Eva Hellsing

Changes in lip pressure following extension and flexion of the head and at changed mode of breathing

The changes in upper and lower resting lip pressures following extension and flexion of the head and at changed mode of breathing were studied in a sample of 15 adults with Class I molar relationship. The lip pressure was measured with bonded strain gauge transducers on the upper and lower central incisors. The transducers could be calibrated directly in the subjects mouth. The upper and lower lip pressures during natural head posture had a mean value of 3.91 g/cm2 and 8.58 g/cm,2 respectively. The mean values of the differences between pressures obtained during natural head posture and during 5 degrees, 10 degrees, and 20 degrees of extension showed a continuously, highly significant increase in pressure. During 5 degrees, 10 degrees, and 20 degrees of flexion, the upper lip pressure continuously decreased with highly significant values. Changes in the lower lip pressure during flexion were difficult to measure because of intense muscle activity. A significant decrease was shown for the difference in upper and lower lip pressures between nose breathing and mouth breathing, whereas there was a significant increase in pressure when the subject extended the head 5 degrees during mouth breathing.

Orthodontically induced root resorption in rat molars after 1-hydroxyethylidene-1,1-bisphosphonate injection.

A single injection of 1-hydroxyethylidene-1, 1-bisphosphonate inhibits the formation of acellular cementum in rat molars. Instead, an atypical hyperplastic cementum is formed. In this study the resistance of this cementum to resorption was tested by applying an orthodontic force. It was found that roots lacking acellular cementum were readily resorbed. The readiness with which the atypical hyperplastic cementum was resorbed without any increase in multinucleated osteoblasts may offer useful opportunities to study the different phases of hard-tissue resorption.

Cervical vertebral dimensions in 8-, 11-, and 15-year-old children.

In a sample of 107 boys and girls registered at 8, 11, and 15 years of age and 22 adults the statural height and the height and length of the cervical vertebrae, measured from lateral skull radiographs, were studied. The height and length of the vertebrae increased with age among the children and were non-significantly higher for the girls in each age group. The 15-year-old girls matured earlier, reaching adult values at this age. The 15-year-old boys still showed significantly smaller values for vertebral height and length compared with the adult men. Statural height was significantly correlated with the variables for vertebral growth at 8 and 11 years, whereas there was no correlation at 15 years of age among the children who had passed the pubertal peak height. The development of the vertebrae showed similarities with earlier reported skeletal maturity indicators found in the hand-wrist area and could as such offer an alternative method of assessing maturity without the need for hand roentgenograms.

Increased overbite and craniomandibular disorders--a clinical approach.

This study investigated the effect of a maxillary fixed lingual arch with anterior bite plane on adult patients with craniomandibular disorders (CMD) and increased overbite. The sample comprised 11 patients with an increased overbite (greater than 5 mm) and a normal or Class II molar relationship. The main CMD symptoms were daily tension headache in the region of anterior temporal muscles and/or pain or clicking in the temporomandibular joint. Previous treatment with stabilization splints, removal bite plates, or occlusal grinding had not given satisfactory results. When the maxillary lingual arch with anterior bite plane was fitted, molar separation was approximately 4 mm, and occlusal contact occurred only between the acrylic bite plane and the lower six anterior teeth. The permanent appliance could be removed only by the orthodontist. All patients reported relief of CMD symptoms 1 to 2 weeks after initiation of treatment. After a mean time of 3 months, a flatter curve of Spee, molar contact, and reduced overbite could be seen in all cases. The excessive overbite had decreased approximately 3.4 mm. Subsequent treatment involved orthodontic or prosthetic therapy to normalize and stabilize the sagittal and vertical dimensions. After an average posttreatment observation period of 2 years, all patients remained free of CMD pain.

Effect of fixed anterior biteplane therapy-a radiographic study

Orthodontic treatment of eight overbite cases with a maxillary fixed lingual arch appliance with anterior biteplane involved a reduction in overbite of 4 to 7 mm between the upper and the lower front teeth and a first molar separation of 2 to 4 mm. After a treatment period of 3.5 to 5 months, occlusal contact between the upper and the lower molars was established. The appliance was then removed, and permanent overbite reduction was secured with an edgewise appliance. With the subtraction technique, 15 temporomandibular joints were radiographically investigated in the retruded position for change of condylar position on the glenoid fossa before and directly after insertion of the appliance, as well as after achieved molar contact. All condyles changed position directly after the bite opening, indicating that pure rotation did not occur. The direction of movement varied not only between subjects but also between the two condyles of each subject. With one exception, none or very small further positional changes occurred during treatment. No imaged signs of hard structure remodeling were observed. It may be concluded that other factors than change of condylar position must be responsible for the therapeutic effect of the bite-opening appliance that has been demonstrated in an earlier study.