Tubular permeability to calcium hydroxide and to bleaching agents

pH-changes during Intracoronal Bleaching: An in vivo Study

“…However, there is no significant difference in pH values at baseline and at 14 days for the group CP + SP. Several studies state that the alkalinity of bleaching agents increases with time, regardless of the diluting agent used, 7,8,15 contradicting the findings of this study. According to Haywood, 9 the pH value of carbamide peroxide is slightly alkaline at baseline, because it will decompose when in contact with the dental substrate.…”

“…Also, the pH value in extraradicular environment increases with bleaching time. 8,15,26 This result probably is because the peroxide decomposes into oxygen and water. 7 However, the pH values at 14 days of measurement showed significant decrease when compared with other times of measurement.…”

“…7 However, the pH values at 14 days of measurement showed significant decrease when compared with other times of measurement. Fuss et al 8 evaluated the dentinal tubular permeability of bleaching agents and found that the baseline mean pH value of the medium surrounding the teeth with bleaching agents (sodium perborate and hydrogen peroxide 30%) was 7.0, after 1 hour increased to 7.9, increased to 9.0 after 3 days, however, after 10 days showed a slight drop to the mean 8.3. Although the bleaching agents showed significant differences between them, all bleaching agents showed pH values above 7.0 or alkaline characters.…”

“…5,6 The pH decrease caused by bleaching agents at the periodontal tissue 7 can stimulate osteoclastic activity resulting in bone resorption. 8 Additionally, peroxides might change the organic and inorganic compounds of dentin tissue 9,6 and can generate denaturation of dentin proteins, which induces a foreign body reaction. 6,10 Some authors state that pH variation of the bleaching agents can cause this denaturation.…”

“…14 However, most studies have been carried in vitro, 7,8,15 and it is difficult to consider the real change of pH values that occur in vivo. Due to the occurrence of side effects associated to pH decrease of bleaching agents inside pulp chamber and because the available data on the pH values of bleaching agents were conflicting and the need of in vivo studies, the purpose of this study was to measure, in vivo, the pH values of the materials commonly used for bleaching pulpless teeth (walking bleach technique) at different time intervals after application.…”