Abstract: The shift from reparative to regenerative dentistry reflects the current trend in medicine and also mirrors the new understanding of caries as a chronic disease. Selfassembling peptide P11-4 showed promising results in the regenerative biomimetic remineralization of initial carious lesions. This approach may present safe and acceptable preventive and minimal invasive treatment for initial caries in children and adolescents. Further studies it is suggested to investigate this novel approach in treatment of molar incisor hypomineralization and cavitated carious lesions.
Preventive & Pediatric Dentistry University of Greifswald, Fleischmannstr. 42, 17487 Greifswald: OA Priv.-Doz Dr. Mohammad Alkilzy, Prof. Dr. Christian Splieth
Citation: Alkilzy M, Splieth CH: Self-assembling peptides for caries prevention and treatment of initial carious lesions, a review. Dtsch Zahnärztl Z Int 2020; 2: 021–025
Peer-reviewed article: submitted: 04.09.2019, revised version accepted: 30.10.2019
Dental caries is a chronic, infectious, progressive disease, starting with initial loss of tooth minerals and leading to total tooth destruction over time. Caries occurs when an imbalance between re- and de-mineralization takes place at the site of loss of minerals in hard dental tissue . Therefore, the classic “treatment” of cavities by drilling and filling constitutes repair of the damage, but does not treat the disease itself. “Real” caries treatment would consist of shifting the equilibrium to re-mineralization, for instance by improving the daily oral hygiene regime, healthy diet and fluoride application. The new understanding of caries kinetics and monitoring the de-/re-mineralization equilibrium can indicate measures for correcting the mineralization balance . In the early stages of caries, prior to the cavitation of the enamel surface, many non- and minimally invasive treatments have been suggested to avoid further tooth destruction and subsequently restorations. The primary aim of non-invasive treatments is to inactivate or arrest the caries. This can be achieved by diet control and plaque removal which allows the carious lesions to remineralize naturally through saliva . The presence of fluorides clearly enhances remineralization and prevents further demineralization [19, 22]. Unfortunately, most preventive approaches rely on changes in the patient’s behaviour, but this is not always an easy job especially in children and adolescences. A possible alternative is sealing caries risk surfaces mechanically , but sealants are prone to microleakage and subsequent caries in the long run  (Fig. 1).
An alternative approach to the current strategies for managing initial non-cavitated carious lesions is the recently introduced self-assembling peptide P11-4  for regenerating demineralized tooth tissue. This peptide forms a 3D-matrix within demineralized carious lesions, which enables novo hydroxyapatite crystal formation facilitating the regeneration of the lost enamel structure [10, 15] (Fig. 2). The peptide has shown encouraging results as a scaffold for enamel regeneration . This paper presents the current scientific evidence and clinical implementations for the self-assembling peptide P11-4 in a modern caries management.
Biomimetics with self- assembling peptides
The self-assembling peptide P11-4 is clinically available as Curodont Repair and it has the chemical structure: Ace-Gln-Gln-Arg-Phe-Glu-Trp-Glu-Phe-Glu-Gln-Gln-NH2. It is synthetic and manufactured under cGMP and contains no human- or animal-derived components. Biocompatibility studies (according to ISO 10993 or equivalent) have shown that P11-4 did not raise any cytotoxic effects or any immunological response [7, 12, 18]. P11-4 has been proven safe in animals and patients in vivo. No adverse device effects have been reported so far .
Conditions and indications for minimal invasive caries treatment with SAP
Limitations and contra-indications for minimal invasive caries treatment with SAP
Active initial lesions without cavitation (Fig. 4)
Carious lesion with cavitation
Lack in the patient’s compliance with toothbrushing and dental hygiene
Good patient’s compliance to dental hygiene
Moderate caries risk and activity
Patients with low caries risk
Age groups with elevated caries activity such as adolescences and young adults
Elderly patients with slow caries progression or already arrested lesions
Progression of the lesion in spite of preventive approaches
Patients with allergy to one or more elements of the product
Table 1 Indications and limitations for minimal invasive caries treatment with SAP
P11-4 undergoes under specific physicochemical conditions and above a critical concentration a hierarchical self-assembly to form tapes and ribbons within seconds, and fibrils and fibers within the following 24 h [1, 6, 8] (Fig. 3). These resulting self-assembling peptide fibres forming the 3D Self-Assembling Peptide Matrix (SAPM) can grow to a significant length. If the conditions for self-assembly are given, the assembly process cannot be stopped at the intermediates unless no more monomeric peptides are available. Confocal microscopy and mass spectroscopy showed that monomeric P11-4 diffuses through the pores of demineralized enamel, where fibre formation is triggered and the 3D matrix is formed . Furthermore, C-labeled P11-4 indicated that about 35 % of P11-4 remained within artificial carious lesions  being available for de novo hydroxyapatite crystal formation. Two studies [10, 15] used the microtomography (microCT) analysis of remineralized specimens and found a remineralization of up to 90 % of the original enamel density.
A series of in-vitro studies insured the high affinity of the P11-4 matrix for Ca2 ions and its action as a nucleator for de novo hydroxyapatite formation [6, 16, 17, 25]. Furthermore, the P11-4 fibers bind to the already existing Ca2 ions of the hydroxyapatite lattice of the tooth enamel , enabling stable bridge binding of the new regenerated enamel to the tooth hard tissue. A study of Kind et al.  investigated the diffusion of P11-4 into a carious lesion by time resolved confocal microscopy pictures. The results showed that the P11-4 diffuses beyond the volume of the carious lesion into the enamel layer below as was defined as the carious lesion on a microradiograph. After the formation of fibres is complete the formed fibers seem to occupy the observed lesion.
Clinical implementation of self-assembling peptide
Feasibility of clinical application, safety and clinical effect of P11-4 were first examined in an un-controlled safety trial treating arrested carious lesions on buccal surfaces in 15 adults . As no adverse events were recorded by the use of the product and the blinded evaluation of the lesions showed a significant improvement of lesions judged by colour, size and perceived progression, further clinical studies were feasible. Table 1 lists some clinical indications and limitations for minimal invasive caries treatment with self-assembling peptides (SAP).
Self-assembling peptide for non- and minimal invasive treatment of occlusal initial caries
Occlusal surfaces of erupting permanent molars are highly prone to caries. Because of the infra-occlusal position of these teeth during the eruption, an effective toothbrushing is difficult. Even sealing of these teeth presents almost difficulties because of the gingiva covering the occlusal surfaces in partially erupted teeth (Fig. 4). Therefore, a randomized controlled single-blind study was conducted by Alkilzy et al. [3, 4] on children with visible active early caries on erupting permanent molars to investigate the safety and clinical efficacy of P11-4 for treatment of initial caries. Subjects were randomized to either the test group (P11-4 fluoride varnish) or control group (fluoride varnish alone). Caries was assessed at baseline and at 3– and 6-month post treatment per laser fluorescence, a visual analog scale, the International Caries Detection and Assessment System (ICDAS), and the Nyvad caries activity criteria . Safety and clinical feasibility of the treatment approaches were also assessed. The P11-4 (Curodont Repair) was applied according to the instruction of the manufacturer (Fig. 5). Compared with the control group, the test group showed clinically and statistically significant improvement in all outcomes at 3– and 6-month follow-ups. The laser fluorescence readings (odds ratio = 3.5, P = 0.015) and visual analog scale scores (odds ratio = 7.9, P < 0.0001) were significantly lower for the test group, and they showed regression in ICDAS scores (odds ratio = 5.1, P = 0.018) and conversion from active to inactive lesions according to Nyvad criteria (odds ratio = 12.2, P < 0.0001, Fig. 6). Results suggest that Curodont Repair may present a simple, safe and effective non-invasive treatment for early occlusal carious lesions on erupting teeth in conjunction with topical fluoride. Figure 3 shows a treatment of an initial carious lesion in the occlusal surface of first permanent molar during eruption using Curodont Repair.
Self-assembling peptide for caries prevention in patients with orthodontic brackets
Jablonski-Momeni et al.  investigated in a randomised, cross-over in situ trial the ability of 1,000 ppm self-assembling peptide P11-4 (Curodont Protect) to remineralize artificial initial caries lesions compared to the use of 22,600 ppm fluoride varnish. Laser fluorescence values (LF) and Micro-CT analysis was used to assess mineral changes within the specimens. The test group with P11-4 showed significantly more remineralization than the negative (p = 0.01) and positive control with fluoride (p = 0.003). The authors concluded that P11-4 showed prevention of caries and remineralization of enamel around orthodontic brackets.
The manufacturer of Curodont Protect claims that once the product is applied on the surface of the tooth the fibres can bind to the tooth via the Ca2 -binding sites to the aprismatic HA crystal on the surface of the tooth. As the surface of the tooth – which undergoes constant re-, demineralisation – is not prismatic in structure the long axis of the HA crystal is available for binding, and the natural zeta-potential of the enamel surface seems to facilitate the binding. As a result, the 3D matrix will bind onto the tooth surface with multiple binding sites.
Self-assembling peptide for treatment of buccal caries and white spots
Bröseler et al.  compared in a prospective, randomized, split-mouth, clinical trial the efficacy of the self-assembling peptide P11-4 to fluoride varnish in the treatment of early buccal carious lesions. Subjects with at least 2 clinically affected teeth were treated at day one D0 and day 90 D90 with P11-4 (test) or fluoride varnish (control). At day 180, fluoride varnish was applied on all study lesions. Standardized photographs were taken at D0, D30, D90, D180 and D360 and the decrease in size between test and control groups was blindly morphometrically assessed. The results showed a significant difference between test and control groups, indicating a decrease in test lesions and stabilization of control lesions size (p = 0.001). The authors concluded that the size of early carious lesions treated with P11-4 was significantly reduced and this size reduction was superior to that of fluoride varnish treatment.
Self-assembling peptide for treatment of proximal caries
A study by Schlee et al.  investigated the clinical performance of self-assembling peptide P11-4 on non-cavitated initial proximal carious lesions 12 months after treatment. Twenty-six patients with 35 carious lesions were included in a practice-based case series. The x-rays of the proximal lesions at baseline and at day 360 were evaluated pairwise in a randomized and blinded manner with respect to the time point. The one-year results showed a predominant shift toward regression of the initial lesions, with 20 of 28 lesions showing total or partial regression, 4 unchanged, and 4 progressing. The authors suggested that the initial proximal carious lesions can regress after treatment with P11-4, but additional factors might influence the overall treatment outcome.
Summary and suggestions
The shift from reparative to regenerative dentistry reflects the current trend in medicine and also mirrors the new understanding of caries as a chronic disease. Self-assembling peptide P11-4 showed promising results in the regenerative biomimetic remineralization of initial carious lesions. This approach may present safe and acceptable preventive and minimal invasive treatment for initial caries in children and adolescents. However, studies with longer observation periods are needed to confirm the consistent effect of P11-4. Further studies are suggested to investigate this approach in treatment of molar incisor hypomineralization and cavitated carious lesions.
Conflict of interest:
The authors state that they have no conflict of interest as defined by the guidelines of the International Committee of Medical Journal Editors.
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