PubMed · 284679
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R Diernberger. 1978. [Errors and relapse in orthodontic practice].. https://pubmed.ncbi.nlm.nih.gov/284679/
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The development of the paranasal or accessory sinuses begins very early in utero. In the newborn the ethmoidal sinus, which gives rise to all the other sinuses, as well as the maxillary sinus, can already be identified on x-rays. The frontal sinus appears as a triangle at the age of four and oversteps the supraorbital margin at the age of six. The sphenoidal sinus begins to excavate the concha sphenoidalis at the age of four and can be seen on x-rays at the age of eight, when it extends to the hypophyseal fossa. In the twelve-year-old child all sinuses almost reach their final sizes. However, the size and shape of all sinuses, particularly of the frontal and the sphenoidal sinuses are very different.
A 24-month study was conducted to determine changes in the mandibular rest position after removal of the remaining teeth and insertion of complete dentures. A total of 24 patients with at least 10 teeth acting as occlusal stops were included in this study. Serial lateral cephalometric radiographs were made for each patient on four occasions (1) before extraction (2) 7 to 10 days after the initial denture insertion (3) 12 months later, and (4) 24 months later. Two angular measurements and one linear measurement were made for each radiograph and compared. A statistically significant increase in the face rest height with a tendency for posterior mandibular rotation was recorded between stages 1 and 2. This initial posterior rotation was followed by a gradual forward and upward movement, which finally brought the mandibular rest position even below the preextraction levels. The findings confirm the concept of the variability of posture and suggest that the mandibular rest position is an unreliable means of reestablishing the vertical dimension of occlusion that existed before extraction of the natural teeth.