Journal of Advanced Prosthodontics最新文献

Purpose: Titanium implants are widely used to replace pathological joints, bones, and teeth, with successful engraftment requiring osteoblast attachment to the metal surface for bone regeneration. However, the immune response at the bone-implant interface remains unclear, and few studies have examined why titanium elicits a reduced foreign-body reaction (FBR) compared to other metals. This study aimed to elucidate the mechanism underlying titanium biocompatibility by characterizing the immune response at the bone-implant interface in a rat model.

Materials and methods: Copper, machined titanium, and sandblasted/acid-etched titanium rods were fabricated for implantation into rat tibiae. Topographical and chemical features of each rod surface were evaluated. Rods were inserted into rat tibiae, and immune cell subtypes were analyzed by flow cytometry, histomorphometry, and immunohistochemistry. Statistical analyses were performed at a significance level of 0.05.

Results: Flow cytometry of bone marrow cells collected on Days 1, 7, and 35 post-implantation revealed recruitment of macrophages and neutrophils at all implant sites. Histological analysis confirmed immune cell infiltration at the metal-bone interface, with a pronounced FBR surrounding copper rods. Immunohistochemistry demonstrated an abundance of osteoclast-like M1 macrophages at the copper-implant interface. In contrast, M1 macrophages were absent near titanium implants, where reparative M2 macrophages were present.

Conclusion: The recruitment of M1 macrophages at the copper implantation site, but not at the titanium implant, indicates the FBR to copper and underlies the biocompatibility of titanium. Titanium may affect the differentiation of intrabony macrophages to increase its biocompatibility.

Purpose: This study evaluated how implant scan body (ISB) design affects trueness and operator convenience of digital implant impressions. The null hypothesis stated no significant differences in trueness or usability between ISB designs.

Materials and methods: A cast metal model with nine implants and silicone mucosal masks (1 mm and 3 mm thickness) were used. Seven ISB prototypes were developed by modifying a commercial ISB (ELOS Accurate IO2A-B, ELOS Medtech) in four aspects: length (30% shorter and 50% longer), material (polyetheretherketone (PEEK) or titanium), surface reflectance (polished or aluminium oxide-blasted titanium), and top surface (concave top and screw holes enlarged by 100% and 200%). Each prototype was scanned ten times using an intraoral scanner (NeoScan1000, Neoss), with a desktop scanner (E3, 3Shape) providing reference scans. Deviations in depth, angulation, and rotation were analyzed in CAD software (GOM Inspect, Zeiss). Statistical analysis included the Welch test (P < .05) and Games-Howell post hoc test (P < .007).

Results: Material affected depth accuracy; blasted titanium (89 ± 86 µm) and polished titanium (80 ± 72 µm) outperformed PEEK (149 ± 131 µm). Shorter ISBs showed greater angular deviations (0.64 ± 0.70°) compared to control (0.31 ± 0.21°). Rotational deviations were not significant. Scanning times increased for reflective, longer ISBs with reduced top areas, while shorter ISBs improved usability.

Conclusion: ISB design influences digital impression accuracy. Titanium ISBs with reduced reflectivity improve trueness, and larger screw holes enhance usability. Shorter ISBs reduce scanning time but compromise angular trueness. Stitching errors remain the primary source of depth inaccuracies.

Purpose: This diagnostic study evaluated the accuracy and time efficiency of digital surveying compared to the conventional method for partially edentulous arches.

Materials and methods: Thirty Standard Tesselation Language (STL) files of partially edentulous arches were analyzed. Conventional surveying was performed on 3D-printed diagnostic casts, while digital surveying was conducted using CAD software (Dental Wings Inc., Straumann, Montreal, Canada). The path of insertion and removal, and determining factors (guiding planes, undercut areas, and reciprocation) were assessed. Sensitivity and specificity tests were used to measure accuracy. Sensitivity was defined as the proportion of true positives identified by both techniques, while specificity was measured as a percentage of true negatives compared with the conventional method. Accuracy was assessed as the ability to correctly differentiate true positives and negatives. The paired t-test (95% CI) compared the mean working time between the techniques.

Results: Agreement on reciprocation was 2.91 times higher in regions with a greater number of edentulous areas compared to those with fewer edentulous areas (P = .025). The agreement of guiding planes in tooth-supported abutments was 2.59 times greater than in distal extension cases (P = .031). Accuracy ranged from 0.73 to 0.85. The working time was significantly longer for the digital technique (P = .030).

Conclusion: Both techniques demonstrated high levels of agreement, especially for reciprocation and guiding planes. The digital method exhibited accuracy ranging from good to very good; however, it required a longer working time compared to the conventional approach.

Purpose: The aim of this study was to compare the marginal and internal adaptation of polymethyl methacrylate interim fixed partial denture (FPD) restorations fabricated by three-dimensional (3D) printing with different layer thicknesses.

Materials and methods: A standard typodont was scanned by a laboratory scanner. The maxillary left first premolar and first molar teeth received an all-ceramic full-coverage crown preparation, and the second premolar was removed to create a pontic space. The prepared teeth were then scanned, and metal dies were fabricated by a milling machine. Restorations were designed and fabricated in 3 groups (n = 12 in inch) with 25, 50 and 100 µm layer thicknesses. The marginal and internal gaps were measured by the replica technique. Data were analyzed by one-way ANOVA (α = 0.05).

Results: The mean gap size (MGS) in the cervical area of premolar restorations was significantly higher in 100 µm than in 50 and 25 µm thicknesses (P < .05). The MGS in the marginal area of premolar restorations was significantly higher in 100 µm thickness than in 50 µm thickness (P < .05), with no statistically significant difference with 25 µm thickness (P > .05). The MGS at the occlusal and cervical areas of the molar restorations was significantly higher in 100 µm thickness than in 50 µm thickness (P < .05), with no statistically significant difference with 25 µm thickness (P > .05).

Conclusion: Different thicknesses of additive layers in 3D printing affected the marginal and internal gaps. The smallest gap size was recorded in 50 µm layer thickness.

Purpose: This study evaluates the fracture strength and failure mode of implant-supported provisional resin composite crowns fabricated over hydroxyapatite-coated sulfonated polyetheretherketone (PEEK) and sandblasted PEEK abutments after thermomechanical loading.

Materials and methods: Thirty customized PEEK provisional abutments were surface-treated by (1) sandblasting with 50 µm aluminum oxide (n = 15) (Sa) and (2) HA coating after sulfonation (n = 15) (HA). These abutments were veneered to create crowns for the mandibular right first permanent molar using bulk-fill resin composites after applying a thin layer of universal adhesive. All specimens were stored in distilled water at 37℃ for 24 hours, underwent thermocycling for 1000 cycles at 5℃ and 55℃ (30 s dwell time and 10 s transfer time), and were subjected to mechanical cyclic loading for 120,000 cycles with 50 N using a chewing simulator at room temperature. Fracture strength was evaluated with a universal testing machine, and failure mode was analyzed using a 3D surface profilometer. The Mann-Whitney U test was used for statistical analysis (α = 0.05).

Results: The HA group exhibited significantly higher fracture strength (1469.71 N ± 200.36 N) than the Sa group (1152.36 N ± 180.89 N). Most failures were adhesive and included irreparable fractures of the crown.

Conclusion: HA coating after sulfonation effectively enhances the fatigue strength of PEEK abutments veneered with resin composites for implant-supported provisional crowns.

Purpose: The location of the edentulous area in the dental arch can influence the design of the bridge prosthesis in the surrounding region and the forces it will encounter. This study assessed the fracture strength of restorations with various geometric designs produced using different additive and subtractive manufacturing methods.

Materials and methods: Co-Cr metal and zirconia fixed partial denture (FPD) frameworks were designed in both linear and curved geometries. The Co-Cr metal frameworks were produced through casting (C) and laser sintering (L), while the zirconia (Z) frameworks were obtained through milling (n = 10). After veneering the frameworks, a four-point bending test was conducted on the specimens to assess their fracture strength. All obtained values were statistically analyzed (P < .05).

Results: In both linear and curved groups, Z group showed the lowest fracture resistance values followed by C and L groups and the differences between the groups were found statistically significant (P < .05). In L group, curved FPDs showed statistically significantly higher fracture resistance values than linear FPDs (P < .05). In both Z and C groups, curved FPDs showed statistically significantly lower fracture resistance values than linear FPDs (P < .05).

Conclusion: The geometric configuration of the restoration and manufacturing technique affects the fracture resistance of different framework materials in FPDs.

Purpose: This study aimed to analyze the relationship between self-perceived dental esthetics and the selected esthetic mathematical proportions.

Materials and methods: Descriptive cross-sectional study was conducted among 48 dental students who fit into the inclusion criteria. The subjects rated their self-perceived dental esthetics based on the given Likert scale. Standardized portrait photographs of each subject were taken and the mesiodistal measurements of the maxillary anterior teeth were measured using a graphic editing software. The golden proportion, golden percentage and RED proportion in maxillary anterior teeth were then calculated.

Results: Most subjects were pleased with the size, form, and color of their maxillary anterior teeth. Only 2.1% of the maxillary canines and 10.4% of the left maxillary lateral incisors complied with the golden proportion. The maxillary lateral incisors demonstrated its occurrence to golden percentage. For the RED proportion, 29.2% of the left maxillary teeth and 16.7% of the contralateral teeth complied with the proportion. Self-perceived dental esthetics and the occurrence these mathematical proportions have no association.

Conclusion: Within the limitations of the study, it can be concluded that most subjects were satisfied with their self-perceived dental esthetics. Only a small percentage of the subjects having their natural dentition coincide with the golden proportion, golden percentage and RED proportion with a higher percentage occurring on the RED proportion. Hence, the mathematical proportions do not represent the naturally occurring dentition. These mathematical proportions can serve as a guide and the perceived teeth width can be customized accordingly.

Purpose: Digitalization in dentistry has increased interest in the use of intraoral scanners (IOs) in clinical practice. However, knowledge of implant digitalization is primarily limited to in vitro studies. This study aimed to compare implant-supported fixed dental prostheses (FDP) fabricated following complete digital workflow using various implant scan bodies (SB) in treatment of short-span partial edentulism.

Materials and methods: Patients with 25 short-span posterior edentulous sites, each receiving two implants to support a fixed restoration, were included. Digital implant records were made consecutively with original, non-original, and generic SBs using IOs. A practitioner implemented a two-stage full-arch scanning protocol, beginning with continuous arch scanning, followed by individual scanning of SBs. For clinical evaluation, each site received screw-retained full-contour restorations to qualify the connection fit to the implants and contacts to the adjacent and antagonist teeth. For analytical comparison, implant axes calculated from SB scans were quantified using reverse engineering software to compare the differences three-dimensionally. Restorative outcomes and implant axes records were statistically analyzed using the chi-square test and generalized estimating equations, respectively.

Results: Clinical delivery conditions did not differ significantly among the three intraoral SBs (P > .05). The analytical implant-position calculations for non-original and generic SBs did not present significant differences compared to original SBs (P > .05).

Conclusion: SBs with different hardware and software characteristics for an implant system are clinically acceptable for fabricating screw-retained short-span implant-supported FDPs using a complete digital workflow.

Purpose: The purpose of this study was to compare the surface characteristics and healing patterns after implantation of implants treated with SLA and those treated with both SLA and femtosecond laser.

Materials and methods: A total of 10 male New Zealand white rabbits were used to compare recovery levels between implants treated with SLA (SLA group) and those treated with both SLA and femtosecond laser (SF group). The implants' surface characteristics were determined through topographic evaluation, element analysis, surface roughness, and wettability evaluation. In total, 4 implants were placed in each rabbit (2 in each tibia), with 20 implants per treatment group. Using the implant stability quotient (ISQ), marginal bone volume, and histological analysis (bone-to-implant contact (BIC), bone volume/tissue volume (BV/TV)), and post implantation outcomes were assessed. Outcome data were analyzed using independent t-tests, Mann-Whitney U tests, Wilcoxon signed-rank tests, and one-way ANOVA (α = 0.05).

Results: No significant differences were noted between SLA and SF groups in terms of ISQ, marginal bone volume, BIC, and BV/TV (P > .05). However, significant differences in ISQ were observed within each group over time (P < .05). Furthermore, significant differences were noted in the marginal bone volume of the SF group (P < .05) and the BV/TV of the SLA group between weeks 4 and 6 (P < .05).

Conclusion: Surface treatment via SLA and femtosecond laser is feasible compared with SLA treatment alone in terms of ISQ, marginal bone volume, BIC, and BV/TV. However, further clinical research is warranted.

Purpose: The aim of this study was to evaluate the clinical performance and survival rate of implant-supported zirconia-lithium disilicate (Zr-LiSi) bilayered ceramic prostheses over 3 years.

Materials and methods: This study included 71 patients, including 34 with implant-supported metal-ceramic prostheses (control group) and 37 with implant-supported Zr-LiSi bilayered ceramic prostheses (test group). The implant survival rate and incidence of prosthetic and biological complications (veneer fractures, dislodgement of screw-access hole filling material, screw loosening, peri-implant mucositis and peri-implantitis, and marginal bone loss) were investigated. The survival rate was analyzed using Kaplan-Meier survival curves, and the identity between two groups was confirmed by the log-rank test.

Results: Both groups showed a 100% survival rate, whereas the prosthetic survival rates were 77% and 73% for the metal-ceramic and Zr-LiSi groups, respectively. Biological complications did not appear in the metal-ceramic group, and 16.2% of peri-implant mucositis occurred in the Zr-LiSi group, which was significant (P < .05). Prosthetic complications occurred in 5.8% of the metal-ceramic group with veneer fractures and did not occur in the Zr-LiSi bilayered ceramic group.

Conclusion: This study revealed that posterior Zr-LiSi bilayered ceramic implant prostheses showed high survival rates and similar survival rates to metal-ceramic implant prostheses; however, additional consideration should be given to avoid overcontouring. Zr-LiSi bilayered ceramic implant prostheses may be an option for posterior implant-supported prosthetic treatment.