Bjørn Øgaard

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.

Prevalence of white spot lesions in 19-near-olds: A study on untreated and orthodontically treated persons 5 years after treatment

In the present study the prevalence of white spot lesions (initial enamel lesions) on the vestibular surfaces was recorded in 19-year-olds subjected to and not subjected to orthodontic treatment. Fifty-one orthodontic patients and 47 untreated subjects were examined. On the average, 5.7 years had elapsed since orthodontic appliances were removed. The median white spot score was significantly higher in the orthodontic group than in the untreated group. The orthodontically treated subjects also had more teeth with white spot lesions than the untreated subjects. The highest prevalence was noted on the first molars in both groups. In the orthodontic group the mandibular canines and premolars and the maxillary lateral incisors were also affected. The present study showed that white spot lesions after orthodontic treatment with fixed appliances may present an esthetic problem, even more than 5 years after treatment.In the present study the prevalence of white spot lesions (initial enamel lesions) on the vestibular surfaces was recorded in 19-year-olds subjected to and not subjected to orthodontic treatment. Fifty-one orthodontic patients and 47 untreated subjects were examined. On the average, 5.7 years had elapsed since orthodontic appliances were removed. The median white spot score was significantly higher in the orthodontic group than in the untreated group. The orthodontically treated subjects also had more teeth with white spot lesions than the untreated subjects. The highest prevalence was noted on the first molars in both groups. In the orthodontic group the mandibular canines and premolars and the maxillary lateral incisors were also affected. The present study showed that white spot lesions after orthodontic treatment with fixed appliances may present an esthetic problem, even more than 5 years after treatment.

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.

The effect of sucking habits, cohort, sex, intercanine arch widths, and breast or bottle feeding on posterior crossbite in Norwegian and Swedish 3-year-old children.

The upper and lower intercanine arch widths and the prevalence of posterior crossbite were registered for 445 3-year-old children with and without a continuing or previous dummy-sucking or finger-sucking habit in different areas in Sweden and Norway. Sami children from northern Norway also took part in the study, as well as 15 medieval skulls with intact deciduous dentitions. Compared with the nonsuckers, an increased prevalence of posterior crossbite was observed for the finger suckers, especially the Swedish girls. Stepwise logistic regression showed that posterior crossbite could be predicted with upper intercanine arch width alone. The finger sucking variable would not improve prediction; neither did other entities such as cohort (residental area), sex, lower intercanine arch width, nor the difference between upper and lower intercanine arch width. High prevalences of posterior crossbite were registered for dummy suckers (pacifiers) especially the Swedish girls (26%). Stepwise logistic regression showed that posterior crossbite in dummy suckers could be predicted with upper and lower intercanine arch width. Stepwise linear regression showed that both arches tended to be narrower in Swedes and girls, and that dummy sucking decreased the upper and increased the lower intercanine arch width. Analyses of covariance revealed that at least 2 years of dummy sucking is necessary to produce a significant effect in the upper jaw and 3 years in the lower jaw. (AM J ORTHOD DENTOFAC ORTHOP 1994;106:161-6.).The upper and lower intercanine arch widths and the prevalence of posterior crossbite were registered for 445 3-year-old children with and without a continuing or previous dummy-sucking or finger-sucking habit in different areas in Sweden and Norway. Sami children from northern Norway also took part in the study, as well as 15 medieval skulls with intact deciduous dentitions. Compared with the nonsuckers, an increased prevalence of posterior crossbite was observed for the finger suckers, especially the Swedish girls. Stepwise logistic regression showed that posterior crossbite could be predicted with upper intercanine arch width alone. The finger sucking variable would not improve prediction; neither did other entities such as cohort (residential area), sex, lower intercanine arch width, nor the difference between upper and lower intercanine arch width. High prevalences of posterior crossbite were registered for dummy suckers (pacifiers) especially the Swedish girls (26%). Stepwise logistic regression showed that posterior crossbite in dummy suckers could be predicted with upper and lower intercanine arch width. Stepwise linear regression showed that both arches tended to be narrower in Swedes and girls, and that dummy sucking decreased the upper and increased the lower intercanine arch width. Analyses of covariance revealed that at least 2 years of dummy sucking is necessary to produce a significant effect in the upper jaw and 3 years in the lower jaw.

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.

CaF2 Formation: Cariostatic Properties and Factors of Enhancing the Effect

CaF(2) or a CaF(2)-like material/phosphate-contaminated CaF(2) is a major reaction product during topical treatment of dental hard tissues. Recently, evidence has suggested that CaF(2) is formed not only on surfaces but also to some extent in the enamel. The minimum concentration of fluoride required for CaF(2) formation is not well known and may depend on whether calcium is available from plaque fluid or only through dissolution of the dental hard tissue. Furthermore, surface adsorption of fluoride to crystals may cause local concentrations necessary for CaF(2) formation. It has been suggested that CaF(2) acts as a pH-controlled reservoir of fluoride. The rate-controlling factor appears to be phosphate, which controls the dissolution rate of CaF(2) at high pH. Increasing fluoride concentration, prolonging the exposure time or using a fluoride solution with low pH can increase CaF(2) formation. CaF(2) formed at low pH contains less internal phosphate which has been shown to be less soluble. This may be of clinical significance for fluoride applied topically a few times per year.CaF2 or a CaF2-like material/phosphate-contaminated CaF2 is a major reaction product during topical treatment of dental hard tissues. Recently, evidence has suggested that CaF2 is formed not only on surfaces but also to some extent in the enamel. The minimum concentration of fluoride required for CaF2 formation is not well known and may depend on whether calcium is available from plaque fluid or only through dissolution of the dental hard tissue. Furthermore, surface adsorption of fluoride to crystals may cause local concentrations necessary for CaF2 formation. It has been suggested that CaF2 acts as a pH-controlled reservoir of fluoride. The rate-controlling factor appears to be phosphate, which controls the dissolution rate of CaF2 at high pH. Increasing fluoride concentration, prolonging the exposure time or using a fluoride solution with low pH can increase CaF2 formation. CaF2 formed at low pH contains less internal phosphate which has been shown to be less soluble. This may be of clinical significance for fluoride applied topically a few times per year.

The Protective Effect of TiF4, SnF2 and NaF on Erosion of Enamel by Hydrochloric Acid in vitro Measured by White Light Interferometry

The purpose of this in vitro study was to compare the protective effect of TiF4, SnF2 and NaF (all 0.5 M F) on the development of erosion-like lesions in human dental enamel. Four enamel specimens from each of 6 extracted molars were polished and embedded in epoxy resin. The enamel surfaces of 3 specimens from each tooth were treated with the different fluoride solutions for 2 min. Following fluoride treatments, the specimens were immersed in 0.01 M HCl (pH 2.0), for 2, 4 and 6 min in order to mimic a gastric reflux situation. One specimen from each tooth was used as a control and was only exposed to acid. The etching depths (in micrometres) after 6 min were: TiF4 0.8 (SD 0.8), SnF2 3.5 (SD 0.7), NaF 5.3 (SD 0.4), and 7.0 (SD 0.3) for the control specimens. Compared to the control, TiF4 protected the enamel surface from acid attack almost completely (88%), while SnF2 reduced the etch depth after 6 min by 50% and NaF by 25%.

Effects of Fluoride on Caries Development and Progression in vivo

The dissolution rate of calcium-fluoride-like material from the enamel surface in vivo appears to be much slower than previously thought. This could be due to adsorption of phosphate ions and/or protein molecules to the surface of the calcium-fluoride-like particles. During cariogenic challenges, the phosphate/protein coating is released, resulting in increased solubility rate of the calcium-fluoride-like material. Due to this mechanism, calcium-fluoride-like material may be a major aspect of the cariostatic mechanism of topically applied fluoride. Topically applied neutral fluoride agents are able to inhibit caries development in enamel but not completely stop lesion development. A fluoride solution at low pH has been found to be more effective in caries model studies than neutral fluoride agents, which might be due to the formation of a larger depot of calcium fluoride. Data from fluoridated areas indicate that the fluoride ion as such has a limited effect on lesion development, and a major mechanism of the cariostatic effect may be reformation of apatite (remineralization). The product of lesion consolidation (a fluoridated apatite) may have a limited effect, since Intraoral caries model studies show that even pure fluorapatite, in the form of shark enamel, demineralizes. In fissures and around orthodontic appliances, conventional fluoride agents appear to have only a small effect.

Craniofacial structure and soft tissue profile in patients with severe hypodontia.

This study compares craniofacial structure and soft tissue profile in persons with mild hypodontia (group I: 2 to 5 congenitally missing teeth, n = 43), moderate hypodontia (group II: 6 to 9 congenitally missing teeth, n = 15) and severe hypodontia (group III: 10 or more congenitally missing teeth, n = 29) with the structure of persons without hypodontia and with normal occlusion (n = 50). The mean age was about 12 years. In group I, the lower second premolars were the most frequently missing teeth, followed by the upper second premolars and the upper lateral incisors. The relative prevalence of missing second premolars decreased with increasing severity of hypodontia. No consistent pattern could be observed when more than five teeth were missing, indicating a different genetic mechanism than for mild hypodontia. A significant retroclination of the incisors and an increased interincisal angle were observed with increasing severity of hypodontia. This was accompanied by a reduction of lip protrusion, being most evident for the upper lip. Increasing numbers of missing teeth resulted also in a decrease in the mandibular plane angle and a reduction in the anterior lower facial height. Few differences in the skeletal parameters were observed. It was concluded that the typical dentofacial structure in persons with advanced hypodontia may be due to dental and functional compensation rather than to a different growth pattern.

The Effect of Fluoride Application on Fluoride Release and the Antibacterial Action of Glass lonomers

The aim of this study was to investigate whether the release of fluoride and the antimicrobial effect of freshly mixed glass ionomers could be prolonged by application of fluoride on aged material. Test slabs of freshly mixed and aged (14 d in water) conventional and silver glass ionomer (Ketac-Fil and Ketac-Silver, Espe, Seefeld, Germany) and composite (Silux Plus, 3M, St. Paul, MN) were fitted into the bottom of a test tube. A layer ofS. mutans Ingbritt cells was centrifuged onto the test slabs, and the samples were incubated for 20 h in 1.7% sucrose solution. After the incubation, pH, F, and Ca contents of the fluid phase, and F, Mg, P, and K contents of the cells were determined. The aged glass-ionomer samples were then covered with toothpaste (0.1% F) or with fluoride gel (1.25% F), and the composite samples with fluoride gel. After being thoroughly rinsed, S. mutans cells were incubated on the samples as above. The pH fall was significantly inhibited by freshly mixed glass ionomers, and there were changes in cellular cation and phosphorus contents. Large amounts of fluoride were found in the fluid and cells. For old glass ionomers, no inhibitory effect on pH fall could be seen. Fluoride release had decreased to a low level. Application of fluoride toothpaste on the material resulted in a small increase in the release of fluoride and slight inhibitory effects on bacteria. After application of fluoride gel, the fluoride contents of the fluid phase and cells were as high as in freshly mixed samples, and the inhibitory effect on pH fall and electrolyte metabolism was even more pronounced than initially. Fluoride release from old glass ionomers and their antimicrobial effect could be significantly increased by application of fluoride gel on the material.