Influence of Restoration Thickness and Resin Cement on Translucency and Color of Different Types of Monolithic Zirconia and Lithium Disilicate Ceramic.

In recent years, high esthetic expectations and natural appearance demands from patients have increased the popularity of ceramic restorations. The purpose of this study was to investigate the influence of restoration thicknesses and different resin cement brands on the translucency and final color of different types of monolithic zirconia and lithium disilicate ceramics. A total of 160 disc-shaped specimens (10-mm diameter; 1 mm, or 1.5 mm thick) were produced using different types of monolithic zirconia (Katana Zirconia UTML, Katana Zirconia ML, Katana Zirconia STML Blocks; Kuraray) and lithium disilicate ceramic (IPS e.max Press, Ivoclar Vivadent) (n = 40 discs per material, with 20 discs per thickness). Two different brands of dual-cured resin cements (RelyX Ultimate, 3M ESPE; and BisCem, Bisco) were applied to the specimen surfaces. The translucency and color changes of the lithium disilicate and monolithic zirconia ceramics were examined before and after cementation using a spectrophotometer. Within the limitations of this in vitro study, the resin cement brand and ceramic thickness variation influenced the translucency and final color of the monolithic zirconia and lithium disilicate ceramic specimens.

Evaluation of the effects of bruxism on oral health-related quality of life in adults.

OBJECTIVE: The aim of this study was to evaluate the effects of bruxism on oral health-related quality of life (OHRQoL) in adults in relation to temporomandibular disorders (TMD). METHODS: Three hundred-fifteen adults of both sexes were divided into two groups: bruxers (n = 172) and controls (n = 143). The participants with TMD were divided into three subgroups based on myofascial pain, disc displacement, or both. The Oral Health Impact Profile (OHIP-14) was used to assess OHRQoL. RESULTS: Bruxers had poorer OHRQoL than controls, and the highest mean OHIP-14 domain scores were observed in physical pain. Bruxers with TMD had higher total OHIP-14 scores and individual domain scores than those without TMD. Bruxers without TMD demonstrated higher OHIP-14 scores than controls. CONCLUSION: Bruxism was associated with poor OHRQoL. Where bruxism was accompanied by TMD, OHRQoL could be more negatively affected. The presence of bruxism without TMD was also associated with poor OHRQoL.

Effect of cigarette smoking on the color stability and surface roughness of two different denture base materials.

PURPOSE: To evaluate the effect of cigarette smoking on the color stability and surface roughness of heat-polymerized poly(methylmethacrylate) (PMMA) and computer-aided design and computer-aided manufacturing (CAD-CAM) PMMA denture base materials. METHODS: A total of 40 disc-shaped specimens (diameter 15 mm x thickness 2 mm) were divided into two groups according to their processing technique: Group CC, CAD-CAM PMMA; and Group HP, heat-polymerized PMMA. The specimens were exposed to cigarette smoke with 20 cigarettes daily for 5 days. Before the procedure, the color of the denture base was measured using a spectrophotometer in accordance with the Commission Internationale de I'Eclairage (CIE) color system. The surface roughness (Ra) of each sample was measured five times before and after exposure to smoke using a profilometer, and the mean roughness (Ra) values were calculated. The color change and surface roughness were statistically analyzed (P< 0.05). RESULTS: Greater discoloration was observed in the HP group, whereas the CC group showed clinically acceptable color change. Smoking increased the surface roughness of both denture base materials. However, the HP group had higher mean values than the CC group. CLINICAL SIGNIFICANCE: Denture base materials are susceptible to changes in color and surface roughness due to oral habits such as cigarette smoking. This in vitro study suggested that smoking can exacerbate the color changes and surface roughness of denture base materials, especially in heat-cured acrylic resins.

Influence of fiber insertion and different material type on stress distribution in endocrown restorations: a 3D-FEA study.

The study aimed to evaluate the effects of fibers insertion and restorative material type on the stress distribution in endocrowns with finite element analysis. Five 3D models of first mandibular molars were created and restored as follows: (1) IN: intact tooth, (2) IPS-E: tooth restored with lithium disilicat ceramic endocrowns, (3) C-E: tooth restored with composite endocrowns, (4) IPS-E + F: lithium disilicate ceramic endocrowns + fiber, (5) C-E + F: composite endocrowns + fiber. Vertical masticatory load was imitated with finite element analysis. The equivalent stress of von Mises failure criterion (mvM) was calculated. The maximum mvM stress, enamel/crown, dentin and cement were compared among models and strength of the materials. Endocrowns presented a lower mvM stress level than intact tooth. In IPS-E, the mvM stress values in the crown and dentin were higher than C-E, while the mvM stress values in cement were higher in C-E group. Fibers insertion did not affect the stress level of IPS-E and C-E groups. In IPS model, fiber showed more stress absorption than C-E. The restorative material type changed the stress distribution of endocrown restorations. The fiber application did not affect the stress distribution in either endocrown group. But, more stress absorption was observed in fiber under IPS-E than C-E.

Custom and prefabricated PolyEtherKetoneKetone (PEKK) post-core systems bond strength: Scanning electron microscopy evaluation.

The present study evaluated the bond strengths of prefabricated PolyEtherKetoneKetone (PEKK) posts, PEKK posts custom-configured according to root-canal size, and conventional fiber posts. A total of 30 maxillary incisors were randomly divided into three groups, as follows: Group 1: fiber posts; Group 2: prefabricated PEKK posts; Group 3; custom-made PEKK posts. Following endodontic treatment, post spaces were prepared, and posts were cemented with resin cement. Push-out bond strength testing was performed using a universal testing machine, and fractures modes were examined under a scanning electron microscope. Data were analyzed using One-way ANOVA and Tukey's HSD tests, with the level of significance set at .05. The highest bond-strength values in the cervical section were observed with the custom-made PEKK post (17.3470 MPa), whereas the highest bond-strength values in the middle and apical sections were observed with the conventional fiber posts (11.5375 MPa and 6.8625 MPa, respectively). Bond-strength values for all posts systems decreased in a cervical to apical direction. PEKK posts are a suitable alternative to fiber posts. Although custom-made PEKK posts demonstrated better bond strength than prefabricated PEKK posts, further studies are needed to evaluate their clinical performance.

The Effect of Different Combinations of Surface Treatments and Bonding Agents on the Shear Bond Strength Between Titanium Alloy and Lithium Disilicate Glass-Ceramic.

In order to obtain a more-natural esthetic prothesis, the use of hybrid abutments is becoming widespread in implant dentistry. The aim of this in vitro study was to assess the effects of different surface treatments, as well as the effects of different combinations of surface treatments and cementation protocols, on the shear bond strength between titanium alloy disks and lithium disilicate glass-ceramics. Forty titanium-alloy disks (4 × 6.6 mm) were fabricated using computer-aided designed/computer-assisted manufacturing, and an identical number of lithium disilicate glass-ceramic disks of similar sizes were fabricated by a heat-pressing technique to be attached to the titanium disks. The specimens from each material group were divided into two groups (n = 20 each) according to the surface treatment type: alumina airborne-particle abrasion or etching with hydrofluoric acid. Each group was then divided into two subgroups (n = 10) depending on the resin-cement type: Multilink Hybrid Abutment Cement (Ivoclar Vivadent) or PANAVIA SA Cement Plus (Kuraray). After thermocycling (5,000 cycles), a shear bond strength (SBS) test was conducted using a universal testing machine. Statistical analysis was performed by analysis of one-way analysis of variance and unpaired tests (P < .05). Statistically, the highest SBS values were obtained using airborne-particle abrasion. The surface treatment of titanium alloys by sandblasting led to a higher SBS compared to etching with hydrofluoric acid. The cement type also had a significant influence on SBS results.

A Comparison of the Color Stability of Conventional and CAD/CAM Polymethyl Methacrylate Denture Base Materials.

OBJECTIVE: The aim of this study was to evaluate the color stability of a heat polymerized resin, an auto-polymerizing resin, a urethane dimethacrylate resin and a CAD/CAM PMMA block resin stored in different storage media. MATERIALS AND METHODS: 60 disc-shaped specimens (15×2 mm) were fabricated for each group. A total of 240 disc-shaped specimens were thermal-cycled for 5,000 cycles. Then specimens were randomized into 4 groups (n= 15) according to storage media: coffee, coke, red wine and distilled water (control group). The color measurement of each sample was performed using a spectrophotometer before and after storage (after 7 and 30 days), and color changes (ΔE) were calculated. RESULTS: All the denture base materials demonstrated dissimilar color changes after stored in the different storage media in both evaluation stages. In all storage media, CAD-CAM denture base resins showed the minimum in color change. In all denture base resins, red wine showed a higher degree of color change than coke or coffee. CONCLUSION: The color stability of CAD-CAM denture base resins is better than any of the other kind of denture base resins. The color change values of all groups except Eclypse stored in red wine had clinically detectable values.

Effect of Over-the-Counter Topical Agents on Denture-Induced Traumatic Lesions: A Clinical Study.

PURPOSE: To investigate the effects of over-the-counter products on the healing of denture-induced ulcerations and patients' self-reported pain. MATERIALS AND METHODS: A total of 140 patients with acute denture-induced ulcerations were randomized into seven treatment groups: denture grinding (control); topical application of corn oil gel (placebo); triester glycerol oxide gel; D-panthenol gel; D-panthenol mouthwash; L-arginine mouthwash; and hyaluronic acid gel. Healing and self-reported pain were assessed after 1, 3, and 7 days of treatment. RESULTS: The percentage of healed lesions in the mandible and maxilla after 7 days was 67% and 65%, respectively. The only significance in healing was for mandibular lesions at 3 days after application of L-arginine mouthwash; at this period, the healing rate was significantly higher than d-panthenol gel, d-panthenol mouthwash, and hyaluronic acid gel (P < .05). CONCLUSION: Denture grinding as the current protocol for acute denture-induced ulcerations should remain as the default.