Mode Of Retention Research Articles

Removal force of conometric caps and abutments subjected to dynamic loading

Background Instead of using a cement- or screw-retained coupling, a conometric connection can be used. The retention of a single tooth friction-retained connection is dependent on the cone angle, coefficient of friction, push in force and the external load situation. Lateral forces, mainly occurring in the anterior region, can have an impact on the stability of a conical connection. This study was set up to investigate the stability of the conometric connection under dynamic lateral loading. Aim/Hypothesis The aim of the study was to evaluate the retention of a conical connection between cap and abutment loaded with dynamic lateral forces after an initial axial load. Material and Methods Conometric caps (Ankylos size A, Dentsply Sirona Implants) were assembled on conometric abutments (straight and angled) that were screwed into embedded implants. A spherical loading cap was plugged on and the samples were loaded axially (0°). The samples then were subjected to dynamic loading of 100 N (R = 0.1) at 5 Hz in an 82.5° setup for 10,000 cycles. Subsequently, the caps were pulled off to measure the retention of the conometric cap to the conometric abutment. Results After dynamic lateral loading all caps showed sufficient retention to the abutment. No cap was separated from the abutment during the tests. Tukey test shows that there is a significant difference between the retention of the conometric caps to straight and angled abutments (P = 0.05). This difference is related to the different connection geometries at the conometric connection for straight and angled abutments. Conclusions and Clinical Implications The conometric mode of retention is able to withstand lateral forces that are deemed to occur mainly in the anterior region (incisors). This implies that the conometric connection is feasible for use in single-tooth restorations in the anterior jaw segment.

Enigma of Fixed Retainers

Fixed retainers are a reliable form of retention for avoiding relapse and maintaining dental arch shape. They function regardless of patient cooperation, and they fulfill high esthetic expectations. Teeth have tendency to return to their former position, as time required for retaining the treatment result. The most appropriate mode of retention for the post-treatment situation should be used, based on a careful evaluation of the patient’s pretreatment diagnostic records, habits, cooperation, growth pattern, and age. Retention after orthodontic intervention is as important part of the therapy as the active treatment. Age and maturity of the patients, result of the orthodontic intervention, origin and character of the anomaly, type of the retainer, compliance of the patients; all can influence the chance of relapse. The retention period should be twice longer than the active orthodontic treatment. This article covers various aspect of fixed retention in detail

Experimental verification of the steric-entropic mode of retention in centrifugal field-flow fractionation using illite clay plates

The commonly used theory to describe the normal Brownian mode of field-flow fractionation (FFF) assumes the particles to be point masses and hence the shape is ignored. Beckett and Giddings extended this theory to include the effect of thin rods and discs being forced very close to the accumulation wall. By including the decrease in the entropy this causes, they derived new expressions for the retention of such nonspherical particles in FFF. The steric-entropic theory predicts that when the sample cloud thickness is less than the major dimension of the rods or discs then particles elute earlier than predicted by the Brownian mode theory. This leads to an underestimation of the buoyant mass and equivalent spherical diameter calculated from FFF data. In this paper we report for the first time experimental data for the retention of thin illite particles in centrifugal FFF that agrees well with these steric-entropic predictions. Not only do the size distributions calculated using the Brownian mode theory shift to lower size when the field is increased but the shift in the retention ratio of the peak maxima of the FFF fractograms could be predicted fairly accurately by the steric-entropic equations.

Mechanical performance of cement- and screw-retained all-ceramic single crowns on dental implants.

This in-vitro study was performed to compare the contact wear, fracture strength and failure mode of implant-supported all-ceramic single crowns manufactured with various fabrication and fixation concepts. Fifty dental implants (Conelog Ø 4,3mm/L11mm, Camlog Biotechnologies AG) were embedded and treated with all-ceramic molar single-crowns. Three groups received hand-layered zirconia crowns (IPS e.max Ceram/ IPS e.max ZirCAD, Ivoclar Vivadent AG): CZL (cement-retained zirconia-based layered) group crowns were cemented conventionally, SZL (screw-retained zirconia-based layered) group crowns were screw-retained, MZL (modified zirconia-based layered) group crowns showed a different coping design with screw retention. The specimens of SST (screw-retained sintering-technique) and SFL (screw-retained full-contour lithium-disilicate) group were CAD/CAM (Computer-aided design/computer-aided manufacturing) fabricated in the sintering technique (IPS e.max ZirCAD/IPS e.max CAD, Ivoclar Vivadent AG) and full-contour of lithium disilicate (IPS e.max CAD, Ivoclar Vivadent AG) respectively and screw-retained. All specimens underwent artificial aging, load until failure and a scanning electron microscopy (SEM) analysis. The received data were statistically compared (one-way ANOVA; Student-Newman-Keuls test; Mann-Whitney U-test) at a significance level of 5%. Mouth-motion fatigue testing caused two abutment fractures (SST group and SZL group) and two chipping events (CZL group). Specimens of MZL group showed statistically significant less contact wear compared to the other groups (p<0.001). There was no statistical difference between the groups in terms of the maximum fracture load. SEM-analysis showed a more homogenous structure and surface of CAD/CAM fabricated specimens towards manually veneered components. The mode of retention did not influence the fracture resistance but the failure patterns of the specimens. CAD/CAM milled lithium-disilicate crowns seemed to be a preserving factor for dental implants. The mode of retention and veneering influences the mechanical performance of implant-supported single crowns.

Comparison of Clinical, Radiographic, and Immunologic Inflammatory Parameters Around Dental Implants with Cement-Retained and Screw-Retained Restorations: A 5-Year Prospective Cohort Study in Men

To compare bleeding on probing (BoP), probing depth (PD; ≥ 4 mm), radiographic (peri-implant crestal bone loss [CBL]), and immunologic inflammatory (interleukin-1beta [IL-1β] and matrix metalloproteinase-9 [MMP-9]) parameters around dental implants with cement-retained (CR) and screw-retained (SR) implant-supported crowns. Based on the mode of retention of the restoration, 51 patients were divided into two groups: Group 1, consisting of 26 single implants restored with CR crowns, and Group 2, consisting of 25 single implants restored with SR crowns. Peri-implant BoP, PD, and CBL were scored, and levels of IL-1β and MMP-9 in the peri-implant crevicular fluid (PICF) in both groups were measured in duplicate using enzyme-linked immunosorbent assay. Full-mouth mechanical debridement was performed biannually in both groups. Statistical analysis was performed using Kruskal-Wallis test with the significance level set at P < .05. The mean CBL among implants in groups 1 and 2 was 1.7 ± 0.5 mm and 1.7 ± 0.4 mm, respectively. There was no statistically significant difference in mean BoP, PD, and CBL among implants in both groups (P > .05). There was no statistically significant difference between groups 1 and 2 in the PICF levels of IL-1β (7.3 ± 0.5 and 7.2 ± 0.5, respectively) and MMP-9 (165 ± 9.4 and 182 ± 10.6, respectively) (P > .05). The mode of retention of implant-supported crowns does not appear to affect their clinical correlations with BoP, PD, CBL, and levels of IL-1β and MMP-9 in the PICF when zinc oxide eugenol cement is used.

Effect of intermittent versus continuous bladder catheterization on duration of the second stage of labor among nulliparous women with an epidural: a randomized controlled trial.

Catheterization type among women laboring with epidural analgesia who develop bladder retention has been reported to affect labor duration and mode of delivery. We aimed to compare the effect of continuous bladder catheterization (CC) with that of intermittent bladder catheterization (IC) on the duration of the second stage of labor. In a randomized trial, term nulliparous women with singleton gestation who requested epidural analgesia and were unable to void spontaneously were eligible and randomized to either CC or IC. Epidural analgesia was maintained with patient control until delivery. The primary outcome was duration of the second stage of labor. Secondary outcomes were mode of delivery, and incidences of postpartum hemorrhage, bladder retention, and infection. It was assumed that, compared with IC, CC might better prevent bladder distention, which is thought to delay fetal descent. A sample size of 90 women in each group was calculated to be adequate to detect a reduction of 30min in the duration of the second stage of labor among the CC group. Between July 2014 and May 2015, a total of 184 women were randomized and included in the analysis; 90 and 94 women in the CC and IC groups respectively. Demographic and obstetric characteristics were similar. Duration of the second stage was 121.0±89.4 and 131.9±87.5min in the CC and IC groups respectively (p=0.29). The two groups did not differ significantly with regard to delivery mode, third-stage duration, and incidences of postpartum hemorrhage, bladder retention, and urinary tract infection. Duration of the second stage of labor is not influenced by bladder catheterization type in nulliparous women receiving an epidural.

Investigation of ethosomes as surrogate carriers for bioactives

Background: Ethosomal vesicular system delivering a bioactive phytochemical, chrysin, was developed for transdermal delivery to increase its permeability and penetrability. Materials and Methods: Ethosomal system was optimized by keeping lecithin and ethanol concentration as independent variable while size and size distribution were taken as dependent variables. The optimized formulation was then subjected to various in vitro characterization parameters. Results: Ethosomal vesicle with an optimum size and polydispersity index of 134 ± 35 nm and 0.153, respectively, and entrapment efficiency of 80.05 ± 2.6% was considered as optimized and subjected to characterization. The scanning electron microscopy and transmission electron microscopy showed spherical entities with uniform surface whereas in vitro permeation and retention study showed the sustained mode of drug release and better skin retention as compared to hydroethanolic solution of the drug. The confocal laser scanning microscopy study reiterated high penetrability of vesicles into the skin. Histopathological and Fourier transform infrared spectroscopy analysis revealed its mechanism of penetration. Conclusion : The study thus demonstrated the ability of the ethosomal vesicles as surrogate carriers for delivery of bioactive agents through the skin for better amelioration of skin inflammation and other diseases.

The angiogenic and adipogenic modes of adipose tissue after free fat grafting.

The major drawback of adipose grafting is its clinical unpredictability, which leads to surgeon and patient dissatisfaction. The mechanisms underlying angiogenesis and regeneration of the graft tissue are still unclear. Mouse adipose tissue was processed using two different methods (fragmental and integral) and was used to identify the mode of angiogenesis of the graft. Cross-grafting of tissue from normal mice and transgenic mice expressing green fluorescent protein was used to observe the origin of cells during the adipose regeneration. Almost all the CD31 endothelial cells of the new vessels were derived from the recipient. The new vessels in the graft were mainly formed through recipient vessels growing into the graft rather than the reassembly of donor endothelial cells or the reconnection of recipient and donor vessels. Angiogenesis depends largely on recipient-site environment. The retention of donor-derived tissue dropped to only 10 percent 8 weeks after grafting, and the majority of the key regeneration cells, the CD34 cells, came from the recipient during adipogenesis (p < 0.05). In total, the retention of the recipient-derived tissue was up to 73 percent in the fragmental group and 47.5 percent in the integral group. The angiogenesis of the graft occurs by the classic "vessel branching" mode, in which the recipient plays a dominant role. The mode of graft tissue retention primarily involves CD34 adipose precursor cells derived from the recipient.

Structure of Co(II) Species Formed on the Surface of γ-Alumina Upon Interfacial Deposition

The mode of retention of Co(H 2 O) 6 2+ species at the γ-alumina/aquatic solution interface is refined using simulations, adsorption isotherm, potentiometric mass titrations and mainly proton - ion titrations jointly with diffuse reflectance spectroscopy. It was found that the increase in the Co(II) surface concentration affects considerably the kind of the Co(II) species deposited. Mononuclear/mono-substituted inner sphere Co(II) complexes are formed at extremely low Co(II) surface concentration. A mixed surface state involving mononuclear/mono-substituted and binuclear/bi-substituted Co(II) complexes is formed at relatively low Co(II) surface concentration. Only binuclear/bi-substituted Co(II) complexes are formed at intermediate Co(II) surface concentration. Finally, oligo-nuclear inner sphere Co(II) species are formed at relatively high Co(II) surface concentration, in addition to the bi-nuclear ones. The above species concern a range of surface Co(II) concentration extending from zero to 2.7 theoretical surface layers of (Co(H 2 O) 6 ) 2+ . The formation of Co(II) surface precipitate starts above these theoretical surface layers. The above indicates that one may control the surface Co(II) concentration, by adjusting the Co(II) concentration in the impregnating solution, and thus the Co(II) surface species formed. This control allows tailoring the preparation of cobalt catalysts supported on γ-alumina and thus the development of effective Co/γ-alumina catalysts.

Fabrication of bar-retained tooth-supported mandibular overdenture

The problem of stability and retention of conventional mandibular complete dentures is far from a solution that is universally satisfactory. However, the use of overdenture therapy preserves the sensation of proprioception, preserves the edentulous ridge, maintains the border seal and provides the patient with good speaking ability and chewing efficiency. The retention and stability of such prosthesis is enhanced greatly in bar-supported overdentures. This case report depicts the step by step procedure for the fabrication of a canine splint bar for a bar and clip-retained mandibular overdenture that opposes a conventional complete maxillary denture. The bar was fabricated from readily available castable bar system and female clips were attached by an indirect technique. The mode of retention was primarily through frictional resistance. It is a relatively simple and easy technique, overcoming the limitations of the direct technique for clip attachment.

The Influence of Restorative Procedures on Esthetic Outcomes in Implant Dentistry: A Systematic Review

The objectives of this review were to (1) identify if prosthodontic parameters influence the esthetic outcome of implant-supported restorations and (2) make clinically relevant recommendations based upon the findings. Electronic and manual searches of dental literature were performed to collect information on esthetic outcomes based on objective criteria. The prosthodontic parameters included optimal three-dimensional implant position, the utilization of provisional restorations, the timing of provisional restoration with regard to implant placement, the choice of prosthodontic platform size and form, the abutment and definitive restoration material, and the mode of prosthesis retention. Regions including maxillary and mandibular anterior teeth and premolars were considered. All levels of evidence, including case studies, were accepted. From 472 titles, 152 full-text articles were evaluated and 58 records included for data extraction (15 randomized controlled trials, 6 cohort studies, and 37 case series studies). Considerable heterogeneity in study design was found. A meta-analysis of controlled studies was not possible. It was consistently reported that facial malpositioning of implants increases the likelihood of mucosal recession. No studies directly compared esthetic outcomes associated with the use or non-use of provisional restorations. The literature contains a greater number of case series studies evaluating esthetic outcomes for protocols including, rather than excluding, provisional restorations. It is not possible to identify any significant variation in esthetic outcomes based on the character of the abutment platform from the current literature. Based on the findings, no significant difference can be established between all-ceramic and metal-ceramic prostheses with regard to esthetic indices over short observation periods. No firm conclusions relating esthetic benefits for cement in comparison to screw retention can be identified. There is a need for RCTs comparing accepted procedures in routine practice. The utilization of provisional restorations remains strongly recommended in order to trial the planned definitive restoration, to facilitate maturation of healing tissues and for patient convenience. Implant positioning according to the planned prosthesis remains a requirement to achieve a long-lasting esthetic outcome. The majority of studies reported on single-tooth replacement, and many of the outcomes may not be relevant or applicable to the large number of esthetic indications involving more than one tooth.

Mineralogical Associations of Mercury in FGD Products

The natural mode of retention of mercury (Hg) in flue gas desulfurization (FGD) gypsum used in wallboard manufacturing has been investigated using a series of phase-targeted reagents. The sequence ...

Size Selectivity in Field-Flow Fractionation: Lift Mode of Retention with Near-Wall Lift Force

A simple theoretical model for the size selectivity, S(d), in the lift mode of retention in field-flow fractionation (FFF) is developed on the basis of the near-wall lift force expression. S(d) is made up of two contributions: the flow contribution, S(d,f), arising from the variation of the flow velocity at center of particle due to a change in particle position with particle size, and a slip contribution, S(d,s), arising from the concomitant change in the extent of retardation due to the presence of a nearby channel wall. The slip contribution is minor, but not negligible, and amounts to 10-20% of the overall size selectivity. It contributes to reduce S(d) in sedimentation FFF but to enhance it in flow FFF. S(d) would steadily increase with particle size if the flow profile was linear (Couette flow). Because of the curvature of the flow profile encountered in the classical Poiseuille flow, S(d) exhibits a maximum at some specific particle size. The model predicts a significant difference in S(d) between sedimentation FFF and flow FFF, arising from the different functional dependences of the field force with particle size between these two methods. The predictions are in good agreement with the various S(d) values reported in the literature in both sedimentation and flow FFF. On the basis of the model, guidelines are given for adjusting the operating parameters (carrier flow rate and field strength) to optimize the size selectivity. Finally, it is found that S(d) generally decreases with decreasing channel thickness.

Transient Device Simulation of Floating Gate Nonvolatile Memory Cell With a Local Trap

The single-electron general-purpose device simulator is improved to carry out a wide-range transient analysis from 1 ps to 10 years. We apply this simulator to a floating gate (FG) nonvolatile memory cell in order to simulate a degradation mode of data retention owing to the direct tunneling enhanced by the fixed charge stored by a local trap in an interpoly dielectric. The scaling impact of ideal high-K interpoly dielectric FG nonvolatile memory cell is also investigated.

Evaluation of Chromatographic Methods for Drug Products Containing Polar and Non-Polar Molecules Using Reversed Phase, Hydrophilic Interaction, and Ion Exchange Chromatography

In recent years the pharmaceutical industry has developed an increasing variety of complex double or triple combination drug therapies. Method development for these combination drug products is particularly challenging when the analytes have significantly different polarities, often requiring multiple chromatographic methods for each active component. An alternative to the commonly used practice of developing multiple reversed phase chromatographic methods for analyzing small molecules in combination drug products is discussed herein. Ion exchange chromatography offers many advantages to other chromatographic techniques for the analysis of combination products if one of the molecules is highly polar (log P < 0) and the other moderately polar to non-polar (log P ≥ 0). As the primary mode of retention for ion exchange chromatography is based upon the charge of the molecule, the hydrophobicity of the molecule does not play as large of a part in the retention mechanism. As long as all of the molecules being analyzed are ionizable, retention on an ion exchange column should be possible. The analysis of polar and non-polar molecules simultaneously using ion exchange chromatography is a unique process, and the approach of developing accurate and robust analytical methods for analysis of all active pharmaceutical ingredients in a combination product by a single fast ion exchange method differs from the industry standard of using reverse phase methodology first. Six well characterized pharmaceuticals with varying degrees of polarity (metformin HCl, isoniazid, sodium nitroprusside, timolol maleate, naproxen sodium, and clonidine hydrochloride) have been chromatographically evaluated using RP, HILIC, and ion exchange chromatography. In addition, a well characterized pharmaceutical product, Metaglip™ Tablets, containing the highly polar molecule metformin HCl and the moderately non-polar glipizide, has been analyzed using a cation exchange (CE) HPLC method and compared to chromatography and results generated using RP-HPLC and hydrophilic interaction (HILIC)-HPLC.

Chemical fractionation of metals in freshly deposited marine estuarine sediments of sundarban ecosystem, India

Sediment metal profiles were carefully examined for their distribution, chemical fractions, and mobility in three major marine-estuarine transects in the world’s largest mangrove (Sundarban) ecosystem because anthropogenic influences had been very often noticed. The level of pollutants was determined by CF and PLI. Metal contents in the freshly deposited sediment of Hugli transect were relatively high (Pb, Fe, Zn, Mn, Ni, and Co) in comparison to Matla and Saptamukhi due to lithogenic contribution from large catchments area (8 × 105 km2). Principal component analysis and correlation coefficient revealed that the concentrations of metals were mainly governed by the variability of the sediment properties. Sediment was subjected to sequential chemical extractions to delineate metal fractions, namely exchangeable, carbonate, Fe–Mn oxide, organic, and residual. This indicated a valuable insight into the geochemical mode of the metal retention and their environmental behavior. Single extraction did not help significantly to explain the metal profiling.

Experience with prosthetic reconstruction of ear defects at LUTH, Lagos, Nigeria

The aim of the article is to report our experience with prosthetic reconstruction of ear defects in Nigerians. A review of all consecutive cases of alloplastic (prosthesis) reconstruction of auricular defects was conducted at the Department of Oral and Maxillofacial Surgery of the Lagos University Teaching Hospital. Data collected included age and sex of patients, aetiology of defects, site of defects (left or right), lost tissue (partial or total), material used for the fabrication, and mode of retention of the prosthesis. A total of 33 consecutive patients who had prosthetic reconstruction of auricular defects during the period were included. The male-to-female ratio was 3.7: 1. Six cases (18.2%) were congenital defects and 27 (81.8) cases were acquired defects. Three (50%) of the congenital cases were microtia. Majority (63%) of the acquired cases were due to road traffic crashes. Total loss of the auricle was recorded in 22 (66.7%) patients. Of the patients with partial loss of the auricle, pinna was the major structure lost in 5 patients while pinna +lobe were lost in another 5 patients. Silicone elastomers was the most frequently used material for the fabrication of auricular prostheses (29 patients). The most frequently used retention method was silastic medical grade adhesive. Prosthetic option is a valuable technique for the reconstruction of ear defect. The primary indication for prosthetic reconstruction of ear defect in the present study is acquired ear deformity; mainly due to road traffic crashes.

A 10‐year prospective study of ITI dental implants placed in the posterior region. II: Influence of the crown‐to‐implant ratio and different prosthetic treatment modalities on crestal bone loss

To evaluate the influence of the crown-to-implant ratio (C/I) ratio and different implant prosthetic treatment modalities on crestal bone loss around dental implants placed in the posterior region. A total of 192 ITI dental implants were consecutively placed in premolars and molars of 83 partially edentulous patients. All implants were restored by means of ceramic-to-metal fused fixed partial dentures or a single crown. Patients were followed as part of a prospective longitudinal study focusing on implant success. Surgical, radiographic and clinical variables were collected at the 1-year recall after implant placement and at the most recent clinical evaluation. Radiographic parameters were evaluated on periapical radiographs taken with a standardized long-cone paralleling technique. Implant restorations were divided into three groups according to their respective clinical C/I ratios: (a) 0-0.99, (b) 1-1.99 and (c) >or=2. The mean clinical C/I ratio was 1.77+/-0.56 mm. A total of 51 implants (26.5%) showed a clinical C/I ratio equal to or greater than 2. In this group, three implants failed, giving a cumulative survival rate of 94.1%. Crestal bone loss was -0.34+/-0.27 mm in group a, -0.03+/-0.15 mm in group b and -0.02+/-0.26 mm in group c. Differences among groups were statistically significant (P=0.009). Mode of retention, splinting or presence of cantilever extensions did not have an effect on crestal bone loss around ITI dental implants. Implant restorations with C/I ratios between 2 and 3 may be successfully used in the posterior areas of the jaw.

Sedimentation field-flow fractionation: Size characterization of food materials

Sedimentation field-flow fractionation (SdFFF) was applied to characterize particle size distributions of food materials. Two types of food particles were examined, including milk suspensions and flour samples. Milk eluted in the normal mode SdFFF, whereas the steric mode of retention was used for flour samples. Various types of milk being investigated were from cereal and cow’s origins. The cereal milk samples included corn, job’s tear, rice, and soy milk, whereas the bovine milk included chocolate and fresh full-fat milk. Most samples exhibited monomodal size distributions, whereas corn milk displayed a slight deviation from monomodal characteristic. The mean particle sizes were detected to be approximately 0.4 μm for all cereal milk, except that they were approximately 0.5 μm for corn and all bovine milk. The application of SdFFF for micrometer size food particles was demonstrated for four types of flour samples, including corn, mung bean, rice, and tapioca flours. Significantly differences in the particle size characteristics of all flour samples were observed, by which corn, mung bean, rice, and tapioca yielded mean particle sizes of 16.7, 31.5, 13.5, and 19.9 μm, respectively. The ability of SdFFF for size separation of flours was confirmed by comparing the results obtained with those from scanning electron microscopy (SEM). Further, a new way to examine flour swelling was proposed. This study has demonstrated the potential value of SdFFF technique for food scientists.

Effects of Substrate Interactions in Liquid Chromatography of Star Homopolymers and Star Block Copolymers

A theoretical study of the behavior in liquid chromatography of star polymers of two different kinds of arms is presented, including the special cases of diblock copolymers and regular star polymers. The two different kinds of interactions between the substrate and the monomeric units which can be repulsive attractive or neutral combine in these heteroarm stars. They can act cooperatively or antagonistically determining, in connection with the effects of the architecture and the sizes of the branches, the mode of retention of the macromolecules. The compensation point, where no surface effects remain when the surface−monomer interactions are negligible, can also be reached by cancellation of the opposite but not negligible interactions of the two different kinds of arms with the substrate.