Do nanofilled/nanohybrid composites allow for better clinical performance of direct restorations than traditional microhybrid composites? a systematic review

This systematic review was carried out to assess the clinical effectiveness of nanofilled and nanohybrid composites used for direct restorations in comparison with microhybrid composites. The guidelines for the preferred reporting items for systematic reviews and meta-analyses were followed. A search of articles published from July 1996 to February 2017 was performed in PubMed, SciVerse Scopus, Latin American and Caribbean Health Sciences, the Scientific Electronic Library Online, and the Cochrane Library. The present review selected only randomized controlled trials comparing the clinical performance of a nanofilled or nanohybrid composite for direct restorations with that of a microhybrid composite. The research found 201 studies. Twenty-one articles fulfilled the criteria of the present review. However, the included studies were characterized by great methodological diversities. As a general trend, nanofilled and nanohybrid composites were found to be capable of clinical performance, marginal quality, and resistance to wear similar to that of traditional composites without showing improved surface characteristics. The risk of bias of included studies was judged unclear or high. The clinical performance of nanofilled/nanohybrid composites was found to be comparable to that of traditional composites in the posterior area. The data concerning anterior and cervical restorations were insufficient. With regard to the esthetic properties, there is a compelling need for studies on anterior teeth in which the operators are kept unaware of the restorative material. Nanofilled/nanohybrid composites seem to be a valid alternative to traditional microhybrid composites, and at the moment, there is low-level evidence attesting a lack of their superiority

Evaluation of degree of conversion, rate of cure, microhardness, depth of cure and contraction stress of three nano hybrid composites containing pre-polymerized spherical filler

Aim: Manufacturers aim at improving filler technology to enhance the properties of the restorative materials, thus maximising the aesthetic and functional outcome of the restored tooth. The present study tested the degree of conversion (DC), rate of cure (RC), microhardness (VHN), depth of cure (VHR) and contraction stress (CS) of three new nano hybrid composites with pre-polymerized spherical filler. Methods: Three commercially available composite resin were characterised in the present study, namely the Ceram.X\uae universal shade A3 (CXUA3), Ceram.X\uae duo enamel shade E2, and Ceram.X\uae duo dentin shade D3 (CXDE2 and CXDD3). The materials were light-cured with a LED light (SmartLite Focus, measured output 1301 mW/cm2) following the protocol recommended by the manufacturer. DC was assessed by means of Fourier-transform infrared spectroscopy, calculating RC from a second-grade polynomial fitting of the kinetic curve. A microhardness testing machine equipped with a Vickers indenter served to measure the top and bottom VHN of 2 mm-high disc-shaped specimens, using the bottom/top surface values ratio (VHR) as indirect evaluation of the depth of cure. CS vs time was evaluated by a universal testing machine provided with an extensometer as feedback system, CS was normalized for the specimen bonding area. All data sets underwent statistical analysis with dedicated software and tested for the assumptions for the use of parametric tests. Multiple analyses of variance with Scheff\ue9 post hoc test were carried out to compare the dependent variables of interest among the tested materials. Results: All tested materials exhibited a DC lower than 50%, with CXUA3 reaching the lowest DC value after 10 s. RC of CXUA3 at 5 s was comparable to that of CXDE2, while after 10s RC of CXUA3 decreased to a value proportional to that of CXDD3. For all the tested materials, top-VHN was greater than bottom-VHN. Top-VHN of CXDE2 was lower than CXUA3 and CXDD3. CXDD3 was the only material achieving VHR>80%. The main differences in CS among the tested materials were found during the irradiation with curing-light: CXDE2 displaying the lowest CS after 10 s and CXDD3 the highest after 30 s. Conclusion: The present study proved that the light curing protocol suggested by the manufacturer for the three composites might be improved: 10 s of irradiation seemed insufficient to adequately cure CXUA3 and CXDE2. Longer curing times for these materials appear advisable

Use of reciproc instruments with different motions: cyclic fatigue testing with simulation of the body temperature

Aim: To assess the influence of different motions on the cyclic fatigue resistance of Reciproc instruments simulating the temperature of the clinical conditions. Methods: The sample size was determined using statistical software set with the following parameters: \u3b1=0.05, \u3b2=0.20, \u3b4=30.0, \u3c3=28.0. The experiment required 54 Reciproc files. Brand new R25 files were randomly allocated to three groups defined by the tested motion: continuous rotation at 300 rpm (n=18), \u201cRECIPROC\u201d mode (n=18), and \u201cWAVEONE\u201d mode (n=18). The same endodontic motor was used for all groups (X-Smart IQ). All files were rotated/reciprocated until fracture inside a custom-designed artificial canal with 60\ub0 angle and 5-mm radius of curvature milled in a stainless-steel block. The testing device was electrically heated to keep its internal temperature at 35\ub11\ub0C, which was constantly monitored with a thermometer. After file separation, the time to failure was registered with a digital chronometer and the length of the fractured fragment measured with a digital calliper. The fracture surface of each file was observed at the scanning electron microscope to perform a qualitative fractographic analysis. The collected data (time to fracture and fracture length) were tested for the normality of the distribution and the equality of variances with a Shapiro-Wilk and a Levene test, respectively. The dependent variables were compared amongst groups by means of a multivariate analysis of variance and Tuckey post-hoc test (p=0.05). Results: The continuous rotation group exhibited the shortest lifespan among the considered groups (85.4\ub19.5 s to failure). Both reciprocating motions were associated with a significant improvement of fatigue resistance (p<0.001). The \u201cRECIPROC\u201d mode allowed for longer time to failure than the \u201cWAVEONE\u201d mode, with 141.6\ub119.4 s and 117.2\ub111.2 s to failure, respectively. The absence of differences among the considered groups in terms of fracture length confirmed the correct positioning of the files inside the artificial canal. The scanning electron microscopic analysis showed signs of file separation ascribable to cyclic fatigue. Conclusion: The present study preliminary demonstrated that the native \u201cRECIPROC\u201d motion use of R25 Reciproc files should be preferred over other types of motions to prevent file separation in the clinical setting

CROWN-TO-ROOT RATIO IN ENDODONTIC SURGERY: A SURVIVAL STUDY

Aim: to assess the influence of the crown height (CH), root length (RL) and crown-to-root ratio (CRR) on the survival of te- eth subjected to surgical endodontic retreatment and classi- fied as periapically healed. Methods: a single operator performed all the endodontic mi- crosurgery interventions. The present analysis selected the te- eth classified as ‘‘complete periapical healing’’ according to the Molven-Halse-Grung scale. The periapical radiographs were analyzed by two independent calibrated examiners, who measured CH and RL in a blind manner. The CRR was calcula- ted as the ratio of the two variables CH and RL. The measure- ments were performed by comparing the post-operative radio- graphs (t0) with those taken for a previous retrospective analysis (t1) and the most recent available (t2). An independent statistician conducted a survival analysis using Kaplan-Meier plots and a log-rank test (a = 0.05). Results: thirty-eight patients were evaluated, each one contri- buting to the study with a single tooth. The mean follow-up pe- riod was 5,96 ± 3,36 years. Comparing the CRR and RL values between t1 and t2, the difference was found statistically signifi- cant (p = 0.03). Survival was improved for the teeth with roots longer than 7 mm. There were no statistically significant diffe- rences among the remaining comparisons. Conclusions: root length ≥ 7mm exhibited better chances of long-term survival. Over time, a risk of further decrease of cli- nical RL due to periodontal disease and consequent increase of CRR could be critical by a mechanical point of view. Other studies are needed

Fibrin clot adhesion to conditioned root surfaces: an in vitro study with scanning electron microscopy analysis

Aim: Periodontal regeneration is contingent on the adhesion and maturation of fibrin clot to a root surface exposed to periodontal disease. Root surface demineralization in vitro improves the formation of a stable union between the fibrin clot and the root surface. In scientific literature there are not studies of comparison that stand which demineralizing agent is the best in promoting fibrin clot adhesion. The aim of this study was to evaluate and compare the efficacy of six root conditionings in removing the smear layer and developing the fibrin clot in static and dynamic conditions. Methods: 36 single-root teeth extracted for periodontal disease were cut with a microtome in order to obtain 72 specimens that were divided in three groups: 24 samples not covered with blood, 24 covered with fresh human whole blood, 24 covered with blood and rinsed in a rotary shaker table (Vortex\uae). 4 specimens from each group were conditioned for 3 minutes with: physiological saline solution (FISIO) as the control group, saturated solution of citric acid 25% (AC), ethylenediaminetetraacetic acid 24% (EDTA), a solution of tetracycline 200mg/mL (TETRA), a solution of tetracycline and citric acid (TETRA+AC), Prefgel\uae and successively Emdogain\uae (EMD). Then the 48 samples from group 2 and 3 were covered with blood, which was allowed to coagulate for 20 minutes in a 37\ub0C chamber. The blocks were rinsed and dehydrated under standardized conditions; specimens of group 3 were vortexed (100rpm). All the blocks were then sputtered with gold and analyzed with SEM. SEM images were evaluated by two blinded examiners, starting from the cementoenamel junction (CEJ), at 5 standardized points 2 mm distant from each other. A statistical analysis was performed. Results: EMD samples showed a more disorganized smear layer, in which is probably present the residual vehicle (propylene glycol alginate). However, in the 90% of all the specimens smear layer was found. AC treated samples showed a firmly adherent fibrin clot that covered the surfaces for the 70% of the specimens (the data was statistically relevant). Same results were found in TETRA+AC samples. The conditioning with EDTA, TETRA and EMD resulted in a sparsely organized clot worsened by the application of tensile forces, especially in TETRA samples. Only few blood cells without any clot organization were found in the control group, confirming that conditioning root surfaces improves the fibrin clot adhesion. Conclusion: The best formation of fibrin clot was observed for AC treated samples; this is probably due to the increase of root surface wettability caused by AC. The other root conditioning agents, even if lead to results better than the control group, are more susceptible to external forces and do not promote a stable fibrin clot adhesion

Comparative evaluation of the penetration depth into dentinal tubules of three endodontic irrigants

This study aimed to examine the penetration depth into dentinal tubules of some chelating agents. The 17% EDTA and two preparations containing surfactants (Smear Clear, Bioakt Endo) were tested. Surface tension and liquid viscosity were measured using a Dynamic Contact Angle Analyzer and a Haake rotational rheometer. To measure the penetration depth inside dentinal tubules, thirty maxillary central incisors were selected from a pool of extracted human permanent teeth and allocated to three experimental groups (10 samples each), as well as were mechanically shaped and cleansed with 5.25% NaOCl, followed by each of the chelators being labeled with 0.1 wt % Rhodamine B according to final irrigation protocol established. The samples were embedded in an epoxy resin, after which 200 μm thick transverse sections were obtained at 2, 5, and 8 mm from the apex with a saw microtome. The specimens were then observed using a confocal laser microscope (CLSM) and the penetration of the labeled solution was measured in every third of each sample. Statistical analysis was performed using ANOVA or Kruskal–Wallis tests according to the distribution of data, evaluated with the Shapiro–Wilk normality test. Viscosity and surface tension tests have shown that BioAKT Endo has the lowest values compared to EDTA and Smear Clear. The medium penetration depth did not significantly differ among the three irrigants, while it increased considerably from the apical to the coronal level in all groups. Additionally, the maximum penetration depth increased significantly from the apical to coronal level, while among groups, BioAKT Endo showed the highest values at the apical and middle level compared to the other irrigants. No significant differences were observed among the three groups in medium and maximum penetration depths when the entire root was considered. New irrigants containing surfactants show reduced surface tension and, in one case (BioAKT Endo), viscosity. The lowering of the surface tension allows for better penetration of liquids into dentinal tubules than EDTA alone, thus improving the cleaning of the root canal system

Calcium hydroxide removal using four different irrigation systems: A quantitative evaluation by scanning electron microscopy

This study compares conventional endodontic needle irrigation, passive ultrasonic irriga-tion, apical negative pressure irrigation, and mechanical activation to remove calcium hydroxide from single straight root canals. Eighty-four mandibular premolars were prepared in a crown-down manner up to size #40. Two teeth represented a negative control, and another two served as a positive control. Calcium hydroxide paste was placed inside root canals. The remaining eighty samples were analyzed based on the activation techniques, and the cleanliness of the canals was quantified using Fiji’s software on 500× magnified SEM backscattered electron micrographs. Considering the whole canal, all instruments showed better performance than conventional endodontic needle irrigation in removing calcium hydroxide (p &lt; 0.05). Irrisafe and XP-endo Finisher could remove a significantly higher amount of calcium hydroxide than Endovac (p &lt; 0.05). Irrisafe and XP-endo Finisher have been able to remove more calcium hydroxide than EndoVac

Spectrophotometric analysis of immediate implant-supported rehabilitations: in vitro study

Aim: Temporary rehabilitation on implants, whether fixed or removable, requires resin thickness that makes it aesthetic, durable and comfortable for the patient. However, these requirements are not always clinically attainable mainly due to the limited dimensions of the final structure. For this reason, it is desirable to create a framework with, on one hand constrained dimensions and, on the other hand, sufficient resistance to cyclic stresses. In addition, other factors must be taken into account, such as the economic aspect and the timing required to finalize the rehabilitation, to name some. One possibile solution to these requests was found to be the use of intraoral welding technique. The aim of this in vitro pilot study is to establish the minimum thickness of resin required to mask the metal framework used into intraoral welding technique. Methods: Three specimens were produced with three titanium bars of grade two (2 mm diameter) (Dentsply Implants Manufacturing; Germany): the first remained untreated, the second was sandblasted, the third was opacified; three specimens of dimensions of 12x6 mm were prepared of PMMA (BreCam Multicom, Bredent GmbH & Co.) of A3 color that differ in thickness 1, 2, 3 mm; three specimens were prepared of pink resin (Palapress, Kulzer dental) of the same size as the previous ones. These were then superimposed on each other and images of the different combinations were acquired with a spectrophotometer (Spectroshade Micro, MHT) evaluating the color difference (\u394E) at three points between the different specimens and their combinations on the basis of the application of the CIEL*a*b color space system. ANOVA test were used for statistical analysis. Results: The study shows that at least 3 mm of A3 color resin is required to mask the untreated or sandblasted metal framework 01). The two factors \u201cthickness\u201d and \u201cmetal condition\u201d examined seem to influence the outcome \u394E significantly (p value <0.05). Conclusion: The results obtained in this in vitro study showed that was possible to mask the opaque titanium framework with a combination of at least 3 mm of pink resin and 3 mm of A3 color resin. A clinical alternative to mask the titanium framework could be the palatally/lingually placement of welded bar, compatibly with the clearance available for prosthetic rehabilitation

Influence of an acid environment on hardening of SuperEBA and MTA

Background. Super EBA (SE) and MTA are considered to be among the best retrograde filling materials used in endodontic surgery. Since the post-operative course is characterised by phlogosis and an acid pH, it is worth asking whether this environment influences the hardening of these materials. The aim of this study was to evaluate in vitro the influence of pH on the Vickers hardness of MTA and SuperEBA. Methods and materials. Twelve MTA and 12 SuperEBA disks were prepared and left to harden, for 24 hours and 1 hour respectively, in pH5 and pH7 buffer solutions (n. 6 for each group). After careful polishing of the free surface the final hardness was evaluated using a micro-hardness meter; an optical microscopy assessment was also performed as a qualitative analysis to evaluate the indentations. Data were analysed with one-way ANOVA and Scheffe post hoc test. Results. Means of Vickers values and standard deviation were: pH7 MTA 38,59(2,59); pH5MTA 4,02(1,57); pH7 SE 18,46(5,38); pH5 SE 20,65(5,49). MTA at neutral pH is associated with the best hardness; this is dramatically reduced if the samples are exposed to an acid solution. Instead, SuperEBA, characterised by a lower hardness, is practically unaffected by changes in the pH level, showing only a slight increase in an acid pH environment. The differences were statistically significant (p<0,001) except for the groups of ph7 SE vs pH5 SE. Conclusions. An acid pH significantly influences the hardness of MTA but not of SuperEBA