Multiple Dens Evaginatus of Premolars and Molars in Chinese Dentition:A Case Report and Literature Review

Dens evaginatus （DE） is a dental anomaly that occurs as an accessory tubercle on the occlusal or lingual surface of a tooth. The authors provide a literature review and report a rare case in which DE occurs on multiple mandibular premolars and maxillary molars. The patient is a 26-year-old Chinese woman, with a chief complaint of gingival bleeding. DE affecting teeth 17, 27, 35,and 45 was found during clinical examination. For treatment of the patient, we reduced the opposing occluding teeth, while undertaking progressive grinding of the tubercles for six months. We followed-up for a year. This suggests the importance of examining for multiple DE during clinical practice.

Fracture resistance and pattern of the upper premolars with obturated canals and restored endodontic occlusal access cavities

We studied whether obturing canals and restoring endodontic occlusal access cavities on upper premolars could provide acceptable resistance and pattern to fracture.Eighteen upper premolars were divided equally into 3 groups.Group 1 consisted of intact controls;group 2 had access cavities and root canal preparations;group 3 as in group 2 but obturated with gutta-percha and AH26,and the access cavity restored with glass ionomer and composite.Specimens were submitted to compressive strength testing using the Hounsfield Universal H50KM testing machine with a load cell of 2000 Newtons and a crosshead speed set at 1.0 mm/min until fracture.The results from the compressive strength tests showed that intact controls （1105.83±90.93 MPa） and restored premolars （936.67±44.67 MPa） were significantly different from premolars with unrestored access cavities 568.33±105.49 MPa.There was no significant difference between intact controls and restored premolars.The predominant fracture pattern for intact teeth was an oblique fracture.For premolars that had endodontic access cavities,restored or unrestored,the most common fracture pattern was a vertical fracture.The restoration of occlusal access cavities with glass ionomer and composite provided fracture resistance close to that of intact controls,but when restored teeth fractured,they were predominantly non-restorable.

Maxillary first premolars:Ⅰ.Morphology of the apical constriction

Objective： To investigated the apical constriction morphology of maxillary first premolars in the Chinese population. Methods： Eighty recently extracted human maxillary first premolars from a native Chinese population were used. The number and shape of apical constrictions were recorded under a dental operating microscope （DOM） at 12.5 × 2.5 magnification. After access preparation, a new K-file was inserted into the canal until the tip of the file was just seen at the apical constriction under the DOM. The teeth with files in the canals were X-rayed from a mesiodistal direction using a direct digital radiography （DDR） system, and the distance between the file tip and the center of radiographic apex was directly measured from the computer screen using DDR measurement software. Results： The percentage of teeth with an apical constriction was 78.5% （102/130）. The most common apical constriction shapes were oval （55.9%） and round （35.3%）. The mean distance between the apical constriction and the anatomical tip of the root was 0.61 mm, and 84.3% （86/102） were within 1 mm. Conclusion： The most common shape of an apical constriction was oval or round, and the distance to the apex was mostly within 1 mm, indicating that root canal therapy should stop 1 mm from the radiographic apex.

Root Canal Morphology of Maxillary Premolars among the Elderly

Reportedly,maxillary premolars are the most complex teeth for performing endodontic treatment,[1] with root canals varying based on race,genetic predisposition,diet,region,gender,[2] and perhaps age.To date,few detailed studies have been conducted to assess number of roots and root canal morphology of maxillary premolars in the elderly.The present study analyzed root canal morphology of maxillary premolars in elderly individuals using cone-beam computed tomography （CBCT）,which has substantial clinical value in guiding endodontic treatment.[3]

Root and Canal Morphology of Maxillary First Premolar Teeth in a Ugandan Population

Aim : To determine the variations in the root and canal morphology of the maxillary first premolar teeth in a Ugandan population. Methodology : Extracted maxillary first premolar teeth (n = 202) were evaluated in this study. The specimens had their pulp chambers de-roofed. They were decalcified in nitric acid and made transparent with methyl salicylate. Indian ink was injected into the root canals to display their configuration. Results : One hundred and forty eight (73.3%) of the specimens had two roots, of which 16.9% (n = 25) had fused roots. About 26.7% (n = 54) of the specimens were single rooted. Eleven (20.4%) of the single rooted specimens had one canal of either Vertucci type I, III, V or VII configuration while 79.6% (n = 43) of the specimens had two canals of either Vertucci type II, IV or VI configuration. The two-rooted specimens exhibited Vertucci type IV and VIII canal configuration: 96.6% and 3.4%, respectively. The single rooted teeth had a higher prevalence of lateral canals, canal intercommunications and multiple apical foramina as compared to the two-rooted specimens. Conclusion : The maxillary first premolar teeth in this Ugandan population showed a higher prevalence of two-root morphology with majority of the roots having Vertucci type IV canal configuration. There was no three-root anomaly recorded in the present material.

Three-dimensional Finite Element Modeling of a Maxillary Premolar Tooth Based on the Micro-CT Scanning: A Detailed Description

This study describes the details of how to construct a three-dimensional （3D） finite element model of a maxillary first premolar tooth based on micro-CT data acquisition technique, MIMICS soft- ware and ANSYS software. The tooth was scanned by micro-CT, in which 1295 slices were obtained and then 648 slices were selected for modeling. The 3D surface mesh models of enamel and dentin were created by MIMICS （STL file）. The solid mesh model was constructed by ANSYS. After the material properties and boundary conditions were set, a loading analysis was performed to demonstrate the ap- plicableness of the resulting model. The first and third principal stresses were then evaluated. The re- suits showed that the number of nodes and elements of the finite element model were 56 618 and 311801, respectively. The geometric form of the model was highly consistent with that of the true tooth, and the deviation between them was ~）.28%. The loading analysis revealed the typical stress patterns in the contour map. The maximum compressive stress existed in the contact points and the maximum tensile stress existed in the deep fissure between the two cusps. It is concluded that by using the micro-CT and highly integrated software, construction of the 3D finite element model with high quality will not be difficult for clinical researchers.

Double Roots of Mandibular Premolar in Full-mouth Periapical Films

Objective To evaluate the incidence of two-rooted mandibular premolar morphology using full-mouth periapical film series in a Chinese population,with particular emphasis on bilateral incidence,so as to provide a clinical anatomical basis for root canal treatment in mandibular premolars.Methods A total of 2015 patients who underwent dental treatment and had full mouth periapical radiographs at the Peking University School of Stomatology from April 2011 to April 2012 were enrolled in this study.Three experienced dentists reviewed the patients' periapical films and classified the root morphology of mandibular premolars bilaterally.The incidence of unilateral and bilateral double roots were recorded and calculated,including confirmed and suspected bucco-lingual root types.Results In terms of the morphology of two-rooted mandibular first premolars,of the 2015 cases with complete root formation,two-rooted first premolars were detected in 120 cases,with a total number of 159 teeth.According to the number of teeth,the overall incidence of double roots was 4.03%(159/3972).In terms of the morphology of two-rooted mandibular second premolars,of the 2015 cases with complete root formation,two-rooted second premolars were detected in 24 cases,with a total number of 33 teeth.According to the number of teeth,the overall incidence of double roots was 0.85%(33/3880).Conclusions The roots of mandibular premolars display specific morphological patterns.Based on a large sample,we observed and calculated not only the occurrence rate of bucco-lingual and mesio-distal double roots in first and second mandibular premolars,but also the incidence of unilateral or bilateral double roots within the same mandible.These findings could provide useful information on the anatomical structure of mandibular premolars for endodontic,prosthodontic and surgical procedures,and could improve the quality of treatment and reduce complications.

Two-Phase Transplantation (TPTX) Concept: A New Approach for Instant Rehabilitation of Young Children after Avulsion of Central Incisor

Background: To present a new idea for rapid management of tooth avulsion in young children and adolescents (age: 6 to 16) by this case report. Case presentation: A nine-year-old boy presented with loss of upper permanent central incisor in early mixed dentition (6 to 10 years, phase I). The not yet fully resorbed primary canine was used as tooth transplant for the lost incisor. The intentional renounce on endodontic treatment of the primary transplant permits natural exfoliation of the transplant occurring either spontaneously or due to undermining resorption through the adjacent erupting teeth. In the late mixed dentition (10 to 16 years, phase II), the primary tooth transplant is electively removed and replaced by a premolar autotransplant for long-term rehabilitation of the meanwhile adolescent patient. Results: Primary canine autoTX acts as a temporary denture with instant surgical gap closure. Ensuing premolar autoTX in phase II then acts as permanent denture with excellent 10 years survival rates. Patient satisfaction issued by a questionnaire resulted in good to very good school grades for both phases of autotransplantation. Conclusions: The “TPTX” concept is a new surgical approach that immediately restores the patient’s function and aesthetics after tooth loss in early childhood supporting the growth of local bone and soft tissue in the growing adolescent jaw.

Comparison of Chemical Elements on Carious &Normal Premolar’s Enamel Layers Using Energy Dispersive X Ray Spectrometer (X Ray-EDS)

Objectives: To compare the distribution of chemical elements among the carious and normal enamel layers on teenagers, using energy dispersive X ray spectrometer (EDS Rx). Materials and Methods: The EDS Rx analyzer is integrated to scanner electron microscope. The macro and mi-croelements were made in 30 premolars of teenager: 14 carious enamel layers and 16 normal enamel layers. Results: The quantitative and qualitative microanalyses of macro and microele-ments were found between the enamel layers of carious and normal premolar in term of variation and concentration expressed in percentage atomic weight. The statistical data analysis of ANOVA showed that the macroelements [C, Ca, P] and the microelements [Al, Cl, Mg, Na] were significantly different (P < 0.05) while, the macro [O] and the microelements [In, Si, W, S] were not significantly different (P < 0.05) among the carious and normal enamel layers. Moreover, the microelements Sb, Ba, Br, I, Ir, K, Pt, Sc, Sr, Sn and Yb were absent in carious enamel layers and present in normal enamel layers. Conclusion: The macro and microelements differ in composition and variation from the external to the internal enamel layers between the carious and the normal premolars. However, the deficiency or excess of these elements in the enamel layers determines the degree of susceptibility to carious and other dental disease. Clinical Relevance: The carious enamel in dental structure could be a major dental problem due to the deficiency or excess of macro and microele-ments which are responsible for secondary or recurrent caries, discoloration, pulpal inflammation, re-infection, abscess in jaw bone and dental disease.

Correlation between Anatomy and Root Canal Topography of First Maxillary Premolar on Kosovar Population

Aim: In this in vitro study the variation of root anatomy and canal system of the first human maxillary premolar was evaluated. Materials and Methods: Two hundred and twenty one maxillary first premolars (#221 teeth) were examined. All of the teeth were identified using the accepted criteria of Woelfel as maxillary first premolars. Selected teeth are analyzed using operating microscope (OP) and computed dental radiography (CDR). Results: There was a higher incidence of two-roots form 70.14% (n = 155), 21.72% (n = 48) had one root, and 8.14% (n = 18) had three roots. In the two-root category, 16.29% (n = 36) had bifurcation on apical third, 21.72% (n = 48) had bifurcation on middle third, and 32.13% (n = 71) had bifurcation on cervical third. The examination of root canal systems of the teeth was based on Vertucci’s classification type of canal: 64.58% (#31) of the cases had type IV (2-2-2), 25.00% (#12) type II (2-2-1), 8.33% (#4) type I (1-1-1), and 2.09% (#1) type III (1-2-1). Conclusion: This study showed a high incidence of two-rooted maxillary first premolars collected from different regions in Kosovo. Internal root canal system morphology reflects the external root anatomy. Furthermore, there is correlation between the shape of the outer surface of the root and the shape of the root canal. The cases with one root of the maxillary first premolar with a deep depression on the mesial side contain a double root canal system more often than a single canal.