In vitro damping and strain distribution for implant-supported crowns using 5 different CAD-CAM crowns and 3 different luting cements.

STATEMENT OF PROBLEM: Dental implants are particularly susceptible to occlusal overloading because, unlike natural teeth, they lack a periodontal ligament to help absorb occlusal forces. However, studies evaluating the impact of different crown and luting materials on the damping behavior and strain distribution of implant-supported crowns are lacking. PURPOSE: The purpose of this in vitro study was to investigate the damping behavior and strain distribution of peri-implant bone associated with 5 different CAD-CAM implant-supported crowns and 3 luting materials. MATERIAL AND METHODS: A titanium implant was embedded in a plastic tube with epoxy resin and 5 different crown materials (polymethyl methacrylate, resin-infiltrated ceramic, lithium disilicate, titanium, and zirconia) luted to prosthetic abutments with 3 different luting materials (zinc oxide non-eugenol cement, zinc phosphate cement, and adhesive resin cement) and an uncemented condition were tested (n=5). Strain gauges were attached at the crestal and apical levels of the implant model. All specimens were load tested from 0 to 200 N. Slopes of load/time, microstrain/time, and time required to reach the maximum load were examined to represent the damping behavior. Absolute maximum strain (AMS) and its occurrence level were examined to represent the strain distribution. Two-way ANOVA, followed by the Tukey HSD test, were used for statistical analysis (α=.05). RESULTS: All slopes and times to reach the maximum load in each crown material were statistically similar (P>.05), except for the polymethyl methacrylate group, which showed less steepness in all slopes and more time required to reach the maximum load significantly (P<.05). Both the polymethyl methacrylate group (224.5 ±30.2) and the titanium group (224.0 ±24.3) exhibited significantly higher AMS at the crestal level compared with the resin-infiltrated ceramic group (210.6 ±5.0) (P<.05). The lithium disilicate (218.1 ±15.0) and zirconia groups (217.3 ±14.8) demonstrated comparable AMS values with the others (P>.05). The uncemented group demonstrated steeper slopes and less time required to reach the maximum load compared with the adhesive resin group (P<.05), while slopes and times of the zinc phosphate and zinc oxide non-eugenol groups were comparable (P>.05). The uncemented group (242.7 ±25.3) exhibited significantly higher AMS at the crestal level than the other groups (P<.05). CONCLUSIONS: The crown material significantly affected the damping behavior of peri-implant bone, unlike the luting material. Polymethyl methacrylate with a high damping behavior exhibited high strain at the crestal level. In contrast, resin-modified ceramic with a moderate damping behavior exhibited low strain at the crestal level. Strain at the crestal level could be effectively reduced by approximately 13% through cementation.

Accuracy of implant placement with a combined use of static and dynamic computer-assisted implant surgery in single tooth space: A randomized controlled trial.

OBJECTIVE: To compare implant accuracy of combined static and dynamic (SD) computer-assisted implant surgery (CAIS) with static (S), dynamic (D) CAIS, and freehand surgery (FH) for single implant placement. MATERIALS AND METHODS: One hundred and twenty patients were randomized into four groups. Implants were placed using both stereolithographic surgical guide and dynamic navigation in the SD group, stereolithographic surgical guide in S group, dynamic navigation in D group, and conventional freehand in FH group. Analysis of deviation between planned and final implant position, as well as K means analysis was conducted for implant deviation at platform, apex, and angle (primary outcomes) and directional distribution at platform and apex (secondary outcome). RESULTS: Significant differences were found among the four groups (p < .001): The 3D deviation at the platform (mm) of SD, S, D, and FH groups was 0.62 ± 0.50, 1.06 ± 0.67, 1.02 ± 0.45, and 1.48 ± 0.68, respectively, at apex (mm) was 0.75 ± 0.57, 1.40 ± 0.71, 1.28 ± 0.50, and 2.18 ± 0.95, respectively, and angle (degrees) was 1.24 ± 1.41, 3.18 ± 2.04, 3.28 ± 1.57, and 7.50 ± 4.06, respectively. Deviation at the platform of FH group was significantly more toward mesial (p = .026) and coronal (p = .014) direction, while at the apex, toward distal (p = .004) and lingual (p = .002) than SD group. CONCLUSION: The use of combined static and dynamic CAIS provided significantly higher accuracy than the two alone and freehand surgery for single implant placement.

Effect of Restoration Design on the Removal Torque Loss of Implant-supported Crowns after Cyclic Loading.

AIM: To compare the removal torque loss (RTL) percentage of screw-retained, cement-retained, and combined screw- and cement-retained implant-supported crowns after cyclic loading and measure the impact of cyclic loading on removal torque. MATERIALS AND METHODS: Thirty-two dental implants (4.0 × 10 mm) in resin blocks and abutments were divided into four groups (n = 8) based on restoration design: combined screw- and cement-retained group (SC), two cement-retained groups: cemented with adhesive resin cement (AR) (Panavia V5) or provisional cement (PR) (RelyX Temp NE), and screw-retained one-piece titanium group (TI). Removal torques were measured in Newton-centimeter (Ncm) before and after 500,000-cycle cyclic loading with forces ranging from 20 to 200 N at 15 Hz. The RTL percentage in each group was calculated. The paired t-test was used to detect the difference between pre-loading (RT1) and post-loading removal torque (RT2) in each group and 1-way ANOVA was used to detect the difference of RTL percentage between groups. RESULTS: The post-loading removal torques in all groups were significantly lower than their pre-loading removal torques (p < 0.001). The 1-way ANOVA test found no significant difference in the RTL% between the study groups. The PR group exhibited the lower RTL% (30.74 ± 7.3%), followed by the TI (30.78 ± 5.6%), AR (32.12 ± 2.5%), and SC (35.71 ± 5.1%) groups. CONCLUSION: Combined screw- and cement-retained restorations exhibited similar RTL compared with other restoration designs, and cyclic loading significantly affected the removal torque. CLINICAL SIGNIFICANCE: Combined screw- and cement-retained restorations can be utilized in single-tooth situations, offering a comparable impact on screw joint stability while providing benefit of retrievability. Cyclic loading significantly influences joint stability, periodic checkup for screw loosening is recommended. How to cite this article: Jongsiri S, Arksornnukit M, Homsiang W, et al. Effect of Restoration Design on the Removal Torque Loss of Implant-supported Crowns after Cyclic Loading. J Contemp Dent Pract 2023;24(12):951-956.

Brushing effect on the retentive force of retentive inserts in three denture attachments: An in vitro study.

STATEMENT OF PROBLEM: Daily denture brushing results in wear on implant-retained overdenture attachments. However, studies on the remaining denture attachment retention after brushing are lacking. PURPOSE: The purpose of this in vitro study was to evaluate the retentive force of the retentive inserts in 3 denture attachments after brushing with different media. MATERIAL AND METHODS: Three retentive insert types in 3 denture attachments (LOCATOR, LOCATOR R-Tx, and Novaloc) were tested. Three abutments and 20 metal housings of each denture attachment were separately embedded into individual acrylic resin blocks, and 20 retentive inserts of each retentive type in each denture attachment were placed in the metal housing. The blocks embedded with a metal housing of each denture attachment were divided into 2 brushing media groups (n=10), mounted on a brushing machine, and brushed with deionized water (DI) or toothpaste slurry (TP). After 0, 10 000, and 20 000 brushing cycles, the block specimens were mounted on a universal testing machine, and the retentive force was evaluated by pulling the blocks apart until complete separation. The maximum retentive force was measured 5 times and averaged. The evaluated retentive insert was removed and replaced with a new retentive insert. The specimen blocks were subjected to another brushing test with the same protocol. Representative specimens of each group were examined with scanning electron microscopy. The retentive force of each retentive insert type in each denture attachment was analyzed by 2-way repeated measures ANOVA, followed by the Bonferroni test (α=.05). RESULTS: The retentive force of each LOCATOR and LOCATOR R-Tx retentive insert demonstrated significant differences in the interaction between brushing media and brushing cycles (P<.05). Between baseline and 20 000 brushing cycles with DI, the retentive force of the LOCATOR and LOCATOR R-Tx retentive inserts decreased significantly (P<.05). Between baseline and 20 000 brushing cycles with TP, the retentive force of the LOCATOR retentive inserts increased significantly (P<.05), while the retentive force of the LOCATOR R-Tx retentive inserts was statistically similar (P>.05). The retentive force of the Novaloc retentive inserts demonstrated significant differences only for brushing cycles (P<.05). The Novaloc retentive inserts decreased in average retentive force over time. CONCLUSIONS: After brushing with deionized water, the retentive forces of the LOCATOR, LOCATOR R-Tx, and Novaloc retentive inserts decreased, while, after brushing with toothpaste, the retentive force of the retentive inserts increased in the LOCATOR group, was unchanged in the LOCATOR R-Tx group, and decreased in the Novaloc group.

Subjective and objective measures for evaluating masticatory ability and associating factors of complete denture wearers: A clinical study.

STATEMENT OF PROBLEM: The masticatory ability of complete denture (CD) wearers can be evaluated subjectively and objectively. Although an objective measure reflects a person's ability to masticate food, it is rarely used in clinical practice. Moreover, the factors associated with subjective and objective masticatory ability of CD wearers remain unclear. PURPOSE: The purpose of this clinical study was to identify subjective and objective measures that better reflect the masticatory ability of CD wearers and to investigate their associating factors. MATERIAL AND METHODS: Masticatory ability was evaluated in 130 CD wearers by using subjective and objective measures. The subjective indicators were oral impact on eating and denture satisfaction based on eating or mastication ability. Masticatory performance was objectively measured by using a median peanut particle size. The maximum occlusal force, number, and area of occlusal contacts were determined from a pressure-sensitive sheet. CD retention and stability were classified into acceptable and unacceptable denture quality following the CU-modified Kapur criteria. The occlusal pattern and oral conditions were examined and recorded. Intraexaminer reliability in determining CD quality and oral condition was shown by a Kappa score of 0.90 to 0.95. Multivariable linear and logistic regressions were performed to analyze the associations between CD quality, maximum occlusal force, and masticatory ability. The Spearman correlation was used to determine the association between subjective and objective measures. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) between subjective and objective measures were calculated. RESULTS: Unacceptable CD quality was significantly associated with oral impact on eating, eating dissatisfaction, and larger peanut particle size (P<.001). Peanut particle size increased with lower maximum occlusal force, which was related to fewer occlusal contacts and the female sex. The highest to lowest adjusted R2 values were related to masticatory performance, oral impact on eating, and eating satisfaction models. Among participants with unacceptable CD quality, 16% had higher masticatory performance, 25%, had no oral impact on eating, and 33% reported eating satisfaction. The sensitivity and specificity values of subjective measures in predicting lower masticatory performance were approximately recorded at 74% and 90%, respectively, whereas PPV and NPV were at 90% and 77%, respectively. CONCLUSIONS: CD retention and stability impact objective and subjective masticatory ability. Objective masticatory performance is the best measure for evaluating the masticatory ability of CD wearers, followed by oral impact on eating and eating satisfaction. A 3.6-mm peanut particle size is suggested as a cutoff value for identifying CD wearers with impaired masticatory ability.

Intermittent compressive force induces human mandibular-derived osteoblast differentiation via WNT/ß-catenin signaling.

Mechanical force induces an efflux of ATP that regulates osteoblast differentiation. However, the effect of mechanical force-induced ATP efflux on WNT/ß-catenin signaling remains unclarified. The aim of this study was to investigate the effect of intermittent compressive force (ICF) and ICF-induced extracellular ATP on osteoblast differentiation via WNT/ß-catenin signaling in human mandibular-derived osteoblast precursors (hMOBPs). The hMOBPs were subjected to ICF (1.5 g/cm2 , 0.3 Hz) for 20 h. To investigate the role of ATP, Apyrase (0.5 units/mL), an enzyme that hydrolyzes ATP, was added 30 min before ICF was applied. The extracellular ATP levels were measured immediately after ICF was removed. The mRNA expression of osteogenic related genes, including WNT was evaluated via quantitative real time polymerase chain reaction. In vitro mineralization was determined by Alizarin Red S staining. The localization of ß-catenin was detected using immunofluorescence staining and lentiviral-TOP-dGFP reporter assay. The results demonstrated that ICF increased ATP efflux and in vitro mineralization by hMOBPs. In addition, OSX, ALP, and WNT3A mRNA expression and ß-catenin nuclear translocation increased when ICF was applied. The upregulation of these genes was reduced by Apyrase, suggesting the role of ICF-induced ATP on osteoblast differentiation. Notably, ICF altered the mRNA expression of purinergic 2X receptors (P2XRs). A P2X1R antagonist (NF449) downregulated ICF-induced WNT3A, OSX, and ALP mRNA expression. Moreover, when 25 µM α, ß-meATP, a P2X1R agonist, was added, WNT3A, and OSX expression increased. In conclusion, our results demonstrate that ICF-induced ATP enhanced hMOBP differentiation. This enhancement was associated with WNT/ß-catenin signaling and P2X1R activation.

Modified retention and stability criteria for complete denture wearers: A risk assessment tool for impaired masticatory ability and oral health-related quality of life.

STATEMENT OF PROBLEM: Some complete denture wearers report difficulty with daily activities, especially activities related to denture retention and stability. However, no standard criteria are available for professionally based assessment of complete denture quality. PURPOSE: The purpose of this clinical study was to determine the association between professionally based assessment of complete denture quality, evaluated by conventional and Chulalongkorn University (CU)-modified Kapur criteria and multiple patient-based outcomes: oral health-related quality of life (OHRQoL), eating satisfaction, and masticatory performance. The sensitivity and specificity of these criteria in estimating the outcomes were investigated. MATERIAL AND METHODS: The participants were 126 individuals with removable acrylic resin complete dentures. Denture retention and stability were scored based on the Kapur method, with excellent intraobserver reliability indicated by a Kappa score of 0.91 to 0.99. The clinical quality of the complete denture was classified according to conventional and CU-modified Kapur criteria. The participants were interviewed for OHRQoL by using the Thai version of the Oral Impacts on Daily Performances (OIDP) index and responses were reported as the absence or presence of oral impacts. Participants' satisfaction eating with their dentures was determined by using a 5-point Likert scale and dichotomized into satisfied and dissatisfied categories. Masticatory performance was evaluated by the multiple sieve method of peanut mastication. After adjusting for covariates, the associations between denture quality and overall and condition-specific (CS) impacts on eating and on eating satisfaction were analyzed by using binary logistic regression, while its association with masticatory performance was determined using linear regression. Goodness-of-fit post estimation was conducted to determine the sensitivity and specificity of each denture quality criterion in estimating patient-based outcomes. RESULTS: Complete denture retention and stability, evaluated by conventional and CU-modified Kapur criteria, were associated with multiple patient-based outcomes. However, denture stability showed a stronger association than retention. The CU-modified criteria assessed the quality of maxillary and mandibular dentures individually and revealed a higher sensitivity in estimating all patient-based outcomes. CONCLUSIONS: Retention and stability were important indicators in estimating the masticatory ability and OHRQoL of complete denture wearers. The CU-modified Kapur criteria can identify impaired masticatory ability and OHRQoL in complete denture wearers better than conventional criteria.

Effect of complete denture occlusal schemes on masticatory performance and maximum occlusal force.

STATEMENT OF PURPOSE: Masticatory performance and maximum occlusal force may be different, depending on the occlusal schemes of the complete dentures used. PURPOSE: The purpose of this study was to evaluate the effect of 2 complete denture occlusal schemes on masticatory performance and maximum occlusal force. MATERIAL AND METHODS: Two complete denture occlusal schemes, bilateral balanced occlusion and neutrocentric occlusion, were delivered to 10 participants who were completely edentulous (6 men and 4 women; mean age, 67.3 years). Masticatory performance was evaluated with the multiple sieve method and maximum occlusal force with pressure-sensitive films. The 2 occlusal schemes were interchanged on the participants' denture bases. Two-way repeated-measures ANOVA was used to examine the differences between the occlusal schemes and chewing strokes and their interactions. The paired t test was used to compare the maximum occlusal force of the 2 occlusal schemes (α=.05). RESULTS: No difference was found in masticatory performance (P=.07) or maximum occlusal force (P=.31) between the occlusal schemes. For both schemes, a significant difference was found in masticatory performance (P<.001) with increased numbers of chewing strokes. CONCLUSIONS: Complete dentures with bilateral balanced occlusion and neutrocentric occlusion found no significant differences in masticatory performance and maximum occlusal force. However, more chewing strokes resulted in better masticatory performance.

Effect of thermocycling on the retentive force of the retentive inserts in three denture attachments and their water absorption ability.

This study aimed to evaluate the thermocycling effect on the retentive force of 3 different retentive inserts in 3 denture attachments (Blue, Pink, Clear retentive inserts in LOCATOR; Blue, Pink, Clear retentive inserts in LOCATOR R-Tx; and White, Yellow, Green retentive inserts in Novaloc) (n=10). Maximum retentive force of each retentive insert was evaluated at baseline, 7-day water storage, and after 5,000-, and 10,000- cycle thermocycling. The water absorption percentage of the retentive inserts was also determined. Comparing between baseline and 7-day water storage, the retentive forces of the LOCATOR and LOCATOR R-Tx groups were significantly reduced (p<0.05), while the retentive force of the Novaloc group was significantly increased (p<0.05). Comparing between 7-day water storage and 10,000-cycle thermocycling, the retentive force of most retentive inserts remained unchanged (p>0.05). The water absorption percentage of the LOCATOR and LOCATOR R-Tx groups was significantly greater than that of the Novaloc group (p<0.05).

Association of prosthetic angles of the Implant Supracrestal Complex with peri-implant tissue mucositis.

OBJECTIVES: The aim of this study was to investigate the association of the Mucosal Emergence Angle (MEA) with peri-implant tissue mucositis. MATERIAL AND METHODS: Forty-seven patients with 103 posterior bone level implants underwent clinical and radiographic examination. Three-dimensional data from Cone Bean Computer Tomography and Optica Scan were transposed. Three angles were defined: MEA, Deep Angle (DA) and Total Angle (TA) and measured at six sites for each implant. RESULTS: There was a significant correlation between MEA and Bleeding on Probing for all sites with an overall odds ratio of odd ratio 1.07 (95% confidence interval [CI] 1.05-1.09, p < 0.001). Sites with MEA ≥ 30°, 40°, 50°, 60°, and 70° had a higher risk for bleeding with an odds ratio of 3.1, 5, 7.5, 11.4 and 33.55, respectively. When all 6 sites of an implant prostheses had MEA ≥ 40°, the risk of having bleeding at all 6 sites was 9.5 times higher (95% CI 1.70-52.97, p = 0.010). CONCLUSIONS: Maintaining MEA no wider than 30°-40° is advisable, while the aim should be to keep this angle as narrow as clinically feasible. Registered in Thai Clinical Trials Registry: http://www.thaiclinicaltrials.org/show/TCTR20220204002.

Pressure transmission and distribution under denture bases using denture teeth with different materials and cuspal angulations.

STATEMENT OF PROBLEM: Pressure transmission and distribution under denture bases may be variable depending on the different materials and cuspal angulations of denture teeth. PURPOSE: The purpose of this study was to evaluate pressure transmission and distribution under impact load using denture teeth made with different materials and cuspal angulations. MATERIAL AND METHODS: Three types (acrylic resin, microfilled composite resin, and ceramic) and 4 different cuspal angulations (0 degree, 20 degree, 33 degree, and 35 degree) of denture teeth were evaluated. Pressure transmission, distribution, and maximum pressure (n=10) were observed with pressure-sensitive sheets under an impact load. Data were statistically analyzed with 2-way ANOVA (α=.05) to determine significant interactions between denture tooth materials and cuspal angulations with respect to pressure transmission, followed by 1-way ANOVA (α=.05) to examine how materials and angulations jointly affected the pressure. Two 1-way ANOVAs were performed on the acrylic resin and ceramic denture teeth with the inclusion of 20-degree denture teeth groups. Tukey HSD and Tamhane's post hoc tests were used to evaluate data differences among groups. RESULTS: Denture tooth materials and cuspal angulations had significant interactions with respect to average pressure (P<.001) and maximum pressure transmission (P=.007). Zero-degree denture teeth showed significantly lower average and maximum pressures than 33- and 35-degree denture teeth for all 3 denture tooth materials (P<.001). Denture teeth with greater cuspal angulations demonstrated significantly higher average pressure transmission for all ceramic denture teeth groups (P<.05). CONCLUSIONS: Pressure transmission and distribution varied among denture teeth made of different materials and with different cuspal angulations. Cusped denture teeth presented significantly higher average pressure and maximum pressure transmission compared to 0-degree denture teeth.

Effect of zinc oxide nanoparticles incorporated into tissue conditioner on antifungal, physical, and mechanical properties.

This study evaluated the antifungal, physical, and mechanical properties of tissue conditioner incorporated with different amounts of zinc oxide nanoparticles (ZnOnps) at different storage times (0, 7, and 14 days). Specimens of 0, 5, 10, 15 wt% ZnOnps, or 15 wt% nystatin incorporated into tissue conditioner were fabricated (control, 5Zn, 10Zn, 15Zn, and Nys). The direct contact test (n=6) was performed to evaluate the antifungal effect against C. albicans suspension. The penetration depth (n=6) and tensile bond strength (n=8) were evaluated following ISO 13139. The 15Zn significantly reduced C. albicans cell number compared with control at all storage times (p<0.001). The penetration depths and tensile bond strengths of the 5Zn, 10Zn, 15Zn, and Nys were not significantly different compared with control at all storage times (p>0.05). In conclusion, the 15Zn provides antifungal effect up to 14 days without adverse effects on penetration depth and tensile bond strength.

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).

Pressure transmission and distribution under impact load using artificial denture teeth made of different materials.

STATEMENT OF PROBLEM: Pressure transmission and distribution under denture bases may be different depending on the material of the artificial denture teeth used. PURPOSE: The purposes of this study were to evaluate pressure transmission and distribution under impact load using artificial denture teeth composed of different materials, and to examine the modulus of elasticity of the artificial denture teeth. MATERIAL AND METHODS: The denture base specimens with artificial denture teeth made of 4 different materials (acrylic resin, microfilled composite resin, nanocomposite resin, and ceramic) were evaluated. Pressure transmission, distribution, and maximum pressure (n=10) were observed with pressure-sensitive sheets under an impact load. Modulus of elasticity of the artificial denture teeth (n=10) was measured by using an ultramicroindentation system. Data were statistically analyzed with 1-way ANOVA, followed by Tukey HSD and Tamhane's multiple range post hoc tests (alpha=.05). RESULTS: Maximum pressure transmission observed from ceramic denture teeth was significantly higher than that of other groups (P<.001). Nanocomposite resin denture teeth presented the lowest pressure transmission, whereas a localized stress transmission area was observed in the ceramic denture teeth group. Significant differences in the modulus of elasticity were observed among the 4 types of artificial denture teeth (P<.001). CONCLUSIONS: Pressure transmission and distribution varied among the denture tooth materials. Differences in the modulus of elasticity of each type of denture tooth were demonstrated.

Effects of plasma treatment on the shear bond strength between fiber-reinforced composite posts and resin composite for core build-up.

The aim of this study was to evaluate the effects of plasma treatment on adhesion between fiber-reinforced posts and a composite core material. Two types of posts, methacrylate-based (FRC Postec) and epoxy resin-based (DT Light-Post), were treated with oxygen plasma (O(2)), argon plasma (Ar), nitrogen plasma (N(2)), or helium mixed with nitrogen plasma (He+N(2)) using a radio-frequency generator before bonding to a methacrylate-based composite. Pull-out tests were performed using a universal testing machine. Surface roughness of each group was evaluated using a profilometer. On tensile-shear bond strength, statistical analysis revealed that the type of post, type of plasma treatment, and their interaction significantly influenced the results (p<0.05). Tukey's test revealed significant differences in tensile-shear bond strength between the control and other plasma treatment groups (p<0.05). On surface roughness, Tukey's test revealed significant differences between the control group and the Ar group (p<0.05) with DT Light Post. Plasma treatment appeared to increase the tensile-shear bond strength between post and composite.

Impacts of Denture Retention and Stability on Oral Health-Related Quality of Life, General Health, and Happiness in Elderly Thais.

PURPOSE: This study investigated denture and patient related factors associated with oral health-related quality of life (OHRQoL) of complete denture wearers and their association with general health and happiness. METHODS: This retrospective cohort study comprised 130 participants with complete edentulism, with maxillary and mandibular complete dentures treated at Chulalongkorn University Dental School during 2010-2017. The primary outcome was the presence of overall and domain-specific Oral Impacts on Daily Performances (OIDP). Secondary outcomes were diagnosed and perceived general health, and happiness. Denture retention and stability were classified as acceptable or unacceptable following the CU-modified Kapur criteria. Five esthetic-assessment criteria of the harmonization and proportions between facial and dental anatomical landmarks were measured from patient's photographs. Age, sex, previous complete denture experience, and denture age were recorded. The associations between each variable and oral impacts were analyzed using bivariate logistic regression, and the factors with p < 0.25 were further adjusted using multivariable analysis. Associations between oral impact scores and general health and happiness were assessed using Spearman's rank correlation. RESULTS: The most frequent oral impacts were on physical domain, while social domain was the least affected. Denture retention/stability was significantly associated with both overall and specific domains of oral impact. Happiness was found to be strongly correlated with perceived general health, but marginally with oral impact scores. CONCLUSIONS: Unacceptable complete denture retention and stability are substantial risk factors for impaired OHRQoL in complete edentulism. Maintaining optimal denture retention and stability in denture wearers is essential for good oral health and well-being with the goal of enhancing happiness.

The synthesis, modification, and application of nanosilica in polymethyl methacrylate denture base.

This study aimed to investigate amount of γ-methacryloxypropyltrimethoxysilane (MPS) silanized on experimental nanosilica particles (NPs), amount of NP and amount of MPS silanized NP on flexural strength (FS), flexural modulus (FM), and fracture toughness (FT) of NP reinforced polymethyl methacrylate (PMMA). The chemisorbed amount of MPS was determined using elemental analysis. Six groups (n=8) were prepared with chemisorbed amount and mixed with PMMA-monomer to make 0.25, 0.5, 1, 5, 10 and 15% (w/w) of NP reinforced PMMA. PMMA without NP served as control. Seven groups (n=8) were prepared with 1% of NP silanized with 0, 0.061, 0.123, 0.246, 0.493, 0.987, and 1.974 gMPS/gsilica and mixed with PMMA-monomer to make NP reinforced PMMA. FS, FM, and FT were determined using 3-point bending test. One-way ANOVA and multiple comparisons showed that 0.246 gMPS/gsilica of 1% amount of silanized NP group was significantly highest in FS, FM, and FT compared to the others (p<0.05).

Pressure transmission area and maximum pressure transmission of different thermoplastic resin denture base materials under impact load.

PURPOSES: The purposes of the present study were to examine the pressure transmission area and maximum pressure transmission of thermoplastic resin denture base materials under an impact load, and to evaluate the modulus of elasticity and nanohardness of thermoplastic resin denture base. METHODS: Three injection-molded thermoplastic resin denture base materials [polycarbonate (Basis PC), ethylene propylene (Duraflex), and polyamide (Valplast)] and one conventional heat-polymerized acrylic resin (PMMA, SR Triplex Hot) denture base, all with a mandibular first molar acrylic resin denture tooth set in were evaluated (n=6). Pressure transmission area and maximum pressure transmission of the specimens under an impact load were observed by using pressure-sensitive sheets. The modulus of elasticity and nanohardness of each denture base (n=10) were measured on 15×15×15×3mm3 specimen by using an ultramicroindentation system. The pressure transmission area, modulus of elasticity, and nanohardness data were statistically analyzed with 1-way ANOVA, followed by Tamhane or Tukey HSD post hoc test (α=.05). The maximum pressure transmission data were statistically analyzed with Kruskal-Wallis H test, followed by Mann-Whitney U test (α=.05). RESULTS: Polymethyl methacrylate showed significantly larger pressure transmission area and higher maximum pressure transmission than the other groups (P<.001). Significant differences were found in modulus of elasticity and nanohardness among the four types of denture bases (P<.001). CONCLUSIONS: Pressure transmission area and maximum pressure transmission varied among the thermoplastic resin denture base materials. Differences in the modulus of elasticity and nanohardness of each type of denture base were demonstrated.

Effects of different sulfuric acid etching concentrations on PEEK surface bonding to resin composite.

This study evaluated the effects of surface pretreatment with different concentrations of sulfuric acid etching on surface properties and bonding between Polyetheretherketone (PEEK) and a resin composite. Six groups of surface pretreatment (no pretreatment, etched with 70, 80, 85, 90, and 98% sulfuric acid for 60 s) were treated on PEEK. Surface roughness, scanning electron microscopy (SEM) and atomic force microscopy (AFM) analyses were examined. Shear bond strength (SBS) and cross-sectional observations of the interfaces were performed. One-way ANOVA analysis revealed differences in surface roughness and SBS between groups. The 90 and 98% sulfuric acid etching significantly achieved the highest SBS (p<0.05). SEM and AFM demonstrated etched surfaces with wide and deep pores. The 90 and 98% sulfuric acid etching were suggested to be the optimal concentration to improve adhesion between PEEK and the resin composite.

Antifungal, optical, and mechanical properties of polymethylmethacrylate material incorporated with silanized zinc oxide nanoparticles.

BACKGROUND: Fungal infected denture, which is typically composed of polymethylmethacrylate (PMMA), is a common problem for a denture wearer, especially an elderly patient with limited manual dexterity. Therefore, increasing the antifungal effect of denture by incorporating surface modification nanoparticles into the PMMA, while retaining its mechanical properties, is of interest. AIM OF THE STUDY: This study aimed to evaluate antifungal, optical, and mechanical properties of heat-cured PMMA incorporated with different amounts of zinc oxide nanoparticles (ZnOnps) with or without methacryloxypropyltrimethoxysilane modification. MATERIALS AND METHODS: Specimens made from heat-cured PMMA containing 1.25, 2.5, and 5% (w/w) nonsilanized (Nosi) or silanized (Si) ZnOnps were evaluated. Specimens without filler served as control. The fungal assay was performed placing a Candida albicans suspension on the PMMA surface for 2 h, then Sabouraud Dextrose Broth was added, and growth after 24 h was determined by counting colony forming units on agar plates. A spectrophotometer was used to measure the color in L* (brightness), a* (red-green), b* (yellow-blue) and opacity of the experimental groups. Flexural strength and flexural modulus were determined using a three-point bending test on universal testing machine after 37°C water storage for 48 h and 1 month. RESULTS: The antifungal, optical, and mechanical properties of the PMMA incorporated with ZnOnps changed depending on the amount. With the same amount of ZnOnps, the silanized groups demonstrated a greater reduction in C. albicans compared with the Nosi groups. The color difference (ΔE) and opacity of the Nosi groups were greater compared with the Si groups. The flexural strength of the Si groups, except for the 1.25% group, was significantly greater compared with the Nosi groups. CONCLUSION: PMMA incorporated with Si ZnOnps, particularly with 2.5% Si ZnOnps, had a greater antifungal effect, less color differences, and opacity compared with Nosi ZnOnps, while retaining its mechanical properties.