Fluoride concentration of dental calculus, surface enamel and cementum

The effect of oral-like environment on dental implants' fatigue performance

AIM AND OBJECTIVES

The aim of this study was to evaluate the influence of fluid environment mimicking intra-oral conditions on fatigue performance of standard diameter, 3.75-mm implants. Dental implants placed intra-orally are repeatedly submitted to mastication loads in the oral environment, which differ substantially from room-air standard laboratory conditions. Several studies that examined fracture surfaces of intra-orally fractured dental implants have identified corrosion fatigue as the main failure mechanism. Yet, fatigue performance of dental implants has been essentially studied in room air, based on the premise that the implant material is relatively resistant to corrosion in the intra-oral environment.

MATERIAL AND METHODS

Thirty-two 3.75-mm titanium alloy implants were tested under cyclic compressive loading. The tests were performed in artificial saliva substitute containing 250 ppm of fluoride. The loading machine stopped running when the implant structure collapsed or when it completed 5 × 10(6) cycles without apparent failure. The load vs. number of cycles was plotted as curve for biomechanical fatigue analysis (S-N curve). The S-N curve plotted for the artificial saliva test was compared to the curve obtained previously for the same implants tested in a room-air environment. Failure analysis was performed using scanning electron microscopy (SEM).

RESULTS

A comparison of the S-N curves obtained in artificial saliva and in room air showed a considerable difference. The S-N curve obtained in the artificial saliva environment showed a finite life region between 535N and 800N. The transition region was found below 465N, with a probability of survival of 50%, while in room air, the transition region was between 810N and 620N and an infinite life region below 620N was identified.

CONCLUSIONS

The results of this study show that environmental conditions adversely affect implants' fatigue performance. This fact should be taken into account when evaluating the mechanical properties of dental implants.

Effect of fluoride on root resorption following heavy and light orthodontic force application for 4 weeks and 12 weeks of retention

OBJECTIVE

To evaluate the null hypothesis that fluoride intake via drinking water has no effect on orthodontic root resorption in humans after orthodontic force application for 4 weeks and 12 weeks of retention.

MATERIALS AND METHODS

Forty-eight patients who required maxillary premolar extractions as part of their orthodontic treatment were selected from two cities in Turkey. These cities had a high and low fluoride concentration in public water of ≥2 pm and ≤0.05 pm, respectively. The patients were randomly separated into four groups of 12 each: group 1HH, high fluoride (≥2 ppm) and heavy force (225 g); group 2LH, low fluoride (≤0.05 ppm) and heavy force; group 3HL, high fluoride and light force (25 g); and group 4LL, low fluoride and light force. Light or heavy buccal tipping force was applied on the upper first premolars for 28 days. At day 28, the left premolars were extracted (positive control side); the right premolars (experimental side) were extracted after 12 weeks of retention. The samples were analyzed with microcomputed tomography.

RESULTS

On the positive control side, under heavy force application, the high fluoride groups exhibited less root resorption (P  =  .015). On the experimental side, it was found that fluoride reduced the total volume of root resorption craters; however, this effect was not statistically significant (P  =  .237). Moreover, the results revealed that under heavy force application experimental teeth exhibited more root resorption than positive control groups.

CONCLUSION

The null hypothesis could not be rejected. High fluoride intake from public water did not have a beneficial effect on the severity of root resorption after a 4-week orthodontic force application and 12 weeks of passive retention.

Fluoride and magnesium concentrations in human dental calculus obtained from Japanese and Chinese patients

Calculus deposited on a total of 68 permanent teeth from patients 30-60 years old from Nagoya in Japan and Beijing in China was investigated. An abrasive microsampling method was used to examine the fluoride (F) and magnesium (Mg) distribution, using a fluoride ion-specific electrode and atomic absorption spectrophotometry, respectively. F concentrations decreased from the surface towards the interior of the calculus. Mg concentrations, however, gradually rose towards the innermost surface adjacent to the tooth. In all parts of the depth profiles, the average concentrations of both magnesium and fluoride were higher in the Japanese than in the Chinese calculus. Towards the inner surface of the calculus, F and Mg concentrations were also much higher in the Japanese than in the Chinese group. A greater intake of sea foods and greater use of fluoride dentifrices are possible reasons for the higher F and Mg concentrations in the Japanese individuals.

Fluoride profiles in dental calculus from Japanese, Chinese and British residents

Whether the fluoride concentrations and profiles differ in human dental calculus obtained from different countries was investigated. A total of 203 dental calculus deposits on 203 permanent teeth from residents (mean age, 52.1 years) of Nagoya (Japan), Shanghai (China), Leeds (Great Britain) and the Wuhan mountainous area (China, fluoridated area) were analysed. An abrasive microsampling procedure was used to examine fluoride distribution. There were five types of fluoride profiles in dental calculus in each area/country (designated types L, J, U, T, W). In supragingival calculus, type L (highest in the outermost layers) and type J (highest in the innermost layers) both had significantly higher values than type U (high in the surface and innermost layers) but were relatively identical. In subgingival calculus, type W (high in the outermost, mid and innermost layers) was characteristics. Calculus from the Wuhan mountainous area (fluoridated) had the highest fluoride concentration, followed by Leeds (non-fluoridated), and Nagoya and Shanghai (non-fluoridated) calculus had the lowest. Fluoride concentrations in supragingival calculus were higher in teeth extracted because of periodontal diseases than dental caries. It is concluded that fluoride concentrations and distribution in dental calculus differ from country to country, probably due to different fluoride environments.

Fluoride distribution in human dental calculus obtained from different sites on the tooth surface

We examined the site specificity of fluoride (F) distribution in human dental calculus. Teeth with supra- and subgingival calculus were obtained from patients who resided in non-fluoridated areas in Japan and China. Sequential layers of the dental calculus (30 microns thick) were abraded by an abrasive micro-sampling technique and fluoride and phosphorus in the powdered samples were analyzed. Fluoride concentrations were highest in the outer, lowest in the middle and intermediate in the inner layers of dental calculus in general. In the outermost layers fluoride concentrations were highest in calculus found near the tooth cervix both in supra- and subgingival calculus. Fluoride concentrations decreased markedly toward the apical region in subgingival calculus, while it did not change toward the incisal or occlusal region in supragingival calculus. In the inner layers, fluoride concentrations in both supra- and subgingival calculus were not affected by position on the teeth. Fluoride concentrations in subgingival calculus near the apex were lower than in supragingival calculus near the incisal or occlusal region. It was concluded that the fluoride concentrations differ in different regions of dental calculus, probably due to their different mechanisms of formation.

Root surface caries: a critical literature review

Little information is available on the prevalence and clinical appearance of root surface caries. The literature shows that root surface caries is thought to be similar to coronal caries, but that certain diet-bacterial interactions might predispose to root surface caries. A scan of the literature concerning the epidemiology, etiology, microbiology, periodontology, as well as reporting methods and restoration treatment of root surface caries shows current practices and suggests future research.

Shallow fluorine depth profiles of cementum in periodontal disease--a pilot study

A nuclear resonant reaction depth profiling technique was used to analyze elemental fluorine distribution in the first 20 microns of human dental cementum. A pilot sample of six periodontally-involved teeth indicated greater levels of fluorine in exposed cementum (0.9 leads to 2.4%) compared to cementum apical to the zone of epithelial attachment (0.4 leads to 1.1%). Furthermore, the exposed cementum appeared to have fluorine levels within the surface 5 microns comparable to the hypermineralized layer previously reported by x-ray diffraction and microprobe techniques. The nuclear resonant reaction is a non-destructive technique which yields useful information of surface elemental distribution as a function of depth, and may be regarded as a potential means of analyzing changes in the inorganic constitution of cementum during various physico-chemical pre-treatments.

The effects of age and fluoride exposure on fluoride, citrate and carbonate content of human cementum

A study was conducted to determine the values of several chemical components of dental cementum. Extracted teeth from continuous residents of low, optimal, and high natural fluoride areas were selected to determine the effects of fluoride exposure and age on the fluoride, citrate and carbonate content of cervical and apical areas of sound and periodontally diseased human cementum. 1. For normal cementum the mean fluoride content of all 18 groups was 0.443 plus or minus 0.04%on an ash basis and 0.253 plus or minus 0.02% on a dry weight basis; the mean citrate content was 1.52 plus or minus 0.10% on an ash basis and 0.86 plus or minus 0.06% on a dry weight basis; the mean carbonate content was 4.95 plus or minus 0.39% on an ash basis and 2.79 plus or minus 0.22% on a dry weight basis. 2. For diseased cementum the mean fluoride content of all 12 groups was 0.575 plus or minus 0.03% on an ash basis and 0.342 plus or minus 0.02% on a dry weight basis; the mean citrate content was 1.19 plus or minus 0.07% on an ash basis and 0.71 plus or minus 0.05% on a dry weight basis; the mean carbonate content was 5.95 plus or minus 0.47% on an ash basis and 3.50 plus or minus 0.28% on a dry weight basis. 3. There is a general increment in fluoride content of normal cervical and apical cementum, both with age and fluoride exposure. For diseased cementum this held true for fluoride exposure but not age. 4. The mean fluoride content of cervical cementum is greater than that of apical cementum for both normal and diseased groups. For citrate and carbonate no definite statistical differences were noted between cervical and apical areas. 5. The diseased cementum has a significantly higher mean fluoride content, a significantly lower citrate content, and a slightly, but not statistically significant, higher carbonate content than normal cementum. 6. Unlike bone, no inverse fluoride/citrate or fluoride/carbonate relationship was observed. 7. For both normal and diseased groups the carbonate content of cementum of individuals over age 40 tended to be lower than for individuals 20-40 years of age.