Associação de prótese fixa, implantes e estética periodontal para reabilitação de pacientes parcialmente edêntulos

Periodontitis is a chronic inflammatory disease that results in the destruction of teeth and their supporting tissues with subsequent tooth loss. The replacement of missing teeth for implant-supported restorations has proven to be a highly predictable treatment method with good long-term prognosis. However, some consequences of tooth loss prevents dental implant placement in an ideal position, where regenerative procedures are necessary for this type of rehabilitation. Less invasive procedures such as conventional prosthesis emerge as a therapeutic option in cases where there is enough bone structure for implants and patient´s non-acceptance for invasive procedures. Thus, this paper aims to present the resolution of rehabilitation through a noninvasive and multidisciplinary treatment. One female patient referred to the clinic presented maladaptive bilateral mandibular fixed prostheses, endodontic lesions, gingival recession, and root sensitivity. For proper resolution of this case, an association among osseointegrated implants, fixed partial prosthesis, tooth extraction, and aesthetic periodontal procedures with the use of subepithelial connective tissue graft was proposed. After two years, the patient shows excellent aesthetics and chewing. Within the limits of this scenario, this paper discusses the various factors that may affect the choice of a particular treatment modality for the rehabilitation of edentulous single spaces.

Zirconia-based dental crown to support a removable partial denture: a three-dimensional finite element analysis using contact elements and micro-CT data

Veneer fracture is the most common complication in zirconia-based restorations. The aim of this study was to evaluate the mechanical behavior of a zirconia-based crown in a lower canine tooth supporting removable partial denture (RPD) prosthesis, varying the bond quality of the veneer/coping interface. Microtomography (μCT) data of an extracted left lower canine were used to build the finite element model (M) varying the core material (gold core - MAu; zirconia core - MZi) and the quality of the veneer/core interface (complete bonded - MZi; incomplete bonded - MZi-NL). The incomplete bonding condition was only applied for zirconia coping by using contact elements (Target/Contact) with 0.3 frictional coefficients. Stress fields were obtained using Ansys Workbench 10.0. The loading condition (L = 1 N) was vertically applied at the base of the RPD prosthesis metallic support towards the dental apex. Maximum principal (σmax) and von Mises equivalent (σvM) stresses were obtained. The σmax (MPa) for the bonded condition was similar between gold and zirconia cores (MAu, 0.42; MZi, 0.40). The incomplete bonded condition (MZi-NL) raised σmax in the veneer up to 800% (3.23 MPa) in contrast to the bonded condition. The peak of σvM increased up to 270% in the MZi-NL. The incomplete bond condition increasing the stress in the veneer/zirconia interface.

Estudo retrospectivo de implantes osseointegrados instalados imediatamente após exodontias

Objectives: to evaluate implant survival immediately placed after tooth extraction considering different sites, prosthodontic modalities, and the need for biomaterials. Material and methods: dental records of 500 patients treated with dental implants between 2004 and 2011 were screened. Results: only 200 records (20%) corresponded to immediate implants. Reasons for tooth extraction included extensive caries, bone loss, and root fractures. From the 197 immediate dental implants, 86 were placed in the maxilla with a survival rate of 93.9% and 111 in the mandible (survival rate of 99.1%). The overall survival rate was 97.46%. Prosthodontic modalities identified were: Brånemark classic complete denture screwed prostheses (36%), overdentures (5.6%), fixed partial denture (31%), and single-tooth prostheses (27.4%). Also, it was observed that in 33% of cases there was a need for the use of grafts and/or biomaterials. Conclusion: it can be concluded that, when correctly indicated, immediate implants are an excellent choice. The anterior mandibular region, screwed and overdenture-type prostheses presented higher success rates when associated to immediate implant placement. The need for bone graft/biomaterial does not affect the clinical results.

Internal fit of two all-ceramic systems and metal-ceramic crowns

Objectives: The aim of this study was to investigate the internal fit (IF) of glass-infiltrated alumina (ICA - In-Ceram Alumina), yttria-stabilized tetragonal zirconia polycrystals (Y-TZP - IPS e.max ZirCAD), and metal-ceramic (MC - Ni-Cr alloy) crowns. Material and Methods: Sixty standardized resin-tooth replicas of a maxillary first molar were produced for crown placement and divided into 3 groups (n=20 each) according to the core material used (metal, ICA or Y-TZP). The IF of the crowns was measured using the replica technique, which employs a light body polyvinyl siloxane impression material to simulate the cement layer thickness. The data were analyzed according to the surfaces obtained for the occlusal space (OS), axial space (AS) and total mean (TM) using two-way ANOVA with Tukey's multiple comparison test (p<0.05). Results: No differences among the different areas were detected in the MC group. For the Y-TZP and ICA groups, AS was statistically lower than both OS and TM. No differences in AS were observed among the groups. However, OS and TM showed significantly higher values for ICA and Y-TZP groups than MC group. Comparisons of ICA and Y-TZP revealed that OS was significantly lower for Y-TZP group, whereas no differences were observed for TM. Conclusions: The total mean achieved by all groups was within the range of clinical acceptability. However, the metal-ceramic group demonstrated significantly lower values than the all-ceramic groups, especially in OS.

Preload Evaluation of Different Screws in External Hexagon Joint

Purpose: This study compared the maintenance of tightening torque in different retention screw types of implant-supported crowns. Materials and Methods: Twelve metallic crowns in UCLA abutments cast with cobalt-chromium alloy were attached to external hexagon osseointegrated implants with different retention screws: group A: titanium alloy retention screw; group B: gold alloy retention screw with gold coating; group C: titanium alloy retention screw with diamond-like carbon film coating; and group D: titanium alloy retention screw with aluminum titanium nitride coating. Three detorque measurements were obtained after torque insertion in each replica. Data were evaluated by analysis of variance (ANOVA), Tukey's test (P < 0.05), and t test (P < 0.05). Results: Detorque value reduced in all groups (P < 0.05). Group A retained the highest percentage of torque in comparison with the other groups (P < 0.05). Groups B and D retained the lowest percentage of torque without statistically significant difference between them (P < 0.05). Conclusions: All screw types exhibited reduction in the detorque value. The titanium screw maintained the highest percentage of torque whereas the gold-coated screw and the titanium screw with aluminum titanium nitride coating retained the lowest percentage. (Implant Dent 2012;21:46-50)

Torque removal evaluation of prosthetic screws after tightening and loosening cycles: an in vitro study

Objectives: The aim of this study was to evaluate the variation in removal torque of implant prosthetic abutment screws after successive tightening and loosening cycles, in addition to evaluating the influence of the hexagon at the abutment base on screw removal torque. Material and methods: Twenty hexagonal abutments were tightened to 20 regular external hex implants with a titanium alloy screw, with an insertion torque of 32 N cm, measured with a digital torque gauge. The implant/abutment/screw assemblies were divided into two groups: ( 1) abutments without hexagon at the base and ( 2) abutments with a hexagon at the base. Each assembly received a provisional restoration and was submitted to mechanical loading cycles. After this, the screws were removed and the removal torque was measured. This sequence was repeated 10 times, then the screw was replaced by a new one, and another cycle was performed. Linear regression analysis was performed. Results: Removal torque values tended to decrease as the number of insertion/removal cycles increased, for both groups. Comparisons of the slopes and the intercepts between groups showed no statistical difference. There was no significant difference between the mean values of last five cycles and the 11th cycle. Within the limitations of this in vitro study, it was concluded that ( 1) repeated insertion/removal cycles promoted gradual reduction in removal torque of screws, ( 2) replacing the screw with a new one after 10 cycles did not increase resistance to loosening, and ( 3) removal of the hexagon from the abutment base had no effect on the removal torque of the screws.

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.

Maintenance of implant-supported maxillary prostheses: a 2-year controlled clinical trial

To analyze maintenance service of fixed maxillary prostheses and overdentures based on conventional gold bars or titanium bars and frameworks fabricated with computer-aided design/computer-assisted manufacture (CAD/CAM) technology.

Implants versus short-span fixed bridges: survival, complications, patients' benefits. A systematic review on economic aspects

To systematically evaluate the existing evidence to answer the focused question: For a patient with a single tooth to be replaced, is the implant crown, based on economic considerations, preferred to a conventional fixed partial denture?

Clinical Performance of Screw- Versus Cement-Retained Fixed Implant-Supported Reconstructions- A Systematic Review.

PURPOSE To assess the survival outcomes and reported complications of screw- and cement-retained fixed reconstructions supported on dental implants. MATERIALS AND METHODS A Medline (PubMed), Embase, and Cochrane electronic database search from 2000 to September 2012 using MeSH and free-text terms was conducted. Selected inclusion and exclusion criteria guided the search. All studies were first reviewed by abstract and subsequently by full-text reading by two examiners independently. Data were extracted by two examiners and statistically analyzed using a random effects Poisson regression. RESULTS From 4,324 abstracts, 321 full-text articles were reviewed. Seventy-three articles were found to qualify for inclusion. Five-year survival rates of 96.03% (95% confidence interval [CI]: 93.85% to 97.43%) and 95.55% (95% CI: 92.96% to 97.19%) were calculated for cemented and screw-retained reconstructions, respectively (P = .69). Comparison of cement and screw retention showed no difference when grouped as single crowns (I-SC) (P = .10) or fixed partial dentures (I-FDP) (P = .49). The 5-year survival rate for screw-retained full-arch reconstructions was 96.71% (95% CI: 93.66% to 98.31). All-ceramic reconstruction material exhibited a significantly higher failure rate than porcelain-fused-to-metal (PFM) in cemented reconstructions (P = .01) but not when comparing screw-retained reconstructions (P = .66). Technical and biologic complications demonstrating a statistically significant difference included loss of retention (P ≤ .01), abutment loosening (P ≤ .01), porcelain fracture and/or chipping (P = .02), presence of fistula/suppuration (P ≤ .001), total technical events (P = .03), and total biologic events (P = .02). CONCLUSIONS Although no statistical difference was found between cement- and screw-retained reconstructions for survival or failure rates, screw-retained reconstructions exhibited fewer technical and biologic complications overall. There were no statistically significant differences between the failure rates of the different reconstruction types (I-SCs, I-FDPs, full-arch I-FDPs) or abutment materials (titanium, gold, ceramic). The failure rate of cemented reconstructions was not influenced by the choice of a specific cement, though cement type did influence loss of retention.

Technical complications and failures of zirconia-based prostheses supported by implants followed up to 7 years: a case series.

PURPOSE To evaluate technical complications and failures of zirconia-based fixed prostheses supported by implants. MATERIALS AND METHODS Consecutive patients received zirconia-based single crowns (SCs) and fixed dental prostheses (FDPs) on implants in a private clinical setting between 2005 and 2010. One dentist performed all surgical and prosthetic procedures, and one master technician performed and coordinated all laboratory procedures. One-piece computer-aided design/ computer-assisted manufacture technology was used to fabricate abutments and frameworks, which were directly connected at the implant level, where possible. All patients were involved in a recall maintenance program and were finally reviewed in 2012. Data on framework fractures, chipping of veneering ceramics, and other technical complications were recorded. The primary endpoint was failure of the prostheses, ie, the need for a complete remake. A life table analysis was calculated. RESULTS A total of 289 implants supported 193 zirconia-based prostheses (120 SCs and 73 FDPs) in 127 patients (51 men, 76 women; average age: 62.5 ± 13.4 years) who were reviewed in 2012. Twenty-five (13%) prostheses were cemented on 44 zirconia abutments and 168 (87%) prostheses were screw-retained directly at the implant level. Fracture of 3 frameworks (1 SC, 2 FDPs) was recorded, and significant chipping resulted in the remake of 3 prostheses (1 SC, 2 FDPs). The 7-year cumulative survival rate was 96.4% ± 1.99%. Minor complications comprised 5 loose screws (these were retightened), small chips associated with 3 prostheses (these were polished), and dislodgement of 3 prostheses (these were recemented). Overall, 176 prostheses remained free of technical problems. CONCLUSIONS Zirconia-based prostheses screwed directly to implants are clinically successful in the short and medium term.

Zirconia-Based Screw-Retained Prostheses Supported by Implants: A Retrospective Study on Technical Complications and Failures

BACKGROUND Little information is yet available on zirconia-based prostheses supported by implants. PURPOSE To evaluate technical problems and failures of implant-supported zirconia-based prostheses with exclusive screw-retention. MATERIAL AND METHODS Consecutive patients received screw-retained zirconia-based prostheses supported by implants and were followed over a time period of 5 years. The implant placement and prosthetic rehabilitation were performed in one clinical setting, and all patients participated in the maintenance program. The treatment comprised single crowns (SCs) and fixed dental prostheses (FDPs) of three to 12 units. Screw-retention of the CAD/CAM-fabricated SCs and FDPs was performed with direct connection at the implant level. The primary outcome was the complete failure of zirconia-based prostheses; outcome measures were fracture of the framework or extensive chipping resulting in the need for refabrication. A life table analysis was performed, the cumulative survival rate (CSR) calculated, and a Kaplan-Meier curve drawn. RESULTS Two hundred and ninety-four implants supported 156 zirconia-based prostheses in 95 patients (52 men, 43 women, average age 59.1 ± 11.7 years). Sixty-five SCs and 91 FDPs were identified, comprising a total of 441 units. Fractures of the zirconia framework and extensive chipping resulted in refabrication of nine prostheses. Nearly all the prostheses (94.2%) remained in situ during the observation period. The 5-year CSR was 90.5%, and 41 prostheses (14 SCs, 27 FDPs) comprising 113 units survived for an observation time of more than 5 years. Six SCs exhibited screw loosening, and polishing of minor chipping was required for five prostheses. CONCLUSIONS This study shows that zirconia-based implant-supported fixed prostheses exhibit satisfactory treatment outcomes and that screw-retention directly at the implant level is feasible.

Accuracy of stone casts obtained by different impression materials

Several impression materials are available in the Brazilian marketplace to be used in oral rehabilitation. The aim of this study was to compare the accuracy of different impression materials used for fixed partial dentures following the manufacturers' instructions. A master model representing a partially edentulous mandibular right hemi-arch segment whose teeth were prepared to receive full crowns was used. Custom trays were prepared with auto-polymerizing acrylic resin and impressions were performed with a dental surveyor, standardizing the path of insertion and removal of the tray. Alginate and elastomeric materials were used and stone casts were obtained after the impressions. For the silicones, impression techniques were also compared. To determine the impression materials' accuracy, digital photographs of the master model and of the stone casts were taken and the discrepancies between them were measured. The data were subjected to analysis of variance and Duncan's complementary test. Polyether and addition silicone following the single-phase technique were statistically different from alginate, condensation silicone and addition silicone following the double-mix technique (p < .05), presenting smaller discrepancies. However, condensation silicone was similar (p > .05) to alginate and addition silicone following the double-mix technique, but different from polysulfide. The results led to the conclusion that different impression materials and techniques influenced the stone casts' accuracy in a way that polyether, polysulfide and addition silicone following the single-phase technique were more accurate than the other materials.

Al(2)O(3)/GdAlO(3)fiber for dental porcelain reinforcement

The aim of this study was to test the hypothesis that the addition of continuous or milled GdAlO(3)/Al(2)O(3) fibers to a dental porcelain increases its mechanical properties. Porcelain bars without reinforcement (control) were compared to those reinforced with long fibers (30 vol%). Also, disk specimens reinforced with milled fibers were produced by adding 0 (control), 5 or 10 vol% of particles. The reinforcement with continuous fibers resulted in significant increase in the uniaxial flexural strength from 91.5 to 217.4 MPa. The addition of varied amounts of milled fibers to the porcelain did not significantly affect its biaxial flexural strength compared to the control group. SEM analysis showed that the interface between the continuous fiber and the porcelain was free of defects. On the other hand, it was possible to note the presence of cracks surrounding the milled fiber/porcelain interface. In conclusion, the reinforcement of the porcelain with continuous fibers resulted in an efficient mechanism to increase its mechanical properties; however the addition of milled fibers had no significant effect on the material because the porcelain was not able to wet the ceramic particles during the firing cycle. (C) 2008 Elsevier Ltd. All rights reserved.

Effect of the microstructure on the lifetime of dental ceramics

Objectives. To evaluate the effect of the microstructure on the Weibull and slow crack growth (SCG) parameters and on the lifetime of three ceramics used as framework materials for fixed partial dentures (FPDs) (YZ - Vita In-Ceram YZ; IZ - Vita In-Ceram Zirconia; AL - Vita In-Ceram AL) and of two veneering porcelains (VM7 and VM9). Methods. Bar-shaped specimens were fabricated according to the manufacturer`s instructions. Specimens were tested in three-point flexure in 37 degrees C artificial saliva. Weibull analysis (n = 30) and a constant stress-rate test (n = 10) were used to determine the Weibull modulus (m) and SCG coefficient (n), respectively. Microstructural and fractographic analyzes were performed using SEM. ANOVA and Tukey`s test (alpha = 0.05) were used to statistically analyze data obtained with both microstructural and fractographic analyzes. Results. YZ and AL presented high crystalline content and low porosity (0.1-0.2%). YZ had the highest characteristic strength (sigma(0)) value (911 MPa) followed by AL (488 MPa) and IZ (423 MPa). Lower sigma(0) values were observed for the porcelains (68-75 MPa). Except for IZ and VM7, m values were similar among the ceramic materials. Higher n values were found for YZ (76) and AL (72), followed by IZ (54) and the veneering materials (36-44). Lifetime predictions showed that YZ was the material with the best mechanical performance. The size of the critical flaw was similar among the framework materials (34-48 mu m) and among the porcelains (75-86 mu m). Significance. The microstructure influenced the mechanical and SCG behavior of the studied materials and, consequently, the lifetime predictions. (C) 2011 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.