An in vitro comparasion of effectiveness of various bleaching agents and intracoronal bleaching techniques using spectrophotometric measurements

The purpose of this study was to compare the color changes achieved withvarious types of bleaching agents and intracoronal bleaching techniques on the basis ofspectrophotometric analysis.Sixty dentin slabs derived form extracted bovine teeth stained artificially withfresh blood over a period of 15 days and evenly distributed among four groups. Eachdentin slab was treated with one of the following bleaching techniques: Group 1:walking bleach with sodium perborate ( Sultan Chemists, USA ) +distilled water. Group2: walking bleach with 35% Hydrogen peroxide ( Opalescence Endo, Ultradent, SouthJordan, UT, USA ). Group 3: Thermophotobleach with 35% Hydrogen peroxide( Opalescence® Xtra®, Ultradent Products, UT, USA )+light ( Optilux 501, DemetronResearch Corp. Danbury Conn. ), Group 4: Control group, the specimens were kept indistilled water.All specimens were subjected to repeated treatment with fresh bleaching pasteson days 0, 7, 14, 21. CIELAB color parameters were evaluated prior to the experiment,following staining and each treatment by using spectrophotometer ( CM-2600d-Minolta, Japan ).Results of total color change ( ?E ) of two walking bleach groups were similarat all weeks and no further changes were recorded after second week. The teeth in thethermophotobleach group were significantly darker than the teeth bleached withwalking bleach method at all time periods. The teeth in all groups did not turn to theiroriginal shade. There is no significant difference of bleaching effectiveness between thehydrogen peroxide and sodium perborate when they are used in walking bleachtechnique.Two weeks is necessary and enough time period for walking bleach. The teeth ingroup 3 continue to bleach at the 3rd week although the walking bleach groups reached a plateu at the second week. Receiving intracoronal and extracoronal bleaching at thesame time showed a significant decrease of yellowness comparing the teeth which havebeen bleached only from the pulp chamber.Key words: Intracoronal bleaching, Internal discoloration, spectrophotometer