Association between dental diseases and oral hygiene care and the risk of vertebral fracture: a nationwide cohort study.

Periodontal disease and increased missing teeth were associated with incident vertebral fractures. In contrast, professional dental cleaning and frequent tooth brushing, was associated with a lower risk of vertebral fracture. Better oral hygiene care attenuated the risk associated with dental diseases. PURPOSE: To investigate the association between oral health and the risk of vertebral fractures. METHODS: We included 2,532,253 individuals aged ≥40 years who underwent the Korean National Health Insurance Service health examinations in 2008 and followed up until December 31, 2017. We performed multivariable Cox proportional hazard regression analyses to evaluate the association between dental diseases and oral hygiene care and the risk of vertebral fractures. RESULTS: Over the 9.3-year median follow-up, 1.46% (n = 36,857) experienced vertebral fractures. Individuals with dental diseases had a higher risk of vertebral fracture than those without (hazard ratio [HR] 1.04, 95% confidence interval [CI]: 1.02-1.07 for periodontal diseases; 1.02, 1.00-1.05 for dental caries; 1.12, 1.05-1.20 for ≥15 missing teeth). Good oral hygiene care was associated with a lower vertebral fracture risk (HR 0.89, 95% CI: 0.86-0.91 for ≥1 time/year [vs. <1 time/year] of professional dental cleaning; 0.90, 0.87-0.93 for ≥2 times/day [vs. 0-1 time/day] of toothbrushing). The combined dental diseases was significantly associated with an increased vertebral fracture risk, whereas combined oral hygiene care was associated with further risk reduction. Better oral hygiene care reduced vertebral fracture risk associated with dental diseases (all P <0.001). CONCLUSION: Periodontal disease, dental caries, and an increased number of missing teeth were independently associated with higher risks for vertebral fractures. Conversely, improved oral hygiene care, such as personal dental cleaning and frequent tooth brushing, may modify vertebral fracture risks associated with dental disease.

Comparative analysis of flexural strength of 3D printed and milled 4Y-TZP and 3Y-TZP zirconia.

STATEMENT OF PROBLEM: The mechanical properties of 3 dimensionally (3D) printed zirconia have been reported to be comparable with those of milled zirconia, except for the flexural strength. However, most previous studies tested 3 mol% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP), making it necessary to study 3D printed zirconia with 4 mol% yttria content (4Y-TZP). PURPOSE: The purpose of this in vitro study was to compare the flexural strength of 3D printed 4Y-TZP with 3Y-TZP materials and milled 4Y-TZP. MATERIAL AND METHODS: A total of 80 disk specimens (Ø15×1.5 mm) were fabricated and divided into 4 groups (n=20) using the fabrication method and yttria content: milled 3Y-TZP (Katana HT; Kuraray Noritake), 3D printed 3Y-TZP (TZ-3Y-E; Tosoh), milled 4Y-TZP (Katana STML; Kuraray Noritake), and 3D printed 4Y-TZP (3DMAT; Genoss). The biaxial flexural strength was determined with a piston-on-3-ball test (n=15). The flexural strength of each specimen was measured, and the Weibull modulus (m) and characteristic strength (σ0) were estimated from the fracture load distribution. Two intact and fractured specimens were examined with scanning electron microscopy (SEM). The crystalline phase of the specimens in each group was identified through X-ray diffraction (XRD) analysis (n=5). A 1-way ANOVA was used to compare the flexural strength among different groups. Subsequently, pairwise comparisons were conducted with the Tukey post hoc method (α=.05). RESULTS: The flexural strength of 3D printed 4Y-TZP was significantly higher than that of milled 4Y-TZP (P<.001). In contrast, the flexural strength of 3D printed 3Y-TZP was significantly lower than that of milled 3Y-TZP (P<.001). X-ray diffraction (XRD) analysis revealed that the tetragonal phase was the dominant phase in all groups, with the identification of some cubic phase peaks. CONCLUSIONS: Three dimensionally printed 4Y-TZP showed significantly higher flexural strength than milled 4Y-TZP and exhibited a clinically acceptable flexural strength exceeding 800 MPa.

Color and surface stainability of additively and subtractively manufactured interim restorative materials against mouth rinses.

STATEMENT OF PROBLEM: Interim restorations are often used along with mouth rinses during the healing period following surgical procedures. However, evidence regarding the color and surface properties of digitally fabricated interim restorations after oral rinsing is lacking. PURPOSE: The purpose of this in vitro study was to evaluate whether different mouth rinses could affect the color and surface roughness of milled and printed interim restorations after simulated oral rinsing. MATERIAL AND METHODS: Disk-shaped specimens (Ø15×2 mm; N=180) were fabricated by using conventional (Jet Tooth Shade), milled (Yamahachi PMMA Disk), and printed (NextDent C&B) resin materials. All resin specimens were divided into 3 different groups according to the rinsing material: distilled water, whitening mouth rinse (Listerine Healthy White), and conventional mouth rinse (Listerine Cool Mint). The specimens were further allocated into short- and long-term subgroups, and oral rinsing simulation was performed (n=10). Short-term rinsing simulated the conditions in a usual interim restoration period, and long-term rinsing was performed to evaluate the properties of the interim materials. The color differences (CIEDE2000, ΔE00) between the baseline and each time point were determined by using a spectrophotometer. The surface roughness of the tested specimens was measured by using a confocal laser scanning microscope. Kruskal-Wallis and Friedman tests with nonparametric pairwise comparisons were used to analyze the data (α=.05). RESULTS: On simulation of a 6-month use of the mouth rinse, the color change in the milled resin did not differ from that in the conventional resin (P>.334), but the printed resin showed a significantly greater color change than the other resins (P<.007). The greatest color change with the printed resin was observed when a conventional mouth rinse was used. However, all color changes were below a perceptible threshold of 1.30. When daily rinsing for 14 years was simulated, all resin groups showed a perceptible color change when conventional mouth rinse was used, and the printed resin showed the greatest median ±interquartile range ΔE00 (2.24 ±0.2). In both short- and long-term simulations, the printed resin rinsed with the conventional mouth rinse showed significantly greater roughness than that rinsed with distilled water (P<.009). CONCLUSIONS: The printed resin showed higher stainability than the conventional resin, and the color change was greatest with the conventional mouth rinse. However, in 6 months of daily mouth rinse simulation, all the tested resin materials exhibited imperceptible color change and clinically acceptable surface roughness.

In vivo real-time temperature measurement on the surface of intact and gold-restored teeth during consumption of hot and cold drinks.

This study aimed to measure real-time temperature changes in gold-restored teeth compared with intact teeth during the intake of hot and cold drinks. Sixteen molars, including eight natural intact teeth and eight restored teeth with gold inlays, were selected from the participants. Custom-made thermocouple sensors were attached to the coronal third of the buccal surface of teeth. Participants consecutively consumed hot and cold drinks according to a standardized regimen. Resting, maximum, and minimum temperatures; time to reach peak temperatures; and heating and cooling velocities were obtained. Statistical analysis was performed using independent two-sample t-test. Teeth with gold restorations showed a significantly higher maximum temperature (44.7 °C [SD 2.9]) than did natural teeth (40.5 °C [SD 1.2]) during hot water drinking and showed a lower minimum temperature (25.0 °C [SD 4.9]) than did natural teeth (31.5 °C [SD 3.1]) during cold water drinking. The heating and cooling rates for the teeth with gold restorations were two and three times higher than those of the natural teeth. Gold-restored teeth showed greater temperature change than intact teeth in terms of magnitude and velocity in response to temperature changes induced by hot and cold drinks.

Effect of layer thickness and printing orientation on the color stability and stainability of a 3D-printed resin material.

STATEMENT OF PROBLEM: Although 3-dimensional (3D)-printed resin prostheses are widely used, studies on the effects of the manufacturing parameters of 3D printing on the color stability and stainability of these prostheses are lacking. PURPOSE: The purpose of this in vitro study was to investigate the effects of layer thickness and printing orientation on the color stability and stainability of a 3D-printed resin. In addition, the influence of roughness and water contact angle was evaluated. MATERIAL AND METHODS: Color changes (ΔE00) in tooth-colored resin specimens produced by 3D printing with 2 different layer thicknesses and 3 different printing orientations and immersed in 3 types of aging media (distilled water, coffee solution, and wine) were evaluated (n=10). The CIELab color values were measured with a spectrophotometer at baseline and different time points (1, 3, 7, 15, and 30 days). The surface roughness (Ra) of resin specimens was measured at various time points (baseline, 7, 15, and 30 days) by confocal laser scanning microscopy after immersion in coffee solution (n=15). The water contact angle was determined by using the sessile drop method (n=10). The ΔE00 values were analyzed by using the 3-way repeated measures ANOVA followed by the Bonferroni test and Dunnett T3 test (α=.05). Ra values were analyzed by 3-way repeated measures ANOVA (α=.05). The water contact angle data were analyzed by 2-way ANOVA (α=.05). RESULTS: The 3-way repeated measures ANOVA showed that layer thickness, printing orientation, and storage time significantly influenced the ΔE00 values of the 3D-printed resin specimens in each aging medium (P<.001). The ΔE00 values in the 0-degree subgroups were significantly lower than those in the 45- and 90-degree subgroups (P<.05). The ΔE00 values in the 25-µm thick groups were significantly higher than those in the 100-µm thick groups (P<.05). The ΔE00 values demonstrated an increase up to 15 days in all aging media. In distilled water, the ΔE00 values of the specimens increased or decreased depending on the groups, whereas in the coffee solution, the values decreased after 15 days (P<.001); in red wine, the values demonstrated a continuous increase up to 30 days in all groups (P<.001). The 3-way repeated measures ANOVA showed that the Ra values did not change significantly with immersion time (P=.444). The 2-way ANOVA showed that the water contact angle was not significantly affected by layer thickness (P=.921) or printing orientation (P=.062). CONCLUSIONS: Layer thickness and printing orientation affected the color stability and stainability of the 3D-printed resin. The discoloration of the 3D-printed resin differed with time, depending on the type of aging media used.

Biochemical and structural characterization of a keratin-degrading M32 carboxypeptidase from Fervidobacterium islandicum AW-1.

Comparative genomics of the keratin-degrading extremophilic eubacterium Fervidobacterium islandicum AW-1 and the closely related Fervidobacterium nodosum with no keratinolytic activity suggested that the FIAW1_1600 gene encoding a carboxypeptidase (CP) plays an important role in keratin degradation. The presumptive 489 amino acid sequence of the gene showed a conserved HEXXH motif with low levels of sequence identity (<38%) to reported thermostable M32 CPs. To identify its functional role, the FIAW1_1600 gene was overexpressed in Escherichia coli, and the recombinant enzyme was purified and characterized in detail. F. islandicum AW-1 CP (FisCP) formed a homodimer with a molecular mass of 107 kDa, and its apoenzyme exhibited maximal activity at 80 °C and pH 7.0 in the presence of Co(2+). This metalloenzyme mainly cleaved the C-termini of peptides with a basic amino acid sequence. The crystal structure of FisCP at 2.2 Å resolution showed high levels of structural similarities (root-mean-square deviations of <1.7 Å) to those of other M32 CP homologs. Remarkably, the enzyme significantly enhanced the degradation of native chicken feathers. This study suggests that FisCP, a keratinolytic member of the thermostable M32 CP family, plays an important role in keratin degradation for cellular metabolism in F. islandicum AW-1.

Dental Hetero-Graft Materials with Nano Hydroxyapatite Surface Treatment.

We report the development of hydroxyapatite nanoparticle (HAp NP)-functionalized hetero-graft materials (HGMs) for dental applications. These HGMs were prepared by attaching platelet-, needle-, and sphere-shaped HAp NPs to the surface of xenograft materials through chemical conjugation. Although all three HAp NPs contributed to increase the surface area of bone graft material (BGM), the shape of the HAp NPs was a determining factor. Platelet HAp NPs were most effective, because they caused a 48.9% increase in BGM surface area whereas the influence of the spherical NP was only a 6.7% increase. This suggests that geometric factors regarding both the attached HAp NPs and graft material surface are essential in controlling the surface roughness of graft materials. Among the three HAp NPs, it was the platelet HAp NPs that helped to increase the efficacy of the BGM most significantly. Compared with BGM with no HAp NP attachment, HGM with platelet HAp NP ('platelet-HGM) treatment had ~46.1% higher cell attachment and proliferation rate. The MTT assay also showed that the HAp NP-treated hetero-graft materials had negligible cytotoxicity.

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.

The Association of Job Stress, Quality of Sleep, and the Experience of Near-Miss Errors among Nurses in General Hospitals.

This study investigated the association of job stress, quality of sleep, and near-miss error experiences among nurses working in general hospitals. A convenience sample of 195 nurses with over 3 months of work experience in a general hospital participated in the study. Statistical analyses were performed using SPSS 27.0. Factors influencing experiences of near-miss errors were examined through univariable and multivariate logistic regression. In total, 58.5% of nurses in a general hospital had experienced near-miss errors. Nurses in the upper job stress tertile (≥118) were 2.24 times more likely to encounter near-miss errors (95% CI: 1.07-4.69) and particularly 2.58 times (95% CI: 1.26-5.26) in falls and medical equipment-related near-miss errors. Nurses working more than 3 h of overtime per week had a 2.72 times higher (95% CI: 1.35-5.48) likelihood of experiencing near-miss errors related to falls and medical equipment and 4.03 times higher (95% CI: 1.92-8.45) likelihood of experiencing near-miss errors associated with examination procedures. To prevent near-miss errors among nurses in general hospitals, effective management of organizational job stress is crucial. Particularly for departments with a high level of overtime work (more than 3 h/week), it is essential to provide and manage educational programs on patient safety.

Correlation of two different devices for the evaluation of primary implant stability depending on dental implant length and bone density: An in vitro study.

Non-invasive objective implant stability measurements are needed to determine the appropriate timing of prosthetic fitting after implant placement. We compared the early implant stability results obtained using resonance frequency analysis (RFA) and damping capacity analysis (DCA) depending on the implant length and bone density. Total 60, 4.0 mm diameter implants of various lengths (7.3 mm, 10 mm, and 13 mm) were used. In Group I, low-density bone was described using 15 PCF (0.24 g/cm3) polyurethane bone blocks, and in Group II, 30 PCF (0.48 g/cm3) polyurethane bone blocks were used to describe medium density bone. RFA was performed using an Osstell® Beacon+; DCA was performed using Anycheck®. Measurements were repeated five times for each implant. Statistical significance was set at P <0.05. In Group I, bone density and primary implant stability were positively correlated, while implant length and primary implant stability were positively correlated. In Group II, the implant stability quotient (ISQ) and implant stability test (IST) values in did not change significantly above a certain length. Primary implant stability was positively correlated with bone density and improved with increasing implant length at low bone densities. Compared with the Osstell® Beacon+, the simplicity of Anycheck® was easy to use and accessible.

Exposure assessment of workers in printed electronics workplace.

Printed electronics uses converging technologies, such as printing, fine mechanics, nanotechnology, electronics and other new technologies. Consequently, printed electronics raises additional health and safety concerns to those experienced in the traditional printing industry. This study investigated two printed electronics workplaces based on a walk-through survey and personal and area sampling. All the printed electronics operations were conducted in a cleanroom. No indication of exposure to excess silver nanoparticles or carbon nanotubes (CNTs) was found. While the organic solvents were lower than current occupational exposure limits, there was a lack of engineering controls, such as local exhaust ventilation, correct enclosure and duct connections. There was also an insufficient quantity of personal protective equipment, and some organic solvents not described in the safety data sheets (SDSs) were detected in the air samples. Plus, the cleaning work, a major emissions operation, was not conducted within a hood, and the cleaning waste was not properly disposed of. Therefore, the present exposure assessment results from two printed electronics workplaces suggest that the printed electronics industry needs to take note of the occupational safety and health risks and hazards already established by the traditional printing industry, along with new risks and hazards originating from converging technologies such as nanotechnology.

The influence of a continuous increase in thickness of opaque-shade composite resin on masking ability and translucency.

OBJECTIVES: This study was conducted to determine the minimum thickness of opaque-shade composite resin required to mask discolored tooth structures or darkness of the oral cavity and to determine the effect of the brand and shade of composite resins on masking ability and translucency. MATERIALS AND METHODS: Discs and beveled specimens were manufactured using six opaque-shade light-curing composite resins (Charisma, Heraeus Kulzer; Estelite Sigma Quick, Tokuyama; Gradia Direct Anterior, GC). The discolored tooth structures and darkness of the oral cavity were reproduced using background tiles. The disc specimen colors were measured using a spectroradiometer by increasing the thickness of the beveled specimens on the backing by 0.05 mm in series, and color difference (ΔE*(ab)) and translucency parameter (TP) were calculated. RESULTS: The thicknesses of opaque-shade composite resins that masked the C4 shade and black backings were 0.80-1.45 and 1.85-2.00 mm, respectively. Overall, the ΔE*(ab) and TP values decreased as the thickness of the opaque-shade composite resins increased. When the shades of the composite resins were identical, the TP decreased in the order of Charisma, Estelite Sigma Quick and Gradia Direct Anterior. When the brand was fixed, the TP was higher in the OA3 shade than in the OA2 shade. A significant correlation was seen between ΔE*(ab) and TP (p < 0.05). CONCLUSIONS: The brands and shades of the composite resins were shown to have a clear effect on TP, but an inconsistent tendency for ΔE*(ab).

Synergistic effects of arginine-glycine-aspartic acid and phosphatidylserine on the surface immunomodulation and osseointegration of titanium implants.

The control of macrophage polarization is important in bone tissue regeneration such as osseointegration. In this study, a coating method was developed to improve the osseointegration of titanium (Ti) implants by generating an immunomodulatory effect. The surface of the Ti discs was coated with a poly(lactide-co-glycolide)(PLGA) polymer, phosphatidylserine (PS), and arginine-glycine-aspartic acid (RGD) peptide conjugated phospholipid. In in vitro assay using mouse bone marrow-derived macrophages (BMDMs), the most significant expression of the M2 marker genes (Arg-1, YM-1, FIZZ1) and CD206, an M2 surface marker, was obtained with coatings containing 6 mol% RGD conjugates and phospholipids consisting of 50 mol% PS. The M2-inducing effect of RGD and PS was also verified in rat femurs where coated Ti rods were implanted. The RGD and PS coating significantly enhanced the osseointegration of the Ti implants. Moreover, a biomechanical push-out test showed that the RGD and PS coating increased the interfacial binding force between the bone and implants. These results indicate that PS and RGD can be applied to the solid surface of implantable biomedical devices to improve immunomodulation and tissue regeneration.

Influence of thermo-mechanical aging on fracture resistance and wear of digitally standardized chairside computer-aided-designed/computer-assisted-manufactured restorations.

OBJECTIVES: To investigate the influence of thermal cycling and mechanical loading (TCML) aging on fracture resistance and wear behavior of various chairside computer-aided-designed/computer-assisted-manufactured (CAD/CAM) premolar crowns cemented on standardized tooth abutments. METHODS: Eighty chairside CAD/CAM crowns were prepared using lithium disilicate (IPS e.max CAD; EM), zirconia-infiltrated lithium silicate (Celtra Duo; CD), polymer-infiltrated ceramic network (Vita Enamic; VE), and resin nanoceramics (Cerasmart; CS) (n = 20). The specimens were divided into two groups (n = 10). In one group, they were subjected to TCML: thermocycling (6000 cycles in distilled water at 5-55 °C) and mechanical loading (50 N for 1.2 × 106 cycles), while in control group they were stored in distilled water (37 °C for 24 h). The fracture load, height loss, and volume wear of the crowns were measured after TCML. Fractography was performed on fractured specimens. Data were analyzed using analysis of variance and multiple comparison tests (α=0.05). RESULTS: The mean fracture loads of EM and CD were significantly higher than those of EC and CS (p<0.05). There was no significant change in the fracture load of any CAD/CAM crowns after TCML (p>0.05). CS exhibited a significantly higher volume wear than the other materials investigated. The wear tracts of all TCML crowns acted as failure origins during the fracture test. CONCLUSIONS: The fracture resistance of glass-ceramic CAD/CAM crowns was significantly higher than that of resin composite crowns. A 5-year TCML aging did not affect the fracture resistance of CAD/CAM crowns investigated. However, TCML treatment produces a larger wear track in CS than in other materials. CLINICAL SIGNIFICANCE: Appropriate chairside CAD/CAM restorative material should be selected for successful clinical practice after considering the fracture and wear resistance of the crowns.

Effect of hemispherical dimples at titanium implant abutments for the retention of cemented crowns.

PURPOSE: The aim of this study was to assess the effect of hemispherical dimple structures on the retention of cobalt-chromium (Co-Cr) crowns cemented to titanium abutments, with different heights and numbers of dimples on the axial walls. MATERIALS AND METHODS: 3.0-mm and 6.0-mm abutments (N = 180) and Co-Cr crowns were prepared. The experimental groups were divided into two and four dimple groups. The crowns were cemented by TempBond and PANAVIA F 2.0 cements. The retention forces were measured after thermal treatments. A two-way Analysis of Variance (ANOVA) and post-hoc Tukey HSD test were conducted to analyze change in retention forces by use of dimples between groups, as well as t test for the effect of abutment height change (α = .05). RESULTS: Results of the two-way ANOVA showed a statistically significant difference in retention force due to the use of dimples, regardless of the types of cements used (P < .001). A significantly higher mean retention forces were observed in the groups with dimples than in the control group, using the post hoc Tukey HSD test (P < .001). Results of t test displayed a statistically significant increase in the retention force with 6.0-mm abutments compared with 3.0-mm abutments (P < .001). The groups without dimples revealed adhesive failure of cements, while the groups with dimples showed mixed failure of cements. CONCLUSION: Use of hemispherical dimples was effective for increasing retention forces of cemented crowns.

Effects of ultraviolet weathering aging on the color stability and biocompatibility of various computer-aided design and computer-aided manufacturing glass-ceramic materials.

OBJECTIVES: This study assessed the changes in color stability and biocompatibility of computer-aided design and computer-aided manufacturing (CAD-CAM) glass-ceramics after ultraviolet weathering (UW) aging. METHODS: A total of 300 plate-shaped specimens (12.0 × 14.0 × 1.5 mm3) were prepared using a leucite-reinforced glass-ceramic (IPS Empress CAD; E), a lithium disilicate (IPS e.max CAD; M), and two zirconia-reinforced lithium silicate (Celtra Duo; C, Vita Suprinity; V) glass-ceramics. Specimens were divided into three groups (n = 25, each), subjected to water storage at 37 °C for 24 h (control group), or UW aging at 150 kJ/m2 (first-aged group) or 300 kJ/m2 (second-aged group). The color stability, mechanical and surface properties, and biocompatibility of the CAD-CAM glass-ceramics were investigated experimentally, followed by statistical analysis. RESULTS: The brightness and redness or greenness were reduced in all groups after aging. After the first aging, V exhibited the largest color change and E exhibited the smallest color change. After the second aging, E exhibited the highest nanoindentation hardness and Young's modulus. The surface roughness was the highest for V after the first aging. Furthermore, the hydrophilicity of the materials increased after aging process. The cell proliferation/viability of human gingival fibroblasts was the highest in E before and after aging. Almost all cells survived for all groups based on a live/dead assay. CONCLUSIONS: Leucite-reinforced glass-ceramic exhibit the highest color stability and biocompatibility after aging. The color stability and biocompatibility of CAD-CAM glass-ceramics depend on the aging process and material type. CLINICAL SIGNIFICANCE: Various CAD-CAM glass-ceramics exhibit adequate color stability after UW aging. The leucite-reinforced glass-ceramics exhibit the highest color stability, cell proliferation, and viability after aging. The color stability, mechanical and surface properties, and biocompatibility of the glass-ceramics depend on the aging process and material type.

Association of Dental Diseases and Oral Hygiene Care With the Risk of Heart Failure in Patients With Type 2 Diabetes: A Nationwide Cohort Study.

Background To evaluate the association of dental diseases and oral hygiene care with incidence of heart failure (HF) among patients with type 2 diabetes. Methods and Results This study included 173 927 patients with type 2 diabetes aged ≥40 years, who underwent Korean National Health Insurance Service health examinations in 2008 and were followed up until the end of 2017. Hazard ratios (HRs) and 95% CIs for HF were estimated using multivariable Cox proportional hazards regression analysis. During a median follow-up of 9.3 years, 1.94% of participants developed HF. An increased number of missing teeth was associated with a higher risk of HF (P<0.001). HRs of HF increased among individuals with ≥15 missing teeth (HR, 1.37 [95% CI, 1.14-1.64]) compared with those without missing teeth. Decreased risk of HF was observed in individuals with ≥1 time/year of professional dental cleaning (HR, 0.93 [95% CI, 0.87-0.99]) and in those with ≥2 times/d of toothbrushing (HR, 0.90 [95% CI, 0.82-0.98]) compared with those without these practices. While combined presence of missing teeth and periodontal disease (P=0.004) or dental caries (P=0.007) increased HF risk, combined oral hygiene care was associated with further HF risk reduction (P=0.024). Better oral hygiene care was associated with decreased HF risk, even as the number of missing teeth increased (P<0.001). Conclusions Among patients with type 2 diabetes, dental diseases and oral hygiene care are important determinants of HF development. Dental disease management and good oral care may prevent HF in patients with type 2 diabetes.

Association between Dental Diseases and Oral Hygiene Care and the Risk of Dementia: A Retrospective Cohort Study.

OBJECTIVES: To investigate the associations of dental diseases and oral hygiene care with the risk of dementia. DESIGN: Retrospective longitudinal cohort study. SETTING AND PARTICIPANTS: We conducted a population-based study of individuals in the Korean National Health Insurance System. A total of 2,555,618 participants who underwent cardiovascular and dental screenings in 2008 were included. METHODS: Dental diseases including periodontal diseases, dental caries, and tooth loss were assessed by dentists. Information on oral hygiene care, including professional dental cleaning and the frequency of tooth brushing, was collected using a self-administered questionnaire. Study outcomes were all-cause dementia, Alzheimer's disease (AD), and vascular dementia (VaD). RESULTS: Periodontal diseases [adjusted hazard ratio (aHR) 1.07, 95% CI 1.04-1.09], dental caries (aHR 1.03, 95% CI 1.00-1.05), and 8-14 missing teeth (aHR 1.07, 95% CI 1.02-1.12) were associated with an increased risk of all-cause dementia. In contrast, either professional dental cleaning or frequent tooth brushing were associated with decreased risks of all-cause dementia (aHR 0.91, 95% CI 0.89-0.93 each; aHR 0.83, 95% CI 0.80-0.86 for both). The increased risks by dental diseases were reduced by oral hygiene care: periodontal diseases with professional dental cleaning (aHR 0.94, 95% CI 0.91-0.98) or tooth brushing ≥2 times/day (aHR 0.97, 95% CI 0.94-1.00) and 1 to 7 missing teeth with professional dental cleaning (aHR 0.94, 95% CI 0.89-0.98) or tooth brushing ≥2 times/day (aHR 0.92, 95% CI 0.89-0.95). Consistent results were noted for AD and VaD and in various subgroup analyses. CONCLUSION AND IMPLICATIONS: Periodontal disease, dental caries, and a high number of missing teeth were independently associated with a higher risk of dementia. Conversely, improved oral hygiene care, such as professional dental cleaning and frequent tooth brushing, may modify the risk of dementia associated with dental diseases.

Three-dimensional interpretation of intercanine width change in children: a 9-year longitudinal study.

INTRODUCTION: The immutability of intercanine width has long been the subject of discussion. The aims of this study were to describe the longitudinal intercanine width changes of children from 6 to 14 years of age and to interpret them with a 3-dimensional method. METHODS: Complete dental stone casts were annually prepared for 66 subjects (50 girls, 16 boys) from 6 to 14 years of age. By using 3-dimensional laser scanning and reconstruction software, virtual casts were constructed. Intercanine width was measured as well as the related 3-dimensional measurements, such as the area of the intercanine triangle, the intercanine angle, the radius of the inscribed circle, and the angles formed by the virtual axes of the canines and the occlusal plane. The measurement changes over time were analyzed by using mixed-effects analysis for longitudinal data. RESULTS: There were slight decreases in intercanine widths for both sexes and both arches. However, the amounts of change were relatively small when compared with the initial values and individual random variability. The values of area, the angles formed by the virtual axes of the canines and the occlusal plane, and the radius showed decreasing trends, whereas the intercanine angle exhibited increasing trends during the observation period. Although the intercanine width changed over time, it was not clinically significant, showing relative stability. CONCLUSIONS: The intercanine width of an untreated subject after stabilization in the mouth is considered to be quite stable, even though individual variation is great.