Brachycephalic breeds of dogs, and more recently cats, have been gaining popularity as pets. According to the Cat Fanciers' Association, Persian and Exotic cats have ranked as the most popular purebred cats in the United States in the past few years.1 The structure of their skulls gives these cats a unique appearance but may also result in developmental dental anomalies2,3 that can be categorized on the basis of number, shape, structure, and position. These anomalies can cause problems on their own but can also contribute to oral and dental diseases,4 the most commonly reported diseases in feline veterinary practice.5,6 Thus, information on the prevalence and types of dental anomalies in brachycephalic cats, particularly Persian and Exotic cats, would help veterinarians counseling owners of these cats and individuals considering obtaining them.
To the authors' knowledge, only 1 published report7 has suggested that certain cat breeds are predisposed to dental disease, and studies8–10 evaluating and characterizing dental abnormalities according to breed or skull anatomy are scarce and mainly address dog breeds. The goals of the study reported here were to determine the prevalence of dental anomalies in a population of purebred, brachycephalic Persian and Exotic cats from various geographic regions and analyze potential relationships with oral disease.
Materials and Methods
Animals
The study was designed as a prospective cross-sectional study. Cats were eligible for inclusion in the study if they were a purebred cat of a brachycephalic breed and were scheduled at 1 of 3 participating practices to undergo general anesthesia related or unrelated to dental disease. All cats examined between January and December 2015 that met the inclusion criteria were considered for inclusion in the study. Owner consent for a dental examination and full-mouth radiography was required.
Procedures
In all cats, a complete history was obtained and preoperative clinicopathologic testing was performed. Cats were anesthetized, and a complete dental examination (including periodontal probing and dental inspection with an explorer), 3-view oral photography, and full-mouth digital dental radiographya-c were performed by 1 of 3 individuals (LAM, JPG, and JGF). For each cat, data pertaining to all teeth were collected; all findings were recorded by means of standard dental charting.
Variables
Anatomic variables recorded for all cats included the class (1 to 4) of occlusion according to AVDC nomenclature described for dogs,11 the presence or absence of ventral bowing of the mandibles (determined to be present if mesioversion of the mandibular canine teeth and crowding of the mandibular P4 with the mandibular M1 were observed), any anomalies of dentition (number, eruption, shape, position, or persistent deciduous teeth), stage (1 to 4) of PD11 for each tooth, and radiographic anomalies (root retention, supernumerary roots, tooth fractures, and TR). Tooth resorption was classified as external replacement resorption when the periodontal ligament was absent or as inflammatory resorption when the periodontal ligament was present.12,13 Positional anomalies were assessed by evaluating each tooth individually on the basis of oral photographs and radiographs of the patient and classifying each positional anomaly in accordance with AVDC nomenclature for orientation (mesio-, disto-, palato-, linguo-, labio- or buccoversion), rotation, and impaction.
Statistical analysis
All variables were recorded, summarized, and analyzed with commercially available statistical software.d,e For categorical data, the Pearson χ2 or Fisher exact test was used to evaluate associations between resorption type and tooth type. For continuous variables, ANOVA (parametric data) or the Mann-Whitney-Wilcoxon test (nonparametric data) was used to evaluate associations between numerical anomalies, PD, or TR and age. For all analyses, values of P < 0.05 were considered significant.
Results
Cats
Fifty client-owned cats (Persian, n = 42; Exotic, 8) were included in the study. Cases were from California (n = 4); Lisbon, Portugal (27); and Krakow, Poland (19). The cats ranged in age from 8 months to 16.2 years. Twenty-four cats were female (19 spayed), and 26 were male (20 castrated). Thirty-five of the 50 (70%) cats underwent general anesthesia for procedures related to dental disease, and 15 (30%) underwent general anesthesia for procedures not related to dental conditions.
Occlusion and tooth position
Fourteen of the 50 (28%) cats had normal occlusion, and 36 (72%) had malocclusion (class 1 or neutroclusion, 18 [36%]; class 3 or mandibular mesioclusion, 14 [28%]; class 4 or maxillomandibular asymmetry, 3 [6%]; and class 2 or mandibular distoclusion, 1 [2%]; Figure 1). Malocclusion of the canine teeth (cats, 30% [15/50]; teeth, 2.1% [28/1,349]) and crowding of the incisor teeth (cats, 50% [25/50]; teeth, 5.9% [79/1,349]) were most common. Twenty-eight of the 50 (56%) cats had crowding of the teeth. This was especially true for the incisor teeth (25 cats) but was also observed to involve the mandibular premolar and molar teeth in 9 cats (Figure 2). Thirty-two of the 50 (64%) cats had at least 1 tooth with some type of position change, and of the total 1,349 teeth evaluated, orientation was the most common positional abnormality (7.9% [106/1,349]), followed by rotation (1.4% [9/1,349]) and impaction (0.37% [5/1,349]). The teeth most commonly affected were the mandibular incisor teeth (5.9% [79/1,349]) with mesio- or distoversion; canine teeth (2.1% [28/1,349]) with mesio-, disto-, palatal-, or linguoversion; mandibular premolar and molar teeth (0.50% [7/1,349]) with rotation; and maxillary P3s and P4s (0.59% [8/1,349]) with rotation (Figure 3).
Photographs of the mouths of 4 cats for comparison of mandibular neutroclusion (A), mandibular distoclusion (B), mandibular mesioclusion (C), and maxillomandibular asymmetry (D).
Citation: Journal of the American Veterinary Medical Association 253, 1; 10.2460/javma.253.1.66
Photographs of the mouths of 2 brachycephalic cats illustrating crowding of the mandibular incisors (301 and 401; A) and crowding of the left mandibular P4 and M1 (308 and 309; B).
Citation: Journal of the American Veterinary Medical Association 253, 1; 10.2460/javma.253.1.66
Photographs of malpositioned maxillary canine teeth in 2 brachycephalic cats.
Citation: Journal of the American Veterinary Medical Association 253, 1; 10.2460/javma.253.1.66
In 9 of the 50 (18%) cats, ventral bowing of the mandibles, evidenced by mesioversion of the mandibular canine teeth and crowding of the mandibular P4 by the mandibular M1, was observed.
Numerical abnormalities
Fifteen of the 50 (30%) cats had a normal number of teeth, whereas 3 (6%) had hyperdontia and 32 (64%) had hypodontia. Hyperdontia resulted from persistent deciduous teeth (4% [2/50]) or supernumerary teeth (2% [1/50]). Hypodontia was identified when there was an absence of clinical crowns, corresponding to retained roots (cats, n = 15; teeth, 29); absence of radiographic evidence of tooth structures (cats, 27; teeth, 151); or impaction of teeth (cats, 5; teeth, 6).
There were 151 clinically absent teeth that were confirmed absent by radiography (Figure 4). The most common teeth missing were the maxillary P2s as observed in 36% (18/50) of the cats. Patients missing 1 or both of these premolar teeth were significantly (P = 0.034) older than those that still had both.
Distribution of missing teeth in 50 brachycephalic cats.
Citation: Journal of the American Veterinary Medical Association 253, 1; 10.2460/javma.253.1.66
Eruption and anatomic abnormalities
Five of the 50 (10%) cats had impacted or embedded teeth (maxillary canine teeth, n = 4; maxillary third incisor tooth, 1). Shape abnormalities were present in 9 of the 50 (18%) cats, 3 of which had supernumerary roots, 3 had canine teeth with deformed roots, 2 had two-rooted maxillary P2s, and 1 had suspected gemination (Figure 5).
Photograph (A) and radiograph (B) of a brachycephalic cat with gemination of the left mandibular P4 (308).
Citation: Journal of the American Veterinary Medical Association 253, 1; 10.2460/javma.253.1.66
Periodontal disease
Periodontal disease affected at least 1 tooth in 88% (44/50) of the cats (Figure 6). Mean age of the cats with healthy periodontium (PD stage 0; mean, 2.6 years, 95% confidence interval, 0 to 8.5 years) was significantly (P = 0.016) less than the mean age of those with PD (stages 1 to 4; mean, 7.11 years; 95% confidence interval, 2.0 to 16.2 years). Of the 1,349 teeth evaluated, 66.8% (901/1,349) did not have any signs of PD and were classified as PD stage 0; however, 30.0% (405/1,349) were classified as PD stage 1, 3.3% (44/1,349) were classified as PD stage 2, 0.74% (10/1,349) were classified as PD stage 3, and 1.3% (17/1,349) were classified as PD stage 4.
Distribution of PD stages for teeth (n = 1,349) in the same 50 brachycephalic cats depicted in Figure 4.
Citation: Journal of the American Veterinary Medical Association 253, 1; 10.2460/javma.253.1.66
Tooth fractures
Tooth fractures were identified in 22% (11/50) of the cats. Fractures most commonly involved the canine teeth, representing 90% (19/21) of all tooth fractures.
Tooth resorption
In 35 of the 50 (70%) cats, at least 1 tooth was found to have TR. Mean ± SD age of cats with TR (7.9 ± 4.13 years) was significantly (P < 0.001) higher than that for cats without TR (2.5 ± 3.36 years). On the basis of analysis of radiographs of each tooth, 9.1% (123/1,349) of the teeth were determined to have external inflammatory resorption, with the premolar teeth most commonly affected, and 6.1% (82/1,349) had external replacement resorption, with the canine teeth most commonly affected (Figures 7 and 8). Resorption type (inflammatory vs replacement resorption) was significantly (P < 0.001) associated with tooth classification (incisor, canine, premolar, or molar tooth) in that there were more premolar and molar teeth with inflammatory resorption lesions than expected and more canine teeth with replacement resorption lesions than expected. For incisor teeth, observed numbers with inflammatory and replacement resorption did not differ from expected numbers.
Distribution of external inflammatory (black bars) and replacement (gray bars) resorption for teeth (n = 1,349) in the same 50 brachycephalic cats depicted in Figures 4 and 6.
Citation: Journal of the American Veterinary Medical Association 253, 1; 10.2460/javma.253.1.66
Prevalence of external inflammatory (black bars) and replacement (gray bars) resorption according to tooth type in the same 50 brachycephalic cats depicted in Figures 4, 6, and 7.
Citation: Journal of the American Veterinary Medical Association 253, 1; 10.2460/javma.253.1.66
Discussion
Results of the present study suggested that because of their brachycephaly, Persian and Exotic cats have unique oral and dental features that may predispose them to dental disease such as TR and PD.
In the group of cats studied, malocclusions were commonly observed (72% [36/50]). The finding that mandibular mesioclusion affected only 28% (14/50) of the cats was unexpected, because the mandibles tend to achieve a more normal length despite the short maxillas in brachycephalic animals. One could expect this maxillary-mandibular discrepancy to predispose affected cats to mandibular mesioclusion, similar to that observed in some brachycephalic dog breeds. However, this did not seem to be the case in the present study. The findings suggested that the maxillary-mandibular interlock caused by the canine teeth may have helped maintain a more normal occlusion in the brachycephalic cats evaluated.
In the present study, maxillary canine mesioversion, mandibular canine distoversion, and crowding of the mandibular P4 by the mandibular M1 was observed in 9 of 50 (18%) cats, with most having neutroclusion. This suggested that the dental interlock opposed the growth of the mandibles and may have led to 2 consequences: ventral bowing of the mandibles and tipping of the canine teeth. Findings of the present study supported those of a previous study14 in which one of the common features of the brachycephalic craniofacial type was dorsorotation of the jaw, or bowing of the mandibles. Mesioclusion of the maxillary canine teeth is considered genetic in origin in Persian cats4 and has been suggested as a good phenotypical screening criterion to help evaluate and categorize the severity of brachycephaly in cats.14
For cats in the present study, all cases of maxillomandibular asymmetry were associated with maxillary canine palatoversion, and with or without mandibular mesioclusion. This skeletal malocclusion seemed to be a consequence of the absence of unilateral maxillary interlock, which is thought to guide the growth of the mandibles so that they are longer than the maxillas in brachycephalic cats.15
A relationship between malocclusion and persistent deciduous teeth has been described frequently in some dog breeds, but has been found less often in cats.16 In the present study, only 2 of 50 (4%) cats were identified with persistent deciduous teeth, and 1 of these cats also had an impacted permanent canine tooth.
Numerical dental abnormalities were present in 76% (38/50) of the cats in the present study: 12% (6/50) had polydontia and 64% (32/50) had hypodontia. Maxillary P2s were the most commonly absent teeth, and maxillary M1s were the second most commonly absent. Indeed, 18 of the 50 (36%) cats were missing at least 1 maxillary P2, and 14 (28%) were missing premolar teeth bilaterally. It seemed that the brachycephalic cats of the present study had more congenital absences of teeth than what has been reported previously for domestic cats.17 Although the authors were not aware of previously published reports on congenital dental absences in Persian or Exotic cats, the population of brachycephalic cats in the present study exhibited more maxillary premolar and molar tooth absences than other breeds. However, this finding may have been an artifact resulting from an overestimation of early tooth loss. For instance, maxillary P2 absences were consistently identified in geriatric cats of the present study, potentially contributing to an overestimation of true tooth absence not attributed to tooth loss. Although no radiographic evidence of any tooth structures was observed for the missing maxillary P2s, these teeth are small and, if affected with PD or TR, could be lost early in life.
Supernumerary roots are anatomic variations occasionally identified in cats.17 Only 1 cat in the present study had bilateral supernumerary mandibular premolar roots.
Impaction was frequently observed (10% [5/50]) in the present study. However, the study's population of 50 cats may not have been representative of all cats in general; thus, the reported prevalence of this dental abnormality could have been overestimated. Nevertheless, 2 cats in the present study shared a common ancestor and had impaction of the same maxillary canine tooth. Lineage and hereditary pattern studies are needed to evaluate whether there are any heritability patterns in brachycephalic cat breeds.
Tooth fractures were diagnosed in 22% (11/50) of the cats in the present study. By contrast, a Flemish survey18 reported about an 11% tooth fracture incidence. Inclusion criteria used for the present study may have contributed to the difference between studies because most of the cats in the present study were anesthetized for dental reasons. Nevertheless, canine teeth in cats, similar to those in dogs, seem more vulnerable to fracture, probably attributable to their position in the oral cavity and their function in prehension and defense.19
Eighty-eight percent (44/50) of the cats in the present study had PD. The authors were not aware of studies addressing prevalence of PD in specific cat breeds; however, experts have mentioned a higher incidence of PD in purebred cats.18 An association between breed and furcation exposure has been reported,7 and Exotic cats were among the breeds studied. Purebred cats in that study more commonly had gingivitis, furcation exposure, and bone loss, and Persian and Exotic cats were described as notably more affected with these conditions, when compared with a mixed-breed population.7
In the veterinary literature, reported prevalence of TR in cats has varied from 28% to 67%, depending on availability of dental radiography and whether cats were examined for dental disease or problems unrelated to the oral cavity.5,20-23 Approximately one-third of cats reported in previous studies21,24 had at least 1 resorptive lesion. When considering just the purebred cat population, this value has been reported as 69.6%.24 Although the cats included in the present study were anesthetized for dental and nondental procedures, the results obtained here cannot be said to reflect the prevalence of TR in the entire brachycephalic cat population. Nevertheless, findings of the present study were consistent with those of an earlier report24 in that 70% (35/50) of the cats in the present study had at least 1 resorptive lesion.
The AVDC Nomenclature Committee classifies TR according to severity (stage 1 to 5) and location (type 1 to 3) of resorption on the basis of radiographic appearance. In the present study, the classification of external replacement resorption versus external inflammatory resorption was made on the basis of radiographic appearance of the tooth's periodontal ligament (absent vs present). Because the periodontal ligament is present in TR types 1 and 3, they were grouped together in the present study. The authors were aware that TR type 3 shows both radiographic features (presence and absence of a periodontal ligament); however, in the authors' opinions, this type of resorptive lesion should be included with external inflammatory resorption because it tends to be associated with advanced disease and inflammation.25
There was a notable association between TR type and tooth classification in the present study. The canine teeth were more commonly affected with external replacement resorption, and the premolar teeth were more commonly affected with external inflammatory resorption. To the authors' knowledge, no previous studies assessing inflammatory and noninflammatory resorption in specific breeds of cats have been published; however, experts have mentioned that there are anatomic features that lead to cementum and periodontal ligament changes in brachycephalic cats. This could be secondary to excessive compression, lack of occlusal stress, or the use of suboptimal forces during mastication.24,26,27 Brachycephalic breeds may present anatomic features that favor the occurrence of TR in some specific teeth, and occlusal stress may differ from that which occurs in other breeds. In the cats of the present study, chronic mechanical occlusal trauma to the maxillary incisor and canine teeth as a result of bowing of the mandibles was observed. A lack of mesial occlusal stress may occur as a result of tipping of the mesial teeth, which was more evident in the canine teeth. Theoretically, incisor teeth should be more affected by this phenomenon and TR. However, this was not observed in the present study because incisor teeth were frequently absent (30.5% [46/151 radio-graphically absent teeth]). Of the 29 retained roots identified, 15 (51.7%) were of incisor teeth. This also supported the probable underestimation of the percentage of incisor teeth with resorption. Further investigations with larger populations are needed to assess TR prevalence in incisor teeth.
Acknowledgments
Preliminary results were published in Portuguese as part of a dissertation research project of Dr. Louro supervised by Drs. Mestrinho and Requicha. Presented in abstract form at the 25th European Congress of Veterinary Dentistry, Dublin, Ireland, May 2016.
Funded by the Fundação para a Ciěncia e Tecnologia Project UID/CVT/00276/2013.
The authors thank Sue McTaggart for language correction and Ricardo Santos for technical assistance.
ABBREVIATIONS
| AVDC | American Veterinary Dental College |
| M1 | First molar tooth |
| P2 | Second premolar tooth |
| P3 | Third premolar tooth |
| P4 | Fourth premolar tooth |
| PD | Periodontal disease |
| TR | Tooth resorption |
Footnotes
VistaScan, Dürr Dental AG, Bietigheim-Bissingen, Germany.
Progeny, Midmark Corp, Dayton, Ohio.
CR 7 Vet, iM3 Pty Ltd, NSW, Australia.
Microsoft Excel, version 14.3.8 for Mac, Microsoft Corp, Redmond, Wash.
SPSS Statistics Developer, version 22.0 for Mac, IBM Corp, Armonk, NY.
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