| BackgroundAt present,the prevalence of pulpitis and periapical periodontitis is very high,Root Canal Treatment(RCT)can effectively prolong the survival time of the tooth,so it has become the first choice for clinical treatment of pulpitis and periapical periodontitis.Clinical studies have shown that the success of RCT largely depends on the clinician’s familiarity with the dental anatomy.The incidence of wedge-shaped defects in maxillary first premolars is relatively high,and the incidence of pulpitis and periapical periodontitis is also high due to the lack of timely treatment of wedge-shaped defects and caries.Studies have also shown that the maxillary first premolar is mostly prone to vertical root fracture after root canal treatment and restoration treatment.This trend is believed to be related to the unique anatomical structure Furcation Groove(FG)of the double root type.Cone beam computed tomography(CBCT)technology is a non-invasive imaging method used in dental and endodontics research in recent years.It has the advantages of repeatability,quantification,isotropy and high spatial resolution that traditional X-ray films do not possess.Finite Element Analysis(FEA)is a finite element analysis software based on a computer hardware platform to analyze the force of a research object,it has become an effective analysis tool in the field of oral biomechanics research.ObjectiveThe purpose of this study is to use CBCT to study the number of roots,root canal types,the incidence of buccal root and palatal sulcus and its morphological characteristics of the maxillary first premolars,and to further use three-dimensional finite element analysis of its mechanical properties.It is expected to provide a reliable theoretical basis for clinical diagnosis and treatment activities.MethodsWe selected the CBCT images of 800 maxillary first premolars that met the inclusion criteria and recorded the basic information of the patients in the Shandong University Stomatological Hospital from June 2018 to December 2020.Then we observed the incidence of furcation groove,root canal type and root type distribution of maxillary first premolars.We determined five horizontal plane images perpendicular to the long axis of the tooth on the CBCT image of the tooth containing the furcation groove:(1)The bifurcation plane;(2)The apical plane;(3)The plane of the top of the groove;(4)The plane of the bottom of the groove;(5)The plane of the maximum groove depth.Then we measured the buccal wall thickness,palatal wall thickness,root canal diameter,the depth of the furcation groove in the horizontal plane,and measured the tooth length,the distance from the furcation plane to the top plane of the groove,the length of the furcation groove,the distance from the bottom plane of the groove to the apical plane,and the distance from the apical plane to the maximum groove depth plane in the sagittal plane.Then we used the measured data to establish a representative maxillary first premolar model in Mimics,Geomagic Wrap,Siemens NX and other software,and used Ansys software to analyze the correlation between the furcation groove and the high incidence of root fractures after the treatment of maxillary first premolars.Results1.The results of the study showed that the incidence of single-root type was 62.6%,36.1%of teeth were double-rooted,and 1.3%of teeth were triple-rooted.This study found that the most common root canal type of maxillary first premolars was Vertucci type Ⅳ(2-2):44%.Vertucci type Ⅱ(2-1)was the most common in single-rooted maxillary first premolars:36.1%.2.The results showed that the incidence of furcation groove in double-rooted maxillary first premolars was 61.6%.The minimum buccal wall thickness of the furcation plane of the maxillary first premolar was 1.43±0.42mm,the root canal diameter was 1.43±0.31mm,and the minimum palatal wall thickness was 1.37±0.23mm.The minimum thickness of the buccal side wall at the deepest part of the furcation groove was 1.07±0.22mm,the minimum thickness of the palatal side wall was 0.59±0.17mm,and the depth of the buccal root palatal groove was 0.60±0.21mm.The length of the buccal root palatal groove was 3.26±1.00mm.We used the Person correlation coefficient to analyze the results.The depth of the furcation groove and the thickness of the buccal root palatal wall were positively correlated between the plane(5)and the plane(1).There was no significant correlation between the depth of the furcation groove and the difference between the buccal root buccal wall in the plane(5)and the plane(1).The depth of the buccal root palatal sulcus was positively correlated with the diameter of the buccal root canal.3.The results of three-dimensional finite element analysis showed that the presence of the furcation groove could cause the stress distribution trend towards furcation groove of the maxillary first premolar and increase the Von Mises stress peak.ConclusionIn this study,we observed a large number of CBCT images and found that the root and root canal types of the maxillary first premolars were complex,the furcation groove had a higher incidence,and the furcation groove would affect the thickness of the buccal root palatal wall.Subsequently,we used finite element analysis to verify that the presence of the furcation groove would increase the risk of root fractures of the maxillary first premolars.The results of this study provided early warning and reference for possible dangerous situations during the treatment of maxillary first premolars. |
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