Role of the transcription factor NFIC in odontoblast gene expression.

The transcription factor NFI-C is essential for root development. Mice lacking NFI-C develop abnormal roots and lose their teeth, resembling radicular dentin dysplasia I in humans. The purpose of this study was to understand the role of NFI-C in dentinogenesis. The authors found statistically significant increases in the expression of several mRNAs in cells lacking NFI-C, suggesting that these molecules might interfere with odontoblast cell migration and differentiation, and consequently with root development.

Amelogenin and ameloblastin show growth-factor like activity in periodontal ligament cells.

Enamel proteins, particularly amelogenin, have been associated with other functions in addition to regulating enamel biomineralization. Extracts of enamel proteins are currently being used to regenerate periodontal tissues, and new studies suggest that enamel proteins might have chondrogenic and osteogenic properties. In this study, we wanted to determine the effect, if any, of purified recombinant amelogenin and ameloblastin on the adhesion, proliferation, and differentiation of periodontal ligament cells in vitro. Immortomouse-derived periodontal ligament (PDL) cells were grown under permissive and differentiation conditions in the presence of different concentrations of mouse recombinant amelogenin, recombinant ameloblastin, or both. Cells were collected after 4 h to determine attachment, after 24 h to determine proliferation, and after 7, 14, 21 and 28 d to determine differentiation using reverse transcription-polymerase chain reaction (RT-PCR). Both amelogenin and ameloblastin had a small, but statistically significant, effect on increasing the cell attachment and proliferation of PDL cells. Both amelogenin and ameloblastin modulated bone morphogenetic protein (BMP) expression, down-regulated the expression of collagen type I, and induced the de novo expression of osteocalcin. Amelogenin also induced the expression of bone sialoprotein. These results suggest that amelogenin, as well as ameloblastin, might have some 'growth factor' activity during periodontium development and regeneration.

Morphoregulation of teeth: modulating the number, size, shape and differentiation by tuning Bmp activity.

During development and evolution, the morphology of ectodermal organs can be modulated so that an organism can adapt to different environments. We have proposed that morphoregulation can be achieved by simply tilting the balance of molecular activity. We test the principles by analyzing the effects of partial downregulation of Bmp signaling in oral and dental epithelia of the keratin 14-Noggin transgenic mouse. We observed a wide spectrum of tooth phenotypes. The dental formula changed from 1.0.0.3/1.0.0.3 to 1.0.0.2(1)/1.0.0.0. All mandibular and M3 maxillary molars were selectively lost because of the developmental block at the early bud stage. First and second maxillary molars were reduced in size, exhibited altered crown patterns, and failed to form multiple roots. In these mice, incisors were not transformed into molars. Histogenesis and differentiation of ameloblasts and odontoblasts in molars and incisors were abnormal. Lack of enamel caused misocclusion of incisors, leading to deformation and enlargement in size. Therefore, subtle differences in the level, distribution, and timing of signaling molecules can have major morphoregulatory consequences. Modulation of Bmp signaling exemplifies morphoregulation hypothesis: simple alteration of key signaling pathways can be used to transform a prototypical conical-shaped tooth into one with complex morphology. The involvement of related pathways and the implication of morphoregulation in tooth evolution are discussed.

Celebrex offers a small protection from root resorption associated with orthodontic movement.

UNLABELLED: Tooth movement results from alveolar bone resorption/deposition following application of orthodontic forces, and root resorption can be an undesirable complication associated with this process. No treatment for external root resorption is available to date. OBJECTIVE: To determine if COX-2 inhibitors like Celebrex are effective in protecting root resorption associated with orthodontic forces. METHODS: A force of 80 grams was applied to the left maxillary first molars of 7-week-old female Wistar rats using nickel titanium closed coil springs attached to the cervical area of the incisors with 0.010 stainless-steel ligature wires. Twenty animals were divided into three experimental groups: one receiving no treatment, the second receiving 25mg/kg, and the third receiving 50 mg/kg of celecoxib (Celebrex) in their drinking water. Rats were maintained on a soft diet and euthanized two weeks after initial placement of the force. Paraffin-embedded sections of the right (control) and left (experimental) maxillae were stained with H&E and the areas of root resorption were examined by counting the number of lacunaes in the roots. RESULTS: No difference in the distance of tooth movement (0.5 mm/two weeks) was seen in all three groups. The rats that received the low dose of Celebrex showed no statistically significant difference in root resorption than that of the rats that received no dose. The rats that received the high dose of Celebrex showed a lower number of lacunaes (mean = 3.5) than that of the control group (mean 10.2; p=0.02). CONCLUSIONS: Administration of Celebrex during the application of orthodontic forces does not interfere with tooth movement and appears to offer some slight protection against root resorption.