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The hypothesis of the present study was that immediate loading of implant-supported restorations replacing single missing teeth could be a successful procedure. The present study compared the clinical success of immediately loaded single-tooth implants placed in fresh extraction sites to that of immediately loaded single-tooth implants placed in healed sites. From the years 1997 to 1998, 26 patients, ranging in age from 18 to 70 years, presented for the placement of 28 immediately loaded implants intended to support single-tooth ceramometal restorations. Nineteen implants were placed into fresh extraction sites, and 9 implants were placed into healed sites. Temporary prefabricated acrylic resin crowns were prepared and adjusted. At the time of traditional second-stage surgery (3 to 6 months after implantation), the implants were restored with single-tooth ceramometal prostheses. The survival rates were 82.4% and 100% for immediate and non-immediate implants, respectively. Follow-up ranged from 6 to 24 months from the day of implant placement, with a mean of 13 months for the immediate implants and 16.4 months for the non-immediate implants. Radiographic marginal bone loss after 3 to 6 months did not extend beyond the abutment-implant junction. Within the limits of the present investigation, immediate loading of single-tooth implants placed in healed sites is a possible treatment alternative. Immediate loading of single-tooth implants placed in fresh extraction sites carried a risk of failure approximating 20% in this patient population. [ABSTRACT FROM AUTHOR]

Abstract: A plethora of choices is available as potential tooth-colored restoratives for the posterior dentition. Advances in adhesive technology and esthetic chairside microhybrid composite resins have permitted clinicians to perform inlay/onlay restorations The use of adhesive indirect procedures offers advantages such as better control of polymerization shrinkage and anatomical form, when compared to conventional, direct restorative techniques. This article describes the use of a new chairside microhybrid composite system as an indirect restorative material, using semidirect and direct techniques that can be accomplished within the realm of a dental operatory. [ABSTRACT FROM AUTHOR]

Summary: With increasing patient demands for esthetic dentition, composite resin restorations enjoy great popularity due to excellent esthetics, acceptable longevity, and relatively low costs. Shading concepts used by manufacturers, however, may be confusing to many clinicians. Purpose: To review and describe the current main shading concepts, evaluate their potential for creating natural esthetics, and provide guidelines for application. [ABSTRACT FROM AUTHOR]

Excessive heat generation at the implant-bone interface may cause bone damage and compromise osseointegration. Autopolymerizing acrylic resins are commonly used intraorally to join impression copings and suprastructure components for soldering. The effect of heat generation at the implant surface related to the exothermic setting reaction of autopolymerizing acrylic resins applied to an attached abutment was examined in vitro. Two brands of autopolymerizing acrylic resin, Duralay and GC Pattern Resin, were compared. Acrylic resin was applied to a titanium alloy abutment connected to a titanium alloy cylindric implant in varying controlled volumes, with both bulk application and brush paint-on techniques. The implant was embedded in an acrylic resin mandible in a 37°C water bath. Temperature changes were recorded via embedded thermocouples at the cervical and apical of the implant surface. Analysis of variance for repeated measures was used to compare treatment groups. A mean maximum increase in temperature of 4 to 5°C was seen at the implant cervical for both materials, with a maximum temperature increase of 6°C. No difference between Duralay and GC Pattern Resin was seen, except for bulk application to medium-sized copper bands at the implant cervical (P < .05). No difference between the bulk and brush techniques was seen for all options, except for GC, where bulk application to medium-sized copper bands produced higher temperatures than the brush technique (P < .05). Spray coolant reduced temperatures for bulk application of both Duralay and GC (P < .05). [ABSTRACT FROM AUTHOR]

A technique tor manufacturing direct resin composite veneers is presented. Described are the advantages of using an acrylic resin matrix, made before the preparation is begun, to copy anatomic details. An additional step to mask previously prepared dark enamel with opaquers is also described. The advantages and limitations of the procedures are discussed. [ABSTRACT FROM AUTHOR]

Purpose: This investigation studied the effects of 3 surface treatments on the shear bond strength of a light-activated composite resin bonded to acrylic resin denture teeth. Materials and Methods: The occlusal surfaces of 30 acrylic resin denture teeth were ground flat with up to 400-grit silicon carbide paper. Three different surface treatments were evaluated: (1) the flat ground surfaces were primed with methyl methacrylate (MMA) monomer for 180 seconds; (2)light-cured adhesive resin was applied and light polymerized according to the manufacturer's instructions; and (3)treatment 1 followed by treatment 2. The composite resin was packed on the prepared surfaces using a split mold. The interface between tooth and composite was loaded at a cross-head speed of 0.5 mm/min until failure. Results: Analysis of variance indicated significant differences between the surface treatments. Results of mean comparisons using Tukey's test showed that significantly higher shear bond strengths were developed by bonding composite resin to the surfaces that were previously treated with MMA and then with the bonding agent when compared to the other treatments. Conclusion: Combined surface treatment of MMA monomer followed by application of light-cured adhesive resin provided the highest shear bond strength between composite resin and acrylic resin denture teeth. [ABSTRACT FROM AUTHOR]

Purpose: There have been numerous attempts to improve the mechanical properties of acrylic resin. However, the fracture of dentures is still an unresolved problem. The potential advantage of self-reinforcement should be improved mechanical properties over the amorphous random polymer. This study investigated the addition of poly(methyl methacrylate) (PMMA) beads in a variety of percentages on a range of mechanical properties of PMMA denture base acrylic resin. Materials and Methods: The transverse and impact strengths and hardness of acrylic resin specimens stored in water for periods of 1 week and 6 months prior to testing were investigated. Results: The results showed that for specimens stored for 1 week, the addition of up to 25% beads produced a significant increase in the modulus of elasticity. Addition of 5% beads produced a slight but nonsignificant increase in the modulus of rupture, although additions of increasing percentages produced a decrease in the modulus of rupture. The impact strength was increased for 5% to 25% beads and decreased for 40% beads. The hardness showed only small changes. For specimens stored in water for 6 months, the modulus of rupture decreased with increasing percentages of beads. The addition of beads up to 10% significantly increased the modulus of elasticity. There was no significant increase in impact strength but a significant increase in hardness for 5% beads. Conclusion: The addition of PMMA beads to acrylic resin did not produce a substantial improvement in the mechanical properties and cannot be recommended as a method of reinforcement in its present form. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of the investigation was to compare the performances of teeth restored with quartz fiber, carbon-quartz fiber, and zirconium-dioxide posts covered with all-ceramic crowns when subjected to a cyclic loading test performed in a wet environment. Materials and Methods: Forty single-rooted human lower premolars having similar dimensions were endodontically treated and mounted in acrylic resin blocks with a simulated periodontal ligament. The teeth were divided into three experimental groups and one control group. Post holes 8 mm long were prepared in the roots of the experimental groups in which quartz fiber, carbon-quartz fiber, and zirconium dioxide posts were cemented. In the control group, no posts were used. The crown buildup was made with composite resin. The teeth were covered with all-ceramic crowns and intermittently loaded at an angle of 45 degrees to the long axis of the tooth at a frequency of two loads per second. Results: Only one failure (root fracture + post fracture) was observed in each of the fiber post groups, while in the zirconium dioxide post group, six failures were observed (one crown fracture and 5 root fractures + post fractures). The Kaplan-Meier analysis of the three experimental groups showed that the survival rate of zirconium dioxide posts was significantly lower than that of both types of fiber post. All the experimental groups showed a survival rate higher than that of the control group. Conclusion: Fiber posts reduced to a minimum the risk of root fractures of teeth restored with composite cores and Empress crowns under the present experimental conditions (intermittent loading in a wet environment]. [ABSTRACT FROM AUTHOR]

Objective: This in vitro investigation aimed to determine the radiopacity of eight recently introduced "flowable" restorative resin composites and to compare their radiodensities to those of enamel, dentin, and a widely used composite marketed tor universal application in anterior and posterior teeth. Method and materials: A total of 45 composite specimens were fabricated in cylindrical molds and exposed to a curing light for 120 seconds. Two methods were used to determine radiopacity: a transmission densitometer and a computer-assisted densitometric image analysis station. Results: Of the eight flowable resin composites tested, only three exhibited a radiopacity equal to or greater than that of enamel, a widely followed guideline for clinicians' diagnostic ability. The radiopacity of the remaining five materials was not statistically significantly greater than that of dentin. Conclusion: The level of radiopacity of the tested flowable composites was variable; those with low radiodensity should be avoided in Class II restorations, where a clear determination of recurrent caries by the examining clinician could be compromised. (Quintessence Int 1999;30:179-184) [ABSTRACT FROM AUTHOR]

Objective. Infection control protocols in dentistry dictate that orthodontic acrylics have to be disinfected. No specific products for orthodontic acrylics are available. The objective of this study was to investigate the influence of chemical disinfectants on mechanical properties of orthodontic acrylics. Materials and Methods. 260 test specimens of two cold-curing orthodontic acrylics were manufactured. Three chemical disinfecting agents were tested: Impresept, D050 Instru-Gen, and Stammopur DR. Test specimens were stored in distilled water and divided into test groups. E-Modulus, flexural strength, macro hardness, micro hardness, average roughness, and colour change were measured. Results. Disinfection agents showed no significant influence on E-modulus. Values ranged from 1783.80 ± 163.80 MPa (Forestacryl colourless) to 2474.00 ± 135.00 MPa (Orthocryl green) after storage in distilled water. Disinfection agents performed no significant influence on flexural strength. Values ranged from 18.64±1.59 N/mm2 (Forestacryl colourless) to 25.64 ± 1.43 N/mm2 (Orthocryl green) after storage in distilled water. Orthocryl colourless showed a reduction of the macro hardness after disinfection (Stammopur DR (p≤0.001), D050 Instru-Gen (p≤0.037)). Disinfection of Orthocryl green with D050 Instru-Gen (p<0.001) and Forestacryl colourless with Impresept (p≤0.001) led to a reduction of macro hardness. Micro hardness of Orthocryl colourless altered significantly after disinfection with D050 Instru-Gen (p≤0.001). Micro hardness of Forestacryl colourless increased (Impresept (p≤0.039)) and decreased (Stammopur DR (p≤0.006) Instru-Gen (p≤0.001)) after disinfection. Average roughness did not change significantly (Orthocryl colourless). Forestacryl colourless performed a significant change after disinfection with Stammopur DR (p≤0.05). This is also true for the disinfection of Orthocryl green and Forestacryl pink with Instru-Gen (p≤0.05). Disinfection performed no significant influence on colour change. ΔE-values were in a range of 1 to 2. Conclusions. Some orthodontic acrylics disinfection caused significant changes of determined parameters. Changes were specific for the applied disinfectant and tested orthodontic acrylic. Further studies should verify the impact of long-term disinfection intervals. Thus, from manufacturers of orthodontic acrylics recommendations for appropriate disinfectants would be desirable. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Antimicrobial silver-charged dental acrylic resin is prepared. • The material is active against C. albicans , S. mutans and F. nucleatum. • Antimicrobial activity against C. albicans remains unchanged for 45 d. Abstract The insertion of prosthetic devices into the oral cavity affects the oral microflora and results in accumulation of microorganisms on the prosthetic surface. Such fouling of denture surfaces can lead to a number of oral diseases and consequently to the replacement of the denture. Here, we report the post-synthesis introduction of silver in zeolite-loaded dental acrylic (DAZ) resins that does not influence the mechanical or aesthetic properties of the DA resins, and provides them with a long-term antimicrobial activity. Na-FAU zeolite (2 wt%) was incorporated into DA resin, which was conventionally processed and cut into 10 mm × 20 mm × 3 mm coupons. The Na+ in the zeolite was then exchanged with Ag+ via immersion of the DAZ coupons in 0.01 M AgNO 3 solution to obtain DAZ/Ag-treated coupons used in antimicrobial tests. Antimicrobial tests showed that the DAZ/Ag-treated coupons were active against Candida albicans (a reference and a clinically relevant strain), Streptococcus mutans and Fusobacterium nucleatum. Ag leaching tests on the Ag-charged coupons at 1, 2, 3, 4, 7, 14, 30 and 45 days of incubation in distilled water at 37 °C, indicated sustained release of silver. Antimicrobial tests using a reference Candida albicans strain showed that the leached coupons retained antimicrobial activity after 45 days immersion in distilled water, but, after 60 days incubation no antimicrobial activity was observed. Cytotoxicity assay results indicated that the DAZ/Ag-treated coupons showed no additional cytotoxicity compared to neat dental acrylic coupons. [ABSTRACT FROM AUTHOR]

The success of removable prostheses ultimately depends on a number of factors such as retention, stability, support, esthetics, and masticatory function. Increased intraoral inter‐arch distance leads to an increase in the weight of the prosthesis. This may compromise the retention and resistance, which are key for a successful removable prosthesis. Various methods, techniques, and materials have been reported to minimize the weight of a prosthesis. This article describes a simple, unique, precise single‐flask technique for the fabrication of a lightweight maxillary prosthesis using caramel as a 3D spacer, which was "indexed" to obtain a uniform thickness of acrylic around the hollow cavity. [ABSTRACT FROM AUTHOR]

Ideal implant placement is ultimately determined by the requirements of the final restoration. For the surgeon placing implants, proper angulation, parallelism, and spacing are critical to the final restoration. The use of a stainless-steel drill guide sleeve in an acrylic resin surgical template can make it possible to achieve optimal placement. Communication between the restoring dentist, surgeon, and laboratory technician is enhanced by this system since dowel pins fit precisely into the sleeves and determine sleeve and, ultimately, implant position. This system allows the surgeon to negotiate bony irregularities and ramping defects with ease while preparing a more concentric implant site. [ABSTRACT FROM AUTHOR]

Three impression techniques were assessed for accuracy in a laboratory cast that simulated clinical practice. The first technique used autopolymerizing acrylic resin to splint the transfer copings. The second involved splinting of the transfer copings directly to an acrylic resin custom tray. In the third, only impression material was used to orient the transfer copings. The accuracy of stone casts with implant analogs was measured against a master framework. The fit of the framework on the casts was tested using strain gauges. The technique using acrylic resin to splint transfer copings in the impression material was significantly more accurate than the two other techniques. Stresses observed in the framework are described and discussed with suggestions to improve clinical and laboratory techniques. [ABSTRACT FROM AUTHOR]

A case report of a chairside-fabricated indirect resin composite restoration is used to introduce a modification to a newly released one-appointment resin inlay-onlay technique. Fast-setting poly(vinyl siloxane) die material accommodates an articulated working cast within 10 minutes. The technique allows the economical construction of large, occlusal, load-bearing, extracoronal resin composite restorations. The guarded prognosis associated with extensive posterior resin composite restorations i acknowledged; nevertheless this technique remains a realistic option for those financially compromised patients who request tooth-colored restorations. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study was to determine the effect of water on the flexural properties of fiber-reinforced denture base polymers. Materials and Methods: Continuous woven silanized electrical glass or E-glass, fibers and woven silica fibers were used to reinforce heat-cured and autopolymerized denture base polymers. Fibers were oriented at a 45-degree angle to the long axis of the test specimens. Control specimens were unreinforced. Dry test specimens and those stored in water for up to 48 weeks were tested with a three-point loading apparatus. The surfaces of the fibers of the test specimens stored dry or 48 weeks in water were analyzed with a scanning electron microscope to evaluate the degree of adhesion between fibers and polymer matrix. Results: The ultimate transverse strength of unreinforced and reinforced denture base polymers decreased during 48 weeks' storage in water (P < 0.05, one-way analysis of variance, n = 5), and most of this reduction occurred during the first 4 weeks of storage in water. The flexural modulus of the unreinforced test specimens decreased significantly (P < 0.001), whereas there was less, if any, change in the flexural modulus of the fiber-reinforced test specimens. Scanning electron microscopic examination revealed no differences in adhesion of E-glass fibers to the polymer matrix when the specimens stored in water were compared with those stored dry. Reduced adhesion between the silica fibers and matrix was observed after 48 weeks' storage in water. Conclusion: The results of this study suggest that the ultimate transverse strength of the E-glass fiber-reinforced test specimens decreased 14% and that of the silica fiber-reinforced test specimens decreased 36% after 48 weeks of storage in water. [ABSTRACT FROM AUTHOR]

Purpose: This in vitro study compared the effects of four surface treatments on the bond strength between porcelain denture teeth and heat-polymerized denture base acrylic with and without a ceramic primer and bonding agent and after three storage conditions. Materials and Methods: Polished porcelain specimens (120) were divided into 24 groups of five each as follows: surface treatments (none, etched, sandblasted, and air abraded), ceramic primer and bonding agent (yes and no), and storage conditions (water storage, thermocycling, and accelerated aging). All the specimens were tested to failure in tension on a testing machine. Results: Hydrofluoric acid etching, sandblasting, and air abrasion did not improve the bond strength of specimens without ceramic primer and bonding agent compared to those polished with 600-grit silicon carbide paper. Use of ceramic primer and light-activated bonding agent (Scotchbond MP) increased the bond strength. For thermocycled specimens treated with ceramic primer and bonding agent, the bond strengths ranged from 10 to 31 MPa in the following order: air abraded = etched < no treatment < sandblasted. Conclusions: Ceramic primer and bonding agent dramatically improved the bond strength of porcelain teeth to heat-polymerized denture resin. Sandblasting improved bond strength of bonded samples compared to those that were etched or polished only. [ABSTRACT FROM AUTHOR]

Four groups of autopolymerizing acrylic resins used for various purposes in current dental practice were investigated by monitoring their temperature changes during the polymerization process. Resins were compared in terms of characteristic parameters (such as the time interval needed to reach mechanical stability and the maximum temperature generated during the polymerization process) and interpretations were made of such temporal temperature profiles. [ABSTRACT FROM AUTHOR]

The bond strength of denture teeth to acrylic resin denture bases was determined by producing tensile test specimens from standardised and anonymously presented partial dentures. Ten dentures were produced by randomly selected commercial dental laboratories and five were produced in a university dental laboratory. The tooth debonding forces exhibited a wide range of variation both within and between dentures. The university-produced dentures showed, on average, a slightly improved tooth bond strength. This study highlights the need for further investigation of this problem and for the development of a standardised technique to provide satisfactory denture tooth bonding. [ABSTRACT FROM AUTHOR]

This in vitro study determined the fracture toughness of four classes of resin using wet and dry test environments, following 48 hours of wet storage. Two of the resins were light initiated, while the other two were chemically initiated. No significant difference in fracture toughness was detected for the wet and dry test environments using miniature compact tension specimens. The light-initiated, urethane dimethacrylate resin demonstrated a significantly higher fracture toughness than the poly(methyl methacrylate) resin. [ABSTRACT FROM AUTHOR]

The fracture strengths of four types of all-ceramic premolar crowns (conventional Vita-Dur, In-Ceram, Dicor, and IPS-Empress) were compared after a preload cycling in aqueous atmosphere. Preload cycling significantly decreased the strength of Vita-Dur crowns. Fracture strength of Vita-Dur crowns was improved when they were luted with either polyalkenoate or adhesive resin cement. The average (standard deviation) of load to fracture of ceramic crowns luted using zinc phosphate cement and after applied preload cycling in distilled water were: Vita Dur, 770 (237) N; Vita In-Ceram, 1060 (341) N; Dicor, 840 (226) N; and IPS-Empress: 891 (185) N. The In-Ceram crowns fractured in two modes: complete fractures at 1276 (207) N; and fractures with the core remaining intact at 808 (292) N. [ABSTRACT FROM AUTHOR]

Reinforcement of acrylic denture base resin with high-performance polyethylene fiber in woven form produced a substantial improvement of stiffness and impact strength, as well as reducing the sensitivity of the material to notches that mimic anatomic features. The mechanical properties of the new systems were not affected by water immersion. Reinforced complete maxillary and mandibular dentures having good appearance and satisfactory fiber/resin integration were achieved using conventional laboratory techniques. These prostheses are undergoing clinical trials with encouraging results. [ABSTRACT FROM AUTHOR]

Aluminum is one type of metal base material used as an alternative to acrylic resin. This study evaluated whether commonly used denture cleansers cause leaching of the metal base into the cleaning solution. Seven cleansers (Efferdent, Polident, Clorox, Clorox/Cascade, vinegar, Tartar and Stain Remover, and Ivory soap) and two controls (tap water and distilled water) were evaluated. One hundred thirty-five wax samples (30 × 30 × 1 mm) were cast in 99.4% pure aluminum. The 135 samples were randomly assigned to the nine cleanser groups. Each sample was soaked in a cleanser for 0.5, 1, or 8 hours, and the amount of aluminum present in each cleanser was then analyzed by atomic flame-emission spectrometry. The results indicated that all cleansers leached aluminum into solution in varying amounts. Tartar and Stain Remover and Clorox caused the greatest leaching, whereas Ivory soap and Efferdent leached the least. [ABSTRACT FROM AUTHOR]

The effect of increasing the occlusal vertical dimension on the mandibular postural relation was studied for eight subjects. Interocclusal rest space measurements were made weekly for 1 month prior and subsequent to increasing the occlusal vertical dimension by 3.5 to 4.5 mm interincisally using luted acrylic resin, complete-arch, fixed partial dentures. Interocclusal rest space measurements were made at the clinical rest position, which was established by requesting the subjects to close in maximum intercuspation and immediately relax their mandible. Interocclusal rest space measurements were also made at the more open resting position when the subjects were repeatedly instructed to relax and lapse into a semi-hypnotic condition termed "relaxed resting posture." Initial speech difficulties and muscle discomfort subsided after 1 to 2 weeks. Analysis of variance using repeated measures showed no significant difference in interocclusal rest space after increasing the occlusal vertical dimension for both clinical rest position and relaxed resting posture. A significant difference was found between clinical rest position and relaxed resting posture (P = .001), and no interaction was determined between clinical rest position, relaxed resting posture, and time. [ABSTRACT FROM AUTHOR]

Visible light-polymerized resin composite tabs were bonded to the flattened, acid-etched surface of teeth that were scheduled for extraction. Half of the teeth (group I) were isolated with cotton rolls in conjunction with a saliva ejector. The remaining teeth (group II) were isolated using a rubber dam. Both methods of isolation were used for each patient so that to some extent all patients served as their own controls. Following extraction, all samples were thermocycled 500 times alternating between 6°C and 60°C, after which they were immersed in 5% methylene blue for 4 hours. Each tooth was then mounted in acrylic resin and sectioned on a hard tissue microtome. Microleakage was assessed using a light microscope at × 20 magnification. The use of rubber dam isolation resulted in less microleakage at the enamel resin interface. [ABSTRACT FROM AUTHOR]

This article describes a technique for fabricating interlocking custom tracheostoma vents for use in patients with bidirectional tracheostomas or tracheostoma fistulas secondary to tracheostenosis. The interlocking nature of the tracheostoma vents allows easy placement and removal from a tracheostoma or tracheostoma fistulas that would not be possible with a single tracheostoma vent A 5 x 10-mm opening in the inferior portion of the prosthesis allows the patient with intact vocal cords to phonate by occluding the opening of the prosthesis and forcing air through the prosthesis into the subglottal area. The rigid acrylic resin of the prosthesis maintains the patency of the tracheostoma or tracheostoma fistula while a resilient material in the peristomal area reduces the pressure and potential irritation. The steps involved in the fabrication of the dual interlocking custom tracheostoma vents are easy and require no elaborate laboratory equipment. [ABSTRACT FROM AUTHOR]

This in vitro study measured the changes in the fracture resistance of posterior crowns as a function of crown length. The crowns, 10 for each group, were made of a feldspathic porcelain (Ceramco), a glass-ceramic material (Dicor), and an alumina-reinforced glass (In-Ceram). Three different crown lengths were tested on acrylic resin dies. The restorations were fractured in a testing machine using a steel ball, 12.7 mm in diameter, that contacted the occlusal surface at three distinct points. Statistical analysis was performed using the Weibull distribution. The fracture resistance increased significantly with increasing crown length for all crown materials. [ABSTRACT FROM AUTHOR]

An in vitro study was conducted to determine the accuracy of fit of the acrylic resin pattern for the implant-supported prosthesis to the implant abutments. A master model containing five Nobelpharma titanium implants was fabricated using Ivocap acrylic resin. Using this model, five standardized acrylic resin patterns were fabricated from the three test dental acrylic resins. The fabricated patterns remained on the master model for 24 hours before removal and subsequent measurement. To compute the accuracy of each pattern, three special measuring points were firmly attached to each gold cylinder prior to pattern fabrication and the x, y, and z coordinates of these measuring points were determined. Measurements were made prior to pattern fabrication, with the cylinders on their respective abutments and after pattern fabrication, when the pattern had been removed from the master model. The results of this study showed that there was a significant difference in accuracy between the test acrylic resins and that none of these materials was completely accurate. [ABSTRACT FROM AUTHOR]

The Michigan Computer Graphics Coordinate Measurement System was used to measure the wear of three composite resins and an amalgam alloy control. The validity of the Latin Square experimental design for analysis in a clinical study was demonstrated, and statistically significant differences in wear were established for main effect for the materials under investigation. None of the composite resins examined approximated the amalgam alloy control in wear properties. Rank ordering of the materials with respect to wear was possible using this experimental design. Ranking of the materials for wear resistance using this research approach opens up other future research opportunities to correlate such properties as filler particle size, composition, and distribution with the data derived. [ABSTRACT FROM AUTHOR]

Retainers for composite retained prostheses ("Maryland bridges") have traditionally relied upon an etched base metal alloy for micromechanical retention. This study compared the tensile bond strength of three resin cements using two alloy surface treatments. Rexillium III and Olympia disks were cast, oxidized, and given simulated porcelain firings. Paired specimens were cemented with Comspan, Panavia EX, or C & B Metabond after air abrasion with aluminum oxide or silicoating. Air-abraded Olympia disks were tin plated prior to luting with Panavia EX. Electrolytically etched Rexillium III specimens luted with Comspan served as controls. Specimens were thermocycled and tested in tension. Highest tensile bond strengths were achieved with: (1) Olympia specimens, where the bonding surface was air abraded but tin plated before cementation with Panavia EX, and (2) Rexillium III specimens, where the bonding surface was air abraded or silicoated and the disks were cemented with C & B Metabond. [ABSTRACT FROM AUTHOR]

A holographic interferometer for investigating deformations of dental prostheses is described. Residual stress relaxation resulting from the polymerization of acrylic resin dentures is qualitatively studied during the first 48 hours following fabrication. The resulting fringe patterns show a symmetry that is correlated to the shape of the denture. A quantitative analysis of the interferograms was performed with the aid of a computer program. The computer-aided holographic interferometer was tested using disk-shaped acrylic resin materials. Dimensional deformations resulting from temperature changes were measured with an accuracy better than 0.2 μm. Because of the aging of the resin material, the reaction to temperature changes may differ as a function of time and may be studied using quantitative comparison of deformation plots. For convenience, the original object shape can be added to or subtracted from the graphical deformation data. [ABSTRACT FROM AUTHOR]

The design of removable partial dentures has progressed both clinically and in laboratory research. Nonetheless, there still appears to be a conflict between the empirical practice and the scientific data available. On this basis, the authors question several aspects of the lingual connector. If lingual connectors are required to be rigid, how is this best achieved and can it be assured that designs impart sufficient rigidity? On the contrary, is it possible to make the connector too rigid? No conclusions are attempted in this theoretical discussion, but research to resolve the dilemma is encouraged. [ABSTRACT FROM AUTHOR]

Three bonding agents were evaluated to determine their effect on the strength of the bond when Silskin II and Cosmesil SM4 silicone facial elastomers were polymerized to a light-activated denture resin. A silane bonding agent proved to be superior, whereas a light-activated bonding agent had inferior bonding characteristics. Intensive heat aging had no significant effect on bond strength. [ABSTRACT FROM AUTHOR]

This study measured the retention profiles of 11 commercially available stud-type attachment systems suitable for use with overdentures. The vertical distance over which resistance to separation existed was recorded and related to the configuration of the attachments. In many of the systems tested, only a small portion of the vertical length of the attachment contributed to the retention of the unit. [ABSTRACT FROM AUTHOR]

This study determined the dimensional accuracy of dies made using a combination of four impression materials and three Type IV die stones. A metal die was prepared for a molar complete cast crown, and 10 stone replicas were made using 12 different combinations of impression materials and die stones. The distances between reference points on the metal and stone dies were measured in three directions with a traveling microscope. Analysis of variance and Duncan's MR comparisons (P ≤ .05) showed that all of the stone dies were larger than the metal die. Although there were significant differences between some of the impression material/die stone combinations, all of the stone dies were measured to be within 9 μm of each other. No one impression material/die stone combination consistently produced the smallest or largest die in the three measured directions. [ABSTRACT FROM AUTHOR]

The potential correlation of the force versus time behavior of four resilient lining materials and their acceptance by patients was investigated. Two modified acrylic resins and two silicone denture lining materials were tested. The response of the soft lining materials to a programmed indentation test was used to define a parameter for each denture liner product. A parameter defined as the "Rebound Index," using force-time data obtained from the indentation measurements, was significantly different for the modified acrylic resins compared to the silicone materials. Improved patient acceptance was correlated with higher values of this index. [ABSTRACT FROM AUTHOR]

The rate of plaque accumulation on various materials used for fixed prostheses was investigated, and the composition of plaque formed on each surface was evaluated. Enamel, metal, acrylic resin, and porcelain surfaces were studied. Amounts of plaque that formed on the teeth and fixed restorations were scored using the method of Silness and Loe. Different individuals formed plaque at different rates, and the character and quantity of the plaque was different on the various materials. In a second study, acrylic resin, metal, and porcelain crowns were made for each of 10 patients. The amount of plaque absorbed onto each material after 1, 3, and 24 hours was recorded using scanning electron microscopy. The samples of dental plaque at 24 hours on each type of crown material were collected and investigated in a CHN Analyzer 184, revealing differences in the chemical composition of plaque adsorbed onto different surfaces. The results of SEM examination and biochemical analysis are presented. [ABSTRACT FROM AUTHOR]

Clay or wax is used extensively as a modeling material for trial facial prostheses. This article describes a technique that uses a resilient acrylic resin as a matrix to lodge the ocular component and wax as the sculpturing medium for orbital prostheses. The technique can be adapted and used for all facial prostheses. [ABSTRACT FROM AUTHOR]

Mandibular movements and the activity of the masseter and digastric muscles were evaluated in ten subjects as their vertical dimension of occlusion was altered using three different acrylic resin occlusal devices. Data were recorded on an electromyograph and kinesiograph. The degree of maximum opening increased with the increase in vertical dimension of occlusion. No major changes were noted in the patterns of mandibular movement, but significant changes were observed in the activity of the masseter and digastric muscles. [ABSTRACT FROM AUTHOR]

The article discusses issues related to the use of IMZ implants to stabilize the position of a removable or fixed-removable denture. It is noted that the use of bars with IMZ implants to support complete prostheses has been proven with a 98 percent success rate over a study period of 13 years in 267 cases. The stages involved in the implantation method with IMZ implants are described. Several images of procedures involved in the use of bars with IMZ implants are also presented, including an acrylic resin record base.

The article discusses a study which examined some of the treatment possibilities for achieving maximum esthetics with varying degrees of alveolar bone deficiency without using an acrylic resin-based restoration. A case that describes a cosmetic and functional restoration of a young woman who was left with a substantial hard and soft tissue defects after an automobile accident is presented. Laboratory procedures involved in a complete wax-up of the restoration are described and several images of the procedures are presented.

The article discusses a study which investigated the accuracy of reproducing acrylic resin denture base that was processed against an edentulous master cast. The master casts utilized in the study were obtained by duplicating the original patient master cast. The study used a three-dimensional measuring machine (MMT) to test the denture. It included seven types of heat and autopolymerizing acrylic resin. It discovered that all the acrylic resin polymers demonstrated small variability in the discrepancy between the tissue-fitting surface of the denture base and the master cast.

Removable partial denture production in Scotland was studied by analyzing photographs taken of consecutive casts and dentures and reviewing prescriptions of 539 cases at a large dental laboratory. Of the casts, 70.4% were maxillary and 29.6% mandibular. The mean number of teeth present was 9.9 in the maxilla and 8.4 in the mandible. Of the partial dentures studied, 33.6% were acrylate dentures without any framework. None of these had occlusal rests, and 5.6% had clasps. Of the framework-retained maxillary dentures, the palatal strap (12.9%). horseshoe (15.8%), and anterior palatal bar (18.9%) designs were the most frequent. In the mandible, lingual bars (32.7%) and lingual plates (32.7%) predominated. Of the acrylic dentures, 89.3% were made without any instruction from the dentist. The corresponding figure for prostheses with cobalt-chromium frameworks was 15.0%. [ABSTRACT FROM AUTHOR]

An injection technique can be used to rapidly generate direct post and core patterns with autopolymerizing acrylic resin. The technique uses an autopolymerizing acrylic resin, a serrated plastic pin, and a syringe with a disposable needle tribe and plug to inject acrylic resin into the root canal. The technique is simple, accurate, and faster than the bead-brush technique and eliminates some of its shortcomings. [ABSTRACT FROM AUTHOR]

Achievement of an esthetic single-tooth restoration in the anterior segment is a difficult task for the restorative dentist. A case is described in which two congenitally missing maxillary lateral incisors were replaced with single-tooth implants. A new technique was used to restore the teeth provisionally with a polyethylene ribbon and resin replacement. Light-cured staining systems for acrylic resins and ceramics were employed to customize both the provisional and final restorations. [ABSTRACT FROM AUTHOR]

Forty acrylic resin duplicates of an endodontically treated and extracted human molar were restored with two resin composite materials for core restorations. Two different manipulation techniques, bulk insertion and syringe application, were used. In a simulated clinical setup, the core buildups produced by the different manipulation techniques were investigated for voids. In 20 duplicates, a post was placed to simulate a metal post and resin composite core buildup. The syringe technique produced significantly fewer incorporated voids for both resin composite core materials than did the bulk insertion technique. It was not possible to demonstrate a relationship between the presence of voids and the presence of a metal post. [ABSTRACT FROM AUTHOR]

Tensile bond strengths of a resin composite-dentinal bonding system to air-abraded enamel were determined. Several cutting variables available on an air-abrasion cavity preparation system were investigated. Two tip diameters, two abrasive powder flow rates, and two air pressures were selected, producing cutting actions that ranged from the most to the least aggressive of the air abrasion system. After enamel surfaces were air abraded, they were etched for 30 seconds with 37% phosphoric acid or not etched. Tensile bond strengths of resin composite to air-abraded, acid-etched enamel were significantly greater than were those to air-abraded, unetched enamel. There was no statistically significant difference between any combination of tip diameter, powder flow rate, or air pressure. [ABSTRACT FROM AUTHOR]

The present article introduces a rubber dam system developed for the simultaneous isolation of teeth and gingival tissues. The rubber dam device is fabricated from simple, easy-to-find, and inexpensive materials, such as iron-core elastic tube, latex sheets, expanding screws, dental acrylic resin, and glue. Measurements of the dimensions of the maxillas and mandibles of 100 patients indicated that three prefabricated sizes of the device (small, medium, and large) can be applied in the majority of individuals. [ABSTRACT FROM AUTHOR]

This article describes a technique for fabricating a custom acrylic resin shell that will ensure a properly designed amalgam core for the coronally debilitated, endodontically treated posterior tooth. A few simple procedures result in a core foundation for root protection, an ideal crown preparation, and a more predictable final restoration. [ABSTRACT FROM AUTHOR]

The purpose of this in vitro study was to determine the effects of two 10% carbamide peroxide bleaching solutions on the hardness of enamel from the surface to the dentinoenamel junction. Fifteen anterior teeth were sectioned faciolingually, and their roots were removed. Half of each crown was bleached and half served as its own control. Specimens were bleached with two commerically available 10% carbamide peroxide solutions (Proxigel and Gly-Oxide) for 241-hour periods. A visible color change occurred. Teeth were embedded in acrylic resin rings, sanded with progressively finer silicon carbide papers, and polished. The polishing process removed approximately 800 µm of the cut tooth surface. Specimens were tested with a microhardness tester and a Knoop diamond under a 35-g load; measurements were taken along the cut surface from the outer enamel surface to the dentinoenamel junction. Matching depths from control and test specimens were compared. For teeth treated with Gly-Oxide, no statistically significant changes in enamel hardness were evident at any depth. For teeth treated with Proxigel, no significant changes in hardness were evident at 50 µm or deeper A statistically significant decrease in hardness was noted in the outer 25 µm of the enamel surface. It is unknown whether this decrease would have an effect clinically because the remineralizing effects of saliva should resolve any surface change. [ABSTRACT FROM AUTHOR]