STOMATOLOGY EDU JOURNAL 2017, Volume 4, Issue 2 2 | Page 32

A RADIOGRAPHIC STUDY TO DETERMINE THE POSSIBLE EXISTENCE OF A “SAFE ZONE” AGAINST ENDODONTIC PERIAPICAL EXTRUSION IN THE LOWER PREMOLAR A RADIOGRAPHIC STUDY TO DETERMINE THE POSSIBLE EXISTENCE OF A “SAFE ZONE” AGAINST ENDODONTIC PERIAPICAL EXTRUSION IN THE LOWER PREMOLAR Wei Cheong Ngeow 1a* , Dionetta Delitta Dionyssius 1b , Hayati Ishak 1b Department of Oro-Maxillofacial Surgical and Medical Sciences, Faculty of Dentistry, University of Malaya, Kuala Lumpur, Malaysia 1 BDS (Mal), FFDRCS (Ire), FDSRCS (Eng), MDSc (Mal), PhD (Sheffield), FAMM BDS (Mal) a b Received: March 09, 2016 Revised: May 30, 2016 Accepted: June 29, 2016 Published: July 01, 2016 Academic Editor: Paula Perlea, DMD, PhD, Associate Professor, Dean, “Carol Davila” University of Medicine and Pharmacy Bucharest, Bucharest, Romania Cite this article: Ngeow WC, Dionyssius DD, Ishak H. A radiographic study to determine the possible existence of a “safe zone” against endodontic periapical extrusion in the lower premolar. Stoma Edu J. 2017;4(2):108-113. ABSTRACT DOI: 10.25241/stomaeduj.2017.4(2).art.3 Introduction: Studies have shown that the most common position of the mental foramen in several Asian populations was in line with the apex of the second premolar. Therefore, we seek to determine the average distance of the mental foramen to the apex of the second premolar by using the crown length of the second premolar as a ruler. We hope to define a “safe zone” in this region. Methodology: Measurements were made from the apex of the second premolar to the mental foramen of ninety seven dental radiographs fulfilling the criteria set. Results: Non-detection of mental foramina happened significantly more often in female subjects than male (Pearson Chi-square; p=0.01). Of the mental foramina that were visible, 96% were found to be located within one-crown distance from the apex. More mental foramina (37.1%; 56 sites) were located at the apex than any other locations. This is followed by finding the mental foramina located at ¼-crown distance from the apex (26.5%; 40 sites). The visibility of the mental foramen was found to be significantly limited in females and in patients aged 50 and above (Pearson Chi-square; p<0.05). Conclusion: These findings suggest that there is no safe zone against accidental extrusion of endodontic files and materials in the second premolar region. Keywords: endodontology, complication, inferior alveolar nerve, mental nerve, mental foramen. 1. Introduction The mental foramen is located close to the mandibular premolars, especially the second premolar. 1 A morphometric study by Philips et al. 2 reported the mental foramen to be located on average at a distance of 2.18 mm mesially and 2.4 mm inferiorly from the plain radiographic apex of the second premolar. More precisely, the mental foramina could be located anywhere 3.8 mm mesially 2.7 mm distally, 3.4 mm above or 3.5 mm below the apex of the second premolar. Various cadaveric studies reported the apices of the second premolars to be between 0 and 4.7 mm away from the mental foramen. 3,4 Using a newer technology of cone beam computed tomography (CBCT), BÜrklein et al. 5 also reported similar findings, with an average distance of 4.2 mm. However, 3.2% of the mental foramen was directly in contact with the second premolar. Because of this close proximity, various events affecting the second premolar, such as odontogenic infection and orthodontic, endodontic, periodontal or surgical misadventure, may result in the neurosensory disturbance to the area innervated by the mental nerve that exits the mental foramen. 1,6 A retrospective study found an incidence of 0.96% of mental paraesthesia related to root canal treatment of mandibular premolar teeth. However, all these incidents were related to periapical infection or pathology, instead of being a complication of the root canal treatment itself as the authors excluded 2 (0.24%) cases of severe overfill and iatrogenic root perforation with mechanical instrumentation into the mental nerve. 3 Eliminating infection in the pulp and dentin, followed by adequate intra-canal preparation and proper sealing constitute the basic principles of root canal treatment. Ideally, mechanical preparation and filling should be limited within the root canal as overinstrumentation or the extrusion of chemical fillings beyond the apical foramen to the adjacent nerve can give rise to NSD such as paraesthesia or anaesthesia. 7,8 Paresthesia related to overinstrumentation usually resolves within several days. 9 In addition, minor material extrusions are generally well tolerated by the periradicular tissues as long as they do not spread to the adjacent nerve. 10 However, long-term NSD has been reported in cases where the nerve fibre is lacerated due to overinstrumentation or in contact with toxic overfilled endodontic materials. 8,11 *Corresponding author: Professor Dr Wei Cheong Ngeow, Department of Oral & Maxillofacial Clinical Sciences, Faculty of Dentistry, University of Malaya, 50603 Kuala Lumpur, Malaysia Tel: 603-79674862, Fax: 603-79674534, e-mail: [email protected] 108 Stoma Edu J. 2017;4(2): 108-113 http://www.stomaeduj.com As the close proximity of the apices of the mandibular premolar to the mental foramen acts as an important contributory factor for NSD when overinstrumentation or overfilling of endodontic materials happen, it is the aim of this study to determine the distance of the mental foramen to the second mandibular premolar tooth. We chose to concentrate on the second premolar only as an earlier study has shown that most of the terminal end of the inferior alveolar nerve is located in line with the apex of the second premolar. 12 In this pilot study, also conducted on a selected Malay population, we seek to determine the average distance of the mental foramen from the apex of the second premolar by using the crown height of the second premolar as a ruler. The identification of this distance, will hopefully enable us to come up with a so called “safe zone” to ensure that root canal treatment in the lower premolar region can be performed with minimum complications in case files or endodontic filling materials are accidentally extruded beyond the apices of these premolars. 2. Methodology 2.1. Materials One hundred twenty panoramic radiographs of Malay patients of 4 different age-groups, taken between 2003 and 2005 were obtained from the records stored by the Dental Faculty of the University of Malaya, Kuala Lumpur, Malaysia. The age-groups were categorised as 20-29 years-old, 30-39 years- old, 40-49 years-old and 50 years and above. All panoramic radiographs were taken using Siemen Orthophos® (Sirona, Bensheim, Germany) or Planmeca® (Planmeca, Helsinki, Germany) machines. The magnification factors reported by the manufacturers were 1.2 and 1.25, respectively. The radiographs were chosen according to the following criteria: 1. High quality with respect to geometric accuracy and contrast of the image. 2. Radiographs in which the lower teeth (between 36 and 46) were missing, had deep caries, root canal treatment or various restorations were excluded because of possible associated periapical radiolucency. 3. Radiographs must be free from any radiolucent or radiopaque lesion in the lower arch. There should be no evidence of jaw fracture around the mental foramen region. 4. Radiographs with supernumeraries and unerupted teeth were excluded because the impacted/ unerupted teeth might obscure the appearance of mental foramen. 5. Films should be devoid of any radiographic exposure or processing artefacts. 6. Radiographs where the lower canine was missing were excluded because of the possibility of mesial premolar drift. 7. Radiographs in which the upper premolars were missing were excluded because of the possibility of overeruption of the lower premolars. 2.2. Methods The dental panoramic radiographs were placed on Stomatology Edu Journal a radiograph view-box. A transparent tracing paper was placed over the radiograph and fixed properly to ensure it remain static in relation to the film. An imaginary line was drawn to outline the second premolar. A line was drawn to join the mesial and distal points of the cement-enamel junction (CEJ). Another line was drawn at the tip of the crown, parallel to the line joining the CEJs. A line vertical to both these lines was then drawn. It represents the crown height of the second premolar. A pair of caliper was used to transfer this distance to a metal ruler to obtain an exact measurement. This measurement was then divided by 4 (calculated to the nearest millimeter) to give the height of a quarter-crown. The distance from the mental foramen to the apex was measured using the second premolar crown height as a ruler (Fig. 1) and was categorised as below: I. II. III. IV. V. VI. VII. VIII. located at apex within ¼-crown-distance within ½-crown-distance within ¾-crown-distance within 1-crown-distance within 1½ -crown-distance within 2- crowns-distance Could not be identified ENDODONTICS Figure 1. An illustration showing the method used to determine the distance of the mental foramen to the apex of the second premolar using the crown height as a ruler (Note: In this dental panoramic radiograph, the mental foramen is located at the apex of the second premolar). 3. Results There were a total of 97 radiographs with bilateral sites that fulfilled the criteria and were examined. Thirty-one of the subjects fell into those aged between 20-29 years, 24 subjects were between 30-39 years old, 22 between 40-49 years old and the final 20 were aged 50 years and above. The number of subjects (hence radiographs) that fulfilled the criteria set became less with the age increase as there was a high number of subjects who become fully edentulous or partially edentulous beginning from the first premolar. The mental foramen was visible in 77.8% (151) of the sites reviewed. It was slightly more pronounced on 109