Saliva exposure reduces gingival keratinocyte growth on TiO2-coated titanium.

Bioactive, nanoporous TiO2-coating has been shown to enhance cell attachment on titanium implant surface. The aim of this study was to evaluate, whether the saliva proteins affect the epithelial cell adhesion on TiO2-coated and non-coated titanium. Grade V titanium discs were polished. Half of the discs were provided with TiO2-coating produced in sol with polycondensation method. Half of the TiO2-coated and non-coated discs were treated with pasteurized saliva for 30 min. After saliva treatment, the total protein amounts on surfaces were measured. Next, the hydrophilicity of discs were measured with water contact angle measurements. Further, the gingival keratinocyte adhesion strength was measured after 2 and 6 h of cultivation using serial trypsinization. In addition, cell growth and proliferation were measured after 1, 3, and 7 days of cell culture. Finally, cell morphology, spreading and adhesion protein signals were detected with high resolution confocal microscopy. As a result, in sol coated TiO2-surface had significantly higher hydrophilicity when compared to non-coated titanium, meanwhile both non-coated and TiO2-coated surfaces with saliva treatment had a significant increase in hydrophilicity. Importantly, the amounts of adhered saliva proteins were equal between TiO2-coated and non-coated surfaces. Adhesion strength against enzymatic detachment was weakest on non-coated titanium after saliva exposure. Cell proliferation and cell spreading were highest on TiO2-coated titanium, but saliva exposure significantly decreased cell proliferation and spreading on TiO2-coated surface. To conclude, even though saliva exposure makes titanium surfaces more hydrophilic, it seems to neutralize the bioactive TiO2-coating and decrease cell attachment to TiO2-coated surface.

Surface roughness and optical characteristics evaluations after chairside adjustment of different zirconia types.

STATEMENT OF PROBLEM: Limited evidence is available for the effect of chairside adjustment using rotary cutting instruments on the surface roughness and optical properties of different zirconia types. PURPOSE: To evaluate the effect of simulated adjustments on surface roughness and optical properties of different zirconia types. MATERIALS AND METHODS: Three Partially Stabilized Zirconia (PSZ) types based on mole percent yttria (Y) concentration from the same manufacturer (Katana; Kuraray) were used: 3Y-PSZ, 4Y-PSZ, and 5Y-PSZ. Thirty disk-shaped specimens (Ø14 × 1.2 mm) from different zirconia types (N = 90) were prepared. Specimens were either left without adjustment (NA), adjusted with Dialite ZR finishing and polishing system (Brasseler) (APol), or adjusted with course diamond instruments only (ADia). The specimens were distributed into 9 groups (n = 10): Group 3Y-PSZ/NA, Group 3Y-PSZ/APol, Group 3Y-PSZ/ADia, Group 4Y-PSZ/NA, Group 4Y-PSZ/APol, Group 4Y-PSZ/ADia, Group 5Y-PSZ/NA, Group 5Y-PSZ/APol, and Group 5Y-PSZ/ADia. The surface roughness of specimen was analyzed using an Atomic Force Microscope (AFM) (Bruker's Dimension Icon, Bruker) and Root Means Square (RMS) were recorded (nm). Surface Gloss (SG), Translucency Parameter (TP), and Contrast Ratio (CR) values of all groups were recorded using an integrating sphere spectrophotometer. Statistical analysis was performed using analysis of variance (ANOVA) and Tukey's multiple comparison tests for pairwise comparisons at p < 0.05 and 95% confidence interval. RESULTS: APol had no effect on the surface roughness (p = 0.88) while ADia had a significant negative effect (p < 0.05) despite the type of zirconia. Out of the three testes optical properties, only SG was negatively affected by ADia for all types of zirconia (p < 0.05). The two adjustment types did not affect the TP of all the tested zirconia (p = 0.91). The CR was not affected by the tested adjustments for all zirconia types (p = 0.726). CONCLUSION: Proper zirconia adjustment following a sequence of burs and polishers can maintain acceptable roughness and optical properties. Adjustment of zirconia with rough diamond can lead to deleterious effects and should be avoided. CLINICAL SIGNIFICANCE: Chairside adjustment of zirconia could lead to rougher surface and unpredictable changes of surface gloss. Therefore, zirconia adjustment should be minimized to the greatest extent possible and a proper protocol should be followed if had to be done.

Effect of Er:YAG laser on debonding zirconia and lithium disilicate crowns bonded with 2- and 1-bottle adhesive resin cements.

INTRODUCTION: Erbium-doped yttrium-aluminum-garnet (Er:YAG) laser debonding of zirconia and lithium disilicate restorations is increasingly used for a range of clinical applications. Using rotary instruments to remove such restorations for any purpose has proven to be challenging. Erbium laser has been reported to be a conservative method for removing ceramic restorations. There is little data in the literature about the effect of adhesive resin cement type on the debonding time of the ceramic restoration using the Er:YAG laser. OBJECTIVES: To evaluate and compare the time required for the Er:YAG laser to debond zirconia and lithium disilicate crowns bonded with a 2- and 1-bottle adhesive resin cement systems. MATERIALS AND METHODS: Forty extracted premolar teeth were prepared and scanned for milled 40 CAD/CAM crowns. Teeth were randomly assigned into groups (n = 10 per group): 3 mol% yttria-partially stabilized zirconia crowns 3Y-PSZ (G1a) bonded with Panavia™ V5 (2-bottle adhesive resin cement), Zirconia 3Y-PSZ crowns (G1b) bonded with RelyX™ Ultimate (1-bottle adhesive resin cement), and for the lithium disilicate crowns bonded with the two types of cements (G2a, G2b). Each specimen was irradiated with an Er:YAG laser at 335 mJ, 15 Hz, 5.0 W, and 50-ms pulse duration (super short pulse mode). The irradiation time required for crowns to be successfully debonded was recorded for each specimen. Data were statistically analyzed using ANOVA and Tukey HSD post-hoc test (p < 0.05), at the 95 percent level of confidence. The intaglio surface of the debonded crown was analyzed using scanning electron microscopy (SEM). RESULTS: The mean ± standard deviation times needed for crown debonding were 5.75 ± 2.00 min for the G1a group, 4.79 ± 1.20 min for group G1b, 1.69 ± 0.49 min for group G2a, and 1.12 ± 0.17 for group G2b. There was no statistically significant difference in debonding time between the 2- and 1- bottle adhesive resin cement within the groups G1a and b (p = 0.2914), or between groups G2a b (p = 0.7116). A statistically significant difference (p < 0.05) was found between groups G1a and G2a and b and between groups G1b and G2a and b were SEM analysis showed no changes in the microstructure of the ceramic surface after Er:YAG laser irradiation. CONCLUSION: Zirconia and lithium disilicate restorations can be debonded using Er:YAG lasers in a safe and efficient manner. There is no significant difference in the debonding time between the 2- and 1- bottle adhesive resin cement systems used in this study. CLINICAL SIGNIFICANCE: Retrieving zirconia and lithium disilicate ceramics can be a challenging process when using diamond rotary instruments. ER:YAG lasers may efficiently debond these ceramics from the tooth structure, independent of the bonding process used for bonding them.

Er:YAG laser debonding of zirconia and lithium disilicate restorations.

STATEMENT OF PROBLEM: Yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) restorations of different formulations are being used increasingly in monolithic form for a range of clinical applications. Using rotary instruments to remove such restorations for any purpose is challenging, but they can be removed conservatively with erbium lasers. However, studies on how a laser penetrates different zirconias to break the cement bond between the tooth surface and the zirconia are lacking. PURPOSE: The purpose of this in vitro study was to evaluate and compare the time required for an erbium-doped yttrium-aluminum-garnet (Er:YAG) laser to remove different types of zirconia and lithium disilicate crowns. MATERIAL AND METHODS: Forty extracted premolar teeth were prepared, scanned, designed, and milled to fabricate 40 computer-aided design and computer-aided manufacturing (CAD-CAM) crowns, which were assigned to 4 groups (n=10): 3 mol% Y-TZP, 4 mol% Y-TZP, 5 mol% Y-TZP, and lithium disilicate as a control. All crowns were bonded to the teeth with a self-adhesive resin cement (Panavia SA Cement Universal). Each specimen was irradiated with an Er:YAG laser with the following parameters: 300 mJ, 15 Hz, 5.0 W, and a 50-microsecond pulse duration (supershort pulse mode). The irradiation time required for crowns to be retrieved successfully was recorded for each specimen. Data were statistically analyzed using analysis of variance and the Tukey honestly significant difference post hoc test (α=.05). The intaglio surfaces of the restorations were analyzed using scanning electron microscopy (SEM). RESULTS: The mean ±standard deviation times in minutes needed for crown debonding were 12.46 ±4.17 for the 3 mol% Y-TZP group, 10.30 ±3.33 for the 4 mol% Y-TZP group, 4.03 ±1.62 for the 5 mol% Y-TZP group, and 2.08 ±0.92 for the lithium disilicate group. A statistically significant difference (P<.05) in the debonding time was found for all investigated groups, expect between the 3 mol% and 4 mol% Y-TZP groups and between the 5 mol% Y-TZP and lithium disilicate groups. SEM analysis of the ceramic surfaces showed no visual damage associated with Er:YAG laser irradiation. CONCLUSIONS: Zirconia crown retrieval time with the Er:YAG laser was influenced by the yttria content of the zirconia, with decreasing retrieval time with increasing yttria content. Er:YAG laser debonding of zirconia crowns is a noninvasive, efficient, and rapid approach to the removal of crowns and could be applied in clinical practice.

Gastric acid challenge of lithium disilicate-reinforced glass-ceramics and zirconia-reinforced lithium silicate glass-ceramic after polishing and glazing-impact on surface properties.

OBJECTIVES: To investigate the impact of simulated gastric acid on the surface properties of lithium disilicate-reinforced glass-ceramics and zirconia-reinforced lithium silicate glass-ceramic after certain polishing and glazing procedures. MATERIALS AND METHODS: Four different types of square-shaped specimens (10 × 10 × 2 mm3, n = 13) were manufactured: lithium disilicate-reinforced glass-ceramic milled and polished (LDS-P); milled, polished, and glazed (LDS-PG); milled, glazed, and no polishing (LDS-G); and milled and polished zirconia-reinforced lithium silicate glass-ceramic (ZR-LS). Specimens were immersed in hydrochloride acid (HCl 0.06 M, pH 1.2) to simulate gastric acid irritation and stored in the acid for 96 h in 37 °C. Specimen weight, surface gloss, Vickers surface microhardness and surface roughness (Ra, Rq, with optical profilometer), and surface roughness on nanometer level (Sq, Sal, Sq/Sal, Sdr, Sds with atomic force microscope) were measured before and after the acid immersion. RESULTS: ZR-LS specimens lost significantly more weight after acid immersion (p = 0.001), also surface microhardness of ZR-LS was significantly reduced (p = 0.001). LDS-G and LDS-PG showed significantly lower surface roughness (Sa, Sq) values compared to LDS-P before (p ≤ 0.99) and after (p ≤ 0.99) acid immersion and ZR-LS after acid immersion (p ≤ 0.99). CONCLUSIONS: Gastric acid challenge affects the surface properties of lithium disilicate-reinforced glass-ceramic and zirconia-reinforced lithium silicate glass-ceramic. Glazing layer provides lower surface roughness, and the glazed surface tends to smoothen after the gastric acid challenge. CLINICAL RELEVANCE: Surface finish of lithium disilicate-reinforced glass-ceramic and zirconia-reinforced lithium silicate glass-ceramic has a clear impact on material's surface properties. Gastric acidic challenge changes surface properties but glazing seems to function as a protective barrier. Nevertheless, also glazing tends to smoothen after heavy gastric acid challenge. Glazing can be highly recommended to all glass-ceramic restorations but especially in patients with gastroesophageal reflux disease (GERD) and eating disorders like bulimia nervosa.

Oral health-related quality of life among home-dwelling older people with and without domiciliary care.

OBJECTIVES: The aim was to compare oral health-related quality of life (OHRQoL) between home-dwelling older people with and without domiciliary care when adjusted for gender, education, use of dental services and removable dental prostheses. BACKGROUND: OHRQoL of home-dwelling older people with and without domiciliary care is a neglected area of research, with few studies having been conducted. MATERIALS AND METHODS: A secondary analysis was conducted on the Finnish Health 2011 interview data. Home-dwelling participants (age ≥ 70) with or without domiciliary care were included (n = 758). OHRQoL was measured with the Oral Health Impact Profile questionnaire (OHIP-14) calculating three outcomes: prevalence of at least one impact reported: "occasionally," "fairly often" or "very often" (OFoVo), severity as mean sum score and mean of the seven OHIP-14 dimensions. These were evaluated by use of domiciliary care using logistic and negative binomial regression analyses. RESULTS: Domiciliary care clients tended to have poorer OHRQoL than non-clients (severity mean 4.33 vs 4.11, P = .057), especially men (6.71 vs 4.15, P = .027), and reported more psychological discomfort than non-clients (mean 1.10 vs 0.82, P = .039). The use of removable dental prostheses was the strongest predictor (OR 2.84, P < .001) of poor OHRQoL. CONCLUSION: Domiciliary care clients tended to report poorer OHRQoL, especially with regard to psychological discomfort dimension than non-clients. Thus, support of oral hygiene and regular utilisation of oral health services should be part of domiciliary care among older people to enhance OHRQoL.

Strength and phase transformation of different zirconia types after chairside adjustment.

STATEMENT OF PROBLEM: Limited evidence is available for the effect of chairside adjustment using diamond instruments on different types of zirconia. PURPOSE: The purpose of this in vitro study was to evaluate the effect of simulated adjustments on the biaxial flexural strength and phase transformation of 3 different zirconia types. MATERIAL AND METHODS: Three zirconia types from the same manufacturer (Katana; Kuraray) were used: High Translucency (3Y-PSZ), Super Translucent Multi Layered (4Y-PSZ), and Ultra Translucent Multi Layered (5Y-PSZ). Thirty disk-shaped specimens (Ø14×1.2 mm) were fabricated according to the International Organization for Standardization (ISO) Standard 6872 from different zirconia types (N=90). Specimens were either left without adjustment (NA), adjusted with Dialite ZR finishing and polishing system (Brasseler) (APol), or adjusted with course diamond instruments only (ADia). The specimens were distributed into 9 groups (n=10): group 3Y-PSZ/NA, group 3Y-PSZ/APol, group 3Y-PSZ/ADia, group 4Y-PSZ/NA, group 4Y-PSZ/APol, group 4Y-PSZ/ADia, group 5Y-PSZ/NA, group 5Y-PSZ/APol, and group 5Y-PSZ/ADia. The biaxial flexural strength of each specimen was measured by using a universal testing machine (Model 4411; Instron) and according to ISO 6872. X-ray diffraction analysis was conducted to quantify the monoclinic phase transformation. Scanning electron microscopy images were obtained to evaluate the fracture pattern. Statistical analysis was performed by using analysis of variance (ANOVA) and Tukey multiple comparison tests for pairwise comparisons (α=.05). RESULTS: The mean biaxial flexural strengths ranked from the highest to the lowest were for 3Y-PSZ, 4Y-PSZ, and 5Y-PSZ under any test condition (P=.007). Chairside adjustment with a diamond instrument significantly decreased the flexural strength of all zirconia types (P<.05). No statistically significant difference was found between the effect of APol and ADia on the strength of zirconia 3Y-PSZ (P=.603), 4Y-PSZ (P=.993), and 5Y-PSZ (P=.660). Phase transformation did not occur in the 5Y-PSZ groups. ADia groups had significantly higher phase transformation values regardless of zirconia type (P<.05). CONCLUSIONS: The biaxial flexural strength of zirconia decreased significantly after chairside adjustment with diamond instruments regardless of the yttria percentage. Adjustment with the Dialite ZR finishing and polishing system caused less tetragonal to monoclinic phase transformation than adjustment with a course-grit diamond instrument.

Perceived oral health and oral health behaviours among home-dwelling older people with and without domiciliary care.

OBJECTIVES: The aim was to compare the perceived oral health and oral health behaviours of home-dwelling older people with and without domiciliary care. BACKGROUND: Oral health is poor in long-term care, but less is known about perceived oral health of home-dwelling older people receiving domiciliary care. MATERIALS AND METHODS: Data from the Health 2000 and Health 2011 surveys (BRIF8901) were used. Interview participants were at least 70 years old and living at home with or without domiciliary care (n = 1298 in 2000 and n = 1027 in 2011). Differences in perceived oral health (subjective oral health, pain, eating difficulties) and oral health behaviours (hygiene, use of services) were compared based on the use of domiciliary care and stratified by gender. Differences between groups were compared with the chi-square test. RESULTS: In 2011, compared to non-clients, domiciliary care clients more often had poor subjective oral health (40.3% vs. 28.9%, P = .045). In both surveys, they also used oral health services less recently (2000, 76.4% vs. 60.9%; and 2011, 61.1% vs. 46.6%) and more often had difficulties chewing hard food (2000, 50.6% vs. 34%, P < .001; and 2011, 38.4% vs. 20.7%, P < .001) than non-clients. In 2000, clients had more difficulty eating dry food without drinking (39.5% vs. 21.6%, P < .001) and cleaning their teeth and mouth (14.3% vs. 1.1%, P < .001) than non-clients. Women clients in 2011 brushed their teeth less often than non-clients (43.5% vs. 23.7%, respectively, P = .001). CONCLUSION: Domiciliary care clients have poorer perceived oral health, and greater difficulties with eating and oral hygiene maintenance than non-clients.

Effect of bioactive glass air-abrasion on Fusobacterium nucleatum and Porphyromonas gingivalis biofilm formed on moderately rough titanium surface.

This aim of this study was to investigate the effects of three types of air-abrasion particles on dual-species biofilms of Fusobacterium nucleatum and Porphyromonas gingivalis, both of which were cultured on sandblasted and acid-etched (SA) titanium discs. Out of 24 SA discs with biofilm, 18 were exposed to either air-abrasion using Bioglass 45S5 (45S5 BG; n = 6), novel zinc (Zn)-containing bioactive glass (Zn4 BG; n = 6), or inert glass (n = 6). The efficiency of biofilm removal was evaluated using scanning electron microscopy (SEM) imaging and culturing techniques. Air-abrasion using 45S5 BG or Zn4 BG demonstrated a significant decrease in the total number of viable bacteria compared to discs air-abraded with inert glass or intact biofilm without abrasion. Moreover, P. gingivalis could not be detected from SEM images nor culture plates after air-abrasion with 45S5 BG or Zn4 BG. The present study showed that air-abrasion with 45S5 or Zn4 bioactive glasses can successfully eradicate dual-biofilm of F. nucleatum and P. gingivalis from sandblasted and acid-etched titanium discs.

Organotypic in vitro block culture model to investigate tissue-implant interface. An experimental study on pig mandible.

In vitro studies of implant-tissue attachment are primarily based on two-dimensional cell culture models, which fail to replicate the three-dimensional native human oral mucosal tissue completely. Thus, the present study aimed to describe a novel tissue culture model using pig mandibular block including alveolar bone and gingival soft tissues to evaluate the tissue attachment to titanium implant provided with hydrothermally induced TiO2 coating. Tissue attachment on TiO2 coated and non-coated implants were compared. Ti-6Al-4V alloy posts were used to function as implants that were inserted in five pig mandibles. Implants were delivered with two different surface treatments, non-coated (NC) titanium and hydrothermal induced TiO2 coated surfaces (HT). The tissue-implant specimens were cultured at an air/liquid interface for 7 and 14 days. The tissue-implant interface was analyzed by histological and immunohistochemical stainings. The microscopic evaluation suggests that pig tissue explants established soft and hard tissue attachment to both implant surfaces. The epithelial cells appeared to attach to the coated implant. The epithelium adjacent to the implant abutment starts to change its phenotype during the early days of the healing process. New bone formation was seen within small pieces of bone in close contact with the coated implant. In conclusion, this in vitro model maintains the viability of pig tissue and allows histologically and immunohistochemically evaluate the tissue-implant interface. HT-induced TiO2 coating seems to have a favorable tissue response. Moreover, this organotypic tissue culture model is applicable for further studies with quantitative parameters to evaluate adhesion molecules present at the implant-tissue interface.

Midline denture base strains of glass fiber-reinforced single implant-supported overdentures.

STATEMENT OF PROBLEM: The fracture incidence of implant-supported overdentures is more frequent in the area of attachment because of stress concentration and denture deformation in this area. How E-glass fiber reinforcement can address this problem is unclear. PURPOSE: The purpose of this in vitro study was to evaluate the influence of unidirectional E-glass fiber reinforcement on the mid-line denture base strains of single implant-supported overdentures. MATERIAL AND METHODS: An experimental acrylic resin cast was constructed with a single implant placed in the mid-line area and a ball attachment screwed to the implant. Twenty-four experimental overdentures were constructed and divided into 4 groups: group AP fabricated from autopolymerizing acrylic resin without fiber reinforcement, group APF fabricated from autopolymerizing acrylic resin with unidirectional E-glass fiber reinforcement running over the residual ridge and the ball matrix, group HP fabricated from heat-polymerized acrylic resin without fiber reinforcement, and group HPF fabricated from heat-polymerized acrylic resin with unidirectional E-glass fiber reinforcement running over the residual ridge and the ball matrix. A biaxial rosette strain gauge was attached to the incisor areas of each overdenture above the attachment level (Ch1, Ch2) and to a multichannel digital strain meter. A static vertical load of 100 N was applied to the first molar area bilaterally by using a universal testing device during strain measurement procedures. The differences in the mean strain and deflection values among the investigated groups were evaluated for statistical significance using 1-way analysis of variance (ANOVA) with the Tukey post hoc multiple comparison (α=.05). RESULTS: The type of acrylic resin did not have a statistically significant effect on the mean strain values among groups (P=.350), while the reinforcement did significantly affect them (P<.001). The interaction between reinforcement and acrylic resin was not statistically significant (P=.552). Both strain gauge channels in group APF and group HPF recorded significantly lower strain values by almost 50% than those of group AP and group HP (P<.05). CONCLUSIONS: Unidirectional E-glass fiber reinforcement placed over the residual ridge and implant attachment significantly reduced denture base strains and deformation of single implant-supported overdentures.

Effect of bioactive glass air-abrasion on the wettability and osteoblast proliferation on sandblasted and acid-etched titanium surfaces.

The aim of this study was to evaluate the hydrophilicity, surface free energy, and proliferation and viability of human osteoblast-like MC3T3-E1 cells on sandblasted and acid-etched titanium surfaces after air-abrasion with 45S5 bioactive glass, zinc-containing bioactive glass, or inert glass. Sandblasted and acid-etched titanium discs were subjected to air-abrasion with 45S5 bioactive glass, experimental bioactive glass (Zn4), or inert glass. Water contact angles and surface free energy were evaluated. The surfaces were studied with preosteoblastic MC3T3-E1 cells. Air-abrasion with either type of glass significantly enhanced the hydrophilicity and surface free energy of the sandblasted and acid-etched titanium discs. The MC3T3-E1 cell number was higher for substrates air-abraded with Zn4 bioactive glass and similar to that observed on borosilicate coverslips (controls). Confocal laser scanning microscopy images showed that MC3T3-E1 cells did not spread as extensively on the sandblasted and acid-etched and bioactive glass-abraded surfaces as they did on control surfaces. However, for 45S5- and Zn4-treated samples, the cells spread most at the 24 h time point and changed their morphology to more spindle-like when cultured further. Air-abrasion with bioactive glass and inert glass was shown to have a significant effect on the wettability and surface free energy of the surfaces under investigation. Osteoblast cell proliferation on sandblasted and acid-etched titanium discs was enhanced by air-abrasion with 45S5 bioactive glass and experimental Zn4 bioactive glass compared with air-abrasion with inert glass or no air-abrasion.

Fracture Load of Different Zirconia Types: A Mastication Simulation Study.

PURPOSE: To assess the effect of yttria mol% concentration and material thickness on the biaxial fracture load (N) of zirconia with and without mastication simulation. MATERIALS AND METHODS: Disk-shaped specimens (N = 120) of 3 mol% yttria-partially stabilized zirconia, 3Y-PSZ (Katana High Translucent, Kuraray Noritake), 4 mol% yttria-partially stabilized zirconia, 4Y-PSZ (Katana Super Translucent Multi Layered) and 5 mol% Yttria-partially stabilized zirconia, 5Y-PSZ (Katana Ultra Translucent Multi Layered) were prepared to thicknesses of 0.7 and 1.2 mm. For each thickness, the biaxial fracture load (N) was measured with and without mastication simulation with 1.2 million cycles at a 110-N load and simultaneous thermal cycling at 5°C to 55°C. The data were analyzed by three-way Analysis of Variance (α = 0.05) and Tukey-Kramer adjusted multiple comparison test. RESULTS: Yttria mol% concentration and material thickness had a statistically significant effect on the mean biaxial fracture load (F = 388.16, p < 0.001 and F = 714.33, p < 0.001 respectively). The mean biaxial fracture load ranged from the highest to the lowest; 3Y-PSZ, 4Y-PSZ, and 5Y-PSZ (p = 0.012). The mean biaxial fracture load of the 1.2 mm thickness groups was significantly higher than 0.7 mm thickness at any given condition (p = 0.002). Not all specimens survived the mastication simulation protocol. Fifty percent of the 0.7-mm-thick 4Y-PSZ specimens, 70% of the 0.7-mm-thick 5Y-PSZ specimens and 20% of 1.2-mm-thick 5Y-PSZ specimens fractured during mastication simulation. Mastication simulation had no statistically significant effect on the biaxial fracture load (F = 1.24, p = 0.239) of the survived specimens. CONCLUSIONS: Lowering yttria mol% concentration and increasing material thickness significantly increases the fracture load of zirconia. At 0.7 mm thickness, only 3Y-PSZ survived masticatory simulation. A minimum material thickness of 1.2 mm is required for 4Y-PSZ or 5Y-PSZ.

Fatigue resistance of a simulated single LOCATOR overdenture system.

STATEMENT OF PROBLEM: The incidence of fracture in a single-implant overdenture base increases in the region adjacent to the fulcrum implant. PURPOSE: The purpose of this in vitro study was to evaluate the effect of bidirectional woven electrical glass (E-glass) fiber reinforcements on the fatigue resistance of a simulated single LOCATOR-retained overdenture. MATERIAL AND METHODS: Test specimens with a centrally positioned metal housing for a LOCATOR stud attachment were fabricated from autopolymerizing acrylic resin. Specimens for the control group were fabricated without glass fiber reinforcements. The 4L group specimens had 4 layers of E-glass fiber weaves and were divided according to the fiber location into the following 3 subgroups: 4L-A with 4 fiber layers above the metal housing; 4L-N with 4 fiber layers adjacent to the metal housing; and 4L-A+4L-N with 4 fiber layers above and 4 fiber layers adjacent to the housing. Specimens were stored in distilled water for 1 week at 23 °C before cyclic fatigue testing at 10 000 cycles by using a staircase approach (n=12). The results were analyzed with 1-way ANOVA and the Tukey multiple comparisons post hoc analysis (α=.05). A 2-way ANOVA (α=.05) was conducted to detect the effect of fatigue cyclic loading and the position of the fiber layers and their interaction on the fatigue resistance. RESULTS: The results of the investigated compressive fatigue limits for the test groups were 190 ±15.9 N for the control group, 265 ±15.9 N for the 4L-A subgroup, 220 ±15.9 N for the 4L-N subgroup, and 275 ±15.9 N for the 4L-A+4L-N subgroup. A nonsignificant difference was found for creep values between the control group and reinforced subgroups (P>.05). The postfatigue flexural strength values in the 4L-A and 4L-A+4L-N subgroups were significantly higher than those in the control group (P<.001) and the 4L-N subgroup (P=.004 and P=.005). However, no significant difference was found in postfatigue flexural strength between the control group and the 4L-N subgroup (P=.828). CONCLUSIONS: Placing 4 layers of bidirectional E-glass fiber weaves above the metal housing can increase the fatigue resistance and the postfatigue flexural strength of single LOCATOR-retained overdentures.

Air Abrasion With Bioactive Glass Eradicates Streptococcus mutans Biofilm From a Sandblasted and Acid-Etched Titanium Surface.

Streptococcus mutans is able to form a high-affinity biofilm on material surfaces. S mutans has also been detected around infected implants. Bioactive glasses (BAGs) have been shown to possess antibacterial effects against S mutans and other microorganisms. This in vitro study was performed to investigate the influence of BAG air abrasion on S mutans biofilm on sandblasted and acid-etched titanium surfaces. Sandblasted and acid-etched commercially pure titanium discs were used as substrates for bacteria (n = 107). The discs were immersed in an S mutans solution and incubated for 21 hours to form an S mutans biofilm. Twenty colonized discs were subjected to air abrasion with Bioglass 45S5 (45S5 BAG), experimental zinc oxide containing BAG (Zn4 BAG), and inert glass. After the abrasion, the discs were incubated for 5 hours in an anaerobic chamber followed by an assessment of viable S mutans cells. Surface morphology was evaluation using scanning electron microscopy (n = 12). The thrombogenicity of the glass particle-abraded discs (n = 75) was evaluated spectrophotometrically using whole-blood clotting measurement at predetermined time points. Air abrasion with 45S5 and Zn4 BAG eradicated S mutans biofilm. Significantly fewer viable S mutans cells were found on discs abraded with the 45S5 or Zn4 BAGs compared with the inert glass (P < .001). No significant differences were found in thrombogenicity since blood clotting was achieved for all substrates at 40 minutes. Air abrasion with BAG particles is effective in the eradication of S mutans biofilm from sandblasted and acid-etched titanium surfaces. Zn4 and 45S5 BAGs had similar biofilm-eradicating effects, but Zn4 BAG could be more tissue friendly. In addition, the steady release of zinc ions from Zn4 may enhance bone regeneration around the titanium implant and may thus have the potential to be used in the treatment of peri-implantitis. The use of either BAGs did not enhance the speed of blood coagulation.

Ultraviolet photofunctionalization of nanostructured titanium surfaces enhances thrombogenicity and platelet response.

The purpose of this study was to evaluate blood and platelet response to nanostructured TiO2 coatings and to investigate the effect of Ultraviolet (UV) light treatment on blood clotting ability, platelet activation and protein adhesion. Ti-6Al-4V titanium alloy plates (n = 138) were divided into three groups; a sol-gel derived MetAliveTM coating (MA); hydrothermal coating (HT); and a non-coated group (NC). Sixty nine titanium substrates were further treated with UV light for 1 h. The thrombogenicity of the titanium substrates was assessed using fresh human blood with a whole blood kinetic clotting time method. The platelet adhesion test was conducted to evaluate the morphology and adhesion behavior of the platelets on the titanium substrates. Human diluted plasma and bovine fibronectin were used to evaluate protein adsorption. Total clotting time for the UV treated HT, MA and NC titanium substrates was almost 40 min compared to 60 min for non-UV substrates, the total clotting time for the UV treated groups were significantly lower than that of the non UV NC group (p < 0.05). UV light treatment had significantly enhanced coagulation rates. The HT and MA substrates presented more platelet aggregation, spreading and pseudopod formation in comparison with the NC substrates. UV treatment did not affect the platelet activation and protein adsorption. This in vitro study concluded that nanostructured titanium dioxide implant surfaces obtained by sol-gel and hydrothermal coating methods increased coagulation rates and enhanced platelet response when compared with non-coated surfaces. UV light treatment clearly improved thrombogenicity of all examined Ti-6Al-4V surfaces.

Knowledge, perceived skills and activities of nursing staff to support oral home care among older domiciliary care clients.

BACKGROUND: Increasing number of older adults lives in their own homes, but needs help in many daily routines. Domiciliary care nursing staff (DCNS) is often needed to support oral home care. However, information of nursing staff's knowledge, skills and activity in this task is sparse. OBJECTIVES: The study aimed to assess DCNS knowledge, perceived skills and activities to support oral home care of older domiciliary care clients. MATERIAL AND METHODS: The study was conducted among DCNS in one of the largest cities in Finland. All DCNS members (n = 465) received a questionnaire with 14 multiple choice and open questions regarding the perceived skills, knowledge and activities of oral health guidance of older domiciliary care clients. In total, 115 (25%) DCNS members returned the questionnaires. Frequencies, percentages, means and standard deviations were used to describe the samples and study variables. DCNS was categorised according to age and working years for group comparisons, which were assessed with chi-squared test. RESULTS: Knowledge concerning oral health was mostly on a high level. Around 50% of DCNS considered their knowledge regarding dental prosthesis hygiene as sufficient. Of the DCNS, 67% informed that they had received education on oral health care. However, over 50% of the DCNS had a need for further education in issues related to oral home care. DCNS were active in supporting most oral and prosthesis hygiene means, yet less in guidance concerning toothbrushing. Activity to support cleaning the interdental spaces was the weakest, in which only 12% of the respondents considered having average or excellent skills. Younger DCNS had better knowledge on oral home care due to recent education, but older staff members were more skilful in performing oral hygiene measures. CONCLUSIONS: There is a need for structured instructions and training on oral home care for DCNS. Oral home care should be taken into account more often and regularly.

Load-bearing capacity of simulated Locator-retained overdenture system.

STATEMENT OF PROBLEM: Acrylic resin overdenture bases usually fracture because of stress concentrations at the area of the abutments. PURPOSE: The purpose of this study was to evaluate the reinforcing effect of bidirectional woven electrical glass (E-glass) fiber weaves with a different number of layers and different locations on the load-bearing capacity of simulated Locator-retained overdenture specimens. MATERIAL AND METHODS: Test specimens with a centrally located metal housing for a Locator stud attachment were fabricated from autopolymerizing acrylic resin (polymethylmethacrylate based) and reinforced with bidirectional woven E-glass fiber layers. The control group specimens were fabricated without fiber reinforcement. The 2L group had 2 layers of E-glass fiber weaves and was divided according to the fiber location within the specimens as follows: 2L-A subgroup with 2 fiber layers above the metal housing; 2L-N subgroup with 2 fiber layers adjacent to the housing; and 2L-A+2L-N subgroup with 2 fiber layers above and 2 fiber layers adjacent to the housing. The 4L group had 4 layers of E-glass fiber weaves and was divided according to the fiber location as follows: 4L-A subgroup with 4 fiber layers above the housing; 4L-N subgroup with 4 fiber layers adjacent to the housing; and 4L-A+4L-N subgroup with 4 fiber layers above and 4 fiber layers adjacent to the housing. Dry specimens were submitted to a 3-point static loading test, and the mean flexural strength, flexural modulus, and strain values were analyzed with 1-way ANOVA and Tukey post hoc tests (α=.05). Two-way ANOVA was conducted to detect the influence of the number and location of the reinforcing layers (α=.05). RESULTS: The results revealed a significant difference (P<.001) in flexural strength values between the control group (92.4 ±14 MPa) and the 2 subgroups, 4L-A (116 ±7.3 MPa) and 4L-A+4L-N (117.1 ±6 MPa), with a significant effect only from the number of the reinforcing layers (P<.001) and not the location (P=.153). No significant differences were found with flexural modulus (P=.195) and strain values (P=.174) among the tested groups. CONCLUSIONS: The load-bearing capacity of a Locator-retained overdenture can be significantly increased by placing 4 layers of bidirectional woven E-glass fiber weaves either only above the metal housing or in both locations above and adjacent to the metal.

Fracture Strength and Precision of Fit of Implant-Retained Monolithic Zirconia Crowns.

New monolithic zirconia materials can be used to fabricate full-contour fixed dental prostheses with the computer-aided design/computer-aided manufacturing (CAD/CAM) method. The aim of this study was to examine the fracture strength and precision of fit of screw-retained monolithic zirconia crowns made directly on implants or by cementing on prefabricated titanium (Ti) bases. Monolithic screw-retained implant crowns (n = 6) were produced by CAD/CAM method using partially (PSZ) and fully stabilized (FSZ) zirconia. Industrially produced zirconia crowns were used as a reference. A lateral incisor study model was made onto an implant replica. Crowns were produced either directly on the implant or through cementing on a prefabricated titanium base (PSZ+Ti, FSZ+Ti). The crowns were tightened to implant replicas with a torque of 35 Ncm. The gap between the replica and the abutment or crown was measured from ×400 scanning electron microscope images for precision of fit. Mechanical testing until failure was completed with a universal testing machine with loading angle of 45°. Statistical analysis was performed (analysis of variance). Mean (±SD) failure loads were 259 ± 23 (PSZ), 140 ± 13 (FSZ), 453 ± 25 (PSZ+Ti), 439 ± 41 (FSZ+Ti), and 290 ± 39 (Procera). Mean (±SD) gap values were 2.2 ± 0.2 (PSZ), 2.5 ± 1.0 (FSZ), 7.0 ± 1.0 (PSZ+Ti), 7.7 ± 1.6 (FSZ+Ti), and 6.7 ± 1.7 (Procera). Monolithic zirconia crowns with a Ti base clearly show higher fracture strengths than the crowns fixed directly on the implant surface. Better marginal fit can be achieved with direct zirconia crowns than with crowns on a titanium base or industrially produced zirconia crowns.

Optical Properties and Failure Load of Thin CAD/CAM Ceramic Veneers.

This study aimed to compare optical properties and failure load of leucite (IPS Empress CAD LT) and lithium disilicate glass ceramic (IPS e.max CAD LT) materials in incisor veneers. Four groups of veneers were made on 36 bovine incisors with Cerec 3D milling unit (n=9/group): 0.5 and 0.3 mm thick leucite glass and 0.5 and 0.3 mm lithium disilicate glass veneers. The optical features were measured with CM-700d spectrophotometer using white and yellow try-in pastes. Differences were determined by means of ΔE value and luminance. The bovine teeth with veneers were mounted on acrylic resin blocks (Palapress, Heraeus Kulzer) and static loading test was conducted (LR30K plus, Lloyd Instruments). The color difference of veneers could be noticed with yellow and white cements when the material thickness increased from 0.3 to 0.5 mm (leucite ΔE yellow 4.4, white 6.0; lithiumdisilicate ΔE yellow 2.1, white 4.1). Both materials showed similar failure load with 0.5 mm veneers (leucite 1906 +/-319 N; lithiumdisilicate 2098 +/- 309 N). The failure load of 0.3 mm thick lithium dilisilicate veneers (2002 +/- 427 N) was comparable with the 0.5mm veneers. Ultrathin lithium disilicate glass ceramic veneers (0.3 mm) could be a potential option for clinical use.