Three-rooted mandibular first molar: A consideration in periodontal therapy.

A deep understanding of the relationship between root morphology and periodontal destruction is crucial to successful periodontal care. Most mandibular molars have two roots (one mesial and the other distal) and three canals. The major variant of this tooth type is the presence of an additional third root distally or mesially or a supernumerary lingual root. This article presents a case report of a 14-year-old girl with mandibular first molar having three roots bilaterally which is contributing to the periodontal destruction. There were three walled defect distal to first molar with Grade II furcation involvement distally. Regenerative surgeries were performed and patient was kept under maintenance. The relationship between additional third root and periodontal destruction seldom has been described clearly. This paper has been presented in 34(th) national conference at Dharwad.

INTRODUCTION

Developmental variations and morphological abnormalities such as cervical enamel projections, enamel pearls, and palatogingival grooves contribute to localized periodontal disease progression. Most mandibular first molars have two roots (one mesial and another distal). The major variant of this tooth type is the presence of an additional third root or a supernumerary lingual root called Radix entomolaris (RE). The role of RE in the dental treatment, especially in root canal therapy, has been discussed broadly. However, the relationship between RE and periodontal destruction seldom has been described clearly.[1]

The presence of two distal roots is rare, but does occur. This macrostructure when found lingually was first mentioned in the literature by Carabelli (1844) and was labeled as Radix entomolaris by Bolk (1915).[23] The additional root can also be found distolingually which was first mentioned by De Moor et al.[4]

In India, presence of an additional third root has a prevalence of 0.2% which depicts its rarity. It has a frequency of less than 4% in Whites and 2.8% in African population, whereas in populations with Mongoloid traits (American Indian, Eskimos, and Chinese), this additional root occurs with a frequency between 5% and more than 30%. In these populations, the RE is considered to be normal morphologic variant and can be seen as an Asiatic trait (Yew SC, Chan K 1993).[5]

It was suggested that the three rooted mandibular molar has certain impact as a genetic marker and therefore has a certain anthropologic significance (Tratman ER 1938, Walker RT 1988).[6] More specifically, only Curzon[7] (1974) suggested that certain traits such as the ‘three rooted molar’ had a high degree of genetic penetrance as its dominance was reflected in pure Eskimo/Caucasians mixes who had similar prevalence of trait.[2]

Although this observation suggests that the formation of the RE could be related to penetrance of an atavistic gene or polygenetic system (Calberson 2007),[8] the etiology behind this trait is still unclear.

The [Table 1] below[23] depict the prevalence of mandibular first molar in Europeans and Non- Europeans populations.

Table 1

The prevalence of mandibular first molar in Europeans and Non-Europeans populations

There was no evidence of extra root in South Africans Bushmen or in Australian Aborigines (Drennan 1929 and Campbell 1929).[9]

The RE was found on the first, second, and third mandibular molars, occurring least frequently in second molars.[8] Table 2 presents the incidence of 3 roots found in Mongolian, Caucasian, and Negro populations among different molars.[10]

Table 2

The incidence of 3 roots found in Mongolian, Caucasian, and Negro populations among different molars

The incidence of mandibular molars with three roots according to race and sex is mentioned in Table 3.[10]

Table 3

The incidence of mandibular molars with three roots according to race and sex

CASE REPORT

A case of 14-year-old girl presented to the department of Periodontics, in government dental college and hospital Aurangabad (India), with deep periodontal pockets with mandibular first molars bilaterally on distal aspect.

Radiographs were taken at 90° and other with a 30° mesial shift on both mandibular molars which depicted presence of three roots in mandibular molars Figures 1 and 2. The extra distolingual root contributed for chronic localized periodontitis with mandibular first molars. Patient was referred to endodontic department and teeth were found to be vital on pulp vitality test.

Figure 1

IOPA of mandibular right posterior region depicts three rooted mandibular first molar

Figure 2

IOPA of mandibular left posterior region depicts three rooted mandibular first molar

On surgical interventions under local anesthesia, conventional flaps were reflected and thorough debridement of root surfaces was done. Three walled defects were explored bilaterally Figures 3 and 4 with grade II furcation involvement between distobuccal and distolingual roots Figures 5 and 6. Regenerative therapy with hydroxyapatite grafting was carried out Figures 7 and 8 and flaps were approximated with direct sutures. On radiographic evaluation after six months, some bone gain was seen on right side, while on left side no change in level of bone Figures 9 and 10.

Figure 3

Right lateral buccal view (mirror view) of posterior mandibular region, showing 10 mm of pocket distal to mandibular first molar (measured by UNC-15 probe)

Figure 4

Left lateral lingual view (mirror view) of posterior mandibular region, showing 8 mm of pocket distal to mandibular first molar (measured by UNC-15 probe)

Figure 5

Right lateral buccal view (mirror view) of posterior mandibular region, showing grade II distal furcation with mandibular first molar

Figure 6

Left lateral lingual view (mirror view) of posterior mandibular region, showing grade II distal furcation with mandibular first molar

Figure 7

Right lateral buccal view of posterior mandibular region, showing regenerative therapy with mandibular first molar

Figure 8

Left lateral lingual view of posterior mandibular region, showing regenerative therapy with mandibular first molar

Figure 9

Postoperative IOPA of mandibular right side depicting some bone gain

Figure 10

Postoperative IOPA of mandibular left side depicting no bone gain

DISCUSSION

Morphological features of lingual root such as small sized and curved root shape were observed frequently. The study by Huang, Lin, Lee et al, suggested that the presence of distolingual root contributes to the formation of a distal furcation, which can be complex.[1] This unfavorable furcation involvement is more noticeable in the presence of advanced destruction.

The case presented here was of a Non-European young female probably of Caucasian genetic origin. Yew and Chan (1993) considered RE to be a normal morphological variant for Mongoloids and called it as “Asiatic trait”.[5] The repeated southeastern movement of Caucasoid people from their original area of characterization has resulted in an extraordinary mixture of racial types.[11] Henceforth, we can say, that this female patient might be of Caucasian mix race with this Asiatic trait.

According to Quackenbush (2002), the extra root occurred unilaterally in approximately 40% of all cases and predominantly on right side.[4] Tratman (1938) suggested that there was a sex difference in which females were inclined to display the anomaly bilaterally symmetrical on both the sides, while males presented the anomaly asymmetrically frequently on the right side.[11] According to Schafer (2009), the incidence was 1.52% in women and 1.15% in men.[3] This case was similar with the finding with that of Tratman (1938) and Schafer (2009).[3]

According to Ferraz (1992), this trait is common in mandibular first molars and in females which is in accordance with this case report.[10]

The present case was of type II Radix entomolaris which contributed to the chronic localized periodontitis with mandibular first molars. The unfavorable distal furcation involvement became noticeable due to poor oral hygiene, food impaction, and short root trunk of mandibular first molar. The three wall defects were thoroughly debrided and root planning was done. Regenerative therapy was carried out in both the defects measuring 10 mm on right side and 8 mm on left side.

After six months on radiographical evaluation, some bone gain was observed with right mandibular first molar, while no further bone loss was evident with left mandibular first molar. A deep understanding of the relationship between root morphology and periodontal destruction is crucial for periodontal care. The anatomy of human teeth presents racial variations which can lead to therapy failure when not recognized.