Over-the-Counter Whitening Strips

Robert W. Gerlach, Britta E. Magnuson, and Gerard Kugel

INTRODUCTION

Whitening strips were introduced to the dental profession in 2000 (Gerlach 2000). The technology behind whitening strips is based on the use of a barrier (in this case, a flexible strip) that holds a peroxide-containing gel (see Figure 14.1). Developed as an easy-to-use option, these strips can be readily self-applied directly to the teeth daily for at-home whitening (see Figure 14.2).

Whitening strips have become a very popular over-the-counter choice for whitening teeth. Patients generally feel comfortable using strips and confident in their success. Since the introduction of these whitening strips, there have been numerous clinical studies on their efficacy and safety demonstrating significant whitening of teeth and minimal side effects (Garcia-Godoy et al. 2004, Swift et al. 2004, Farrell et al. 2008, Gerlach et al. 2009). Studies have generally shown significant whitening even after a few days of use, with the minor occurrence of adverse events mainly consisting of localized irritation or sensitivity (Gerlach et al. 2009).

The literature since the introduction of the strips in 2000 is quite broad. Color change (Swift et al. 2004), side effects and safety (Farrell et al. 2008), color retention (Swift et al. 2009), and special populations, including patients with tetracycline staining (Kugel et al. 2002), pediatric patients (Donly 2005), and patients with xerostomia (Papas et al. 2009), have all been studied. The studies have shown whitening strips to be both safe and effective.

CONSIDERATIONS FOR USE

INDICATIONS

Visible tooth discoloration in adults (general discoloration of any origin).

•  Intrinsic discoloration caused by aging (Gerlach and Zhou 2001).

•  Intrinsic discoloration associated with diet or tobacco use (Gerlach 2004).

Whitening needs in special groups.

•  Adolescents (Donly 2005).

•  Seniors (Gerlach and Zhou 2001).

Atypical tooth discoloration.

•  Mild, fluorosis-related white spots (Donly and Gerlach 2002).

•  Postorthodontic discoloration (Donly and Gerlach 2002).

•  Staining associated with long-term use of tetracycline (Kugel et al. 2011).

Cases in which other whitening approaches may be contraindicated.

•  Recession that could contribute to sensitivity during treatment (Gerlach et al. 2005a).

•  Cases in which cost or convenience is a factor (Gerlach 2000).

CONTRAINDICATIONS

General areas of caution.

•  Existing tooth sensitivity on the anterior facial teeth (compliance).

•  Use in young children (primary dentition).

Specific conditions that may affect outcomes.

•  Severely misaligned or crowded teeth (strip adaptation).

•  Isolated white spot lesions (possible need for microabrasion or restoration).

Preexisting or concurrent dentistry.

•  Fixed orthodontic devices on the anterior facial dentition (strip placement).

•  Extensive esthetic restorations on the anterior facial surfaces (unless replacement is planned).

ADVANTAGES AND DISADVANTAGES

There are obvious advantages and disadvantages to the use of whitening strips (Table 14.1). Strips are easy to obtain over the counter or from a dental professional and are easy to use at home (Gerlach 2000, 2007). Cost is likely to be considerably lower than either in-office or tray treatments, and the duration of use is short—anywhere from 5 minutes to 2 hours per day. Another important advantage to whitening strips is that there is less peroxide exposure than with other whitening treatments (Gerlach and Sagel 2004). The newest whitening strips also have the added advantage that patients are able to drink water while wearing the strips.

The primary disadvantage to whitening strips is that they may not be ideal for use in patients with severely misaligned or crowded teeth. Although whitening strips may be adapted to simple misalignment, use in more severe cases may not be optimal. Whitening strips primarily whiten the anterior teeth, which may be problematic for some smile types.

Finally, use may be initiated and completed without dental supervision—which potentially represents both an advantage and a disadvantage.

CASE TYPES AND SIDE EFFECTS

Clinical research demonstrates that whitening strips may be indicated for the most common case types, including intrinsic discoloration associated with chromogenic foods, smoking, and aging (Swift et al. 2004), and complex case types such as tetracycline staining (Kugel et al. 2002, 2011). Clinical research has also shown safe and effective whitening strip use by adolescents (Donly and Gerlach 2002, Donly 2005, Donly et al. 2006, 2007b) and by individuals with reduced salivary flow (Papas et al. 2009). Unlike trays, which may be contraindicated in patients with bruxism or temporomandibular joint problems (Robinson and Haywood 2000), whitening strips do not typically interfere with occlusion.

For tooth whitening in general, there are relatively few safety concerns with peroxide-containing whitening products (Mahony et al. 2006). The main side effects are transient tooth sensitivity and gingival irritation (Li 1996), which may affect up to two thirds of peroxide tray users (Haywood et al. 1994), and the custom tray alone (without peroxide) may contribute to some discomfort (Leonard et al. 1997). For whitening strips specifically, numerous clinical studies have established in-use safety (Garcia-Godoy et al. 2004, Swift et al. 2004, Farrell et al. 2008, Gerlach et al. 2009). Compared with the literature reports on peroxide-containing custom trays, the side effects with whitening strips are similar in nature but generally fewer in occurrence. For example, in one whitening strip study, side effects were confined to minor local irritation, involving 10% of subjects (Kugel 2004). Side effects (if any) were typically transient in nature, resolved during treatment, and were not different from placebo when evaluated head-to-head over a 12-month continuous-use period (Farrell et al. 2008).

Although many whitening strip applications have been evaluated in clinical trials, other uses are possible. Examples include cases of touch-up or follow-up care, or other specialized use situations (Table 14.2). Other applications are possible, but because the evidence may not include controlled clinical testing, the potential risks and benefits should be carefully evaluated.

PRODUCT DESIGN

Whitening strips were originally introduced in the United States by the Procter and Gamble Company (Cincinnati, OH) in 2000 under the brand name Crest Whitestrips. Subsequently, this technology has been modified through research and development and expanded to various geographic locations (sometimes under different brand names tied to Whitestrips) (Gerlach 2007). In total, there are approximately a dozen marketed variations of the Whitestrips technology that were designed to address different aspects of the desired whitening experience.

In general, there are three main variations of Whitestrips that may be encountered in the marketplace and/or the academic literature. All three rely on a common flexible barrier approach to maintain peroxide contact with teeth over a sufficient period for diffusion and intrinsic whitening (Table 14.3). In brief, the three major variations include (1) original strips, (2) very thin gel strips, and (3) high-adhesive strips.

ORIGINAL WHITENING STRIPS

The Whitestrips technology was introduced via a supplement to Compendium of Continuing Education in Dentistry. This 2000 supplement ambitiously characterized Whitestrips as a paradigm shift in vital whitening (Gerlach 2000). Therein, whitening strips were described as the first major discontinuity and technologic upgrade since the introduction of overnight, tray-based whitening over a decade earlier (Haywood and Heymann 1989). The original Whitestrips technology was a 9-μm polyethylene strip coated with approximately 0.2 g/cm² of an adhesive 5.3% hydrogen peroxide gel (Sagel et al. 2000). (Maxillary and mandibular strips had different shapes to account for the different arch forms, and each strip was packaged in a foil pouch.) The supplement described clinical and preclinical research establishing the safety and comparative efficacy of the original strips, along with some early research on the visualization of tooth color (Gerlach et al. 2000, Kugel and Kastali 2000, Odioso et al. 2000, Sagel et al. 2000, White et al. 2000). In clinical trials, these original strips demonstrated a whitening response similar to that of the well-known carbamide peroxide trays (Gerlach et al. 2000). With a higher peroxide concentration and extended treatment, these professional whitening strips showed a response superior to that of popular professional tray systems in clinical trials (Gerlach and Zhou 2001, Kugel et al. 2002) without appreciable effects on tooth surface hardness or surface or subsurface ultrastructural properties in laboratory studies (White et al. 2002).

VERY THIN GEL WHITENING STRIPS

Whereas original Whitestrips challenged conventional paradigms regarding peroxide delivery, the introduction of very thin peroxide gel strips in 2004 provided a new option to increase whitening effectiveness (Gerlach 2004). Previously, clinical research had established the relationship among peroxide concentration, treatment duration, and whitening response (Ferrari et al. 2004). As an alternative to increasing length of treatment, research was undertaken to assess use of higher peroxide concentrations via very thin gels—increasing concentration but not total dose—to yield faster whitening outcomes. This novel technology involved use of as little as 0.1 g of peroxide gel, which, when spread across a whitening strip, had a gel layer approximating the thickness of paper (see Figure 14.3). This allowed safe use of concentrations of 14% hydrogen peroxide—nearly two and one-half times the level in original whitening strips (Gerlach and Sagel 2004). Despite the much higher concentration, these novel very thin gel strips contained one half to one eighth the total peroxide used in popular overnight trays (Sagel and Landrigan 2004), enabling direct strip contact with gingival tissue without additional oral irritation. Clinical research described outcomes versus various positive and negative controls, showing tooth whitening within a few days as a result of higher peroxide contact (Garcia-Godoy et al. 2004, Swift et al. 2004, Gerlach and Zhou 2004b). In an important head-to-head clinical study, the higher concentration strips showed superior whitening to the original strip (a differential concentration effect), without added oral irritation (an equivalent dose effect), thereby confirming the usefulness of this very thin gel approach (Gerlach and Sagel 2004). Other studies extended the evidence on very thin peroxide gels to different concentrations, including numerous studies involving 10% hydrogen peroxide strips (Gerlach et al. 2004b, 2005b, Shahidi et al. 2005), integrated analyses of studies involving 14% hydrogen peroxide (Gerlach and Barker 2004), and other research assessing the use of this very thin gel technology in special populations (Donly and Gerlach 2002, Donly et al. 2005, Papas et al. 2009).

HIGH-ADHESIVE WHITENING STRIPS

The most recent innovation involved a highly adhesive, peroxide-containing gel to enable improved retention of whitening strips during use. Increased retention (relative to the original strips) was obtained through use of polymers that offer unique adhesive and cohesive properties. Although these newest strips generally looked and functioned like the previous versions, the high-adhesive strips offered two clear improvements: better retention during use and clean removal after use (see Figure 14.4). Numerous positively controlled clinical studies have been conducted. Two recent examples are noteworthy: one study compared a 9.5% hydrogen peroxide high-adhesive strip with an earlier variant in a study conducted among adolescents (Donly et al. 2010), and another showed comparable effects to professional tooth whitening (Perry et al. 2013). Clinically, the increased retention with high-adhesion technology has enabled longer wearing times, especially on the mandibular arch, extending use well beyond 30 minutes.

PRODUCT USE

All three whitening strip technologies employ a common, easy-to-use approach for strip application and removal, as demonstrated in Figures 14.5A–E. In brief:

•  Strip (and plastic backing liner) is removed from its foil pouch.

•  Strip with peroxide gel is separated from plastic backing liner (which is discarded).

•  Strip is applied with the peroxide side toward the facial anterior teeth (and adjacent gingiva).

•  Strip is folded over incisal edge and gently pressed into place for use.

During use, whitening strips deliver peroxide for a sustained period (Sagel et al. 2000). Research on peroxide pharmacokinetics shows relatively high sustained peroxide concentrations on tooth surfaces with each of the three strip types (Gerlach et al. 2004a, Gerlach et al. 2008, Farrell et al. 2009), whereas in contrast, salivary concentrations (a measure of systemic exposure) remain trivial (see Figures 14.6A and 14.6B). Tooth and salivary concentrations drop below the level of detection on removal.

Whitening onset may be visible after the first application. Although both arches may be treated simultaneously, single-arch application (typically starting with the maxillary arch) may aid visualization and support compliance during strip use. Alternatively, comparing pretreatment and post-treatment photographs or shade tabs may be useful in communicating outcomes (see Figure 14.7).

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