## Materials and Methods
### Bite Force Measurements  
The bite force was measured with a bite fork device (Occlusal Force-Meter, GM10, [PERSON], Tokyo, Japan), which comprised a hydraulic pressure gauge (Figure 1). The top surface of the device was covered with a diaphragm, and the pressure of liquid charged in the housing was measured with a built-in nanometer. A biting element, made of a vinyl material, was encased in a polyethylene tube termed the \"disposable occlusal cap\". The bite fork specifications were as following: force range, 0-1000 N; accuracy, \(\pm\)1 N; and the dimensions, 17 mm in width, 5.4 mm in height, and 63.5 mm in length. Several in vivo studies have successfully used this device for recording bite force [30; 31; 32; 33; 34; 35; 36; 37; 38]. The subjects did not experience any discomfort or pain while biting on the instrument [16; 17]. In addition, previous research showed that this specific bite fork has substantial test-retest reliability and is suitable for substantial inter-rater reliability [35]. The bite fork in the current study was modified by using an adhesive to attach the head of a rigid Tooth Slooth (Professional Results, Inc., Laguna Niguel, CA) to the fork, according to the modification described in the study of [PERSON] et al. (Figure 2) [14]. This modification acted as an occlusal guide and fulfilled two main purposes as following: to coordinate the forces in a vertical direction in order to prevent fractures and to raise the height of the fork to obtain an interocclusion height of 18 mm. It was shown that the maximum masseter bite force magnitudes are recorded when vertical jaw openings are between 15 and 20 mm [39]. Before each use, the bite fork was covered with a thin nylon sheet to protect the users from contamination (Figure 3). Figure 1: Occlusal Force-Meter, GM10. Figure 3: The bite fork covered with a thin nylon sheet. The bite forces (N) were calculated by the device and were displayed digitally. A cutoff value of 775 N was imposed to prevent tooth injury [14]. The accuracy and repeatability of this device has been validated previously [40]. All bite force readings were conducted by one examiner (G.P.). The intra-tester reliability was estimated using intra-class correlation (ICC) by the same examiner (G.P.) For measurements, all participants were asked to sit in an upright position without head support, with the Frankfort plane nearly parallel to the floor and feet resting on the floor. They were instructed to bite on the device as hard as they could until they felt pain and held for at least five seconds without moving the head [40]. The device was positioned between the subject's maxillary and mandibular teeth in such a way that the acrylic cone of the bite fork was placed side up on the palatal cusp of maxillary molars and pre- molars and on the buccal cusp of mandibular molar and pre-molar teeth (Figure 4). All subjects were given the same standardized instructions in both a written and verbal form, before they started the procedure as following: \"I am going to place this bite fork between your upper and lower posterior teeth in order to measure how hard you can bite. After the placement of the bite fork, I would like you to close your teeth together. When I signal you, please, increase your bite force slowly until you feel discomfort or pain and then relax. The bite force measurement from my signal to start should take about five seconds\". Each patient was tested in one or two posterior hemi arches; three occluding pairs (premolars and molars) were tested on each posterior hemi arch, with an interval of 30 s between the measurement of each occluding pair, in order to avoid the fatigue of masticatory muscles. The examiner (G.P) performed two repeated readings in each segment with a 5 min break between them, in order to determine the test-retest reliability. Therefore, every pair of occlusal unit received two readings and the highest reading, which represented the maximal bite force, was documented.