Sulfur Free Crosslinking of EPDM Composites via Silane Grafting and Silica Incorporation.

This study aims at evaluating and developing an environmental-friendly and sulfur-free cured ethylene propylene diene monomer (EPDM) composites. Silane grafted EPDM (SiEPDM) composites incorporated with silica is prepared via a solvent-free, one-step reactive mixing process. The silane grafting and silica filler bonding are characterized using Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The mechanical properties of the developed composites are examined. The fracture morphology is observed using an environmental scanning electron microscopy. The rheology and thermomechanical properties are evaluated by using a rotational rheometer and dynamic mechanical analyzer. Notably, a robust bonding between silica and the grafted silane is established, yielding a crosslinking network within the composite structure. This phenomenon is substantiated by the observed gel efficiency and rheology behavior. Consequently, a pronounced augmentation of up to 75% in tensile strength and 29% in tear strength are observed in the optimized SiEPDM-silica composites, distinguishing them from their EPDM-silica counterparts. The introduction of paraffin oil contributes to enhanced processability; however, it is concomitant with a reduction in gel efficiency and associated mechanical properties. Furthermore, subsequent UV weathering test unveils that the SiEPDM-silica composites exhibit the highest levels of residual tensile strength and modulus, indicative of their exceptional UV stability.

Effect of high irradiance and short exposure times on the depth of cure of six bulk-fill resin composites.

This study examined the effect of high irradiance and short exposure times on the depth of cure of six resin-based composites (RBCs). Bluephase PowerCure and the Valo X light-curing units (LCUs) were used to photocure bulk-fill RBCs for their recommended exposure times: Admira Fusion x-tra (AFX/20s), Aura Bulk Fill (ABF/20s), Filtek One Bulk Fill (FOB/20s), Opus Bulk Fill APS (OBF/30s), Tetric EvoCeram Bulk Fill (TEC/10s) and Tetric PowerFill (TPF/10s). In addition, all bulk-fill RBCs were tested for depth of cure with one short 3 s exposure time from the Bluephase PowerCure or the Valo X in the Xtra Power mode. The RBCs (n = 10 per RBC) were inserted into a 4 mm diameter metal mold and covered by a polyester strip before being photocured. After 24 h of storage, uncured RBC was scraped away to determine the depth of cure of the RBCs. None of the RBCs achieved a 4 mm depth of cure. The depth of cure of TEC and TPF was unaffected by the exposure times (recommended or short) when using the Valo X. The depth of cure of AFX/20s, AFX/Xtra Power, ABF/Xtra Power, FOB/Xtra Power, and OBF/30s RBCs was greater when using Valo X compared to the Bluephase PowerCure. It was concluded that short exposure times can reduce depth of cure and should only be used for some RBCs.

Effects of erosion and abrasion on resin-matrix ceramic CAD/CAM materials: An in vitro investigation.

The aim of the study was to evaluate the effects of erosion and abrasion on resin-matrix ceramic CAD/CAM materials [CERASMART (GC); VITA ENAMIC (VITA Zahnfabrik); Lava Ultimate (3 M)] in comparison to feldspar ceramic (VITABLOCS Mark II, VITA Zahnfabrik) and resin composite materials (ceram.x universal, Dentsply Sirona). Daily brushing and acid exposure were simulated using a brushing apparatus and a solution of 0.5 vol% citric acid. Microhardness, surface roughness, and substance loss were measured at baseline and after simulation of 1 and 3 years of function. All materials showed a decrease in microhardness after 3 years and an increase in surface roughness (Ra) after 1 and 3 years. The Ra increase was statistically significantly lower for the resin-matrix ceramics than for feldspar ceramic and similar to composite material. After 3 years, only feldspar ceramic showed no significant substance loss. In conclusion, resin-matrix ceramics demonstrate reduced roughening compared to feldspar ceramics, potentially improving restoration longevity by preventing plaque buildup, but differences in abrasion resistance suggest the need for further material-specific research. Future research should aim to replicate clinical conditions closely and to transition to in vivo trials.

Influence of residues from bioceramic sealer on the bond interface with universal adhesive in different application modes.

This study evaluated the effect on adhesive layer thickness, bond strength, and adhesive failure pattern of the application of universal adhesive (Scotchbond Universal) using either manual or rotary brush in dentin previously impregnated with bioceramic sealer (Sealer Plus BC) using a manual brush, at 24 h and 1 year. Eighty-eight bovine crowns were divided into four groups (n = 22) according to the intervention: (i) use of bioceramic sealer and adhesive application using manual brush, (ii) use of bioceramic sealer and adhesive application using rotary brush, (iii) use of resin sealer and adhesive application using manual brush, and (iv) use of resin sealer and adhesive application using rotary brush. Subsequently, specimens were restored with a composite resin (Filtek Z-250). Adhesive layer thickness was evaluated using confocal microscopy. Bond strength was assessed using the microtensile bond strength test, and adhesive failure pattern was evaluated under a stereomicroscope. Data were analyzed using two-way ANOVA/Tukey tests. Specimens where a rotary brush had been used exhibited lower adhesive layer thickness. Specimens treated with resin sealer and using a manual brush showed lower bond strength values and a higher occurrence of adhesive failures at 24 h and 1 year than specimens treated with bioceramic sealer and using rotary brush for adhesive application.

Influence of different immediate dentin sealing strategies on bond strength of indirect resin nanoceramic restorations.

In this study, we evaluated the effect of four different strategies for bonding a CAD/CAM resin nanoceramic restoration (Lava Ultimate, 3M) to the dentin surface using a universal adhesive (Scotch Bond Universal, 3M) and adhesive resin cement (RelyX Ultimate, 3M) on the shear bond strength (SBS) and failure mode. The strategies comprised: (i) immediate sealing, immediate bonding; (ii) immediate sealing, bonding after 2 weeks with provisional restoration; (iii) immediate sealing with flowable resin composite reinforcement and bonding after 2 weeks with provisional restoration; and (iv) no immediate sealing, and bonding after 2 weeks with provisional restoration. After bonding, all the specimens were thermocycled, shear tests were performed using a universal testing machine, and failure modes were determined using stereomicroscope and scanning electron microscopy. The highest mean SBS was recorded with immediate sealing, immediate bonding strategy. Most adhesive failures with exposed dentinal tubules were noted in specimens exposed to bonding after 2 weeks with no immediate sealing, which was associated with the lowest SBS. Mixed failures predominated in all immediate dentin sealing groups. Immediate sealing with universal adhesives improves SBS, particularly in the single-visit approach, which has shown significantly better performance, whereas the provisional phase has a negative effect.

Optical effects of graphene addition on adhesives for orthodontic lingual retainers.

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.

Effects of alpha-tocopherol antioxidant on fracture strength and adhesion of endodontically treated teeth restored after dental bleaching.

This study evaluated the effect of different concentrations of alpha-tocopherol in gel form on fracture strength, hybrid layer formation, and microtensile bond strength of endodontically treated teeth bleached with 40% hydrogen peroxide (H2 O2 ). Sixty bovine incisors were randomized into one of six groups (n = 10 incisors per group) defined by the interventions carried out after endodontic treatment. In the control group, no additional intervention was carried out, while all teeth in the five intervention groups were bleached with 40% H2 O2 and subsequently treated with alpha-tocopherol at concentrations of 15% (15AT), 20% (20AT), or 25% (25AT), with 10% sodium ascorbate (10SA), or with nothing (40HP). Fracture strength was evaluated in a mechanical testing machine, hybrid layer formation was assessed using scanning electron microscopy, and bond strength was determined using microtensile bond-strength testing. Data were analyzed using Kruskal-Wallis and Dunn's tests. No statistically significant difference regarding fracture strength was observed among groups. Hybrid layer formation was greater in the 15AT group than in groups 40HP and 10SA. Teeth in groups 15AT, 20AT, and 25AT demonstrated higher bond strength than teeth in groups 40HP and 10SA. Alpha-tocopherol, preferably at 15%, effectively reverses the deleterious effects, of bleaching, on hybrid layer formation and bond strength to dentin.

Chemical analysis of n-propyl gallate used as pre-treatment for resin-dentin bond strength: In vitro study.

This study aimed to evaluate the effect of n-propyl gallate as pre-treatment for resin-dentin bond strength. The dentin pre-treatments evaluated included propyl gallate of concentrations 0.1% (w/v), 1.0% (w/v), and 10.0% (w/v), as well as glutaraldehyde 5.0% (v/v), and distilled water as a control treatment. Dentin specimens were prepared for Fourier Transformed Infrared Spectroscopy (FT-IR) (n = 3/pre-treatment). Pre-treatments were actively applied to dentin blocks before performing the adhesive procedure to composite resin. Microtensile bond strength to dentin (µTBS) (n = 8/pre-treatment) was determined after 24 h and 6 months of storage. Data were submitted to a two-way ANOVA, followed by Tukey's post hoc test. As for FT-IR, propyl gallate 1%-treated specimens presented higher water, carbonate, collagen, and amide absorbance rates compared to other tested groups, while specimens pre-treated with glutaraldehyde and distilled water presented similar absorbance curves. Regarding µTBS, all concentrations of propyl gallate resulted in statistically significant higher bond strength values than distilled water at 24 h. After 6 months of storage, propyl gallate 0.1% was the only group that maintained µTBS over time. Propyl gallate 0.1% might be a suitable dentinal pre-treatment due to being able to present chemical bonds with demineralized dentin and providing resin-dentin bond stability after 6 months of storage.

Effects of Artificial Aging of Direct Resin Nano-Hybrid Composite on Mean Bond Strength Values for Veneer Ceramic Samples.

BACKGROUND This study investigates the effect of artificial aging of direct resin nanohybrid composites on mean bond strength values for veneer ceramic samples. MATERIAL AND METHODS Ninety direct nanohybrid composite resin (Tetric N-Ceram) cylindrical discs were divided into 5 groups (n=18 each) based on aging cycles (thermocycling), as follows: TC=no aging (control), T1=850, T3=2500, T6=5000, and T12=10000 cycles, representing 1, 3, 6, and 12 months of clinical usage, respectively. Lithium disilicate glass ceramic (IPS e.max Press) cylindrical discs were cemented to resin discs using resin cement (Variolink N) after surface treatments (ceramic etching, silaning, composite abrasion). Differences in means between subgroups were calculated using one-way ANOVA, followed by the Tukey honestly significant differences post hoc test. Differences were considered statistically significant with a P value ≤0.05. RESULTS The highest SBS between ceramic and aged composite was observed at 1 month (m=20.35) but did not differ significantly from the control group (m=20.97). For all other subgroups (3, 6, 12 months) SBS was significantly less than that of the control (P≤0.05). At 1 and 3 months, cohesive failures were more common, whereas adhesive failures were more common in 6- and 12-month-old composites. CONCLUSIONS SBS of aged composites was less than that of non-aged composites, with SBS decreasing proportionally as the resin aged. When cementing a ceramic restoration over existing composite restorations, those older than 1 month should be removed and replaced with new ones.

Shear Bond Strength of Adhesives Placed following Selective Removal of Red-Fluorescing Carious Dentine in vitro.

Red-fluorescing dentine indicates bacterial contamination [Caries Res 2002; 36: 315-319]. We investigated effect of removal of red fluorescent dentine caries on shear bond strength and fracture mode of 4 adhesive approaches. Sixty-five carious teeth and 50 noncarious controls were distributed into 4 groups: Clearfil™ self-etch (CSE), OptiBond™ FL total etch (OTE), Scotchbond™ Universal total etch (STE) and self-etch (SSE). Samples were excited at 405 nm and viewed through 530 nm filter. Carious samples were ground flat exposing strongly red-fluorescing (StrongRF) dentine, on which a composite cylinder was placed, using one of 4 adhesives. After 22 h in water, shear bond strength and fracture mode were analysed. StrongRF was removed; composite cylinders were placed on weakly red-fluorescing (WeakRF) dentine and tested as described above. Finally, red-fluorescing dentine was removed, and composite cylinders were placed on non-fluorescing (NonRF) dentine and tested. Composites were placed at 3 corresponding heights in controls. After 22 h in water, shear bond strength testing and fracture mode analysis were performed. Differences were tested using Mann-Whitney or Wilcoxon tests (p ≤0.05). Median (Q1, Q3) shear bond strength on StrongRF was SSE 14.4 (9.2, 18.2) MPa >CSE 10.2 (6.4, 17.3) MPa >STE 9.1 (6.9, 11.2) MPa >OTE 6.8 (4.0, 10.8) MPa. Shear bond strength increased statistically significantly for all adhesives on WeakRF: SSE 19.8 (13.6, 24.3) MPa >STE 19.5 (12.7, 23.1) MPa >CSE 17.5 (12.0, 22.5) MPa >OTE 15.8 (11.9, 20.9) MPa. Only STE 25.6 (22.4, 29.1) MPa and CSE 22.1 (17.6, 24.6) MPa were significantly different on NonRF compared to WeakRF. For controls tested at corresponding depths, superficial shear bond strength was OTE 18.7 (16.0, 22.1) MPa >STE 18.4 (12.0, 25.9) MPa >CSE 18.1 (12.7, 20.7) MPa >SSE 13.0 (9.6, 17.8) MPa. This was significantly higher compared to StrongRF except for SSE. Central shear bond strength was not significantly different to WeakRF, deep shear bond strength was significantly lower for SSE and CSE but higher for OTE compared to carious. Conclusion: StrongRF dentine should be removed for higher shear bond strength, but WeakRF dentine can often be preserved without compromising adhesive bond strength.

Blue Laser for Polymerization of Bulk Fill Composites: Influence on dentin bond strength and temperature rise during curing and co-curing method.

Blue diode lasers are alternative curing devices for dental composites. The aim of this study was to investigate the influence of blue diode laser polymerization on shear bond strength of bulk fill composites to human dentin and temperature rise during two types of polymerization. Composite cylinders of SDR Plus(SDR) and Ever X Flow(EX) were bonded to dentin slabs using Adhese Universal and curing devices blue diode laser (449 nm, 1.6 W) and Power Cure LED. For each material and curing device there were two polymerization approaches: 1)conventional: separate curing of adhesive; 2)co-curing: simultaneous adhesive and composite curing. Polymerization modes for each material in conventional and co-curing(c) approach were: blue laser 2000 mW/cm2 for 5 s (L5 and L5c); blue laser 1000 mW/cm2 for 10 s (L10 and L10c); Power Cure 2000 mW/cm2 for 5 s (LED5 and LED5c); Power Cure 1000 mW/cm2 for 10 s (LED10 and LED10c). Temeperature was measured using thermal vision camera. For SDR, the highest bond strength was 24.3 MPa in L10c, and the lowest 9.2 MPa in LED5c. EX exhibited the highest bond strength(21.3 MPa) in LED5, and the lowest in L5(7.7 MPa). The highest temperature rise for SDR was in L10 and L5 (7.3 and 7.2 °C), and the lowest in LED5(0.8 °C). For EX, the highest temperature rise was in L5 (13.0 °C), and the lowest in LED5 (0.7 °C). Temperature rise was higher during blue laser polymerization, especially at high intensity and with conventional curing. Preferable blue laser curing mode is co-curing at 1000mW/cm2 for 10 s.

Longevity of composite restorations in posterior teeth placed by dental students: a 12-year retrospective study.

OBJECTIVES: To evaluate the longevity of resin composite restorations placed in posterior teeth by dental students, using data from electronic records from 2008 to 2019. MATERIALS AND METHODS: Demographic (gender and age) and clinical variables (dental group, position in dental arch, and the number of restored surfaces) were evaluated. The 5-year follow-up was assessed according to the day the restoration was placed. Kaplan-Meier curves were generated to calculate the annual failure rate. Data were analyzed by Chi-Square, Kruskal-Wallis, and Mann-Whitney tests (α = 0.05). RESULTS: In total, 3.883 records relative to return periodicity were analyzed. The final sample consisted of 900 restorations from 479 patients. The majority were females, aged between 31 and 60. In total, 256 failures were reported (success rate = 78%), showing an annual failure rate of 2.05%. The main reasons for failures were restoration replacement (55.5%), endodontics (21.9%), prosthetics (14.5%) and extraction (8.2%). There was a higher risk of failure in restorations involving three or more surfaces (p = 0.000) and in patients over 60 years (p < 0.001). In females (p = 0.030), molars (p = 0.044), and maxillary teeth (p = 0.038) failed in a shorter time. CONCLUSIONS: Resin composite restorations placed in permanent posterior teeth by dental students had high survival rates. The main reason for failure was the replacement of restorations. The age group and the number of restored surfaces significantly affected the success of the restorations. CLINICAL RELEVANCE: The electronic health records over 12 years showed that 78% of the resin restorations in posterior teeth placed by dental students were successful for a minimum of five years.

Two-year clinical performance of dual- and light-cure bulk-fill resin composites in Class ӀӀ restorations: a randomized clinical trial.

OBJECTIVE: This study aimed to compare the clinical performance of dual- and light-cure bulk-fill resin composites (BFRCs) in Class ӀӀ restorations after 2 years. MATERIALS AND METHODS: A double-blinded, prospective, randomized clinical trial (RCT) was conducted following the CONSORT (Consolidated Standard of Reporting Trials) guidelines. Forty patients were enrolled in the study. Each patient received three compound Class ӀӀ restorations. One dual-cure (Fill-Up; Coltene Waledent AG) and two light-cure (QuiXfil; Dentsply, and Tetric N-Ceram Bulk Fill; Ivoclar Vivadent) BFRCs were used for 120 Class ӀӀ restorations. A universal adhesive (ONE COAT 7 UNIVERSAL; Coltene Waledent AG) was used with all restorations. Restorations were clinically evaluated after 1 week (baseline), 6 months, 12 months, 18 months, and finally after 24 months using the FDI World Dental Federation (FDI) criteria. The Kruskal-Wallis test was used for comparison between BFRCs groups at baseline and at each recall period, and the Wilcoxon signed-rank test was used for comparing different follow-up times of each BFRC to baseline. The level of significance was set at p < 0.05. RESULTS: All BFRCs restorations showed only minor changes and revealed no statistically significant differences between their clinical performance for all evaluated parameters at all recall periods; also, there was no statistically significant difference between all recall periods and baseline for all evaluated parameters. CONCLUSION: The two-year clinical performance of dual-cure BFRC was comparable to light-cure BFRCs in Class ӀӀ restorations. CLINICAL RELEVANCE: Dual- and light-cure BFRCs showed excellent clinical performance in Class ӀӀ restorations after a 2-year clinical follow-up.

Marginal integrity and physicomechanical properties of a thermoviscous and regular bulk-fill resin composites.

OBJECTIVES: To evaluate the marginal integrity (MI%) and to characterize specific properties of a thermoviscous bulk-fill resin composite, two regular bulk-fill resin composites, and a non-bulk-fill resin composite. MATERIALS AND METHODS: VisCalor bulk (VBF), Filtek One Bulk Fill (OBF), and Aura Bulk Fill (ABF) were evaluated. Filtek Z250 XT (ZXT) was used as non-bulk-fill control. MI% was evaluated in standardized cylindrical cavities restored with the composites by using a 3D laser confocal microscope. The following properties were characterized: volumetric polymerization shrinkage (VS%), polymerization shrinkage stress (Pss), degree of conversion (DC%), microhardness (KHN), flexural strength (FS), and elastic modulus (EM). Data were analyzed by one-way and two-way ANOVA, and Tukey HSD post-hoc test (α = 0.05). RESULTS: VBF presented the highest MI% and the lowest VS% and Pss (p < 0.05). DC% ranged from 59.4% (OBF) to 71.0% (ZXT). ZXT and VBF presented similar and highest KHN than OBF and ABF (p < 0.05). ABF presented the lowest FS (p < 0.05). EM ranged from 5.5 GPa to 7.7 GPa, with the values of ZXT and VBF being similar and statistically higher than those of OBF and ABF (p < 0.05). CONCLUSIONS: Thermoviscous technology employed by VisCalor bulk was able to improve its mechanical behavior comparatively to regular bulk-fill resin composites and to contribute to a better marginal integrity in restorations built up in cylindrical cavities with similar geometry to a class I cavity as well. Although presenting overall better physicomechanical properties, Z250 XT presented the worst MI%. CLINICAL RELEVANCE: The marginal integrity, which is pivotal for the success of resin composite restorations, could be improved using VisCalor bulk-fill. The worst MI% presented by Z250 XT reinforces that non-bulk-fill resin composites shall not be bulk-inserted in the cavity to be restored.

Bonding performance and interfacial adaptation of modern bulk-fill restorative composites after aging in artificial saliva: an in vitro study.

OBJECTIVES: This study aimed at comparing the microtensile bond strength (MTBS) and interfacial adaptation of a modern self-curing and a light-curing restorative bulk-fill composite to a conventional composite applied with the layering technique. METHODS: Forty-eight occlusal cavities were divided in three main groups (16/group) based on tested materials: (i) STELA, bulk-fill self-curing restorative (STELA, SDI Ltd.); (ii) 3 M-BULK, bulk-fill composite (Filtek One Bulk-Fill, 3 M Oral Care); and (iii) 3 M-CTR, a conventional composite (Filtek Supreme XTE, 3 M Oral Care). These were used in combination with their adhesives in self-etch (SE) or etch-and-rinse (ER) mode. Specimens stored in artificial saliva (24 h or 12 months) were evaluated for MTBS and fractography. The interfacial analysis was performed through confocal microscopy. ANOVA and Fisher's LSD post hoc tests were performed with a level of significance of 5%. RESULTS: All the tested materials applied in ER mode presented (24 h) greater bond strength than in SE mode. Although all materials showed a significant drop in the bond strength after prolonged storage, STELA showed the highest bonding performance and interfaces with few gaps. 3 M-BULK had the lowest bond strength and an interface with several voids and gaps. CONCLUSIONS: All materials were affected by interface degradation and bonding reduction over prolonged aging. However, their use in combination with adhesives applied in ER mode may offer greater immediate bonding performance. CLINICAL RELEVANCE: The use of restorative light-curing bulk-fill composites may generate gaps at the bonding interface and voids. STELA may represent a suitable alternative to avoid such issues.

The impact of inorganic fillers, organic content, and polymerization mode on the degree of conversion of monomers in resin-matrix cements for restorative dentistry: a scoping review.

PURPOSE: The main aim of the present study was to carry out a scoping review on the differences in degree of conversion of monomers regarding several types resin cements, indirect restorative materials, and light-curing procedures used in dentistry. METHOD: A bibliographic review was performed on PubMed using the following search items: "degree of conversion" OR "filler" AND "resin cement" OR "inorganic cement" AND "organic" OR "radiopacity" OR "refractive" OR "transmittance" OR "type" AND "resin composite." The search involved articles published in English language within the last thirteen years. A research question has been formulated following the PICO approach as follow: "How different is the degree of conversion of monomers comparing several types of resin-matrix cements?". RESULTS: Within the 15 selected studies, 8 studies reported a high degree of conversion (DC) of the organic matrix ranging from 70 up to 90% while 7 studies showed lower DC values. Dual-cured resin-matrix cements revealed the highest mean values of DC, flexural strength, and hardness when compared with light- and self-polymerized ones. DC mean values of resin-matrix cements light-cured through a ceramic veneer with 0.4 mm thickness were higher (~ 83%) than those recorded for resin-matrix cements light-cured through a thicker ceramic layer of 1.5 mm (~ 77%). CONCLUSIONS: The highest percentage of degree of conversion of monomers was reported for dual-cured resin-matrix cements and therefore both chemical and light-induced pathways promoted an enhanced polymerization of the material. Similar degree of conversion of the same resin-matrix cement were recorded when the prosthetic structure showed a low thickness. On thick prosthetic structures, translucent materials are required to allow the light transmission achieving the resin-matrix cement. CLINICAL RELEVANCE: The chemical composition of resin-matrix cements and the light-curing mode can affect the polymerization of the organic matrix. Thus, physical properties of the materials can vary leading to early clinical failures at restorative interfaces. Thus, the analysis of the polymerization pathways of resin-matrix cements is significantly beneficial for the clinical performance of the restorative interfaces.

Sixty-month comperative evaluation of a glass hybrid restorative and a composite resin in non-carious cervical lesions of bruxist individuals.

OBJECTIVE: To compare the clinical performance of a glass hybrid (GH) restorative and a nano-ceramic composite resin (CR) in the restoration of non-carious cervical lesions (NCCLs) of bruxist individuals in a 60-month randomized clinical trial. MATERIALS AND METHODS: Twenty-five bruxist candidates having NCCLs were recruited in this clinical study. The depth, height (cervico-incisal), width (mesio-distal), internal angles of the NCCLs, degree of tooth wear (TWI) and gingival index (GI) were measured. One hundred-and-forty-eight NCCLs were restored either with a GH restorative (Equia Forte Fil) or a CR (Ceram.X One Universal). Modified USPHS criteria was used to evaluate restorations after 1 week and 12, 24, 36 and 60 months. Pearson's Chi-Square, Fisher's Exact and Cochran Q tests were run for analysis. Survival rates of the restorations were compared with Kaplan-Meier analysis (p < 0.05). RESULTS: After 60 months, 97 restorations in 15 patients were examined. The recall rate was 60.0%. Retention rates were 73.5% for CR and 66.7% for GH. A total of 29 restorations were lost (13CR (26.5%), 16GH (33.3%)). There was not a significant difference between tested restoratives in retention (p = 0.464), marginal adaptation (p = 0.856) and marginal discoloration (p = 0.273). There was no relationship between internal angle, depth, height or width and retention of the GH or CR restorations (p > 0.05). The increase in retention loss and marginal discoloration of both restorations over time were significant (p < 0.001). Sensitivity or secondary caries were not detected after 60 months. CONCLUSION: GH and nano-ceramic CR showed similar clinical performances in NCCLs after 60 months in patients with bruxism. CLINICAL SIGNIFICANCE: After 60 months, CR and GH materials showed clinically acceptable performances in restoration of NCCLs in patients with bruxism.

In-vitro evaluation of fracture resistance of teeth restored with different high-viscosity glass ionomer restorative materials and bulk-fill composite resins.

OBJECTIVES: This study aimed to evaluate the effect of restorations made with a glass-hybrid restorative system (GHRS), a high-viscosity glass ionomer restorative material (HVGIC), a high-viscosity bulk-fill composite resin (HVB), a flowable bulk-fill composite resin (FB), and a nanohybrid composite resin (NH), which are commonly preferred in clinical applications on the fracture resistance of teeth in-vitro. MATERIALS AND METHODS: One hundred intact human premolar teeth were included in the study. The teeth were randomly divided into ten groups (n = 10). No treatment was applied to the teeth in Control group. Class II cavities were prepared on the mesial surfaces of the remaining ninety teeth in other groups. For restoration of the teeth, a GHRS, a HVGIC, a HVB, a FB, and a NH were used. Additionally, in four groups, teeth were restored using NH, GHRS, and HVGIC with open and closed-sandwich techniques. After 24 h, fracture resistance testing was performed. One-way ANOVA and Tukey HDS tests were used for statistical analysis of the data. RESULTS: The fracture resistance values of Control group were statistically significantly higher than those of GHRS, HVGIC, FB, NH, HVGIC-CS, GHRS-OS, and HVGIC-OS groups(p < 0.05). There was no statistically significant difference observed between the fracture resistance values of Control, HVB, and GHRS-CS groups (p > 0.05). CONCLUSION: It can be concluded that the use of HVB and the application of GHRS with a closed-sandwich technique may have a positive effect on the fracture resistance of teeth in the restoration of wide Class II cavities. CLINICAL RELEVANCE: The use of high-viscosity bulk-fill composite resin and the application of glass-hybrid restorative system with the closed-sandwich technique in the restoration of teeth with wide Class II cavities could increase the fracture resistance of the teeth.

Effect of fiber-reinforced direct restorative materials on the fracture resistance of endodontically treated mandibular molars restored with a conservative endodontic cavity design.

OBJECTIVE: This study aimed to evaluate the fracture strength of teeth restored using fiber-reinforced direct restorative materials after endodontic treatment with a conservative mesio-occlusal access cavity design. MATERIALS AND METHODS: A total of 100 extracted intact mandibular first molars were selected and distributed into a positive control group where teeth left intact and the following four test groups comprised of teeth with conservative mesio-occlusal access cavities that had undergone root canal treatment (n = 20/group): access cavity without restoration (negative control), bulk-fill resin composite with horizontal glass fiber post reinforcement, fiber-reinforced composite with bulk-fill resin and bulk-fill resin composite. Following thermocycling (10,000 cycles), fracture resistance was measured using a universal testing machine. Statistical analyses (one-way analysis of variance and the Tamhane test) were performed, and statistical significance was set at p < 0.05. RESULTS: Groups with minimally invasive access cavities had lower fracture strength than intact teeth, regardless of the restoration material (p < 0.05). Fiber-reinforced composite groups demonstrated higher fracture strength than bulk-fill resin composite alone (p < 0.05). Fracture types varied among groups, with restorable fractures predominant in the fiber-reinforced composite groups. CONCLUSION: This study suggests that using fiber-reinforced composite materials, especially in combination with bulk-fill resin composites, can effectively enhance the fracture strength of endodontically treated teeth with conservative access cavities. However, using only bulk-fill resin composite is not recommended based on the fracture strength results. CLINICAL SIGNIFICANCE: When teeth that undergo endodontic treatment are restored using a conservative access cavity design and fiber-reinforced composite materials, especially in combination with bulk-fill resin composites, the fracture strength of the teeth can be effectively increased.

Marginal integrity of prototype bioactive glass-doped resin composites in class II cavities.

OBJECTIVES: This in vitro study examined the marginal integrity of experimental composite materials doped with bioactive glass (BG). MATERIALS AND METHODS: Class-II MOD cavities were prepared and restored with one of the following composite materials: a commercial composite material as a reference (Filtek Supreme XTE), an experimental composite doped with BG 45S5 (C-20), and an experimental composite doped with a fluoride-containing BG (F-20). Six experimental groups (n = 8) were used, as each of the three composites was applied with (+) or without (-) a universal adhesive (Adper Scotchbond Multipurpose). All specimens were subjected to thermocycling (10,000 x, 5-55 °C) and then additionally stored in artificial saliva for eight weeks. Scanning electron micrographs of the mesial and the distal box were taken at three time points (initial, after thermocycling, and after eight weeks of storage in artificial saliva). The margins were classified as "continuous" and "non-continuous" and the percentage of continuous margins (PCM) was statistically analyzed (α = 0.05). RESULTS: In most experimental groups, thermocycling led to a significant decrease in PCM, while the additional 8-week aging had no significant effect. F-20 + performed significantly better (p = 0.005) after 8 weeks storage in artificial saliva than the reference material with adhesive, while no statistically significant differences were observed at the other two time points. C-20 + exhibited significantly better PCM than the reference material with adhesive after thermocycling (p = 0.026) and after 8 weeks (p = 0.003). CONCLUSIONS: Overall, the experimental composites with BG showed at least as good marginal adaptation as the commercial reference, with an indication of possible re-sealing of marginal gaps. CLINICAL RELEVANCE: Maintaining or improving the marginal integrity of composite restorations is important to prevent microleakage and its likely consequences such as pulp irritation and secondary caries.