Anut Itthagarun

Adverse surface interactions between one-bottle light-cured adhesives and chemical-cured composites

OBJECTIVES This study examined the effect of one-bottle adhesives with different acidities on bonding to chemical-cured and light-cured resin composites. METHODS Twenty-four non-carious human third molars were divided into eight groups. A flat dentin surface was created for each tooth. Acid-conditioned dentin surfaces were bonded with Prime&Bond NT (Dentsply), OptiBond SOLO (Kerr), Single Bond (3M) or One-Step (Bisco). Each adhesive group was covered with composite buildups, using either a light-cured (Z100, 3M) or a chemical-cured composite (BisFil 2, Bisco). Specimens were vertically sectioned into 0.9x0.9 mm beams. Microtensile bond strengths were recorded and failure modes were classified using a stereoscopical microscope. Four representative beams from each group were further prepared for SEM examination. RESULTS Two-way ANOVA showed that the effect of adhesive types, composite curing modes and their interaction were statistically significant (P<0.001). Multiple comparison tests revealed no statistically significant difference in the bond strength of the four adhesives with the light-cured composite (P>0.05). However, they were significantly lower when used with the chemical-cured composite (P<0.01). A positive correlation was observed between the acidity of adhesives and the bond strengths of the chemical-cured composite. Failure occurred predominantly along the composite-adhesive interface, with microporosities on the adhesive surface and voids within the chemical-cured composite. SIGNIFICANCE Air incorporated during mixing of chemical-cured composites only contributed partially to the decreased bond strength observed in simplified-step adhesives. Ultrastructural observations suggested the presence of a surface interaction between the uncured, acidic resin monomers from the oxygen inhibition layer of the adhesive and the initiator components in the chemical-cured composite.

The effect of casein phosphopeptide-amorphous calcium phosphate on remineralization of artificial caries-like lesions: an in vitro study.

BACKGROUND The aims of this study were to investigate the efficacy of CPP-ACP containing Tooth Mousse on the remineralization of enamel lesions and to compare its efficacy to that of a fluoride-containing toothpaste. METHODS Permanent teeth were placed in demineralizing solution for 96 hours to produce artificial caries-like lesions 120-200 microm in depth. They were sectioned into 100-150 microm thick samples and randomly assigned to five groups: for Group A, a fluoridated toothpaste (1100 ppm) was used as a positive control and in Group B, a non-fluoridated toothpaste was used as a negative control. Tooth Mousse containing CPP-ACP was tested by three different means: as a toothpaste (Group C); as a topical coating (Group D); and (Group E) as a topical coating after treating the sections with the same fluoridated toothpaste as in Group A. RESULTS The lesion depth decreased significantly by 7 per cent in Group A, 10.1 per cent in Groups C and D, and 13.1 per cent in Group E (Paired t- test, p < 0.05), while in Group B the lesion depth increased significantly by 23 per cent. CONCLUSIONS Based on the data obtained, CPP-ACP containing Tooth Mousse remineralized initial enamel lesions and it showed a higher remineralizing potential when applied as a topical coating after the use of a fluoridated toothpaste.

Micro-tensile bond strengths to sclerotic dentin using a self-etching and a total-etching technique

OBJECTIVES To evaluate the in vitro regional micro-tensile bond strengths of a self-etching/self-priming adhesive system to sclerotic dentin, in the absence or presence of phosphoric acid conditioning. METHODS Naturally-occurring, non-carious cervical lesions on extracted premolars were hand-cleaned with a slurry of pumice and chlorhexidine, then bonded without further cavity preparation. One group was bonded using Clearfil Liner Bond 2V (Kuraray Co. Ltd., Osaka, Japan). The other group was first conditioned with K-etchant; 40% phosphoric acid gel (Kuraray) prior to the application of the self-etching primer. Artificially prepared wedge-shaped cavities were also made in sound premolars and bonded with the two methods as controls. Resin composite build-ups were made using Clearfil Protect Liner F and AP-X resin composite (Kuraray). After storage in water for 24h, the teeth were sectioned into 0.7 x 0.7 mm composite-dentin beams along the occlusal and gingival walls, and at the apex of the lesions. The use of two conditioning methods, two substrate types, and three different locations yielded 10-14 beams for each of the 12 groups. After testing for the microTBS, representative beams that were stressed to failure were examined with SEM. Remaining fractured beams were demineralized and processed for TEM examination. Statistical analysis was performed using a three-way ANOVA and Student-Newman-Keuls tests. RESULTS Regardless of the conditioning methods, bond strengths to sound dentin were significantly higher than to sclerotic dentin (P< 0.05). With sclerotic dentin, there was no significant difference for the conditioning methods used, except that K-etchant significantly improved the bond strength at the gingival aspect of the lesions. Fractographic analysis revealed that the self-etching primer could not etch beyond the surface hypermineralized layer of sclerotic dentin. Interfacial failure occurred along the surface of the mineralized intermicrobial matrix and/or hypermineralized layer. With the use of phosphoric acid, a hybrid layer was only seen when the surface layers were thin. Incompletely removed sclerotic casts were evident in both groups. SIGNIFICANCE Removal of the surface layers of sclerotic dentin and/or conditioning with stronger acids may be beneficial to obtain stronger bonding to sclerotic dentin.

Comparing two quantitative methods for studying remineralization of artificial caries

OBJECTIVES To compare the detection of changes before and after remineralization of artificial enamel and dentin caries by microCT scanning, polarized light microscopy (PLM) and transverse microradiography (TMR). METHODS Fourteen extracted premolars were cut into tooth blocks and painted with an acid-resistant varnish leaving one enamel and one dentin surface exposed. The tooth blocks were immersed into demineralizing solution for 4 days to produce artificial caries-like lesions and scanned by microCT. Then the 14 tooth blocks were randomly allocated into two groups. Seven tooth blocks in Group I were cut longitudinally through the exposed surface into 100-150 microm thick sections and microradiographs were taken. The other seven tooth blocks in Group II were left intact. All the tooth blocks and sections were then immersed into remineralizing solution for 5 days. PLM and TMR of the tooth sections in Group I were taken again. Depth of the lesion on the TMR was measured. Tooth blocks in Group II were scanned by microCT. RESULTS Mean lesion depth in Group I reduced by 13.0% and 8.2% after remineralization for enamel and dentin, respectively (paired t-test, P<0.001). In Group II, linear attenuation coefficient (LAC) of the region of interest (ROI) increased by 11.1% and 23.8% after remineralization for enamel and dentin lesions, respectively (paired t-test, P<0.001). CONCLUSION Both microCT and microradiography are able to detect a change of similar magnitude in the artificial caries lesions after remineralization. MicroCT may be used to substitute TMR and PLM in in vitro studies about caries.

Submicron hiati in acid-etched dentin are artifacts of desiccation.

OBJECTIVES The submicron hiatus represents a potential space between the base of the collagen network and the mineralized dentin when dentin is acid-etched for bonding. These spaces were observed in SEM studies after acid-etched dentin specimens were critical point dried or dehydrated in hexamethyldisilasane. However, they have never been identified in TEM studies of dentin hybrid layers. This study critically examined the cause of submicron hiati formation using a silver staining technique to measure nanoleakage. METHODS Two multi-step, total-etch adhesives (One-Step, Bisco; Single Bond, 3M) and two single-step, self-etching adhesives (Prompt L-Pop, ESPE; One-Up Bond F, Tokuyama) were examined. Flat dentin surfaces were bonded with these adhesives and a lining composite. In each adhesive group, 0.8mm thick slabs from the same bonded tooth were coated with nail varnish applied 1mm from the bonded interfaces. The varnish was either left to dry completely for 10min before immersing in 50wt% silver nitrate (AgNO(3)) for 24h (group D), or painted on blotted tooth slabs that were immediately dropped into the AgNO(3) solution (group M). After developing, undemineralized, unstained, epoxy resin-embedded sections were prepared for transmission electron microscopy (TEM) to identify the amount and distribution of silver uptake. RESULTS Nanoleakage patterns were observed in all adhesive-bonded teeth, regardless of brand. Fine reticular silver deposits were also found in the underlying undemineralized dentin. In group D, submicron hiati were seen as tunnels of heavy silver deposits beneath hybrid layers. Specifically, a hiatus occurred between the undemineralized intertubular dentin and a cohesively fractured layer of the same matrix that was attached to the base of the hybrid layer. Hiati were completely absent in group M, regardless of the brand of adhesive. SIGNIFICANCE Submicron hiati are artifacts created by desiccation during specimen processing, and should be referred to as such in future studies of bonded dentin interfaces.

The Effect of Chewing Gums Containing Calcium Phosphates on the Remineralization of Artificial Caries-Like Lesions in situ

Caries-Like Lesion Preparation Sound, extracted molars were cleansed of soft tissue debris and inspected for cracks, hypoplasia, and white spot lesions. The teeth were then coated with acid-resistant nail varnish (Lancester, Germany), leaving a narrow horizontal window, approximately 1 mm wide, on the buccal and lingual surfaces. Each tooth was immersed in 10 ml of a demineralizing solution [ten Cate and Duijsters, 1983] for 96 h to produce artifi cial caries lesions approximately 100–120 m deep. The teeth were sectioned with a Silverstone-Taylor hardtissue microtome buccolingually through the lesions, in an occlusalapical direction, to produce longitudinal sections approximately 100–150 m thick. One hundred and forty-four buccal or lingual sections were selected and randomly divided into three equal-sized groups, i.e. 48 sections per group. Every section was studied using polarized light microscopy and microradiography in order to record the depth and mineral content of the lesions before and after each of the three 21-day intra-oral periods. Prior to being attached to an intra-oral appliance, each section was carefully painted with acidresistant nail varnish, leaving only the lesion surface exposed to the oral environment. After the intra-oral test phase of the experiment, this nail varnish was removed by immersion in acetone for 10 s and by thorough rinsing with deionized water. All the sections were stored in an environment with 100% humidity until required for the experiment.

Effects of different amounts of a low fluoride toothpaste on primary enamel lesion progression: a preliminary study using in vitro pH-cycling system

Aims: To evaluate and compare the efficacy of pea and halfpea portions of child formula fluoride (500ppm) toothpaste on artificially created enamel lesions in primary teeth. Methods: Sound primary incisors were painted with nail varnish, leaving a 1 mm wide window and then placed in a demineralising solution for 96 h to produce artificial carious lesions 60–100μm deep. The teeth were longitudinally sectioned (100μm thick) and divided into 3 groups. Group A: treated with a pea-sized portion of a non-fluoride containing toothpaste (1:3, toothpaste: deionized water), while Groups B and C were treated with half-pea-sized and pea-sized portions of a 500 ppm fluoride containing toothpaste, respectively. The pH-cycling model was utilized for 7 days. Results: Groups A and B lesions increased in depth by 60% while those in Group C increased by 19%. The mineral content of the surface zone decreased significantly in Groups A and B but not in Group C. Conclusion: Reduction of the amount of fluoride toothpaste to less than a pea-size in order to minimize the risk of fluorosis should be undertaken with caution because it may compromise the cariostatic effects of the toothpaste.

Effects of fluoridated milk on artificial enamel carious lesions: A pH cycling study

OBJECTIVE To investigate the relationship between concentration of fluoride in milk and its re-mineralizing efficacy, and to test whether increasing the volume of fluoridated milk has any effect on its re-mineralizing efficacy. METHODS Third molars were painted leaving a 1 mm window on the buccal and/or lingual surfaces. Artificial carious lesions were induced using a de-mineralizing solution. The teeth were then sectioned longitudinally. Specimens were randomly assigned to 15 groups according to different concentrations and volume; i.e., 2.5 ppm, 5 ppm, 7.5 ppm, 10 ppm, 15 ppm, 20 ppm, and 250 ppm of fluoride with 25 ml/section and 50 ml/section. De-ionized water and plain milk were used as controls. Sections were subjected to pH cycling for 20 days. Polarized light microscopy and micro-radiography were utilized to record the lesion characteristics before and after pH cycling. RESULTS Mean lesion depths decreased significantly in all the fluoride groups, and increased significantly in the control groups. There were no differences in percentage of lesion depth decrease when the volume was doubled for the same fluoride concentration. There were also no statistically significant differences between percentages of decrease in lesion depth when the concentration of fluoride in milk was increased. CONCLUSION Fluoridated milk demonstrated a remineralization efficacy on early enamel carious lesions. A 2.5 ppm fluoride milk concentration provided similar remineralization potential to that of higher fluoride concentration in milk.

Comparison of the remineralizing potential of child formula dentifrices

BACKGROUND Although child formula fluoridated dentifrices can be used safely by young children their remineralizing capability remains questionable. AIMS To evaluate the remineralizing potential of child formula dentifrices on primary teeth. DESIGN In vitro single-section technique utilizing a 7 days pH-cycling model. METHODS Primary teeth were placed in demineralizing solution for 96 h to produce artificial carious lesions 100 μm deep, and then cut longitudinally into 50 sections 100-150 μm thick and randomly assigned to five groups. Sections in Groups A to D were treated with dentifrices containing 500 ppm AmF, 500 ppm MFP, 500 ppm MFP and xylitol, or 500 ppm NaF, respectively. Group E sections were treated with a nonfluoridated dentifrice. OUTCOME MEASUREMENTS Lesions were evaluated using polarized light microscopy and microradiography. RESULTS Group D (500 ppm NaF) sections exhibited a significant decrease in lesion depth, whereas those in Group E (nonF) showed a significant increase in depth (P<0.05, paired t-test). Decrease in lesion progression was observed in Groups A, B and C. CONCLUSIONS The 500 ppm NaF dentifrice demonstrated remineralization of carious lesions by virtue of a significant decrease in lesion depth; whereas dentifrices that contained AmF, MFP and MFP with xylitol decelerated the progression of demineralization.

Remineralization of initial enamel carious lesions using fluoridated milk in vitro

Abstract Objectives. Milk is a universal dietary component and it is now recognized as an effective medium for the delivery of fluoride (F). This study sought (i) to evaluate fluoridated milk (2.5 ppm, 5 ppm, 10 ppm) for remineralizing carious lesions and (ii) to determine the optimum frequency for treating carious lesions with fluoridated milk. Materials and methods. Artificial carious lesions, 90–180 μm deep, were created on extracted third molar teeth that were sectioned to produce specimens of 100–120 μm thickness. Specimens were randomly divided into 13 groups (n = 20) for treatment with deionized water, plain milk or fluoridated milk (2.5 ppm, 5 ppm, 10 ppm); once daily, twice daily or on alternate days as part of a 20-day pH cycling model. Lesion depth (LD) and mineral content were evaluated before and after pH cycling. Paired t-test, ANOVA and Student-Newman-Keuls tests were employed to make comparisons within and between the different groups. Results. Fluoridated milk significantly reduced LD and increased the mineral content of the lesions compared to plain milk and deionized water (p < 0.05). The greatest reduction in LD was with 2.5 ppm F milk used twice daily (p < 0.05). Conclusions. Milk with 2.5 ppm F used twice daily demonstrated the greatest remineralization of artificial enamel carious lesions in vitro.