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This study aimed to assess the key physico-mechanical properties and bonding performance of orthodontic adhesives with graphene addition for bonding a fixed retainer. Transbond LR (3M) and Transbond LV (3M) with no graphene were set as the control groups. Graphene was added into LR and LV at concentrations of 0.01 wt%, 0.05 wt% and 0.1 wt%. The stickiness of the uncured samples (n = 5) and real-time degree of conversion (DC) of the samples (n = 3) were measured over a 24-h period using Fourier-transform infrared spectroscopy. The hardness and other mechanical parameters, including the Martens hardness (HM), indentation modulus (EIT), elastic index (ηIT) and creep (CIT), were measured (n = 5). To measure the shear bond strength (SBS), adhesive composites were applied using a mold to bond the retainer wire to the lingual surfaces of bovine incisors (n = 10). Fracture modes subsequent to the SBS test were examined under light microscopy. Statistical analysis was conducted using ANOVA and Tukey tests (α = 0.05). In the LR groups, the LR + 0.01 showed the highest SBS (12.6 ± 2.0 MPa) and HM (539.4 ± 17.9 N/mm2), while the LV + 0.05 (7.7 ± 1.1 MPa) had the highest SBS and the LV + 0.1 had the highest HM (312.4 ± 17.8 N/mm2) among the LV groups. The most frequent failure mode observed was adhesive fracture followed by mixed fracture. No statistical difference was found between the graphene-added groups and the control groups in terms of the EIT, ηIT and CIT, except that the CIT was significantly lower in the LR + 0.01 than in the control group. Graphene addition had no significant adverse effect on the stickiness and DC of both LR and LV.
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PURPOSE: This study examined the effect of whitening and abrasive regular dentifrices on the surface characteristics and stain susceptibility of polymer-based CAD-CAM blocks subjected to artificial toothbrushing abrasion (TB). MATERIALS AND METHODS: Two resin composite blocks [CeraSmart (CS) and Grandio Blocs (GB)], one polymer-infiltrated ceramic [Vita Enamic (VE)], and one direct resin composite [GrandioSO (RC)] were used to produce 60 specimens. The baseline mass, gloss, roughness, Vickers hardness (Hv), and color were measured after 7 days of water storage. The specimens were then separated into three TB treatment groups (n = 5): water control (C), regular daily dentifrice (R), and whitening dentifrice (W). Measurements were repeated post-TB (20,000 cycles). All specimens were immersed in coffee, and the CIE ΔE00 was measured after 1, 7, and 14 days. Two-way, one-way ANOVA, and Tukey's post hoc tests were performed to determine any significant differences between the materials and TB groups. To determine the stain resistance, repeated measures of ANOVA, one-way ANOVA, and Tukey's post hoc tests were used (α = 0.05). RESULTS: The R and W mass changes were minimal (-3.77 to 3.16 g%). W reduced the gloss of all the materials by 12.6%-65%. All materials in W were slightly rougher (Ra, 0.107-0.144 µm) than those in R (Ra, 0.049-0.072 µm). The ΔE00 ranged from 0.6 to 1.6 in W and 0.4 to 1.4 in R. VE was the hardest material at baseline (Hv = 362), whereas brushing and staining lowered Hv in all TB groups (282.8-300.6). After brushing in W, VE, and RC were more susceptible to coffee stains than were CS and GB. CONCLUSIONS: The whitening dentifrice roughened CAD-CAM specimens, reducing gloss, yet lightened some materials. Polymer-infiltrated ceramic and direct resin composite specimens brushed with abrasive regular or whitening dentifrice resulted in more intense staining than the CAD-CAM resin composites.
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Three-dimensional (3D) printing is becoming more prevalent in the dental sector due to its potential to save time for dental practitioners, streamline fabrication processes, enhance precision and consistency in fabricating prosthetic models, and offer cost-effective solutions. However, the effect of aging in artificial saliva of this type of material has not been explored. To assess the physical and mechanical properties of the two types of 3D-printed materials before and after being subjected to artificial saliva, a total of 219 acrylic resin specimens were produced. These specimens were made with two types of 3D-printed materials, namely, NextDent (ND) and Formlabs (FLs), and a Schottlander heat-cured (HC) resin material that was used as a control. Water sorption and solubility specimens (n = 5) were tested after three months of storage in artificial saliva. Moreover, the Vickers hardness, Martens hardness, flexural strength/modulus, and impact strength were evaluated both under dry conditions and after three months of storage in artificial saliva. The degree of conversion (DC), elemental analysis, and filler content were also investigated. The ANOVA showed that 3D-printed resins had significantly greater sorption than the control group (p < 0.05). However, the flexural strength values of the 3D-printed materials were significantly greater (p < 0.05) than those of the heat-cured material. The DC of the 3D-printed resins was lower than that of the control group, but the difference was not significant (p > 0.05). The 3D-printed materials contained significantly more filler than the control (p < 0.05). Moreover, the artificial saliva had a significant effect on the Vickers hardness for all tested groups and on the Martens hardness for the control group only (p < 0.05). Compared with conventional heat-cured materials, 3D-printed denture base materials demonstrated relatively poorer performance in terms of sorption, solubility, and DC but exhibited either comparable or superior mechanical properties. The aging process also influenced the Vickers and Martens' hardness. The strength of the 3D-printed materials was in compliance with ISO recommendations, and the materials could be used alongside conventional heat-cured materials.
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BACKGROUND: Three-dimensional (3D) printing is increasingly used to fabricate dental restorations due to its enhanced precision, consistency and time and cost-saving advantages. The properties of 3D-printed resin materials can be influenced by the chosen printing orientation which can impact the mechanical characteristics of the final products. PURPOSE: The objective of this study was to evaluate the influence of printing orientation and artificial ageing on the Martens hardness (HM) and indentation modulus (EIT) of 3D-printed definitive and temporary dental restorative resins. METHODS: Disk specimens (20 mm diameter × 2 mm height) were additively manufactured in three printing orientations (0°, 45°, 90°) using five 3D-printable resins: VarseoSmile Crownplus (VCP), Crowntec (CT), Nextdent C&B MFH (ND), Dima C&B temp (DT), and GC temp print (GC). The specimens were printed using a DLP 3D-printer (ASIGA MAX UV), while LavaTM Ultimate (LU) and Telio CAD (TC) served as milled control materials. Martens hardness (HM) and indentation modulus (EIT) were tested both before and after storage in distilled water and artificial saliva for 1, 30, and 90 days at 37 °C. RESULTS: 90° printed specimens exhibited higher HM than the other orientations at certain time points, but no significant differences were observed in HM and EIT between orientations for all 3D-printed materials after 90 days of ageing in both aging media. LU milled control material exhibited the highest HM and EIT among the tested materials, while TC, the other milled control, showed similar values to the 3D printed resins. CT and VCP (definitive resins) and ND displayed higher Martens parameters compared to DT and GC (temporary resins). The hardness of the 3D-printed materials was significantly impacted by artificial ageing compared to the controls, with ND having the least hardness reduction percentage amongst all 3D-printed materials. The hardness reduction percentage in distilled water and artificial saliva was similar for all materials except for TC, where higher reduction was noted in artificial saliva. SIGNIFICANCE: The used 3D printed resins cannot yet be considered viable alternatives to milled materials intended for definitive restorations but are preferable for use as temporary restorations.
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Dureza , Teste de Materiais , Impressão Tridimensional , Módulo de Elasticidade , Materiais Dentários/química , Propriedades de Superfície , Resinas Compostas/química , Fatores de Tempo , Restauração Dentária Permanente , Resinas Sintéticas/químicaRESUMO
PURPOSE: Bioceramic coatings have been shown to promote bone repair, which aids in the early integration of implants. This study aimed to evaluate the influence of air abrasion with a bioceramic abrasive on the surface characteristics of different implant materials and surfaces. The dissolution of the applied treatment from the surfaces over 3 weeks was also assessed. MATERIALS AND METHODS: Discs of three alloys used for dental implants were studied and compared: two types of commercially pure titanium (CpTi)/ (CpTi SLActive) and titanium-zirconia (TiZr). The tested surfaces were: CpTi control (CpC), sandblasted (SB), sandblasted and acid-etched (SBE), and CpTi SLActive®, (TiZr) Roxolid®. Three discs from each group underwent air abrasion with apatite bioceramic powders, 95% hydroxyapatite (HA)/5% calcium oxide (CaO), and 90% hydroxyapatite (HA)/10% calcium oxide (CaO). The treated discs were surface characterized by optical profilometry to obtain surface roughness, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS) to compare element weight percentages of titanium, calcium, and phosphate. Dissolution was assessed using inductively coupled plasma optic emission spectrometry (ICP-OES). RESULTS: Bioceramic powders were deposited on all tested surfaces leading to changes in surface characteristics. The only statistically significant differences between the material groups for surface roughness were found with 95% HA/5% CaO powder in the Sp and Rp parameters (p = 0.03 and 0.04, respectively). There were no significant differences in the Ca and P wt% between all groups and powders 95% HA/5% CaO and 90% HA/10% CaO (p = 0.14, 0.18, and p = 0.15, 0.12, respectively). A non-uniform dispersion of the treatment on the surface layer was visible on all treated surfaces. The bioceramic powder continued to dissolute from the tested surfaces for 3 weeks. CONCLUSION: Bioceramic abrasion modifies implant surface characteristics, although the change in surface characteristics resulting from such treatment was not influenced by the implant material or surface treatment. Air abrasion with hydroxyapatite and calcium oxide bioceramics leaves powder deposits on the treated implant surfaces that could potentially influence the healing of implants affected by peri-implantitis.
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STATEMENT OF PROBLEM: The influence of different thicknesses, translucencies, and fabrication methods on the spectrophotometric and topographical properties of zirconia-reinforced lithium silicate glass-ceramics (ZLSs) for dental restorations remains unclear. PURPOSE: The purpose of this in vitro study was to investigate the effect of thicknesses, translucencies, and fabrication methods on the color stability, translucency parameter, opalescence parameter, whiteness stability, transmitted irradiance, light transmittance, opacity, gloss, and roughness of ZLSs exposed to coffee staining and bleaching treatments. MATERIAL AND METHODS: Two pressable ZLSs (VITA AMBRIA, VA and Celtra Press, CP) and 2 machinable ZLSs (VITA Suprinity, VS and Celtra Duo, CD) were examined at high translucency (HT) and low translucency (LT) levels in 2 thicknesses (n=160). The specimens were evaluated at baseline, after coffee staining, and after bleaching. The color stability (ΔE2000), translucency parameter (TP), opalescence parameter (OP), whiteness index (WID), and whiteness stability (ΔWID) were measured with a spectrophotometer. Transmitted irradiance (It), light transmission (T), and opacity (O) were obtained from a light-polymerizing unit and a polymerization light collection device. Roughness stability (ΔSa%) was determined with an optical profilometer, and gloss stability (ΔGU%) was recorded with a gloss meter. Data of ΔCIE2000, ΔWID, ΔSa%, and ΔGU% were analyzed by 4-way ANOVA, and data of the TP, OP, WID, It, T, and O were analyzed by repeated 4-way ANOVA (α=.05). RESULTS: VS-HT exceeded the ΔCIE2000 acceptability threshold after coffee staining and bleaching protocols. Pressable ZLSs exhibited greater color stability than machinable ZLSs. The 1-mm-thick VA, CP, and CD materials exceeded the ΔWID perceptibility threshold after bleaching. The highest TP and OP was displayed by the 1-mm-thick CP after bleaching. ΔGU increased after water storage and decreased after coffee staining and bleaching. ΔSa% significantly increased after bleaching (P<.05). CONCLUSIONS: The color stability and other spectrophotometric properties of ZLSs depended on material thickness. The effects of ZLS fabrication methods and translucency levels on their measured properties were inconsistent. Subjecting 1-mm-thick ZLS materials to acidic media adversely impacted their stainability and surface texture.
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Café , Lítio , Zircônio , Silicatos , Coloração e Rotulagem , Cerâmica/uso terapêuticoRESUMO
STATEMENT OF PROBLEM: The influence of different firing protocols on the topographical, optical, and mechanical properties of fully crystallized computer-aided design and computer-aided manufacturing (CAD-CAM) lithium silicate-based glass-ceramics (LSCs) for dental restorations remains unclear. PURPOSE: The purpose of this in vitro study was to investigate the effect of different firing regimens on the surface roughness, gloss, Martens hardness, indentation modulus, biaxial flexural strength, and crystalline structure of fully crystallized CAD-CAM LSCs and the effect of their interposition on the irradiance of a light-polymerization unit. MATERIAL AND METHODS: Three fully crystallized CAD-CAM LSC blocks were evaluated (N=150): lithium disilicate (Initial LiSi Blocks; LS), zirconia-reinforced silicate (Celtra Duo; CD), and lithium aluminum disilicate (CEREC Tessera; CT). Specimens were allocated to 5 subgroups according to their firing protocol. LSC roughness (Sa) was measured with an optical profilometer, and gloss (GU) was detected with a gloss meter. Martens hardness (HM) and indentation modulus (EIT) data were obtained from a hardness testing machine. The irradiance of a light-polymerization unit and transmittance of LSCs were measured with an instrument (Managing Accurate Resin Curing-Light Collector; BlueLight analytics, Inc) subsequent to ceramic interposition. Crystalline phases were analyzed by X-ray diffraction, and biaxial flexural strength (σ) was determined by the ball-on-3-ball method in a universal testing machine followed by Weibull analysis to calculate characteristic strength (σ0) and Weibull modulus (m). Two-way ANOVA and Tukey HSD post hoc tests (α=.05) were used to analyze the data. RESULTS: Statistically significant differences were found among different treatment groups based on Sa, GU, HM, and EIT values (P<.001). Delivered irradiance was significantly reduced following CT (P<.01) and glazed LSC (P<.005) interposition. CD displayed highest biaxial flexural strength and reliability after 1 firing cycle (σ=568.2 MPa, m=16.8) CONCLUSIONS: The type of material and firing regimens had a significant effect on the topographical, optical, and mechanical properties of fully crystallized CAD-CAM LSCs. Glazing significantly reduced delivered irradiance, Martens hardness, and biaxial flexural strength.
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Cerâmica , Lítio , Reprodutibilidade dos Testes , Teste de Materiais , Propriedades de Superfície , Cerâmica/química , Porcelana Dentária/química , Silicatos , Desenho Assistido por ComputadorRESUMO
The objective of this study was to determine the effects on the colour of adding increasing concentrations of graphene to orthodontic fixed retainer adhesives and to evaluate changes in optical transmission during light curing and the resultant degree of conversion. Two different types of adhesives commonly used for fixed retainers were investigated: A packable composite (Transbond) and a flowable composite (Transbond Supreme). Graphene was added to the adhesives in three different concentrations (0.01, 0.05, and 0.1 wt%). Adhesives without graphene addition were set as control groups. A Minolta colourimeter was used to measure the colour and translucency parameters. Irradiance transmitted during curing was quantified using MARC Light Collector. Fourier-transform infrared spectroscopy was used to record degree of conversion. Data were statistically analysed with the Student's t-test and one-way ANOVA with Tukey's tests (α = 0.05). The findings showed that incorporating graphene darkened the adhesive colour significantly and reduced translucency. As the graphene concentration reached 0.1 wt%, samples became opaque; yet, no adverse effect on degree of conversion was observed. The addition of graphene reduces optical transmission of lingual retainer adhesives; the effect increases with graphene concentration.
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Bis-Fenol A-Glicidil Metacrilato , Colagem Dentária , Grafite , Cimentos Dentários , Cimentos de Resina/química , Teste de Materiais , Resinas Compostas/química , Adesivos/químicaRESUMO
PURPOSE: To develop a biocompatible denture base resin/TiO2 nanocomposite material with antifungal characteristics that is suitable for 3D-printing denture bases. MATERIALS AND METHODS: TiO2 nanoparticles (NPs) with a 0.10, 0.25, 0.50, and 0.75 weight percent (wt.%) were incorporated into a commercially available 3D-printed resin material. The resulting nanocomposite material was analyzed using Lactate dehydrogenase (LDH) and AlamarBlue (AB) assays for biocompatibility testing with human gingival fibroblasts (HGF). The composite material was also tested for its antifungal efficacy against Candida albicans. Fourier transform infrared (FTIR) and Energy Dispersive X-ray Spectroscopy (EDX) mapping were conducted to assess the surface coating and the dispersion of the NPs. RESULTS: LDH and AB assays confirmed the biocompatibility of the material showing cell proliferation at a rate of nearly 100% at day 10, with a cytotoxicity of less than 13% of the cells at day 10. The concentrations of 0.10, 0.25, and 0.50 wt.% caused a significant reduction (p < 0.05) in the number of candida cells attached to the surface of the specimens (p < 0.05), while 0.75 wt.% did not show any significant difference compared to the control (no TiO2 NPs) (p > 0.05). FTIR and EDX analysis confirmed the presence of TiO2 NPs within the nanocomposite material with a homogenous dispersion for 0.10 and 0.25 wt.% groups and an aggregation of the NPs within the material at higher concentrations. CONCLUSION: The addition of TiO2 NPs into 3D-printed denture base resin proved to have an antifungal effect against Candida albicans. The resultant nanocomposite material was a biocompatible material with HGFs and was successfully used for 3D printing.
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OBJECTIVES: To evaluate the physical and mechanical properties of three-dimensional (3D) printed denture base resin incorporating TiO2 nanoparticles (NPs), subjected to a physical ageing process. METHODS: Acrylic denture base samples were prepared by a Stereolithography (SLA) 3D printing technique reinforced with different concentrations (0.10, 0.25, 0.50, and 0.75) of silanated TiO2 NPs. The resulting nanocomposite materials were characterized in terms of degree of conversion (DC), and sorption/solubility flexural strength, impact strength, Vickers hardness and Martens hardness and compared with unmodified resin and conventional heat-cured (HC) material. The nanocomposites were reassessed after subjecting them to ageing in artificial saliva. A fractured surface was studied under a scanning electron microscope (SEM). RESULTS: The addition of TiO2 NPs into 3D-printed resin significantly improved flexural strength/modulus, impact strength, Vickers hardness, and DC, while also slightly enhancing Martens hardness compared to the unmodified resin. Sorption values did not show any improvements, while solubility was reduced significantly. The addition of 0.10 wt% NPs provided the highest performance amongst the other concentrations, and 0.75 wt% NPs showed the lowest. Although ageing degraded the materials' performance to a certain extent, the trends remained the same. SEM images showed a homogenous distribution of the NPs at lower concentrations (0.10 and 0.25 wt%) but revealed agglomeration of the NPs with the higher concentrations (0.50 and 0.75 wt%). SIGNIFICANCE: The outcomes of this study suggested that the incorporation of TiO2 NPs (0.10 wt%) into 3D-printed denture base material showed superior performance compared to the unmodified 3D-printed resin even after ageing in artificial saliva. The nanocomposite has the potential to extend service life of denture bases in future clinical use.
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Bases de Dentadura , Nanopartículas , Propriedades de Superfície , Saliva Artificial , Teste de Materiais , Impressão TridimensionalRESUMO
OBJECTIVE: To measure the flexural strength (FS) of bulk-fill resin composites and assess their long-term water absorption and solubility properties with and without the inclusion of short glass fibres. METHODS: One resin composite, everX Flow with fibres, and four commercially available bulk-fill composites without fibres, namely, PALFIQUE, Activa, SDR Plus, and Filtek Bulk Fill One, were tested. Six specimens (2 × 2 × 25 mm) were fabricated for each material and stored in water for 1 day and 30 days to measure the flexural strength using a three-point bending test. To evaluate water absorption and solubility, circular disks measuring 15 × 2 mm (n = 5) were immersed in water for 60 days, and their weights were recorded periodically. After 60 days, the specimens were dried for an additional 21 days to determine solubility. RESULTS: Flexural strength values ranged from 101.7 to 149.1 MPa. Significant distinctions were observed among the resin composites at the onset of the study (p < 0.05). The highest FS value was identified in everX Flow, while ACT exhibited the lowest (p < 0.05). However, the flexural strength values exhibited a significant decrease with increased storage time (p < 0.05), except for ACT, which demonstrated a noteworthy increase. Concerning water absorption and solubility, ACT displayed the highest absorption, while the range of solubility varied from -0.88 to 5.8 µg/mm3. ACT also had the highest solubility, whereas everX Flow exhibited negative solubility. SIGNIFICANCE: The addition of short fibres, along with potential differences in matrix composition, enhanced the flexural strength of everX Flow. However, the substantial reduction in flexural strength observed in everX Flow and SDR following exposure to water corroborates the manufacturers' recommendation to apply a conventional resin composite cap on these materials.
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OBJECTIVES: To investigate the effect of different surface treatments on optical, topographical and mechanical properties of CAD/CAM lithium silicate-based glass ceramics (LSC's) and their combined effect on the output of a light curing unit (LCU). METHODS: Four CAD/CAM LSC's were investigated: Lithium Disilicate (Emax CAD; EC), Zirconia-reinforced silicates (Vita Suprinity; VS and Celtra Duo;CD) and Lithium Aluminum Disilicate (CEREC Tessera; CT). Ceramic specimens (n = 240) were divided into six subgroups according to their surface treatment: (a) Control, (b) Hydrofluoric acid (HF) 5%, (c) HF 5% + Neutralizing agent (N), (d) HF 9%, (e) HF 9% +N and (f) Self-etching ceramic primer (SEP). Irradiance, power and radiant exposure of a LCU were measured with MARC-LC following ceramic specimen interposition. Direct light transmission (T%) and absorbance (Abs%) of the specimens were measured with UV-Vis spectrophotometry. Roughness (Sa, Sq) and wettability (θ°) were measured with optical profilometry and sessile drop profile analysis, respectively. Biaxial flexural strength (σ) of the ceramic specimens was measured by the ball-on-three-balls method and ceramic specimens were examined microscopically. Statistical analyses was performed by two-way ANOVA followed by post hoc multiple comparisons (α = 0.05). RESULTS: Acid neutralization decreased T% and increased Abs% in all LSC's and highest T% was exhibited with VS. Neutralized EC, VS and CD displayed higher Sa in HF9, while neutralized CT displayed higher Sa in HF5. Self-etch primer significantly reduced θ° (p < 0.001). σ was observed in the followed ascending order: HF9 +N < HF9 < HF5 +N < HF5 < SEP < Control for all LSC's. SIGNIFICANCE: Optical, topographical and mechanical properties of the CAD/CAM ceramic blocks were strongly dependent on the type of surface treatment. Results of neutralization post-etching indicate promising potential for future investigations.
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Cerâmica , Lítio , Propriedades de Superfície , Porcelana Dentária , Silicatos , Teste de Materiais , Desenho Assistido por ComputadorRESUMO
Purpose: Evaluate the effect of different mini-implant numbers on overdenture retention and evaluate attachment wear following one year of simulated placement/removal. Material and Methods. Nine models simulating atrophic mandibles held 27 mini dental implants in three groups of 2, 3, and 4 mini-implants. A total of 1080 simulated placement/removal cycles were carried out, and a digital force gauge was used to measure the overdenture dislodgment force. The means of the retention forces were analyzed using SPSS with one-way ANOVA and post hoc (p < 0.05). The inner diameter of attachment inserts was evaluated using a light microscope before and after testing. A paired t-test was used to compare the mean of inner ring diameters (p < 0.05). Results: The retention was significantly reduced regardless of the mini dental implant number, but the number affected overdenture retention. The placement of 4 mini dental implants provided higher retention and less reduction in retentiveness. However, no significant difference was found when 3 mini dental implants were compared to 2 mini dental implants (p = 0.21). Microscopic examination showed abrasion wear in all inserts following testing. However, the inserts of the 4 mini dental implants showed less wear than those used for 2 or 3 mini dental implants with p ≤ 0.001 and p ≤ 0.001, respectively. Conclusion: Mini dental implant overdenture retention force and attachment wear could improve by increasing the mini dental implants to 4. However, there was no difference in retention force or attachment wear when 2 or 3 mini dental implant overdentures were compared.
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Implantes Dentários , Revestimento de Dentadura , Retenção de Dentadura , Mandíbula/cirurgia , Microscopia , Análise do Estresse DentárioRESUMO
PURPOSE: Orthodontic treatment involving premolar extractions might improve the angulation of lower third molars, which are the teeth most often impacted. This study analyzes the impact of first/second lower premolar extraction during orthodontic therapy on the angulation of mandibular third molars. METHODS: A total of 120 patients treated non-extraction (nâ¯= 40), with extraction of first (nâ¯= 40), or second lower premolars (nâ¯= 40) were included. The mesiodistal angulation of lower third molars relative to the adjacent tooth and their developmental stage were evaluated from posttreatment orthopantomograms. Between-group differences were statistically evaluated at a significance level of 0.05. RESULTS: The orthopantomograms of 120 patients (51% female) with a median age of 15.2 years at the time of debonding were evaluated after a mean treatment duration time of 2.9 years. No difference (Pâ¯> 0.05) was seen between the average angulation of the lower third molars of the right (meanâ¯= 24.4°, standard deviation [SD] 13.6°) and the left side (meanâ¯= 23.6°, SD 14.1°). No differences in the angulation of the lower third molar were found between the non-extraction and extraction groups for the right (Pâ¯= 0.44) or the left side (Pâ¯= 0.22). Likewise, no differences were found when comparing the first and second premolars for the right (Pâ¯= 0.26) or the left side (Pâ¯= 0.10). Premolar extraction was associated with an advanced root development stage of the right third molar (odds ratio 7.1; 95% confidence interval 1.1-48.1; Pâ¯= 0.04), with no differences between extraction of the first or second premolar (Pâ¯= 0.10). CONCLUSION: Orthodontic treatment involving premolars extractions might be associated with a small acceleration in root development, but not with the angulation, of lower third molars.
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OBJECTIVES: This study investigated potential variations in polymerisation of light- and dual-cured (LC and DC) resin cements photoactivated through four CAD/CAM restorative materials as a function of substrate thickness. METHODS: Four CAD/CAM materials [two resin composites CeraSmart (CS) and Grandio Blocs (GB); a polymer infiltrated ceramic Vita Enamic (VE) and a feldspathic ceramic Vita Mark II (VM)], with five thicknesses (0.5, 1, 1.5, 2, and 2.5 mm) were prepared and their optical characteristics measured. 1 mm discs of LC and DC resin cement (Variolink® Esthetic, Ivoclar AG) were photoactivated through each specimen thickness. After 1 h post-cure, polymerisation efficiency was determined by degree of conversion (DC%) and Martens hardness (HM). Interactions between materials, thicknesses and properties were analysed by linear regressions, two-way ANOVA and one-way ANOVA followed by post hoc multiple comparisons (α = 0.05). RESULTS: All substrates of 0.5- and 1.0-mm thickness transmitted sufficiently high peak irradiances at around 455 nm: (It = 588-819 mW/cm2) with translucency parameter TP = 21.14 - 10.7; ranked: CS> GB = VM> VE. However, increasing the substrate thickness (1.5-2.5 mm) reduced energy delivery to the luting cements (4 - 2.8 J/cm2). Consequently, as their thicknesses increased beyond 1.5 mm, HM of the cement discs differed significantly between the substrates. But there were only slight reduction of DC% in LC cements and DC cement discs were not affected. SIGNIFICANCE: Photoactivating light-cured Ivocerin™ containing cement through feldspathic ceramics and polymer-infiltrated ceramics achieved greater early hardness results than dual-cured type, irrespective of substrate thickness (0.5 - 2.5 mm). However, only 0.5 and 1 mm-thick resin composites showed similar outcome (LC>DC). Therefore, for cases requiring early hardness development, appropriate cement selection for each substrate material is recommended.
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Estética Dentária , Cimentos de Resina , Desenho Assistido por Computador , Polimerização , Cimentos de Ionômeros de Vidro , Cimentos Dentários , Materiais Dentários , Cimentos Ósseos , PolímerosRESUMO
OBJECTIVES: To investigate the depth of cure (DoC), fracture toughness (KIC) and wear of ion releasing resin-based composite (RBC) restorative materials. METHODS: Two ion releasing RBCs, Activa (ACT) and Cention-N (CN) were compared to a conventional RBC (Z350) and a resin-modified glass ionomer cement (Fuji-II-LC). The DoC was measured in a 10-mm deep semi-circular metal mold with a 2-mm internal radius (n = 8). The molds were irradiated from one end for 20-s. The Knoop hardness (KH) was measured at 0.5-mm intervals from the surface after the specimens had been stored at 37 °C for 24-h. To measure the KIC, single-edge-notched specimens (n = 15/group) were prepared (25×5x2.5-mm) for a 3-point bending test and then stored for either 1 or 30-days in water at 37 °C. Disk-shaped specimens (n = 10) were subjected to 250,000-load cycles of 49-N using a chewing simulator against spherical steatite antagonists. DoC and wear data were analyzed by one-way ANOVA and Tukey post hoc tests (p ≤ 0.05). KIC data were analyzed by two-way ANOVA and one-way ANOVA, and the Tukey post hoc test (p ≤ 0.05). In addition, an independent t-test was used to determine if storage time had any effect (α = 0.05) on the KIC of each material. RESULTS: Maximum hardness value was the highest for Z350 and the lowest for ACT. The depth at which 80% of the maximum KH, was the highest for CN (9.2 mm) and the lowest for Z350 (2 mm). All tested materials met the manufacturers' claims for DoC. After 1-day, the highest KIC values were recorded for ACT and the lowest for Fuji-II-LC. Water storage (30-days) significantly reduced the KIC value for all materials except Fuji-II-LC. The highest wear rate values were recorded for CN followed by ACT. SIGNIFICANCE: All tested materials met their manufacturers' claims for DoC. Water storage for 30-days significantly reduced the fracture toughness for ACT and CN. Wear was significantly higher for ACT and CN.
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Resinas Compostas , Cimentos de Ionômeros de Vidro , Teste de Materiais , Materiais Dentários , Dureza , Água , Propriedades de SuperfícieRESUMO
OBJECTIVE: Three-dimensional (3D) printing is increasingly being utilised in the dental field because of its time-saving potential and cost effectiveness. It enables dental practitioners to eliminate several fabrication steps, achieve higher precision, and attain consistency in complex prosthetic models. The properties of 3D-printed resin materials can be affected by many factors, including the printing orientation (PO) and insufficient post-curing time (CT). This study aimed to investigate the effect of PO and CT on the mechanical and physical properties of a 3D-printed denture base resin (NextDent). METHODS: 3D-printed specimens were fabricated in 0°, 45°, and 90° POs, followed by three CTs (20, 30, and 50 min). The microhardness was tested using a Vickers hardness test, while the flexural property was evaluated using a three-point bending test. Sorption and solubility were measured after the specimens had been stored in an artificial saliva for 42 days, and the degree of conversion during polymerisation was analysed using Fourier Transform Infra-red (FTIR) spectroscopy. RESULTS: The flexural strength of the material significantly increased (p < 0.05) when the printing orientation was changed from 0° to 90°. A similar increase was observed in the hardness, degree of conversion, and water sorption results. In general, no significant difference (p > 0.05) in any of the tested properties was found when the post-curing times were increased from 20 to 50 min. SIGNIFICANCE: The highest physical and mechanical properties of the 3D-printed denture base resin can be obtained by printing vertically (90° angle to the platform base). The minimal post-curing time to achieve ideal results is 30 min, as further curing will have no significant effect on the properties of the material.
Assuntos
Materiais Dentários , Bases de Dentadura , Humanos , Materiais Dentários/química , Teste de Materiais , Odontólogos , Propriedades de Superfície , Papel Profissional , Polimetil Metacrilato/química , Impressão TridimensionalRESUMO
Purpose: To assess the surface roughness of two different light-cured resin-composites when opposed by monolithic zirconia after simulated mastication. Materials and Methods: Materials included a direct restorative nanohybrid (n = 10) and an indirect microhybrid (n = 10) resin-composite (Tetric EvoCeram and Sinfony, respectively). The antagonist material was 3 mol% yttria-stabilized tetragonal zirconia polycrystalline ceramic. Each material was subjected to in vitro chewing against zirconia using a chewing simulator for 250,000 cycles. A 3D profilometer was used to assess the surface roughness parameters of each resin-composite before and after the simulated chewing. Independent t-test and paired sample t-test were performed to compare roughness values for both materials and to compare baseline and after chewing simulation values (p = 0.05). Results: Sinfony showed significantly greater roughness values compared to Tetric EvoCeram (p ≤ 0.025) before and after simulated chewing, except for Sa and Sv parameters after simulated chewing where the difference between the two materials was insignificant (p = 0.06 and 0.89, respectively). Surface roughness increased for both materials after simulated chewing compared to baseline values, but the difference was insignificant (p ≥ 0.065). However, Sa (p = 0.04) and Sv (p = 0.012) for Tetric EvoCeram were significantly higher after compared to before chewing simulation. Conclusion: Tetric EvoCeram had a smoother surface than Sinfony before and after simulated chewing. Surface roughness for both materials was higher after simulated chewing compared to baseline values which represent surface damage that was significant for Tetric EvoCeram while Sinfony showed better resistance.
Assuntos
Mastigação , Zircônio , Teste de Materiais , Propriedades de SuperfícieRESUMO
Objective: We aimed to evaluate the failure resistance of different lengths of mini dental implants from the same manufacturer, and to assess their failure following overloading. Materials and Methods: According to the ISO 14801, 15 mini dental implants 2.4 mm in diameter, with lengths of 8.5 mm, 10 mm, or 13 mm, were subjected to compression loading until failure using a universal testing machine. The mean load-to-failure values for each length of the mini dental implants were calculated and analysed using SPSS®, via one-way ANOVA (p < 0.05). Results: The mean load to failure for mini dental implants was 329 N (SD 6.23), 326 N (SD 5.95), and 325 N (SD 6.99) for the 13 mm, 10 mm, and 8.5 mm implants, respectively. A comparison of means showed no significant difference between the groups (p = 0.70). The tested mini dental implants exhibited bending failure modes below the first thread. Conclusion: Under high compressive loading testing, there was no effect of the length on the failure of the mini dental implants following overloading. Moreover, all tested mini dental implants with different lengths showed the same failure mode and distortion location.
RESUMO
OBJECTIVES: This study investigated the effect of ageing in three food-simulating liquids (FSLs) on mechanical properties of three prosthodontic CAD/CAM polymer composites intended for construction of implant-supported frameworks. METHODS: Materials investigated were: (i) a carbon fibre-reinforced composite (CarboCAD 3D dream frame; CC), (ii) a glass fibre-reinforced composite (TRINIA; TR), and (iii) a reinforced PEEK (DentoKeep; PK). Filler contents and microstructural arrangements were determined by thermo-gravimetry and tomography (µ-CT), respectively. Flexural properties (FS and Ef) were measured by 3-point bending (3PB) of 1 mm and 2 mm thick beam specimens. Fracture toughness (KIC) was measured by single-edge-notched-bending (SENB). All measurements were made at baseline (dry) and after 1-day and 7-day storage at 37 â in either water, 70 % ethanol/water (70 % E/W) or methyl ethyl ketone (MEK). Failed specimens were examined microscopically. Statistical analyses included four-way ANOVA, two-way ANOVA and multiple Tukey comparison tests (α = 0.05). Multiple independent t-tests were performed regarding thickness effects on FS and Ef (α = 0.05). RESULTS: At baseline, the mechanical properties increased in the sequence: PK< TR< CC (p < 0.001). FS ranged from 192.9 to 501.5 MPa; Ef from 4.2 to 18.1 GPa; and KIC from 4.9-12.4 MPa.m0.5. Fibre-reinforced composites (CC and TR) were significantly stronger than PK. However, all properties of CC and TR reduced after 1 d storage in 70 % E/W and MEK with FS ranging from 58.6 to 408 MPa; Ef from 1 to 15.4 GPa; KIC from 6.87 to 10.17 MPa.m0.5. Greater reductions occurred after 7 d storage. MEK was more detrimental than 70 % E/W and water on fibre-reinforced composites. SIGNIFICANCE: Mechanical properties of each CAD/CAM composite were strongly dependent upon media and ageing. Although the mechanical properties of PK were initially inferior, it was relatively stable in all FSLs. All three materials exhibited sufficient mechanical properties at 1 mm thickness, but thicker specimens were more tolerant to ageing.