Root And Canal Morphology Of Maxillary First Premolar Of Han Nationality

Tooth morphology is an important part of Stomatology. Premolars have bothcharacteristics of the anterior and posterior premolars from location form and function,there have important clinical significance about anatomical morphological study ofpremolar. We collected the maxillary first premolars of Han nationality in Northwestregion as the research objects, then researched systematacially the internal and externalmorphology by cone beam CT and micro-CT, which provided reference for the researchand the clinical treatment of maxillary first premolar. The main methods and results wereas follows:Experiment One: To evaluate roots and canals morphologic study of maxillary firstpremolars by using cone-beam computed tomographyCBCT images of dentitions were collected retrospectively from400Chinese patientsand analysed for the type of root and canal, the shape of root curvature, the place of theroot branch and the occurrence of furcation groove of buccal root of maxillary firstpremolars. The differences between sexes and sides were tested by using Chi-square tests.Results:①Of the800maxillary first premolars, the incidence of single root, double root, and three root were respectively70.50%,29.00%, and0.50%. The incidence had differsignificantly between the male and the female in the single root and double root (P <0.05).29.13%had one canal(typeⅠ),72.13%had two canals(typeⅡ-Ⅶ) and0.50%had threecanals(typeⅧ).②The incidence of root curvature was18.25%of maxillary firstpremolars, buccal curvature10.96%, Lingual curvature12.33%, mesial curvature45.21%,distal curvature28.77%, S-shaped curvature2.74%.③The incidence of root branch was40.13%of maxillary first premolars,9.97%of maxillary first premolars divided in thecrown one-third of the root,62.31%divided in the middle one-third of the root, and27.73%divided in the apical one-third of the root.Experiment Two: Evaluation the root and root canal thickness of maxillary firstpremolars by using micro-computed tomographySenvety-two maxillary frst premolars were obtained and scanned by micro-computed tomography. Thirty maxillary first premolars were divided into three groups:1roots with1canals (1-1type),1roots with2canals (2-2type),2roots with2canals (2-2type), and each cross section of the root diameter and the cancal wall thickness weremeasured. Results: The root diameters of maxillary first premolars were increasing fromthe apical third to coronal third. The cancal wall thickness of1root with1canal maxillaryfirst premolars on the buccal and palatal side were larger than on the mesial and distal side(P <0.05); There were not significant differences at the buccal, palatal side and themesial, distal side in cancal wall thickness of1root with2canal maxillary first premolars(P>0.05); The cancal wall thickness at the palatal were thinner than other side in buccalroot canal of2root with2canal maxillary first premolars, they had significant differences(P <0.05); On the middle third and coronal third of palatal root canal of2root with2canal maxillary first premolars, the cancal wall thickness at the palatal side were largerthan the mesial and distal side (P <0.05).Experiment Three: To determine the initial taper of root canal of maxillary firstpremolar by using micro-computed tomographySenvety-two maxillary frst premolars were obtained and scanned by micro-computedtomography. Thirty maxillary first premolars were divided into three groups:1root with 1canal (1-1type)，1root with2canals (2-2type)，2roots with2canals (2-2type), and eachcross section of the root canal diameter, root canal taper and the cancal cross-sectionmorphology were measured. Results:①The root canal diameters of maxillary firstpremolars were increasing from the apical third to coronal third. The root canal diameterof1root with1canal and1root with2canals in buccal-lingual direction was greater thanthat in mesial-distal direction (P <0.05). The buccal canal of2roots with2canalsmaxillary first premolars in buccal-lingual direction was less than that in mesial-distaldirection, the lingual canal of2roots with2canals maxillary first premolars in buccal-lingual direction was greater than that in mesial-distal direction (P <0.05).②The rootcanal taper of1root with1canal maxillary first premolars were increasing from the apicalthird to coronal third, it was greater in buccal-lingual direction was greater than that inmesial-distal direction (P <0.05). The root canal taper of1root with2canals and2rootswith2canals maxillary first premolars were the greatest in the middle third, and the leastin the apical third(P <0.05).③The root canal cross-section morphology in maxillaryfirst premolars is complicated, consist of round canal, oval canal, long oval canal, flatcanal and irregular canal.Experiment Four: Morphology study on the furcation groove of buccal root ofmaxillary first premolars by using micro-computed tomographyTwenty-one furcated maxillary frst premolars with furcation grooves were obtainedand scanned by micro-computed tomography and morphometric horizontal and verticalmeasurment were taken. The prevalence of furcation grooves in bifurcated maxillary frstpremolars was95.45%. This groove extends from just below the bifurcation to the apexand the deepest invagination was found to be at coronal slice. The most deep place of thefurcation groove in maxillary first premolars was the weakest part of cancal wall. The wallthickness on the buccal aspect was larger than on the palatal aspect of the buccal root (P <0.05).