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Abstract: Background: Improvements of soft tissue to the abutment surface results in more stable peri‐implant conditions, however, few human histological studies have compared soft tissue responses around different abutment materials. Purpose: To describe the peri‐implant tissue around 3 abutment materials; titanium, zirconia, and gold alloy, over an 8‐week healing period. Materials and Methods: Fifteen edentulous sites were treated with implants. Eight weeks later, peri‐implant tissue was harvested and processed using a nonseparation resin embedded technique. The tissue attachment characteristics were assessed at clinical stages using the gingival index (GI) score, surgical stage (surgical score), and histological stage (histological attachment percentage). Additionally, the inflammatory responses were evaluated using inflammatory extent and inflammatory cellularity grades. Nonparametrical statistics were used to describe the GI and surgical scores, and analytical statistics were used to analyze the histological attachment percentages as well as the inflammatory extent and cellularity grades amongst the 3 groups. Results: There were no statistically significant differences among the groups for GI score (P = .071) and surgical score (P = .262). Titanium and zirconia exhibited nearly similar mean histological attachment percentages while gold alloy had a significantly lower percentage (P = .004). For the inflammatory extent and cellularity grades, the odds of being one grade higher for gold alloy abutment was 5.18 and 17.8 times that of titanium abutment, respectively. However, for the zirconia abutment, the odds were 0.87 and 7.5 times higher than the titanium group. Conclusions: The tissue around the gold alloy abutments resulted in worse attachment conditions compared with the titanium and zirconia abutments. Inflammation tended to be higher in the tissue around the gold alloy abutments than the titanium and zirconia abutments. [ABSTRACT FROM AUTHOR]

The purpose of this study were: to perform stress analyses using three-dimensional finite element analysis methods; to analyze the mechanical stress of different framework designs; and to investigate framework designs that will provide for the long-term stability of both cantilevered fixed partial dentures (FPDs) and abutment teeth. An analysis model was prepared for three units of cantilevered FPDs that assume a missing mandibular first molar. Four types of framework design (Design 1, basic type; Design 2, framework width expanded buccolingually by 2 mm; Design 3, framework height expanded by 0.5 mm to the occlusal surface side from the end abutment to the connector area; and Design 4, a combination of Designs 2 and 3) were created. Two types of framework material (yttrium-oxide partially stabilized zirconia and a high precious noble metal gold alloy) and two types of abutment material (dentin and brass) were used. In the framework designs, Design 1 exhibited the highest maximum principal stress value for both zirconia and gold alloy. In the abutment tooth, Design 3 exhibited the highest maximum principal stress value for all abutment teeth. In the present study, Design 4 (the design with expanded framework height and framework width) could contribute to preventing the concentration of stress and protecting abutment teeth. [ABSTRACT FROM AUTHOR]

In the modern era of science and technology, nanotechnology is becoming popular science field because materials at nanoscale contain improved physical, chemical and biological properties. This study aimed to explore the capacity of bimetallic nanoparticle alloys of silver (Ag), copper (Cu), gold (Au) in different ratios to evaluate the effects on medicinally important plant Eruca sativa. Biochemical parameters of Eruca sativa were studied by applying bimetallic alloy nanoparticles. Seeds of Eruca sativa were germinated on Murashige and Skoog medium with various combinations of nanoparticles suspension employed in concentration of (30 µg/ml). Bimetallic alloys were considered as a stress inducing factor in plants while studying the phytotoxicity. Many secondary metabolites were released because defensive mechanism of plants was active in response to stress. Such secondary metabolites produced in medicinal plants have a great capability in treating the human diseases. In the authors' study, nanoparticles of small size and of high toxicity effect produced more secondary metabolites like total protein content, total flavonoids and total phenolic content. [ABSTRACT FROM AUTHOR]

With the introduction of commercially available handheld XRF analysers, there is a growing problem that the results, simply taken at face value, are regarded as representative of the bulk gold alloys of the objects analysed in museums and used for treasure analysis. It is well known that surface analysis is problematic, and the aim of this study was to test whether non-destructive surface analysis could be useful in grouping the very large numbers of fragmentary pieces in the Anglo-Saxon Staffordshire Hoard. Surface and subsurface analyses of 16 objects from the Hoard were carried out by X-ray fluorescence (XRF) and scanning electron microscopy with energy-dispersive X-ray analysis (SEM-EDX). The results indicate that there are significant but inconsistent levels of enrichment of the gold at the surface of many of these objects, due to the loss of both copper and silver. The significant loss of silver (up to 50% relative in some cases) suggests that some form of deliberately induced depletion gilding was carried out during manufacture to remove both silver and copper from the surface. In three cases, an increase in silver at the surface compared to the core metal was detected: this might tentatively be explained by redeposition from contact with silver objects during burial. These results have clear implications for the reliability and interpretation of surface analysis data of gold alloys from this period. [ABSTRACT FROM AUTHOR]

The objective of this study was to quantitatively investigate the elemental ion release from the fixed gold alloy and ceramic crowns into patient saliva. Twenty patients who participated in the study were divided into two equal groups; 1) full coverage type IV gold crowns and 2) full coverage CAD- CAM-fabricated ceramic crowns. Saliva collection and clinical evaluation of marginal integrity and gingival health were performed before crowns preparation, 3 months and 6 months after crowns placement. Clinical evaluations were conducted using California Dental Association criteria. Collected saliva samples were analysed for element release using inductively coupled plasma mass spectrometer. The zinc, copper, palladium, gold and silver were released from type IV gold crowns into saliva, while the silicon and aluminium were released from ceramic crowns. A clinically significant number of subjects had increased release of zinc from baseline to three-month recall and increased silicon release from baseline to both three-month and six-month recalls. For all elements, the subjects' counts for the case of three-month recall to six-month recall were never higher than that of the case of baseline to three-month recall except for palladium. No obvious adverse effects on marginal integrity or gingival health were noticed. Significant increased releases of zinc from cast gold crowns and silicon from CAD- CAM-fabricated ceramic crowns into the saliva were evident after 3 months of clinical service. [ABSTRACT FROM AUTHOR]

Background: An association between the long-term success and survival of implant-supported prostheses as a function of biomaterial combinations has not been established. The use of cast cobalt-chromium for the suprastructure framework may be an alternative to the conventional approach of using type 3 gold alloys. Materials and methods: A retrospective chart audit of all patients who had received implant-supported fixed dental prostheses (FDP) before 1996 was identified in a private practice clinic. Data were recorded for FDPs made from four combinations of alloy frameworks and veneering material, i.e. type 3 gold and cobalt-chromium with ceramic or prefabricated acrylic teeth. The extracted data from the charts were subjected to explorative statistical tests including Kaplan-Meier survival analyses. Results: Patients ( n=198) with 270 short and extensive FDPs supported entirely by 1117 implants were identified. The average follow-up observation periods varied between 4 and 220 months, with an average of 120 months. The success and survival, as well as event rates and types of biological and technical complications, were similar for implant-supported FDPs using cobalt-chromium and type 3 gold alloy frameworks veneered with ceramics or prefabricated acrylic teeth. An influence of the suprastructure biomaterial combination on the clinical performance of the individual supporting implants could not be established. Conclusions: Implant-supported FDPs made from type 3 gold or cobalt-chromium frameworks and veneered with ceramic or prefabricated acrylic teeth demonstrate comparable clinical performance. The biomaterial combinations do not appear to influence the success or survival of the individual implants. To cite this article: Teigen K, Jokstad A. Dental implant suprastructures using cobalt-chromium alloy compared with gold alloy framework veneered with ceramic or acrylic resin: a retrospective cohort study up to 18 years. Clin. Oral Impl. Res. 23, 2012; 853-860. doi: 10.1111/j.1600-0501.2011.02211.x [ABSTRACT FROM AUTHOR]

Objective: The aim of the present study was to analyze the soft tissue barrier formed to implant abutments made of different materials. Material and methods: Six Labrador dogs, about 1 year old, were used. All mandibular premolars and the first, second and third maxillary premolars were extracted. Three months later four implants (OsseoSpeed™, 4.5 × 9 mm, Astra Tech Dental, Mölndal, Sweden) were placed in the edentulous premolar region on one side of the mandible and healing abutments were connected. One month later, the healing abutments were disconnected and four new abutments were placed in a randomized order. Two of the abutments were made of titanium (Ti), while the remaining abutments were made of ZrO2 or AuPt-alloy. A 5-months plaque control program was initiated. Three months after implant surgery, the implant installation procedure and the subsequent abutment shift were repeated in the contra-lateral mandibular region. Two months later, the dogs were euthanized and biopsies containing the implant and the surrounding soft and hard peri-implant tissues were collected and prepared for histological analysis. Results: It was demonstrated that the soft tissue dimensions at Ti- and ZrO2 abutments remained stable between 2 and 5 months of healing. At Au/Pt-alloy abutment sites, however, an apical shift of the barrier epithelium and the marginal bone occurred between 2 and 5 months of healing. In addition, the 80-μm-wide connective tissue zone lateral to the Au/Pt-alloy abutments contained lower amounts of collagen and fibroblasts and larger fractions of leukocytes than the corresponding connective tissue zone of abutments made of Ti and ZrO2. Conclusion: It is suggested that the soft tissue healing to abutments made of titanium and ZrO2 is different to that at abutments made of AuPt-alloy. [ABSTRACT FROM AUTHOR]

This study examined the effects of laser welding and heat treatment on the dimensional change of cast gold alloy frameworks. Pairs of cast gold alloy plates were matched, fixed in a jig, and welded in a laser-welding machine at constant welding parameters. The specimens were welded unilaterally (on one surface) or bilaterally (on two surfaces) with five spots as follows: two ends fixed/unilaterally welded (A); two ends fixed/bilaterally welded (AA); one end fixed/unilaterally welded (B); two ends fixed/welded on one surface and then one end fixed/welded on the opposite surface (AB); or one end fixed/bilaterally welded (BB). The dimensional change was determined by measuring the gap between the jig base and one end of the specimen after each welding application. Dimensional change was also measured after two different heat treatments (softening and hardening). The results were analyzed using a two-way ANOVA and Duncan's test ( p < 0.05). The dimensional change of the specimens fixed at only one end on either surface (AB, B, and BB) was higher compared with the two ends-fixed specimens (A and AA) after laser welding. The heat treatments also increased the dimensional change in all groups except for the B group. The dimensional change was similar for each fixing method between the two types of heat treatment. The method of fixing the specimens in the jig significantly affected the amount of dimensional change of the gold alloys. The heat treatments of the laser-welded specimens increased the dimensional change by releasing the residual stress. [ABSTRACT FROM AUTHOR]

Objectives: The aim of the study is to compare the peri-implant hard and soft tissue integration around dental implants made of commercially pure (c.p.) titanium or a gold alloy but with the same shape and surface roughness. Material and methods: In four beagle dogs, all mandibular premolars were extracted. Three months later, four experimental non-submerged implants were placed in each edentulous premolar region. Each implant comprised three different zones: zone A (coronal), zone B (central) and zone C (apical). Each zone was made of either c.p. titanium or a gold alloy. Four different combinations of metal and zone were used. A plaque control program was initiated and 6 months later, the animals were sacrificed and biopsies were obtained. The biopsies including the implant and the surrounding tissues were processed for ground sectioning. Results: The height of the peri-implant mucosa and the length of the barrier epithelium were similar at the four experimental sites. The marginal bone level in the different metal combinations was located between 4.5 and 4.8 mm apical of the implant rim. The percent of mineralized bone that was in direct contact with the implant surface (BIC%) was consistently greater in the marginal than in the apical portion of the implants. The BIC% for the marginal and apical zone were consistently greater for implant portions made of titanium than for portions made of gold alloy (zone B: 42.7% vs. 36.5%, zone C: 33.2% vs. 19%). Conclusions: Osseointegration was achieved to surfaces made of both c.p. titanium and a gold alloy. BIC% was higher at titanium than at gold surfaces. Moreover, the peri-implant soft tissue dimensions were not influenced by the metal used in the ‘marginal’ zone of the implant. [ABSTRACT FROM AUTHOR]

This study investigated the effect of surface preparation on the Nd:YAG laser penetration into cast titanium and gold alloy. Cast blocks of each metal were given four different surface preparations: (i) coloured with black marker; (ii) air-abraded with 50 μm Al2O3; (iii) ground with SiC points and (iv) polished with 1 μm Al2O3 (mirror-polished). Two blocks with each of the surface preparations were abutted and laser-welded at their interface using the voltages of 210–260 V in increments of 10 V. After the welded blocks were mechanically separated, the laser penetration was measured using computer graphics. Regardless of the surface preparation, an increase in voltage increased the laser penetration for both metals. The laser penetration into titanium prepared with black marker and air-abrasion was significantly deeper than into the titanium ground with SiC points and mirror-polished. Although there were no statistical differences in penetration among the surface preparations for the gold alloy, the penetration in the mirror-polished specimens was shallower than any of the other preparation methods at higher voltages of 240–260 V. The results obtained in this study suggested that broken metal frameworks with finished surfaces should be painted with black marker or air-abraded before laser welding. [ABSTRACT FROM AUTHOR]

The relative strengths of ceramic-to-metal and composite-to-metal bonds were compared after prolonged thermocycling. A total of 104 cast discs were produced from a gold alloy (Pontor LFC). A ceramic material (Duceragold) was fused to 24 discs to assess the strength of the metal–ceramic bond. An indirect composite material (New Metacolor Infis) was bonded to the remaining discs after surface preparation by Rocatec tribochemical coating, tin plating and priming with a phosphate conditioner [10-methacryloyloxydecyl dihydrogen phosphate (MDP), Cesead II], priming with a thione conditioner (V-Primer) or no treatment (unprimed control). Shear bond strengths were determined before and after thermocycling at 20 000 and 100 000 cycles. Pre-thermocycling bond strengths were ranked in the order: metal–ceramic (40·5 MPa); Rocatec treatment (33·1 MPa) and tin plating–MDP (31·0 MPa); V-Primer (20·9 MPa); and control (11·9 MPa). The bond strengths of the first three groups were not significantly different after 20 000 thermocycles, whereas those of the V-Primer and control groups were significantly reduced. After extended thermocycling (100 000 cycles) the metal–ceramic group had the highest mean shear bond strength (28·5 MPa; P < 0·05), followed by the Rocatec (23·9 MPa) and tin plating–MDP (22·1 MPa) groups. The metal–ceramic bond was the most durable, although its strength was reduced by 29·6% after extended thermocycling. On the basis of these results, we recommend the Rocatec and tin plating–MDP systems for composite-to-metal bonding. Metal–ceramic bonding, however, is superior to metal–composite bonding within the limitation of the current experiment. [ABSTRACT FROM AUTHOR]

Contact allergy to gold as demonstrated by patch testing is very common among patients with eczematous disease and seems to be even more frequent among patients with complaints from the oral cavity. There is a positive correlation between gold allergy and the presence of dental gold. Gold allergy is often found in patients with non-specific stomatitides as well as in those with lichenoid reactions or with only subjective symptoms from the oral cavity. The therapeutic effect of substituting other dental materials for gold alloys is conspicuous in casuistic reports but less impressive in larger patient materials. The amount of dental gold is correlated qualitatively and quantitatively to the blood level of gold and the effects if any of circulating blood gold are unknown. There is clearly a need for prospective studies in the field and gold sodium thiosulfate is considered an important item in the dental series for patch testing. [ABSTRACT FROM AUTHOR]

Restoration of tooth surfaces with materials that inhibit formation of heavy bacterial plaque accumulations could be important in the treatment of patients with existing oral disease or in reducing the likelihood for periodontal diseases. Captek® is a dental gold composite material used to produce copings for ceramometal restoration that has been reported to inhibit plaque accumulation. In this study, the oral bacteria of nine periodontally healthy subjects with a total of 42 gold composite copings were sampled. Contralateral teeth with normal tooth surfaces were also sampled as controls. The quantitative presence of forty bacteria was determined in each sample by DNA-DNA hybridization. The results indicated that the porcelain/gold composite alloy coping surfaces had significantly fewer bacteria than the control normal tooth surfaces (71% reduction). The percentage composition, however, did not differ significantly between surfaces. [ABSTRACT FROM AUTHOR]

The effect of different sodium chloride concentrations on the integrated currents (charge transfers) between dental amalgams and a gold alloy was studied in a bimetallic cell containing saliva or saline solutions. The integrated currents were only to a minor degree affected by increasing chloride concentrations for the high copper amalgams both in saliva and saline solutions. The integrated currents in the experiments involving conventional amalgam were several times higher than those for high copper amalgams. In saline solutions a charge transfer maximum was found at 0.2 M chloride. In saliva an increase of the charge transfer was found with increasing chloride content. [ABSTRACT FROM AUTHOR]

The galvanic currents between amalgam and gold alloy electrodes were higher in saline solutions than in saliva. Conventional amalgam supported higher currents than high copper amalgams when short-circuited with a gold alloy. The galvanic currents were not affected or affected only to a very small degree when whole saliva from different persons were compared. Higher currents were recorded when short-circuiting conventional amalgam and gold alloy electrodes using parotid saliva than when using whole saliva collected from one person. However, removing molecules with a molecular weight higher than 104 from whole and parotid saliva did not seem to affect the galvanic currents. [ABSTRACT FROM AUTHOR]

Short-circuited electrodes of dental amalgams and a gold alloy were used in an attempt to study a possible relationship between the quantity of copper and tin ions released into an electrolyte and the charge transferred between the electrodes. It was found that under the experimental conditions used the quantity of tin ions released was related to the charge transferred between the conventional amalgam and the gold alloy. The same tendency was found using a saliva sample which confined and collected the released tin ions into a small volume when the conventional amalgam specimen was short-circuited to the gold alloy specimen in vivo. [ABSTRACT FROM AUTHOR]