An in vitro scanning microradiography study of the reduction in hydroxyapatite demineralization rate by statherin‐like peptides as a function of increasing N‐terminal length

Abstract

Enamel demineralization is slowed by salivary proteins that inhibit calcium hydroxyapatite (HA) demineralization. Statherin (StN43), a 43-residue phosphorylated salivary protein with primary sequence similarities to osteopontin and caseins, binds calcium and HA. The aim of this study was to identify the minimum length of the functional domain of the statherin molecule required for cariostatic function by measuring the efficacy of peptides of progressively shorter length (i.e. containing only the N-terminal 21 (StN21), 15 (StN15), 10 (StN10), or 5 (StN5) residues) to reduce HA demineralization rates (RD(HA) ). Porous HA blocks were used as enamel analogues, and were exposed to 0.1 M acetic acid at pH 4 for 120 h, rinsed, and treated with StN21, StN15, StN10, or StN5 peptides (1.88 × 10(-5) M) for 24 h, then demineralized for a further 120 h. The RD(HA) was measured, before and after peptide treatment, using scanning microradiography. Hydroxyapatite blocks treated with StN21 and StN15 demonstrated a 50-60% reduction in the RD(HA) . However, no reduction in the RD(HA) was observed following treatment with either StN10, StN5, or buffer only. The mechanism by which statherin-like peptides reduce RD(HA) may be associated with their binding to HA surfaces. Comparisons with previously published binding energies of statherin to HA also suggest that statherin-like peptides containing 15 N-terminal residues or more, are required for binding, suggesting a link between binding and demineralization reduction.

Changes in the Proteomic Profile of Acquired Enamel Pellicles as a Function of Their Time of Formation and Hydrochloric Acid Exposure

“…In fact, solid-state nuclear magnetic resonance studies confirmed that the N-terminus of statherin strongly binds to hydroxyapatite, while the middle and C-terminal regions are mobile and dynamic [Naganagowda et al, 1998]. In order to protect against demineralization, it is suggested that statherin-like peptides containing at least 15 N-terminal residues or more are required [Shah et al, 2011]. It was recently reported that the calcium concentration in the AEP of patients with dental erosion is 50% reduced, while the concentration of statherin is 35% reduced [Carpenter et al, 2014].…”

Inhibitory Effects of Zinc Ions on Enamel Demineralisation Kinetics in vitro

“…Details of the SMR technique have been given elsewhere [Anderson et al, 2004;Kosoric et al, 2010;Shah et al, 2011;Mohammed et al, 2013]. The SMR cells containing the samples were mounted on the X-Y stage, which can be moved and repositioned with high precision (±0.5 μm) under computer control.…”

“…However, there is a paucity of data regarding reductions in demineralisation effected by zinc in the literature. Scanning microradiography (SMR) is a real-time X-ray absorption technique which enables directly quantitative, continuous and precise measurements in enamel mineral mass at fixed local positions Elliott, 1985, 1992;Anderson et al, 2004;Shah et al, 2011]. Comparisons of SMR with other measurement techniques have been made elsewhere [Mohammed et al, 2013], but in brief, SMR can be used to continuously measure the physical changes in bulk enamel concentration during the process of demineralisation, in a non-destructive fashion.…”

Adverse reactions to orthodontic materials

“…Peptides such as a statherin‐like peptide have been found to reduce the rate of hydroxyapatite demineralisation in caries‐simulating solutions by 50%. Research efforts have also focused on salivary proteins, which can bind to hydroxyapatite surfaces and form a selectively permeable pellicle. The management of post‐orthodontic white spot lesions is based on remineralisation strategies or minimal‐invasive camouflage of the lesions, micro‐abrasion and resin infiltration.…”