Influence of ovariectomy and masticatory hypofunction on mandibular bone remodeling.
BACKGROUND
This study was designed to examine the effect of masticatory hypofunction and estrogen deficiency on mandible bone mass and compare this site with spine and femoral bone.


METHODS
Twenty-four rats were ovariectomized (OVX) or Sham-operated (Sham) and analyzed after feeding with hard diet (Hard) or soft diet (Soft). They were divided into four groups: (GI)Sham-Hard; (GII)OVX-Hard; (GIII)Sham-Soft and (GIV)OVX-Soft. Bone mineral density (BMD) was measured in the spine and femur in the baseline and at the end of the study, and DeltaBMD (final BMD - baseline BMD) was calculated. In mandible bone, BMD and histomorphometry were analyzed at the end of the experiment.


RESULTS
Sham rats showed higher spine (GI: 13.5%vs GII: 0.74%, P < 0.01; GIII: 10.67%vs GIV: -4.36%, P < 0.001) and femur DeltaBMD (GI: 14.43%vs GII: 4.42%, P < 0.01; GIII: 10.58%vs GIV: 0.49%, P < 0.001) than OVX, but no difference was observed in mandible BMD among these groups (P > 0.05). Soft-diet groups showed decreased mandible BMD compared with hard-diet groups (GIV vs GII, P < 0.01; GIII vs GI, P < 0.01). Similarly, mandibular condyle histomorphometry showed that soft-diet groups presented a significant decrease in trabecular thickness and volume (GIV vs GII, P < 0.05; GIII vs GI, P < 0.01) compared with hard diet.


CONCLUSIONS
Our results suggest that mandibular bone loss resulted from decreased of mechanical loading during mastication, and was not affect by estrogen depletion.
Patullo
I M F
IM
Bone Metabolism Laboratory of Rheumatology Division, Universidade de São Paulo, Sao Paulo 01246-903, Brazil.
Takayama
L
L
Patullo
R F
RF
Jorgetti
V
V
Pereira
R M R
RM
D000821:Animal Feed; D000818:Animals; D001732:Bite Force; D015519:Bone Density / Q000502:physiology*; D004195:Disease Models, Animal; D004967:Estrogens / Q000172:deficiency* / Q000502:physiology; D005260:Female; D005269:Femur / Q000033:anatomy & histology / Q000502:physiology; D006801:Humans; D008334:Mandible / Q000033:anatomy & histology / Q000502:physiology; D008336:Mandibular Diseases / Q000150:complications / Q000209:etiology* / Q000503:physiopathology; D008409:Mastication / Q000502:physiology; D015663:Osteoporosis, Postmenopausal / Q000150:complications / Q000209:etiology* / Q000503:physiopathology; D010052:Ovariectomy; D051381:Rats; D017208:Rats, Wistar; D013131:Spine / Q000033:anatomy & histology / Q000502:physiology; D018709:Statistics, Nonparametric; D013314:Stress, Mechanical
D004967:Estrogens