Donald James White

Reactivity of fluoride dentifrices with artificial caries. I. Effects on early lesions: F uptake, surface hardening and remineralization.

A pH-cycling model has been used to examine the effects of fluoride dentifrices on the saliva-mediated repair of early carious lesions in vitro. Fluoride reactivity was characterized by fluoride uptakA pH-cycling model has been used to examine the effects of fluoride dentifrices on the saliva-mediated repair of early carious lesions in vitro. Fluoride reactivity was characterized by fluoride uptake, surface microhardness and lesion mineral content (microradiographic) analyses. The fluoride dentifrices, in particular the sodium and amine fluoride preparations, were found to be extremely effective in enhancing the remineralization and acid resistance of early carious lesions. The most prominent effect of the fluoride topicals, however, was found to be the fluoride enrichment of the remineralized enamel. The rank ordered efficacy of the fluoride dentifrices was NaF = AmF > MFP ≥≥ placebo. The remineralization of the early carious lesions was linearly associated with the increased surface hardening of specimens.

A Longitudinal Microhardness Analysis of Fluoride Dentifrice Effects on Lesion Progression in vitro

The longitudinal microhardness technique has been used to determine the effect of a sodium fluoride dentifrice on the progression of artificial carious lesions in a pH cycling model in vitro. The NaF dentifrice was found to be extremely effective in reducing the progression of caries in enamel, limiting both the depth of acid damage and the degree of mineral loss measured at discrete intervals within specimens. Lesion progression areas, estimated using Simpson’s rule to integrate hardness data, indicated that the NaF dentifrice effected a 73 and 82% overall reduction in lesion advancement, relative to placebo and untreated controls. This area analysis appeared to represent a useful means for simplifying comparisons of treatment effects in remineralization studies using cross-sectional microhardness as the measurement tool. In terms of comparative accuracy to microradiography, analysis of published data indicated that the longitudinal microhardness technique, while limited in some respects, can provide useful estimates of remineralization/lesion-progression areas.

Use of Synthetic Polymer Gels for Artificial Carious Lesion Preparation

Synthetic polymer gels have been examined as decalcifying media for the preparation of artificial carious lesions in tooth enamel. Enamel specimens were demineralized in lactic acid/calcium phosphate buffers containing 0.1–0.5% (w/w) polyacrylic acid (Carbopol C907, MW = 450,000 daltons) to act as a surface-protective agent. The rate, histology and physical characteristics of lesions were characterized by surface microhardness, polarized light, and microradiographic analyses. Following demineralization, selected lesions were remineralized in solutions supersaturated with respect to fluoroapatite. The results show that polyacrylic acid is extremely useful and effective as a surface-protective agent for artificial carious lesion preparation. The histology of lesions formed in C907 gels can be carefully controlled by adjusting the undersaturation of the demineralization medium with respect to tooth mineral salts. Lesions formed in C907 gels are extremely reactive towards remineralization and the rate and histology of mineral repair are not noticeably influenced by the resin content in solution. The use of synthetic polymer gels is recommended for the systematic reproducible preparation of artificial carious lesions in dental enamel.

Physical and Chemical Considerations of the Role of Firmly and Loosely Bound Fluoride in Caries Prevention

Historically, there has been considerable debate concerning the roles of loosely bound (calcium fluoride) and firmly bound (fluorapatite) fluoride for caries prevention. Research now shows that fluorapatite (FAP) is a finite reaction product of enamel/apatite fluoridation with or without CaF2 formation, suggesting that CaF2 always be considered as a supplement to, rather than a substitute for, FAP formation. In the presence of low levels of fluoride in the solution phase, the crystallization of hydroxyapatite is enhanced, while the corresponding dissolution is retarded. Fluoride in the bulk FAP or CaF2 solid phase, in contrast, has limited impact on crystal growth or dissolution kinetics. Both FAP and CaF2 can provide F to the solution phase to enhance remineralization and retard demineralization of enamel HAP crystallites. The FAP provides most of this F under low pH conditions, while CaF2 provides F at neutral or lower pH. The reactivity of fluoride on sound and carious enamel differs significantly. Carious enamel acquires more fluoride, acquires it more quickly, and itself acts as a source of retained fluoride in comparison with the more limited reactivity of sound enamel. Overall, the most important question concerning fluoride reactivity relates to its efficiency in enhancing remineralization or retarding demineralization processes. This is influenced not only by the reaction products, e.g., loosely or firmly bound fluoride, but also by the nature of the enamel substrate and frequency of application of the topical fluoridating agent. Inasmuch as the reactivity of bulk HAP is dominated by surface layers of FAP material, the debate over usefulness of various fluoride reaction products solely on a chemical level is no longer critical. Instead, all factors influencing the efficiency of a fluoridating regimen must be considered in the development of improved systems for caries prevention.

Effect of an Anticalculus Dentifrice on Lesion Progression under pH Cycling Conditions in vitro

The aim of the present study was to examine a sodium fluoride anticalculus dentifrice product containing soluble pyrophosphate for its ability to promote remineralization and/or inhibit demineralization of dental enamel in a pH cycling model in vitro. Enamel crowns with windows were subjected to 14 days of alternating demineralization and remineralization periods at 37 degrees C. Teeth were immersed 5 min daily in one of the test dentifrice systems (1:3 slurry in deionized water) between the demineralization and remineralization cycles. Test dentifrices included (1) sodium fluoride (NaF; 1,100 ppm F)/silica abrasive (Crest) and (2) NaF (1,100 ppm F) with 3.3% soluble pyrophosphate/silica abrasive (Crest Tartar Control). Controls included a placebo dentifrice (silica abrasive) with no added fluoride and a group which received no treatment at all, i.e., demineralization/remineralization only. Overall, both of the NaF dentifrices were very effective in limiting in vitro caries progression and were not significantly different from each other. Inclusion of pyrophosphate in the NaF dentifrice did not affect the net outcome of the cycling demineralization/remineralization processes which is in agreement with recent clinical and in situ studies of these products.

19F MAS-NMR and solution chemical characterization of the reactions of fluoride with hydroxyapatite and powdered enamel

Solution chemical and 19F magic angle spinning-nuclear magnetic resonance (MAS-NMR) methods have been utilized to study the effects of fluoride dose, fluoridating pH, and mineral surface area on the dynamics of fluoride reactivity with hydroxyapatite and powdered human dental enamel in vitro. Both solution chemical fluoride uptake and NMR measurements demonstrated that the reaction products of ionic fluoride with apatite include mixtures of FAP, FHAP, and CaF2, with increased amounts of CaF2 promoted by increased F concentration or decreased pH. NMR analysis showed FAP or FHAP as a reaction product of fluoride uptake under all conditions, regardless of whether CaF2 was formed, unambiguously demonstrating fluorite as an additive rather than substitute form of F reactivity. pH stat measurements demonstrated the release of OH- during F reactivity with apatites corresponding to ion exchange formation of FAP/FHAP or dissolution/reprecipitation formation of CaF2. Phosphate release into solution accompanied fluoride uptake under all conditions, including regions where ion exchange predominated. Whereas powdered dental enamel demonstrated fluoride uptake behavior similar to that of synthetic apatite, the resulting reaction products differed as analyzed by 19F MAS-NMR.

Kinetic and Physical Aspects of Enamel Remineralization – A Constant Composition Study

The constant composition crystallization technique has been used in conjunction with surface hardness and radiographic methods to investigate kinetic and physical aspects of remineralization of artifi

Plaque levels of patients with fixed orthodontic appliances measured by digital plaque image analysis.

INTRODUCTION A digital plaque image analysis system was developed to objectively assess dental plaque formation and coverage in patients treated with fixed orthodontic appliances. METHODS The technique was used to assess plaque levels of 52 patients undergoing treatment with fixed appliances in the Department of Orthodontics at Johannes Gutenberg University in Mainz, Germany. RESULTS Plaque levels ranged from 5.1% to 85.3% of the analyzed tooth areas. About 37% of the patients had plaque levels over 50% of the dentition, but only 10% exhibited plaque levels below 15% of tooth coverage. The mean plaque coverage was 41.9% ± 18.8%. Plaque was mostly present along the gum line and around the orthodontic brackets and wires. CONCLUSIONS The digital plaque image analysis system might provide a convenient quantitative technique to assess oral hygiene in orthodontic patients with multi-bracket appliances. Plaque coverage in orthodontic patients is extremely high and is 2 to 3 times higher than levels observed in high plaque-forming adults without appliances participating in clinical studies of the digital plaque image analysis system. Improved hygiene, chemotherapeutic regimens, and compliance are necessary in these patients.

Surfactive and antibacterial activity of cetylpyridinium chloride formulations in vitro and in vivo

AIM To compare effects of three cetylpyridinium chloride (CPC) formulations with and without alcohol and Tween80 on physico-chemical properties of salivary pellicles, bacterial detachment in vitro and bacterial killing in vivo. MATERIAL AND METHODS Adsorption of CPC to salivary pellicles in vitro was studied using X-ray photoelectron spectroscopy and water contact angle measurements. Adhesion and detachment of a co-adhering bacterial pair was determined in vitro using a flow chamber. Killing was evaluated after live/dead staining after acute single use in vivo on 24- and 72-h-old plaques after 2-week continuous use. RESULTS The most pronounced effects on pellicle surface chemistry and hydrophobicity were observed after treatment with the alcohol-free formulation, while the pellicle thickness was not affected by any of the formulations. All CPC formulations detached up to 33% of the co-adhering pair from pellicle surfaces. Bacterial aggregate sizes during de novo deposition were enhanced after treatment with the alcohol-free formulation. Immediate and sustained killing in 24 and 72 h plaques after in vivo, acute single use as well as after 2-week continuous use were highest for the alcohol-free formulation. CONCLUSIONS CPC bioavailability in a formulation without alcohol and Tween80 could be demonstrated through measures of pellicle surface properties and bacterial interactions in vitro as well as bacteriocidal actions on oral biofilms in vivo.

Processes contributing to the formation of dental calculus

Dental calculus is a petrified plaque biofilm. Calculus removal requires professional scaling procedures as a result of its physical hardness and strong attachment to the teeth. The aim of this paper is to review chemical (MD, Ca, P, F), physical (hardness, adhesive strength), ultrastructural (SEM, TEM), and clinical data on calculus in order to provide perspective on the roles that adhesion and cementation play in tartar development. SEM, TEM and microradiographic analyses of deposits in cross section show that calculus mineralizes in successive layers of varying thickness. Chemical analysis shows that plaque mineralization occurs rapidly (on a clinical time scale, < 2 wks on average) with the formation of calcium phosphate crystals contributing up to 80% of the weight of deposits. Although calculus adheres strongly to the teeth (up to 4,000 kN.m‐2 in attachment force) the hardness measures only 10–20% of sound enamel (20–40 Vickers Hardness Numbers). The clinical formation of calculus (measured as the a...