Pavlychko R. Specific Features of Restoration of the Crown Part of the Masticatory Teeth with Significant Loss of Hard Tissue by Endocrowns

Pavlychko, R. R. Specific Features of Restoration of the Crown Part of the Masticatory Teeth with Significant Loss of the Hard Tissue by Endocrowns. – PhD Thesis Manuscript. Thesis for a Candidate of Sciences Degree (PhD) for specialty 14.01.22 Stomatology. - Danylo Halytsky Lviv National Medical University, Ministry of Health of Ukraine, Lviv, 2020. The materials most widespread from the practical point of view and used in dental orthopaedics for the restoration of the lost hard tissues of the masticatory teeth have been studied using the techniques for detection of the nucleation and propagation of destructive processes, evaluation of the strength and plasticity, viscosity of fracture caused by the static and cyclic loads (created by the pressure of the masticatory force and higher loadings) based on the parameters of acoustic emission, and electronic microscopy has been used to study the nucleation and propagation of fractures and their structure. Based on the results of the conducted tests, the dental materials were ranged for their applicability for direct and indirect restorations of the endodontically treated tooth, which will improve the efficiency of their use in dental practice. The fracture resistance of the structures with endocrowns is determined by the tooth strength, the destruction of which causes a premature failure of the structure. It was scientifically substantiated that only endocrowns made of metal ceramics and zirconia can ensure the restoration of the strength characteristics of the teeth prepared for endocrowns to those of the intact tooth. Pressable ceramics and zirconia demonstrated the best durability under the cyclic load. The clinical assessment of the results was done in three groups of restorations: composite restorations, metal ceramic endocrowns and pressable ceramic endocrowns. They were compared relying on such criteria as secondary decay, debonding, staining of the interface, micro chipping of the restoration, complete loss of the restoration, partial chipping of the tooth wall. The endocrowns made of metal ceramics and pressable ceramic showed the best results in terms of functioning and absence of expected complications during the whole follow-up period as compared to the composite onlay and inlay restorations. Key words: metal ceramics, pressable ceramics, zirconia, endocrowns, physico-mechanical properties, acoustic emission, dental materials science.