Surface alterations and compound release from aligner attachments in vitro.

AIM: The aim of the present study was to assess the alterations in morphology, roughness, and composition of the surfaces of a conventional and a flowable composite attachment engaged with aligners, and to evaluate the release of resin monomers and their derivatives in an aqueous environment. METHODS: Zirconia tooth-arch frames (n = 20) and corresponding thermoformed PET-G aligners with bonded attachments comprising two composite materials (universal-C and flowable-F) were fabricated. The morphological features (stereomicroscopy), roughness (optical profilometry), and surface composition (ATR-FTIR) of the attachments were examined before and after immersion in water. To simulate intraoral use, the aligners were removed and re-seated to the frames four times per day for a 7-day immersion period. After testing, the eluents were analyzed by LC-MS/MS targeting the compounds Bis-GMA, UDMA, 2-HEMA, TEGDMA and BPA and by LC-HRMS for suspect screening of the leached dental material compounds and their degradation products. RESULTS: After testing, abrasion-induced defects were found on attachment surfaces such as scratches, marginal cracks, loss of surface texturing, and fractures. The morphological changes and debonding rate were greater in F. Comparisons (before-after testing) revealed a significantly lower Sc roughness parameter in F. The surface composition of the aligners after testing showed minor changes from the control, with insignificant differences in the degree of C = C conversion, except for few cases with strong evidence of hydrolytic degradation. Targeted analysis results revealed a significant difference in the compounds released between Days 1 and 7 in both materials. Insignificant differences were found when C was compared with F in both timeframes. Several degradation products were detected on Day 7, with a strong reduction in the concentration of the targeted compounds. CONCLUSIONS: The use of aligners affects the surface characteristics and degradation rate of composite attachments in an aqueous environment, releasing monomers, and monomer hydrolysates within 1-week simulated use.

Salivary levels of eluents during Invisalign™ treatment with attachments: an in vivo investigation.

BACKGROUND: The aim of the present study was to investigate qualitatively and quantitatively the elution of substances from polyester-urethane (Invisalign™) aligners and resin composite attachments (Tetric EvoFlow) in vivo. METHODS: Patients (n = 11) treated with the aligners and attachments (16 per patient, without other composite restorations) for an average of 20 months, who were planned for attachment removed were enrolled in the study. Patients were instructed to rinse with 50 mL of distilled water upon entry and the rinsing solution was collected (before removal). Then, the attachments were removed with low-speed tungsten carbide burs for adhesive residue removal, a thorough water rinsing was performed immediately after the grinding process to discard grinding particle residues, and subsequently, after a second water-rinsing the solution was collected for analysis (after removal). The rinsing solutions were analyzed for targeted (LC-MS/MS: Bis-GMA, DCDMA, UDMA, BPA) and untargeted (LC-HRMS: screening of leached species and their degradation products) compounds. RESULTS: Targeted analysis revealed a significant reduction in BPA after attachment removal (4 times lower). Bis-GMA, DCDMA, UDMA were below the detection limit before removal but were all detectable after removal with Bis-GMA and UDMA at quantifiable levels. Untargeted analysis reviled the presence of mono-methacrylate transformation products of Bis-GMA (Bis-GMA-M1) and UDMA (UDMA-M1), UDMA without methacrylate moieties (UDMA-M2), and 4-(dimethylamino) benzoic acid (DMAB), the degradation product of the photo-initiator ethyl-4-(dimethylamino) benzoate (EDMAB), all after attachment removal. Several amino acids and endogenous metabolites were also found both before and after removal. CONCLUSIONS: Elevated levels of BPA were traced instantaneously in patients treated with Invisalign™ and flowable resin composite attachments for the testing period. BPA was reduced after attachment removal, but residual monomers and resin degradation products were found after removal. Alternative resin formulations and attachment materials may be utilized to reduce eluents.

Intraoral ageing of aligners and attachments: Adverse effects on clinical efficiency and release of biologically-active compounds.

The clinical application of aligners is accompanied by the ageing of the polymer appliances and the attachments used, which may result in inefficiency in reaching the predicted range of tooth movement, and release of compounds and microplastics in the oral cavity as a result of the friction, wear and attrition of the aligner and composite attachment. The purpose of this review is to present the mechanism and effects of in vivo ageing; describe the hydrolytic degradation of aligners and enzymatic degradation of composite attachments; examine the ageing pattern of aligners in vivo, under actual clinical scenarios; and identify a link to the discrepancy between predicted and actual clinical outcome. Lastly, strategies to deal with three potentially critical issues associated with the use of aligners, namely the necessity of weekly renewal, the dissimilar mechanical properties of aligner and attachment resulting in wear and plastic deformation of the aligner, and the development of integuments and biofilms with microbial colonization of the appliance, are discussed.

Degree of cure of orthodontic composite attachments underneath aligners.

The aim of this study was to assess the percentage degree of cure (DC%) of 2-mm-thick resin composite attachments used for aligner treatment. Three types of aligner - two thermoformed aligners (Clear Aligner [CLA], polyethylene terephthalate glycol modified; and Invisalign [INV], polyester urethane) and a three-dimensional-printed aligner (Graphy TC-85DAC [GRP], an acrylate-methacrylate copolymer) - were selected, along with two universal resin composites (3M Filtek Universal [FTU] and Charisma Topaz ONE [CTO]). Samples of each composite were placed under each aligner, and the degree of cure of each composite was evaluated on the top (facing the aligner) and the bottom (facing the substrate) attachment surfaces after curing. Five specimens were used per combination of aligner and composite, and an additional group of composites irradiated without aligners served as the control. The DC% measurements were performed using attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. The DC% across the aligners were (median values) 33.8%-44.8% for CLA, 33.6%-40.8% for INV, 32.8%-40.6% for GRP, and 40.0%-51.7% for the control group. The DC% values of the attachments cured under any aligner were significantly lower than that of the corresponding control, with the values recorded on the top surfaces being 6% higher than those on the bottom surfaces after adjusting for aligner group and composite type.

Short fiber-reinforced composite resins as post-and-core materials for endodontically treated teeth: A systematic review and meta-analysis of in vitro studies.

STATEMENT OF PROBLEM: As the use of traditional posts has been associated with complications and failure outcomes, the introduction of novel materials and minimally invasive dentistry has shifted toward the use of composite resin post-and-core restorations for endodontically treated teeth. As a further process, to improve stress absorption environment in restored teeth, the invention of short fiber-reinforced composite resins (SFRCs) as post-and-core restorations has recently emerged. However, evidence regarding its performance is still scarce, and a synthesis of existing data is lacking. PURPOSE: The purpose of this systematic review and meta-analysis was to assess the performance of SFRC post-and-core restorations, regarding fracture resistance and failure mode and considering both cyclic and static loading. MATERIAL AND METHODS: An electronic search in 5 databases was conducted up to August 2022, and the protocol of the study was registered a priori. The search terms included "fiber reinforced composite," "core build-up," and "post." Studies were considered if they compared SFRC restorations with other types of conventional posts and teeth restored using bulk fill composite resin. The internal validity of the studies was assessed by using a custom-made risk of bias tool. RESULTS: A total of 1271 records were identified, of which 13 were considered for full-text assessment. Eight were ultimately included, all being in vitro studies, and 7 of them were deemed eligible for quantitative syntheses. The results varied considerably across studies with divergent fracture resistance values and percentages of catastrophic failure being reported. Standard depth (6 mm) SFRCs presented fewer repetitions until fracture on average, compared with the individually made FRCs (3 studies: mean difference (MD): -4062; 95% CI: -6148, -1975; P<.001) under cyclic loading. Under static loading, SFRCs (standard depth) presented a nearly 300 N lower fracture force compared with that of intact teeth, (3 studies: MD: -297; 95%CI: -378, -216; P<.001). CONCLUSIONS: Evidence on the laboratory fracture and failure performance of SFRCs is limited, and future studies should incorporate more standardized experimental conditions, as well as SFRCs with limited sacrifice of tooth substrate within the root canal of endodontically treated teeth.

Development of Bi- and Tri-Layer Nanofibrous Membranes Based on the Sulfated Polysaccharide Carrageenan for Periodontal Tissue Regeneration.

Periodontitis is a microbially-induced inflammation of the periodontium that is characterized by the destruction of the periodontal ligament (PDL) and alveolar bone and constitutes the principal cause of teeth loss in adults. Periodontal tissue regeneration can be achieved through guided tissue/bone regeneration (GTR/GBR) membranes that act as a physical barrier preventing epithelial infiltration and providing adequate time and space for PDL cells and osteoblasts to proliferate into the affected area. Electrospun nanofibrous scaffolds, simulating the natural architecture of the extracellular matrix (ECM), have attracted increasing attention in periodontal tissue engineering. Carrageenans are ideal candidates for the development of novel nanofibrous GTR/GBR membranes, since previous studies have highlighted the potential of carrageenans for bone regeneration by promoting the attachment and proliferation of osteoblasts. Herein, we report the development of bi- and tri-layer nanofibrous GTR/GBR membranes based on carrageenans and other biocompatible polymers for the regeneration of periodontal tissue. The fabricated membranes were morphologically characterized, and their thermal and mechanical properties were determined. Their periodontal tissue regeneration potential was investigated through the evaluation of cell attachment, biocompatibility, and osteogenic differentiation of human PDL cells seeded on the prepared membranes.

In vitro evaluation of a silane containing self-adhesive resin luting agent.

OBJECTIVES: To investigate the setting characteristics, wettability and bonding capacity with a lithium disilicate ceramic of a silane containing self-adhesive resin luting agent (Panavia SA Universal-PU). METHODS: The degree of conversion (DC %) and extent of acid neutralization (SY %) of PU were measured on dual- (DC) and self-cured (SC) specimens after 10, 30 and 60 min storage by ATR-FTIR spectroscopy, whereas the presence of silanols was traced by curve-fitting the 60 min spectra, using the silane-free analog (Panavia SA Plus-PS) as a control. The role of a dedicated adhesive (Clearfil Universal Bond Quick-CU) in assisting the early DC % in PU-SC was investigated on 10 min-stored specimens. The water contact angles on polished and HF acid-etched lithium disilicate surfaces (IPS e.max Press), were assessed before and after silanization by unset PU or a silane primer (Ultradent Silane-SL). Finally, the shear strength of PU-DC specimens bonded to the acid-etched ceramic surfaces was determined before and after SL treatment. RESULTS: The DC % was higher in DC than SC (PU, PS; all time intervals), in PU-SC than PS-SC (30, 60 min) and in the CU assisted PU-SC group. The SY % was lower in DC than SC (PU, PS) and higher in PS-SC than PU-SC groups. Silanols were found only in unset PU and PU-DC groups. SL treatment provided higher water contact angles on polished and acid-etched ceramic surfaces and higher shear bond strength on acid-etched ceramic surfaces than PU (p < 0.05 for all comparisons). SIGNIFICANCE: Although the degree of conversion of the silane containing luting agent was improved in the self-curing mode, especially in the adhesive assisted group, it was still inferior to light-curing. Acid-neutralization and presence of silanols were affected by the setting modes. The use of a silane primer enhanced the hydrophobicity and bond strength of the silane containing luting agent with the etched ceramic substrate.

Strength of implant-supported lithium disilicate and polymer-infiltrated ceramic network restorations after thermomechanical aging.

AIM: To evaluate the fracture load and type of failure of two different monolithic restorative materials bonded to standardized titanium bases and fabricated by two different procedures regarding the bonding interface. MATERIALS AND METHODS: All screw-retained implant crown specimens (n = 40), subjected to fatigue by thermomechanical loading, differed in the restorative material (lithium disilicate [LDS] or polymer-infiltrated ceramic network [PICN], referred to as 'hybrid ceramic' [HYC]) and the interface type between the restorative material and the titanium base abutment (prefabricated ex-factory or produced during a CAM-milling procedure). This resulted in the following groups (n = 10/group): 1) LDS-M: lithium disilicate crown with a CAM-milled interface; 2) LDS-P: lithium disilicate crown with a prefabricated interface; 3) HYC-M: PICN crown with a CAM-milled interface; and 4) HYC-P: PICN crown with a prefabricated interface. Aged specimens underwent static fracture load testing. The load (N) at which the initial crack occurred was denoted as Finitial, and the maximal load (N) at which the restorations fractured as Fmax. All specimens were examined under a stereomicroscope to determine the failure mode. RESULTS: The median Finitial values were 180 N for LDS-M, 343 N for LDS-P, 340 N for HYC-M, and 190 N for HYC-P. The median Fmax values were 1822 N for LDS-M, 2039 N for LDS-P, 1454 N for HYC-M, and 1581 N for HYC-P. The intergroup differences were significant for Finitial (KW: P = 0.0042) and for Fmax (KW: P = 0.0010). The failure types also showed differences between the restorative groups. CONCLUSIONS: The choice of restorative material had a stronger influence on the fracture load than the abutment interface workflow. Lithium disilicate showed the highest load for initial crack appearance (Finitial) and for complete fracture of the restoration (Fmax).

Leaching from a 3D-printed aligner resin.

AIM: To quantitatively assess the degree of conversion and the water-leaching targeted compound from 3D-printed aligners. MATERIALS AND METHODS: 3D-printed aligners were made of photopolymerized resin (Tera Harz TC85A). The molecular structure and degree of conversion of the set resin were investigated by ATR-FTIR spectroscopy (n = 5). The aligners (n = 10) were immersed in double distilled water for 1 week at 37°C and the eluents were analysed using liquid chromatography/mass spectrometry methods (LC-ESI-MS/MS for urethane dimethacrylate [UDMA] and LC-APCI-MS/MS for bispenol-A [BPA]). RESULTS: The resin was composed of aliphatic vinyl ester-urethane monomers, with acrylate and/or methacrylate functionalization. The degree of conversion was estimated as to 83%. There was no detection of BPA in any of the assessed samples (0.25 µg/l). Quantifiable amounts of UDMA were detected in all the exposed samples, ranging from 29 to 96 µg/l. CONCLUSIONS: Although efficiently polymerized and BPA free, the great variability in the amount of UDMA monomer leached from the examined samples may raise concerns on potential health hazards after repeated intraoral exposure, which is indicated for this class of materials.

The effect of cooling procedures on monomer elution from heat-cured polymethyl methacrylate denture base materials.

OBJECTIVE: To evaluate the amount of methyl methacrylate (MMA) released in water from heat-cured polymethyl methacrylate (PMMA) denture base materials subjected to different cooling procedures. METHODOLOGY: Disk-shaped specimens (Ø:17 mm, h:2 mm) were fabricated from Paladon 65 (PA), ProBase Hot (PB), Stellon QC-20 (QC) and Vertex Rapid Simplified (VE) denture materials using five different cooling procedures (n=3/procedure): A) Bench-cooling for 10 min and then under running water for 15 min; B) Cooling in water-bath until room temperature; C) Cooling under running water for 15 min; D) Bench-cooling, and E) Bench-cooling for 30 min and under running water for 15 min. A, B, D, E procedures were proposed by the manufacturers, while the C was selected as the fastest one. Control specimens (n=3/material) were fabricated using a long polymerization cycle and bench-cooling. After deflasking, the specimens were ground, polished and stored in individual containers with 10 ml of distilled water for seven days (37oC). The amount of water-eluted MMA was measured per container using isocratic ultra-fast liquid chromatography (UFLC). Data were analyzed using Student's and Welch's t-test (α=0.05). RESULTS: MMA values below the lower quantification limit (LoQ=5.9 ppm) were registered in B, C, E (PA); E (PB) and B, D, E (QC) procedures, whereas values below the detection limit (LoD=1.96 ppm) were registered in A, D (PA); A, B, C, D (PB); C, D, E (VE) and in all specimens of the control group. A, B (VE) and A, C (QC) procedures yielded values ranging from 6.4 to 13.2 ppm with insignificant differences in material and procedure factors (p>0.05). CONCLUSIONS: The cooling procedures may affect the monomer elution from denture base materials. The Ε procedure may be considered a universal cooling procedure compared to the ones proposed by the manufacturers, with the lowest residual monomer elution in water.

In-house 3D-printed aligners: effect of in vivo ageing on mechanical properties.

OBJECTIVE: To investigate alterations in the mechanical properties of in-house three-dimensional (3D) printed orthodontic aligners after intraoral ageing. MATERIALS AND METHODS: Sixteen 3D-printed aligners (TC-85DAC resin, Graphy, Seoul, Korea) were used for the purpose of the study, which were divided into 10 control (not used) aligners and 6 materials retrieved from 4 patients after 1-week service (retrieved group). Samples from the control group were analysed by attenuated total reflectance-Fourier-transform infrared (ATR-FTIR) spectroscopy. Samples from control/retrieved groups were embedded resin and subjected to instrumented indentation testing (IIT) to record force-indentation depth curves, calculating the following (as per ISO 14577-1, 2002 standard): Martens hardness (HM), indentation modulus (EIT), and elastic index (ηIT), and the indentation relaxation index (RIT). Differences between control and retrieved 3D-printed aligners were checked with Mann-Whitney/t-tests at an alpha = 5%. RESULTS: ATR-FTIR analysis showed that aligners were made of a vinyl ester-urethane material. The results of the IIT testing were: HM (control: median 91.5 N/mm2, interquartile range [IQR] 88.0-93.0/as-retrieved: median 90.5 N/mm2, IQR 89.0-93.0); EIT (control, mean 2616.3 MPa, standard deviation [SD] 107.0 MPa/retrieved, mean 2673.2 MPa, SD 149.4 MPa); ηIT (control: median 28.6%, IQR 28.2-30.9%/as-retrieved: median 29.0%, IQR 28.7-29.2%); and RIT (control: median 45.5%, IQR 43.0-47.0%/as-retrieved: median 45.1%, IQR 45.0-45.3%). No differences between as-retrieved and control aligners were found for any of the mechanical properties tested (P > 0.05 in all instances). CONCLUSION: The mechanical properties of the in-house 3D-printed aligners tested were not affected after 1 week in service period.

The effect of cooling procedures on monomer elution from heat-cured polymethyl methacrylate denture base materials

Abstract Objective To evaluate the amount of methyl methacrylate (MMA) released in water from heat-cured polymethyl methacrylate (PMMA) denture base materials subjected to different cooling procedures. Methodology Disk-shaped specimens (Ø:17 mm, h:2 mm) were fabricated from Paladon 65 (PA), ProBase Hot (PB), Stellon QC-20 (QC) and Vertex Rapid Simplified (VE) denture materials using five different cooling procedures (n=3/procedure): A) Bench-cooling for 10 min and then under running water for 15 min; B) Cooling in water-bath until room temperature; C) Cooling under running water for 15 min; D) Bench-cooling, and E) Bench-cooling for 30 min and under running water for 15 min. A, B, D, E procedures were proposed by the manufacturers, while the C was selected as the fastest one. Control specimens (n=3/material) were fabricated using a long polymerization cycle and bench-cooling. After deflasking, the specimens were ground, polished and stored in individual containers with 10 ml of distilled water for seven days (37oC). The amount of water-eluted MMA was measured per container using isocratic ultra-fast liquid chromatography (UFLC). Data were analyzed using Student's and Welch's t-test (α=0.05). Results MMA values below the lower quantification limit (LoQ=5.9 ppm) were registered in B, C, E (PA); E (PB) and B, D, E (QC) procedures, whereas values below the detection limit (LoD=1.96 ppm) were registered in A, D (PA); A, B, C, D (PB); C, D, E (VE) and in all specimens of the control group. A, B (VE) and A, C (QC) procedures yielded values ranging from 6.4 to 13.2 ppm with insignificant differences in material and procedure factors (p>0.05). Conclusions The cooling procedures may affect the monomer elution from denture base materials. The Ε procedure may be considered a universal cooling procedure compared to the ones proposed by the manufacturers, with the lowest residual monomer elution in water.

The Effect of Touch-Cure Polymerization on the Conversion and Hardness of Core Build-Up Resin Composites: A Laboratory Study.

To improve the self-curing capacity and interfacial strength with dentine of dual-cured composite materials, touch-cure activators have been introduced. The aim of the study was to evaluate the effect of these activators on the hardness and conversion of dual-cured resin composite core build-up restoratives. The materials tested were Clearfil DC Core Plus (CF) and Gradia Core (GC) with the corresponding adhesives Clearfil S3 Bond Plus (for CF) and G-Premio Bond/G-Premio DCA activator (for GC). Disk-shaped specimens (n = 6/group) were prepared for the following groups: dual-cured, self-cured and self-cured in contact with the adhesive activators at the bottom surface. After a 3-week storage period (dark/dry/37 °C) the Martens hardness (HM) and degree of conversion (DC%) were determined for the previously mentioned groups and the top surfaces of groups in contact with the adhesives. A statistical analysis was performed by a one-way ANOVA and Holm-Sidak test per material and a Pearson's correlation analysis (HM vs. DC%) at an α = 0.05. The self-cured specimens resulted in significantly lower HM and DC% values from the dual-cured group, as expected. However, in the presence of the adhesives with touch-cure activators, the conversion of the self-cured groups showed insignificant differences in HM and DC% from the dual-cured in both composite materials. The improvements on the bottom composite surfaces in contact with the adhesives did not extend to the entire specimen length. Nevertheless, improved interfacial curing may improve interfacial durability.

Effect of Water Storage on Hardness and Interfacial Strength of Resin Composite Luting Agents Bonded to Surface-Treated Monolithic Zirconia.

BACKGROUND: Durable bonding between resin composite luting agents (CLA) and zirconia is still a matter of controversy. The purpose of this study was to evaluate the effect of water storage on hardness and interfacial strength of three CLA, a non-adhesive (Multilink Automix/ML), an adhesive (Panavia F 2.0/PF) and a self-adhesive (PermaCem 2.0/PC), bonded to polished (CL) and grit-blasted (AL: 50 µm alumina, SJ: Sil-Jet + Monobond Plus silane) monolithic zirconia surfaces. METHODS: CLA specimens (n = 5/cement, condition) were prepared, stored under dry conditions or immersed in water, and Vickers hardness (VH) measurements were obtained at 1 h, 24 h, 1 week and 3 weeks intervals. Optical profilometry was used to determine the roughness parameters (Sa, Sz, Sdr, Sci) of zirconia surfaces (n = 5/treatment). A shear strength test (SBS, n = 10 × 2/cement) was performed to assess the strength and fractography of the cements bonded to zirconia after isothermal water storage and thermal-cycling (TC). RESULTS: PF demonstrated significantly lower VHN after water storage at all time intervals, PC at 1 w, 3 w and ML at 3 w. SJ and AL showed significantly higher values from CL in all roughness parameters. Weibull analysis revealed the following significance in σο ranking within the same material: AL, SJ, ALTC > SJTC, CL > CLTC (PF); SJ, SJTC, AL, ALTC > CL, CLTC (PC) and SJ, SJTC > AL > ALTC > CL, CLTC (ML). Within the same surface treatment subgroups, the significance in σo ranking was PC, ML > PF (before/after TC) for SJ; PC > PF > ML (before TC), PC, PF > ML (after TC) for AL, and PC > PF > ML (before/after TC) for CL. For the m ranking, the only significant difference within each material group was found in PC (AL > ALTC) and for the same surface treatment in AL (PC > ML). CONCLUSION: There are significant differences in the water plasticization susceptibility of the CLA tested; the materials with adhesive monomers were the most affected. Tribo-chemical silica coating combined with a silane coupling agent was the most efficient bonding treatment for the non-adhesive and the self-adhesive materials. The adhesive CLA performed better on alumina-blasted than on tribo-chemically coated surfaces.

Fracture toughness of dental incremental composite-composite interfaces at elevated temperatures.

The aim of the present laboratory study was to mechanically characterize the interface between two dental resin-based composite (RBC) increments, and to investigate if elevated temperatures have an influence on the quality of the interface mimicking clinical filling procedure. Four RBCs (CLEARFIL MAJESTY™ Posterior, Kuraray (CMP)/Filtek™ Supreme XTE, 3M (FSX)/Grandio®SO, VOCO (GSO)/VisCalor® bulk, VOCO (VCB)) were tested with a fracture toughness test using Chevron notched beams (KI,CNB) at 23, 37 and 54 °C. KI,CNB specimens (3 × 4x25mm) with a V-shaped notch at the incremental interface were loaded until failure in a 4-point bending set-up. Failure modes were characterized using light microscopy, microstructural interface was analyzed using SEM. Statistical analysis was performed using Kolmogorov-Smirnoff test, two-way ANOVA and Tukey Post-Hoc test (p = 0.05). Mean KI,CNB ranged between 0.73 ±0.14 MPam0.5 (VCB, 23 °C) and 1.11 ± 0.11 MPam0.5 (FSX, 23 °C). The tested conventional highly filled RBCs presented fracture toughness at the incremental interface comparable to the cohesive strength of the bulk materials. VCB showed reduced interfacial fracture toughness at 23 and 37 °C, but performed well at elevated temperature of 54 °C.

The effect of universal adhesives on dentine collagen.

OBJECTIVES: The purpose of the study was to evaluate the integrity of dentine type I collagen after self-etching (SE) treatments with strong and mild universal adhesives. METHODS: Coronal dentine specimens (n=10/product) were imaged by optical microscopy and analyzed by ATR-FTIR spectroscopy before and after treatment with 32% phosphoric acid gel (PA-negative control), 17% neutral EDTA (ED-positive control) conditioners and Adhese Universal (AD), Clearfil Universal Bond Quick (CQ), G-Premio Bond (GP), Prelude One (PR) and Scotchbond Universal (SB) adhesives. From the spectroscopic analysis the following parameters were determined: a) Extent of dentine demineralization (DM%) and b) percentage area of the Amide I curve-fitted components of ß-turns, 310-helix/ß-turns, α-helix, random coils, ß-sheets and collagen maturation (R) index. Statistical analysis was performed by one-way ANOVA (DM%), paired t-test/Wilcoxon test (Amide I components) and Spearman correlation coefficient (DM% vs Amide I components) at an a=0.05 level. RESULTS: PA, ED and GP removed the smear-layer and opened tubule orifices, whereas all other treatments removed only the intratubular smear-layer fraction. The ranking of the statistically significant differences in DM% was PA>GP>ED>AD, SB, CQ, PR, with AD being significantly different from PR. Regarding the Amide I components, PA demonstrated a significant reduction in ß-turns, α-helices and an increase in ß-sheets, GP a reduction in ß-turns, AD an increase in ß-turns and random coils, and CQ an increase in ß-turns. PR, SB and ED showed insignificant differences in all the Amide I components. Significant correlations were found between DM%-random coils and DM%-R. SIGNIFICANCE: The universal adhesives used in the SE mode induced none to minimal changes in dentine collagen structure, without evidence of the destabilization pattern observed after conventional phosphoric acid treatments.

The Effect of Prenatal Food Restriction on Brain Proteome in Appropriately Grown and Growth Restricted Male Wistar Rats.

BACKGROUND: Fetal growth restriction (FGR) has been associated with a higher risk of developing adverse perinatal outcomes and distinct neurodevelopmental and neurobehavioral disorders. The aim of the present study was to investigate the impact of prenatal food restriction on the brain proteome in both FGR and appropriately grown rats and to identify potential pathways connecting maternal malnutrition with altered brain development. METHODS: Ten time-dated pregnant Wistar rats were housed individually at their 12th day of gestation. On the 15th day of gestation, the rats were randomly divided into two groups, namely the food restricted one (n = 6) and the control group (n = 4). From days 15 to 21 the control group had unlimited access to food and the food restricted group was given half the amount of food that was on average consumed by the control group, based on measurements taken place the day before. On the 21st day of gestation, all rats delivered spontaneously and after birth all newborn pups of the food restricted group were weighed and matched as appropriately grown (non-FGR) or growth restricted (FGR) and brain tissues were immediately collected. A multiplex experiment was performed analyzing brain tissues from 4 FGR, 4 non-FGR, and 3 control male offspring. Differentially expressed proteins (DEPs) were subjected to bioinformatics analysis in order to identify over-represented processes. RESULTS: Proteomic analysis resulted in the profiling of 3,964 proteins. Gene ontology analysis of the common DEPs using DAVID (https://david.ncifcrf.gov/) showed significant enrichment for terms related to cellular morphology, learning, memory and positive regulation of NF-kappaB signaling. Ingenuity Pathway Analysis showed significant induction of inflammation in FGR pups, whereas significant induction of cell migration and cell spreading were observed in non-FGR pups. CONCLUSION: This study demonstrated that in both FGR and non-FGR neonates, a range of adaptive neurodevelopmental processes takes place, which may result in altered cellular morphology, chronic stress, poor memory and learning outcomes. Furthermore, this study highlighted that not only FGR, but also appropriately grown pups, which have been exposed to prenatal food deprivation may be at increased risk for impaired cognitive and developmental outcomes.

Viscosity and stickiness of dental resin composites at elevated temperatures.

OBJECTIVE: To investigate the influence of pre-heating different classes of dental resin composites on viscosity and stickiness at five different temperatures. METHODS: Six flowable, five conventional packable, and one thermo-viscous bulk-fill resin composites were heated up to 54°C in a plate-plate rheometer to determine their complex viscosity. Normal force measurements were carried out for the six packable materials to determine the unplugging force and unplugging work (stickiness) over the same temperature range. Data were analyzed using Kolmogorov-Smirnoff test, one-way ANOVA and Tukey Post Hoc test with α=0.05 as level of significance. RESULTS: At 23°C packable composites showed viscosity between 6.75 and 19.14kPas, while flowable composites presented significantly lower viscosities between 1.31 and 2.20kPas. Pre-heating led to a drop of 30-82% in the viscosity of packable materials. The thermo-viscous material dropped to the level of flowables at 45 and 54°C thus behaving as a packable composite at room temperature with flowable-like viscosity at higher temperatures. No statistically significant differences for viscosity were observed among flowable composites at any temperature. The unplugging force decreased for packable composites, while their unplugging work generally increased at elevated temperature. At 23°C unplugging force was measured between 7.50 and 19.18N, while pre-heating up to 54°C led to values between 2.9 and 6.2N. Regarding unplugging work at 23°C the calculated values were between 3.0 and 8.9×10-3J and at 54°C between 8.8 and 13.0×10-3J. SIGNIFICANCE: Pre-heating significantly reduced viscosity of highly viscous resin composites, while no influence was shown for flowable composites. In general stickiness, measured as unplugging work, increased at elevated temperatures. The thermo-viscous material showed low viscosity comparable to flowable composites at 45 and 54°C, yet its stickiness did not increase significantly compared to the values at 23°C.

Effect of Thermomechanical Loading on the Cementation Interface of Implant-Supported CAD/CAM Crowns Luted to Titanium Abutments.

PURPOSE: To investigate the effect of aging on the morphology of the interface between monolithic implant crowns and standardized titanium base abutments. MATERIALS AND METHODS: Four groups of hybrid abutment crowns differing in restorative material (lithium disilicate [LD] or polymer-infiltrated ceramic network [PICN]) and in fabrication procedure of the interfacial zone for luting to a titanium abutment (milled during CAD/ CAM procedure [M] or prefabricated [P]) were formed: LDS-M, LDS-P, PICN-M, and PICN-P (n = 10 each). The morphology of the crown-abutment interface was examined before and after artificial aging using scanning electron microscopy. The total gap length per specimen was measured at both time points, and intergroup (Kruskal-Wallis [KW]) plus pairwise (Wilcoxon Mann-Whitney [WMW]) comparisons were performed (α = .05). RESULTS: Before aging, statistically significant differences in gap length were identified among groups (KW: P = .0369) for PICN-P > LDS-P (WMW: P = .0496) and LDS-M > LDS-P (WMW: P = .0060). The effect of aging among the groups, expressed as an increment of total gap length, was 50% in LDS-M, 30% in LDS-P, 20% in PICN-M, and 30% in PICN-P. After aging, the statistically significant differences in gap length identified among groups (KW: P = .0048) were for PICN-P > LDS-P (WMW: P = .0134); LDS-M > PICN-M (WMW: P = .0204); PICN-P > PICN-M (WMW: P = .0486); and LDS-M > LDS-P (P = .0022). However, comparison of the difference in gap length from before to after aging among the groups was not statistically significant (KW: P = .3549). CONCLUSION: The cementation interfaces of CAD/CAM crowns on standardized titanium base abutments demonstrated a high percentage of gaps before and after thermomechanical loading. The composition of the restorative material and the nature of the interface influenced the interfacial gap dimension.