Oral Rehabilitation

Purpose: Atraumatic, oscillating ultrasonic instruments have recently been developed for prosthodontic margin finishing. This in vitro observational pilot study aimed to compare the condition of crown preparation margins finished using new ultrasonic instruments with margins finished with conventional rotary instruments.

Objective: The aim of this study was to evaluate cracks on root ends following resection and cavity preparation with a laser and two established techniques. Background data: If root canal treatment of a tooth fails, an apicoectomy operation may be indicated. Three millimeters of the root tip is resected and a cavity of similar depth with parallel walls is cut to receive a root-end filling. Materials and methods: Sixty extracted human maxillary anterior teeth were used. Their root canals were prepared with rotary instruments, and they were filled with gutta-percha. Twenty teeth were resected with tungsten carbide fissure burs, and their root-end cavities cut with tungsten carbide round burs at a slow speed (Group 1). The other 40 teeth were resected with an Er:YAG laser, and root-end cavities were made with the same laser (Group 2), or with an ultrasonically-powered zirconium nitride coated retrotip (Group 3). The number and types of cracks on the resected surfaces were assessed using a stereomicroscope before and after cavity preparation. Results: Cracking was not significantly different between the more conventional group and the laser groups after resections ( p > 0.05) or following cavity preparation ( p > 0.05). Conclusions: In this in vitro study, the laser resection and root-end preparation technique did not influence the number or type of cracks formed on the root surfaces.

The butterfly effect is an optical phenomenon seen in some sections of tooth roots. The aim of this work was to investigate the density of dentinal tubules in mesiodistal and buccolingual cross-sections of roots exhibiting the butterfly effect and to determine if the effect is featured throughout the length of roots and is age related. Methods: Thirty extracted single-rooted teeth were allocated to the following groups according to patient age: group 1: 15-24 years, group 2: 25-44 years, and group 3: 45 years and over. The teeth were decoronated, and their roots were embedded in acrylic and cut into ten 1 mm-thick cross-sections. Sections were viewed under a light microscope and coded (1 or 2) according to presence or absence of the butterfly effect. A root scored 20 when all levels exhibited the butterfly appearance. The 2 teeth with the highest score from each group and 2 control teeth with the minimum score (of 10) were selected. Two adjacent, consecutive cross-sections were chosen with the most coronal cut mesiodistally and the other buccolingually. Scanning electron micrographs (Â850) were taken of the central portion of their canal lumina and the density of the dentinal tubules determined. Results: The butterfly effect was found at all levels in the roots of the affected teeth. The tubule density was highest in the buccolingual root sections (45,348 mm À2 ) and lowest mesiodistally (12,605 mm À2 ), a significant difference (P = .02). This trend was found across all age groups. Conclusions: Root sections with the butterfly effect have a lower density of dentinal tubules mesiodistally corresponding to the wings of the butterfly. The pattern was observed in teeth from all age groups and was absent in controls. (J Endod 2013;39:208-210)

Introduction: Most vertical root fractures occur in root canal treated teeth, and they usually run in a buccolingual direction. The butterfly effect is an optical phenomenon seen in some sections of tooth roots. The aim was to investigate the microhardness of dentin in mesiodistal and buccolingual cross sections of roots exhibiting the effect. Methods: Thirty extracted single-rooted teeth were allocated according to patient age: group 1, 15-24 years; group 2, 25-44 years; and group 3, 45 years and older. Roots were embedded in acrylic and cut into ten 1-mm-thick cross sections. Sections were viewed under a light microscope and coded (1 or 2) according to presence or absence of the butterfly effect. A root scored 20 when all levels featured the butterfly appearance. The 2 teeth with the highest score from each group and 2 control teeth with the minimum score (10) were selected. Two adjacent, consecutive cross sections were chosen from the middle of the roots. Vickers microhardness testing was carried out on the dentin walls. Results: Mean hardness scores were highest mesiodistally (83.7 kgf/ mm 2 ) and lowest buccolingually (56.4 kgf/mm 2 ), a significant difference (P = .028). This trend was found across all age groups. Conclusions: Root sections with the butterfly effect are harder mesiodistally. This might explain the high prevalence of vertical root fractures that run buccolingually. (J Endod 2014;40:842-844) HV, Vickers hardness of 32 indents from 16 sections. *1 = young (15-24 years); 2 = middle-aged (25-44 years); 3 = old (45 years and older). † P = .028. ‡ P = .079.

Background: Health care depends, in part, on the ability of a practitioner to see signs of disease and to see how to treat it. Visual illusions, therefore, could affect health care. Yet there is very little prospective evidence that illusions can influence treatment. We sought such evidence.