UNUSUAL MORPHOLOGY OF MANDIBULAR 1ST MOLAR -SIX CUSPS WITH RADIX ENTOMOLARIS

Endodontics

Dr. Bonny Koul (P.G Student) , Dr. Divyam Girdhar (P.G Student), Dr. Ajay Nagpal (Reader) Department of Conservative Dentistry and Endodontics, K.D Dental College & Hospital , Mathura -Delhi National Highway#2, P.O.Chttikara, Mathura, India

ABSTRACT

Teeth are vertebrate organs that arise from complex and progressive interactions between an ectoderm, the oral epithelium and an underlying mesenchyme. A significant amount of research has focused on determining the processes that initiate tooth development. It is widely accepted that there is a factor (multiple signaling molecules, including BMPs, FGFs) within the tissues of the first branchial arch that is necessary for the development of teeth. A8-year-old reported to our department with the chief complaint of pain in the lower right back teeth region. On clinical examination, mandibular molar revealed the presence of an extra cusp on the lingual surface. Occurrence of six cusps in permanent mandibular molar is a rare phenomenon, and numbers of cases reported are very few. But one case has been reported with six cusps and three roots in mandibular first molar.

INTRODUCTION

Human teeth of both dentitions show morphological variationswhich may be associated either with crown such as extra, reduced oraberrant cusps or with roots such as extra, reduced or fused roots. It is generally believed that the numerous morphologic characteristics of the teeth are genetically determined.1,2 Detailed description and study of these traits could provide valuable information regarding phylogeny of man and distinctions between races and subraces.1,3The study of the number of cusps is not only important in anthropology, it is also important in the study of dental occlusion, orthodontics, restorative dentistry andprosthetic dentistry.4 Similarly, the number of cusps can increase, and this is attributed to local proliferation of enamel knot.5The purpose of this case report is to add knowledge to the existing literature about the presence and treatment modality of tooth with unusual anatomy i.e radix and six cusp in mandibular 1st molar.

CASE REPORT

A 8-year-old girl reported to the Department Of Conservative Dentistry and Endodontics, K.D. Dental College, Mathura, with a chief complaint of pain in the lower left and right back region ofjaw since 3 days.Pain was moderate, continuous and aggravated on lying down. On examination, there was grossly decayed mandibular left first molar (36) and proximal caries in mandibular right first molar (46).Another striking finding was the presence of six cusps in both mandibular first molars(Fig.). The permanent maxillary first molars had four cusps. There was no positive family history of extra cusp. On radiographic examination there was involvement of pulp by carious lesion in relation to 36(Fig.2)and 46(Fig.3). Also there was presence of extra root in both the teeth.Two radiographs were taken at different angulations to confirm the presence of extra root in relation to 36 and 46. On pulp vitality testing both 36 and 46 showed a lingering response.A diagnosis of symptomatic irreversible pulpitis was made in relation to 36 and 46 and root canal treatment was advised in both 36 and 46.The tooth was anaesthetized and isolated under rubber dam. Carious part was removed and the access cavity was prepared.Four distinct canal orifices were located using a DG-6 (Dentsply Maillefer, Ballaigues, Switzerland) endodontic explorer in both 36(Fig.4) and 46(Fig.5).The canal length was determined radiographically. Canal orifices were enlarged with Gates Glidden drills.A glide path was established using 5 k file and finally canals were shaped using Protaper rotary files (Dentsply Maillefer, Ballaigues, Switzerland) till F2 master apical file and 7% EDTA (Glyde, DentsplyMaillefer, Ballaigues, Switzerland).The root canals were irrigated with a sodium hypochlorite solution (3%) and normal saline. The root canals were filled with F2 protapergutta-percha and AH Plussealer (Dentsply, Maillefer, Ballaigues, Switzerland) using single cone obturation in both 36(Fig.6)and 46(Fig.7).The coronal cavity was sealed with nanofilled composite (Brilliant NG, Coltene)(Fig.8).

Fig: Pre Operative photograph Fig2: Pre Operative Radiograph Of 36
Fig3:Pre Operative Radiograph Of 46 Fig4: Canal Orifices In 36
Fig5: Canal Orifices In 46 Fig6: Post Operative radiograph 36
Fig7: Post Operative radiograph 46 Fig8: Post Operative photograph

DISCUSSION

The patterns of the occlusal surfaces of molars are polygenically conditioned and determined by a combination of allele on twoor more sites and they occur in one of the final stages ofmolar growth, as a result of the terminal deposition of enamel.6Numerous studies have shown that the genes of the X-chromosomeregulate the deposition of enamel, while genes ofthe Y-chromosome influence the division of the cell connectedwith the formation of the dentine-enamel bond and thedeposition of enamel.7The mandibular first molar generally has five cusps, other variations exist in the presence of a sixth or seventh cusp at the distobuccal and distolingual surfaces. The fifth or distobuccal cusp is the most variable, whichmay be absent. If the fifth cusp is present, it is often placed lingually, out of line with the other two buccal cusps. Suzuki and Sakai found no significant differences in firstand second molar cusp numbers of 392 male and femaleJapanese.8The frequency ofsixth cusp on first and second molars(65 and 63% respectively) from Indian crania was found to beabout three times that of Aleuts (2 and 8%) and Eskimos (22and 8%). All three groups (Indian, Aleuts and Eskimos)showed five or six cusped first lower molars. No four cuspedmolars were found. Four-cusped second lower molars occurredmost often in the Aleuts (9%), less in Indians (3%) and least inthe Eskimos (%).9According to the number of cusps, a tooth can be classifiedas follows:

  1. The presence of cusps -4 (–protoconid; 2–metaconid;3–hypoconid; 4–entoconid).
  2. The presence of five cusps (hypoconulid)
  3. The presence of six cusps (entoconulid).10

The mandibular molars show more variations than the maxillarymolars. The typical Y5 pattern has been found in 62.% of thetotal population; however 28.% exhibit the Y6 pattern, that is,the Y groove shape with a sixth cusp. The frequency of +5 and+6 is relatively low and only 0.6% exhibit the four cusp pattern.No ethnic differences were found, but there is a significant(0.005 < p < 0.0005, f) sex effect, principally, because malesexhibit the six cusp pattern more frequently.11Like the number of root canals, the number of roots mayalso vary. An additional third root, first mentioned in the literature by Carabelli is called the radix entomolaris (RE). Thissupernumerary root is located distolingually in mandibular molars, mainly first molars. An additional root at the mesiobuccal side is called the radix paramolaris (RP).12‘Radix Entomolaris’ (RE) in first mandibular molar isassociated with certain ethnic groups.

  • In African populations a maximum frequency of 3% isfound, while in Eurasian and Indian populations thefrequency is less than 5%
  • Survey of population of Mongoloid origin indicates a highprevalence, ranges from 5 to more than 30%
  • Bolk reported that the occurrence of radix paramolaris is very rare and occurs less frequently than the radix entomolaris
  • Curzon (974) suggested that the ‘three rooted molar’ traithas a high degree of genetic penetrance as its dominance
  • Its formation could be related to external factors duringodontogenesis.13

CONCLUSION

The presence of increased number of cusps has been reportedin permanent maxillary first molar, mandibular second, thirdmolars and also in deciduous mandibular molars. Accessorycusps have been reported in permanent mandibular first molarsin hominoid ancestors only. Radix entomolaris has been reported to occur with a frequency of 0.2–32% in different populations.14It is crucial to ascertain the exact nature/characteristic of the RE in terms of curvature and conformation to carry out a proper treatment. Therefore, such cases require judicial application of diagnostic tools and endodontic skills for their management. Careful interpretation of the radiograph, using different horizontal cone projections and advanced tools such as CBCT, may facilitate their recognition. Once diagnosed, management of the extra canal and root can be done using equipments such as magnification aids, orifice locators and flexible files.

REFERENCES

  1. Lundstrom A. Tooth morphology as a basis for distinguishingmonozygotic and dizygotic twins. Swed Med Res Counc962;34-43.
  2. Hrdlicka A. Shovel-shaped teeth. Am J PhysAnthropol920;429-66.
  3. Hrdlicka A. Further studies of tooth morphology. Am J PhysAnthropol 92;4-76.
  4. Dahlberg AA. The dentition of the American Indian. In: LaughlinWS (Ed). Dental anthropology.Papers on the physicalanthropology of the American Indian.Fourth Viking FundSummer Seminar.TheViking Fund Inc., New York 95; 38-76.
  5. Lasker GW. Observations on the teeth of Chinese born and rearedin China and America. Am J PhysAnthropol 945;29-50.
  6. Lasker GW. Genetic analysis of racial traits of the teeth. ColdSpring Harbor Symposia on Quantitative Biology, XV95;9-203.
  7. Tratman EK. A comparison of the teeth of people: Indo-European racial stock with the Mongoloid. Dent Rec950;63-88.
  8. Suzuki, Sakai. Occlusal surface pattern of the lower molars andthe second deciduous molar among the living Polynesians.American journal of physical anthropology 973;88-93.
  9. Moorrees CFA. Genetic considerations in dental anthropology.Genetics and dental health. New York: McGraw Hill 962;0-2.
  10. Turner II CG. The dentition of the Arctic peoples.Dissertation.Univ Wisconsin, Madison 967;34-37.

More references are available on request.