The color-matching ability of single-shade universal composites in extracted human teeth.

OBJECTIVES: To evaluate the color-match with extracted natural teeth of three single-shade universal composites, a group-shade universal composite, and a highly translucent-shade conventional composite. METHODS: Twenty extracted human teeth were divided into light- and dark-shade groups (n = 10, LSG and DSG). A preparation was restored with the 3 single-shade universal composites, OMNICHROMA (OMC), Admira Fusion x-tra U (AFU), and Essentia U (ESU); a highly translucent-shade conventional composite, Tetric EvoCeram T (TEC-T); and two shades of a group-shade universal composite-Filtek Universal Restorative (FUR A1 and A4). Composites were photopolymerized, polished, and stored in water for 24 h. The ΔE00 value between the unprepared and restored surfaces was obtained using a spectrophotometer. Composite placement and measurements were repeated three times per tooth. Color differences were statistically analyzed with the within-between-subjects t-test and repeated-measures analysis of variance (ANOVA), followed by post hoc pairwise comparisons with a Bonferroni adjustment (α = 0.05). RESULTS: There were no statistically significant differences between OMC and FUR (A1 and A4). AFU and ESU showed significantly higher ΔE00 values than OMC and TEC-T (p < 0.05). Single-shade composites exhibited significantly higher ΔE00 values in the DSG than in the LSG except ESU (p < 0.05). None of the composites satisfied the criteria for an acceptable match (ΔE00 >1.8). CONCLUSION: OMC showed the same color matching ability as a group-shade universal composite. A highly translucent-shade conventional composite and OMC exhibited better color matching ability than other single-shade composites. Overall, single-shade universal composites performed better in lighter-shaded teeth. CLINICAL SIGNIFICANCE: Single-shade universal composites have the potential to reduce chair time by eliminating shade selection in cavities with lighter-shade teeth. Highly translucent incisal conventional composites also may be used if the appropriate shade of composite is not available.

Coaxial Placement of Balloon-Expandable and Self-Expanding Stents: Impact on Crush Resistance and Luminal Recovery in a Benchtop Model.

During endovascular interventions, coaxial deployment of stents may be required to preserve luminal gain. This study characterized in vitro the effect on crush resistance and postcompression recovery when 316L stainless steel balloon-expandable (BE) and laser-cut nitinol self-expanding (SE) venous stents were deployed coaxially. Various stent configurations were parallel-plate compressed from a fully expanded state to 50% diameter reduction (Criterion, Model 42; MTS, Eden Prairie, Minnesota) in a 37 °C ± 1 water bath. Coaxial deployments of SE stent inside BE stent and BE stent inside SE stent demonstrated higher crush resistances compared with each stent individually or their mathematical summation (analysis of variance P < .0001; pairwise comparison P < .01). The configuration of SE stent inside BE stent showed higher postcompression luminal recovery at 48.7% compared with that of BE stent inside SE stent at 27.5% (P = .0001). Coaxial deployment of SE stent inside BE stent may improve crush resistance and luminal recovery after compression in the appropriate clinical context.

Real-Time Monitoring of Biofilm Formation Using a Noninvasive Impedance-Based Method.

Biofilms are complex three-dimensional microbial communities that adhere to a variety of surfaces and interact with their surroundings. Because of the dynamic nature of biofilm formation, establishing a uniform technique for quantifying and monitoring biofilm volume, shape, and features in real-time is challenging. Herein, we describe a noninvasive electrochemical impedance approach for real-time monitoring of dental plaque-derived multispecies biofilm growth on a range of substrates. A working equation relating electrochemical impedance to live biofilm volume has been developed that is applicable to all three surfaces examined, including glass, dental filling resin, and Ca2+-releasing resin composites. Impedance changes of 2.5, 35, 50, and 65% correlated to biofilm volumes of 0.10 ± 0.01, 16.9 ± 2.2, 29.7 ± 2.3, and 38.6 ± 2.8 µm3/µm2, respectively. We discovered that glass, dental filling resin, and Ca2+-releasing dental composites required approximately 3.5, 4.5, and 6 days, respectively, to achieve a 50% change in impedance. The local pH change at the biofilm-substrate interfaces also monitored with potentiometry pH microsensor, and pH change varied according to biofilm volume. This impedance-based technique can be a useful analytical method for monitoring the growth of biofilms on a variety of substrates in real-time. Therefore, this technique may be beneficial for examining antibacterial properties of novel biomaterials.

3D-printed microgels supplemented with dentin matrix molecules as a novel biomaterial for direct pulp capping.

OBJECTIVES: To develop a 3D-printed, microparticulate hydrogel supplemented with dentin matrix molecules (DMM) as a novel regenerative strategy for dental pulp capping. MATERIALS AND METHODS: Gelatin methacryloyl microgels (7% w/v) mixed with varying concentrations of DMM were printed using a digital light projection 3D printer and lyophilized for 2 days. The release profile of the DMM-loaded microgels was measured using a bicinchoninic acid assay. Next, dental pulp exposure defects were created in maxillary first molars of Wistar rats. The exposures were randomly capped with (1) inert material - negative control, (2) microgels, (3) microgels + DMM 500 µg/ml, (4) microgels + DMM 1000 µg/ml, (5) microgels + platelet-derived growth factor (PDGF 10 ng/ml), or (6) MTA (n = 15/group). After 4 weeks, animals were euthanized, and treated molars were harvested and then processed to evaluate hard tissue deposition, pulp tissue organization, and blood vessel density. RESULTS: All the specimens from groups treated with microgel + 500 µg/ml, microgel + 1000 µg/ml, microgel + PDGF, and MTA showed the formation of organized pulp tissue, tertiary dentin, newly formed tubular and atubular dentin, and new blood vessel formation. Dentin bridge formation was greater and pulp necrosis was less in the microgel + DMM groups compared to MTA. CONCLUSIONS: The 3D-printed photocurable microgels doped with DMM exhibited favorable cellular and inflammatory pulp responses, and significantly more tertiary dentin deposition. CLINICAL RELEVANCE: 3D-printed microgel with DMM is a promising biomaterial for dentin and dental pulp regeneration in pulp capping procedures.

Isolated effect of filler particle size on surface properties of experimental resin composites before and after toothbrush abrasion.

OBJECTIVE: This study aimed to isolate the relationship between filler size and the surface properties of roughness and gloss before and after toothbrush abrasion for experimental resin-based composites (RBCs) containing uniform spherical fillers. MATERIALS AND METHODS: Five experimental light-cured RBCs with different spherical filler sizes and three commercial RBCs were studied. Forty specimens were polished using silicon carbide papers. Gloss was measured after 0, 90, 180, and 360 min of simulated toothbrushing, and surface roughness was measured before and after 360 min of toothbrushing. Two-way ANOVA/Tukey's multiple comparison tests were used to compare the RBCs, and the correlation between particle size and surface roughness or gloss was also determined. RESULTS: After polishing and toothbrushing, RBCs with smaller fillers exhibited significantly higher gloss and lower surface roughness, and RBCs with larger fillers exhibited lower gloss and higher surface roughness. A significant correlation was found between filler particle size and gloss and surface roughness both before and after toothbrush abrasion. CONCLUSIONS: Gloss of RBCs containing fillers with larger particle sizes was significantly reduced. After toothbrushing abrasion, the surface roughness increased for all RBCs, except those containing the finest-sized fillers. The particle size of the filler is a critical determinant of the surface roughness and gloss of RBCs, after polishing and after toothbrushing. CLINICAL SIGNIFICANCE: Increased surface roughness caused by toothbrush abrasion reduces the gloss of resin-based composites. Resin-based composites containing finer fillers best maintain glossiness after routine tooth brushing.

Outcomes of treatment and monitoring of posterior teeth with cracks: three-year results from the National Dental Practice-Based Research Network.

OBJECTIVES: To describe treatment and monitoring outcomes of posterior teeth with cracks at baseline followed in the National Dental Practice-Based Research Network for up to three years. MATERIALS AND METHODS: Two hundred and nine dentists enrolled a convenience sample of 2,858 patients, each with a posterior tooth with at least one visible crack and followed them for three years. Characteristics at the patient, tooth, and crack level were recorded at baseline and at annual recall visits. Data on all teeth referred for extraction were reviewed. Data on all other teeth, treated or monitored, seen at one or more recall visits were reviewed for evidence of failure (subsequent extraction, endodontics, or recommendation for a re-treatment). RESULTS: The survival rate for teeth with cracks at baseline exceeded 98% (only 37 extractions), and the failure rate for teeth that were treated restoratively was only 14%. Also, only about 14% of teeth recommended at baseline for monitoring were later recommended to be treated, and about 6.5% of teeth recommended for monitoring at baseline were later treated without a specific recommendation. Thus, about 80% of teeth recommended at baseline for monitoring continued with a monitoring recommendation throughout the entire three years of the study. Treatment failures were associated with intracoronal restorations (vs. full or partial coverage) and male patients. CONCLUSIONS: In this large 3-year practice-based study conducted across the USA, the survival rate of posterior teeth with a visible crack exceeded 85%. Clinical relevance Dentists can effectively evaluate patient-, tooth-, and crack-level characteristics to determine which teeth with cracks warrant treatment and which only warrant monitoring.

Development and maintenance of surface gloss of dental composites after polishing and brushing: Review of the literature.

OBJECTIVE: To describe the effect of the composites' composition to produce high surface smoothness/gloss using finishers/polishers, and to assess maintained smoothness/gloss under toothbrush abrasion. MATERIALS AND METHODS: PubMed papers published from January 01, 2000 to September 01, 2021 were included, and keywords used were: filler particle size, shape, amount of dental composites; finishing/polishing, gloss/roughness, and toothbrush abrasion of composites. Seventy-five in-vitro studies were included in this literature review. Forty-six articles assessed filler particle size/composition/shape and distribution to obtain high gloss/smoothness on different formulations; and the finishers/polishers effect on these materials. Twenty-nine papers assessed toothbrush abrasion of composites. RESULTS: Suprananofill/nanofill/microfills typically showed the smoothest and glossiest surfaces compared to nanohybrid, microhybrid and hybrid composites. Microfill (0.04-0.07 µm, 71-88 GU); suprananofill (0.001-0.8 µm, 52-92 GU), microhybrids (0.05-0.35 µm, 35-95 GU) and nanohybrids (0.05-0.21 µm, 66-97 GU). Composites with small, spherical particles tend to show smoother, glossier surfaces and more wear resistant compared to resin composites with larger or irregular particles. Several studies showed higher roughness and reduced gloss after toothbrush abrasion. CONCLUSIONS: Within the limitations of this study, suprananofill/nanofill/microfill composites tended to show the smoothest/glossiest surfaces due to smaller particle size. Composites with small, spherical particles tended to show smoother/glossier surfaces. Overall, toothbrush abrasion showed higher surface roughness and reduced gloss. CLINICAL SIGNIFICANCE: Suprananofills/nanofills/microfills had good polishability and polish retention due to their smaller particle size. The effectiveness of a polishing system is material-dependent. In general, Enhance-PoGo, Sof-Lex discs, and Sof-Lex Spiral wheels showed similar level of smoothness.

Effect of ethyl cellulose coating as an evaluation agent against contamination on the bond strength of zirconia restorations: An in vitro study.

STATEMENT OF PROBLEM: During the trial placement of zirconia restorations, contamination of the bonding surface is inevitable. Although cleaning methods for contaminated surfaces have been described, a method of preventing saliva contamination of the bonding surface of zirconia restorations is lacking. PURPOSE: The purpose of this in vitro study was to investigate an ethyl cellulose coating as an evaluation agent to mitigate the effects of saliva contamination on the bond strength of zirconia restorations. MATERIAL AND METHODS: Experimental groups representing different cleaning methods of tetragonal yttria-stabilized tetragonal zirconia polycrystal (4Y-TZP) surfaces were investigated for shear bond strength with a resin luting agent, and the failure mode was analyzed. The 9.0×7.0×5.0-mm zirconia blocks (n=72) were assigned as follows: Group N: uncontaminated control; Group CU: contaminated with saliva, followed by ultrasonic cleaning with ethanol; Group CI: contaminated with saliva, followed by application of a zirconia cleaner; Group PCW: preapplication of a zirconia primer, contaminated with saliva, followed by cleaning with water spray; Group ECU: precoating with the ethyl cellulose agent, contaminated with saliva, followed by removal of the agent in an ultrasonic bath with ethanol. Each group was divided into 3 subgroups (immediate, short-term aging, and long-term aging), and the shear bond strength was measured (n=24). To analyze the bonding surface characteristics, the contact angle was measured (n=5). The surfaces of the zirconia specimens in each experimental group were evaluated by using a field emission scanning electron microscope (n=5). Time-of-flight secondary ion mass spectroscopy was used for the chemical analysis of the conditioned surfaces (n=3). A 2-way analysis of variance (ANOVA) with main effect model for shear bond strength results and a 1-way ANOVA for contact angle data were performed as statistical analysis, followed by the Bonferroni post hoc test (α=.05). RESULTS: The shear bond strength was significantly higher in the ECU group than in the groups with the other cleaning methods (P<.05). After the removal of ethyl cellulose with ethanol, the contact angle and surface topography were found to be similar to those of the control group, and no saliva contaminants were identified in the spectroscopy analysis. CONCLUSIONS: Coating with ethyl cellulose may protect the bonding surface of zirconia restorations from salivary contamination better than cleaning a contaminated surface.

"Fatigue-Crack Propagation Behavior in Microcapsule-Containing Self-Healing Polymeric Networks".

Over the last years, research on the design of dental self-healing polymers has grown dramatically. It is related to the promising potential of maximizing the clinical lifespan of dental restorations that this strategy holds. In this manuscript, the microcapsule-based strategy is innovated by incorporating the high toughness component N,N-Dimethylacrylamide (DMAM) into the healing agent systems and analyzing in-depth the change in crack propagation behavior induced by the addition of microcapsules into the highly crosslinked polymeric network. In general, the addition of the hydrophilic and high vapor pressure DMAM into the healing agent systems imposed a challenge for the microencapsulation, which highlighted the importance of tailoring the properties of the capsules' shells according to the core composition. The addition of DMAM as cushioning agent proved to be a successful strategy since it resulted in increased G'/G" crossover time from 0.06 (control) to 0.57 s and decreased storage modulus from 8.0 (control) to 0.5GPa. In addition, the incorporation of microcapsules within the polymerized networks provided obstacles to crack propagation, which translated to an overall reinforcement of the polymeric network, as evidenced by the increase in toughness up to 50 % and energy required to propagate cracks up to 100 % in systems containing DMAM at 20 wt%.

Clinical Performance of CAD/CAM Monolithic Lithium Disilicate Implant-Supported Single Crowns Using Solid or Predrilled Blocks in a Fully Digital Workflow: A Retrospective Cohort Study With Up To 33 Months of Follow Up.

PURPOSE: To assess the clinical performance of CAD/CAM monolithic implant-supported restorations manufactured using a fully digital workflow and two different types of ceramic blocks. MATERIALS AND METHODS: One hundred and one patients received single-unit implant-supported restorations at a University predoctoral clinic. All restorations were designed and fabricated using either a predrilled LS2 block (group P, n = 59) or a conventional solid LS2 block with an occlusal opening drilled manually prior to crystallization (group M, n = 42). The mean follow-up time after restoration delivery was 18.4 ± 4.8 months (range 12 to 33 months). Patients with less than a 12-month follow-up were excluded. Electronic health records were reviewed to identify number and type of complications during the follow-up time. Clinical outcomes were classified as success, survival, and failure of the restoration. Chi-square tests were used to identify differences in success and survival rates between the groups. Nonparametric Mann-Whitney U tests were used to identify differences in the number of major and minor complications as well as the total number of complications that were observed among groups. RESULTS: Overall success and survival rates were 80.2% and 97%, respectively. Seventy one restorations (70.3%) were complication-free. There were no significant differences between the groups with regards to the number of complications or success and survival rates. CONCLUSIONS: Single-unit CAD/CAM monolithic implant-supported restorations that are fabricated in a fully digital workflow present relatively high complication rates and moderate short-term clinical outcomes. Clinical studies with longer follow-up times are needed to evaluate long-term outcomes of these restorations.

Probing the hierarchy of evidence to identify the best strategy for placing class II dental composite restorations using current materials.

OBJECTIVE: The objective of this review is to present a synopsis of the existing clinical and in vitro evidence regarding placement of direct class II restorations with dental composites of varying viscosities, focusing on the marginal integrity achievable. OVERVIEW: The literature on class II composites placed with various techniques was searched through PubMed, Scopus, and the citations of identified articles, focusing on aspects related to adaptation and clinical performance. Studies comparing layering of conventional composite to layering with a flowable liner, including the "snow plow technique," use of warmed composite, flowable bulk-fill liners with a conventional composite capping layer, and bulk-fill restorative in a single or incremental fill (including placement with sonic energy and dual-curing) CONCLUSIONS: In vitro and clinical evidence does not support any one specific method or material type for achieving optimal performance when restoring class II cavity preparations with current dental composites. CLINICAL SIGNIFICANCE: Although there are many available placement methods and types of composite materials on the market for use in class II restorations, the reasonable success presented in the clinical and laboratory literature for the various approaches suggests that the most important factor for achieving success is likely careful and proper placement and light-curing technique, independent of the approach.

Effect of biofilm exposure on marginal integrity of composite restorations.

PURPOSE: To evaluate the effect of bacterial exposure on the marginal integrity of dentin-resin interfaces for composites with and without bioactive glass (BAG). METHODS: Cavity preparations of 5 mm width and 1.5 mm depth were machined into dentin disks by means of a computer controlled milling system. After applying the bonding agent, cavity preparations (n=3-5) were restored by incremental technique with experimental resin composites (50:50 BisGMA/TEGDMA: 72wt% filler) with different filler compositions: control - 67 wt% silanated strontium glass and 5wt% aerosol-silica filler and BAG - 57 wt% silanated strontium glass and 15 wt% BAG-65 wt% silica. Samples were then stored in sterile Todd-Hewitt media or co-incubated with Streptococcus mutans (UA 159), at 37°C, 5% CO2 for 1-2 weeks. For samples co-incubated with a living biofilm, a luciferase assay was performed in order to assess its viability. Surfaces were impressed before and after each storage condition and replicas examined in a scanning electron microscope. Using image analysis software (Image J), the discontinuous margins percentage (%DM) was quantitatively assessed. Data were analyzed using two-way ANOVA followed by Tukey's test (α= 0.05). RESULTS: Gap size ranged between 7-23 µm. The bacterial exposure significantly increased the %DM in both groups predominantly due to the formation of new gap regions. There was no difference between control and BAG composites regarding %DM and the biofilm viability. Bacterial exposure promoted degradation of composite restoration marginal integrity, with no difference between composites with and without BAG. CLINICAL SIGNIFICANCE: The samples incubated with living biofilm had a higher gap percentage in the margins, confirming the negative effect of cariogenic bacteria on margin degradation. The parameters defined for such synergy can help to understand the multi-factorial aspect of marginal discontinuity and therefore, predict the behavior of composite restorations subjected to the challenging oral environment.

Recommended treatment of cracked teeth: Results from the National Dental Practice-Based Research Network.

STATEMENT OF PROBLEM: Despite the high prevalence of posterior cracked teeth, questions remain regarding the best course of action for managing these teeth. PURPOSE: The purpose of this clinical study was to identify and quantify the characteristics of visible cracks in posterior teeth and their association with treatment recommendations among patients in the National Dental Practice-Based Research Network. MATERIAL AND METHODS: Network dentists enrolled patients with a single, vital posterior tooth with at least 1 observable external crack. Data were collected at the patient, tooth, and crack levels, including the presence and type of pain and treatment recommendations for subject teeth. Frequencies according to treatment recommendation were obtained, and odds ratios (ORs) comparing recommendations for the tooth to be restored versus monitored were calculated. Stepwise regressions were performed using generalized models to adjust for clustering; characteristics with P<.05 were retained. RESULTS: A total of 209 dentists enrolled 2858 patients with a posterior tooth with at least 1 crack. Mean ±standard deviation patient age was 54 ±12 years; 1813 (63%) were female, 2394 (85%) were non-Hispanic white, 2213 (77%) had some dental insurance, and 2432 (86%) had some college education. Overall, 1297 (46%) teeth caused 1 or more of the following types of pain: 1055 sensitivity to cold, 459 biting, and 367 spontaneous. A total of 1040 teeth were recommended for 1 or more treatments: restoration (n=1018; 98%), endodontics (n=29; 3%), endodontic treatment and restoration (n=20; 2%), extraction (n=2; 0.2%), and noninvasive treatment, for example, occlusal device, desensitizing (n=11; 1%). The presence of caries (OR=67.3), biting pain (OR=7.3), and evidence of a crack on radiographs (OR=5.0) were associated with over 5-fold odds of recommending restoration. Spontaneous pain was associated with nearly 3-fold odds; pain to cold, having dental insurance, a crack that was detectable with an explorer or blocked transilluminated light, or connected with a restoration were each weakly associated with increased odds of recommending a restoration (OR<2.0). CONCLUSIONS: Approximately one-third of cracked teeth were recommended for restoration. The presence of caries, biting pain, and evidence of a crack on a radiograph were strong predictors of recommending a restoration, although the evidence of a crack on a radiograph only accounted for a 3% absolute difference (4% recommended treatment versus 1% recommended monitoring).

Methacrylate saccharide-based monomers for dental adhesive systems.

The aim of this in vitro study was to synthesize three new methacrylate monomers based on the modification of saccharides structures (glucose-Gluc, sucrose-Sucr and chitosan-Chit) with glycidyl methacrylate, and to use them in the composition of dental adhesives. Three methacrylate saccharide monomers were synthesized and characterized by mid-IR, 1H and 13C NMR, antioxidant activity and cytotoxic effect. Monomers included: one monosaccharide - Gluc-MA; one disaccharide - Sucr-MA; and one polysaccharide - Chit-MA. Primers containing HEMA, methacrylate saccharide monomers at concentrations of 0 (control), 1, 2 or 4 wt%, 60 wt% ethanol aqueous solution (pH3.0) and initiator system were formulated. Primers were used in conjunction with a bond step and composite paste to restore caries-free third molars, and dentin bond strength (24 hours and 6 month of storage in water), and antimicrobial activity (Alamar Blue test) were tested. Degree of conversion (DC) and maximum rate of polymerization (Rpmax) of the primers themselves were also analyzed. The mid-IR, 1H and 13C spectrum confirmed the presence of vinyl group on the structure of saccharides. Chit-MA showed low antioxidant activity and did not present a cytotoxic effect. Gluc-MA and Sucr-MA possess antioxidant and cytotoxic activity, concentration dependent. In the presence of methacrylate saccharide monomers, the primers showed DC comparable to the control group, except Gluc-MA4%, Sucr-MA4% and Chit-MA1%, which showed a range of 64.6 from 58.5 %DC. Rpmax was not statistically different for all the groups (p = 0.01). The bond strength of Sucr-MA1% increased from 25.7 (±2.8) to 40.6 (±5.3) MPa after 6 months of storage. All the synthesized monomers showed some antimicrobial activity after polymerization. Gluc-MA and Chit-MA 4% and Sucr-MA 1, 2 and 4% led to decrease bacterial metabolism. Sucr-MA 1% showed better results regarding the decrease in bacterial metabolism and increasing the bond strength after 6 months of storage.

Effect of Crystallization Firing on Marginal Gap of CAD/CAM Fabricated Lithium Disilicate Crowns.

PURPOSE: To evaluate the marginal gaps of CAD/CAM (CEREC 3) produced crowns made from leucite-reinforced glass-ceramic (IPS Empress CAD) blocks (LG), and lithium-disilicate (IPS e.max CAD) blocks before (LD-B), and after (LD-A) crystallization firing. MATERIALS AND METHODS: A human molar tooth (#19) was mounted with adjacent teeth on a typodont and prepared for a full-coverage ceramic crown. The typodont was assembled in the mannequin head to simulate clinical conditions. After tooth preparation 15 individual optical impressions were taken by the same operator using titanium dioxide powder and a CEREC 3 camera per manufacturer's instructions. One operator designed and machined the crowns in leucite-reinforced glass-ceramic blocks (n = 5) and lithium-disilicate blocks (n = 10) using the CEREC 3 system. The crowns were rigidly seated on the prepared tooth, and marginal gaps (µm) were measured with an optical microscope (500×) at 12 points, 3 on each of the M, B, D, and L surfaces of the leucite-reinforced glass-ceramic crowns and the lithium-disilicate crowns before and after crystallization firing. Results were analyzed by two-way ANOVA followed by a Tukey's post hoc multiple comparison test (α = 0.05). RESULTS: The overall mean marginal gaps (µm) for the crowns evaluated were: LG = 49.2 ± 5.5, LD-B = 42.9 ± 12.2, and LD-A = 57.2 ± 16.0. The marginal gaps for LG and LD-B were not significantly different, but both were significantly less than for LD-A. CONCLUSIONS: The type of ceramic material did not affect the marginal gap of CAD/CAM crowns. The crystallization firing process required for lithium-disilicate crowns resulted in a significant increase in marginal gap size, likely due to shrinkage of the ceramic during the crystallization process. CLINICAL RELEVANCE: The marginal gap of CAD/CAM-fabricated lithium disilicate crowns increases following crystallization firing. The marginal gap still remains within clinically acceptable parameters.

Effect of shade, opacity and layer thickness on light transmission through a nano-hybrid dental composite during curing.

OBJECTIVE: The aim of this study was to investigate the effect of shade and opacity on the change in light transmission through different thicknesses of a nano-hybrid composite during curing. MATERIALS AND METHODS: Twelve different shades of Venus Diamond (Heraeus Kulzer) were placed in disk shaped molds with thickness of 1, 2, and 3 mm (n = 3 per group) and cured with an LED light-curing unit. Initial, final and average irradiance, and the total amount of energy passing through the specimen were measured using the MARC Resin Calibrator at every 10s for a total of 40s. The translucency parameter and the contrast ratio were obtained using a chromameter. Results were analyzed with ANOVA/Tukey's test (α = 0.05). RESULTS: All shades and all thicknesses (up to 3 mm) experienced an increase in light transmittance during curing. The majority of the increase occurred during the initial 10s exposure, with significant increase occurring from subsequent exposures only in thicker specimens (i.e., 3 mm). The increase in irradiance at the bottom during curing was dependent on shade, with darker shades and greater depths of material showing less increase. CONCLUSIONS: For one specific resin composite formulation, an increase in translucency occurs as cure progresses, and the increase is enhanced for composites with greater lightness and lower contrast ratio. CLINICAL SIGNIFICANCE: Composites demonstrate increased light transmittance as curing progress, which may improve depth of cure. The thicker composite showed the least increase in light transmission within the same shade. The increase in translucency is enhanced for composites with great lightness and lower contrast ratio.

Effect of Nanofiller Loading on Cure Efficiency and Potential Color Change of Model Composites.

OBJECTIVES: To evaluate the effect of nanofiller loading on cure efficiency and potential color change of experimental composites. MATERIALS AND METHODS: Four different polymeric materials were produced using the same organic matrix blend. To this matrix, different amounts of 0.05 µm fumed silica filler were added: no filler, 13, 52, and 65wt%. Fourier transform infrared spectroscopy was used to evaluate the degree of conversion (DC) for each composite using near-IR analysis, and spectrophotometry according to CIELab chromatic space was used to evaluate the color change.To induce color change, composites were artificially aged with exposure to cycles of UV-B light for 300 hours. Trasmission electron microscopy was used to illustrate nanoffiler aglomeration in the resin matrix. Data were analyzed using correlation analysis (α = 0.05). RESULTS: There was an excellent inverse linear correlation between filler wt% and either DC or color change. Greater changes to red (+Δa) and yellow (+Δb) were observed as the filler wt% increased. CONCLUSIONS: A higher percentage of nano-sized filler particles in dental resin composites directly affects their cure efficiency and potential for color change. CLINICAL SIGNIFICANCE: The increase in filler particle loading negatively affected monomer conversion and color stability of resin-based composites. As reduced filler loading results in poorer mechanical properties, to enhance color stability, resin-based composites should be formulated by making the refractive index of the polymeric matrix more closely match that of the filler throughout the polymerization process. (J Esthet Restor Dent, 2016).

Sol-gel-derived bioactive glasses demonstrate antimicrobial effects on common oral bacteria.

PURPOSE: To determine the antibacterial effect of nano-structured, sol-gel processed bioactive glasses that may be used for implants, coatings, and as adjuncts to dental restorative materials. METHODS: Six bioactive glasses (BAG), three made with differing amounts of silica (65, 75 and 85 mole%), and three with different amounts of silica (61, 71, and 81 mole%) and 3 mole% fluoride were prepared by a sol-gel synthesis method and tested against clinically important bacteria species, Streptococcus sobrinus (ATCC33478), Streptococcus mutans (ATCC25175) and Enterococcus faecalis (ATCC19433). Bacterial suspensions were independently incubated with bioactive glass in particulate form (< 3 µm) for 4 and 24 hours. Viability was determined by colony-forming units. RESULTS: At 4 hours, all BAG produced an order of magnitude reduction in all three bacteria. After 24 hours, all BAG produced a significant reduction in S. sobrinus colonies, but no further reduction in S. mutans; all BAG, except BAG 61-F, significantly reduced E. faecalis compared to the control. At 4 hours, an increase in the pH of the BAG groups (to pH 9) could also have contributed to the bactericidal effect. In further experiments it was found that the viability of S. sobrinus was significantly reduced following exposure to an extract of BAG in media adjusted to a pH of 7.4. Additionally media with pH adjusted to 9 exerted a significant antibacterial effect against S. sobrinus after 4 hours. To determine the influence of the calcium ions released from the BAG in the absence of the pH effect, a typical dose response was demonstrated after 4 hours of exposure of S. sobrinus to media containing various levels of calcium. The results of this study clearly suggest that the effect of BAG extract on bacteria is not only related to a pH effect, but is also linked to an effect of liberated ions, such as calcium, extracted from the surface of the bioactive glasses.

Effect of Different In Vitro Aging Methods on Color Stability of a Dental Resin-Based Composite Using CIELAB and CIEDE2000 Color-Difference Formulas.

PURPOSE: To evaluate the effect of different in vitro aging methods on color change (CC) of an experimental dental resin-based composite using CIELAB (ΔEab ) and CIEDE2000 (ΔE00 ) color-difference formulas. MATERIALS AND METHODS: The CC was evaluated with a spectrophotometer (CM700d, Konica Minolta, Tokyo, Japan) according to the CIE chromatic space. Disk-shaped specimens (Φ = 5 × 1 mm thick) (N = 10) were submitted to different in vitro aging methods: 30 days of water aging (WA); 120 hours of ultraviolet light aging (UVA); or 300 hours of an accelerated artificial aging (AAA) method with cycles of 4 hours of UV-B light exposure and 4 hours of moisture condensation to induce CC. The temperature was standardized at 37°C for all aging methods. CC was evaluated with ΔEab and ΔE00 formulas. Differences in individual Lab coordinates were also calculated. Data for the individual color parameters were submitted to one-way analysis of variance and Tukey's test for multiple comparisons (α = 0.05). RESULTS: All in vitro aging methods tested induced CC, in the following order: WA: ΔEab = 0.83 (0.1); ΔE00 = 1.15 (0.1) < AAA: ΔEab = 5.64 (0.2); ΔE00 = 5.01 (0.1) < UVA: ΔEab = 6.74 (0.2); ΔE00 = 6.03 (0.4). No changes in L* or a* coordinates were ≥1; the methods with UV aging showed a yellowing effect due a large positive change in b*. CONCLUSIONS: All in vitro aging methods tested induced a CC, but to different extents. Changes in color followed similar trends, but with different absolute values when calculated with the CIELAB and the CIEDE2000 formulas. CLINICAL SIGNIFICANCE: Establishing the efficacy of different artificial aging methods and differences between color change using CIELAB and CIEDE2000 formulas are important to standardize color stability evaluations and facilitate the comparison of outcomes from different studies in the literature.