This work presents a stress-strain state analytical estimation of restored tooth hard tissues with consideration of their contact interactions with a monolithic filling or a dental onlay. The tooth with a defect is simulated as a continuous isotropic cylindrical body with a non-through hole, and the filling or onlay is simulated as an elastic deformable cylinder. The contact between the tooth and the fillings (onlay) is simulated as the ideal contact. The final strength estimation of the restored tooth is carried out according to the energy criterion. The authors suggest a linear index of tooth damage for practical application of the obtained results. This index can be easily obtained by direct measurement. The differential approach is developed to select a restoring method of the tooth with the defect to provide a reliable restoration of the anatomical crown of the tooth.

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Background. Restoring large defects with proximal caries extending below the cemento-enamel junction and cavity margins located beneath the gingival tissues represents a very common clinical situation. The aim of this article is to propose a clinical classification of the localization subgingival margins of cavity.Material and methods. Diagnosis is carried out by periodontal probe perpendicular to the long axis of the tooth in the deepest point of the cavity’s margin. To describe the localization subgingival margins of cavity we use exponent which value is equal to the distance (integer number expressed in millimeters) of the level of epithelial attachment to the margin of the cavity. Three periodontal examiners, with >10 years of periodontal practice, were required to attend a calibration session aimed at the validation of the proposed classification. Results. The intrarater and interrater agreement among the localization subgingival margins of cavity: for intrarater agreement ranged from 0.74 to 0.95 (almost perfect agreement), whereas interrater agreement ranged from 0.26 to 0.59 (moderate agreement).Conclusions. The classification the localization subgingival margins of cavity is useful for reaching a more precise diagnosis.

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The selection of an optimal treatment is one of the problems when restoring the defects of dental hard tissues after endodontic treatment. The work aims at studying the percentage ratio of the volume of the coronal portion of the tooth to its crown that will allow us to optimize the determination of the extent of dental hard tissue defect after endodontic treatment as well as to choose the optimal method of treatment. The objective of the research was to optimize the diagnostic process when treating damaged coronal portion of the tooth after endodontic treatment through the determination of the percentage ratio of the volume of the coronal portion of the tooth to the total volume of tooth crown for different groups of teeth. Materials and methods. 42 extracted teeth with preserved coronal portions served as the material for our study. The volume of the coronal potion of the tooth as well as the total volume of tooth crown was determined using the method developed by us. Having calculated the ratio of the volume of the coronal portion of the tooth to the volume of tooth crown, we received the volume which is occupied by the coronal cavity of the tooth. Results. We obtained the percentage ratio of the volume which is occupied by the coronal cavity of the tooth compared to its crown for different groups of teeth. Conclusions. To estimate the extent of damage to the coronal portion of the tooth after endodontic treatment, it is recommend using the obtained data, namely, in the maxillary and mandibular front teeth, the coronal portion of the tooth occupies up to 10% of tooth crown volume, while in the maxillary and mandibular grinding teeth, the coronal portion of the tooth occupies up to 5% of tooth crown volume.