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PubMedDate not supplied

Some variables influencing the bond strength between PMMA and a silicone denture lining material.

PURPOSE: The purpose of the present study was to investigate the effect of roughening the denture base surface on the tensile and shear bond strengths of a poly(dimethylsiloxane) resilient lining material (Molloplast-B) bonded to a heat-cured acrylic resin denture base material. These measured bond strengths were compared to those obtained by packing the soft lining material against poly(methyl methacrylate) (PMMA) denture base acrylic resin dough. MATERIALS AND METHODS: Three groups of 10 specimens each were constructed for both tensile and shear tests. In the first group, Molloplast-B was packed against cured PMMA denture base surface. In the second group, Molloplast-B was packed against cured PMMA denture base whose surface had been roughened with an acrylic bur. In a third group, Molloplast-B was packed against PMMA denture base acrylic resin dough. RESULTS: Molloplast-B exhibited significantly higher tensile and shear bond strengths when packed against acrylic resin dough. Roughening the denture base surface prior to the application of Molloplast-B had a statistically significant weakening effect on tensile bond strength compared with the smooth surface and the acrylic resin dough. For the shear bond strength, roughening the surface produced a nonsignificant increase compared with the smooth surface, but the bond was weaker than when packed against acrylic resin dough. CONCLUSION: Significant differences in tensile and shear bond strength were recorded between the three methods used to bond Molloplast-B to denture base material.

Analysis of Variance↗
PubMed2002

Dimensional accuracy of dental casts: influence of tray material, impression material, and time.

PURPOSE: This study evaluated the influence on dimensional accuracy of dental casts made with different types of trays and impression materials and poured at different and multiple times. MATERIALS AND METHODS: Two types of stock trays (plastic stock tray, perforated metal stock tray) and 4 types of custom tray materials (autopolymerizing acrylic resin, thermoplastic resin, and 2 types of light-polymerized acrylic resins) were used with 2 types of impression materials (addition polymerizing silicone and polyether), to make impressions of a metal master model. Each tray and impression material was used to make 5 impressions. Casts were made by multiple pourings at 30 minutes, 6 hours, 24 hours, and 30 days after impression making. Using a measuring microscope, 12 distances were calculated based on measurements of 8 reference points. The absolute value of the difference of each measurement was calculated, as was the corresponding measurement on the master model. A Bayesian model using a simple noninformative prior was used to analyze these data. RESULTS: Statistical differences within 6 microm were found only with thermoplastic resin tray material for addition silicone, and for thermoplastic resin tray material and 1 type of light-polymerized acrylic resin for polyether. Neither stock trays nor custom trays contributed to the differences in accuracy of the casts. All deviations in casts made with silicone impression material were within a clinically acceptable range. For the polyether, distortions occurred that were clinically unacceptable. Impressions made from polyether distorted over time. Silicone impression material has dimensional stability up to 30 days. CONCLUSION: Accurate casts can be made with either stock trays or custom trays. An impression made from polyether should be poured only once and within 24 hours after impression making, because of the distortion of the material over time. Silicone impression material has better dimensional stability than polyether. .

Acrylic Resins↗
PubMed1999

Adherence of enamel matrix derivatives on root-end filling materials.

It was recently shown that application of enamel matrix derivatives (EMDs) on denuded root dentin promotes periodontal regeneration. EMD is shown to adhere to the etched dentin, but its adherence to root-end filling materials is not known. The purpose of this study was to evaluate the adherence of a commercially available EMD product to root-end filling materials. Dentin sections were embedded in blocks made of acrylic resin. Cavities were prepared in similar acrylic resin blocks and were filled with amalgam, IRM, or composite resin. EMD was labeled with radioactive iodine and applied to the surfaces of the dentin sections, freshly made fillings, or acrylic resin controls. The specimens were rinsed, and the amount of radioactive iodine was determined in a gamma counter. Substantial amounts of EMD adhered to dentin sections. EMD adherence to amalgam and IRM was significantly less than to dentin or composite resin.

Cementogenesis↗
PubMed1977

Processing complete dentures.

The processing of acrylic resin dentures is an exacting art but is relatively simple to carry out to perfection day after day, even when several dentures are processed at the same time. Nine salient factors in the proper processing of acrylic resin dentures were sequentially listed. Unfortunately, a number of these technical procedures are frequently overlooked or shortcuts may be substituted. Herein lie the causes of some hitherto unexplained clinical failures attributed to the acrylic resin denture base material. The acrylic resin denture base materials have been and are currently the best plastic for making dentures. This material has many unique assets and few faults. Its fine properties are often overlooked by the dentist who has several edentulous patients experiencing problems with dentures he made for them. Sore spots, faulty occlusion, looseness, and even breakage are most likely due to inadequate mouth conditioning or poor impressions, incorrect jaw relations, or the dentist's failure to remount the dentures prior to insertion. We have sufficient knowledge and scientific evidence to realize that most, if not all, denture problems are caused by the dentist's technique or by dentist-patient relationship. These problems should not be attributed to the acrylic resin material nor to the hard-working, conscientious dental laboratory technician. I doubt that more than 2 per cent of all complete denture difficulties experienced by frustrated patients would be solved by the introduction and availability of a new perfect denture base material.

Acrylic Resins↗
PubMed1989

Comparative bond strengths of light-cured, heat-cured, and autopolymerizing denture resins to denture teeth.

Standard and interpenetrating polymer network acrylic resin denture teeth were milled into cylinders 8 mm in diameter and processed against cylinders of the three different resins. The specimens were reduced by milling to a diameter of 6 mm in the region of the tooth-resin interface and thermocycled for 24 hours. Specimens were then subjected to tensile loading until fracture. Group means were compared by using the Duncan multiple range test at the 5% level of significance. The strongest bond occurred between the heat-cured resin and the standard acrylic resin teeth. Intermediate strength was achieved with the heat-cured resin to the IPN teeth and the autopolymerizing resin to both types of teeth. Lowest strength was measured with the light-cured resin to both types of teeth.

Acrylic Resins↗
PubMed1997

A laboratory evaluation of the construction of resin-bonded cast restorations.

OBJECTIVE: To compare the effect of two construction techniques and two pattern materials on the fit of resin-bonded cast restorations. DESIGN: In-vitro study carried out by one operator. SETTING: Postgraduate university hospital. SUBJECTS AND METHODS: 65 nickel-chrome castings were constructed using refractory die and lift-off techniques with wax and acrylic resin pattern material. They were cemented onto master silver dies, embedded in self-curing acrylic resin and sectioned along their long axes. Interfacial distance between the master silver die and casting was measured. RESULTS: A significant different between the range of figures in each group (Mann-Whitney Test, P < 0.01) was found. Construction techniques can be ranked in order of fit of castings: 1. Refractory die, wax patterns: 42.6 microns (SD 12.03). 2. Refractory die, acrylic resin patterns: 53.7 microns (SD.16.06).3. Conventional technique, acrylic resin patterns: 85.5 microns (SD 31.62). 4. Lift-off technique, wax patterns: 139 microns (SD 53.15).5. Lift-off technique, acrylic patterns: 172.8 microns (SD 74.04). CONCLUSIONS: Castings constructed using refractory die technique and subsequently cemented resulted in a more accurate and less variable fit than those produced with the lift-off technique. Wax patterns lead to more accurate castings than acrylic resin and locating indentations may interfere with the cementation of castings when lift-off techniques are used.

Acrylic Resins↗
PubMed1976

The use of methylmethacrylate in the fixation of mandibular fractures in dogs. Experimental results.

The efficacy of self-curing acrylic resin in the fixation of fractured mandibles was studied in eight adult mongrel dogs. Three dogs were killed at 1 month, two at 3 months, and three at 6 months after insertion of the resin. Roentgenograms taken after operation and after the dogs had been put to death demonstrated satisfactory fracture reduction and bony healing. The retentive grooves appeared larger on the postmortem roentgenograms, apparently from fibrous tissue that formed between the acrylic resin and the bone. Sections through the groove and fracture site did not show any fibrocartilage formation between the bone and the resin. Active osteoblastic activity was present at the fibrous capsule-bone interface as well as in the fracture calluses. Most sections showed acute inflammation, with a few giant cells. Whether the inflammatory component resulted from tissue breakdown over the acrylic resin or from the polymethylmethacrylate itself was not determined. There was no evidence of abnormal healing or nonunion along the fracture line and no evidence of necrotic bone. The undecalcified tetracycline-labeled sections confirmed active bone formation at the fibrous capsule-bone interface and in the fracture calluses at 1, 3, and 6 months. No mobility could be detected across the fracture site at any time after the insertion of the acrylic resin. Two of the three dogs that were killed at 1 month had incomplete bony union, as demonstrated by mobility along the fracture line seen in the resected specimens. Mucosal dehiscence over the superior acrylic fixation bar was a consistent finding. Once the resin had been either exfoliated or removed, the mucosa healed uneventfully. The insertion of methylmethacrylate did not result in blood pressure change in the dogs. The dogs maintained their preoperative weight, appetite, and jaw mobility. Although satisfactory bony healing resulted from the intraoral open reduction and fixation with self-curing acrylic resin in dogs, several factors need additional investigation before this technique can be considered for use in human subjects. The following findings in this study may contribute to healing complications in man: (1) loosening of the acrylic resin due to fibrous tissue formation between it and the bone, (2) mucosal dehiscence, (3) inflammation in and around the fibrous tissue adjacent to the acrylic resin, and (4) the necessity of bone removal to facilitate the insertion of the resin.

Animals↗
PubMedDate not supplied

Accuracy of implant impression splinted techniques: effect of splinting material.

Three implant impression techniques, using 3 different splinting materials, were assessed for accuracy in a laboratory model that simulated clinical practice. For group A, an autopolymerizing acrylic resin was used to splint transfer copings. In group B, a dual-cure acrylic resin was used, and for group C, plaster, which was also the impression material, was used. A metal implant master cast with an implant master framework was made to accurately fit to the cast. This cast was the standard for all impressions. For each group, 15 impressions were made. Polyether impression material was used for groups A and B. The accuracy of the stone casts with the implant analogues was measured against the master framework, using strain gauges. A multiple analysis of variance with repeated measures was performed to test for significant differences among the 3 groups. Additional analyses of variance were carried out to locate the source of difference. The statistical analyses revealed that a significant difference existed between groups A and B and between groups B and C but not between groups A and C. Impression techniques using autopolymerizing acrylic resin or impression plaster as a splinting material were significantly more accurate than dual-cure acrylic resin. Plaster is the material of choice in completely edentulous patients, since it is much easier to manipulate, less time consuming, and less expensive.

Acrylic Resins↗
PubMedDate not supplied

A clinical 5-year longitudinal study on the dimensional changes of complete maxillary dentures.

PURPOSE: Acrylic resin complete dentures exhibit dimensional changes mainly because of processing shrinkage and expansion because of water uptake. The aim of this 5-year clinical study was to determine the dimensional changes occurring during construction and in service in maxillary complete dentures made of two types of acrylic resin. MATERIALS AND METHODS: Complete dentures were constructed for 17 edentulous patients. Nine patients received dentures made of conventional heat-cured acrylic resin, and eight patients received dentures made of rapid heat-cured acrylic resin. Measurements were taken across three reference points (second molars bilaterally and central incisors) on six occasions: at the flasking stage, at the denture insertion appointment, and after 1 week, 1 month, 3 months, and 5 years of use. The data obtained were analyzed using one-factor repeated-measures ANOVA, one-way ANOVA, and Duncan's multiple comparisons test. RESULTS: The two types of dentures showed the same pattern of dimensional changes. A shrinkage of up to 0.27% was estimated at the insertion stage. During the first 3 months of use, a decrease of the initial dimensional change was observed. After a 3-month period, a gradual compensation for the initial shrinkage started to take place. At the end of the study period (5 years), an expansion of up to 0.35% was measured. CONCLUSION: Maxillary complete dentures made of either conventional or rapid heat-cured acrylic resin exhibited dimensional changes that were considered clinically acceptable.

Acrylic Resins↗
PubMed1979

Abrasive properties of commonly used dentifrices.

This study was conducted to examine the effect of various dentifrices on the abrasion of acrylic resin and extracted human tooth. The influence of the difference in the hardness of the filament of the toothbrush on the abrasion was also studied, using three kinds of toothbrushes. The specimens (acrylic resin and extracted human tooth) were brushed 3,000 times by the back- and -forth stroke movement using a toothbrushing machine for two hours. The surface irregularities of the specimen were analyzed by the surface analyzer and observed by the scanning electron microscopy before and after the brushing procedure. Moreover, the weight loss of the test specimens of the acrylic resin materials was determined, weighing them by a microbalance before and after brushing. The abrasiveness of the dentifrices showed a wide range, but the abrasiveness of the toothbrush itself was not observed. All dentifrices except one which did not contain the abrasive materials had abrasive effects on both the acrylic resin and human tooth. There was a high correlation (r = 0.96) between the weight loss and the surface irregularities in the case of acrylic resin.

Acrylic Resins↗
PubMed1992

Light-cured resin for post patterns.

A method of using light-cured acrylic resin as an alternative to the use of chemically-cured acrylic resins with elastomeric impressions for direct post patterns is presented. The GC Unifast LC acrylic resin is a powder/liquid type resin cured by exposure to visible light. The polymerization process has four stages before final curing: slurry, stringy, dough-like (plastic), and rubber-like (elastic). Advantages over current direct and indirect procedures include ease of manipulation of the material and no change in laboratory handling procedures. While in the dough-like state, the material can be contoured. In the rubber-like state, it is flexible to disengage from minor undercut areas.

Dental Impression Materials↗
PubMed2001

Repair of denture base resins with visible light-polymerized reline material: effect on tensile and shear bond strengths.

STATEMENT OF PROBLEM: Triad visible light-polymerized (VLP) reline resin has the potential to repair denture bases from other resin systems with the elimination of flasking/deflasking procedures. PURPOSE: This study measured the tensile and shear bond strengths of Triad VLP, PMMA, and glass-fiber-reinforced PMMA (GF-PMMA) acrylic resins before and after repair with Triad VLP reline material. MATERIAL AND METHODS: Fifty-six specimens were fabricated from Triad VLP, PMMA, and GF-PMMA denture base resins. Both Triad VLP reline material and autopolymerizing acrylic resins were used to repair identical laboratory fabricated resin joints. Twenty-eight rectangular specimens (in 4 different groups of 7 each) were prepared to study the shear bond strength of Triad reline material used to repair different denture base resin joints. RESULTS: Statistically significant differences (P< .0001) were found between the tensile strengths of specimens repaired with the Triad VLP reline resin used as a repair agent and those repaired with the autopolymerizing resin. The tensile strength of the Triad VLP denture base resin was found to be higher than that of both the PMMA and GF-PMMA acrylic resins. CONCLUSION: The low tensile and shear bond strengths found after the repair of PMMA and GF-PMMA acrylic resins with Triad VLP reline material were attributed to a lack of cohesion/adhesion between the Triad VLP reline material and the interfaces of the treated sites. The use of Triad VLP reline material to repair Triad VLP denture base resin produced the highest strengths.

Acrylic Resins↗
PubMed2004

Evaluation of varying amounts of thermal cycling on bond strength and permanent deformation of two resilient denture liners.

STATEMENT OF PROBLEM: Two problems found in prostheses with resilient liners are bond failure to the acrylic resin base and increased permanent deformation due to material aging. PURPOSE: This in vitro study evaluated the effect of varying amounts of thermal cycling on bond strength and permanent deformation of 2 resilient denture liners bonded to an acrylic resin base. MATERIAL AND METHODS: Plasticized acrylic resin (PermaSoft) or silicone (Softliner) resilient lining materials were processed to a heat-polymerized acrylic resin (QC-20). One hundred rectangular specimens (10 x 10-mm 2 cross-sectional area) and 100 cylindrically-shaped specimens (12.7-mm diameter x 19.0-mm height) for each liner/resin combination were used for the tensile and deformation tests, respectively. Specimen shape and liner thickness were standardized. Specimens were divided into 9 test groups (n=10) and were thermal cycled for 200, 500, 1000, 1500, 2000, 2500, 3000, 3500, and 4000 cycles. Control specimens (n=10) were stored for 24 hours in water at 37 degrees C. Mean bond strength, expressed as stress at failure (MPa), was determined with a tensile test using a universal testing machine at a crosshead speed of 5 mm/min. Analysis of failure mode, expressed as a percent (%), was recorded as either cohesive, adhesive, or both, after observation. Permanent deformation, expressed as a percent (%), was determined using ADA specification no. 18. Data from both tests were examined with a 2-way analysis of variance and a Tukey test (alpha=.05). RESULTS: For the tensile test, Softliner specimens submitted to different thermal cycling regimens demonstrated no significantly different bond strength values from the control; however, there was a significant difference between the PermaSoft control group (0.47 +/- 0.09 MPa [mean +/- SD]) and the 500 cycle group (0.46 +/- 0.07 MPa) compared to the 4000 cycle group (0.70 +/- 0.20 MPa) ( P <.05). With regard to failure type, the Softliner groups presented adhesive failure (100%) regardless of specimen treatment. PermaSoft groups presented adhesive (53%), cohesive (12%), or a combined mode of failure (35%). For the deformation test, there was no significant difference among the Softliner specimens. However, a significant difference was observed between control and PermaSoft specimens after 1500 or more cycles (1.88% +/- 0.24%) ( P <.05). CONCLUSIONS: This in vitro study indicated that bond strength and permanent deformation of the 2 resilient denture liners tested varied according to their chemical composition.

Acrylic Resins↗
PubMed2002

Flexural strength of provisional crown and fixed partial denture resins.

STATEMENT OF PROBLEM: Provisional prostheses are subject to flexure under function. Selection of the appropriate material for their fabrication is difficult given the limited evidence-based information on the flexural strength of provisional resins. PURPOSE: This study compared the flexural strength of 5 methacrylate-based resins and 8 bis-acryl resins used to fabricate provisional crowns and fixed partial dentures. MATERIAL AND METHODS: Bar-type specimens were fabricated according to American National Standards Institute/American Dental Association specification 27. After being immersed in artificial saliva at 37 degrees C for 10 days, the specimens were fractured under 3-point loading in a universal testing machine at a crosshead speed of 0.75 mm/min. Maximal loads to fracture in Newtons were recorded. Mean flexural strengths were calculated in MPa (n = 10 per group). Comparisons were made with analysis of variance and Duncan's multiple range test (P<.05). RESULTS: Mean flexural strengths ranged from 56.2 to 123.6 MPa. There were 4 statistically similar groups. The group with the highest strengths consisted of 4 bis-acryl materials (Provipont, Integrity, Protemp 3 Garant, and Luxatemp). CONCLUSION: Within the limitations of this study, flexural strengths were material- rather than category-specific. Some, but not all, bis-acryl resins demonstrated significantly superior flexural strength over traditional methacrylate resins.

Acrylic Resins↗
PubMed1996

Color stability: denture base resins processed with the microwave method.

Several quick heat-cured denture base resin systems and microwave processing resins have been introduced to provide easier and faster processing. The microwave processing method is the fastest of the heat-cured processing methods. Conventional acrylic resins processed with the microwave method seem to possess adequate physical properties, and one study indicated that a microwave acrylic resin was reasonably color stable under conditions of accelerated aging, although manufacturers do not recommend using them for microwave processing. The purpose of this study was to evaluate the color stability of seven conventional and one microwave heat-cured denture base materials processed with the microwave method. The samples were subjected to conditions of accelerated aging to test for color stability. The color stability was quantitatively measured and color measurements were made before weathering and at 300, 600, and 900 hours. The mean color change for each sample group was statistically analyzed with polynomial regression to determine the pattern of color change over time. The differences in color change for the acrylic resins were significant for all materials, but the color change for Lucitone Hy-pro was not noticeable on visual examination. The results of this study revealed that color changes occurred after accelerated aging in heat-cured denture base resins and Acron GC microwave acrylic resins processed with the microwave method. Hy-pro and TruTone materials exhibited the least color change; Hy-pro material was the most color stable material.

Acrylic Resins↗
PubMed1996

An injection technique for generating direct resin post and core patterns.

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 tube 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.

Acrylic Resins↗