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PubMedDate not supplied

Bond strength of denture teeth to denture base resins.

PURPOSE: The study examined the bond strength between 2 types of denture teeth and 3 denture base resins. The denture teeth were untreated, prepared with diatorics, or treated with dichloromethane, a solvent. MATERIALS AND METHODS: Conventional denture teeth and cross-linked denture teeth were bonded to either a heat-cured denture base resin, a microwave-cured denture base resin, or a pour-type denture base resin. Compressive load was applied at 45 degrees on the palatal surface of each tooth until fracture. RESULTS: Conventional resin teeth possessed higher bond strength than cross-linked denture teeth. The heat-cured denture base resin significantly surpassed the microwave-cured denture base resin in bond strength. Both materials were better than the pour-type resin. The application of dichloromethane resulted in a significantly better improvement in bond strength compared to the use of diatorics. CONCLUSION: It is recommended that dichloromethane be applied on the denture teeth ridge-lap area prior to denture base processing.

Acrylic Resins↗
PubMed2000

Mechanical disruption of dentin collagen fibrils during resin-dentin bond testing.

PURPOSE: To determine if collagen fibrils on the dentin side of failed resin-dentin interfaces undergo mechanical disruption during microtensile bond testing. MATERIALS AND METHODS: Extracted, caries-free human third molars were divided into four groups. The occlusal enamel was removed, leaving a flat dentin surface for bonding. Resin composite buildups were made after the acid-conditioned dentin was bonded with either Single Bond (S) or One-Step (O), and using either moist bonding (M) or air drying for 5 s (D). After storage in water for 24 h, the teeth were vertically sectioned into an array of 0.9 x 0.9 mm resin composite-dentin beams. They were stressed to failure using the nontrimming version of the microtensile bond test. Fractured dentin and resin composite sides of representative beams from each group that exhibited adhesive failures under light microscopy examination were prepared for scanning (SEM) and transmission electron microscopy (TEM). RESULTS: A two-way ANOVA showed that moist bond strengths were significantly higher than those made to dry dentin (M > D; p < 0.001), but that there was no difference between the adhesives (S vs O; p = 0.547). SEM analysis showed the presence of loose collagen fibrils within fractured hybrid layers in the dry groups, but not in the moist groups. TEM examination of the dry-bonded groups revealed collagen fibrils that were thinner and exhibited abnormally wide interfibrillar spaces when hybrid layers were intact. Within dry-bonded fractured hybrid layers, broad mechanical disruption zones could be seen, consisting of fibrils that were devoid of cross banding, defibrillation of the subfibrillar architecture, and gross disaggregation into microfibrils. In the moist-bonded groups, only short mechanical disruption zones were found along the torn edges of the collagen fibrils. The rest of the fibrils beyond the fracture site were intact and retained their periodicity. Mechanical testing of demineralized matrices yielded a maximum modulus of elasticity of 43.9 +/- 6.1 MPa. CONCLUSION: We speculate that adhesive resin has a protective function for demineralized collagen in well-infiltrated hybrid layers. We propose that both the collagen and resin contribute to load sharing during stress application until the final moment of rupture. On the other hand, collagen fibrils in poorly infiltrated hybrid layers, being unsupported by resin, undergo various degrees of irreversible mechanical disruption depending on how the stress is dissipated. The collagen fibril network has a much lower modulus of elasticity compared to those of resin-infiltrated fibrils or the demineralized dentin.

Acid Etching, Dental↗
PubMedDate not supplied

Polymerization shrinkage of densely-filled resin composites.

A new group of restorative materials called "packable" composites has recently been introduced. These products are essentially highly-filled or densely-filled hybrid resin composites. One of the many claims made about these materials is that they undergo less polymerization shrinkage than their conventional counterparts. This in vitro investigation compared the amount of linear shrinkage that occurs within a variety of densely filled resin composites (DFC) and conventional hybrid resin composites when cured with a visible halogen light. Six DFC resins (Alert, Ariston, P60, Prodigy, Solitaire and Surefil) and two hybrids (TPH-Spectrum, Z100) were used in this study. Dimensional change was measured in a linear direction using a calibrated light microscope. Eighty samples of resin composite were tested, resulting in eight groups of 10 samples (N=10) each. The one-way ANOVA with Student-Newman-Keuls post-hoc test was used to compare the shrinkage between groups, and Pearson's Correlation was used to test the relationship between filler characteristics and shrinkage. Alert and P-60 had significantly less shrinkage than Solitaire, Ariston, Prodigy, Z-100 and TPH-S. Thus, the shrinkage values of some DFC resins were significantly less and others were no different from conventional hybrid resins. There is a moderate association between filler volume and shrinkage. Filler size and resin chemistry are other factors that may also effect shrinkage.

Analysis of Variance↗
PubMed2003

Resin-dentin interfaces of endodontically-treated restored teeth.

PURPOSE: To compare by confocal and scanning electron microscopy the post-resin-dentin interfaces of endodontically-treated teeth which had been restored with dentin-bonding systems and composite and needed to be extracted after 6 months to 6 years of clinical service. MATERIALS AND METHODS: Sixteen single rooted teeth showing proximal lesions penetrating the pulp chamber were included in the investigation and divided into two groups. Group 1 teeth were endodontically-treated, restored with carbon fiber posts and resin-based composite. Group 2 teeth were treated in the same way and covered with porcelain fused-to-metal crowns. RESULTS: Two thirds of the observed interfaces showed resin penetration of the root dentin in the middle and coronal third of the post space preparation, while only one third of the interface showed resin infiltration in the apical third of the post space preparation. Debonding of the adhesive from the resin infiltrated dentin area and debonding of the composite cement from the adhesive were the most frequently observed failure modes and were observed in one third of the observed interfaces. There was no difference between the post-resin-dentin interfaces of teeth covered and teeth not covered with porcelain-fused to metal crowns. Teeth extracted after longer periods of clinical service showed more abundant areas of debonding of the adhesive from the resin-dentin interdiffusion zone. The presence of bacteria in resin infiltrated dentin tubules was observed in two specimens.

Carbon↗
PubMed2003

[Contact allergy to epoxy resins plastics based on materials collected by the Nofer Institute of Occupational Medicine].

Of the 5604 patients examined in 1984-2001 for suspected occupational dermatitis, 160 persons (2.8%) showed allergy to epoxy resins plastics. Allergy was more frequent in men (4.9%) than in women (1.2%); in 154 persons, allergy was of occupational etiology (in a group of 160 patients with allergy to epoxy resins, the following proportions were observed: bricklayers, platelayers--17.5%; fitters, turners, machinist millers--13.8%; plastics molders--13.1%; laminators--11.3%; electrical equipment assemblers--10.6%; painters--10.0%). Having compared the frequency of allergy to components of epoxy resins in the years 1984-1993 and 1994-2001, it was found that allergy to resin, reactive diluents and plasticizers was on increase, whereas allergy to amines and acid anhydrides hardeners was on decrease. In a group of 13 chemical compounds entering into the composition of epoxy resins, epoxy resin contributed to the largest number of positive patch tests (77.5% of epoxy-allergic persons). This was followed by triethylenetetramine (23.1%), ethylenediamine (13.1%), phthalic anhydride (8.1%), diethylenetetramine (6.9%) and phenylglycidylether (6.2%). In addition, three patients reacted to both epoxy resin and cycloaliphatic resin.

Dermatitis, Allergic Contact↗
PubMed2003

[Study on the defluoridation of drinking water with model-La cation exchange resin].

Model-La cation exchange resin was transformed from strong acid cation exchange resin, which was used for the defluoridation of drinking water. The 001 x 7 strong acid cation exchange resin was transformed into model-La cation exchange by soaking in the La(NO3)3 solution. The F- in the water was removed by model-La cation exchange resin under the optimum condition because it was combined into fluoride with the La3+ in the model-La cation exchange resin. The used resin was regenerated with the La(NO3)3 solution and was used to defluoridate many times. The optimum conditions of transform and defluoridation and regeneration were d(rasin) = 0.315-0.600 mm, V(rasin):V(regeneration) = 1:6, t(transform) = 48 h, T = 298.16 K(25 degrees C). The defluoridation capacity was 5.60 mg/g in column test, and 4.08 mg/g in batch test. The model-La cation exchange resin could be used for defluoridation for 8 times. The results suggest that the model-La cation exchange resin is a novel material of defluoridation. This method is easy to master and the pH value of the solution doesn't need to be regenerated that the cost of defluoridation can be reduced significantly and it can be used for a long time.

Cation Exchange Resins↗
PubMed2004

[Comparison of fracture resistance of pulpless teeth restored with fiber reinforced composite posts and three kinds of resin core material].

OBJECTIVE: To compare the fracture resistances of pulpless teeth restored with FRC (Fiber Reinforced Composite) posts and three kinds of resin core material. METHODS: A total of 42 recently extracted upper incisors were randomly divided into 3 groups. Group A was restored with prefabricated glass-fiber posts and Artglass polymer core; group B with prefabricated glass-fiber posts and Charisma composite resin core; and group C with prefabricated glass-fiber posts and AB composite resin core. In every group, the core material was processed by hot-press and non hot-press respectively. The posts size and shape were identical in the 3 groups. All teeth were fully covered with polycarbonate resin crowns. Fracture resistance was measured by applying point force at 130 degrees to the long axis of the teeth on an universal testing machine. RESULTS: Mean fracture threshold was 505.4 N +/- 42.0 N and 564.1 N +/- 41.7 N in group A, 411.3 N +/- 23.3 N and 315.3 N +/- 19.1 N in group B and 358.4 N +/- 36.1 N and 423.4 N +/- 47.5 N in group C. In all groups, there was no posts fracture and polycarbonate resin crowns fragmentation. CONCLUSION: The composite restoration of FRC posts combined with resin core and resin crown can improve the fracture resistance of the pulpless roots. The strength of resin core material can be increased by hot-press methods.

Composite Resins↗
PubMedDate not supplied

Reaction exothermia of 2 relining resins for temporary crowns.

AIM: The aim of the study was to evaluate the reaction exothermia of 2 relining resins for temporary crowns. The resins used were Duralay, a methacrylate-based resin, and Protemp II, a bisacrylic resin. METHODS: The coronal parts of an adult molar and of an impacted one were used. Abutments were obtained from the crowns, while the radicular part was sectioned in order to insert a thermocouple into the pulpal chamber. During the experiment the tooth with the polymerising resin was put into an oral cavity simulator to keep a constant temperature. The thermal increase during polymerisation of the 2 resins was recorded for 6 minutes at 5 seconds intervals and with 1 and 2.5 mm dentin thickness (n = 10). Data were statistically analysed by variance analysis with Scheffe test. RESULTS: The intrapulpal thermal increase was significantly higher in relation to the type of resin (Duralay p < 0.0001), thickness (1 mm p < 0.0001) and type of dentin (young dentin p < 00001). CONCLUSIONS: In order to protect the pulp, during the direct relining of a temporary crown, it is recommendable to choose the best combination among resin, type of dentin and its residual thickness, besides adequate cooling techniques.

Composite Resins↗
PubMedDate not supplied

Effect of original water content in acrylic resin on processing shrinkage.

PURPOSE: The aim of this study was to determine the original water content of a supplied acrylic resin powder and a monomer and of dry heat-processed acrylic bars. The effect of the original water content of acrylic resin on processing shrinkage was also investigated. MATERIALS AND METHODS: Ten bar specimens were fabricated using dried and as-supplied (control) acrylic resins. The resins were polymerized and cooled, then weighed and measured to determine the amount of shrinkage. The initial water content of the specimens was determined by thorough drying, and results were compared with the Student ttest. RESULTS: The initial water content and processing shrinkage of the dried acrylic resin bars were both significantly lower (P < .0001) than those of the as-supplied acrylic resin bars. CONCLUSION: The processing shrinkage of acrylic resin made from dried constituents was significantly less than that of resin made from products as supplied by the manufacturer. However, it is not known if this change is of clinical significance.

Acrylic Resins↗
PubMed2006

Effect of low O2-gas transmission rate barrier films on knoop hardness and toothbrush abrasion of resin cements.

PURPOSE: To investigate the influence of utilizing films with different oxygen transmission rates (O2-GTR) on Knoop hardness and toothbrush abrasion of resin cements for luting. METHODS: Four dual-activated, composite-type resin cements, and a chemically activated PMMA-type resin cement, were used. Three different types of barrier films (Techbarrier HI, Harden Film N130, and Lix-2) were used. Resin cement was mixed and inserted into a cylindrical mold (4 mm in diameter, 3 mm in height), then chemically activated. The specimens were stored in the dark at 37 +/- 1 degrees C, 90 +/- 5%RH conditions for 1 hour. Knoop hardness on the top surface of the resin cement was measured with a microhardness tester. The top surface of specimens (8 mm in diameter, 3 mm in height) polymerized under the same conditions were used for toothbrush abrasion testing. One-way ANOVA followed by Tukey HSD test (P< 0.05) were done. RESULTS: When the cement surface was covered by low O2-GTR film, a significant increase in Knoop hardness and resistance to toothbrush abrasion was observed for the dual activated, composite-type resin cements, but not for the chemically activated PMMA type resin cement. From the results of this study, the use of low O2-GTR matrix barrier films for the dual activated, composite-type resin cements could be effective in eliminating the oxygen inhibited layer on the cement surface.

Hardness↗
PubMed1991

New restoration and direct pulp capping systems using adhesive composite resin.

There have been many arguments on the irritating mechanisms of the composite resin on the dental pulp. While the direct irritative effect of the resin has been preferred, some authors considered that the marginal microleakage and the resulting bacterial infection play a more important role in inducing the complicating pulp irritation. We developed a new filling technique, called the direct inlay restoration method, which could prevent the marginal leakage associated with the polymerization shrinkage of the adhesive composite resin. In this study, we tried to apply our method clinically. None of the 440 cases which were filled with the adhesive composite resin and 60 cases out of 64 cases in which the pulps were directly capped with the adhesive composite resin developed any signs and symptoms of pulp irritation. The other 4 cases developed signs of pulp irritation. Two of those 4 cases were pulpectomized due to spontaneous pain and the other 2 cases turned out to be well after re-restoration. With the informed consent of the patients, the direct pulp capping using the adhesive composite resin was experimentally performed on 6 caries-free 3rd molars and the histopathological examination of these capped molars revealed that neither significant degenerative nor inflammatory changes were brought about in the dental pulp. These clinical and histopathological observation suggest that the dental pulp irritation after resin filling is not induced by the composite resin itself.

Adolescent↗
PubMed1991

[Surface properties of resins used for removable dentures].

The comparative study of the gingival aspect of dentures made from different flasking procedures, using scanning electronic microscopy, permits the differences in the surface texture of the resins to be assessed. This surface texture will show specific aspects for each technique. The Futurajet resin presents a surface texture with cracks of 100 microns to 200 microns long and 5 microns wide. The appearance of the polymer pellets reveals a good cohesion amongst them. The Futuracryl 2000 resin has an overall surface like an orange peel, with a hills and valleys revealing a rather weak attack of the monomer on the polymer. The palatal surface of the SR-Ivocap resin shows pleats and perpendicular fractures. The surface of the buccal aspect of the ridge is relatively smooth. The Lucitone resin shows a surface with very few irregularities, in which the polymer pellets are well dissolved. In conclusion, no porosities are found on the surface of the various resins. We think that the chemical composition of the resin influences this surface texture and the flasking technique being able to disturb the surface of the resin.

Acrylic Resins↗
PubMed1990

Bond strengths and pulpal response of light-cured composite resin inlays in primary molars.

The purpose of this study was to: 1) determine the most effective combination of composite resin and adhesive resin cement in the cementation process when fabricating esthetic inlays in severely broken down posterior primary teeth; 2) evaluate the pulpal response to adhesive resin cement in the primary teeth of young dogs. In Part I of the study, P-30 and Dentacolor composite resin inlays were evaluated with regard to their bonding strengths with Panavia-EX and Chemiace adhesive resins. Test samples of the composite resin inlays were prepared in molds according to the manufacturer's instructions. Each sample was polished on a flat, wet surface of 320 grit carborundum until a uniformly flat surface, perpendicular to the long axis of the cylinder was attained. Composite resin plugs, similarly fabricated, were bonded to the test samples using either Panavia-EX or Chemiace adhesive resin cements. A total of 160 samples were divided into four groups. Three of the groups were tested for bonding strength at intervals of 24 hours, 7 days and 30 days. The fourth group was thermocycled through 4 degrees C and 60 degrees C immersion periods. The results were analyzed using Tukey's studentized range test with an alpha (significance level) of 0.05. In Part II of the study, the pulpal response to Panavia-EX as a luting medium was compared with that of HY-Bond polycarboxylate cement. Cavities were prepared in 92 teeth from 8 young dogs and contralateral pairs of teeth were restored with Panavia-EX and HY-Bond polycarboxylate cement respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

[Bonding of visible light cured composite resins to glass ionomer and Cermet cements].

The "sandwich" technique involves combination of composite resins to etched glassionomer cements, is used today in restorative dentistry. The purpose of this study is to evaluate the bond strength between several composite resins and glass ionomer or cerment cements. Cylindrical specimens of the cements Ketac-Silver, Ionobond and GC-Lining Ce-ment were inserted in a mold and their flat free surfaces were etched for 30". Cylindrical plastic tubes were set upon each one of these surfaces and filled with the Composite resins Durafill, Brilliant Lux, Estilux posterior, Estilux posterior CVS and Herculite XR. Half of the specimens transferred in tap water for 24 hours and the others after thermocycling in the first month, kept for 4 months. Shear bond strengths were determined in Monsanto Testing Machine and some fractured surfaces were examined under SEM. The results of this investigation indicate that this technique produces bond strengths between composite resins and glassioners and the combination type of resin and type of cement, affects the values of the strength. Glass cermeet--small particle resin provides the most effective strength and glass ionomer--microfill resins the least. Storage time and thermocycling don't significantly effect the bond strength. SEM examination showed that all fracture failures were obtained in the cement while the opposite resin surfaces were covered with particles of the cements.

Cermet Cements↗
PubMed1990

[SEM observation for composite resin filler].

The nature and the type of fillers in composite resin are multifarious. The purpose of this study is to determine the methods of distinguishing the fillers. After the treatments stated below, the surface of polymerized composite resins was observed by means of SEM. 1) The air-inhibited layer on the surface of composite resins was removed by acetone. Observations showed inorganic filler and prepolymerized filler protrusions on the resin surface; submicron filler and microfiller were noticeable. 2) Following the treatment in #1, composite resins were soaked in fluoric acid in order to dissolve any inorganic filler substance. Results displayed pores in the area of the dissolved inorganic filler while a microporous surface was observed on the prepolymerized filler. By this process the type of prepolymerized filler can be classified according to the forms of the contained inorganic filler. 3) The surface of the composite resin was polished with #1200 sand paper. This method shows the difference between the fillers and the matrix resin; however, a clear distinction of the type of filler is difficult to determine. 4) After treatment in #3, the specimen was soaked in fluoric acid. Similar results as treatment in #2 were found; however, microstructure of the syntered filler was easily observed. It is possible to distinguish the filler types of the composite resins by the above mentioned treatments.

Composite Resins↗
PubMed1990

[Influences of composition on brush wear of composite resins. Influences of particle size and content of filler].

The influences of the composition on abrasion resistance of composite resins were examined using various experimental composite resins which had various matrix resin, filler size and content. The abrasion test was conducted by the experimental toothbrush abrasion testing machine developed in our laboratory. Three series of heat-curing composite resins were tested. One series was made from a Bis-MPEPP or UDMA monomer, and a silica filler with an average particle size of 0.04, 1.9, 3.8, 4.3, 7.5, 13.8 and 14.1 microns. The filler content of this series was constant at 45 wt%. The second series contained a silica filler of 4.3 microns in a content ranging from 35 to 75 wt%. The third series contained a microfiller (0.04 microns) and macrofiller (4.3 microns) in total content of 45 wt%. In this series, the microfiller was gradually replaced by 5, 15, 25 and 45 wt% of the macrofiller. The results obtained for these three series indicated that the abrasion resistance of composite resins was controlled by the inorganic filler, mainly filler size and content. The abrasion loss did not vary with the difference of matrix resin. When the particle size of the filler was below about 5 microns, the abrasion resistance decreased markedly with the decrease in filler size. The composite resin which contained a 0.04 or 1.9 micron filler was less resistant to toothbrush wear than the unfilled matrix resin. However, the microfiller also contributed to abrasion resistance when used in combination with the macrofiller, although abrasion resistance decreased with the increase in the microfiller concentration. The increase of filler content clearly improved the abrasion resistance when used the macrofiller. The analysis of these results and SEM observations of the brushed surfaces of samples suggested that the toothbrush abrasion was three-body abrasion caused by the abrasive in the toothpaste, and affected by the difference in the particle size between abrasive and filler, and between the abrasive size and the interparticle distance of the filler.

Absorption↗
PubMed1989

Effect of environmental temperature and humidity on bonding of acrylic resin to enamel.

The bond strength of acrylic resin to enamel is easily affected by moisture, temperature, etc. It is especially true that if there is water on the enamel surface, the bond strength declines drastically. In cases of orthodontic treatment which required bonding of many brackets at once we cannot practice perfect dry field techniques such as with a rubber dam. Accordingly the bond strength of acrylic resin under varying environmental conditions temperature and humidity was measured. The results were as follows; 1) The bond strength of acrylic resin to non-etched enamel was effected by temperature and humidity rather than by liquid/powder ratio. 2) The bond strength of acrylic resin to non-etched enamel declined with an increase in temperature at the same humidity. 3) The bond strength of acrylic resin to etched enamel was effected by the liquid/powder ratio, rather than by humidity when compared with non-etched enamel cases. 4) The bond strength of acrylic resin to etched enamel was not affected by temperature or humidity at a certain liquid/powder ratio. 5) There was no significant difference of formation of resin tags between the liquid/-powder ratio at low temperature and low humidity. Formation of resin tags at high humidity had sharp appearance in proportion to the low liquid/powder ratio.

Acid Etching, Dental↗
PubMed1989

[Effects of composite resin materials on gingiva and pulp].

Composite resin materials are now widely used for dental therapy. The purpose of this study was to clarify the effect of composite resins on gingiva and pulp in case of application of them for temporally splint in periodontal treatment. 60 teeth in 6 female dogs ranging between 1 and 2 years of age with healty teeth and gingiva were divieded to 4 groups; (1) 12 teeth, controls; (2) 12 teeth, self-cured composite resin (Clearfil F II, CF II); (3) 18 teeth, light-cured resin (Belfel LX, BLX), curing time 20 sec. and (4) 18 teeth, BLX, 40 sec., and then 48 class V composite resins were restored supragingivally. The experimental procedure were carried out for 5 days and 30 days. Histopathological observations of 60 teeth inclusive of controls were made by applying to specimens with Hematoxylin eosin staining. For the materials and time periods in this study it was found that; 1. Light-cured composite resin was superior to self-cured composite resin on handlings. 2. There were no significant differences in periodontium between the experimentals (BLX, CF II) and controls in 5 days. At the 30 days the histologic score showed more gingivitis for the experimental teeth than for the controls (BLX-40 greater than BLX-20 greater than CF II greater than Cont.). 3. At 5 days hyperemia occurred in some cases of experimentals (both BLX and CF II). The appearance of predentin and changes of odontblastic layer were observed slightly in 30 days. But there were no significant differences between BLX and CF II. 4. The result suggested that applying to composite resin materials for temporally splint, both gingiva and pulp have to be protected.

Animals↗