Flowable Resin Research Articles

Evaluating the effect of preheating on resin composites in pit-and-fissure caries treatments with a digital intraoral scanner.

To evaluate the effect of preheating on the microleakage and surface hardness of resin composites in the treatment of pit-and-fissure caries with various widths,as measured by an intraoral scanner. A total of 153L-shaped cavities with different widths (1mm, 1.6mm and 2mm) were prepared on the buccal or palatal/lingual surfaces of human molars. The cavities were measured in three dimensions by a TRIOS scanner and then filled with various resins (room temperature Z350 flowable resin and room temperature and 60℃ Z350 universal resin). Microleakage and gap formation at 2 sites were evaluated by stereomicroscopy and scanning electron microscope. Resin samples were prepared, and the top surface Vickers hardness (VHNtop) of all samples was measured at 1day and 30 days postirradiation. No difference were observed in the 3D scans for the cavities sizes among groups with the same width. For the 1mm-wide cavity, the lowest microleakage was obtained with the flowable group; for the 1.6mm-wide cavity, the nonpreheating universal group showed the highest microleakage at site 1, and the preheating group exhibited lower microleakage than that of the nonpreheating universal group at site 2; and for the 2mm-wide cavity, the preheating group presented lower microleakage at site 2. The gap formations were consistent with the microleakage degrees. The preheating group exhibited the highest VHNtop at 1day and 30 days postirradiation. A digital intraoral scanner could be used to scan the cavities in three dimensions. Preheating technology could reduce the microleakage of Z350 universal resin and enhance its surface hardness.

Effect of viscosity of experimental universal adhesive on bond strength to dentin prepared with Er:YAG laser

The aim of this study was to clarify the effect of universal adhesive (UA) viscosity on the bond strength of resin composite to dentin prepared with Er:YAG laser. Four experimental UAs (SI-1, SI-2, SI-3, and SI-4) were developed by adding 1, 2, 3, and 4 wt/% nanosilica to BeautyBond Xtreme (Shofu), respectively. BeautyBond Xtreme was used as a control (SI-0). The viscosities of experimental UAs were measured using a B-type viscometer. After bovine mandibular anterior teeth were ground with #600 emery paper to obtain the flattened dentin surfaces, the dentin surfaces were cut thinly by irradiating the Er:YAG laser. Specimens were prepared using the respective UA and flowable resin composite and subjected to the microtensile bond strength (µTBS) test. The data from viscosity measurement and the μTBS test were statistically analyzed using the Kruskal–Wallis test. The mean values of viscosity significantly differed among the all experimental groups (p < 0.01). The μTBS of SI-1 and SI-2 was significantly higher than that of SI-0, SI-3, and SI-4 (p < 0.001). The μTBS of SI-0 was significantly lower than that of SI-4 (p < 0.001). The viscosities of the experimental universal adhesives significantly affected their bond strength to laser-cut dentin.

Effect of collagen sponge and flowable resin composite on pain management after free gingival graft harvesting: A randomized controlled clinical trial.

The aim of this study was to compare the effect of the application of a flowable resin composite coating, over a collagen sponge stabilized with suture, on postoperative pain after free gingival graft harvesting. Thirty-two free gingival grafts were harvested from the palate in 32 patients, who were subsequently randomized to have only a collagen sponge stabilized with sutures applied to the palatal wound (control), or to have the collagen sponge coated with a flowable resin composite (test). Patients were observed for 14 days, and the pain level was evaluated by using a numerical rating scale. The consumption of analgesics during the postoperative period and the characteristic of the graft were also analyzed. The patients in the test group reported having experienced significantly less pain statistically than the patients in the control group throughout the study. The consumption of analgesics was lower in the test group. The dimensions of harvested grafts in the control and test groups showed no significant differences in height, width, and thickness. In conclusion, the addition of flowable resin composite coating to the hemostatic collagen sponge on the palatal wound following free gingival graft harvesting helped to minimize postoperative pain.

Effect of Type of Resin Composite Material on Porosity, Interfacial Gaps and Microhardness of Small Class I Restorations.

This study aimed to compare the best restorative approach for the conservative class I cavity by comparing flowable and nanohybrid composites versus the placement technique regarding surface microhardness, porosity, and presence of interface gaps. Forty human molars were divided into four groups (n = 10). Standardized class I cavities were prepared and restored using one of the following materials: Group I - Flowable composite placed by incremental technique; group II - Flowable composite placed in one increment; group III - Nanohybrid composite placed by incremental technique; and group IV - Nano-hybrid composite placed in one increment. After finishing and polishing, specimens were sectioned into two halves. One section was chosen randomly for the Vickers microhardness (HV) evaluation and the other section was used for the assessment of porosities and interfacial adaptation (IA). The surface microhardness range was 28.5-76.2 (p < 0.05), mean pulpal microhardness range was 27.6-74.4 (p < 0.05). Flowable composites had lower HV than conventional counterparts. The mean pulpal HV of all materials exceeded 80% of occlusal HV. Restorative approaches did not statistically differ in porosities. However, IA percentages were higher in flowable materials compared to nanocomposites. Flowable resin composite materials have lower microhardness than Nanohybrid composites. In small class I cavities, the number of porosities was similar between the different placement techniques and the interfacial gaps were highest in the flowable composites. The use of nanohybrid resin composite to restore class I cavities will result in better hardness and less interfacial gaps compared to flowable composites.

Effect of full pulpotomy using a calcium silicate–based bioactive ceramic in adult permanent teeth with symptoms indicative of irreversible pulpitis: A retrospective study

BackgroundThe authors studied the treatment effect of full pulpotomy using a calcium silicate–based bioactive ceramic in adult permanent teeth with symptoms indicative of irreversible pulpitis. MethodsEighty-one adult permanent teeth with symptoms indicative of irreversible pulpitis in 78 patients aged 18 through 72 years were evaluated for inclusion in the study. After caries excavation, the pulp was amputated to the level of the canal orifices. After hemostasis was achieved, calcium silicate–based bioactive ceramic was placed as the capping agent. The cavity was sealed temporarily with a glass ionomer cement and then restored with flowable resin and composite resin after 2 weeks if no positive symptoms were reported or detected. Postoperative evaluation was performed by means of clinical and radiographic examination at 2 weeks and 3, 6, and 12 months. ResultsOverall success rates of the procedure were 96.3% (78 of 81), 93.8% (76 of 81), 92.6% (75 of 81), and 92.6% (75 of 81) at the 2-week, 3-month, 6-month, and 12-month recall visits, respectively. Six of the 81 teeth failed and required root canal therapy. In these 6 teeth, 3 exhibited severe cold stimuli pain and spontaneous pain at the 2-week follow-up, 2 had no response to electric pulp testing with apical percussion pain and periapical rarefaction at the 3-month follow-up, and 1 tooth exhibited periapical rarefaction and labial mucosal fistula at the 6-month follow-up. ConclusionsUnder the conditions of this study, full pulpotomy using a calcium silicate–based bioactive ceramic was a successful option for the treatment of adult permanent teeth with carious originated symptoms indicative of irreversible pulpitis. Practical ImplicationsVital pulp therapy is no longer impossible for adult permanent teeth with carious originated symptoms indicative of irreversible pulpitis.

Presentation and management of advanced occlusal caries affecting the maxillary cheek teeth of four horses

SummaryThis case series describes the management of advanced occlusal caries of the maxillary cheek teeth in four horses. All horses presented with grade 4 caries, i.e., affecting cementum, enamel, dentine and the integrity of the tooth. Food packing in deep cavities on the occlusal surface were present in all horses. Two horses presented with pulpitis of teeth adjacent to the occlusal caries lesions. The carious lesions were mostly limited to the occlusal surface of maxillary cheek teeth, whereas the peripheral cementum to a large degree remained unaffected. Management of these cases included cleaning, flushing, and debriding of carious surfaces and placing a flowable resin composite on areas with extensive tooth loss to prevent food packing and further destruction of dental tissues. Endodontic therapy was performed in two cases. Some of the horses that exhibited clinical signs showed improvement after treatment and none of the cases showed deterioration of caries lesions. One horse showed complete resolution of occlusal caries.

Fracture Resistance Evaluation and Failure Modes Rating Agreement for Two Endocrown Designs: An In Vitro Study

This in vitro study aimed to evaluate the fracture resistance and mode of failure of endocrowns with proximal extension design compared to the conventional design, and to assess the agreement of evaluators on the failure mode. Twenty mandibular third molars free of caries with approximately similar root lengths and crown dimensions were sectioned parallel to the occlusal plane 2 mm above the cementoenamel junction (CEJ). Then, pulp chambers and canals were accessed, cleaned, and smoothed for the path of insertion. To achieve a symmetrical pulp chamber with an average depth of 3 mm, chambers were filled with flowable resin composite. Then, teeth were randomly divided into two groups (n = 10). The control group has all the walls at the same level. The test group had a box extension on the proximal wall 2 mm apical to the buccal and lingual wall level. Endocrowns (n = 20) of two different designs (conventional and proximal extensions) were fabricated using lithium disilicate (IPS e.max CAD, Ivoclar Vivadent, Schaan, Liechtenstein). After cementation, specimens were loaded with a round-end vertical loading tip at a rate of 0.5 mm per minute until fracture (INSTRON, Norwood, MA, USA). Then, the fractured specimens were collected for evaluation and assessment. Statistical analyses were performed using the Mann-Whitney U-test (α = 0.05) for fracture test analysis and Cohen’s Kappa for inter-rater reliability. The Mann-Whitney U-test showed a non-significant difference between the two groups (p = 0.142). However, the mode of failure of the endocrown with proximal extension showed more catastrophic failures than the conventional design. Adding proximal boxes to the endocrown design did not negatively impact the fracture resistance of the restoration. Visualization of the fracture line and tracing their apical end by direct vision or other diagnostic tools is an essential part of the evaluation of failures of endocrowns. Endodontically treated molar teeth with proximal caries extension might be restored with an endocrown with proximal extension. Clinicians should take extra care when visualizing the fracture lines and tracing their apical end as it might be very misleading.

Effect of Ceramic Thickness on Light Attenuation, Degree of Conversion, Knoop Hardness, and Elastic Modulus of Four Luting Resins.

This study evaluated the influence of the thickness of disilicate ceramic on the light attenuation (mW/cm2), degree of conversion (DC, %), Knoop hardness (KH, N/mm2) and the elastic modulus (E, MPa) of four luting resins. Three resin cements: RelyX Veneer (RV, 3M Oral Care, Monrovia, CA USA); Allcem Veneer APS (AC, FGM); Variolink Esthetic LC (VE, Ivoclar Vivadent, Schaan, Liechtenstein) and one flowable resin composite Tetric N-Flow (TF, Ivoclar Vivadent) were photocured for 20 seconds. The irradiance (mW/cm2) and emission spectrum (mW/cm2/nm) from a broad-spectrum LED light unit (Bluephase G2, Ivoclar Vivadent) were measured over the luting material (control) and through 0.3 mm, 0.7 mm, and 1.0 mm thick ceramic discs (e.max CAD, Ivoclar Vivadent). The LED light delivered 26.1 J/cm2 to the surface and 6.2 J/cm2 through the 1.0 mm thick ceramic. The distribution of violet and blue light across the light tip of the light-curing unit (LCU) was relatively homogeneous, but there was less violet range. The irradiance and spectral radiant power decreased significantly as the ceramic thicknesses increased (p<0.001). The luting material type had significant effect on KH and E values (p<0.001). The RV had the greatest KH and E values, and VE had the lowest. Ceramic thickness had no significant effect on KH (p=0.213) and E (p=0.130). The KH (p=0.265) and E (p=0.165) were also not influenced by the location where these measurements were made across the specimens. No significant reduction of the DC was observed as the ceramic thickness increased (p=0.311). Increasing the ceramic thickness exponentially reduced the irradiance. This reduction was more pronounced at the shorter wavelengths (violet) of light, with an 82% decrease for 1 mm-thick ceramic. Increasing the ceramic thickness did not affect the DC, irrespective of photoinitiators used in the tested resins. The position of the violet and blue LEDs within the body of the LCU did not influence KH or E in any of the resins tested. The KH and E of VE were significantly lower than the other 3 luting materials tested.

Microleakage Study of a Bulk Fill over an Uncured Adhesive System

This study aimed to evaluate and compare the microleakage of composite resin restorations under a total-etch adhesive system applied with two different techniques, with and without cure. Cavities were made on the buccal surface of twenty-six intact teeth and subsequently restored with bulk-fill flow composite resin (SDR®® flow+) and conventional resin (Spectra™ ST HV). Two experimental groups were created, one where the total-etch adhesive (Prime &amp; Bond Active®) was cured and another where the adhesive was not cured before placing the flowable resin. Two control groups were also created, negative and positive. After the restorations were finished the, teeth were submerged in a solution of sodium pertechnetate (99mTcNaO4) for 3 h to evaluate the microleakage. The results showed more infiltration of radioisotopes characterized by the highest total count values of microleakage in group 1 (cured adhesive) and in the positive control. Group 2 (noncured adhesive) and the negative control showed lower values. We therefore considered that these groups were similar since their p-value was less than 0.05, with no statistically significant difference. Group 4 showed a statistically significant increase in relation to group 3 (p = 0.027). We concluded that the method of bulk-fill composite resins with noncured adhesive agents can have a positive effect on the longevity of bond strengths, with reduced microleakage.

Effects of Streptococcus mutans and its fluoride resistant strains on the adhesion of CAD/CAM ceramics to teeth and resin.

The similar elastic modulus of resin-matrix ceramics to dentin has resulted in their recent widespread application clinically. Nevertheless, the bacterial environment of oral cavity can degrade the resin composite. The objective was to analyse the effect of S. mutans and its fluoride-resistant strains on the adhesion of three CAD/CAM ceramics. S. mutans UA159 (UA) was identified, and its fluoride-resistant strain (FR) was induced. For crack observation, three kinds of CAD/CAM ceramics (IPS Empress, Lava Ultimate and Vita Enamic) were bonded with tooth complex (enamel, dentin and flowable resin) through adhesive. For micro-tensile test, ceramics were bonded with flowable resin, and cut into strip test pieces. Then specimens were immersed into the UA, FR and the control solution (BHI) separately for 14 d. Ceramic-adhesive interface and adhesive-tooth complex interface were observed and analyzed through electron microscope and stereomicroscope. Micro-tensile test was conducted. Specimens in bacterial solutions had more cracks and comparatively weaker micro-tensile strength than those in BHI. In ceramic-adhesive interface, Lava Ultimate produced the most cracks. In adhesive-tooth complex interface, adhesive-dentin produced the most cracks. Meanwhile, IPS Empress had the strongest micro-tensile strength when bonded with resin. S. mutans and its fluoride resistant strain can cause cracks in the bonding of ceramics and dental tissue, especially resin-matrix ceramic and dentin, and weaken the bonding strength between ceramics and resin.

Restauração de molares afetados pela Hipomineralização Molar-Incisivo utilizando a técnica da réplica oclusal

ABSTRACT The aim of this study was to report the clinical case of an 8-year-old male patient seen at the Pediatric Dentistry outpatient clinic at the Universidade Federal do Paraná, Brazil, diagnosed with molar-incisor hypomineralization (MIH) after presenting with pain in teeth 16, 36, and 46, which had extensive atypical cavities and opacities on the adjacent enamel. A diagnostic wax-up of affected teeth was performed for manufacture of silicone occlusal matrix. Encapsulated high-viscosity glass ionomer cement was handled and inserted into the occlusal matrix which was fitted onto the teeth by slight finger pressure. After setting time, excess of material was removed, and occlusion was checked. A flowable resin coating material was applied, and the restorations were finished. Six months later, the restorations performed for treatment of the severe MIH lesions proved to be efficient, lowering the sensitivity reported by the patient, reshaping the teeth, improving their function, and refining dental esthetics.

Optimal post height and diameter in preformed zirconia crown restoration on 3D-printed primary incisors.

In this in vitro study, fracture resistance was evaluated according to the post-diameter and -length in zirconia crown restorations on three-dimensional printed primary incisors undergone pulpectomy. One hundred-and-sixty primary incisor abutments were used which were artificially fabricated through 3D-printing. Each group was divided into two subgroups based on the zirconia post-diameter (1.5 mm and 2.0 mm) employed for post setting after pulpectomy. Furthermore, each group was divided into four subgroups based on the zirconia post-height (3.0, 4.0, 5.0 and 6.0 mm). Zirconia post setting was made by applying flowable resin after filling the pulp cavity with calcium hydroxide up to 3.0 mm below cemento-enamel junction (CEJ). Finally, a preformed zirconia crown of size #1 was cemented to the abutment through resin cement. A compressive load was applied to the middle palatal surface of incisors restored with zirconia crowns by using a universal testing machine at 145° angle which is the normal interincisal angle of children. The root fracture specimens were excluded and the samples fractured within crown and core parts were included in the final fracture resistance analysis. The group with 1.5-mm post-diameter and 5.0-mm post-height had the highest fracture resistance strength (130.63 ± 55.75 N) under masticatory pressure condition. Fracture resistance was statistically greater in 5.0-mm than in 4.0-mm and 3.0-mm post-height groups for 1.5-mm post-diameter subgroup. Moreover, 5.0-mm post-height subgroup had a statistically greater fracture resistance than that of 3.0-mm post-height subgroup for 2.0-mm post-diameter group. The 2.0-mm post-diameter subgroup had a statistically greater fracture resistance than that of 1.5-mm post-diameter subgroup for 3.0-mm and 4.0-mm post-heights. If zirconia post incorporation is required for deciduous incisor restoration, a post-length equal to facial CEJ level is recommended for gaining additional retention against masticatory pressure.

143 - Bonding and wear properties of self-adhesive flowable resin composites

143 - Bonding and wear properties of self-adhesive flowable resin composites

Traditional versus conservative endodontic access impact on fracture resistance of chairside CAD-CAM lithium disilicate anterior crowns: An in vitro study.

To evaluate the effect of traditional and conservative endodontic access hole preparation on fracture resistance of chairside computer-aided design and computer-aided manufacturing (CAD-CAM) lithium disilicate maxillary right central incisor crowns. Fifty-seven milled lithium disilicate maxillary right central incisor crowns were designed and fabricated with a chairside CAD-CAM system (Planmeca Romexis, Planmeca). The abutment preparation had a 1.0mm incisal reduction and 1.0mm chamfer finish. The restorations were bonded with resin cement to printed resin dies (n = 19 per group) and were treated and divided into three groups, (1) no endodontic access, (2) traditional triangular endodontic access, and (3) conservative ovoidal endodontic access. The endodontic access of the crowns was sealed with flowable resin composite. Restorations were subjected to 10,000 cycles of thermal cycling between 5° and 55°C. Then, restorations were loaded and exposed to compressive loading force, and the crack initiation (CI) and complete fracture (CF) were recorded. SEM micrographs of broken specimens on the printed dies were captured. ANOVA test and Bonferroni's correction were used for statistical comparison. The fracture resistance among the three groups varied. Crowns with no endodontic access displayed significantly (p < 0.001) higher resistance [CI: 1025 (121) N; CF 1134 (127) N], followed by crowns with conservative ovoidal endodontic access [CI: 924 (60) N; CF: 1000 (72) N. Crowns with traditional triangular endodontic access showed the significantly (p < 0.001) lowest fracture resistance [CI: 635 (82) N; CF: 709 (75) N]. The fracture resistance of chairside CAD-CAM lithium disilicate maxillary anterior crowns is influenced by the type of endodontic access provided. Conservative ovoidal endodontic access provides crowns with higher fracture resistance than traditional triangular endodontic access. Crowns with no endodontic access provided the highest resistance than other types of endodontic access.

Thickness and Substrate Effect on the Mechanical Behaviour of Direct Occlusal Veneers

This study aimed to evaluate the fracture resistance and stress magnitude of occlusal veneers made of conventional or flowable resin composites at different minimal thicknesses bonded on enamel or dentin. A total of 120 sound bovine incisors were flattened and used as substrates (enamel or dentin) for the restorations. The teeth were embedded into polymethyl methacrylate and allocated into 4 groups according to the resin composite (Clearfil AP-X PLT and Clearfil Majesty Flow, Kuraray Dental) and substrate. Further, the substrates were randomly subdivided in 12 groups (N=120, n=10) according to the occlusal veneer minimal thickness: 0.5, 1.0, or 2.0 mm. The teeth were directly restored with a standardised procedure. Then, the specimens were loaded until fracture in a universal testing machine (Instron 6022, Instron Corp.). A 3-way and a 1-way analysis of variance were used to determine significant differences for each factor. Three-dimensional finite element analysis was carried out following the in vitro boundary conditions to assess the stress magnitude in the restoration during compressive loading. The fracture loads were recorded into initial load to failure (ILF) and fatal load to failure (FLF). Differences were found in material for ILF and FLF, leading to an overall equal good performance in fracture load and stress distribution for both materials, regardless of the substrate. Differences in thickness were apparent in both ILF and FLF. Direct conventional and flow resin composite occlusal veneers present a promising mechanical behaviour when bonded on enamel or dentin. However, caution is advised when preparing 0.5-mm minimal thickness restorations.

Minor Orthodontic Treatment Using NiTi Wire Exerting Light Force: Case Reports

Minor orthodontic treatment using a thin wire with high elasticity can shorten the treatment period and reduce the load on the anchorage by the application of light force. Since it can be applied immediately without a dental laboratory procedure and does not require the patient's cooperation, it can be clinically useful. The cases reported here have led to positive results in short periods of treatment, using only a segmented straight 0.012 inch NiTi wire and flowable resin to address various locations within the oral cavity, such as the anterior teeth, premolars, and molars.

Comparative Evaluation of Microtensile Bond Strength in Three Different Dentin Luting Agents: An In vitro Study.

Long-term clinical success on indirect restorations is largely determined by bonding efficiency of the luting agent, with adhesion to dentin being the main challenge. Therefore, aim of this study was to assess the microtensile bond strength when using flowable resin composite, preheated resin composite and dual self-adhesive resin cement as dentin luting agents. Occlusal thirds of molar teeth were cut and randomly divided into 3 groups to be cemented: RelyX™U200, Filtek™ Z250 XT- preheated to 70° and Filtek Flow™ Z350XT. They were then thermocycled 5000 times between 5+/-2°C and 55+/-2°C. Subsequently, 10 microbars per group were prepared. The 30 samples were placed in saline solution for 24 hours at room temperature prior to microtensile test. This was performed with a digital universal testing machine at a crosshead speed of 0.5 mm/min. The bond strength values obtained were analyzed in Megapascals (MPa). Measures of central tendency such mean and measures of dispersion such standard deviation were used. In addition, the Kruskall Wallis non-parametric test with Bonferroni post hoc test was applied, considering a significance value of 5% (P < 0.05), with type I error. The dentin microtensile bond strengths of preheated resin composite, flowable resin composite and dual self-adhesive cement were 6.08 ± 0.66 Mpa, 5.25 ± 2.60Mpa and 2.82 ± 1.26Mpa, respectively. In addition, the preheated resin composite exhibited significantly higher microtensile bond strength compared to the dual self-adhesive cement (P < 0.001). While the flowable resin composite showed no significant difference with the dual self-adhesive cement (P = 0.054) and the preheated resin composite (P = 0.329). The microtensile bond strength in dentin was significantly higher when using a preheated resin composite at 70°C as a luting agent compared to dual self-adhesive cement. However, the preheated resin composite showed similar microtensile bond strength compared to the flowable resin composite.

Appropriate Immediate Dentin Sealing to Improve the Bonding of CAD/CAM Ceramic Crown Restorations.

This study aimed to use quantitative and qualitative evaluations based on micro-tensile bond strength (μTBS) to clarify the appropriate immediate dentin sealing (IDS) approach for improving the bonding of CAD/CAM ceramic crown restorations. Forty-eight extracted human molars were prepared to obtain standardized abutment specimens and divided into three groups: no IDS (group C: control), IDS performed by a single application of an all-in-one adhesive system (group A), and IDS performed by the combined application of an adhesive system and a flowable resin composite (group F). All specimens were restored with a ceramic crown fabricated by a chair-side CAD/CAM system and were divided into no-stress and stressed groups. After cyclic loading (78.5 N; total, 3 × 105 cycles; 90 cycles/min) on the specimens in the stressed group, all specimens were sectioned. The μTBS values for the occlusal and mesioaxial walls were measured (n = 16) and analyzed statistically. The quantitative bonding performance of groups A and F were superior to that of group C, regardless of the cyclic loading and abutment wall conditions. Group F showed the maximum bond strength and the highest bond durability in the qualitative bonding performance even under the cyclic loading condition simulating clinical mastication.

Effect of contamination of bulk-fill flowable resin composite with different contaminants during packing on its surface microhardness and compressive strength: in vitro study

BackgroundProper isolation and restoration of class V subgingival cavities are technique sensitive, thus the resin composite restoration is liable to contamination. This in vitro study was conducted to evaluate the surface microhardness and compressive strength of bulk-fill flowable resin composite after being contaminated during its packing.MethodsResin composite discs were prepared using split mold. The contaminated specimens were allocated into four groups (n = 20) according to the contaminant used: hemostatic agent (Group 1), alcohol (Group 2), artificial saliva (Group 3) and powdered gloves (Group 4). The non-contaminated specimens (n = 20) were used as control group. The surface microhardness and compressive strength of each group were tested 1-day post-photocuring (n = 5) and 1 month post-photocuring (n = 5). Values were presented as mean, standard deviation values and confidence intervals.ResultsThe surface microhardness of all groups didn’t show a significant difference for different tested groups except for alcohol which showed a significant reduction on surface microhardness compared to control at 1 day post-photocuring (p = 0.001). The highest compressive strength mean values at 1 day and 1 month post-photocuring were recorded in control groups (110.42 MPa and 172.87 MPa respectively), followed by alcohol groups, then hemostatic agent groups, followed by artificial saliva with the least value recorded in powdered gloves groups (56.71 MPa and 49.5 MPa respectively).ConclusionsContamination of bulk-fill flowable resin composite with hemostatic agent, alcohol, artificial saliva, or powdered gloves during its packing decreased its compressive strength after 1 month post-photocuring rather than affecting its surface microhardness.

Evaluation of microleakage and push-out bond strength of various composite resins for sealing the screw-access channel in implant-supported restorations

Statement of problemMicroleakage and loss of the composite resin sealing the screw-access channel are frequent complications of screw-retained implant-supported prostheses. How the screw-access channel should be best restored to reduce such complications is unclear. PurposeThe purpose of this in vitro study was to evaluate the microleakage and bond strength of 3 types of composite resins (flowable, packable, and bulk-fill) with or without a bonding agent treatment to seal the screw-access channel of 2 types of restorative materials (zirconia and Co-Cr alloy) with or without thermocycling. Material and methodsIn total, 240 yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) specimens (IPS e.max ZirCAD) and 240 Co-Cr alloy (Vera PDS) specimens were prepared with a Ø3×3-mm cylindrical cavity at the center to simulate the screw-access channel. Three types of composite resins (flowable, packable, and bulk-fill resin) (Filtek Z350 XT Flowable Restorative, Filtek Z350 XT Universal Restorative, and Filtek One Bulk Fill Restorative) were applied to restore the access channel of the zirconia and Co-Cr specimens with or without a bonding agent (Single Bond Universal Adhesive). Microleakage and push-out bond strength were determined and compared by dividing the specimens into experimental groups with or without thermocycling (1000 times with 30 seconds at 5 ±2 °C and 55 ±2 °C). The results were analyzed by using a 1-way ANOVA and 4-way ANOVA. Adjustment for multiple comparisons was made with the Tukey Honestly Significant Difference (HSD) test. ResultsThe specimens subjected to thermocycling showed a lower bond strength (P<.001) and higher microleakage (P<.001) than specimens stored in a constant-temperature water bath. Specimens treated with bonding agents showed a higher bond strength (P<.001) and lower microleakage (P<.001) than specimens not treated with a bonding agent. Higher bond strengths were observed in the order of bulk-fill resin, packable resin, and flowable resin (P<.001). Packable resin showed higher microleakage than flowable resin and bulk-fill resin (P<.05). No significant difference in microleakage was found between the flowable resin and bulk-fill resin (P>.05). ConclusionsHigher bond strengths were observed in the order of bulk-fill resin, packable resin, and flowable resin. Less microleakage was observed in the flowable resin and bulk-fill resin than in the packable composite resin. Bonding agent treatment was effective in increasing bond strength and decreasing microleakage. Zirconia and Co-Cr showed a bond strength similar to that of composite resins, but zirconia showed higher microleakage than Co-Cr. Restoring the screw-access channel with the bulk-fill resin should increase bond strength and reduce microleakage.