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PubMedDate not supplied

Facial skeletal growth in growing "toothless" osteopetrotic (op/op) mice: radiographic findings.

The defective bone resorption in the osteopetrotic (op/op) mouse brings about failure of tooth eruption. Furthermore, the op/op mouse has been studied as a "toothless" mouse in recent morphological and physiological investigations of the relationship between mastication and masseter muscle development. The present study was conducted to examine in detail the nasal bone and the premaxillary bone in this mutant mouse and to assess the roles of incisor growth and the mechanical stress of mastication in nasal bone and premaxillary bone growth. The forms of the nasal bone and the premaxillary bone were observed using roentgenography in both toothless op/op and normal (control) mice. In the op/op mouse, the nasal bone and the premaxillary bone show remarkable deformity. In contrast, the normal mouse appears well developed. This suggests that growth of the incisor root is important to normal upper jaw growth in the mouse. Furthermore, it is proposed that the upper facial phenotype seen in the op/op mice results from not only decreased bone resorption, but also from absence of the mechanical stress provided by normal mastication.

Age Factors↗
PubMed2005

Bones, teeth, and genes: a genomic homage to Harry Sicher's "Axial Movement of Teeth".

AIM: The model of the unopposed rodent molar was used to study the morphologic and genetic mechanisms of tooth eruption. METHODS: Left maxillary molar teeth of 12-day-old Swiss-Webster mice were extracted under anesthesia, and mandibular molars were allowed to supererupt. To trace areas of tissue remodeling and to determine areas of new tissue formation, mice were injected with fluorescent dyes, tetracycline, alizarin red, and calcein blue. Subsequent to sacrifice, mandibular tissue blocks were prepared for ultrathin ground sections, fluorescent microscopy, and von Kossa's mineral detection procedure. A second set of specimens was prepared for RNA extraction and microarray analysis. RESULTS: The data established significant eruption of first and second mandibular mouse molars 12 days after complete extraction of antagonists, exceeding the control side by 0.13 mm. Labeled tissue sections revealed significant amounts of new bone and cementum apposition on the unopposed side compared to the control side, as revealed by fluorescent markers and ultrathin ground sections. Microarray transcript level comparisons between the experimental and the control groups demonstrated significant (more than twofold) increase in gene expression of elastin and tenascin C extracellular matrix proteins; brevican, lumican, and biglycan proteoglycans; as well as fibroblast growth factor 9. CONCLUSION: In this study, the authors have established the unopposed mouse molar as a model to study tissue dynamics during the axial movement of teeth. The data indicated significant new formation of bone and cementum in tandem with increased expression of extracellular matrix-related genes.

Animals↗
PubMed1991

Immunolocalization of transforming growth factor beta in rat molars.

A prominent cellular event in tooth eruption is the influx of mononuclear cells (monocytes?) into the dental follicle at the onset of eruption. In the mandibular first molar of the rat, this influx of cells reaches its peak at three days postnatally. Because transforming growth factor-beta 1 (TGF-beta 1) is chemotactic for monocytes, we used immunocytochemical methods to determine its localization in the rat molar during postnatal days 1-4 and day 7. The results indicate that TGF-beta 1 displays both a spatial and temporal localization in the rat molar. It is present in the stellate reticulum (SR) on days 1 and 2 postnatally but is absent in all the subsequent days examined. None of the other soft tissue layers-ameloblasts, stratum intermedium or dental follicle--immunostain for TGF-beta 1. This localization of TGF-beta 1 in the SR at a time that just precedes that influx of monocytes into the dental follicle, coupled with the fact that fenestrated capillaries are abundant in the follicle adjacent to the SR, suggests that TGF-beta 1 could play a role in attracting monocytes from the peripheral blood into the follicle.

Animals↗
PubMed2006

Dental and medical students' knowledge and opinions of infant oral health.

Primary care providers' involvement with and perceptions of the epidemic of early childhood caries could be related to attitudes and knowledge of the disease as well as to differences in discipline-based recommendations. A cross-sectional survey of demographics, opinions on infant oral health care visits and importance of infant oral health care, knowledge of tooth eruption, and knowledge of health care guidelines of the American Academy of Pediatrics (AAP) and American Academy of Pediatric Dentistry (AAPD) was administered by several methods to first- and fourth-year dental and medical students at two University of Illinois campuses. Some expected variations were found among dental and medical students pertaining to perceptions and knowledge of infant oral health. Higher proportions of dental students responded correctly or considered the issues very important. However, Rockford medicine students were more likely to know when children should be weaned, yet less likely to agree with recommendations for time of first dental visit. Furthermore, fourth-year dental students were less likely than first-year dental students to give the recommended answer for age of first dental visit. Variances of opinions and basic knowledge of infant oral health of dental and medical students showed inconsistencies with desired outcomes of educational and clinical experiences. Further research is needed to understand the role of experience and other factors to effectively educate primary care providers in this area.

Adolescent↗
PubMedDate not supplied

Toxicological consequences of feeding PCB congeners to infant rhesus (Macaca mulatta) and cynomolgus (Macaca fascicularis) monkeys.

In a study designed to minimize interspecies extrapolation of toxicological data, nine rhesus (Macaca mulatta) and 15 cynomolgus (M. fascicularis) day-old infant monkeys were separated from their dams following parturition and hand-reared using a liquid non-human primate formulation. The infants were randomly divided into a control and a treated group which received a mixture of polychlorinated biphenyl (PCB) congeners analogous to those found in breast milk from Canadian women. The concentration of congeners in the dosing media resulted in each infant receiving a total of 7.5 microg PCB congeners/kg body weight/day. The congeners were added either to the liquid formulation or to corn oil and administered to the back of the monkey's mouth for 20 weeks. Monthly blood and adipose specimens were obtained during the dosing period and then periodically until the monkey was necropsied or taken off test (minimum of 66 weeks on test) for congener analysis. Parameters such as body weight, formula consumption, tooth eruption, somatic measurements, haematology and serum biochemistry were monitored throughout the study. In addition, a qualitative evaluation of the absorption and depletion of the various congeners was undertaken as was an immunological evaluation. For the monitored parameters, very few differences were found to be statistically significant. For the immunological parameters, the only statistically differences found were a reduction over time for immunoglobulins M and G antibodies to sheep red blood cells (cyno, P = 0.025; rhesus, P = 0.002) and a treatment-related reduction in the levels of the HLA-DR cell surface marker (mean percent, P = 0.016; absolute levels, P = 0.027). There were some qualitative differences regarding absorption and depletion rates for the various congeners, but it could not be definitely ascertained whether these differences were due to species differences or dosing mode. However, statistically significant differences were found for treatment (P = 0.0293) as well as for species and vehicle regarding the concentration of PCB in blood (species;--P = 0.0399; treatment--P = 0.0001) and adipose tissue (species--P = 0.0489; treatment--P = 0.0001).

Adipose Tissue↗
PubMed2006

Effect of interleukin-10 on gene expression of osteoclastogenic regulatory molecules in the rat dental follicle.

The aim of this study was to determine the effect of interleukin-10 (IL-10) on the gene expression of osteoclastogenic regulatory molecules in rat dental follicle cells. Interleukin-10 is an anti-inflammatory cytokine that inhibits alveolar bone resorption, but the molecular basis for this is unknown. Alveolar bone resorption is required for tooth eruption and the dental follicle functions to regulate the osteoclastogenesis needed for eruption. It does this by regulating its expression of receptor activator of nuclear factor-kappa B ligand (RANKL), colony-stimulating factor-1 (CSF-1), and osteoprotegerin (OPG). In this study, dental follicle cells were treated with IL-10, and the effect on gene expression of CSF-1, RANKL, and OPG was measured by reverse transcription-polymerase chain reaction (RT-PCR). Interleukin-10 enhanced the expression of OPG and down-regulated the expression of RANKL and CSF-1. Laser capture microdissection was carried out to detect IL-10 gene expression in the dental follicle. Knockdown of the IL-10 gene expression in the follicle cells was accomplished using a short interfering RNA (siRNA) targeting IL-10 mRNA. In these knockdowns, RANKL expression was increased and OPG expression was decreased. All of these results suggest that IL-10 inhibits bone resorption by up-regulating OPG expression while down-regulating expression of RANKL and CSF-1.

Alveolar Bone Loss↗
PubMed1994

Effects of prenatal exposure to 50 Hz magnetic fields on development in mice: II. Postnatal development and behavior.

To investigate the potential of magnetic fields to act as a behavioral teratogen, pregnant CD1 mice were exposed or sham-exposed for all of gestation to a 50 Hz/20 mT magnetic field. Maturation of offspring was assessed using a range of standard developmental indices (eye opening, pinna detachment, hair coat, tooth eruption, sexual maturity, and weight) and simple reflexive behaviors (air righting, surface righting, forepaw grasp, cliff avoidance, and negative geotaxis). Activity and coordination levels were explored in juvenile and adult mice using an open field arena, a head-dip board, an accelerating Rotarod, and a residential activity wheel. All assessments were carried out without knowledge of exposure condition. Results from 168 sham-exposed mice from 21 litters and from 184 exposed mice from 23 litters were compared using survival analysis techniques and multivariate regression methods. Three possible field-dependent effects were found: Exposed animals performed the air righting reflex earlier (P < 0.01); exposed males (but not females) were significantly lighter in weight (P = 0.008) at 30 days of age; and exposed animals remained on a Rota-rod for less time as juveniles (P = 0.03). Some of these results have not been reported in other studies and may reflect spurious statistical significance, although some effect of magnetic field exposure cannot be ruled out. Overall, these results suggest that prenatal exposure to a 50 Hz magnetic field does not engender any gross impairments in the postnatal development or behavior of mice. This does not preclude such exposure affecting more subtle aspects of behavior.

Animals↗
PubMed2001

Ectopic eruption of maxillary molar tooth--an unusual cause of recurrent sinusitis.

A 17-year-old male presented with a 3-month history of cough associated with right-sided purulent rhinorrhoea and right facial pain. Nasal endoscopy confirmed the presence of mucopus from the right middle meatus. Plain sinus X-ray assessment showed the presence of an ectopic molar in the right anterosuperior aspect of the maxillary sinus entrapped in soft tissue. Surgical removal of the tooth and the diseased antral tissue was undertaken via a Caldwell-Luc procedure with resolution of symptoms.

Adolescent↗
PubMed1992

Early eruption and advanced root development of the permanent cuspids in a six-year-old boy.

A case report showing the eruption of the left maxillary and mandibular permanent cuspids in a six-year-old boy, is presented. In addition, the dental age of all the permanent cuspids as seen by the eruption and tooth development suggested that the cuspids are comparable to those seen in a 13 to 14 year-old-boy. A search of the literature has not revealed any such reports.

Age Factors↗