Scanning electron microscopic description of cellular activity and mineral changes in feline odontoclastic resorptive lesions

The cellular activity and changes in mineral composition of dental tissues involved in feline odontoclastic resorptive lesions were investigated. Teeth with at least 1 lesion (n = 10) were extracted from 10 different cats that were presented primarily for chronic gingivostomatitis and/or severe periodontal disease. Scanning electron microscopic methods were used to determine the presence of resorptive cells in 8 teeth while 2 teeth were evaluated for pathologic changes in dental mineral composition. Observations were complicated by the presence of organic wear on the dental surfaces, however resorptive cells could be clearly identified in feline odontoclastic resorptive lesions. Resorptive cells had morphologic features indicative of "osteoclast-like" cells or odontoclasts. Resorptive cell activity created a resorption area of darker dentin continuous with physiologic dentin. The darker dentin area seemed poorly mineralized and showed a significantly lower calcium/phosphorous ratio compared with adjacent physiologic denting in 1 tooth. A significantly higher level of magnesium combined with available carbonate ions may have increased the solubility in areas of darker dentin.     

Risk factors for odontoclastic resorptive lesions in cats.

A cross-sectional study evaluating potential risk factors for odontoclastic resorptive lesions (ORL) in feline teeth was conducted. Owners of 32 cats with ORL and 27 cats without ORL were interviewed regarding their respective cat's demographic characteristics, diet, and medical and dental histories. Four factors were identified as significantly associated with ORL using unconditional logistic regression. A history of dental disease (gingivitis, calculus, or periodontal disease; odds ratio [OR], 4.5); city residence (OR, 4.4); and being an exclusively indoor cat (OR, 4.5) were associated with an increased risk for ORL. Consumption of commercial treats (OR, 0.3) appeared protective for ORL.     

Feline odontoclastic resorptive lesions: unveiling the early lesion

The purpose of this study was to increase understanding of the factors initiating feline odontoclastic resorptive lesions (FORLs). Fifty-six teeth (clinically and radiographically unaffected by ORLs) were harvested. Of these, 43 were from cats that had ORLs in other teeth (group A) and 13 were from cats with no clinical or radiographic evidence of ORLs in any teeth (group B). Twenty-six teeth in group A and one tooth in group B showed histological evidence of external root resorption (surface resorption and replacement resorption resulting in ankylosis). Some teeth in group B showed healed cementum resorption. It has previously been assumed that FORLs were similar to lesions associated with peripheral inflammatory root resorption, and were associated with periodontal disease. These histological findings suggest instead that a FORL is a non-inflammatory replacement resorption, resulting in ankylosis. The periodontal ligament of resorbing teeth lacked normal fibrous architecture, but was not inflamed. Resorption was not identified in cervical cementum. However, the histological appearance of the cervical cementum differed between the two groups. Several aetiopathogenetic explanatory models which arise from these observations are discussed.     

Evaluation of calciotropic hormones in cats with odontoclastic resorptive lesions

OBJECTIVE: To assess associations between epidemiologic and laboratory variables and calciotropic hormones in cats with odontoclastic resorptive lesions (ORLs). ANIMALS: 182 client-owned cats older than 1 year of age with oral disease. PROCEDURE: Information on medical history, behavior, living environment, and feeding management was assessed by use of a questionnaire. After induction of general anesthesia, oral examination was performed following standardized protocols and included dental probing and full-mouth radiography. Laboratory analyses included evaluation of FeLV-FIV status, serum biochemical analyses, CBC, urinalysis, and serum concentrations of intact parathyroid hormone (iPTH), parathyroid hormone-related peptide (PTHrP), 25-hydroxyvitamin D (25-OHD), free thyroxine (fT4), and ionized calcium (iCa). RESULTS: ORLs were identified in 72.5% of cats. Mandibular third premolars were the most commonly affected teeth. Cats with ORLs were significantly older (mean, 9.2 years) than cats without ORLs (mean, 6.6 years). Multivariate logistic regression analysis revealed that 25-OHD, urine specific gravity, jaw-opening reflex on probing, and missing teeth were significant variables, even after accounting for age. Cats with ORLs had significantly higher mean serum concentration of 25-OHD (112.4 nmol/L) and significantly lower mean urine specific gravity (1.0263), compared with cats without ORLs (89.8 nmol/L and 1.0366, respectively). CONCLUSIONS AND CLINICAL RELEVANCE: Results did not indicate associations between iPTH, PTHrP, or fT4 and development of ORLs. In affected cats, the importance of high serum 25-OHD and low urine specific gravity has not been determined.     

Feline odontoclastic resorptive lesions an unsolved enigma in veterinary dentistry.

This article presents a comprehensive review of the literature on feline odontoclastic resorptive lesions (FORLs), including etiopathogenesis, prevalence and predisposition, classification, histopathologic appearance, diagnosis, and treatment. Approximately one-third of all domestic cats may develop FORLs during their life span, and the risk of developing FORLs increases with age. Sophisticated dental treatments promise neither cure nor permanent improvement of affected teeth. Extraction is the current treatment of choice. Research on the etiology of FORLs has not been rewarding in recent years, and the causative factors contributing to the development of FORLs are still unknown.     

Prevalence of odontoclastic resorptive lesions in a population of clinically healthy cats

The prevalence of odontoclastic resorptive lesions (ORLs) was determined in a clinically healthy cat population (228 cats) using both clinical (oral examination) and radiographic (full-mouth series with intraorally positioned dental film) methods. The overall prevalence rate was 29 per cent (mean age of the cat population 4.9 years). The mandibular third premolars (307, 407) were the most commonly affected tooth and the pattern of ORL development was symmetrical in most cats. The risk of having ORLs was found to increase with increasing age and cats with clinically and radiographically missing teeth were more likely to have the condition. Neutering, gender, age at neutering or mean whole mouth gingivitis index did not affect the prevalence of ORLs.     

Etiopathogenesis of feline dental resorptive lesions.

There are several factors in the etiopathology of feline resorptive lesions. They may be considered as local immune-response mediating cell and humoral factors; release of biochemical components in dental and paradental tissues to attract odontoclasts; mechanical stress, including occlusal mechanism; and local and systemic calcium regulation, including remodeling of mineralized tissue and dietary intake of calcium.     

Subgingival odontoclastic resorptive lesions. Classification, treatment, and results in 58 cats.

A commonly recognized dental problem in cats is the resorption of tooth structure and subsequent loss of the tooth. These tooth defects are often very painful, because the sensitive dentin layer is exposed. The destruction of the tooth through odontoclastic resorption is considered a consequence of inflammatory resorption, probably secondary to periodontal inflammation. Because these resorptive lesions are progressive in nature, it is best to stage this progression of resorption in order to address treatment planning. The purpose of this study was to evaluate a group of 58 cats with resorptive lesions to determine the outcome of treatment 6 months or longer after restoration. In 81% of the cats, there was loss of the tooth, evidence of further resorption, or loss of the restoration at one or more resorption sites. Of the 154 teeth restored, only 33% showed no further evidence of loss of tooth structure.     

Radiographic evaluation and treatment of feline dental resorptive lesions.

Many feline resorptive lesions are easily diagnosed by clinical oral examination, whereas others require dental radiographs. Radiographs can reveal the presence of resorption, and often the nature of the resorptive process as well. Removal of affected teeth when they cause discomfort, or of the portion of the tooth causing the discomfort, remains the only treatment that provides long-term resolution. Until we understand the etiology of the inciting causes and of the factors contributing to the progression of resorptive lesions, reliable prevention cannot be offered.     

Mapping of the radiographic central point of feline dental resorptive lesions

Intraoral dental radiographs of 217 cats presented for dental treatment were examined. Radiographic signs of dental resorptive lesions were identified in 107 cats, and the apparent central point of each lesion was mapped on a diagram of the tooth. Mapping was only possible on maxillary and mandibular canine teeth and on mandibular third premolar, fourth premolar, and first molar teeth. Resorptive lesions were most common on the molar teeth (n = 103) and maxillary canine teeth (n = 96), and least common on fourth premolar teeth (n = 56). Resorptive lesions on premolar and molar teeth were widely scattered, noted more commonly in the coronal portions of the root. Resorptive lesions in canine teeth had a tendency to be located more apically on the roots.     

Odontoclastic resorptive lesions in a dog

We found odontoclastic resorptive lesions on premolars and molars in a 4- year-old miniature dachshund. The teeth had been extracted because the dentin was resorbed. In some teeth, the roots had been replaced by hard tissue, and so we amputated the crowns and curetted roots and alveolar bone. Histopathological examination revealed that the dentin was resorbed by odontoclasts and was replaced with bony tissue. Ten months later we found resorptive lesions in other teeth, and we treated them along with the first treatment. At the time of writing, since this is the first report of a dog with the same lesion in other teeth after the first treatment, we hope to establish better treatment and prevention methods.     

Feline dental resorptive lesions. Prevalence patterns.

Surveys were carried out in cats presented for dental examination in the Netherlands (432 cats) and in the United States (78 cats). In 62% of the Dutch cats and 67% of the US cats, resorptive lesions were present. In the Dutch study, Asian Short-hair (principally Siamese) cats were most commonly involved, and male cats were more commonly affected than females. The most commonly affected teeth were the fourth maxillary premolar and the mandibular premolar and molar teeth.     

Prevalence of dental resorptive lesions in Swedish cats

Ninety-six, randomly selected Swedish cats were evaluated for the presence of dental resorptive lesions. All cats were examined while receiving general anesthesia. Diagnosis was based on oral examination and full-mouth, intraoral dental radiographs. Information concerning age, sex, vaccination status, eating habits, food type, environment (indoor or outdoor housing), oral, discomfort, dental care, and medical treatment was recorded. Hematologic samples included analysis for FeLV, FIV, and calcivirus. Of the cats examined in this study, 32% had gross or radiographic signs of dental resorptive lesions. There was a positive relationship between the occurrence of dental resorptive lesions and increasing age.     

Elemental composition of teeth with and without odontoclastic resorption lesions in cats

OBJECTIVE: To determine elemental composition of teeth with and without odontoclastic resorption lesions (ORL) in cats. SAMPLE POPULATION: Normal teeth from 22 cadaver cats and ORLaffected teeth from 21 cats admitted to the veterinary hospital for dental treatment. PROCEDURE: An electron microprobe was used to analyze weight percentages of calcium, phosphorus, fluorine, sodium, magnesium, sulfur, potassium, and iron in enamel, dentin, and cementum. RESULTS: Calcium and phosphorus were the most abundant elements. Fluorine, sodium, and magnesium combined were < 5% and sulfur, potassium, and iron combined were < 0.1% of total elemental composition. In enamel of normal teeth, a significant sex-by-jaw location interaction was seen in mean (+/- SD) phosphorus content, which was higher in mandibular teeth of females (1764+/-0.41%) but lower in mandibular teeth of males (16.71+/-0.83%). Mean iron content in dentin of normal teeth was significantly lower in mandibular teeth than maxillary teeth (0.014+/-0.005% vs 0.023+/-0.019%). Mean enamel sodium content was significantly higher (0.77+/-0.046% vs 0.74+/-0.025) and mean enamel iron content was significantly lower (0.017+/-0.008% vs 0.021+/-0.005%) in ORLaffected teeth, compared with normal teeth. In cementum, mean fluorine content was significantly lower (2.98%+/-0.27 vs 2.99+/-0.20%) and mean magnesium content was significantly lower (0.54+/-0.13% vs 0.60+/-0.13%) in ORL affected teeth, compared with normal teeth. CONCLUSIONS AND CLINICAL RELEVANCE: Results of our study establish baseline mineral content of enamel, dentin, and cementum for normal teeth in cats. Minimal differences in mineral content of enamel and cementum of normal and ORL-affected teeth were detected.