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At least 811 records · Page 45Linked to original sources
PubMed1996

Colour changes in acrylic teeth--comparison of an objective and subjective method.

Colour changes in four currently used brands of acrylic dental teeth were measured objectively and assessed subjectively following the application of heat, acrylic monomer and light. The data indicated that no clear correlation existed between the results of visual inspection and opto-electronic measurements. It is suggested that visual assessment is an unreliable method of detecting colour change, and an objective colorimetric method is therefore recommended.

Acrylic Resins↗
PubMed1996

A new technique for determining the denture tooth bond.

Defective bonds between resin teeth and denture base material remain a continuing source of failure. Findings from the limited number of studies on this topic are diminished by the numerous experimental approaches adopted. National and international standard specifications also adopt different methods of specimen preparation and physical straining. A critical appraisal of the various standards is carried out and a new procedure for determining the denture tooth to acrylic resin bond is described. A study using this technique found that physical modification and alginate contamination of the tooth had no significant effect on the bond strength. Ineffectual wax elimination was the main cause of failure.

Acrylic Resins↗
PubMed2006

Hardness of enamel exposed to Coca-Cola and artificial saliva.

The purpose of this study was to determine the rate of change in indentation hardness of enamel in permanent teeth exposed to Coca-Cola. In a further experiment, the ability of a commercially available artificial saliva to remineralize enamel treated with Coca-Cola was tested. Ten enamel specimens were randomly chosen to be treated with Coca-Cola (experimental groups) and seven with water (control group). The fluids were applied for 1, 2, 3 h and overnight (15 h), washed off with a few drops of water and the moist enamel indentation hardness tested after each interval. With Coca-Cola treatment, the mean enamel hardness was 92.6% (s.d. = 7.9) of the original baseline hardness after 1 h, 93.25% (s.d. = 10.15) after 2 h, 85.7% (s.d. = 12.03) after 3 h and 80.3% after 15 h. The mean indentation hardness of control specimens treated with water was 108.7% (s.d. = 16.09) of the original hardness after 1 h, 99.09% (s.d. = 18.98) after 2 h, 98.97% (s.d. =11.24) after 3 h and 98.42% (s.d. = 22.78) after 15 h. In a separate experiment, the hardness of 9 enamel specimens was tested, as previously described, before and after treatment with Coca-Cola overnight and again after application of artificial saliva for 3 min. Coca-Cola reduced the mean indentation hardness of enamel in the teeth, but the hardness was partially restored with artificial saliva (Salivart) and increased by 18% from the demineralized enamel hardness.

Carbonated Beverages↗
PubMed2006

Effect of various Ca2+/PO4(3-) concentrations of linseed-based saliva substitutes on enamel in vitro.

Remineralization might be hampered by various polymers used in saliva substitutes. Thus, the present study evaluated the effects of various calcium and phosphate concentrations of linseed-based solutions on the mineral loss of pre-demineralized bovine enamel in vitro. A commercially available saliva substitute (Salinum) based on linseed was tested as well. Enamel specimens were prepared from bovine incisors and embedded in epoxy resin. One-third of each sample was covered with nail varnish (control of sound enamel). After demineralization (37 degrees Celsius; pH 5.0; 14 days) another third of the samples was nail-varnished again. Subsequently, the specimens (n = 10) were exposed to 12 linseed-based solutions (Ca(2+) addition 0-2 mM; PO4(3-) addition 0-3.2 mM) at pH 5.5 and 6.5 as well as to Salinum) for 14 days (37 degrees Celsius). The differences in mineral loss between the values prior to and after the storage in the various solutions were evaluated from microradiographs of thin sections (100 mum). The general linear model revealed a significant dependency for the mineral loss on 'calcium' (P = 0.003), but not on 'pH' (P = 0.397) and 'phosphate' (P = 0.094). Salinum) induced a significant greater mineral loss compared with equivalently saturated solutions (P < 0.05; anova, Bonferroni). The solution with the highest calcium and phosphate concentration showed the greatest mineral gain (P = 0.033; paired t-test). The addition of calcium and phosphate seems to have a positive effect on the remineralizing qualities of linseed-based saliva substitutes.

Animals↗
PubMed2005

Evaluation of the airway of the SimMan full-scale patient simulator.

BACKGROUND: SimMan is a full-scale patient simulator, capable of simulating normal and pathological airways. The performance of SimMan has never been critically evaluated. METHODS: Sixty subjects (anesthesiologists, nurse anesthetists, and anesthesia residents) performed mask ventilation, laryngeal mask insertion and endotracheal intubation on SimMan. The simulator's airway was evaluated using visual analog scales (VAS) and by measuring the subject's performances. RESULTS: The SimMan full-scale patient simulator's airway is generally acceptably realistic but it significantly differs from the human airway in important aspects. Mask seal was more difficult than in humans whereas Laryngeal mask (LMA) insertion and function was acceptable. The distance from the teeth to the vallecula was too short. Cervical spine mobility was significantly reduced in the 'reduced neck movement' mode but the intubation was only slightly more difficult than in the 'normal' mode. CONCLUSION: The SimMan full-scale patient simulator's airway is generally acceptably realistic but it significantly differs from the human airway in important aspects. The user must be aware of these aspects in order to obtain maximum benefit from training and evaluation scenarios and when using the simulator for testing new equipment and techniques.

Anesthesiology↗
PubMed1995

Repair of a removable partial denture using gold occlusals.

Limited interarch space causes maintenance problems with removable partial dentures. The problem of abrasion and breakage of acrylic resin teeth, the concomitant supraeruption of opposing natural teeth, and possible decrease of vertical dimension of occlusion can be prevented or minimized with cast-gold occlusals. Use of metal occlusals has been advocated on newly constructed removable partial dentures, but not on existing prostheses with severely worn or broken denture teeth. This article describes a repair procedure for a removable partial denture where minimal interarch distance resulted in wear and breakage of denture teeth. A thin, abraded denture tooth that had been repaired numerous times was prepared and covered with a cast gold restoration. The problem of abrasion and breakage of the acrylic resin tooth was solved and the service life of the prosthesis was extended.

Acrylic Resins↗
PubMed1996

The results of a brief survey of complete denture prosthodontic techniques in predoctoral programs in North American dental schools.

A brief mail survey of North American dental schools was undertaken to ascertain the current techniques in complete denture prosthodontics regarding preliminary and final impressions, record bases, and denture teeth. Of the 64 schools surveyed, 54 responded (84%). Seventy-four percent of the respondents used only irreversible hydrocolloid (alginate) for their preliminary impressions; 15% used only modeling plastic impression compound. Eighty-one percent used only modeling plastic impression compound for border molding of the final impression tray; 7% used only polyether impression material. Forty-eight percent used only polysulfide rubber (PR) impression material for their final impression material; 4% used only polyether impression material. Only 1 school still used shellac as one of its materials for record bases. Thirty-five percent used only Triad; 35% used only acrylic resin; 24% used both of these materials. Thirteen percent of responding schools used only nonanatomic teeth. The majority (54%) used all three options (nonanatomic, semianatomic, and anatomic). Eleven percent used lingualized occlusion. As compared with a survey performed in 1985, the use of irreversible hydrocolloid as a preliminary impression material, the use of visible light-cured resins for record bases, and the use of anatomic teeth have increased. The use of plastic impression compound for border molding and PR as the final impression material has largely remained the same.

Canada↗
PubMed2000

Periodic evaluation of the occlusal vertical dimension of maxillary dentures from the wax trial denture through 48 hours after polymerization.

PURPOSE: This study measured the effects of commercial resin type on maxillary complete dentures with monoplane teeth by periodically comparing the occlusal vertical dimension of the polymerized dentures with the baseline, wax trial denture fiducial measurements. MATERIALS AND METHODS: Commercially available compression-molded, injection-molded, and fluid poly(methyl methacrylate) resins, as well as one compression-molded methyl acrylate ester copolymer, were evaluated. Ten dentures were fabricated from each resin using monoplane teeth. The occlusal vertical dimension at the articulator pin was measured at the wax denture stage for each specimen, and changes in occlusal vertical dimension for each denture were evaluated at a simulated laboratory remount, and at 0, 3, 6, 24, and 48 hours after a simulated clinical remount. Repeated measures analysis of variance (alpha = 0.05) and post hoc one-way factorial analysis of variance and Scheffe's F-Tests for each resin group were performed using ranks of raw data. RESULTS: Changes in the maxillary denture mean occlusal vertical dimensions were recognized throughout the evaluation periods compared with the wax-denture baseline, and time was a significant influence on displacement (p = .0001). Only the compression-molded poly(methyl methacrylate) dentures exhibited a mean laboratory remount occlusal vertical dimension that was significantly greater than the mean wax denture measurement, and all resin systems exhibited occlusal error that was significantly less than the laboratory remount measurements at 48 hours. At 48 hours, all resin groups exhibited mean occlusal vertical dimension changes that were less than 1 mm compared with the wax denture. Only compression-molded poly(methyl methacrylate) dentures exhibited a mean 48-hour clinical remount measurement that was statistically similar to the mean wax denture occlusal vertical dimension. CONCLUSIONS: Individual maxillary dentures from all resin types and at all intervals exhibited dimensional change. At the last evaluation period, the compression-molded poly(methyl methacrylate) showed no change in mean occlusal vertical dimension from baseline, whereas remaining groups exhibited occlusal vertical dimensions significantly less than baseline.

Acrylates↗
PubMed2001

The implant-supported milled-bar mandibular overdenture.

Osseointegrated dental implants have been proven successful in the treatment of edentulism. The predictability of the implant-supported prosthesis has also been established. Several techniques have been described for the successful restoration of the edentulous mandible: fixed-detachable prostheses with either the original Brånemark hybrid prosthesis design or conventional implant-supported fixed partial dentures, implant-retained overdentures, and implant-supported overdentures. However, in cases of advanced ridge resorption in which facial tissue support is needed from the flanges of the prosthesis or when a removable type of prosthesis is preferred by the patient, an implant-supported prosthesis is indicated. Electric discharge machining is often used in the fabrication of the bar for an implant-supported overdenture. This procedure is very costly and technique sensitive. An alternative procedure to fabricate a milled-bar implant-supported overdenture is described. This procedure is simple and uses inexpensive equipment and materials. The milled-bar minimizes lateral and rotational displacement. The overdenture incorporates attachments that provide retention, minimizing possible movement along the path of insertion. This type of prosthesis is available to a broad patient population, especially those with advanced ridge resorption, providing an excellent result at a reduced cost. J Prosthodont 2001;10:46-51.

Aged↗
PubMed2001

A nontraditional technique for obtaining optimal esthetics for an immediate denture: a clinical report.

Bimaxillary protrusion and severe labioversion of anterior teeth complicate impression procedures and increase the difficulty in making esthetic predictions for the immediate complete denture patient. The presented technique, performed in reverse order of traditional methods, is accomplished in stages in which the anterior and nonessential posterior teeth are extracted and interim removable partial dentures placed. An opportunity is thus created to evaluate esthetics, phonetics, and anterior tooth function before extraction of the remaining dentition and delivery of immediate complete dentures. This technique facilitated the determination of the need for alveoplasty of the anterior maxilla.

Alveoloplasty↗
PubMed2004

Maximizing mandibular prosthesis stability utilizing linear occlusion, occlusal plane selection, and centric recording.

The stability of mandibular complete dentures may be improved by reducing the transverse forces on the denture base through linear (noninterceptive) occlusion, selecting an occlusal plane that reduces horizontal vectors of force at occlusal contact, and utilizing a central bearing intraoral gothic arch tracing to record jaw relations. This article is intended to acquaint the reader with one technique for providing stable complete denture prostheses using the aforementioned materials, devices, and procedures.

Centric Relation↗
PubMed2004

Biomechanics of cantilever fixed partial dentures in shortened dental arch therapy.

PURPOSE: The purpose of the present study was to investigate, by means of 3-dimensional finite element analysis, aspects of the biomechanics of cantilever fixed partial dentures replacing the maxillary canine in shortened dental arch therapy. The null hypothesis was that no differences would be identified by finite element analysis in the mechanical behavior of the 2 designs of cantilever fixed partial denture under different scenarios of occlusal loading. MATERIALS AND METHODS: Single- and double-abutted cantilever fixed partial dentures were modeled and analyzed using the finite element packages PATRAN and ABAQUS. Displacement and maximum principal stresses (magnitude and location) within the fixed partial dentures, supporting structures, and the periodontal ligament/bone and abutment/retainer interfaces were examined under 20 different scenarios of axial and lateral occlusal loading. RESULTS: The results indicate that more displacement occurred in the 2 rather than the 3-unit cantilever fixed partial denture, with the greatest displacement having occurred under lateral loading. The maximum principal stresses observed in the periodontal ligament/bone interfaces were greatest buccocervically, with the highest value being observed in the 2-unit fixed partial denture under lateral loading. The highest maximum principal stresses observed in the retainer/abutment interfaces were located cervically in relation to the distal margin of the retainer of the 2-unit fixed partial denture under axial loading. CONCLUSIONS: It was concluded that in adopting a cantilever fixed partial denture approach for the replacement of a missing maxillary canine in shortened dental arch therapy, there may be merits, in terms of mechanical behavior, in selecting a double-rather than a single-abutment design. Furthermore, prostheses' displacement and functional stresses may be minimized by reducing lateral loading and avoiding pontic only loading.

Biomechanical Phenomena↗
PubMed2004

In vitro wear of nano-composite denture teeth.

PURPOSE: Few laboratory tests have been able to substantiate and quantify the wear resistances of polymeric denture teeth. This study evaluated the relative wear resistance of several types of denture teeth using an in vitro wear testing device. MATERIAL AND METHODS: Four different types of denture teeth [nano-filled (Veracia) and micro-filled composites (SR-Orthosit, Endura, Duradent, Surpass), cross-linked acrylic (SR-Postaris, Genios-P, Creapearl, Vitapan Physiodens, Premium 8, Integral), and a conventional acrylic (Biotone)] were used. The flattened buccal surface of each denture tooth was subjected to the evaluation of Knoop hardness (n=5) and localized wear for 100,000 cycles (n=10). Wear values were determined in micrometers using a profilometer. The data for the hardness, wear depth, and worn surface areas were individually analyzed by one-way ANOVA. RESULTS: Knoop hardness values (KHN) ranged from 28.2 to 29.8 for micro-filled composite, 18.9 to 21.6 for cross-linked acrylic, 22.7 for nano-composite, and 18.6 for conventional acrylic teeth. All micro-filled composite teeth were significantly harder than other teeth (p <0.0001). The wear depth values were 90.5 microm for the nano-composite, 69.8 to 93.0 microm for the micro-filled composite, 80.8 to 104.0 microm for the cross-linked acrylic, and 162.5 microm for conventional acrylic teeth. The worn surface areas were 5.1 mm2 for the nano-composite, 2.6 to 3.6 mm2 for the micro-filled composite, 4.4 to 5.7 mm2 for the cross-linked acrylic, and 10.1 mm2 for conventional acrylic teeth. The wear values of the acrylic control were significantly different from all other denture teeth (p <0.001). CONCLUSION: The nano-composite tooth was harder and more wear resistant than the acrylic teeth but not significantly different from most of the cross-linked and micro-filled composite teeth tested.

Acrylic Resins↗
PubMed2005

The role of abutment-attachment selection in resolving inadequate interarch distance: a clinical report.

A critical factor that needs to be evaluated during the diagnosis and treatment planning phase for patients seeking an implant-tissue-supported overdenture or metal-resin implant fixed denture is the presence of adequate interarch distance. The amount of interarch distance is critical to the selection of appropriate implant abutments and attachments for both implant-tissue-supported overdentures and metal-resin implant fixed complete dentures. This clinical report describes a patient with complications related to the failure to diagnose inadequate interarch distance, and the methods used to resolve the patient's chief complaint. A guide for abutment-attachment selection using one commercially available implant system is given.

Aged↗
PubMedDate not supplied

Influence of flask closure and flask cooling methods on tooth movement in maxillary dentures.

PURPOSE: This study investigated the tooth movement of standardized simulated dentures processed by traditional closure or the new Rafael Saide (RS) tension system when cooled in the curing water itself or in curing water followed by bench storage for 3 hours. MATERIALS AND METHODS: Forty stone casts were formed from a mold of an edentulous maxillary arch. The wax denture record bases were made on the casts; the height of the wax rim occlusion was 20 mm in the labial sulcus of the cast and 10 mm in the posterior region. The upper stone cast was mounted on a Mondial 4000 semi-adjustable articulator with wax rim interocclusal references in relation to the lower stone cast teeth. Metallic pins were placed in the incisal border of the maxillary central incisors (I), labial cusp of the first premolars (PM), and mesiolabial cusp of the second molars (M). The incisor-to-incisor (I-I), premolar-to-premolar (PM-PM), and molar-to-molar (M-M) transversal distances and left incisor-to-left molar (LI-LM), and right incisor-to-right molar (RI-RM) anteroposterior distances were measured before and after denture polymerization with an optical microscope with a tolerance of 0.0005 mm. For traditional closure, the dentures were flasked conventionally in standard metallic flasks, which were afterward placed in spring clamps. For the new RS system closure, the flasks were pressed between the metallic plates of the tension system after the final closure. The Clássico heat-polymerizing acrylic resin dough was packed in the flasks under a final packing pressure of 1.250 kg f. Twelve hours after flask closure, the dentures were polymerized in a moist heat-polymerizing cycle for 9 hours at 74 degrees C. The denture was deflasked after cooling in the water of the polymerizing cycle (groups A and C) or in the water of the polymerizing cycle and then bench-stored for 3 hours (groups B and D). Collected data were analyzed with analysis of variance and Tukey's test (p< 0.05). RESULTS: There was no statistically significant difference (p> 0.05) between the conventional and new RS system closure methods for the transversal distances after polymerization in all studied groups. The anteroposterior distances did not change with deflasking after water bath cooling. There were statistically significant differences (p< 0.05) in the anteroposterior distances with deflasking after water bath cooling and then bench storage for 3 hours. CONCLUSION: Tooth movement was similar in dentures processed by traditional closure and by the new RS tension system, with the exception of the anteroposterior distances when the flasks were cooled in their own curing water and bench-stored for 3 hours.

Analysis of Variance↗
PubMed1976

Marginal fracture of dental amalgams.

The purpose of this study was to determine the marginal fracture of different amalgams, using a semiclinical method which facilitates standardization and minimizes the observation time, in 10 patients receiving complete dentures. Cavities were cut occlusally in acrylic premolars and molars. The margin was then beveled to 45 degrees with a cone-shaped diamond. Two dispersion-strengthened amalgams and one conventional amalgam were used in each mouth. The cavities of each quadrant were filled with the same amalgam. Thus, conventional amalgam fillings were always placed in opposing quadrants to those filled with a dispersion-strengthened amalgam. The degree of marginal fracture was evaluated from the prints (magnification X 5-7) by five dentists separately and blindly. After 6 months' service, severe marginal fracturing was frequently seen.

Acrylic Resins↗