Flowable Liner Research Articles

Marginal Adaptation of Direct Class II Composite Restorations with Different Cavity Liners

The aim of this study was to evaluate how cavity linings with different elastic modulus can influence the marginal adaptation (MA) of Class II composite restorations before and after thermo-mechanical loading. Forty Class II cavities with margins extending 1 mm below the cement-enamel junction were prepared in extracted human third molars. In each group except the control group, a lining material of 1-mm thickness was applied to the bottom of the cavity and polymerized before placing the resin composite Herculite XRV Ultra (group A: control; group B: Premise Flowable lining; group C: Herculite XRV Ultra lining; and group D: Optibond FL lining). MA was evaluated (with a scanning electron microscope) before and after loading (200,000 loading cycles). Statistical analysis was done using the Shapiro-Wilks test, the analysis of variance test, and Duncan post hoc test at p<0.05. Before loading, the percentages of continuous margins in dentin were superior (p<0.05) for groups C and D (71.1% and 87.2%, respectively) compared to groups A and B (55.7% and 48.3%, respectively). After loading, group D (79.8%) was statistically superior in dentin compared to all of the other groups (43.6%, 35.9%, and 54.4%, respectively). In occlusal enamel, no significant difference was found between groups. The percentage of enamel fractures and the percentage of noncontinuous margins in proximal enamel were high, with no significant difference between liners. It can be concluded that for the materials used in this study, a 1-mm-thick lining with an extremely low elastic modulus (2-3 GPa) could redistribute shrinkage stress. The use of a flowable composite did not significantly improve MA.

Effect of layering methods, composite type, and flowable liner on the polymerization shrinkage stress of light cured composites

ObjectivesThe aim of this study was to investigate the effect of layering methods, flowable composite liner and use of low shrinkage silorane-based composite on the polymerization shrinkage stress of light cured composites. MethodsAluminum blocks were used to prepare MOD cavities and divided into four groups. A universal hybrid methacrylate-based composite (Z250), a flowable composite (Z350 flowable), and a silorane-based composite (P90) were used to fill the cavities. Cavities were restored using four different filling protocols. Group 1 was filled in bulk with Z250, group 2 was restored by an increment technique with the same composite, group 3 by an increment technique with Z250 and a Z350 flowable lining, and group 4 was restored by an increment technique with P90. The axial shrinkage strain and flexural modulus of the three composites were determined, and cuspal deflection of each group was measured with LVDT probes and compared among groups using ANOVA and Tukey's post hoc test (α=0.05). ResultsThe axial shrinkage strains of P90, Z250, and Z350 flowable were 1.09 (0.11), 2.29 (0.06), and 4.12 (0.08)%, respectively. The flexural modulus of P90 was 10.1 (0.9), Z250 was 13.6 (2.0), and that of Z350 flowable was 7.6 (0.9) GPa. The cuspal deflections at 33min in groups 1–4 were 18.2 (1.54), 14.5 (0.47), 16.2 (1.10), and 6.6 (0.44) μm, respectively. The incremental filling technique yielded significantly lower cuspal deflection than the bulk filling technique. Flowable composite lining under universal composite (Z250) layering showed higher cuspal deflection than that without flowable composite lining. Silorane-based (P90) composite exhibited lower cuspal deflection than metacrylate based (Z250) composite. SignificanceCuspal deflection resulting from polymerization shrinkage stress may be reduced by an incremental filling technique and by the use of low shrinking composite to obtain optimal clinical outcomes. Flowable composite lining under conventional composite layering did not reduce polymerization shrinkage stress as assessed by cuspal deflection.

Evaluation of gingival microleakage of class II resin composite restorations with fiber inserts: An in vitro study

Aims/Objectives:To evaluate the effect of glass and polyethylene fiber inserts and flowable composite as a liner on the microleakage of Class II composite restorations with gingival margins on root surfaces.Materials and Methods:Class II slots were prepared on both the proximal sides of thirty freshly extracted mandibular molars and were divided into six groups, according to the type of fiber insert and use of flowable composite (Filtek Z350) as a liner. Filtek P-60 (3M/ESPE) posterior composite was used to restore all cavities. The specimens were thermocycled and stained with 2% Basic Fuchsin dye, and sectioned to evaluate the dye penetration under Stereomicroscope. Statistical analysis was done using Kruskalwallis test and Mann whitney U test.Results and Conclusion:This study showed that, fiber insert groups, with or without flowable liner, had reduced microleakage scores as compared to the control groups. However, statistically no significant difference was found between the groups with fiber inserts. Less microleakage was seen in Group IV (With flowable liner and without Fiber inserts) as compared to Group I (Without flowable liner and Fiber inserts).

Evaluation of the influence of flowable liner and two different adhesive systems on the microleakage of packable composite resin

Aim: The aim of the study was to evaluate the microleakage of a packable resin composite using two adhesive systems (self-etch and total-etch) with and without a flowable liner. Materials and Methods: Class II cavities were prepared on 50 human molars, with standardized dimensions. The teeth were divided into five groups. In group I, the cavities were total-etched with phosphoric acid and bonded with an Adper single bond and then restored with a packable resin composite. In group II, the cavities were total-etched, bonded with an Adper single bond and a flowable resin composite was placed as a liner and restored with a packable resin composite. In group III, self-etching adhesive was used instead of total-etch and a procedure similar to group II was performed. In group IV, a procedure similar to group III was performed, except with the placement of a flowable resin composite liner. Group V served as a control where neither adhesive nor a flowable liner was used. All the samples were placed in a dye for 24 hours and examined for leakage. Results: Packable resin composite, when used alone with self-etch adhesive, demonstrated minimum microleakage when compared to the total-etch system (P = 0.30). The lining of class II cavities with a flowable resin composite, followed by packable restoration, demonstrated higher leakage values than when the packable resin composite was used alone (P = 0.001). Conclusion: The use of a self-etch adhesive system was superior to the total-etch system when the cavities were restored with a combination of a flowable resin composite liner, overlaid with a packable resin composite.Clinical Relevance to Interdisciplinary Dentistry A flowable resin composite can be used as a liner material between dentin and a packable resin composite to reduce microleakage. Use of a proper adhesive system is one of the key factors in reducing microleakage in packable composite resin.

Effect of Pre-heated Composites and Flowable Liners on Class II Gingival Margin Gap Formation

To evaluate the effect of preheated composites (PHC) and flowable liners (FL) on the gingival margin gap formation of Class II composite restorations compared to the placement of room temperature composites (RTC). Class II composite restorations were prepared on 40 extracted mandibular third molars, with the gingival margin located 1 mm below the CEJ in dentin. Optibond FL (Kerr), microhybrid Filtek Z-250 (3M ESPE) and Flow-It (Jeneric Pentron) were used to evaluate five study groups: 1) PHC, 130 degrees F/54.4 degrees C; 2) PHC, 155 degrees F/68.3 degrees C; 3) FL cured prior to the first increment composite; 4) FL cured simultaneously with the first increment composite and 5) RTC (Control). Impressions were taken with quick set polyvinyl siloxane impression material, and epoxy resin replicas were evaluated under SEM (200x). Gingival margin adaptation was quantitatively evaluated in terms of percentage of gap formation according to a modified ordinal scoring criteria. All margins were evaluated twice for reliability assessment. A non-parametric Kruskal-Wallis test was used to determine whether significant differences in gap formation existed among the study groups. A high level of agreement was observed between duplicate measurements of the percentage of gap formation (intra-class correlation = 0.956, p < 0.0001). There was no evidence of a difference among groups defined by placement technique (p = 0.82). Overall, the mean gap-percentage for the 40 margins evaluated was 6.3 (Median = 1.1; SD = 14.8). Gingival margin adaptation was not improved relative to the control by any of the placement techniques tested. No significant differences in gap formation were found among the study groups. A high degree of intra-examiner reliability was confirmed.

Effect of Aging on Coronal Microleakage in Access Cavities through Metal Ceramic Crowns Restored with Resin Composites

The purpose of this in vitro study was to determine if packable resin composite with/without flowable resin composite has the ability to prevent coronal leakage in restored endodontic access openings following aging. Eighty simulated standardized access cavities of metal-ceramic crowns were fabricated and fixed on Vitrebond cavities filled with an epoxy resin. The specimens were randomly divided into two main groups: (1) Group A-Access cavities filled with only packable composite (Filtek P60); (2) Group B-Access cavities filled with Filtek P60 and a flowable composite (Filtek Z350) as liner. Each main group was further subdivided randomly into four subgroups according to water storage and thermocycling periods. All specimens were immersed in blue ink solution for 24 hours and then sectioned into quadrants. The extension of blue ink along the metal-ceramic crown/composite resin interface was measured linearly using image analyzer and then analyzed by three-way ANOVA and independent t-test with a Mann-Whitney test. The level of significance was set at p < 0.05. All tested subgroups demonstrated different levels of microleakage. There was no significant difference related to restorative technique; however, there was a significant difference related to water storage and thermocycling. All tested techniques and materials in this study showed microleakage. Packable composite while a flowable liner showed a marginally better result than packable composite alone. Excessive thermocycling resulted in significant differences among the test groups.

Effect of low-elastic modulus liner and base as stress-absorbing layer in composite resin restorations

Objectives The aim of this study was to evaluate the effectiveness of liner and base materials to reduce the stress resulting from polymerization shrinkage. The null hypothesis tested was that the presence of low-viscosity liner and base materials under the composite resin restoration reduces the polymerization shrinkage stress. Methods A quasi-three-dimensional photoelastic model of a second premolar with a class I preparation was restored using four experimental groups ( n = 7): RC, resin composite (Filtek Z250); FLRC, flowable liner (Filtek Flow) + resin composite restoration; VLRC, resin-modified glass-ionomer liner + resin composite restoration; and VBRC, resin-modified glass-ionomer base + resin composite restoration. The maximum shear stresses ( τ max) were calculated along the adhesive interface in 13 predefined and standardized point locations. Data were submitted to one-way ANOVA, followed by a Tukey's post hoc test ( p < 0.05). Results A significant difference was found among the experimental groups ( p = 0.001); therefore, the null hypothesis was rejected. The mean maximum shear stress was: 38.0 kPa for RC, 52.1 kPa for FLRC, 72.8 kPa for VLRC, and 90.2 kPa for VBRC. The polymerization shrinkage stress level from least to greatest was: RC < FLRC < VLRC < VBRC. The overall stress distribution in class I restoration indicated that stresses were primarily accumulated at the cavosurface and internal line angles. Significance Using a flowable composite or resin-modified glass-ionomer as liner or base material under composite resin restoration increases the polymerization shrinkage stresses at the adhesive interface leading to a possible adhesive failure.

Comparison of microleakage after load cycling for nanofilled composite resin fillings with or without flowable resin lining

I. 서론 = 1 II. 실험 재료 및 방법 = 4 1. 재료 = 4 1) 치아 = 4 2) 레진 접착제 = 4 3) 레진 = 4 4) 광중합기 = 6 2. 치아삭제와 충전 = 6 3. 반복부하실험 = 8 4. Statistical analysis = 10 III.연구 결과 = 11 IV.총괄 및 고찰 = 17 V. 결론 = 20 참고 문헌 = 21 Abstract = 24

Influence of flowable materials on microleakage of nanofilled and hybrid Class II composite restorations with LED and QTH LCUs

Class II composite restorations are more frequently being placed with margins apical to the cementoenamel junction (CEJ) and margins within the dentin are prone to microleakage. This in vitro study was used to evaluate the influence of flowable composite and flowable compomer as gingival liner on microleakage in Class II composite restorations and compare a light-emitting diode (LED) unit with a quartz tungsten halogen (QTH) unit for light-activating composite resins. Mesioocclusal and distoocclusal Class II cavity preparations were made in 72 sound extracted premolars. The buccolingual width was 2.5 mm and the gingival margins of all the cavities were placed 1.0 mm apical to the CEJ. The boxes were prepared 1.5 mm deep axially, making 144 slot cavities. Teeth were randomly divided into the following two groups (n = 72): (I) Universal Filtek Supreme XT; Universal Filtek Supreme XT + Flwable Filtek XT and Universal Filtek Supreme XT + Dyract Flow and (II) Filtek Z250; Filtek Z250 + Flwable Filtek XT and Filtek Z250 + Dyract Flow. Flowable materials were injected into the gingival floor of the cavity to a thickness of 1.0 mm. Each increment was cured for 20 s. One-half of the subgroups in each group were cured with QTH and the other half with LED light curing units (LCUs). After 1 week of incubation at 37 degrees C, the specimens were thermocycled (5-55 degrees C, x1500), immersed in 0.5% basic fuchsine dye for 24 h and sectioned and microleakage was evaluated at the gingival margin by two examiners using a 0-3 score scale. The data were analyzed using the Kruskal-Wallis and Mann-Whitney U tests. The groups utilizing flowable liners had significantly less microleakage (P < 0.05). No significant difference was identified between Universal Filtek Supreme XT and Filtek Z250 composites with and without flowable materials. There was no significant between utilizing flowable composite or flowable compomer and between each similar subgroup when polymerized with either the LED or the QTH LCUs. A layer of flowable materials at the gingival floor of Class II composite restorations may be recommended to improve the marginal seal of a restoration.

The effects of cavity size and filling method on the bonding to Class I cavities.

The effects of incremental filling technique and flowable liner on the bond strength of resin composite in different sized cavities were investigated in this study. Two sizes of cylindrical Class I cavities were prepared in bovine dentin (98.1 mm3 and 21.2 mm3). A light-curing resin composite (Clearfil Photocore) with a self-etching primer adhesive (Clearfil SE Bond) was used to bulk fill the cavities (C-factor 5), with and without flowable liner (Clearfil FLOW-FX) or incremental filling (2 layers, C-factor 3). As control, a 3-mm or 5-mm buildup was placed on the flat dentin surface (C-factor 0.2). After 24 h storage in 37 degrees C water, the microtensile bond strength was measured at a crosshead speed of 1 mm/min. Mode of failure in the fractured specimens was observed using a scanning electron microscope. The obtained results were statistically analyzed. In large cavities, incrementally filled and lined cavities showed higher bond strength values than the bulk-filled subgroup (p < 0.05). However, in small cavities, neither the incremental technique nor flowable liner improved the bond strength. Not only the filling techniques but also the cavity size affected the bond strength to the cavity floor in cylindrical Class I cavities.

Effect of Pre-heating Resin Composite on Restoration Microleakage

Improving the adaptation of resin composites during placement is necessary to increase durability and reduce microleakage. Flowable resin liners have been introduced to improve adaptation in composite restorations. In addition, a device that lowers the viscosity of regular dental composites has been introduced (Calset, AdDent Inc, Danbury, CT, USA). This device lowers the viscosity of composites by preheating them to 54.4 degrees C, which should lead to improved adaptation. This study compared microleakage in Class II composite restorations prepared using: 1) preheated resin composite, 2) unheated composite and 3) a flowable liner followed by unheated composite. Class II cavities were prepared on the mesial and distal surfaces of extracted third molars. Ten preparations were restored with resin composite (Esthet-X, Dentsply, York, PA, USA) for each of the following four techniques: Control (Esthet-X with Prime & Bond NT, Dentsply), Flowable (f) (as Control but used Esthet-X Flow liner), Preheated (p) (as Control but with preheating composite to 54.4 degrees C) and Delay (d) (as Preheated but followed by a 15-second delay before curing). The teeth were restored, finished, stored in distilled water for 24 hours, then thermocycled between water bath temperatures of 5 degrees C and 55 degrees C with a one-minute dwell time for 1000 cycles. Tooth apices were sealed with epoxy and varnish was applied to within 1 mm of the restoration margins. The teeth were placed in 0.5% basic fuschin dye for 24 hours, rinsed, then embedded in self-curing resin. The embedded teeth were sectioned mesiodistally with a slow-speed diamond saw, providing multiple sections per restoration. Microleakage was rated by two evaluators using a 0-4 ordinal scale at the occlusal and cervical margins of each restoration and light microscopy (40x). The data were analyzed with Kruskal-Wallis ANOVA and pairwise testing with the Sign test (alpha=0.05). No statistical differences were observed among materials at the occlusal margin. However, at the cervical margin, the preheated samples P showed statistically lower microleakage than the controls and all other treatments. The D samples showed higher microleakage than the P and F samples. Ranked sum scores for the cervical were D (4516), C (3974), F (2756) and P (1958). There was a statistically greater amount of leakage at the cervical margins compared to the occlusal p<0.05. Preheating the composite resulted in significantly less microleakage at the cervical margins compared to the flowable liner and control. Delaying light curing of the preheated composite for 15 seconds (D) was counterproductive and led to increased microleakage.

In vivo interfacial adaptation of class II resin composite restorations with and without a flowable resin composite liner

The aim of this study was to evaluate in vivo the interfacial adaptation of class II resin composite restorations with and without a flowable liner. In 24 premolars scheduled to be extracted after 1 month, 48 box-shaped, enamel-bordered class II cavities were prepared and restored with a flowable liner (FRC, Tetric Flow/Tetric Ceram/Syntac Single-Component) or without (TRC), cured with three different curing modes: soft start and 500- or 700-mW/cm2 continuous irradiation. Interfacial adaptation was evaluated by quantitative scanning electron microscopic analysis using replica method. Gap-free adaptation in the cervical enamel (CE) was observed for FRC and TRC in 96.2 and 90.2%, for the dentin (D) in 63.6 and 64.9%, and for occlusal enamel (OE) in 99.7 and 99.5%, respectively. The difference between the two restorations was not statistically significant (ns). Significant better adaptation was observed for OE than CE and D (p<0.01), and for CE than D (p<0.01). Gap-free adaptation with the soft-start and 500- and 700-mW/cm2 continuous-curing modes was observed for CE: 88.7%, 92.7%, 97.9% (ns); OE: 99.8%, 98.7%, 100% (ns); and D: 64.0%, 63.9%, and 64.6% (ns), respectively. It can be concluded that neither the use of flowable resin composite liner nor the curing mode used influenced the interfacial adaptation.

Fracture resistance of class II packable composite restorations with and without flowable liners

This study evaluated fracture resistance in class II slot packable composite restorations with and without the use of a flowable composite liner. A conventional microhybrid composite was used as a control. Thirty-six sound, caries-free human mandibulary molar teeth were used. Separate mesio-occlusal and disto-occlusal class II slot cavity preparations were made in each tooth. The prepared teeth were randomly divided into three groups of 12 teeth. Two packable composites (Surefil, Filtek P60) and one microhybrid composite (Filtek Z250) with their respective manufacturer's bonding agents were used to restore the cavities. One side of each tooth was restored with composite alone, while the other side was restored with the composite lined with that manufacturer's flowable liner. The marginal ridges of the restorations were loaded at an angle of 13.5 degrees to the long-axis of the tooth in an Instron Testing Machine until failure. The data were analysed using a one-way anova. There was no significant difference in fracture resistance between composite restorations with and without flowable liners.

Influence of c-factor and layering technique on microtensile bond strength to dentin

Objective. Due to polymerisation shrinkage of resin-based composites, a high configuration factor in deep Class I cavities leads to a certain amount of stress when the material is bonded. The aim of this in vitro study was to evaluate the influence of c-factor and different layering approaches on bonding to dentin with three different adhesive systems. Materials and methods. Dentin bond strengths of Z250 bonded with OptiBond FL, Single Bond, and One Up Bond F were measured on flattened dentin surfaces without cavity walls and on the cavity floor of Class I cavities (10 layering concepts). The resin composite increments were applied horizontally, vertically and obliquely, both with and without a flowable liner. The tests were carried out in a microtensile apparatus at a crosshead speed of 1 mm/min after 24 h of storage at 37 °C in water. Mean bond strengths were analysed using the Wilcoxon test and multiple comparisons according to the Mann–Whitney U-test. Specimens having failed prior to the bond strength test were included as 0 MPa. Results. The groups bonded on flat surfaces exhibited significantly higher bond strengths than specimens cut from filled cavities. Within the cavity groups, OptiBond FL and Single Bond exhibited no significant differences, however, being above One Up Bond F. Within the groups of each adhesive, major differences between the layering concepts were detectable. Bulk technique led to low dentin adhesion at the cavity floor, above all for Single Bond and One Up Bond F. Horizontal layers resulted in significantly higher bond strengths than did vertical or oblique. Lining with a flowable composite did not promote bond strength for OptiBond FL. For the other adhesives, a lining improved adhesion when vertical or oblique layers were applied, for horizontal increments no effect was evident. Conclusions. The c-factor is an influencing factor for dentin adhesion. However, using an appropriate layering technique, high bond strengths to deep cavity floors can be achieved.