Effect of microwave treatment on the shear bond strength of different types of commercial teeth to acrylic resin

doi:10.1111/j.1741‐2358.2009.00333.x
Effect of microwave treatment on the shear bond strength of different types of commercial teeth to acrylic resin Objective: The purpose of this study was to verify the effect of microwave treatment on the shear bond strength of commercial types of teeth to acrylic resin, when the glossy ridge laps were unmodified (groups 1 and 5), bur abraded (groups 2 and 6), bur grooved (groups 3 and 7) or etched by monomer (groups 4 and 8). Background: Controversial findings have shown that mechanical or chemical changes in ridge‐lap surface of the tooth increase or decrease the bond strength between tooth and acrylic resin, and the microwave disinfection may cause different changes on this bond strength. Materials and methods: Eighty specimens (n = 10) were made with the acrylic resin bonded to tooth glossy ridge lap, polymerised in water at 74°C for 9 h, and deflasked after flask cooling. Specimens of the groups 5, 6, 7 and 8 were individually immersed in 150 ml of water and submitted to microwave treatment in an oven at 650 W for 3 min. Control specimens (groups 1, 2, 3 and 4) were not microwave treated. Shear bond strength test was performed in an Instron machine with a cross‐speed of 1 mm/min. Collected data were submitted to anova and Tukey’s test (α = 0.05). Results: Microwave treatment decreased the shear bond strength values of the tooth/resin bond. In the microwaved and non‐microwaved procedures, mechanical retention improved the shear bond strength when compared with the control and monomer treatments. Conclusion: Shear bond strength of the tooth/resin bond was influenced by the microwave treatment and different commercial teeth association, and was lower for the Biotone tooth.     

Effect of monomer treatment and polymerisation methods on the bond strength of resin teeth to denture base material

Background: The fracture between acrylic denture base material and artificial teeth is a common clinical occurrence in dental prosthodontic practice. Objective: To evaluate the bond strength between acrylic resins and resin denture teeth when submitted by two protocols of monomer liquid application on the tooth surface and using different polymerisation methods. Material and methods: Microwave‐polymerised (Onda‐Cryl), heat‐polymerised (Clássico) and autopolymerising (Jet) acrylic resins and a brand of resin denture teeth (Biotone) were used. The acrylic resins were polymerised according to the cycles: (A) microwave – fast cycle, Onda‐Cryl; (B) microwave – long cycle, Onda‐Cryl; (C) microwave – manufacturer’s cycle, Onda‐Cryl; (T) water bath – long cycle, Clássico and (Q) bench polymerisation cycle, Jet. Thirty specimens were prepared for each polymerisation method; 10 were packed with acrylic resin after 60 s of monomer liquid application on the tooth surface, 10 after 180 s and 10 without any monomer liquid application. For the purpose of the study, a shear test was used. anova and Tukey tests were performed to identify significant differences (α = 0.05). Results: The highest bond strength values were found for monomer surface treatments, regardless of the polymerisation cycles. The highest significant values were found for cycles B (15.4 ± 1.8 MPa), C (11.9 ± 4.9 MPa) and T (15.4 ± 2.6 MPa) for non‐treated and 60 s methylmethacrylate treated groups. Comparing the monomer liquid treatment, they did not differ significantly (p > 0.05), except for cycle A (p < 0.05). Conclusion: Chemical treatment using monomer on the tooth surface prior to the acrylic resin packing improved the bond strength between resin denture tooth and acrylic resin, regardless of monomer liquid treatment protocols. The microwavable resin, polymerised by fast cycle and autopolymerising resin should be avoided for processing denture and denture repairs, respectively.     

Bond strength of denture teeth to acrylic resin: effect of thermocycling and polymerisation methods

Background: Failure of bonding between acrylic resin teeth and denture base material is a considerable problem for patients who wear complete dentures. Objective: The purpose of this study was to evaluate the bond strength between acrylic resins and resin denture teeth with different thermocycling and polymerisation methods. Materials and methods: Microwave‐polymerised (Onda‐Cryl), heat‐polymerised (Clássico) and autopolymerising (Jet) acrylic resins and resin denture tooth (Biotone) were used. The acrylic resins were polymerised according to the following: (A) microwave – fast cycle, Onda‐Cryl; (B) microwave – long cycle, Onda‐Cryl; (C) microwave – manufacturer’s cycle, Onda‐Cryl; (T) water bath – long cycle, Clássico; and (Q) bench polymerisation cycle, Jet. Twenty specimens were prepared for each polymerisation method. Ten were thermocycled, and 10 did not receive thermocycling. For the purpose of the study, a shear test was used. Data were analysed with the Kruskal–Wallis test and Dunn’s multiple comparisons test (p = 0.05). Results: Cycles B, C and T were similar (p > 0.05), and had statistically higher bonding values than cycles A and Q (p < 0.05) for the thermocycled and non‐thermocycled groups. For all cycles, there were no statistically significant differences between thermocycled and non‐thermocycled groups (p > 0.05), except for cycle Q (p = 0.0038). Conclusion: Thermocycling decreased the bond strength, but not significantly for microwave and heat‐polymerised cycles. Regarding the bond strength of denture teeth to acrylic resin, the fast microwave polymerisation cycle should be avoided when polymerising Onda‐Cryl acrylic resin. In addition, Jet acrylic resin is not adequate for use in denture repair.     

Effect of pre-processing methods on bond strength between acrylic resin teeth and acrylic denture base resin

doi: 10.1111/j.1741‐2358.2011.00480.x
Effect of pre‐processing methods on bond strength between acrylic resin teeth and acrylic denture base resin Objectives: This study evaluated the effects of various pre‐processing methods on the bond strength between resin and denture teeth. Backgrounds: Debonding of acrylic resin teeth from denture base material is a problem for patients wearing complete dentures. Materials and Methods: Four experimental groups (n = 30) were investigated by subjecting tooth–resin bonding to tensile loading. Specimens were prepared and tested according to the methods of the International Standards Organization (ISO 22112:2005) using a special assembly. Four pre‐processing surface treatments of teeth were applied: (i) ST₁, no treatment applied (control); (ii) ST₂, wax solvent (Dewaks, Faber Kimya & Ilaç, Turkey); (iii) ST₃, boiling water followed by conditioning with methyl methacrylate (MMA) monomer (Meliodent, Bayer Dental, Germany); (iv) ST₄, boiling water followed by wax solvent agent and finally MMA monomer application. Bond strength test was performed using a universal testing machine. Results: All the strength values of the test groups were within clinically acceptable limits. The lowest values were from the ST₁ group and the highest values were in the ST₄ group. Conclusions: Wax elimination methods affected bonding strength. Application of wax solvent and MMA monomer to the ridge lap surfaces of the teeth gave the best results. In clinical practice, this application procedure may decrease the bonding failure of denture teeth.     

Shear bond strength between different materials bonded with two resin cements

doi: 10.1111/j.1741‐2358.2011.00565.x
Shear bond strength between different materials bonded with two resin cements Background: The aim of this study was to compare the shear bond strength between Ni–Cr alloy specimens bonded to air‐abraded Ni–Cr, bur‐abraded Ni–Cr, etched ceramic and etched enamel substrates using the resin cements RelyX ARC or Enforce. Materials and methods: Ni–Cr specimens were made and sandblasted with Al₂O₃ airborne‐particles. Disc‐shaped patterns were made for each of the four experimental substrates: Ni–Cr treated with Al₂O₃ airborne‐particles, Ni–Cr treated with diamond bur abrasion, etched enamel and etched ceramic. Results: Significant differences in shear bond strength were found between the different materials and luting agents evaluated. The Ni–Cr alloy cylinders bonded to Ni–Cr surfaces sandblasted with 50 μm Al₂O₃ particles and bonded with Enforce achieved the highest bond strength when compared with other substrates (28.9 MPa, p < 0.05). Bur‐abraded metal discs had lowest values, regardless the cement used (2.9 and 6.9 MPa for RelyX and Enforce, respectively). Etched enamel and etched ceramic had similar shear bond strengths within cement groups and performed better when RelyX was used. Conclusions: Bonding Ni–Cr to Ni–Cr and ceramic may result in similar and higher bond strength when compared to Ni–Cr/enamel bonding. For metal/metal bonding, higher shear bond strength was achieved with resin cement Enforce, and for metal/ceramic and metal/enamel bonding, RelyX had higher results.     

预酸蚀乳牙牙本质对自酸蚀粘接系统粘接强度的影响

目的:探讨预酸蚀乳牙牙本质对自酸蚀粘接系统粘接强度的影响。方法:随机选取28颗健康乳磨牙,磨除颊舌面釉质,暴露牙本质粘接面,沿近远中向劈开形成56个样本,随机分为7组(n=8)。直接涂布组(A1组,A2组和A3组)分别涂布AdperTM Easy One(AEO),Xeno-V(XV)和OptiBond All In One(AIO)三种自酸蚀粘接剂,预酸蚀组(B1组,B2组和B3组)在涂布三种自酸蚀粘接剂前先使用35%磷酸酸蚀乳牙牙本质15 s,对照组(C组)使用Prime&Bond NTTM(NT)全酸蚀粘接剂,每个样本用Z350复合树脂堆砌成直径为3 mm的树脂小柱,通过剪切试验测试剪切粘接强度,并通过扫描电子显微镜观察断裂表面形态。结果:B1组,B2组的剪切粘接强度值明显高于A1组,A2组(P<0.001);B3组与A3组的剪切粘接强度值比较无明显差别(P=0.94)。A2组的剪切粘接强度值低于C组(P<0.05);B1组的剪切粘接强度值明显高于C组(P<0.001)。扫描电镜观察结果显示各组试件断裂面形态多为牙本质和复合树脂界面破坏。直接涂布组(A1组,A2组和A3组)断裂多发生在混合层的底部,树脂突较少且低于小管口。B1组和B2组试件断裂面可见多数牙本质小管被树脂突填满,断裂多发生在混合层的中上部。B3组试件断裂面可见牙本质小管空虚,树脂突较少。结论:预酸蚀乳牙牙本质可以提高AEO,XV两种自酸蚀粘接剂的剪切粘接强度。自酸蚀粘接剂处理乳牙牙本质可以达到全酸蚀粘接剂处理的粘接强度,但应用自酸蚀粘接剂前预酸蚀乳牙牙本质可以获得更高的粘接强度。     

Effect of toothbrushing, chemical disinfection and thermocycling procedures on the surface microroughness of denture base acrylic resins

doi: 10.1111/j.1741‐2358.2011.00582.x Effect of toothbrushing, chemical disinfection and thermocycling procedures on the surface microroughness of denture base acrylic resins Objective: This study verified the surface microroughness of denture acrylic resins submitted to toothbrushing, chemical disinfection and thermocycling procedures. Material and methods: Samples were prepared according to conventional, microwaved and boiled resins and submitted to microroughness measurements before and after procedures using a profilometer (Ra). Data were subjected to anova and Tukey’s test (5%). Results: Before thermocycling, a difference was found among treatments for microwaved and boiled resins, with greater values for toothbrushing and lower values for Efferdent and hypochlorite; control was intermediate. Differences among resins were observed for treatments, with higher values for boiled resin and lower values for conventional and microwaved resins. After thermocycling, differences were found for microwaved resin, with a higher value for toothbrushing and a lower value for Efferdent and hypochlorite; control was intermediate. Tooth‐brushed boiled resin presented higher values and hypochlorite lower values; control and Efferdent were intermediates. Differences among resins were seen for treatments, with higher values for boiled resin and lower values for conventional and microwaved resins. Boiled resin presented differences for toothbrushing and hypochlorite, before and after thermocycling procedures were compared. Conclusions: For microwaved and boiled resins, toothbrushing and chemical disinfection promoted different levels of surface microroughness when associated or not with thermocycling.     

Shear bond strength between Ni-Cr alloy bonded to a ceramic substrate

doi: 10.1111/j.1741‐2358.2011.00585.x Shear bond strength between Ni‐Cr alloy bonded to a ceramic substrate Introduction: The aim of this study was to evaluate the shear bond strength between a Ni‐Cr alloy and a ceramic system submitted or not to thermocycling. Materials and methods: Forty‐eight cylinder blocks of Ni‐Cr with 3.0 mm diameter by 4.0 mm hight and 48 disc‐shaped specimens (7.0 mm in diameter by 2.0 mm thick) composed of ceramic were prepared. The Ni‐Cr cylinder blocks were randomised in two groups of 24 specimens each. One group was submitted to air‐particle abrasion (sandblasting) with 50 μm Al₂O₃ (0.4–0.7 MPa) during 20 s, and the other group was submitted to mechanical retentions with carbide burrs. Each group was subdivided into other two groups (n = 12), submitted or not to thermocycling (500 cycles, 5–55°C). The cylinder blocks were bonded to the disc‐shaped ceramic specimens under 10 N of load. The shear bond strengths (MPa) were measured using a universal testing machine at a cross head speed of 0.5 mm/min and 200 kgf of load. The data were submitted to statistical analysis (anova and Tukey’s test). Results: The air‐particle abrasion group exhibited significantly higher shear bond strength when compared to drilled group (p < 0.05). Conclusions: Thermocycling decreased significantly the bond strengths for all groups tested.     

Effect of the addition of silanated silica on the mechanical properties of microwave heat-cured acrylic resin

doi: 10.1111/j.1741‐2358.2011.00604.x
Effect of the addition of silanated silica on the mechanical properties of microwave heat‐cured acrylic resin Objectives: The purpose of this study was to evaluate fthe flexural strength and Vickers hardness of a microwave energy heat‐cured acrylic resin by adding different concentrations of silane surface‐treated nanoparticle silica. Methods: Acrylic resin specimens with dimensions of 65 × 10 × 2.5 mm were formed and divided into five experimental groups (n = 10) according to the silica concentration added to the acrylic resin mass (weight %) prior to polymerisation : G1, without silica; G2, 0.1% silica; G3, 0.5% silica; G4, 1.0% silica; and G5, 5.0% silica. The specimens were submitted to a three‐point flexural strength test and to the Vickers hardness test (HVN). The data obtained were statistically analysed by anova and the Tukey test (α = 0.05). Results: Regarding flexural strength, G5 differed from the other experimental groups (G1, G2, G3 and G4) presenting the lowest mean, while G4 presented a significantly higher mean, with the exception of group G3. Regarding Vickers hardness, a decrease in values was observed, in which G1 presented the highest hardness compared with the other experimental groups. Conclusion: Incorporating surface‐treated silica resulted in direct benefits in the flexural strength of the acrylic resin activated by microwave energy; however, similar results were not achieved for hardness.     

Er,Cr:YSGG激光切割对牙体与充填物粘结力影响的研究

本文用 1千牛电液疲劳实验机检测充填材料与牙面之间的粘结力 ,发现 :在牙釉质组中 ,酸蚀组、6瓦激光切割组及 6瓦激光切割联合酸蚀组抗剪切粘结强度无显著性差异 (P >0 .0 5) ;在牙本质组中 ,酸蚀组、4瓦激光切割组及 4瓦激光切割联合酸蚀组抗剪切粘结强度也无显著性差异 (P >0 .0 5)。并通过SEM观察激光处理后牙体表面结构的变化 ,发现激光切割后牙釉质表面不平呈层状 ,无玷污层 ,釉柱未见破坏 ;牙本质小管开放 ,表面无玷污层 ,达到酸蚀的效果。因此Er,Cr :YSGG激光切割牙体硬组织具有传统钻切割与酸蚀刻的联合作用 ,可以代替传统的酸蚀方法。     

Flexural and bond strengths of relined denture polymers assessed by four‐point bending tests and Weibull analysis

doi: 10.1111/j.1741‐2358.2011.00515.x Flexural and bond strengths of relined denture polymers assessed by four‐point bending tests and Weibull analysis Objectives: The aim of this study was to (1) investigate the flexural strengths of three denture resins i.e. heat, photopolymerised and microwaved and how it was affected by relining with auto‐ and visible light–polymerised hard reliners, (2) investigate the bond strengths between denture resins and hard reliners and (3) interpret the results of both tests by utilising Weibull analysis. Materials and methods: Specimens (65 × 10 × 2.5 mm) from denture resins, relined and bonded combinations were tested using a four‐point bending test in a universal testing machine and a crosshead speed of 5 mm/min. Ten specimens for each bulk resin and denture resin–reliner combination for a total of 150 were tested. Results: Statistical analysis indicated significant differences between bulk materials (p < 0.001) and between reliners (p < 0.001) for flexural and bond strength tests. Conclusion: It was concluded that (1) the four‐point flexural strength was different between the denture base materials, (2) flexure strength between bulk and relined or between relined with autopolymerised and photopolymerised bases was different, (3) flexural strength among relined denture bases was different and (4) bond strengths among relined denture bases were different.     

Various Effects of Sandblasting of Dental Restorative Materials

Background

Sandblasting particles which remain on the surfaces of dental restorations are removed prior to cementation. It is probable that adhesive strength between luting material and sandblasting particle remnants might exceed that with restorative material. If that being the case, blasting particles adhere to sandblasted material surface could be instrumental to increasing adhesive strength like underlying bonding mechanism between luting material and silanized particles of tribochemical silica coating-treated surface. We hypothesize that ultrasonic cleaning of bonding surfaces, which were pretreated with sandblasting, may affect adhesive strength of a resin luting material to dental restorative materials.

Methods

We therefore observed adhesive strength of resin luting material to aluminum oxide was greater than those to zirconia ceramic and cobalt-chromium alloy beforehand. To measure the shear bond strengths of resin luting material to zirconia ceramic and cobalt-chromium alloy, forty specimens of each restorative material were prepared. Bonding surfaces were polished with silicon abrasive paper and then treated with sandblasting. For each restorative material, 40 sandblasted specimens were equally divided into two groups: ultrasonic cleaning (USC) group and non-ultrasonic cleaning (NUSC) group. After resin luting material was polymerized on bonding surface, shear test was performed to evaluate effect of ultrasonic cleaning of bonding surfaces pretreated with sandblasting on bond strength.

Results

For both zirconia ceramic and cobalt-chromium alloy, NUSC group showed significantly higher shear bond strength than USC group.

Conclusions

Ultrasonic cleaning of dental restorations after sandblasting should be avoided to retain improved bonding between these materials.     

Flexural properties of repaired heat‐polymerising acrylic resin after wetting with monomer and acetone

doi:10.1111/j.1741‐2358.2009.00321.x
Flexural properties of repaired heat‐polymerising acrylic resin after wetting with monomer and acetone Objectives: Repair strength can be improved by treating fractured surfaces of a denture. Background: This study investigated flexural properties of heat‐polymerised acrylic resin specimens repaired with auto‐polymerising and visible light curing (VLC) resins after the repair surfaces were wetted with monomers or acetone. Materials and Methods: Fifty‐four specimens (65 × 10 × 2.5 mm) were prepared and 48 of them were sectioned to simulate denture fracture. Butt‐joint designed repair surfaces were wetted with heat‐, auto‐polymerising monomers and acetone for 180 s and repaired with auto‐polymerising and VLC resins. After repairs, specimens were subjected to three‐point bending test and flexural strength, strain, fracture load, modulus of elasticity and deflection values were recorded. Data were analysed with Student t and LSD tests (p ≤ 0.05). Results: Overall flexural strength, strain, fracture load and deflection values of specimens repaired with VLC resin were significantly higher than the specimens repaired with auto‐polymerising resin for all types of wetting agent (p < 0.05). Within the wetting agents, heat‐ and auto‐polymerising monomers produced the best mechanical properties, while wetting with acetone did not provide superior effect over both monomers. Conclusion: In clinical use, wetting the repair surfaces may result in stronger repairs. The use of bonding agent in VLC resin repairs in combination with wetting agent results in improved flexural properties.     

The effect of long‐term disinfection procedures on hardness property of resin denture teeth

doi: 10.1111/j.1741‐2358.2011.00520.x The effect of long‐term disinfection procedures on hardness property of resin denture teeth Objective: The aim of the study was to evaluate the effect of long‐term disinfection procedures on the Vickers hardness (VHN) of acrylic resin denture teeth. Material and methods: Five acrylic resin denture teeth (Vipi Dent Plus‐V, Trilux–T, Biolux‐B, Postaris‐P and Artiplus‐A) and one composite resin denture teeth (SR‐Orthosit‐O) were embedded in heat‐polymerised acrylic resin within polyvinylchloride tubes. Specimens were stored in distilled water at 37°C for 48 h. Measurements of hardness were taken after the following disinfection procedures: immersion for 7 days in 4% chlorhexidine gluconate or in 1% sodium hypochlorite (CIm and HIm group, respectively) and seven daily cycles of microwave sterilisation at 650 W for 6 min (MwS group). In the WIm group, specimens were maintained in water during the time used to perform the disinfection procedures (7 days). Data were analysed with anova followed by the Bonferroni procedure (α = 0.01). Results: Microwave disinfection decreased the hardness of all acrylic resin denture teeth (p < 0.001). Immersion for 7 days in 4% chlorhexidine gluconate or distilled water had significant effect on the hardness of the acrylic resin denture teeth A (p < 0.01), and 1% sodium hypochlorite on teeth T (p < 0.01). All disinfection procedures decrease the hardness of the composite resin denture teeth (p < 0.01). Teeth O exhibited the highest and teeth V the lowest hardness values in the control group (p < 0.01). Conclusions: Disinfection procedures changed the hardness of resin denture teeth.     

Relining of prosthesis with auto‐polymerizing hard denture reline resins: effect of post‐polymerization treatment on flexural strength

Background: It has been suggested that microwave irradiation and prosthesis immersion in hot water after its polymerization may improve mechanical and viscoelastic properties of acrylic resins. Purpose: This study was proposed to verify the influence of microwave post‐polymerization (PP) treatment over the flexural strength of thermo‐polymerizing acrylic resin specimens (QC‐20) relined or not with two different composition hard chairside auto‐polymerizing reliners [Kooliner (K) and New Truliner (NT)]. Materials and Methods: For this study, 50 specimens of 64 × 10 × 3.3 mm were polymerized and distributed into five groups. G1 (control) specimens without relining and PP; G2 specimens relined with K, without PP; G3 specimens relined with NT, without PP; G4 specimens relined with K, with PP (microwave irradiation with 650 W for 5 min); G5 specimens relined with NT, with PP. Tests were performed on a universal testing machine Instron 4411 with compression speed of 5 mm/min. Results: Specimens of K without PP did not show statistically different results (p < 0.05) when compared with control. However, when submitted to PP these specimens showed a significant increase in flexural strength. Specimens of NT showed the lowest flexural strength of all groups, with or without PP when compared with control and K groups. Conclusion: Microwave PP (650 W for 5 min) proved to be an effective method of improving the flexural strength of K relined prosthesis. However, it did not seem to affect NT specimens.     

Effect of Er,Cr:YSGG Laser at Different Output Powers on the Micromorphology and the Bond Property of Non-Carious Sclerotic Dentin to Resin Composites

Background

The objective of this study was to investigate the influence of Er,Cr:YSGG laser irradiated at different powers on the micromorphology and the bonding property of non-carious sclerotic dentin to resin composites.

Methods

Two hundred bovine incisors characterized by non-carious sclerotic dentin were selected, and the seventy-two teeth of which for surface morphological analysis were divided into nine groups according to various treatments (A: the control group, B: only treated with the adhesive Adper Easy One, C: diamond bur polishing followed by Adper Easy One, D-I: Er,Cr:YSGG laser irradiating at 1W, 2W, 3W, 4W, 5W, 6W output power, respectively, followed by Adper Easy One). The surface roughness values were measured by the non-contact three-dimensional morphology scanner, then the surface micromorphologies of surfaces in all groups were assessed by scanning electron microscopy (SEM); meanwhile, Image Pro-Plus 6.0 software was used to measure the relative percentage of open tubules on SEM images. The rest, one hundred twenty-eight teeth for bond strength test, were divided into eight groups according to the different treatments (A: only treated with the adhesive Adper Easy One, B: diamond bur polishing followed by the above adhesive, C-H: Er,Cr:YSGG laser irradiating at 1 W, 2 W, 3 W, 4 W, 5 W, 6 W output power, respectively, followed by the above adhesive), and each group was subsequently divided into two subgroups according to whether aging is performed (immediately tested and after thermocycling). Micro-shear bond strength test was used to evaluate the bond strength.

Results

The 4W laser group showed the highest roughness value (30.84±1.93μm), which was statistically higher than the control group and the diamond bur groups (p<0.05). The mean percentages ((27.8±1.8)%, (28.0±2.2)%, (30.0±1.9)%) of open tubules area in the 4W, 5W, 6W group were higher than other groups (p<0.05). The 4W laser group showed the highest micro-shear bond strength not only in immediately tested (17.60±2.55 PMa) but after thermocycling (14.35±2.08MPa).

Conclusion

The Er,Cr:YSGG laser at 4W power can effectively improve the bonding property between non-carious sclerotic dentin and resin composites by increasing the roughness and mean percentage area of open tubules.     

Evaluation of the flexural strength and elastic modulus of resins used for temporary restorations reinforced with particulate glass fibre

doi: 10.1111/j.1741‐2358.2010.00410.x
Evaluation of the flexural strength and elastic modulus of resins used for temporary restorations reinforced with particulate glass fibre Objective: The flexural strength and the elastic modulus of acrylic resins, Dencor, Duralay and Trim Plus II, were evaluated with and without the addition of silanised glass fibre. Materials and methods: To evaluate the flexural strength and elastic modulus, 60 test specimens were fabricated with the addition of 10% ground silanised glass fibres for the experimental group, and 60 without the incorporation of fibres, for the control group, with 20 test specimens being made of each commercial brand of resin (Dencor, Duralay and Trim Plus II) for the control group and experimental group. After the test specimens had been completed, the flexural strength and elastic modulus tests were performed in a universal testing device, using the three‐point bending test. For the specimens without fibres the One‐Way Analysis of Variance and the complementary Tukey test were used, and for those with fibres it was not normal, so that the non‐parametric Mann‐Whitney test was applied. Results: For the flexural strength test, there was no statistical difference (p > 0.05) between each commercial brand of resin without fibres [Duralay 84.32(±8.54), Trim plus 85.39(±6.74), Dencor 96.70(±6.52)] and with fibres (Duralay 87.18, Trim plus 88.33, Dencor 98.10). However, for the elastic modulus, there was statistical difference (p > 0.01) between each commercial brand of resin without fibres [Duralay 2380.64 (±168.60), Trim plus 2740.37(±311.74), Dencor 2595.42(±261.22)] and with fibres (Duralay 3750.42, Trim plus 3188.80, Dencor 3400.75). Conclusion: The result showed that the incorporation of fibre did not interfere in the flexural strength values, but it increased the values for the elastic modulus.     

Prevention of trauma to edentulous ridge from opposing natural teeth

doi: 10.1111/j.1741‐2358.2010.00397.x Prevention of trauma to edentulous ridge from opposing natural teeth Objective: To suggest a technique to prevent trauma of the edentulous ridge from opposing natural or restored teeth. Background: The prevalence of the condition where one edentulous arch opposes a natural or restored dentition is quite common. In most of cases, the maxillary arch is completely edentulous and either all teeth or only anterior teeth are present in the mandibular arch. These remaining teeth may continuously cause trauma to the opposing edentulous ridge during the night when a removable prosthesis is kept out of the mouth. Materials and methods: A thermoplastic acrylic resin mouthguard was fabricated on a cast of the remaining teeth dentition. Conclusion: This article presents a simple and inexpensive procedure to prevent self‐induced trauma of the edentulous ridge from opposing natural teeth by using a thermoplastic acrylic resin mouthguard.     

Pattern of tooth loss in an elderly population from Ibadan, Nigeria

Objectives: To determine tooth loss, edentulousness, causes of tooth loss and pattern of tooth loss in the elderly in South East Local Government area (SELGA) in Ibadan. Background data: SELGA is one of the largest in Oyo State, Nigeria and has a population of 225 800. Design: A cross‐sectional survey. Methodology: A total of 690 elderly individuals who were 65 years and above living in various wards in SELGA were interviewed by two interviewers and examined by two trained and calibrated examiners whilst two record clerks recorded all the findings of the examination. Result: Forty‐eight per cent of the subjects in the study had not lost any teeth. The mean tooth loss was 4.5 ± 7.6. Percentage edentulousness was 1.3% and this was higher in males than in females. This difference was not statistically significant (χ² = 0.07 p = 0.7). The total number of teeth lost was 3102, 14% of the total number of teeth examined. The study showed that caries was not a major cause of tooth loss. Only 22 (0.7%) teeth were lost as a result of caries, 19 (0.6%) were lost because of trauma and periodontal disease contributed to loss of 3061 (98.7%) teeth. Mandibular teeth exhibited a higher rate of retention than maxillary teeth. The percentage of elderly individuals with tooth loss increased with age. Conclusion: The study highlights the high life expectancy of a tooth among the elderly in SELGA. Despite the different cause of tooth loss in this area, in comparison with developed countries, the pattern of tooth retention appeared similar.     

Effect of the physical properties of acrylic resin of overnight immersion in sodium hypochlorite solution

doi:10.1111/j.1741‐2358.2009.00336.x
Effect of the physical properties of acrylic resin of overnight immersion in sodium hypochlorite solution Objectives: This study evaluated colour stability, surface roughness and flexural strength of microwave‐polymerised acrylic resin after overnight immersion in sodium hypochlorite, simulating 180 days use. Materials and methods: Forty disc‐shaped (15 mm × 4 mm) and 40 rectangular specimens (65 mm × 10 mm × 3 mm) were prepared from microwave‐polymerised acrylic resin. The specimens were immersed in 0.5, 1% sodium hypochlorite, Clorox/Calgon and distilled water. Colour measurements (ΔE) were determined by a portable colorimeter. A surface analyser was used to measure roughness (μm). The flexural strength (MPa) was measured using a three‐point bending test in a universal testing machine. Data were evaluated by one‐way anova , followed by Student–Newman–Keuls test (α = 0.05). Results: Statistical analysis found significantly higher colour changes (SNK, p < 0.001) for the 1% sodium hypochlorite, but mean ΔE value quantified by National Bureau of Standards was classified as slight. When comparing the surface roughness, no statistical significance was found among the solutions (anova , p = 0.637). The 1% sodium hypochlorite presented significantly lower flexural strength compared with the control group (SNK, p = 0.034). Conclusion: It was concluded that immersion in 1% sodium hypochlorite solutions for 8 h does influence the colour stability and flexural strength of microwave‐polymerised acrylic resin, during the simulated period of 180 days.