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The Cochrane Database of Systematic... Apr 2018Edentulism is relatively common and is often treated with the provision of complete or partial removable dentures. Clinicians make final impressions of complete dentures... (Meta-Analysis)
Meta-Analysis Review
BACKGROUND
Edentulism is relatively common and is often treated with the provision of complete or partial removable dentures. Clinicians make final impressions of complete dentures (CD) and removable partial dentures (RPD) using different techniques and materials. Applying the correct impression technique and material, based on an individual's oral condition, improves the quality of the prosthesis, which may improve quality of life.
OBJECTIVES
To assess the effects of different final-impression techniques and materials used to make complete dentures, for retention, stability, comfort, and quality of life in completely edentulous people.To assess the effects of different final-impression techniques and materials used to make removable partial dentures, for stability, comfort, overextension, and quality of life in partially edentulous people.
SEARCH METHODS
Cochrane Oral Health's Information Specialist searched the following databases: Cochrane Oral Health's Trials Register (to 22 November 2017), the Cochrane Central Register of Controlled Trials (CENTRAL) (Cochrane Register of Studies, to 22 November 2017), MEDLINE Ovid (1946 to 22 November 2017), and Embase Ovid (21 December 2015 to 22 November 2017). The US National Institutes of Health Trials Registry (ClinicalTrials.gov) and the World Health Organization International Clinical Trials Registry Platform were searched for ongoing trials. No restrictions were placed on language or publication status when searching the electronic databases, however the search of Embase was restricted by date due to the Cochrane Centralised Search Project to identify all clinical trials and add them to CENTRAL.
SELECTION CRITERIA
We included randomised controlled trials (RCTs) comparing different final-impression techniques and materials for treating people with complete dentures (CD) and removable partial dentures (RPD). For CD, we included trials that compared different materials or different techniques or both. In RPD for tooth-supported conditions, we included trials comparing the same material and different techniques, or different materials and the same technique. In tooth- and tissue-supported RPD, we included trials comparing the same material and different dual-impression techniques, and different materials with different dual-impression techniques.
DATA COLLECTION AND ANALYSIS
Two review authors independently, and in duplicate, screened studies for eligibility, extracted data, and assessed the risk of bias for each included trial. We expressed results as risk ratios (RR) for dichotomous outcomes, and as mean differences (MD) or standardised mean differences (SMD) for continuous outcomes, with 95% confidence intervals (CI), using the random-effects model. We constructed 'Summary of findings' tables for the main comparisons and outcomes (participant-reported oral health-related quality of life, quality of the denture, and denture border adjustments).
MAIN RESULTS
We included nine studies in this review. Eight studies involved 485 participants with CD. We assessed six of the studies to be at high risk of bias, and two to be at low risk of bias. We judged one study on RPD with 72 randomised participants to be at high risk of bias.Overall, the quality of the evidence for each comparison and outcome was either low or very low, therefore, results should be interpreted with caution, as future research is likely to change the findings.Complete denturesTwo studies compared the same material and different techniques (one study contributed data to a secondary outcome only); two studies compared the same technique and different materials; and four studies compared different materials and techniques.One study (10 participants) evaluated two stage-two step, Biofunctional Prosthetic system (BPS) using additional silicone elastomer compared to conventional methods, and found no evidence of a clear difference for oral health-related quality of life, or quality of the dentures (denture satisfaction). The study reported that BPS required fewer adjustments. We assessed the quality of the evidence as very low.One study (27 participants) compared selective pressure final-impression technique using wax versus polysulfide elastomeric (rubber) material. The study did not measure quality of life or dentures, and found no evidence of a clear difference between interventions in the need for adjustments (RR 0.81, 95% CI 0.38 to 1.70). We assessed the quality of the evidence as very low.One study compared two stage-two step final impression with alginate versus silicone elastomer. Oral health-related quality of life measured by the OHIP-EDENT seemed to be better with silicone (MD 7.20, 95% CI 2.71 to 11.69; 144 participants). The study found no clear differences in participant-reported quality of the denture (comfort) after a two-week 'confirmation' period, but reported that silicone was better for stability and chewing efficiency. We assessed the quality of the evidence as low.Three studies compared single-stage impressions with alginate versus two stage-two step with elastomer (silicone, polysulfide, or polyether) impressions. There was no evidence of a clear difference in the OHIP-EDENT at one month (MD 0.05, 95% CI -2.37 to 2.47; two studies, 98 participants). There was no evidence of a clear difference in participant-rated general satisfaction with dentures at six months (MD 0.00, 95% CI -8.23 to 8.23; one study, 105 participants). We assessed the quality of the evidence as very low.One study compared single-stage alginate versus two stage-two step using zinc-oxide eugenol, and found no evidence of a clear difference in OHIP-EDENT (MD 0.50, 95% CI -2.67 to 3.67; 39 participants), or general satisfaction (RR 3.15, 95% CI 0.14 to 72.88; 39 participants) at six months. We assessed the quality of the evidence as very low.Removable partial denturesOne study randomised 72 participants and compared altered-cast technique versus one-piece cast technique. The study did not measure quality of life, but reported that most participants were satisfied with the dentures and there was no evidence of any clear difference between groups for general satisfaction at one-year follow-up (low-quality evidence). There was no evidence of a clear difference in number of intaglio adjustments at one year (RR 1.43, 95% CI 0.61 to 3.34) (very low-quality evidence).
AUTHORS' CONCLUSIONS
We conclude that there is no clear evidence that one technique or material has a substantial advantage over another for making complete dentures and removable partial dentures. Available evidence for the relative benefits of different denture fabrication techniques and final-impression materials is limited and is of low or very low quality. More high-quality RCTs are required.
Topics: Dental Impression Materials; Dental Impression Technique; Denture Design; Denture Retention; Denture, Partial, Removable; Dentures; Humans; Mouth, Edentulous; Quality of Life; Randomized Controlled Trials as Topic
PubMed: 29617037
DOI: 10.1002/14651858.CD012256.pub2 -
Cureus Oct 2022Otitis media is a disorder of the middle ear, which can occur at any age but is more common among infants and children. The patient usually presents with earaches,... (Review)
Review
Otitis media is a disorder of the middle ear, which can occur at any age but is more common among infants and children. The patient usually presents with earaches, impaired hearing, and fever. If antibiotics and decongestants do not suit the patient, a myringotomy can be performed to achieve middle ear aeration. In myringotomy, a slit is created in the tympanic membrane, and fluid is removed with suction. In cases where myringotomy, aspiration, and medical care don't help and the fluid recurs, a tympanostomy tube is inserted to create continuous aeration of the middle ear. A tympanostomy tube is a small tube inserted in the tympanic membrane which helps in the prevention of fluid accumulation in the middle ear. These tubes are temporary and often fall off after the ear heals. Other names for tympanostomy tubes are grommet, myringotomy tube, or pressure equalizing tube. Initially, tympanostomy tubes were made of metal but now fluoroplastic or silicone elastomers are used to make them. The two basic designs of a tympanostomy tube are short-term tube and long-term tube. The choice of a tympanostomy tube depends on factors like age, the period needed for ventilation, socioeconomic status, and the extent of the retracted eardrum. The incidence of occlusion, infection, functional duration, and persistent perforation following extrusion varies between the designs and materials. Every year, many children are affected by recurrent otitis media, which can negatively influence their quality of life and their ability to hear and communicate. With so many children requiring tympanostomy tubes, choosing the appropriate tube is vital to provide optimal treatment and limit complications.
PubMed: 36397911
DOI: 10.7759/cureus.30166 -
JPRAS Open Jun 2022Modern breast implants are a staple of plastic surgery, finding uses in esthetic and reconstructive procedures. Their history began in the 1960s, with the first... (Review)
Review
Modern breast implants are a staple of plastic surgery, finding uses in esthetic and reconstructive procedures. Their history began in the 1960s, with the first generation of smooth devices with thick silicone elastomer, thick silicone gel, and Dacron patches on the back. They presented hard consistency, high capsular contracture rates and the patches increased the risk of rupture. In the same decade, polyurethane coating of implants was implemented. A second generation was introduced in the 1970s with a thinner shell, less viscous gel filler and no patches, but increased silicone bleed-through and rupture rates. The third generation, in the early 1980s, featured implants with a thicker multilayered elastomer shell reinforced with silica to reduce rupture risk and prevent silicone bleed-through. A fourth generation from the late 1980s combined thick outer elastomer shells, more cohesive gel filler, and implemented for the first-time outer shell texturing. In the early 1990s, the fifth generation of devices pioneered an anatomical shape with highly cohesive form-stable gel filler and a rough outer shell surface. Surface texturing was hampered by the discovery of Breast Implant Associated-Anaplastic Large Cell Lymphoma and its link with textured devices. From the 2010s, we have the era of the sixth generation of implants, featuring innovations regarding the surface, with biomimetic surfaces, more resistant shells and variations in gel consistency. The road to innovation comprises setbacks such as the FDA moratorium in 1992, the PIP scandal, the Silimed CE mark temporary suspension and the FDA-requested voluntary recall of the Allergan BIOCELL implants.
PubMed: 35434240
DOI: 10.1016/j.jpra.2022.02.004 -
Macromolecular Rapid Communications Mar 2016Silicone elastomers are promising materials for dielectric elastomer transducers (DETs) due to their superior properties such as high efficiency, reliability and fast... (Review)
Review
Silicone elastomers are promising materials for dielectric elastomer transducers (DETs) due to their superior properties such as high efficiency, reliability and fast response times. DETs consist of thin elastomer films sandwiched between compliant electrodes, and they constitute an interesting class of transducer due to their inherent lightweight and potentially large strains. For the field to progress towards industrial implementation, a leap in material development is required, specifically targeting longer lifetime and higher energy densities to provide more efficient transduction at lower driving voltages. In this review, the current state of silicone elastomers for DETs is summarised and critically discussed, including commercial elastomers, composites, polymer blends, grafted elastomers and complex network structures. For future developments in the field it is essential that all aspects of the elastomer are taken into account, namely dielectric losses, lifetime and the very often ignored polymer network integrity and stability.
Topics: Dimethylpolysiloxanes; Electric Conductivity; Electric Power Supplies; Electrodes; Silicone Elastomers
PubMed: 26773231
DOI: 10.1002/marc.201500576 -
Nanomaterials (Basel, Switzerland) Dec 2021The effect of multiwall carbon nanotubes (MWCNTs) and magnesium oxide (MgO) on the thermal conductivity of MWCNTs and MgO-reinforced silicone rubber was studied. The...
The effect of multiwall carbon nanotubes (MWCNTs) and magnesium oxide (MgO) on the thermal conductivity of MWCNTs and MgO-reinforced silicone rubber was studied. The increment of thermal conductivity was found to be linear with respect to increased loading of MgO. In order to improve the thermal transportation of phonons 0.3 wt % and 0.5 wt % of MWCNTs were added as filler to MgO-reinforced silicone rubber. The MWCNTs were functionalized by hydrogen peroxide (HO) to activate organic groups onto the surface of MWCNTs. These functional groups improved the compatibility and adhesion and act as bridging agents between MWCNTs and silicone elastomer, resulting in the formation of active conductive pathways between MgO and MWCNTs in the silicone elastomer. The surface functionalization was confirmed with XRD and FTIR spectroscopy. Raman spectroscopy confirms the pristine structure of MWCNTs after oxidation with HO. The thermal conductivity is improved to 1 W/m·K with the addition of 20 vol% with 0.5 wt % of MWCNTs, which is an ~8-fold increment in comparison to neat elastomer. Improved thermal conductive properties of MgO-MWCNTs elastomer composite will be a potential replacement for conventional thermal interface materials.
PubMed: 34947767
DOI: 10.3390/nano11123418 -
International Journal of Pharmaceutics:... Dec 2021A dapivirine-releasing silicone elastomer vaginal ring for reducing women's risk of HIV acquisition has recently been approved. A next-generation multipurpose vaginal...
A dapivirine-releasing silicone elastomer vaginal ring for reducing women's risk of HIV acquisition has recently been approved. A next-generation multipurpose vaginal ring releasing dapivirine and levonorgestrel is currently in development, offering hormonal contraception and HIV prevention from a single device. Previously, we reported challenges with incorporating levonorgestrel into rings manufactured from addition-cure silicone elastomers due to an irreversible chemical reaction between the levonorgestrel molecule and the hydride-functionalised crosslinker component of the silicone elastomer formulation, leading to low drug content assay, cure inhibition, and reduced ring mechanical properties (which may account for the increased incidence of ring expulsion in vivo). Here, we report on the development and testing of various custom silicone elastomer materials specifically formulated to circumvent these issues. After extensive testing of the custom silicones and subsequent manufacture and testing (Shore M hardness, pot life, content assay, oscillatory rheology, mechanical testing) of rings containing both dapivirine and levonorgestrel, a lead candidate formulation was selected that was amenable to practical ring manufacture via injection molding, exhibited no substantial levonorgestrel binding, and offered suitable mechanical properties.
PubMed: 34977558
DOI: 10.1016/j.ijpx.2021.100091 -
The Journal of Surgical Research Dec 2022Capsular contracture is a common complication associated with breast implants following reconstructive or aesthetic surgery in which a tight or constricting scar tissue... (Review)
Review
Capsular contracture is a common complication associated with breast implants following reconstructive or aesthetic surgery in which a tight or constricting scar tissue capsule forms around the implant, often distorting the breast shape and resulting in chronic pain. Capsulectomy (involving full removal of the capsule surrounding the implant) and capsulotomy (where the capsule is released and/or partly removed to create more space for the implant) are the most common surgical procedures used to treat capsular contracture. Various structural modifications of the implant device (including use of textured implants, submuscular placement of the implant, and the use of polyurethane-coated implants) and surgical strategies (including pre-operative skin washing and irrigation of the implant pocket with antibiotics) have been and/or are currently used to help reduce the incidence of capsular contracture. In this article, we review the pharmacological approaches-both commonly practiced in the clinic and experimental-reported in the scientific and clinical literature aimed at either preventing or treating capsular contracture, including (i) pre- and post-operative intravenous administration of drug substances, (ii) systemic (usually oral) administration of drugs before and after surgery, (iii) modification of the implant surface with grafted drug substances, (iv) irrigation of the implant or peri-implant tissue with drugs prior to implantation, and (v) incorporation of drugs into the implant shell or filler prior to surgery followed by drug release in situ after implantation.
Topics: Humans; Implant Capsular Contracture; Polyurethanes; Breast Implants; Breast Implantation; Contracture; Anti-Bacterial Agents
PubMed: 35969932
DOI: 10.1016/j.jss.2022.06.073 -
Nanomaterials (Basel, Switzerland) Oct 2023Carbon nanotube (CNT) hybrid composites were formed by combining a CNT and silicone elastomer solution with Kevlar yarn, Kevlar fabric, and Kevlar veil materials. The...
Carbon nanotube (CNT) hybrid composites were formed by combining a CNT and silicone elastomer solution with Kevlar yarn, Kevlar fabric, and Kevlar veil materials. The integration of a CNT-silicone matrix with Kevlar yarn and fabric materials produced a composite with moderate electrical and thermal conductivity due to CNT fabric combined with the strength of Kevlar fabric or yarn. In the material synthesis, a notable difficulty was that the CNT-silicone did not bond strongly to the Kevlar. The composites passed the Vertical Flame Test ASTM D6413 and the Forced Air Oven Test NFPA 1971. These hybrid composites can have multiple applications in areas requiring favorable conductivity, strength, and flame and heat resistance. The application areas include firefighter apparel, military equipment, conductive/smart structures, and flexible electronics. The synthesis process used to manufacture CNT-silicone/Kevlar composites yielded composite sheets with an area of 2250 cm. The process is scalable and customizable for the synthesis of CNT composites with tailored properties. Improvements in the bonding of CNT-silicone to Kevlar are being investigated.
PubMed: 37836369
DOI: 10.3390/nano13192728 -
Polymers Oct 2022General information concerning different kinds of chemical additives used in the textile industry has been described in this paper. The properties and applications of... (Review)
Review
General information concerning different kinds of chemical additives used in the textile industry has been described in this paper. The properties and applications of organofunctional silanes and polysiloxanes (silicones) for chemical and physical modifications of textile materials have been reviewed, with a focus on silicone softeners, silane, and silicones-based superhydrophobic finishes and coatings on textiles composed of silicone elastomers and rubbers. The properties of textile materials modified with silanes and silicones and their practical and potential applications, mainly in the textile industry, have been discussed.
PubMed: 36297958
DOI: 10.3390/polym14204382 -
Nature Communications Aug 2022Force and strain sensors made of soft materials enable robots to interact intelligently with their surroundings. Capacitive sensing is widely adopted thanks to its low...
Force and strain sensors made of soft materials enable robots to interact intelligently with their surroundings. Capacitive sensing is widely adopted thanks to its low power consumption, fast response, and facile fabrication. Capacitive sensors are, however, susceptible to electromagnetic interference and proximity effects and thus require electrical shielding. Shielding has not been previously implemented in soft capacitive sensors due to the parasitic capacitance between the shield and sensing electrodes, which changes when the sensor is deformed. We address this crucial challenge by patterning the central sensing elastomer layer to control its compressibility. One design uses an ultrasoft silicone foam, and the other includes microchannels filled with liquid metal and air. The force resolution is sub-mN both in normal and shear directions, yet the sensor withstands large forces (>20 N), demonstrating a wide dynamic range. Performance is unaffected by nearby high DC and AC electric fields and even electric sparks.
PubMed: 35945227
DOI: 10.1038/s41467-022-32391-0