Fiber Post Cementation Strategies: Effect of Mechanical Cycling on Push-out Bond Strength and Cement Polymerization Stress

Purpose: To evaluate the effect of mechanical cycling and cementation strategies on the push-out bond strength between fiber posts and root dentin and the polymerization stresses produced using three resin cements. Materials and Methods: Eighty bovine mandibular teeth were sectioned to a length of 16 mm, prepared to 12 mm, and embedded in self-curing acrylic resin. The specimens were then distributed into 8 groups (n = 10): Gr1 - Scotchbond Multi Purpose + RelyX ARC; Gr2 - Scotchbond Multi Purpose + RelyX ARC + mechanical cycling; Gr3 - AdheSE + Multilink Automix; Gr4 - AdheSE + Multilink Automix + mechanical cycling; Gr5 - phosphoric acid + RelyX U100 (self-adhesive cement); Gr6 - phosphoric acid+ RelyX U100 + mechanical cycling; Gr7 - RelyX U100; Gr8 - RelyX U100 + mechanical cycling. The values obtained from the push-out bond strength test were submitted to two-way ANOVA and Tukey's test (p = 0.05), while the values obtained from the polymerization stress test were subjected to one-way ANOVA and Tukey's test (alpha = 0.05). Results: Mechanical cycling did not affect the bond strength values (p = 0.236), while cementation strategies affected the push-out bond strength (p < 0.001). Luting with RelyX U100 and Scotch Bond Multi Purpose + RelyX ARC yielded higher push-out bond strength values. The polymerization stress results were affected by the factor "cement" (p = 0.0104): the self-adhesive cement RelyX U100 exhibited the lowest values, RelyX ARC resulted in the highest values, while Multi link Automix presented values statistically similar to the other two cements. Conclusion: The self-adhesive cement appears to be a good alternative for luting fiber posts due to the high push-out bond strengths and lower polymerization stress values.

Influence of artificial accelerated ageing on the colour stability of paints used for ocular prosthesis iris painting

Objectives: To evaluate the colour stability of paints used for ocular prosthesis iris painting submitted for accelerated artificial ageing (AAA). Materials and methods: Forty specimens of acrylic resin for sclera (16 x 2 mm) were made and separated into eight groups (n = 10) according to the type of paint (gouache, GP; oil, OP; acrylic AP; and composite resin for characterisation, CR) and the colours used (blue/brown). After drying (72 h), a new layer of colourless acrylic resin was applied and the initial colour readout was performed (Spectrophotometer PCB 6807). New colour readouts were performed after AAA, and Delta E was calculated. Results: Statistical analysis (two-way ANOVA-Bonferroni, p < 0.05) demonstrated that the brown colour showed lower Delta E means in comparison with the blue colour, with statistically significant difference for AP only. Blue colour showed no statistically significant difference with regard to the type of paint used. Brown AP showed lower Delta E than the other groups, with significant difference for OP and GP. GP showed greater alteration in Delta E for the brown colour, being statistically similar only to OP. Conclusions: Only the AP group for brown pigment shows clinically acceptable values for colour stability after AAA.

Microencapsulation of Ketoprofen in Blends of Acrylic Resins by Spray Drying

Microparticles of ketoprofen entrapped in blends of acrylic resins (Eudragit RL 30D and RS 30D) were successfully produced by spray drying. The effects of the proportion ketoprofen : polymer (1: 1 and 1: 3) and of spray-drying parameters (drying gas inlet temperatures of 80 and 100 degrees C; microencapsulating composition feed flow rates of 4 and 6 g/min) on the microparticles properties (drug content, encapsulation efficiency, mean particle size, moisture content, and dissolution behavior) were evaluated. Differential scanning calorimetry (DSC) thermograms and X-ray diffractograms of the spray-dried product, the free drug, and the physical mixture between the free drug and spray-dried composition (blank) were carried out. Microparticles obtained at inlet temperature of 80 degrees C, feed flow rate of 4 g/min, and ketoprofen : acrylic resin ratio of 1: 3 presented an encapsulation efficiency of 88.1%, moisture content of 5.8%, production yield around 50%, and a higher reduction in dissolution rate of the entrapped ketoprofen. Sigmoidal shape dissolution profiles were presented by the spray-dried microparticles. The dissolution profiles were relatively well described by the Weibull model, a showing high coefficient of determination, R-2, and a mean absolute error between experimental and estimated values of between 4.6 and 10.1%.

Microtensile bond strength of composite resin to glass-infiltrated alumina composite conditioned with Er,Cr:YSGG laser

Tribochemical silica-coating is the recommended conditioning method for improving glass-infiltrated alumina composite adhesion to resin cement. High-intensity lasers have been considered as an alternative for this purpose. This study evaluated the morphological effects of Er,Cr:YSGG laser irradiation on aluminous ceramic, and verified the microtensile bond strength of composite resin to ceramic following silica coating or laser irradiation. In-Ceram Alumina ceramic blocks were polished, submitted to airborne particle abrasion (110 mu m Al(2)O(3)), and conditioned with: (CG) tribochemical silica coating (110 mu m SiO(2)) + silanization (control group); (L1-L10) Er,Cr:YSGG laser (2.78 mu m, 20 Hz, 0.5 to 5.0 W) + silanization. Composite resin blocks were cemented to the ceramic blocks with resin cement. These sets were stored in 37A degrees C distilled water (24 h), embedded in acrylic resin, and sectioned to produce bar specimens that were submitted to microtensile testing. Bond strength values (MPa) were statistically analyzed (alpha a parts per thousand currency sign0.05), and failure modes were determined. Additional ceramic blocks were conditioned for qualitative analysis of the topography under SEM. There were no significant differences among silicatization and laser treatments (p > 0.05). Microtensile bond strength ranged from 19.2 to 27.9 MPa, and coefficients of variation ranged from 30 to 55%. Mixed failure of adhesive interface was predominant in all groups (75-96%). No chromatic alteration, cracks or melting were observed after laser irradiation with all parameters tested. Surface conditioning of glass-infiltrated alumina composite with Er,Cr:YSGG laser should be considered an innovative alternative for promoting adhesion of ceramics to resin cement, since it resulted in similar bond strength values compared to the tribochemical treatment.

Antimicrobial Properties and Cytotoxicity of an Antimicrobial Monomer for Application in Prosthodontics

Purpose: This study aimed to investigate the antimicrobial properties and cytotoxicity of the monomer methacryloyloxyundecylpyridinium bromide (MUPB), an antiseptic agent capable of copolymerizing with denture base acrylic resins. Materials and Methods: The antimicrobial activity of MUPB was tested against the species Candida albicans, Candida dubliniensis, Candida glabrata, Lactobacillus casei, Staphylococcus aureus, and Streptococcus mutans. The minimum inhibitory and fungicidal/bactericidal concentrations (MIC, MFC/MBC) of MUPB were determined by serial dilutions in comparison with cetylpyridinium chloride (CPC). The cytotoxic effects of MUPB at concentrations ranging from 0.01 to 1 g/L were assessed by MTT test on L929 cells and compared with methyl methacrylate (MMA). The antimicrobial activity of copolymerized MUPB was tested by means of acrylic resin specimens containing three concentrations of the monomer (0, 0.3, 0.6% w/w). Activity was quantified by means of a disc diffusion test and a quantification of adhered planktonic cells. Statistical analysis employed the Mann-Whitney test for MIC and MFC/MBC, and ANOVA for the microbial adherence test (a= 0.05). Results: MUBP presented lower MIC values when compared with CPC, although differences were significant for C. dubliniensis and S. mutans only (p= 0.046 and 0.043, respectively). MFC/MBC values were similar for all species except C. albicans; in that case, MUPB presented significantly higher values (p= 0.046). MUPB presented higher cytotoxicity than MMA for all tested concentrations (p < 0.001) except at 0.01 g/L. Irrespective of the concentration incorporated and species, there was no inhibition halo around the specimens. The incorporation of MUPB influenced the adhesion of C. albicans only (p= 0.003), with lower CFU counts for the 0.6% group. Conclusions: It was concluded that non-polymerized MUPB has an antimicrobial capacity close to that of CPC and high cytotoxicity when compared with MMA. The antimicrobial activity of MUPB after incorporation within a denture base acrylic resin did not depend on its elution, but was shown to be restricted to C. albicans.

Evaluation of Chemical Treatment on Zirconia Surface with Two Primer Agents and an Alkaline Solution on Bond Strength

Objectives: This study evaluated the effect of an alkaline solution and two 10-methacryloyloxydecyl dihydrogen phosphate (MDP)-based primer agents on bond strength to zirconia (yttria-stabilized tetragonal zirconium polycrystal [Y-TZP]) through the shear bond strength (SBS) test. Materials and Methods: Sixty square-shaped Y-TZP samples were embedded in an acrylic resin mold, polished, and randomly assigned to one of six groups (n=10) according to treatment surface: group CR, no treatment (control); group NaOH, 0.5 M NaOH; group AP, Alloy Primer; group ZP, Z-Primer Plus; group NaOH-AP, 0.5 M NaOH + Alloy Primer; and group NaOH-ZP, 0.5 M NaOH + Z-Primer Plus. The resin cement (Rely X U100) was applied inside a matrix directly onto the Y-TZP surface, and it was light-cured for 40 seconds. The samples were stored in distilled water at 37 C for 24 hours prior to the test, which was performed in a universal machine at a crosshead-speed of 0.5 mm/min. The data were analyzed by one-way analysis of variance and Tukey tests (p<0.05). Light stereomicroscopy and scanning electron microscopy were used to assess the surface topography and failure mode. Results: The SBS was significantly affected by the chemical treatment (p<0.0001). The AP group displayed the best results, and the use of NaOH did not improve SBS results relative to either AP or ZP. The samples treated with Alloy Primer displayed mainly mixed failures, whereas those conditioned with Z-Primer Plus or with 0.5 M NaOH presented a balanced distribution of adhesive and mixed failure modes. Conclusions: The use of a NaOH solution may have modified the reactivity of the Y-TZP surface, whereas the employment of a MDP/6-4-vinylbenzyl-n-propyl amino-1,3,5-triazine2,4-dithione-based primer enhanced the Y-TZP bond strength.

Detorque evaluation of dental abutment screws after immersion in a fluoridated artificial saliva solution

Purpose: Implant-abutment connections still present failures in the oral cavity due to the loosening of mechanical integrity by detorque and corrosion of the abutment screws. The objective of this study was to evaluate the detorque of dental abutment screws before and after immersion in fluoridated solutions. Materials and Methods: Five commercial implant-abutment assemblies were assessed in this investigation: (C) Conex˜aoR , (E) EmfilsR , (I) INPR , (S) SINR , and (T) Titanium FixR . The implants were embedded in an acrylic resin and then placed in a holding device. The abutments were first connected to the implants and torqued to 20Ncmusing a handheld torque meter. The detorque values of the abutments were evaluated after 10 minutes. After applying a second torque of 20 Ncm, implant-abutment assemblies were withdrawn every 3 hours for 12 hours in a fluoridated solution over a period of 90 days. After that period, detorque of the abutments was examined. Scanning electronicmicroscopy (SEM) associated to energy dispersive spectroscopy (EDS) was applied to inspect the surfaces of abutments. Results: Detorque values of systems C, E, and I immersed in the fluoridated solution were significantly higher than those of the initial detorque. ANOVA demonstrated no significant differences in detorque values between designs S and T. Signs of localized corrosion could not be detected by SEM although chemical analysis by EDS showed the presence of elements involved in corrosive processes. Conclusion: An increase of detorque values recorded on abutments after immersion in fluoridated artificial saliva solutions was noticed in this study. Regarding chemical analysis, such an increase of detorque can result from a corrosion layer formed between metallic surfaces at static contact in the implant-abutment joint during immersion in the fluoridated solutions.

Riabilitazione protesica ed implanto-protesica di pazienti in età evolutiva affetti da Displasia Ectodermica

Introduction. Ectodermal Dysplasias are a heterogeneous group of inherited disorders characterized by dysplasia of tissues of ectodermal origin (hair, nails, teeth, skins and glands). Clinically, it may be divided into two broad categories: the X-linked hypoidrotic form and the hidrotic form. Hypohidrotic Ectodermal Dysplasia (H.E.D) is characterized by the triad oligo-anodontia, hypotricosis, hypo-anhydrosis (Christ-Siemens-Tourane syndrome). The incidence of HED is about 1/100,000. Mutation in the actodysplasin-A (EDA) and ectodysplasin-A receptor (EDAR) genes are responsible for X-linked and autosomal HED. The clinical features include sparse, fine hair, missing or conical-shaped teeth, decreased sweat and mucous glands, hypoplastic skin, and heat intolerance with exercise or increased ambient temperature. Complete or partial anodontia and malformation of teeth are the most frequent dental findings. Incisors and canines are often conical-shaped while primarily second molars, if present, are mostly affected by taurodontism. Treatment is supportive and includes protection from heat exposure, early prosthetic rehabilitation, skin, hair ear, nose and nail care, and genetic counseling for family planning. The diagnosis of HED in the neonatal and early infancy period may be difficult since sparse hair and absent teeth are normal finding at this age. In childhood the diagnosis is more easily made on the basis of history and clinical examination. Dental abnormalities are the most common complaint. Prosthetic rehabilitation has been recommended as an essential part of the management of HED because is important from functional, esthetic, and psychological standpoint. A team approach that includes input from a pediatric dentist, an orthodontist, a prosthodontist, and an oral and maxillofacial surgeon is necessary for a successful outcome. Conventional prosthodontic rehabilitation in young patient is often difficult because of the anatomical abnormalities of existing teeth and alveolar ridges. The conical shaped teeth and “knife-edge” alveolar ridges result in poor retention and instability of dentures. Moreover, denture must permit jaws expansion and a correct pattern of growth. Materials and Methods. Complete removable dentures were provided to allow for normal physiological development and a corrected masticatory function. Initial maxillary and mandibular impressions were made with smallest stock trays and irreversible hydrocolloid and then final impressions ware made with light-bodied polysulfide rubber base impression material. A base of autopolymerizing resin was constructed and a wax rim was added to the base. The patient’s vertical dimension of occlusion was established by assessing phonetic and esthetic criteria. Preliminary occlusal relations were recorded, and the mandibular cast was mounted on the articulator. Acrylic resin teeth specific for children dentures were selected and mounted. The dentures were tried in and, after proper adjustments, were inserted. The patients were monitored clinically every month to fit prostheses. Cephalometric radiographs were taken every 6 month with the prostheses in place in order to evaluate correct pattern of growth. Cephalometric measurements were realized and used to evaluate the effect of rehabilitation on craniofacial growth. Cephalometric measurements of sound patients were compared with ED patients. After two month expander screws (three-way screw in the upper denture and two-way the lower one)were inserted in each denture in order to permit the expansion of the denture and the jaws growth. Where conical teeth were present, composite crown were realized and luted to improve the esthetic and phonesis. In order to improve retention the placement of endosseous implants was carried out. TC 3D Accuitomo was performed and a resin model of mandibular bone of the patient was realized. At the age of 11 years two implants were inserted into anterior mandible in a child with anodontia. Despite a remarkable multi-dimensional atrophy of the mandibular alveolar process, the insertion of two tapered screw implants (SAMO Smiler, diameter 3.8, length 10 mm). After a submerged healing period of two-three month, the implants were exposed. Implants were connected with an expansion guide that permits mandibular growth and prosthetic retention. The amount of mandibular growth was also evaluate dusing the expansion guide. Results. Early oral rehabilitation improve oral function, phonesis and esthetic, reducing social impairment. Treated patients showed normal cephalometric measurement. Early rehabilitation is able to prevent the prognatissm of the mandibula . The number of teeth was significantly related to several changes in craniofacial morphology. Discussion. In the present study the 5,3% of ED patients showed hypodontia, the l’89,4% di oligodontia, and the 5,3% di anodontia. The cephalometric analysis supports that ED patients showed midface hypoplasia. ED groups showed an increased pogonion to nasion measurement than sound patients, indicative of class III tendency. The present study demonstrated that number of teeth was significantly correlated with deviation of cephalometric measurements from normality. Oligoanodontia is responsible for changing of cephalometric measuraments also on sagittal plane with a class III tendency. Maxillary jaw showed a retrused position related to the presence of hypodontia.

Torque efficiency of different archwires in 0.018- and 0.022-inch conventional brackets.

OBJECTIVE To compare the archwires inserted during the final stages of the orthodontic treatment with the generated moments at 0.018- and 0.022-inch brackets. MATERIALS AND METHODS The same bracket type, in terms of prescription, was evaluated in both slot dimensions. The brackets were bonded on two identical maxillary acrylic resin models, and each model was mounted on the orthodontic measurement and simulation system. Ten 0.017 × 0.025-inch TMA and ten 0.017 × 0.025-inch stainless steel archwires were evaluated in the 0.018-inch brackets. In the 0.022-inch brackets, ten 0.019 × 0.025-inch TMA and ten 0.019 × 0.025-inch stainless steel archwires were measured. A 15° buccal root torque (+15°) and then a 15° palatal root torque (-15°) were gradually applied to the right central incisor bracket, and the moments were recorded at these positions. A t-test was conducted to compare the generated moments between wires within the 0.018- and 0.022-inch bracket groups separately. RESULTS The 0.017 × 0.025-inch archwire in the 0.018-inch brackets generated mean moments of 9.25 Nmm and 14.2 Nmm for the TMA and stainless steel archwires, respectively. The measured moments in the 0.022-inch brackets with the 0.019 × 0.025-inch TMA and stainless steel archwires were 6.6 Nmm and 9.3 Nmm, respectively. CONCLUSION The 0.017 × 0.025-inch stainless steel and β-Ti archwires in the 0.018-inch slot generated higher moments than the 0.019 × 0.025-inch archwires because of lower torque play. This difference is exaggerated in steel archwires, in comparison with the β-Ti, because of differences in stiffness. The differences of maximum moments between the archwires of the same cross-section but different alloys were statistically significant at both slot dimensions.

In Vitro Implant Impression Accuracy Using a New Photopolymerizing SDR Splinting Material

PURPOSE The study aims to evaluate three-dimensionally (3D) the accuracy of implant impressions using a new resin splinting material, "Smart Dentin Replacement" (SDR). MATERIALS AND METHODS A titanium model of an edentulous mandible with six implant analogues was used as a master model and its dimensions measured with a coordinate measuring machine. Before the total 60 impressions were taken (open tray, screw-retained abutments, vinyl polysiloxane), they were divided in four groups: A (test): copings pick-up splinted with dental floss and fotopolymerizing SDR; B (test): see A, additionally sectioned and splinted again with SDR; C (control): copings pick-up splinted with dental floss and autopolymerizing Duralay® (Reliance Dental Mfg. Co., Alsip, IL, USA) acrylic resin; and D (control): see C, additionally sectioned and splinted again with Duralay. The impressions were measured directly with an optomechanical coordinate measuring machine and analyzed with a computer-aided design (CAD) geometric modeling software. The Wilcoxon matched-pair signed-rank test was used to compare groups. RESULTS While there was no difference (p = .430) between the mean 3D deviations of the test groups A (17.5 μm) and B (17.4 μm), they both showed statistically significant differences (p < .003) compared with both control groups (C 25.0 μm, D 19.1 μm). CONCLUSIONS Conventional impression techniques for edentulous jaws with multiple implants are highly accurate using the new fotopolymerizing splinting material SDR. Sectioning and rejoining of the SDR splinting had no impact on the impression accuracy.

Effect Of Composite Containing An Iodonium Salt On The Bond Strength Of Brackets To Bovine Enamel.

This study investigated the effect of the incorporation of an iodonium salt in experimental composites, on the bond strength of metallic brackets bonded to bovine teeth. Two hundred and seventy bovine teeth were embedded in self-curing acrylic resin and divided into 18 groups (n=15), according to the experimental composite with an iodonium salt at molar concentrations 0 (control), 0.5, or 1%; the light-activation times (8, 20 and 40 s); and the storage times (10 min or 24 h). Metallic brackets were fixed on the tooth surface using experimental composites. Photoactivation was performed with a quartz-tungsten-halogen light-curing unit curing unit for 8, 20 and 40 s. The specimens were stored in distilled water at 37 °C for 10 min or 24 h and submitted to bond strength test at 0.5 mm/min. The data were subjected to three-way ANOVA and Tukey's test (α=0.05). The Adhesive Remnant Index (ARI) was used to classify the failure modes. The shear bond strengths (MPa) at 10 min for light-activation times of 8, 20 and 40 s were: G1 - 4.6, 6.9 and 7.1; G2 - 8.1, 9.2 and 9.9; G3 - 9.1, 10.4 and 10.7; and at 24 h were: G1 - 10.9, 11.1 and 11.7; G2 - 11.8, 12.7 and 14.2; G3 - 12.1, 14.4 and 15.8. There was a predominance of ARI score 3 for groups with 10 min storage time, and ARI score 2 for groups with 24 h storage time. In conclusion, the addition of iodonium salt (C05 and C1) to the experimental composite may increase the bond strength of brackets to bovine enamel using reduced light exposure times.

Comparison Of Different Transfer Impression Techniques Accuracy For Osseointegrated Implants.

Abstract The aim of this study was to evaluate three transfer techniques used to obtain working casts of implant-supported prostheses through the marginal misfit and strain induced to metallic framework. Thirty working casts were obtained from a metallic master cast, each one containing two implant analogues simulating a clinical situation of three-unit implant-supported fixed prostheses, according to the following transfer impression techniques: Group A, squared transfers splinted with dental floss and acrylic resin, sectioned and re-splinted; Group B, squared transfers splinted with dental floss and bis-acrylic resin; and Group N, squared transfers not splinted. A metallic framework was made for marginal misfit and strain measurements from the metallic master cast. The misfit between metallic framework and the working casts was evaluated with an optical microscope following the single-screw test protocol. In the same conditions, the strain was evaluated using strain gauges placed on the metallic framework. The data was submitted to one-way ANOVA followed by the Tukey's test (α=5%). For both marginal misfit and strain, there were statistically significant differences between Groups A and N (p<0.01) and Groups B and N (p<0.01), with greater values for the Group N. According to the Pearson's test, there was a positive correlation between the variables misfit and strain (r=0.5642). The results of this study showed that the impression techniques with splinted transfers promoted better accuracy than non-splinted one, regardless of the splinting material utilized.

Alteração dimensional linear de resinas para bases de próteses polimerizadas com microondas

This study examined the influence of three polymerization cycles (1: heat cure - long cycle; 2: heat cure - short cycle; and 3: microwave activation) on the linear dimensions of three denture base resins, immediately after deflasking, and 30 days after storage in distilled water at 37± 2ºC. The acrylic resins used were: Clássico, Lucitone 550 and Acron MC. The first two resins were submitted to all three polymerization cycles, and the Acron MC resin was cured by microwave activation only. The samples had three marks, and dimensions of 65 mm in length, 10 mm in width and 3 mm in thickness. Twenty-one test specimens were fabricated for each combination of resin and cure cycle, and they were submitted to three linear dimensional evaluations for two positions (A and B). The changes were evaluated using a microscope. The results indicated that all acrylic resins, regardless of the cure cycle, showed increased linear dimension after 30 days of storage in water. The composition of the acrylic resin affected the results more than the cure cycles, and the conventional acrylic resin (Lucitone 550 and Clássico) cured by microwave activation presented similar results when compared with the resin specific for microwave activation.

In vitro wear resistance of three types of polymethyl methacrylate denture teeth

The wear resistance of denture teeth is important to the longevity of removable prostheses of edentulous patients. The ability of denture teeth to maintain a stable occlusal relationship over time may be influenced by this property. The purpose of this in vitro study was to evaluate the wear resistance of polymethyl methacrylate (PMMA) denture teeth based on their chemical composition when opposed by a ceramic antagonist. The maxillary canines (n=10) of 3 PMMA denture teeth (Trubyte Biotone, cross-linked PMMA; Trilux, highly cross-linked IPN (interpenetrating polymer network)-PMMA; and Vivodent, highly cross-linked PMMA) were secured in an in vitro 2-body wear-testing apparatus that produced sliding contact of the specimens (4.5 cycles/s, sliding distance of 20 mm, under 37°C running water) against glazed or airborne particle abraded ceramic. Wear resistance was measured as height loss (mm) under 300 g (sliding force) after 100,000 cycles, using a digital measuring microscope. Mean values were analyzed by 2-way ANOVA and Tukey's test (a=0.05). The wear of Trubyte Biotone (0.93 ± 0.14 mm) was significantly higher than that of both other types of teeth tested against abraded ceramic (p<0.05). The Vivodent tooth (0.64 ± 0.17 mm) exhibited the best wear resistance among the denture teeth tested against airborne particle abraded ceramic. There were no statistically significant differences (p>0.05) in wear among the 3 denture teeth evaluated against glazed ceramic. Trilux and Vivodent teeth tested against either glazed or airborne particle abraded ceramic did not differ significantly from each other (p<0.05). All teeth showed significantly more wear against airborne particle abraded ceramic than against glazed ceramic (p<0.05). In conclusion, the three types of PMMA denture teeth presented significantly different wear resistance against the abraded ceramic. The high-strength PMMA denture teeth were more wear-resistant than the conventional PMMA denture tooth.

Influence of different catilever extensions and glass or polyamaramid reinforcement fibers on fracture strength of implant-supported temporary

In long-term oral rehabilitation treatments, resistance of provisional crowns is a very important factor, especially in cases of an extensive edentulous distal space. The aim of this laboratorial study was to evaluate an acrylic resin cantilever-type prosthesis regarding the flexural strength of its in-balance portion as a function of its extension variation and reinforcement by two types of fibers (glass and polyaramid), considering that literature is not conclusive on this subject. Each specimen was composed by 3 total crowns at its mesial portion, each one attached to an implant component (abutment), while the distal portion (cantilever) had two crowns. Each specimen was constructed by injecting acrylic resin into a two-part silicone matrix placed on a metallic base. In each specimen, the crowns were fabricated with either acrylic resin (control group) or acrylic resin reinforced by glass (Fibrante, Angelus) or polyaramide (Kevlar 49, Du Pont) fibers. Compression load was applied on the cantilever, in a point located 7, 14 or 21 mm from the distal surface of the nearest crown with abutment, to simulate different extensions. The specimen was fixed on the metallic base and the force was applied until fracture in a universal test machine. Each one of the 9 sub-groups was composed by 10 specimens. Flexural strength means (in kgf) for the distances of 7, 14 and 21 mm were, respectively, 28.07, 8.27 and 6.39 for control group, 31.89, 9.18 and 5.16 for Kevlar 49 and 30.90, 9.31 and 6.86 for Fibrante. Data analysis ANOVA showed statistically significant difference (p<0.05) only regarding cantilever extension. Tukey's test detected significantly higher flexural strength for the 7 mm-distance, followed by 14 and 21 mm. Fracture was complete only on specimens of non-reinforced groups.