Selecting the Appropriate Electrode Placement Site for Electrical Pulp Testing of Molar Teeth

Selecting the Appropriate Electrode Placement Site for Electrical Pulp Testing of Molar Teeth.
FerozeAliKalhoro *, AnwarAli**, FoziaRajput***, Laila Sangi****


OBJECTIVE

The objective of the present experimental study was to report an appropriate electrode placement site on firstmolar teeth.

METHODOLOGY

Fifty volunteerswith soundmandibular andmaxillary firstmolar teeth (without any lesion or restoration) were selected from the DentalOPDof Dept of Operative Dentistry LUMHS Jamshoro from July 2008 to June 2009. Seven sites on each tooth were tested two times. The Elements Diagnostic Unit EPT was used to record the lowest threshold response of each site. Data was analyzed with one-way analysis of variance and the tukey test.

RESULTS

The central fossa/pit of bothmaxillary andmandibular firstmolar teethwas found to be an appropriate site forEPTtesting.Whereas, the tip ofmesiobuccal cuspwas the second sitewhere lowest thresh holdwas found to elicit pulpal response. No significant difference was observed between male and female subjects and between mandibular andmaxillarymolars.

CONCLUSION KEYWORDS

Pulp,molar, diagnosis, endodontics, electrical pulp testing

Introduction

Diagnosis in dentistry can be defined as the process to obtain data by questioning, examining and testing the subject to identify deviations from the normal. The determination of pulpal status is crucial step in diagnosis before embarking restorative or endodontic treatment and that can only be done by remaining adherent to the rules of diagnosis like proper history, clinical examination, radiographic evaluation and special tests.

These special tests include thermal test, electrical pulp test (EPT) Laser Doppler flowmetry, pulse oximetry etc. The Electric pulp tester is being widely used as a diagnostic tool of diseases involving pulp and periapical tissues. EPT is a battery-operated instrument, which is connected to two electrodes (Anode and Cathode) One electrode is put in the patient’s hand and other placed over the surface of tooth under investigation. An electrical current starts to flow across both the electrodes and tooth surface which in turn elicits a response in terms of a tingling sensation by stimulating the Aδ nerves in the pulp-dentine complex. That response threshold can be achieved onlywhen sufficient numbers of nerve terminals are activated by electrical current, which is called a summation effect.

A positive response indicates vital pulp where as a negative response indicates necrosed pulp. Thus, EPT only provides nformation about nerve supply of the pulp not vascular supply which is the true determinant of vitality. Despite this EPT is indeed an integral part of diagnostic tools of diseases of pulpal origin.

There are several clinical considerations regarding pulp vitality testing with EPT including isolation of the tooth, conductingmedia, wearing of gloves, type of tooth, thickness of enamel and dentine and site of placement of the tip of probe. Ideally, the tip of probe (electrode) should be placed over area of high neural density to produce early and powerful response least electrical current. A few tudies have reported appropriate position for the placement of electrode tip on incisors and premolars

The incisal edge has been suggested an optimum site in anterior teeth for placing the probe tip to evoke a response with the least amount of electrical current. On other hand the site for posterior teeth has yet to be reported as the EPTin posterior teeth has limited role. The surface area ofmolars ismore and so the thickness of both dentine and enamel to minimize the role of EPT in teeth. As very few tudies have reported electric pulp testing ofmolar teeth, the dilemma optimumsite of electrode positioning on molar teeth is yet to be solved. The aim of present study is to report suitable site for placement of electrode during pulp testing of molars to elicit themaximumresponse at lowest threshold level.

Methodology

Fifty volunteers of either gender were selected of 18- 30 year old age group at the department of operative dentistry from July 2008 to June 2009. All participants were fully informed in detail about the study procedure and risk. A written informed consent was signed prior to procedure. Healthy right and left 1st Molars of both mandibular and maxillary arches were selected for study purpose.Carious teeth, restored teeth or teethwith signs of surface loss were excluded from the study.

Periapical and bite-wing radiographs were taken of the teeth under study to rule out any proximal caries or apical pathology. Rubber dam was applied to prevent any salivary contamination of the surfaces of teeth. Seven sites on each molar were selected for testing with electrical pulp tester elements diagnostic. (sybronEndo Redmond, WA, USA).
Cervical 1/3 ofmesio-buccal surface
Middle 1/3 of buccal surface
Mesio-buccal cusp tip
Mesio-lingual/palatal cusp tip
Mesio-lingual/palatal surfacemiddle 1/3
Mesio-lingual palatal surface cervical 13
Central fossa

A fluoride gel (Fluocal Septodont) was applied over the tooth surface as conducting media. Each site was tested two times with a 5 minutes interval as nerve recovery Period.

The thresh hold values were recorded on prescribed Performa. Data was analyzed by SPSS.10 computer soft ware. One-way analysis of variance test and t-test as used at the 0.05 level to determine significance of difference in the thresholds of seven site.

Results

Out of fifty participants there were 28 males and 22 females.Age ranged from18-28 yearswith 23 years as the mean age. The EPT values for all sites ranged from 6-75 and theirmean ranged from15-61.Themean values of the seven sites recorded on right and left 1stmolars of both the arches are shown inTableNo.1.

The response at lowest thresh hold was found at the Central Fossa of all the four molar teeth. The next site which responded where as at low threshold was the mesiobuccal cusp tip. The mean values for each sites progressed from low to high begining with central fossa, tip of mesiobuccal cusp, middle 3rd of mesiobuccal surface, tip of mesiolingual cusp, cervical 3rd of mesiobuccal cusp, middle 3rd of mesiolingual cusp and cervical 3rd ofmesiolingual cusp.

The difference in EPT response values of mandibular and maxillary molars was not found significant P =0.018 (Figure.1)


The difference in response for both male and female object was also not significant P=0.89 (Figure.2) and

similarly between different sites (Figure. 3).

Discussion

The central fossa of both maxillary and mandibular molars found the site with lowest EPT value in our study. Perhaps, this site was never examined in previous studies . To avoid flow of current to the adjacent teeth and gingiva a rubber dam was used to isolate the tooth being examined.Anarrow range of age of subject selected to avoid sensitivity variation caused by secondary dentine deposition which causes reduction in volume of pulp,dental caries and toothwear.Molars aremulti-rooted teeth in dental arch and usually their roots containmore than one pulp canal. There is well defined pulp chamber in the trunk of the toothwith pulp horns elongated under each cusp but more profound under the mesiobuccal cusp of mandibular molars and mesiopalatal cusp of maxillary molars. Due to these typical anatomical features it is very difficult to perform pulp vitality procedures especially Electrical PulpTestingwithmore chances of getting falsepositive and false-negative responses. It is not uncommon an infected molar contain necrosed pulp in one canal and some vital pulp in other canal elicit false-positive response in otherwise necrosed pulp.Whereas, the enamel over the crown is also thicker compared to incisor teeth especially over the cusps can hamper the conduction of electrical current towards the pulp to produce response. So, it should be more important to place electrode at appropriate site on molars to produce optimum response. But, the selection of appropriate site is yet to be confirmed and there are several considerations and lack of research. The response threshold can be achieved only when sufficient numbers of nerve terminals are activated electrical current, is called a summation effect. The level of response to a given stimulus depends upon how close the nerve terminals are present in the area of stimulus. Therefore, an area where a neural density is found high can give an early and powerful response on least electric current as compared to an area with low neural density. Lilja J. eported that in permanent molar teeth the highest concentration of neural elements are present in the pulp horns, w progressively decrease in the cervical and radicular regions of the pulp. was confirmed by lin et al in the their study that the early response observed on low electric current at the area of cupal tip as compare to the cervical regions of the molars. On the contrary, the findings of our study are suggesting that the central fossa of 1st molar teeth of both maxillary and mandibular arch is the site where response can be elicited on lowest EPT value whereas, the cusp tip of mesiobuccal cusp is second lowest site for EPT testing. However, the central fossa site has never been examined in previous studies. It has been suggested that the most desirable area of placement of electrode tip is where enamel is thin or absent and inmolar teeth central pit/fossa is the area where enamel is seen thin or usually absent. Another laboratory based study by Jacobson used an oscilloscope to find the electrode placement site on extracted incisors and premolars He observed incisal third and occlusal third of labial/facial surface appropriate site for pulp testing in incisors and premolars respectively. However, his study was performed on extracted teeth where neural density was not considered. The ender of the subjectwas not found as a factor which impact threshold during pulp testing of the teeth in almost all previous studies The present study also found no statistically significant difference in the responses of male and female subjects nor between maxillary and mandibular teeth as similar the study of lin et al Although different conducting mediums are suggested in literature we used Fluoride gel to ensure that maximum current passes from the electrode to the tooth surface Alaboratory study byMartin and co-workers found no profound difference in using different mediums on either the voltage or the electric current transmitted during the pulp testing of the teeth. On contrary , a more recent study reported difference in the response of same teeth to EPT testing by using different conducting media. The present experiment found central fossa/pit as the best electrode site for pulp testing of 1stmolar teeth of both mandibular and maxillary arch in contrast with previous study which found the cusp tip of mesiobuccal cusp as the appropriate site. However it should be noted that in the previous study central pit was not included among the seven sites tested by the operators. It is important to select appropriate site for diagnostic purpose and for future studies on local analgesics inwhich EPTis often used to assess the effectiveness and longevity of anesthesia.

Conclusion

The present experiment showed that the central fossa/pit of all first molar teethwas an appropriate site for the placement of the tip of EPT. Where as, mesiobuccal cusp tip was found next site with low threshold response. No significant difference were found between male and female subjects and between mandibular and maxillary molars.

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