The impact of an alkasite restorative material on the pH of Streptococcus mutans biofilm and dentin remineralization: an in vitro study.

BACKGROUND: It has been claimed that an alkasite restorative material can neutralize acids produced by cariogenic bacteria from released hydrogen ions and enable to remineralization via calcium and fluoride ions. However, there is no evidence to support this assertion. Therefore, the aims of this study were to investigate the effect of the alkasite restorative material on the pH of Streptococcus mutans biofilm and dentin hardness. METHODS: Streptococcus mutans biofilms were formed on Filtek™ Z350 (FZ, a resin composite) and Cention® N (CN, the alkasite restorative material) and their pH determined after 24 h. Hydroxide, fluoride, and calcium-ions released from the materials were determined at 6 h, 1, 3, 7, 14, and 28 days. Dentin specimens were prepared from 14 human molars and divided into four quadrants. Quadrant 1 was a sound dentin control, quadrants 2-4 were chemically demineralized, and a cylinder of FZ and CN placed on the surfaces of quadrants 2 and 4, respectively. The microhardness of quadrants 1 and 3 were measured at depths of 20, 40, and 60 µm from the occlusal surface, and similarly of quadrants 2 and 4, after 30 days. Independent t-test, Mann-Whitney-U, and repeated-measure-ANOVA were used for data analysis. RESULTS: The pH of biofilm on CN (4.45) was significantly higher (p < 0.05) than that on FZ (4.06). The quantity of all ions released from CN was significantly higher than from FZ. The hardness of demineralized dentin under CN was significantly higher than that of demineralized dentin at all depths, and higher than that of demineralized dentin under FZ at 20 and 40 µm. CONCLUSIONS: CN released hydroxide, fluoride, and calcium ions, which was associated with raising the biofilm pH and the hardness of demineralized dentin. All results indicated that CN had the potential to reduce the incidence of secondary caries.

Procedures Used in Managing SARS-CoV-2 Infected Dental Personnel or Patients: A Case Study From a Thai Dental Hospital.

SARS-CoV-2 can transmit undetected from asymptomatic and pre-symptomatic patients in dental clinics. Triaging dental patients using temperature and questionnaire screening cannot completely exclude asymptomatic SARS-CoV-2 infected individuals. Hence, asymptomatic SARS-CoV-2 infected individuals might visit dental hospitals/clinics seeking dental treatment without knowing that they are infected and might infect others, especially in a pandemic area. Ideally, a nasopharyngeal swab for real-time polymerase chain reaction or rapid antigen screening for dental personnel and patients prior to their appointment should be done. However, the implementation of this approach is impractical in some situations. Here, we describe the procedures for dental hospitals/clinics in case of an asymptomatic SARS-CoV-2 infected individual involved in dental service/treatment and later after testing positive for SARS-CoV-2. Potential closely contacted individuals were traced and classified according to their exposure risk. The recommended course of action is to identify individuals based on their risk and take the risk-appropriate action. We also discuss the implementation of these procedures in a dental setting during the COVID-19 pandemic in our school as a case study.

The effect of dentin age on the microshear bond strength and microleakage of glass-ionomer cements.

OBJECTIVE: To compare the microshear bond strength (µSBS) and microleakage of glass-ionomer cements when bonded to aged and young dentin. BACKGROUND: Glass-ionomer cement (GIC) is frequently used to restore root caries in elders. Many studies of GIC have been conducted using young dentin; however, few studies have assessed adhesion and microleakage of GICs to aged dentin. MATERIALS AND METHODS: Seventy-eight non-carious human molars (patient age 16-30 = 39; patient age ≥ 65 = 39) were tested with three GICs (Fuji II LC, Equia Forte Fil and Fuji BULK). For µSBS, teeth were horizontally sectioned, embedded in resin and three tubes attached to the sectioned surface. Materials were mixed and injected into the tubes, allowed to set and the tubes removed leaving the GIC cylinders. Specimens were stored in deionised water for 24 hours and tested in a universal testing machine. For microleakage, a buccocervical cavity was prepared, restored with GIC and stored in deionised water. The specimens were polished, coated with varnish, placed in 0.5% basic fuchsin for 24 hours, sectioned at the midpoint and evaluated for microleakage under a stereomicroscope and scanning electron microscope. RESULTS: For µSBS, Fuji II LC showed the highest bond strength among three products. There was no significant difference between age groups. (P = .93) For microleakage, Fuji II LC had more dye penetration (P < .01) and there was significant difference between age groups. CONCLUSION: After bonding of GICs, aged dentin showed no difference in µSBS but less microleakage when compared to young dentin.

Microshear bond strength to dentin of self-adhesive flowable composite compared with total-etch and all-in-one adhesives.

BACKGROUND/PURPOSE: Because of the lack of data on long-term survival of a flowable self-adhesive composite (SAC) restoration, the purpose of this study was to compare the microshear bond strengths (µSBSs) of flowable resin composites to dentin, either with self-adhesive ability or with the combined use of a total-etch adhesive and all-in-one adhesive, before and after thermocycling. MATERIALS AND METHODS: Coronal dentin specimens of 60 extracted sound third human molars were divided into three groups (n = 20) as follows: Group 1, flowable SAC (VF); Group 2, total-etch adhesive + flowable composite (FL); Group 3, all-in-one adhesive + flowable composite (AL). For each adhesive, half of the specimens were subjected to µSBS testing after 24-hour water storage, and the other half of the specimens were subjected to 5000 thermocycles followed by µSBS testing. The morphologies of the adhesive interfaces were evaluated under a scanning electron microscope. Data were analyzed using one-way analysis of variance (ANOVA) and independent t test. RESULTS: One-way ANOVA showed similar results for both 24-hour water storage and thermocycled groups. The FL group showed the highest µSBS values (P < 0.001). The VF and AL groups were not statistically significantly different. Thermocycling had no effect on µSBS values (P = 0.578). The interfacial observation revealed that VF had a gap at the resin-dentin interface. By contrast, both FL and AL specimens had distinct adhesive layers without any gap formation. CONCLUSION: The results from this study indicated that laboratory bonding effectiveness of flowable SAC was approximately that of all-in-one adhesive.

The repair potential of resin composite materials.

OBJECTIVES: To measure the 'repair' strength of various combinations of composite using four manufacturers' adhesive systems, to compare the bond strengths with the cohesive strength of the original, unrepaired products and to assess whether the chemical nature of the resin matrix influenced the repair strength. METHODS: Specimens were prepared of three composite materials Durafill, Heraeus Kulzer; P90 (Silorane) 3M ESPE; Z250 (3M ESPE) and aged in water at 60°C for 1 month. One surface of each specimen was faced with 80-grit silicone carbide paper, one of four adhesives placed (Ecusit, DMG; Clearfil Repair, Kuraray; P90 System Adhesive; Single Bond 2, 3M ESPE) and 'repair' composite added of the same type as above, such that all combinations of original and repair composite and adhesive were used. 'Stick' samples, approximately 6 mm × 0.8 mm × 4 mm were prepared from each repair specimen, a neck created at the junction of original and repair composites and the hour-glass sample tested in tension at 1 mm/min. The microtensile bond strength of the repair was calculated and the mode of failure (adhesive; cohesive in the original composite; cohesive in the repair composite) recorded. RESULTS: There was no significant difference between the cohesive strengths of Filtek P90 and Filtek Z250 (both ≈106 MPa); both were significantly stronger than Durafill (67.0 MPa). For bonding to Durafill the bond strengths ranged from 17.6 MPa to 50.9 MPa; for bonding to P90, the bond strengths ranged from 5.0 MPa to 54.2 MPa; for bonding to Z250, the bond strengths ranged from 17.2 MPa to 75.4 MPa. Clearfil Repair appeared to provide the most consistently high bond strengths, followed by the P90 System Adhesive, Single Bond 2 and Ecusit. Overall, the majority of failures (74%) was adhesive. SIGNIFICANCE: It appears that bonding of new dimethacrylate-based composite to old dimethacrylate-based composite can be a viable clinical procedure. However, if the original composite is silorane-based (e.g., P90), then using the silane-based adhesive may be the best repair option, and similarly if it is planned to effect a repair with a silorane-based composite, using a silane-based adhesive may give the best outcome. The null hypotheses are thus rejected.

The effectiveness of a calcium sodium phosphosilicate desensitizer in reducing cervical dentin hypersensitivity: a pilot study.

BACKGROUND: NovaMin (NovaMin Technology, Alachua, Fla.) was introduced into the dental market as a desensitizer in December 2004. However, to the authors' knowledge, no researchers yet have evaluated the effectiveness of 100 percent NovaMin powder with NovaMin-containing toothpaste in reducing dentin hypersensitivity compared with the effectiveness of NovaMin-containing toothpaste only and a desensitizing toothpaste containing potassium nitrate as a control. METHODS: The authors divided 60 participants randomly into three groups: NovaMin powder with NovaMin-containing toothpaste (group 1), a placebo powder with NovaMin-containing toothpaste (group 2) and a placebo powder with the control toothpaste (group 3). The authors used tactile and cold stimuli and a visual analog scale to evaluate participants' pain at baseline, immediately after powder application and at one week, two weeks and four weeks after powder application. They analyzed data by using Friedman and Wilcoxon signed-rank tests for within-group comparison. They used Kruskal-Wallis and Mann-Whitney U tests for between-group comparison. They considered P < .05 to be statistically significant. RESULTS: Groups 1 and 2 showed significant hypersensitivity reduction over baseline at all time points. Group 3 showed significant hypersensitivity reduction at one week onward. Group 1 showed significant improvement compared with groups 2 and 3, except for response to tactile stimulus at four weeks with group 2. Between groups 2 and 3, there were significant differences at two and four weeks. CONCLUSIONS: and CLINICAL IMPLICATIONS: The use of NovaMin powder and NovaMin-containing toothpaste for hypersensitivity reduction is more effective than the use of a desensitizing toothpaste containing potassium nitrate and fluoride.

Adhesion of resin core foundation composites to root canal dentin using different dentin adhesives.

PURPOSE: To evaluate the microtensile bond strengths (microTBS) of two core composites; LuxaCore and MultiCore Flow, to root canal dentin when using different adhesive systems. METHODS: Bonded specimens were allocated into six groups (N=20) according to the combination of two core composites and three adhesive systems (All-Bond 2, Excite DSC and Contax). The materials were used according to the manufacturers' instructions. The microTBS were measured using a universal testing machine with a crosshead speed of 1 mm/minute. Data were analyzed utilizing two-way ANOVA (alpha=0.05). RESULTS: Excite DSC showed the highest mean microTBS, which was significantly different from those of All-Bond 2 and Contax in LuxaCore groups. Excite DSC showed the highest microTBS but significant differences (P=0.154) were not detected in MultiCore groups. There were significant differences in microTBS between two resin composites (P<0.001). With Contax, microTBS of MultiCore Flow to dentin were significantly higher than those of LuxaCore (P=0.003).

The repair potential of resin-modified glass-ionomer cements.

OBJECTIVES: To assess the repair potential of resin-modified glass-ionomer cements (RMGICs) with additional RMGIC and resin composite. METHODS: Specimens of two proprietary RMGICs (Ketac N100 (Ketac Nano), 3M/ESPE, St Paul, MN; Fuji II LC, GC Corporation, Tokyo) were prepared and stored in water at 37 degrees C for 4 days. The surface of the RMGIC was finished flat with 600-grit silicon carbide paper. After treatment of the original surface by either phosphoric acid or polyacrylic acid for 20s, fresh RMGIC of the same brand was added in a plastics cylinder. Untreated specimens were used as a control. Further specimens were either left untreated (control) or etched with phosphoric acid for 20s, and resin composite added. Specimens were stored in water at 37 degrees C for 24h, and the shear bond strength measured. The fractured surfaces were examined for mode of failure. Additional RMGIC specimens were prepared for the examination of replicas of the finished and acid treated surfaces. RESULTS: The bond strength of new Ketac N100 to old Ketac N100 was in the order of 1.7 MPa, irrespective of the surface treatment, and many specimens failed before testing. The bond strength of new Fuji II LC to old Fuji II LC was in the order of 10 MPa, irrespective of the surface treatment. The bond strength of resin composite bonded to both RMGICs approximated 9-16 MPa. The mode of failure of the RMGIC to RMGIC bond varied depending on the products, and the mode of failure of the resin composite to RMGIC bond was predominantly cohesive in the RMGIC. SEM examination of the RMGIC surfaces showed little effect from acid treatment. SIGNIFICANCE: Based on this laboratory study, repair of RMGIC with additional RMGIC maybe clinically unpredictable, depending on the products used; repair with resin composite appears to be the preferred option.

Raman spectroscopic study of noncarious cervical lesions.

The surface of noncarious cervical lesions (NCCLs) consists of sclerosed dentin. This type of dentin may affect the ability of adhesive restorative materials to bond well to its surface, but little information exists on the chemical nature of this dentin surface and how it may be affected during acidic treatment. The inorganic part of normal dentin and dentin from NCCLs before and after acid conditioning with phosphoric acid or polyacrylic acid was investigated. Ten premolars with NCCLs and four human third molars (control) were used. Replicas of NCCLs were examined using scanning electron microscopy (SEM). Surfaces and longitudinal sections of four NCCLs and control dentin discs were analyzed using Raman spectroscopy. The discs and NCCLs were sectioned, and treated with 35% phosphoric acid or 20% polyacrylic acid/3% aluminum chloride, and Raman spectra obtained. The area under phosphate nu1 of the dentin spectrum was computed to obtain a ratio with the area under the second-order spectrum of a silicon phonon comparative standard. Mean phosphate nu1 and silicon phonon ratios from normal dentin and NCCLs were compared using a linear model with repeated measurements and Tukey's pairwise tests. Mean ratios from different locations of the NCCLs were compared using one-way analysis of variance (ANOVA) and Tukey's pairwise tests. SEM micrographs of NCCL surfaces showed variation from relatively smooth with no dentinal tubule openings to surfaces with occluded tubules. The mean phosphate nu1 and silicon phonon ratios for NCCLs were higher than those of normal dentin in all treatment groups (P < 0.05). Ratios from the untreated specimens were higher than those of the polyacrylic acid-treated specimens, and those for the phosphoric acid-treated group were the lowest (P < 0.05). The ratios obtained for the surfaces of NCCLs were higher than those halfway towards the pulp, and those adjacent to the pulp were the lowest (P < 0.05).

Interfacial micromorphology of three adhesive systems created in caries-affected dentin.

PURPOSE: To investigate the morphology of the resin-dentin interface of three dentin adhesive systems (One Coat Bond, Clearfil SE Bond and One-Up Bond F) bonded to caries-affected dentin, exposed using either rotary instrumentation in conjunction with a caries detector dye or a chemo-mechanical caries removal system (Carisolv). MATERIALS AND METHODS: 60 extracted human molars with occlusal caries were used. 30 teeth had carious dentin removed using slow-speed round steel burs after staining with the caries detector dye, and carious dentin from the remaining teeth was removed using Carisolv. The teeth from each caries removal technique were randomly divided into three groups, bonded with one of the three adhesive systems above according to the manufacturers' instructions, and a thin layer of resin-based composite applied. The teeth were sectioned parallel to the bonded surface to obtain a 3 mm thick bonded dentin disc. The specimens were assigned to one of two observation techniques: a fracture technique or an acid-base technique. Fracture technique: a shallow groove was prepared across the dentin surface of the specimen, fixed in 10% buffered formalin, dehydrated in an ascending ethanol series up to 100%, critical-point dried, and fractured along the prepared groove. Acid-base technique: the specimens were sectioned vertically across the bonded interface, fixed in 10% phosphate buffered formalin, polished with diamond paste down to 0.25-microm particle size, immersed in 10% orthophosphoric acid for 3-5 s and 5% sodium hypochlorite for 10 min. All specimens were gold sputter-coated and observed using FE-SEM. RESULTS: All groups showed hybrid layer formation. However, the thickness varied depending on the adhesive system and the carious dentin removal technique used. One Coat Bond (a "one-bottle" system) showed the thickest hybrid layer (approximately 2 microm) in acid/base treated specimens when bonded to caries-affected dentin, whereas One-Up Bond F (an "all-in-one" system) bonded to normal dentin exhibited the thinnest hybrid layer (approximately 0.3 microm).