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Ex-Vivo Evaluation of X-Ray Horizontal Angle for Separating the Canals of Four-Canal First Mandibular Molars. PDF

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ORIGINALARTICLE Ex-Vivo Evaluation of X-Ray Horizontal Angle for Separating the Canals of Four-Canal First Mandibular Molars JahangirHaghani1,MaryamRaoof2*,SadeghPourahmadi3 1.DepartmentofOralRadiology,DentalSchool,KermanUniversityofMedicalsciences,Kerman,Iran 2.DepartmentofEndodontics,DentalSchool,KermanUniversityofMedicalsciences,Kerman,Iran 3.GeneralPractitioner,Kerman,Iran ABSTRACT INTRODUCTION:Avarietyofmesialanddistalprojectionshavebeensuggestedforseparating the canals in a multi-canaled root. But there is no general agreement on the best angulation for each tooth. The purpose of this study was to evaluate the X-ray horizontal angle for separating thecanalsoffour-canalfirstmandibularmolars. MATERIALS AND METHODS: Forty four-canaled mandibular molars were selected. After preparationofcoronalaccesscavities,fileswereinsertedintotherootcanalsandthespecimens wereradiographedat10,15,20,25degreesmesialanddistalhorizontalangulations.Apicesand canalswereevaluated.Chi-squaretestwasusedforstatisticalanalysis. RESULTS: Although 10° and 15° mesial and distal angulations were best for the most obvious apices manifestation (P<0.001), it was found that 20° mesial angulation is significantly better thantheotherconeangulations(P<0.001)forseparatingtherootcanals. CONCLUSION:20°mesialangulationimproveddetectionofboththecanalsandcanalterminus visibility. Keywords:Endodontics;Molar;Radiology;RootCanal Received:26Feb2007;Revised:15Jul2007;Accepted:17Sep2007 *Correspondingauthorat:MaryamRaoof,DepartmentofEndodontic,KermanDentalSchool,ShafaAve,Jomhuri EslamiBlvd,Kerman,Iran.E-mail:[email protected] INTRODUCTION However, as the horizontal angulation increases, the clarity of the radicular anatomy A key objective of successful nonsurgical decreases (5). So having a clear image of the endodontic treatment is effective chemo- apex and therefore the WL determination mechanical debridement of the root canal wouldbemoredifficult. systems(1).Onefactorinachievingthisgoalis A variety of mesial and distal projections have establishment of precise working length (WL) been suggested for effective “opening-up” the (2). canals (5-7). But, there is no general agreement Different techniques have been used for onthe bestangulationforeachtooth.Therefore determining WL including: radiography, sometimes we need to obtain several electronic devices, using paper point, tactile radiographs that involve different cone angles methods and patient reaction. None are totally with respect to the target tooth to have an accurate, so all the techniques must be used acceptable image of all canals (8). This can onlyasanadjuncttoradiography(2). result in economic and also biologic side Conventional intraoral radiography using silver effects. halidefilmisawidelyusedandreliableclinical The prevalence of four canals especially in methodofdeterminingWL(3). mandibular first molar is noticeable and varies In a multi-canaled root the canals are in different studies (9-12). On the other hand, superimposedoneupontheother.Usingspecial this is the earliest permanent posterior tooth to cone angulations, these structures can be erupt and seems to be the tooth that most often movedaparttosolvethisproblem(4). requires root canal treatment (13). So, IEJ -Volume2,Number4,Winter2008 143 Haghanietal. Table 1. Frequencyand distributionofcanalsseparation Table 2. Frequencyanddistributionofcanalsseparation inmesialconeangulations indistalconeangulations Cone Separationoffourcanals(#40) Cone Separationoffourcanals(#40) angulation Yes No angulation Yes No (degree) Number Percent Number Percent (degree) Number Percent Number Percent 10 0 0 40 100 10 0 0 40 100 15 15 37.5 25 62.5 15 10 25 30 75 20 33 82.5 7 17.5 20 16 40 24 60 25 20 50 20 50 25 19 47.5 21 52.5 suggesting an appropriate radiographic cone designed and a rectangular cardboard was angulation may be helpful to better performing installed on the radiographic tube head as a rootcanaltherapy. marker,theseenabledprecisevariationsincone The purpose of this ex-vivo study was to angulation.Thespecimenswereadjustedonthe evaluate the effect of different x-ray tube scaled plate and the teeth were radiographed. angulations on defining the apices and The samples and dental x-ray unit were separationofnumerousrootcanals. positioned to obtain a 0.8 cm focal spot–object distance. Conventional E–Speed intra-oral MATERIALSANDMETHODS radiographic films (Kodak, Eastman Kodak, NY, USA) were exposed at 10,15,20,25 Included in this study were mandibular recently degreesmesialanddistalhorizontalangulations extracted molars with fully formed roots. The with the x-ray unit operating at 70 kvp, 8mA, specimens with dilacerations, external root for 0.32 s (Planmeca intra X-ray unit, Finland). resorptionandfracturehadtobeexcluded.Teeth Vertical angle was -5° for all the specimens. were washed immediately after extraction and Films were developed in an automatic stored in normal saline until the collection was processor (Velopxe, Extrax medien, UK) using completed. Thereafter, the teeth were properly champion developer and fixer solutions washedundertapwaterandimmersedin5.25% (champion photochemistry, Iran). A board- sodium hypochlorite for 30 min for the removal certified radiologist compared the images of organic debris on the surface. The specimens without magnification on a light viewing box were radiographed from buccal view to assess (Shayanteb, Iran). He determined the apices canalmorphologyandthoseidentifiedashaving and separation of the canals. No time limit was abnormal anatomy or calcified root canal set for viewing and the observer was allowed a systemswereexcluded. rest periodwhenever he felt fatigue.Chi-square Coronal access opening were prepared using test was performed for the statistical analysis tungsten carbide burs in a high speed usingSPSSversion15. handpiece. The canals were located using an endodontic explorer and 40 four-canal teeth RESULTS were selected. The teeth immersed in 2.5% sodium hypochlorite solution for 24 hours to Results presented in Table 1 and Table 2 show dissolve any pulp tissue. Root canal working that the mesial 20° radiograph is significantly length was set at 1 mm short of the apical better than the other cone angulations for foramen based on visual inspectionof a size 10 separatingtherootcanals(P<0.001).Therewas stainless steel K-file penetrating beyond the no separation when 10° mesial and distal apicalforamen.Theteethwerethenmountedin angulations applied. The results concerning the self–cure acryl boxes. The teeth aspects were apices defining with regard to different mesial marked as M: mesial, B: buccal, D: distal and and distal cone angulations are shown in Table L: lingual. Canals were then prepared ( if 3, and Table 4, respectively. An increase in necessary) by hand until a size 20 K-file horizontal angle was found to be related to (Maillefer, Dentsply, Swiss) bound at the decrease of defining ability of the apices. working length. Files were inserted passively Specifically, the angulations of 10° and 15° into the root canals. A horizontal goniometer mesial and distal were best for the most which was able to show every5degreeswas obviousapicesmanifestation(P<0.001). 144 IEJ -Volume2,Number4,Winter2008 Separatingtherootcanals Table 3. Frequency and distribution of radiographic Table 4. Frequency and distribution of radiographic apicesdefininginmesialconeangulations apicesdefiningindistalconeangulations Cone Separationoffourcanals(#40) Cone Separationoffourcanals(#40) angulation Yes No angulation Yes No (degree) Number Percent Number Percent (degree) Number Percent Number Percent 10 40 100 0 0 10 40 100 0 0 15 40 100 0 0 15 40 100 0 0 20 36 90 4 10 20 32 80 8 20 25 11 27.5 29 27.5 25 6 15 34 85 DISCUSSION another in vitro study, Naoum et al. stated that The prevalence of four canals in mandibular conventionalradiographstakenata0°orientation molars varies in different studies (8-11). The were significantly better than 30° images for mesial root of the mandibular first molar detectingthenumberofvisiblecanals(7). usually has two canals. The prevalence of two In all 10° mesial and distal images the canals canals in the distal root ranges from 11.2% to were superimposed one upon the other and 43.3% (9-15). About the mandibular second appeared as a single line. Moreover, when 10° molar,21.4%to56.9%ofthemesialrootshave or 15° mesial or distal radiographs were beenshowntohavetwocanals(9,11,16,17). considered,it was obviousthat theapicescould This range is about 1/3% to 4% in distal root be clearly visualized but the canals were not (9,11,16,17). Therefore, the prevalence of four separated adequately. So, 20° mesial angulation rootcanalsinmandibularmolarsisnoticeable. improvedbothdetectionofthecanalsandcanal Careful assessment of pulp anatomy obtained terminusvisibility. from a diagnostic radiograph is very important In the present study we attempted to follow to eradicate intra-radicular infection. steps that could be applied in vivo. It was Radiologic evaluation of the three dimensional difficult to achieve a precise horizontal angle. configuration of the root and canal system is We solved this problem by designing a recommended in endodontics (18). We goniometer. The limitations of this ex-vitro preferred conventional radiographs rather than studyshould be taken into account andindicate digital radiographs because the dentists are theneedforfurtherwork. more familiar with the former and the conventional radiography equipments are more CONCLUSION available in many dental clinics. Moreover, the image quality of the conventional radiographs According to this study, it looks like that using hadbeenbetterthantheolderdigitalsystemsin 20° mesial angulation improves detection of some studies (19-21). The dental x-ray films boththecanalsandapices. used in this study (Kodak, E-speed, Eastman Kodak,Ny,USA) were chosenbecause of their ACKNOWLEDGEMENT routine use in dental clinics, while they have alsohigherresolutionandbettercontrast(22). This study was Dr. S. Pourahmadi’s thesis and It is more probable that an angled radiographic was supported by Kerman dental school, view will reveal additional information about Kerman, Iran.The authors wishtothankDr.H. the number of canals and apex visibility (23). Safizadeh and Dr. AA. Haghdoost for their According to this study, images taken at 20° invaluablehelps. mesial angulation were significantlybetter than 10°, 15° and 25° angulations for detecting the ConflictofInterest:‘Nonedeclared’. number of canals. 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