It was used healthy teeth, provided
from Central Animals House of the University of Sao Paulo, Ribeirao
Preto, Sao Paulo, Brazil and according to the rules proposed by the
Ethics Committee. The left molars attached to the mandible arch were
removed and fixed in formaldehyde 10%, during 24 hours.
Microwave oven standardization. The
standardization method used in this research was proposed by Login
& Dvorak (1990), in that was used a domestic microwave oven
(Panasonic /700W/2450mHZ) that had its rotative plate turned off. A
Becker of glass containing lOOmL of distilled water was inserted on the
left side ofthe pre-heated oven in maximal potency by 2 minutes. An
Agar/Giemsa block (0.5cm), prepared with 5% of agar/agar in saline
solution in that was added Giemsa stained solution (Sigma Chemical St
Louis, MO), was soaked in 5mL of fixative solution or decalcification
solution, in Petri plastic plate, 35mm, inserted in various positions
inside ofthe oven and irradiated with 100% potency in different periods
of time. The color alteration ofthe Agar/ Giemsa blocks was used to
watch the better irradiation focus and the temperature change.
Establishing the area with most microwave incidence into the oven, as
well as the exposition time, it was performed the decalcification
the individual differences on teeth mineralization, it was decided to
use the same teeth in the analysis by two decalcification methods.
Thus, the teeth were longitudinal sectioned in bucolingual orientation,
separated into three fragments and decalcified with nitric acid or
Washawsky solution (EDTA 8.5% pH 7.4). The full teeth were initially
weighted and sectioned into three samples, and the measures were
respectively, 1.7x1.0cm of width and 2.6cm of length. All the fragments
showed the same structures, enamel, dentin, alveolar bone and soft
tissues. After fixative period, it was inserted 30mL of decalcified
solution and irradiated for 1 minute in ice bath microwave, in sequence
the decalcified solution was despise and replaced by another for new
irradiation period. Each five irradiation periods, one sample ofthe
decalcified solution, was collected for calcium dosage in atomic
spectrophotometer. It was performed 10 irradiations per day and the
sample stayed into the decalcified solution at freezer until the next
day. After fixative period, the group A (control) was placed in 30mL
ofthe decalcified solution and this was replaced by another after the
sample remotion for calcium dosage, each 5 days.
Calcium dosage. The calcium
concentration ofthe selected samples was determined by atomic
absorvance spectrophotometry (Shimadzu AA680G spectrophotometer).
Microscopic study. After
decalcification period, the samples were dehydrated, included in
paraffin and the histologic sections stained by Masson Trichrome. In
sequence, they were analyzed and photographed usinga photomicroscope
Jenaval, Carl-Zeiss, Ober Kochem, Germany.