Real understanding and investigation of crack propagation in natural teeth and dental orthodontics: Common dangerous crack paths under occlusal loads

Abstract

Abstract Current research introduces understanding of dental cracks with fundamental fracture behavior in natural teeth and dental materials studying of mixed mode cracks under compression-shear, tension-shear, mode I under tension, mode I under compression and mode II. The study is experimental work using models of PMMA for different cracks with different orientations. Cracking aspects of crack initiation, propagation direction, fracture distance, load and failure path are predicted experimentally and theoretically based on directional fracture approach and theories. The tests are carried out for (50) samples for compression and tension in LEFM. The friction between crack surfaces is investigated based on coefficient of friction and directional strain energy density fracture theory. The newly investigated negative critical stress intensity factor is considered for solving the complicated problems of cracks under compression loading like the occlusal stresses. The occlusal loads are compression loads with static will produce lateral tensile loads. The relations between crack orientation angle, fracture propagation angle, fracture load and fracture envelope are presented with comparisons. These results are important to predict the fracture and propagation before teeth failure. It will help for prevention and control of dental-cracks, correct restoration, prosthodontics, orthodontics, development of new technologies and new dental-materials.