The Occurrence of an Optical Phenomenon: "The Butterfly Effect" in Cross Section of Extracted Mandibular First Premolars.

Background The butterfly effect is an optical phenomenon with endodontic and a restorative significance that can be seen in cross-sections of some of the tooth roots. Objective To investigate occurrence of butterfly effect in roots of extracted human mandibular first premolars and to determine differences in tubule density in mesio-distal and bucco-lingual direction of sections of root having buttery effect. Method It was an prospective experimental study comprised of twenty single rooted extracted mandibular first premolars. Each tooth was divided into three sections: coronal, middle and apical third. Then, nine sections of each sample were taken, three from each section i.e., coronal, middle and apical third, hence making sample size of total 180. All the selected samples were ground into 1 mm thickness and examined under 20X magnification microscope. Five samples presenting with the butterfly effect were selected and prepared for Scanning Electron Microscope to evaluate the difference in density of dentinal tubules among mesio-distal and buccolingual direction. Mann Whitney U test was applied to find out the significance of butterfly effect among different sections. The data was entered in Microsoft excel sheet and transferred to Statistical Package for Social Sciences (SPSS) version 20 for statistical analysis. Ethical approval was obtained from Kathmandu University School of Medical Sciences institutional review committee (IRC No.:127/16). Result Butterfly effect was seen in 19.4% of sample. Apical sections had more occurrence rate (30%) followed by middle (23.3%), and coronal sections (5%). Female predilection (30%) for occurrence was seen. Under SEM, the samples with butterfly effect presented with higher median density (2349.32 number/mm2 ) of dentinal tubules in bucco-lingual section as compared to mesio-distal section (1208.23 number/mm2 ). Conclusion Butterfly effect was present in 19% of the samples. Butterfly effect is more seen on aplical section of tooth. Female have more chance of having butterfly effect than male.