Comparative analysis of flexural strength of 3D printed and milled 4Y-TZP and 3Y-TZP zirconia.

STATEMENT OF PROBLEM: The mechanical properties of 3 dimensionally (3D) printed zirconia have been reported to be comparable with those of milled zirconia, except for the flexural strength. However, most previous studies tested 3 mol% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP), making it necessary to study 3D printed zirconia with 4 mol% yttria content (4Y-TZP). PURPOSE: The purpose of this in vitro study was to compare the flexural strength of 3D printed 4Y-TZP with 3Y-TZP materials and milled 4Y-TZP. MATERIAL AND METHODS: A total of 80 disk specimens (Ø15×1.5 mm) were fabricated and divided into 4 groups (n=20) using the fabrication method and yttria content: milled 3Y-TZP (Katana HT; Kuraray Noritake), 3D printed 3Y-TZP (TZ-3Y-E; Tosoh), milled 4Y-TZP (Katana STML; Kuraray Noritake), and 3D printed 4Y-TZP (3DMAT; Genoss). The biaxial flexural strength was determined with a piston-on-3-ball test (n=15). The flexural strength of each specimen was measured, and the Weibull modulus (m) and characteristic strength (σ0) were estimated from the fracture load distribution. Two intact and fractured specimens were examined with scanning electron microscopy (SEM). The crystalline phase of the specimens in each group was identified through X-ray diffraction (XRD) analysis (n=5). A 1-way ANOVA was used to compare the flexural strength among different groups. Subsequently, pairwise comparisons were conducted with the Tukey post hoc method (α=.05). RESULTS: The flexural strength of 3D printed 4Y-TZP was significantly higher than that of milled 4Y-TZP (P<.001). In contrast, the flexural strength of 3D printed 3Y-TZP was significantly lower than that of milled 3Y-TZP (P<.001). X-ray diffraction (XRD) analysis revealed that the tetragonal phase was the dominant phase in all groups, with the identification of some cubic phase peaks. CONCLUSIONS: Three dimensionally printed 4Y-TZP showed significantly higher flexural strength than milled 4Y-TZP and exhibited a clinically acceptable flexural strength exceeding 800 MPa.

Fit analysis of stereolithography-manufactured three-unit resin prosthesis with different 3D-printing build orientations and layer thicknesses.

STATEMENT OF PROBLEM: Printing conditions can affect the fit of a 3-dimensionally (3D) printed prosthesis. Therefore, it is important to determine the optimal printing conditions for stereolithography (SLA)-manufactured prostheses. PURPOSE: The purpose of this study was to analyze the fit according to the build orientations and layer thicknesses in SLA-manufactured 3-unit resin prostheses. MATERIAL AND METHODS: SLA 3D printed prostheses were produced in 5 build orientations (0, 30, 45, 60, and 90 degrees) and 2 layer thicknesses (50 and 100 µm). Milled prostheses were fabricated from the same design. The mounted prostheses on the master model were scanned with microcomputed tomography (µCT). Data were processed with the NRecon software program. For quantitative analysis, marginal and internal fits were measured by using the imageJ software program in terms of the following metrics: absolute marginal discrepancy, marginal gap, cervical area, midaxial wall area, line-angle area, and occlusal area. Internal gap volume was also measured with the CTAn software program. For statistical analysis, ANOVA and Tukey HSD tests were used (α=.05). For qualitative analysis, µCT cross-sections were compared among groups, and intaglio surfaces were imaged with a scanning electron microscope. RESULTS: A layer thickness of 50 µm with build orientations of 45 and 60 degrees exhibited smaller mean gap values (P<.05) than the other conditions for all measurements except line-angle area and occlusal area. The scanning electron microscope images showed voids on the intaglio surfaces for the 0- and 90-degree groups. CONCLUSIONS: For SLA 3D printed resin prostheses, a difference in fit occurred based on the printing conditions, although both 3D printed and milled prostheses showed a clinically acceptable fit. When an SLA 3D printed prosthesis is manufactured under appropriate conditions, a clinically acceptable fit can be obtained.

Quality of life in patients in South Korea requiring special care after fixed implants: a retrospective analysis.

BACKGROUND: The study on oral health-related quality of life (OHRQoL) of disabled patients is rare but critical for welfare of patients. The aim of this study was to examine the effect of fixed implants in edentulous areas on OHRQoL in Korean disabled patients. METHODS: The OHRQoL of 63 disabled individuals was evaluated using the Oral Health Impact Profile (OHIP)-14 questionnaires and studied by potential affecting variables such as age, sex, disability severity, and time of disability acquisition. Wilcoxon-signed rank tests were used to examine the OHIP-14 scores for those who had pre/post-fixed implants. Multiple linear regression analysis was used to examine the relationships between factors and OHIP-14 scores before and after implants. A partial correlation analysis was also performed to determine which variables influenced OHIP-14 scores before and after treatment. The Mann-Whitney test was employed for sex and time of disability acquisition analysis (α = 0.05). RESULTS: Significant improvement was found in OHIP-14 post-implant treatment scores (P < .001). After implant treatment, the severity of disability produced significantly different results (P = .009). Pearson's correlation coefficient between severity of disability and pre/post-implant OHIP-14 scores was 0.265 (P = .030). After controlling for severity of disability, the results showed older patients had lower OHIP-14 scores (P = .032). No differences were found for sex or time of disability acquisition (congenital vs. acquired). CONCLUSIONS: Fixed implant treatment improved OHRQoL for disabled patients, and the severity of disability was positively correlated with improvement of OHRQoL. For patients with a similar level of disability, the OHRQoL decreased with age.

Comparison of Fit and Stability Between 3D-Printed and Milled Implant Abutments with Titanium-6Al-4V and Co-Cr Metal Alloys.

PURPOSE: To compare the fit of 3D-printed titanium (Ti) and cobalt-chromium (Co-Cr) abutments with implants to computer numerical control (CNC)-milled, ready-made abutment-implant assemblies. Their clinical applicability was also evaluated by measuring removal torque values (RTVs) and percentage torque loss of abutment screws. MATERIALS AND METHODS: A total of 138 abutments were included in the study: 92 abutments were fabricated with Ti and Co-Cr alloys using computer-assisted design (CAD) through selective laser melting, and 46 ready-made abutments were prepared. The fit of interfaces between 90 abutments from the three groups (30 ready-made, 30 3D-printed Ti, and 30 3D-printed Co-Cr abutments) and implant assemblies was demonstrated by scanning electron microscopy (SEM) and confocal scanning laser microscopy (CSLM). After 30-Ncm torque tightening of Ti abutment screws twice within 10 minutes, the RTVs and percentage torque loss of screws of 48 abutments (16 ready-made, 16 3D-printed Ti, and 16 3D-printed Co-Cr) were evaluated after 10 minutes of thermocycling and cyclic loading. RESULTS: The fits of 3D-printed Co-Cr abutments were not statistically different from those of ready-made abutments (P = .383), while the fit of 3D-printed Ti abutments was inadequate (P < .001). The RTVs of 3D-printed abutments after cyclic loading were significantly decreased compared with those of CNC-milled abutments (P < .001). CONCLUSION: The fit of interfaces between 3D-printed Co-Cr abutments and implants was adequate. The RTVs of 3D-printed Co-Cr abutments were not significantly different from those of CNC-milled abutments after 10 minutes of 30-Ncm torque tightening and thermocycling.

Splinting or Nonsplinting Adjacent Implants? A Retrospective Study Up to 15 Years: Part I-Biologic and Mechanical Complication Analysis.

PURPOSE: To analyze the biologic and mechanical complications of splinted and nonsplinted implant restorations. MATERIALS AND METHODS: A total of 423 patients (n = implants: 888) were included in the study. Biologic and mechanical complications that occurred for 15 years were analyzed using the multivariable Cox regression model, and the significant effect of the splinting of prostheses and other risk factors were evaluated. RESULTS: Biologic complications occurred in 38.7% of implants: 26.4% of nonsplinted implants (NS) and 45.4% of splinted implants (SP). Mechanical complications occurred in 49.2% of implants: 59.3% NS and 43.9% SP. Implants splinted with both mesial and distal adjacent implants (SP-mid) had the highest risk of peri-implant diseases. As the number of implants splinted increased, the risk of mechanical complications decreased. Long crown lengths increased the risk of both biologic and mechanical complications. CONCLUSION: Splinted implants had a higher risk of biologic complications and lower risk of mechanical complications. The implant splinted to both adjacent implants (SP-mid) had the highest risk of biologic complications. The greater the number of implants splinted, the lower the risk of mechanical complications. Long crown lengths increased the risk of both biologic and mechanical complications. Int J Oral Maxillofac Implants 2023;38:435-442. doi: 10.11607/jomi.10053.

Splinting or Nonsplinting Adjacent Implants? A Retrospective Study Up to 15 Years: Part II-Success and Survival Rate Analysis.

PURPOSE: To analyze the success and survival of splinted and nonsplinted implants. MATERIALS AND METHODS: A total of 423 patients (n = implants: 888) were included in the study. The success and survival of implants for 15 years were analyzed using a multivariable Cox regression model, and the significant effect of the splinting of prostheses and other risk factors were evaluated. RESULTS: The cumulative success rate was 34.2%: 33.2% in nonsplinted (NS) and 34.8% in splinted implants (SP). The cumulative survival rate was 92.9% (94.1%, NS; 92.3%, SP). Whether to splint was not related to the success and survival of implants. The smaller the implant diameter, the lower the survival rate. The crown length and implant length were significantly associated only with NS implants: The longer the crown length and the shorter the implant length, the greater the risk of implant failure. The emergence angle (EA) and the emergence profile (EP) had a significant effect on only the SP implants: EA3 showed a higher risk than EA1, and EP2 and EP3 had a higher risk of implant failure. CONCLUSION: Crown length and implant length affected only the nonsplinted implants: The higher the crown length and the shorter the implant length, the greater the risk of implant failure. A significant effect for emergence contour was found only in SP implants: the implants restored with prostheses with EA ≥ 30 degrees on both the mesial and distal sides, and convex EP on at least one side had higher risks of failure. Int J Oral Maxillofac Implants 2023;38:443-450. doi: 10.11607/jomi.10054.

Could Fixed Implants Be a Viable Treatment Option in Disabled Patients? A Clinical Retrospective Study.

PURPOSE: To verify the survival rates and marginal bone loss (MBL) of implants in patients with different disability types. MATERIALS AND METHODS: Clinical and radiographic assessments were performed in a total of 189 implants for fixed implant prostheses in 72 patients. Data were collected on loaded implants at least 1 year in function, and the mean observation time was 37.3 months. Implant survival was examined, and MBL was observed around the implants of two groups (mental disability vs physical disability) based on age, sex, implant location (anterior vs posterior), and prosthetic connection (internal vs external). RESULTS: Of the 189 implants, 4 failed; the total implant survival rate was 97.8% across a mean of 37.3 months. The cumulative survival rate at 85 months in a Kaplan-Meier survival curve analysis was 94.3% ± 3% in patients with mental disability and 50% ± 35.4% in patients with physical disability, which was a statistically significant difference between the disability groups (P = .006). Fisher exact test showed significant differences in MBL only with age (P < .001). The implant MBL by disability type-adjusted for age and observation period-showed significant differences in multiple linear regression analyses (P = .003). CONCLUSION: The implant survival rates in patients with disability were in line with those reported for nondisabled patients. The MBL of the implants was within the physiologic bone loss after implant loading. Implants in patients with mental disability showed higher cumulative survival rates than in patients with physical disability, but also a higher amount of MBL. Within the limitations of this study, dental implants for patients with disability are viable. These results can establish future implant treatment plans for this population. Int J Oral Maxillofac Implants 2023;38:562-568. doi: 10.11607/jomi.9880.

Effect of hemispherical dimples at titanium implant abutments for the retention of cemented crowns.

PURPOSE: The aim of this study was to assess the effect of hemispherical dimple structures on the retention of cobalt-chromium (Co-Cr) crowns cemented to titanium abutments, with different heights and numbers of dimples on the axial walls. MATERIALS AND METHODS: 3.0-mm and 6.0-mm abutments (N = 180) and Co-Cr crowns were prepared. The experimental groups were divided into two and four dimple groups. The crowns were cemented by TempBond and PANAVIA F 2.0 cements. The retention forces were measured after thermal treatments. A two-way Analysis of Variance (ANOVA) and post-hoc Tukey HSD test were conducted to analyze change in retention forces by use of dimples between groups, as well as t test for the effect of abutment height change (α = .05). RESULTS: Results of the two-way ANOVA showed a statistically significant difference in retention force due to the use of dimples, regardless of the types of cements used (P < .001). A significantly higher mean retention forces were observed in the groups with dimples than in the control group, using the post hoc Tukey HSD test (P < .001). Results of t test displayed a statistically significant increase in the retention force with 6.0-mm abutments compared with 3.0-mm abutments (P < .001). The groups without dimples revealed adhesive failure of cements, while the groups with dimples showed mixed failure of cements. CONCLUSION: Use of hemispherical dimples was effective for increasing retention forces of cemented crowns.

Mechanical complications of implant-supported restorations with internal conical connection implants: A 14-year retrospective study.

STATEMENT OF PROBLEM: Internal conical connections have become the primary choice for implant-supported restorations. However, studies that identified the risk indicators for mechanical complications and diagnosed the prognosis of the implant-supported restorations are lacking. PURPOSE: The purpose of this retrospective clinical study was to evaluate the incidence and consequences of mechanical complications in components of internal conical connection implants and to analyze the risk indicators. MATERIAL AND METHODS: A total of 428 patients with 898 internal conical connection implants were included in the study, and mechanical complications over the 14-year observation period were evaluated. The Cox proportional hazard regression model was used to analyze significant effects on mechanical complications, which were presented as hazard ratio and 95% confidence interval. RESULTS: Mechanical complications occurred in 430 (47.9%) implants and 248 (57.9%) patients: screw loosening (46.4% of implants, 56.8% of patients); screw fracture (2.6% of implants, 4.4% of patients); abutment fracture (11.4% of implants, 21.3% of patients); and implant fracture (3.5% of implants, 5.4% of patients). Implant restorations replacing molars showed the highest risk for mechanical complication (hazard ratio 12.82; 95% confidence interval 2.73-60.31) and for fracture of all components. Men had a higher risk of mechanical complication than women (hazard ratio 2.00; 95% confidence interval 1.55-2.59), and the risk of fracture was higher in all components. With increased splinted implants, the risk of mechanical complication (hazard ratio 0.67; 95% confidence interval 0.49-0.93) and component fracture (hazard ratio 0.73; 95% confidence interval 0.29-0.89) decreased. Gold screws had a lower risk of screw loosening (hazard ratio 0.74; 95% confidence interval 0.58-0.94) than titanium screws, but a higher risk of fracture (hazard ratio 3.45; 95% confidence interval 1.42-8.36). The smaller the implant diameter, the higher the risk of implant fracture (hazard ratio 0.01; 95% confidence interval 0.00-0.05). CONCLUSIONS: Abutments were most frequently fractured among the components of internal conical connection type implants. Molar implant-supported restorations and male patients had higher risks of mechanical complications, and as the number of splinted implants in a prosthesis increased, the risk decreased. Gold screws showed less risk of screw loosening and higher risk of fracture than titanium screws. Narrow-diameter implants had a higher risk of fracture.

Antiviral activity of CAVAC-1901, a combination of 3 standardized medicinal plants, against highly pathogenic influenza A virus in chickens.

Three different medicinal plants that consisted of the formulated mixture (CAVAC-1901) have been traditionally used for distinct medicinal purposes in different areas. Angelica dahurica has been used as an important ingredient of a prescription, Gumiganghwal-tang, for the common cold and influenza. Curcuma longa has been utilized for the treatment of asthma, and jaundice. Pinus densiflora (Korean red pine) has been used to improve memory and brain function for the treatment of vascular. Industrial livestock, which are characterized by dense breeding, are vulnerable to influenza infection, causing severe economic loss and social problems. However, there are no viable alternatives due to the risk of the occurrence of variants. Therefore, the aim of this study was to discover anti-influenza combinations of different medicinal plants with the concept of a multicomponent and multitarget (MCMT) strategy in traditional Chinese medicine (TCM). As part of a continuous project, 3 medicinal plants whose inhibitory activity against influenza A was previously reported at the compound level, and the inhibition of cytopathic effects (CPEs) by these formulated mixtures was evaluated against influenza A virus H1N1. A selected combination with an optimal ratio exhibiting synergistic activity was assessed for its antiviral activity in chickens against the highly pathogenic avian influenza (HPAI) H5N6. The selected combination (CAVAC-1901) showed potent inhibitory effects on the expression of neuraminidase and nucleoprotein, by RT-qPCR, Western blot, and immunofluorescence assays. The antiviral activity was more evident in chickens infected with H5N6. The sample-treated group (50 mg/kg/d) decreased mortality and virus titers in various organs. Our results indirectly suggest synergistic inhibitory activity of the combination of 3 different medicinal plants with different modes of action. Taken together, an optimally formulated mixture (CAVAC-1901) could serve as an effective alternative to current measures to minimize damage caused by HPAIs.

Clinical Outcomes of Implant-Assisted Removable Partial Dentures According to Implant Strategic Position.

PURPOSE: To retrospectively analyze the success of implant-assisted removable partial dentures (IARPDs) according to three types of strategic positions in distal extension areas of Kennedy Class I and II arches. MATERIALS AND METHODS: The data included 102 arches in 95 patients with Kennedy Class I/II arches treated with IARPDs with implants in three strategic positions: Type 1a, assisted by P-1a implants on the anterior area adjacent to the abutment tooth; Type 1b, assisted by P-1b implants on the anterior area apart from the abutment tooth with or without P-1a; Type 2, assisted by P-2a implants on the posterior area adjacent to the natural tooth or P-2b implants on the posterior area apart from the abutment tooth to modify from Kennedy Class I /II to Class III. The success was defined as the IARPDs without abutment tooth-related, denture-related, and implant-related complications. Kaplan-Meier curves and the multivariable Cox regression model were used to analyze the success of IARPDs and implants. RESULTS: The overall success rate of IARPD treatment was 66.7%; 77.8% in Type 1a, 60.0% in Type 1b, and 68.0% in Type 2. There was no significant effect of treatment type on success rate of IARPDs. However, there was significant differences at the level of implant supporting IARPDs: 83.3% in Type 1a implants, 62.6% in Type 1b implants, and 73.2% in Type 2 implants. The implants of IARPD's adjacent to the natural tooth abutments (P-1a and P-2a) had higher success rates than those away from the natural tooth abutments. CONCLUSIONS: Within the limitations of this study, there was no significant difference in the prosthodontic complications of IARPDs depending on the treatment type. However, the success of implants of IARPD is associated with the strategic position. Strategic implant abutments adjacent to the natural tooth had higher success rates than those away from the natural teeth abutments.

A retrospective comparison of clinical outcomes of implant restorations for posterior edentulous area: 3-unit bridge supported by 2 implants vs 3 splinted implant-supported crowns.

PURPOSE: To compare the clinical outcomes of two types of implant restoration for posterior edentulous area, 3-unit bridge supported by 2 implants and 3 implant-supported splinted crowns. MATERIALS AND METHODS: The data included 127 implant-supported fixed restorations in 85 patients: 37 restorations of 3-unit bridge supported by 2 implants (2-IB), 37 restorations of 3 implant-supported splinted crowns (3-IC), and 53 single restorations (S) as controls. Peri-implantitis and mechanical complications that occurred for 14 years were analyzed by multivariable Cox regression model. Kaplan-Meier curves and the multivariable Cox regression model were used to analyze the success and survival of implants. RESULTS: Peri-implantitis occurred in 28.4% of 2-IB group, 37.8% of 3-IC group, and 28.3% of S control group with no significant difference. According to the implant position, middle implants (P2) of the 3-IC group had the highest risk of peri-implantitis. The 3-IC group showed a lower mechanical complication rate (7.2%) than the 2-IB (16.2%) and S control group (20.8%). The cumulative success rate was 52.8% in S (control) group, 62.2% in 2-IB group, and 60.4% in 3-IC group. The cumulative survival rate was 98.1% in S (control) group, 98.6% in 2-IB group, and 95.5% in 3-IC group. There was no significant difference in the success and survival rate according to the restoration type. CONCLUSION: The restoration type was not associated with the success and survival of implants. The risk of mechanical complications was reduced in 3 implant-supported splinted crowns. However, the middle implants of the 3 implant-supported splinted crowns had a higher risk of peri-implantitis.

Investigation of the marginal fit of a 3D-printed three-unit resin prosthesis with different build orientations and layer thicknesses.

PURPOSE: The purpose of this study was to analyze the marginal fit of three-unit resin prostheses printed with the stereolithography (SLA) method in two build orientations (45°, 60°) and two layer thicknesses (50 µm, 100 µm). MATERIALS AND METHODS: A master model for a three-unit resin prosthesis was designed with two implant abutments. Forty specimens were printed using an SLA 3D printer. The specimens were printed with two build orientations (45°, 60°), and each orientation was printed with two layer thicknesses (50 µm, 100 µm). The marginal fit was measured as the marginal gap (MG) and absolute marginal discrepancy (AMD), and MG and AMD measurements were performed at 8 points per abutment, for 16 points per specimen. All statistical analyses were performed using SPSS software. Two-way analysis of variance (ANOVA) was separately performed on the MG and AMD values of the build orientations and layer thicknesses. Moreover, one-way ANOVA was performed for each point within each group. RESULTS: The margins of the area adjacent to the pontic showed significantly high values, and the values were smaller when the build orientation was 45° than when it was 60°. However, the margin did not differ significantly according to the layer thicknesses. CONCLUSION: The marginal fit of the three-unit resin prosthesis fabricated by the SLA 3D method was affected by the pontic. Moreover, the marginal fit was affected by the build orientation. The 45° build orientation is recommended.

Clinical and radiographic evaluations of implants as surveyed crowns for Class I removable partial dentures: A retrospective study.

PURPOSE: The purpose of this study was to evaluate survival rates and marginal bone loss (MBL) of implants in IC-RPDs. MATERIALS AND METHODS: Seventy implants were placed and used as surveyed crowns in 30 RPDs. The survival rates and MBL around implants based on multiple variables, e.g., position, sex, age, opposing dentitions, splinting, type of used retainer, and first year bone loss, were analyzed. Patient reported outcome measures (PROMs) regarding functional/esthetic improvement after IC-RPD treatment, and complications were also inspected. RESULTS: The 100% implant survival rates were observed, and 60 of those implants showed MBL levels less than 1.5 mm. No significant differences in MBL of implants were observed between implant positions (maxilla vs. mandible; P = .341) and type of used retainers (P = .630). The implant MBL of greater than 0.5 mm at 1 year showed significantly higher MBL after that (P < .001). Splinted implant surveyed crowns showed lower MBL in the maxilla (splinted vs. non-splinted; P = .037). There were significant esthetic/functional improvements observed after treatment, but there were no significant differences in esthetic results based on implant position (maxilla vs. mandible). Implants in mandible showed significantly greater improvement in function than implants in the maxilla (P = .002). Prosthetic complication of IC-RPD was not observed frequently. However, 2 abutment teeth among 60 were failed. The bone loss of abutment teeth was lower than MBL of implants in IC-RPDs (P = .001). CONCLUSION: Class I RPD connected to residual teeth and strategically positioned implants as surveyed crowns can be a viable treatment modality.

The Clinical Features of Inflammatory Bowel Disease in Patients with Obesity.

Methods: We retrospectively reviewed the medical records of IBD patients who visited Asan Medical center. We used a large, well-characterized referral center-based cohort. The clinical features of IBD patients with body mass index (BMI) over 30 and matched controls with BMI under 30 were compared. Results: Among the 6,803 IBD patients enrolled in the Asan IBD Registry between June 1989 and December 2016, we identified 16 patients with Crohn's disease (CD) and 27 patients with ulcerative colitis (UC) whose BMI was over 30 at the time of diagnosis. Their clinical characteristics and course were compared with those of 64 and 108 matched patients with CD and UC, respectively. There were no significant differences in the risk of using steroids (hazards ratio (HR) = 0.633 and P=0.254), immunomodulators (HR = 0.831 and P=0.517), and anti-tumor necrosis factor (TNF) therapy (HR = 1.539 and P=0.351) and risk of bowel resections (HR = 1.858 and P=0.231) between CD patients with BMI over 30 and those with BMI under 30; similarly, UC patients did not show significant differences in the risk of using steroids (HR = 0.613 and P=0.145), immunomodulators (HR = 0.492 and P=0.111), anti-TNF therapy (HR = 0.385 and P=0.095), and risk of colectomy (HR = 0.262 and P=0.104). In the subgroup analysis, under-weight UC patients had a higher cumulative probability of needing steroids (HR = 0.2510 and P=0.042), needing immunomodulators (HR = 0.097 and P=0.014), and a higher risk of receiving colectomy (HR = 0.024 and P=0.019) than obese UC patients. Conclusions: Obese IBD patients with CD or UC did not show significantly different clinical features from nonobese IBD patients.

Clinical Performance of Implant Crown Retained Removable Partial Dentures for Mandibular Edentulism-A Retrospective Study.

The studies on implant-crown-retained removable partial dentures (IC-RPDs) for edentulism are scarce. The purpose of this study was to evaluate survival rates and marginal bone loss (MBL) of IC-RPDs compared to implant overdentures (IODs) in mandibular edentulism. Variables that influenced survival and marginal bone loss (MBL) of implants in both treatment modalities were analyzed and the functional/esthetic satisfaction of patients as well as prosthetic complications were also observed. Eighteen IC-RPDs with a total of 60 implant-supported survey crowns and 24 IODs with a total 94 implants retained with magnet attachments were observed. After a median observation period of 46.6 months (up to 149 months), we observed 98.3% implant survival rates for IC-RPDs and 92.5% for IODs. Kaplan-Meier survival curves based on the treatment modality showed that, at 96 months, cumulative survival rates were 98.3% in IC-RPD and 83.1% in IOD. For implant survival rates, no statistical differences were observed according to age, sex, opposing dentition, or implant positions (p = 0.515, 0.666, 0.201, 0.749, respectively). The implant MBL measurements for IC-RPD and IOD groups at the final recall check were 0.93 ± 1.22 mm and 2.12 ± 2.09 mm, respectively. Additionally, there were no significant differences between groups (p = 0.554). The implants with peri-implantitis at year 1 showed significantly higher MBL at final check-up (p < 0.001). The MBL of implants showed significant differences based on age (p = 0.008) and opposing dentition (p = 0.003). No significant differences of implant MBL were observed for the position of placed implants (p = 0.621) or sex (p = 0.666). Patient-reported outcome measures (PROMs) on functional and esthetic satisfaction were significantly improved after IC-RPD or IOD treatment (p < 0.001). The most frequent prosthetic complication of IC-RPD was clasp loosening, while for IOD group, it was attachment dislodgement. Within the limitations of this retrospective study, we concluded that IC-RPDs could be considered as a viable treatment option for edentulous patients who need few fixed abutments for satisfaction.

Dimensional Accuracy of Dental Models for Three-Unit Prostheses Fabricated by Various 3D Printing Technologies.

Previous studies on accuracy of three-dimensional (3D) printed model focused on full arch measurements at few points. The aim of this study was to examine the dimensional accuracy of 3D-printed models which were teeth-prepped for three-unit fixed prostheses, especially at margin and proximal contact areas. The prepped dental model was scanned with a desktop scanner. Using this reference file, test models were fabricated by digital light processing (DLP), Multi-Jet printing (MJP), and stereo-lithography apparatus (SLA) techniques. We calculated the accuracy (trueness and precision) of 3D-printed models on 3D planes, and deviations of each measured points at buccolingual and mesiodistal planes. We also analyzed the surface roughness of resin printed models. For overall 3D analysis, MJP showed significantly higher accuracy (trueness) than DLP and SLA techniques; however, there was not any statistically significant difference on precision. For deviations on margins of molar tooth and distance to proximal contact, MJP showed significantly accurate results; however, for a premolar tooth, there was no significant difference between the groups. 3D color maps of printed models showed contraction buccolingually, and surface roughness of the models fabricated by MJP technique was observed as the lowest. The accuracy of the 3D-printed resin models by DLP, MJP, and SLA techniques showed a clinically acceptable range to use as a working model for manufacturing dental prostheses.

New Rehabilitation Concept for Maxillary Edentulism: A Clinical Retrospective Study of Implant Crown Retained Removable Partial Dentures.

There have been no studies of implant-crown-retained removable partial dentures (IC-RPD) for the treatment of maxillary edentulism. The purpose of this study was to perform clinical and radiographic evaluations of implants in IC-RPD compared to implant overdentures (IOD) in maxillary edentulous patients. Twenty IC-RPDs with 74 splinted implant crowns and 18 IODs with 71 implants retained with magnet attachments were observed in 38 patients. We statistically analyzed survival rates and marginal bone loss (MBL) of implants based on multiple variables including first year pathologic condition, location of placed implant, age, and sex in both treatments. Patient reported oral measurements (PROMs) regarding functional/esthetic improvement after IC-RPD or IOD treatments and prosthetic complications were also statistically analyzed. After a median observation period of 47.1 months (up to 147 months), we observed 97.3% implant survival rates for IC-RPD and 70.4% for IOD (p < 0.001). Among variables, first year pathologic condition (p < 0.001) and sex (p = 0.027) influenced implant survival rates. The MBL of implants for IC-RPD and IOD groups at the final check-up were 1.12 ± 1.19 mm and 3.31 ± 1.71 mm, respectively (p < 0.001). In both groups, patients with peri-implantitis (p < 0.001) and patients older than 65 years (p = 0.029) showed significantly higher implant MBL regardless of treatment modality. Functional and esthetic satisfaction were significantly improved (p < 0.001) after both treatments. The IOD group showed more frequent prosthetic complications compared to the IC-RPD group. Within the limitations of a retrospective study, we concluded that RPD with few splinted implant crowns is a feasible alternative treatment modality for maxillary edentulous patients with anatomical limitations.

Dimensional accuracy and surface characteristics of 3D-printed dental casts.

STATEMENT OF PROBLEM: Although studies have reported the accuracy of 3D-printed dental casts, studies addressing cast distortion throughout the complete-arch range are lacking. PURPOSE: The purpose of this in vitro study was to evaluate the dimensional accuracy of different areas in complete-arch casts made with various 3D printing methods. MATERIAL AND METHODS: A computer-aided design (CAD) reference cast was modified from a mandibular cast by adding 6 cylinders in the canine, second premolar, and second molar locations and 3 spheres to define a coordinate system. A total of 50 casts were printed with 5 group materials, which included fused deposition modeling (FDM), digital light processing (DLP1 and DLP2), photopolymer jetting (Polyjet), and stereolithography (SLA). After scanning the 3D printed casts, the overall consistency was examined by superimposing them on the CAD reference cast and measuring the deviations. For dimensional accuracy, cylinder top coordinates were extracted from each printed cast, and X-, Y-, and Z-deviations and the 3D deviation were calculated by subtracting the coordinates of the CAD reference cast from the cast values. Statistical analyses were conducted by the Kruskal-Wallis test and the Mann-Whitney post hoc test (α=.05). Surface characteristics were examined with photographs and scanning electron micrographs. RESULTS: FDM showed more systemic deviations than DLP, Polyjet, and SLA from superimposing analysis (P<.01). In the X-axis, FDM and DLP showed contraction, while Polyjet and SLA showed expansion (P<.01). In the Y-axis, FDM showed forward deviations on the right side and DLP showed contraction (P<.01). Three-dimensional deviation at each cylinder location was lowest in the left canine region, and deviations increased with distance from this site in all groups. The qualitative features of casts varied among 3D printers in terms of shape, surface smoothness, and edge sharpness. CONCLUSIONS: FDM and DLP casts tended to contract, whereas casts in the Polyjet and SLA groups expanded buccolingually and anterioposteriorly. Vertically, deviations were smaller than those in the other directions.

Alternative approach to salvaging an implant with a fractured screw fragment: A clinical report.

Managing fractures of implant abutment screws is challenging because of the uncertainty associated with the removal of the fractured screw fragments. In case of unsuccessful retrieval of the fractured fragment with known techniques, removal and replacement of the implant becomes traumatic and financially burdensome to the patient. This clinical report describes a conservative solution for the management of nonretrievable fractured screws by reconnecting the prostheses to the existing implants by using cut screws. This alternative, cost-effective method obviates the need for surgery and has proved successful and satisfactory for patients.