Aims: To identify the cephalometric features of three skeletal jaw relations (Class I, II and III). Materials and methods: one hundred thirty four students were selected aged 12-15 years from secondary schools in Mosul City, 45 with Class I normal occlusion as control, 44 with Class II malocclusion and 45 with Class III malocclusion, after taking the lateral cephalometric radiographs according to ANB angle. A 20 variables (12 angular and 8 linear) were used in this study to correlate these variables in the three skeletal Classes. Results: No significant sex differences were observed for the majority of angular and linear measurements for the three skeletal types. Anterior cranial base length (S-N) and saddle angle (NSAr) didn't show significant difference among the three skeletal Classes, the posterior cranial base (S-Ar) was shorter in Class III which indicate the anterior articulation of the mandible. The length of maxillary base (ANS-PNS) was longer in Class II than Class I and III which lead to maxillary prognathism. The body length of the mandible (Go-Pog),effective mandibular length (Ar-Gn) and lower anterior face height was significantly longer in Class III which lead to mandibular prognathism. The SNA angle was significantly smaller in Class III than in the others. SNB and SNPog angles were larger in Class III followed by Class I and then Class II. The gonial angle (Ar-Go-Me) was larger in Class III which acts to increase mandibular effective length. The (N-A-Pog) showed as convex in Class II and concave in Class III. (The U1-PP) angle was larger in Class II followed by Class I and then by Class III. The (L1-MP) angle in Class II and III was significantly smaller than in Class I. Conclusion: Most of the angular and linear measurements indicated that the skeletal differences between the Class I, Class II and Class III are concentrated with in the maxillary and mandibular bases in both the anteroposterior and vertical dimensions and their type of articulation. The dental measurements appear to be compensated with that of skeletal one. Also these variables showed no significant sex differences in the majority of their measurements.

The purpose of this study was to compare two mixed dentition prediction methods that do not require the use of periapical radiographs of the unerupted permanent lower teeth. The two compared methods were the Tanaka/Johnston (T/J) and the Boston University (BU) prediction approaches. Study casts of 52 children (20 males and 32 females) were used; those children were selected from primary and secondary schools located in different areas of Mosul City. All subjects have normal Class I molar relationship. The finding indicated that on the average the T/J approach overestimated the tooth size of the unerupted teeth (mean + SD = 1.02 + 1.07 mm). On the other hand, the BU approach underestimated the tooth size of the unerupted teeth (mean + SD =-0.2 + 1.07 mm). The findings further indicated that there were statistically significant correlation between the predicted and actual tooth size. The error involved in the use of the prediction equations was expressed as the standard error of the estimate (SEE). The present findings indicated that the SEE for T/J prediction ranged between 0.52-0.63 mm and the corresponding values for BU equation ranged between 0.45-0.68 mm. Depending on the stage of dental development; i.e., which deciduous and permanent teeth are present, the T/J approach can be used when the only permanent four mandibular incisors have completely erupted, whereas the BU approach can be used when all the deciduous (canines and first molars) are still present.

Aims: The current study aims to investigate the rate of space closure, tipping and rotation of canine during its retraction by laceback and tieback using standard ceramic brackets along 2 types of archwires using typodont simulation system (Ormco). Materials and Methods: The standardization criteria were all typodont teeth situated in well aligned position, covered and immobilized by the acrylic bite except canine, laceback and tieback were used to slide the canine. Results: The present study showed that when slide the canine on 0.017x 0.025 inch archwire gave rise to significant decrease in the rate of space closure, degree of tipping and rotation as compared when sliding it on 0.020 inch archwire, also sliding the canine using laceback as a method of retraction gave rise to a significant decrease in the rate of space closure, degree of tipping and rotation as compared with tieback. Conclusions: It was concluded that canine retraction using laceback retraction method along 0.017x0.025 inch archwire gave rise to a significant decrease in the rate of space closure, degree of tipping and rotation.

Aims: The aim of this study was to investigate if there is a correlation between the shape of the crowns of the incisors and crowding. Materials and Methods: Plaster models of 100 individuals having class I molar relationship were chosen .By using the irregularity index, 51 individuals (22 males and 29 females) were considered to be the crowding group(irregularity index >3mm),and 49 individuals (23 males and 26 females) were considered to be the normal group(irregularity index< 3mm).The casts were selected from the POP department at the college of dentistry in Mosul University. Repeated measurements of the maximum mesiodistal width of the incisal and cervical areas of the incisors were taken by means of a vernier caliper and a ratios of these measurements were calculated. Results:The mean value for the crowding group was significantly higher in the incisal area of lower incisors and upper central incisors than corresponding values in the normal group. A significant correlation was present between upper irregularity index and upper lateral incisor mesiodistal width ratio. Conclusions: The lower incisors were more triangulary shaped in the crowding group than those in the normal one.

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