Final answer:
The initial movement of the mandible during opening is an anterior gliding motion that allows the mouth to open horizontally. On average, this movement produces about 35-50 mm of mouth opening.
Step-by-step explanation:
The initial movement of the mandible during opening is an anterior gliding motion of the articular disc and mandible. This motion allows the mouth to open horizontally. The amount of mouth opening produced by this movement can vary depending on the individual, but on average, it is about 35-50 mm.
This motion produces a moderate amount of mouth opening, but to fully open the mouth, the mandible also needs to perform an anterior gliding motion along with the articular disc. This combination of motions allows the temporomandibular joint (TMJ) to function properly during mouth opening.