Biomedical subjects

G Handel

Publications and source records attributed to G Handel.

At least 37 records · Page 2Linked to original sources

PubMed2000

Comparison of in vitro fracture strength of metallic and tooth-coloured posts and cores.

In root-treated anterior teeth a better aesthetic can be achieved by using translucent and tooth-coloured post and core restorations instead of traditional metal post systems. The aim of this in vitro study was to compare the fracture strength of tooth-coloured ceramic and fibre-reinforced posts as well as titanium posts with clinically proven gold alloy posts as a control. Two all-ceramic, one gold alloy and three combined post restoration systems (titanium and ceramic, respectively, fibre-reinforced posts with composite core) were each applied to upper incisors and after thermal cycling and mechanical loading (TCML) the fracture strength was determined. The variant providing the most reliable fracture strength values and the experimental fibre-reinforced composite (FRC) posts were - in combination with adhesively luted crowns - used to determine the fracture strength of the restoration after thermal cycling and mechanical loading. The median fracture strength of the luted posts and cores fluctuated between 114 and 546 N. Posts with composite cores demonstrate a higher fracture strength in comparison to the all-ceramic and gold alloy systems. Typical failure of metal systems was marked by loosening of the bonding and pulling out of the post in contrast to fracture of the ceramic posts. After the application of the crowns the ceramic system with composite core provided a fracture strength of 338 N and the FRC system a fracture strength of 228 N. Regarding fracture strength, the ceramic posts with composite cores are an alternative to commonly used gold posts and cores. A standardized technical manufacture of FRC posts and cores would provide better fracture strength results of this new dental material. Post and core restorations with tooth-coloured, translucent material offer an improved aesthetic especially in anterior restorations. Because of the high fracture strength prefabricated ceramic posts in combination with composite cores should prove their clinical applicability.

Aluminum Silicates↗

PubMed2000

[A simple and cosmetically ideal method large cranioplasty].

Repair of large skull defects is indicated as well to improve cosmetic as to protect the brain. A simply and easy to use procedure for exact duplication of cranial bone flaps used in cranioplasty is described. The original bone flap must be available to produce the definitive prosthesis.

Humans↗

PubMed2000

In vitro repair of all-ceramic and fibre-reinforced composite crowns.

Shear bond strength between fibre reinforced composite and all-ceramic frameworks and veneering/repair composites was investigated after different surface treatments for evaluating the possibility of a repair. Then, 24 crowns were adhesively luted on human teeth and artificially aged. Repair quality was characterized by a loading to fracture test, where undamaged crowns were compared to repaired crowns. To simulate repeated damage, aging and repair, the procedure was performed three times for each crown. A combined silicate-silane treatment of the fibre-reinforced composite frameworks and the hydrofluoric acid etching of the ceramic showed good repair qualities and a sufficient fracture strength for clinical application.

Analysis of Variance↗

PubMed1999

In-vitro study of fracture strength and marginal adaptation of fibre-reinforced adhesive fixed partial inlay dentures.

The aim of this study was to examine in-vitro whether adhesive fixed posterior inlay dentures (AFPID) made with the fibreglass-reinforced Vectris/Targis system (Ivoclar, Schaan, FL) have a fracture strength and a satisfactory marginal adaptation which can occur under clinical conditions. Extracted human third molars were embedded in a PMMA resin 10 mm apart to represent a molar gap. Two preparation methods were used: a box-shaped preparation technique (n = 8) and a tub-shaped preparation technique (n = 8). All AFPIDs were adhesively inserted using the dual curing composite cement, Variolink-high-viscosity (Vivadent, Schaan, FL). After thermocycling and mechanical loading (TCML: 6000 x 5 degrees C/55 degrees C, 1.2 Mio x 50 N, 1.66 Hz) in an artificial environment, the bridges were loaded to failure. Marginal adaption was investigated before and after TCML with the replica technique. After TCML, no significant difference was found in fracture strength between tub-shaped-preparation (median = 722 N, bending median = 0.9 mm) and box-shaped preparation (median = 696 N, bending median = 1.2 mm). A 'perfect margin' was observed in more than 60% of the investigated areas in both preparation techniques. With these values, the bridges can occur under clinical conditions and thus a clinical employment should be considered.

Acid Etching, Dental↗

PubMed1999

Veneering composites - a thermoanalytical examination.

Differential thermal analysis and thermal gravimetric analysis were used to characterize veneering composites. Samples weighing 4-20 mg, made from the composite materials Visio-Gem (Espe, Germany), Sinfony (Espe, Germany), Artglass (Kulzer, Germany), Dentacolor (Kulzer, Germany) and Targis (Ivoclar, Liechtenstein), were examined. The samples were subjected to various thermal curing times of between 4 s and 25 min, using the relevant devices of the manufacturers. As a control group, samples of all materials were examined unreacted. In order to avoid post-curing during storage, all samples were subjected, immediately after manufacture, to the appropriate dynamic temperature programme of the thermoanalytical unit at a heating rate of 10 degrees C min(-1). The materials showed specific material characteristics which can, for instance, be used to analyse the curing behaviour of the materials. The position of the glass transition, polymerization and post-polymerization peaks at temperatures between 30 and 100 degrees C, as well as 150 and 300 degrees C, and the filler and matrix content, allow the classification of the veneering composites.

Journal Article↗

PubMed1999

[Effect of various dressings on the point of entry of an intravenous drip].

In modern health care systems nosocomial infection is a major cause of patient suffering and leads to high financial costs. Overall nursing care that is part of nursing staff's daily routine is not brought under scrutiny often enough. The goal of this research project is to look at a small part only of optimal intravenous drip care. The focus of the paper is the influence that the use of two different kinds of dressings and two different types of cleansing methods have on the general appearance, as well as the microbiological results at the point of entry of the i.v. drip into the central veins. In order to examine this, test patients from different types of intensive care units were used for an experiment under highly controlled conditions. The results show that a variation in nursing care of the i.v. drip leads to a variation in germ development and in the general appearance at the point of entry.

Bandages↗

PubMed1999

In vitro study of the effect of thermo- and load-cycling on the bond strength of porcelain repair systems.

Fracture of porcelain fused to metal veneering may cause premature failure of fixed partial prosthodontics. Through the use of intra-oral composite bonded porcelain repair systems, the replacement of the prosthetic reconstruction can be avoided. The aim of this study was to evaluate the shear bond strength of porcelain repair systems currently in use and the effect of thermocycling and mechanical loading (TCML) on the adhesion of composite to ceramic surfaces in comparison with the composite to metal bonding system Rocatec. Specimens were fabricated by fusing the veneering ceramic VMK-68 (Vita) to Co-Cr-Mo-alloy base plates. Twenty cylindrically shaped composite samples in each series were bonded to the porcelain surface using porcelain repair systems currently in use. The shear bond strength of 10 samples was evaluated after 24 h (baseline) and after loading in an artificial oral environment. The repair systems Z 100 Kit, Monobond S/Tetric and Porcelain Etch were not impaired by TCML and exhibited a shear bond strength of greater than 12 MPa, which was comparable to the control group Rocatec. The shear strength of the repair systems Silistor and All-Bond 2 decreased significantly after TCML. Using the appropriate repair system, the repair of ceramic-veneered fixed partial prosthodontics can be recommended as a medium term alternative to a new reconstruction.

Adhesiveness↗

PubMed1999

Finishing and polishing of the ceromer material Targis. Lab-side and chair-side methods.

UNLABELLED: The aim of the study was to check four lab-side and four chair-side methods for finishing and polishing the ceromer material Targis. Eighty bar-shaped specimens (20 mm x 10 mm x 2 mm) of Vectris were produced; 72 were covered with a 2 mm (thickness) layer of the Ceromer Targis and eight samples with the composite Tetric. All specimens were ground plane parallel with 320 Silicium carbide grit sandpaper in order to start with the same level of roughness. Then the specimens were finished and polished using the following methods: (1) Artglass toolkit, (2) pumice-stone and brushes/linen brush and polishing paste P3, (3) Robinson brush/Ivoclar Universal paste and wool brush, (4) Silicone wheel and rag wheel, (5) Shofu Rainbow set, (6) Sof-Lex discs, (7) Vivadent Politip set and (8) Nupro-pastes and brushes. The surface roughness was determined with a profilometer. The arithmetical roughness value Ra was calculated. From each group one specimen was randomly chosen and sputtered with gold in order to observe the surface with a scanning electron microscope to evaluate its smoothness. The methods were ranked as followed: 2, 3 and 5 with the lowest roughness, then 8, 6, 7, 4, 1. The best ranked chair-side method (5) and the best ranked lab-side methods (2, 3) did not differ significantly between the Ra values. No difference was observed between the composite Tetric and the ceromer Targis when these materials were polished using the same method. CONCLUSION: the lab-side-methods 2 and 3 and the chair-side-method 5 can be recommended for finishing and polishing the new ceromer material Targis.

Carbon Compounds, Inorganic↗

PubMed1998

Colour stability of provisional crown and bridge restoration materials.

OBJECTIVE: In an in vitro study to determine the colour stability of provisional restoration materials, the PMMA synthetics Trimm and Cronsin and the bis-acrylic composites Protemp Garant, Protemp Garant NF, Protemp II and Provipont DC were investigated. MATERIALS AND METHODS: The colour changes of the cylindrical untreated samples were measured in comparison with samples after 24 and 72 hours of artificial ageing in a Suntest CPS+ UV ageing device using the Minolta CM 3500d spectrophotometer according to the CIE-L*a*b* system. RESULTS: Trimm (light), Cronsin (brown, yellow and universal), Provipont DC (yellow) and Protemp Garant NF (extra light) displayed the greatest discoloration with values > or = 4-21 delta E, where discoloration toward yellow could be discerned. The remaining materials showed lower luminance reflectance values of < or = 1-4 delta E, and therefore greater colour stability. CONCLUSIONS: Because of their colour stability the materials Cronsin (grey), Protemp Garant (yellow), Protemp II (light), Protemp Garant NF (yellow, light and extra light) could also be used as long-term interim prosthetics.

Analysis of Variance↗

PubMed1998

Adhesive-fixed partial dentures in anterior and posterior areas. Results of an on-going prospective study begun in 1985.

Within the framework of an on-going prospective clinical study begun in 1985, 120 adhesive-fixed partial dentures (AFPD) continued to be examined. The manufacture and the fitting of the AFPDs were carried out following a standard procedure. The preparation technique and the metal framework conditioning (silica-coating, sand-blasting and electrochemical etching) has varied throughout the duration of the study. Using Kaplan-Meier analysis, the survival rate was determined and an analysis of risk with regard to location factors (anterior, posterior; maxilla, mandible), conditioning and preparation techniques (retentive/non-retentive) was determined using the Cox regression model. The location of the AFPD had no influence on the survival rate. The survival time was determined mainly by the preparation technique. Strict preparation of seating grooves and pin holes made a 95% survival rate possible after 10 years (Kaplan-Meier estimation). Without retention, the risk of failure increased by a factor of 3.7.

Adolescent↗

PubMed1998

Intraoral repair of fiber-reinforced composite fixed partial dentures.

STATEMENT OF THE PROBLEM: Fractured composite facings may result in replacement of a fixed partial denture unless a reliable intraoral repair method can be provided. PURPOSE: This in vitro study tested the quality of an intraoral repair method for fractured facings of fixed partial dentures made of a fiber-reinforced composite system. MATERIAL AND METHODS: Shear bond strengths of a light-curing composite to a fiber-reinforced composite material were determined after different mechanical surface treatments. Aluminum oxide air abrading provided the most reliable bond strength values and therefore was used as a pretreatment for the facing repair of three-unit posterior fixed partial dentures. Facing repair was performed with the tested light-curing hybrid composite. Facing fracture strengths of repaired and original fixed partial dentures were determined after thermocycling and mechanical loading. RESULTS: Median facing fracture strength of the original fixed partial dentures was 1450 N after a simulated clinical service of 5 years. Facing fracture strengths of the repaired fixed partial dentures were significantly lower compared with the control group after an additional simulated 2-year interval. However, the median fracture force was still 1000 N. CONCLUSIONS: The facing repair of a fiber-reinforced fixed partial denture with a hybrid composite in combination with aluminum oxide air-abrading pretreatment and silanization provided sufficient fracture strength. Therefore the replacement of the complete restoration may be avoided.

Acrylates↗

PubMed1998

Complication rate with prosthodontic reconstructions on ITI and IMZ dental implants. Internationales Team für Implantologie.

The aim of this study was to compare the complication rate of two implant systems with different prosthodontic concepts: rigid conical or resilient support of the suprastructure. In 66 patients, 138 ITI implants were inserted whereas 31 patients received a total of 50 IMZ implants. Over an average observation period of 3.5 years (range from 0.5 to 8 years), not only was implant survival recorded, but also prosthodontic complications such as screw loosening, fractures of screws, inserts (intramobile elements, intramobile connectors) and abutments, as well as fractures of metal framework and veneers. With the ITI system, 28.8% of all devices placed exhibited such problems during the observation period. With the IMZ system, this rate was significantly higher (P < 0.05), in that 77.4% of all reconstructions required a repair at some point. The various complications were divided into those occurrences which affected only the suprastructure, i.e., failures of frameworks, veneers, bar devices or other retentive elements, and those which involved implant components per se, such as screws and abutment components. In the first category, adverse effects occurred more frequently with ITI-supported prostheses (15.1%) versus IMZ suprastructures (6.4%). Regarding complications with implant components, the rate with IMZ components was considerably higher (71%) compared with ITI (13.5%). This was mainly due to the presence of intramobile elements (IME) and connectors (IMC) in the IMZ system. In this retrospective study, precise fitting, non-resilient abutment components leading to rigid connections of suprastructures, proved to be clinically more successful than resilient anchoring components.

Adolescent↗

PubMed1998

In vivo color stability of resin composite veneers and acrylic resin teeth in removable partial dentures.

OBJECTIVE: The color stability of laboratory-made composite veneers was compared to that of artificial resin teeth under in vivo conditions. METHOD AND MATERIALS: Veneers and resin teeth of removable partial dentures were measured colorimetrically with reflection spectrophotometry; the color changes were characterized in the Commission Internationale d'Eclairage L*a*b* color space. The color was first determined 24 hours after manufacture and again after 6, 12, and 18 months at incisal, cervical, and centrofacial tooth positions. The denture teeth and veneers were measured, cleaned to eliminate the influence of surface discoloration, and measured again at every recall. The food consumption and tooth cleaning habits of the patients were taken into account. RESULTS: In all groups the maximum color changes from the baseline measurement were delta L* = 2.1, delta a* = 0.4, and delta b* = 1.8. The changes in the delta E* values were between 1.0 and 2.5 units. Despite polishing, the delta E* values increased by approximately 0.2 to 0.3 units in relation to the previous measurement with increased wearing time. External discolorations were eliminated by polishing, depending on the type of material; the maximum color change because of polishing was between 0.8 and 2.0 units for delta E*. The resin teeth showed no significant changes in the delta E* values. CONCLUSION: After a wearing period of 18 months, the discolorations of the tested materials were clinically acceptable. The artificial resin teeth showed statistically smaller color changes than did the veneering materials.

Color↗

PubMed1998

In vitro study of fracture strength and marginal adaptation of fibre-reinforced-composite versus all ceramic fixed partial dentures.

In this in vitro study fracture strength and marginal adaptation of adhesive-fixed three-unit posterior fixed partial dentures made with two different fabrication modifications--with and without the retainer material "Single"--of the new fibreglass system Vectris/Targis and from the metal-free Al2O3-ceramic In-Ceram were examined. The quality of the marginal adaptation was characterised using SEM evaluation and dye penetration techniques. In-Ceram and Vectris/Targis with "Single" showed good marginal adaptation, both statistically significantly better than the modification without "Single". After thermal cycling and mechanical loading the fibreglass reinforced systems showed a significantly higher fracture strength than the In-Ceram.

Aluminum Oxide↗

PubMed1997

[Artifacts in MR imaging of the temporomandibular joint caused by dental alloys: a phantom model study at T1.5].

PURPOSE: The influence of dental alloys on MRI of the temporomandibular joint was studied using a phantom model for this joint. METHODS: At 1,5 T, 15 dental alloys and 14 of their most important components were investigated acquiring sagittal (FOV: 150 mm) and transverse (FOV: 250 mm) T1-weighted SE images. In 11 cases, T1- and T2*-weighted FLASH images were measured additionally. The artifacts were assessed qualitatively as well as quantitatively, and the samples were subdivided into four artifact categories. RESULTS: Ag, Cu, Ga, In, Tl, Sn, Zn, amalgam, the precious alloys, the Au-Pd and Ag-Pd alloys showed no artifacts (category I). Minimal artifacts below 10 mm on transverse images (category II) were found for Cr, Pd, Pt and for the Ni-Cr alloy. Mn and the remaining non-precious alloys induced artifacts up to 30 mm (category III). Significant artifacts-more than 30 mm-(category IV) were caused by Ni-Cr and 18/8 wires and by Co, Fe, and Ni. T2*-weighted FLASH proved to be more susceptible for artifacts than T1-weighted SE and FLASH techniques. CONCLUSIONS: In contrast to dental alloys for fixed prosthodontics, Ni-Cr- or 18/8 wires used for orthodontic bands can influence not only the image quality, but also the diagnostic reliability of MRI of the temporomandibular joint.

Artifacts↗

PubMed1997

Colour stability of visible light-curing hybrid composites.

The colour stability of six visible light-curing fine hybrid composites was evaluated after 24 and 120 hours of irradiation using a xenon lamp. Discoloration of four shades of each material (A1, A2, A3.5 and B2- Vita shade guide) was measured using a reflection spectrophotometer with the CIE-L*a*b* system. The discoloration after 24 hours of irradiation had values of between 0.7 and 3.8 DE*, and was therefore, with the exception of Z 100 (colours A1 and B2), clinically acceptable. The results showed that the differences in colour of all shades of Pekafill NF and Tetric tested were significantly less than those of the other products. All samples, with the exception of Pekafill NF (A3.5 and B2), showed increased discoloration to values of 3.7 to 7.8 DE* after 120 hours of exposure to UV light. In general, all the composites tended to become more yellow (b*), darker (L*) and slightly greener (a*).

Analysis of Variance↗

PubMed1996

Diagnostic potential of pseudo-dynamic MRI (CINE mode) for evaluation of internal derangement of the TMJ.

In addition to the patient's history and a thorough clinical investigation, magnetic resonance imaging (MRI) of the temporomandibular joint (TMJ) has been introduced to complete the findings for the diagnosis of internal derangement of the TMJ. However, 'dynamic information' is desirable to help us to understand the mechanism of internal derangement. This information is given for example by electronic axiography recording systems. The lack of any ability to assess joint function dynamically in MRI is a point of criticism. Using a computer-driven pseudodynamic MRI system (CINE mode) 'dynamic information' should be now available. In this investigation 21 patients with TMJ disorders were examined using both conventional static MRI and CINE mode. For the diagnosis of an anterior displaced disc with or without reduction in 18 cases (86%) it was only necessary to consider two static MRIs: a closed mouth position and a maximal open mouth position. Comparison showed there was no advantage in using CINE mode. Contrast and resolution of the static MRIs were shown to be better and so additional findings such as joint effusion and disc deformation could be diagnosed on static MRIs with greater certainty. Only in three (14%) cases was the dynamic information from CINE mode useful for the diagnosis of the displacement of the disc.

Adult↗

PubMed1996

MR-imaging of the TMJ: artefacts caused by dental alloys.

The aim of the study was to investigate the influence of dental alloys and their components on magnetic resonance imaging of the temporomandibular joint. A plaster and a water- filled acrylic resin phantom - representing the disc and the condyle of the TMJ - were used. Cylindrical crow-type samples of 13 alloys and 14 pure substances were investigated. All alloys were examined with regard to their magnetic susceptibility, using a vibrating sample magnetometer. Metallic artefacts appeared on spin-echo technique as distortions, and on gradient-echo technique signal loss could be observed. Precious alloys were shown to be diamagnetic. The non precious alloys we investigated were paramagnetic. Paramagnetic alloys with a magnetic molar-susceptibility Cmol > 2000 x10(-6) cm3/mol can produce clinically relevant artefacts.

Artifacts↗