Development of methods to enhance extrinsic tooth discoloration for comparison of toothpastes. 1. Studies in vitro.
BACKGROUND
The interaction of chlorhexidine with dietary chromogens to cause extrinsic dental staining has been exploited in vitro and in vivo to study tooth discoloration and its control. These studies in vitro investigated factors that might enhance stain formation, and evaluated formulations to inhibit the stain with the primary aim of devising a protocol for use in vivo.


METHODS
The standard method cycled acrylic specimens through saliva, 0.2% chlorhexidine and tea on the hour 8 times per day and stain was measured using a spectrophotometer. Test interventions were 3 "whitening" toothpastes (A, P, R), a fluoride toothpaste (C) and water. In studies 1 and 3 interventions were at 09:00 and 16:00, and in studies 2 and 4 at 09:00 and 13:00. Between cycles, specimens remained dry in studies 1 and 2 and were maintained in water day and night in studies 3 and 4. Studies 5-7 determined the influence of tea temperature, exposure time and concentration, and chlorhexidine temperature and exposure time on stain development. Studies 8-10 modified the standard procedure using tea at triple strength and 50 degrees C, and assessed stain inhibition by toothpastes and water using optical density, colorimetric and visual assessment recordings.


RESULTS
In studies 1-4, there were highly significant differences between interventions. Overall, the experimental whitening paste (P) produced the most stain inhibition, and water or the proprietary whitening paste (R), produced the least stain inhibition. More stain inhibition was seen with interventions at 09:00 and 16:00. Both tea concentration and temperature significantly influenced staining. Chlorhexidine temperature did not influence staining. Exposure time to tea and chlorhexidine had a small effect on staining. In studies 8 and 9, interventions at 09:00 and 16:00 were more effective; the most stain inhibition was with paste P and the least with water, paste R being intermediate. In study 10, P was the most effective and R the least effective interventions.


CONCLUSIONS
These studies in vitro suggest that the chlorhexidine tea stain model can be manipulated to enhance stain and thereby should improve discrimination between stain inhibition formulations. The timing of interventions in the model appears to be important. These studies in vitro were used to plan a clinical protocol.
Pontefract
H
H
Division of Restorative Dentistry, Dental School, Bristol, UK.
Courtney
M
M
Smith
S
S
Newcombe
R G
RG
Addy
M
M
D000180:Acrylic Resins / Q000737:chemistry; D000891:Anti-Infective Agents, Local / Q000009:adverse effects; D002710:Chlorhexidine / Q000009:adverse effects; D003118:Color Perception; D003124:Colorimetry; D045424:Complex Mixtures; D003802:Dentifrices / Q000627:therapeutic use; D006801:Humans; D009067:Mouthwashes / Q000009:adverse effects; D055095:Optics and Photonics; D010545:Peroxides / Q000627:therapeutic use; D011122:Polyphosphates; D011145:Polyvinyls / Q000627:therapeutic use; D012463:Saliva; D012824:Silicic Acid; D012822:Silicon Dioxide / Q000627:therapeutic use; D012969:Sodium Fluoride / Q000627:therapeutic use; D013053:Spectrophotometry; D013662:Tea / Q000009:adverse effects; D013696:Temperature; D013997:Time Factors; D014073:Tooth Bleaching / Q000379:methods; D014075:Tooth Discoloration / Q000209:etiology* / Q000517:prevention & control; D014100:Toothpastes / Q000627:therapeutic use*; D014867:Water / Q000737:chemistry
D000180:Acrylic Resins; D000891:Anti-Infective Agents, Local; D045424:Complex Mixtures; D003802:Dentifrices; D009067:Mouthwashes; D010545:Peroxides; D011122:Polyphosphates; D011145:Polyvinyls; C112939:Rembrandt Lighten; D013662:Tea; D014100:Toothpastes; C546060:hydrated silica gel-based toothpaste; D014867:Water; D012824:Silicic Acid; D012822:Silicon Dioxide; D012969:Sodium Fluoride; D002710:Chlorhexidine