title: Comparison between two experimental protocols to promote osteoporosis in the maxilla and proximal tibia of female rats.
abstract: The effects of two experimental protocols (ovariectomy associated or not with a low calcium diet) used to promote osteoporosis in the rat maxilla and proximal tibia were compared 5 and 11 weeks after surgery. Female Wistar rats were ovariectomized or sham-operated. Half of the ovariectomized rats were fed a low Ca++ diet (ovx*) and the remaining ovariectomized (ovx) and sham animals received a standard chow. At sacrifice, the proximal metaphysis was excised from the tibia and the molars were extracted from the hemi-maxilla. Dry (60 degrees C overnight) and ash (700 degrees C/14 h) weights were measured and the ashes were used for Ca++ measurement by means of a colorimetric method. After 5 weeks, ovx caused no alteration while ovx* decreased proximal metaphysis (17%) and maxilla (35%) bone mass. After 11 weeks, ovx caused a 14% bone mass reduction in the proximal metaphysis but not in the maxilla, while ovx* caused a comparable bone mass reduction (30%) in both bone segments. Calcium concentration was not altered in any experimental condition. The results show that estrogen deficiency is insufficient to cause maxillary osteoporosis in rats over an 11-week period and a long-term ovariectomy is needed to exert deleterious effect on proximal metaphysis bone mass. When a low Ca++ diet is associated with estrogen deficiency, however, a relatively precocious harmful effect is observed, twice as pronounced in the maxilla than in the proximal metaphysis. On a long-term basis, ovariectomy associated with a low Ca++ diet seems to be equally injurious to both proximal metaphysis and maxilla.
authors.affiliation: Oral Rehabilitation Area, School of Dentistry of Ribeirão Preto.
authors.forename: Juliana Mazzonetto
authors.initials: JM
authors.lastname: Teófilo
authors.forename: Ana Carolina Bernardes
authors.initials: AC
authors.lastname: Azevedo
authors.forename: Sérgio Olavo
authors.initials: SO
authors.lastname: Petenusci
authors.forename: Renata
authors.initials: R
authors.lastname: Mazaro
authors.forename: Teresa Lúcia
authors.initials: TL
authors.lastname: Lamano-Carvalho
mesh_terms: D016301:Alveolar Bone Loss / Q000209:etiology*; D000818:Animals; D015519:Bone Density / Q000502:physiology; D002118:Calcium / Q000172:deficiency; D002136:Calcium, Dietary / Q000008:administration & dosage*; D004195:Disease Models, Animal; D004967:Estrogens / Q000172:deficiency; D005260:Female; D008437:Maxilla / Q000503:physiopathology; D008439:Maxillary Diseases / Q000209:etiology*; D010024:Osteoporosis / Q000209:etiology*; D010052:Ovariectomy / Q000009:adverse effects; D051381:Rats; D017208:Rats, Wistar; D018709:Statistics, Nonparametric; D013977:Tibia / Q000503:physiopathology
chemical_list: D002136:Calcium, Dietary; D004967:Estrogens; D002118:Calcium