A. Tallgren

Changes in jaw relations, hyoid position, and head posture in complete denture wearers

In a group of 18 partially edentulous patients provided with immediate complete dentures, changes in hyoid bone position and craniocervical posture were examined on cephalometric radiographs made during 1 year of denture use. The findings indicated that the changes in hyoid bone position largely followed the pattern of forward-upward rotation of the mandible due to ridge resorption. During this course the hyoid position in relation to the cervical spine showed a mean increase. The hyocervical changes, however, showed less variability than the hyomaxillary and hyomandibular changes. The posture of the head and cervical column showed no definite mean changes during the 1-year period. On the other hand, analysis of individual changes revealed that a pronounced decrease in mandibular inclination due to ridge resorption was associated with retroclination of the cervical column and decreased craniocervical angulation. These postural changes may be regarded as adaptive changes to a marked initial change in mandibular position.

Jaw muscle activity in complete denture wearers—A longitudinal electromyographic study

EMG study of subjects wearing immediate complete upper and lower dentures revealed marked alterations in activity of the jaw closing muscles during the biting actions recorded. This finding suggests that changes in jaw and occlusal relationships due to resorption of residual ridges and settling of the dentures also affects jaw muscle activity. The relations between EMG and morphologic findings will be analyzed further in a separate article.

Effects of a myofunctional appliance on orofacial muscle activity and structures.

The aim of the study was to examine the effect of an oral shield treatment on orofacial muscle activity and facial morphology in children with lip and/or tongue dysfunction. The sample consisted of 7 girls and 2 boys, 7 to 12 years old. EMG recordings with and without the shield in situ were obtained when the shield was placed, and 3, 6, and 12 months later. Lateral cephalograms were obtained at the initial and 1-year stages. The lip muscles showed dominant activity when the subjects were sucking on an empty straw and during swallowing; this was strongest during the first 3 months. The mentalis, buccinator, and digastric muscles generally showed weaker activity. The anterior temporal muscle showed dominant activity during maximal clench, but after the 3-month stage a significant decrease was noted. After 1 year of treatment, no significant changes in overjet or overbite were observed. Most of the craniofacial growth changes were normal for the age group. The results indicate that treatment with an oral shield caused a decrease in orofacial muscle activity during oral functions. Although there was a slight average retraction of the maxillary incisors, the change in position was not statistically significant.

A two-year kinesiographic study of mandibular movement patterns in denture wearers

Changes in functional jaw movements during a 2-year period of denture wear were investigated. The sample consisted of 27 partially edentulous subjects who were provided with an immediate complete maxillary denture and a removable partial mandibular denture. Recordings of habitual chewing of apple and empty open-close cycles were made with a mandibular kinesiograph. At the pretreatment stage, when the patients occluded on a residual anterior dentition, irregular patterns of movement were observed. After placement of the dentures, which restored posterior occlusion, the chewing and open-close patterns showed marked improvement and were characterized by significant mean decreases in sagittal and transversal range of movement. Relining of the maxillary dentures further stabilized the functional patterns. During the second year, significant reductions in vertical range of movement and lateral chewing excursions were observed, and were probably related to impaired retention of the complete upper denture.