Impact of optical fiber-based photo-activation on dental composite polymerization.

OBJECTIVES: The study aimed to introduce a novel two-step optical fiber-based photo-activation of dental resin-based composites (RBCs) for reducing polymerization shrinkage stress (PSS). METHODS: Proposed protocol design - in the first step, two flexible plastic optical fibers connected to a dental light curing unit (LCU), were used as light guides inserted into the filling to initiate low-irradiance polymerization from within; in the second step, fibers were extracted and remaining voids were filled with RBC, followed by conventional high-irradiance curing to finalize polymerization. Three bulk-fill RBCs were tested (Beautifil-Bulk Restorative, Filtek Bulk-fill Posterior, Tetric PowerFill) using tooth cavity models. Three non-invasive examination techniques were employed: Digital Holographic Interferometry, Infrared Thermography, and Raman spectroscopy for monitoring model deformation, RBC temperature change, and degree of conversion (DC), respectively. A control group (for each examined RBC) underwent conventional photo-activation. RESULTS: The experimental protocol significantly reduced model deformation by 15 - 35 %, accompanied by an 18 - 54 % reduction in RBC temperature change, emphasizing the impact of thermal shrinkage on PSS. Real-time measurements of deformation and temperature provided indirect insights into reaction dynamics and illuminated potential mechanisms underlying PSS reduction. After a 24-hour dark-storage period, DC outcomes comparable to conventional curing were observed, affirming the clinical applicability of the method. CONCLUSIONS: Protocol involving the use of two 1.5 mm fibers in the first step (300 mW/cm2 x 10 s), followed by a second conventional curing step (1000 mW/cm2 x 10 s), is recommended to achieve the desired PSS reduction, while maintaining adequate DC and ensuring efficient clinical application. CLINICAL SIGNIFICANCE: Obtained PSS reduction offers promise in potentially improving the performance of composite restorations. Additionally, leveraging the flexibility of optical fibers improves light guide approach for restorations on posterior teeth. Meanwhile, implementation in clinical practice is easily achievable by coupling the fibers with commercial dental LCUs using the provided plastic adapter.

Mechanical properties of conventional versus microwave-polymerized denture base acrylic resins.

STATEMENT OF PROBLEM: New denture base acrylic resins have been introduced that are specifically formulated for microwave polymerization. Microwave polymerization is a time-efficient procedure, but few studies have evaluated how these new acrylic resin formulations compare with conventionally processed acrylic resins. PURPOSE: The purpose of this in vitro study was to compare the stiffness and strength of denture base acrylic resins formulated for microwave polymerization with conventionally processed acrylic resin. MATERIAL AND METHODS: Rectangular beams were fabricated from 2 microwave-polymerized denture base acrylic resins, microwave-specific resin (Nature-Cryl MC), resin with the option of microwave polymerization (Diamond D), and a conventionally processed resin as a control (Lucitone 199). Specimens (n=10) were stored in water for 1 week and subjected to a 3-point bend test to determine the flexural modulus (stiffness) and flexural strength before (initial properties) or after 120 000 load cycles. The load cycles, conducted between 5 and 25 N at 2 Hz, simulated 6 months of mastication. Data were analyzed by using 2-way ANOVA, followed by pairwise comparisons (α=.05). RESULTS: The initial flexural modulus (mean ±standard deviation) was conventionally processed resin, 2.65 ±0.33 GPa; microwave-specific resin, 3.01 ±0.20 GPa; and microwave-option resin, 2.63 ±0.04 GPa. After load cycling, the mean flexural modulus was conventionally processed resin, 2.34 ±0.32 GPa; microwave-specific resin, 2.69 ±0.20 GPa; and microwave-option resin, 1.96 ±0.11 GPa. The initial flexural strength was conventionally processed resin, 77.6 ±11.0 MPa; microwave-specific resin, 83.6 ±3.5 MPa; and microwave-option resin, 78.9 ±2.6 MPa. After load cycling, the mean flexural strength was conventionally processed resin, 68.7 ±9.0 MPa; microwave-specific resin, 73.3 ±3.3 MPa; and microwave-option resin, 65.5 ±3.5 MPa. Resin and loading state significantly affected the stiffness and strength (P<.01); the interaction resin×state was not significant (P≥.558). CONCLUSIONS: Microwave-polymerized denture base acrylic resins were comparable in stiffness and strength with conventionally processed acrylic resin. All acrylic resins decreased in stiffness and strength after load cycling. The microwave-specific resin was significantly stiffer and stronger than the other denture base acrylic resins, initially and after 120 000 load cycles.

Effect of Two Different Ultrafast Curing Exposure Durations on the Surface Hardness of Bulk Fill Composite - An In-Vitro Study.

AIM: The aim of the present study is to assess the microhardness of resin-based composites (RBCs) cured with ultrafast curing mode at two different exposure durations. STUDY DESIGN: This is an experimental in-vitro study. Forty-five cylindrical composite specimens were prepared to a dimension of 5 mm height and 4 mm diameter. Curing was done using three different exposure modes and duration with dual mode LED curing light as follows: Group I: Ultrafast curing mode for 1 second at 2300 mW/cm2 (n = 15); Group II: Ultrafast curing mode for 3 second at 2300 mW/cm2 (n = 15) and Group III: Standard exposure mode for 20 second at 1000 mW/cm2 (n = 15). Vicker's microhardness measurement was done on both the curing and non-curing sides of the specimen using a motorised diamond-faced micro-indenter (Wilson Wolpwert, Germany) using a load of 50 gram and a dwell time of 30 second. STATISTICAL ANALYSIS: Kruskal Wallis ANOVA was used to test for difference between the three groups followed by Mann-Whitney U test for post-hoc analysis. RESULTS: The microhardness values of the composite cured with a conventional curing unit were significantly higher than the ultrafast cured specimens. CONCLUSION: Low-intensity conventional curing lights were found to perform better than the high-intensity ultrafast curing units.

Effect of Q-switched Er:YAG laser irradiation on bonding performance to dentin surface.

The use of Q-switched erbium:yttrium-aluminum-garnet laser (Er:YAG laser), which have much less thermal effects than conventional Er:YAG lasers, has been proposed mainly in the medical field. The purpose of this study was to evaluate the bonding ability of dentin after Q-switched Er:YAG laser irradiation.The effects of dentin irradiation with Q-switched and conventional lasers were evaluated in terms of dentin morphology, roughness, hardness, elemental content, and resin bonding strength. Q-switched Er:YAG laser at average power densities of 20, 40, and 60 W/cm2 and conventional Er:YAG laser at 909 W/cm2 were used, and their performance was compared with that of the untreated group. Significant differences (p<0.05) were observed between 20 W/cm2 and the other groups in term of surface roughness and surface hardness. The resin adhesion of the 20 W/cm2 group was significantly higher than that of the other groups (p<0.05).

Carbon nanotubes functionalized with sodium hyaluronate: Sterilization, osteogenic capacity and renal function analysis.

AIM: This study determined the optimum gamma irradiation dosage to sterilize sodium hyaluronate (HY), single-walled carbon nanotubes (SWCNT), multi-walled carbon nanotubes (MWCNT) and CNT functionalized with HY (HY-SWCNT and HY-MWCNT), evaluated the structural integrity of the materials and assessed whether sterilized materials kept biological properties without affecting renal function. MAIN METHODS: Materials were submitted to dosages of 100 gγ to 30 Kgγ and plated onto agar mediums for colony forming units (CFUs) counting. Sterilized samples were inoculated with 107Bacillus clausii, submitted again to gamma irradiation, and plated in agar mediums for CFUs counting. Scanning electron microscope was used for structural evaluation of sterilized materials. Tooth sockets of rats were treated with sterilized materials for bone formation assessment and renal function of the animals was analyzed. KEY FINDINGS: The optimum gamma dosage for sterilization was 250 gγ for HY and 2.5 Kgγ for the other materials without meaningful structural changes. Sterilized materials significantly increased bone formation (p < 0.05) and they did not compromise renal function and structure. SIGNIFICANCE: Gamma irradiation efficiently sterilized HY, SWCNT, MWCNT, HY-SWCNT and HY-MWCNT without affecting structural aspects while maintaining their desirable biological properties.

Synchrotron radiation-based analysis of fatigue in dental restorative materials.

Few studies performed a microstructural analysis of dental restorations to evaluate fatigue impact under various tensions, because of a lack of analytical equipment. In this study, the fatigue of restorative materials was evaluated using the force tester's fatigue method at 0.30, 0.3, 0.40, and 0.45 N. The fatigue effect analysis of tooth restorations was performed with each sample by randomly dividing the sequence into grades 0-4 and the evaluators were blinded to the test results. The evaluation methods involved visual and stereoscopic approaches, and used synchrotron radiation (SR). The evaluation facilitated the observation of microscopic cracks in the material using SR. The initiation of cracks was attributed to air bubbles, invisible to the naked eye or under the microscope. The fatigue effect analysis using SR enabled closer observations compared with other types of evaluation. We expect that this strategy will provide a basis for the study of physical and mechanical properties of dental materials.

Effect of Er:YAG Laser Etching on the Shear Bond Strength and Microleakage of Self-Glazed Zirconia Ceramics.

Objective: To investigate the effect of Er:YAG laser irradiation on the shear bond strength (SBS) and microleakage of self-glazed zirconia (SZ) ceramics. Background: SZ is a novel type ceramic; laser irradiation has started to be used in the surface treatment of different ceramics, while SZ has been rarely studied to improve the bond quality. Methods: One hundred twenty blocks (5 mm × 5 mm × 5 mm) of SZ ceramics were produced and split into eight groups following different surface treatments (n = 15): Group A: no treatment; Group B: standard grid processing; and Group C-H: different Er:YAG laser power settings (100, 200, 300, 400, 500, and 600 mJ). Ten blocks of each group received the measurement of SBS and fracture mode analysis, three blocks underwent the evaluation of the microleakage depths, and the other two blocks were observed under the scanning electronic microscopy (SEM). Results: Group F obtained the highest SBS and the lowest microleakage depth without damaging the ceramic surface structure, which was statistically significant compared with the control group and gridding group (p < 0.05), whereas the difference was not statistically significant (p > 0.05) between group E and group F. The results of bonding performance were consistent with failure types and observation of surface characterizations in SEM images. Conclusions: According to the results here, Er:YAG irradiation had effect on surface treatment. In addition, 400 mJ Er:YAG could increase the SBS and decrease the microleakage depth on SZ ceramics without damaging the surface structure.

Nd:YAG Laser Treatment of Bioglass-coated Zirconia Surface and Its Effect on Bond Strength and Phase Transformation.

PURPOSE: To evaluate the morphological properties, phase transformation, and microshear bond strength of composite cement to bioglass-coated zirconia surfaces treated with Nd:YAG laser. MATERIALS AND METHODS: Seventy-five zirconia disks were divided into five groups (n = 15). Group C received no surface treatment (control). Group S was subjected to sandblasting with 50-µm aluminum oxide particles. Group B samples were coated with bioglass 45S5. Groups BL9 and BL5 received bioglass coating and laser irradiation with 9 J/cm2 and 5 J/cm2 energy density. Morphological assessment was done using atomic force microscopy (AFM) and scanning electron microscopy (SEM). Zirconia phase transformation was assessed by XRD. Microhear bond strength testing was performed using a modified microtensile tester. The data were analyzed using the Welch test and the Games-Howell test (p < 0.05). RESULTS: The sandblasted and bioglass-coated groups showed the highest bond strengths compared to other groups (p < 0.05). Group S showed the highest surface roughness and the highest frequency of cohesive failure. In all samples, the tetragonal phase decreased after surface treatment. Groups BL9 and BL5 showed some levels of tetragonal to cubic phase transformation. CONCLUSION: Bioglass coating of zirconia surfaces (using the slurry method) can increase its microshear bond strength comparable to that of sandblasting. Surface roughness of sandblasted zirconia was the highest among all methods. Irradiation of Nd:YAG laser on bioglass-coated zirconia surfaces is not effective and decreases its bond strength compared to sandblasting and bioglass coating. Increasing the Nd:YAG laser energy density cannot increase the surface roughness of bioglass-coated zirconia surfaces. Bioglass coating results in transformation of the tetragonal to the cubic phase.

Effect of Photofunctionalization on Early Implant Failure.

PURPOSE: This study retrospectively evaluated the effects of bone density, staging strategy, implant stability, healing process, implant length, surface type, and photofunctionalization on early implant failure. MATERIALS AND METHODS: Consecutive study samples at Yokohama City University Hospital were analyzed for their early implant failure potentially influenced by patient-, surgical protocol-, and implant-related factors. Through the screening process using univariate analysis for those factors, candidate influential factors such as bone density, staging strategy, the level of initial implant stability, postoperative wound breakdown, the length of implants, the surface type of implants, and use or nonuse of photofunctionalization were selected as independent variables in forward multivariate logistic regression analysis. The odds ratio (OR) for candidate factors was calculated. RESULTS: A total of 563 implants placed in 219 patients from 2005 to 2017 were analyzed for their early implant failure. Stepwise logistic regression analysis finally identified postoperative wound breakdown (OR = 0.21) and the use of photofunctionalization (OR = 0.30) that significantly reduced the risk of early implant failure (P < .01 and P < .05, respectively). The implant failure rate was 10.0% with postoperative wound breakdown and 1.0% without it, whereas it was 4.3% without photofunctionalization and 1.3% with it. CONCLUSION: Among various patient-, surgical protocol-, and implant-related factors, the absence of postoperative wound breakdown and use of photofunctionalization significantly reduced the risk of early implant failure. It was notable that photofunctionalization, a unique, chairside measure to improve implant surfaces, was effective exclusively among implant-related factors.

Effect of photodynamic therapy on the mechanical properties and bond strength of glass-fiber posts to endodontically treated intraradicular dentin.

STATEMENT OF PROBLEM: The use of photosensitizers in photodynamic therapy promotes intraradicular microbial reduction during nonsurgical endodontic therapy. However, studies are lacking on the consequences of the application of these agents on the mechanical properties of intraradicular dentin and on the bond strength of glass-fiber posts. PURPOSE: The purpose of this in vitro study was to evaluate the influence of photodynamic therapy on the bond strength of glass-fiber posts using a push-out test and, additionally, to measure the Martens hardness (MH) and elastic indentation modulus (Eit) of intraradicular dentin when different photosensitizers are used. MATERIAL AND METHODS: Eighty bovine teeth were used to simulate experimental endodontic treatments. Biomechanical instrumentation was performed for all root canals, and the teeth were distributed into 5 groups: control-deionized water; methylene blue 50 mg/L + red laser; methylene blue 100 mg/L + red laser; curcumin 500 mg/L + blue LED; and curcumin 1000 mg/L + blue LED. The MH and Eit of intraradicular dentin were measured using an ultramicrohardness tester under a load of 3 mN (n=8). The push-out bond strength of glass-fiber posts to dentin was measured using a universal testing machine (n=8). Mechanical properties and bond strength data were subjected to the Kruskal-Wallis test, ANOVA, and Fisher least significant difference test (α=.05). Images of representative specimens were obtained using a scanning electron microscope. RESULTS: The MH, Eit, and bond strength of intraradicular dentin were influenced by the photosensitizer used. In general, curcumin promoted lower mechanical properties values but higher bond strength values. CONCLUSIONS: Photosensitizers influenced the mechanical properties of intraradicular dentin and the bond strength of glass-fiber posts, and methylene blue at 50 mg/L had no marked effect on the mechanical properties of the dentin or the bond strength values.

Real-time curing characteristics of experimental resin composites containing amorphous calcium phosphate.

The real-time polymerization of light-curable experimental resin composites filled with amorphous calcium phosphate (ACP) was monitored. Experimental composites were based on a 2,2-bis[4-(2-ethoxy-3-methacryloyloxy propoxy)phenyl]propane (Bis-EMA)/triethyleneglycol dimethacrylate (TEGDMA)/2-hydroxyethyl methacrylate (HEMA) resin photoactivated by a camphorquinone/tertiary amine system. Four ACP composites were prepared, containing 40 wt% ACP and 0/10 wt% reinforcing fillers (barium glass and silica). Additionally, two control composites were prepared which contained only reinforcing fillers (40-50 wt%). The degree of conversion (DC) was monitored in real time using a Fourier-transform infrared (FTIR) spectrometer with an attenuated total reflectance accessory. During the light curing (1,219 mW cm-2 ) for either 20 or 40 s, infrared spectra were collected from the bottom of 2-mm-thick composite specimens at the rate of two spectra per second over 5 min. When cured for 40 s, the ACP composites attained a high DC (89.1%-92.4%), while the DC of control composites was significantly lower (53.5%-68.4%). All materials showed a lower DC for the shorter curing time (20 s) and various extents of 5-min postcure polymerization: 12.9%-21.5% for the ACP composites and 2.7%-5.2% for the control composites. The control composites reached the maximum reaction rate much earlier (4.1-4.3 s) and at lower DC (9.9%-10.4%) than did the ACP composites (17.4-22.0 s and 43.5%-49.3%, respectively).

Longevity of bond strength of resin cements to root dentine after radiation therapy.

AIM: To evaluate the bond strength and adhesive interface between several resin cements and root dentine immediately and 6 months after radiotherapy. METHODOLOGY: Sixty maxillary canines were selected and randomly assigned to two groups (n = 30): one group was not irradiated and the other one was subjected to a cumulative radiation dose of 60 Gy. The teeth were sectioned to obtain roots 16 mm long and the canals were prepared with the Reciproc system (R50) and filled using a lateral condensation technique with an epoxy resin sealer. Each group was divided into three subgroups (n = 10) according to the resin cement used for fibreglass fibre post cementation: RelyX-U200, Panavia-F2.0 and RelyX ARC. The posts were cemented in accordance with the manufacturer's recommendations. Three 1-mm-thick dentine slices were then obtained from each root third. The first two slices in the crown-apex direction of each third were selected for the push-out test. The failure mode after debonding was determined with a stereo microscope. The third slice from each root third was selected for scanning electron microscopy (SEM) analyses to examine the resin cement-dentine interface with 100, 1000, 2000 and 4000× magnification. Bond strength data were analysed by anova and Tukey's test (α = 0.05). RESULTS: Significantly lower bond strength (P < 0.0001) was obtained after irradiation compared to nonirradiated teeth. RelyX-U200 cemented fibre posts had the higher bond strength (15.17 ± 5.89) compared with RelyX ARC (P < 0.001) and Panavia-F2.0 (P < 0.001). The evaluation after 6 months revealed lower bond strength values compared to the immediate values (P < 0.001) for irradiated and nonirradiated teeth. Cohesive failures occurred in the irradiated dentine. SEM revealed fractures, microfractures and fewer collagen fibres in irradiated root dentine. RelyX-U200 and Panavia-F2.0 were associated with a juxtaposed interface of the cement with the radicular dentine in irradiated and nonirradiated teeth, and for RelyX ARC, hybrid layer formation and tags were observed in both irradiated and nonirradiated teeth. CONCLUSION: Radiation was associated with a decrease in the push-out bond strength and with lower resin cement/root dentine interface adaptation. Self-adhesive resin cement was a better alternative for fibre post cementation in teeth subjected to radiation therapy. The bond strength decreased after 6 months.

Surface Characterization and Cell Adhesion of Different Zirconia Treatments: An in vitro Study.

AIM: The aim of this study was to characterize the surface of zirconia subjected to different treatments and evaluate its effect on cell adhesion and proliferation. MATERIALS AND METHODS: A total of 80 zirconia disks were divided into four groups (n = 20) according to the surface treatments used: group I: as-sintered (AS), no surface treatment applied; group II: abrasion treatment applied using Rocatec (ROC; 3M ESPE) system with silica-coated alumina powder of grit size 110 µm; group III: erbium, chromium:yttrium, scandium, gallium, garnet (Er, Cr:YSGG) laser (LAS; BIOLASE) was used at a frequency of 20 Hz and output power of 3 W; and group IV: specimens were subjected to the selective infiltration etching (SIE) technique. Surface characterization was evaluated for the different groups (roughness, hardness, and morphology), and cell behavior (adhesion and proliferation) was tested (a = 0.05). RESULTS: The ROC group reported a significant increase in surface roughness (2.201 ± 0.352) and Vickers hardness (1758 ± 16.6) compared with the other surface treatments. The SIE surface-treated group reported a significantly higher number of cells (64.5 ± 2.6 and 53.5 ± 2.2 respectively) compared with the other surface-treated groups. CONCLUSION: The SIE is a promising surface treatment for zirconia that significantly enhances cell adhesion and osseointegration. CLINICAL SIGNIFICANCE: The SIE treatment of zirconia implants may help in a faster and better osseointegration.

Changes in polymerization stress and elastic modulus of bulk-fill resin composites for 24 hours after irradiation.

The objective of this study was to investigate changes in polymerization stress and elastic modulus for light-cured bulk-fill resin composites following irradiation. Crack analysis was applied to obtain the stresses for 24 h after irradiation, which were calculated from the lengths of cracks in a glass mold bonded to the composites. The elastic modulus was repeatedly measured by nano-indentation tests performed over 24 h. The lengths of the cracks, the interfacial stress, and the elastic modulus were significantly affected by the material and time after irradiation (p<0.01). The stress and elastic modulus continued to increase for more than 6 and 1 h, respectively (p<0.05). Strong relationships (r>0.85) were revealed between the stress and elastic modulus. The bulk-fill resin composites generated smaller stresses than a flowable resin composite reported to generate relatively low stress. Post-irradiation polymerization during the first 1 h is a major determinant for the magnitude of stress.

Dose-dependent effect of radiation on resorbable blast material titanium implants: an experimental study in rabbits.

BACKGROUND: Radiotherapy is a commonly used treatment modality in head and neck cancer; however, it also negatively affects healthy structures. Direct damage to oral soft and hard tissue frequently occurs with radiotherapy. In this study, we aimed to evaluate the effect of radiotherapy on bone surrounding titanium dental implants via biomechanical and molecular methods. MATERIALS AND METHODS: Fifty-four implants were inserted in the left tibiae of 18 adult male New Zealand rabbits (3 implants in each rabbit). After 4 weeks of the implant surgery, the left tibiae of 12 rabbits were subjected to a single dose of irradiation (15 Gy or 30 Gy). Four weeks after the irradiation, rabbits were sacrificed and removal torque test was done for the biomechanical evaluation. Bone morphogenetic protein-2 (Bmp-2) and fibroblast growth factor-2 (Fgf-2) expression analyses were performed with Real-time PCR. Statistical analysis was done using SPSS. RESULTS: The control group showed significantly higher removal torque value than the 15 and 30 Gy irradiation groups, and the 15 Gy irradiation group had higher removal torque value than the 30 Gy irradiation group (p < .001). The 15 Gy and 30 Gy irradiation groups had significantly lower Bmp-2 and Fgf-2 mRNA expressions than the control group (p < .001). In addition, the 30 Gy irradiation group had significantly lower Bmp-2 (p < .01) and Fgf-2 mRNA expressions (p < .001) than the 15 Gy group. CONCLUSION: Radiotherapy with 15 and 30 Gy doses can adversely affect osseointegration of implants by reducing the quality of bone and impairing the bone-to-implant contact. The mechanism of action seems to be related to alterations in Bmp-2 and Fgf-2 mRNA expressions.

Effect of ionizing radiation on properties of restorative materials.

OBJECTIVE: To evaluate the effect of ionizing radiation from high energy X-ray on properties of restorative materials. METHODS: Study materials (3M-ESPE) were: Z250-microhybrid resin-based composite (Filtek Z-250); Z350-nanofilled resin-based composite (Filtek Z-350XT); VIT-resin-modified glass ionomer cement (Vitremer); and KME-conventional glass ionomer cement (Ketac Molar Easymix). Sixty bar-shaped and cylinder-shaped specimens were fabricated from each material. Specimens were light activated (980mW/cm2, Radii, SDI) for 60s (3×20s for Z250 and Z350) and 120s (3×40s for VIT) and thirty specimens from each shape were irradiated (IR) with 1.8Gy/day for 39days (total IR=70.2Gy). IR and non-irradiated (NI) specimens were evaluated for flexural strength (σ, n=30) followed by fractography (SEM), diametral tensile strength (DTS, n=30), hardness (H, n=10), surface roughness (Ra, n=10) and chemical composition (n=3). The IR effect on each material property was statistically analyzed using Student's t test (α=0.05). Data from σ and DTS were also analyzed using Weibull statistics. RESULTS: IR significantly increased the mean σ values of VIT and KME and the mean DTS value of VIT (p<0.05). IR increased Ra and H values for VIT and decreased H value for Z-250 (p<0.05). The remaining materials and properties were not significantly affected by IR (p>0.05). There was no significant change on materials composition after IR. SIGNIFICANCE: The recommended radiotherapy protocol for head and neck cancer altered some material properties, mainly for glass ionomer cements. Such variations on material properties are not related to chemical composition changes.

Impact of light transmittance mode on polymerisation kinetics in bulk-fill resin-based composites.

OBJECTIVES: to determine the mode of light transmission and its impact on the polymerisation kinetic in modern bulk-fill resin-based composites (B-RBC). MATERIALS AND METHODS: Four low-viscosity methacrylate-based and one high-viscosity ormocer-based B-RBCs were considered. One material was available in three different shades that were all analyzed. Polymerization kinetic and light transmittance were assessed in 2 and 4mm specimen depths. Incident and transmitted irradiance and radiant exposure were measured in real-time on a laboratory-grade spectrometer. RESULTS: A progressive enhanced light transmittance during polymerisation was identified in all materials except for TetricEvoFlow BulkFill, which became progressively opaque in all shades. One-way ANOVA and multivariate analysis (α=0.05) were performed. The parameter material has a significant (p<0.001) effect on DC (ηP2=0.856) and light transmittance parameters (irradiance, ηP2=0.965; radiant exposure, ηP2=0.956); specimen depth influences only transmittance (ηP2=0.978; 0.980). DC variation in time was best described by an exponential sum function (R2>0.95), differentiating between the gel- and the glass-phase and revealing a faster initiation of polymerization and a slower transition into the glass-phase by lowering the filler volume. Depth retarded the transition into the glass-phase, but did not alter DC measured 300s post-irradiation. Moderate inverse correlation was identified among DC and filler volume% (-0.646) or filler weight% (-0.403), while no correlation among DC and light transmittance (p=0.141; 0.125). The maximal rate of carbon-carbon double bond conversion varied within the analyzed materials but was independent from specimen's depths. CONCLUSIONS: Light transmission changes during polymerization do not alter polymerization kinetics in modern B-RBCs. DC 300s post-irradiation was maintained with depth, while light was attenuated, the faster the more translucent the material was. DC and quality of curing cannot be related to light transmittance in B-RBCs.

Own brand label restorative materials-A false bargain?

OBJECTIVES: This study aims at evaluating and comparing mechanical, chemical, and cytotoxicological parameters of a commercial brand name composite material against two 'own brand label' (OBL) composites. METHODS: Parameters included depth of cure, flexural strength, degree of conversion, polymerization shrinkage, filler particle morphology and elemental analyzes, Vickers hardness, surface roughness parameters after abrasion, monomer elution, and cytotoxicity. RESULTS: The conventional composite outperformed the OBLS in terms of depth of cure (p<0.001), degree of cure at the first and last time intervals (p<0.001), hardness (p<0.001), and post-abrasion roughness (p<0.05). The polymerization volumetric shrinkage ranged from 2.86% to 4.13%, with the highest shrinkage seen among the OBLs. Both Monomer elution from the OBLs was statistically significantly higher (p<0.001). Statistically significantly higher cytotoxicity combined with altered morphology and loss of confluence was detected in the cells exposed to extracts from the OBLs. CONCLUSIONS: The OBLs were in general outdone by the conventional composite. CLINICAL SIGNIFICANCE: OBLs restorative materials have become pervasive in the dental market. Manufacturers often promise equal or better characteristics than existing brand-name composites, but at a lower price. Dentists are highly recommended to reconsider utilization of OBLs lacking sound scientific scrutiny, and our findings underscore this recommendation.

Implant Stability Development of Photofunctionalized Implants Placed in Regular and Complex Cases: A Case-Control Study.

PURPOSE: The objective of this study was to compare the rate of implant stability development of as-received and photofunctionalized dental implants in regular and complex cases. MATERIALS AND METHODS: Forty-nine implants (24 as-received and 25 photofunctionalized) placed in regular or complex cases (simultaneous guided bone regeneration, sinus elevation, or fresh extraction sockets) were studied. Photofunctionalization was performed by ultraviolet (UV) treatment of implants for 15 minutes using a photo device immediately prior to placement, and the generation of superhydrophilicity was confirmed. Implant stability was evaluated by measuring the implant stability quotient (ISQ) at placement (ISQ1) and at stage-two surgery (ISQ2). The rate of implant stability development was evaluated by calculating the osseointegration speed index (OSI), defined as the ISQ increase per month ([ISQ2-ISQ1]/healing time in months). The percentage of innate bone support at placement was evaluated clinically and radiographically. RESULTS: The average OSI was considerably greater for photofunctionalized implants (3.7 ± 2.9) than for as-received implants (0.0 ± 1.0). The OSI in complex cases was 4.2 ± 3.2 for photofunctionalized implants and 0.2 ± 0.9 for as-received implants. The OSI in cases with simultaneous sinus elevation was 5.5 ± 3.5 for photofunctionalized implants and 0.2 ± 1.1 for as-received implants. Photofunctionalized implants showed significantly higher ISQ2 values than as-received implants. Photofunctionalized implant ISQ2 values were greater than 60, regardless of primary stability and innate bone support at placement. In multivariate analysis including the effects of photofunctionalization, age and sex of patients, and diameter and length of implants, photofunctionalization showed the strongest influence on the OSI for both regular and complex cases, while other factors influenced the OSI only in certain conditions. CONCLUSION: Photofunctionalization accelerated the rate and enhanced the final level of implant stability development compared with as-received implants, particularly for implants placed into poor-quality bone and other complex cases. Photofunctionalization was a stronger determinant of implant stability than all the other tested implant- and host-related factors.

Effect of Er,Cr:YSGG laser on the surface of composite restoratives during in-office tooth bleaching.

The aim of this in vitro study was to investigate the effect of Er,Cr:YSGG laser on the surface roughness and microhardness of various composite restoratives during in-office tooth bleaching. Five highly viscous composite restoratives and three flowable composite restoratives were investigated. Thirty cylindrical specimens of each material were made using Teflon molds. The specimens of each composite were randomly divided into three groups (n = 10). Group 1 specimens did not receive bleaching treatment, group 2 received a conventional in-office bleaching treatment, and group 3 received a laser-assisted in-office bleaching treatment using an Er,Cr:YSGG laser. Two-way ANOVA was used to determine significant interactions between materials and bleaching methods. One-way ANOVA and Tukey's post hoc test were used to compare the mean surface microhardness and roughness between materials for each treatment group (a = 0.05). Τhere were no significant differences in surface microhardness between the two bleached experimental groups for all the tested composites (p > 0.05). The reduction of surface microhardness after bleaching procedures ranged from 0.72 to 16.93 % for the specimens received conventional treatment and from 1.30 to 11.51 % for those received laser-assisted treatment. Moreover, there were no significant differences in Ra values between the experimental groups (p > 0.05) in all cases. The increase of surface roughness after the bleaching treatments was negligible and was between 0.43 and 4.78 %. The use of Er,Cr:YSGG laser during in-office tooth bleaching treatment did not affect the surface microhardness and roughness of the tested composite restorative materials.