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This paper reports analysis obtained from 200 implant cases retrieved from humans and submitted to the American Academy of Implant Dentistry Research Foundation, Medical College of Georgia implant retrieval center. The samples that were not decalcified were embedded in polymethylmethacrylate and examined with scanning electron microscopy and routine light, polarized, or Nomarski microscopy. Cases included both orthopedic and dental implants, as well as entire mandibles and portions of maxillae obtained at autopsy. A significant number of submitted implants had substantial amounts of adhered bone, which permitted evaluation of human bone remodeling to osseointegrated implants. These implants failed because of implant fracture. As was observed with animal studies, healthy bone supported these implants, with the bone containing an interdigitating canaliculi network that provided communication between interfacial osteocytes and osteocytes deeper within the remodeled osteonal and trabecular bone. Earl...

The effectiveness and limitations of dioxo-3-oxabicyclo[3.2.0]hept-6-ene-2,4-dione (cyclobut-3ene-1,2-dicarboxylic anhydride) as an acetylene equivalent in both 1,3-dipolar and Diels–Alder cycloadditions is reported; it reacted readily with a variety of reagents, including N-benzylideneaniline N-oxide, nitrile oxides, diazomethane, cyclopentadiene, tetracyclone, anthracene, 1,2,5-triphenylphosphole 1-oxide and 1,3-diphenylisobenzofuran. The structures and stereochemistry of the adducts were deduced from their NMR data; in all cases, the sterically favoured anti-isomers are formed exclusively. The configuration of the Diels–Alder adducts are assigned as endo with the exception of that from tetracyclone (and possibly 1,3-diphenylisobenzofuran) for which an exo-structure is assumed on the basis of steric arguments. Adducts were not obtained with several other reagents; possible reasons for this lack of reactivity are discussed. When subjected to flash vacuum pyrolysis, the adducts underwent thermal fragmentation, either by a retro-cleavage, or by loss of maleic anhydride to form products that are derived formally from reaction of acetylene in the cycloaddition step. A concerted pathway is proposed for the pyrolytic conversion into the ‘formal acetylene cycloadduct’ rather than a stepwise radical mechanism.

This paper reports analysis obtained from 200 implant cases retrieved from humans and submitted to the American Academy of Implant Dentistry Research Foundation, Medical College of Georgia implant retrieval center. The samples that were not decalcified were embedded in polymethylmethacrylate and examined with scanning electron microscopy and routine light, polarized, or Nomarski microscopy. Cases included both orthopedic and dental implants, as well as entire mandibles and portions of maxillae obtained at autopsy. A significant number of submitted implants had substantial amounts of adhered bone, which permitted evaluation of human bone remodeling to osseointegrated implants. These implants failed because of implant fracture. As was observed with animal studies, healthy bone supported these implants, with the bone containing an interdigitating canaliculi network that provided communication between interfacial osteocytes and osteocytes deeper within the remodeled osteonal and trabecular bone. Early dental implants containing a coating of beads showed a connective tissue interface, which corresponded to the bead surface of specific orthopedic implants that underwent some degree of micromovement. This is in contrast with the excellent response reported for successful contemporary beaded implants. Significant numbers of osseointegrated fractured hydroxyapatite (HA)-coated dental implants demonstrated the adequate serviceability of these implants before biomaterial fracture. In contrast, the HA coating was dissociated from retrieved orthopedic implants, leading to extensive cup loosening and case failure. This study, therefore, underscores the need for evaluation of failed human dental and orthopedic implants. Correlations can be drawn between human retrieval and experimental animal studies.

The effectiveness and limitations of dioxo-3-oxabicyclo[3.2.0]hept-6-ene-2,4-dione (cyclobut-3ene-1,2-dicarboxylic anhydride) as an acetylene equivalent in both 1,3-dipolar and Diels–Alder cycloadditions is reported; it reacted readily with a variety of reagents, including N-benzylideneaniline N-oxide, nitrile oxides, diazomethane, cyclopentadiene, tetracyclone, anthracene, 1,2,5-triphenylphosphole 1-oxide and 1,3-diphenylisobenzofuran. The structures and stereochemistry of the adducts were deduced from their NMR data; in all cases, the sterically favoured anti-isomers are formed exclusively. The configuration of the Diels–Alder adducts are assigned as endo with the exception of that from tetracyclone (and possibly 1,3-diphenylisobenzofuran) for which an exo-structure is assumed on the basis of steric arguments. Adducts were not obtained with several other reagents; possible reasons for this lack of reactivity are discussed. When subjected to flash vacuum pyrolysis, the adducts underwent thermal fragmentation, either by a retro-cleavage, or by loss of maleic anhydride to form products that are derived formally from reaction of acetylene in the cycloaddition step. A concerted pathway is proposed for the pyrolytic conversion into the ‘formal acetylene cycloadduct’ rather than a stepwise radical mechanism.

The ease of formation of aziridine and/or epoxides from a series of bicyclic olefins, where distant sulphonyl groups are present, is very variable. There is some correlation between reactivity of the vinyl group and its π-ionisation potential which is high in the present molecules relative to comparison olefins. This increase is thought to be due to the presence of orbital interactions through bonds and/or through space between the sulphone group and the double bond, making the latter electron deficient. The ionisation potentials were determined by UV-photoelectron spectroscopy and the assignments made by recourse to ab initio configuration interaction methods.

The reactivity of a series of bicyclic olefins with nitrenes is profoundly influenced by the nature of remote functional groups. There is a marked lack of reactivity for reactions with carboethoxynitrene as compared to phthalimidonitrene which is distinctly nucleophilic in character. An explanation for the reluctance to form aziridines is offered in terms of orbital interactions between the distant groups and the olefinic bond, making the latter remarkably electron deficient as evidenced by UV-photoelectron spectrosoopy. Because of the complexity of the spectra, identification of the Ip associated with the reactive π-centre was made by recourse to ab initio configuration interaction calculations for key members of the series.

Except in a two-phase system and contrary to expectation, ethoxycarbonylnitrene when generated from Lwowski's reagent by α-elimination does not add to the unsaturated cyclic sulphones (1)–(10) owing to the presence of orbital interactions (through bonds and through space)between the SO2 group and the double bond, as evidenced by u.v.–photoelectron spectrosocopy.

The novel approach used in trying to control the social desirability of the alternatives in Fricke's forced-choice Self-descriptive Check List is discussed. Evidence is presented which indicates that the test does not succeed in producing clusters of alternatives which are functionally equivalent in desirability.

Tetrahydroisoquinoline-1-carboxylic acids with a 6- or 7-hydroxy substituent undergo oxidative decarboxylation on treatment with horseradish peroxidase or fungal laccase to give high yields of the corresponding 3,4-dihydroisoquinolines. Attempts to apply this reaction to the formation of an aporphine were unsuccessful.

The Self-perception Inventory (SPI) contains 200 true-false items yielding scores on Uncommon Response, Consistency, Self-acmalization, Supervision, Rigidity-Dogmatism, Authoritarianism, Anxiety, Depression, Paranoia, General Adjustment, and General Maladjusunent (Martin, 1968, 1969) . A faking study was conducted with an earlier 70-item form of the SPI containing only six subscales. College Ss ( N = 25) were to fake so as to create the most favorable impressions of themselves. "They were unable to do so with any degree of statistical significance on any of the six subscales" (Martin, 1969, p. 9). -,The present study investigated fakability of the 200-item SPI, using 37 undergraduates and graduate students enrolled in introductory courses in tests and measurements. All completed the SPI anonymously in a regular class meeting, with 17 having instructions to fake "good" (create most favorable impression) and 20 having instructions to fake "bad" (create least favorable impression). These opposed instructions had been placed in alternate test booklets prior to distribution of the booklets to the class. Mann-Whitney U tests were computed to assess the significance of the differences between the means under the opposed instructions. Table 1 presents the basic descriptive data.