Analytical Objectives

1 • Use acellular human enamel blocks as the test substrate to compare the whitening effect of 3 tooth whitening strips and 4 tooth whitening gels after 1, 7, and 14 applications of the whitening treatments. • Use acellular human enamel blocks as the test substrate to compare the whitening effect of 3 tooth whitening strips after 21 and 28 applications of the whitening treatments. • To quantify the whitening effect in terms of the number of VITA® Bleachedguide tooth shades whiter.

27 subjects were enrolled because we pre-determined that this number caused our power calculation for the study to be greater than 95%. This number of subjects also allowed us to have sufficient data to detect statistical differences in mean tooth shades of ± 0.50 within a high degree of confidence of the data being accurate.

Blind research protocol

In order to avoid influencing users’ perception during the trial, the 27 subjects were given the products in white paper bags with the manufacturer's instructions for use. The study followed a blind research protocol that complied with industry and ADA standards.

Assessment

Tooth color measurement (using Vita Easyshade)

The Vita Easyshade spectrophotometer is a handheld probe device widely used for determining tooth shade color. The machine readouts were measured in triplet and the mean was taken for each subject visit. Conversion of Vita units to mathematical scores we performed are shown below:

Oral hard and soft tissue evaluation

Presence of blanching, irritation, erythema, desquamation or ulceration of soft tissues and gross changes in teeth or restorations were documented if present.

Löe and Silness Gingival Index

The Löe and Silness Gingival Index is an assessment of periodontal health that evaluates the severity of gingivitis on the basis of color, consistency, and bleeding on probing (BOP). Six gingival areas on each of the anterior maxillary teeth were scored from 0 to 3, and an average score for each participant was derived by dividing the sum of individual scores by the number of evaluable sites. Scoring criteria was as follows:

0 = normal gingiva

1 = mild inflammation (slight color changes and edema; no BOP);

2 = moderate inflammation (redness, edema, and glazing; BOP);

3 = severe inflammation (marked redness, edema, ulceration; tendency toward spontaneous bleeding);

8 = ungradable site;

9 = missing tooth.

Visual analog scale (VAS) dentinal hypersensitivity score

Subjects were asked to self-assess sensitivity by recording their perceived sensitivity on each of the six maxillary teeth using a scale of 0-10 with the pain defined as:

0 = No pain or barely noticeable tooth sensitivity

1-3 = Mild pain

4-6 = Moderate pain

7-9 = Severe pain, not constant

10 = The most excruciating pain, constant

Assessment for adverse reactions

Subjects were asked to report any adverse reactions to the whitening treatment.