Glass polyalkenoate bond strength to dentine after chemomechanical caries removal

Development of a zinc chloride-based chemo-mechanical system for potential minimally invasive dental caries removal system

Background/purpose

The chemo-mechanical caries-removal technique is known to offer advantages of selective dentin caries treatment while leaving healthy dental tissues intact. However, current sodium hypochlorite based reagents usually excessively damage dentin collagen. Therefore, the purpose of this study was to develop a novel chemo-mechanical caries-removal system to preserve the collagen network for subsequent prosthetic restorations.

Materials and methods

The calfskin-derived collagen was chosen as a model system to investigate the dissolution behavior of collagen under different operating conditions of chemical-ultrasonic treatment systems. The molecular weight, triple-helix structure, the morphology, and functional group of collagen after treatment were investigated.

Results

Various concentrations of sodium hypochlorite or zinc chloride together with ultrasonic machinery were chosen to investigate. The outcomes of circular dichroism (CD) spectra demonstrated stability of the triple-helix structure after treatment of a zinc chloride solution. In addition, two apparent bands at molecular weights (MWs) of 130 and 121 kDa evidenced the stability of collagen network. The positive 222 nm and 195 nm negative CD absorption band indicated the existence of a triple-helix structure for type I collagen. The preservation of the morphology and functional group of the collagen network on the etched dentin surface were investigated by in vitro dentin decalcification model.

Conclusion

Unlike NaOCl, the 5 wt% zinc chloride solution combined with ultra-sonication showed dissolution rather than denature as well as degradation of the dentin collagen network. Additional in vivo evaluations are needed to verify its usefulness in clinical applications.

A comparative evaluation of micro shear bond strength and microleakage between the resin-modified glass ionomer cement and residual dentin following excavation of carious dentin using Carie CareTM and conventional caries removal in primary teeth: an in vitro study

Background: The bond between the dentin and restorative material contributes to the success of the restoration. Structural changes associated with prepared dentin may influence the bonding of restorative materials. The present study evaluates the bond between the resin-modified glass ionomer cement (RMGIC) and residual dentin following excavation of carious dentin using Carie Care ^TM and conventional caries removal in primary teeth.

METHODS

52 primary teeth with dentinal caries were randomly grouped into group I, where caries removal was done using the conventional method, and group II which used Carie Care ^TM. All the teeth were restored using RMGIC. Micro shear bond strength between the residual dentin and the cement was tested using universal testing machine and the dye penetration method was used for microleakage testing. Independent t-test was performed for intergroup comparison. Pearson chi-square test was carried out to evaluate the microleakage patterns in the enamel and dentin.

RESULTS

The mean micro-shear bond strength of group I was 6.03±1.6 and that of group II was 8.54±2.92; this difference was statistically significant with a p-value of 0.012. Microleakage was higher in the test group (1.38±0.51) than the control group (0.77±0.6) and was significant with a p -value of .036.

CONCLUSIONS

Papain-based chemomechanical agent Carie Care ^TM can be used as an alternative method to conventional caries removal. However, further studies need to explore methods to improve the marginal sealing capacity of RMGIC to the residual dentin after chemomechanical caries removal.

Bond Strength and Microleakage of a Novel Glass Ionomer Cement Containing Silver Diamine Fluoride

Objectives  To investigate the shear bond strength and microleakage of glass ionomer cement (GIC) containing silver diamine fluoride (SDF).

Materials and Methods  Sound human permanent premolars were divided into the following three groups: 1) GIC (Fuji IX), 2) GICSDF-S: GIC + SDF (Saforide), and 3) GICSDF-T: GIC + SDF (Topamine). Shear bond strength ( n  = 14/group) was measured using a universal testing machine and compared between groups (one-way ANOVA and Tukey HSD, p  < 0.05). Microleakage ( n  = 15/group) at enamel and dentin margins was scored using a stereomicroscope (10x) and compared between groups (Chi-square, p  < 0.05).

Results  There were significant differences in shear bond strength between the GIC and GICSDF-S groups and between the GIC and GICSDF-T groups. The GIC group had the lowest shear bond strength among the groups; however, there was no significant difference between the GICSDF-S and GICSDF-T groups. The microleakage test results were not significantly different between groups at the enamel margin or dentin margins. Although the GIC group demonstrated a higher dye penetration score at the enamel and dentin margins, the difference was not significant.

Conclusions  Within the limitations of this study, we conclude that incorporating SDF into GIC results in higher shear bond strength while not increasing microleakage at the enamel and dentin margins.

Effects of Powdery Cellulose Nanofiber Addition on the Properties of Glass Ionomer Cement

In this study, we aimed to evaluate the effect of the addition of powdery cellulose nanofibers (CNFs) on the mechanical properties of glass ionomer cement (GIC) without negatively affecting its chemical properties. Commercial GIC was reinforced with powdery CNFs (2–8 wt.%) and characterized in terms of flexural strength, compressive strength, diametral tensile strength, and fluoride-ion release properties. Powdery CNFs and samples subjected to flexural strength testing were observed via scanning electron microscopy. CNF incorporation was found to significantly improve the flexural, compressive, and diametral tensile strengths of GIC, and the corresponding composite was shown to contain fibrillar aggregates of nanofibers interspersed in the GIC matrix. No significant differences in fluoride-ion release properties were observed between the control GIC and the CNF-GIC composite. Thus, powdery CNFs were concluded to be a promising GIC reinforcement agent.

Comparative evaluation of microshear bond strength of the caries-affected dentinal surface treated with conventional method and chemomechanical method (papain)

Background:

There is a growing interest in chemomechanical excavation (papain) in permanent molar teeth. There are several studies dealing with primary molar teeth.

Aim:

The aim of this study was to evaluate the influence of conventional method and Carie-care (chemomechanical method) on the microshear bond strength (μSBS) and the type of failure of an adhesive system to caries-affected dentin of permanent molar teeth.

Materials and Methods:

Twenty permanent molar teeth with carious lesions extending into the dentin were selected. Through the center of the carious lesion, teeth were sectioned mesiodistally and divided into two groups based on the method of caries excavation (conventional and chemomechanical method). The time required for the completion of excavation procedure was noted. Samples were again divided into two subgroups in each according to the method of restoration (Ketac N100 and Filtek Z350 composite). The bonded interface was subjected to μSBS testing in a universal testing machine. Fractured surfaces were examined under a stereomicroscope, and representative specimens were examined under scanning electron microscope for the type of failure.

Statistical Analysis:

It was achieved with unpaired t-test and Kruskal-Wallis H-test at 5% level of significance.

Results:

The μSBS values of Carie-care groups were similar to that of the conventional method. The μSBSs of resin composite were significantly (P < 0.001) more than that of resin glass ionomer bonded irrespective of the method of caries excavation.

Conclusion:

A papain-based chemomechanical agent can be used safely as a method for caries removal when employing conventional adhesive systems.

In situ antibiofilm effect of glass-ionomer cement containing dimethylaminododecyl methacrylate

OBJECTIVE

The aim of this study was to investigate antibiofilm effects of a recently developed glass ionomer cement (GIC) containing dimethylaminododecyl methacrylate (DMADDM) under oral conditions.

METHODS

Biofilms were allowed to form in situ on GIC specimens (n=216) which contained DMADDM (1.1wt.% or 2.2wt.%). Samples without DMADDM served as control (n=108). GIC specimens were fixed on custom made splints and exposed to the oral cavity in six healthy volunteers for 24, 48 and 72h, respectively. Biofilm viability and coverage were analyzed by fluorescence microscopy (FM) and evaluated by red/green ratios and an established scoring system. Bacterial morphology and biofilm accumulation were determined by scanning electron microscopy (SEM). Additionally, material properties as surface charge density of quaternary ammonium groups, surface roughness and DMADDM release were recorded.

RESULTS

FM results showed a higher ratio (24h: 0%: 0.5, 1.1%: 1.2, 2.2%: 2.5) of red/green fluorescence on GIC samples containing DMADDM. Biofilm coverage and viability scores were significantly reduced (24h: q1/median/q3 for: 0%: 3/4/5, 1.1%: 2/3/3, 2.2%: 1/2/2) on DMADDM containing samples compared to controls after 24h as well as 48 and 72h in situ (p<0.05). While surface charge density of quaternary ammonium groups and DMADDM release increased with the DMADDM concentration, surface roughness was lowest on specimens containing 2.2wt.% DMADDM.

SIGNIFICANCE

An in situ dental biofilm model was used to evaluate the novel GIC containing DMADDM. This material strongly inhibited biofilms in situ and is promising to prevent bacterial colonization on the surface of restorations.

Microleakage under orthodontic bands cemented with nano-hydroxyapatite-modified glass ionomer

OBJECTIVES

To estimate the in vivo effect of nano-hydroxyapatite (HA) modification of banding glass-ionomer cement on microleakage under orthodontic bands.

MATERIALS AND METHODS

Eighty noncarious premolars scheduled for extraction in 20 orthodontic patients were randomly divided into four groups. Grouping was based on the ratio of nano-HA (0%, 5%, 10%, 15% by weight) added to the luting glass-ionomer cement (GIC) Ketac-Cem, which was used for cementation of prefabricated micro-etched orthodontic bands. Dye penetration method was used for microleakage evaluation at the cement-band and cement-enamel interfaces. Statistical evaluation was performed with a Kruskal-Wallis test and a Mann-Whitney U-test, and a Bonferroni-adjusted significance level was calculated.

RESULTS

Bands cemented with conventional GIC showed the highest microleakage scores in comparison to those cemented with nano-HA-modified GIC. No significant difference was found between teeth banded with 10% and 15% modified GIC.

CONCLUSIONS

Modification of the banding GIC with 15% nano-HA revealed a positive effect on reducing microleakage around orthodontic bands.

Permeability evaluation after decay removal in primary teeth with current caries-excavation techniques

AIM

The goal of the study was to evaluate the effect of caries removal by three various methods on the permeability of class II composite resin restorations in primary molar teeth.

MATERIALS AND METHODS

Forty-five recently extracted primary molars were randomly assigned to three groups for three different methods of caries removal; group 1-mechanical, group 2-caries detector dye, and group 3-Carisolv (n = 15). After that, class II cavities in all groups were restored with the adhesive (Opti Bond Solo Plus) that was applied according to the manufacturer's instruction and a posterior composite (Herculite XRV), which was used incrementally. After 24 hours the samples were thermocycled in water for 500 cycles between 5 and 55°C with a dwell time of 30 sec. Permeability was assessed by the fluid filtration method. The data were analyzed using the ANOVA test while study groups were compared with Tukey test for statistically significant differences at a 5% significance level.

RESULTS

The evaluation of tested groups indicated that the highest (0.80) and least (0.37) mean of permeability was observed in group 2 and 3 respectively. Significant difference was revealed among the tested groups (p = 0.045). The comparison of Carisolv and caries detector dye groups indicated a statistically significant difference (p = 0.037). There was not any significant difference between Carisolv or caries dye in the conventional group.

CONCLUSION

Using the chemomechanical and staining methods for caries removal had no more detrimental effect on permeability than the conventional technique. However, caries detection dye for caries removal could be more harmful than chemomechanical method.

CLINICAL SIGNIFICANCE

None of the current caries-excavation techniques could eliminate permeability in class II composite resin restorations. Furthermore, staining methods do not have an adverse effect on sealing ability in comparison to the conventional technique.

Hydroxyapatite particle characteristics influence the enhancement of the mechanical and chemical properties of conventional restorative glass ionomer cement

The aims of this study were to improve the mechanical and chemical properties of conventional restorative glass ionomer cement (GIC) by adding hydroxyapatite (HAp) preparations with different characteristics, and to investigate the underlying reaction mechanisms. Fuji IX GP® was used as the control GIC. The experimental GICs consisted of four HAp-particles with different characteristics added at 8 mass% to Fuji IX-powder. All cements were prepared by mixing with Fuji IX-liquid (P/L=3.6). Four HAp-particles were analyzed, and then the mechanical strengths and the fluoride-ion- release-recharge-behaviors of five GIC groups were evaluated. The results of this study demonstrate that the addition of HAp particles with highly reactive properties such as high specific surface area can enhance the flexural strength and fluoride ion release properties of conventional restorative GIC. Our results further indicate that HAp functions as an adsorbent and an ion exchangeable agent, resulting in improved mechanical and chemical properties of GIC.

Shear bond strengths of glass-ionomer cements to sound and to prepared carious dentine

The aim of this study was determine whether bonding of glass-ionomer cements to non-carious dentine differed from that to carious dentine. Five commercial cements were used, namely Fuji IX GP, Fuji IX capsulated, Fuji IX Fast capsulated (all GC, Japan), Ketac-Molar and Ketac-Molar Aplicap (both 3M-ESPE, Germany). Following conditioning of the substrate with 10% poly (acrylic acid) for 10 s, sets of 10 samples of the cements were bonded to prepared teeth that had been removed for orthodontic reasons. The teeth used had either sound dentine or sclerotic dentine. Shear bond strengths were determined following 24 h storage. For the auto-mixed cements, shear bond strength to sound dentine was found not to differ statistically from shear bond strength to sclerotic dentine whereas for hand-mixed cements, shear bond to sound dentine was found to be higher than to carious dentine (to at least p < 0.05). This shows that the chemical effects arising from interactions of glass-ionomer cements with the mineral phase of the tooth are the most important in developing strong bonds, at least in the shorter term.

Bonding of contemporary glass ionomer cements to dentin

OBJECTIVE

The objective of this study was to investigate the microtensile bond strength (microTBS) of contemporary glass ionomer cements (GIC) to sound coronal dentin.

METHODS

Three specimen teeth were prepared for each material tested: Fuji IX GP (GC), ChemFlex (Dentsply) and Ketac-Molar Aplicap (ESPE). GIC buildups were made according to the manufacturers' instructions. After being stored at 37 degrees C, 100% humidity for 24h, the teeth were vertically sectioned into 1x1mm beams for microTBS evaluation. Representative fractured beams were prepared for scanning (SEM) and transmission electron microscopic (TEM) examination.

RESULTS

Results of the microTBS test were: Fuji IX GP (12.4+/-8.6MPa), ChemFlex (15.0+/-9.3MPa) and Ketac-Molar Aplicap (11.4+/-7.7MPa). One-way ANOVA and a multiple comparison test showed that ChemFlex had a statistically higher microTBS (p<0.05). SEM fractographic analysis showed that the predominant failure modes were interfacial and mixed failures. The GIC side of the fractured beams revealed dehydration cracks, a high level of porosity, and voids with an eggshell-like crust. TEM analysis of the demineralized dentin sides of the fractured beams revealed the presence of an intermediate layer along the GIC-dentin interface. This zone was present on the fractured dentin surface in the case of interfacial failure, and beneath GIC remnants in specimens that exhibited a mixed failure mode.

SIGNIFICANCE

The findings suggest that the bonding of GIC to dentin is not weak and that the microTBS values probably represent the weak yield strengths of GICs under tension.

Chemochemical caries removal: a review of the techniques and latest developments

Chemomechanical caries removal involves the chemical softening of carious dentine followed by its removal by gentle excavation. The reagent involved is generated by mixing amino acids with sodium hypochlorite; N-monochloroamino acids are formed which selectively degrade demineralised collagen in carious dentine. The procedure requires 5-15 minutes but avoids the painful removal of sound dentine thereby reducing the need for local anaesthesia. It is well suited to the treatment of deciduous teeth, dental phobics and medically compromised patients. The dentine surface formed is highly irregular and well suited to bonding with composite resin or glass ionomer. When complete caries removal is achieved, the dentine remaining is sound and properly mineralised. The system was originally marketed in the USA in the 1980's as Caridex. Large volumes of solution and a special applicator system were required. A new system, Carisolv, has recently been launched on to the market. This comes as a gel, requires volumes of 0.2-1.0 ml and is accompanied by specially designed instruments.

Scanning electron microscopic observations of human dentine after mechanical caries excavation

OBJECTIVES

The structural integrity and surface characteristics of dentine remaining after caries excavation may be relevant to the subsequent bonding of adhesive restorative materials to the prepared cavity. This in vitro investigation aimed to analyse the different surface characteristics of the dentine cavity floor created after preparation using five different mechanical and chemo-mechanical methods of excavation: hand excavation, slow-speed bur, sono-abrasion, air-abrasion and Carisolv gel.

METHODS

Ten cavities were prepared using each excavation method in extracted teeth with occlusal carious lesions. Epoxy resin replicas of the 50 cavities were manufactured from silicone impressions and then analysed using secondary electron scanning electron microscopy (SEM) to ascertain the surface characteristics of the dentine at the cavity floor.

RESULTS AND CONCLUSIONS

Results from the 50 cavities examined suggested that each alternative excavation technique produced a different and characteristic dentine surface. Carisolv gel was the only method examined that consistently removed the smear layer during excavation to leave exposed dentine tubules at the end of cavity preparation.