See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/331351088 Effect of time on tooth dehydration and rehydration Article in Journal of Esthetic and Restorative Dentistry · February 2019 DOI: 10.1111/jerd.12461 CITATIONS READS 9 592 6 authors, including: Taiseer A. Sulaiman Vilhelm G Olafsson University of North Carolina at Chapel Hill University of Iceland 41 PUBLICATIONS 427 CITATIONS 7 PUBLICATIONS 68 CITATIONS SEE PROFILE SEE PROFILE Alex J. Delgado University of Florida 24 PUBLICATIONS 145 CITATIONS SEE PROFILE Some of the authors of this publication are also working on these related projects: The quality of fixed prosthodontic impressions: An assessment of crown and bridge impressions received at commercial laboratories View project Impact of gastric acidic challenge on surface topography and optical properties of monolithic zirconia View project All content following this page was uploaded by Taiseer A. Sulaiman on 30 January 2020. The user has requested enhancement of the downloaded file. Received: 3 February 2019 Revised: 7 February 2019 Accepted: 10 February 2019 DOI: 10.1111/jerd.12461 RESEARCH ARTICLE Effect of time on tooth dehydration and rehydration 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 1 Division of Operative Dentistry and Biomaterials, Department of Restorative Sciences, University of North Carolina School of Dentistry, Chapel Hill, North Carolina Abstract Objective: To estimate the time required for teeth to dehydrate and rehydrate and its relation to the accuracy of tooth shade selection. 2 Operative Dentistry and Cariology, Faculty of Odontology, Division of Health Sciences, University of Iceland, Reykjavic, Iceland 3 Division of Operative Dentistry, Department of Restorative Dentistry, University of Florida School of Dentistry, Gainesville, Florida Correspondence Taiseer A. Sulaiman, Division of Operative Dentistry and Biomaterials, Department of Restorative Sciences, UNC School of Dentistry, 440 Brauer Hall, CB 7450, Chapel Hill, NC 27599. Email: [email protected] Materials and Methods: Thirty-two participants were recruited, and color measurements were conducted using a spectrophotometer placed with a custom jig. After isolation, baseline measurements were made at 1, 2, 3, 5, 7, 10, and 15 min intervals to determine dehydration time. After mouth rinsing, measurements were made to determine rehydration time. CIEDE2000 values were obtained for color change between the baseline recordings and all intervals and compared to the 50:50% perceptibility and acceptability thresholds. Analysis of variance (ANOVA) and Tukey test was used for multiple comparisons. Result: The tooth color changes were beyond the ΔE00 perceptibility threshold (0.8) within the first minute of dehydration (P > 0.0001). After the first minute, 87% of the teeth were beyond the ΔE00 perceptibility threshold (0.8), and 72% of the teeth were beyond the ΔE00 acceptability threshold (1.8). After 15 min of rehydration, 90% of the teeth were beyond the perceptibility Funding information University of North Carolina at Chapel Hill. threshold, and 65% were beyond the acceptability threshold. Conclusions: Shade selection procedures should be carried out within the first minute and before teeth dehydrate by means of isolation. Teeth do not rehydrate within 15 min after rehydration. Clinical Significance: Teeth dehydration has a negative impact on shade selection, which can affect the final esthetic outcome. Shade selection should be performed at the beginning of any restorative procedure. KEYWORDS operative dentistry, prosthodontics, shade selection, teeth dehydration, teeth rehydration 1 | I N T RO D UC T I O N Eclairage (CIE) L*a*b* color space. The three coordinates that determine color are L* coordinate represents lightness, while a* represents Shade selection for direct and indirect restorations is one of the most green-red, and b* represents blue-yellow coordinate. This system is the challenging components of esthetic dentistry.1 Clark in 1931, the first basis for transforming spectral energy data into meaningful color data.6,7 to address the problem of color in dentistry, stated that “we as den- Recently, the CIE published a new CIEDE2000 formula model which is 2 extended to the CIE 1976 (L*a*b*) color-difference model with correc- This statement applies to this day despite numerous advances in tions for variation in color-difference perception dependent on Light- shade matching techniques in recent decades. Based on current pro- ness, Chroma, Hue and Chroma-Hue interaction. Additionally, the CIE spective and retrospective clinical studies, 50% of cemented ceramic investigated the nonuniformity of the CIELAB space and developed this tists are not educationally equipped to approach a color problem”. empirical correction to improve agreement between perceived visual 3–6 crowns exhibit incorrect color matches. The CIELAB system is frequently used to measure color and color differences, which is based on the 1976 Commision Internationale de l´ color difference and numerical color difference.8 In the CIELAB system, Delta E (ΔEab) is the color difference, or the distance separating two points of color. It is defined by the follow- Abstract presented at the 96th General Session of the IADR, London, July, 25-28. J Esthet Restor Dent. 2019;1–6. ing equation: ΔE = √(L1-L2)2 + (a1-a2)2 + (b1-b2)2.9 In the CIEDE2000 system, Delta E (ΔE00) is the total color-difference between two color wileyonlinelibrary.com/journal/jerd © 2019 Wiley Periodicals, Inc. 1 2 SULIMAN ET AL. samples with Lightness (L), Chroma (C), and Hue (H) differences. It is 8 determined by the following equation: ΔE00 sffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 0 2 0 2 2 ΔL ΔC ΔH0 ΔC0 ΔH0 = + + + RT kL SL k c Sc k H SH kC SC kH SH before, and 10, 20, and 30 min after application. The levels of ΔE obtained after relatively short intervals of rubber dam isolation are well above the acceptability thresholds for incorrect shade match (ΔE = 2.7)10. Further studies are warranted to examine how fast perceptibility and acceptability thresholds of shade mismatch are reached. Where ΔL’, ΔC’, and ΔH’ are the differences in Lightness, In a typical clinical scenario, shade determination for direct and Chroma, and Hue for a pair of specimens, and RT is a function that indirect restorative work is usually not performed with a rubber dam accounts for the interaction between Chroma and Hue differences in in place. Retraction methods are commonly used which provide rela- the blue region. Weighting functions SL, SC, and SH adjust the total tive levels of isolation by relieving the tooth of contact with wet soft color difference for variation in the location of the color difference tissues, while keeping the tooth within the confines of the oral cavity, pair and KL, KC, KH are empirical terms used for correcting (weight- which facilitate placement of shade guides or shade determination ing) the metric differences to the CIEDE2000 differences for each devices. Regardless of the means of isolation, the degree of dehydra- coordinate. When the color difference between two compared objects tion that occurs and how rapidly it manifests is of great importance can be seen by 50% of the observers, it is a 50:50% perceptibility with regard to the timing and length of the shade selection procedure. threshold. Similarly, a 50:50% acceptability threshold has been defined An accurate color match of the final restoration can only be expected when a color difference is considered acceptable by 50% of the if the shade was registered with the tooth in a hydrated state. observers. A prospective multicenter study10 concluded that the The purpose of the present study was to estimate the time CIELAB 50:50% perceptibility threshold was ΔEab = 1.2, whereas the required for teeth to dehydrate to perceivable and acceptable thresh- 50:50% acceptability threshold was ΔEab = 2.7. The corresponding olds of color change using methods of relative isolation, and to deter- CIEDE2000 (ΔE00) values were 0.8 and 1.8, respectively, for under mine the time required for the color change to return to a normal simulated clinical settings. level after isolation removal. The null hypothesis is that there is no Color determination is an interplay where color perception and matching abilities need to meet in the best of conditions. Color perception occurs when light from a particular source is reflected by 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. 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 and the color interpretation ability of the observer himself.1 The light source should be spectrally balanced in 2 | M A T E R I A L S A N D M ET H O D S the visible range (370-780 nm), have a color temperature of approximately 5500 K and a color rendering index of >90, so that the light source itself does not become a limiting factor.11 Among optical properties of the object itself, translucency and light scattering impact color perception. Translucency is the amount of incident light transmitted and scattered. Scattering makes the object opaque and is dependent on the size, shape, number of the scattering centers and refractive index.11 The color matching ability of the operator is influ- 2.1 | Participant selection Thirty-two participants were recruited for this clinical study that was conducted after approval of the institutional review board (IRB) (XX-XXXX). These participants were selected among students and staff members at the School of Dentistry at University of XXXX based on the following criteria: Inclusion criteria: enced by viewing conditions, color fatigue of the eye, age, experience, and presence or absence of color blindness.7 Tooth dehydration makes teeth appear whiter due to increasing enamel opacity. The inter-prism spaces become filled with air instead of water so light can no longer scatter from crystal to crystal. Loss of translucency due to dehydration therefore causes more reflection, which masks the underlying color of dentin, making the tooth appear lighter.6,11 Color determination therefore must be carried out in controlled circumstances before the tooth dehydrates, if a successful match is to • 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. be obtained. Few clinical studies have examined how rapidly teeth dehydrate to a perceivable color difference. One study made measure- Exclusion criteria: ments with a reflectance spectrophotometer on a single central incisor before and after 15 min of rubber dam isolation.12 The purpose of their • Participants have adverse medical condition and are on medication. study was to determine the changes in the ΔE after 15 min of rubber • Presence of a restoration. dam application and the time for tooth color to return to original values. • Presence of an orthodontic fixed appliance including the central Another study conducted an in vivo study to assess the effects of dehydration on tooth color. 13 They isolated a central incisor with a rubber dam. They made measurements with a spectrophotometer incisors. • Recent bleaching. • Dry mouth, or low unstimulated salivary flow levels. 3 SULIMAN ET AL. patient to close and waiting a few minutes, to ensure no pretesting dehydration. The custom-made jig was seated in place, and three measurements per time interval were made using the calibrated VITA Easyshade spectrophotometer determining mean L, C, H values in accordance with the Commission Internationale de l'eclairage (CIEDE2000) system (Figure 2C). 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 in all study subjects. For rehydration time determination, the Optragate isolation device was removed from the mouth, and 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. The L, C, and H values obtained were used to calculate CIEDE2000 color differences (ΔE00) between baseline and other intervals for dehydration and rehydration. These values were compared to the perceptiFIGURE 1 The VITA Easyshade spectrophotometer bility and acceptability thresholds as determined by Paravina et al.10 to evaluate the time clinicians have to determine a shade under relative 2.2 | Instruments used The VITA Easyshade spectrophotometer (VITA Zahnfabrik, Bad levels of isolation before dehydration causes perceptible levels of color change. Säckingen, Germany) was used in this clinical study for color measurements (Figure 1). A custom-made jig was made for the central incisor 2.4 | Data management and statistical analysis of each participant from a clear silicone impression material (Affinity The data were analyzed for color differences (ΔE00) over time using Crystal Clear, Clinician's Choice New Milford, CT) to ensure consistency an analysis of variance (ANOVA). Post-ANOVA contrasts were made in the positioning of the Easyshade tip. The clear jig allowed visualiza- between baseline and each time interval (baseline and, 1, 2, 3, 5, 7, 10, tion of the entire facial surface, where an access opening of 6 mm 15 min) by using Tukey test with P-values adjusted for multiple com- diameter was made in the middle third using a disposable tissue punch, parisons (P < 0.0001). Percentage changes between baseline and each to accommodate the Easyshade tip (Figure 2AB). time interval were assessed for color differences by using ClopperPearson (Exact) test with a 95% confidence level. Additionally, this 2.3 | Color measurements All participants were seated and reclined to a 45 position relative to test was used to assess the proportion of the population that exceeded the ΔE00 perceptibility threshold of 0.8 or acceptability threshold of 1.8 at each time interval of dehydration and rehydration. the floor, to eliminate any shadowing effects from the nose or lips. Color measurements were conducted under controlled light settings (color temperature 5500 K and a Color Rendering Index [CRI] of 95) 3 | RE SU LT S with neutral color surroundings. Lips were retracted by using an Optragate (Ivoclar Vivadent, Amherst, NY). Optragate placement was The values for the mean, SD, and 95% confidence interval of the color accomplished within 15 s, otherwise it was repeated allowing the differences, expressed by ΔE00 at baseline, 1, 2, 3, 5, 7, 10, and FIGURE 2 Jig fabrication: A, Disposable tissue punches used to make a 6 mm hole through the clear polyvinyl siloxane impression material. B, Easyshade tip fitting through the 6 mm hole. C, Positioning of the Easyshade through the custom-made jig in the middle third of the central incisor 4 SULIMAN ET AL. TABLE 1 Mean and SD of change in color (ΔE00) of dehydration with 95% confidence level Variable Mean SD Lower 95% CL for Mean Upper 95% CL for Mean D__Delta_E_1 3.94 2.62 3.00 4.89 D__Delta_E_2 4.09 2.79 3.08 5.10 D__Delta_E_3 4.54 2.76 3.54 5.53 D__Delta_E_5 4.55 2.54 3.63 5.46 D__Delta_E_7 4.78 2.57 3.85 5.71 D__Delta_E_10 4.88 2.48 3.99 5.78 D__Delta_E_15 5.11 2.39 4.25 5.97 15 min time intervals of dehydration and rehydration can be seen in Tables 1–2 and Figure 3. Analysis of variance (ANOVA) indicated that there was statistically significant change in color over time in the mean ΔE00 for both dehy- FIGURE 3 Color change (ΔE00) after tooth dehydration and rehydration with different time intervals dration and rehydration procedure (P < 0.0001). As time increases, the mean ΔE00 increases as well within the dehydration procedure. The While 65% of the participants were beyond the ΔE00 acceptability values were compared to the 50:50% perceptibility and acceptability threshold after 15 min of rehydration (Figure 6). thresholds at ΔE00 of 0.8 and 1.8 respectively. 10 Within the first minute there was a statistically significant change in ΔE00, already beyond the acceptability threshold. Average change in L, C, and H values are displayed in Figure 4 (A-C). Mean L value showed a significant spike within the first minute of dehydration, while it returned to its original value after 15 min of rehydration. Mean C value remained increasing until 15 min of dehydration and did not return to its original value after 15 min rehydration. The mean H value continued decreasing until 15 min of dehydration and did not return to its original value after 15 min of rehydration. Therefore, continued increase in ΔE to 15 min is not only attributed to the change in L values, but also due to the changes in C and H values. Clopper-Pearson (Exact) test with 95% confidence interval was used to assess the proportion of the population that exceeded the ΔE00 perceptibility threshold of 0.8 or the ΔE00 acceptability threshold of 1.8 at each time interval of dehydration and rehydration. 87% of teeth were beyond the ΔE00 perceptibility threshold (0.8) within 4 | DI SCU SSION The present study revealed statistically significant and visually perceptible differences in tooth color measurements after dehydration and rehydration within the defined time intervals, rejecting the null hypothesis. ΔE00 values were calculated to assess the changes in tooth color by using a hand-held spectrophotometer (VITA Easyshade). ΔE00 values were compared to 50:50% ΔE00 perceptibly (0.8) and acceptability (1.8) thresholds. Within the first minute of dehydration there was a significant change in the ΔE00 (3.9) beyond the perceptibility threshold (87% of the participants) and acceptability threshold (72% of the participants). The ΔE00 increased constantly during the 15 min (ΔE00 = 5.1). Thereafter, participants were asked to rinse with water and close for 5 min to allow for teeth to rehydrate. ΔE00 measurements were calculated at the defined intervals. Tooth color the first minute of dehydration. While 90% of teeth were beyond did not return to its original value after 15 min of rehydration. ΔE00 the perceptibility threshold after 15 min of rehydration as shown in decreased from 4.1 to 2.7, with 65% of the participants still being Figure 5. beyond the acceptability threshold after the rehydration phase. Fur- Furthermore, 72% of the participants were beyond the ΔE00 thermore, the L (Lightness) returned to its original value after rehy- acceptability threshold (1.8) within the first minute of dehydration. dration, while the C (Chroma) retained a higher value and a lower H (Hue) value after rehydration. Therefore, tooth color determination TABLE 2 Mean and SD of change in color (ΔE00) of rehydration with 95% confidence level 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 typi- Upper 95% CL for Mean cal clinical setting one cannot expect to determine a shade shortly after matched dehydrated. Variable Mean SD Lower 95% CL for Mean R__Delta_E_0 4.14 2.67 3.17 5.10 R__Delta_E_1 3.98 2.27 3.16 4.80 To understand the change in tooth color due to dehydration, the R__Delta_E_2 3.77 2.52 2.86 4.68 tooth's enamel and dentin have a defined refractive index (RI) when R__Delta_E_3 3.35 1.96 2.64 4.06 light passes through the tooth structure. The refractive index is the R__Delta_E_5 3.60 2.07 2.85 4.34 R__Delta_E_7 3.38 2.56 2.46 4.31 R__Delta_E_10 3.10 2.05 2.32 3.80 R__Delta_E_15 2.73 2.14 1.96 3.50 a clinical procedure has been performed during which the tooth to be change in the light's direction when the transmitting medium changes. Air and water have refractive indices of 1.00 and 1.33, respectively.14 When light passes through enamel (RI = 1.63) and then through dentin (RI = 1.54) the light refracts in a certain direction.15 When the 5 SULIMAN ET AL. FIGURE 4 A, Change in L (Lightness) value (A). B, C (Chroma) value (B). C, H (Hue) value (C) after tooth dehydration and rehydration tooth is moist, the inter-prism space is filled with saliva, and light will In the literature, little is known about how long it takes for teeth refract in a defined path. When the tooth dehydrates, the inter-prism to dehydrate/rehydrate and the effect time has on the shade selection space will be replaced with air, and the light will refract differently process. A few clinical studies have been published where the effect due to the difference in RI. The increased light refraction reduces the of dehydration and rehydration on color change was examined. An tooth's translucency and increases its luminosity, giving the tooth a in vivo study to determine the changes in color measurements of nat- whiter appearance. When the tooth is rehydrated, it may require a urel teeth in seven subjects before and after isolation by using rubber longer period, more than 15 min, for the saliva to refill the inter-prism dam for 15 min, also estimating the time taken for the tooth color to spaces and restoring the original path of light refraction through the return to its original color.12 Color measurements were made by using tooth, and finally restoring the tooth's original color. a spectrophotometer with no mentioning of using a positioning jig, Isolation is considered one of the pillars to the success of most and CIELab coordinates were calculated. The authors concluded that restorative procedures. Although the use of rubber dam is essential teeth become brighter and less saturated after 15 min of rubber dam toward this success, it is unfortunately becoming an uncommon application, which agrees with the present study. They also found that practice. Other method of isolation have been introduced and offer baseline values of the tooth's color were regained after 30 min of relative isolation. The rationale for using the Optragate isolation rehydration whereas the baseline values were not regained after device in the present study instead of the rubber dam, for docu- 15 min of rehydration in the present study. menting the dehydration process, is due to that rubber dam applica- In a more recent studyl,13 color change due to dehydration was tion can be time-consuming and would have precluded timely investigated in 20 subjects. For each subject a left or right maxillary cen- measurements of the tooth dehydration process. According to a previ- tral incisor was used with a positioning jig made for placement of the ous study, rubber dam application took an average time between VITA Easyshade spectrophotometer. Baseline measurements were col- 16 Consequently, the color measurement process will be lected followed by rubber dam isolation. Measurements were obtained adversely affected. In this study, a single operator (SS) was trained on at 10-min intervals for 30 min. The rubber dam was removed and sub- the Optragate application in a timely manner (less than 15 s) to ensure jects were instructed to drink a glass of water followed by additional consistency of the results. color measurements for rehydration with same time intervals. They FIGURE 5 FIGURE 6 3-5 min. Percentage of participants with perceivable color changes during dehydration and rehydration Percentage of participants with acceptable color changes during dehydration and rehydration 6 SULIMAN ET AL. concluded significant changes in the color of teeth occur after 10 min of CON F L I C T S OF IN TE RE S T S dehydration. Additionally, the tooth's original color had not returned to The authors have no financial interest in any of the companies whose baseline color within 30 min of rehydration, contrasting previous finding products are used in this study. and in agreement with the findings of the present study. Deficiencies of the previously mentioned studies include long time intervals. Ten-minutes intervals were used without the ability to specify exactly color change in a timely manner. Moreover, small sample sizes were used which may have significant effects on the outcome. A larger sample size, with greater diversity of age and gender, ORCID Taiseer A. Sulaiman https://orcid.org/0000-0002-3826-316X Vilhelm G. Olafsson https://orcid.org/0000-0002-9372-8003 could reveal a more complete picture regarding the dehydration/rehydration patterns. Senior patients may have reduced salivary flow, enhancing the dehydration effects on color and time, and also requir- RE FE RE NC ES ing longer time for the tooth to rehydrate and return to its original 1. Sproull RC. Color matching in dentistry. III. Color control. J Prosthet Dent. 1974;31:146-154. 2. Clark EB. An analysis of tooth color. J Am Dent Assoc. 1931;18:20932103. 3. Milleding P, Haag P, Neroth B, Renz I. Two years of clinical experience with Procera titanium crowns. Int J Prosthodont. 1998;11:224-232. 4. Bergman B, Nilson H, Andersson M. A longitudinal clinical study of Procera ceramic-veneered titanium copings. Int J Prosthodont. 1999; 12:135-139. 5. Sjogren G, Lantto R, Tillberg A. Clinical evaluation of all-ceramic crowns (Dicor) in general practice. J Prosthet Dent. 1999;81:277-284. 6. Haselton DR, Diaz-Arnold AM, Hillis SL. Clinical assessment of highstrength all-ceramic crowns. J Prosthet Dent. 2000;83:396-401. 7. Feller RL, Stenius AS. On the color space of sigfrid forsius, 1611. Color Eng. 1970;8:48-51. 8. Sharma G, Wu W, Dalal EN. The CIEDE2000 color-difference formula: Implementation notes, supplementary test data, and mathematical observations. Col Res Appl. 2004;30:21-30. 9. Judd DB, Wyszecki G. Color in Business, Science and Industry. 2nd ed. New York (NY): John Wiley & Sons; 1963. 10. Paravina RD, Ghinea R, Herrera LJ, et al. Color difference thresholds in dentistry. J Esthet Rest Dent. 2015;27(Suppl 1):S1-S9. 11. Munsell AH. A Color Notation. 11th ed. Baltimore (MD): Munsell Color Company Inc; 1961. 12. Russell M, Gulfraz M, Moss B. In vivo measurement of colour changes in natural teeth. J Oral Rehabil. 2000;27:786-792. 13. Burki Z, Watkins S, Wilson R, Fenlon M. A randomised controlled trial to investigate the effects of dehydration on tooth colour. J Dent. 2013;41:250-257. 14. Edlén B. The refractive index of air. Metrologia. 1966;2:71-80. 15. Meng Z, Yao XS, Yao H, et al. Measurement of the refractive index of human teeth by optical coherence tomography. J Biomed Opt. 2009; 14:034010. 16. Gilbert GH, Litaker MS, Pihlstrom DJ, Amundson CW, Gordan VV, DPBRN Collaborative Group. Rubber dam use during routine operative dentistry procedures: findings from the dental PBRN. Tex Dent J. 2013; 130:337-347. color. Rubber dam isolation was used in both studies for the dehydration process. As specified earlier, the time required for rubber dam placement may adversely affect the results. Ideally, longer time intervals for the rehydration color measurements would precisely predict when tooth rehydration would occur. This information is important for the clinician when missing the initial shade selection opportunity and would be suggested for further research. Another potential limitation of this study relates to the accuracy of the VITA Easyshade device. A positioning jig was fabricated ensuring repeatability when measurements are collected. In addition, the mean of three measurements per interval was calculated ensuring reliability. 5 | CO NC LUSIO N 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. ACKNOWLEDGMENTS The authors are sincerely grateful to Mr. Brandon Rodgers, Ms. Safa Aldali and Dr. Tariq Alsahafi for their laboratory support. We are also very thankful to Drs. Ceib Phillips and William Johnston for their statistical support. Thirty-two participants were recruited for this clini- How cal study that was conducted after approval of the institutional Olafsson VG, Delgado AJ, Donovan TE, Heymann HO. Effect review board (IRB) (16-1620). These Participants were selected of time on tooth dehydration and rehydration. J Esthet Restor among students and staff members at the School of Dentistry at Uni- Dent. 2019;1–6. https://doi.org/10.1111/jerd.12461 versity of North Carolina at Chapel Hill. View publication stats to cite this article: Suliman S, Sulaiman TA,
