Objective: To observe the reaction of dental pulp and periapical tissues in dogs less than 2 years of age after tooth fracture.

Results: The first group including 3 dogs 11 months old in which we fractured all third incisors, canines, fourth premolars and third upper molars (84 teeth together), showed by the F-test, significantly different results in pulp vitality resulting in dentin production compared with second group. In the first group, 21 teeth (50%) mainly premolars survived for 10 months. During that time,the size of pulp cavity in these teeth decreased 25-30% depending on kind of tooth. The lowest ability to survive was observed in incisors (2-3 months). In the second group, 9 tooth pulps (21,4%) survived for 10 months but the size of pulp cavity did not decreased as significantly as in the first group. The size of pulp cavity decreased in values between 5-15%. 60% tooth pulps necrotized in two months after injury involving prevailingly incisors and canines.

Conclusion: Fractured teeth in the early stages of maturation, consisting of 40-50% hard tissue, have much higher ability to continue dentin deposition despite chronic pulp inflammation. By comparison, teeth in the second year of life consist of more then 60% hard tissue, have a lower ability to survive, and significantly decreased dentin production.