includes the eruption of hypsodontic teeth.
Periodontal disease (PD) is an altered state of the periodontium. PD is an inflammatory process consisting of cyclic intervals of active destruction (periodontitis) and inactive quiescence. These repetitive stages cause progressive attachment loss resulting in increased tooth mobility and eventually premature exfoliation of the tooth. Periodontal disease was reported to be the primary reason for extraction of cheek teeth (75%) in primary practice.1
Evidence based medicine (EBM) dictates that the best evidence available be integrated with the practitioner’s clinical expertise to formulate a treatment plan for each unique patient. While numerous papers have been published reporting expert opinion on PD therapy, no strong evidence validates the periodontal procedures currently being practiced on horses. This lack of evidence leaves the equine practitioner to formulate a PD treatment plan based on the (probably biased) opinions of experts and his/her personal clinical experiences.
Making informed treatment decisions requires an understanding of PD pathophysiology and treatment principles. This paper presents a review of the scientific literature and expert opinion related to the incidence, causes, diagnostic evaluation, and treatment of the equine PD.
II. Incidence
Equine PD has been recognized for hundreds of years and is classically associated with senior horses, with reported incidences consistently above 60% in this population subset. While the incidence of PD has been shown to increase with age, PD affects all age groups and is present in approximately one-third of the general horse population. (Table 1) A recent study evaluating the prevalence of diastemata in horses presenting for primary dental care in the UK reported statistically significant higher incidence of periodontal disease in females and ponies, as well as with increasing age.2
PD affects all equine teeth; but is most deleterious to the permanent cheek teeth. PD of the cheek teeth is seen almost exclusively in the interproximal spaces,15 and the association between widened interproximal spaces (diastemata) and PD is well established. Anthony reported the odds of periodontal pockets were 31 times higher in horses with diastemata.14 Most research indicates that the incidence of diastema formation is significantly higher in the mandibular cheek teeth.
III. Suspected causative factors
PD in brachydontic species is most commonly associated with an increase in pathogenic oral bacteria secondary to the chronic accumulation of plaque and calculus in the gingival sulcus. However, this brachydont model is unlikely to be the primary cause of equine PD because of the continuous eruption of the hypsodontic teeth which limits plague accumulation within the gingival sulcus. Several potential causes for equine PD have been suggested with malocclusion, feed type, and husbandry management, being the most commonly accepted factors.
Malocclusion is a known initiator of PD in mammals (including humans) and has been suggested as a primary contributing factor to PD in equids.16-19 Diastemata formation secondary to Class 1 Malocclusionsa (MAL1) creates a space for feed impaction. This feed acts as a local irritant to the periodontium which can directly stimulate an inflammatory response. Chronic feed stasis allows for pathogenic bacterial proliferation and putrefaction of the feed, producing toxins and other products which further stimulate the inflammatory response. Finite element analysis has been used to show PDL strain from masticatory mechanical loading increases with tooth age and could be a factor causing positional changes (malocclusion) within the dentition as well as causing direct damage to the periodontium which allows for bacterial infiltration.20
The types of feed being ingested may influence the incidence of PD. It has been suggested that horses grazing pasture have a lower incidence of PD, while horse fed dried hay, chopped forage, and hard concentrates are at increased risk. The reduced chewing time required to masticate processed feeds and concentrates could cause abnormal attrition of hypsodontic teeth resulting in Class 1 Malocclusions. A survey of dental abnormalities in skulls of free-ranging zebras reported a 5% prevalence of “periodontitis.”21 A recent study comparing dental abnormalities in free-living and stabled horses demonstrated significantly higher incidence of PD, and other dental conditions, in stabled horses.22 Additionally, saliva maintains the correct pH of the oral cavity, decreases bacterial adherence to and mechanically cleanses the oral tissues, delivers antibodies, and is anitbacterial; therefore, hyposalivation in horses with decreased access to grazing may also contribute to PD by facilitating the proliferation of pathogenic bacteria. Local irritants such as weed awns (seed heads) in poor quality hay commonly cause severe ulcerative glossitis and gingivitis of the incisors and canine teeth.23
Finally, since PD is a chronic inflammatory disease, poor general health and host modulation may play important roles in PD. Current research in brachydontic periodontology suggests that attachment loss is the result of the host’s genetic predisposition to mount an exaggerated or inappropriate inflammatory response regardless of the pathogen load and that this predisposition places the host at increased risk of other systemic inflammatory disease.
IV. Associations between PD and regional and systemic disease
Professional dentistry not only includes the treatment of diseases of the teeth and oral cavity but also the evaluation of disease extension into the maxillofacial area as well as the evaluation of the contribution of oral conditions on the overall health of the individual patient. Bacterial infection secondary to PD can extend directly into the mandibular and facial bones and into the sinuses through oromaxillary fistulae.24,25 Systemic diseases that have been associated with PD include esophageal obstruction, weight loss, and colic.26,27 While systemic sequelae to PD in horses have not been investigated, associations with heart, liver, & kidney disease, obesity, diabetes, and pregnancy complications are documented in other species. [...]
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