Quantitative microleakage analysis of endodontic temporary filling materials using a glucose penetration model.

OBJECTIVE: The purpose of this study was to analyze the sealing ability of different temporary endodontic materials over a 6-week period using a glucose penetration model. MATERIALS AND METHODS: Standardized holes were formed on 48 dentin discs from human premolars. The thicknesses of the specimens were distributed evenly to 2 mm, 3 mm and 4 mm. Prepared dentin specimens were randomly assigned into six groups (n = 7) and the holes in the dentin specimens were filled with two kinds of temporary filling materials as per the manufacturers' instructions as follows: Caviton (GC Corporation, Tokyo, Japan) 2 mm, 3 mm, 4 mm and IRM (Dentsply International Inc., Milford, DE) 2 mm, 3 mm, 4 mm. The remaining specimens were used as positive and negative controls and all specimens underwent thermocycling (1000; 5-55°C). The sealing ability of all samples was evaluated using the leakage model for glucose. The samples were analyzed by a spectrophotometer in quantitative glucose microleakage test over a period of 6 weeks. As a statistical inference, a mixed effect analysis was applied to analyze serial measurements over time. RESULTS: The Caviton groups showed less glucose penetration in comparison with the IRM groups. The Caviton 4 mm group demonstrated relatively low glucose leakage over the test period. High glucose leakage was detected throughout the test period in all IRM groups. The glucose leakage level increased after 1 week in the Caviton 2 mm group and after 4 weeks in the Caviton 3 mm and 4 mm groups (p < 0.05). CONCLUSIONS: Caviton had better sealing ability than IRM in the glucose penetration model during 6 weeks. Temporary filling of Caviton to at least 3 mm in thickness is necessary and temporary filling periods should not exceed 4 weeks.

Cytotoxicity of four denture adhesives on human gingival fibroblast cells.

OBJECTIVE: The purpose of this study was to compare the cytotoxicity of four denture adhesives on human gingival fibroblast cells. MATERIALS AND METHODS: Immortalized human gingival fibroblasts were cultured with one of four different denture adhesives, Polident, Protefix, Staydent or Denfix-A, which was placed in insert dishes (10% w/v concentration) for 48 h. The MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay and flow cytometric apoptosis assay were used to evaluate cell viability and apoptosis rates. The fibroblasts were also examined under a scanning electron microscope. RESULTS: The MTT assay showed that all denture adhesives resulted in a significantly lower cell viability compared to the control cells propagated in normal culture medium (p < 0.05), with Staydent demonstrating the lowest cell viability. According to the flow cytometric apoptosis assay, Staydent and Protefix showed significantly higher apoptosis rates than the control group (p < 0.05), whereas Polident and Denfix-A did not demonstrate any significant differences (p > 0.05). Staydent showed the highest apoptosis rate. Scanning electron microscopy showed that the cells of the Staydent group underwent cytoplasmic membrane shrinkage, with cell free areas containing residual fragments of the membrane of dead cells. CONCLUSIONS: The four denture adhesives evaluated in this study imparted cytotoxic effects on human gingival fibroblast cells. Staydent showed the highest toxicity.

Neutral Position Facilitates Nasotracheal Intubation with a GlideScope Video Laryngoscope: A Randomized Controlled Trial.

The optimal head position for GlideScope facilitated nasotracheal intubation has not yet been determined. We compared the neutral and sniffing positions to establish the degree of intubation difficulty. A total of 88 ASA I-II patients requiring nasotracheal intubation for elective dental surgery with normal airways were divided into two groups according to head position, neutral position (group N), and sniffing position (group S). The primary outcome was the degree of intubation difficulty according to the Intubation Difficulty Scale (IDS): Easy (IDS = 0), mildly difficult (IDS = 1 to 4), and moderately to severely difficult (IDS ≥ 5). Eighty-seven patients completed the study and their data were analyzed. The degree of intubation difficulty was significantly different between the two groups (p = 0.004). The frequency of difficult intubation (IDS > 0) was 12 (27.9%) in group N and 28 (63.6%) in group S (difference in proportion, 35.7%; 95% confidence interval [CI], 14.8 to 52.6%; p = 0.001). The neutral position facilitates nasotracheal intubation with GlideScope by aligning the nasotracheal tube and the glottis inlet more accurately than the sniffing position.

Comparison of photopolymerization temperature increases in internal and external positions of composite and tooth cavities in real time: Incremental fillings of microhybrid composite vs. bulk filling of bulk fill composite.

OBJECTIVES: This study evaluated temperature increases in the composite and pulpal side of dentin from incremental and bulk fillings in composite restorations. METHODS: Class-1 cavities (5 mm × 4 mm × 3 mm) were prepared in ten extracted third molars, filled with composite, and restored with two separate horizontal layers of Filtek Z250 (3M ESPE) in the incremental group or a single layer of SureFil SDR Flow (Dentsply) in the bulk-fill group (n=5). After placing the specimens in a 36.5°C water bath, temperatures were measured with eight thermocouples at the bottom center (BC), middle center (MC), top center (TC), bottom corner (BE), middle corner (ME), and top corner (TE) of the cavity, at the pulpal side of the dentin within the pulp chamber (PD), and in the curing light (CL) tip during light curing at 750 mW/cm(2) for 20s and then analyzed with one-way analysis of variance and Tukey's HSD tests (α=0.01). RESULTS: Maximum temperatures ranged from 39.0°C (PD 1st increment) to 60.0°C (MC 1st increment) in the incremental group and from 42.0°C (PD) to 74.9°C (TC) in the bulk-fill group. In the incremental group, temperatures were similar between the 1st and 2nd increments, except at MC and BC. CONCLUSIONS: Bulk-fill group exhibited a greater increase in temperature during composite restoration. Regardless of the filling technique, more heat was generated at the center than at the corner and at the top than at the bottom of the composite. PD temperatures increased by 3.1°C and 5.5°C in the incremental group and bulk-fill group, respectively. CLINICAL SIGNIFICANCE: Although bulk fillings save clinical chair time, clinicians should be aware of the greater heat that is generated with increasing amounts of composites during polymerization, which can jeopardize the pulpal health, especially when a large and deep cavity is being restored.

Epigenetics: general characteristics and implications for oral health.

Genetic information such as DNA sequences has been limited to fully explain mechanisms of gene regulation and disease process. Epigenetic mechanisms, which include DNA methylation, histone modification and non-coding RNAs, can regulate gene expression and affect progression of disease. Although studies focused on epigenetics are being actively investigated in the field of medicine and biology, epigenetics in dental research is at the early stages. However, studies on epigenetics in dentistry deserve attention because epigenetic mechanisms play important roles in gene expression during tooth development and may affect oral diseases. In addition, understanding of epigenetic alteration is important for developing new therapeutic methods. This review article aims to outline the general features of epigenetic mechanisms and describe its future implications in the field of dentistry.

Analysis of Self-Adhesive Resin Cement Microshear Bond Strength on Leucite-Reinforced Glass-Ceramic with/without Pure Silane Primer or Universal Adhesive Surface Treatment.

OBJECTIVE: To evaluate the microshear bond strength (µSBS) of self-adhesive resin (SA) cement on leucite-reinforced glass-ceramic using silane or universal adhesive. MATERIALS AND METHODS: Ceramic blocks were etched with 9.5% hydrofluoric acid and divided into three groups (n = 16): (1) negative control (NC) without treatment; (2) Single Bond Universal (SBU); (3) RelyX Ceramic Primer as positive control (PC). RelyX Unicem resin cement was light-cured, and µSBS was evaluated with/without thermocycling. The µSBS was analyzed using one-way analysis of variance. The fractured surfaces were examined using stereomicroscopy and scanning electron microscopy (SEM). RESULTS: Without thermocycling, µSBS was highest for PC (30.50 MPa ± 3.40), followed by SBU (27.33 MPa ± 2.81) and NC (20.18 MPa ± 2.01) (P < 0.05). Thermocycling significantly reduced µSBS in SBU (22.49 MPa ± 4.11) (P < 0.05), but not in NC (20.68 MPa ± 4.60) and PC (28.77 MPa ± 3.52) (P > 0.05). PC and NC predominantly fractured by cohesive failure within the ceramic and mixed failure, respectively. CONCLUSION: SBU treatment improves µSBS between SA cement and glass ceramics, but to a lower value than PC, and the improvement is eradicated by thermocycling. NC exhibited the lowest µSBS, which remained unchanged after thermocycling.

Real-Time Analysis of Temperature Changes in Composite Increments and Pulp Chamber during Photopolymerization.

OBJECTIVE: The aim of this study was to evaluate the temperature change at various sites within the composite and on the pulpal side of dentin during polymerization of two composite increments. MATERIALS AND METHODS: Class I cavities prepared in third molars were restored in two composite increments (n = 5). Temperatures were measured for 110 s using eight thermocouples: bottom center of cavity (BC), top center of 1st increment (MC), top center of 2nd increment (TC), bottom corner of cavity (BE), top corner of 1st increment (ME), top corner of 2nd increment (TE), pulpal side of dentin (PD), and center of curing light guide tip (CL). RESULTS: Maximum temperature values (°C) measured during polymerization of 1st increment were MC (59.8); BC (52.8); ME (51.3); CL (50.7); BE (48.4); and PD (39.8). Maximum temperature values during polymerization of 2nd increment were TC 58.5; TE (52.6); MC (51.7); CL (50.0); ME (48.0); BC (46.7); BE (44.5); and PD (38.8). CONCLUSION: Temperature at the floor of the cavity was significantly higher during polymerization of 1st increment compared to 2nd increment. Temperature rise was higher at the center than at the corner and at the top surface than at the bottom surface of each increment.