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.

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.

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.

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.

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.

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.

Association of prosthetic features and peri-implantitis: A cross-sectional study.

OBJECTIVE: To identify the influence of prosthetic features through a comprehensive analysis with other known risk factors. MATERIALS AND METHODS: A total of 169 patients (n = implants: 349) was retrospectively included in the present study. Peri-implantitis was diagnosed based on peri-implant bone loss and probing depth. Using radiographs taken 1 and 5 years following prosthesis insertion, the following features were determined: peri-implant marginal bone loss (MBL), emergence angle (EA), emergence profile (EP) and crown/implant ratio (CIR). The splinted position of prosthesis was also recorded. Multivariable generalized estimating equation was used to analyse the influence of each feature on the prevalence of peri-implantitis. The final prediction model was constructed by Cox proportional hazard regression analysis. RESULTS: The EA showed a significant correlation with MBL. A statistically greater prevalence of peri-implantitis was observed if EA ≥ 30 degrees, when EP is convex and in middle implant splinted with both mesial and distal adjacent implants in bone-level implant. A similar correlation was not observed in tissue-level implants. CIR had no significant effect on the prevalence of peri-implantitis. CONCLUSION: Over-contoured implant prosthesis is a critical local confounder for peri-implantitis. The implant splinted to both mesial and distal adjacent implant has a higher risk of peri-implantitis.

Comparison of digital intraoral scanner reproducibility and image trueness considering repetitive experience.

STATEMENT OF PROBLEM: Because the digital workflow can begin directly in the oral cavity, intraoral scanners are being adopted in dental treatments. However, studies of the relationship between the experience of the practitioner and the accuracy of impression data are needed. PURPOSE: The purpose of this clinical study was to investigate the effect of the experience curve on changes in trueness when a patient's complete dental arch is scanned. MATERIAL AND METHODS: Twenty dental hygienists with more than 3 years of experience in dental clinical practice (group 1 had 3 to 5 years; group 2 had >6 years) were recruited to learn to operate 2 intraoral scanner systems. All learners scanned the assigned patient's oral cavity 10 times during the experience sessions. Precision was calculated as the mean deviation among all superimposition combinations from the 10 scanned data sets of each learner [n=10C2=45]. Trueness was evaluated by superimposing the 10 consecutive intraoral scan data onto the impression scan data from each patient's rubber impression body (n=10). The acquired images were processed and analyzed using a 3-dimensional analysis software. For statistical analysis, the independent 2-sample t test and repeated measures ANOVA were performed (α=.05). RESULTS: The mean precision of the Trios scanner was greater than that of the iTero (Trios, 52.30 µm; iTero, 60.46 µm; P<.01). The iTero group showed an improvement in trueness upon repeated experience (P<.05), whereas the Trios group did not (P>.05). In the iTero group but not in the Trios group, the length of clinical experience influenced the change of trueness as a result of repeated experience (P<.05). In terms of the scanned region, the results for trueness were better for the maxillary arch than the mandibular arch with repeated scanning in the iTero group (P<.05). CONCLUSIONS: The single-image based system required repeated learning sessions for effective clinical application. The newer system offered better trueness and precision and was less likely to be influenced by the length of clinical career or the region being scanned.

Accuracy of a digital removable partial denture fabricated by casting a rapid prototyped pattern: A clinical study.

STATEMENT OF PROBLEM: A limited number of clinical studies have evaluated the accuracy of a digitally generated removable partial denture (RPD) intraorally. An analysis of the accuracy of the digital RPD on a larger number of participants was needed. PURPOSE: The purpose of this clinical study was to analyze the accuracy of digital RPDs by using the replica technique. MATERIAL AND METHODS: The fit accuracy of digital RPDs fabricated using electronic surveying was analyzed by fabricating replicas with silicone registration material and measuring with a stereomicroscope and image program. A total of 348 measurements in 10 participants were analyzed. The internal discrepancy of the metal framework was evaluated among participants using different Kennedy classifications. The accuracy of fittings in the cingulum and occlusal rest areas were compared according to the denture support type and the measured position below the rest. A 2-way and 1-way ANOVA and an independent 2-sample t test were used for statistical analysis (α=.05). RESULTS: Statistically significant differences were found in the internal discrepancy of the various framework components (P<.05), but no differences were found among participants with different Kennedy classifications (P>.05). The discrepancy under the periphery of the rest was determined to be smaller than that of the center, especially for the cingulum rest (P<.01). CONCLUSIONS: Digital RPDs fabricated using electronic surveying varied in accuracy of fit. According to the rest contact positions, the accuracy observed at the periphery was better than at the center.

Comparison of experience curves between two 3-dimensional intraoral scanners.

STATEMENT OF PROBLEM: Conventional impression-making methods are being replaced by intraoral digital scanning. How long dental professionals take to master the new technologies is unknown. PURPOSE: The purpose of this human subject study was to compare the experience curves of 2 intraoral scanners among dental hygienists and determine whether repeated scanning experience could change the scan time (ST). MATERIAL AND METHODS: A total of 29 dental hygienists with more than 3 years of working experience were recruited (group 1: 3-5 years; group 2: >6 years of clinical experience) to learn the iTero and Trios systems. All learners scanned the oral cavities of 4 human participants (participants A, B, C, and D) 10 times (T1-T10) throughout the learning sessions and the experimental dentoform model twice at the beginning and end of the 10 sessions. ST was measured, and changes in ST were compared between the 2 devices. RESULTS: The average ST for 10 sessions was greater with iTero than with Trios, but the decrease in the measured ST was greater for iTero than for Trios. Baseline and postexperience STs with iTero showed statistically significant differences, with a decrease in time related to the clinical experience levels of the dental hygienists (group 1: T2 and T4, P<.01; group 2: T2 and T5, P<.01). The experience curve with iTero was not influenced by the human participant's intraoral characteristics, and greater ST was shown for participants B and C than for participants A and D with Trios. CONCLUSIONS: Although the learning rate of iTero was rapid, the average ST for iTero was longer than Trios, and clinical experience levels influenced the operator's ability to manipulate the device. In contrast, the learning rate of Trios was slow, and measured ST was shorter than iTero, and was not influenced by clinical experience.

Clinical evaluations of cast gold alloy, machinable zirconia, and semiprecious alloy crowns: A multicenter study.

STATEMENT OF PROBLEM: Few studies have compared the marginal and internal fits of crowns fabricated from machinable palladium-silver-indium (Pd-Ag-In) semiprecious metal alloy. PURPOSE: The purpose of this clinical study was to evaluate and compare the marginal and internal fits of machined Pd-Ag-In alloy, zirconia, and cast gold crowns. MATERIAL AND METHODS: A prospective clinical trial was performed on 35 participants and 52 abutment teeth at 2 centers. Individuals requiring prosthetic restorations were treated with gold alloy or zirconia crowns (2 control groups) or Pd-Ag-In alloy crowns (experimental group). A replica technique was used to evaluate the marginal and internal fits. The buccolingual and mesiodistal cross-sections were measured, and a noninferiority comparison was conducted. RESULTS: The mean marginal gaps were 68.2 µm for the gold crowns, 75.4 µm for the zirconia crowns, and 76.9 µm for the Pd-Ag-In alloy crowns. In the 5 cross-sections other than the distal cross-section, the 2-sided 95% confidence limits for the differences between the Pd-Ag-In alloy crowns and the 2 control groups were not larger than the 25-µm noninferiority margin. The control groups displayed smaller internal gaps in the line angle and occlusal spaces compared with the Pd-Ag-In crown group. CONCLUSION: The marginal gaps of machinable Pd-Ag-In alloy crowns did not meet the noninferiority criterion in the distal margin compared with zirconia and gold alloy crowns. Nonetheless, all 3 crowns had clinically applicable precision.

Optimizing third molar autotransplantation: applications of reverse-engineered surgical templates and rapid prototyping of three-dimensional teeth.

The success of autogenous tooth transplantation depends on the vitality of the periodontal ligament attached to the donor tooth, and its viability decreases when it is exposed extraorally. This report describes the case of a 16-year-old patient in whom a rapid prototyped tooth model was performed using cone-beam technology and a surgical template guide for autotransplantation as an effective technique for a critical time-based procedure.

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.

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.

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 effect of Er:YAG laser irradiation on the scanning electron microscopic structure and surface roughness of various implant surfaces: an in vitro study.

The purpose of this study was to evaluate the surface roughness (R(a)) and microscopic change to irradiated dental implant surfaces in vitro and ultimately to determine the proper pulse energy power and application time for the clinical use of Er:YAG lasers. Anodic oxidized surface implants and sand-blasted, large-grit, and acid-etched (SLA) surface implants were used. Each experimental group of implant surfaces included ten implants. Nine implants were used for the laser irradiation test groups and one for the control group. Each test group was equally divided into three subgroups by irradiated pulse energy power. Using an Er:YAG laser, each subgroup of anodic oxidized surface implants was split into 60-, 100-, and 140-mJ/pulse groups, with each subgroup of SLA surface implants irradiated with a 100-, 140-, or 180-mJ/pulse. Three implants in every test subgroup were respectively irradiated for 1, 1.5, and 2 min. The R(a) values for each specimen were recorded and every specimen was observed by SEM. Irradiation by Er:YAG laser led to a decrease in implant surface roughness that was not statistically significant. In anodic oxidized surfaces, the oxidized layer peeled off of the surface, and cracks appeared on implant surfaces in the 100- and 140-mJ/pulse subgroups. However, with SLA surfaces, no significant change in surface texture could be found on any implant surface in the 100- and 140-mJ/pulse subgroups. The melting and fusion phenomena of implant surfaces were observed with all application times with 180 mJ/pulse irradiation. The SLA implant surfaces are stable with laser intensities of less than 140 mJ/pulse and an irradiation time of less than 2 min. The anodic oxidized surfaces were not stable with laser intensities of 100 mJ/pulse when an Er:YAG laser was used to detoxify implant surfaces.

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.