Development of Yorkshire Terrier Dentition

SIMPLE SUMMARY: Several problems, particularly in smaller breed dogs, have been associated with tooth development, e.g., over-crowding, missing teeth, and persistent deciduous teeth (where a juvenile tooth remains in the mouth at the same time as its permanent counterpart). This opportunistic study of 61 Yorkshire terrier puppies aimed to determine the average age of deciduous tooth loss and permanent tooth eruption, the incidence of persistent deciduous teeth, and potential influencing factors such as body weight. The age at which deciduous teeth were lost, and permanent teeth erupted, varied according to body weight; dogs weighing less than 3 kg lost their deciduous teeth and gained their permanent teeth later than dogs weighing more than 3 kg. The sequence of tooth loss and eruption (i.e., incisors first followed by canines, premolars, and then molars) was disrupted in dogs < 3 kg. Persistent deciduous teeth were common, affecting 69% of puppies. Those with lower body weights (<3 kg) had greater proportions and were more likely to require surgical extractions by a veterinarian. This study highlights the importance of regular checks by a veterinary professional during the active phases of tooth development. ABSTRACT: The development of dentition in dogs has been associated with several problems including tooth over-crowding, missing permanent dentition, and persistent deciduous teeth (PDT). Information on dentition development in different breeds is lacking. This study of 61 Yorkshire terriers aimed to determine the (i) average age at deciduous tooth exfoliation, (ii) average age at permanent tooth eruption, (iii) PDT incidence, and influencing factors such as body weight. The ages of exfoliation of deciduous teeth and eruption of permanent dentition were influenced by body weight and tooth type. These dentition changes tended to occur later in dogs ≤ 3 kg versus dogs > 5 kg. Generally, incisors were exfoliated first, followed by premolars and then canines. At a body weight of 4.5 kg, the middle of the data range, the estimated age at loss of deciduous teeth (with 95% confidence intervals) was 21.9 (21.1, 22.9) weeks for incisors, 26.1 (24.9, 27.4) weeks for canines, and 23.9 (22.9, 24.9) weeks for premolar. The estimated age at eruption of permanent dentition was 22.3 (21.6, 23.0) weeks for incisors, 23.8 (23.0, 24.6) weeks for canines, 24.7 (24.0, 25.5) weeks for premolars, and 26.4 (25.5, 27.3) for molar teeth. However, this sequence was disrupted in dogs ≤ 3 kg. Yorkshire terriers had a high incidence of PDT. At a body weight of 4.5 kg, the estimated proportion of PDT was: incisors 0.86% (0.32, 2.31), canines 15.62% (7.62, 29.37) and premolars 3.57% (1.62, 7.66). Canines constituted the most frequently retained tooth type, with 89.1% retained in dogs ≤ 3 kg compared to 12.0% in dogs > 5 kg. This information will enable veterinarians to provide personalised advice regarding the oral care requirements for Yorkshire terriers and highlights the need to regularly monitor this breed between the ages of two and seven months, during the active phases of tooth development.