A diode laser (Sirolaser blue laser system, Sirona Dental Systems GmbH, Fabrikstraße 31, 64625 Bensheim, Germany) of Wavelength 660 nm will be used and the laser parameters will be set as follows: Power 0.1 W, energy 6 J, Continuous wave, Irradiation time 60 Seconds; energy Tip area 0.5 cm2, fluence 12 J/cm2 will be applied at the site of needle penetration.

It should be noted that before each application, the output of the laser device will be checked using the aiming beam on flat surface; both the patient and the operator will wear safety goggles during the irradiation.

A brief demonstration of the pulse oximeter will be performed, and the patient will be instructed to remain still and avoid hand movement in order to obtain accurate readings. The pulse oximeter will be placed on the patient's index finger to measure the baseline heart rate (prior to administering the LA), and another measurement will be taken during the LA administration. Heart rate will be recorded at 2-minute intervals and the mean heart rate measurement will be calculated.

The Sound, Eye, Motor (SEM) Scale will be used to assess pain. It encompasses the following parameters: (1) Sound, (2) Eye and (3) Motor. The sounds, eye symptoms and body movements of each child will be independently evaluated by a blind impartial observer using the recorded video tapes. The slightest manifestation of the patient's sound, eyes, or motion is graded in four levels: comfort, mild, moderate, and severe discomfort, and subsequently given grades 1, 2, 3, 4, respectively. The SEM score will be calculated by adding the three parameter grades.

To subjectively record pain during LA injection, a modified face scale will be used. It comprises three schematic faces with different facial expressions for happy and sad faces representing: (A) satisfaction; (B) indifference; and (C) dissatisfaction, respectively. Each child will be taught before injection how to use the scale by modelling and then asking each participant to recall the last time she or he felt something painful and select the facial expression that best represented his or her experience of discomfort.