Gunnar Rölla

Orthodontic appliances and enamel demineralization. Part 1. Lesion development.

A clinical trial was conducted to investigate carious lesion development associated with fixed orthodontic therapy. Specially designed orthodontic bands for plaque accumulation were attached to premolars scheduled to be extracted as part of an orthodontic treatment. Visible white spot lesions were seen within 4 weeks in the absence of any fluoride supplementation. Both microradiographic and SEM examinations showed surface softening of the enamel surface--that is, a surface layer was not seen in the lesions. The clinical significance of the present study is that enamel demineralization associated with fixed orthodontic therapy is an extremely rapid process caused by a high and continuous cariogenic challenge in the plaque developed around brackets and underneath ill-fitting bands. Careful inspection of the appliance at every visit and preventive fluoride programs are therefore required.

Orthodontic appliances and enamel demineralization Part 2. Prevention and treatment of lesions

Clinical experiments were performed to investigate the effect of fluoride on carious lesion development and on lesions established during fixed orthodontic therapy. All presently available fluoride agents are developed from the concept of fluoridating the enamel in the form of fluorhydroxyapatite. Recent research has indicated, however, that calcium fluoride formation may be a major aspect of the mechanism of the cariostatic effect of topical fluoride. Therefore a fluoride solution with very low pH (1.9) that induced large amounts of calcium fluoride also was tested on lesion development underneath orthodontic bands. Daily fluoride mouth rinsing with a 0.2% solution sodium fluoride (NaF) retarded lesion development significantly, whereas the fluoride solution with low pH inhibited lesion formation completely. Fluoride applied as a mouth rinse to plaque-covered lesions underneath orthodontic bands retarded lesion progression. The remineralizing capacity of saliva was found to be rapid in the absence of any fluoride. Although white spot lesions may remineralize and even disappear, most of the emphasis should be directed against prevention of carious lesion development during treatment with fixed orthodontic appliances.

Chemical analysis of the acquired pellicle formed in two hours on cleaned human teeth in vivo. Rate of formation and amino acid analysis

A method for the collection of the proteins film formed on pumiced teeth in vivo is described. The amount of adsorbed protein increased during the first 1.5 h. No differences were d

Retention of chlorhexidine in the human oral cavity after mouth rinses

Abstract The retention of chlorhexidine after mouth rinses was measured by the use of [ 14 C]-chlorhexidine. The fraction swallowed was estimated using [ 51 Cr]-EDTA. The mean total retention after 0.2 per cent chlorhexidine-digluconate mouth rinses (10 ml for 1 min) averaged 34 ± 7 per cent (6.9 ± 1.4 mg), and the oral retention 30 ± 7 per cent (6.0 ± 1.5 mg). The intra-individual variation, estimated by five mouth rinses at 1-week intervals, averaged ±4 per cent. The 14 C-activity in saliva showed a sharp fall during the first few hours, followed by a slow release, with activity still present after 24 hr.

Relationship between plaque-inhibiting effect and retention of chlorhexidine in the human oral cavity

Abstract Two clinical trials were performed. In the first experiment, five subjects rinsed with 0.2 per cent aqueous solutions of chlorhexidine digluconate (pH 6.4) with radioactive markers (14C) and then performed five consecutive after-rinses with diluted acetic acid pH 3.0. The amount of chlorhexidine initially retained and the amount eluted with the acid was estimated. About 65 per cent of the drug initially retained was released by three acetic after-rinses. The same principle was employed in the second clinical study to investigate the clinical significance of loss of retained chlorhexidine. This procedure caused a markedly reduced plaque inhibition. Thus the clinical effect of chlorhexidine as a plaque inhibitor seems to be dependent on the retention of the agent in the oral cavity.

Professional topical fluoride applications--clinical efficacy and mechanism of action.

All currently used topical fluoride agents deposit soluble fluoride as calcium fluoride on enamel or in lesions. Calcium fluoride serves as a source of fluoride for the formation of fluorapatite. The latter phase is formed when pH drops in plaque, not during topical application. The potential for calcium fluoride formation should probably be increased in topical fluoride agents. In countries with low caries prevalence, the clinical recommendations for topical fluoride need to be reconsidered. Toothpaste is the basic fluoride regimen recommended for everybody. The need for additional fluoride supplementation depends on caries activity. There is no distinct difference in the caries-preventive effects of concentrated fluoride solutions, gels, or varnishes. Thus, the choice of method depends on costs, convenience, patient acceptance, and safety. The use of fluoride varnishes has proven to be a feasible and safe method of fluoride application. With fluoride varnishes, the amounts of fluoride exposure can be better controlled, and less chair-time is required compared with conventional solutions and gels. No dose-response effect to concentrated fluoride agents is apparent, and the benefit of frequent application is not clearly established. In individuals with the most severe cariogenic challenge, combinations of fluoride and antimicrobials may give better clinical effects than fluoride alone.

Influence of concentration, time, temperature and pH on the retention of chlorhexidine in the human oral cavity after mouth rinses.

Abstract The oral retention of chlorhexidine-digluconate from rinsing solutions of 0.05, 0.1, 0.2 and 0.4 per cent was measured by means of [ 24 C]-chlorhexidine. Corrections were made for the fraction swallowed by the use of [ 51 Cr]-EDTA. The retention was essentially proportional to the concentration, with a slight deviation towards less retention at the 0.4 per cent concentration. Approximately half of the chlorhexidine retained after a 60-sec rinse was retained within the first 15 sec, and about 75 per cent within 30 sec. Increasing the temperature of the rinsing solution from 22 to 60 °C had little effect on retention. Increasing the pH of the rinsing solution from 6.4 to 9.0 did not change the retention. At pH 3.0 and 1.5 the retention was less than half of that at pH 6.4.

Electron Microscopy, Carbohydrate Analyses and Biological Activities of the Proteins Adsorbed in Two Hours to Tooth Surfaces in vivo

Further investigation of the pellicle formed in 2 h on cleaned human teeth in vivo is reported. Electron micrographs demonstrating the presence of a thin organic layer 2 h after the

On the role of calcium fluoride in the cariostatic mechanism of fluoride.

The literature concerning the formation and stability of CaF2 in the oral environment is reviewed. In early work the CaF2 formed during topical application with fluoride was assumed to be beneficial. It was suggested that it could protect the enamel surface directly or provide free fluoride ions for subsequent incorporation into the hydroxyapatite lattice. However, McCann claimed, in 1968, that CaF2 is soluble in saliva (12-15 mg/l), that it would be rapidly lost in the oral cavity, and that the clinical effect of fluoride was related to formation of firmly bound fluoride only. In this period many authors reported total loss of CaF2 during 24 h after a topical application of fluoride. It has now been shown in several laboratories that calcium fluoride is stable in saliva at neutral pH owing to surface adsorption of HPO2-4 to the crystal surface and formation of a solubility-limiting phase. Extended exposure of saliva can cause formation of a fluorapatite layer on the CaF2 crystals, restricting their dissolution further. Low pH (pH less than 5) causes loss of the solubility-limiting adsorbed HPO2-4 and a slow dissolution of CaF2. The CaF2 crystals may thus serve as pH-controlled reservoirs of fluoride ions on the enamel or in plaque and release fluoride during caries challenges. It is suggested that calcium fluoride is an essential phase explaining important aspects of the mechanism of topically applied fluoride, contrary to what was assumed in the past.

In vivo Progress of Enamel and Root Surface Lesions under Plaque as a Function of Time

This paper deals with enamel and root surface demineralization under plaque in vivo as a function of time. The enamel was demineralized using the Ogaard method in which preformed orthodontic bands are attached to the premolars in situ for 4, 6, and 8 weeks; a niche in the bands is responsible for plaque accumulation. In a second experiment cement-covered root surfaces (and enamel) were mounted on a removable appliance (Hawley retainer). Also in this case an orthodontic band was placed over the samples to create a space for plaque accumulation of about 0.8 mm between sample and band. All samples were analyzed by means of microradiography. The results show that (1) demineralization of enamel with the Ogaard method and using the Hawley retainer gives values for lesion depth and mineral loss that are statistically not significantly different; (2) lesion progress and mineral loss in vivo is about 2.5 times faster in roots than in enamel; (3) the demineralization in enamel is roughly linear with time, and (4) roots demineralize in vivo very fast during the 1st week and much more slowly there after.