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J Am Dent Assoc, Vol 139, No 7, 915-924.
© 2008 American Dental Association |
CLINICAL PRACTICE |
A Systematic Review of the Literature
| ABSTRACT |
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Types of Studies Reviewed. The authors included clinical studies that examined the efficacy of casein derivatives in dentistry. They excluded in vitro studies, case series, case reports, letters to editors (not containing primary data), editorials, review articles and commentaries, but read them to identify any potential studies.
Results. The authors searched 98 articles for relevance, determined according to title, abstract and full text, resulting in a yield of 12 original studies. Nine were clinical trials that focused on caries prevention, seven of which showed that CPP-ACP (as found in sugar-free pellet or slab chewing gum, lozenges, milk or mouthrinse) was effective in preventing dental caries by remineralizing subsurface carious lesions in situ in a dose-response fashion. One was a clinical trial with conflicting results regarding the effect of CPP-ACP on the regression of white-spot lesions; one was a survey of the relief of dry-mouth symptoms; and one was an uncontrolled clinical study that showed the lack of effectiveness and lack of short-term therapeutic effect in treating dentin hypersensitivity.
Clinical Implications. The quantity and quality of clinical trial evidence are insufficient to make conclusions regarding the long-term effectiveness of casein derivatives, specifically CPP-ACP, in preventing caries in vivo and treating dentin hypersensitivity or dry mouth.
Key Words: Anticariogenicity; casein derivative; casein phosphopeptide–amorphous calcium phosphate; remineralization; demineralization; systematic review
Abbreviations: CaCO3: Calcium carbonate CaHPO4/CaCO3: Calcium hydrogen phosphate/ calcium carbonate CD-CP: Casein derivatives coupled with calcium phosphate CPP-ACP: Casein phosphopeptide–amorphous calcium phosphate FDA: Food and Drug Administration NaF: Sodium fluoride RCT: Randomized controlled trial WSL: White-spot lesion
Casein is the predominant phosphoprotein in bovine milk and accounts for almost 80 percent of its total protein, primarily as calcium phosphate stabilized micellular complexes.1 Several laboratory and animal experiments2–9 have investigated the low cariogenic potential and the possible cario-static activity of dairy products (milk, casein, caseinates and cheeses). Casein phosphopeptides (CPP) contain the cluster sequence of -Ser (P)-Ser (P)-Ser (P)-Glu-Glu from casein.10,11 Through these multiple phosphoseryl residues, CPP can remarkably stabilize calcium phosphate (which usually is highly insoluble) in a state-forming CPP-amorphous calcium phosphate (ACP) complex.12,13 This complex is a nanocluster of ACP with four multiphosphorylated peptides that prevent its growth to the critical size required for nucleation, phase transformation and precipitation.13,14
On the basis of the generally accepted molecular formula for ACP [Ca3 (PO4)2 - nH2O], ACP also may be considered a tricalcium phosphate. There is no conclusive evidence that ACP is an integral mineral component in hard tissues. It likely plays a special role as a precursor to bioapatite and as a transient phase in biomineralization. In solutions, ACP is converted readily to stable crystalline phases such as octacalcium phosphate or apatitic products.15
The CPP-ACP complex was patented by the University of Melbourne, Australia, and the Victorian Dairy Industry Authority, Abbotsford, Australia. Bonlac Foods Limited (an Australian company owned by 2,300 dairy farmers in Victoria and Tasmania) has exclusive manufacturing and marketing rights for CPP-ACP and is the owner of the trademark (Recaldent). In early 1999, the U.S. Food and Drug Administration (FDA) accepted Recaldent as "generally recognized as safe" for its intended use as a texturizer in chewing gum (Trident White, Cadbury Adams USA, Parsippany, N.J.) at up to 5 percent weight per weight.16
The FDA has approved products marketed in the United States (MI Paste and MI Paste Plus containing 900 parts per million fluoride, GC America, Alsip, Ill.) for use primarily as abrasive prophylaxis pastes and secondarily for the treatment of tooth sensitivity (after in-office bleaching procedures, ultrasonic scaling, hand scaling or root planing). However, its use for remineralizing dentin and enamel and preventing dental caries is an off-label application.17 Outside the United States, the products are marketed as GC Tooth Mousse and Tooth Mousse Plus (GC Europe N.V., Leuven, Belgium).
Reynolds and colleagues12,24 reported that CPP-ACP binds readily to the surface of the tooth, as well as to the bacteria in the plaque surrounding the tooth. In this way, CPP-ACP deposits a high concentration of ACP in close proximity to the tooth surface. The authors proposed that under acidic conditions, this localized CPP-ACP buffers the free calcium and phosphate ions, substantially increasing the level of calcium phosphate in plaque and, therefore, maintaining a state of supersaturation that inhibits enamel demineralization and enhances remineralization.
Several laboratory and animal experiments have demonstrated the anticariogenic potential of CPP-ACP. In a group of specific-pathogen-free rats inoculated with Streptococcus sobrinus, Reynolds and colleagues25 applied CPP-ACP solution to the animals molar teeth twice daily. They found that the caries activity of the enamel smooth surfaces was reduced significantly in a dose-response fashion (0.1 percent and 1.0 percent weight per volume CPP-ACP, respectively, produced a 14 percent and a 55 percent reduction in smooth-surface caries activity). The authors found a similar reduction in the caries activity of fissures (0.1 percent and 1.0 percent w/v CPP-ACP, respectively, produced a 15 percent and a 46 percent reduction in fissure caries activity).
In an in vitro study, Reynolds26 demonstrated that CPP-stabilized calcium phosphate solutions maintained high concentration gradients of calcium and phosphate ions and ion pairs in subsurface carious lesions in the enamel of human third molars, resulting in high rates of enamel remineralization. The remineralizing capacity was greater for solutions with higher levels of CPP-stabilized free calcium and phosphate ions.
Rose27 conducted a laboratory experiment in which he showed that CPP-ACP binds well to dental plaque, providing a large calcium reservoir that may inhibit demineralization and assist in subsequent remineralization. In a second experiment, Rose28 also showed that in streptococcal model plaques, 0.1 percent CPP-ACP provides a large number of possible binding sites for calcium and reduces the free calcium diffusion coefficient by about 65 percent at pH 7 and 35 percent at pH 5. During a cariogenic episode, 0.1 percent CPP-ACP prevented mineral loss and provided a potential source of calcium for subsequent remineralization, thus restricting the caries process.
In 2005, Ramalingam and colleagues29 immersed human enamel specimens in an erosive sports drink (Powerade [Coca-Cola, Atlanta] alone, Powerade with four concentrations of CPP-ACP [0.063, 0.09, 0.125 and 0.25 percent] and double deionized water as the placebo). Scanning electron microscopic examination of the specimens showed that the erosive lesions that developed in specimens immersed in Powerade were eliminated with the addition of CPP-ACP at all concentrations except 0.063 percent. The taste panel could not distinguish Powerade from Powerade with 0.125 percent CPP-ACP. The authors concluded that adding CPP-ACP to the sports drinks significantly reduced the beverages erosivity without affecting the products taste.
However, in another in vitro study, Lennon and colleagues30 applied a tooth cream containing 5 percent casein/calcium phosphate to bovine enamel specimens for 120 seconds twice daily. They found no significant difference with respect to erosive enamel loss (bovine enamel specimens rinsed with artificial saliva interrupted by 1 percent citric acid (pH 2.3) for 30 seconds six times daily for 14 days) when compared with the no-treatment control specimens after seven and 14 days of erosive cycling.
Clinical picture.
According to the manufacturer (GC America),31 CPP-ACP is a useful cario-static agent for the control of dental caries, and it can be used as an adjunct preventive therapy to reduce caries in high-risk patients, to reduce dental erosion in patients with gastric reflux or other disorders, to reduce decalcification in orthodontic patients, to repair enamel in cases involving white-spot lesions, orthodontic decalcification or fluorosis or before and after tooth whitening) and to desensitize teeth (for example, reducing hypersensitivity resulting from whitening procedures, treating sensitive dentin in patients with dental erosion and reducing sensitivity resulting from exposed root surfaces after professional tooth cleaning).
One advantage of this therapy is that the products (MI Paste, Tooth Mousse, Trident White Gum) are ingestible. In contrast, topical fluoride therapy poses a risk if the patient ingests a significant amount of fluoride.32 However, for any clinical application, clinicians should consider potential side effects from ingestion of casein derivative protein in people with immunoglobulin E allergies to milk proteins. We should note that CPP-ACP is digestible by people with lactose intolerance.
MI Paste Plus is a recently introduced product that contains 900 ppm fluoride. Although it is designed to increase enamel remineralization through the deposition of fluoride-containing calcium-phosphate precipitates, no reports, to our knowledge, have been published that demonstrate its efficacy in vivo. Furthermore, at 900 ppm fluoride, this product is not considered ingestible and, therefore, children younger than 6 years should not use it. Moreover, fluoride potentially can interact with the ACP component of the casein complex and may precipitate out as calcium fluoride, rendering both inorganic components ineffective. Development of the carrier for calcium and phosphate in the Recaldent technology (as casein in MI Paste Plus) has greatly reduced this problem. However, independent research is required to study the interaction of the fluoride-enriched CPP-ACP complex with enamel.
Three main calcium phosphate products have been tested or are on the market to inhibit or reverse caries:
To our knowledge, no systematic reviews of the clinical trials of these products have been conducted to date. Therefore, the purpose of this report is to systematically review the clinical trials of one of these types of products used in dentistry: products composed of the CPP-ACP complex. Several laboratory and animal experiments have demonstrated the anticariogenic potential of casein phosphopeptide–amorphous calcium phosphate.
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RATIONALE FOR USE OF CASEIN DERIVATIVES
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ABSTRACT
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METHODS
SUMMARY OF EVIDENCE AND...
EVIDENCE-BASED RECOMMENDATIONS
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Although several studies have investigated the use of casein4,18–23 as an anticariogenic additive to food, toothpaste or drinking water, its use has not been implemented because of its adverse organoleptic properties and the large amount required for efficacy.13 In contrast, CPP does not have these limitations. The potential for a specific anticariogenic activity is at least 10 times greater on a weight basis for CPP than it is for casein. Therefore, CPP can be used as a food or tooth-paste anticariogenic additive, especially if it is consumed at the same time as the cariogenic challenge.13
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METHODS
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ABSTRACT
RATIONALE FOR USE OF...
METHODS
SUMMARY OF EVIDENCE AND...
EVIDENCE-BASED RECOMMENDATIONS
CONCLUSION
REFERENCES
Data sources.
We conducted a comprehensive literature search of databases Ovid MEDLINE, Cumulative Index to Nursing & Allied Health Literature, Evidence Based Medicine of Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, Database of Abstracts of Reviews of Effects, EMBASE, Health and Psychosocial Instruments, HealthSTAR/Ovid Healthstar and International Pharmaceutical Abstracts for any published and unpublished studies (from their inception until October 2007). We also searched the Web sites of product manufacturers ("www.gcamerica.com", "www.recaldent.com"), as well as Google Scholar. Table 1
shows the key words and their combinations used in the literature search.
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Study selection, data extraction and quality assessment. We retrieved 98 articles. After removing duplicates, we limited the searches to articles in English and to studies that involved human subjects. We selected 53 citations and searched for relevance (determined by title), which resulted in 16 articles. We reviewed the abstracts of these articles for relevance, which resulted in 12 articles that we selected for retrieval and copying. Both of us reviewed all articles at each stage independently and we resolved discrepancies by consensus. One of us (A.A.) printed the abstraction sheets for annotated references (that is, with citation, author/date, population, age, sex, geographic location, intervention or test treatment (number of subjects), control treatment (number of subjects), outcome, critical appraisal comments, conclusion, strength of evidence and classification of recommendations. We then read and reviewed the abstraction sheets to determine relevance and scored them to rate the evidence for this review. In reading the articles, we checked the reference lists to identify any other articles that may have been relevant to the research question or provided additional information. All of these were found in the original searches.
Best available evidence.
We summarized the best available evidence by using inclusion criteria and measuring the strength and quality of the studies according to the evidence classification system developed by the Canadian Task Force on Preventive Health Care34 (Tables 2
and 3
). This system includes a hierarchy of evidence from the highest (level I)—a properly randomized controlled trial—to the lowest (level III)—opinions of respected authorities, based on clinical experience, descriptive studies or reports of expert committees. This system also includes a bidirectional classification of its recommendations (that is, strength of the recommendation for or against specific clinical preventive actions).
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| SUMMARY OF EVIDENCE AND COMPARISON OF OUTCOMES |
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To create the demineralized lesion, the investigators polished sound enamel, covered it with an acid-resistant coating (nail varnish or epoxy resin) and then subjected the enamel to demineralizing solutions. This procedure produced consistent subsurface lesions of 80 to 110 micrometers in depth.
At the end of each treatment period (that is, after subjects consumed sugar-free gum, lozenge, milk or mouthrinse containing CPP-ACP), the investigators took the remineralized enamel half-slabs and their paired demineralized control half-slabs (retained in a humidified environment) and embedded and sectioned them. Then they subjected the slabs to microradiography and computer-assisted microdensitometric analysis to evaluate the mean subsurface lesion depth, percentage of subsurface remineralization and/or change in mineral profile.
For each test group, the length of study varied from seven to 21 days. Only one study39 had a washout period of four weeks; the rest had a washout period of five to seven days. Overall, all of the studies except one41 showed that CPP-ACP had caries-preventive potential and resulted in subsurface remineralization of the enamel with the in situ carious lesion in a dose-response fashion.
The only study that did not show a difference between the CPP-ACP–containing chewing gums and the control chewing gums was a 2007 randomized crossover in situ study.41 While investigators in the other studies placed enamel slabs at the palate of midpalatal appliances, subjects in the study by Schirrmeister and colleagues41 wore custom-made removable buccal appliances in the mandible; these appliances had a buccal resin wing on each side, and two bovine enamel specimens were mounted in each wing flush with the buccal surface. This may have resulted in less direct contact between the slabs and the chewing gums.
The other two studies37,43 in the caries-prevention category were in vivo (rather than in situ) studies. The first study37 was a randomized clinical trial comparing a mouthrinse that contained casein derivatives coupled with calcium phosphate (CD-CP) with a sodium fluoride (NaF) mouthrinse. Subjects with salivary gland dysfunction (resulting from radiotherapy for head and neck cancer or Sjögren syndrome) used one of the two mouthrinses three times per day for one year. The investigators measured the coronal caries increment with posterior bitewing radiographs obtained at baseline and at the 12-month follow-up visit. The results showed no difference between the NaF mouthrinse and the CD-CP mouthrinse with regard to caries preventive efficacy.
The other study43 was a single-blinded randomized clinical trial of 26 healthy adolescents with 152 visible white-spot lesions on 60 incisors and canines. Immediately after undergoing debonding of fixed orthodontic appliances and receiving a professional cleaning, subjects were randomly assigned to two groups. The test group (n = 13 subjects with 70 sites) applied a topical dental cream containing CPP-ACP (Topacal C-5, Nulite Systems International, Hornsby, Australia) daily for three months followed by a three-month regimen of daily toothbrushing with a fluoridated dentifrice. The control group (n = 13 subjects with 62 sites) rinsed daily with a 0.05 percent sodium fluoride mouthwash and used fluoridated dentifrice for six months.
The results showed a significant improvement (regression) in white-spot lesions within each group across a 12-month follow-up period with the use of clinical assessment of the lesions (visual scoring on a scale from 0 to 4, with 0 being no visible color change and 4 being a distinct white color change) and laser fluorescence reading (DIAGNOdent, KaVo, Biberach, Germany). Moreover, the clinical visual scoring showed significant improvements (P < .01) for the group that underwent the CPP-ACP regimen with regard to the number of sites that disappeared completely after three months (55 percent in the test group versus 18 percent in the control group) and after 12 months (63 percent in the test group versus 25 percent in the control group). However, the study results showed no significant differences between the groups—at baseline or at any of the follow-up visits—when the investigators considered the laser fluorescence measurements.
The authors found insufficient clinical trial evidence to make a recommendation regarding the long-term effectiveness of casein derivatives in preventing caries in vivo.
Treating dry mouth.
As an extension to the study by Hay and Thomson,37 Hay and Morton44 administered a self-evaluation survey to 38 patients in the original sample. The survey asked them to compare the CD-CP mouthrinse with their usual mouth-moistening strategies (for example, sipping water, chewing gum, using artificial saliva). The authors concluded that the CD-CP mouthrinse, when used as an atomized spray in the mouth, provided good moistening and lubrication. However, some methodological flaws (Table 2
) limited the level of evidence and strength of the recommendation.
Treating dentin hypersensitivity. We identified one prospective study45 that evaluated the efficacy of CPP-ACP (GC Tooth Mousse) in the treatment of patients with dentin hypersensitivity. The study concluded that the efficacy and short-term therapeutic effect of CPP-ACP were insufficient in treating dentin hypersensitivity. However, the study lacked an appropriate control group and masking of the evaluators.
| EVIDENCE-BASED RECOMMENDATIONS |
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Investigators. First, six of the eight in situ studies were conducted by the same group of investigators who patented the CPP-ACP complex.10,11,36,39,40,42 These six studies, as well as another study,38 followed the same in situ protocol that resulted in significant findings in favor of this technology.
Findings. Second, of the four studies conducted by groups independent of those that patented the complex, one38 used a similar in situ model. Although the findings point to significant caries preventive potential of CPP-ACP when added to urea-containing chewing gum, the study38 found no difference in outcomes between CPP-ACP and dicalcium phosphate dihydrate. Consequently, the results of this study38 do not support the conclusion that the CPP-ACP molecule consists of any special properties in comparison with dicalcium phosphate dehydrate.
The other independent study41 was conducted in Germany using a different in situ model, as described earlier. This study found no significant differences between chewing gums that contained or did not contain calcium with regard to both mineral change and depth of demineralized lesions. The third independent study37 was an in vivo trial that assessed carious lesions in patients with salivary gland dysfunction. The results showed no difference between a NaF mouthrinse and a CD-CP mouthrinse. However, the number of teeth lost was significantly higher in the CD-CP group. We should note that the population recruited for this study was at high risk of experiencing tooth loss and dental caries; thus, the results may not be generalizable to a general population.
The results of the last independent study,43 which was conducted in Sweden, were conflicting. Using a clinical visual scoring system, the researchers found significant regression of white spot lesions (resulting from one year of fixed orthodontic treatment) in the CPP-ACP group compared with the control group (which received 0.05 percent NaF mouthrinse daily). However, when analyzing the laser fluorescence measurements, the authors found no significant differences between the groups over time.
Third, a limitation of the in situ methodological approach, however, is that long-term caries prevention has yet to be fully explored. In vivo clinical trials with adequate follow-up are needed to determine the efficacy of CPP-ACP in caries prevention.
Finally, none of the studies tested for the potential formation of calculus resulting from the supersaturated calcium phosphate state in plaque.
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| FOOTNOTES |
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