جستجوی مقالات مرتبط با کلیدواژه « all ceramic » در نشریات گروه « پزشکی »

 Dental crowns are effective on the gingival tissue around the teeth. However, using zirconia as crowns due to the method and type of material can effectively improve this effect.

 This is a pre-post clinical trial conducted on 35 teeth with metal-ceramic crowns and 35 teeth with zirconia crowns. Teeth were prepared for fabricating metal-ceramic and zirconia crowns. Plaque index (PI), modified gingival index (MGI), pocket probing depth (PPD), papilla bleeding index (PBI), and gingival level (GL) were measured before and six months after getting the dental crown. The data were analyzed using the Mann–Whitney test.

 In both groups, the GL remained the same after six months of crown placement (P>0.05). In the metal-ceramic group, the PI decreased significantly (P=0.000), but MGI and PBI significantly increased (P=0.000 and P=0.000, respectively) six months after crown placement. Based on the results, PPD increased significantly only on the midlingual surface (P=0.02). The PI significantly decreased in the zirconia group (P=0.000). Nevertheless, PPD represented no change (P>0.050). The comparison between the two groups six months after crown placement indicated that the PI, MGI, and PBI were significantly higher in the metal-ceramic group (P=0.010, P=0.011, and P=0.044, respectively). The metal-ceramic group showed a significantly greater increase in PPD on the midlingual surface (P=0.043).

 Both crown types on teeth could significantly increase the incidence of gingivitis, and compared with zirconia crowns, metal-ceramic crowns demonstrated significantly more inflammation.

Implant‑supported prostheses could serve as a reliable restorative option for partial edentulism. Various restorative materials have been utilized in fabricating these prostheses, impacting both esthetics and peri‑implant health. The present systematic review aimed to assess the survival rate and mechanical complications of zirconia ceramic compared to metal‑ceramic implant‑supported multiunit fixed dental prostheses (FDPs). We conducted searches in online databases such as MEDLINE (PubMed), Scopus, and Cochrane up until December 2022. A risk‑of‑bias assessment was done for all the included studies. Data extraction was performed based on the following parameters: author, year, study design, number of implants, abutment material, age range, observation period, incidence of mechanical complications, and survival rate. This systematic review included six studies (four randomized controlled trials and two retrospective studies). The meta‑analysis significantly favored metal‑ceramic restorations regarding mechanical complications with a risk ratio (RR) value of 1.64 and P = 0.001. Meta‑analysis showed no difference in metal‑ceramic FDPs in prostheses survival rate (P = 0.63; RR: 1.27, 95% confidence interval: 0.52–3.37; heterogeneity: P = 0.65; I2: 0%). While metal‑ceramic multiunit implant‑supported prostheses exhibited fewer mechanical complications compared to zirconia‑ceramic prostheses, there was no significant difference in terms of prosthesis survival rate between the two. Hence, both treatments appear to be viable options for long‑term implant‑supported prostheses.

The purpose of this review is to investigate the contribution of non-surgical endodontic treatment in the healing process of large periapical lesions as well as looking over other potential non-surgical endodontic treatment options.

two females and one male patient were referred to the private office, complaining of having pain in the anterior maxillary region which was pertinent to the presence of a large periapical lesion, and subsequently were managed by a non-surgical endodontic approach using cold ceramic. The archive of PubMed and Google Scholar databases was also searched for finding relevant articles in which a nonsurgical endodontic approach was performed to improve the healing process of large periapical lesions.

Clinical examination of the case series subjects revealed no signs and symptoms following treatment while relative improvement of the lesion and apical closure was apparent in radiographs 7 months, 9 months, and 4 years subsequently. In twenty-two reviewed clinical trials, a total number of 107 teeth with large periapical lesions were treated by nonsurgical endodontic approaches using MTA, biodentine, gutta-percha, and bioceramic iRoot Bp plus. Complete healing occurred in 38 cases (35.5%) after 12-17 months.

Although surgical interventions have been used previously in the management of large periapical lesions, a nonsurgical endodontic approach with cold ceramic seems to be effective, leading to complete healing of the periapical lesion in treated subjects. Further clinical research is recommended to identify the effectiveness of cold ceramic for the treatment of extensive periapical lesions.

It is a major concern to select a proper ceramic with acceptable strength and esthetic and minimum antagonist wear. Therefore, different ceramics were introduced to obtain these advantages with various surface treatments. The aim of this study is to evaluate and report the wear behavior of polished and glazed feldspathic and zirconia crowns in published articles up to 2020. Five electronic databases which were used in this research were MEDLINE (via PubMed), Web of Science, Cochrane Library, Embase, and Scopus from the starting date of databases to January 2020. The Keywords “zirconia,” “feldspathic,” “dental ceramic,” ”enamel,” “Y‑TZP,” “wear,” “glazed,” and “polished” were used. English articles were selected in this paper. The Preferred Reporting Items for Systematic Reviews and Meta‑Analyses statement was used as a reporting template as much as possible. Among the initially 133 articles, 59 duplicated articles were removed, and finally, 52 articles were screened and among them, only 16 articles remained for full‑text regaining. The results showed that zirconia had significantly less antagonist wear than feldspathic groups, and polishing had less enamel wear than other types of surface treatment like glazing. Only one study showed that glazed zirconia can have more antagonist wear than feldspathic porcelain. Monolithic zirconia had less enamel wear than conventional zirconia and low‑fusing feldspathic porcelain showed lower antagonist wear in comparing with other types of feldspathic porcelains.

Marginal adaptation highly affects the long-term success of crowns. This study intends to investigate the marginal adaptation of monolithic zirconia and veneered zirconia crowns.

Based on our searches in PubMed and Google Scholar from 2011 to 2020, 22 articles were obtained, and after studying their full-texts. Five articles that were most related to our subject were selected. 

In almost all articles, the greatest mean marginal gap value was recorded for monolithic zirconia, whereas layered zirconia crowns demonstrated the lowest mean marginal gap values. 

  Based on finding of the current study, monolithic zirconia restorations had a superior marginal adaptation than layered zirconia restorations. However, clinically both restorations have an acceptable marginal fit

Intraoral repair has been suggested as a treatment option to repair the chipping or fracture of veneered zirconia; the success of the procedure is mainly determined by the bonding between zirconia and composite resin. The present study aimed to investigate and compare the shear bond strength (SBS) of two intraoral repair systems to zirconia ceramic treated with a laser or air-abrasion surface modification.

Ninety tube-shaped samples (diameter of 10 mm and height of 4 mm) were divided into three main groups: Group I (zirconia 100%, n = 30); Group II (veneer ceramic 100% n = 30); Group III (zirconia with a veneer ceramic n = 30). Each main group was subdivided into two subgroups (n = 15): Subgroup A: samples repaired with Ceramic Repair N; Subgroup B: samples repaired with the Cimara Repair System. The subgroup samples were further subdivided based on the treated surface (n = 5 samples): Control (no surface modification), Er,Cr:YSGG laser surface modification, and air-abrasion surface modification. The SBS was employed using a universal testing machine. The mode of failure was observed using a stereomicroscope.

Significant differences were observed in the mean SBS values between the different surface modifications (P ˂ 0.05). Tukey’s post hoc test showed that the air-abrasion surface modification of the veneer ceramic repaired with the Ceramic repair N system had the highest mean value (13.74 MPa) among the different groups, while no surface modification of zirconia repaired with the Cimara repair system had the lowest mean value (2.84 MPa). The control group (no surface modification) had the lowest mean value among all the treated groups.

The SBS is surface modification-dependent, and higher SBS is obtained by air-abrasion than Er, Cr:YSGG laser surface modifications with the selected parameters. The Ceramic repair N system had significantly higher SBS for all surface-treated substrates than the Cimara repair system.

Masking dark tooth structure or darkness of oral cavity with ceramic restorations is an important concern. The aim of this study was to determine the minimum thickness of a multilayer all‑ceramic restoration (IPS‑emax Press) required for a proper masking in these situations.

In this experimental in vitro study, 36 multilayer ceramic disks of IPS e.max Press (IvoclarVivadent, Schaan, Liechtenstein) with the diameter of 13 mm were prepared and allocated in six groups of different core/veneer thicknesses: 0.4/0.4 mm (G1), 0.5/0.5 mm (G2), 0.6/0.6 mm (G3), 0.8/0.7 mm (G4), 1.0/0.8 mm (G5), and 1.1/0.9 mm (G6). For backgrounds, the standard black tile of spectrophotometer (B) was used to stimulate the darkness of oral cavity, and an opaque ceramic (OC) of IPS‑emax Press (OC) was fabricated to determine the masking ability. CIELAB values of all disks on B and OC backgrounds were measured, and ΔE was calculated between two backings. One‑way ANOVA and post hoc tukey test were used to analyze the data. ΔE ≤3.3 and P < 0.05 were considered, respectively, as the clinically acceptable limit and the level of statistical significancy.

The mean ΔE between B and OC of groups 4 (2.83 ± 0.80) and 5 (1.46 ± 0.36) were within the range of the clinically acceptable color difference (ΔE ≤3.3); thus these groups could properly mask the black background. A trend was existed in the results as by increasing the thickness, ΔE was decreased.

A thickness of 1.5 mm of a multilayer ceramic restoration (IPS e.max Press) is required to mask a dark discoloration.

This study investigated the effect of various laser powers on the shear bond strength (SBS) of resin cement to the zirconia surface.

Seventy-five zirconia disks were prepared and assigned to five groups including no surface treatment (control group), sandblasting with 50 μ Al2O3 particles (second group), and Nd:YAG laser treatments with 2 W, 2.5 W and 3 W powers respectively (third, fourth and fifth groups). Afterwards, composite resin cylinders were cemented on zirconia disks using dual-curing resin cement. Before thermocycling (2000 cycles, 5-55°C), all samples were placed in distilled water at 37°C for 24 hours. Using a universal testing machine at the crosshead speed of 0.5 mm/min, the SBS was examined. Also, using a stereomicroscope, the failure type was determined. Data analyses were performed using Welch and Games-Howell tests (P < 0.05).

The mean bond strength difference between the control group and the other groups was significant. The respective bond strength from the highest to the lowest was observed in the sandblast group, the laser group with 2.5 W power, the laser group with 3 W power, the laser group with 2 W power, and finally the control group. However, no significant difference was observed between different laser groups (P < 0.05). Also, there was no significant difference between the sandblast and laser groups with 2.5 W and 3 W power (P < 0.05). Most of the failures in the sandblasting and laser groups with powers of 2.5 W and 3 W were mixed, but in the control and 2 W laser groups, most of the failures were of adhesive nature.

The highest bond strength was achieved by sandblasting with Al2O3 particles and then using an Nd: YAG laser with a power of 2.5 W

Statement of the Problem: 

Success of metal-ceramic restorations depends on the bond strength between porcelain and alloy. These restorations can be fabricated through different casting and computer-aided design/compute-aided manufacturing (CAD-CAM) techniques.

This study aimed to compare the bond strength of porcelain to milled sintered (Sintron) and casting (Co-Cr and Ni-Cr) base metal alloys.

In this in-vitro experimental study, 63 rectangular bars (25×3×0.5 mm) were fabricated of three base metal alloys: casting Ni-Cr, casting Co-Cr, and milled sintered Co-Cr alloy. Feldspathic porcelain (3×8 mm) was applied at the center of each bar with 1.5 mm thickness. The specimens were thermally aged. Bond strength was evaluated through three-point flexural test. Failure mode was evaluated by optical and electron microscope. Data were analyzed with one-way ANOVA and Tukey's post hoc test (α=0.05).

The mean flexural bond strength of porcelain to milled sintered Co-Cr alloy (24.58±5.16 MPa) was significantly higher than that of casting Ni-Cr (21.13±6.34 MPa) (p = 0.03) and casting Co-Cr (20.98±4.84 MPa) alloys (p = 0.04). However, the two casting alloys were not significantly different in this regard (p = 0.93). Failure mode in all specimens was of cohesive type.

Bond strength of CAD-CAM milled sintered Co-Cr alloy was better than that of the conventional casting alloys and can serve as a suitable alternative to those alloys.

This study aimed to evaluate the effects of hydrofluoric acid (HF) concentration and etching time on the surface roughness (SR) and three-point flexural strength of Suprinity and to analyze the surface elements before and after etching.

To measure the SR, 70 specimens of Suprinity (2×4×5mm3) were assigned to seven groups (n=10). Six groups were etched for 20, 60, and 120 seconds with 5% and 10% HF and 7th group was the control group. Specimens were evaluated using atomic force microscopy (AFM). One specimen from each group was used to analyze the surface elements using scanning electron microscopy (SEM). For measuring the three-point flexural strength, 60 specimens were divided into six groups (n=10) and etched as previously described. The flexural strength was measured using a universal testing machine. T-test, one-way analysis of variance (ANOVA), and two-way ANOVA were used for statistical analyses (P<0.05).

The 10% concentration of HF caused higher SR compared to the 5% HF. The effect of HF concentration on the flexural strength was significantly different in the 20- and 60-second etching groups. Different etching times had no significantly different effect on the SR. With 5% HF, the flexural strength was significantly higher for 20-second etching time than for the etching times of 60 and 120 seconds. With 10% HF, there was a significant difference in flexural strength between etching times of 20 and 120 seconds. 

The best surface etching protocol comprises 10% HF used for 20 seconds.

While different preparation designs on anterior laminates have been investigated in several studies, a clear understanding of the tooth subtract type support on laminate veneer structural integrity using finite element analysis is still lacking. Therefore, the aim of present study is to evaluate stresses and displacements with different thickness restoration material and prepared tooth subtract using Finite Element Analysis (FEA). A 3D FEA models of maxillary central incisors restored with two ceramic systems Feldspathic ceramic and IPS e.max press, according to three different preparation surfaces (all-enamel, half-enamel-half-dentin, all-dentin). It has been evaluated von Mises and principle stress and displacement on the incisal surface along with the long axis by applying 50 N. Load. The smallest von Mises stresses were found at Feldspathic ceramic. The lowest stresses were seen in veneers adhered to enamel surface. The greatest stress occurred in the incisal third of IPS e.max press, which is only adhered to dentin surface. While the other five veneers displayed the highest von Mises stress values on cervical margin. Displacement analysis showed that the most ideal result was obtained by using 0.3 mm thick IPS e.max press laminate veneer adhered on enamel. The highest principal stresses were obtained in the cervical area. The greatest stresses occurring on tooth was seen in the dentine in IPS e.max press with the greatest restoration thickness. As the thickness of the restorations increased, the stress on the restoration and tooth increased.

The aim of this present study was to investigate the effect of different surface treatments of a hybrid ceramic, Vita Enamic (VE), on the micro-tensile bond strength (µ-TBS) to a resin cement.

10 blocks (3×10×8 mm)were retrieved from the original blocks and divided into five groups according to the different surface treatment performed: Groups 1: 35% Acid phosphoric for 60 seconds (PA); group 2: Sandblasting with 50µm Al2O3 particles for 10 seconds (SB); groups 3: 9.5% hydrofluoric acid for 60 seconds(HF), group 4: Er:YAG laser (2 W,10 Hz) (ER1), group 4: Er:YAG laser (3 W, 10 Hz) (ER2). All treated surfaces were salinizedand the blocks with similar surface treatments were bonded together using a dual cured resin cement and light cured. After 24-hour storage in water, blocks were cut into beams(1mm2). Half of the specimens in each group(n=16) were tested immediately and the rest were subjected to thermocycling between 5°C and 55°C for 6000 cycles before µ-TBS test at a crosshead speed of 0.5 mm/min. The data were analyzed using two-way ANOVA and Tukey HSD tests considering 0.05 as significance level. The failure mode was evaluated using a stereomicroscope.

µ-TBSwas clearly influenced by surface treatment methods(P˂0.001) and thermocycling significantly decreased the bond strength values in all groups (P=0.007). The highest value (66.07 MPa±11.3) was obtained for HF groups with no thermocycling and the lowest values were observed in laser groups with no significant difference among different irradiation parameters. Adhesive failure was mainly observed in PA and SB groups while mixed failure was predominantly shown in laser and HF groups.

 This study demonstrates that surface treatment of VE with HF and salinization can improve the bond strength to a dual cured resin cement and Er:YAG laser irradiation with the evaluated parameters  did not promote adhesion of the resin cement to VE.

There is currently significant interest in all-ceramic dental restorations. A potential non-metallic material for such restorations is an apatite-mullite glass-ceramic that could be processed to shape using different processing techniques. The aim of this study was to assess and evaluate the ability of an apatite-mullite glass-ceramic material to be processed using three routes: lost-wax casting, hot pressing and CAD-CAM milling. A batch of glass for an apatite-mullite glass-ceramic material was produced based on the formula (4.5SiO2-3Al2O3-1.5P2O5-3CaO-0.5 CaF 2). The batch was converted into glass by heating at 1050˚C/1450˚C for two hours. The final melt was quenched to obtain a glass frit. The glass was thermally treated based on the DTA data. The sequence of crystallization and their micro structural evaluation were analysed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). An anatomically correct mould of an upper right first molar was selected to trial the three different manufacturing techniques. Empress II and VITA block mark II materials were used as control materials. The apatite-mullite material being evaluated can be cast and milled to shape, but the ceramic form of the material is not capable of being hot pressed. The materials tested show great possibility as restorative materials and could be heat treated inside and outside the investment casting material to produce a crystalline microstructure of apatite and apatite-mullite. It is possible to produce acceptable restorations using the milling technique. Hot pressing the material is not recommended due to its high liquidus temperature.

This study sought to assess the effect of glazing and polishing surface treatments on the optical behavior of zirconia-reinforced lithium silicate ceramics thermocycled in different solutions. Computer-aided design/computer-aided manufacturing ceramics (VITA Suprinity) were cut into samples (n=104) measuring 1.5x14x10 mm according to the manufacturer’s instructions. Also, the samples were then randomly divided into four groups for immersion in artificial saliva, tea, orange juice and cola. A spectrophotometer was used to assess the color change and changes in L* coordinate against a white and a black background. The translucency parameter and contrast ratio were also calculated. The ∆E and L* values were analyzed using two-way ANOVA test. Student’s t-test was applied to analyze TP and CR. The interaction effect of the type of solution and type of surface treatment on color change against a white (P=0.008) and black (P<0.001) background was statistically significant. Immersion of ceramic samples in orange juice and cola caused significant changes in TP and CR in the polishing and glazing groups (P < 0.05). Immersion in orange juice causes clinically perceivable color change in glazed ZLS ceramics. Immersion in cola decreases the translucency of both polished and glazed ZLS ceramics.