Effect of laser engraving on shear bond strength of polyetheretherketone to indirect composite and denture-base resins.

Background/purpose: Polyetheretherketone (PEEK) is a highly sought-after thermoplastic due to its exceptional mechanical properties and biocompatibility. However, bonding PEEK to indirect composite resin (ICR) or denture-based resin (DBR) can be challenging. Laser engraving technology has shown potential to improve bonding for other materials; thus, this study aims to evaluate its effectiveness for PEEK. Materials and methods: The experiment involved preparing ingot-shaped PEEK samples, which were then categorized into four groups based on the treatment method employed: without treatment, air abrasion, sulfuric acid etching, and laser engraving (LS). Subsequently, the samples were bonded to ICR or DBR, and their shear bond strength (SBS) was tested with or without thermocycling using a universal testing machine. Furthermore, the failure mode was observed, with statistical analyses conducted to compare the results. Results: The grid-like microslit structure of LS group displayed the highest SBS for bonding PEEK to ICR or DBR (P < 0.05). During the bonding of PEEK to ICR, resin residue and penetration into the microslits were frequently observed in the LS group, indicating cohesive failure. However, when PEEK was bonded to DBR, mixture failure was frequently observed without thermocycling. After thermocycling, only the LS group showed cohesive failure, while the majority of specimens exhibited mixture failure. Conclusion: Laser engraving significantly improves the SBS between PEEK and both ICR and DBR. Furthermore, it was observed that resin had penetrated the microslits, indicating that laser engraving has great potential as a surface treatment method.

An in vitro study of digital impressions and three-dimensional printed models of orbital defects using mobile devices and monoscopic photogrammetry.

PURPOSE: The purpose of this study was to perform an in vitro evaluation of digital impressions using a mobile device and monoscopic photogrammetry in cases of orbital defects with undercuts. METHODS: Three 10-mm-square cubes were attached to a diagnostic cast of a patient with a right orbital defect. Still images acquired with a mobile device were used to generate facial three-dimensional (3D) data. Two types of still images were used: one was a whole face image, and the other was a defect site-focused image. For comparison, an extraoral scanner was used to obtain facial 3D data. Five dental technicians fabricated 3D printed models using additive manufacturing and measured the distances between the measurement points using a digital caliper. The discrepancy between the distances measured on the diagnostic cast of the patient and the 3D printed model was calculated. Friedman test was used to analyze the discrepancy, and the Bonferroni test was used to verify the differences between the pairs. RESULTS: Statistical significance was found with respect to the type of 3D model fabrication method. CONCLUSION: Within the limitations of this in vitro study, the results suggested that the workflow can be applied to digital impressions of the maxillofacial region.

Innovation Glass-Ceramic Spray Deposition Technology Improving the Adhesive Performance for Zirconium-Based Dental Restorations.

Glass-ceramic spray deposition (GCSD) is a novel technique for coating lithium disilicate (LD) glass-ceramics onto zirconia through simple tempering steps. GCSD has been proven to improve the bonding of zirconia to resin cement, but the effect of etching time on GCSD and the long-term durability of the bond achieved remain unknown. The effects of air abrasion with aluminum particles (ABB) and air abrasion (GAB) or etching with 5.0% hydrogen fluoride (HF) for 20, 60, 90, and 120 s (G20, G60, G90, and G120) on the resin cement−zirconia bond were studied. LD was included as a control (LDG). The microstructure, sub-micron roughness, wettability, and phase changes of samples were analyzed. After resin cement was bonded to zirconia, half of the samples were subjected to thermocycling (5000 cycles at 5−55 °C). The bond strengths of the samples were determined in shear bond strength (SBS) tests (n = 10 per group). An LD structure can be formed on zirconia after GCSD and proper etching processes, which result in high roughness and a hydrophilic nature. GCSD and HF etching significantly improved SBS, with G90 and G120 samples with pre- or post-thermocycling exhibiting SBS values comparable to those of LDG (p > 0.760). The surface characteristics of the LD layer are influenced by the etching time and affect the SBS of the bond of zirconia to resin cement. HF etching for 90−120 s after GCSD results in zirconia with SBS and bond durability comparable to LD.

Influence of dental abrasives on surface roughness, gloss, and color of titanium.

PURPOSE: The influence of three dental abrasives on the surface roughness, glossiness, and color of titanium (Ti) after mechanical polishing was investigated. METHODS: The specimens were divided into groups, referred to as SM, SR, and TP, to distinguish the different polishing processes. SM: rubber polishing using a rubber point containing SiC abrasive particles at 20,000 rpm, followed by gloss polishing; SR: rubber polishing using a rubber point containing Al2O3 abrasive particles at 20,000 rpm, followed by gloss polishing; TP: rubber polishing using a rubber point containing TiO2 abrasive particles at 6,000 rpm, followed by gloss polishing. Gloss polishing was carried out at 10,000 rpm using a leather buffing wheel. Measurements to evaluate the surface conditions of Ti were performed after each polishing process. RESULTS: There were no significant differences in the Ra and glossiness values between the SM and TP groups; these specimens were not as smooth and glossy as the SR group. The SM group showed relatively high values of lightness and chroma after gloss polishing. CONCLUSION: Rubber polishing with abrasives containing SiC or TiO2 particles before gloss polishing did not achieve appropriate surface conditions on Ti.

Dual Corrective Osteotomy of the Radius and Ulna for Mature Madelung Deformity Using CT-based 3D Simulation: A Case Report.

We report a patient with mature Madelung deformity who underwent radial and ulnar corrective osteotomy using three-dimensional (3D) simulation. An osteotomy model was created using the computer-aided design (CAD) software based on the computed tomography (CT) data. After correcting the ulna, the osteotomy angle of the radius was determined using the location of the lunate as a landmark in the 3D plane created by the longitudinal axis of the corrected ulna. Consequently, the ulna was flexed 3° and shortened by 5 mm, and the radius was extended at 36° and ulna deviated at 25° by open wedge osteotomy. The radial inclinations, volar tilt and ulnar variance were 25°, 45° and 5 mm preoperatively, and improved to 22°, 10° and 0 mm after surgery. At the 18-month follow-up, the patient reported no pain even during sports activity. The preoperative 3D simulation enabled precise preoperative planning and accurate correction of the Madelung deformity. Level of Evidence: Level V (Therapeutic).

Effects of dimensions of laser-milled grid-like microslits on shear bond strength between porcelain or indirect composite resin and zirconia.

PURPOSE: Zirconia cores and frameworks are widely used in restorative dentistry. Although these structures are veneered with porcelain for esthetic reasons, the use of indirect composite resins (ICRs) is expected to increase in the future. The purpose of this study was to investigate the effects of microslits of different dimensions formed by Nd:YVO4 laser machining on the bond strength between two types of zirconia (3 mol% yttria-partially stabilized zirconia (Y-TZP) and ceria-partially stabilized zirconia/alumina nanocomposite (Ce-TZP/A)) and porcelain or an ICR. METHODS: The zirconia disks were assigned as follows: 1) blasted with alumina particles (AB) and 2-4) surface machined with gridded microslits with a width, pitch, and depth of 50, 75, or 100 µm (MS50, MS75, and MS100, respectively). After the bonding of the veneering materials to the disks, half of the specimens veneered with the ICR were subjected to thermocycling (4-60°C, 20000 cycles). All the specimens were subsequently shear tested (n = 10/group). RESULTS: There was no significant difference between the groups of the disks bonded to porcelain. On the other hand, for the disks bonded to the ICR, the bond strengths of the MS groups after thermocycling were statistically higher than that of the AB group. However, there was no significant difference in the bond strengths of the disks with different microslits. CONCLUSION: Within the study limitations, it can be concluded that, for porcelain, the design of the mechanical retentive structure must be modified. However, for the investigated ICR, a simple gridded pattern can improve the bond strength with zirconia.

A web-based survey of denture adhesive use among denture wearers 40 years of age and older.

The purpose of this study was to clarify the usage and understanding of denture adhesives among 1,825 denture wearers, aged 40 years and older in Japan, using a web-based survey. The NTTCom Online survey (a closed investigation) was conducted over a period of 4 days using a 13-item questionnaire about denture adhesives. Results showed that 67.1% of the respondents were satisfied with their dentures; 81.5% of respondents knew about denture adhesive, but only 347 (19.0%) had used the product. Products used by the 347 denture wearers included cream type (79.7%), cushion type (16.2%), and powder type (3.2%). The most common reason for the selection of a particular type was "Saw the product" (59.9%), followed by "Saw an advertisement" (19.3%), and "Explanation at a dental clinic" (8.4%). The response of "Ill-fitting denture" significantly affected the response of "Use of denture adhesives" (chi-square test; P < 0.001). Moreover, the sensitivity (0.56) was lower than the specificity (0.75). These findings show that denture adhesives were not always necessary for those with ill-fitting dentures.

Laser-Milled Microslits Improve the Bonding Strength of Acrylic Resin to Zirconia Ceramics.

Heightened aesthetic considerations in modern dentistry have generated increased interest in metal-free "zirconia-supported dentures." The lifespan of the denture is largely determined by the strength of adhesion between zirconia and the acrylic resin. Thus, the effect on shear bond strength (SBS) was investigated by using an acrylic resin on two types of zirconia ceramics with differently sized microslits. Micromechanical reticular retention was created on the zirconia surface as the novel treatment (microslits (MS)), and air-abrasion was used as the control (CON). All samples were primed prior to acrylic resin polymerization. After the resin was cured, the SBS was tested. The obtained data were analyzed by using multivariate analysis of variance(α = 0.05). After the SBS test, the interface failure modes were observed by scanning electron microscopy. The MS exhibited significantly higher bond strength after thermal cycles (p < 0.05) than the CON. Nevertheless, statistically comparisons resulted in no significant effect of the differently sized microslits on SBS (p > 0.05). Additionally, MS (before thermal cycles: 34.8 ± 3.6 to 35.7 ± 4.0 MPa; after thermal cycles: 26.9 ± 3.1 to 32.6 ± 3.3 MPa) demonstrated greater SBS and bonding durability than that of CON (before thermal cycles: 17.3 ± 4.7 to 17.9 ± 5.8 MPa; after thermal cycles: 1.0 ± 0.3 to 1.7 ± 1.1 MPa), confirming that the micromechanical retention with laser-milled microslits was effective at enhancing the bonding strength and durability of the acrylic resin and zirconia. Polycrystalline zirconia-based ceramics are a newly accessible material for improving removable prosthodontic treatment, as the bond strength with acrylic resin can be greatly enhanced by laser milling.

Finite-element analysis and optimization of the mechanical properties of polyetheretherketone (PEEK) clasps for removable partial dentures.

PURPOSE: Polyetheretherketone (PEEK), a high-strength, aesthetic, and non-allergic thermoplastic polymer, recently became a candidate for replacing metallic components in dental prosthesis. However, as PEEK is flexible, the need for retention presents a key challenge in terms of its clinical application. In this study, clasps prepared using PEEK were optimized and evaluated to provide the mechanical properties required by dentures. METHODS: Seventy-two three-dimensional rod-shape models, based on four thickness/width ratios, three base widths, and six taper ratios were created. These models were analyzed using finite-element methods to determine which modified clasp arm shape provided the most appropriate mechanical properties. Three shape-optimized PEEK specimens and one standard-shape Co-Cr alloy specimen were then fabricated. Constant-displacement fatigue testing was performed to calculate load values and deformations after ten years of clinical use. RESULTS: Shape optimization indicated a maximum stress concentration that was consistently located at the base of the specimen, a correlation between mean load values and thickness that was greater than that with the width, and a correlation between taper ratio and mean load values. Fatigue testing showed that although PEEK exhibited significantly lower average load values than the Co-Cr alloy, these were sufficient for clinical use. All specimens exhibited significant deformation during the first period of cycling; however, there was no significant difference in the deformation between the two materials after fatigue testing. CONCLUSIONS: PEEK exerts fewer stresses on abutments compared to standard-alloy clasps, provides adequate retention, and satisfy aesthetic demands, indicating that PEEK presents a promising alternative to conventional metal clasps.

Influence of various airborne-particle abrasion conditions on bonding between zirconia ceramics and an indirect composite resin material.

STATEMENT OF PROBLEM: Indirect composite resins (ICRs) have been suggested as veneering materials for implant-supported zirconia-based fixed dental prostheses; however, obtaining a durable bond between the zirconia ceramic and the ICR is a challenge. PURPOSE: The purpose of this in vitro study was to evaluate the influence of airborne-particle abrasion conditions on the bond strength between 2 kinds of zirconia (yttria-stabilized tetragonal zirconia polycrystal [Y-TZP] and ceria-stabilized tetragonal zirconia/alumina nanocomposite [Ce-TZP/A]) and an ICR. MATERIAL AND METHODS: Zirconia disks were prepared by using computer-aided design and computer-aided manufacturing (CAD-CAM) systems. Specimens were airborne-particle abraded with different particle sizes (25, 50, 90, 125 µm) and jet pressures (0.1, 0.2, 0.3, 0.4 MPa). The control group (CO) was not subjected to airborne-particle abrasion. The surface roughness (Ra) of the specimens was measured. Subsequently, the specimens were treated with a primer and bonded with a light-activated composite resin, and the shear bond strength (SBS) was tested. The obtained data were analyzed by using multivariate analysis of variance, the Spearman rank-order correlation, and the Mann-Whitney U test (α=.05). After the SBS test, the interface failure modes were observed by scanning electron microscopy, and X-ray photoelectron spectroscopy (XPS) was used to analyze the chemical changes of the zirconia surface. RESULTS: The Ra values increased significantly (P<.05) after airborne-particle abrasion with a positive correlation with both particle size and jet pressure. The airborne-particle abraded specimens exhibited significantly higher bond strength after thermocycling (P<.05) than the CO. Nevertheless, the bond strength was not significantly different among different airborne-particle abrasion treatments (P>.05). Additionally, Y-TZP had higher mean bond strength values than Ce-TZP/A. The XPS results revealed that after airborne-particle abrasion, the alumina particles mechanically adhered to the zirconia surface. CONCLUSIONS: Within the limitations of this in vitro study, airborne-particle abrasion improved the bond strength between zirconia and ICR; however, particle size or jet pressure were not influencing factors.

Effect of microslit retention on the bond strength of zirconia to dental materials.

The aim of this study was to investigate the effect of microslits formed by Nd:YVO4 laser beam machining on the bond strength between two types of zirconia, yttria-partially stabilized zirconia (Y-TZP) and ceria-partially stabilized zirconia/alumina nanocomposite (Ce-TZP/A), and porcelain or two types of resin. Zirconia disks were divided into three groups: 1) non-treated (NT); 2) blasted with alumina particles (AB); 3) microslits fabricated on a zirconia surface by laser beam machining (MS). After veneering porcelain or resins on zirconia specimens, halves of the resin specimens were thermocycled up to 20,000 cycles. The shear bond strength between porcelain and both types of zirconia was not improved by the microslits. Before and after thermocycling, the bond strength between an indirect composite resin or acrylic resin and Y-TZP with microslits was the highest. It was concluded that the microslits on Y-TZP enabled micromechanical interlocking and improved the bond strength and durability of the resins.

Usefulness of personalized three-dimensional printed model on the satisfaction of preoperative education for patients undergoing robot-assisted partial nephrectomy and their families.

OBJECTIVE: To clarify the usefulness of a personalized three-dimensional (3D) printed model of the kidney for preoperative education among patients who underwent robot-assisted partial nephrectomy (RAPN). METHODS: Twenty-nine cases of patients who planned to undergo RAPN and 19 of their families participated in this study. A three-dimensional model consisting of the kidney, tumors, ureter, inferior vena cava, and abdominal aorta in each case was generated using a Z Printer 450 based on the findings of preoperative enhanced CT. After preoperative education using enhanced CT and a 3D-printed model, two anatomy-related issues, three tumor-related issues, and two surgical procedure-related issues were evaluated using a visual analogue scale. RESULTS: The median age of all participants was 64 years old. The rate in male patients was significantly higher than that in families. In all three issues in patients and in two of three issues in families, scores in the 3D model were significantly higher than those in CT. In all issues in CT, scores of patients 64 years old or younger were higher than those of patients 65 years old or higher. On the other hand, no significant difference was found in the 3D model for scores on two of three issues regardless of the age of participants. CONCLUSION: Our data indicate that the personalized 3D printed model of the kidney is useful for preoperative education among patients and their families who underwent RAPN, especially in elderly people.