Journal of prosthodontic research最新文献

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.

Purpose: We aimed to verify the hypothesis that patients who undergo prosthetic treatment with a definitive obturator following maxillectomy for oral tumors show decreased oral functions when the maxillary defects are extensive.

Methods: This study comprised 77 patients (46 men, 31 women; mean age, 71.0 years) who underwent prosthetic treatment with definitive obturators designed to restore maxillary defects following maxillectomy owing to an oral tumor. Oral function, masticatory performance, maximum bite force, tongue pressure, and tongue-lip motor function (oral diadochokinesis /pa/, /ta/, /ka/) were evaluated. The extent of maxillary defects was evaluated based on Aramany's classification. The maxillary defects were classified into three groups, namely, no oroantral communication (NOC), small oroantral communication (SOC), and large oroantral communication (LOC) groups. Multiple regression analyses were performed with each oral function as the objective variable and age, sex, maximal mouth opening, history of radiotherapy, number of functional teeth, and the extent of the maxillary defect as explanatory variables.

Results: The number of functional teeth and LOC were significant as explanatory variables for masticatory performance, while sex, number of functional teeth, and LOC were significant as explanatory variables for maximum bite force. Regarding other oral functions, the extent of the jaw defect was not significant as an explanatory variable.

Conclusions: In patients with maxillary defects wearing definitive obturators, a defect exceeding half of the palate and communicating with the nasal cavity was significantly associated with lower masticatory performance and maximum bite force.

Purpose: To investigate the effects of coffee and orange juice on 3 different esthetic ceramic materials regarding color changes, Vickers microhardness, and solubility & sorption changes among patients with reflux.

Methods: A glass-ceramic material (IPS Emax CAD), a polymer-infiltrated ceramic material (Vita Enamic), and a nano-hybrid ceramic material (Cerasmart) were selected for this study (n=32/group). Following the polishing procedure, all the samples were immersed in artificial saliva for 21 days. Half the samples were assigned to the control group and exposed only to artificial saliva (pH 7.3). The remaining 16 samples were exposed to saliva or simulated gastric acid. Sixteen samples from each group were exposed to gastric acid 3 times daily for 30 seconds. The color, Vickers microhardness, and solubility & sorption were then measured. Following this procedure, the samples were exposed to coffee and orange juice (n=8/per group). The samples were exposed to the solutions for 16 hours and 48 minutes to simulate 21 days of consumption. Final measurements were then obtained. Statistical significance was determined using Levene's test to compare variances, and three-way analysis of variance (ANOVA) followed by Tukey's post-hoc test, Welch's ANOVA, and Games-Howell's test were applied to reveal differences between groups.

Results: According to ANOVA, restorative material type and immersion media had a significant effect on color change (P < 0.001), microhardness (P < 0.001), and solubility & sorption (P < 0.001).

Conclusions: The choice of material is crucial for erosion-prone patients.

Purpose: To evaluate the trueness of denture bases fabricated using digital light processing (DLP) and milling methods using three-dimensional (3D) models with varying residual ridge morphologies.

Methods: Edentulous mandibular 3D models representing a well-rounded ridge (WR), knife-edge ridge (KR), and flat ridge (FR) were designed using computer-aided design (CAD) software. Denture bases for these models were created using dental CAD software and fabricated via DLP 3D printing at build angles of 0 and 45 degrees (DLP0 and DLP45) and by milling (MIL). A total of 90 denture bases were fabricated, with 10 bases per model-method combination. These bases were digitized and compared to their original CAD data to assess the adaptation across three regions: denture border, alveolar ridge, and retromolar pad. Measurements were performed at three time points: before water storage, after 1 day of water storage, and after 7 days of water storage.

Results: The MIL bases exhibited significantly lower 3D surface deviations than the DLP0 and DLP45 bases. The KR models generally exhibited greater 3D surface deviations than the WR and FR models. Temporal changes in the denture bases were significant across almost all ridge types and manufacturing methods.

Conclusions: The trueness of digitally fabricated denture bases is influenced by the residual ridge morphology and manufacturing method. Milling demonstrated superior trueness compared to DLP. Temporal dimensional changes were observed in almost all the bases.