~ 183 ~  International Journal of Applied Dental Sciences 2020; 6(1): 183-188  ISSN Print: 2394-7489 ISSN Online: 2394-7497 IJADS 2020; 6(1): 183-188 © 2020 IJADS www.oraljournal.com Received: 26-11-2019 Accepted: 29-12-2019 Ausma Jan Post Graduate Student, Department of Orthodontics and Dentofacial Orthopaedics, M.R. Ambedkar Dental College and Hospital, Bangalore, Karnataka, India Rabindra S Nayak Professor and Head Department of Orthodontics and Dentofacial Orthopaedics, M.R. Ambedkar Dental College and Hospital, Bangalore, Karnataka, India Kavya BR Post Graduate Student, Department of Orthodontics and Dentofacial Orthopaedics, M.R. Ambedkar Dental College and Hospital, Bangalore, Karnataka, India Suresh S Nair Senior Lecturer, Department of Orthodontics and Dentofacial Orthopaedics, M.R. Ambedkar Dental College and Hospital, Bangalore, Karnataka, India Srishti Galav Post Graduate Student, Department of Orthodontics and Dentofacial Orthopaedics, M.R. Ambedkar Dental College and Hospital, Bangalore, Karnataka, India Rachana Chopra Post Graduate Student, Department of Orthodontics and Dentofacial Orthopaedics, M.R. Ambedkar Dental College and Hospital, Bangalore, Karnataka, India Corresponding Author: Ausma Jan Post Graduate Student, Department of Orthodontics and Dentofacial Orthopaedics, M.R. Ambedkar Dental College and Hospital, Bangalore, Karnataka, India Correlation between curve of spee and various dental and skeletal cephalometric parameters. A radiological study Ausma Jan, Rabindra S Nayak, Kavya BR, Suresh S Nair, Srishti Galav and Rachana Chopra Abstract The aim of this study was to correlate Curve of Spee (COS) with various dental and skeletal cephalometric parameters. The study comprised of 110 lateral cephalograms and orthodontic study models. The subjects were divided into 5 groups on the basis of ANB angle and Angle’s molar relation. A statistically significant correlation was found between Angle’s molar relation and COS. A statistically significant linear positive relationship of COS with Jarabak Ratio and L7 to MP distance was seen. The direction of the relationship was negative in relation to L1 to MP angle. It was concluded that depth of COS was greater in Group IIb > Group IIa >GroupIIc >Group I >Group III. COS increases with an increase in Jarabak’s ratio and L7 to MP distance and decreases with increase with L1 to MP angle. Keywords: Curve of Spee, Angles molar relation, Jarabak ratio . 1. Introduction Curve of Spee (COS) is defined as the line on a cylinder which is tangent to incisal edges of lower anteriors, occlusal surface of lower second molar and anterior border of condyle [1] . Ferdinand Graf von Spee a German embryologist (1855-1937) was the first to describe the Curve of Spee in 1890. He used skulls with abraded teeth to define the line of occlusion. This line on a cylinder which is tangent to incisal edges of lower anteriors, occlusal surface of lower second molar and anterior border of condyle Von Spee located the center of this cylinder in the mid orbital plane having radius of 6.5 to 7.0 cm. [1, 2] Clinically COS is measured from distal marginal ridges of the most posterior teeth in the arch to the incisal edges of the anteriors [3] . Andrews [4] described six keys to normal occlusion. The curve of Spee is the sixth key to occlusion. He found that the curve of Spee ranges from flat to mild in subjects with proper occlusion and hence best static occlusion can be achieved with flat occlusal plane. The understanding of how the curve of Spee develops is limited in literature. Some have suggested that its development probably results from a combination of many factors which include growth of orofacial structures, eruption of teeth and development of neuromuscular system [5, 6] .It has been mentioned that the mandibular sagittal & vertical position relative to cranium is related to curve of Spee, which is present in various forms in mammals. In humans an increased curve of Spee is often seen in brachycephalic facial patterns and associated with short mandibular bodies [7, 8, 9]. Several theories have been proposed to explain the presence of COS in natural dentition. It has been mentioned that an imbalance between the anterior and posterior components of occlusal force can lead to supra eruption of lower incisors, infra eruption of premolars, mesial inclination of lower molars. This altered condition requires special skills for the practitioner. Thorough knowledge would be useful of how and when this this COS develops so that it will help us in treatment planning [10, 11] . Levelling the curve of Spee represents a routine procedure in orthodontic practice [12] and more pronounced the curve is, additional space is required to flatten the dentition [13] . The assessment of depth of curve of Spee represents a critical point for orthodontic diagnostic & treatment protocol [14] .