Dislodgement Forces Research Articles

The effect of cyclic dislodgement and denture cleanser storage on various attachment systems used in implant-overdenture prostheses.

The present study aims to evaluate and compare the retention forces of nylon and polyetheretherketone (PEEK) attachments with different color codes over time and denture cleansers. Two plexiglass models were prepared for this study. In the first model, two Astra-Tech EV implants and two Locator abutments were placed, followed by the placement of two corresponding housings in the opposite blocks where nylon attachments were fitted. The second model was mounted with two Medentika Microcone RI implants and two Novaloc abutments. PEEK attachments were then placed in the corresponding housings. Blue-pink-clear nylon and white-yellow-green PEEK attachments' (n=8 for each group) maximum dislodgement forces were measured at baseline (T0). Second measurements were conducted after 1080 insertion and removal cycles (T1). Corega denture cleanser solution was prepared by adding one tablet to 200mL of tap water. All attachments were soaked in the solution for three minutes and rinsed under running water. Each group of attachments was soaked for 1080min in total, corresponding to 1 year of clinical use. The final measurements were conducted after storage in the solution. One specimen and abutment were randomly selected from each group and examined using a scanning electron microscope. The data were analyzed by repeated measures ANOVA and Bonferroni multiple comparison test (p<0.05). The percentage decrease in the dislodgement force of the attachments was also calculated. Insertion and removal cycles significantly affected the retention values (p<0.001). Storage in the cleanser did not significantly affect the retention (p>0.05). The lowest retention value was observed in blue nylon attachments (501.50±33.39gf [gram force]) after insertion-removal (T1), with a similar trend after immersion (476.13±39.75gf) (T2). The highest retention was observed similarly in clear nylon attachments (1660.38±41.73gf) after insertion-removal after immersion (1636.50±62.20gf) (T2). In terms of percentage loss of retention, yellow PEEK attachments were the most affected group after all test procedures (36.88%), while the lowest affected group was pink nylon attachments (21.56%). PEEK attachments were the least affected by the denture cleanser but the most affected by insertion and removal cycles. Corega denture cleanser had no significant effect on nylon or PEEK attachments, whereas the insertion-removal cycle had a significant effect on both attachment systems.

Tensile Bond Strength, Fit Accuracy and Failure Types of Zirconia and Cast Gold Root Copings for Overdentures.

To compare the tensile strength, dislodgement forces, marginal gap and failure types between digitally fabricated zirconia root copings and conventionally manufactured cast gold root copings. Extracted human teeth (N=30) were prepared for the root copings and randomly divided into 2 groups: (1)zirconia root copings(ZC) and gold root copings(GC). The specimens were tested for tensile bond strength and dislodgement forces in a universal testing machine and the types of the coping failures modes were analyzed. In addition, the marginal gap was measured. Data were analyzed using one-way ANOVA and Pearson correlation test. Mean tensile bond strength in the total horizontal adhesive area for ZC group was 7.5±2.8MPa and for GC group 10.5±4.8 MPa(p⟩0.05). The mean dislodgement forces for the ZC and GC groups were 242±107N and 311±118N, respectively and with no significant differences between the groups (p=0.12). The mean vertical marginal gap in the ZC group amounted to 27±11.05μm, while in the GC group it was 35.33±10.49μm, showing no statistically significant difference between the two groups (p=0.058). Mixed failure modes were more common (93%) in both groups. In terms of all tested parameters, the zirconia root copings were comparable to the gold copings.

Evaluation of the dislodgement force of splinted restorations with engaging conical abutments over multiple nonparallel implants (in-vitro study)

BackgroundSplinted multiunit cement-retained restorations with screw access channels over engaging abutments are viable implant prosthetic options. However, information regarding the maximum degree of divergence between multiple implants is lacking. The purpose of this in vitro study was to determine the maximum degree of divergence between 2 adjacent implants with conical connections that allows insertion and removal of splinted restorations with engaging preparable abutments or titanium base abutments.MethodsTwo implants were aligned in a stone base, one straight and the other at an angle ranging from 0 to 20 degrees. The implants represented an implant system that had an internal conical connection and a hexed abutment engaging the base of the connection. Two straight preparable engaging cement retained abutments were screwed onto the implants and splinted together using acrylic resin. A total of 11 angles were tested, with 7 specimens for every angle. Evaluation of dislodging force was performed by pulling out the splinted abutments after unscrewing them. This was performed subjectively by 3 blinded investigators who applied a tactile pulling force. A scale of 0–10 was used to estimate the pulling force. Objectively the dislodging force was measured in Newtons using a universal testing machine. A statistical correlation was made between the subjective and objective dislodging force values using Spearman’s rank correlation coefficient.ResultsThe mean subjective values increased gradually from 0 to 16 degrees. A sudden rise was noticed at 18 degrees (9.71 ± 0.23) and, at 20 degrees, the investigators were not able to remove the splinted abutments from the implants. The mean objective dislodgement force values increased gradually from 0 to16 degrees and abruptly from 16 degrees (13.57 ± 0.45 N) to 18 degrees (25.40 ± 0.66 N) and 20 degrees (35.22 ± 0.64). The correlation between the subjective and the objective evaluations assessed using the Spearman’s rank correlation coefficient was 0.98 indicating a statistically significant correlation (P < .001). As the objective dislodging force increased, the subjective dislodgement difficulty increased.ConclusionsSplinting cement retained restorations with screw access channels on engaging abutments is possible when multiple implants with conical connections having an internal flare angle of 8 degrees are used, with implant divergence of up to 16 degrees.

Influence of Denture Cleansers on the Retention Loss of Attachment Systems Retained Implant Overdenture.

This study aimed to evaluate the effects of different denture cleansing solutions (DCSs) on the retention of Locator and Locator R-Tx attachment systems of implant retained overdentures (IRO). Two part acrylic resin blocks were fabricated, upper part contained metal housing and plastic inserts and lower part contained implant analogs and abutments. Eighty pink plastic inserts (40/attachment, 10/solution) were immersed in Corega, Fittydent, sodium hypochlorite, and water for a time simulating upto 1-year of clinical usage. Acrylic blocks were held on a universal testing machine for a pull-out test to record the dislodgement force. Measurements were conducted after 6 months (T1) and 12 months (T2). One-way ANOVA followed by Tukey's HSD test was used to analyze the results (α = 0.05). For both attachments, retention significantly decreased after immersion in different solutions at T2 (P < 0.001). Locator R-Tx attachment in NaOCl showed a significant decrease in retention compared with other solutions at T1. At T2, there was a significant decrease in retention for all DCS compared with water (P < 0.001). Locator R-TX showed higher retention values per solution compared to Locator attachment (P < 0.001). In terms of retention loss %, NaOCl recorded the highest (61.87%) loss, followed by Corega (55.54%) and Fittydent (43.13%), whereas water demonstrated the best retention (16.13%) in both groups. Locator R-TX has better retention with different DCS immersion. The loss of retention varied with different types of DCS and NaOCl recorded the highest retention loss. Therefore, denture cleanser selection must be guided by the type of IRO attachment.

An In vitro Comparison of Retention of Provisional Crowns Cemented with Provisional Cement Enriched with Three Different Additives

Introduction: Dental caries remains a constant problem in clinical practice. The rates of recurrent caries around long-term provisional restorations may be even higher due to poor marginal adaptation and less stable materials. Since provisional crowns luted with provisional cement are susceptible to bacterial infiltration and caries, antibacterial and anticariogenic agents have been added to provisional cement, and retention of the provisional crown has been evaluated in this study. Materials and Methods: Ten extracted maxillary first premolar teeth were selected. Standardised tooth preparation was done. A total of 40 provisional crowns were fabricated using tooth-coloured auto-polymerising acrylic resin. The prepared provisional crowns were divided into four groups of 10 crowns each. Crowns were cemented on the prepared teeth after enriching with the three solutions individually. All specimens were stored in 100% humidity at 37°C for 1 h, thermocycler 100 times between 5°C and 55°C with a dwell time of 10 s and then stored at 100% humidity at 37°C. Cemented crowns were subjected to tensile dislodgement force using a universal testing machine with a crosshead speed of 5 mm/min. Results: Provisional cement enriched with Profluorid Varnish has shown properties of the highest tensile dislodgement force, with chlorhexidine-reduced retention. Conclusion: The present study concluded that Profluorid Varnish, as an additive in non-eugenol provisional cement (Provicol), is more effective in increasing retention.

Dislodgement pushout resistance of five bioceramic root-end filling materials.

This study evaluated the dislodgement push-out resistance of five bioceramic materials. One hundred single-rooted teeth with one canal had the apical 3 mm and crown resected to create a 14 mm standardized length. The canals were instrumented to an apical size 80 with a 3 mm root-end preparation made with ultrasonic diamonds. The prepared roots were randomly divided into 5 root-end restorative groups (n=20). ProRoot MTA, Biodentine, EndoSequence Root Repair Material, EndoSequence Fast Set Putty, and EndoSequence BC Sealer with each material placed following manufacturer's instructions and stored at 100% humidity for 2 weeks. An apical-to-coronal static testing load with the identified dislodgement force converted into MPa with mean results analyzed with Kruskal-Wallis and Dunn's post hoc tests (α=0.05). ProRoot MTA and Biodentine displayed similar push-out stress resistance and exhibited significantly greater stress resistance than the similar Endosequence materials. However, all materials failed cohesively and were not dislodged from the root canal surface.

Stent dislodgement force of drug-eluting coronary stents: a bench test.

Coronary stent dislodgement can cause critical complications. The dislodgement force of coronary drug-eluting stents (DES) remains unknown. This study aimed to compare the dislodgement force and pattern of contemporary DES. Five DES designs which commonly used in clinical practice were tested. The force at which the stent dislodges relative to the balloon was measured. For the shim test, peak displacement force, defined as the first peak force that occurs during stent displacement and peak dislodgement force, defined as the peak force required to completely dislodge the stent from the delivery system, were measured. Three examples of each of the stents were tested using the shim test. The peak displacement force of Orsiro (3.1±0.8 N) was lower than that of Xience Sierra (5.8±0.5 N) [Firehawk 3.8±0.2 N, Resolute Onyx 4.5±1.5 N, Synergy 4.8±0.5 N (P=0.024)]. The peak dislodgement force was lowest in Orsiro (3.2±0.8 N) when compared to the other stents (Firehawk 6.6±0.6 N, Resolute Onyx 7.4±0.3 N, Synergy 11.8±0.4 N, Xience Sierra 11.1±1.6 N) (P<0.001); this remained significant in the multiple comparison analysis. During pullback of the stents, most stents buckled without removal. However, the whole Orsiro stent was completely removed from the delivery system. The dislodgement force of DESs differed between stent designs. The Orsiro stent was lower than that of other DES; additionally, it easily removed the whole stent from the delivery system. During the coronary intervention, operators should consider stent design and be cautious when pulling DES back in lesions with calcifications or a previously implanted stent, which are at high risk for stent dislodgement.

Combining Suction and Friction to Stabilize a Soft Gripper to Shear and Normal Forces, for Manipulation of Soft Objects in Wet Environments

Soft robotic gripping in wet environments is generally limited by the presence of a liquid that lubricates the interface between the gripper and an object being manipulated. The use of soft grippers is particularly beneficial for manipulating soft, delicate objects, yet is further limited by low grip strengths. We propose the use of suction, a form of adhesion that functions well in wet environments, to enhance soft robotic grippers. We stabilized the suction against shear disturbances using soft actuated fingers decorated with fluid-channeling patterns to enhance friction, counteracting the interfacial lubrication experienced in wet environments. We therefore combined the uses of attachment via suction and shear stability via friction to create an adhesive soft gripper. We evaluated the contributions to attachment of each component to help stabilize it against dislodgement forces that act in parallel and normal to an object that it aimed to manipulate. By identifying these contributions, we envision that such an adhesive gripper can be used to benefit soft robotic manipulation in a variety of wet environments, from surgical to subsea applications.

Anchorage by seed mucilage prevents seed dislodgement in high surface flow: a mechanistic investigation.

Seed mucilage is a common and highly diverse trait shared among thousands of angiosperm species. While it has long been recognized that mucilage allows seeds to anchor to substrates (antitelechory), resisting abiotic and biotic dislodgement, we still lack a mechanistic understanding of this process. We propose a mechanistic model of how mucilage affects substrate anchorage and fluid resistance, ultimately contributing to dislodgement resistance. To test this model, we subjected mucilaginous seeds of 52 species, varying in eight measured seed traits, to 7 d of continuous water flow at a range of dislodgement potentials. Supporting our model, mucilage mass increased the force necessary to dislodge both dry and wet seeds; our measurement of the dislodgement force of dry mucilage explained time to dislodgement well. The effect size was remarkably large; increasing the standardized mucilage mass by 1 s.d. resulted in a 280-fold increase in the time to dislodgement. Fluid resistance was largely dependent on the speed of water flow and the seed's modified drag coefficient, but not seed traits. Neither mucilage expansion speed nor mucilage decay rate explained dislodgement potential well. Our results suggest that the degree of anchorage to a substrate, measured with a simple dislodgement force assay, is highly predictive of mucilaginous seed retention in highly erosive environments. In contrast, we found that other seed and mucilage traits are of lesser importance to anchorage.

Evaluation of Retention Forces of Implant-Supported Zirconia Copings on Titanium Abutments Coated with Metal Opaquers Using Different Cements.

To evaluate the use of a new resin metal opaquer on the surface of titanium abutments, in combination with two luting agents, and its effect on the retentive strength of implant-supported zirconia copings. Sixty customized titanium abutments were designed and fabricated with virtual design software and a milling machine. Thirty abutment specimens were coated with metal opaquers, and the others were not coated. Then, the titanium abutments were fitted into the implant analogs, and the abutment-implant analog complexes were embedded in acrylic resin blocks. Sixty CAD/CAM-fabricated zirconia copings were seated on the abutments and secured with glassionomer cement or self-adhesive resin cement. The specimens were stored in 100% humidity for 1 hour and artificial saliva for 23 hours at 37°C before thermocycling for 5,000 cycles of 5°C to 55°C with a 30-second dwell time. The retentive strength was measured using a pull-out test with a universal testing machine. The dislodgment forces were statistically analyzed via two-way analysis of variance (ANOVA). The failure modes were evaluated and categorized by examining the fracture surface. The metal opaquer material had a significant negative effect on retention of zirconia copings. The nonopaquer titanium abutments showed significantly (P < .05) higher retentive strength than the metal opaquer abutments. Comparing the cements, the retentive strength values of self-adhesive resin cement were significantly higher than those of glass-ionomer cement. The metal opaquer groups exhibited mostly mixed-type failures, a combination of adhesive failures and cohesive failures, whereas the nonopaquer groups showed mostly adhesive-type failures. The titanium abutments coated with the new metal opaquer material resulted in a reduction of retentive strength. Self-adhesive resin cements exhibited significantly higher retention than glass-ionomer cements.

Performance evaluation of biodegradable polymer sirolimus and ascorbic acid eluting stent systems

The purpose of this study was to evaluate the performance of biodegradable polymer sirolimus and ascorbic acid eluting stent systems with four commercially available drug-eluting stents (DES). We investigated the characterization of mechanical properties by dimension, foreshortening, recoil, radial force, crossing profile, folding shape, trackability, and dislodgement force. Additionally, we identify the safety and efficacy evaluation through registry experiments. Each foreshortening and recoil of D + Storm® DES is 1.3 and 3.70%, which has better performance than other products. A post-marketing clinical study to evaluate the performance and safety of D + Storm® DES is ongoing in real-world clinical settings. Two hundred one patients were enrolled in this study and have now completed follow-up for up to 1 month. No major adverse cardiovascular event (MACE) occurred in any subjects, confirming the safety of D + Storm® DES in the clinical setting. An additional approximately 100 subjects will be enrolled in the study and the final safety profile will be assessed in 300 patients. In conclusion, this study reported the objective evaluation of DES performance and compared the mechanical responses of four types of DES available in the market. There is little difference between the four cardiovascular stents in terms of mechanical features, and it can help choose the most suitable stent in a specific clinical situation if those features are understood.Graphical abstract

Mucilage binding to ground protects seeds of many plants from harvester ants: A functional investigation

Abstract The seeds of many plant species produce mucilage on their surfaces that when wetted and dried, firmly adheres seeds to surfaces and substrates. Previous studies have demonstrated that seed anchorage to the ground can reduce seed predation, although only a few species have thus far been tested. Here we investigated whether binding to the ground reduces seed removal by harvester ants Pogonomyrmex subdentatus, an important granivore, for 53 species with mucilaginous seeds. We also explored functional traits that associate with seed removal risk to understand the ecological and evolutionary context of this granivory resistance trait. Using a field cafeteria choice experiment, we compared harvester ant seed removal of wetted ground‐bound seeds to dry unbound control seeds for these 53 species. We developed a simple assay to score dislodgement force. We examined whether this force, seed mass and seed mucilage production explained the interspecific variation in protection that we observed in field seed removal. We integrated these experiments with a broad scale test of correlates of seed attachment using a previously published dataset of attachment potential of mucilaginous seeds for 432 species, examining correlations of attachment potential with 13 plant traits and the climate characteristics of the species' range. Binding to the ground reduced seed removal in 42 of 53 species tested. The benefit increased with seed dislodgement force, which itself increased with mucilage production, but not with seed mass. In the larger dataset, shorter plant life span, higher temperature, more solar radiation, higher humidity, fewer wet days per year and higher seed density correlated positively with the odds of seed attachment. We also found that attachment potential showed a concave down quadratic relationship with latitude, peaking at roughly 30°. No strong evidence that any of the other six predictors correlated with attachment potential was found. We demonstrate that protection from granivores is a widespread convergent function of seed mucilage and is associated with mucilage production. We highlight the need for increased mechanistic investigations into this common but poorly studied trait, particularly in relation to functional drivers of the broad patterns we found. A free Plain Language Summary can be found within the Supporting Information of this article.

Self-Expanding Anchors for Stabilizing Percutaneously Implanted Microdevices in Biological Tissues.

Percutaneously implanted miniaturized devices such as fiducial markers, miniaturized sensors, and drug delivery devices have an important and expanding role in diagnosing and treating a variety of diseases. However, there is a need to develop and evaluate anchoring methods to ensure that these microdevices remain secure without dislodgement, as even minimal migration within tissues could result in loss of microdevice functionality or clinical complications. Here we describe two anchoring methods made from biocompatible materials: (1) a self-expanding nitinol mesh anchor and (2) self-expanding hydrogel particles contained within pliable netting. We integrate these anchors into existing drug-screening microdevices and experimentally measure forces required to dislodge them from varying tissues. We report similar dislodgement forces of 738 ± 37, 707 ± 40, 688 ± 29, and 520 ± 28 mN for nitinol-anchored microdevices, and 735 ± 98, 702 ± 46, 457 ± 47, and 459 ± 39 mN for hydrogel-anchored microdevices in liver, kidney, fat, and muscle tissues, respectively—significantly higher compared with 13 ± 2, 15 ± 3, 15 ± 2, and 15 ± 3 mN for non-anchored microdevices (p < 0.001 in all tissues). The anchoring methods increased resistance to dislodgement by a factor of 30–50× in all tissues, did not increase the required needle gauge for insertion, and were compatible with percutaneous implantation and removal. These results indicate that anchoring significantly improves microdevice stability and should reduce migration risk in a variety of biological tissues.

Dislodgement Forces and Cost Effectiveness of Dressings and Securement for Peripheral Intravenous Catheters: A Randomized Controlled Trial.

Objectives: Peripheral intravenous catheters (PIVC) are the most frequently used invasive devices in medicine. PIVC failure before treatment completion is a significant concern and occurs in 33–69% of patients. Partial dislodgement and accidental removal are some of the reasons for PIVC failure. The most effective dressing and securement method for preventing accidental removal remains unclear. It was the aim of this study to compare the force required to dislodge a PIVC with four commonly used dressing and securement methods. Additionally, costs were calculated. Methods: Truncated 18-gauge i.v. cannulas were attached onto the forearm of 209 volunteers using four different dressings and securements (sterile absorbent wound dressing covered by two different types of elastic polyester fleece, bordered and non-bordered polyurethane). The force during continuously stronger pulling until dislodgement was recorded. Results: The highest resistance against dislodgement forces could be observed with a sterile absorbent wound dressing covered by two incised elastic polyester fleece dressings. Commercially-manufactured bordered and non-bordered polyurethan film dressings were 20% to 75% more expensive than sterile absorbent wound dressings covered by elastic polyester fleece dressing. Conclusions: Elastic polyester fleece secured a PIVC against accidental removal by external force best, compared to commercially-manufactured bordered and non-bordered polyurethane film dressing.

Long-term retention of zirconia crowns cemented with current automixed cements

Statement of problemAutomixing and dispensing cements is a straightforward approach with consistent dosing. Previous studies have demonstrated clinically significant differences in crown retention between power-liquid and paste-paste forms of the same cement, as the composition between the 2 differs. A self-adhesive modified-resin (SAMR) and a resin-modified glass ionomer (RMGI) cement, originally offered as a powder-liquid, are now in common use as paste-paste automixed cements. With the increased use of zirconia restorations, the long-term retention of zirconia crowns for these 2 automixed cements should be evaluated. PurposeThe purpose of this in vitro study was to determine whether zirconia crowns cemented with 2 automixed cements provided clinically acceptable retention after 6 months of aging with monthly thermocycling. Material and methodsExtracted molars were mounted in resin and prepared with a flat occlusal surface, 20-degree taper, approximately 4-mm axial length, and with the axio-occlusal line angle slightly rounded. Prepared teeth were equally distributed into 3 cementation groups (n=12) to achieve nearly equal mean preparation surface areas for each group. Zirconia crowns (IPS ZirCAD LT) were fabricated with an added occlusal bar to facilitate removal of the cemented crowns. Cement space was set at 45 μm axially and 55 μm occlusally. After sintering and before delivery, the intaglio surfaces were airborne-particle abraded with 50-μm alumina at 275-kPa pressure for 3 seconds and then steam cleaned. Cements were the original powder-liquid RelyX Luting (RMGI; RXL) as the control, paste-paste, automixed systems RelyX Luting Plus Automix (RMGI; RXLA), and RelyX Unicem 2 Automix (SAMR; RXUA). Crowns were cemented under 196 N force, placed in an oven at 37 °C and 100% humidity during setting and then thermocycled (5 °C-55 °C) for 5000 cycles monthly for 6 months. The crowns were removed axially with a universal testing machine at 0.5 mm/min. Removal forces were recorded and dislodgement stress calculated by using the surface area of each preparation. One-way ANOVA was used for dislodgement stress and force. Chi-square test was used for cement location after testing (α=.05). ResultsRXLA demonstrated considerably lower crown retention (1.3 MPa) and differed significantly (P<.001) from RXUA (3.1 MPa) and RXL (3.1 MPa). Modes of failure showed most of the cement remaining only in the crown intaglio for RXLA for all specimens, whereas half of the crowns for RXL and RXUA demonstrated cement adhesion to both dentin and the intaglio surface, indicating cohesive failure of the cement at separation. As the Levene test was significant, the Games-Howell test was used for mean differences. The χ2 analysis was significant. ConclusionsAfter long-term aging with monthly thermocycling, high-strength zirconia crowns were strongly retained by 2 (RXL, RXUA) of the 3 cements. Crown retention for RelyX Luting Plus Automix was less than half in comparison and with cement found only on the intaglio surface after separation.

THE EFFECT OF IMPLANT LOCATIONS ON THE STRESS TRANSMITTED TO IMPLANT-TOOTH-ASSISTED PARTIAL OVERDENTURE (IN VITRO STUDY)

Introduction: Posterior free end edentulous areas are more prevalent among population. Absence of posterior abutments to support and retain partial dentures affects the prognosis of prostheses. A problem of support, retention and stability is usually associated with distal extension removable partial dentures. Objectives: To evaluate and compare the effect of implant locations on the retention of the prostheses of implant tooth assisted partial overdenture for mandibular Kennedy class II with implant located in first premolar area and second molar area. Second objective was to evaluate the wear of female parts of the attachments attached to these implants. Materials and methods: The study was conducted on two parallel groups according to the different implant locations: Group (A) implant in first premolar area, Group (B) implant in second molar area. Two acrylic models with Kennedy class II were used in this study. Two implants with (2.3mm length and 3.6mm width), two positioner attachments were attached to implants and inserted in the previous locations for both groups. Each group had 9 sets of attachments with 3 different colored plastic matrices (27 matrices) with different retention force. A metallic overdenture with acrylic resin base and teeth was constructed for each group. By using the universal testing machine, vertical load dislodgment forces were measured at anterior of the saddle of the denture and posterior of the saddle of the denture for both groups at the beginning of the study (initial retention) and after 50,000 cyclic with load of 20 K at first molar area, the retention test was repeated and the mean value was recorded. All retention parts were imaged under stereomicroscope to study wear and attrition of internal components. All data from both groups in this in-vitro study was gathered, tabulated and statistically analyzed. Results:In vertical dislodging, Group (B) posterior of the saddle, recorded the highest retention force. In Group (B) anterior of the saddle recorded the lowest retention force. After 50,000 cyclic loading, Group (B) posterior of the saddle was higher than Group (A) in retention force. Dimensional changes and wear scratches appeared in the metal housing and plastic matrices in central and outer lines. Conclusions: The distal position of the implant with positioner attachment has great retention during vertical dislodgment compared with mesial implant location with positioner attachment.

Plated metal adhesion to picosecond laser-ablated silicon solar cells: Influence of surface chemistry and wettability

This study investigated the influence of UV picosecond laser fluence, used to ablate the SiNx antireflection coating for Ni/Cu/Ag plated p-type Si solar cells, on busbar and finger adhesion and cell electrical performance. Surface chemistry was characterised post-ablation and post-pre-treatment in 7:1 buffered oxide etch (BOE) using a combination of X-ray photoelectron spectroscopy and contact angle measurements. Although growth of laser-induced Si oxides increases with increasing laser fluence, these oxides are effectively removed in the BOE pre-treatment and therefore do not impact plated metal adhesion with busbar pull forces of 1.9 ± 0.7 N/mm being achieved when a laser fluence of 0.63 J/cm2 was used to ablate the busbar openings. It is also revealed that the use of high laser fluence leads to a more hydrophobic surface due to reduced residual SiNx, however the complete wetting of the ablated Si surface can be ensured by the use of surfactants in Ni plating electrolytes. Residual SiNx impacts Ni silicidation and reduces the busbar pull force to values of only 0.8 ± 0.5 N/mm when average laser fluences ≤0.45 J/cm2 are used. Finger dislodgement forces are interestingly shown not to be affected by laser fluence and presence of residual SiNx, providing an opportunity to optimise the laser ablation process separately for finger and busbar openings. Finally, it is demonstrated that the use of higher laser fluences does not impact the electrical performance of the Al back surface field cells, with open-circuit voltages of ≥637 mV and fill factors ≥80.4% being demonstrated for cells where the average laser fluence used was varied between 0.35 and 0.63 J/cm2.

Dislodgement force analysis of an overdenture attachment system

Statement of problemThe performance of a recently introduced overdenture attachment system after cyclic dislodgement is not known. PurposeThe purpose of this in vitro study was to compare a conventional attachment system and a recently introduced attachment system for their dislodgement forces before and after cyclic dislodgement. Material and methodsThree acrylic resin models were fabricated with 2 implant analogs (4.1 mm; Zimmer Dental) in different angulations; parallel in the first, divergent by 30 degrees in the second, and divergent by 60 degrees in the third model. Six acrylic resin blocks containing 2 metal housings of 2 different LOCATOR attachments (LOCATOR Legacy [LL], R-Tx, n=3; Zest Dental Solutions) were also fabricated. LOCATOR abutment pairs (LL and R-Tx) were placed onto the analogs. Seven specimens for LL and R-Tx with pink attachments were tested for dislodgement forces, and the values were recorded before and after 1440 times (simulated 1-year use) of cyclic dislodgement using an occlusal loading simulator machine. A 3-way ANOVA was used for dislodgement force comparison before and after cyclic dislodgement for different angulations and for 2 different LOCATOR attachments. Any significant differences were identified with the Tukey HSD test (α=.05). The percentage decrease in the dislodgement force was also calculated. ResultsA significant 3-way interaction was found for the LOCATOR type, implant angle, and time (P<.001). LOCATOR type made a difference for only parallel and 60 degree–divergent implants before cyclic dislodgement (P≤.022). After cyclic dislodgement, a significant effect of the LOCATOR type on dislodgement force was found for only parallel implants (P=.034). In both LOCATOR systems, the dislodgement force was different (P<.001) among different implant angulations, except for parallel to 30-degree comparison, before and after cyclic dislodgement. For both LL and R-Tx, significant differences (P≤.022) were found between before and after cyclic dislodgement for all angulations except LL in parallel (P=.214). ConclusionsWhen implants were parallel, initially, the dislodgement force of R-Tx was higher than that of LL; however, the forces were similar after cyclic dislodgement. When implants were divergent by 30 degrees, there were no differences between the dislodgement forces of the LOCATOR systems before and after cyclic dislodgement. When implants were divergent by 60 degrees, initially, the dislodgement force of LL was higher than that of R-Tx; however, the forces were similar after cyclic dislodgement. Before and after cyclic dislodgement, in each system, dislodgement forces were greater when implants were divergent by 60 degrees than when parallel and 30 degrees. After cyclic dislodgement, dislodgement forces decreased for both systems, except for LL when the implants were parallel.

Comparative evaluation of retention of zirconia copings and cast metal copings cemented onto titanium abutments: An In vitro study

Aim: This in vitro study was conducted to evaluate the retention of zirconia and cast metal copings luted to implant abutments using different luting agents. Subjects and Methods: Implant analogs were embedded in acrylic resin blocks, and titanium abutments were torqued at 35 N/cm onto the implant analogs. The samples were divided into two groups. Both Group A and B samples were then randomly divided into four groups each comprising specimens – Group 1, Group 2, Group 3, and Group 4. Copings were then cemented with resin modifies glass ionomer cement (GIC), GIC, zinc phosphate cement, and noneugenol zinc oxide cement, respectively. The cemented copings were subjected to tensile dislodgment forces using a crosshead speed of 5 mm/min. Results for the retention of the copings were statistically analyzed using factorial analysis of variance test. Results: Between the two copings, higher mean retention is recorded in zirconia compared to metal, and the difference between them is found to be statistically significant (P

Paracoccus seriniphilus adhered on surfaces: Resistance of a seawater bacterium against shear forces under the influence of roughness, surface energy, and zeta potential of the surfaces.

Bacteria in flowing media are exposed to shear forces exerted by the fluid. Before a biofilm can be formed, the bacteria have to attach to a solid surface and have to resist these shear forces. Here, the authors determined dislodgement forces of single Paracoccus seriniphilus bacteria by means of lateral force microscopy. The first measurement set was performed on very flat glass and titanium (both as very hydrophilic samples with water contact angles below 20°) as well as highly oriented pyrolytic graphite (HOPG) and steel surfaces (both as more hydrophobic surfaces in the context of biological interaction with water contact angles above 50°). The different surfaces also show different zeta potentials in the range between -18 and -108 mV at the measurement pH of 7. The second set comprised titanium with different RMS (root mean square) roughness values from a few nanometers up to 22 nm. Lateral forces between 0.5 and 3 nN were applied. For Paracoccus seriniphilus, the authors found as a general trend that the surface energy of the substrate at comparable roughness determines the detachment process. The surface energy is inversely proportional to the initial adhesion forces of the bacterium with the surface. The higher the surface energy (and the lower the initial adhesion force) is, the easier the dislodgement of the bacteria happens. In contrast, electrostatics play only a secondary role in the lateral dislodgement of the bacteria and may come only into play if surface energies are the same. Furthermore, the surface chemistry (glass, titanium, and steel as oxidic surfaces and HOPG as a nonoxidic surface) seems to play an important role because HOPG does not completely follow the above mentioned general trend found for the oxide covered surfaces. In addition, the roughness of the substrates (made of the same material) is limiting the lateral dislodgement of the bacteria. All examined structures with RMS roughness of about 8-22 nm on titanium prevent the bacteria from the lateral dislodgement compared to polished titanium with an RMS roughness of about 3 nm.