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Validation of Tanaka and Johnston Method on Iraqi Population

Authors: Younis MS Hasan --- Khawla M Awni --- Hind T Jarjees
Journal: Al-Rafidain Dental Journal مجلة الرافدين لطب الأسنان ISSN: 18121217 Year: 2009 Volume: 9 Issue: 1 Pages: 17-23
Publisher: Mosul University جامعة الموصل


Aims: To validate Tanaka and Johnston's analysis on (50) Iraqi patients (29 females and 21 males)
aged 14–22 years. The patients had normal class I molar relation ship with full permanent dentition.
Materials and Methods: Plaster models of 50 (14–22) years old patients were selected. Mesio–distal
crown diameter for maxillary and mandibular permanent teeth were measured. Statistical descriptive,
probability theory, correlation coefficients between individual and grouped teeth were calculated using
Tanaka and Johnston method. Results: Tanaka and Johnston's analysis tables, equations and approximations
were modified in order to improve the accuracy of the prediction. The correlation coefficients
found between the size of the permanent mandibular central incisors and maxillary first molars (1, 1, 6
and 6) and maxillary and mandibular canines and premolars were high (r = 0.62 and r = 0.67, respectively).
New, more accurate prediction tables applicable at earlier ages, and new regression equations
were constructed. In addition, new easier approximations were developed to allow the prediction of the
size of the unerupted maxillary canines and premolars by adding 5.6 mm to the half–widths of teeth 1,
1, 6 and 6. The analogous prediction of the size of unerupted mandibular canines and premolars was
obtained by adding 5.4 mm to the half widths of same teeth 1 ,1 , 6 and 6. Conclusions: The new analysis
prediction tables and new regression equations based on teeth 1 ,1, 6 and 6, which erupt earlier
than teeth used by Tanaka and Johnston, proved even more accurate than both previous equations.


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