Retention Force Values Research Articles

Effect of different surface treatments on the retention force of additively manufactured interim implant-supported crowns.

To compare the effect of different pre-cementation surface treatments and bonding protocols on the retention force of additively manufactured (AM) implant-supported interim crowns. A total of 50 AM interim crowns (Temporary CB resin) were cemented on implant abutments. Five groups (n = 10) were established based on the different surface pre-treatments performed in the intaglio surface of the specimens: no surface pre-treatment (Group C or control), air-abraded with 50-μm aluminium oxide particles (Group AP), air-abraded with 50-μm aluminium oxide particles followed by the application of silane (Group AMP), silane (Group MP), and air-abraded with 30μm silica-coated aluminum oxide particles followed by the application of silane (Group CMP). Each specimen was cemented into an implant abutment using a composite resin cement (Rely X Unicem2). Afterward, the specimens underwent retention testing with a Universal Instron machine. Pull-off forces (N) and modes of failure were registered. Statistical analysis was performed using Mann-Whitney U tests with Bonferroni corrections for multiple tests (α = .05). The median retention force values were 233.27 ±79.28 N for Group Control, 398.59 ±68.59 N for Group MP, 303.21 ±116.80 N for Group AMP, 349.31 ±167.73 N for Group CMP, and 219.85 ± 55.88 N for Group AP. The pull-off forces were significantly greater for Group MP, while the differences between the remaining groups were not statistically significant (P>0.05). Group AP showed the lowest retention force values among all the groups. Failure modes after the pull-off testing were predominantly adhesive and substrate failure of the AM interim material. The surface treatment of the intaglio AM crown tested significantly influenced the retention force values measured. Pre-treatment with an MDP-containing silane improved the retentive force values computed, whereas pre-treatment with 50-μm Al2 O3 air-particle abrasion alone is not recommended prior to cementation on a titanium-based implant abutment. This article is protected by copyright. All rights reserved.

Retention of titanium copings to implant-supported fixed dental prostheses.

The aim of this in vitro study was to assess the effects of using different cements and titanium copings designs on the retention of implant-supported fixed dental prostheses (IFDPs) using a pull-out test. Fifty zirconia (ZirCAD; Ivoclar Vivadent) and 20 prepolymerized denture acrylic resin (AvaDent) rectangular (36mm × 12mm × 8mm) specimens were milled to mimic the lower left segmental portion of the All-on-Four IFDPs. Cylindrical titanium copings (Variobase; Straumann) (V) were used in 2 prepolymerized denture acrylic resin groups (n = 10) while conical titanium copings (Straumann) (C) were used as a control group for zirconia with 4 groups using cylindrical titanium copings. Before cementation, the outer surfaces of all titanium copings and the intaglio bonding surface of prosthetic specimens were airborne-particle abraded. All specimens were cemented following the manufacturer's recommendations and instructions according to the experimental design. After artificial aging (5000 cycles of 5°C 55°C, dwelling time 20s; 150 N, 1.5Hz in a 37°C water bath), all specimens were subjected to retention force testing using a pull-out test using a universal testing machine and a custom fixture with a crosshead speed 5mm/min. Modes of failure were classified as Type 1, 2, or 3. Retention force values were analyzed by the t-test for the prepolymerized denture acrylic resin specimen groups, and 1-way ANOVA and the Tukey test for the zirconia groups at α = 0.05. Mean and standard deviation retention force values varied from 101.1±67.1 to 509.0±65.2 N for the prepolymerized denture acrylic resin specimen groups. The zirconia groups ranged from 572.8±274.7 to 1416.1 ±258.0 N. There is no statistically significant difference in retention force values between V and C specimens cementing to zirconia with Panavia SA cement (Kuraray Noritake) (p = 0.587). The retention forces and failure modes were influenced by the cement used (p < 0.05). Modes of failure were predominantly Type 2 (mixed failure) and Type 1 (adhesive fracture from prosthetic materials) except for the quick-set resin group (Type 3, adhesive failure from coping). When bonding IFDPs onto titanium copings, quick-set resin provided significantly higher retention force for prepolymerized denture acrylic resin prostheses. Conical and cylindrical titanium copings performed similarly when cemented to zirconia with Panavia SA cement under the same protocol. The stability of the bonded interface and retention forces between zirconia prostheses and titanium copings varied from the cement used.

Impact of material combinations and removal and insertion cycles on the retention force of telescopic systems

ObjectivesA variety of dental materials are available for the fabrication of telescopic crowns. The aim was to investigate the impact of material combinations and removal and insertion cycles on their retention forces.Materials and methodsCAD/CAM-fabricated cobalt–chromium–molybdenum (CoCr) and zirconia (ZrO2) primary crowns were combined with polyetheretherketone (PEEK), polyetherketoneketone (PEKK), CoCr, and ZrO2 secondary crowns (four combinations included PEEK/PEKK secondary crowns in a thickness of 0.5 mm bonded to the CoCr tertiary construction), resulting in 12 different material combinations: CoCr–PEEK; CoCr–PEKK; CoCr–ZrO2; CoCr–CoCr; CoCr–PEEK 0.5; CoCr–PEKK 0.5; ZrO2–PEEK; ZrO2–PEKK; ZrO2–ZrO2, ZrO2–CoCr; ZrO2–PEEK 0.5; and ZrO2–PEKK 0.5 (n = 15 pairings per material combination). Pull-off tests were performed with a universal testing machine initially and after 500, 5000, and 10,000 removal and insertion cycles in a mastication simulator. Descriptive statistics with the Kolmogorov–Smirnov, Kruskal–Wallis, and Mann–Whitney U tests were computed (α = 0.05).ResultsThe tested parameters, material combination, and removal and insertion cycles had significant impact on the retention force values (p < 0.001). An increase in removal and insertion cycles was associated with a decrease in retention forces within CoCr and ZrO2 secondary crowns, regardless of the primary crown material. In contrast, PEEK and PEKK secondary crowns presented higher retention load values after 10,000 cycles than initially.ConclusionDifferent material combinations behaved differently after simulated removal and insertion regimens. This difference should be considered during treatment planning.Clinical relevanceTelescopic crown systems should be made of materials with predictable retention forces that do not deteriorate with time. The implementation of new materials and technologies facilitates reproducibility and time-saving fabrication.

Dimensional Optimization of Graphene-Modified Polymethyl Methacrylate Material Used as an Aesthetic Removable Partial Denture Clasp Material

Abstract Objective Although graphene-modified polymethyl methacrylate material is a good candidate for partial denture clasp material, it lacks adequate strength. Therefore, the study aims to assess the optimal dimension of this nanomodified material required for such an application. Materials &amp; Methods A parametric finite element analysis study was conducted on 54 clasp 3D models at two displacement levels (0.25–0.5 mm) placed 3 mm from the clasp tip. The clasp models were categorized based on the dimensions into A, B, and C (3 subgroups in each) and six tapers from the tip to the base (0.5–1). Both reaction force in (N) and maximum principal stress in (MPa) were recorded and analyzed. The study was validated using the mechanical tester after digital manufacturing of the clasp specimens that showed satisfactory results. Statistical Analysis The correlations between width and thickness against reaction force and maximum principal stress were checked by a statistical analysis software package (SPSS version 22; IBM Corp., Armonk, New York, United States). Data of the reaction force demonstrated nonparametric behavior, as tested by the Kolmogorov–Smirnov test. Accordingly, Spearman's rho test for correlation was used. In contrast, the maximum principal stress data showed normal distribution, as tested by the Kolmogorov–Smirnov test. Thus, Pearson's test of correlation was applied. Results The results demonstrated the best retention force values, considering aesthetics, in subgroups C3 (taper 0.6), C3 (taper 0.8), and B3 (taper 1). The maximum principal stress results showed the highest values in group C followed by group B and then group A. Positive correlations were calculated between thickness and width versus reaction force and maximum principal stress. The correlation coefficient value between thickness and reaction force was 0.699 and that between width and reaction force was 0.621, while the correlation coefficient between thickness and maximum principal force was 0.899 and that between the width and maximum principal force was 0.740. Conclusion It could be concluded that the studied material might be recommended as a valid aesthetic clasp material. Both clasp thickness and width showed a positive correlation with the clasp retention force with more impact by the thickness.

The effect of thermomechanical aging on the retention of a conometric system in a chewing simulator.

To evaluate the retention force of a novel conometric system after thermomechanical aging. In addition, the conometric system's retention force was compared with that of the cemented implant-retained crowns. Two systems to retain implant crowns were tested in this study: a conometric system and a cement-retained system. Forty-eight zirconia crowns were fabricated using computer-aided design and computer-aided manufacturing technology. Twenty-four zirconia crowns were cemented onto conometric caps with resin-modified glass ionomer cement, which were then connected with abutments. These specimens were divided into three groups, and each group was subjected to the pull-out test. A-control group: 12 specimens directly subjected to pull-out test; A-aged group: 12 specimens subjected to thermomechanical aging followed by pull-out test; A-repeat group: After the pull-out, the specimens in the aging group (A-aged) were reconnected, and the pull-out test was repeated once more. The remaining 24 zirconia crowns were cemented on standard abutments with zinc phosphate cement, and two groups were formed. C-control group: 12 specimens directly subjected to the pull-out test; C-aged group: 12 specimens subjected to thermomechanical aging followed by pull-out. Scanning electron microscope (SEM) was used to evaluate the surfaces of caps and abutments. To analyze the data, repeated measures, one-way ANOVA, and Bonferroni tests were used (p<0.05). The mean retention force value of the A-control group was 148.22±16.37N. The highest mean retention force value was measured in the A-aged group (204.93±51.67N), and the lowest mean retention force value was seen in the A-repeated group (77.02±21.48N). Thermomechanical aging had a significant influence (p<0.05) on both systems. No significant differences in retention force were found between the thermomechanical aged groups of both systems (p>0.05). SEM analysis revealed that aging had an impact on the surface of the conometric system's caps and abutments. The retention force of the conometric system increased significantly following thermomechanical aging. No crown separation occurred during the thermomechanical aging of the conometric system. There was no significant difference in the retention of the conometric and cemented systems after thermomechanical aging.

Comparative Evaluation of the Effect of Degree of Convergence and Surface Area on the Retentive Force of Titanium Crowns Cemented with Various Adhesive Luting Agents on Extracted Human Teeth – A Laboratory Study

Introduction: The retention of base metal crowns and noble metal crowns cemented with various luting agents is well documented. However, little emphasis was given to the degree of convergence and surface area of tooth preparation. Aim and Objective: A study was planned to analyze the effect of the degree of convergence and surface area of the tooth preparation on the retention of titanium crowns with various adhesive luting agents. Materials and Methods: Forty-five caries-free extracted human premolars were obtained. They were divided into three groups according to the degree of convergence and further subdivided based on the type of luting agents used. The teeth were prepared with an angle of convergence of 5°, 10°, and 15° with a flat occlusal surface using K9 crown finishing installation, complete. Light body copper band impressions were made to determine the surface area. Titanium crowns thus obtained were sandblasted, ultrasonically cleaned, and cemented using Panavia F, Calibra, and Glass Ionomer Cement. Results: Results showed that Panavia F was the best luting agent exhibiting maximum retentive force to dislodge the crown in a vertical direction using the universal tensile testing machine at a cross-head speed of 1 mm/min. Conclusion: The force required to dislodge the titanium crown from the prepared tooth was maximum for Panavia F on 5°, 10°, and 15° angle of convergence at 65.23 kgf, 48.52 kgf, and 40.14 kgf. Retentive force values drastically reduced as the degree of convergence increased. There was a reduction in the surface area due to an increase in the taper.

Parameters Affecting the Retention Force of CAD/CAM Telescopic Crowns: A Focused Review of In Vitro Studies.

Telescopic systems constructed using computer aided design and computer aided manufacture (CAD/CAM) can overcome many drawbacks associated with conventionally constructed ones. Since retention is considered the most important function of these retainers, this scoping review aimed to discuss and summarize the parameters that affect this function in CAD/CAM-manufactured telescopic crowns and to compare their retention force values with the recommended retention force. An electronic search was done in Pubmed and Google Scholar databases using different keyword combinations to find the related articles. Seventeen articles that follow the eligibility criteria for this review were selected and analyzed for detection of each of the tested parameters and their effect on retention force. The parameters tested in these articles were divided into parameters related to design, manufacturing, material type, and test condition. Regardless of the effect of these parameters, the retention force values recorded in most of the selected studies laid within or were higher than the recommended retention force (2.5–10 N), which indicated the need to design and set the combination of materials of telescopic systems according to oral biomechanics.

In Vitro Investigations in a Biomimetic Approach to Restore One-Piece Zirconia Implants.

The objective of this study was to evaluate the fracture load and retention force of different bonding systems while restoring one-piece zirconia implants with a novel cementation approach using a mesostructure. Polymer-infiltrated ceramic mesostructures (n = 112) were therefore designed as caps on the implant abutment, and a molar feldspathic ceramic crown was constructed on top of it as a suprastructure. For cementation, different bonding systems were used. Fracture load and retention force were measured immediately after storage in water at 37 °C for 24 h (n = 8) as well as after artificial aging in a chewing simulator and subsequent thermal cycling (n = 8). Combined restorations showed higher fracture load compared to monolithic restorations of polymer-infiltrated ceramic (n = 8) or feldspathic ceramic (n = 8) identical in shape. However, the fracture load of the combined restorations was significantly affected by aging, independent of the primers and cements used. Restorations cemented with primers containing methyl methacrylate and 10-methacryloyloxydecyl dihydrogen phosphate exhibited the highest retention force values. Aging did not affect the retention force significantly. Similar fracture load values can be expected from combination restorations when compared with monolithic crowns.

Retention Forces of Monolithic CAD/CAM Crowns Adhesively Cemented to Titanium Base Abutments-Effect of Saliva Contamination Followed by Cleaning of the Titanium Bond Surface.

The aim of this study was to investigate the effects of saliva contamination and the cleaning of the bond surface of titanium base (ti-base) abutments on the bonding stability and retention force values. The bond surface of the ti-base abutments was treated with airborne-particle abrasion. After contamination, the ti-base abutments underwent different cleaning protocols: water spray (H2O); alcohol (ALC); suspension of zirconium particles (SZP); reapplied airborne-particle abrasion (APA); and a control condition without contamination and cleaning (CTR). All lithium disilicate crowns were bonded to the ti-base abutments using a primer and a self-curing composite. Bonded specimens underwent thermo-mechanical aging. Bond failure analysis and pull-off testing were performed. Bond failure occurred more frequently in groups H2O, ALC, SZP, and APA (p < 0.05). Significant differences in retention force values were only found between CTR and ALC (p < 0.05). Specimens which did not show bond failure after ageing had higher retention force values than the specimens that showed bond failure (p < 0.05). Saliva contamination with cleaning can degrade the bonding properties to titanium. For the retention force values, only the protocol with alcohol after contamination could not restore the values.

Retention of a telescopic overdenture on customized abutments after the simulation of 1 year in function.

Telescopic implant-retained overdentures are considered one of the most common treatment modalities for edentulous patients. The aim of the study was to evaluate the retention of a BioHPP (biocompatible highperformance polymer) telescopic overdenture supported by customized abutments made from 2 different materials after the simulation of 1 year in function. Twelve models of a completely edentulous mandible were three-dimensionally (3D)-printed. Two implants and 2 groups of customized abutments - group Bio: BioHPP (n = 6) and group Ti: titanium (n = 6) - were used to support BioHPP telescopic overdentures. A vertically dislodging force was applied to each denture until its separation before and after 240,000 cycles of chewing simulation and 1,440 iterations of cyclic dislodgement for the simulation of 1 year in function in order to measure maximum tensile loads needed to dislodge the overdenture. Student's t test and the paired t test were used for the statistical analysis (α = 0.05). The initial and final retentive forces of the Ti group were significantly higher than in the case of the Bio group. A significant decrease in the retentive forces within the 2 groups after chewing simulation was observed and it was higher in group Ti; however, there was no statistically significant difference between the 2 groups. The retentive force values for implant-retained telescopic overdentures significantly decreased after the simulation of 1 year of overdenture use. Both BioHPP and titanium are considered suitable abutment materials to retain telescopic overdentures.

Laboratory efficiency of additive manufacturing for removable denture frameworks: A literature-based review.

The purpose of this literature review was to verify the laboratory efficiency of additive manufacturing (AM) systems for removable partial denture (RPD) frameworks. All available relevant articles in English published from 1990 to 2020 were found by searching online databases and by hand research. A total of 17 articles dealt with the surface roughness, fitness accuracy, and retentive forces of AM frameworks. The surface roughness of AM was inferior to that of casting and milling. Whether conventional cast or AM RPD frameworks had superior fitness accuracy could not be clarified. As compared with casting and AM, milling enabled the fabrication of RPD clasps with comparable or better fitness accuracy. Over time, AM clasps had retentive force values of superior consistency as compared with those of conventional cast clasps. Clasps fabricated by repeated laser sintering and high-speed milling could obtain smoother surfaces and more suitable retention than those of AM clasps.

Effect of airborne-particle abrasion of a titanium base abutment on the stability of the bonded interface and retention forces of crowns after artificial aging

Statement of problemPublished data have shown that a mechanical surface treatment of titanium surfaces increases bonding potential. However, most of the studies are based on shear or tensile tests performed on flat-surfaced specimens and do not take into consideration the retention given by the titanium base (ti-base) axial walls and the thermomechanical loading seen in a clinical setting. PurposeThe purpose of this in vitro study was to evaluate the influence of different airborne-particle abrasion (APA) methods of the ti-base surface on the stability of the bonded interface and retention forces between these titanium bases and lithium disilicate crowns after thermomechanical aging. Material and methodsSixty internal connection implants (Conelog) were restored with lithium disilicate crowns and bonded to the corresponding ti-bases (Conelog). The ti-bases were divided into 4 groups (n=15), 3 experimental groups applying different APA methods, 30-μm silica-modified Al2O3 particles (CoJet) (30-SiO-AlO), 50-μm Al2O3 (Cobra Aluoxyd) (50-AlO), 110-μm silica-modified Al2O3 particles (Rocatec Plus) (110-SiO-AlO), and 1 control group (NoT). Ti-bases were airborne-particle abraded (10 seconds, 0.25 MPa at a 10-mm distance) under standardized conditions in a custom-made APA device. All crowns were cemented with a resin cement (Multilink Hybrid Abutment). After aging (1 200 000 cycles, 49 N, 1.67 Hz; 5 °C-55 °C, 120 seconds), all specimens were assessed for the presence of bond failures by optical microscopy (×50). The retention forces (N) were tested by using a pull-off test (0.5mm/min). Modes of failure were classified (Type 1, 2, or 3). An additional ti-base representing each group was prepared for surface roughness (μm) calculation (Ra, Rc, Rz) with a noncontact laser profilometer, and representative scanning electron microscope (SEM) images were recorded (×1000). Chi-squared tests were performed to analyze the bonded interface failure and modes of failure, and a Kruskal-Wallis test was selected to evaluate retention force values (α=.05). ResultsThe percentages of bonding failure after aging were 73.3% (NoT), 40% (30-SiO-AlO), 6.7% (50-AlO), and 40% (110-SiO-AlO). The stability of the bonded interface was influenced by the APA method applied (P<.05). Mean ±standard deviation retention force values varied from 206.3 ±86.3 N (NoT) to 420 ±139.5 N (50-AlO), and the differences between these 2 groups were significant (P<.05). Modes of failure were predominantly Type 2 (30-SiO-AlO; 50-AlO; 110-SiO-AlO) and Type 3 (NoT). ConclusionsAirborne-particle abrasion of the titanium surface increased the bond stability and retention forces between the ti-base and the respective crown. The use of 50-μm Al2O3 provided the most stable bonded interface among the different treatments.

Six Sigma Implementation in Connector and Terminals Manufacturing Company : A Case Study

This research was conducted at an electronic component company located in Bekasi, Indonesia. Quality is a characteristic of this company, with the company's mission, one of which is eliminating customer claims. The application of the Six Sigma DMAIC method is expected to be used as a guideline for making durable product quality and reducing the high variation in the manufacturing process for bullet type products. This study aims to determine the variables of the factors that can affect the retention force value of bullet type terminal products, using the Taguchi method experiment. The research results with the Taguchi method experiment found that three variables affect the product retention force value, namely the largest outer diameter dimension, the most significant input diameter size dimension, and the smallest length position size dimension. After monitoring and data collection on the retention force dimension, it was found that the overall Cp process capability was 3.38, and Cpk was 1.58, so it could be said that the machine performance was excellent and stable.

Undetected Excess Cement at Marginal Areas of Zirconia Crown Copings: In Vitro Analysis of Two Luting Agents and Their Influence on Retention.

To evaluate the amount of residual cement (ECL) around the margins of zirconia crown copings after careful luting and cleaning procedures and to investigate these factors in relation to two tested luting materials. An experimental model of a maxillary arch was selected for this in vitro study. The maxillary first molar was prepared to receive an all-ceramic, single, full-crown restoration with a finish line located 1 mm below the artificial gingiva. After scanning of the prepared tooth, 20 paired zirconia coping-abutment assemblies were CAD/CAM fabricated. A slot in the model allowed for insertion and removal of the assemblies for each new test. Specimens were divided into two groups according to the cementation procedure: half (n = 10) were luted using a resin-modified glass-ionomer (RMGI) (Ketac-Cem Plus) (GI group), and the other half with a dual-curing self-adhesive resin agent (RelyX Unicem 2) (UN group). The substructures were loaded with cement, and a customized preseating device was adopted for preliminary reduction of excess. The zirconia copings were finally seated on their respective abutments located on the simulation model. A blinded investigator attempted to remove all excess cement with clinically available instruments. The amount of excess cement left in situ after cleaning procedures was weighed in grams. Dislodging forces of luted coping-abutment assemblies were obtained by using pull-off tests in a universal testing machine (crosshead speed of 0.5 mm/minute) after 24 hours of water storage. Means and standard deviations were calculated for ECL and for retention force values, and Mann-Whitney and ANOVA tests were carried out to detect significant differences (α = .05) among groups. Cement remnants were found in all specimens despite the cleaning procedures, with a typical distribution in interproximal areas. Mean ECL values for the GI and UN groups were 0.0079 ± 0.0060 and 0.0107 ± 0.0081, respectively. No statistically significant differences were found between tested cements (P = .3284). Removal stress values (MPa) were significantly higher (P = .0313) for the UN group (12.4 ± 6.5) than for the GI group (6.57 ± 4.69). Similar amounts of undetected cement remnants were discovered around the esthetic margins of zirconia crown copings regardless of cement type. The luting procedure using the self-adhesive resin cement provided significantly higher early retention values than the RMGI material.

Retention force of overdenture retained with telescopic crowns: A comparison of polyether ether ketone and zirconia ceramic telescopic crowns

Introduction/Objective. Recently, new materials for double crowns have been introduced, such as zirconia and polyether ether ketone (PEEK). However, some characteristics of these materials, such as retentive force and duration of ?settling in phase,? have not been investigated sufficiently. During the ?settling in phase,? telescopic overdenture has not yet achieved its definitive retention force, and it can be harmful for periodontal tissue if the value is above optimal for a long period of time. The objective was to measure the in vitro overall pull-off force of telescopic crowns where primary crowns were made from zirconia ceramics and a survey of the ?settling in phase? duration. Methods. Forty zirconia primary telescopic crowns were produced on prepared canine teeth. Twenty secondary crowns were of PEEK and other 20 of zirconia with electroplated gold copings. The pull-off force measurements were conducted utilizing a dynamometer until a constant value was obtained. Results. The specimens of the PEEK group showed higher initial retentive force values. Settling in phase was finished between 800 and 900 cycles of separation for both groups. Comparing the value of the pull-off force between individual different cycles, a statistically significant reduction was recorded up to the 800th cycle, while between the 800th and the 900th cycle there was no difference. Conclusions. The settling in phase was finished between 800 and 900 cycles of separation in both groups. Final retentive force values for both tested telescopic groups were in the optimal range which is 5?9 N per one telescopic crown.

Internal porosities, retentive force, and survival of cobalt–chromium alloy clasps fabricated by selective laser-sintering

PurposeThe purpose of this study was to evaluate internal porosities, retentive force values and survival of cobalt–chromium (Co–Cr) alloy clasps fabricated by direct metal laser-sintering (DMLS) and compare them to conventionally cast clasps. MethodsEmbrasure clasps were digitally designed fitting teeth 35 and 36 on identical metal models (N = 32). Sixteen clasps were fabricated using DMLS (group DMLS) and another sixteen clasps were additively manufactured from wax and then cast from a Co–Cr alloy (group CAST). Internal porosities were examined using micro-focus X-ray (micro-CT) and analyzed applying Kolmogorov–Smirnov test, Mann–Whitney test, and T test (significance level: p < 0.050). A universal testing machine was used to determine the retentive force values at baseline and after 1095, 5475, 10,950 and 65,000 cycles of simulated aging. Data were analyzed employing Kolmogorov–Smirnov test, one-way ANOVA, and Scheffé’s post-hoc test (significance level: p < 0.050). Survival was estimated for 65,000 cycles of artificial aging using Kaplan–Meier analysis. ResultsMicro-CT analysis revealed a higher prevalence (p < 0.001), but a more homogeneous size and a significantly smaller mean (p = 0.009) and total volume (p < 0.001) of internal porosities for group DMLS. The groups showed mean initial retentive force values of 13.57 N (CAST) and 15.74 N (DMLS), which significantly declined over aging for group CAST (p = 0.003), but not for group DMLS (p = 0.107). Survival was considerably higher for group DMLS (93.8%) than for group CAST (43.8%) after 65,000 cycles of aging. ConclusionsClasps made by laser-sintering could be an alternative to conventional cast clasps for the fabrication of removable partial denture frameworks.

Chewing simulation of zirconia implant supported restorations

PurposeTo test three potential prosthetic material options for zirconia implants in regard to their mechanical properties, loading and retention capacity as well as to record abrasion after chewing simulation followed by thermocyclic aging. MethodsMolar crowns (n = 96) of three different computer-aided design/computer-aided manufacturing (CAD/CAM) materials were produced and cemented on zirconia implants (ceramic.implant, Vita) with a diameter of 4.5 mm. Monolithic zirconia (Vita YZ [YZ] with RelyX Unicem 2 Automix [RUN], polymer-infiltrated ceramic (Vita Enamic [VE]) with Vita Adiva F-Cem [VAF] and acrylate polymer (CAD Temp [CT]) with RelyX Ultimate [RUL]. Fracture load and retentive force of the crowns were measured after 24 h water storage at 37 °C and after a chewing simulation followed by thermocyclic aging. Abrasion was recorded by matching stereolithography-data of the crowns obtained before and after chewing simulation. Additionally, the mechanical properties and bonding capabilities of the crown and cement materials were assessed. ResultsFracture load values were significantly highest for YZ > VE = CT. Retention force values did not differ significantly between the materials. The aging procedure did not affect the fracture load values nor the retention force significantly. Abrasion depth of the crowns was lowest for YZ followed by VE and CT. On unpolished crowns, abrasion of YZ and VE tended to be higher than on polished specimens. ConclusionsBased on the obtained in-vitro results, all tested materials can be recommended for the use on zirconia implants, although CT is only approved for temporary crowns. The loading and retention capacity of the materials were not significantly affected by aging.

Retentive force of PEEK secondary crowns on zirconia primary crowns over time.

The purpose of the present study was to evaluate the retentive forces of CAD/CAM-fabricated polyetheretherketone (PEEK) secondary crowns on zirconia primary crowns over an artificial aging period representing 10years of clinical service and compare them to electroformed secondary crowns made from pure gold. Implant-supported zirconia primary crowns (N = 20) were CAD/CAM milled and provided either with electroformed secondary crowns (group ZE; N = 10) or CAD/CAM-fabricated PEEK secondary crowns (group ZP; N = 10). All secondary crowns were attached to a casted tertiary structure to ensure adequate stability. A universal testing machine was used to determine the retentive force values at baseline and after 1, 3, 5, and 10years of simulated aging in the presence of artificial saliva. Data were analyzed applying Kolmogorov-Smirnov, Kruskal-Wallis, and Mann-Whitney U test. Level of significance was set at p < 0.05. Retentive forces were not different for the groups ZE and ZP at baseline (median ZE 2.85N; ZP 2.8N; p ≤ 0.218). Because retentive force values changed significantly over simulation time for group ZE (Kruskal-Wallis; p ≤ 0.028), the values between the test groups ZE and ZP differed significantly (Mann-Whitney U) at 5years (ZE 3.03N; ZP 2.76N; p ≤ 0.003) and 10years (ZE 3.1N; ZP 2.78N; p ≤ 0.011). PEEK secondary crowns exhibit stable retentive force values over 10years of simulated aging showing no signs of deterioration while the retentive force values of electroformed secondary crowns increase over time. PEEK might be a suitable alternative to proven metallic materials for the fabrication of secondary crowns.

ANALYSIS OF EFFECTS OF MECHANICAL LOADS, THERMAL FLUCTUATIONS AND CHEMICAL FACTORS ON THE BOND STRENGTH OF RESIN CEMENT TO TITANIUM AND CoCrMo ALLOYS IN IMPLANT SYSTEMS – IN VITRO STUDY

Introduction: Cements in the oral cavity are subjected to many factors affecting cement retention, the major ones being masticatory loads and thermal stress. The gold standard in cementing restorations in the contemporary implant prosthodontics are resin cements while their predisposition to the effects of oral cavity environment presents a major factor for the efficiency of dental implant treatment. Material and method: In the study, we used 40 test models made up of a combination of original components of the Nobel Biocare system (implant replica NobRplN and titanium suprastructure Easy abatement NP 0.75) and the restoration cast in CoCrMo alloy. The specimens were divided in 4 test groups with 10 specimens each. The specimens in each group were cemented with resin composite cement with or without using the metal primer. Group I – Multilink Implant, IvoclarVivadent, Liechtenstein, Group II – Multilink Implant, IvoclarVivadent, Liechtenstein + Monobond Plus, Group III G-CEM LinkAce®, Group IV - G-CEM LinkAce® + GC Metalprimer II. The specimens were stored in 100% relative humidity for 24 hours whereupon each group underwent 5 rounds of testing. The specimens were subjected to thermal and mechanical load cycling tests whose number reflected the period of simulation of the function in the oral cavity (unloaded specimens, 7 days of function, 3 months, 6 months and 12 months). The retention force was measured by the Universal testing machine. Results: The highest retention values of the resin composite cement were recorded during the initial tests, which then declined in the subsequent rounds of testing. The biggest fall was measured in the first week after the cementation, while the cross-comparison of the later rounds of testing did not show any statistically significant differences. The values of the retention force of resin composite cements 12 months after the cementation dropped by one third of the initial values. All recorded values were higher in the specimens with primer coating. Conclusion: Masticatory forces and temperature changes in the oral cavity reduced the retention values of resin cement, but its values after 12 months of function were still high and provided stability and retention of the restoration in function. The usage of metal primer had a significant effect on retention force values at all levels of testing.

The Evaluation of Changes in Retention Force Values in Three-Element Telescopic Crown Systems using Simulated Load Cycles

The Evaluation of Changes in Retention Force Values in Three-Element Telescopic Crown Systems using Simulated Load Cycles