Mohammed F.doc J Bagh College Dentistry Vol. 25(3), September 2013 Prediction the widths Pedodontics, Orthodontics and Preventive Dentistry153 Prediction the widths of maxillary and mandibular canines and premolars from the widths of maxillary incisors and first molars (Iraqi study) Mohammed Nahidh, B.D.S., M.Sc. (1) ABSTRACT Background: This study aimed to use the combined mesio-distal crowns widths of maxillary incisors and first molars as predictors to the combined mesio-distal crowns widths of maxillary and mandibular canines and premolars. Materials and methods: The sample included 110 Iraqi Arab subjects with an age ranged between 17-25 years and class I skeletal and dental relations. The crown widths of maxillary teeth and mandibular canines and premolars were measured at the largest mesio-distal dimension on the study casts using digital electronic caliper with 0.01 mm sensitivity. Pearson’s correlation coefficient was used to determine the relation between the combined mesio-distal crowns widths of maxillary incisors and first molars and the combined mesio-distal crowns widths of maxillary and mandibular canines and premolars. Regression analysis was used to determine the equations that predict the widths of maxillary and mandibular canines and premolars. Paired sample t-test was used to compare between the actual and predicted mesio-distal crown widths. Results and Conclusions: The findings showed a non-significant difference between the predicted and actual mesio- distal crown widths; hence the combined mesio-distal widths of maxillary incisors and first molars can be used as predictors for the combined mesio-distal widths of maxillary and mandibular canines and premolars. Key words: Prediction, regression analysis, space analysis. (J Bagh Coll Dentistry 2013; 25(3):153-157). الخالصة الضواحك و رض االسنان االنسي الوحشي المجتمع لالنیاببع ؤللتنب العلویة األولىاألضراس و للقواطع العرض االنسي الوحشي المجتمع استخدام ھدفت ھذه الدراسة إلى :خلفیةال .العلویة والسفلیة الفك عرض االنسي الوحشي السنانال تم قیاس. السنیةو ھیكلیةال العالقات الصنف األول من من ذوي سنة و 25-17بعمر یتراوح بین عراقي شخص 110 شملت العینة :الطرقالمواد و لتحدید بیرسون معامل ارتباط تم استخدام. على القوالب الدراسیة خاصتھم ملم 0.01 تصل الى حساسیةوب الرقمي االلكتروني الفرجار باستخداملي الفك السف ضواحكو وانیاب العلوي تحلیل استخدامب. العلویة و السفلیة الضواحكو عرض االسنان االنسي الوحشي المجتمع لالنیابمع العلویة األولىاألضراس و للقواطع العرض االنسي الوحشي المجتمع العالقة بین تم المتوقعالفعلي و عرض االسنان االنسي الوحشي بین للمقارنة. الضواحك العلویة و السفلیةو بعرض االسنان االنسي الوحشي المجتمع لالنیاب التي تتنبأ المعادالت تحدیدتم االنحدار . المقترن t اختبار استخدام للقواطع العرض االنسي الوحشي المجتمع یمكن استخدام ، وبالتاليالفعلي و المتوقع عرض االسنان االنسي الوحشي بین ةمعنوی قوفرعدم وجود ت النتائجأظھر :النتائج واالستنتاجات .العلویة والسفلیة الضواحكو بعرض االسنان االنسي الوحشي المجتمع لالنیابتنبؤ ل العلویة األولىاألضراس و .راغالف تحلیل، تحلیل االنحدار، التنبؤ :مفتاحیةالكلمات ال INTRODUCTION Accurate prediction of the space available to accommodate the un-erupted canines and premolars forms an important part of an orthodontic assessment in the mixed dentition as it is reported to assist dental practitioners to determine the treatment options for the patients (1). The accuracy, safety and simplicity are important criteria for a predictive method to become a part of the comprehensive case analysis in contemporary orthodontic practice (2). Many methods had been employed to predict space for un-erupted teeth (3-17). Two of them are the most commonly used methods; Moyers’ probability tables (5) and the prediction equation of Tanaka and Johnston (14). However, these methods were developed on Caucasian populations and their predictive accuracy on populations from other races is doubtful. This led to development of prediction equations and probability tables for different populations. Many methods used regression equations based on the high linear correlation between relevant groups of teeth. The main factor in this (1)Lecturer. Department of Orthodontics, College of Dentistry, University of Baghdad. category is the possibility of predicting the sizes of un-erupted teeth by using the widths of other fully erupted permanent teeth (2). In Iraq, many researches had been performed to predict the widths for un-erupted canines and premolars. Al-Khashan (18) studied some of the dimensional features of the permanent teeth that had a relevance of orthodontic treatment in Iraqi sample and compare to the results from different racial and ethnical groups. He found that the probability charts for prediction the width of cuspid and bicuspid utilizing the width of the lower incisor (Moyer's chart) not to be accurate to be used for Iraqi subjects. Sofia (19) developed regression equations to predict the widths of maxillary and mandibular canines and premolars from maxillary and mandibular incisors. On the other hand, Jargees (20) predicted the widths of premolars from the widths of deciduous molars. Awni (21) compared two mixed dentition prediction methods that do not require the use of periapical radiographs of the un-erupted permanent lower teeth. The two compared methods were the Tanaka/Johnston (T/J) and the Boston University (BU) prediction approaches. J Bagh College Dentistry Vol. 25(3), September 2013 Prediction the widths Pedodontics, Orthodontics and Preventive Dentistry154 She found that 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 the deciduous canines and first molars are still present. Abdulrasool (22) predicted the combined mesio-distal width of the maxillary and mandibular canines and premolars from the width of maxillary and mandibular first molar respectively, while Al-Bustani (23) used the sum of the mesio-distal widths of the left permanent maxillary central incisor, first molar and mandibular lateral incisor as predictor for the combined mesio-distal width of un-erupted maxillary and mandibular canines and premolars and compared her findings with Sofia (19) and Abdulrasool (22). In 2011, Al-Dabagh (24) predicted the width of maxillary canine from the width of mandibular canine, while Jargees (25) was able to estimate the widths of un-erupted canines and premolars from the vistibulo-oral crown dimensions of permanent teeth using multiple regression equations. This study aimed to use the combined mesio- distal crowns widths of maxillary incisors and first molars as predictors to the combined mesio- distal crowns widths of maxillary and mandibular canines and premolars. MATERIALS AND METHODS Sample The sample comprised 110 Iraqi Arab subjects (55 males and 55 females) with an age ranged between 17-25 years had full complement of permanent teeth regardless the third molars, class I skeletal and dental relations (26) with no history of orthodontic treatment, bad oral habits, maxillofacial surgeries or defects. The teeth are free from caries, restorations, attrition or malformations. Methods The subjects examined extra- and intra-orally to fulfill the inclusion criteria. Impressions for maxillary and mandibular arches were taken using Alginate impression material, and then poured with dental stone. After setting, the impressions were inverted over a plastic mold containing Plaster of Paris to make the bases for the casts. The teeth in maxillary arch from the first molar to the first molar in the other side and the mandibular canines and premolars were measured at the largest mesio-distal dimension. The anatomic mesial and distal contact areas of each tooth were marked by a fine marker on the dental cast and then the greatest mesio-distal crown width was measured using electronic digital calipers (sensitivity 0.01 mm) held parallel to the occlusal plane (27). Statistical analyses The data were subjected to computerized statistical analyses using SPSS program (version 19). The statistical analyses included: 1. Descriptive statistics (means, standard deviations and the numbers and percentages of the cases that over and underestimated the actual widths of canines and premolars). 2. Inferential statistics that comprised: • Pearson’s correlation coefficient (r) to find out the relation between the combined mesio-distal widths of maxillary and mandibular canines and premolars with the combined mesio-distal widths of maxillary incisors and first molars. • Independent sample t-test to test the presence of gender difference for the measurements. • Simple regression analysis to determine the regression equations that can be used to predict the combined mesio-distal widths of maxillary and mandibular canines and premolars. • Paired sample t-test to show whether there is significant difference between the predicted and actual mesio-distal widths of maxillary and mandibular canines and premolars in both genders. RESULTS AND DISCUSSION Most of the published articles tried to determine the width of canines and premolars using the methods of Moyers or Tanaka and Johnston. Nourallah et al. (28) depended upon the mandibular central incisors and maxillary first molars. Bernabé et al. (29) depended on the maxillary and mandibular central incisors and maxillary first molar, while Melgaço et al. (30), Memon and Fida (31) and Mittar et al. (32) utilized the mandibular incisors and first molars. On the other hand, Jaju et al. (33) depended on three measurements; the sum of width of mandibular incisors, the latter with mandibular and maxillary first molars separately and finally Paredes et al. (34) found that the widths of maxillary central incisors and lower first molars were the best predictor for the widths of canines and premolars. In the present study, the maxillary first molars and incisors were chosen to predict the widths of maxillary and mandibular canines and premolars because they are erupted early in the oral cavity. The first step in the statistics is to demonstrate the relation between the combined mesio-distal J Bagh College Dentistry Vol. 25(3), September 2013 Prediction the widths Pedodontics, Orthodontics and Preventive Dentistry155 crowns dimensions of maxillary incisors and first molars (MDDIFM) with combined mesio-distal crowns dimensions of maxillary and mandibular canines and premolars (MDDCP). As shown in table 1, there was strong direct highly significant correlation (p ≤ 0.001) between the measured variables; this comes in agreement with the previous findings (23,24,28-34). For practical purposes only, correlation coefficient values greater than 0.70 should be considered as reliable for prediction procedures (35). The value of the Pearson’s correlation coefficient was ≥ 0.70 in this study. The results in table 2 showed the genders difference for the dimensions of teeth measured. Like many findings (2,5,23,24,29-32), the males have wider teeth than females with a high significant difference; hence, the data were analyzed separately for males and females. Table 1. The relation between the combined mesio-distal crowns dimensions of maxillary incisors and first molars (MDDIFM) with combined mesio-distal crowns dimensions of maxillary and mandibular canines and premolars (MDDCP) MDDIFM MDDCP Maxillary Mandibular Males Females Males Females r 0.8 0.7 0.75 0.7 p 0.000 (HS) 0.000 (HS) 0.000 (HS) 0.000 (HS) (HS)=Highly significant P ≤ 0.001 Table 2. Descriptive statistics and genders difference for the measured variables Variables Genders Descriptive Statistics Genders difference Mean S.D. t-test p-value MDDIFM Males 52.168 2.38 3.72 0.000 (HS) Females 50.539 2.21 Maxillary MDDCP Males 43.570 1.88 4.20 0.000 (HS) Females 42.037 1.95 Mandibular MDDCP Males 42.483 1.89 2.10 0.000 (HS) Females 40.998 1.89 (HS)=Highly significant P ≤ 0.001 A linear regression analysis was performed to develop the regression equations. The equation was calculated as; Y= a + b X where “Y” is the combined mesio-distal crowns widths of mandibular or maxillary permanent canines and premolars, “X” is the combined mesio-distal crowns widths of maxillary incisors and first molars, “a” is constant and “b” is the regression coefficient. The results showed the following equations: Genders For maxillary arch For mandibular arch Males MDDCP= 10.758 + 0.629 × MDDIFM MDDCP= 11.279 + 0.598 × MDDIFM Females MDDCP= 12.183 + 0.591 × MDDIFM MDDCP= 11.209 + 0.589 × MDDIFM After calculation the predicted widths, paired sample t-test was applied to compare between the actual and predicted measurements. The results showed that there was non-significant difference between the predicted and actual mesio-distal crowns dimensions of both maxillary and mandibular canines and premolars (Table 3), this is in accordance with the other studies (23,28-34). Table 3. Descriptive statistics and comparison between the predicted and actual combined mesio-distal crowns dimensions of maxillary and mandibular canines and premolars Arch Genders Actual MDDCP Predicted MDDCP Difference between the predicted and actual MDDCP Mean S.D. Mean S.D. Mean difference S.D. t-test p-value Maxillary Males 43.570 1.88 43.572 1.49 0.002 1.14 0.013 0.99 (NS) Females 42.037 1.95 42.052 1.31 0.015 1.45 0.079 0.937 (NS) Mandibular Males 42.483 1.89 42.476 1.42 -0.007 1.26 -0.044 0.965 (NS) Females 40.998 1.89 40.977 1.3 -0.021 1.38 -0.115 0.909 (NS) (NS)=Non-significant P > 0.05 J Bagh College Dentistry Vol. 25(3), September 2013 Prediction the widths Pedodontics, Orthodontics and Preventive Dentistry156 The ideal prediction method should determine no difference between predicted and actual widths of permanent canines and premolars. The mean differences and their standard deviations between the two methods are very small in its magnitude and are not clinically significant (Table 3). Prediction methods are not 100% precise and can overestimate or underestimate the actual size of un-erupted teeth. Overestimation seems to be better to prevent lack of space, but this approach could suggest tooth extractions for some patients. Overestimation of only 1 mm beyond the actual widths of the permanent canine and premolars on each side of the arch would not seriously affect an extraction or non- extraction decision (5,30,33). The numbers and percentages of cases that lie within the limit of 2 mm, over and underestimated the actual widths of the permanent canines and premolars (both sides of the maxillary and mandibular arches and both genders) were presented in Table 4. The findings revealed small numbers of cases that did not lie within the limit of 2 mm. for both sides. This is considered as a point of strength to this method of prediction in addition to the proper selection of teeth that used in prediction, the high correlation between the variables and non-significant methods difference. In conclusion, the findings showed a non- significant difference between the predicted and actual mesio-distal crown widths; hence the combined mesio-distal widths of maxillary incisors and first molars can be used as predictors for the combined mesio-distal widths of maxillary and mandibular canines and premolars. This novel method of prediction is easy, simple, needs study models only (no radiographs) and depends on six teeth that erupt early and can be applied to predict the widths of canines and premolars in both jaws with high reliability. Table 4. The numbers and percentages of cases that lie within the limit of 2 mm, over and underestimated the actual combined width of canines and premolars Arch Genders Within the limit Overestimation Underestimation Maxillary Males 51 (92.73%) 2 (3.64%) 2 (3.64%) Females 46 (83.64%) 5 (9.09%) 4 (7.27%) Mandibular Males 49 (89.09%) 4 (7.27%) 2 (3.64%) Females 49 (89.09%) 3 (5.45%) 3 (5.45%) REFERENCES 1. 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