Influence of crosshead speed on failure load and failure mode of restored maxillary premolars

Abstract

Abstract:We analyzed the effect of the crosshead speed of an applied load on failure load and failure mode of restored human premolars. Fifty intact, noncarious human premolars were selected. Class II mesio-occlusodistal preparations were made with a water-cooled high-speed preparation machine, and the teeth were restored with composite resin. The specimens were divided into five groups (n = 10 each) and tested individually in a mechanical testing machine, in which a 6.0-mm-diameter steel cylinder was mounted to vary the crosshead speed: v0.5: 0.5 mm/min; v1: 1.0 mm/min; v2.5: 2.5 mm/min; v5: 5.0 mm/min; and v10: 10.0 mm/min. The cylinder contacted the facial and lingual ridges beyond the margins of the restorations. Peak load to fracture was measured for each specimen (N). The means were calculated and analyzed with one-way analysis of variance followed by Tukey's test (a = 0.05). The mean load at failure values were (N) as follows: v0.5, 769. 4 ± 174.8; v1, 645.2 ± 115.7; v5, 614.3 ± 126.0; v2.5, 609.2 ± 208.1; and v10, 432.5 ± 136.9. The fracture modes were recorded on the basis of the degree of the tooth structural and restorative damage: (I) fracture of the restoration involving a small portion of the tooth; (II) fractures involving the coronal portion of the tooth with cohesive failure of the composite resin; (III) oblique tooth and restoration fracture with periodontal involvement; and (IV) vertical root and coronal fracture. Varying crosshead speeds of 0.5-5.0 mm/min did not influence the failure load of restored maxillary premolars; however, increasing the crosshead speed to 10 mm/min decreased the failure load values and the degree of tooth structural damage.

Effect of cavity preparation design and ceramic type on the stress distribution, strain and fracture resistance of CAD/CAM onlays in molars

“… 21 Tooth fracture is defined by the moment when stress intensity exceeds a critical value prompting rupture. 32 The periodontal ligament plays an important role in this failure process, because it can deform and accommodate the tooth in the alveolus, which alleviates stress in the cervical region of the tooth. In this experiment, a polyether impression material was used with polystyrene resin to simulate more realistic fractures observed clinically.…”

“… 27 Other important aspect is the speed employed on the fracture resistance test, structures with ductile characteristics tend to be brittle when submitted to higher crosshead speed load applications. 32 To simulate the tooth fracture with compressive loading, crosshead speeds of 0.5 were used in this study, which allows a better stress distribution inside the restored tooth. 32 In the biomechanical analysis of tooth structures and restorative materials, destructive mechanical tests used to determine fracture resistance are important means of analyzing tooth behavior in situations of high intensity load application.…”

“… 32 To simulate the tooth fracture with compressive loading, crosshead speeds of 0.5 were used in this study, which allows a better stress distribution inside the restored tooth. 32 In the biomechanical analysis of tooth structures and restorative materials, destructive mechanical tests used to determine fracture resistance are important means of analyzing tooth behavior in situations of high intensity load application. However, these tests do show limitations with regard to obtaining information about the internal behavior of the tooth-restoration complex.…”

“…The strain gauges were placed in the region in which a finite element model indicated the presence of the highest polymerization stresses. The specimens were subjected to nondestructive axial compressive loading using a metal sphere 6mm in diameter at this orientation and a crosshead speed of 0.5 mm/min 32 in a mechanical testing machine (DL2000; EMIC) until reaching 100 N, when the first strain value was recorded. Then, the load was applied until failure, and the second strain value was recorded (n=7).…”

Influence of voxel size on cone-beam computed tomography-based detection of vertical root fractures in the presence of intracanal metallic posts

“…In the VRF group, the periodontal ligament was simulated before induction of the fracture, as described previously. 16 The VRF was then induced by an Instron machine (Instron, TTDML®, Canton, MA, USA) by using a 2000 kilogram-force load cell and a cross-speed of 0.5 mm/min. After confirmation of the fracture, fragments that showed complete separation were glued with cyanoacrylate cement (Loctite®, Henkel Ltda., Sao Paulo, SP, Brazil).…”