Indian Journal of Dental Research

: 2012  |  Volume : 23  |  Issue : 1  |  Page : 104--106

Single-rooted primary first molars

Ganesh Jeevanandan1, EMG Subramanian2, MS Muthu3,  
1 Department of Pediatric Dentistry, Meenakshi Ammal Dental College, Chennai, India
2 Department of Pediatric Dentistry, Ultra's Best Dental Science College, Madurai, India
3 Department of Pediatric Dentistry, Saveetha Dental College and Hospital, Chennai, India

Correspondence Address:
M S Muthu
Department of Pediatric Dentistry, Saveetha Dental College and Hospital, Chennai


Knowledge regarding the morphological variations in roots and root canals aids in successful dental treatment. However, literature regarding dysmorphology of roots in primary dentition is sparse. The purpose of this article is to present a case of bilateral primary mandibular first molars with an unusual morphology of single root. Review of literature regarding variations in root number in primary dentition has been discussed in this article. The etiology for occurrence of such variations has also been briefly reviewed.

How to cite this article:
Jeevanandan G, Subramanian E, Muthu M S. Single-rooted primary first molars.Indian J Dent Res 2012;23:104-106

How to cite this URL:
Jeevanandan G, Subramanian E, Muthu M S. Single-rooted primary first molars. Indian J Dent Res [serial online] 2012 [cited 2022 May 21 ];23:104-106
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Full Text

The physiology of root formation and tooth eruption is a complex process. The root formation is initiated by the derivatives of enamel organ. Failure in invagination of these derivatives may result in dysmorphological roots. The tooth development begins at about the sixth week of intra uterine life and occurs in several stages. [1] Developmental anomalies may occur during any stage of tooth development. [2] These developmental anomalies are manifested clinically later in life once the tooth is fully formed. Root genesis occurs following the completion of crown formation as a result of intricate interaction between dental epithelium and mesenchymal tissue. [3] After root formation is initiated, eruption pathway is laid down by the dental follicle. The coronal movement of the developing tooth is accompanied by root growth. [4] Generally the root formation of primary teeth is completed by three years of age. [5]

Incidence/prevalence of root abnormalities

Morphological dental anomalies with respect to roots may involve a single tooth, a group of teeth or the entire dentition. [6] Root abnormalities are classified as dilaceration, concrescence, rizomegali and hypercementosis. [7] A number of terms have been used to describe single rooted molars like conical, fused, and pyramidal. [8] The term conical would appear to be self-explanatory. The term fused roots refers to teeth with roots connected but still maintaining at least two distinct canals. The term pyramidal refers to teeth with solitary enlarged root canal [Table 1].{Table 1}

Single tapering root forms may be found in any molar tooth, but are seen most frequently in second and third permanent molars. Only four cases of single rooted primary molars have been reported. [1],[2],[3] Females are seen to be more frequently affected than males with respect to root dysmorphology. [23] The cause for this female predilection is unknown. [23]


Environmental factors such as chemotherapy, radiation therapy and trauma may affect the morphology of the developing roots. [24] Literature regarding etiology of single rooted molars reveals failure in invagination of Hertwig's epithelial root sheath (HERS) resulting in dysmorphological roots. The HERS originates as a double layer of cells from the inferior surface of the developing dental organ. The root sheath has been compared to a collar or skirt that hangs down from the enamel organ between dental papilla and outer dental follicle. During normal development, the root sheath grows down and encompasses the entire dental papilla. The most apical portion of dental papilla represents the future apical foramen. In case of double rooted teeth, two tongue- like projections grow inward towards the center from the lateral walls of the root sheath. When these projections merge in the center, the developing root structure is divided into two portions. Three rooted molars develop in a similar fashion but with three projections growing from the walls of the root sheath, dividing the developing root structure into three portions. [25] Occurrence of pyramidal molars is due to failure of HERS to completely encompass the dental papilla during its initial (vertical) growth or the failure of the lateral tongue-like projections to form completely. [25]

Genetic and biochemical information about root genesis is limited. [26] In humans, genes msx-1 and pax-9 has been shown to be associated with selective tooth agenesis. [27] Recent research has shown that agenesis of molar roots occurs in mice devoid of the gene nfic. [28] Literature regarding the developmental biology of root formation in terms of gene expression and signaling molecules are also limited in availability. [28] Only a handful of genes have been described in relation to root formation. However gene expression and signaling molecules for occurrence of single rooted molars have to be studied. [28]

This clinical report presents a case of bilateral primary mandibular first molars with single root. It also describes the factors to be considered prior to treatment of dysmorphological roots in primary dentition.

 Case Report

In February 2009, a three-year six-months-old girl was referred to the Department of Pediatric Dentistry, Meenakshi Ammal Dental College, Chennai, India. She presented with a chief complaint of pain in her right lower back tooth region for the past two months. Her medical history appeared non contributory.

Clinical evaluation

Intraoral examination revealed all erupted primary teeth. Dental caries was found in right primary maxillary first molar, right and left primary mandibular first molars and left primary mandibular second molar.

Radiographic evaluation

Intraoral periapical radiographs of the decayed teeth were taken using bisecting angle technique. It revealed caries involving the pulp in right primary mandibular first molar and right primary maxillary first molar. In left primary mandibular first and second molars, caries was extending up to the dentin. While evaluating the root morphology right and left primary mandibular first molars had single root [Figure 1] and [Figure 2].{Figure 1}{Figure 2}

Treatment plan

Pulp therapy and stainless steel crowns for right primary maxillary first molar, right primary mandibular first molars and restorations for left primary mandibular first and second molars were planned. As the child was uncooperative for dental treatment on the dental chair, treatment under general anesthesia was considered. The patient's parents were not keen on dental treatment under general anesthesia. Hence, we were unable to provide dental treatment for the child.


The occurrence of single rooted primary mandibular first molars is extremely rare. No reports were found in the literature until Ackerman et al., described the first case of single rooted primary molars in a 10-year-old child. [8] Later Gideon et al., reported single rooted molars in primary and permanent dentition in two siblings. [9] Investigators suggested that single pyramidal shaped root in molars were inherited as an autosomal dominant condition. [9] This case report describes a girl child with decayed bilateral single rooted primary mandibular first molars. The child had no siblings. Her mother was unaware of any other family members with dental anomalies. Since no lineage was obtained, it was not possible to assess the occurrence of these dental findings on the basis of genetic transmission.

Several factors should be taken into consideration before endodontically treating single rooted primary molars. Excessive tooth removal and perforation are the common iatrogenic access opening errors. These errors occur during the search for the extra canals in teeth with unusual root morphology. [29] These iatrogenic errors can be minimized if the clinician has the knowledge of the general location and dimension of the pulp chamber. [29] The use of a pre-operative radiograph and an additional radiographic view from a 20-degree mesial and distal projection is a good way to detect any abnormalities in root canal morphology. [30] Mechanical debridement and cleaning the canal would be easy in primary single rooted mandibular molars during root canal treatment compared to multi rooted primary molars. It is not known if these dysmorphology of roots in primary molars will affect the eruption of premolars. Documentation of such developmental abnormalities can help the clinicians to assess its prevalence.


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