Prevention and early treatment in orthodontics: a perspective

The effects of dietary loading on the transdifferentiation of condylar chondrocytes

INTRODUCTION

Transdifferentiation of chondrocytes into bone cells explains most condylar growth during prenatal and early postnatal stages, but the mechanisms regulating chondrocyte transdifferentiation during late postnatal growth remain unknown. This study aimed to quantify the effects of dietary loading on chondrocyte-derived osteogenesis during late postnatal condylar growth.

METHODS

Two compound mouse lines were used to trace the fate of chondrocyte lineage in vivo. Twelve 3-week-old male Aggrecan-CreERT2 (AcanLineage); R26RTdTomato; 2.3 Col10a1-GFP and twelve 3-week-old male Col10a1-Cre (Col10a1Lineage); R26RTdTomato; 2.3Col1a1-GFP were randomly divided into experimental (soft-food diet, n = 6) and control (hard-food diet, n = 6) groups and kept for 6 weeks. One time, tamoxifen injections were given to AcanLineage mice at 3 weeks. Radiographic, microcomputed tomographic, and histomorphometric analyses were performed.

RESULTS

Radiologic analysis showed that mice with a soft-food diet had smaller mandible lengths as well as decreased bone volume and density for their condylar process. Histologically, mice with soft diets had reduced activity in chondrocyte proliferation and maturation compared with the controls. Cell lineage tracing results showed the number of AcanLineage-derived bone cells (293.8 ± 39.8 vs 207.1 ± 44.6; P = 0.005), as well as total bone cells (445.6 ± 31.7 vs 360.7 ± 46.9; P = 0.004), was significantly higher in the hard-diet group than in the soft-diet group, whereas the number of non-AcanLineage-derived bone cells was not significantly different among groups (P = 0.938). Col10a1Lineage mice showed the same trend.

CONCLUSIONS

Dietary loading directly affects condyle chondrogenesis and chondrocyte transdifferentiation, which alters the extent of condylar growth and remodeling.

The Jaw Epidemic: Recognition, Origins, Cures, and Prevention

Contemporary humans are living very different lives from those of their ancestors, and some of the changes have had serious consequences for health. Multiple chronic "diseases of civilization," such as cardiovascular problems, cancers, ADHD, and dementias are prevalent, increasing morbidity rates. Stress, including the disruption of traditional sleep patterns by modern lifestyles, plays a prominent role in the etiology of these diseases, including obstructive sleep apnea. Surprisingly, jaw shrinkage since the agricultural revolution, leading to an epidemic of crooked teeth, a lack of adequate space for the last molars (wisdom teeth), and constricted airways, is a major cause of sleep-related stress. Despite claims that the cause of this jaw epidemic is somehow genetic, the speed with which human jaws have changed, especially in the last few centuries, is much too fast to be evolutionary. Correlation in time and space strongly suggests the symptoms are phenotypic responses to a vast natural experiment-rapid and dramatic modifications of human physical and cultural environments. The agricultural and industrial revolutions have produced smaller jaws and less-toned muscles of the face and oropharynx, which contribute to the serious health problems mentioned above. The mechanism of change, research and clinical trials suggest, lies in orofacial posture, the way people now hold their jaws when not voluntarily moving them in speaking or eating and especially when sleeping. The critical resting oral posture has been disrupted in societies no longer hunting and gathering. Virtually all aspects of how modern people function and rest are radically different from those of our ancestors. We also briefly discuss treatment of jaw symptoms and possible clinical cures for individuals, as well as changes in society that might lead to better care and, ultimately, prevention.

Prevalence of malocclusion in urban libyan preschool children

OBJECTIVES

This cross-sectional observational study aimed at quantifying primary dentition parameters and exploring differences in those parameters between included age groups.

MATERIALS AND METHODS

The examined sample comprised 800 preschool children, 3- to 5-year-old in Benghazi city, of which 500 fulfilled the inclusion criteria. Primary canine relationship, spacing/crowding, overjet (OJ) and overbite (OB), occlusal relationship was carried out using Federation Dentaire Internationale (1973), modified to the primary dentition.

RESULTS

The prevalence of bilateral Class I, Class II, and Class III canine relationship was 69.6%, 22.4%, and 4.4%, respectively. The prevalence of asymmetric canine relationship was 3.6% with no significant difference between gender and age groups. Spacing, closed dentition, and crowding were observed in: 81.6%, 13,4% and 5% respectively in the upper arch, and 58.5%, 24.8%, and 16.7% correspondently in the lower arch. OJ and OB ranging between 1 and 3 mm were found in 82.6% and 56.5%, respectively. An OJ and OB of >3 mm was observed in 11.4% and 35%, respectively, and of edge to edge incisal relationship anteroposteriorly and vertically in 4.6% and 6% in this order. Anterior crossbite and anterior openbite were noted in 1.4% and 2.6%, respectively. There was no significant correlation between OJ and OB and age (P≥0.241). Additionally, there was no significant sex difference in the value of OJ (P=0.561). But, the mean OB value in boys was significantly greater than in girls.

CONCLUSIONS

The current findings provide an insight into the prevalence of occlusal traits in urban Libyan preschool children and highlight the significance of early detection of malocclusion to assist in achieving effective and individualized long-term treatment planning.

Anterior open bite: a case-control study

OBJECTIVE

The aim of this study was to assess the influence of sucking habits and facial pattern measurements on the development of anterior open bite (AOB).

METHODS

A case-control study was carried out on 60 children aged 7 and 8 years attending municipal public schools in the city of Recife, Brazil. Data collection included interviews with guardians, oral examinations, and facial growth pattern analysis using cephalometric radiographs. The following cephalometric measurements were assessed: SN.Gn, SN.GoGn, FMA, and Facial Axis. Statistical analyses were performed using the Student's t-test and Pearson's chi-square test at a 5% level of significance.

RESULTS

The percentage of children with sucking habits in the case group was much higher than in the control group (53.3%vs 16.7%) (P = 0.003). Children with sucking habits were six times more likely to develop AOB. Regarding the measurements assessed, no statistically significant differences were observed between groups.

CONCLUSION

This study found no evidence that variations in cephalometric angles (SN.Gn, FMA, SN.GoGn, and facial axis) are risk factors for AOB. Only sucking habits demonstrated a positive correlation with an increased AOB.

Avaliação ultra-sonográfica dos músculos mastigatórios e dimensões faciais em crianças com oclusão normale mordida cruzada posterior unilateral

OBJETIVO: avaliar a espessura dos músculos masseter e porção anterior do temporal por meio da ultra-sonografia e as dimensões faciais de crianças com oclusão normal e mordida cruzada posterior unilateral, na dentição decídua e mista inicial. MÉTODOS: foram selecionadas 49 crianças, de ambos os gêneros, divididas em quatro grupos: decídua-oclusão normal, decídua-mordida cruzada, mista-oclusão normal e mista-mordida cruzada. A espessura muscular foi comparada entre os lados direito e esquerdo (oclusão normal); e normal e cruzado (mordida cruzada) (teste "t" Student), e relacionada às dimensões faciais e variáveis corporais (teste de correlação de Pearson e Spearman). As dimensões faciais foram mensuradas sobre fotografias frontais padronizadas: altura facial anterior (AFA), distância bizigomática (DB) e intergoniana (DI) e razões AFA/DB e AFA/DI. RESULTADOS: observou-se que o músculo temporal no repouso apresentou espessura maior no lado cruzado no grupo mista-cruzada (p=0,05). O masseter não apresentou diferença significativa entre os lados em todos os grupos. As variáveis peso e altura não apresentaram correlação com a espessura muscular; já DB e DI apresentaram correlação positiva e as razões AFA/DB e AFA/DI, correlação negativa, com a espessura do masseter em todos os grupos, indicando que crianças com faces mais longas possuem menor espessura deste músculo. CONCLUSÃO: na amostra estudada, os exames da espessura dos músculos mastigatórios e das dimensões faciais demonstraram que a influência das características funcionais sobre as estruturas craniofaciais pôde ser observada já em crianças de pouca idade.

Nonnutritive sucking habits in Brazilian children: effects on deciduous dentition and relationship with facial morphology

This study assessed the relationship between nonnutritive sucking habits, facial morphology, and malocclusion in 3 planes of space (transverse, vertical, and anteroposterior) in 330 Brazilian children (4 years of age) attending state schools in the city of Recife, Brazil. The data were collected by interviews with the children's mothers or minders and by clinical examinations carried out by a calibrated examiner (kappa = 1). The chi-square test, Fisher's exact test, and multivariate analysis were used for statistical analysis. The prevalence of malocclusion in the sample was 49.7%, according to occlusal classification, and 28.5% of the children had 2 or 3 factors contributing to their malocclusion. Posterior crossbite was detected in 12.1%, anterior open bite in 36.4%, and increased overjet in 29.7%. A significant association was found between malocclusion and sucking habits (P <.001). Most of the children had a high facial skeletal pattern, although no association was found between facial morphology and malocclusion. The results draw attention to the magnitude of the problem in childhood and emphasize the need for longitudinal studies to support clinical practice guidelines for the target population.

Are severe occlusal problems more frequent in permanent than deciduous dentition?

OBJECTIVE

To determine the prevalence and severity of occlusal problems in populations at the ages of deciduous and permanent dentition and to carry out a meta-analysis to estimate the weighted odds ratio for occlusal problems comparing both groups.

METHODS

Data of a probabilistic sample (n=985) of schoolchildren aged 5 and 12 from an epidemiological study in the municipality of São Paulo, Brazil, were analyzed using univariate logistic regression (MLR). Results of cross-sectional study data published in the last 70 years were examined in the meta-analysis.

RESULTS

The prevalence of occlusal problems increased from 49.0% (95% CI =47.4%-50.6%) in the deciduous dentition to 71.3% (95% CI =70.3%-72.3%) in the permanent dentition (p<0.001). Dentition was the only variable significantly associated to the severity of malocclusion (OR=1.87; 95% CI =1.43-2.45; p<0.001). The variables sex, type of school and ethnic group were not significant. The meta-analysis showed that a weighted OR of 1.95 (1.91; 1.98) when compared the second dentition period with deciduous and mixed dentition.

CONCLUSIONS

In planning oral health services, some activities are indicated to reduce the proportion of moderate/severe malocclusion to levels that are socially more acceptable and economically sustainable.

A study of occlusal variation in the primary dentition of Australian twins and singletons

In this study, we quantified the extent of variation in different occlusal features of Australian children of European descent with complete primary dentitions, but no permanent teeth present in the mouth. The study group consisted of 412 individuals, aged between 3 and 7 years, including 70 monozygous (MZ) twin pairs, 68 same-sexed dizygous (DZ) twin pairs, 11 opposite-sexed DZ twin pairs, and 114 singletons. Occlusal traits, including inter-dental spacing, incisal overbite and overjet, arch breadth and arch depth, were obtained directly from dental casts or indirectly from photocopies or impressions of the casts. Descriptive statistics summarised the data and indicated that distributions were similar to those published for other populations. Univariate genetic analysis, using the structural equation modelling package Mx, was carried out on the quantitative data using the normal assumptions of the twin model. Genetic modelling indicated that a model incorporating additive genetic (A) and unique environmental variation (E) was the most parsimonious for interdental spacing, overbite, overjet and arch dimensions. Estimates of heritability for interdental spacing ranged from 0.62 to 0.81. Estimates for overbite and overjet were 0.53 and 0.28, respectively, and estimates for arch dimensions ranged from 0.69 to 0.89. These results indicated a moderate to relatively high genetic contribution to observed variation.

Association between early weaning, non-nutritive sucking habits and occlusal anomalies in 3-year-old Finnish children

OBJECTIVES, DESIGN AND SUBJECTS: Earlier results on the effect of breastfeeding on the one hand, and non-nutritive sucking habits (pacifier and/or digit sucking) on the other, on the orofacial development of infants are inconclusive. Thus we studied the prevalence of malocclusions and their relationship to the duration of breastfeeding and to non-nutritive sucking habits in a group of randomly selected 3-year-old children (n = 148).

RESULTS

Posterior crossbite was detected in 13%, anterior open bite in 18% and large overjet (> 3 mm) in 26% of the children. The proportion of children with anterior vertical open bite was significantly larger among children with non-nutritive sucking habits than among the other children (P < 0.001). Neither posterior crossbite nor large overjet were associated with non-nutritive sucking habits. The duration of exclusive breastfeeding was 5.8 +/- 3.6 months while that of total breastfeeding was 7.3 +/- 3.8 months on average. The exclusive and total breastfeeding periods of children with posterior crossbite were both significantly shorter than those of the other children (P < 0.01 and P < 0.002, respectively). Children's height and weight were unrelated to the duration of breastfeeding or occlusal anomalies.

CONCLUSION

We suggest that an early introduction of bottlefeeding, indicating a pattern of low-impact muscular activity, may interfere with the normal development of alveolar ridges and hard palate, and hence lead to posterior crossbite.

Early developmental traits in class II malocclusion

The occlusal traits of Class II occlusion in the deciduous dentition include distal terminal plane of the second deciduous molars, distal canine relation, large overjet, and large overbite. Other findings are narrow upper dental arch and maxillary base and poor anterior spacing. Skeletally, Class II children differ less from normal children. The cranial base, including the base flexure, and the maxilla are normal. The mandibular corpus and lower facial height are short, the gonial angle is large, and the dentoalveolar position of the mandible is retruded. The height of the ramus is normal, as is the skeletal position of the mandible, with the exception of the chin, which becomes slightly retruded after 5 years of age. As most skeletal traits of Class II occlusion develop later than the occlusal characteristics, it is suggested that no evidence can be found for a skeletal Class II growth pattern in the deciduous dentition. The deficient transversal growth of the maxilla and the sagittal growth of the mandible seem to cause the typical Class II occlusion. Further skeletal changes are likely to develop as secondary adaptations.

Genetic aspects of dental disorders

This paper reviews past and present applications of quantitative and molecular genetics to dental disorders. Examples are given relating to craniofacial development (including malocclusion), oral supporting tissues (including periodontal diseases) and dental hard tissues (including defects of enamel and dentine as well as dental caries). Future developments and applications to clinical dentistry are discussed. Early investigations confirmed genetic bases to dental caries, periodontal diseases and malocclusion, but research findings have had little impact on clinical practice. The complex multifactorial aetiologies of these conditions, together with methodological problems, have limited progress until recently. Present studies are clarifying previously unrecognized genetic and phenotypic heterogeneities and attempting to unravel the complex interactions between genes and environment by applying new statistical modelling approaches to twin and family data. Linkage studies using highly polymorphic DNA markers are providing a means of locating candidate genes, including quantitative trait loci (QTL). In future, as knowledge increases; it should be possible to implement preventive strategies for those genetically-predisposed individuals who are identified to be at risk.

The occlusal theory further complicated

This paper reviews the critique presented against the occlusal theory of the temporomandibular disorders (TMD) and presents a new hypothesis. Although no empirical evidence has been found to refute the role of occlusion in the etiology of TMD, we argue that the occlusal theory in its present form is biased in that it is based on the findings in adults and assumes that the causal chain proceeds from structure to function. However, the close developmental relationship between function and structure and the recent changes in the functional environment of the stomatognathic organ indicate that the causal influences take place in both directions. We suggest that the occlusal theory should be reformulated in such a way that it includes mutual interactions between function and structure during growth. We assume that the structural adaptations taking place in the growing child in response to functional stimuli may play an important role in the etiology of TMD. Testing of our hypothesis requires longitudinal studies which focus on both functional and structural development.

Extent and provision of orthodontic services for children and adolescents in Finland

Orthodontic services for Finnish children and adolescents up to the age of 18 in 1992 were monitored by a questionnaire sent to all municipal health centres responsible for children's dental care in Finland, and 96% responded. All health centres provided some orthodontic treatment, but the percentage of 0 18-year-old children receiving treatment ranged from 1% to 19%. One-quarter of all dental visits of the 0 18-year-olds were in connection with orthodontics. The timing of treatment was early, the average age for starting was 9.5 years. In statistical analyses, the number of children receiving treatment was associated with the timing of treatment. At the age of 7, the most frequently used appliances were quad helix, removable appliance and orthopaedic headgear and, at the age of 13, fixed appliance and activator. Most treatments were provided by nonspecialists. The specialist expertise needed was usually purchased from an outside orthodontist by means of consultation contracts. Every fifth health centre, usually the largest, had employed one or more specialist orthodontists. The regional distribution of orthodontists was uneven, emphasizing regional variation in the delivery of orthodontic services.