[Impacted third molar root abnormality with mandibular canal close position as a presupposing factor to inferior alveolar nerve trauma].

Objective: The aim of the study is reducing the risks of surgical injury to the inferior alveolar nerve, by taking into account individual topographic and anatomical features, improving diagnostic methods, and techniques for removing retinated teeth with a close fit to the mandibular canal.

Material and methods: An examination was conducted in the Department of Surgical Dentistry (CBCT/OPG) and surgical treatment of 223 patients, with a close fit of the roots of the retinated lower third molar to the mandibular canal. Microslips of teeth with roots intact during removal (n=96) of the main group and the control group (n=52) were prepared with a Micromet Remet manual petrographic machine. The sections were carried out along the longitudinal axis of the tooth with the capture of the area of close fitting of the nerve, the teeth from the control group were sawed longitudinally along the axis of the root. The measurement of the macroanatomic features of the roots was carried out with a micrometer (MCC-MP-100 0.001 electronic «CHEESE», manufactured in the Russian Federation), measurements of the thickness of dentine and cement tissues on macroglyphs were carried out using a microscope calibration ruler with an accuracy of 0.01 mm.

Results: In the main group, three types of attachment of the mandibular canal to the root of the third molars were distinguished: 20 (96) cases of inter-root attachment of the mandibular canal, 42 (96) apical, 34 (96) lateral (buccal and lingual). A number of anomalies in the structure of the roots of the third molars have been revealed, which are a factor in injury to the neurovascular bundle of the mandibular canal during tooth extraction. The surface of the roots, as well as the microscopes of the tooth sections adjacent to the mandibular canal, were studied under a microscope.

Conclusion: A number of specific anomalies of the roots of retinated third molars formed by root dilaceration, thinning of cement tissues, hypercementosis, which are formed at the site of the mandibular canal.In the presence of a deep indentation on the root of the tooth, as well as in the presence of areas of apical hypercementosis in the form of a «spike», the probability of nerve injury during tooth extraction increases many times, which must be taken into account when removing retinated third molars.