International Poster Journal of Dentistry and Oral Medicine, 04/2009

The technology of combined dentures brings often the need for joining dissimilar alloys. Purpose: The aim of the study was to provide information for successfully joining of used alloy combinations. Materials and methods: For experimental tests Ni-Cr and Co-Cr alloys plates were cast conventionally using an induction melting centrifugal casting machine. They were welded bilaterally with and without filler material, using a microplasma Welder. Welded specimens were analyzed macroscopically, microstructural and the microhardness were determined in the base metal (BM), welded metal (WM) and heat affected zone (HAZ). Results: Metallographic analyses and microhardness tests showed structural changes particularly in the HAZ, with precipitates of some compounds, which harden the respective area. At samples where the filling material was used, voids were present in the WM. Conclusion: The microstructure depends on the processing parameters and the composition of the filler material. Schlagwörter: processing parametrs, dissimilar welding, dental alloys

Objectives: In this investigation, the tensile bond strength of two different post systems (CP: CeraPost, Komet, Lemgo and DP: DentinPost, Komet Lemgo) in combination with four different dual-curing resin cements was tested. Methods: Eighty freshly extracted single-rooted were included in this study. The specimens were randomly assigned to eight experimental groups of ten each. The posts were inserted into 80 artificial root canals in bovine dentin using four different dual-curing resin cements (P: Panavia F 2.0; R: RelyXUnicem; B: Bifix QM; N: Nexus 2). After cementation all teeth were stored in 0.9% saline at 37 degrees. The retentive bond strength was measured after 24 hours storage using a universal testing machine (Zwick Z005). Results: For the eight test series following tensile bond strengths were evaluated (mean values and standard deviations in N): CP/P: 290.47 (± 59.86), CP/R: 159.81 (±56.42), CP/B: 60.37 (±14.61), CP/N: 74.49 (±16.09), DP/P: 233.61 (±53.76), DP/R: 323.26 (±55.51), DP/B: 245.65 (±81.76), DP/N: 110.46 (±27.80). The statistical analysis, using ANOVA and Tuckey test at a significance level of 5 %, showed that using Panavia F 2.0 with Cerapost and RelyXUnicem with Dentinpost resulted in the significant highest bond strength values. Nexus 2 had the significant lowest tensile bond strength in both fiber post systems. Between the different types of posts significantly higher bond strengths, except Panavia F 2.0 with DentinPost, could be tetected in the glas fiber group. Conclusions: It can be concluded that all tested resin cements are basically suitable for cementation of fiber posts. The combination of dual-curing resin cements with the type of fiber post has a great influence on the tensile bond strength. Schlagwörter: Retention, adhäsive Befestigungssysteme, Dentinadhäsive, Wurzeldentin, Glasfaserstifte

Cast and combination clasps are widely used in removable partial dentures technology. The aim of the study was to achieve 3D models in order to develop applications for basic research use, to design and optimize dental clasps. Plaster teeth were scanned and used to construct three dimensional models. The 3D models were used as a support for clasp modeling. Purposely designed experimental three-dimensional models of the clasp arms were constructed on the teeth surface and exported in a finite element analysis software to be used for structural simulations. Generated stresses and deformations were calculated numerically and plotted graphically. Results were displayed as colored stress contour plots to identify regions of different stress concentrations. This in vitro study demonstrated that structural analyses of cast clasps may offer a powerful tool in order to vizualize fracture risk areas. Schlagwörter: 3D modeling, stress distribution, dental clasps

The medical Licensure Act schedules to train the future dentist in practical skills as well as science-based. As many homepages and university calenders do not give information on the integration of evidence-based medicine (EbM) into the education, a questionnaire was sent to the ordinaries and their senior physicians of the 30 german universities where dental education is possible. The integration of EbM into a lecture was specified by 31 departments. As many lectures/seminars and courses remain without consequences for the students (no test or oral exams) it can hardly be estimated whether a knowledge gain will develop on the long run. Schlagwörter: Evidence-based medicine, dental education, examination, medical statistics

Ceramic inlays can be used on premolars requiring a class II restoration instead posterior composite resins, amalgam or gold inlays and offer a durable and aesthetic alternative. MOD inlays may increase the susceptibility to fracture. The aim of the study was to investigate the effect of preparation design on stress distribution in premolars with different class II and MOD cavity preparations restored with ceramic inlays. The study was performed on an upper first premolar, using a finite element analysis. Enlarged plaster teeth (scale 2:1) were scanned using a manufactured device. Twenty-two 3D models of maxillary first premolars, with the following designs of class II and MOD ceramic restorations were generated: eleven class II inlays with butt joint margins, eleven MOD inlays with butt joint margins, both with different tapers (between 0 and 10 degree). Computational simulation of an occlusal load of 200 N was conducted, and stresses occurring in the ceramic restorations, and teeth structures were calculated using Ansys finite element analysis software. Occlusal load on inlays restored teeth produces stress surrounding the contact areas. In the teeth restored with ceramic class II inlays, the von Mises equivalent stress values were similar to those the intact tooth. In the teeth restored with ceramic MOD inlays, the von Mises equivalent stress values were higher than in the intact tooth. Within the limitations of the study, it was demonstrated that ceramic inlays on premolars prevent failure and produce a low stress values, even if MOD restorations are used. A taper between 0 and 10 degree of the preparation is not decisive for the stress values. Acknowledgements: This study was supported by the Grant ID_1264 from the Ministry of Education and Research, Romania. Schlagwörter: ceramic inlays, class II restoration, preparation design, finite element analysis

Objective: The aim of the study was to test microplasma welding possibilities of cast dental restorations. Background: In classical conditions some lack of substance defects of cast restorations need their renewal, but modern techniques of dental alloys welding in protective gas shield allow correction of these defects, without repeating all of the clinical and technical stages. Materials and methods: Different Ni-Cr cast restorations with defects were chosen in order to add proximal contacts, to repair casting voids and to lengthen short cast crowns using microplasma welder. The optimal welding parameters were correlated with the defect type, size, and working stage. Nondestructive and destructive analyses tested the welding quality. Results: The welding parameters were determined for each defect type. An adequate combination of them allowed to obtain optimal repairs. These were proved by testing methods. Conclusion: Minor defects of cast restorations are suitable for correction, by welding with filling material and the used time is much more reduced than those needed for restoration renewal. Acknowledgements: This study was supported by the Grant CNCSIS 171/2007 from the Ministry of Education, Research, and Youth Romania Schlagwörter: cast dental restorations, defects, welding

Introduction: Prosthetic treatment failures related to the mechanical deficiencies of post and core systems still represent a problem of clinical significance and justify the researches orientated through the increasing of their performances and clinical longevity. The fatigue resistance tests represent an essential research tool because it simulate the repetitive cyclic way of the occlusal forces and replace the clinical tests that are time consuming.The aim of this study was to compare the behavior of different types of post and core systems when subjected to a cyclic loading test. Materials and method: Forty upper central incisors were endodontically treated and mounted in acrylic blocks. After anatomic crowns were removed, the teeth were reconstructed with carbon fiber, ceramic and titanium posts. In the control group, no posts were used. The crown build-up was made with composite resin and covered with metal crowns. An intermittent load was applied at an angle of 45 degrees to the long axis of the tooth at a frequency of 1,3 loads per second. The Kaplan-Meier analysis of the results obtained after 400.000 cycles showed that the survival rates for all experimental groups was lower than that of the control group, and the survival rate of carbon fiber group was higher than that of titanium and zirconium group. Conclusions: Fiber posts reduce the risk of root fracture and is the best choice in reconstruction of endodontically treated teeth. Schlagwörter: Post-and-core, fatigue resistance

Aim: Aim of the investigation was a comparison of the clinical, microbiological and immunological situation of the peri-implant tissues in edentulous patients wearing long-standing lower complete dentures retained by either Dolder bar or ball attachments. Methods: During a regular recall visit (mean time since implant insertion: 7 years) the following findings were examined in 10 individuals with good oral hygiene, matched for age and gender (mean age 71 years) and wearing either a Dolder bar or ball retained complete mandibular denture: sulcular fluid flow rate (with Periotron device), plaque- and bleeding scores, pocket probing depth, implant stability (Periotest device), subgingival bacterial plaque samples (PCR diagnostics, Hain MicroIdent), and sulcular concentrations of the mediators interleukin 1 beta and prostaglandin E2 (total concentration per site and per µl sulcular fluid in 120 seconds). Results: No statistically significant differences could be observed between the two groups of patients with Dolder bar and ball retained implant restorations with regard to their peri-implant clinical, microbiological, and immunological findings. Conclusions: Having in mind the relatively small number of patients included in the investigation the microbiological and immunological findings confirm the nearly identical pattern of influence , for either retentive concept, on the peri-implant soft tissue observed clinically even after a long period of function. Schlagwörter: Implant supported complete denture, Dolder bar, ball attachment, microbiology, sulcular fluid, interleukin 1 beta, prostaglandin E2

Ni-Cr alloys used in dental technology belong to the precipitation hardened alloys and their mechanical properties are developed by heat treatment. The purpose of the study was to evaluate the effect of heat treatments on microplasma welded Ni-Cr alloys with different composition used in dental technology, by metallographic analyses and microhardness tests. For the experimental study 16 plates were cast conventionally. Half of them were coold slowly at room temperature and half quickly, quenching them in cold water. The plates were matched and welded using microplasma Welder. Half of the welded specimens were heat treated using a furnace 60 min at 800°C and then cooled uniformly to room temperature. They were analyzed metallographic, and the microhardness was determined in the base metal (BM), weld metal (WM) and heat affected zone (HAZ). The cracks and the modification of the microstructure due to the rapid heating and solidification process can be a real problem and affect the quality of the weld. Even the chemical composition of the alloys was similar; their behavior at heat treatment was different. Therefore it is important that the heat treatments procedures be particularized for each alloy type. Schlagwörter: Ni-Cr alloys, heat treatment, prostheses technology

Dentinal adhesives Excite, Single bond, Prime bond, Prompt-L-pop Adper, Xeno III and AdheSe were applicated into class I cavities preparated into extracted primary teeth and they were restored with EvoCeram. The teeth were prepared for investigation under scanning electron microscope using Epovac and Struers Tegra polishing system. There was no substantial difference in morphology of the dentine/resin interface between the techniques studied. This fact may be of importance in the restoration of primary teeth because the number of steps and the procedure duration can be significantly reduced. Schlagwörter: Primary dentition, dentine adhesives, hybride layer, SEM, esthetic filling, self-etching technique, total-etch technique

Restorations produced with computer assistance are increasingly being adopted in dental technology. The aim of the study was to evaluate the effectiveness of the technological procedures in achieving zirconia based ceramics frameworks using Cercon CAD/CAM system. Data capture from models were made using an 3D laser scanner The virtual 3D dental restorations were designed on the computer screen following the specific steps. The CAD software transforms the virtual model into specific set of commands which drive the CAM unit. CAM complete restorations were created by substraction from presintered soft prefabricated zirconium oxide blocks, and finally these were sintered. Using Cercon system a wide variety of frameworks from zirconia based ceramics can be fabricated. After initiation, handling with Cercon CAD/CAM system is easy for the practitioner. Schlagwörter: CAD/CAM, dental technology, zirconia frameworks

Objectives: The aim of this study was to evaluate marginal bone resorption at two different implant shapes focussing on differences between high recruiting implant centers and low recruiting implant centers. Materials and Methods: Inclusion criteria were two missing teeth in the lower jaw distal of the incisor. No augmentation procedures and a planned fixed restauration. In all patients one straight Astra implant (3.5 or 4.0 mm) and one conical Astra (4.5 or 5.0 mm) were inserted. 18 centers participated and included 125 patients with 318 implants. Panoramic X-ray images were taken at 5, 12 and 24 months. Results: Mean insertion depth at implant insertion was 0.18 mm subcrestal for straight implants and 0.27 for conical implants. One implant loss was observed. The table lists mean radiologic bone resorption in mm: 6 months12 months24 months Implant shape:Straight implants0,830,830,96 Conical implants0,710,630,95 Center:=15 implants0,710,611,46 > 15 Implants0,830,790,81 Schlagwörter: Astra Tech, marginal bone resorption, high recruiting implant centers, low recruiting implant centers

Growth factors lead to the induction of tissue regeneration in bone healing when coated on biomaterials. Basic fibroblast growth factor (bFGF) combines osteoinduction and neoangiogenesis. This study evaluated bFGF-coated hydroxylapatite implants in two experimental groups with 10µg or 100µg (n=5 per group) compared with uncoated control implants in the rabbit patellar groove model. We observed an unexpected ineffectiveness compared to the control groups with no significant difference of bone growth after 35 days. However all samples from the 100µg experiment (control and coated implant) showed significantly stronger 19-25 day label than both 10µg groups (control and coated implant). Earlier bone labels are stronger in the 10µg group with equal observation of similarity between experiment and control site and may indicate a possible inhibitory effect of the higher dosing or osteoclast induction. This result indicates a possible systemic effect of the transient growth factor coating. Schlagwörter: Bone repair, Growth factors, Fibroblast growth factor, Hydroxyapatite, drug delivery, press-fit