Table 4.

Percentage for number of canal orifices in the mandibular first premolar.

Reference	Method of study	Population	Coronal orifice
			One canal	⩾2 canals
Pineda and Kuttler [9]	Radiography	Mexico	69.3%	30.7%
Zillich and Dowson [10]	Radiography	USA	75.1%	24.9%
Walker [13]	Radiography	China	64%	36%
Geider et al. [16]	Sectioning and radiography	France	68.9%	31.1%
Baisden et al. [12]	Tooth sectioning	USA	74%	26%
Sabala et al. [6]	Review of patient records	USA	81.8%	18.2%
Çaliskan et al. [17]	Tooth clearing	Turkey	64%	36%
Zaatar et al. [15]	Radiographs of RCT teeth	Kuwait	60%	40%
Yoshioka et al. [18]	Tooth clearing	Japan	80.6%	19.4%
Sert and Bayirli [7]	Tooth clearing	Turkey	60.5%	39.5%
Yoshioka et al. [18]	Radiography and tooth clearing	Japan	80.6	19.4
Lu et al. [14]	Radiography and sectioning	China	54%	46%
Cleghorn et al. [33]	Review article	Global	75.8%	24.2%
Awawdeh and Al-Qudah [24]	Tooth clearing	Jordan	58.2%	41.8%
Peiris [19]	Tooth clearing	Seri Lanka	95.1%	4.8%
		Japan	98.9%	1.1%
Velmurugan and Sandhya [21]	Tooth clearing	India	83%	17%
Jain and Bahuguna [32]	Tooth clearing	India	88.40%	11.59%
Current study	Tooth clearing	Egypt	80.8%	19.2%