Nanohybrid Composite Resin Research Articles

Effect of acidic media on flexural strength and fatigue of CAD-CAM dental materials.

To investigate the effect of acidic media, including beverages and gastric fluids on flexural strength and fatigue of CAD-CAM materials. Four CAD-CAM materials (high-translucency zirconia (Ceramill Zolid HT+), lithium disilicate (IPS e-max CAD), hybrid ceramic (Vita Enamic), and nanohybrid resin composite (Grandio Blocs) were prepared and immersed in one of five media (gastric HCl, white wine, Coca-Cola, orange juice, and artificial saliva) in an incubator (37℃, 24h). Surface topography and roughness were obtained using a scanning electron microscope (SEM) and a stylus contact profilometer, respectively. Initial 3-point flexural strength was measured for half of the bars (n=20/gp) using a universal testing machine (0.5mm/min). The other bars underwent 106 cyclic fatigue loadings before measurement of residual 3-point flexural strength. Data were statistically analyzed (two-way and three-way ANOVA, Tukey's post-hoc, p<0.05). Weibull distributions were plotted for reliability analysis. Zirconia bars has the highest initial flexural strengths followed by lithium disilicate, while resin composite and hybrid ceramic groups had the lowest strength regardless of the erosive medium. Cyclic fatigue significantly reduced initial flexural strengths for all materials except for hybrid ceramic and resin composite. Weibull moduli were the highest for zirconia, lithium disilicate and resin composite and lowest for hybrid ceramic. Erosive media significantly changed surface roughness of CAD-CAM materials except for zirconia and resin composite without jeopardizing the flexural strength of the CAD-CAM materials. Despite the higher flexural strengths for zirconia and lithium disilicate, resin composite and hybrid ceramic were more resistant to cyclic fatigue.

Influence of filler types on wear and surface hardness of composite resin restorations.

Wear and surface hardness of resin composites are of relevance from the clinical standpoint. With the incorporation of novel filler system, more studies need to be performed to investigate newly marketed resin composites. The objective of this study was to investigate the abrasive wear and surface hardness of dental restorative with different filler types. Nanohybrid filled Harmonize (HM) and Tetric N-Ceram (TNC), microhybrid filled Filtek Z250 (Z250), nanofilled Filtek Z350 (Z350) were included in the study. Twelve cylindrical resin composites specimens with 10 mm in diameter and 6 mm in thickness were prepared for abrasive wear test. Eight hundred cycles under 17 kg load were conducted for final wear by CW3-1 wear machine. The specimen was cleaned with an ultrasonic unit for 3 min followed with drying procedure. After measurement of weight loss and the density of specimens, the specimens were kept for measurement of surface hardness. Surface hardness was measured using a micro-hardness tester with a Vickers diamond indenter after polishing. Three specimens of each material were observed by scanning electron microscopy (SEM) after the abrasion to evaluate the morphology of the surface. Data were analyzed using one-way analysis of variance (ANOVA), followed by Tukey HSD test (α = .05). Z250 performed the least volume wear loss (41.1 ± 2.1 mm3), as well as the hardest value (102.7 ± 2.9 HV). There was no significant difference with the volume wear loss (p = 1.000) and surface hardness (p = 0.874) of HM and TNC. SEM images of nanohybrid filled HM and TNC represented smoother surface compared with other types of resin composites. Microhybrid Z250 showed the highest wear resistance and surface hardness, nanofilled and nanohybrid resin composites may still face the insufficient of wear and surface hardness quality.

The Effect of Pre-Heating on Fracture Toughness in Three Distinct Composite Resin Systems at Two Different Temperatures: A Protocol for an In-vitro Study

Introduction: Composite resins are considered the pinnacle of esthetic restorations, but they have their own disadvantages, such as polymerization shrinkage, low fracture toughness, and the formation of microcracks, all of which eventually results in failure of the restoration. Fracture toughness is an important factor for failure. Warming the same composites to certain temperatures will show drastic improvements in the abovementioned flaws, especially the fracture toughness. Need for the study: Therefore, the objective of this study is to evaluate and compare the fracture toughness of three different types of composite resin systems at two different pre-heating temperatures. The study aims to provide valuable information to clinicians in choosing the most appropriate restorative material for posterior composite restorations, which can ultimately improve the treatment's success rate and reduce the risk of complications such as secondary caries, postoperative sensitivity and ultimately restoration failure. Objective: In summary, this study will compare and evaluate the fracture toughness of nanohybrid, micro-hybrid, and bulkfill composite resins pre-heated at 50 degrees Celsius and 60 degrees Celsius. Methodology: The methodology involves dividing 72 freshly extracted premolars with intact occlusal anatomy and fully developed apical foramina into three main groups based on three different composites and further dividing each group into two sub-groups based on two different pre-heating temperatures, with 12 teeth in each group. Each tooth will then be prepared with a Class-II Mesio-Occlusal-Distal (MOD) cavity and receive pre-heated composite restoration according to its assigned group and sub-group. The prepared samples will be tested for fracture toughness using a universal testing machine.

Determination of the Impact of Various Commonly Consumed Beverages on the Colour Stability of Universal Nanohybrid, Nanofilled, and Microhybrid Composite Resins: An In-vitro Spectrophotometric Study

Introduction: The challenge in restorative dentistry is related to changes in the colour of composite over time when exposed to a variety of common beverages, which necessitates additional expenses for the patients. Aim: To compare the colour changes of various composites currently available on the market after exposure to commonly consumed beverages. Materials and Methods: This in-vitro study was conducted from May 2022 to December 2022 in the Department of Conservative Dentistry and Endodontics at Karnavati School of Dentistry in Gandhinagar, Gujarat, India. A total of 120 disc-shaped composite pellets, with 40 specimens for each type of composite (nanohybrid, nanofilled, and microhybrid), measuring 6×2 mm, were prepared and divided into four subgroups based on the beverages used (Distilled water, coca-cola, Tea, and Coffee). The samples were submerged in the respective beverages and kept at 37°C for seven days. Colour assessment was performed using a spectrophotometer before and after immersion. The obtained Commission International de l Eclairage (CIE) ΔE values were recorded after measuring the CIE L*a*b* values. Data analysis was conducted using Statistical Package for Social Sciences (SPSS) software version 20.0, utilising a paired t-test, post hoc Tukey’s test, and one-way Analysis of Variance (ANOVA). A significance level of p&lt;0.05 was used. Result: Among all the beverages, the nanofilled composite showed the highest mean colour change, while the nanohybrid composite exhibited the lowest. Overall, the greatest colour change was observed with tea, followed by coffee, coca-cola, and the least with distilled water. In tea, coffee, and cocacola, the nanohybrid composite and nanofilled composite showed a statistically significant difference in mean colour change: 16.74 (p&lt;0.001), -7.29 (p&lt;0.001), and -1.02 (p=0.018), respectively. However, the difference between the nanohybrid and microhybrid composite was statistically insignificant. Conclusion: The nanohybrid composite demonstrated the least mean colour change, followed by the microhybrid composite, while the nanofilled composite exhibited the highest colour change.

Marginal adaptation of thermoviscous bulk-fill composite in class II cavities

ObjectiveTo evaluate the marginal adaptation of thermoviscous bulk-fill, preheated, and conventional nanohybrid composite resins in class II cavities.Patients and methodsThirty extracted human sound molars were selected in this in vitro study. Simple class II cavities were prepared using carbide bur. The overall dimensions and depth of cavities were standardized as follows: 4 mm length occlusocervically, 4 mm width buccolingually, and 2 mm depth axially. The teeth were randomly divided into three groups (n = 10 each). Futurabond DC (one-step self-etch adhesive) was applied in all groups. Group 1: cavities were restored with VisCalor bulk composite, group 2: cavities were restored with Grandio composite, group 3: cavities were restored with preheated Grandio composite. The specimens of each group were thermocycled in a thermocycling apparatus by alternating immersion in a water bath at 5 and 55°C with a dwell time of 2 min for 600 thermal cycles. Impressions of the teeth were made and then poured with epoxy resin and replicas were examined under scanning electron microscopy to examine marginal gaps. All data were collected, tabulated, and statistically analyzed.ResultThe highest percentage of marginal gap length was recorded for group 2, recording 22.93%, while there was no significant difference between group 1 and group 3, recording 13.44 and 13.83%, respectively. One-way analysis of variance test was used to compare the tested groups at a level of significance (P < 0.05).ConclusionThe marginal gaps decreased when VisCalor bulk and Grandio composite resins were applied after preheating so preheating composite resins considerably improves marginal adaptation.

Effects of different toothpastes on the color and whiteness of stained anterior composite resin.

To evaluate changes in the color of an anterior nanohybrid composite resin and differences in its whitening index after 30 days of brushing with six brands of whitening toothpaste in vitro to simulate the situation in individuals with high coffee consumption. Eighty-four disk-shaped resin specimens were prepared (shade A2). For initial staining, the samples were immersed in coffee solution for 14 days and then divided into eight groups for treatment with various toothpastes. Color was assessed at the baseline, after initial staining, and on days 7, 14, and 30 of the staining-and-brushing cycle. Color stability was evaluated based on the CIEDE2000 color difference (ΔE00), and differences in whiteness were determined using the whitening index for dentistry (WID). The highest ΔE00 and ΔWID values were obtained with Colgate Herbal, followed by Opalescence Whitening and Crest Baking Soda and Peroxide, whereas the lowest values were obtained with distilled water, followed by Yotuel Pharma B5, on day 30 of the staining-and-brushing cycle. In terms of improving the color and whiteness of coffee-stained anterior nanohybrid composite resin, Colgate Herbal, Opalescence Whitening, and Crest Baking Soda and Peroxide yielded promising results after 30 days of continuous use.

Effect of Polydopamine on Bonding Characteristics of Mineral Trioxide Aggregate to Resin Composite.

The success of vital pulp therapy is crucial to preserve the integrity of the teeth and to enable an uninterrupted root formation in a young permanent tooth. This warrants placement of an intact permanent seal immediately in contact with the pulp capping material. Mineral trioxide aggregate (MTA) sets by hydration and deters placement of an immediate permanent resin composite restoration over it. The aim of this in vitro study is to evaluate the wettability, surface morphology and shear bond strength (SBS) of polydopamine (PDA)-pretreated MTA to resin composite (RC). The contact angle (CA) and morphological changes caused by self-etch (SE) adhesive on untreated and PDA-pretreated MTA was analyzed using contact angle meter and scanning electron microscope (SEM) respectively. To evaluate SBS, 144 MTA samples were prepared using a custom-made mold of 5 mm diameter and 3 mm height. The samples were randomly divided into two groups of 72 samples each based on whether their surface was pretreated with PDA or not. Under each group, nano-hybrid RC restoration was done either immediately or after a delay of 3 h, 24 h and 96 h. SBS of the MTA/resin composite assembly was tested in a universal testing machine. CA values were analyzed using One-way analysis of variance and Games-Howell Post Hoc test. Mann-Whitney test and Friedman post-hoc Dunn test were used to analyze SBS values. SE adhesive made a significantly lesser mean CA with PDA-pretreated MTA (27.20°+-2.28) compared to untreated MTA (34.22°+-1.45, p<0.05). SEM micrographs showed that while etching with SE primer eroded the surface characteristics, PDA coating minimized the erosive effect of the acidic primer and preserved the original crystalline plate-like structure of MTA. At all tested time intervals, PDA pretreatment significantly increased the SBS of MTA to RC, compared to untreated control. Immediate bond strength of PDA pretreated MTA (26.30+-7.60 MPa) was equivalent to the SBS value achieved at 96 h with untreated MTA (27.82+-2.96 MPa). Within the limitations of this in vitro study, it can be concluded that PDA pretreatment of MTA surface improved its wettability, prevented loss of surface integrity following etching and increased the SBS of RC to MTA. (EEJ-2022-11-144).

The effect of different herbal teas on the color stability of nanohybrid and bulk-fill composites

Aim: The aim of this study is to investigate the effects of green tea and rosehip tea, on the color stability of nanohybrid and bulk-fill composite resins. Methodology: A total of 60 disc-shaped samples were made from two types of A2 resin with nanohybrid (Tetric N Ceram, Ivoclar Vivadent, Schaan, Liechtenstein) and bulk-fill (Filtek Bulk-Fill, 3M ESPE, MN, USA) structure with the help of 10 mm diameter and 2 mm thick Teflon molds in this study. All samples were finished and polished with 4-stage (thick, medium, fine, superfine) polishing discs (Sof-lex, 3M ESPE, MN, USA) and kept in an oven at 37 °C for 24 hours. The samples, whose initial color measurements were made by spectrophotometer, were divided into subgroups for the control group and two different herbal teas (Green tea, Rosehip) (n=10). Color measurements were repeated, and ΔE values were calculated. Wilcoxon, Kruskal-Wallis, and Bonferroni tests were used to analyze the data (p &lt; 0.05). Results: There was no statistically significant difference in color change between the composite resins (p &gt; 0.05). No significant color change was found for either the Tetric N-Ceram or Filtek Bulk-Fill composite resin samples immersed in distilled water (p &gt; 0.05, ΔE&lt;3.3). Conclusion: Rosehip and green tea affect the color stability of composite resin restorations. Whereas the color change caused by green tea is at a clinically acceptable level, that stemming from rosehip tea falls within clinically unacceptable levels. How to cite this article: Tunçdemir MT, Dereli Z, Bahar A. The effect of different herbal teas on the color stability of nanohybrid and bulk-fill composites. Int Dent Res 2022;12(Suppl.1):103-7. https://doi.org/10.5577/intdentres.445 Linguistic Revision: The English in this manuscript has been checked by at least two professional editors, both native speakers of English.

Micro-computed tomography assesment of structural microporosity and marginal gaps in different flowable composites placed with different instruments

Objectives: The aim of this study was to evaluate the structural microporosity (MP) and marginal gap (MG) of different flowable composite resins placed with different instruments using micro-computed tomography (μCT). &#x0D; Materials and Methods: Standard Class II MOD cavities were prepared on 108 lower third molar teeth. Three different flowable composite resins; Filtek Bulk-fill, SDR Bulk-fill and I-Flow conventional flowable composite resin were applied to the cavities using a sharp explorer, a microbrush or an injector. After they were covered with a paste-like nanohybrid composite resin, μCT images were examined in terms of MP and MG. Statistical analysis of the data was performed using two-way ANOVA and Tukey’s post hoc tests. &#x0D; Results: MP was observed less in explorer group than microbrush and injector groups (p &lt; 0.05). There was no significant difference between microbrush and injector groups (p &gt; 0.05). i-FLOW flowable composite resin showed the highest MP rate compared to the other two groups (p &lt; 0.05). There was no significant difference between SDR and Filtek Bulk-fill in MP (p &gt; 0.05). In terms of MG, i-FLOW presented higher MG values than other two materials (p &lt; 0.05), while the instruments showed similar results (p &gt; 0.05). &#x0D; Conclusions: Additional occluso-gingivally vibration of flowable materials with an explorer may be useful in the placement. Bulk-fill composite resins are better than conventional flowable composite resin in terms of MP and MG.

Evaluation of Microleakage of a New Bioactive Material for Restoration of Posterior Teeth: An In Vitro Radioactive Model

Hybrid bioactive composite resins combine the benefits of glass ionomer cements with composite resins. Its self-adhesiveness is achieved through functional polyacrylic acids and carboxylic groups, hybridizing the smear layer and establishing ionic interactions between calcium and dentin. These materials are defined as having good aesthetics, moisture tolerance, durability, simplicity in technique and handling and are able to maintain a low microfiltration rate while releasing calcium, phosphate and fluorine. The aim of the present study was to evaluate microleakage in restorations using Surefill One™ bioactive resin. The null hypothesis is that this type of resin does not obtain a lower microleakage rate when compared to other materials. An in vitro study was carried out using thirty-six premolars and molars extracted for orthodontic reasons. Identical preparations were thus performed in all of them (Class V with 4 mm mesio-distal, 3 mm occluso-gingival and 3 mm in depth) and divided into different experimental groups: one positive control, one negative control and two tests with bioactive composite resin and conventional composite resin (Surefill One™ and Spectra™ ST HV, respectively). Through quantitative techniques using nuclear medicine, it was possible to evaluate microleakage through the use of a radioactive isotope, technetium. Radioactivity emitted by the specimens was detected by a gamma camera. The different groups were compared using the Kruskal–Wallis test and the Games–Howell test for multiple comparisons. The results of the experimental study point to statistically significant differences between the test groups (p = 0.002) with increased microleakage in the bioactive composite resin group. Based on the present microleakage study, it was possible to conclude that the bioactive composite resin (Surefill One™) does not reduce the microleakage rate when compared to a conventional nanohybrid composite resin (Spectra™ ST HV). However, Surefill One™ can be used in temporary restorations, primary teeth and in cases of tissue remineralization, thus avoiding more invasive procedures.

The effect of different energy levels of the Er: YAG laser on the repair bond strength of a nanohybrid composite resin.

This study evaluates the durability of repair microshear bond strength (µSBS) of nanohybrid composite resins which surfaces are treated with different laser parameters and bur. A total of 240 nanohybrid composite resin disk shaped specimens were prepared. Then, specimens were divided into eight test groups as regards to surface treatment types (Erbium (Er:YAG) laser with seven different parameters and bur). Half of the specimens in each group were subjected to 5000 thermal cycling (TC) and the other half to 20,000 TC. Universal testing machine was used for µSBS test. The data were analyzed with a two-way analysis of variance and Tukey test. Among the specimens treated with ER:YAG laser+5000 TC, we detected the highest mean µSBS test values in the subgroups L200 and L250. Among the specimens treated with ER:YAG laser+20,000 TC, the highest mean µSBS test values were seen in the L200 subgroup. The µSBS values after the 20,000 TC were significantly lower than those after 5000 TC for all different treatment types. Thermal cycling and laser energy levels have effects on repair µSBS. Considering the bond strength and durability it seems more effective to use Er:YAG laser at 200 mJ. To repair an aged nanohybrid composite resin, Er:YAG laser surface treatments may provide some benefits by acquiring a reliable bond strength with durability. This study may give information on which parameters are more suitable to use Er:YAG laser for the repair of nanohybrid composite resins.

Comparison of the effect of preheating on the flexural strength of giomer and nanohybrid composite resin.

Background. Considering the increased use of preheating and novel resin-based materials to restore teeth, the present study investigated the impact of preheating on the flexural strength of a giomer and compared it with a nanohybrid composite resin. Methods. Two restorative materials (Beautifil II giomer and Alpha III nanohybrid composite resin) were used. Thirty rod-shaped samples (adding up to 60 samples) were prepared from the materials above and divided into two subgroups: with and without preheating (n=15). Before sample preparation, the giomer and nanohybrid composite resin tubes were preheated at 68ºC for 15 minutes in the preheating subgroups. In the subgroups without preheating, the tubes were kept in a room at 25ºC. Then the flexural strength was compared between the two groups with two-way ANOVA at a significance level of P<0.05. Results. The results showed significantly higher flexural strength in the preheated subgroups than in the non-preheated subgroups (P<0.001). In addition, the mean flexural strength values were significantly higher in the giomer groups than in the nanohybrid composite resin groups (P<0.001). Conclusion. Preheating increased the studied materials' flexural strengths significantly. The flexural strength of the giomer restorative material was higher than that of the nanohybrid composite resin, irrespective of preheating.

Resistance to fracture of simulated external cervical resorption cavities repaired with different materials.

The aim of the study was to evaluate the fracture resistance (FR) of teeth with simulated external cervical resorption (ECR) cavities repaired with different materials. Following the shaping of the 80 human permanent maxillary central incisors, standard ECR cavities were prepared and restored with a nanohybrid composite resin; a high viscosity GIC Equia Forte Fill; Biodentine; Biodentine + nanohybrid composite resin; MTA BIOREP; MTA BIOREP + nanohybrid composite resin. Then, the root canals were obturated with AH Plus and gutta-percha. The roots were embedded acrylic resin blocks and fracture strength test was applied. The highest FR was observed in the Biodentine group, while the lowest was in Equia group (p < 0.05). No significant results were observed among composite, Biodentine + composite, MTA BIOREP + composite and MTA BIOREP (p > 0.05). Biodentine may be a preferable material for repairing ECR cavities. Adding a composite layer on MTA BIOREP and Biodentine did not improve the FR of these materials.

THE EFFECT OF HIGH TEMPERATURE HEATING ON WEIGHT AND COLOR CHANGES IN COMPOSITE RESIN AS FORENSIC IDENTIFICATION

Background: Fire disaster is a non-natural disaster that often occurs. The impact is that victims are difficult to identify. One of the identification methods that can be used is dental restorative materials with observing changes in color and weight that occur in dental restorative materials due to exposure to high temperatures. Composite resin is a dental restorative material that is often used because it has good aesthetics, physical and mechanical properties. Purpose: This study to determine the effect of high temperature on weight and color changes in nanohybrid and bulkfill composite resin as a reference for forensic identification. Method: This research is an experimental laboratory with a pre and post-test control group design. A total of 30 nanohybrid composite resin samples and 30 bulkfill composite resin samples were divided into 5 groups consisting of 4 treatment groups and 1 control group. The treatment group was heated at four temperature groups, 30°C-200°C, 30°C- 400°C, 30°C-800°C and 30°C-1100°C using a furnace (Thermo Scientific, USA). Weight changes were measured using a digital scale (Ohaus,China) and color changes were observed using the Shade Guide (Vitapan Classical, Germany). Result: A change in color and weight of the nanohybrid composite resin and bulkfill after being heated at high temperatures. Two-Way ANOVA test and Post Hoc LSD test showed that there was a significant difference in weight between nanohybrid composite resin and bulk fill composite resin at each temperature interval (p&lt;0.001). Conclusions: High temperature heating affects the color and weight changes of nanohybrid and bulkfill composite resin. Keywords: Bulkfill composite resin, High temperature heating, Nanohybrid composite resin

The shear bond strength difference of 8th generation bonding on nanocomposite resin and nanohybrid composite resin

Composite resins are increasingly being used in dentistry, particularly as restorative materials. There are currently nanoscale composite resins, such as nanocomposite resins and nanohybrid composite resins. Composite resins with smaller particle sizes can produce more aesthetically pleasing fillings. The disadvantage of composite resin as a restorative material is that it cannot bond directly to the tooth structure, so bonding as an intermediate material is required. Nano-sized particles are used in eighth-generation bonding, which is expected to increase bond strength. A total of 24 maxillary premolars were selected and randomly divided into 4 groups. Six maxillary premolars were in each group. Group I was treated with the application of nanocomposite resin without a bonding material, group II was treated with the application of a nanohybrid composite resin without a bonding material, group III was treated with the application of nanocomposite resin with an eighthgeneration bonding material, and group IV were treated with the application of nanohybrid composite resin with an eighthgeneration bonding material. The mean shear bond strength was 0.16 MPa, 0.51 MPa, 2.30 MPa, and 3.00 MPa, respectively. In conclusion, the eighth-generation bonding material has a higher shear bond strength on nanohybrid composite resin than it does on nanocomposite resin

Evaluation of Fracture Strength of Fiber-Reinforced Direct Composite Resin Restorations: An In Vitro Study

This in vitro study aimed to compare the fracture strength of direct non-reinforced class II composite resin restorations and polyethylene fiber-reinforced restorations, and also to investigate the influence of the locations of polyethylene fibers within the cavity on the fracture strength. Sixty freshly extracted human teeth were disinfected and prepared (class II cavity design). The teeth were assigned randomly into four groups (n = 13). Group I (control) was restored with nano-hybrid composite resin. The other three experimental groups were restored with the same composite resin material reinforced by polyethylene fibers (Ribbond) at different locations. Fibers were placed either on the axial wall (Group II), on the gingival floor (Group III), or on the axial wall and pulpal/gingival floor (Group IV) of the proximal cavity. All the teeth were subjected to thermocycling to simulate the oral environment. The fracture strength was measured using a universal testing machine. Group IV had the highest mean fracture strength at maximum load (148.74 MPa), followed by Group II (140.73 MPa), Group III (136.34 MPa), and Group I (130.08 MPa), with a statistically significant difference from the control group (p = 0.008) but not between groups II and III.

Post-gel shrinkage strain and degree of conversion of nanohybrid resin composite containing graphene oxide nanoparticles

Post-gel shrinkage strain and degree of conversion of nanohybrid resin composite containing graphene oxide nanoparticles

12-months Clinical Evaluation of Fiber Reinforced Bulk Fill Resin Composite versus Incremental Packing of Nanohybrid Resin Composite in Restoration of Deep Proximal Lesions of Permanent Molars: A Randomized Controlled Trial.

The present clinical trial was conducted to evaluate the clinical performance of the biomimetic, bilayered structure utilizing a fiber reinforced bulk fill resin composite with a nanohybrid capping layer, compared to incremental packing of nanohybrid resin composite, in deep proximal cavities in permanent molars. A total of 36 deep proximal cavities in vital molars were restored either with a bilayered structure of fiber reinforced composite resin as a dentine substitute and a capping layer of nanohybrid composite resin (n=18) or conventional, nanohybrid composite resin incrementation (n=18). The restorations were assessed over a period of 12 months using the modified USPHS criteria. The criteria evaluated were: fracture and retention, marginal integrity, marginal discoloration, anatomic form, proximal contact, surface texture, radiographic evaluation, postoperative sensitivity and secondary caries. There was no statistically or clinically significant difference between fiber-reinforced resin composite and conventional incremental resin composite. There was no risk for failure regarding all the evaluated modified USPHS criteria for both materials after 12 months (RR= 1(95% CI 0.0209 to 47.8503; P =1.0000)). The biomimetic approach utilizing a fiber reinforced resin composite dentine substitute showed a comparable clinical performance to nanohybrid resin composite incrementation. Bulk fill fiber reinforced resin composite is an efficient alternative in restoration of deep proximal cavities in posterior teeth. Further long-term studies are necessary to confirm these results.

Fracture strength, pull-out bond strength, and volume of luting agent of tooth-colored CAD-CAM post-and-cores

Statement of problemLittle is known about the fracture strength, retention, and adaptation of post-and-cores fabricated with novel tooth-colored materials by computer-aided design and computer-aided manufacturing (CAD-CAM). PurposeThe purpose of this in vitro study was to investigate the fracture strength, pull-out bond strength (POBS), and volume of luting agent of endodontically treated premolars restored with post-and-cores milled from different CAD-CAM materials. Material and methodsPost spaces were prepared in 80 human premolars in which post-and-cores fabricated with polyetheretherketone (PK; Ceramill PEEK), nanohybrid composite resin (BB; Brava Block), polymer-infiltrated ceramic (EN; VITA Enamic), and fiber-reinforced epoxy resin (GF; Fiber Cad Post & Core) CAD-CAM materials were luted (n=20). All specimens were subjected to thermal aging (3000 cycles at 5 °C and 55 °C with a 20-second dwell time). Half of the specimens were subjected to mechanical fatigue (250 000 cycles at 5 Hz) before fracture strength testing, while the other half was submitted to POBS testing and volume of luting agent measurement. Fracture strength data were analyzed by 1-way ANOVA, while POBS and volume of luting agent data were submitted to Kruskal-Wallis followed by the Bonferroni-Dunn multiple comparison tests. The correlation between POBS and the volume of luting agent was determined by the Spearman test (α=.05). ResultsPOBS of GF was significantly higher than that for PK (P<.001); however, failure load (P=.160) and volume of luting agent (P=.390) values did not differ. EN showed the highest percentage of catastrophic failures (20%), while PK exhibited only core deformations. POBS and cement film volume were not significantly correlated (P>.05). ConclusionsDifferent CAD-CAM materials did not influence the fracture strength and volume of luting agent of post-and-cores. Post-and-cores made with PEEK blocks showed lower bond strength to intracanal dentin than those made with fiber-reinforced epoxy resin blocks. No significant correlation was found between bond strength and the volume of luting agent.

In Vitro Evaluation of Gastric Acid and Toothbrushing Effect on the Surface State of Different Types of Composite Resins.

Background and Objectives: The aim of this in vitro study was to evaluate the effect of gastric acid associated with the effect of toothbrushing on the surface roughness of different types of composite resin used for direct restorations. Materials and Methods: The materials used in this study were two microhybrid (Filtek Z250, Herculite XRV) and two nanohybrid (Filtek Z550, Herculite XRV Ultra) composite resins. Two hundred and forty cylindrical samples with a height of 2 mm and a diameter of 6 mm were divided into four groups (groups A, B, C and D) corresponding to each tested material (n = 60). Each group was divided in two subgroups: subgroup I—the samples were submersed in hydrochloric acid and immediately submitted to toothbrushing; subgroup II—the samples were submitted only to toothbrushing. The simulation of the acid attack was performed by immersing the samples in a 0.01 M hydrochloric acid solution for 90 min. This procedure was followed immediately by toothbrushing simulation with 10,000 cycles. The acid attack and toothbrushing simulation were performed for two times. The surface roughness evaluation was performed with a Proscan 2100 profilometer. Repeated Measures ANOVA and Bonferroni post-hoc tests were used to perform the statistical analysis. Results: Simulation of one year of toothbrushing associated or not to hydrochloric acid exposure increases the surface roughness of microhybrid and nanohybrid composite resins. Six months of toothbrushing associated to six months of hydrochloric acid exposure increase the surface roughness of nanohybrid composite resins. Conclusions: Microhybrid composite resins surface becomes rougher after toothbrush and acid submersion when comparing to nanohybrid composite resins.