External and internal root morphology of premolar teeth in Kenyans of African descent

Abstract

Literature review indicates that there are very few studies that have been carried out on the morphology of Kenyan teeth. Objective: To determine the external and internal root morphology of premolar teeth in Kenyans of African descent. Design: In vitro descriptive cross-sectional study. Setting: Faculty of Dental Sciences, University of Nairobi. Materials: Four hundred and eighty seven premolar teeth (specimens) extracted mainly for orthodontic reasons from Kenyans of African descent. The specimens were obtained from patients aged between 13-30 years attending dental clinics within Nairobi. Only teeth with fully formed roots, intact cusp tips and with no evidence of extensive secondary cementum formation at the apex were included in the study. Methodology: The teeth were grouped according to gender and according to the four premolar tooth types (maxillary first separately from the second and mandibular first separately from the second). The number of roots and direction of root curvature of the teeth were determined by visual observation. Tooth length was measured using a Boley gauge. After decalcification and clearing the internal root morphology was studied under a microscope at a magnification of either xlO or x40 (magnification varied depending on the complexity of the canal pattern). The number and types of root canals were recorded according to Vertucci and Kartal et aI's classifications. Data analysis: Data analysis was done with the help of SPSS and Epi Info computer packages. Cohen's "Kappa and a paired t-test were employed in the assessment of XIV intraexaminer agreement. Descriptive statistics, independent t-test, chi-square test and Fisher's exact tests were applied in statistical evaluation of data. Results: A total of 487 premolar teeth were studied. There were 155 maxillary first, 114 maxillary second, 108 mandibular first and 110 mandibular second premolars. The different tooth types were distributed evenly between males and females. The external morphology of the maxillary first premolar revealed that 83.2% were two-rooted (mean tooth length: buccal root-22.3 mm; lingual root-21.2 mm) 10.3% one-rooted (mean tooth length-22.6 mm) and 6.5% three-rooted. The maxillary second premolar was double rooted in 56.1% (mean tooth length: buccal root-21.9 mm; lingual root-21.5 mm), single rooted in 41.2% (mean tooth length-22.8 mm) and three rooted in 2.6% of the sample. 98.1% of mandibular first premolars were single rooted (mean tooth length-23.6 mm). 99.0% of mandibular second premolars were single rooted (mean tooth length-23.4 mm). There were no significant gender differences in the distribution of number of roots for the maxillary second, mandibular first and second premolar teeth. However, with respect to the maxillary first premolar tooth, three roots occurred significantly more commonly in males than females (P<O.05). Males were found to have larger mean tooth length than females in all the four premolar tooth types except in single-rooted maxillary first and second premolars where there were no significant differences. Majority of the roots (60.6%) in all the premolars were straight. Distal and "S" curvatures were also common (20.5%, 10.1% respectively) while lingual, buccal and mesial curvatures were rare. There were no significant gender differences in direction of root curvature (P>O.05). xv The internal root morphology revealed that maxillary first and second premolars had two canals in 87.1% and 67.6% of the specimens respectively, while the mandibular first and second premolars had one canal in 63% and 92.7% of the specimens respectively. The maxillary first and second premolar teeth had eight root canal types each. The mandibular first premolar tooth had the greatest variation with nine canal types while mandibular second premolar had the least variation with seven-canal types. There were no significant gender differences in number and types of canals. Conclusions: Maxillary first premolars were mostly two-rooted while the maxillary second premolars had either one or two roots. Mandibular first and second premolars were mostly one-rooted. Majority of the roots were straight in all the four premolar tooth types and in both gender. Males had significantly larger mean tooth lengths than females in all the premolar tooth type except in single-rooted maxillary first and second premolars where there were no significant differences. Mandibular first premolars demonstrated the greatest variation in the root canal pattern while the mandibular second premolars had the least variation. Recommendations: Clinicians, teachers and researchers should familiarize themselves with the data reported here for external and internal root morphology of premolar teeth in Kenyans of African descent and apply the information appropriately. Additional studies on external and internal morphology of other tooth types and m specific age groups should be undertaken among Kenyans.