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The difference between paediatric dentistry and most other branches of dentistry is that in the child the occlusion is changing. Consequently 'Good Occlusal Practice' in children is a matter of making the right clinical decisions for the future occlusion. The clinician needs to be able to predict the influence that different treatment options will have on the occlusion when the child's development is complete.
Force generated by the perioral musculature is known to be a potent factor that can affect tooth position and malocclusion. To evaluate the influence of the force of the orbicularis oris muscle on incisor position, we determined the maximum and average strengths of the upper lip of male Class I malocclusion patients with a Y-meter, which was devised to measure the vertical closing force of the lip with a load cell. The skeletal structures and incisor angulation were recorded by lateral cephalograms. Correlation and stepwise regression analyses were performed to determine whether a relationship existed between lip force levels and craniofacial morphology. The average value of the upper lip closing force (AVE) was 7.16 N. Our results showed that the upper incisor angulation was related to the perioral muscle force. The maxillary incisor to Frankfort horizontal angle showed r values of -0.681 (at AVE) and -0.652 (at maximum lip closing force) as determined by correlation analysis. Stepwise regression analysis also showed that the maxillary incisor to Frankfort horizontal angle was more related to the upper lip closing force. Disuse atrophy of the orbicularis oris seems to be an important factor in the development of malocclusion.
Based on previous results showing the expression of ameloblastin (Ambn; amelin) in the formation of mesenchymal dental hard tissues, we investigated its presence during bone development. Immunohistochemistry (IHC), in situ hybridization (ISH), and reverse transcription-polymerase chain reaction (RT-PCR) were used to investigate the expression of ameloblastin protein and mRNA during craniofacial development in rats. Tissue samples were collected on embryonic day 18 and from days 2-28 postnatally. IHC revealed the expression of ameloblastin during bone formation at embryonic and early postnatal stages with different patterns of expression in intramembranous and endochondral ossification. In intramembranous ossification, ameloblastin expression was detected in the superficial layer of the condensed vascularized primitive connective tissue and in the cellular layer covering the surface of the newly formed woven bone. In endochondral ossification, ameloblastin was expressed within the extracellular matrix of the cartilage templates and in the perichondrium. Between days 2 and 28 the expression decreased markedly, concordant with the maturation of the bone, and disappeared after completion of bone remodeling. The results obtained by IHC were confirmed by ISH and RT-PCR, showing the expression of ameloblastin mRNA during craniofacial bone formation. This study indicates the expression of the putative dental protein ameloblastin during craniofacial bone development in rats.
The study is based on a long-term cephalometric follow-up of lateral X-ray films of 48 boys with complete unilateral cleft lip and palate during puberty. The configuration of the face was negatively influenced by the reduced depth of the maxilla and limited vertical growth of the upper lip. As compared with the mandible, the maxilla grew less harmoniously in many respects; on the soft profile the depth of the nose increased most intensely. Retrusion of the maxilla led to a deterioration of sagittal intermaxillary relations in almost 92% of patients. In 32% of these patients the deterioration exceeded 3 of the ANB angle, and in 27% a transition from the 1st to the 3rd skeletal class was recorded. 25% of the subjects already belonged in class III at the age of ten years. In 94% of patients during puberty, flattening of the face occurred, which was frequently associated with a sunken upper lip (63%). Due to successful orthodontic treatment it was possible to restore maxillary overjet in 46% of the patients. In subjects who had a maxillary overjet of at least 2 mm at the age of 10 years, it did not change to negative values by the age of 15 years. Patients with more severe impairment of the jaws were treated more frequently by means of fixed appliances, but they did not differ substantially from the other patients in their further development (with the exception of a significant anteinclination of the palate).
All continuous teeth were unilaterally extracted on the right side of the upper and lower jaws of 57 male and female Vietnamese belly pig. The animals were slaughtered 6, 7, 8, 9, 10, 11 and 12 after the extraction. Our investigations into quantitative changes in the masticatory musculature after unilateral extraction showed the dry weight of the musculature on the extraction side was reduced. This reduction was greatest in the case of the M. temporalis. The findings relating to the muscles are consistent with the results of the skull evaluations reported in the first 2 publications, with indicated that tooth extraction leads to only local changes in the jaw during postnatal development. The findings published in the 3 publications of this series relating to the bones and muscles are discussed.
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At least nine cases of holoprosencephaly (HPE) found in patients with confirmed loss of 7q34----7qter or 7q36----7qter have been reported in the literature. In the present report, balanced rearrangements involving chromosome 7q [inv(7)(p22.1q34) and t(4;7)(q31;q36)] were shown in two mothers examined after the birth of their non-karyotyped infants with HPE and hydronephrosis. In both cases, del(7q) was the most probable imbalance. The available data confirm the association between HPE and del(7q). Predominance of cyclopia and cebocephaly, the severest forms of HPE, suggests that del(7q) may be an important factor in arresting prosencephalon development at the earliest stages.
There is a substantial amount of evidence to support the theory that the spatial relationship of the mandible to the craniomaxillary complex is influenced, in part, by the function of the muscular elevators of the mandible. One factor acting on the elevators of the mandible is the rest position of the mandible, which may be influenced by the patient's mode of respiration. Obstruction of the nasal airway is followed by the lowering of the mandible to establish an oral airway. Allergic rhinitis is one cause of nasal airway obstruction. There are reports that avoidance of the ingestion of foreign airway. The orthodontist should recognize early signs of the development of the long face syndrome and make appropriate referrals to medical colleagues to promote nasopharyngeal health.
To evaluate the relationship between internal derangement(s) of the temporomandibular joint(s) (TMJ) and disturbed facial skeleton growth (dysmorphogenesis), 128 consecutive children (103 girls, 25 boys), who were 14 years of age or younger and had undergone combined radiographic and magnetic resonance (MR) imaging studies of both TMJs, were retrospectively analyzed. Imaging studies had been performed to investigate suspected TMJ derangement because of symptoms that included, either individually or in various combinations, pain, mechanical TMJ dysfunction, and facial skeleton abnormalities, such as mandibular deficiency (particularly retrognathia) and lower facial (mandibular) asymmetry, manifested by chin deviation from the midline. Of these patients, 112 were found to have at least one internally deranged TMJ on imaging studies; in 85 patients, both TMJs were abnormal. Of the 60 retrognathic patients 56 were found to have TMJ derangement, generally bilateral and often of advanced stage. In cases of lower facial asymmetry, the chin was uniformly deviated toward the smaller or more degenerated TMJ. Both TMJs were normal in 16 patients, most of whom had normal facial structure. We conclude that TMJ derangements are both common in children and may contribute to the development of retrognathia, with or without asymmetry, in many cases.
Human arch form varies considerably. This study analyzed the size and shape of the maxillary and mandibular dental arches of 320 adolescents from 155 sibships. A broad battery of measurements (k = 48) was computer-generated from Cartesian coordinates of cusp tips and line angles of the permanent teeth, and heritability estimates were generated from intraclass correlations, controlling for sex and age where indicated. Arch size has a modest genetic component, on the order of 50%, although this estimate may contain shared environmental influences. Tooth rotations have low h2 estimates, most of them indistinguishable from zero. Arch shape, assessed as length-width ratios, also has a modest transmissible component, suggesting that arch length and width growth factors are largely independent. Highest heritability estimates, as a group, were for transverse arch widths, which averaged about 60%. Several measures of left-right asymmetry also were analyzed (k = 31), and, while the arches are systematically asymmetric (generally with left > right), there is only weak evidence of a transmissible component for directional asymmetry and essentially none for fluctuating asymmetry. In all, arch size and shape are seen to be more subject to environmental influences than to heredity. These findings direct attention toward the need to better understand what extrinsic factors modulate arch size and shape during development.
Rapid maxillary expansion (RME) has been shown to increase nasal permeability and reduce nasal airway resistance. A number of studies have examined the relationship between RME and the change in airway resistance, or the relationship between airway resistance and natural head position (NHP). Few studies, to date, have examined the relationship between RME and the change in NHP resulting from the consequent change in airway resistance. A sample of 43 adolescent patients with uni- or bilateral crossbite in the permanent dentition underwent RME as part of normal orthodontic treatment. Cephalograms in NHP were taken before, immediately after expansion, and one year after RME. No significant changes in the craniofacial angles were observed immediately after expansion. One year post-expansion, however, NSL/VER had reduced by 3.14 degrees (P < 0.01), OPT/HOR by 2.13 degrees (P < 0.05), and CVT/HOR by 2.55 degrees (P < 0.05). The results of this study suggest an ongoing change in head posture possibly due to a change in the mode of breathing from oral to nasal as a result of RME, thereby contributing to a change in craniofacial development, supporting and adding to the soft tissue stretching hypothesis.
OBJECTIVE: The objective of this study is to evaluate whether manipulation of the nasal septum, its release, and changing of its abnormal position in infancy has an impact on maxillary growth and facial development in patients with unilateral cleft lip and palate. DESIGN: Roentgencephalometric investigation. SETTING: Cleft Centre at the Clinic of Plastic Surgery, Prague. PATIENTS: Two consecutive groups of male patients (n = 32 and 30) with complete unilateral cleft lip and palate without associated malformations at 15 years of age. INTERVENTIONS: The patients were operated on by the same team of surgeons and by the same method (lip: Tennison and primary periosteoplasty; palate: pushback with pharyngeal flap surgery), with the exception of complete primary repositioning of the nasal septum performed only in one group. MAIN OUTCOME MEASURES: Roentgencephalometric data of both series of patients were compared with a t-test. All measurements were performed by one investigator. RESULTS: Patients with primary repositioning of the nasal septum had a more favorable nasal prominence and better vertical growth of the upper and whole face in posterior height. Better growth in anterior height was only suggested; maxillary retrusion was equal in both groups. CONCLUSIONS: Primary repositioning of the nasal septum has a favorable effect on nasal development, and it neither deteriorates nor markedly improves maxillary growth in patients with unilateral cleft lip and palate.
What is the most important aspect of children's dentistry? Some may argue that it is the restoration orprevention of decay and disease. Others may describe nutrition. The diagnosis and treatment of proper growth and development, I feel is the most important responsibility of our practices. What we do or don't do can affect the child for life. Unfortunately, many of us lack the abilities we need to affectively monitor or augment, if necessary, proper growth and development. The purpose of this paper is to provide us with some basic knowledge, tools and treatments.
Local application of retinoic acid to chick embryos produces severe bilateral clefting of the primary palate but does not affect the lower beak. This paper reviews what is known about the basis and specificity of this retinoid-induced defect by examining three major developmental processes: morphogenesis, cell differentiation, and pattern formation. The conclusion reached is that neither cytotoxicity nor cartilage inhibition is the basis of the specific retinoid-induced defect. Retinoid treatment interferes with reciprocal epithelial-mesenchymal interactions in the upper beak. These interactions are involved in linking pattern formation--the spatial ordering of cell differentiation--to morphogenesis and outgrowth. These results suggest that retinoids are interfering with the process of pattern formation in the upper beak, a conclusion that is supported by the similarities between retinoid effects on face and limb development. Thus, it appears that retinoids may be acting as general signaling molecules throughout the developing embryo. In the lower beak, pattern-forming cues may occur earlier in development. Alternatively, the cells may be unresponsive to retinoids. The molecular basis for the specificity of the facial defect--as well as for the action of retinoids on developing systems--is discussed with reference to recent advances in molecular biology.
Lateral cephalometric radiographs of 21 sets of triplets (4 monozygotic, 12 dizygotic and 5 three zygotic) were used for this study. The following two polygons were analysed: SNA and NSAr Go Me. Superimposition of the cephalometric tracings was made on the S-N line with S as the registration point. Intra- and inter-set comparisons between monozygotic (MZ), dizygotic (DZ) and three zygotic (TZ) triplets were made. Members of MZ triplets demonstrated the greatest similarity in size and form of the polygons. The second greatest similarity was found between MZ members of the DZ triplets, while the third DZ member of all such triplets showed much higher difference compared with the MZ members. Finally, triplets of TZ sets demonstrated the greatest difference between each other. The results obtained from this study indicated that genetic factors played a dominant role in growth and development of the craniofacial complex. However, difference found between members of MZ triplets suggested an importance of environmental factors in these processes as well.
The complex rotation process of the mandible during growth is elucidated by longitudinal roentgencephalometric analyses, using metallic implants as fixed references. Contrasting development of face and mandibular shape is described in three subjects. In the so-called long face syndrome, development is characterized by increasing inclination of the mandible during growth with only moderate remodeling. In the subjects with juvenile rheumatoid polyarthritis and mandibulofacial dysostosis, the increase in mandibular inclination is moderate. However, the mandibular corpus rotates backward to an extreme extent within the more stable soft tissue matrix, giving rise to the characteristic development of angular notching with an extended angular process at the lower border.
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