Micro-shear bond strength of current one-step adhesives to cementum and dentin

PURPOSE

To investigate the bonding performance of current one-step adhesives to human cementum and compare the results with those of two-step adhesives.

METHODS

Four commercially available adhesives were investigated: two one-step adhesives (Clearfil Tri-S Bond and G-Bond), and two two-step adhesives: a self-etch adhesive (Clearfil SE Bond) and a total-etch wet bonding adhesive (Adper Single Bond). The cementum and dentin regions were chosen from the mesial surface of extracted human molars and bonded with each adhesive. A micro-shear bond test was employed to evaluate the bond strength in this study. Morphological micrographs of cementum and dentin after etching, as well as bonded interfaces were obtained using scanning electron microscopy.

RESULTS

The shear bond test results showed significantly lower bonding of all adhesives when they were applied to cementum (P < 0.05). The mean bond strength values in MPa obtained from dentin and cementum were 33.7 and 26.7 for Clearfil Tri-S Bond, 28.9 and 22.4 for G-Bond, 42.9 and 35.2 for Clearfil SE Bond and 38.6 and 32.5 for Adper Single Bond, respectively. One-step adhesives showed significantly lower bond strengths than two-step adhesives to both cementum and dentin (P < 0.05).

Influence of bonded enamel margins on dentin bonding stability of one-step self-etching adhesives

PURPOSE

To evaluate the dentin bonding durability of two one-step self-etching adhesive systems with and without the presence of surrounding enamel.

MATERIALS AND METHODS

Tri-S Bond (Kuraray) and G-Bond (GC), commercially available adhesive systems, were used in this study. The occlusal enamel was removed in order to form a flat, midcoronal dentin surface. The adhesives were applied to both the dentin and the surrounding enamel surfaces according to the manufacturers' instructions. Resin composite crowns (Clearfil AP-X, Kuraray) were incrementally built up with each layer being photocured for 40 s. Half the bonded teeth were sectioned perpendicular to the adhesive interface into 0.7-mm-thick slabs, and then trimmed to an hourglass shape with a 1 mm2 cross-sectional area for microtensile bond strength testing, followed by storage in water for 6 months (direct water exposure group, DE). The other half were left untrimmed and stored in water for 6 months (indirect water exposure group, IE). As control groups, additional bonded teeth were prepared for water storage for 24 h. After the designated periods of water storage, the specimens were subjected to bond strength testing at a crosshead speed of 1.0 mm/min. The microTBS data were statistically analyzed using three-way ANOVA and post-hoc tests (t-test and Tukey's HSD comparison tests) (alpha = 0.05).

RESULTS

Indirect water exposure of the resin/dentin interface did not affect the microTBS of either adhesive after 6 months water storage (p < 0.05). However, direct exposure to water significantly reduced the microTBS of both adhesives to dentin (p < 0.05). In addition, there were no significant differences in muTBS between the two adhesive systems for each experimental storage condition (p > 0.05).

CONCLUSION

The durability of resin-dentin bonds was found to be dependent on the method in which the bonded specimens were aged in water. Significantly lower bond strengths were observed for specimens that were sectioned into an hourglass shape before aging compared to those that were sectioned after water storage.

Effect of Er:YAG laser on dentin bonding durability under simulated pulpal pressure

PURPOSE

To evaluate the effects of Er:YAG laser ablation on the microtensile bond strength and the nanoleakage of Er:YAG-lased dentin bonded to a self-etching adhesive system with and without pulpal pressure.

MATERIALS AND METHODS

Twenty flat dentin surfaces were obtained from extracted molars. Ten specimens were irradiated by Er:YAG laser, other specimens (control group) were ground using #600 SiC paper. Direct communication to the pulp chamber was created by cutting at a level approximately 1 mm below the cementoenamel junction and parallel to the occlusal surface. The experimental groups were exposed to a simulated pulpal pressure of 15 cm H2O. Each specimen was restored using an adhesive and a photocured composite. The specimens were then sectioned vertically to obtain dentin/adhesive slabs. Ninety-six slabs were prepared for microtensile bond testing. Sixty-four slabs were immersed in ammoniacal silver nitrate tracer solution for 18 h, then rinsed thoroughly, and immersed in photodeveloping solution for 6 h prior to their examination by FE-SEM.

RESULTS

The method of dentin preparation and the pulpal pressure storage condition significantly affected the microTBS, while the storage duration did not (p < 0.05). The nanoleakage patterns observed in the dentin/bond interface differed depending on whether the dentin was conventionally prepared or ablated by Er:YAG laser.

CONCLUSION

Er:YAG laser ablation to dentin adversely affected the microTBS and the sealing ability of SE Bond bonded to dentin under simulated pulpal condition.

Assessment of the nanostructure of acid-base resistant zone by the application of all-in-one adhesive systems: Super dentin formation

An acid-base resistant zone (ABRZ) has been shown to be created under a hybrid layer in a self-etching adhesive system at the adhesive/dentin interface. The purpose of this study was to assess the nanostructure of the ABRZ by applying all-in-one adhesive systems. Human premolar dentin was treated with one of two all-in-one adhesive systems; Clearfil Tri-S Bond and G-Bond according to the manufacturers' instructions. After placement of a resin composite, the bonded interface was vertically sectioned and subjected to an acid-base challenge. Following this, the nanostructure of the ABRZ was examined by SEM and TEM. The SEM observations of the adhesive-dentin interface after the acid-base challenge indicated that a hybrid layer less than 1 mum thick was created, and a ABRZ was formed beneath the hybrid layer for each adhesive system. The TEM observations indicated that the ABRZ contained mineral components in both adhesive systems, however, the thickness of the ABRZ was material dependent. The application of the all-in-one adhesive systems created an ABRZ at the underlying dentin, which reinforced normal dentin against dental caries. Therefore, this zone was named 'Super Dentin'. Formation of 'Super Dentin' is a new approach in caries prevention.

Effects of photocuring strategy on bonding of dual-cure one-step self-etch adhesive to root canal dentin

This study evaluated the effects of light power density and light exposure time on regional bond strength of Clearfil DC Bond to root canal dentin. Post spaces were prepared in extracted premolars. Root canal dentin was treated with a dual-cure bonding system, Clearfil DC Bond, and light-cured for 10, 20, or 30 seconds using two halogen light curing units: Optilux 501 (830 mW/cm2) and Hyperlightel (1350 mW/cm2). Following which, all post spaces were filled with a dual-cure resin composite. After 24-hour storage, microtensile bond strengths (microTBS) at the coronal and apical regions were measured. At the coronal region, microTBS values were similar among all the experimental groups. At the apical region, bond strength improved when the curing time was extended to 30 seconds with Optilux 501, and likewise with Hyperlightel when curing time was extended to 20 or 30 seconds. In addition, significant differences in microTBS between the coronal and apical regions disappeared with prolonged curing times.

Bond strength of a resin cement to dentin using the resin coating technique

The aim of this study was to evaluate the bond strength of a resin cement to dentin using different adhesive systems (AS) in the presence or absence of a low-viscosity composite liner (Protect Liner F - PLF) applied over the bonded dentin. The adhesive systems selected were: AdheSE/Vivadent (AD); Clearfil Protect Bond/Kuraray (CP); One-Up Bond F/Tokuyama (OU); Single Bond/3M ESPE (SB); Tyrian SPE/One-Step Plus/Bisco (TY); Xeno III/Dentsply (XE) and Unifil Bond/GC (UN). After removing the labial and lingual enamel surfaces of bovine incisors, dentin fragments were prepared and randomly divided into 15 groups (n = 8). The dentin substrates were bonded with the AS and the PLF was applied or not before application of the resin cement (Panavia F, Kuraray). In the control group, the ED Primer (ED) and the resin cement without PLF were used. The AS, PLF and resin cement tested were used according to the manufacturers' instructions, and all treated dentin surfaces were temporized. After water storage for one week, three cylinders of resin cement were applied to each bonded dentin surface, using tygon tubing molds. The specimens were subjected to micro-shear testing and the data were statistically analyzed (two-way ANOVA, Tukey and Dunnett tests, p < 0.05). The observed mean shear bond strengths in MPa were: ED: 20.2 +/- 2.3; AD: 30.3 +/- 6.5; CP: 25.3 +/- 4.4; OU: 28.3 +/- 6.6; SB: 25.6 +/- 6.9; TY: 24.5 +/- 2.5; XE: 17.3 +/- 3.4; UN: 28.4 +/- 6.2; AD+PLF: 32.8 +/- 4.1; CP+PLF: 29.9 +/- 3.9; OU+PLF: 34.1 +/- 4.1; SB+PLF: 29.5 +/- 8.2; TY+PLF: 29.2 +/- 3.9; XE+PLF: 32.8 +/- 6.7; UN+PLF: 32.2 +/- 4.5. The bond strength of the resin cement to dentin using the tested AS was increased when the low-viscosity composite liner was applied.

Effect of resin coating on adhesion and microleakage of computer-aided design/computer-aided manufacturing fabricated all-ceramic crowns after occlusal loading: a laboratory study

This study investigated the effect of resin coating and occlusal loading on adhesion and microleakage of all-ceramic crowns. Molars were prepared for an all-ceramic crown and were divided into two groups: non-coated (control) and resin-coated with Clearfil Tri-S Bond. Crowns were fabricated using CEREC 3 and cemented using Clearfil Esthetic Cement. After 24 h of storage in water, the restored teeth in each group were divided into two subgroups: unloaded, or loaded while stored in water. Mechanical loading was achieved with an axial force of 80 N at 2.5 cycles s(-1) for 250,000 cycles. After immersion in Rhodamine B, the specimens were sectioned and processed for microleakage evaluation by confocal microscopy, which was followed by further sectioning for microtensile bond testing. Loading had no significant effect on microleakage in either the resin-coated or non-resin-coated groups. Resin coating did not reduce the microleakage at the dentine interface but increased the microleakage at the enamel interface. All the beams fractured during slicing when non-coated and loaded. The bond strengths of non-coated and unloaded, resin-coated and unloaded, and resin-coated and loaded groups were 15.82 +/- 4.22, 15.17 +/- 5.24, and 12.97 +/- 5.82 MPa, respectively. Resin coating with Clearfil Tri-S Bond improved the bonding of resin cement to dentine for loaded specimens. However, it was not effective in reducing the microleakage, regardless of whether it was loaded or unloaded.

Preservation in the liquid media produces alterations in enamel surface properties

OBJECTIVE

The aim of the study was to elucidate any alterations in nanomechanical properties and structural integrity of enamel surfaces after preservation in different liquid media.

METHODS

The nanohardness and modulus of elasticity of bovine enamel blocks were measured before (control) and after storage in all of the following liquid media: human pooled saliva, physiological saline (NaCl), Deionized water (Milli-Q water) and phosphate buffered saline (PBS) for 1, 7, 14 and 30 days. Control and the 30 days preserved samples were examined by scanning electron microscopy (SEM). Data were analysed by one-way ANOVA and Dunnett T(3) test.

RESULTS

Hardness and modulus of elasticity of enamel in saliva up to 14 days showed no significant decrease compared to controls. In the case of PBS, both hardness and modulus did not change up to 30 days. The hardness values of Milli-Q water (12.06%) and NaCl (14.19%) samples were reduced significantly after just for 1 day and after 30 days were reduced to 55.59% and 61.18%, respectively. The Young's modulus of NaCl samples showed significant reduction (8.35%) after 1 day, but not for Milli-Q water samples. From 7 to 30 days, significant reductions for both samples were detected. SEM photomicrographs of samples in saliva showed widening of the inter-prismal space, while in PBS samples the structural damage was less. In the Milli-Q water group, prominent structural damage was observed and in case of NaCl, the enamel prisms were eroded.

CONCLUSIONS

Human saliva and PBS are better for short term preservation of enamel samples compared to NaCl and Deionized water.

Bond Strengths of Resin Cements to Astringent-contaminated Dentin

The contamination of the dentin surface with an astringent-containing aluminum chloride does not reduce the bond strength of either the resin cement used in conjunction with an etch-and-rinse or the resin cement with a self-etching adhesive. However, the contamination probably interferes with the etching ability of the self-etching primer and the adaptation of the resin cement to the dentin surface.

Role of lysine in interaction between surface protein peptides of Streptococcus gordonii and agglutinin peptide

INTRODUCTION

Streptococcus gordonii interacts with the salivary pellicle on the tooth surface and plays an important role in dental biofilm formation. Reports show that the analog Ssp peptide (A11K; alanine to lysine at position 11 in the arranged sequence, (1)DYQAKLAAYQAEL(13)) of SspA and SspB of S. gordonii increased binding to the salivary agglutinin (gp-340/DMBT1) peptide (scavenger receptor cysteine-rich domain 2: SRCRP2). To determine the role of lysine in the binding of the Ssp(A11K) peptide to SRCRP2, we investigated whether an additional substitution by lysine influenced the binding of Ssp(A11K) peptide to SRCRP2 using a BIAcore biosensor assay.

METHODS

Six analogs of the Ssp peptide with positive charges in surface positions on the structure were synthesized using substitution at various positions.

RESULTS

The binding activity of analog Ssp(A4K-A11K) peptide was significantly higher than the other Ssp analogs. The binding activity rose under low ionic strength conditions. The distance between positively charged amino acids in the Ssp(A4K-A11K) peptide between 4K and 11K was 1.24 +/- 0.02 nm and was close to the distance (1.19 +/- 0.00 nm) between Q and E, presenting a negative charged area, on SRCRP2 using chemical computing graphic analysis. The molecular angle connecting 1D-11K-4K in the Ssp(A4K-A11K) peptide secondary structure was smaller than the other peptide angles (1D-11K-XK). The Ssp(A4K-A11K) peptide showed higher inhibiting activity for Streptococcus mutans binding to saliva-coated hydroxyapatite than the (A11K) peptide.

CONCLUSION

The positioning of lysine is important for binding between Ssp peptide and SRCRP2, and the inhibiting effect on S. mutans binding to the tooth surface.

Inhibiting effects of Enterococcus faecium non-biofilm strain on Streptococcus mutans biofilm formation

BACKGROUND AND PURPOSE

Enterococcus faecium is a normal bowel commensal and lactic acid bacterium that is rarely found in the oral cavity. This study investigated whether a non-pathogenic and non-biofilm strain of E. faecium functioned as a probiotic strain toward biofilm formation by Streptococcus mutans, which is an etiological agent for dental caries.

METHODS

The effects of E. faecium on streptococcal biofilm was evaluated by absorbance of safranin-stained biofilm at 492 nm in a 96-well microtiter plate.

RESULTS

The E. faecium strain demonstrated cell-number-dependent inhibition of biofilm in dual cultures with 4 laboratory and 16 clinical S. mutans strains, as well as laboratory strains of Streptococcus sobrinus and Streptococcus sanguinis, in 96-well microtiter plates. The inhibiting effects of E. faecium were not dependent on the production of bacteriocin from streptococci and E. faecium, low pH after mix culture, or biofilm formation levels of S. mutans. A culture supernatant sample of more than 10 kDa from E. faecium showed direct inhibiting effects toward S. mutans biofilm formation. Treatment of heat, butanol, and phenol to a supernatant sample restored biofilm formation in culture of S. mutans with the sample. Moreover, the tendencies of inhibition levels by the supernatant sample were associated with those by bacterial cells of E. faecium to S. mutans strains.

CONCLUSIONS

The E. faecium non-biofilm strain produced an inhibiting protein to streptococci biofilm formation, showed various susceptibilities to inhibit streptococcal biofilm, and acted as a probiotic bacterial inhibitor of streptococcal biofilm formation.

Durability of resin-dentin bonds to water- vs. ethanol-saturated dentin

Higher 24-hour resin-dentin bond strengths are created when ethanol is used to replace water during wet bonding. This in vitro study examined if ethanol-wet-bonding can increase the durability of resin-dentin bonds over longer times. Five increasingly hydrophilic experimental resin blends were bonded to acid-etched dentin saturated with water or ethanol. Following composite build-ups, the teeth were reduced into beams for 24-hour microtensile bond strength evaluation, and for water-aging at 37 degrees C for 3, 6, or 12 months before additional bond strength measurements. Although most bonds made to water-saturated dentin did not change over time, those made to ethanol-saturated dentin exhibited higher bond strengths, and none of them fell over time. Decreased collagen fibrillar diameter and increased interfibrillar spacing were seen in hybrid layers created with ethanol-wet-bonding. Increases in bond strength and durability in ethanol-wet-bonding may be due to higher resin uptake and better resin sealing of the collagen matrix, thereby minimizing endogenous collagenolytic activities.

Microtensile bond strength of etch-and-rinse and self-etching adhesives to intrapulpal dentin after endodontic irrigation and setting of root canal sealer

PURPOSE

To evaluate the effect of endodontic irrigation regimens and calcium hydroxide root canal sealer (Sealapex) on the microtensile bond strengths (muTBS) of dual-curing resin composite (Clearfil DC Core Automix) to the intrapulpal dentin.

MATERIALS AND METHODS

Forty standardized coronal-half root canal dentin specimens obtained from human premolars were divided into 4 groups: group A, no treatment (control); group B, Sealapex; group C, NaOCl/Sealapex; group D, EDTA/NaOCl/Sealapex. After 7 days of storage in 100% relative humidity, Sealapex was removed. Dentin surfaces were bonded with adhesives, either etch-and-rinse (Single Bond) or self-etching (Clearfil SE Bond), and built up with resin composite. The bonded specimens were trimmed into an hourglass shape with a 1-mm2 cross-sectional area for microtensile testing (n = 20). The muTBS to intrapulpal dentin was analyzed using two-way ANOVA and Dunnett's TC test. Two teeth of each group were prepared for micromorphological analysis of dentin surface.

RESULTS

The root canal sealer with or without endodontic irrigation significantly affected the bond strengths of resin composite to intrapulpal dentin compared with the control group (p < 0.05). There were no significant differences in muTBS of each experimental group between etch-and-rinse and self-etching adhesives (p > 0.05). The dentin surface was covered with a mud-like material after sealer application for 7 days.

CONCLUSION

The root canal sealer reduced the muTBS of dual-curing resin composite with etch-and-rinse and self-etching adhesive systems to intrapulpal dentin. Treatment with EDTA followed by NaOCI prior to obturation caused an additional reduction in muTBS of both adhesive systems to intrapulpal dentin.

Association between staining by caries detector dye and the corresponding mineral density in dentin caries

PURPOSE

To examine an association between coloration (red, pink) resulting from staining with Caries Detector Dye (CDD) and the corresponding mineral density in dentin caries lesions determined by transverse microradiography (TMR).

METHODS

CDD coloration of the lesion sections (approx. 190 microm) prepared from extracted caries teeth was photographed, and the corresponding relative mineral densities (RMD: relative values to the sound dentin) were obtained by TMR. A parallel study was performed using artificially demineralized and then remineralized dentin lesions.

RESULTS

The mean RMD values in the naturally black-pigmented, red- and pink-stained portions were 46 +/- 26.7%, 64 +/- 24.5%, and 80 +/- 15.1%, respectively. There were statistical differences in the RMD values among the three portions, as well as a wider range of RMD value distributions in the red and black-pigmented portions than in the pink portion.Even among the black-pigmented and red portions, much higher RMD values more than 90% were observed in several lesions, which were close to the mineral density of the sound (unaffected) dentin tissue. On the other hand, the remineralized surface layer of artificially demineralized lesions did not show the red coloration, and there seemed a threshold value of mineral density (approx. 21%), beyond which the red coloration was not observed. Similar threshold value was noted in the remineralized lesion body. This study showed a remarkable discrepancy regarding the RMD value for the red staining behavior between the naturally occurring caries and artificial carious lesion.

The effects of cavity size and filling method on the bonding to Class I cavities

PURPOSE

The effects of incremental filling technique and flowable liner on the bond strength of resin composite in different sized cavities were investigated in this study.

MATERIALS AND METHODS

Two sizes of cylindrical Class I cavities were prepared in bovine dentin (98.1 mm3 and 21.2 mm3). A light-curing resin composite (Clearfil Photocore) with a self-etching primer adhesive (Clearfil SE Bond) was used to bulk fill the cavities (C-factor 5), with and without flowable liner (Clearfil FLOW-FX) or incremental filling (2 layers, C-factor 3). As control, a 3-mm or 5-mm buildup was placed on the flat dentin surface (C-factor 0.2). After 24 h storage in 37 degrees C water, the microtensile bond strength was measured at a crosshead speed of 1 mm/min. Mode of failure in the fractured specimens was observed using a scanning electron microscope. The obtained results were statistically analyzed.

RESULTS

In large cavities, incrementally filled and lined cavities showed higher bond strength values than the bulk-filled subgroup (p < 0.05). However, in small cavities, neither the incremental technique nor flowable liner improved the bond strength.

CONCLUSION

Not only the filling techniques but also the cavity size affected the bond strength to the cavity floor in cylindrical Class I cavities.

Effect of caries-affected dentin hardness on the shear bond strength of current adhesives

PURPOSE

The aim of this study was to evaluate the microshear bond strength of three current adhesives to normal and caries-affected dentin, and to examine the correlation between dentin nanoindentation hardness and bond strength.

MATERIALS AND METHODS

Nanoindentation hardness of dentin and microshear bond strength of Clearfil SE Bond, Clerafil Tri-S Bond (Kuraray Medical) and Single Bond (3M ESPE) were measured on caries-affected and normal dentin. Modes of fracture for the bonding tests and the resin/dentin interfaces were observed using SEM. Data were analyzed at a statistical significance level of p < 0.05.

RESULTS

Significantly lower hardness values were recorded for caries-affected dentin compared to normal dentin. Two-way ANOVA showed that bonding material, type of dentin, and the interactions of these two factors had significant effects on bond strength. A significant correlation was found between dentin hardness and microshear bond strength. However, ANCOVA analysis revealed that the effect of dentin type was not only due to the mechanical properties of dentin. One-way ANOVA with Tukey's HSD test revealed that the mean bond strength of normal dentin with Tri-S Bond was significantly lower than that with SE Bond and Single Bond; however, bond strengths to caries-affected dentin showed no significant difference between the three adhesives.

CONCLUSION

All three adhesives showed lower bond strength to caries-affected dentin than to normal dentin. The differences between adhesives were not significant with caries-affected dentin as the bonding substrate. Dentin mechanical properties are not the only factors responsible for lower bond strength to caries-affected dentin.

Microtensile bond strengths of composite cores to pulpal floor dentin with resin coating

The purpose of this study was to evaluate the effect of resin coating on the microtensile bond strength (MTBS) of indirect composite cores to pulpal floor dentin. Thirty extracted human molars with root canal fillings were used. After post space preparation, dentin surface was coated with either Clearfil SE Bond (SE) or SE with Clearfil Flow FX (SE+FX) for the resin-coated groups, while dentin was treated with ED Primer II (ED) for the non-coated group. Indirect composite cores were cemented with either Panavia F2.0 (PA) or Clearfil DC Core Automix (DC). After 24-hour storage, MTBSs were measured at a crosshead speed of 1 mm/min. Two-way ANOVA indicated that the MTBSs of resin-coated groups were significantly higher than those of the non-coated groups. In particular, the SE+FX/DC group exhibited the highest MTBS. It was thus concluded that resin coating enhanced the dentin bond strength of indirect composite cores to pulpal floor dentin.

Comparison of enamel and dentin microshear bond strengths of a two-step self-etching priming system with five all-in-one systems

Data on the adhesive strength of new all-in-one adhesives are still relatively limited. This study compared the microshear bond strengths of five recent all-in-one self-etching priming systems (G-Bond, One-Up Bond-F Plus, Clearfil S3 Bond, Adper Prompt L-Pop and Go!) with a widely used two-step self-etching priming system (Clearfil SE Bond). Human molars were sectioned and finished with 600-grit SiC paper. Both enamel and dentin were bonded using adhesives with a 0.7 mm bonding diameter. Bond strengths were tested using a microshear bond test method at a crosshead speed of 1 mm/minute. The mean bond strengths and standard deviations were calculated and analyzed using ANOVA and the Tukey's HSD test. Results showed the two-step self-etching system had significantly higher bond strengths to dentin. However, for enamel bond strength, Clearfil SE Bond showed no statistical difference to G-Bond and Go!; however, all of the other materials were statistically lower. It is necessary to examine these new materials clinically to determine their efficacy.

Comparative analysis of three commercial saliva testing kits with a standard saliva buffering test

BACKGROUND

In 1959, Ericsson developed a laboratory buffer capacity test. Because the Ericsson test is not practical for use as a chair-side test, commercially available saliva buffering capacity tests have been developed for use in the dental office. The purpose of this study was to evaluate the correlation between a modified Ericsson test and three commercially available quantitative and colourimetric tests.

METHODS

Stimulated saliva (by chewing paraffin wax) was collected from 113 patients. Individual saliva buffering capacity was assessed with the following four different methods: modified Ericsson test; quantitative test using a hand-held pH meter; paper strip; or liquid colourimetric test. The correlations of ranking results among the different tests were analysed using the Spearman Rank Correlation Test, p < 0.001.

RESULTS

Spearman Rank Correlation indicated significant positive coefficients between the modified Ericsson test and the quantitative test (rho = 0.857), the paper strip colourimetric test (rho = 0.621) and the liquid-type colourimetric test (rho = 0.689).

CONCLUSION

The detection level of medium and high buffering capacity was test dependent. The quantitative test using a hand-held pH meter showed a stronger positive correlation with the modified Ericsson test. The qualitative tests seemed less reliable, particularly for patients classified as having a medium buffering capacity.

Relationship between quantitative assessments of salivary buffering capacity and ion activity product for hydroxyapatite in relation to cariogenic potential

BACKGROUND

The ion activity product for hydroxyapatite (Ip(HA)) is a comprehensive parameter reflecting pH, calcium and phosphate ion concentration in saliva which govern the degree of saturation with respect to the dissolving tooth mineral. The aim of this study was to evaluate the relationship between quantitative assessments of salivary buffering capacity and Ip(HA) in relation to cariogenic potential.

METHODS

Stimulated whole saliva was collected from 33 patients, and the initial pH of samples was measured using a hand-held pH meter. Then samples were titrated with 0.1 N HCl to evaluate buffering capacities and divided into three groups (high, medium and low). After measuring concentrations of calcium and phosphate ions in the samples, Ip(HA) was calculated using the values of the ion concentrations and pH. Differences in the mean pH values, the concentrations of calcium, phosphate ions and log[Ip(HA)] among three groups were analysed using the Kruskal Wallis and the Mann-Whitney non-parametric test, p < 0.05.

RESULTS

After HCl 50 microL titration, there were statistical differences of the mean pH and Ip(HA) among each buffering capacity group. Moreover, after 50 microL HCl titration, there was an excellent correlation between the buffer capacity and log[Ip(HA)].

CONCLUSIONS

The pH change for saliva after HCl titration has a significant influence on the rate of Ip(HA).

Effects of one-year storage in water on bond strength of self-etching adhesives to enamel and dentin

The aim of this study was to compare the bond strengths of three self-etching materials during one year of storage. Clearfil SE Bond (SE), Clearfil Protect Bond (PB), and Clearfil Tri-S Bond (TS) were used for bonding to dentin and enamel according to manufacturer's instructions. Microshear bond strength values were measured after 24 hours, six months, and one year. Two-way ANOVA showed that the interaction of material type and storage time was significant for dentin. At baseline, SE had the highest bond strength to dentin. There were no significant changes in bond strength for each material during the storage period, except for PB which showed increased bond strength to dentin after one year. All materials performed reliably after one year. However, the antibacterial and fluoride-releasing effects of PB would further contribute to the long-term clinical benefits of this material.