Plastic Denture Research Articles

Methods for studying the ductus venosus in animals

The ductus venosus is a physiological vascular shunt to the umbilical and caudal vena cava in the fetus. The umbilical vein (vena umbilicalis) leaves the placenta, enters the fetus through the foramen umbilical, and goes to the liver hilum. It carries oxygenated and nutrient‐rich blood from the placenta to the fetus. Part of the blood enters the liver through the umbilical vein, through the shunt ‐ the ductus vein enters the central venous line ‐ the caudal vena cava. This mechanism of blood redistribution is necessary for feeding the fetal brain with blood that is more saturated with oxygen. Given the scarce data on the topography, shape, and morphometric parameters of the venous duct in animals, we set the goal of revealing the methods used for its postmortem study. For a complete and comprehensive study of the topography of the venous duct, it is necessary to use a set of anatomical methods: thin anatomical preparation, vasoradiography, production of corrosive preparations, and morphometry. When conducting vasoradiography, a mass for injection prepared according to the recipe was used as a radio‐opaque mass: 45% ‐ lead white, 45% ‐ gum turpentine, 10% ‐ medical gypsum powder (M.V. Shchipakina, A.V. Prusakova, D.S. Bylinskaya, S.A. Kuga, 2013). In the manufacture of corrosive preparations, self‐hardening dental plastic was used. It belongs to the acrylic group of cold curing plastics and consists of powder and solvent components. In both cases, the injection of these substances was carried out through the umbilical vein, without opening the abdominal cavity, by accessing through the umbilical cord. After introducing the X‐ray contrast mass, the objects of study were placed in a fixing solution (10% formalin solution) and left in it for up to 5 days. Subsequently, thin anatomical preparation and photography, as well as radiography, were performed. After introducing a plastic solution, the objects were placed in chambers with a temperature of +4°C for two days. Subsequently, corrosion treatment was carried out in an aqueous potassium hydroxide solution for 4 ‐ 5 days. The morphometry of the venous duct in the study of vaso‐radiographs was carried out in the RadiAnt computer program, in the study of a corrosive preparation ‐ using an electronic caliper (Stainless hardened). On vaso‐radiographs, the ductus venous is identified as a sizeable cone‐shaped vessel located in the area of the liver hilum. The ductus venosus is identified as a craniodorsal blood vessel that flows into the caudal vena cava on the casts of the vascular bed. The proposed methods for studying the ductus venosus make it possible to accurately anatomically describe the position, shape, and size of the ductus venosus in fetuses.

Local and systemic contact dermatitis elicited by dental plastic fillings in a patient allergic to 2-hydroxyethyl methacrylate.

Local and systemic contact dermatitis elicited by dental plastic fillings in a patient allergic to 2-hydroxyethyl methacrylate.

ANALYSIS OF THE ADVISABILITY OF USING DIFFERENT TYPES OF BASE PLASTICS BY STUDYING THE NEEDS OF THE POPULATION IN REMOVABLE PROSTHESIS.

The aim: To determine the needs of the population of the Ternopil region in prosthetics with removable orthopedic dentures and to study the physical and technological properties of different types of base plastics. Materials and methods: The needs of Ternopil and Ternopil region population in removable prosthetics were studied on the basis of consolidated annual reports of city and district dental clinics of Ternopil region. Base dental plastics «Ftoraks» (Stoma, Ukraine) and «Villacryl H Plus» (Zermapol, Poland) were used to study the physical and mechanical properties (deformations during compression and tension). Results: As a result of our research, we found that the need of the Ternopil region population for removable prosthetics is quite high. When analyzing the choice of designs of removable laminar prostheses, it was found that 64.99 ± 0.14% of patients required the manufacture of partial removable dentures, and 35.01 ± 0.18% - complete removable dentures. A significant difference was found in the physical and technical characteristics of the samples of the studied plastics, which were polymerized by various methods. Conclusions: Dental base plastic «Villacryl H Plus», which was packaged and polymerized by casting, has significantly higher physical and mechanical properties than dental base plastic «Ftoraks».

A technique of designing a 3-dimensionally printed elastomeric impression mixing tip for reuse: A step toward eco-friendly dentistry

Single-use plastics in dentistry are significant contributors to biomedical waste. Various plastic tubes and mixing cartridges with different plastic mixing tips are widely used for elastomeric impression materials. To minimize the dental plastic footprint, a technique is described for making reusable plastic mixing tips for elastomeric impression materials.

Reliable surface modification of dental plastic substrates to reduce biofouling with a photoreactive phospholipid polymer

ABSTRACTPlastic substrates have been widely applied in clinical settings for dental treatments. These substrates should be strong enough for long‐term implantation in the oral cavity and should be resistant to biofouling. We developed a new photoreactive phospholipid polymer to reduce biofouling on dental plastics via a photochemical reaction. Poly(methyl methacrylate) (PMMA) and poly(ether ether ketone) (PEEK) were used as dental plastics. To determine the antibiofouling properties on the polymer surface, the phospholipid polymer was covalently immobilized on the substrates by UV irradiation. We evaluated the antibiofouling properties by observing the protein adsorption and cell and bacterial adhesion. Significant protein adsorption and cell adhesion appeared on the bare PMMA and PEEK substrates but decreased dramatically after surface modification with the phospholipid polymer. Thus, this photoreactive polymer shows potential for conferring dental plastics with antibiofouling properties. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46512.

Comparative Analysis of Structural Responses of Rat Subcutaneous Fat on the Implantation of Samples of Polymethyl Methacrylate with Hydrophobic and Hydrophilic Surface

Morphological analysis of the subcutaneous fat was performed in rats after subcutaneous implantation of basic dental plastic materials with different hydrophobic and hydrophilic properties. It was shown that subcutaneous implantation of dental plastics with mostly hydrophobic surface and low biocompatibility induced destructive and inflammatory processes of various intensities, sometimes with allergic component; morphological signs of processes persisted for 6 weeks. Modification of basic plastics using glow-discharge plasma and enhancement of their hydrophilicity and biocompatibility significantly reduced the intensity of destructive and inflammatory processes and ensured more rapid (in 2 weeks) repair of the destroyed tissues with the formation of fibrous capsule around the implant.

The effects of salivas on occlusal forces.

Contacting surfaces of opposing teeth produce friction that, when altered, changes the contact force direction and/or magnitude. As friction can be influenced by several factors, including lubrication and the contacting materials, the aim of this study was to measure the occlusal load alterations experienced by teeth with the introduction of different salivas and dental restorative materials. Pairs of molar teeth were set into occlusion with a weighted maxillary tooth mounted onto a vertical sliding assembly and the mandibular tooth supported by a load cell. The load components on the mandibular tooth were measured with three opposing pairs of dental restorative materials (plastic denture, all-ceramic and stainless steel), four (human and three artificial) salivas and 16 occlusal configurations. All lateral force component measurements were significantly different (P < 0·0001) from the dry (control) surface regardless of the crown material or occlusal configuration, while the effects of the artificial salivas compared to each other and to human saliva depended on the crown material.

New clinical technique for fabrication immediate partial denture

Immediate partial denture is a choice of treatment due to various cases of teeth extraction such as badly carious teeth, periodontal disease, eruption problems, trauma, and other reasons. Many choices are used to replace the lost teeth; one of these choices is a removable plastic denture in which hot cured acrylic resin should be used to fabricate such denture. Aim of Study: To provide an applicable technique to fabricate an immediate partial denture by reducing and declining the prosthetic steps and some materials in proportional to the conventional method. Clinical Procedures: Maxillary and mandibular stone casts are mounted to a simple articulator and the procedures are explained as step by step to fabricate an immediate partial denture without using the conventional methods and material, just using a small quantity of white cold cure acrylic resin to fabricate the artificial teeth, hot cure acrylic resin for the denture base and mold made of a silicon impression material are used to fabricate an immediate partial denture. Conclusion: The finished immediate partial denture showed a good retention and produced the exact shapes and sizes of the extracted teeth with low cost and less time for a dentist and patient.

Tongue laceration during electroconvulsive therapy

Electroconvulsive therapy (ECT) had been used for psychiatric diseases such as depression. Recently, modified ECT is preferred, where the patient is in a state of muscle relaxation induced by muscle relaxant before the influx of electrical current. Although muscle relaxant is used, forceful jaw clenching is inevitable during ECT, since masticatory muscles, particularly the temporalis and the masseter, are directly stimulated by the electrical current. Although biting pressure in a conscious individual is usually controlled by a feedback mechanism to avoid excessive strain, this feedback mechanism does not come into action in an anesthetized patient [1]. Therefore, the teeth or other intraoral structures can be injured from biting or invagination during modified ECT. Psychiatric patients are especially vulnerable to intraoral injuries during modified ECT, because they are more likely to have drug-related dry mouth, smoking, and/or alcohol addiction. In xerostomia patients, the change in the pH and the immune function secondary to reduced salivary flow may also lead to an increased risk of intraoral infection [2]. In order to prevent intraoral injury during modified ECT, mouthguards rather than oral airways are used. Various types of gags and mouthguards have been used such as rubber bite blocks, braided guaze gags, gauze wrapped tongue blades and mouthguards. McClure devised a gag made of dental plastic, and also described about molded mouthguards [1]. But individually molded mouthguards like hard rubber bite blocks are so firm that care should be given to prevent soft tissue injuries such as tongue bites which can occur between the teeth and the mouthguard. We would like to describe a tongue laceration case which occurred during modified ECT despite using a mouthguard. A 71-year-old female patient was admitted for modified ECT under the diagnosis of depression. The mouthguard was made of silicone, immersed in hot water before use and transformed to fit the denture of the patient (Fig. 1A). After modified ECT was given, tongue laceration was found, which seemed to have occurred from biting between the mouthguard and the teeth. Tongue laceration was 1.5 cm long and 0.5 cm deep. Neither active bleeding nor hematoma was observed. After physical examination by an otolaryngologist, it was sutured simply with Vicryl 4-0 under local anesthesia (Fig. 1B). The wound recovered well without complication. Fig. 1 The mouthguard in proper position (A). Tongue laceration repaired with a simple continuous suture. The tongue has an irregular and dry fissured surface, which is a typical characteristic of dry mouth (B). Intraoral soft tissue injuries, especially tongue injuries generally recover well after simple treatment because of the abundant blood supply. Most tongue lacerations do not require sutures. Lacerations that should be repaired with suture include bisecting wounds, lateral border wounds, wounds with active hemorrhage, wounds larger than 2 cm, gaping wounds and amputation injuries [3,4]. If the patient cooperates well, tongue laceration can be sutured under local anesthesia using absorbable material such as Vicryl 4-0 [3]. Some lacerations may cause airway complications including intraoral structure swelling and difficult breathing. In the case of hematoma, blood fills the submandibular space, the floor of the mouth becomes full, and then the tongue is forced upwards and backwards, causing an elevation of the tongue and airway obstruction. If swelling and difficult breathing became severe, early nasotracheal intubation or tracheostomy should be considered for airway protection. Extubation should be performed after the swelling subsides. While active arterial bleeding requires intervention, subsequent treatments are usually conservative, such as steroids, antibiotics and reversal of any coagulopathy [5]. Before all else, one should examine the patient's dental and oral condition carefully and check whether the mouthguard fits well to the patient before performing ECT. If necessary, the patient should get dental treatment in advance to ensure his or her safety during ECT.

Use of Image-Guiding Template for Contouring Surgery of Midfacial Fibrous Dysplasia

Simulation surgery using a 3-dimensional model is common in treatment of the craniofacial region. However, designing the reduction volume on the affected region and precise contouring according to a simulation model are still difficult. We developed a template composed of a thin clear dental plastic plate, which fits on the reduction model obtained from simulation surgery. We made several holes on the reduction model covered with the template and measured the depth of each hole without the template, which represents the thickness to be contoured at each point. This template was a mold of the reduction model and guided contouring of deformed bones intraoperatively. We applied the template to the affected region and marked the outline of the template and points of the holes. With the image designed with this template, we could contour the deformity of midfacial fibrous dysplasia symmetrically and easily.

How to make models of equine feet for accurate measurement and long-term study

The shape of equine hooves is difficult to measure and quantify. Scientific research on the effects of hoof conformation on normal and abnormal locomotion often requires precise characterization of hoof conformation. This technique produces accurate, life-size, permanent models of the hoof quickly and inexpensively from dental plastic powder and dental plaster.

A new approach to fabricating the occlusal surfaces of removable prostheses

A procedure is introduced to fabricate the occlusal surfaces of removable prostheses that oppose ceramic restorations or ceramic denture teeth. It involves the use of a heat-processed glass ceramic material in the form of onlays over the plastic denture teeth. This procedure provides for more wear compatibility, improved esthetics, and individualized occlusion. (J Prosthet Dent 1998;80:133-6.)

硬質レジン歯の構造と接着に関する研究

The purpose of this investigation was to study the Knoop hardness test, absorption and solubilityin MMA, and filler contents of the commercially available several cross-linked plastic denture teeth.In addition, tensile bonding strength of three denture base resins, heat-cured resin, heat-shock resin, andauto-cured resin, bonded to the artificial teeth was measured. Four cross-linked plastic denture teeth and oneconventional acrylic denture tooth were studied.Knoop hardness in the enamel of the specimens was as hard as the commercially available compositeresins for crown and bridge.The enamel contained 25-45% filler. The enamel had high cross-linked polymer, so the rates of swellingand solubility in MMA of the enamel were lower than the body of the specimens and the enamel and body ofplastic denture teeth.The body and dentin of the specimens showed better tensile bond strength than the enamel. Tensile bondstrength of the heat-cured resin and the heat-shock resin bonded to the body was better than the auto-curedresin bonded to the body.There was no difference in results between the body and the conventional acrylic tooth in all examinations.

義歯用硬質レジン歯こう合面部と即時重合レジンとの結合強さについて

The effect of the four types of surface treatment methods was evaluated to improve the bond strength between the self-curing acrylic resin and the abrasion-resistant plasticdenture teeth. All of the surface treatment methods significantly increased the bond strength. Specimens without surface treatment showed surface fractures after the bond test. As for the surface treatments using the silane coupling agent and 5% hydrofluoric acid-UDMA, most specimens showed surface fractures. The mechanically-roughened specimens (polished with # 100-SiC paper, sandblasted) showed cohesive fractures in self-curing acrylic resin. Although the bond strengths of specimens with or without surface treatment were significantly reduced after the thermocycle test (5, 000 cycles), most specimens that underwent the mechanical-roughening treatment showed cohesive fractures. The results of this study suggested that surface treatments of mechanicalroughening were effective methods to improve the bond strength and the bond durability of self-curing acrylic resin to occlusal surfaces of cross-linked abrasion-resistant plastic denture teeth.

義歯用硬質レジン歯の硬質レジン部分と流し込み型レジンとの結合強さについて

Bond strength between abrasion-resistant plastic denture teeth bonded to pour-type denture base resin was measured to evaluate the effect of five kinds of surface treatment. Bond strength to the enamel layer of teeth was significantly improved by applying of silane coupling agent. Etching of the enamel layer by 5% of hydrofluoric acid (HF) also improved the bond strength. The maximum bond strength was obtained from the surface which was etched by HF and then applied urethane dimethacrylate-based light-activated monomers (HF+UDMA treatment). Bond strength to the dentin layer of teeth was also significantly improved by HF+UDMA treatment. There was no significant reduction of the bond strength to the dentin layer after the thermo-cycling test (10, 000 cycles), but statistically significant reduction was observed in the enamel layer. The results of this study suggested that the HF + UDMA treatment would be a useful method to improve the bond strength between highly cross-linked enamel and dentin layers of abrasion-resistant plastic denture teeth and pour-type denture base resin.

Bond strength of denture teeth to acrylic bases

The literature relating to the determination of the bond strength of plastic denture teeth to acrylic resin denture material is reviewed. The papers are presented in chronological order with information on specimen preparation, batch sizes and methods of testing. The lack of uniformity in experimental techniques and the diverse range of products assessed makes recommendations for laboratory practice difficult to formulate. One consistent observation is that tooth surface contamination with wax decreases the bond strength between the teeth and the denture base material. A universal testing method needs to be formulated to replace the various techniques now employed.

Leaf Determination in the Fern Osmunda cinnamomea—A Reinvestigation

Earlier studies of leaf determination in the fern Osmunda cinnamomea L., using the technique of excision and sterile culture, indicated that the apices of incompletely determined leaf primordia are converted into shoot apices after isolation. Subsequently other workers questioned this interpretation, suggesting that a primordium is determined as a leaf shortly after its inception and that any shoot which arises from it is an adaxial adventitious bud. Because of the importance of this distinction in the interpretation of determination, the phenomenon has been reinvestigated by scanning electron microscopy and histological methods. Since fixation for electron microscopy was inconsistence, the work was performed on the primordia using resin models formed in dental plastic moulds. Our data, on explanted P3, P4, and P5 leaf primodia, provide strong confirmation for the interpretation that the leaf apex is indeed converted to a shoot apex in incompletely determined primodia after explantation. This new evidence forms the basis for interpreting leaf determination in this experimental system.

義歯床用流し込み型レジンと硬質レジンの結合耐久性について

Factors affecting bonding durability between three types of denture teeth (two abrasion-resistant plastic denture teeth and a plastic denture tooth) and a pour-type denture base resin were investigated. The bond strengths of Duradent (DU) and Real Crown (RE) were not affected by a water immersion period for up to one week, but significantly decreased after being immersed for one month. Endura (EN) showed a stable bond strength up to one month immersion. Thermocycling (500 cycles) also decreased the bond strengths for all denture teeth. The bond strengthsof Dichloromethane-treated denture teeth did not change even with one month immersion or thermocycling. The results of this investigation suggested that the treatment with Dichloromethane significantly would improve the bonding durability.

注入型レジンと硬質レジン歯の接着強さについて

We have investigated pour-type acrylic denture base resin and are convinced that it is very useful in making removable dentures. Recently, abrasion-resistant plastic denture teeth havebeen used frequently in the clinic. In this study, we made a bond strength test for three kinds ofabrasion-resistant plastic denture teeth and two kinds of pour-type denture base resin, in order toexamine clinical treatment methods when using these materials. These artificial teeth consist oftwo or three layers. The basal layer made of PMMA for adhering to the denture base resin wasremoved in this study. The treatment methods in the bonding surfaces of artificial teeth were asfollows: 1) no treatment, 2) treatment with a synthetic detergent, 3) treatment with a supplementalbonding agent, and 4) scraping off the basal surface of artificial teeth.The results were as follows: 1. In no treatment, most of the teeth peeled completely or partiallyoff the bonding surface, 2. The effect of the treatment with a synthetic detergent was found to beincomplete, 3. In the treatment with a supplemental bonding agent or the scraping off the basalsurface of artificial teeth, we obtained a higher bond strength with all kinds of teeth and foundfractures in artificial teeth or basal resin block, 4. These results show that proper treatments to thebasal surfaces of artificial teeth before curing enable sufficient bonding to the denture base resin.

義歯床用流し込み型レジンと硬質レジン歯の結合強さについて

The purpose of this study was to evaluate the bond strengths of two abrasion-resistant plastic denture teeth (Endura, Duradent) bonded to pour-type denture base resin. The bond strengths of abrasion-resistant plastic denture teeth were compared with plastic tooth and porcelain tooth. The effects on bond strength produced by treatment of ridge-laps were also studied. Specimens were prepared and tested in accordance with JIS specification. The bond strengths of Endura, Duradent and the plastic tooth were not statistically different, and those were significantly lower than that of the porcelain tooth. The bond strengths of Endura and the plastic tooth were increased by treatment of ridge-laps surface with Dichloromethane and Duradent were increased by the same treatment and grinding ridge-laps.