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This in vitro study compared the marginal adaptation of three self-adhesive composite cements with the clinically well-tried dentin adhesive system Panavia F 2.0. A total of 32 Empress 2 all-ceramic MOD-inlays (eight in each group) were luted using the self-adhesive composite cements Maxcem, Multilink Sprint, and RelyX Unicem Clicker; Panavia F 2.0 served as a clinically well-tried control. Each luted inlay underwent long-term water storage of 90 days as well as additional mechanical and thermal loading to simulate oral service. Marginal integrity was evaluated in both dentin and enamel finishing lines using scanning electron microscopy (SEM) and dye penetration tests. Dye penetration was lowest for Panavia followed by RelyX Unicem. Maxcem and Multilink showed a considerable dye penetration of up to 60%. After aging, SEM analysis revealed a reduction of “perfect margin” areas for Multilink Sprint and RelyX Unicem in enamel and for Maxcem and Multilink in dentin. Compared with the well-tried system Panavia—which was assumed as the golden standard of adhesive luting systems—only the self-adhesive luting agent RelyX Unicem showed similar results of marginal adaptation after long-term water storage. [ABSTRACT FROM AUTHOR]

Goal: The aim of this review is to summarize the in vitro and in vivo evidence on the performance of contemporary saliva substitutes in the treatment of xerostomia and hyposalivation caused by radiation therapy for head and neck malignancies.Methods: A literature search was conducted during July to September 2008 in PubMed, using the query terms "saliva substitute", "saliva substitute and xerostomia", "artificial saliva", and "artificial saliva and xerostomia"; for clinical studies, only studies in patients suffering from radiation-induced xerostomia have been included in the review.Results and Conclusion: Fifty-two studies met the inclusion criteria and were allotted either to the in vitro topics "viscosity", "lubrication", "wetting properties", "antimicrobial effects", and "enamel and dentin de- and remineralization", or to the in vivo topics "clinical acceptance" or "influence on plaque formation and oral mucosa and microflora". The findings suggest that there are significant differences in the performance of various saliva substitutes concerning the review parameters, yet indicate that further in vitro and in vivo studies on the properties of saliva substitutes are necessary. [ABSTRACT FROM AUTHOR]

This study evaluated the impact of different mixing ratios and wrongly stored blends of dual-curing composite cements on Empress2 glass–ceramic crowns by means of a flexural strength test and a fracture resistance test. Thermally damaged blends and fresh blends were mixed using different mixing ratios of dual-curing Panavia F and Variolink II composite cement (2:1; 1:1; 1:1.5; 1:1.75; base/catalyst). Sixteen groups of rectangular beams of both cements (two blends, four ratios, chemical-curing, light-curing) were constructed. Their flexural strength was determined in a three-point bending test. Furthermore, 64 Empress2 all-ceramic crowns were luted onto human molars, again using fresh and thermally damaged blends as well as different mixing ratios of the luting agents. After aging, fracture resistance was investigated. The flexural strength of dual-curing composite cements was influenced to a statistically significant extent by mixing ratios and storage conditions. In particular, the chemical curing mode of these cements was affected by the thermal damage of the blends. However, this study could not demonstrate a significant impact on the fracture resistance of Empress2 glass-ceramic crowns when different mixing ratios or wrongly stored cements were used. Dual-curing composite luting agents seem to tolerate a wide range of mixing errors, but their chemical curing mode may be affected by storage errors. [ABSTRACT FROM AUTHOR]

Missing permanent teeth is observed with syndromes or is frequently hereditarily propagated in families. The treatment of these patients is a multi-task of specialists of oral surgery, orthodontics and prosthodontics. Despite functional and aesthetic considerations, the main problem of all treatment is that it had to be performed in a growing child. This article discusses the conventional and implant-driven concepts to treat patients from childhood to adolescence with selective or multiple missing permanent teeth. [ABSTRACT FROM AUTHOR]

This study investigated the influence of electron beam irradiated reinforced fillers on the three body wear and flexural strength of experimental composite blends. Three formulations of reinforced fillers were investigated: (A) high loaded inorganic filler composite with 60 wt.% SiO2, (B) low loaded inorganic filler composite with 40 wt.% SiO2, (C) organic filler composite (precipitated Bis-phenol-A-di-methacrylate). The fillers were assigned to two subgroups of unswollen (A, B, C) and monomer swollen (As, Bs, Cs) fillers. The experimental blends (matrix: Urethane-dimethacrylate) were mixed using un-treated, annealed (90 °C), or electron beam irradiated fillers with 30 and 90 kGy, respectively. All specimens were heat-cured for 20 min at 140 °C. Three-body abrasion and flexural strength tests were performed. The highest flexural strength was evaluated for composites made of the 30 kGy irradiated type Bs filler. The comparison with annealed fillers showed that the effect was independent of increasing temperatures during the radiation process. Blends with a SiO2 content of 60 wt.% (type A, As) had significantly less wear than blends with 40 wt.% (type B, Bs) or blends with organic fillers (type C, Cs). The flexural strength of the composite could be improved by using pre-irradiated reinforced fillers. However, wear was not affected using this procedure. [ABSTRACT FROM AUTHOR]

This study tested the potentiality of dielectric analysis (DEA) for determining the reaction performance of light-curing dental resins. The influence of polymerisation conditions and material properties on the ion viscosity were investigated within a current field. The restoratives were light-cured for 20, 40 or 60 s in a layer thickness between 1, 2 , or 3 mm with a varying distance between curing light and specimen of 1, 3 or 5 mm. The tests were performed at 25°C/37°C with different polymerisation modes. Nine restoratives (two composites and their derivate flowables, two ormocers, one compomer, one nano-filled composite and one siloran) were investigated. The ion-viscosity-time graph was analysed to characterize reaction velocity and polymerisation conversion. The slope of the ion viscosity decreased with increasing distance between polymerisation light and specimen. The time of exposure affected the affinity and the conversion, with a polymerisation maximum at 40 s. A relation between thickness and reaction time and between polymerisation modus and conversion/velocity was found. The temperature influenced the reaction affinity. Different materials showed an individual curing performance. DEA-monitoring of the ion viscosity gives principal insight in the polymerisation reaction of light curing materials. Further investigations are necessary for identifying the relation between ion viscosity and polymerisation. [ABSTRACT FROM AUTHOR]

This study compared fracture resistance of fiber-reinforced and non-fiber-reinforced composite molar crowns under simulated oral stress conditions. Three groups of fiber-reinforced composite crowns were constructed using one polyethylene fiber (belleGlass/Connect) and two glass fiber reinforcement systems (Sculpture/FiberKor, Targis/Vectris). The non-fiber-reinforced crowns based on the facing material alone: Sculpture, Targis or belleGlass. Additionally, crowns were made of the non-reinforced composite Artglass. Each group consisted of eight crowns. All crowns were luted to human molars and exposed to thermal cycling and mechanical loading (6000×5°C/55°C; 1.2×106×50 N; 1.66 Hz). The fracture resistance was measured using a Zwick universal testing machine. Results: The non-reinforced Artglass crowns demonstrated the highest fracture resistance, significantly higher than the resistance shown with belleGlass, belleGlass/Connect or Targis. Artglass showed an extremely wide distribution of values, however. No statistically significant differences were found between the reinforced and non-reinforced composite crowns of Vectris/Targis, FiberKor/Sculpture or Connect/belleGlass although the reinforced crowns showed a tendency towards higher values. The fracture resistance values scattered markedly more for the reinforced crowns, and their lowest fracture values also reached the level of the lowest non-reinforced crowns. The small distribution of fracture values for the non-reinforced crowns indicates that they will be less susceptible for manufacturing faults and more reliable under clinical conditions. Conclusions: Results of this study suggest that single molar composite crowns (tested in this study) do not benefit from fiber-reinforcement. [ABSTRACT FROM AUTHOR]

Objectives. The aim of this study was to evaluate the frequency of technical failure rates and the maintenance costs of clasp- or double crown-retained removable partial dentures (RPDs) (parallel-sided and conical double crowns). Material and methods. According to three different retainer systems used between January 1992 to December 1998, three subgroups were randomly assigned from a group of 181 patients consisting of forty cases each. The average observation time was 4.2±1.7 years, with a minimum of 1.0 years and a maximum of 6.9 years. Technical complications such as fractures of the artificial teeth, loss of cementation, loss of facings as well as fractures of the metal framework and the soldering were recorded due to the medical reports. Results. Twenty percent of all clasp-retained dentures showed technical complications during the observation period, whereas 50% of conical crown-retained (CC) and 32.5% of the parallel-sided retained dentures (PS) required repair. Most often reported was loss of cementation for double crowns (n=13, 32.5% PS; n=8, 20% CC) and fractures of the clasps (n=5). Although clasp-retained dentures had a markedly lower frequency of failures (n=8) than double crown systems (n=31), the calculated repair costs per event during the observation time were more than twice as high for clasp-retained dentures (172.5 Euro) than for double crown systems (8–78 Euro). The hypothesis that the maintenance costs of the more sophisticated double crown system are higher must be rejected. [ABSTRACT FROM AUTHOR]

Wear resistance of restorative composites is important for clinical longevity and aesthetics, especially in posterior areas. In vitro examinations may contribute to improvements in the durability of composites depending on a thorough understanding of the wear behaviour. Artificial wear was performed on four labour fabricated veneering composites in a two-body masticator with all-ceramic antagonists and a three-body wear testing device using two kinds of food bolus. After ageing the wear track was determined in comparison to the unworn surface with a profilometer. Wear was correlated with the total filler amount and universal hardness. After millet three-body ageing all composites showed material loss between 2 and 3.5 μm, after millet sheet/rice of about 50–130 μm. The resulting wear track after mastication was about 180–300 μm deep. The composites showed different wear behaviour according to the used wear method. Between the different wear mechanisms and hardness or filler content no clear correlation could be determined. The wear performance of composites is a complex phenomena, with various in vitro tests different wear results could be obtained. Contrary to the general opinion, hard or highly filled composites must not necessarily show highest wear resistance. [ABSTRACT FROM AUTHOR]

Removable partial dentures (RPD) can be retained using conical crowns or parallel-sided telescopic double crowns. The purpose of this study was to evaluate and compare the technical failure rate of the two retainer systems. One hundred seventeen dentures made by dentists of the medical school were included. Seventy-four RPD were retained with parallel-sided crowns (n=251) and 43 with conical crowns (n=160). Following the medical report follow-ups from January 1992 to December 1998, technical RPD failures were noted and analyzed. Technical problems occurred during the observation time in 48.8% of the conical retained dentures and 34.2% of the parallel-sided retained dentures. In both cases, loss of cementation was most frequently noted, while loss of the facings occurred only with conical crowns. Other technical failures did not depend on the type of retainer system used. These were most frequently problems with the denture base, e.g., fracture of artificial teeth or the metal framework. We conclude that there were different technical failures of both double crown retainer systems. These problems were not insignificant in number but treatable. [ABSTRACT FROM AUTHOR]

The objective was to investigate associations between the results of an in vitro and an in vivo study using an artificial mouth and a study of adhesive fixed partial dentures (AFPD) begun in 1985 [1]. Twenty extracted human molars and 20 human upper incisors were inserted into PMMA resin, 6 mm apart to represent a gap. Two preparation methods (identical to those in in vivo conditions) were used: a retentive preparation technique (posterior) and a non-retentive preparation technique (anterior). The frameworks of the bridges consisted of CoCr-alloy with a ceramic veneered pontic to replace the missing tooth. The bonding surfaces of the posterior AFPDs were conditioned with a tribochemical system, while the anterior AFPDs were sandblasted. All AFPDs were inserted using a dual curing composite cement. During thermal-cycling and mechanical loading (TCML: 6000×5°C/55°C, 1.2×106×50 N, 1.66 Hz) in an artificial environment, the frequency and type of failures were observed. The above mentioned loading parameters were hypothesized to represent a period of 5 years under oral conditions. The results were compared to those of similar bridge-types in the in vivo study. The Kaplan-Meier estimations showed similar graphs for in vivo and in vitro with both types of AFPDs. In vivo and in vitro, the retentively prepared AFPDs were markedly more successful. With regard to the failure types, the simulation-parameters seemed to represent a loading stress that was comparable to in vivo conditions. [ABSTRACT FROM AUTHOR]

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 °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 °C, as well as 150 and 300 °C, and the filler and matrix content, allow the classification of the veneering composites. © 1999 Kluwer Academic Publishers [ABSTRACT FROM AUTHOR]

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, sandblasting 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. [ABSTRACT FROM AUTHOR]