Browsing by Author "Dunipace, Ann J."

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    Fluoride and Cortical Bone: A Histomorphometric Study in Rabbits
    (1997) Acon-Ng, Patricia; Garetto, Lawrence P.; Dunipace, Ann J.; Katona, Thomas R.; Shanks, James C.; Turner, Charles H.
    Fluoride has been used in the treatment of osteoporosis because of its apparent ability to directly initiate bone formation. However, fluoride's therapeutic efficacy is controversial. Clinical trials in the range of 50 to 75 mg/day demonstrated severe side effects and a lack of consistent therapeutic benefits. Animal studies have not fully proven a positive effect of fluoride on bone strength. The objective of this study was to determine the histomorphometric changes in the cortical bone of rabbits caused by high doses of fluoride. The hypothesis was that high-dose fluoride intake enhances bone modeling and inhibits bone remodeling. Twenty-four young adult (four months old) female, Dutch Belted rabbits were randomly divided in two groups. The control group received no fluoride in their drinking water, while the experimental group received 100-ppm fluoride. Both groups received approximately 12-ppm fluoride in their food. A pair of tetracycline labels was given two weeks apart before initiation of the experiment. Fluoride treatment was given for six months. A terminal pair of calcein green labels was given before the animals were euthanized. Histomorphometric measurements were made using stereological point-hit and linear-intercept methods. The histomorphometric findings were correlated with fluoride serum and bone levels and also with strength tests. The study demonstrated that fluoride increases bone modeling by increasing periosteal bone apposition and endosteal bone resorption. The net effect of fluoride was an enlargement of the cortical bone and bone marrow and, therefore, the total tissue cross-section. However, the observed increase in bone mass produced by fluoride did not have a positive effect on the mechanical properties of bone. Fluoride did not produce a change in the primary histomorphometric parameters of osteoid surface (OS/BS%) or mineralizing surface (MS/BS%). Fluoride treatment produced an increase in the cortical periosteal modified mineral apposition rate (CPMAR). The remaining dynamic indices (i.e. endosteal MAR, remodeling MAR, cortical endosteal BFR and total BFR, activation frequency and formation period) were not affected by fluoride. The study failed to show an inhibitory effect of fluoride on bone remodeling.
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    Fluoride and the Rabbit Mandibular Condyle: A Strength and Histomorphometric Study
    (1997) Kizior, John William; Garetto, Lawrence P.; Dunipace, Ann J.; Chen, Jie; Shanks, James C.; Turner, Charles H.
    The specific aims of the project were to assess the histomorphometric and strength changes that occurred in the fluoride treated trabecular and subchondral bone of the mandibular condyle. This project represented a specific part of a larger experiment recently conducted by the Indiana University Oral Health Research Institute. We tested the hypothesis that fluoride treatment inhibits bone remodeling activity, enhances bone modeling activity, and decreases bone strength. The rabbit mandibular condyle, because it is composed of trabecular and subchondral bone and has a high rate of remodeling activity, was used as a model for human trabecular and subchondral bone. The six-month study involved 24 young adult (four months old) female, Dutch Belted rabbits. The rabbits were randomly divided into two groups based on body weight and plasma fluoride levels. The control group received no fluoride in their drinking water while the experimental group received 100-ppm fluoride. Both groups of rabbits received approximately 12-ppm fluoride in their food. A pair of tetracycline labels (10 mg/kg i.m.) was given two weeks before the initiation of the fluoride treatment. A pair of calcein green labels (5mg/kg i.m., bid), administered one week apart, was initiated two weeks before the end of the experiment. The animals were euthanized three days after the final label injection. Histomorphometric measurements were made at X125 magnification on a Nikon FXA epifluorescent microscope utilizing stereological point-point hit (volume-related parameters) and linear intercept (surface related parameters) methods. The fluoride treatment resulted in a significant increase in the percentage of osteoid surface, but no increase in osteoid thickness. The bone formation rate showed a trend toward an increased formation rate in the fluoride treatment group. The observation that the mineralized surface and osteoid thickness showed no change suggests a normal rate of mineralization. However, more surfaces were covered with osteoid. Mechanical testing showed no change in stiffness and a weak trend toward a decrease in ultimate strength in the fluoride group. The data suggest that the influence of fluoride treatment had a minimal affect on the trabecular bone of the rabbit mandibular condyle. The results from the vertebra study in the same animals showed a similar pattern of change following fluoride treatment. It is speculated the limited variability between the vertebra and the condyle could be due to altered functional mechanical loading or regional characteristics.
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    Treatment of Enamel Demineralization Following Orthodontic Therapy
    (1997) Stoll, Lana R.; Garetto, Lawrence P.; Analoui, Mostafa; Dunipace, Ann J.; Hohlt, William F.; Schemehorn, Bruce R.; Shanks, James
    The early-stage, carious, white-spot lesion is a common finding on teeth in patients who have received orthodontic treatment. Recently, a calciumphosphate (Ca-P) treatment was developed to enhance remineralization of white spot lesions. We hypothesized that a rinse containing the Ca-P would promote greater remineralization of demineralized enamel in vivo than a fluoride (F)-containing rinse or a placebo rinse. Thirty post-treatment orthodontic patients with demineralized white spot lesions on one or more of the six maxillary anterior teeth were selected and randomly assigned to three equal groups for a double-blind study. One group was given the placebo rinse. Another group was given a rinse with the same ingredients as the placebo rinse plus 0.055% F. The third group was given a rinse with the same ingredients as the F rinse plus calcium, phosphate, and magnesium salts. In addition, all subjects used a 0.011% F dentifrice before rinsing. Two different methods were used to determine the initial extent and subsequent de- or remineralization of the white spot lesions at the debonding appointment (baseline), and at one, three, and six months after the baseline reading: 1) visual inspection, in which two examiners estimated the severity and location of the lesions, and 2) quantitative laser fluorescence (QLF), in which the depth and area of the lesions were determined more objectively. Lnterexaminer agreement was almost perfect for the clinical exams. All three groups were significantly different with regards to reduction of number of white spots according to the clinical scoring. The placebo rinse group had the greatest reduction followed by the Ca-P group and the fluoride group. The QLF data showed no significant overall group differences for any of the measurements except total lesion depth. The placebo group had a significantly greater reduction of total lesion depth at the last examination than the Ca-P group (p < 0.05). The data suggested that different mechanisms may exist for remineralization of large and small lesions and that remineralization of a lesion with a lower concentration of fluoride, such as that used with the placebo rinse and the fluoride dentifrice, may result in greater remineralization of white-spot lesions.