A Retrospective Study of the Prevalence of First Premolars in 306 Thoroughbred Yearlings.

This study reviewed dental charts from 306 Thoroughbred yearlings to measure the prevalence of the equine first premolar tooth and found that a majority had erupted first premolars during examination, with a higher percentage in females than in males.

Introduction to the Study

• The research paper is a retrospective study of the prevalence of the equine first premolar tooth in Thoroughbred yearlings. The study was conducted in a private veterinary hospital in Lexington, Kentucky.
• The equine first premolar is often considered a vestigial tooth that doesn’t play any significant role in mastication. It has been historically blamed for a variety of abnormalities, mainly biting and chewing issues that concern riders. The treatment for this tooth is highly debated among clinicians.

Study Design and Population

• The sample considered for the study consisted of 306 Thoroughbred yearlings, their average age being 14.73 months (ranging between 8 and 22.7 months). The dental records of these horses were thoroughly scrutinized for the research.

Main Findings

• The study found that about 72.9% of these horses had erupted first premolars at the time of examination, their average age being 14.99 months. The rate of first premolar eruption was greater with age, with up to 90% of Thoroughbred yearlings showing erupted maxillary first premolars by the age of 18 months.
• The research also pointed out that sexual dimorphism was evident as significantly fewer males (67.4%) than females (77.6%) were found to have first premolars; a finding significant at p ≤ .05.
• Mandibular and supernumerary first premolars, which are hardly reported in any existing literature, were reported to be absent in this group. This suggests that maybe these types of premolars either erupt at a later age or are less common in Thoroughbreds.
• Maxillary first premolars were found to be common amongst Thoroughbred yearlings and were observed to continue erupting up until about 18 months of age, which is later than previously reported in some literature.