Analysis of the legume-rhizobia symbiosis in shrubs from central western Spain.

AIMS: This work analyses the diversity of rhizobia associated with some of the predominant shrubby legumes in central-western Spain. Symbiotic promiscuity and effectiveness were studied using cross-inoculation experiments with shrubby species. MATERIAL AND RESULTS: Six new bradyrhizobia strains were isolated from nodules collected from wild plants of six leguminous species, Cytisus balansae, C. multiflorus, C. scoparius, C. striatus, Genista hystrix and Retama sphaerocarpa. These isolates were genetically characterized by 16S rDNA partial sequencing and random amplification of polymorphic DNA-PCR fingerprinting. The phylogenetic analysis revealed that these isolates could represent three new Bradyrhizobium species. Shrubby legumes and bradyrhizobia displayed a high symbiotic promiscuity both for infectivity and effectiveness. Symbioses were effective in more than 70% of the associations established by four of the six plant species. CONCLUSIONS: Native woody legumes in western Spain are nodulated by Bradyrhizobium strains. The high degree of symbiotic promiscuity and effectiveness highlights the complex dynamics of these communities in wild ecosystems under a Mediterranean-type climate. Furthermore, the results from this study suggest a potential importance of inoculation for these legume species in soil-restoration projects. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first study, to our knowledge, that combines both molecular analysis and pot trials to study the rhizobia-legume symbiosis for wild legumes.

The CICERO system for CAD/CAM fabrication of full-ceramic crowns.

The CICERO method of crown fabrication consists of optically digitizing a gypsum die, designing the crown layer buildup, and subsequently pressing, sintering, and milling consecutive layers of a shaded high-strength alumina-based core material, a layer of dentin porcelain, and a final layer of incisal porcelain. Final finishing is performed in the dental laboratory. The CICERO method allows efficient production of all-ceramic restorations without compromising esthetics or function. This article reviews the process involved in the fabrication of a CICERO crown.

Computer modeling of occlusal surfaces of posterior teeth with the CICERO CAD/CAM system.

STATEMENT OF PROBLEM: Static and dynamic occlusal interference frequently needs to be corrected by selective grinding of the occlusal surface of conventional cast and ceramic-fused-to-metal restorations. CAD/CAM techniques allow control of the dimensional contours of these restorations. However, parameters responsible for the occlusal form need to be determined. In most articulators, these parameters are set as default values. Which technique is best for minimizing the introduction of occlusal interference in restorations has not been determined. PURPOSE: This study investigated differences in crown structure of a crown designed in static occlusion (STA) with designs adapted for dynamic occlusal interferences. Therefore, values from an optoelectronic registration system (String-Condylocomp, KAVO), an occlusal generated path (OGP) technique and default settings (DEF) were used in the CICERO CAD/CAM system. MATERIAL AND METHODS: Morphology of CON, DEF, and OGP crowns was compared with that of the STA crown with respect to differences in a buccolingual section and frequency of occlusal distances in an interocclusal range of 1 mm, measured from the occlusal surface of the crown. RESULTS: All crown types fulfilled the esthetic and morphologic criteria for restorations in clinical dentistry. Difference in the morphology of the OGP crown, compared with that of the STA crown, was greater than that for the CON and DEF crowns. These differences were seen especially in the distobuccal part of the occlusal surface; however, the number of occlusal contacts was considered sufficient to stabilize occlusion. CONCLUSION: Functional occlusion, adapted to dynamic occlusion in a CICERO crown for the first mandibular molar, can be obtained using data acquired with the String-Condylocomp registration system. The OGP technique was preferred to other techniques because of the simplicity of the technique for eliminating potential problems with opposing teeth during motion. However, this is achieved at the cost of fewer points of contact during occlusion than with the CON crown.

Computer copings for partial coverage.

Partial coverage posterior tooth preparations are very complex surfaces for computer surface digitization, computer design, and manufacture of ceramic copings. The aim of this study was therefore to determine whether the Computer Integrated Crown Reconstruction (Cicero) system was compatible with a proposed partial coverage preparation design and capable of producing ceramic copings. Posterior teeth were prepared for partial coverage copings with deep gingival chamfers in the proximal boxes and around the functional cusps (buccal of mandibular and lingual of maxillary posterior teeth). The nonfunctional cusps (lingual of mandibular and buccal of maxillary posterior teeth) were prepared with broad bevels following the inclined occlusal plane pattern. Optical impressions were taken of stone dies by means of a fast laser-line scanning method that measured the three-dimensional geometry of the partial coverage preparation. Computers digitized the images, and designed and produced the ceramic copings. The Cicero system digitized the partial coverage preparation surfaces precisely with a minor coefficient of variance of 0.2%. The accuracy of the surface digitization, the design, and the computer aided milling showed that the system was capable of producing partial coverage copings with a mean marginal gap of 74 microns. This value was obtained before optimizing the marginal fit by means of porcelain veneering. In summary, Cicero computer technology, i.e., surface digitization, coping design, and manufacture, was compatible with the described partial coverage preparations for posterior teeth.