REVISTA ROMÂNÅ DE STOMATOLOGIE – VOLUMUL LXI, NR. 3, AN 2015 231 ORTODONŢIE 4 CRANIAL BASE SYMMETRIC AND NORMAL LOWER JAW ROTATION Mohamed Khwanda 1 , Yazan Jahjah 2 1 Department of Orthodontics, Faculty of Dentistry, Tishreen University, Syria 2 Orthodontics and Dentofacial Orthopedic Department, Dental School, Tishreen University Corresponding author: Mohamed Khwanda, MD, Department of Orthodontics, Faculty of Dentistry, Tishreen University, Syria E-mail: M.khwanda88@gmail.com ABSTRACT Understanding the complexities of cranial base development, function, and architecture is important for testing hypotheses about many aspects of craniofacial variation and evolution. Architecturally, the cranial base provides the platform upon which the brain grows and around which the face grows. In addition, the cranial base connects the cranium with the rest of the body: it articulates with the vertebral column and the mandible, provides conduits for all the vital neural and circulatory connections between the brain, the face and the neck, houses and connects the sense organs in the skull, and forms the roof of the nasopharynx. The shape of the cranial base is therefore a multifactorial product of numerous phylogenetic, developmental, and functional interactions. Aim. The aim of this research is to perform a morphometric analysis of the skull base to investigate the symmetry between the two hemibases of the cranial fossa with each other in adult patients with normal type of lower jaw rotation using cone beam copmuted tomography CBCT in transversal plane. Materials and methods. In result of radiographic study, 35 Caucasian adult patients with no prior orthodontics treatment were selected (16 males, 19 females) from 16 to 27 years (mean age of 20.02 years: females average age was 20.15 years; males average age was 21.84 years) of age with normal type of lower jaw rotation according to the sum of Björk. Pearson’s Correlation Coefficient was calculated to investigate the symmetry between the two hemibases of the cranial fossa with each other. Results. A difference was found amongst the two genders of the sample subjects in the strength of the correlation between the CBCT angular measurements evaluating the two hemibases of the cranial base symmetry. Conclusion. A difference was found amongst the two genders. This study found no exact symmetry between the samples, but it was in high level for adult females. Keywords: cranial base, symmetry, CBCT, normal lower jaw rotation INTRODUCTION The cranial base plays a major role in the skull integration and function, which it can be consid- ered as the oldest part of the vertebrate skull ac- cording to its phylogenetic history (de Beer, 1937) (1). Also it effects facial orientation proportionally to neurocranium, on the other hand there isn’t enough information about the probable effect of the cranial base on other aspects of facial shape such as height, length, and width. To what extent is overall facial shape independent of the cranial base? It is supposed that the main facial growth is indepen- dent of cranial base growth, basically because the majority of the face grows in a skeletal growth de- velopment path after the neural growth phase ends. In humans, for example, the human face reaches 95% adult size by 16-18 years, which is after the cranial base reaches adult size by 10 years at least (Stamrud, 1959; Moore and Lavelle, 1974) (2,3). In addition it seems that the most facial and ba- sicranial dimensions are genetically not related in adults (Cheverud, 1996) (4). However, there is some evidence proposes that changes in the ratios of the cranial base can effect facial shape. This kind of interaction is predicted to be particularly important, and exclusive to humans, in which the upper face lies almost completely un- der the anterior cranial fossa (Weidenreich, 1941; Howells, 1973; Enlow and Bhatt, 1984; Enlow, 1990; Lieberman et al., 2000) (5-9). The importance of the cranial base is matched by several challenges that make it difficult to study.