Review article
The Root and Root Canal Morphology of the Human Mandibular First Premolar: A Literature Review

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Abstract

The purpose of this study was to undertake a comprehensive literature review of the root and root canal morphology of the mandibular first premolar. Published studies citing the anatomy and morphology of mandibular premolars report data for over 6,700 teeth. These studies were divided into anatomical studies reporting number of roots, number of canals, and apical morphology. Variations because of sex and ethnic background have also been reported, along with case reports of anomalies.

Approximately 98% of the teeth in these studies were single-rooted. The incidence of two roots was 1.8%. Three roots when reported were found in 0.2% of the teeth studied. Four roots were rare and were found in less than 0.1% of the teeth studied.

Studies of the internal canal morphology revealed that a single canal was present in 75.8% of the teeth. Two or more canals were found in 24.2% of the teeth studied. A single apical foramen was found in 78.9% of the teeth, whereas 21.1% had two or more apical foramina.

The role of genetics and racial variation may result in differences of incidence of root number and canal number in human populations. The dental literature is not unique in studying ethnicity and sex variations. Higher incidences of teeth with additional canals and roots have been reported in Chinese, Australian, and sub-Sahara African populations. Physical anthropology studies seem to show the lowest incidence in Western Eurasian, Japanese and American Arctic populations.

The root and root canal morphology of this tooth can be complex and requires careful evaluation prior to root canal therapy.

Section snippets

Materials and Methods

A review of the literature was performed for the mandibular first premolar with respect to the number and type of roots and root canal morphology. Search topics included “number of roots,” “number of canals,” “root canal morphology,” “extra roots,” “anomalies,” and “abnormal morphology.” Studies of the mandibular first premolar identified through PubMed plus hand searching were included, but pooled data from teeth identified only as “premolars” or “mandibular premolars” were avoided. Over 6,700

Number of Roots

Eight anatomical studies that included 4,462 teeth report on data for the number of roots in the mandibular first premolar (11, 14, 16, 20, 21, 29, 47, 71) (Table 1). The majority of the teeth in these studies (97.9%) had a single root. Two roots were found in 1.8% of the teeth studied. Three-rooted (0.2%) and four-rooted (<0.1%) varieties were quite rare.

A study by Trope et al. (15) reported results by number of patients rather than by the total number of teeth. The results of this study are

Discussion

There is a great deal of variation in the literature with respect to the number of roots and internal canal morphology of teeth.

Only a few studies report ethnic or sex differences. A study of full-mouth series of radiographs from 1,000 patients by Amos (74) in 1955 not only reported on bifurcated canal systems of mandibular first premolar teeth, but also inferred a higher incidence in canal bifurcation in African American patients compared to Caucasian patients. The number of patients in each

Conclusions

Major conclusions that can be drawn from this review article are as follows:

  • 1

    Although most mandibular first premolars have a single root, two-, three-, and even four-rooted forms have been reported as 2.1% incidence when grouped together.

  • 2

    The majority of mandibular first premolar teeth have a single canal but there is a relatively high incidence, or one-quarter of mandibular premolars, that have two or more canals (24.2%).

  • 3

    A single apical foramen may be found in mandibular first premolar teeth in

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