J Esthet Restor Dent. 2019;1–6 Journal -Effect of time on tooth dehydration and rehydration Received: 3 February 2019 Revised: 7 February 2019 Accepted: 10 February 2019 DOI: 10.1111/jerd.12461

1. Sama Suliman DDS1| Taiseer A. Sulaiman BDS, PhD1| Vilhelm G. Olafsson DDS, MS2|
Alex J. Delgado DDS MS3| Terence E. Donovan DDS1| Harald O. Heymann DDS1
Effect of time on
tooth dehydration
and rehydration
Received: 3 February 2019 Revised: 7 February 2019 Accepted: 10 February 2019 DOI: 10.1111/jerd.12461
J Esthet Restor Dent. 2019;1–6
Dr.Athul Chandra.M
2d year postgraduateGuided y Dr. Sheetal K

2. Clark in 1931, the first to address the problem of color in dentistry, stated
that “we as dentists are not educationally equipped to approach a color
problem”.
This statement applies to this day despite numerous advances in shade
matching techniques in recent decades.

3. The CIELAB system is frequently used to measure color and color differences,
which is based on the 1976 Commision Internationale de l´Eclairage (CIE)
L*a*b* color space.
The three coordinates that determine color are
L* coordinate represents lightness,
a* represents green-red
b* represents blue-yellow coordinate.
This system is the basis for transforming spectral energy data into meaningful
color data.
CIE recently published a new CIEDE2000 formula model which is
extended to the CIE 1976 (L*a*b*) color-difference model with
corrections for variation in color-difference perception dependent on
Lightness, Chroma, Hue and Chroma-Hue interaction.

4. In the CIELAB system,
Delta E (ΔEab) is the color difference, or the distance separating
two points of color. It is defined by the following equation:
ΔE = √(L1-L2)2+ (a1-a2)2+ (b1-b2)2.
In the CIEDE2000 system,
Delta E (ΔE00) is the total color-difference between two colors
samples with Lightness (L), Chroma (C), and Hue (H) difference.

5. A prospective multicenter study concluded that the CIELAB
50:50% perceptibility threshold was ΔEab= 1.2,
the 50:50% acceptability threshold was ΔEab= 2.7.
When a color difference is considered acceptable by 50% of the observers,
it is acceptability threshold.
When the color difference between two compared objects can be seen by
50% of the observers, it is a 50:50% perceptibility threshold.

6. Color perception occurs when light from a particular source is reflected by
the object and observed by the viewer.
Hence, color perception is influenced by a triad of events:
• the light source,
• the optical properties of the object observed
• the color interpretation ability of the observer himself.

9. Colour determination therefore must be carried out in controlled
circumstances before the tooth dehydrates, if a successful match is to be
obtained.
In a typical clinical scenario, shade determination is usually not performed
with a rubber dam.
Retraction methods are commonly used which provide relative levels of
isolation by relieving the tooth of contact with wet soft tissues, while
keeping the tooth within the confines of the oral cavity, which facilitate
placement of shade guides or shade determination devices.

10. An accurate color match of the final restoration can only be expected if the
shade was registered with the tooth in a hydrated state.
The purpose of their study was to estimate the time required for teeth to
dehydrate to perceivable and acceptable thresholds of color change using
methods of relative isolation, and to determine the time required for the color
change to return to a normal level after isolation removal.
The null hypothesis is that there is no perceivable difference between tooth
shade before and after dehydration, and the time required to rehydrate the
tooth is not proportional to the tooth's original shade.

11. MATERIALS AND
METHODS

12. 32participants
Inclusion criteria:
• Adult participants, 18-45 years of age.
• Participants have no adverse medical condition and are not on any medication.
Unstimulated salivary flow was measured volumetrically to ensure that it is within
normal limits (0.3-0.4 mL/min).
• The tooth to be observed (central incisor) should be a sound natural tooth with
no restorations, wear, recent bleaching or severe discolorations, with a healthy
periodontal condition.
Exclusion criteria:
• Participants have adverse medical condition and are on medication.
• Presence of a restoration.
• Presence of an orthodontic fixed appliance including the central incisors.
• Recent bleaching.
• Dry mouth, or low unstimulated salivary flow levels

15. Time intervals were: 0 (baseline),
2, 3, 5, 7, 10, and 15 min.
All participants wore a nose clip during
measurements to ensure that the same
mode of breathing was used (mouth vs
nose breathing),ensuring similar air flow

16. For rehydration time determination, the Optragate isolation device
was removed from the mouth.
A full-mouth rinse for 30 s with water was done. Then participants were
asked to close their mouth for 5 min.
Color measurements to determine the extent of tooth rehydration were
performed according to the same intervals as in the dehydration phase
of the study.

17. The data were analyzed for color differences (ΔE00) over time using an analysis of
variance (ANOVA).
Post-ANOVAcontrasts were made between baseline and each time interval
(baseline and, 1, 2, 3, 5, 7, 10, 15 min) by using Tukey test with P-values
adjusted for multiple comparisons (P < 0.0001).
Percentage changes between baseline and each time interval were assessed for
color differences by using Clopper-Pearson (Exact) test with a 95%
confidence level.
This test was used to assess the proportion of the population that exceeded the
ΔE00perceptibility threshold of 0.8 or acceptability threshold of 1.8 at each time
interval of dehydration and rehydration.

18. Analysis of variance (ANOVA) indicated that there was statistically significant
change in color over time in the mean ΔE00for both dehydration and
rehydration procedure (P <0.0001).
As time increases, the mean ΔE00increases as well within the dehydration
procedure. The values were compared to the 50:50% perceptibility and
acceptability thresholds at ΔE00of 0.8 and 1.8 respectively.
RESULTS

19. DISCUSSION
• Tooth color did not return to its original value after 15 min of
rehydration
• the L (Lightness) returned to its original value after rehydration, while
the C (Chroma) retained a higher value and a lower H(Hue) value after
rehydration
• Therefore, tooth color determination should be carried out prior to the
start of any treatment, before the tooth dehydrates if a successful color
match is to be achieved.
• In a typical clinical setting one cannot expect to determine a shade
shortly after a clinical procedure has been performed during which the
tooth to be matched dehydrated

20. • When the tooth dehydrates, the inter-prism space will be replaced with
air, and the light will refract differently due to the difference in RI.
• The increased light refraction reduces the tooth's translucency and
increases its luminosity, giving the tooth a whiter appearance.
• When the tooth is rehydrated, it may require a longer period, more than
15 min, for the saliva to refill the inter-prism spaces and restoring the
original path of light refraction through the tooth, and finally restoring
the tooth's original color.

21. CONCLUSION
Within the limitations of this clinical study, the following conclusions were
drawn:
• Tooth dehydration within the first minute led to perceivable changes in
the tooth's color, adversely affecting the shade selection process.
• Teeth required more than 15 min of rehydration, in order to regain their
original shade after dehydrating.
• It is highly recommended to performing shade selection at the beginning
of the appointment.

22. REFERENCES
1. Sproull RC. Color matching in dentistry. III. Color control. J ProsthetDent. 1974;31:146-154.
2. Clark EB. An analysis of tooth color. J Am Dent Assoc. 1931;18:2093-2103.
3. Milleding P, Haag P, Neroth B, Renz I. Two years of clinical experiencewith Procera titanium
crowns. Int J Prosthodont. 1998;11:224 232.
4. Bergman B, Nilson H, Andersson M. A longitudinal clinical study ofProcera ceramic-veneered
titanium copings. Int J Prosthodont. 1999;12:135-139.
5. Sjogren G, Lantto R, Tillberg A. Clinical evaluation of all-ceramiccrowns (Dicor) in general practice.
J Prosthet Dent. 1999;81:277-284.
6. Haselton DR, Diaz-Arnold AM, Hillis SL. Clinical assessment of high-strength all-ceramic crowns. J
Prosthet Dent. 2000;83:396-401.
7. Feller RL, Stenius AS. On the color space of sigfrid forsius, 1611. ColorEng. 1970;8:48-51.
8. Sharma G, Wu W, Dalal EN. The CIEDE2000 color-difference formula:Implementation notes,
supplementary test data, and mathematicalobservations. Col Res Appl. 2004;30:21-30.
9. Judd DB, Wyszecki G. Color in Business, Science and