Neutral Occlusion Research Articles

Bite force in pre-orthodontic children with unilateral crossbite.

In the present study bite force was examined in pre-orthodontic children with unilateral posterior crossbite and compared with an age- and sex-matched control group. The sample comprised 52 children aged 7-13 years, 26 pre-orthodontic children with unilateral posterior crossbite (crossbite group), and 26 children with neutral occlusion (control group). Unilateral bite force was measured at the first molar by means of a pressure transducer. Furthermore, symptoms and signs of temporomandibular disorders (TMD) and number of teeth in contact in the intercuspal position (ICP) were recorded. In both groups, the maximum bite force increased significantly with age and with increasing stages of dental eruption, but the bite force in both sexes did not differ significantly. There were no significant differences in bite force between sides, but this was significantly smaller in the crossbite group than in the controls (P < 0.001). Regression analysis showed that stage of dental eruption (P < 0.001), number of teeth in occlusal contact (P < 0.01), and unilateral crossbite (P < 0.001) were the only variables significantly correlated with bite force. The number of teeth in contact was significantly smaller in the crossbite group than in the controls (P < 0.05) and the frequency of muscle tenderness was significantly higher in the crossbite group than in the controls (P < 0.05). These results suggest that differences in the muscle function associated with unilateral crossbite lead to a significantly smaller bite force in the crossbite group compared with controls and this difference did not diminish with age and development. These findings indicate that early treatment of unilateral posterior crossbite is advisable to optimize conditions for function.

Comparison of distal and neutral craniofacial pattern in untreated subjects in terms of skeletal harmony and growth

Using conventional comparisons of means and multivariate analyses, the aim of this study was to establish skeletal proportions and their growth-dependent development in untreated subjects with class II/1 malocclusion and compare them with a longitudinally-examined, untreated group with neutral occlusion. 138 untreated children from Nittedal/Norway with an Angle-class II/1 malocclusion were examined longitudinally using radiocephalometry at 2 points in time: average ages of 9.1 and 12.1 years. These class II/1 children were compared to a group of 80 untreated children with class I occlusion (also from Nittedal, similar age group). In addition to the Norwegian participants, untreated children with class II/1 malocclusion from Sweden and Germany were longitudinally analyzed. Besides a comparison of the mean values of the measured basal variables, a multivariate analysis was conducted with the help of graphically converted regression equations (harmony box). In comparison to the class-I children with neutral craniofacial pattern, the mandibles in children with class II/1 malocclusion showed a significant posterior shift at both points in time. According to evaluation with the harmony box, the craniofacial dimensions were harmonious in class I occlusion. In all class II/1 groups, the maxilla was located slightly disharmoniously to the anterior at both time points. The average basal alterations were relatively minor. If not only individual mean values are compared with one another, but also multivariate relations of the viscerocranium are considered, a maxillary anterior shift is more frequently diagnosed in subjects with a class II/1 malocclusion than is possible with a comparison of mean values.

Initial effects of treatment of Class II malocclusion with the Herren activator, activator-headgear combination, and Jasper Jumper

The initial effects of treatment of Class II, Division 1 malocclusion with an activator, according to Herren (27 patients), with an activator-headgear combination (20 patients), or with the Jasper Jumper appliance (25 patients) were studied on lateral cephalograms from before and after 6 to 8 months of treatment. The patients' ages ranged from 9 to 12 years. At the end of the period of observation, the correction in overjet and molar relationship was more complete in the patients with the Jasper Jumper than in the patients with the activator. Whereas all the patients with the Jasper Jumper showed neutral occlusion, this was the case in only 20 of the 47 patients with the activator. The correction of the distal occlusion occurred through a combination of skeletal and dentoalveolar adaptations. Skeletal changes accounted for 42%, 35%, and 48% of the overjet correction by the Herren-type activator, the headgear-activator, and the Jasper Jumper, respectively. The correction of the molar relationship occurred to 55%, 46%, and 38% by skeletal changes in the respective groups. Dentoalveolar compensation (distal movement of the upper molars, mesial movement of the lower molars) appeared to be inversely related to skeletal adaptation. The patients with the Jasper Jumper showed a marked intrusion of the lower incisors with a consequent reduction in overbite. (Am J Orthod Dentofac Orthop 1997;112:19-27.)

The prevalence of malocclusion in 13- to 15-year-old children in Nairobi, Kenya.

Data on occlusal features and the need for orthodontic treatment in Kenya is scanty. This study was carried out to determine the prevalence of malocclusion in children in Nairobi, Kenya. Nine hundred and nineteen children aged 13-15 years (468 male, 451 female) were examined. The registration method used was that described by Björk et al. The prevalence of malocclusion was 72%. The predominant anteroposterior relationship of the dental arches was neutral occlusion (93%). Specific malocclusion traits were highest for crowding (19%), rotations (19%), posterior crossbite (10%), maxillary overjet (10%), and frontal open bite (8%). There was no statistically significant difference in the overall prevalence of malocclusion between males and females, but some occlusal traits were significantly higher in males. Although the findings indicate that the present population is not characterized by a substantial difference in the overall prevalence of malocclusion compared with other communities, some traits differed in prevalence from those reported elsewhere.

SAGİTTAL YÖNDE FARKLI İSKELETSEL İLİŞKİ GÖSTEREN NÖTRAL OKLÜZYONLU BİREYLERDE KESİCİ DİŞ KOMPANZASYONU*-THE INCISOR COMPENSATION OF INDIVIDUALS WITH NEUTRAL OCCLUSION WHO HAD DIFFERENT SAGITTAL SKELETAL RELATIONSHIP

OZET Calismamizin amaci sagittal yonde meydana gelen is-keletsel degisimlerin kesici dislerin eksen egimlerine olan etkisini arastirmaktir. Bu amacla notral okluzyonlu bireyler ANB acisina gore uc gruba ayrilmis ve bu grupla arasindaki degisimler degerlendirilmistir. Yapilan degerlendirmeler sonucunda CLII grubunda hem alt keserlerin prot-ruzyonu hem ust keserlerin retruzyonu; CL III grubunda ise daha cok ust keserlerin protruzyonu belirlenmistir. Anahtar sozcukler: Keser kompansasyonu, keser konumu. ABSTRACT The Purpose of this study was to determine the effectiveness of sagittal skeletal changes on the inclination of incisors. For this reason, Individuals who had neutral occlusion were divided into three groups according to ANB angle and then the differences among the groups were evaluated. From results presented in this paperrr we concluded that retrusion of upper rand protrusion of lower incisors was evaluated in the group of Class If, on the other hand the group of Class III shoved protrusion mostly in upper incisors. Key words: Incisor compentation, incisor position.

Occlusion in the primary dentition in 3-year-old children.

The material for the present study comprises plaster models of 310 Copenhagen children, impressions for which were taken during the month each child attained the age of 3 years. On the basis of fixed criteria a description is given of individual symptoms of occlusion. Using the primary canines as the guide to occlusion it was found that the same occlusion at both sides occurs in 79.7% of the overall total, the remaining 20.3% having different occlusion at each side. Approximately one-half recorded neutral occlusion at both sides, and one-third had distal occlusion at both sides. The termination pattern of the dental arches in centric occlusion were normal or straight in 68.0% and bilateral distal in 14.8%. In 82 subjects or 27% of the degree of overlapping was greater than or equal to half the height of the mandibular central incisors. The number of cross-bites constituted 11.6% of all subjects. Assessment of spacing was undertaken exclusively on the basis of whether or not a space existed. About 3.5% of all subjects had close contact between all teeth in the maxilla or crowding, and about 24% had spacing between all teeth in the maxilla. In the mandible about 5% had close contact between the teeth and only 15% had spacing between all teeth in the mandible.

Morphogenetic response to activator treatment

E xperiments on growing primates have demonstrated that changes induced in the posture of the mandible may cause dental malocclusion.7 Class II, Division 1 malocclusions have been produced by lowering the postural position of the mandible relative to the maxilla which, in turn, caused extrusion of maxillary buccal teeth. In similar experiments, in which no extrusion of the maxillary buccal teeth was allowed, a lowering of the mandible did not result in a Class II malocclusion. The findings from these experiments indicate that the relative eruption of the posterior teeth is an important factor in the establishment of molar relationships. These results constitute the basis of the present clinical study. The purpose of this investigation was to change a Class II molar relationship into neutral occlusion by reversing the effects demonstrated in the primate experiments. This was achieved by impeding the vertical development in the maxillary molar region and concurrently stimulating vertical development in the mandibular molar segments. Correction of a Class II molar relationship by nightly use of a removable orthodontic appliance is a generally accepted procedure.1-41 6p * However, the design of the appliance has been as varied as the interpretation of its effects. For the present experiment, a removable appliance, which was a modification of the conventional activator, was designed. Theoretically, this appliance cquld elicit a series of morphogenetic responses which might contribute to the correction of the Class II malocclusion. Five hypotheses were formulated which, singly or in combination, might explain the structural changes in the transformation from a Class II to a Class I dental occlusion :