Chronology and sequence of emergence of permanent premolar teeth in the horse: study of deciduous premolar 'cap' removal in Thoroughbred racehorses.
Authors: Ramzan P H L, Palmer L, Barquero N, Newton J R
Journal: Equine veterinary journal
Summary
# Editorial Summary: Permanent Premolar Eruption in Thoroughbreds Whilst equine dental textbooks present standardised eruption ages for permanent premolar teeth, little rigorous data actually supports these figures. Ramzan and colleagues examined 508 deciduous premolar 'caps' extracted from 207 Thoroughbred racehorses to establish the true chronology and sequence of permanent premolar emergence, using mixed effects regression analysis to account for individual variation and anatomical factors. The mean extraction ages were substantially later than commonly cited: 35.1 months for PM2, 37.7 months for PM3, and 45.1 months for PM4, with significant influences from tooth position, jaw location, and notably, sex—female horses showed delayed eruption compared to males, providing the first evidence of sexual dimorphism in equine permanent dentition. Since abnormal cheek tooth eruption is implicated in developmental dental disease, retained caps, and occlusal problems, these corrected eruption timelines are critical for practitioners monitoring young racehorses during their competitive years; delayed emergence patterns mean that clinical intervention for cap removal or eruption monitoring may need adjustment, particularly in fillies. This work challenges long-standing assumptions about equine dental development and underscores the need for evidence-based protocols tailored to individual variation and sex differences.
Read the full abstract on PubMed
Practical Takeaways
- •Do not rely on traditional age-based eruption charts; individual variation is substantial and influenced by sex and tooth position—clinical assessment of cap presence remains essential
- •Female Thoroughbreds typically shed premolar caps later than males; adjust routine dental examination schedules accordingly to avoid over-treating or under-treating based on age alone
- •Understanding the complexity of premolar eruption is important for identifying true abnormalities versus normal variation, which may help prevent unnecessary intervention or missed pathology
Key Findings
- •Mean ages at deciduous premolar cap removal were 35.1 months (PM2), 37.7 months (PM3), and 45.1 months (PM4), differing considerably from widely reported emergence ages in equine literature
- •Significant sexual dimorphism identified with female horses showing later cap extraction ages than males
- •Tooth position affects eruption chronology with more caudal teeth, upper jaw teeth, and female horses showing significantly delayed cap removal compared to rostral, lower jaw, and male horses