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Introduction: Aberrant root canal morphology of mandibular premolars has always been associated with high endodontic treatment failures. This study was conducted to assess the canal morphology of the mandibular premolars in the Malaysian population using periapical radiographs and cross-sections of the premolar teeth. Materials and Methods: One hundred extracted permanent mandibular premolars with intact apex were randomly collected from various clinics across Malaysia. Radiographs were taken both in mesiodistal (MD) and buccolingual (BL) views to examine the presence of a second canal and to evaluate the type of canal configuration. The roots were then stained and perpendicularly resected to the long axis at three levels (cervical, middle, and apical one third). Digital photographs were taken for each of the cross-section sample and analyzed according to the number and shape of canals. Results: It was found that 78% of the mandibular premolars had single canal in BL radiographic view and 65% in MD view. Seventy-one percent of the single-canal premolars were observed in all three cross-sectional views (1-1-1 configuration). Furthermore, 37% showed oval-shaped canals and 34% showed irregular-shaped canals mainly found at cervical one third; 20% of the teeth showed the canals to be rounded in shape, most prevalent at the apical one third. Two canals with isthmus were observed in 5% of the all cross-sectional views. Conclusion: The majority of mandibular premolars in Malaysian population have a single canal, and there are a few possibilities of two or more canals in these teeth.

Knowledge of the normal root canal morphology and its variation is essential to ensure a successful root canal therapy. The aim of this report is to describe the endodontic treatment of two mandibular premolars with aberrant root canal morphology with the aid of dental operating microscope. A 29-year-old Saudi male with three mandibular left premolars was referred by the Prosthodontic Department for endodontic evaluation prior to placement of final coronal restorations. The first premolar was diagnosed as having necrotic pulp while the third premolar was previously treated. Root canal treatment and nonsurgical root canal retreatment were performed for the first and third premolars, respectively. The first premolar had a C-shaped configuration and Vertucci′s Type V (1-2) canal system while the third premolar had Type III configuration (1-2-1). One year later, the teeth were asymptomatic with normal periapical tissues radiographically. Root canal aberrations may occur in any tooth type, and the clinicians should always assume the presence of these aberrations and use all the available tools to detect and manage them.

Dens invaginatus (DI) is a developmental anomaly that results from an infolding of the dental papilla during tooth development and simulates the appearance of a tooth within another tooth. It shows a wide spectrum of variations in morphology and usually affects the maxillary lateral incisors. This study presents an unusual case of an Oehlers’ Type I DI involving the bilateral mandibular first and second premolars, which presented as an incidental radiographic finding in the first premolars and was associated with a periapical lesion in the second premolars which was successfully treated using nonsurgical endodontics.