Using Cone-Beam Computed Tomography To Invesgate The Hard Tissue Thickness Of Dental Crwon In The Mandibular First Permanent Molar

Dental caries,pulpitis and periapical periodontitis is the most common oral clinical disease, its morbidity and treatment rate relatively are higher than other oral diseases.According to the third national oral health epidemiological investigation,caries rate averaged 70.35% in China,pulp diseases and periapical diseases are accounting for 60% of the oral medicine clinic. For tooth preservation,cavity filling,root canal therapy and crown restoration are the preferred methods for the treatment of caries,pulpitis and periapical periodontitis. A successful therapy is based on the understanding of the anatomy of the teeth. At present most scholars studied the root canal anatomical morphology, root canal number, root canal curvature, root canal length,and so on to understand root canal system,but few scholars prevented unexpected pulp canalization and medullary perforation by studying the crown of tooth in the hard tissue thickness.At present, the measurement methods of tooth hard tissue mainly include:extracted tooth cut into slices,replicating plaster model,two-di mensional X-ray measurement.But these measurement methods are too complex and less accurate.Cone-beam computed tomography(CBCT) is a new technology developed in the 1990s.It is the latest clinical th ree-dimensional imaging examination method with small dose of radia tion, high image quality, better imaging of tooth hard tissue,reconstr ucting the three-dimensional images by the proportion of 1:1. Recently CBCTis widely used in oral clinic.As the wide application of CBCT in oral clinic,we have accumulated a large number of full teeth of cone beam CT image data recently. This methods is without any man-made destruction, and can get full teeth data. and can locate the quantitative measurement of imaging methods at the same time.CBCT could analyze in positioning and quantity. It has become a new popular method in study the hard tissue thickness of dental crwon.Purpose:1.Using cone-beam computed tomography to invesgate the aging changes of dental crown’s hard tissue thickness in mandibular first permanent molar.2.Using cone-beam computed tomography to invesgate the sexual changes of dental crown’s hard tissue thickness in mandibular first permanent molar.3.Using cone-beam computed tomography to invesgate the tooth position’s changes of dental crown’s hard tissue thickness in mandibular first permanent molar.By studying the above indicators,they can provide relevant data in caries disease preparation, tooth preparation, the access and search for root canal orifice to prevent pulp exposure and perforation for clinical guidance in different age, different gender and different tooth positionshape of mandibular first molarsMethods:645 patients’s cone beam CT dates of mandibular first permanent molar were randomly selected from Stomatological Hospital of Chongqing Medical University.Datas were divided into seven groups according to ages:6～15 years old(n=100)、16～25 years old(n=100)、26～35 years old(n=100)、36～45 years old(n=100)、46～55 years old(n=100)、56～65 years old(n=100)、66～years old(n=45);according to gender:male(n=327),female(n=318).according to tooth position:the left side(n=333),the right side(n=312).CBCT was used to measure the tissue thickness of enamel upon the roof of pulp chamber、dentin upon the roof of pulp chamber、pulp chamber、floor of pulp chamber、the central fossa to the roof of pulp chamber、the top of mesial pulp horn、mesial pulp horn to mesial tooth surface、the top of distal pulp horn、distal pulp horn to distal tooth surface.Results:1. The aging changes of the hard tissue thickness in the enamel upon the roof of pulp chamber、dentin upon the roof of pulp chamber、pulp chamber、floor of pulp chamber、the top of mesial pulp horn、distal pulp horn to distal tooth surface had statistically significant(P<0.05)。The aging changes of the hard tissue thickness in the central fossa to the roof of pulp chamber、mesial pulp horn to mesial tooth surface、the top of distal pulp horn did’s have statistically significant(P>0.05)。2.The sexual changes of the hard tissue thickness in the enamel upon the roof of pulp chamber、dentin upon the roof of pulp chamber、pulp chamber、floor of pulp chamber、the central fossa to the roof of pulp chamber the top of mesial pulp horn、mesial pulp horn to mesial tooth surface、the top of distal pulp horn had statistically significant(P<0.05)。 The sexual changes of the hard tissue thickness in the distal pulp horn to distal tooth surface did’s have statistically significant(P>0.05)。 The male’s hard tissue thickness of dentin、floor of pulp chamber the central fossa to the roof of pulp chamber、the top of mesial pulp horn、mesial pulp horn to mesial tooth surface、the top of distal pulp horn were higher than the female,while the male’s hard tissue thickness of enamel、pulp chamber were lower than the female.3.The tooth positioning changes of the hard tissue thickness in the enamel upon the roof of pulp chamber、dentin upon the roof of pulp chamber、pulp chamber、the top of mesial pulp horn、distal pulp horn to distal tooth surface had statistically significant(P<0.05)。The tooth positioning changes of the hard tissue thickness in the floor of pulp chamber、the central fossa to roof of pulp chamber、mesial pulp horn to mesial tooth surface、the top of distal pulp horn did’s have statistically significant(P>0.05)。The left side’s hard tissue thickness of enamel、pulp chamber、mesial pulp horn to mesial tooth surface were higher than the right side,while the left side’s hard tissue thickness of dentin、the top of mesial pulp horn were lower than the right side.Conclusion:1. The mandibular first permanent molar’s hard tissue thickness of crown in the enamel upon the roof of pulp chamber、dentin upon the roof of pulp chamber、pulp chamber、floor of pulp chamber、the top of mesial pulp horn、distal pulp horn to distal tooth surface existed aging change.However the hard tissue thickness of crown in the central fossa to the roof of pulp chamber、mesial pulp horn to mesial tooth surface、the top of distal pulp horn were no obvious aging change.2. The mandibular first permanent molar’s hard tissue thickness of crown in the enamel upon the roof of pulp chamber、dentin upon the roof of pulp chamber、pulp chamber、floor of pulp chamber、the central fossa to the roof of pulp chamber、the top of mesial pulp horn、mesial pulp horn to tooth surface、the top of distal pulp horn existed obvious sexual change.However hard tissue thickness of crown in the distal pulp horn to distal tooth surface were no obvious sexual change.3.The mandibular first permanent molar’s hard tissue thickness of crown in the enamel upon the roof of pulp chamber、 dentin upon the roof of pulp chamber、pulp chamber、the top of mesial pulp horn、 distal pulp horn to distal tooth surface existed obvious tooth positioning change.However hard tissue thickness of crown in the floor of pulp chamber、the central fossa to roof of pulp chamber、mesial pulp horn to mesial tooth surface、the top of distal pulp horn were no obvious tooth positioning change.