An investigation of some food-approved polymers as agents to inhibit hydroxyapatite dissolution

Dental erosion involves dissolution of the hydroxyapatite fraction of enamel and dentine, so agents that reduce the dissolution rate of hydroxyapatite could find application in food products aimed at reducing erosion. This study was performed to test some common food ingredients and additives for their effect on the dissolution rate of hydroxyapatite in a citric acid solution representative of soft drinks. Pyrophosphate, tripolyphosphate and a linear chain polyphosphate (average 25 phosphate units) significantly reduced the hydroxyapatite dissolution rate by 35, 46 and 64%, respectively. Xanthan gum and carboxymethylcellulose significantly reduced the hydroxyapatite dissolution rate by 29 and 16%, respectively. The protective effect may be ascribed to the binding of condensed phosphate or to the formation of an adsorbed layer of gum at the hydroxyapatite surface. Several other common food additives had no statistically significant effect on the hydroxyapatite dissolution rate. Polyphosphate exhibited a considerable persistence of action, causing a reduction in the dissolution rate for 3 h after treatment. Tripolyphosphate was slightly persistent, and pyrophosphate and xanthan gum did not exhibit a substantial persistence of action. A solution containing polyphosphate and xanthan gum reduced the hydroxyapatite dissolution rate by 70% and exhibited a similar persistence of action to the solution containing only polyphosphate. These compounds are suggested to have potential as erosion-reducing agents in soft drinks.     

Influence of fatigue testing and cementation mode on the load-bearing capability of bovine incisors restored with crowns and FRC posts

The aim of the study was to evaluate the influence of fatigue and cementation mode on the fracture behaviour of endodontically treated bovine incisors restored with fiber-reinforced-composite (FRC) posts and crowns. Forty-eight endodontically treated incisors were restored with FRC posts, composite build-ups, and cast crowns. In 16 teeth, each of the posts were cemented conventionally with KetacCem (3M Espe) or adhesively with Panavia F (Kuraray) or RelyXUniCem (3M Espe). One-half of the specimens in each group were subjected to thermal cycling with 10,000 cycles at 5-55°C and mechanical aging, loading the specimens in 1,200,000 cycles with 50 N. Fracture resistance was determined by loading the specimens until fracture at an angle of 45°. The loading test showed that cementation mode and fatigue testing had an influence on the load bearing capability. Before fatigue testing no statistically significant differences between the different cementation modes could be detected. After fatigue testing, conventionally cemented FRC posts lead to statistically significant higher fracture loads compared to adhesively luted posts. Most specimens fractured in a favourable way, independent from the type of cementation.     

Pharmacokinetic profile of a locally administered doxycycline gel in crevicular fluid,blood, and saliva

BACKGROUND: With the help of so-called controlled release delivery systems, the half-life period of locally administered antibiotics in gingival crevicular fluid (GCF) can be extended significantly. The aim of this study was to characterize the delivery profile of a new one-component 14% doxycycline free amine gel for local application. Pharmacokinetics of doxycycline (DOXY) were analyzed in GCF, saliva, and serum. METHODS: Twenty patients with persisting or recurring pockets (probing depths > or = 5 mm and bleeding on probing) after mechanical treatment (surgical or non-surgical) took part in the study. In each patient 1 periodontal defect was treated with DOXY gel. Samples of GCF, saliva, and serum were obtained before application of DOXY gel; 15 minutes after application; at 2 and 5 hours; and at 1, 2, 3, 4, 7, 9, and 11 days after application. Separation and quantitative measurement of DOXY was performed with high performance liquid chromatography and UV detection at lambda = 260 nm. RESULTS: Coefficients of variation were lower than 2% (intraassay) and 4% (interassay), respectively. For concentrations between 50 to 1000 microg/ml, we found a linear relationship between expected and measured DOXY values (linear coefficient of correlation: r = 0.998). Within the first 5 hours after application, concentration of DOXY in GCF (maximum after 15 minutes 19.97 +/- 5.85 mg/ml) and saliva (maximum after 15 minutes 17.83 +/- 2.84 mg/ml) was similar. Then concentration fell to a lower level (28.90 +/- 19.44 microg/ml) compared to GCF (577.41 +/- 127.34 microg/ml) after 3 days. Up to 10 days after application, the concentration of DOXY in GCF was 34.24 microg/ml. With the exception of 1 patient, all serum samples were DOXY-negative. CONCLUSIONS: 1) After subgingival application of biodegradable 14% doxycycline gel, mean doxycycline levels in GCF that exceeded 16 microg/ml could be maintained for at least 12 days. Thus, the antimicrobial agent may be classified as a controlled release device. 2) The antibiotic effect was limited mainly to the subgingival sites of application of the doxycycline gel. 3) The doxycycline gel possesses the pharmacokinetic and clinical properties to deliver efficacious levels of antibiotics to the periodontal pocket and to maintain these levels for at least 1 week without the need of further drug retention by a periodontal dressing.     

Conservative aesthetic techniques for discoloured teeth: 2. Microabrasion and composite

The first article in this series discussed the minimal intervention approach to discoloured teeth, starting with dental bleaching. This second article goes on to explain the technique of microabrasion and the use of direct composite techniques. CLINICAL RELEVANCE: Microabrasion and composite can provide minimally invasive treatments for discoloured teeth.     

Examiner training and reliability in two randomized clinical trials of adult dental caries

Objectives: This report describes the training of dental examiners participating in two dental caries clinical trials and reports the inter‐ and intra‐examiner reliability scores from the initial standardization sessions. Methods: Study examiners were trained to use a modified International Caries Detection and Assessment System II system to detect the visual signs of non‐cavitated and cavitated dental caries in adult subjects. Dental caries was classified as no caries (S), non‐cavitated caries (D1), enamel caries (D2), and dentine caries (D3). Three standardization sessions involving 60 subjects and 3,604 tooth surface calls were used to calculate several measures of examiner reliability. Results: The prevalence of dental caries observed in the standardization sessions ranged from 1.4 percent to 13.5 percent of the coronal tooth surfaces examined. Overall agreement between pairs of examiners ranged from 0.88 to 0.99. An intra‐class coefficient threshold of 0.60 was surpassed for all but one examiner. Inter‐examiner unweighted kappa values were low (0.23‐0.35), but weighted kappas and the ratio of observed to maximum kappas were more encouraging (0.42‐0.83). The highest kappa values occurred for the S/D1 versus D2/D3 two‐level classification of dental caries, for which seven of the eight examiners achieved observed to maximum kappa values over 0.90. Intra‐examiner reliability was notably higher than inter‐examiner reliability for all measures and dental caries classifications employed. Conclusion: The methods and results for the initial examiner training and standardization sessions for two large clinical trials are reported. Recommendations for others planning examiner training and standardization sessions are offered.     

The correlation of DIFOTI to clinical and radiographic images in Class II carious lesions

BACKGROUND: The authors conducted a study to evaluate the correlation between digital imaging fiber-optic transillumination (DIFOTI) (KaVo Dental, Lake Zurich, Ill.) and clinical and radiographic images in estimating the true clinical axial extension of Class II carious lesions. METHODS: The authors examined 51 Class II carious lesions visually, imaged them by means of DIFOTI and radiographed them with D-speed film and a complementary metal oxide silicon (CMOS)-based digital radiographic sensor. They validated axial extension of the lesions clinically. They compared the clinical and radiographic depths of the carious lesion with the size of the lesion on the DIFOTI images. RESULTS: The authors detected 84 percent of the lesions with DIFOTI, and 82 percent showed a visible dark shadow under the marginal ridge when examined clinically. DIFOTI correlated significantly with the clinical depth of decay (Pearson r = 0.43189). The combination of a CMOS digital sensor and DIFOTI (R2 = 0.7210) provided readings closer to the clinical measures than did the combination of D-speed film and DIFOTI (R2 = 0.6215). CONCLUSIONS: DIFOTI images correlated with clinical depth, especially in smaller lesions, and improved the estimation of lesion size when used in conjunction with the CMOS digital sensor and D-speed images. CLINICAL IMPLICATIONS: Using radiographs in combination with DIFOTI images could help clinicians determine the presence and, to some extent, the size of proximal caries, especially in smaller lesions.