The Case Against Less Than 4 Hours Contact - William M. Hang, DDS, MSD
In this lecture, Dr. William M. Hang challenges the common belief that anterior open bite and excessive gingival display are primarily caused by continuous tongue thrust. He presents a patient case with less than four hours of teeth contact per day, a low tongue posture, and an open mouth. Dr. Hang explains that the open bite results from over‑eruption of the upper molars, which forces the maxilla to descend and rotates the mandible downward, rather than from the tongue preventing incisor eruption. He notes that for each millimeter the upper molars extrude, the incisors would need to erupt three millimeters to achieve contact, a demand that is not met, leading to a gummy smile and unattractive appearance. The speaker emphasizes that the tongue’s low posture, not its thrust, is the key factor, and he systematically debunks the tongue‑thrust hypothesis by detailing the biomechanical chain of events that produce the open bite.
