Harold Henry Messer

Learn More
The purpose of this study was to analyze the type and frequency of defects in nickel-titanium rotary endodontic files after routine clinical use, and to draw conclusions regarding the reasons for failure. All of the files (total: 378, Quantec Series 2000) discarded after normal use from a specialist endodontic practice over 6 months were analyzed. Almost(More)
This study examined used, discarded rotary nickel-titanium instruments obtained from 14 endodontists in four countries, and identified factors that may influence defects produced during clinical use. A total of 7,159 instruments were examined for the presence of defects. Unwinding occurred in 12% of instruments and fractures in 5% (1.5% torsional, 3.5%(More)
The aim of the study was to determine the extent to which canal size, radius of curvature and proximal root concavity influence fracture susceptibility and pattern. A standardized cross-section of the mid-root region of a mandibular incisor was created by averaging the dimensions of 10 extracted teeth, and then the basic finite element analysis (FEA) model(More)
The fracture of endodontic instruments is a procedural problem creating a major obstacle to normally routine therapy. With the advent of rotary nickel-titanium (NiTi) instruments this issue seems to have assumed such prominence as to be a considerable hindrance to the adoption of this major technical advancement. Considerable research has been undertaken to(More)
Nickel-titanium engine-driven rotary instruments are used increasingly in endodontic practice. One frequently mentioned problem is fracture of an instrument in the root canal. Very few studies have been conducted on torsional characteristics of these instruments, and none has been done under dynamic conditions. The purposes of this study were to measure the(More)
AIM To examine if canal enlargement with instruments of controlled taper leads to more uniform stress distributions within a root, thereby reducing fracture susceptibility. METHODOLOGY Finite element models of a mandibular incisor were constructed with round and oval canal profiles, based on measurements from extracted teeth. The shapes of rotary(More)
The purpose of the study was to determine whether rotary nickel-titanium (NiTi) canal preparation strengthens roots, and whether the fracture pattern can be predicted by finite element analysis (FEA) models. From a fracture mechanics viewpoint, structural defects, cracks or canal irregularities are likely to play a major role in fracture susceptibility of(More)
Endodontically treated teeth are thought to be more susceptible to fracture as a result of the loss of tooth vitality and tooth structure. This study was designed to compare the contributions of endodontic and restorative procedures to the loss of strength by using nondestructive occlusal loading on extracted intact, maxillary, second bicuspids. An(More)
OBJECTIVES This study was planned to investigate the variations in strains in enamel under different patterns of occlusal loading, using three-dimensional finite element analysis (3D FEA) and strain gage measurements in extracted teeth. METHODS A 3D FEA model of a mandibular second premolar was used to investigate effects of occlusal load on enamel(More)