Effects of chlorhexidine-containing adhesives on the durability of resin–dentine interfaces

Objectives

This study evaluated the effect of addition of diacetate CHX in different concentrations into two simplified etch-and-rinse (ER) adhesive systems (XP Bond [XP] and Ambar {AM}) on the ultimate tensile strength (UTS), degree of conversion (DC), 60-day cumulative water sorption (WS), solubility (SO) and CHX release (CR) as well as the immediate (IM) and 1-year (1Y) resin–dentine bond strength (μTBS) and nanoleakage (NL).

Methods

Ten experimental adhesive systems were formulated according to the addition of CHX diacetate (0 [control], 0.01, 0.05, 0.1 and 0.2%) in the two ER. For UTS and DC, specimens were constructed and tested after 24 h. For WS, SO and CR, after specimens build-up, they were stored in water and the properties measured after 60 days. The occlusal enamel of fifty molars was removed and the adhesives were applied in dentine surface after 37% phosphoric acid etching. After composite resin build-ups, specimens were longitudinally sectioned to obtain resin–dentine bonded sticks (0.8 mm²). Specimens were tested in tension at 0.5 mm/min in the IM or 1Y. For NL, 2 bonded sticks from each tooth were prepared and analyzed under SEM. The data were submitted to appropriate statistical analysis (α = 0.05).

Results

The addition of CHX did not influence UTS, DC, WS and SO (p < 0.05). Higher CR was observed in adhesives with higher concentration of CHX (p < 0.05). After 1Y, significant reductions of μTBS and increases of NL were observed in the control groups (p < 0.05). Reductions of μTBS and increase of NL over time were not observed (AM) for CHX-containing adhesives or it was less pronounced than the control (XP) regardless of the CHX concentration.

Conclusions

The addition of CHX diacetate in concentrations until 0.2% in the simplified ER adhesive systems may be an alternative to increase the long-term stability of resin–dentine interfaces, without jeopardizing the adhesives’ mechanical properties evaluated.     

The role of spacer carbon chain in acidic functional monomers on the physicochemical properties of self-etch dental adhesives

Objectives

To evaluate the effects of acidic functional monomers with different hydrophilicity and spacer carbon chain length on the degree of conversion (DC), wettability (contact angle), water sorption (WS) and ultimate tensile strength (UTS) of experimental one-step self-etch adhesives (1-SEAs).

Methods

A series of standard resin blends was prepared with each formulation containing 15 mol% of each acidic monomer. The structural variations of the acidic monomers were MEP (spacer chain with 2 carbons), MDP (10-carbons), MDDP (12-carbons), MTEP (more hydrophilic polyether spacer) and CAP-P (intermediate hydrophilicity ester spacer). Dumbbell-shaped and disc specimens were prepared and tested for UTS and WS, respectively. DC was assessed by FTIR, while the wettability of each 1-SEA was evaluated on glass slides and flat dentine surfaces. Results were analysed with one-way ANOVA and Tukey's test (p < 0.05).

Results

The outcomes showed lower UTS for CAP-P, control blend and MEP than MTEP, MDDP and MDP (p < 0.05). The degree of conversion was statistically similar for all resins (p = 0.122). On dentine, the wettability was higher (lower contact angle) with the most hydrophilic monomer MTEP. Higher WS was attained using MTEP. Different lengths of the spacer chains did not result in different wettability and WS (p > 0.05).

Conclusion

At similar molar percentage, different acidic functional monomers induced similar degree of conversion and different UTS when included in a 1-SEA. However, the inclusion of highly hydrophilic monomer may increase the wettability on dentine and the WS.     

Effect of chlorhexidine and ethanol-wet bonding with a hydrophobic adhesive to intraradicular dentine

Purpose

To evaluate the effect of adjunctive application of ethanol-wet bonding and chlorhexidine (CHX) with a hydrophobic adhesive on bond durability of fibre posts to intraradicular dentine.

Methods

Ninety-six extracted human teeth with a single root and root canal were prepared for post placement after endodontic treatment. The teeth were randomly divided into four groups (n = 24) after etching and rinsing for rewetting: Group 1: water-wet bonding, Group 2: water-wet bonding with CHX, Group 3: ethanol-wet bonding and Group 4: ethanol-wet bonding with CHX. Teeth in Groups 1 and 2 were treated with either distilled water or distilled water with 2% CHX for 60 s; while teeth in Groups 3 and 4 were treated with either 100% ethanol or 100% ethanol with 2% CHX. Two coats of primer, followed by neat resin were applied and light-cured for 40 s. Fibre posts were luted to bonded root dentine using dual-cure resin cement. Bonded roots were subjected to push-out bond strength testing and interfacial nanoleakage evaluation after 24 h, 6 and 12 months of storage. Data were analyzed using 3-way ANOVA (rewetting solutions, time and post space regions) and SNK tests.

Results

Groups 3 and 4 showed significantly (p < 0.05) higher bond strengths and lower nanoleakage than Groups 1 and 2 after 12 months of ageing. Addition of 2% chlorhexidine to ethanol-wet bonding with a hydrophobic adhesive did not further improve the bonding of a fibre post to intraradicular dentine, when compared to ethanol-wet bonding alone after 12 months of ageing.

Clinical significance

Ethanol-wet bonding with a hydrophobic adhesive alone could improve the bond durability of fibre post to intraradicular dentine and therefore would increase the success rate of post and core restorations of endodontically treated teeth.     

Correlation between degree of conversion,resin–dentin bond strength and nanoleakage of simplified etch-and-rinse adhesives

Objectives

The aim of this study was to correlate the degree of conversion measured inside the hybrid layer (DC) with the microtensile resin–dentin bond strength (μTBS) and silver nitrate uptake or nanoleakage (SNU) for five simplified etch-and-rinse adhesive systems.

Methods

Fifty-five caries free extracted molars were used in this study. Thirty teeth were used for μTBS/SNU [n = 6] and 25 teeth for DC [n = 5]. The dentin surfaces were bonded with the following adhesives: Adper Single Bond 2 (SB), Ambar (AB), XP Bond (XP), Tetric N-Bond (TE) and Stae (ST) followed by composite resin build-ups. For μTBS and SNU test, bonded teeth were sectioned in order to obtain stick-shaped specimens (0.8 mm²), which were tested under tensile stress (0.5 mm/min). Three bonded sticks, from each tooth, were not tested in tensile stress and they were immersed in 50% silver nitrate, photo-developed and analyzed by scanning electron microscopy. Longitudinal 1-mm thick sections were prepared for the teeth assigned for DC measurement and evaluated by micro-Raman spectroscopy.

Results

ST showed lowest DC, μTBS, and higher SNU (p < 0.05). All other adhesives showed similar DC, μTBS, and SNU (p > 0.05), except for TE which showed an intermediate SNU level. The DC was positively correlated with μTBS and negatively correlated with SNU (p < 0.05). SNU was also negatively correlated with μTBS (p < 0.05).

Significance

The measurement of DC inside the hybrid layer can provide some information about bonding performance of adhesive systems since this property showed a good correlation with resin–dentin bond strength and SNU values.     

Adjunctive application of chlorhexidine and ethanol-wet bonding on durability of bonds to sound and caries-affected dentine

Objectives

To examine the effect of adjunctive application of chlorhexidine (CHX) and ethanol-wet bonding (EWB) on bond durability and nanoleakage of hydrophobic adhesive to sound (SD) and caries-affected dentine (CAD).

Methods

Dentine surfaces of molars were etched after caries removal and randomly allocated to four groups (n = 12). In Groups 1 and 2, dentine surfaces were saturated with either 2 ml of 100% ethanol or 2 ml of ethanol with 2% CHX for 60 s. In Groups 3 and 4, dentine surfaces were saturated with either 15 μL of distilled water or 15 μL of distilled water with 2% CHX for 60 s. Two coats of primer, followed by neat resin were applied and light-cured for 40 s. Resin composite build-ups were placed and bonded specimens were sectioned for bond strength testing after 24 h and 12 months’ storage in artificial saliva. Bond strength data were analyzed using 3-way ANOVA and SNK tests. Interfacial nanoleakage was evaluated after 24 h and 12 months using a field-emission scanning electron microscopy and data were analyzed using Kruskal–Wallis test.

Results

Significant differences were observed for the three factors: “substrate” (p < 0.001), “rewetting agents” (p < 0.001) and “time” (p < 0.001) on bond strength. Incorporation of 2% CHX to EWB preserved bond strength to SD and CAD and reduced interfacial nanoleakage after 12 months. Incorporation of 2% CHX to WWB also preserved bond strength to SD after ageing.

Conclusions

Incorporation of chlorhexidine to ethanol-wet bonding has an interaction effect on preservation of bond durability to sound and caries-affected dentine.

Clinical significance

Incorporation of chlorhexidine to ethanol-wet bonding with hydrophobic adhesive enhances the success rate of aesthetic bonded restorations.     

Influence of 2% chlorhexidine digluconate on bond strength of a glass-fibre post luted with resin or glass-ionomer based cement

Objectives

This study evaluated the influence of 2% chlorhexidine digluconate (CHX) on the bond strength (BS) of a glass-fibre post to the root canal, regarding the cements (dual-cured resin or resin-modified glass-ionomer cement), the root thirds and the time of storage.

Method

Eighty bovine roots were selected and endodontically treated, before being randomly assigned to the following groups according to the luting protocol: ARC (RelyX ARC); ARC + CHX; RL (RelyX Luting 2); and RL + CHX. After 24 h of luting, the roots were sliced to obtain 1 mm-thick slices. Half of each group was submitted to either 7-day or 6-month storage in artificial saliva (n = 10). The specimens were subjected to push-out tests with a crosshead speed of 0.5 mm/min. The data were analysed with four-way ANOVA and Tukey's test (P ≤ 0.05). The failure modes were analysed with a digital microscope (50× and 200×).

Results

ARC yielded a significantly higher BS compared to RL (P < 0.001). Despite CHX exerted a significant effect; it depends on the interaction with the luting cement and time (P < 0.001). Thus, CHX decreased the values of BS to those of ARC after 6 months (P < 0.001). On the 7th day of storage, the ARC + CHX presented higher BS to the cervical and middle thirds compared to RL + CHX (P = 0.012). Time solely was not a significant factor (P = 0.081). Adhesive cement-dentine type and mixed failures were predominant modes for the ARC groups. For the RL groups, the main failures were adhesive cement-post and mixed modes.

Conclusions

Glass-fibre posts luted with RelyX ARC dual-cure resin cement exhibited higher BS than those luted with RelyX Luting 2 resin-modified glass-ionomer cement. Furthermore, CHX was not effective to improve the BS and negatively affected the BS of RelyX ARC after 6 months of storage.

Clinical significance

The use of chlorhexidine solution seems not to improve the bond strength of fibre posts to root canals, disregarding the composition of the luting cement.     

A 2-year in vitro evaluation of a chlorhexidine-containing acid on the durability of resin-dentin interfaces

Objective

This study evaluated the effect of 2% chlorhexidine-containing acid (Ac/CHX) and 2% chlorhexidine digluconate solution (CHX) on immediate (IM) and 2-year (2Y) resin-dentin bond strength (BS) and silver nitrate uptake (SNU) for two simplified etch-and-rinse adhesives.

Methods

Forty-two caries-free extracted molars had a flat dentin surface exposed. In the control groups (groups 1), the surfaces were acid etched with conventional phosphoric acid and the adhesives Prime&Bond NT (PB) or Adper Single Bond 2 (SB) was applied after rinsing, drying and rewetting with water. In groups 2, Ac/CHX groups the adhesives were applied in a similar manner; however a 2% CHX-containing acid was previously applied. In groups 3, the adhesives were applied according to the control group; however the rewetting procedure was performed with an aqueous solution of 2% CHX for 60 s. Composite build-ups were constructed incrementally and microtensile specimens (0.8 mm²) were prepared for microtensile bond strength testing in the IM or 2Y periods at 0.5 mm/min. For SNU, 2 bonded sticks from each tooth were coated with nail varnish, placed in the silver nitrate, polished down with SiC papers and analysed by EDX-SEM. The data from each adhesive was submitted to a two-way repeated measures ANOVA and Tukey's test (α = 0.05).

Results

After 2Y, significant reductions of BS were observed for both adhesives in the control group (p < 0.05). In Ac/CHX or CHX groups the BS remained stable for both systems. SNU was more evident in the control than in the experimental groups (p < 0.05) both in IM and 2Y periods. The use of CHX in an aqueous solution or associated with the acid conditioner was effective to reduce the degradation of dentin bonds over a 2-year period.

Significance

The addition of CHX digluconate in the acidic conditioner may be an excellent tool to increase the long-term stability of collagens fibrils within the hybrid layer against host-derived metalloproteinases without the need for additional steps for the bonding protocol.     

Substantivity of a single chlorhexidine mouthwash on salivary flora: Influence of intrinsic and extrinsic factors

Objectives

To analyse the influence of intrinsic and extrinsic factors on the in vivo antimicrobial activity of a chlorhexidine (CHX) digluconate mouthwash on the salivary flora up to 7 h after its application, using epifluorescence microscopy.

Methods

Ten volunteers performed the following mouthwashes: 0.12% CHX (10 ml/30 s, 15 ml/30 s and 10 ml/1 min); 0.2% CHX (10 ml/30 s, 15 ml/30 s and 10 ml/1 min); 0.2% CHX (10 ml/30 s) plus different daily activities (eating, drinking, chewing or smoking).

Results

On comparing 0.12% CHX (10 ml versus 15 ml), the greatest differences in bacterial viability were detected at 1 h and 3 h. On comparing 0.12% CHX (30 s versus 1 min) the greatest differences in viability were detected at 1 h, 3 h, and 5 h; and with 0.2% CHX (30 s versus 1 min), at 5 h and 7 h. On comparing 0.12% CHX (15 ml) versus 0.2% CHX (10 ml) and 0.12% CHX (1 min) versus 0.2% CHX (30 s), the percentage of viable bacteria was higher with the 0.12% concentration. On comparing 0.2% CHX versus 0.2% CHX plus daily activities, the higher differences were detected after eating and chewing, followed by drinking.

Conclusion

An increase in the volume of 0.12% or 0.2% CHX mouthwashes does not affect the duration of antimicrobial activity in saliva, whereas increasing the duration produces a marked increase in substantivity. Substantivity was greater with 0.2% CHX than 0.12% CHX. Eating, chewing or drinking significantly reduces the 0.2% CHX substantivity in saliva.     

In vitro evaluation of bonding effectiveness to dentin of all-in-one adhesives

Objectives

The study was aimed at assessing the bonding potential of all-in-one adhesives to dentin.

Methods

The microtensile bond strength of the all-in-one adhesives Bond Force (Tokuyama), AdheSE One (Ivoclar-Vivadent), and Xeno V (Dentsply) was measured in comparison with the etch-and-rinse system XP Bond (Dentsply). The ultrastructural characteristics of dentin–adhesive interface were observed under scanning electron microscope (SEM). Twenty human extracted third molars had their mid-coronal dentin exposed and ground with wet 600-grit SiC paper in order to create a standardized smear layer. Bonding procedures were performed according to the manufacturers’ instructions and microtensile beams were obtained with the “non-trimming” technique. The bond strengths in MPa were statistically analyzed including pre-test failures as “zero” values (Kolmogorov–Smirnov test, Levene's test, One-Way ANOVA, Tukey's test p < 0.05).

Results

The following bond strengths were recorded in MPa (mean ± standard deviation): AdheSE One 31.7 ± 21.3; Xeno V 42.8 ± 26.4; Bond Force 43.3 ± 22.1; XP Bond 51.9 ± 18.6. The statistical analysis demonstrated that the bond strengths achieved by Bond Force and Xeno V were similar to that of the etch-and-rinse adhesive, whereas the bond strength of AdheSE One was significantly lower. A distinct hybrid layer with resin tags was seen only in XP Bond specimens. All-in-one adhesives demonstrated a rather superficial interaction with the dentin substrate.

Conclusions

Although the strongest bond to dentin was established by the etch-and-rinse system, however the all-in-one adhesives containing organic solvents reached bond strength levels that were comparable from a statistical point of view.     

A randomized controlled 5-year prospective study of two HEMA-free adhesives,a 1-step self etching and a 3-step etch-and-rinse,in non-carious cervical lesions

Objective

The aim of this study was to evaluate the 5 year clinical dentin bonding effectiveness of two HEMA-free adhesives in Class V non-carious cervical lesions.

Material and methods

A total of 169 Class V restorations were placed in 67 patients with a self-etching adhesive (G-Bond; 67), a 3-step HEMA and TEGDMA free etch-and-rinse (cfm; 51) and a control HEMA-containing etch-and-rinse adhesive (XP Bond; 51) in non-carious cervical lesions without intentional enamel involvement. The restorations were evaluated at baseline and yearly during a 5 year follow-up with modified USPHS criteria. Dentin bonding efficiency was determined by the percentage of lost restorations.

Results

During the 5 years, 159 restorations could be evaluated. Good short time dentin retention was observed for the three adhesives, there all adhesives fulfilled at 18 months the full acceptance ADA criteria. At 5 years a cumulative number of 22 lost restorations (13.8%) was observed. The HEMA-free adhesives showed significantly higher dentin retention compared to the HEMA-containing one. Loss of retention was observed for 5 G-Bond (7.9%), 4 cfm (8.3%) and 13 XP Bond (27.1%) restorations (p < 0.05). No post-operative sensitivity was reported by the participants. No secondary caries was observed.

Significance

The durability in non-carious cervical lesions of the HEMA-free adhesives was successful after 5 years. Despite concerns which have been raised, showed the 1-step SEA one of the best reported clinical dentin bonding effectiveness.     

Can 1% chlorhexidine diacetate and ethanol stabilize resin-dentin bonds?

Objectives

To examine the effects of the combined use of chlorhexidine and ethanol on the durability of resin-dentin bonds.

Methods

Forty-eight flat dentin surfaces were etched (32% phosphoric acid), rinsed (15 s) and kept wet until bonding procedures. Dentin surfaces were blot-dried with absorbent paper and re-wetted with water (water, control), 1% chlorhexidine diacetate in water (CHD/water), 100% ethanol (ethanol), or 1% chlorhexidine diacetate in ethanol (CHD/ethanol) solutions for 30 s. They were then bonded with All Bond 3 (AB3, Bisco) or Excite (EX, Ivoclar-Vivadent) using a smooth, continuous rubbing application (10 s), followed by 15 s gentle air stream to evaporate solvents. The adhesives were light-cured (20 s) and resin composite build-ups constructed for the microtensile method. Bonded beams were obtained and tested after 24-h, 6-months and 15-months of water storage at 37 °C. Storage water was changed every month. Effects of treatment and testing periods were analyzed (ANOVA, Holm–Sidak, p < 0.05) for each adhesive.

Results

There were no interactions between factors for both etch-and-rinse adhesives. AB3 was significantly affected only by storage (p = 0.003). Excite was significantly affected only by treatments (p = 0.048). AB3 treated either with ethanol or CHD/ethanol resulted in reduced bond strengths after 15 months. The use of CHD/ethanol resulted in higher bond strengths values for Excite.

Conclusions

Combined use of ethanol/1% chlorhexidine diacetate did not stabilize bond strengths after 15 months.     

Effect of chlorhexidine incorporation into a self-etching primer on dentine bond strength of a luting cement

Objectives

This study investigated the effect of incorporating chlorhexidine in a self-etching primer on the bond strength of an adhesive resin cement to dentine and on antibacterial activity.

Methods

Experimental self-etching primers were prepared by adding chlorhexidine (CHX) diacetate to ED primer 2.0 (Kuraray Medical Inc.) to obtain chlorhexidine concentrations of 1.0 wt% and 2.0 wt%. Human occlusal dentine surfaces were conditioned for 30 s using the experimental primers or pure ED primer. Composite blocks were luted using Panavia F 2.0 (Kuraray Medical Inc.). After storage in water for 24 h, the bonded teeth were sectioned into 0.9 mm × 0.9 mm beams and stressed to failure in tension to examine microtensile bond strength (μTBS). Fractured surfaces were examined with a field-emission scanning electron microscopy (FE-SEM). The morphology of dentine surfaces that were conditioned with each primer was also observed under FE-SEM. An agar diffusion test was performed to examine the antibacterial effect of each primer against Streptococcus mutans and Enterococcus faecalis.

Results

Addition of chlorhexidine to the primer had significant effects (p < 0.001) on μTBS and antibacterial effect. No significant difference in μTBS was found between the groups that contained 0% and 1% chlorhexidine in the primer (p = 0.095). Conversely, the group that contained 2% chlorhexidine showed significantly lower μTBS and pronounced cohesive failures within the thin layer of the primer.

Conclusions

Incorporation of chlorhexidine into ED primer 2.0 showed significant antibacterial activities. Conditioning with the 1% chlorhexidine-containing primer had no adverse effect on μTBS.     

Effect of a neutralising agent on the evaluation of the antimicrobial activity of chlorhexidine on the bacterial salivary flora

Objective

To test the efficacy of a previously described neutralising agent to counteract any antimicrobial activity of 0.2% of chlorhexidine (CHX) mouthrinse on the salivary flora, which is only exhibited after sampling of surviving bacteria, resulting in false positive efficacy data.

Methods

Unstimulated salivary samples were collected of 20 volunteers under basal conditions and at 30 s and 1 h after of a single mouthrinse of 0.2% CHX. Each salivary sample was divided into 2 equal aliquots; one was mixed with neutralising agent (3% Tween 80, 0.3% lecithin and 0.1% cysteine) and the other with a control solution. The colony forming units (cfu/mL) were determined and expressed as logarithms (log₁₀ cfu/mL).

Results

At baseline, the total bacterial concentrations were similar, independently of the addition of neutralising solution or control solution (8.419 ± 0.346 log₁₀ cfu/mL and 8.462 ± 0.474 log₁₀ cfu/mL, respectively, p = 0.440). At 30 s performing the CHX mouthrinse, the bacterial load reduction was statistically significant between both sampling methods (1.917 ± 1.275 log₁₀ cfu/mL, p < 0.001). One hour after performing the CHX mouthrinse, the bacterial load reduction was statistically significant between both sampling methods (0.537 ± 0.706 log₁₀ cfu/mL, p = 0.003).

Conclusions

Neutralising agent was not toxic to the bacterial salivary flora and effectively deactivated the “residual antimicrobial activity” of the 0.2% CHX (after exposure and during processing of samples). We propose the use of this neutralising agent when evaluating the antibacterial activity of CHX mouthrinses.     

Long-term evaluation of water sorption and ultimate tensile strength of HEMA-containing/-free one-step self-etch adhesives

Objective

The objective of this study was to evaluate the water sorption (Wsp) and ultimate tensile strength (UTS) of HEMA-containing/free one-step self-etch adhesives after long-term water-storage.

Methods

Three HEMA-containing one-step self-etch adhesives (Bond Force (BF), Clearfil S³ Bond (S3) and OptiBond All-In-One (OP)), and one HEMA-free one-step self-etch adhesive, G Bond (GB) was used. After the solvents of each adhesive were evaporated, polymerised adhesive disks and dumbbell-shaped specimens of thirty-two each were prepared and divided into four groups of 14-, 90-, 180- and 360-day water-storage. After immersion in water for the designated storage periods, the disks were subjected to measurement of Wsp, and the dumbbell-shaped specimens were subjected to measurement of UTS. The data of Wsp and UTS were statistically analysed using a two-way ANOVA and Bonferroni test.

Results

Wsp of BF, S3 and OP increased over time, whereas for GB, there were no significant differences in Wsp among all the storage periods. Wsp of GB was lower than those of BF, S3 and OP in each period. The UTS of BF, S3 and OP decreased over time, whereas for GB, there were no significant differences in UTS among all storage periods. The highest UTS was initially seen in BF > GB = S3 = OP, and after 360-day water-storage, seen in BF = GB > OP = S3.

Conclusions

For the HEMA-containing adhesives, Wsp increased and UTS decreased over time. On the other hand, for the HEMA-free adhesive, Wsp and UTS did not significantly change even after 360-day water-storage.     

Influence of chlorhexidine digluconate on the clinical performance of adhesive restorations: A 3-year follow-up

Objectives

The aim of this clinical study was to evaluate the long-term clinical performance of non-carious Class V restorations with and without application of chlorhexidine digluconate to acid-etched dentine.

Methods

After the approval of the Ethics and Informed Consent Committee, 70 non-carious cervical lesions were selected and randomly assigned into two groups, according to the split mouth design. The control group was restored with a two-step etch-and-rinse adhesive (Adper Single Bond 2) following manufacturer's instructions; whereas in the experimental group 2% chlorhexidine digluconate solution was applied to acid etched dentine for 30 s after etching and prior to the adhesive application. All lesions were restored with a nanofilled composite resin (Filtek Supreme XT) and polymerized with a light-curing unit operating at 600 mW/cm². Clinical performance was recorded after 1 week, 6, 12, and 36 months using modified Ryge/USPHS criteria in terms of retention, marginal discoloration, marginal integrity, post-operative sensitivity, and secondary caries incidence. Data were analyzed using Chi-Square, Fisher's exact test and McNemar tests (α = .05).

Results

After 36 months the control group showed a success rate of 88% in comparison to 76% of experimental group; however, no statistically difference between them was found (p = .463). Moreover, no statistical differences were observed between groups in the criteria post-operative sensitivity, marginal discoloration, marginal integrity, and secondary caries incidence between the two groups.

Conclusion

The addition of 2% chlorhexidine digluconate conditioning step does not improve the clinical durability of adhesive restorations.     

Effect of waiting interval on chemical activation mode of dual-cure one-step self-etching adhesives on bonding to root canal dentin

Objectives

The purpose of this study was to evaluate the effect of waiting interval on the chemical activation of dual-cure one-step self-etching adhesives before placing resin core materials on the regional bond strength to root canal dentin.

Materials and methods

Forty-eight post spaces prepared in human lower premolars were applied with four dual-cure one-step self-etching adhesives Estelite Core Quick: ECB/ECQ, Clearfil DC Core Automix: CDB/CDC, Unifil Core EM: UNB/UNC, BeautiCore: BTB/BTC as the manufacturers’ instructions. These adhesives were cured with light activation for 10 s, or chemical activation with 0, 10, and 30 s waiting intervals prior to placing resin core material. Resin core materials were then placed into the post space and light-cured for 60 s. After 24 h water storage, each specimen was serially sliced into 8, 0.6 mm × 0.6 mm thick beams for the μTBS test. The regional μTBS data were analyzed using three-way ANOVA and Dunnett's T3 test (p < 0.05).

Results

For the chemical activation with 10 and 30 s waiting intervals, ECB and CDB exhibited significantly improved μTBS, whereas for UNB and BTB, the μTBS were not significantly different but increased with waiting interval. On the other hand, light-activation of all the adhesives produced significantly higher μTBS to root canal dentin than chemical activation (p < 0.05), except for the UNB group.

Conclusions

For the chemical activation of dual-cure one-step self-etching adhesives, a waiting interval prior to placing resin core material improved μTBS to root canal dentin. Polymerising the adhesives before polymerisation reaction of resin core material would be effective for bonding to root canal dentin.

Clinical relevance

For chemical activation mode as well as light activation mode, pre-curing of adhesive layer before proceeding polymerisation of resin filling material would produce higher bonding performance to dentin in the cavity.     

Effects of Sonic Application of Adhesive Systems on Bonding Fiber Posts to Root Canals

Introduction

Luting posts inside the root canal is still a challenge because of the difficulty of bonding adhesive materials in the apical third of roots. This study evaluated the effect of the application mode of 3 simplified etch-and-rinse adhesives on the push-out bond strength (PBS), nanoleakage (NL), and in situ degree of conversion (DC) of fiber posts in the root canal.

Methods

The roots of human premolars were endodontically prepared and divided into 6 groups according to the combination of the main factors: adhesive (Ambar, FGM, Joinville, SC, Brazil; Adper Single Bond 2, 3MESPE, St Paul, MN; and XP Bond+self-cure activator, DeTrey Dentsply, Konstanz, Germany) and application mode (manual or sonic). The posts were cemented and the PBS tested at 0.5 mm/min. The NL was evaluated by scanning electron microscopy after the immersion of specimens in 50% silver nitrate. Micro-Raman spectroscopy was used to measure the in situ DC. Root third was also considered in the statistical evaluation. Data were analyzed by 3-way repeated measures analysis of variance and Tukey tests (5%).

Results

Under sonic application, the PBS and the in situ DC increased, whereas NL decreased significantly for all groups in the middle and apical thirds (P < .05).

Conclusions

The application of simplified adhesives by sonic mode in the root canal is a feasible tool to increase the fiber post bond to root canals.     

Dental composite materials containing carolacton inhibit biofilm growth of Streptococcus mutans

Objective

Caries adjacent to restorations is one of the main causes for restoration replacement. Antimicrobial substances incorporated into dental materials would potentially be able to reduce secondary caries initiation and progression. This study investigated biofilm growth of Streptococcus mutans UA159 on the surface of composite materials containing the biomolecule carolacton compared to materials containing chlorhexidine (CHX) and triclosan.

Methods

Biofilm inhibition was investigated by counting colony forming units (CFU), viability staining (Life/Dead), and real-time quantitative PCR.

Results

First, the antimicrobial substances were added to the cultivation medium at 2.5 μg/ml (0.0002%) and 0.25 μg/ml (0.00002%). CHX eliminated bacterial growth and biofilm formation completely. Triclosan was effective at 2.5 μg/ml, but at 0.25 μg/ml biofilm mass and viability were unchanged, yet the number of CFU increased due to disruption of cell chains and biofilm aggregates. Carolacton had a limited effect on biofilm growth and mass, but reduced viability significantly. When incorporated into composite materials carolacton (25 μg/ml resp. 0.002%, w/w) had no adverse effect on physical/mechanical properties and retained its biofilm inhibiting effect. Life/Dead staining revealed a reduction of biofilm viability of up to 64%. CFUs were reduced by 98% and qPCR demonstrated a mean inhibition of 87%. In contrast, materials containing CHX or triclosan showed an insignificant effect on biofilm formation, even at a 100fold increased concentration (0.2%). The anti-biofilm activity of composite material containing carolacton was stable over a period of 42 days.

Significance

Carolacton incorporated into dental filling material has a strong biofilm-inhibiting effect on S. mutans and is therefore potentially able to prevent secondary caries formation.     

Cuspal deflection and cervical microleakage scores to determine the adhesive potential of universal bonding systems

Objectives

To assess the adhesive performance of three universal bonding systems (self-etch and total-etch protocols) with cuspal deflection and cervical microleakage score.

Methods

Fifty-six standardised sound maxillary premolar teeth with uniform mesio-occlusal-distal (MOD) cavities were randomly allocated to six groups. Restoration with resin-based composite (RBC) was performed in conjunction with a universal bonding system facilitated by a quartz-tungsten-halogen light-curing-unit. The dependent variable was the universal bonding protocol (self-etch or total-etch). Buccal and palatal cuspal deflections were recorded at 0, 30, 60 and 180 s post-irradiation using a twin channel deflection measuring gauge. Following restoration, the teeth subjected to 500 thermocycles, immersed in a 0.2% basic fuchsin dye for 24 h, sectioned and examined for cervical microleakage.

Results

Comparing between bonding protocol (self-etch or total-etch), a decrease in total cuspal deflection and a concomitant increase in cervical microleakage were evident when employing the total-etch compared with the self-etch protocol for two of the three universal dental adhesives.

Conclusions

The ‘Adhesion-Decalcification concept’ suggests a trend towards ‘mild self-etch’ adhesives. Differences in adhesive performance (cuspal deflection and cervical microleakage) between the teeth restored using the self-etch or total-etch protocols is suggested to be a result of the pH of the self-etch solutions. ‘Mild self-etch’ (pH ∼ 2.0) adhesives out-performed ultra-mild (pH > 2.5) or strong (pH < 1.5) self-etch solutions.

Clinical significance

Poorly performing adhesives could be identified using the cuspal deflection and cervical microleakage protocol reported which could save the complications encountered clinically with Class II RBC restorations.