The long term objective is to provide a better understanding of the role of magnesium (Mg) with and without fluoride (F) or carbonate (CO3) on the formation and stability of calcium phosphate (Ca-P)* phases of enamel, dentin, cementum and bone. Information from this study could be useful in formulating regimens for calculus control and remineralizing solutions for root caries.
Specific aims i nclude: (1) determine Mg distribution (a) in inorganic and organic phases of calcified tissues; (b) between normal and diseased enamel, dentin, bones; (2) define the correlation between Mg levels and (a) those of CO3, F, HPO4, Ca/P; and (b) physico-chemical properties (lattice parameters, crystallinity, dissolution properties, b- TCP/HA ratio after ignition) of biological and synthetic apatites (AP); (3) define the correlation between Mg levels in bones of mice and rats with: (a) age, (b) amount of intraoral injections of Mg and Mg+F; and (c) F supplementation; (4) determine the critical levels of Mg which will prevent the transformation of ACMP* to AP*; (5) determine the effect of CO3, F, HPO4 on the Mg-for-Ca substitution in AP* and in b-TCMP*; (6) to determine the synergistic or antagonistic effect of Mg with CO3, F, HPO4 or P2O7 on the formation and properties of synthetic AP; (7) determine the effect of Mg on the formation of Ca-P phases: (a) under conditions of constant composition, and (b) in gel systems; (7) investigate the transformation of Ca-P phases* in serum and in saliva; (8) determine the critical solution [Mg/Ca] ratio with and without F or which will affect the formation/transformation of Ca-P phases: (a) in solution and (b) in gel systems; (9) prove the non-existence of Mg-containing non-apatitic phases (dolomite, b-TCMP) in the mineral phases of teeth and bones; (10) study synthetic AP (with Mg and CO3) to explain (a) reported 'preferential loss of Mg and CO3 in caries, and (b) occurrence of b-TCMP in dentin but not in enamel caries. Biological materials (normal, carious, fluorotic human teeth; shark teeth; mice, rat, chick bones) and synthetic Ca-P* will be characterized by x-ray diffraction, infrared absorption, thermogravimetry, SEM/TEM, atomic absorption, chemical analyses and dissolution in acid bufer. Data generated will be analyzed for statistical validity. [*Ca-P phases: ACMP, Mg-substituted amorphous calcium phosphate; DCPD, dicalcium phosphate dihydrate; OCP, octacalcium phosphate; b-TCMP, Mg-substituted whitlockite; AP, non-stoichiometric apatite].

Agency
National Institute of Health (NIH)
Institute
National Institute of Dental & Craniofacial Research (NIDCR)
Type
Research Project (R01)
Project #
5R01DE007223-06
Application #
3220823
Study Section
Oral Biology and Medicine Subcommittee 1 (OBM)
Project Start
1985-09-01
Project End
1996-03-31
Budget Start
1993-04-01
Budget End
1994-03-31
Support Year
6
Fiscal Year
1993
Total Cost
Indirect Cost
Name
New York University
Department
Type
Schools of Dentistry
DUNS #
004514360
City
New York
State
NY
Country
United States
Zip Code
10012
Okazaki, M; LeGeros, R Z (1996) Properties of heterogeneous apatites containing magnesium, fluoride, and carbonate. Adv Dent Res 10:252-9
LeGeros, R Z (1993) Biodegradation and bioresorption of calcium phosphate ceramics. Clin Mater 14:65-88
LeGeros, R Z (1991) Calcium phosphates in oral biology and medicine. Monogr Oral Sci 15:1-201
LeGeros, R Z (1990) Chemical and crystallographic events in the caries process. J Dent Res 69 Spec No:567-74;discussion 634-6
Daculsi, G; LeGeros, R Z; Heughebaert, M et al. (1990) Formation of carbonate-apatite crystals after implantation of calcium phosphate ceramics. Calcif Tissue Int 46:20-7
LeGeros, R Z; Daculsi, G; Orly, I et al. (1989) Solution-mediated transformation of octacalcium phosphate (OCP) to apatite. Scanning Microsc 3:129-37;discussion 137-8
Cheng, P T; Grabher, J J; LeGeros, R Z (1988) Effects of magnesium on calcium phosphate formation. Magnesium 7:123-32
LeGeros, R Z; Orly, I; LeGeros, J P et al. (1988) Scanning electron microscopy and electron probe microanalyses of the crystalline components of human and animal dental calculi. Scanning Microsc 2:345-56
Daculsi, G; LeGeros, R Z; Jean, A et al. (1987) Possible physico-chemical processes in human dentin caries. J Dent Res 66:1356-9