الفهرس 
Natural tooth shadeOnly 14 pages are availabe for public view
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Abstract
The purpose of this study is to evaluate effect of frequent bleaching
regimens (at home bleaching and in office bleaching) on the color stability of
bovine teeth enamel.
Thirty sound bovine incisor teeth were used in this study representing
three main groups. They were inspected under atomic force microscope
(AFM) to exclude those with stains, cracks, fractures, dental fluorosis, or
enamel defects as attrition, abrasion or erosion.
The teeth were cleaned from all debris and calculus using tap water
and manual scalars, disinfected and stored from one week to one month
maximum in 0.1% thymol solution until using. The roots were sectioned
using a water-cooled diamond saw and the pulp tissue was removed using
endodontic broach from pulp chamber. Crowns of all the specimens, with the
labial surface faced upward, were individually embeded in chemically cured
acrylic resin, then were polished with polishing brush and washed. The
specimens were stored throughout the experiment in artificial saliva that
were renewed daily.
Specimens of the first group (control group) weren’t subjected to any
bleaching procedure. group II (At home bleaching regimen) was bleached
with 15% (CP) gel; Opalescence PF for 14 days and 4h/day according to
manufacture instructions.
group III (In-office bleaching regimen) chemical-activated bleaching
gel (Opalescence® Boost PF 40%) was applied as done in group II. Two
applications (of 20-minutes each). Another application was performed after 3
days and the teeth were immersed in artificial saliva (renewed every day)
between the two sessions. After the bleaching procedure, and washing with
water, the specimens were dried and re-immersed in artificial daily renewed
saliva.
All the groups were subdivided into two subgroups A and B according
to the storage solution. Subgroup A was not subjected to any staining cycles
but just stored in artificial saliva. Subgroups B was subjected to a staining
cycle containing three staining solutions (Coffee, Tea, and Hibiscus).
Specimens were immersed for two hours period in each staining solution per
day for 30 consecutive days. The solutions were cooled to room temperature
before being used, freshly prepared and changed daily.
The specimens were stored in artificial saliva for two months which
was daily renewed. This enables enamel remineralization. All the bleaching
procedures and the staining cycles were repeated twice with two-month
interval. All the procedures were carried out at room temperature (23±1° C).
The shade was repeatedly determined for all specimens at base line
before any treatment, 2hrs. after bleaching (first and second bleaching
procedure) and after immersion in storage solution (30 days) (first and
second staining cycles) using a spectrophotometer (Vita Easy Shade V).
Data were collected, tabulated, and statistically analyzed by software
SPSS version 23; description statistics were shown as Means ± SD. One-way
ANOVA test, Standard student t- test at a level of significance (P ≤ 0.05)
were used to compare the recorded total color change values of both tested
materials either after bleaching or staining.