Journal of prosthodontic research最新文献

Purpose: With the advancement in digital technology, post-and-cores can be produced using full-digital techniques. This study aimed to evaluate the accuracy of two full-digital impression techniques for scanning the post space with different root canal entrance diameters using an intraoral scanner (IOS) (TRIOS 3) with and without a scan post, compared to the half-digital impression technique.

Methods: Standard models of three intact teeth with varying root canal entrance diameters were prepared. Fifteen post-and-core designs per tooth were created using direct IOS and IOS with scan posts, with the half-digital technique as the control. All files were exported as standard tessellation language (STL) files, and the root mean square (RMS) deviations were analyzed between the experimental and control groups. Deviations were measured at standardized points across four regions: the occlusal external, occlusal internal, middle third, and apical third.

Results: No significant differences in the overall RMS were observed among the different root canal entrance diameters (3 mm, 4 mm, and 5 mm) for direct IOS and IOS with scan posts (P > 0.05). However, an independent samples t-test revealed a significant difference (P < 0.05) in both trueness and precision between the two experimental groups, with IOS with scan posts consistently showing lower RMS values.

Conclusions: For post space lengths less than 7.4 mm in single-rooted teeth, both direct IOS and IOS with scan posts can serve as viable alternatives to half-digital techniques. However, in deeper areas, IOS with scan posts are recommended as alternatives to the half-digital technique.

Purpose: This study compared the scanned data obtained from four conventional silicone impressions using a laboratory scanner to investigate the effects of impression materials on accuracy and precision.

Methods: The master model was a gauge with four small height increments constructed from an assembly of ceramic gauge blocks. Impressions of the master model were made using four silicone impression materials (Imprinsis Regular: blue; Fusion II: pink; Fit Checker: white, Imprint3: yellow). The impressions were scanned under blue light using a laboratory scanner. The points of inquiry were 1) advisability of three-dimensional (3D) reconstruction, 2) reproducibility at the surface level, and 3) microstep detectability. Data were analyzed using a one-way analysis of variance and Tukey's multiple comparison test.

Results: 3D reconstruction was achieved for all impressions except Imprint3. The scanning performance of the impression material affected the spectral reflection factor. There was no significant difference in surface reproducibility among the three impression materials, and the detectability of small step height in Imprinsis Regular was significantly better than that in other impression materials (P < 0.05).

Conclusions: The color of the impression material affected digitization when a blue-light scanner was used. The digitization accuracy of Imprinsis Regular was higher than that of the other impression materials. However, the digitization accuracy of the three impression materials that could be 3D-reconstructed was within clinical tolerance. These findings can broaden the clinical applications of digital dentistry and mitigate the errors associated with dental materials.

Purpose: This study compared the mechanical properties, wear behavior, and shear bond strength (SBS) of resin luting agents in additive-manufactured composite crown materials intended for definitive restorations with those of conventional computer-aided design/computer-aided manufacturing (CAD-CAM) hybrid composite resin (HCR) block materials.

Methods: Sprintray Ceramic Crown (SP) was used as the representative vat photopolymerization (VPP)-fabricated material based on additive manufacturing, whereas Shofu Block HC Hard II (HC) and Cerasmart Prime (CS) were selected as CAD-CAM HCR block materials. The mechanical properties were evaluated using three-point flexural strength and Vickers hardness tests. The wear behavior was examined via a reciprocating sliding test using an alumina ball antagonist. The SBS was measured between each material and various resin-luting agents.

Results: SP showed ~50-60% of the flexural strength and 30-40% of the Vickers hardness of HC and CS. Wear testing revealed that SP exhibited greater wear loss than those of CAD-CAM HCRs. The SBS values of SP with each resin cement were slightly lower than those of HC and CS under most conditions; however, all values exceeded 15 MPa, indicating a clinically acceptable bond strength.

Conclusions: The VPP-fabricated definitive crown material (SP) demonstrated inferior mechanical properties and wear resistance compared to those of conventional CAD-CAM HCRs. However, the acceptable levels of bond strength were observed, highlighting the importance of careful case selection for definitive restorations.

Purpose: This study evaluates the effects of different abutment screw tightening protocols and implant materials on screw loosening and morphological changes after cyclic torsional loading of two-piece implants.

Methods: Titanium (T) and zirconia (Z) two-piece implants were used. Abutment screws were tightened to 35 Ncm. Three protocols were tested: (A) retightening after 5 min, (B) immediate retightening, and (C) no retightening (n = 6 each). All samples underwent 100,000 cycles of cyclic torsional loading. Removal torque values before and after loading (RT-pre and RT-post) and torque loss percentage (TL) were calculated. Surface morphology was assessed using scanning electron microscopy (SEM), and dimensional changes were quantified using root mean square (RMS) values from three-dimensional data.

Results: In the titanium group, protocol A (TA) had lower RT-post values than protocols B (TB) and C (TC) (P < 0.001), and TB was lower than TC (P < 0.05). In the zirconia group, protocol A (ZA) was significantly lower than protocols B (ZB) and C (ZC) (P < 0.05, P < 0.001, respectively). RT-post and RT-pre were significantly lower in the zirconia group than in the titanium group under all conditions (P < 0.001). No differences were observed in TL. SEM revealed wear on the screw heads and threads in all groups. RMS values were significantly lower in the zirconia group (P < 0.05).

Conclusions: Abutment screw retightening does not consistently enhance torque maintenance under torsional loading. The implant material affects torque retention and deformation, where titanium implants demonstrating greater stability than zirconia implants.

Purpose: This study proposes the development of "Motion-DSD", an artificial intelligence-assisted workflow for digital smile design (DSD), which enables a dynamic 2-dimensional (2D) simulation of digital diagnostic waxing by transferring an intraoral design onto a frontal facial video, and validates its clinical feasibility.

Methods: A total of 2,000 facial and 190 intraoral images were used to fine-tune the pre-trained neural network, Segment Anything model (SAM), via two sets of low-rank adaptation (LoRA) modules for facial structures and teeth segmentation respectively. A transformation algorithm incorporating a "standard" facial image was developed to align intraoral and facial structures. A Flask-based web user interface (web-UI) was developed for clinical deployment. A participant sample set was prepared to validate the workflow's performance in a clinical setting.

Results: Two fine-tuned SAMs achieved robust segmentation performance, with a mean Dice score coefficient of 0.886 for the facial dataset and 0.969 for the intraoral dataset. The alignment algorithm effectively transferred the intraoral DSD design onto the participant's frontal facial video and enabled a 2D simulation of digital diagnostic waxing under various facial expressions, demonstrating its clinical feasibility. The web-UI allows dentists to interactively refine the design and preview simulation results in real time.

Conclusions: Motion-DSD enables the 2D simulation of digital diagnostic waxing from intraoral DSD designs in a dynamic facial context. The workflow overcomes the limitations of static imaging methods and manual alignment, bringing dynamics prior to the physical mockup phase. Further investigations are warranted to quantitatively validate the simulation accuracy and demonstrate its potential advantages over conventional static methods.

Purpose: Polyetheretherketone (PEEK), a high-performance thermoplastic polymer, has been explored as a dental material because of its excellent mechanical strength and biocompatibility. Composite resin has been reported as a viable prosthetic material when appropriate surface treatment is applied to PEEK. We evaluated the effects of ultraviolet and ozone (UV/ozone) irradiation on the bond strength of PEEK.

Methods: Eighty-six rectangular PEEK specimens were fabricated and divided into two surface-pretreatment groups: untreated (CO) and UV/ozone-treated (UV). The contact angle, surface roughness, and chemical composition were analyzed using contact angle goniometry, laser scanning microscopy, and X-ray photoelectron spectroscopy (XPS), respectively. The remaining specimens were assigned to two conditioning groups: no conditioning (NT) and primer conditioning (AD). Cylindrical specimens fabricated by Computer-Aided Design, Computer-Aided Manufacturing (CAD-CAM) composite resin blocks were bonded to the PEEK surface using resin cement. Half of the specimens in each group were subjected to 5000 thermal cycles. The shear bond strength was tested using a universal testing machine and the fracture surfaces were examined under a stereomicroscope. Statistical analyses were performed using t-tests (α = 0.05).

Results: UV/ozone treatment significantly reduced the contact angle, improved the surface wettability, and caused slight changes in the surface roughness. XPS analysis revealed a decrease in the C=O bonds and an increase in the C-OH bonds in the UV/ozone-treated group. The shear bond strength improved significantly, particularly in the AD group.

Conclusions: UV/ozone treatment of PEEK surfaces increased the wettability and significantly improved the shear bond strength of the composite resin blocks.

Purpose: We evaluated the effects of the particle size and content of surface pre-reacted glass-ionomer (S-PRG) filler on the mechanical properties and antimicrobial efficacy of a hard denture relining material.

Methods: S-PRG microfiller (0.8-1 μm; 5, 10, and 20 wt%) and nanofiller (0.3-0.5 μm; 2.5, 5, and 10 wt%) were incorporated into a Shofu denture liner. The control group did not contain S-PRG fillers. The surface morphology (scanning electron microscopy), roughness (confocal scanning laser microscopy; Shapiro-Wilk's test followed by Dunnett or Steel's test), ion release after 24 h immersion in ultrapure water (fluoride, aluminum, borate, sodium, silicate, strontium ions; Shapiro-Wilk's test followed by one-way ANOVA with Tukey's test or Kruskal-Wallis and Dunn's tests), three-point flexural strength (Weibull analysis), shear bond strength after 24 h water immersion or 10,000 thermal cycles (linear mixed-effects model), and antimicrobial activity against Candida albicans (confocal microscopy, Shapiro-Wilk's test followed by Dunnett's or Steel's test) were analyzed and compared. The significance level was set at α = 0.05.

Results: Although a higher S-PRG filler content reduced the flexural and bond strengths, it increased the surface roughness and ion release. Groups treated with 10 wt% nanofiller or 20 wt% microfiller displayed significantly inhibited C. albicans adhesion. The nanofiller-containing groups maintained flexural strength comparable to that of the control.

Conclusions: The incorporation of 10 wt% S-PRG nanofiller provided the best balance between antimicrobial efficacy and mechanical performance, indicating that this formulation may be clinically acceptable for use in hard denture relining materials.

Purpose: This study evaluated the effects of two additive manufacturing technologies and three orientations on the accuracy of three-dimensional (3D)-printed complete dentures. Additionally, we examined whether resin differences affected the accuracy of the denture bases under varying printing systems and orientations.

Methods: We printed denture bases using digital light processing (DLP) and a liquid crystal display (LCD) in three orientations (0°, 45°, and 90°) with two photopolymer resins (n = 6). Intaglio surfaces were scanned to obtain experimental data. We evaluated trueness by superimposing experimental data onto master data, and assessed precision by pairing and superimposing two of the six datasets. Deviation was evaluated using root mean square (RMS) and color map data. Statistical analysis was conducted using the Kruskal-Wallis method and Mann-Whitney U test (α = 0.05).

Results: The DLP printer achieved the highest trueness at an orientation of 90°, whereas the precision was minimally affected by the orientation or printing systems. DLP printers performed well with both recommended and non-recommended resins; however, LCD printers demonstrated better accuracy with the recommended resins. At 0° orientation, the trueness color map for both printers showed negative deviation patterns over the entire palatal surface. Across all manufacturing methods, the precision color maps indicated high reproducibility.

Conclusions: Printing system and orientation affect the trueness of 3D-printed dentures. DLP printers set at 90° demonstrated superior trueness for clinical applications. The accuracy was affected by resin, printer, and orientation.

Purpose: This systematic review aimed to investigate and compare peri-implant soft-tissue responses to tooth-colored abutment materials frequently used in implant dentistry.

Study selection: A comprehensive electronic search was performed in three databases (MEDLINE via PubMed, Google Scholar, and Scopus) to identify relevant literature. The study-selection criteria included original research articles written in English that investigated the effects of various tooth-colored abutment materials on peri-implant soft-tissue responses.

Results: In total, 136 articles were included in this systematic review. Tooth-colored abutment materials, particularly zirconia and polyetheretherketone (PEEK), facilitated favorable soft-tissue adaptation, enhanced esthetics, and contributed to long-term implant success. Zirconia demonstrated excellent biocompatibility, enhanced cell viability and attachment, and lower inflammatory responses compared to titanium, suggesting improved soft-tissue integration and reduced biofilm-related risks. PEEK exhibited favorable mechanical properties and biocompatibility but limited cell attachment due to its hydrophobicity, indicating the need for surface modification. Titanium remains the clinical standard for integration but is associated with greater inflammation and biofilm formation than tooth-colored materials.

Conclusions: This review highlights the effects of tooth-colored abutment materials on peri-implant soft-tissue responses and emphasizes the importance of selecting appropriate materials for successful dental implants. Zirconia represents a promising biological alternative to titanium, promoting a stable soft-tissue barrier that contributes to minimizing inflammation and maintaining long-term tissue health. Conversely, while PEEK offers strong mechanical properties, it faces challenges regarding cell proliferation and matrix production, limiting its optimal biological performance. Further research will provide deeper insights into the best options for enhancing patient and esthetic outcomes.