COMPARISON OF TOOTH BLEACHING RESULTS

Brian Millar

VITAL TOOTH BLEACHING

Tooth bleaching is considered to be the treatment of choice for discolored teeth, provided the patient has realistic expectations and the teeth are acceptably shaped and intact. Tooth bleaching is noninvasive and less expensive than porcelain or composite veneers. It also has a place as a prerestorative treatment before other noninvasive esthetic procedures such as edge bonding and after tooth realignment. However, it can be unpredictable in outcome, particularly in the longer term as color regression occurs.

METHODS

The main bleaching techniques are as follows:

1.  Dentist-administered bleaching—in-office bleaching using high-concentration hydrogen peroxide or high-concentration (e.g., 35%) carbamide peroxide.

2.  Dentist-provided and patient-applied bleaching—home bleaching or Nightguard Vital Bleaching (NGVB) using lower concentrations, typically 10–22% carbamide peroxide or 1–10% hydrogen peroxide.

3.  Over-the-counter (OTC) products—these products typically contain low levels of bleaching agent (e.g., 3–8% hydrogen peroxide) that are self-applied to the teeth via gum shields, strips, paint-on products, or toothpaste.

IN-OFFICE VITAL TOOTH BLEACHING TECHNIQUES

In-office vital bleaching is usually performed using high concentrations (35–37%) of hydrogen peroxide in conjunction with heat and/or light (Haywood 1998), often referred to as “power bleaching.” Activation can be by halogen curing lights, light-emitting diodes (LEDs), diode lasers, argon lasers, and plasma arc lamps. The advantage of this method for the patient is questionable, because the more rapid color change observed is largely a result of dehydration, but the disadvantages of in-office bleaching are significant:

1.  The caustic nature of the 35–50% hydrogen peroxide, with the potential for soft tissue damage to patient and provider.

2.  The discomfort of the rubber dam and drying of the oral cavity during treatment, and higher incidence of pain after treatment.

3.  The effect of temperature on the pulp and the resultant post-treatment sensitivity.

4.  If etching is performed, polishing is required after each visit, with some enamel loss (Leonard et al. 1998).

5.  The treatment time required, which makes this procedure more expensive than home bleaching.

6.  The unpredictable nature of the result and greater risk of irreversible damage (see Figure 18.1).

7.  The unknown duration of the treatment (Ritter et al. 2002).

8.  Significant and rapid relapse and the need to repeat the entire procedure.

TRAY-APPLIED BLEACHING

Originally termed Nightguard Vital Bleaching (Haywood and Heymann 1989), this type of bleaching typically involves the application of a 10% carbamide peroxide solution in a custom-fitted nightguard for 6–8 hours at night. Nowadays, shorter bleaching cycles can be used to avoid overnight wear, and hence home bleaching is a more accurate term. Results are typically seen in 2–3 weeks, and the final outcome is complete in 5–6 weeks (Haywood 1998). Some patients prefer daytime wearing of the tray, which has the advantage of more frequent replenishment of the bleaching gel for maximum bleaching effect (Dunn 1998).

Advantages of at-home vital tooth bleaching include a lower cost to patient and clinician with minimal in-office chair time, less post-treatment discomfort, a high percentage of successful treatments, and ease of touch-up re-treatments at low cost. However, the disadvantage with home bleaching is poor compliance because the procedure takes weeks to complete.

COMPARISON OF CARBAMIDE PEROXIDE AND HYDROGEN PEROXIDE

Bleaching with carbamide peroxide differs from use of hydrogen peroxide (Haywood 2006a) because hydrogen peroxide breaks down in minutes into a perhydroxyl free radical (HO₂) and then into H₂O + O₂ (Zantnera et al. 2007). On the other hand, carbamide peroxide breaks down into urea and hydrogen peroxide, which then follows the same path. A 10% carbamide peroxide solution is equivalent to 3.5% hydrogen peroxide and 6.5% urea. The effect of the urea is partly to increase the pH during treatment and give the bleaching medium a longer period of release of peroxide (Haywood 2006b). The urea also converts to carbon dioxide and ammonia, which further raises the pH to facilitate bleaching, explaining why carbamide peroxide is more effective than hydrogen peroxide (Goldstein and Garber 1995).

COLOR REGRESSION AFTER IN-OFFICE BLEACHING

Several in vitro and in vivo studies have demonstrated the efficacy of in-office bleaching procedures with various concentrations of hydrogen peroxide or carbamide peroxide. However, although immediate effects after bleaching were good, color stability was poor. Rosenstiel et al. (1991) measured color and its stability after a single 30-minute session of in-office bleaching with 35% hydrogen peroxide activated with light. The initial color change decreased considerably shortly after treatment, with more than half the color change reversed 1 week after bleaching. Further relapse reduced the color change to only 28% of the original change by 6 to 9 months. Interestingly, repeated in-office bleaching did not significantly increase the immediate or long-term bleaching result (Rosenstiel et al. 1991b).

Gottardi et al. (2006) showed that the number of in-office treatments using 35% hydrogen peroxide with light may influence patients’ satisfaction and color retention. One to four sessions were performed and each session resulted in improvement of 2.1 to 3.7 Vita shade units. A significant color relapse, typically of two units, was observed at the 2-week postbleaching evaluation. Not surprisingly, more relapse was recorded for the patients who had fewer bleaching sessions.

Tooth dehydration associated with in-office treatment could lead to false evaluation of the actual shade change; the new shade regresses quickly as teeth rehydrate (Jones et al. 1999). Kugel et al. (2006) showed greater rebound with a light-activated product than a chemically activated gel despite greater initial color improvement. To allow rehydration of teeth, Al Shethri et al. (2003) postponed color evaluation until 1 week after bleaching. The results showed that relapse began after the bleaching treatments were finished and continued until the fifth week, after which no further significant changes appeared. Other studies have shown similar relapse patterns wherein the color stabilized by 6 weeks at a level still significantly different from the baseline color (Matis et al. 2007).

ACTIVATION METHOD

An evaluation of eight different in-office light-activated products with hydrogen peroxide concentrations of 15–35% found no statistical differences among groups (Matis et al. 2007). As in other reports, there was a significant bleaching immediately after treatment, followed by a sudden drop by week 1 with a mean reversal of 51% of the original gain. This increased to a 65% reversal by 6 weeks after bleaching. Although the sample size was small, the pattern among all the products was similar, with sudden improvement followed by a significant relapse. Fortunately for most products the relapse is to a final color that is lighter than the original.

In a comparison among (1) 25% hydrogen peroxide gel with light enhancement, (2) hydrogen peroxide gel alone, and (3) light alone with no peroxide, improved bleaching was observed when the light was used, but the color rebound was extensive in all groups, with 41–51% of initial gains lost over 30 days (Kugel 2009). This study showed that light activation increased in-office bleaching although the magnitude of the color improvement was relatively small and the improvement was followed by extensive relapse.

Tavares et al. (2003) showed that on average the peroxide-and-light treatment resulted in significantly greater color change (over eight shades) than peroxide alone (under six shades) in shades taken immediately after treatment by one examiner using a shade guide only. However, this is unlikely to be observed after the inevitable rebound has taken place and indicates the importance of measuring shade at least 1 week after bleaching. Also, the accuracy and validity of measuring by a single operator using a shade guide has to be questioned.

Marson et al. (2008) found no statistically significant differences observed with or without the use of a curing light in relation to color change after in-office bleaching treatment. There was a slight color relapse after 6 months, but there were no statistically significant differences between the groups.

Another study reported no statistical difference between results obtained with light irradiation and those obtained without light and proposed that the use of a light source should be considered optional for this technique when using high-concentration hydrogen peroxide (Bernardon et al. 2010). An evaluation of the efficacy of two bleaching agents (35% hydrogen peroxide and 37% carbamide peroxide) with a range of light sources (halogen lamp and plasma arc lamp, LED/diode laser, argon laser) and no light source in a short in vitro study showed that carbamide peroxide significantly differed from hydrogen peroxide and was less effective in color change but provided a more stable outcome (Lima et al. 2009).

COLOR REGRESSION AFTER NIGHTGUARD VITAL BLEACHING

The substantial increase in color value (lightness) and decrease in chroma observed directly after bleaching is often followed by a decrease in bleaching, indicating that the initial bleaching effect is not stable (Wiegand et al. 2008). Initial color relapse can occur because the residual peroxide in the tooth changes its optical qualities (Haywood 2000), then further color regression toward baseline shades can occur (Wiegand et al. 2008). Shade regression is a common problem that can be affected by a number of factors including the bleaching agent, method and duration of treatment, initial color, and cause of discoloration (Burrows 2009).

The process of color reversion toward darker shades is poorly described but is suspected to be the opposite of the bleaching events (Heymann et al. 1998). Some previously oxidized substances may become chemically reduced and so cause the tooth to return to the original discoloration. Also, the enamel may become remineralized with the staining molecule of the original systemic stain (Lyons and Ng 1998). This has been correlated with the presence of the remineralization processes within the tooth tissue (Li et al. 2010). In addition, external chromogens (coffee, wine, nicotine, metallic ions) might contribute to the color regression of bleached teeth. An in vitro study (Berger et al. 2008) suggested that 35% hydrogen peroxide promoted alterations in the enamel surface, which increased wine staining susceptibility up to 1 week after the bleaching when compared with unbleached enamel surfaces. Figure 18.1 illustrates an extreme example of this.

NIGHTGUARD VITAL BLEACHING WITH 10% CARBAMIDE PEROXIDE

This simple technique is popular for bleaching teeth both as a definitive treatment and before reshaping with composite resin (see Figure 18.2). Note that bleaching alone (see Figure 18.2B) does not improve the overall esthetics of the smile because the extreme “white” accentuates the contrasting shape and space defects, the “black” components. Retaining some natural color in the teeth and providing shape correction provides a more natural esthetic appearance (see Figure 18.2C). Even after many years of service, this completely noninvasive therapy looks acceptable (see Figure 18.2D) with no damage to the teeth or surrounding tissues, unlike most esthetic treatments.

Gels vary in efficacy, and one study (Cibirka et al. 1999) that compared two 10% carbamide peroxide gels overnight for 2 weeks found statistically significant lightening for both products (90% and 93% lightening) after 1 week of treatment. A study investigating 3 weeks of overnight bleaching resulted in significant lightening in 96% of the tested group immediately after treatment, and the improvement in lightness was maintained for 6 months in 88% of this group (Dos Santos Medeiros and de Lima 2008). Only 4% of participants had a one-unit reduction on the Vita classical shade guide from day 21 to day 30, and only 12% color reversal was observed at 6 months. It was concluded that NGVB was effective for lightening tooth color both for the period immediately after treatment and for the 6-month follow-up period, with no difference observed in the tooth color immediately after bleaching and after 30 days.

Immediate results are usually impressive, and in some studies all patients had at least a two-shade lightening effect when evaluated immediately after the 2 weeks of bleaching (Swift et al. 1997). However, some loss of the bleaching effect was observed in time, with 97% and 89.6% of patients having teeth lighter than at baseline at the 3-month and 6-month reviews, respectively.

Most studies have reported that color stabilization takes a few weeks, and so studies that record the final shade immediately after the bleaching period will obtain falsely optimistic results. Color relapse begins after bleaching treatment is completed and continues until the sixth week, after which it tends to remain stable for 3 months (Zekonis et al. 2003). Other studies report that color relapse after at-home treatment occurs mainly during the first month after bleaching (Matis et al. 1998). The colors at weeks 6, 12, and 24 were not significantly different from one another, which shows that the main color loss occurred between weeks 2 and 6 of the study.

The type of tooth and the initial tooth color appear to influence the relapse: the yellower the teeth at baseline, the greater the magnitude of the bleaching response (Matis et al. 1998). Canine teeth are usually more chromatic than the adjacent lateral incisors, which can be a concern in some patients in whom the contrast is marked (see Figure 18.3).

Canines show significantly greater color changes immediately after bleaching compared with incisors (Gegauff et al. 1993). However, greater initial bleaching effects often result in greater color relapse. After 5 days of bleaching in a group of 20 young patients, the canines showed the greatest color change (Gegauff et al. 1993). Most of the color relapse occurred by 1 week after treatment, with little difference between 1-month and 3-month measurements, indicating that the color had stabilized. Rosenstiel et al. (1996) conducted a 6-month study in a larger group of older subjects and found that the greatest color change was obtained after 1 week for the canines. The older patients showed less bleaching but also less color reversal. This is in agreement with others, who have reported higher levels of color change for canines than for lateral and central incisors at all points after treatment (Gegauff et al. 1993). Initial color regression occurred sooner for incisors (4 weeks) and took longer for canines (10 weeks), but neither regressed back to baseline for the duration of this 6-month study. Color can therefore be considered to have stabilized by 4 weeks after treatment in incisor teeth and by 10 weeks after treatment in canine teeth.

A particular problem is managing the missing lateral incisor tooth when the canine color is particularly dark (see Figure 18.4). Single-tooth color correction can easily be achieved through the use of a 10% carbamide peroxide gel on a single tooth (Millar 1994).

TOUCH-UPS

Longitudinal studies report satisfactory shade retention once the color stabilizes after the initial relapse. In addition, rebleaching may improve shade stability after active treatment. Among studies, controversy exists over the time period necessary before rebleaching.

Grobler et al. (2010) found that 10% carbamide peroxide used for a period of 14 days provided significant esthetic results for up to 6 months after bleaching. It was suggested that rebleaching after 6 months is not necessary but should be carried out about 14 months after treatment. Better color retention was reported in another small study at 2 years after the initial bleaching treatment (Swift et al. 1999). Although some relapse from the original lightening effect occurred, the median shade measured at 2 years was the same as that measured at 6 months after bleaching. This is in agreement with Small (1994), who indicated that the longevity of the bleaching effect seems to be acceptable and maintained well for 18 months with little or no relapse.

Leonard et al. (2001) reported that 10% carbamide peroxide was effective in lightening teeth in 98% of the patients, with this effect being sustained for 47 months after treatment in 82% of the participants. Leonard et al. reported that 92% of the participants in the active group had at least a two-shade change from baseline after 2 weeks of treatment, whereas at 6 months after treatment 88% still showed at least a two-shade change. At least 82% of the combined group had a two-shade change from baseline 47 months after treatment. Six of the participants had re-treated their teeth at 32 months.

Leonard (2000) stated that 42% of the patients, who had not had additional treatment during the post-treatment period, were satisfied with the shade of their teeth at approximately 7 years after treatment. No patient felt that the teeth had regressed to the original shade. Another study reported shade stability in 43% of the participants at approximately 10 years after treatment (Ritter et al. 2002).

It should be noted that in many studies the data on shade stability were collected from the participants’ responses and so accuracy could be questionable. Although many participants indicated no change in color, the actual color might have relapsed after the original treatment.

NIGHTGUARD VITAL BLEACHING WITH DIFFERENT CONCENTRATIONS OF CARBAMIDE PEROXIDE

Several studies compared the efficacy and shade stability after bleaching with different carbamide peroxide concentrations in a tray system, and different findings were reported. Some studies reported faster color changes with higher concentrations of carbamide peroxide (Leonard et al. 1998).

In a comparison of 10% carbamide peroxide and 17% carbamide peroxide, noticeable changes of shade values were observed after 3 days in the 17% group and after 7 days in the 10% group. After 1 week, in both the 17% group and the 10% group, values for lightness and chroma were significantly different from the control with no statistical difference between the test groups. Two weeks after treatment, a rebound of shade values was observed in both test groups, with a statistically significant decrease in the values for lightness and chroma. Because there was a similar decrease in the 17% group and in the 10% group, final values did not differ. Major changes in shade values were found for canines as reported earlier in this chapter. Figure 18.3 shows a typical outcome for canines. Changes in lightness, chroma, and hue in canines were statistically different from those observed for incisors at each assessment after treatment.

A study comparing 10% carbamide peroxide and 15% carbamide peroxide over 4 weeks found that the difference in shade change from baseline between the two groups (10% and 15% carbamide peroxide) after 1 week of treatment was nonsignificant (Kihn et al. 2000). However, continuation of treatment for a week more revealed a significant difference in the two groups at the end of active treatment (2 weeks) and at the 2-week post-treatment evaluation. The 15% product was associated with significantly more color change than the 10% product (mean ± standard deviation [SD], 9.4 ± 2.3 and 7.7 ± 3.0, respectively). There was no color relapse observed at the end of active treatment or at the 2-week post- treatment evaluation in both groups.

However, the decision to perform the final color evaluation immediately after treatment or to wait 2 weeks is debatable. In studies that included postbleaching color evaluations after the teeth had an adequate time for color rebound, there were no significant differences in efficacy between lower and higher concentration products at the final evaluation, but different rates of color relapse can be observed (Browning and Swift 2007). Matis et al. (2000) reported color relapse for both 10% and 15% concentrations of carbamide peroxide as soon as subjects discontinued use of the bleaching material, with 15% showing greater relapse at 2 and 6 weeks; by the end of the study they reached almost identical values as in the 10% group. Although the post-treatment evaluation period in both studies was short, longer clinical trials of both concentrations seem to be in agreement with these findings.

Meireles (2008) conducted a clinical trial to evaluate two custom tray bleaching systems (10% and 16% carbamide peroxide) at 1 week after 3 weeks of active bleaching (Meireles 2008), at 6-month follow-up (Meireles et al. 2008), and at 1-year follow-up (Meireles et al. 2009). The studies also investigated aspects related to participants’ diet and oral hygiene behaviors to evaluate their influence on the longevity of the bleaching effect of the bleaching treatment. The results of the study 1 year after bleaching showed that the teeth in both treatment groups remained at least 5.7 Vita classical shade guide units lighter than at baseline. Although the participants treated with 16% carbamide peroxide had median tooth shade values lower than those in the 10% carbamide peroxide group at the 1-week and 6-month evaluations, this difference was not present 1 year later. The bleaching effect obtained 1 week after bleaching was maintained in the 10% carbamide peroxide group but was decreased in the 16% carbamide peroxide group.

DIFFERENT CONCENTRATIONS OF CARBAMIDE PEROXIDE AND HYDROGEN PEROXIDE DURING DAYTIME USE

Most studies have agreed that the faster the rate of bleaching, the greater the relapse and the longer the time for the color to become stable. One study found that 20% carbamide peroxide demonstrated faster and greater color change compared with 7.5% hydrogen peroxide during a 2-week bleaching period (Mokhlis et al. 2000). Results obtained using a colorimeter also indicated that for both products, lightness increased rapidly during the first week and continued to increase at a slower rate through the second week. Both products exhibited relatively fast color relapse during the third week of the study. Color relapse continued at a slower rate until 6 weeks (4 weeks after bleaching), after which there was no significant change for either product. The teeth in the 20% carbamide peroxide group reflected color relapses at a higher rate than that for teeth in the 7.5% hydrogen peroxide group during the first 4 weeks after bleaching was discontinued. Use of the 20% carbamide peroxide resulted in significantly more lightness than the 7.5% hydrogen peroxide during the first 14 days of the study, but at the end of the study there was no significant difference between the two products.

EFFECT OF TRAY DESIGN

An evaluation of the effect of tray design on degree of color change using 15% carbamide peroxide suggested that trays with reservoirs had significantly higher amounts of color change initially than trays without reservoirs; however, the reservoir group then showed relapses at a higher rate when compared with the non-reservoir group, with no significant clinical difference (Matis et al. 2002a), in agreement with the findings of others (Javaheri and Janis 2000).

HIGH-CONCENTRATION CARBAMIDE PEROXIDE

Türkün et al. (2010) compared daytime at-home bleaching (28% carbamide peroxide) with the overnight application of 10% carbamide peroxide. The overnight application of 10% carbamide peroxide revealed a greater bleaching response immediately after treatment, and this difference remained significant at 1 year after treatment. Surprisingly, no significant difference was detected between post-treatment and 1-year follow-up. The bleaching effect remained similar 1 year after the bleaching treatment for both at-home bleaching systems, with little relapse occurring during this time, which suggests that touching up was being carried out.

The use of 35% carbamide peroxide in a close-fitting tray fitted by the clinician gives a useful low-cost option to boosting an NGVB regimen during treatment. An in vitro study (Patel et al. 2008) showed this material to be highly effective, and this can be used for single or multiple teeth.

NIGHTGUARD VITAL BLEACHING FOR SPECIFIC COLOR PROBLEMS

Bleaching works particularly well for teeth with a yellow hue (Ishikawa-Nagai et al. 2004). Treatment is less successful in teeth with a yellow-gray tone, and even less with a gray color. Particularly difficult are teeth with a brown-yellow color (Seale and Thrash 1985). For blue-gray stains the prognosis is probably the worst owing to poor bleaching and more frequent and faster relapse (Christensen 1998). Reports of color improvement in teeth having deep dentinal discoloration, such as tetracycline staining or brown staining from dentinogenesis imperfecta, reveal that some degree of color correction is possible and that persistence is the key to success (Haywood 1997). Studies report that longer active treatment is usually followed by a longer color relapse. Figure 18.5 illustrates the outcome of a 10-week regimen for a tetracycline case.

Haywood showed that bleaching with 10% carbamide peroxide in a custom-fitted tray for an extended period of 6 months produces variable amounts of lightening on tetracycline-stained teeth (Haywood et al. 1997). Stable color has been seen in 84% of the teeth treated at the 1-year recall without touch-ups. Most color relapse occurred in the first 6 months after treatment.

Leonard et al. (1999) conducted a longitudinal study to determine the color stability and patient satisfaction after 6 months of active treatment of tetracycline-stained teeth with 10% carbamide peroxide. Eighty-five percent of patients reported no obvious change at 6 and 12 months after treatment. At 54 months after treatment, at least 83% of the participants perceived no obvious change in tooth color or only a slight darkening from immediately after treatment. This had dropped to 60% at the 90-month post-treatment appointment. In this study, no one thought that the shade of his or her teeth was back to the original shade at any time point.

Matis et al. (2002b) compared the effectiveness of 6 months of overnight bleaching with different concentrations (10%, 15%, and 20% carbamide peroxide) in treating tetracycline discoloration. Tooth color changed rapidly in the first month and at 3 and 9 months. Although color lightening continued through 24 weeks for all three products, the teeth bleached with 10%, 15%, and 20% concentrations attained 54%, 60%, and 62% of the maximum lightness, respectively, after 1 month of bleaching.

The color change stabilized 2 months after bleaching for teeth treated with the 10% carbamide peroxide and 1 month after bleaching for teeth bleached with 15% carbamide peroxide. The color change had not stabilized by 3 months after bleaching for teeth treated with 20% carbamide peroxide. At 4.5 years after bleaching (Matis 2006), teeth treated with all three concentrations of bleaching agents had retained more than 65% of their original color change (the 10%, 15%, and 20% concentrations had retained 68%, 67%, and 66% of the total color change, respectively). In summary, it seems that those who bleach to remove stain caused by tetracycline might need to rebleach within 5 years.

White spots can also be managed through the use of tooth bleaching to reduce the color contrast (see Figure 18.6).

COMPARISON OF IN-OFFICE BLEACHING VERSUS NIGHTGUARD VITAL BLEACHING

Matis et al. (2007) reported that some in-office products lightened teeth immediately to the same degree after bleaching as occurs with at-home tray-based bleaching agents, but the color reversal in most of the products occurred more rapidly than was found in at-home tray-based bleaching products. Many opinion leaders agree that the efficacy of in-office bleaching is not as favorable as at-home bleaching treatment.

In a study by Zekonis et al. (2003), at 2 weeks the average ΔE (a measure of color change) reached 12.32 for at-home treatment and 5.32 for in-office treatment. For both groups the color relapse began after bleaching treatments were finished and continued until the sixth week. By 6 weeks, ΔE had decreased to 6.64 for at-home treatment and as low as just 3.63 for in-office treatment. In-office treatment color change and color relapse occurred at a lower rate compared with the at-home treatment. Color stabilized by 6 weeks for both at-home and in-office treatments at a level significantly different from baseline and between the treatments. In addition, 84% of the subjects reported the at-home treatment to be more efficient. None of the subjects reported the in-office bleaching treatment to be superior to the at-home bleaching treatment.

Similar observations were reported by Gottardi et al. (2006). Among patients who had two or three in-office appointments and were recorded as satisfied, 24 asked for at-home bleaching treatment. This indicated that even though results could be seen in one appointment for patients who had lighter teeth, more appointments were necessary to improve shade stability. These results agree with the findings of some researchers who have stated that teeth need more bleaching to achieve stabilization of shade (Goldstein and Garber 1995, Al Shethri et al. 2003).

An in vitro study comparing the different treatments showed that 10% carbamide peroxide was significantly more effective than all other treatments except 35% hydrogen peroxide with halogen activation (Patel et al. 2008). The effect of each treatment regimen over time showed that 10% carbamide peroxide gave a significant gain immediately and 1 week later; however, all the bleaching effects were lost over time after these single treatments.

IN-OFFICE BLEACHING FOLLOWED BY NIGHTGUARD VITAL BLEACHING

To promote better color stability, the use of both in-office and at-home treatments has been recommended (Matis et al. 2009b). This is based on the understanding that in-office bleaching lightens teeth rapidly but is followed by a considerable relapse within 2 weeks of bleaching. In contrast, at-home bleaching usually requires several weeks of treatment but is followed by less reversal.

Bernardon et al. (2010) found that the technique associating one session of in-office bleaching with the home bleaching technique obtained higher ΔE values at the 1-week period only. After the second week, ΔE obtained for the hemi-arches bleached with this combination were not statistically different from ΔE obtained for teeth bleached using custom trays with 10% carbamide peroxide. Both techniques in this group presented color stability for up to 16 weeks. It has been shown that one session of in-office bleaching associated with home bleaching does not influence the maintenance of color with time.

The combination of in-office and at-home bleaching treatments has been reported as responsible for dramatic changes in tooth shade (Matis et al. 2009a), although there are no long-term studies of its efficacy. Figure 18.2 shows an example of this. The combination of 10% carbamide peroxide at home for 3 days after in-office 35% hydrogen peroxide gel resulted in 8.5 shade changes, and use of in-office 38% hydrogen peroxide gel resulted in nine shade changes. Both treatments resulted in an average shade rebound of two shades at 7 days after bleaching cessation.

In-office tooth bleaching followed by at-home bleaching with trays has been shown to be significantly more effective than in-office bleaching without at-home bleaching (Matis et al. 2009b). A review of nine published studies comparing the effectiveness of overnight, daytime, in-office, and OTC bleaching methods using meta-analysis showed that ΔE* values were 9.7 and 6.6 for overnight and daytime bleaching groups immediately after treatment (Matis et al. 2009a). Ten weeks after treatment the ΔE* value was 4.7 for the overnight bleaching group and 3.4 for the daytime bleaching group. For in-office bleaching the ΔE* value was 5.4 immediately after treatment and 2.1 10 weeks after bleaching. This favors the use of at-home bleaching over in-office bleaching, particularly when trays can be worn overnight.

CONCLUSION

The popularity of tooth bleaching has resulted in a dramatic rise in the number of bleaching products and procedures. Despite claims made in advertising, the scientific literature supports the use of at-home techniques (Table 18.1). Most studies have indicated that color improvement should be determined at least 2 weeks after the termination of active treatment and possibly as long as 6 weeks with higher concentrations of materials. This delay allows the oxygen generated from bleaching to dissipate from the tooth and avoids the misinterpretation of the effect of dehydration as true bleaching. Many commercials measure color too early and quote erroneous data.

Bleaching with carbamide peroxide is followed by a color relapse in 4 to 6 weeks, and this time differs for different concentrations. Higher concentrations have demonstrated faster and greater color change initially but also longer and greater color rebound. The color usually stabilizes by 6 weeks at a level still significantly different from baseline, but the reversal can reach 65% 6 weeks after bleaching.

Light use during in-office procedures does not seem to improve the longevity of bleaching. It was observed that the immediate change in the light-activated material seemed to be related to the dehydration effect of the isolation and heat of the light rather than any improvement in bleaching efficacy. There is a noticeable lack of studies showing benefit of the in-office techniques over at-home methods.

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