Birgit Thilander

Prevalence of Temporomandibular Dysfunction and Its Association With Malocclusion in Children and Adolescents: An Epidemiologic Study Related to Specified Stages of Dental Development

A sample of 4724 children (2353 girls and 2371 boys) (5-17 years old) were grouped not only by chronological age but also by stage of dental development (deciduous, early mixed, late mixed, and permanent dentition). The registrations included functional occlusion (anterior and lateral sliding, interferences), dental wear, mandibular mobility (maximal opening, deflection), and temporomandibular joint and muscular pain recorded by palpation. Headache was the only symptom of temporomandibular dysfunction (TMD) reported by the children. The results showed that one or more clinical signs were recorded in 25% of the subjects, most of them being mild in character. The prevalences increased during the developmental stages. Girls were in general more affected than boys. Significant associations were found between different signs, and TMD was associated with posterior crossbite, anterior open bite, Angle Class III malocclusion, and extreme maxillary overjet.

Periodontal tissue response to orthodontic movement of teeth with infrabony pockets.

The aim of this study was to evaluate the effect of orthodontic tooth movement on the level of the connective tissue attachment in sites with infrabony pockets. The experiment was carried out in four beagle dogs. The second and fourth premolars were extracted. After healing, angular bony defects were prepared at the mesial aspect of the third premolars. The exposed root surface was scaled and planed, and a notch was prepared at the bottom of the defect. Plaque-collecting cotton floss ligatures were placed around the neck of the teeth and maintained in situ for 3 weeks, followed by an additional 2 months of plaque accumulation before the orthodontic tooth movement was initiated. In each dog, one premolar was moved away from the angular bony defect and one premolar into and through the angular bony defect. The maxillary third premolars served as control teeth and were not subjected to orthodontic tooth movement. After orthodontic treatment (5 to 6 months), the teeth were stabilized for a period of 2 months before biopsy sampling. Clinical, radiographic, and histologic evaluations revealed that it was possible to establish and maintain an infrabony pocket with a subcrestal, plaque-induced inflammatory lesion during the entire course of the study. While the control teeth had maintained their attachment levels, all but one of the orthodontically moved teeth showed additional loss of attachment.(ABSTRACT TRUNCATED AT 250 WORDS)

Activity of Temporal and Masseter Muscles in Children with a Lateral Forced Bite

The activity of the temporal and masseter muscles with the mandible in postural position and during chewing, maximal bite in the intercuspal position, and swallowing were recorded electromyographically in nineteen children with laterally forced bite. Of the children, aged 8-12 years, sixteen had unilateral crossbite. In all of the individuals there was lateral deviation between the retruded contact position and the intercuspal position. The magnitude of the lateral deviation was measured with a modified gnathothesiometer. The muscle activity was recorded bilaterally from the temporal muscle and from the masseter muscle. In the postural position asymmetric activity was found in the temporal muscle suggesting that the mandible in postural position was still displaced to the side of forced bite. During chewing the activity was asymmetric both in the anterior and the posterior temporal portions. This asymmetric muscle activity was interpreted as an adaptation to avoid cuspal interferences. Also in maximal bite the muscle activity was asymmetric, while the activity during swallowing was affected less than in the other functions. The swallowing activity was, however, less in children with a forced bite than in children with normal occlusion.

Extraction of third molars in cases of anticipated crowding in the lower jaw

The purpose of this study was to ascertain whether the lower third molar, in combination with other variables such as facial morphology and space conditions, can contribute to the occurrence or aggravation of crowding. The subjects consisted of twenty-three boys and twenty-nine girls with impacted third molars on both sides of the mandible. The impacted molar on one side was removed, while the other, nonextracted side was used as a control. Average age at the time of operation was 15.5 years (range, 13 to 19). Close to the operation and annually for at least 3 years afterward, study casts and cephalograms (lateral, frontal, and oblique) were taken. The findings indicated that (1) despite analyses of many variables, this study has not been able to predict which patients should react favorably or unfavorably to removal of the third lower molars in cases of anticipated crowding; (2) in cases with severe crowding removal of the molars could be recommended; (3) correct proximal contacts seem to be of importance in keeping the space that is achieved by extraction, while incorrect ones may spoil it.

Postnatal development of the human temporomandibular joint. I. A histological study.

Temporomandibular joints from 61 humans, aged 2 days to 27 years, were examined histologically. Four layers of the condyle were studied in detail. The outermost layer was richly vascularised in new-borns but by 3 years of age it had become avascular and contained few cells. In neonates the cartilage layer constituted a large part of the condyle but soon decreased in thickness and by 5-6 years of age it constituted only a thin zone of the top of the condyle. In the proliferative zone, mitoses occurred up to 13-15 years of age. This zone then decreased in thickness; the number of cells decreased, while the amount of intercellular substance increased. At birth, the temporal component was flat and was lined by vascularised connective tissue which became richer in collagen with increasing age. The cartilage layer was lacking in the fossa but was present on the tuberculum. A proliferative zone in this cartilage could be seen up to the age of 17-18 years and cartilage having only few cells was found in adults. Remodelling processes were seen in all components of the joints. The significance of the remodelling seen in the fossa and on the mandibular neck is discussed with relation to condylar and periosteal growth of the mandible.

Craniomandibular disorders with special reference to orthodontic treatment: An evaluation from childhood to adulthood*

The purpose of the present study was to reexamine a group of children and adolescents with respect to signs and symptoms of craniomandibular disorders (CMD) and to evaluate whether any differences could be found between persons who had received orthodontic treatment earlier and those who had not. A total of 402 children in three age groups (7, 11, and 15 years) had participated in a cross-sectional study on the relationship between malocclusion and signs and symptoms of CMD. Ten years later they were asked to answer a questionnaire. In the youngest age groups (now 17 and 21 years old) 190 (76%) subjects answered the questionnaire. In the oldest age group (now 25 years old) completed questionnaires were received from 103 (84%) subjects, and 83 (62%) of those subjects appeared for a clinical examination. Subjects with a history of orthodontic treatment had a lower prevalence of subjective symptoms of CMD (TMJ sounds included) than those without any experience of orthodontics. Although the differences were small, it was more evident for the oldest age group. The clinical examination has shown that persons who had undergone orthodontic treatment had a significantly lower clinical dysfunction index than those who had not.

Muscle activity in normal and postnormal occlusion

Abstract The EMG activity in the rest position of the mandible, during chewing, and during swallowing was compared in fifteen boys with normal occlusion and fifteen boys with Angle Class II, Division 1 malocclusion. The childrens ages varied between 9 and 13 years, with a mean of 10 years 6 months in the normal-occlusion group and 10 years 11 months in the group with postnormal occlusion. The EMG activity was recorded unilaterally from the anterior temporal muscle, the posterior temporal muscle, and the masseter muscle and superiorly from the orbicularis oris muscle. The EMG activity during rest was recorded according to a five-grade scale, while the maximum mean voltage and duration of the EMG activity were recorded during chewing and swallowing. The EMG activity was related to the morphology of the face and dentition analyzed with profile roentgenograms. No difference was found between type of occlusion in the EMG activity in the rest position, which was greatest for the posterior temporal muscle for both types of occlusion. The EMG activity at rest in the anterior temporal muscle was greater in children with small gonial angles than in those with large angles. The boys with postnormal occlusion had a tendency to develop less EMG activity during chewing than boys with normal occlusion. In both types of occlusion the chewing activity was greater in the anterior than in the posterior part of the temporal muscle. In the orbicularis oris muscle the activity, irrespective of type of occlusion, was greater during the opening phase than during the closing phase of the chewing cycle. The children with postnormal occlusion showed less EMG activity during swallowing in the anterior temporal muscle and the masseter muscle than those with a normal occlusion. In children with postnormal occlusion the duration of the activity during swallowing was longer in the posterior than in the anterior part of the temporal muscle, while the inverse relationship was found for children with normal occlusion. In boys with small gonial angles, the amplitude of the activity in the masseter muscle during swallowing was smaller and the duration in the posterior temporal muscle was longer than in boys with large gonial angles.

Effect of orthodontic force on periodontal tissue metabolism a histologic and biochemical study in normal and hypocalcemic young rats

The relationship between force and degradation activity after application of orthodontic force is still obscure. Of particular clinical interest are the etiologic factors behind excessive root resorptions appearing in connection with orthodontic movement of teeth that has been proposed to be influenced by systemic factors regulating the tissue-degrading activity in periodontal tissues. Thus, the aim was, by histologic and new biochemical methods, to investigate the effect of orthodontic forces on the periodontal tissues in the normal and the hypocalcemic situation with secondary hyperparathyroidism. Root resorptions were induced in upper incisors of normal and hypocalcemic rats by subjecting the teeth to a moderate orthodontic force. In both groups the resorption of the roots occurred consistently in the vicinity of reorganizing areas of the periodontal ligament (PDL) with ongoing degradative activities and alveolar bone resorption. Furthermore, specific cell metabolic changes in alveolar bone and PDL in tension and pressure zones were detected and quantified by biochemical determination of alkaline phosphatase activity. This biochemical quantification of the metabolic changes together with the morphologic observations gave the clinically valuable information that the observed increase in occurrence and severity of root resorptions in moderate hypocalcemia was related to an increase in alveolar bone turnover. This study has shown that root resorptions were clearly related to the degradation process occurring in the vicinity of the hyaline zone and that in the hypocalcemic situation, the increase in root resorptions was related to an enhanced alveolar bone resorption. Thus, factors that minimize the time for resorptive/degradative activity should be discussed in this context rather than force per se.

Changes in activity of the temporal, masseter and lip muscles after surgical correction of mandibular prognathism.

Abstract The activity of the anterior and posterior portions of the temporal muscle, the masseter muscle and the upper lip was recorded electromyographically in 18 patients before and on three occasions after surgical correction of mandibular prognathism. The muscle activity was recorded in the postural position of the mandible, during maximal bite, during chewing and swallowing of peanuts and during swallowing of water. The postural activity before and 8 months after surgery did not differ much from that in subjects with normal occlusion but there was a tendency towards increased activity during the period of intermaxillary fixation. The activity during maximal bite before surgery was far below that in individuals with normal occlusion. It declined still further during intermaxillary fixation but increased to values approaching those in normal individuals at follow-up examination 8 months after surgery. The number of chewing cycles necessary to triturate the test food and the duration of the act of chewing before surgery were greater than in normal individuals but decreased as a result of treatment to values close to normal. The activity in the posterior temporal and in the masseter muscles during chewing did not change much following surgical correction, while the activity in the anterior muscle increased. Positional changes of the mandible during intermaxillary fixation were related to the muscle activity before surgery. A large backward displacement of the mandible was related to low masseter activity and a large superior displacement of the gonion to high activity of the anterior temporal muscle before surgery.

A study of children with unilateral posterior crossbite, treated and untreated, in the deciduous dentition--occlusal and skeletal characteristics of significance in predicting the long-term outcome.

Abstract.Background and Aim: The generally recommended treatment in children with unilateral posterior crossbite is expansion of the maxillary dental arch. The reported treatment success rate varies between 50% and 96%. The aim of the prsent study was to analyse whether some occlusal and skeletal characteristics could be found in the deciduous dentition of children with treatment success (including self-correction) in contrast to those showing non-correction (including relapse) in the young permanent dentition. Patients and Method: Two groups of children with unilateral posterior crossbite were followed from the age of 5 years up to 13 years of age. The childrfen in one of the groups (n = 32) were treated in the deciduous dentition, while the children in the other group (n = 32) were to be treated in the late mixed or early permanent dentition. Another 25 children (5 years old) with excellent occlusion were included as controls. Results of clinical examination and biometric and cephalometric analyses, performed at the first examination (at 5 years of age), are presented for the three groups (“treated”“untreated” and controls). Results and Conclusions: Compared to the controls, asymmetry was registered in both dental arches. The crossbite side, measured to the midline, was narrower than the non-crossbite side in the upper jaw but broader in the lower jaw. Differences between upper/lower widths (at intercanine and intermolar level) seem to be of importance for correction or non-correction, both for “untreated” and “treated” children. A narrow crossbite side in the upper arch together with a broad crossbite side in the lower arch was found in non-corrected children in both groups, even among those treated with maxillary expansion, where the SNB angle was larger and the ANB angle smaller than in controls as well as in those with correction (including self-correction). Possibilities and limitations of treatemtn planning are discussed.Zusammenfassung.Hintergrund und Ziel: Bei Kindern mit unilateralem Kreuzbiss wird im Allgemeinen eine Dehnungstherapie des oberen Zahnbogens empfohlen. Die angegebene Erfolgsrate variiert dabei zwischen 50% und 96%. Zielsetzung der vorliegenden Studie war zu untersuchen, ob im Milchgebiss charakteristische okklusale und skelettale Parameter bei erfolgreich behandelten Kindern (Spontankorrekturen eingeschlossen) vorliegen im Gegensatz zu anderen, bei denen der Kreuzbiss im frühen bleibenden Gebiss noch bestand bzw. Rezidive aufgetreten waren. Patienten und Methode: Bei zwei Gruppen von Kindern mit unilateralem Kreuzbiss wurden zwischen dem 6. und 14. Lebensjahr fortlaufend Befunde dokumentiert. Die Kinder der ersten Gruppe (n = 32) wurden im Milchgebiss behandelt, die der zweiten (n = 32) hingegen im späten Wechselgebiss oder bleibenden Gebiss. Als Kontrollgruppe dienten 25 weitere 5-jährige Kinder mit einwandfreier Okklusion. Für die drei Gruppen (“behandelt”, “unbehandelt” sowie “Kontrollgruppe”) werden die Ergebnisse der Erstvorstellung im Alter von 5 Jahren, d. h. die Befunde der klinischen Untersuchung sowie der Modell- und röntgenkephalometrischen Analyse dargestellt. Ergebnisse und Schlussfolgerungen: Im Vergleich zur Kontrollgruppe waren Asymmetrien in beiden Zahnbögen festzustellen. Die Kreuzbissseite war gemessen von der Mittellinie aus im Oberkiefer schmaler als die Gegenseite, im Unterkiefer hingegen breiter. Unterschiede zwischen oberen/unteren Bogenbreiten (auf Höhe der Milcheckzähne und Milchmolaren) scheinen im Hinblick auf eine mögliche Korrektur sowohl bei behandelten als auch unbehandelten Kindern bedeutsam zu sein. Eine schmale Kreuzbissseite im oberen Zahnbogen in Kombination mit einer breiten Kreuzbissseite im unteren Zahnbogen wurde bei Kindern beider Gruppen mit persistierendem Kreuzbiss festgestellt, sogar bei einem Teil derjenigen, die mittels einer Erweiterung des Oberkiefers “behandelt” wurden. Bei diesen Kindern war der SNB-Winkel größer und der ANB-Winkel kleiner als in der Kontrollgruppe und in der Gruppe mit erfolgreich korrigiertem Kreuzbiss (Spontankorrekturen eingeschlossen). Möglichkeiten und Grenzen der Behandlungsplanung werden diskutiert.