The Butterfly Effect: An Investigation of Sectioned Roots Assil A. Russell, BDS,* Nicholas P. Chandler, BDS, MSc, PhD,* Catharina Hauman, BDS, MDS,* Amna Y. Siddiqui, BDS, DClinDent, † and Geoffrey R. Tompkins, BSc, PhD* Abstract Introduction: The butterfly effect is an optical phenom- enon 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 ex- hibiting 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 buccolin- gual root sections (45,348 mm À2 ) and lowest mesio- distally (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) Key Words Dentin bonding, dentinal tubule, root canal, sclerosis T he ‘‘butterfly’’ effect was photographed by Beust (1) in 1931 as an optical phenomenon in some cross-sections of tooth roots. In 1983, Vasiliadis et al (2) reported that dentinal tubular sclerosis differs in the mesiodistal and buccolin- gual directions, noting a characteristic butterfly shape in transverse sections of the roots caused by different shades of dentin. Sclerosed dentin is more translucent than normal dentin (3, 4). Literature on the butterfly effect is limited. A recent study (5) proposes that the presence of dentinal tubules causes light to refract and scatter. A decrease in the number of dentinal tubules results in greater light trans- mission to give a translucent appearance. The mechanism behind dentin translucency remains unclear (5). The aim of this study was to investigate the density of dentinal tubules in mesiodistal and buccolingual cross-sections of tooth roots exhibiting the butterfly effect and to determine if the effect is featured throughout the length of roots and is age related. Materials and Methods Ethical approval was granted from the University of Otago, Dunedin, New Zealand, to collect 30 single-rooted human teeth of a known age. These were divided into 3 groups of 10: group 1: 15–24 years old, group 2: 25–44 years, and group 3: 45 years and over. The teeth were decoronated, and their roots embedded in acrylic (Vertex Self Curing; Vertex-Dental BV, Zeist, The Netherlands) and cut into 1-mm-thick cross- sections with a saw (Accutom 50; Struers A/S, Ballerup, Denmark). Each root yielded 10 sections that were marked to indicate orientation. Sections were viewed under a light microscope (EHT; Olympus, Tokyo, Japan) at Â10 magnification by 2 calibrated exam- iners and given a score. A score of 1 represented no butterfly effect, where the dentin had uniform color; a score of 2 represented the butterfly effect defined as a section dis- playing 2 shades of dentin (Fig. 1). Examiners reached a consensus for each section. The scores for each tooth were summed. A score of 20 represented a tooth in which the effect was present in all sections, whereas 10 represented a tooth in which the effect was totally absent. From each age group, the 2 teeth with the highest overall scores were selected (6 teeth) for further examination. As controls, 2 teeth with a score of 10 (no butterfly effect) were selected. For each of the 8 teeth (6 experimental and 2 controls), 2 adjacent sections were chosen. The more coronal section was cut in a mesiodistal direction using a fine finishing bur (Komet 956EF 314010; Brasseler, Lemgo, Germany) in a high-speed handpiece. The other was cut in a buccolingual direction (Fig. 2). Because of the size and fragility of the sections, each was reduced incrementally to yield 1 usable half, giving a total of 16 specimens. To remove organic material and cutting debris, the specimens were placed in 4% sodium hypochlorite for 5 minutes in an ultrasonic bath followed by EDTA (EDTA 18%; Ultradent, South Jordan, UT) for a further 5 minutes. They were then rinsed and stored in 0.9% saline until scanning electron microscopic (SEM) analysis. The specimens were mounted with the canal lumina upward (Fig. 3). An SEM image (850Â) of the center of each canal lumen was taken (JSM 6700F; JEOL Ltd, Tokyo, Japan). Images were coded and printed on A4 size paper, and the number of tubule orifices per square millimeter was counted on the prints, the area of which represented 9,216 mm 2 . Tubules were counted twice by 2 examiners working inde- pendently who were unaware which root/section was under consideration. In cases in which the results differed (under 5% of the micrographs), the tubules were recounted to reach a consensus. A Student’s t test was used with an alpha value of 0.05 to analyze the data. From *Sir John Walsh Research Institute, Faculty of Dentistry, University of Otago, Dunedin, New Zealand; and † Division of Endodontics, King Abdulaziz University, Jeddah, Saudi Arabia. Supported by a Summer Studentship to Dr Russell from the Oral Microbiology and Dental Health Research Theme, Univer- sity of Otago. Address requests for reprints to Dr Nicholas P. Chandler, School of Dentistry, University of Otago, PO Box 647, Dune- din 9054, New Zealand. E-mail address: nick.chandler@otago. ac.nz 0099-2399/$ - see front matter Copyright ª 2013 American Association of Endodontists. http://dx.doi.org/10.1016/j.joen.2012.09.016 Basic Research—Biology 208 Russell et al. JOE — Volume 39, Number 2, February 2013