Cone-beam computed tomographic reconstructions in the evaluation of maxillary impacted canines.

Purpose: Prior to cone-beam computed tomography (CBCT), orthodontic competence included radiological interpretation. Nevertheless, maxillary impacted canines (MICs), because of their position and adjacent complex anatomy, have been challenging to interpret, particularly with regard to root resorption. Although CBCT cross-sectional reconstructions of MICs yielded clearer insights into its diagnosis and treatment planning, the value of simultaneously using 2 different cross-sectional or multiplanar reconstructions of the CBCT datasets - orthogonal and curved/panoramic multiplanar reconstructions - has hitherto not been considered. Materials and Methods: Both orthogonal and curved/panoramic multiplanar reconstruction series of 5 screenshots were each reconstructed from the 5 cm × 5 cm CBCT datasets of 15 separate MICs. Fifteen credentialled and experienced orthodontist volunteers reviewed 2 separate PowerPoints of 15 randomized series each, 1 week apart. Their review considered 6 factors that could affect treatment: the position and level of the MIC, the presence or absence of root resorption, ankylosis, cysts, and dilaceration. Results: All 15 orthodontists were statistically similar regarding overall years of experience and of CBCT use. Although either reconstruction alone allowed the orthodontists to determine whether ankylosis and, to a lesser extent, most of the other features were present or absent in the MIC, reviewing both reconstructions together was necessary to determine whether root resorption was present or absent in the adjacent tooth. Conclusion: Reviewing both orthogonal and curved/panoramic multiplanar reconstructions was necessary to evaluate the presence or absence of root resorption in the teeth adjacent to MICs and that of many other features.

In vitro comparison of two titanium dental implant surface treatments: 3M™ESPE™ MDIs versus Ankylos®.

BACKGROUND: An ideal implant should have a surface that is conducive to osseointegration. In vitro cell culture studies using disks made of same materials and surface as of implants may provide useful information on the events occurring at the implant-tissue interface. In the current study, we tested the hypothesis that there is no difference in the proliferation and differentiation capacities of osteoblastic cells when cultured on titanium disks mimicking the surface of 3M™ESPE™ MDIs or standard (Ankylos®) implants. METHODS: Cells were grown on disks made of the same materials and with same surface texture as those of the original implants. Disks were sterilized and coated with 2% gelatin solution prior to the cell culture experiments. C2C12 pluripotent cells treated with 300 ng/ml bone morphogenetic protein 2 BMP-2 and a stably transfected C2C12 cell line expressing BMP2 were used as models for osteogenic cells. The Hoechst 33258-stained nuclei were counted to assay cell proliferation, while alkaline phosphatase (ALPL) immunostaining was performed to investigate osteogenic differentiation. MC3T3-E1 cells were cultured as model osteoblasts. The cells were differentiated and assayed for proliferation and metabolic activities by Hoechst 33258 staining and Alamar blue reduction assays, respectively. Additionally, cultures were stained by calcein to investigate their mineral deposition properties. RESULTS: Electron microscopy showed greater degree of roughness on the MDI surfaces. Nuclear counting showed significantly higher number of C2C12 cells on the MDI surface. Although immunostaining detected higher number of ALPL-positive cells, it was not significant when normalized by cell numbers. The number of MC3T3-E1 cells was also higher on the MDI surface, and accordingly, these cultures showed higher Alamar blue reduction. Finally, calcein staining revealed that the MC3T3-E1 cells grown on MDI surfaces deposited more minerals. CONCLUSIONS: Although both implant surfaces are conducive for osteoblastic cell attachment, proliferation, and extracellular matrix mineralization, cell proliferation is higher on MDI surfaces, which may in turn facilitate osseointegration via increased ECM mineralization.

Donepezil regulates energy metabolism and favors bone mass accrual.

The autonomous nervous system regulates bone mass through the sympathetic and parasympathetic arms. The sympathetic nervous system (SNS) favors bone loss whereas the parasympathetic nervous system (PNS) promotes bone mass accrual. Donepezil, a central-acting cholinergic agonist, has been shown to down-regulate SNS and up-regulate PNS signaling tones. Accordingly, we hypothesize that the use of donepezil could have beneficial effects in regulating bone mass. To test our hypothesis, two groups of healthy female mice were treated either with donepezil or saline. Differences in body metabolism and bone mass of the treated groups were compared. Body and visceral fat weights as well as serum leptin level were increased in donepezil-treated mice compared to control, suggesting that donepezil effects on SNS influenced metabolic activity. Donepezil-treated mice had better bone quality than controls due to a decrease in osteoclasts number. These results indicate that donepezil is able to affect whole body energy metabolism and favors bone mass in young female WT mice.

Inducible transient expression of Smpd3 prevents early lethality in fro/fro mice.

Sphingomyelin phosphodiesterase 3 (SMPD3) is a pleiotropic lipid metabolizing enzyme involved in multiple physiological processes. A deletion mutation in the murine Smpd3 gene called fragilitas ossium (fro) leads to severe skeletal abnormalities in the developing fro/fro embryos. Although fro/fro mice can be useful to study many different aspects of SMPD3 functions, their perinatal lethality makes it difficult to generate a sufficient number of mice for controlled studies. In fact, on the C57BL/6 genetic background, none of the fro/fro mice survive beyond the perinatal stage. In this study, we used the "Tet-On" inducible gene expression system to express Smpd3 transiently in fro/fro;ROSA-rtTA;TRE-Smpd3 embryos on the C57BL/6 background. This induced Smpd3 expression corrected all the skeletal abnormalities in these embryos and prevented their early death. However, induction of Smpd3 expression in the adolescent fro/fro;ROSA-rtTA;TRE-Smpd3 mice was not sufficient to correct the defects in trabecular bone mineralization and the impaired growth of the long bones. This novel mouse model will be a useful tool to study SMPD3 biology in vivo.