Effects of solvent type and UV post-cure time on 3D-printed restorative polymers.

OBJECTIVES: This study evaluated the impact of different solvents and UV post-curing times on properties of 3D printing resins for provisional restorations. METHODS: The post-processing methods were tested using two solvents (isopropyl alcohol or absolute ethanol) and three UV times (5, 10, or 30 min). The resins tested were Resilab 3D Temp, Printax Temp, and Prizma Bioprov. Microhardness (kgf/mm2), fracture toughness (KIC, MPa√m), surface roughness (Ra, µm), gloss (gloss units), and degree of CC conversion (%DC) were measured (n = 8). All response variables were collected from the same specimen. The specimens were 3D printed using an SLA/LCD printer (150° angulation, 50 µm layer thickness). Light exposure times were adjusted for each material, and the post-processing methods were applied using an all-in-one machine immediately after printing. Data were analyzed using Three-Way ANOVA (α = 0.05). RESULTS: Microhardness was affected by UV post-cure time and 3D resin. Resilab showed higher microhardness with isopropyl alcohol and 30-min UV time, while Printax had higher microhardness with absolute ethanol. KIC was influenced by solvent type, UV time, and 3D resin, with varying effects on different resins. Roughness was affected by 3D resin and UV time, but no significant differences were seen for Resilab or Prizma. Gloss was influenced by 3D resin, and for Prizma, it was lower with specific solvent/UV time combinations. DC was influenced by 3D resin, with each resin behaving differently. SIGNIFICANCE: Tailoring the combination of 3D resin, solvent washing type, and UV post-curing time is important to achieve optimal mechanical and aesthetic outcomes for restorations.

Bonding stability of universal adhesives to feldspathic ceramic with or without prior silane application.

PURPOSE: This study aimed to assess the bonding stability of three universal adhesives to a CAD-CAM feldspathic ceramic with or without prior silane application. MATERIALS AND METHODS: The universal adhesives tested were Ambar Universal (FGM), Single Bond Universal (3M), and Ybond Universal (Yller). Scotchbond Multipurpose Plus (3M) was used as a control. The silane used was RelyX Ceramic Primer (3M). Microtensile bond strength (µTBS) to Vitablocs Mark II was measured after 24 h or 6 months of water aging (n = 20). Failure modes were observed through scanning electron microscopy, and pH and degree of C=C conversion (DC) of the adhesives were measured (n = 3). Data were analyzed using one-, two-, and three-way ANOVA. RESULTS: The pH values differed significantly among the adhesives (p < 0.001), while the DC was similar (p = 0.141). The universal adhesives showed significant differences in µTBS, with higher immediate results when using silane and lower results after aging. Notably, a significant decrease in µTBS was observed after 6 months when silane was applied. In contrast, the control adhesive exhibited consistent results between the 24-h and 6-month storage periods. The universal adhesives showed a decrease in µTBS ranging from 25.5% to 40.1% after prolonged storage. Adhesive failures were predominant in all groups. The presence or absence of silane in the adhesive composition did not affect the bonding performance. CONCLUSIONS: The application of a separate silane coupling agent improved the immediate bond strength of universal adhesives to CAD-CAM feldspathic ceramic. However, this bond strength significantly decreased after 6 months of water aging. The bond strength remained stable for universal adhesives when applied without silane after 6 months of aging.

Residual stresses explaining clinical fractures of bilayer zirconia and lithium disilicate crowns: A VFEM study.

OBJECTIVE: To understand the stress development in porcelain-veneered zirconia (PVZ) and porcelain-veneered lithium disilicate (PVLD) crowns with different veneer/core thickness ratios and cooling rates. To provide design guidelines for better performing bilayer restorations with the aid of Viscoelastic Finite Element Method (VFEM). METHODS: The VFEM was validated by comparing the predicted residual stresses with experimental measurements. Then, the model was used to predict transient and residual stresses in the two bilayer systems. Models with two different veneer/core thickness ratios were prepared (2:1 and 1:1) and two cooling protocols were simulated (Fast: ∼300 °C/min, Slow: ∼30 °C/min) using the heat transfer module, followed by stress analysis in ABAQUS. The physical properties of zirconia, lithium disilicate, and the porcelains used for the simulations were determined as a function of temperature. RESULTS: PVLD showed lower residual stresses than PVZ. The maximum tensile stresses in PVZ were observed in the cusp area, whereas those in PVLD were located in the central fossa. The 1:1 thickness ratio decreased stresses in both layers of PVZ. Slow cooling slightly decreased residual stresses in both systems. However, the cooling rate effect was more evident in transient stresses. SIGNIFICANCE: Slow cooling is preferable for both systems. A thinner porcelain layer over zirconia lowers stresses throughout the restoration. The different stress distributions between PVZ and PVLD may affect their failure modes. Smaller mismatches in modulus, CTE, and specific heat between the constituents, and the use of low Tg porcelains can effectively reduce the deleterious transient and residual tensile stresses in bilayer restorations.

An in situ and ex situ study of the microstructural evolution of a novel lithium silicate glass-ceramic during crystallization firing.

OBJECTIVE: To elucidate the compositional and microstructural developments of a novel lithium silicate glass-ceramic during its crystallization cycle. METHODS: Blocks of a lithium silicate glass-ceramic (Obsidian®, Glidewell Laboratories) were cut into 1mm thick plates and polished to 1µm finish. Some of them were crystallized prior to polishing. Firstly, ex situ compositional and microstructural characterizations of both the pre- and post-crystallized samples were performed by wavelength dispersive X-ray fluorescence, field-emission scanning electron microscopy, and X-ray diffractometry. Secondly, the pre-crystallized samples were subjected to in situ compositional and microstructural characterizations under non-isothermal heating by simultaneous thermogravimetry/differential scanning calorimetry, X-ray thermo-diffractometry, and field-emission scanning electron thermo-microscopy. RESULTS: The microstructure of pre-crystallized Obsidian® consists of an abundant population of perlitic-like/dendritic lithium silicate (Li2SiO3) nanocrystals in a glass matrix. Upon heating, the residual glassy matrix does not crystallize into any form of SiO2; elemental oxides do not precipitate unless over-heated above 820°C; and the Li2SiO3 nanocrystals do not react with the glassy matrix to form typical lithium disilicate (Li2Si2O5) crystals. Nonetheless, the Li2SiO3 nanocrystals grow and spheroidize through the solution-reprecipitation process in the softened glass, and new lithium orthophosphate (Li3PO4) nanocrystals precipitate from the glass matrix. SIGNIFICANCE: The identification of compositional and microstructural developments of Obsidian® indicates that, by controlling the firing conditions, it is possible to tailor its microstructure, which in turn could affect its mechanical and optical properties, and ultimately its clinical performance.

The Effect of Brushing and Aging on the Staining and Smoothness of Resin Composites.

OBJECTIVES: To evaluate the staining and smoothness of resin composites undergoing aging in water or red wine and simulated brushing with or without dentifrice. METHODS: The resin composites (Z250 microfilled and Z350XT nanofilled) were tested according to aging media (deionized water or red wine) and surface treatment (no brushing, brushed with water, or brushed with dentifrice). Specimens (n = 10) were subjected to three aging cycles (5 days) of continuous immersion in the aging media; each followed by simulated brushing (585 strokes). Color coordinates (CIEL*a*b*) were measured with a spectrophotometer (SP60, EX-Rite) and roughness (Ra) measured with a contact profilometer (Surftest SJ-201P, Mitutoyo), in five time points across the experiment. Surface morphology was analyzed using AFM (SPM-9600, Shimadzu) at the end of the experiment. Data for color change (ΔE00 ) and Ra were analyzed by two-way repeated measures ANOVA and Tukey test (p < 0.05). RESULTS: Color change was observed for all groups, and it was always greater for Z350. Surface treatment did not influence the ΔE00 values for the groups aged in water. However, brushing decreased ΔE00 for the groups aged in red wine. In general, ΔE00 increased with time. Little to no differences in smoothness were observed with aging and brushing. The surface morphology analyses showed exposed/lost filler particles for brushed Z250. Such observations were not so clear for Z350. CONCLUSIONS: Within the limitations of the present experiment, short-time simulated toothbrushing with soft-bristle toothbrush and low abrasive dentifrice did not increase roughness and reduced staining for both nanofilled and microfilled materials. CLINICAL SIGNIFICANCE: Staining and surface degradation of the resin composites was reduced, but not prevented by brushing alone. Thus, minimizing the restoration exposure to staining substances is important for maintaining the aesthetic appearance of the restoration. (J Esthet Restor Dent 29:E44-E55, 2017).

Antibodies to rabies virus in terrestrial wild mammals in native rainforest on the north coast of São Paulo State, Brazil.

Rabies causes thousands of human and animal deaths worldwide each year. The emergent importance of rabies in wild animals demonstrates the necessity of epidemiologic studies of infection in these species toward the development of better strategies for prevention and control of rabies. We analyzed the circulation of rabies virus among wildlife species from a native rainforest in São Paulo State, Brazil. We used the rapid fluorescent focus inhibition test (RFFIT) to test for rabies virus-neutralizing antibodies in 139 captured terrestrial mammals and the fluorescent antibody test (FAT), mouse inoculation test (MIT), and reverse-transcriptase (RT)-PCR to test for virus in samples from the central nervous system of 53 animals found dead. The percentage of samples positive by RFFIT was 10.8%. All samples tested by FAT, MIT, and RT-PCR were negative. Research should be continued to obtain a better understanding of the role of wildlife in the circulation and transmission of rabies virus.

Psychological and marital distress in spouses of Vietnam veterans: importance of spouses' perceptions.

Spouses of combat veterans with PTSD have greater psychological and marital distress than spouses of veterans without PTSD; however, few studies have examined how variables related to the spouses (e.g., cognitions) may play a role in their own distress. The current study examined spouses' perceptions of combat veterans' PTSD symptom severity in 465 spouses of veterans from the National Vietnam Veterans Readjustment Study. Spouses' perceptions of veterans' symptom severity were positively associated with spouses' psychological and marital distress; furthermore, spouses' perceptions fully mediated the effects of veterans' self-reported PTSD severity on spouses' distress. Additionally, for spouses who provided complete data with regard to their perceptions of veterans' PTSD, distress was highest when they perceived high levels of symptoms but veterans reported low levels. These results highlight the importance of interpersonal perceptions in intimate relationships and provide preliminary groundwork for future research on cognitions in spouses of combat veterans with PTSD.

Associations of coping processes with posttraumatic stress disorder symptoms in national guard/reserve service members deployed during the OEF-OIF era.

Studies have identified coping processes as one potential factor influencing PTSD in veterans. This study examined the associations between coping, combat exposure, and PTSD among 218 National Guard veterans deployed overseas since 2001. Problem-focused coping was unrelated to combat exposure and PTSD symptoms. In contrast, increased levels of emotion focused coping (EFC) were found in veterans who reported higher levels of combat exposure. Moreover, the severity of combat was a curvilinear moderator of the relation between coping process and PTSD, such that EFC was unrelated to PTSD symptom severity at low levels of combat, associated with higher symptom severity at moderate levels of combat, and associated with lower symptom severity at high levels of combat. These findings indicate that the type and severity of trauma may moderate the association of coping and psychological outcomes, and that these associations might not be linear.

Combat exposure, psychological symptoms, and marital satisfaction in National Guard soldiers who served in Operation Iraqi Freedom from 2005 to 2006.

In current military operations in Iraq and Afghanistan, US National Guard (NG) troops are serving longer deployments than ever before. Little is known, however, about how such deployments affect this population of individuals, relative to active component (AC) troops. This study investigated the extent of combat exposure, severity of post-deployment psychological symptoms, and general interpersonal functioning, as well as the interrelationships of these variables, in 50 NG soldiers who served a 12-month deployment in Iraq from 2005 to 2006. The results indicate that combat exposure and post-deployment post-traumatic stress symptoms in this sample are greater than those in NG veterans of past military operations, and similar to those of full-time soldiers in current operations. Furthermore, the patterns of interrelationships between combat exposure, psychological symptoms, and interpersonal variables were similar to those detected in prior research on AC troops. These results suggest that NG veterans of current military operations may require similar services as active duty veterans. Given that NG troops are less integrated into the military structure, specific outreach efforts may be needed to help NG veterans to receive such services.

Psychological symptoms and marital satisfaction in spouses of Operation Iraqi Freedom veterans: relationships with spouses' perceptions of veterans' experiences and symptoms.

Much research has shown that spouses of combat veterans with posttraumatic stress disorder (PTSD) have higher rates of psychological and marital distress than do spouses of veterans without PTSD; however, very few studies have examined potential mechanisms of this increased vulnerability. The current study examined spouses of National Guard soldiers recently returned from deployments in Iraq. In addition to documenting elevated levels of psychological symptoms in these spouses, the authors found that spouses experienced greater symptom severity when they perceived high levels of symptoms in soldiers but the soldiers endorsed low levels of symptoms. Furthermore, spouses' marital satisfaction was negatively linked to soldiers' self-reported symptom severity only when spouses perceived that soldiers had experienced low levels of combat activity while deployed. When spouses perceived high levels of such activity, soldiers' self-reported symptoms had no relationship with spouses' marital satisfaction. These findings highlight the importance of interpersonal perceptions in intimate relationships and are consistent with the notion that uncontrollable attributions for a relative's mental health problems may provide a buffer against relationship distress. (PsycINFO Database Record (c) 2008 APA, all rights reserved).