The aims of this study were to evaluate ultrasonography as a method for measuring masseter muscle thickness, to quantitate the normal range of the ultrasonically measured thickness of the masseter in adults, and to test whether the variation in the thickness of the muscle is related to the variation in the facial morphology in different individuals. In 40 healthy, fully-dentate young adults, 20 men and 20 women, the masseter thickness was measured bilaterally by a real-time ultrasound imaging technique. The measurements were performed under both relaxed conditions and with maximal clenching. Standardized facial photos of the subjects were taken so that their facial morphology could be determined. The measurement error of the thickness of the masseter was found to be small, not exceeding 0.49 mm. Under relaxed conditions, the mean thickness (+/- S.D.) of the muscle in men was 9.7 (+/- 1.5) mm, and under contracted conditions, 15.1 (+/- 1.9) mm. In women, the respective measurements were 8.7 (+/- 1.6) mm and 13.0 (+/- 1.8) mm. The thickness of the masseter muscle was found to be related to the facial morphology, mainly in women, but not in men; the women with a thin masseter had a proportionally longer face. Ultrasonography was found to be a reliable and accurate method for study of the thickness of the masseter muscle. There was a large variation in the thickness of the muscle between individuals, and the thickness of the masseter was related to facial morphology in women.

This study investigated pain experiences during a common orthodontic treatment. Fifty-five patients (12-18 yr) starting treatment due to crowding were included. Molar elastic separators were inserted bilaterally, and telephone interviews were made during evenings for a week. Pain intensity was assessed on a VAS scale, and pain medications were recorded. Forty-eight patients (87%) reported pain the first evening. The highest intensity of pain was reached the day after placement of separators (VAS mean = 43.7). At day 7, 42% of the patients still reported pain. Pain medication was used by 27% of the patients during the first 2 d, after which no patients used painkillers. While motivational factors and reasons for seeking treatment did not influence pain assessments, patients taking pain medication made significantly higher pain ratings during the days medication was used. Girls made significantly higher pain ratings during the later phase (day 3-7) of the follow-up week. Statistically significant relationships were found between 'late' VAS assessments and reported level of previous general pain experiences. The perceived pain from separators was comparable to previous general and dental pain experiences. It was concluded that pain is common after a simple procedure such as placement of molar separators. The experience of pain varied substantially among subjects. The intensity of pain was gradually reduced, but still more than 40% of the teenagers reported some pain after 1 week.

The aims of this investigation were to study the relation between facial morphology and bite force at different ages during growth and to investigate possible relations between bite force and the variables age, finger force, stature, and sex in growing healthy individuals. One hundred and thirty-six individuals were included, consisting of six groups of males and females, 7-9, 10-12, and 20-24 years old. Standardized photographs were taken to determine the facial type. The occlusal relationship, body height, finger force, maximal bite force, and bite force endurance amplitude were recorded. All bite force variables and finger force increased with age in both sexes. A positive correlation was found between the maximal bite force in the incisor region and the ratio of upper to lower facial height; this is, subjects with a high bite force had a relatively short lower anterior height. The maximal bite force for molars and endurance amplitude were positively correlated to stature and finger force but not to facial characteristics. A longitudinal study to follow each individual child during growth would be of interest to evaluate the importance of muscular influence on facial growth.

Mature adults can exhibit major vertical steps after anterior restorations with osseointegrated fixtures to the same extent as adolescents or "young adult" individuals with residuous growth potential.