Morphology of Sella Turcica in Skeletal Class II Subjects

A study on the morphology of sella turcica in skeletal Class II subjects in an orthodontic patient population showed 50% of the Class II subjects to have normal sella turcica morphology. The proportion of normal sella turcica was statistically significant among Class I as compared to Class II. 15% of the Class II subjects had bridging of sella turcica morphology and 11% of the Class II showed notching of posterior wall.


Introduction
The sella turcica is a saddle-shape depression in the sphenoid bone of the human skull.The anterior border of the sella turcica is represented by the tuberculum sellae and the posterior border by the dorsum sellae.The pituitary gland is surrounded by the sella turcica.Two anterior and two posterior clinoid process project over the pituitary fossa.The anterior clinoid processes are formed by the medial and anterior prolongations of the lesser wing of sphenoid bone, and the posterior clinoid process by the endings of dorsum sellae.During embryological development, the sella turcica is a key point for the migration of the neural crest cells to the fronto nasal and maxillary development fields.
The morphology of sella turcica is of importance in determining the cephalometric position of reference point sella.Variations in sella morphology have been discovered in skeletal Class III subjects1, cleft subjects2, in subjects with severe craniofacial deviations3, in dental anomalies4, and in syndromes5,6,7,8,9,10,11.Morphology of sella turcica in skeletal Class III malocclusion has been studied by various authors12,13,14,15.But the morphology of sella turcica in skeletal Class II subjects has not been reported.So this study was undertaken.

Materials and Methods
This was designed as a cross sectional study.The proportion of oblique anterior wall, double contour of floor and pyramidal shape did not differ between skeletal Class I and skeletal Class II subjects [Table 3].
In gender wise classification, there was not a statistically significant difference in the normal sella turcica morphology between males and females [Table 6].
The data on ANB angle of the study population is presented in Table 7 and Table 8.
Socio Demographic Profile:  the pituitary gland 17 .Abnormal sella turcica morphology was reported in cases with severe craniofacial deviations 3 , various genetic disorders 2 , syndromes [5][6][7][8][9][10][11] and in dental anomalies 4,18 .Variations in sella turcica morphology have been reported by different authors.75% of subjects in Silverman 31 's study had a normal morphology for sella turcica and remaining 25% had an abnormal morphology.In the present study 50% of the adults with skeletal Class II showed a normal morphology of sella turcica.
Gorden 19 (1922) classified the sella turcica morphology into 3 shapes, the circular, the oval or the flat/saucer shaped, their study sample included children of age ranging from 1 year to 12 years and most of them had either circular or oval shaped sella turcica.Davidoff and Epstein 20 (1950) put forward the term J shaped sella while Fournier and Denizet 21 (1965) used the term omega sella.Teal 22 (1977) classified the sella anatomy into round, oval or flat.Bruneton et al 23 (1979) studied the normal variants of sella turcica of adults.
Axelsson et al 16 (2004)  In a recent study by Sathyanarayana et al 24 in South Indian population, 15% of subjects in skeletal Class III subjects and 5% of skeletal Class I subjects were reported to have sella turcica bridging.In the present study 15% of subjects with skeletal Class II malocclusion had sella turcica bridging (Table 5).
Also many authors had concluded that, the prevalence of sella turcica bridging is higher in subjects with dental anomalies, cleft lip and palate and various other anomalies.
Axelsson et al 16 30 's study presented with a pyramidal shape morphology of dorsum sella.In the present study 11% of skeletal Class II and 4% of skeletal Class I subjects presented with a pyramidal shape of sella turcica.
In the present study 11% of skeletal Class II subjects showed notching of the posterior part of sella turcica.17% of Skeletal Class III subjects and 12% of Skeletal Class I subjects in Sathyanarayana et al 24' s study (South Indian population), 3.3% of skeletal Class III subjects and 6% of skeletal Class I subjects Hadeel et al 30

Conclusion
The present study showed 71% of Class I and 50% of Class II subjects to have normal sella turcica morphology.The variation in proportion of normal sella turcica was statistically significant among Class I as compared to Class II.Bridging of sella turcica and the notching of posterior wall were seen to be significantly more among Class II subjects than among Class I subjects.

Table 8 : ANB Values in Class II Subjects
's study, 10% of skeletal Class III subjects and 13.3% of skeletal Class I subjects of Shah et al's study (Islamabad), 11.1% of the orthodontic patient population (Saudi Arabia) in Alkofide 12 's study and 11% of females (Oslo University Craniofacial Growth Archive) in Axelsson et al 16 's study had irregularities of posterior part of dorsum sella.