This critical review aimed to assess the vertical marginal gap that was present when E.max lithium disilicate-based restoration (Press and CAD) are fabricated in-vitro. Published articles reporting vertical marginal gap measurements of in-vitro restorations that had been fabricated from E.Max lithium disilicate were sought with an electronic search of MEDLINE (PubMed) and hand search of selected dental journals. The outcomes were reviewed qualitatively. The majority of studies that compared the marginal fit of E.max press and E.max CAD restorations, found that the E.max lithium disilicate restorations fabricated with the press technique had significantly smaller marginal gaps than those fabricated with CAD technique. This research indicates that E.max lithium disilicate restorations fabricated with the press technique have measurably smaller marginal gaps when compared with those fabricated with CAD techniques within in-vitro environments. The marginal gaps achieved by the restorations across all groups were within a clinically acceptable range.
Human tooth enamel is opalescent, which renders teeth bluish in reflected and orange in transmitted color. The aim was to review opalescent property of teeth and application and mimetic reproduction in esthetic restorations. A PubMed search for articles published in English till 2015 on the opalescence of teeth and esthetic materials revealed 29 relevant papers. Opalescence was measured with OP-RT index, which was calculated as the difference in the yellow-blue and red-green color coordinates between the reflected and transmitted colors. Mean OP-RT value of human enamel was 22.9. OP-RT values of direct resin composites changed after polymerization, and the range in these materials was 5.7–23.7. OP-RT value ranges were 1.6–6.1 and 2.0–7.1 for the core and veneer ceramics, respectively. Since the OP-RT values of esthetic materials were lower than that of enamel, it is recommended that materials that can reproduce the opalescence of enamel be further designed.
This study evaluated the effect of mechanical loading with a new device on the microtensile bond strength (µTBS) of adhesive systems to dentin. Forty molars were divided according to adhesive systems: self-etch (ClearfilTM SE Bond —CSE) and etch-and-rinse (Adper ScotchbondTM 1XT —ASB); and to aging (n=5): control; MC1-250,000; MC2-500,000; and MC3-750,000 mechanical cycles. Microtensile bond strength was measured and fracture modes were analyzed. Data for µTBS were subjected to Kruskal-Wallis and post hoc tests (p<0.05). Mechanical loading (p<0.001) and adhesive systems (p=0.024) affected µTBS values. The adhesive systems showed a similar behavior, except in the MC3 group, which the self-etch CSE showed the highest µTBS. The new device promotes a decreasing of µTBS as the number of cycles increased. Difference between materials was observed only after 750,000 mechanical cycles.
RhBMP-2 has shown great promise for the reconstruction of teeth segmental bone defects due to its osteoinductive properties. But the application of rhBMP-2 is limited by its weak drug controled release. It is usually loaded in a Chitosan Microspheres (CMs) delivery system with excess single cross-linker and then removed before practice. In this study, cross-linkers were replaced with RhBMP-2 which contains vanillin and vitriolic acid, and thus CMs were developed. The materials were studied by SEM, FTIR and drug release experiments. It showed an ideal releasing profile and excellent osteoconductive and osteoinductive performance in the delivery system. Therefore, designing biomaterials with a controllable delivery system composite and releasing profile of rhBMP-2 are critical for applications of bone regeneration and tissue engineering.
This study evaluated the influence of curing devices on marginal adaptation of cavities restored with self-etching adhesive containing CQ and PPD initiators and hybrid composite. Twenty-four class V (3 groups, n=8) with margins located on enamel and dentin were restored with Clearfil S3 Bond and Clearfil APX PLT, light-cured with a monowave LED, multiwave LED and halogen light-curing unit (LCU). Marginal adaptation was evaluated with SEM before/after thermo-mechanical loading (TML). On enamel, significantly lower % continuous margins (74.5±12.6) were found in group cured by multiwave LED when compared to monowave LED (87.6±9.5) and halogen LCU (94.4±9.1). The presence of enamel and composite fractures was significantly higher in the group light-cured with multiwave LED, probably due to an increased materials’ friability resulted from an improved degree of cure. The clinician should aware that due to a distinct activation of both initiators, marginal quality may be influenced on the long-term.
To assess the effect of post-space treatment with chelating agents on the push-out bond-strength of a glass fiber post-system. Fortyeight human teeth were decoronated. The roots were prepared to size 40 and obturated. The post-spaces were prepared with PeesoReamer drills. The post-spaces were irrigated with (i) NaOCl and EDTA with chlorhexidine (QMix), (ii) NaOCl and EDTA, (iii) NaOCl and Citric acid, (iv) NaOCl and saline as a control group. i-TFC glass fiber posts were then luted with i-TFC bond system. The samples were horizontally sectioned. The displacement resistance was measured. Push-out bond-strength (MPa) was calculated. Data were analyzed. NaOCl/QMix group showed highest values to dentine whereas NaOCl/Citric acid group showed lowest values. i-TFC post-system demonstrated equal bond strength values when post-space treated with either NaOCl/EDTA or NaOCl/Saline. It can be concluded that post-space could be treated with NaOCl and QMix in order to increase adhesion of i-TFC post-system to rootdentine.
The shear bond strength (SBS) of TheraCal LC to resin composite was evaluated in comparison to Mineral trioxide aggregate (ProRoot MTA) and conventional glass ionomer cement (GIC) using two adhesive systems. A hole was prepared in 90 acrylic blocks (6 mm diameter, 2 mm deep) then filled with TheraCal LC, MTA or Fuji IX (n=30/group). Each group was bonded with either an etch and rinse or 1-step self-etch adhesive. Filtek Z250 composite was bonded to each capping material. Bond strength was tested in a universal testing machine, and data were analyzed using 2-way ANOVA and Duncan’s Multiple range test (p<0.05). TheraCal LC displayed the highest SBS (p<0.001). MTA bonded with the 1-step self-etch adhesiveshowed the lowest SBS (p<0.001), while SBS of TheraCal LC and Fuji IX did not differ between either adhesive (p>0.05). TheraCal LC is the preferred choice in pulp capping procedures when using resin composite restorations.
This study aimed to investigate the effect of epigallocatechin-3-gallate (EGCG) from green tea extract on the push out bond strength of an epoxy resin sealer to root dentin. Seventy single root canal premolars were decoronated and instrumented. The roots were randomly irrigated with different final irrigation protocols (n=16): 17%EDTA (EDTA), 17%EDTA followed by 2.5%NaOCl (EDTA+NaOCl), 17%EDTA followed by 1 mg/mL EGCG (EDTA+EGCG) and 1 mg/mL EGCG (EGCG). Other six root canals were received only 2.5%NaOCl as a control group. One root from each group (n=1) was excluded and prepared for SEM investigation. All root canals were then obturated and horizontally sectioned to perform the push out test. EDTA+EGCG group had the highest bond strength (p<0.05). EGCG group showed higher bond strength than EDTA group (p<0.05). The use of EGCG as a final irrigant significantly increased the push out bond strength of an epoxy resin sealer to root dentin.
This study compared the fracture toughness values of seven resin composites and analyzed the consistency of data values using three methods: compact tension, three point and four point bending for Mode I failure. Seven resin composites were selected: Estellite Sigma Quick, Esthet X HD, Filtek Supreme XTE, Heliomolar, Ice, Rok, and Vit-l-escence. For each material, 18 specimens (n=6 for each test) were prepared. Maximum load to failure was recorded using a universal testing machine and fracture toughness was calculated. There was a direct significant correlation among all tested methods. Rok showed the highest and Estelite the lowest KIc values. SEM of the fractured surface of compact tension method showed propagation of the cracks from stresses concentrating at the corner of the notch and the surface of the sample. Four-point test gave the largest range in KIc and was a simple method to discriminate between the resin composite values of KIc.
Adequate revascularization is a prerequisite for successful healing of periodontal bone defects. This study characterized three different xenogeneic bone grafting materials: Gen-Os of equine and porcine origins, and anorganic Bio-Oss. We also investigated their angiogenic potential. All materials were composed of poorly crystalline calcium oxide phosphate, with Bio-Oss exhibiting a carbonated phase and larger particle size and both Gen-Os showing the presence of collagen. Both Gen-Os materials significantly enhanced vascular endothelial growth factor (VEGF) secretion by PDL cells. A significant increase in endothelial cell proliferation was observed in cultures with both Gen-Os conditioned media, but not with that of Bio-Oss. Finally, angiogenesis was stimulated by both Gen-Os conditioned media as demonstrated by an increased formation of capillary-like structures. Taken together, these findings indicate an enhanced angiogenic potential of both Gen-Os bone grafting materials when applied on PDL cells, most likely by increasing VEGF production.
We developed a device to evaluate the orthodontic force applied by systems requiring high operability. A life-sized, two-tooth model was designed, and the measurements were performed using a custom-made jointed attachment, referred to as an “action stick”, to allow clearance for the oversized six-axis sensors. This tooth-sensor apparatus was accurately calibrated, and the error was limited. Vector analysis and rotating coordinate transformation were required to derive the force and moment at the tooth from the sensor readings. The device was then used to obtain measurements of the force and moment generated by the V-bend system. Our device was effective, providing results that were consistent with those of previous studies. This measurement device can be manufactured with force sensors of any size, and it can also be expanded to models with any number of teeth.
This study evaluated the effect of C-factor on the bond strength of a resin composite to floor and wall dentin using two adhesive systems. Box-form cavities were prepared on human molars, following the walls of half of the cavities were removed to create flat dentin surfaces for bonding. Each specimen was then restored using one of two adhesives (Clearfil SE Bond or Clearfil tri-S Bond) and filled or built up using Z100 resin composite. After light-curing, the specimen was cut perpendicular to the bonded surface parallel to the floor or wall to obtain beams. The micro-tensile bond strength to the flat floor, flat wall, cavity floor, or cavity wall was determined. Resin composite bonded more strongly to the flat wall dentin than to the flat floor dentin, regardless of the adhesive system used. Bonding to the cavity wall was higher affected by C-factor than to the cavity floor.
During a fiber post cementation, bonding failure often occurs at the junction between the fiber-post and resin-cement. Because this failure requires better characterization, we evaluated if different post surface treatment can affect the bond strength of urethane dimethacrylate (UDMA) fiber-posts with resin-cements. Three groups were created: G1: no treatment/silane; G2: ethyl alcohol (96° GL)/silane; G3: 24% H2O2/silane and further divided into four subgroups: I-Unicem/3MESPE; II-BisCem/Bisco; III-Panavia SA/Kuraray and IV-DuoLink/Bisco. Blocks of cured resin cements and posts placed in the center were serially cut into bar-shaped specimens and loaded into a micro tensile testing machine. ANOVA indicated no significant differences among post surface treatments (p>0.05), however, significant within the resin cements (p<0.05) and the interaction of both (p<0.05). The G3/IV showed the highest bond strength values. SEM showed that surface treatments on UDMA fiber posts presented no benefits in terms of surface roughness, thus, should not be performed.
The purpose of this in vitro study was to investigate the influence of eccentric loading on implant components by measuring screw loosening and observing these components under several load positions and magnitudes. The external and internal joint system implants with butt joint connection were subjected to cyclic loading tests according to the specifications of ISO 14801. Load position was set at 0, 4, or 8 mm, and load was set at 100 or 300 N. On the external joint system, the reverse torque values decreased with distal shift in the loading position and an increase in magnitude of load, and abrasion and deformation on the anti-rotation device were observed. On the internal joint system, no large decrease in reverse torque was observed even though increasing the load position and load, however, abrasion and deformation on the anti-rotation device as well as fracture at implant/abutment connection were observed.
This study evaluated the effect of implant diameter on strain around implants retaining mandibular overdentures with Locator attachments. Three mandibular acrylic resin models were constructed with 2 implants inserted in canine areas and classified according to implant diameter into 3 groups: large (4.2 mm), medium (3.7 mm), and small (3.3 mm) diameter implants. Duplicate dentures were connected to the implants with Locator attachments. Four strain gauges were bonded to the acrylic resin at mesial, distal, buccal and lingual surfaces of each implant and strain was measured at loading and non-loading sides during 1st premolar and 1st molar loading. Small and large diameter implants recorded the highest and the lowest strain, respectively. Buccal and lingual sites recorded the highest strain, and mesial site recorded the lowest. First premolar loading recorded significant higher strain than first molar loading. The largest possible implant diameter is recommended to minimize strains around implants retaining mandibular overdentures with Locator attachments.
To investigate the chemical structure-cytotoxicity relationship of methacrylate-based resin monomers, we studied their effects on anti-oxidant responsive element (ARE)-mediated transcription. HepG2 cells stably expressing an ARE-regulated luciferase reporter gene were cultured for 6 h with various concentrations of several resin monomers and subjected to a luciferase assay. The doseresponse curves observed for hydrophobic monomers with different hydrocarbon chains (MMA, EMA, PMA and BMA) began to rise at concentrations between 0.5 and 1 mM; the curves rose as the monomer concentrations increased up to 5 (BMA), 10 (PMA), or 30 mM (MMA and EMA). In contrast, hydrophilic monomers having a hydroxyl group (HEMA and HPMA) showed bell-shaped curves, and stimulated the reporter expression more strongly than the hydrophobic monomers in a low concentration range (0.5–5 mM). The results suggest that introduction of a hydroxyl group in a methacrylate-based resin monomer increases its intracellular electrophilic reactivity and cytotoxicity.
Mechanical responses of the test specimen under bidirectional and unidirectional loading were investigated using a newly developed masticatory simulator. The simulator adopted a four-bar linkage mechanism to create both loading patterns. Scratch/occlusal contact characteristics, contact force profiles and the fracture of restored tooth samples were investigated. With bidirectional loading, which imitates the nature of human chewing cycle closer than the unidirectional loading does, the occlusal contact was ovoid in shape whereas a small circular area was observed from the test with unidirectional loading. The contact force profiles were also noticeably dependent on the loading patterns. Measured contact forces from bidirectional loading were more uniform than those from unidirectional loading. Bidirectional loading also induced the cuspal fracture with similar characteristics of natural cuspal fractures in humans. The differences of force characteristics between those of bidirectional and unidirectional loadings emphasize the importance of employing bidirectional loading in dental material testing.
The purposes of this study were to examine the shock absorption capability of addition-cured silicone denture relining materials and the bonding strength of addition-cured silicone denture relining materials and a commercial mouthguard material to determine its applicability to mouthguard adjustment. Two addition-cured silicone denture relining materials were selected as test materials. The impact test was applied by a free-falling steel ball. On the other hand, bonding strength was determined by a delamination test. After prepared surface treatments using acrylic resin on MG sheet surface, 2 types of addition-cured silicone denture relining materials were glued to MG surface. The peak intensity, the time to peak intensity from the onset of the transmitted force and bonding strength were statistically analyzed using ANOVA and Tukey’s honest significant difference post hoc test (p<0.05). These results suggest that the silicone denture relining materials could be clinically applicable as a mouthguard adjustment material.