Effect of tack cure time on polymerization shrinkage of dual-cure resin cement

When luting indirect restorations with dual-cure resin cement (DCRC), excess cement can be easily removed by performing tack cure of DCRC for a few seconds. The purpose of this study was to evaluate whether different tack cure times affect polymerization shrinkage (PS) of the selected DCRC. One dual-cure resin cement (G-CEM LinkAce, GC) was used for measuring PS in light-cure (LC group), self-cure (SC group), and two tack-cure modes. In the first tack-cure subgroup, tack cure was performed for 1, 2, 3, and 5 seconds, followed by light cure after 2 minutes of remnant removal time in each case (TC-LC groups). In the other tack-cure subgroup, tack cure was performed for the same lengths of time, but followed by self-cure in each case (TC-SC groups). PS was measured by a modified bonded disc method for 1,800 seconds. One-way analysis of variance followed by Duncan’s post hoc test was used to determine any statistically significant differences among the test groups (α = 0.05). When the DCRC was selfcured after tack cure, PS was significantly lower than when it was only self-cured (p 0.05). When the DCRC was light-cured, PS was not affected by tack cure or tack cure time (p > 0.05). Therefore, tack cure within 5 seconds did not negatively affect the final PS when the DCRC was light-cured after cement remnant removal.

Effect of powder-liquid ratios and powder colors on color stability of 4-META / MMA-TBB resin after immersion in coffee / 대한치과재료학회지

The aim of this study was to evaluate the color stability of 4-methacryloxyethyl trimellitate anhydride (4-META) / methyl methacrylate (MMA) & tri-n-butylborane (TBB) resin with different powder-liquid (P/L) ratios and powder colors after immersion in coffee. Experimental groups (Bondfill SB) were classified by the P/L ratio (0.8:1 / 1:1 / 1.2:1, weight [wt] %) and color of the powder (light / medium). Light-cured resin composite (Filtek Z350 XT flowable) was used as a control group. Each disk-shaped specimen of 7 groups (n = 8 for color difference, n = 10 for translucency parameter [TP]) was immersed in a staining solution of coffee for 4 weeks. The color of the specimen was measured at the time of baseline, 1 day, 1 week, 2 weeks, 3 weeks, and 4 weeks with a spectrophotometer. The color difference (ΔE) and changes in translucency parameter (ΔTP) were statistically analyzed by one-way analysis of variance (ANOVA), followed by Tukey's post-hoc test. Independent t-test was applied to evaluate the effect on the colors of the powder (α = 0.05). The values of color difference (ΔE) of the experimental groups were within the clinically acceptable threshold (ΔE < 3.3), whereas control group showed values over 3.3 after 1 week of immersion. The values of TP ranged from 9.58 to 13.28. The differences of TP (ΔTP) between baseline and 4 weeks were less than 1.0, except in the control group. Conclusively, self-cured resin composite showed excellent color stability in coffee for the period of this study regardless of different P/L ratios and powder colors.

Recognition and management of palatogingival groove for tooth survival: a literature review

Palatogingival groove (PGG) is an anomaly in the maxillary anterior teeth, often accompanied by the area of bony destruction adjacent to the teeth with no carious or traumatic history. The hidden trap in the tooth can harbor plaque and bacteria, resulting in periodontal destruction with or without pulpal pathologic change. Related diseases can involve periodontal destruction, combined endodontic-periodontal lesions, or separate endodontic and periodontal lesions. Disease severity and prognosis related to PGG depend on several factors, including location, range, depth, and type of the groove. Several materials have been used and recommended for cases of extensive periodontal destruction from PGG to remove and block the inflammatory source and recover the health of surrounding periodontal tissues. Even in cases of severe periodontal destruction, several studies have reported favorable treatment outcomes with proper management. With new options in diagnosis and treatment, clinicians need a detailed understanding of the characteristics, treatment, and prognosis of PGG to successfully manage the condition.

In vitro evaluation of a newly produced resin-based endodontic sealer

OBJECTIVES: A variety of root canal sealers were recently launched to the market. This study evaluated physicochemical properties, biocompatibility, and sealing ability of a newly launched resin-based sealer (Dia-Proseal, Diadent) compared to the existing root canal sealers (AHplus, Dentsply DeTrey and ADseal, Metabiomed). MATERIALS AND METHODS: The physicochemical properties of the tested sealers including pH, solubility, dimensional change, and radiopacity were evaluated. Biocompatibility was measured using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. For microleakage test, single-rooted teeth were instrumented, and obturated with gutta-percha and one of the sealers (n = 10). After immersion in 1% methylene blue solution for 2 weeks, the specimens were split longitudinally. Then, the maximum length of staining was measured. Statistical analysis was performed by one-way analysis of variance followed by Tukey test (p = 0.05). RESULTS: Dia-Proseal showed the highest pH value among the tested sealers (p < 0.05). ADseal showed higher dimensional change compared to AHplus and Dia-Proseal (p < 0.05). The solubility values of AHplus and Dia-Proseal were similar, whereas ADseal had the lowest solubility value (p < 0.05). The flow values of sealer in increasing order were AHplus, DiaProseal, and ADseal (p < 0.05). The radiopacity of AHplus was higher than those of ADseal and Dia-Proseal (p < 0.05). The cell viability of the tested materials was statistically similar throughout the experimental period. There were no significant differences in microleakage values among the tested samples. CONCLUSIONS: The present study indicates that Dia-Proseal has acceptable physicochemical properties, biocompatibility, and sealing ability.

Effects of proanthocyanidin, a crosslinking agent, on physical and biological properties of collagen hydrogel scaffold

OBJECTIVES: The purpose of the present study was to evaluate the effects of proanthocyanidin (PAC), a crosslinking agent, on the physical properties of a collagen hydrogel and the behavior of human periodontal ligament cells (hPDLCs) cultured in the scaffold. MATERIALS AND METHODS: Viability of hPDLCs treated with PAC was measured using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The physical properties of PAC treated collagen hydrogel scaffold were evaluated by the measurement of setting time, surface roughness, and differential scanning calorimetry (DSC). The behavior of the hPDLCs in the collagen scaffold was evaluated by cell morphology observation and cell numbers counting. RESULTS: The setting time of the collagen scaffold was shortened in the presence of PAC (p < 0.05). The surface roughness of the PAC-treated collagen was higher compared to the untreated control group (p < 0.05). The thermogram of the crosslinked collagen exhibited a higher endothermic peak compared to the uncrosslinked one. Cells in the PAC-treated collagen were observed to attach in closer proximity to one another with more cytoplasmic extensions compared to cells in the untreated control group. The number of cells cultured in the PAC-treated collagen scaffolds was significantly increased compared to the untreated control (p < 0.05). CONCLUSIONS: Our results showed that PAC enhanced the physical properties of the collagen scaffold. Furthermore, the proliferation of hPDLCs cultured in the collagen scaffold crosslinked with PAC was facilitated. Conclusively, the application of PAC to the collagen scaffold may be beneficial for engineering-based periodontal ligament regeneration in delayed replantation.

Mandibular bone necrosis after use of paraformaldehyde-containing paste

Paraformaldehyde has been used in the past as a pulpotomy agent. However, it has a severe cytotoxic effect and may cause alveolar bone necrosis. Depulpin, a devitalizing agent containing 49% paraformaldehyde, is no longer used frequently due to its severe side effects. In the two cases described in the present study, Depulpin was used as a devitalizing agent during root canal treatment. It caused a gradual loss of sensibility in adjacent teeth, gingival necrosis, and osteomyelitis. This case report demonstrates the serious side effects of using a paraformaldehyde-containing paste as a devitalizing agent for pulp, particularly mandibular bone necrosis.

The effect of saliva decontamination procedures on dentin bond strength after universal adhesive curing

OBJECTIVES: The purpose of this study was to investigate the effectiveness of multiple decontamination procedures for salivary contamination after curing of a universal adhesive on dentin bond strength according to its etch modes. MATERIALS AND METHODS: Forty-two extracted bovine incisors were trimmed by exposing the labial dentin surfaces and embedded in cylindrical molds. A universal adhesive (All-Bond Universal, Bisco) was used. The teeth were randomly divided into groups according to etch mode and decontamination procedure. The adhesive was applied according to the manufacturer's instructions for a given etch mode. With the exception of the control groups, the cured adhesive was contaminated with saliva for 20 sec. In the self-etch group, the teeth were divided into three groups: control, decontamination with rinsing and drying, and decontamination with rinsing, drying, and adhesive. In the etch-and-rinse group, the teeth were divided into four groups: control, decontamination with rinsing and drying, decontamination with rinsing, drying, and adhesive, and decontamination with rinsing, drying, re-etching, and reapplication of adhesive. A composite resin (Filtek Z350XT, 3M ESPE) was used for filling and was cured on the treated surfaces. Shear bond strength was measured, and failure modes were evaluated. The data were subjected to one-way analysis of variation and Tukey's HSD test. RESULTS: The etch-and-rinse subgroup that was decontaminated by rinse, drying, re-etching, and reapplication of adhesive showed a significantly higher bond strength. CONCLUSIONS: When salivary contamination occurs after curing of the universal adhesive, additional etching improves the bond strength to dentin.

Healing after horizontal root fractures: 3 cases with 2-year follow-up

Among dental traumas, horizontal root fractures are relatively uncommon injuries. Proper initial management and periodical evaluation is essential for the successful treatment of a root-fractured tooth. If pulpal necrosis develops, endodontic treatment is indicated, exclusively for the coronal fragment. Fragment diastases exert a great influence on healing at the fracture line and on pulpal necrosis. An adequately treated root-fractured tooth has a good prognosis. This case report describes the treatment and 2-yr follow up of 3 maxillary central incisors, first with horizontal root fracture, second with horizontal root fracture and avulsion, and third with horizontal root fracture and lateral luxation. All three cases were treated with mineral trioxide aggregate (ProRoot, Dentsply). During 2 yr of follow-up evaluation, the root-fractured teeth of the present patients were well retained in the arch, showing periodontal healing, even after endodontic treatment.