RESISTANCE OF ENAMEL IN SUPRA-OCCLUSION CONTACTS OF INDIVIDUAL TEETH IN RATS OF VARIOUS AGES

Abstract

Introduction. Supra-occlusion is a position of a group of teeth or individual teeth, the cutting edge or chewing surface of which is located above the occlusal plane. This condition is characterized as primary traumatic occlusion, supra-contact or traumatic nodes, in which a number of structural and functional changes occur in the hard tissues of the teeth and periodontal tissue. Traumatic occlusion of teeth is often caused by occlusal intervention, such as high fillings or prostheses, parafunctional habits. In physiological conditions, the protection of teeth from chemical and mechanical interventions is provided by their structural and functional resistance. However, the influence of supra-occlusion on the resistance of tooth enamel, and especially in different age groups, has not yet been studied. Therefore, we consider this topic relevant. The objective of the work was to study the state of enamel resistance in supra-occlusal contacts of individual teeth in rats of various ages according to the enamel resistance test (ERT-test). Materials and methods. The study involved 36 white male laboratory rats aged 4 to 22 months and weighing 100 to 210 g. The animals were divided into two groups (control and experimental), each was divided into three subgroups (6 animals each) according to age categories: young, mature, old-aged. In the study group, the state of supra-occlusion was simulated by increasing the height of the lower right second molars via filling 1 mm in height, without preparation of hard tissues of the teeth. Previously, the animals were anesthetized intramuscularly with sodium thiopental solution. After removing the animals from the experiment on the 15th day by decapitation under general anesthesia with sodium thiopental, by intraperitoneal injection, the dental blocks were removed and the structural and functional state of the tooth enamel was determined by the ERT-test. Statistical processing of data was performed using the program AtteStat V.12.5 with the determination of the mean and its error (M ± m). The probable significance of the difference in the obtained data was determined by the Student's t-test (p ≤ 0.05). Study results. In the control group, ERT-test values decreased (enamel resistance increased accordingly) in rats, depending on age. In young rats, enamel resistance to acidic dissolution was the smallest, and in mature and old-aged rats it increased. However, the difference between the age groups was not statistically significant (p > 0.05). A similar situation was registered in animals of the study group. However, statistically significant differences were observed only between young and old-aged rats (p = 0.025). In the control group, the acid resistance of enamel is higher compared to study group (p = 0.007). In young rats from the control group, enamel resistance to acids was 16.7% higher than in the study group (p = 0.025). In mature animals of the control group, the resistance of enamel to acid dissolution is 17.7% higher than in the study group (p = 0.046), and in old-aged – by 15.2% (p = 0.2). Conclusions. The resistance of enamel of teeth that are subjected to increased stress via supra-occlusal interactions is reduced in young, mature and old-aged rats in comparison with the control group. Reduced enamel resistance can be one of the risk factors in the occurrence of dental caries.