In the pipe manufacturing and pipe processing industry, the demand for cost-effective pipes with high strength and good ductility is increasing. In the present study, the inductive longitudinal welding process was combined with a Quenching and Partitioning (Q&P) treatment to manufacture pipes with enhanced mechanical properties. The aim of the Q&P process is to establish a martensitic structure with increased retained austenite content. This allows for the beneficial use of both phases: the strength of martensite as well as the ductility of retained austenite. A 42SiCr steel, developed for Q&P processes, was joined at the longitudinal seam by a high-frequency induction (HFI) welding process and was subsequently heat-treated. The applied heat treatments included normalizing, austenitizing, quenching, and two Q&P strategies (Q&P-A/Q&P-B) with distinct quenching (Tq = 200/150 °C) and partitioning temperatures (Tp = 300/250 °C). Investigations of the microstructures revealed that Q&P tubes exhibit increased amounts of retained austenite in the martensitic matrix. Differences between the weld junction and the base material occurred, especially regarding the morphology of the martensite; the martensite found in the weld junction is finer and corresponds more to the lath-type morphology, compared to the base material in the circumference. In all zones of the welded tube circumference, retained austenite has been found in similar distributions. The mechanical testing of the individual tubes demonstrated that the Q&P treatments offer increased strength compared to all other states and significantly improved ductility compared to the quenched condition. Therefore, the approach of Q&P treatment of HFI-welded tubes represents a route for the mass production of high-strength tubular products with improved ductility.

Zusammenfassung Katja Schwartau Peripartale hämatologische und klinisch-chemische Blutuntersuchungen zur Frühdiagnostik der Dislocatio abomasi, Gebärparese, Retentio secundinarum und Mastitis bei Milchkühen Medizinische Tierklinik der Veterinärmedizinischen Fakultät der Universität Leipzig Eingereicht im Mai 2011 Bibliographische Angaben 94 Seiten, 22 Abbildungen, 19 Tabellen, 210 Literaturangaben, Schlüsselwörter: Labmagenverlagerung, Gebärparese, Retentio secundinarum, Mastitis, Kuh Produktionskrankheiten haben in den letzten Jahren immer mehr an Bedeutung gewonnen. Diese leistungsassoziierten Bestandserkrankungen tragen wesentlich zur kurzen Nutzungsdauer von ca. 2,5 Jahren der Milchkühe bei. Es ist deshalb besonders wichtig, ihre Prophylaxe einschließlich der Früherkennung in den Vordergrund zu stellen. In der vorliegenden Untersuchung wurden deshalb frühdiagnostische Möglichkeiten der LMV (Labmagenverlagerung), GP (Gebärparese), Retentio sec. (Retentio secundinarum) und Mastitis geprüft. Des Weiteren wurden die Kühe in einer Gruppe „krank“ und einer Gruppe „gesund“ gegenübergestellt, um durch Stoffwechselabweichungen generell subklinische Veränderungen zu erkennen, die Hinweise auf bevorstehende Erkrankungen geben. Besondere Beachtung fand für die Bewertung des Erkrankungsrisikos die odds ratio. In die Untersuchung wurden insgesamt 398 Schwarzbunte Kühe einbezogen. 49 Tiere waren an einer LMV, 121 Tiere an einer GP, 131 an einer Retentio sec. und 119 Tiere an einer Mastitis erkrankt. Im Gruppenvergleich gesund/krank wurden 347 erkrankte Kühe mit 51 klinisch gesunden Tieren verglichen. Es wurden bei allen Kühen 14-7 d a.p. (Tage ante partum) und 3 d p.p. (Tage post partum) Blutproben entnommen. Es wurden Parameter des Energie-, Fett- und Leberstoffwechsels (FFS [Freie Fettsäuren], BHB [ß-0H-Butyrat], Cholesterol, Glucose, Insulin, AST [Aspartat-Amino-Transferase], Bilirubin), des Eiweißstoffwechsels (Albumin, Haptoglobin, TP [Gesamt-Eiweiß], Harnstoff, Kreatinin) und der Leukozyten sowie des Mineralstoffwechsels (Na [Natrium], K [Kalium], Cl [Chlorid], Ca [Calcium], Pi [anorganisches Phosphat], AP [Alkalische Phosphatase]) und der CK [Creatinkinase] bestimmt und mit gesunden Kühen verglichen. 92 Auf das Risiko einer LMV weisen a.p. besonders Konzentrationssteigerungen des Haptoglobins hin. Aber auch die Mediane der Glucose und der AP liegen außerhalb des Referenzbereichs bei Tieren, die später an einer LMV erkranken. Drei d p.p. kommen signifikante Konzentrationsanstiege der FFS, des BHB und des Bilirubin sowie signifikante Konzentrationsabnahmen des Insulin (odds ratio 8,43) bis unter den Normbereich hinzu. Die Aktivitäten der AP und auch die Konzentrationen von Cholesterol und Ca bleiben ebenfalls unter dem Normbereich. Die Mediane der AST-Aktivität und der Haptoglobinkonzentration liegen oberhalb des Referenzbereichs. Auf das Risiko einer GP weisen a.p. und p.p die verminderte AP-Aktivität sowie Konzentrationsanstiege der FFS (odds ratio 1,78) hin. Drei d p.p ergänzen die Konzentrationen des BHB, des Bilirubins und des Haptoglobins (odds ratio 4,59) oberhalb der Referenzbereiche die Veränderungen. Der Median der Insulinkonzentration liegt 3 d p.p. unter dem Referenzbereich. Einer Retentio sec. gehen erhöhte Glucosekonzentrationen a.p. voraus. Der Median der AP-Aktivitäten liegt schon a.p. unter dem Normbereich. Drei d p.p. unterscheidet er sich signifikant von Kühen ohne Retentio sec. Hinweise auf Mastitiden liefern p.p. die Konzentrationen des BHB (odds ratio 1,78). Die Mediane der Glucosekonzentrationen liegen a.p. oberhalb und die der AP-Aktivitäten unterhalb der Referenzbereiche. Drei d p.p. kommen Steigerungen der Haptoglobin-, Glucose- und Bilirubinkonzentrationen sowie Aktivitätssteigerungen der AST bis über den Normbereich hinzu. Als Besonderheit liegen die Ca- und Pi-Konzentrationen aufgrund des geringeren Abflusses bei einer verminderten Milchleistung signifikant über denen der gesunden Kühe. Für die Entstehung postpartaler Erkrankungen generell verdienen die signifikanten Konzentrationssteigerungen der Glucose sowie die Abnahme der AP-Aktivität besondere Beachtung. Das BHB (odds ratio 1,92 a.p.) und die CK (odds ratio 2,17 a.p.) weisen auf ein erhöhtes Krankheitsrisiko hin. Drei d p.p. kommen zu den Veränderungen dieser Parameter noch signifikante Konzentrations- bzw. Aktivitätssteigerungen der FFS, des BHB, der CK, des Bilirubins, der AST und des Haptoglobins (odds ratio 4,61) sowie erniedrigte Ca-Konzentrationen hinzu. Die Untersuchungen haben gezeigt, dass a.p. generell Abweichungen des Energiestoffwechsels und im Besonderen gesteigerte Glucosekonzentrationen sowie erniedrigte AP-Aktivitäten ein erhöhtes Risiko für postpartale Erkrankungen anzeigen. Höhere Aussagekraft besitzen Kontrollen am 3. d p.p. mit den Parametern Insulin (odds ratio 8,4), FFS, BHB und Haptoglobin (odds ratio 4,61), deren Konzentrationen gegenüber gesunden Kühen signifikant abweichen. Ähnlich gute Eignung zeigen, Bilirubin, AST und Ca.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第23507号 / 工博第4919号 / 新制||工||1768(附属図書館) / 京都大学大学院工学研究科材料工学専攻 / (主査)教授 辻 伸泰, 教授 安田 秀幸, 教授 奥田 浩司 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

The third-generation advanced high strength steels, AHSS, represent an opportunity for today’s steel development, where lighter materials with maintained strength and toughness are in demand. The unique properties of these materials often stem from a tailored microstructure. In the continued development of these steels, without relying on expensive alloying methods, process design in the form of precise heat treatments plays an increasingly important role. This work focuses on Medium Mn AHSS with the aim of investigating one of these heat treatments, intercritical annealing, which is essential for achieving the desired material properties. Experimental testing of annealing effects is acknowledged to be a challenging process, and this study aims to present a novel approach for these types of tests. During experimental testing of intercritical annealing, the thermomechanical testing system Gleeble 3800 is a recognized tool. The mounting technique employed in the Gleeble results in an inhomogeneous heat distribution in the samples, generating a thermal gradient. This report aims to utilize this gradient as an opportunity to test the effect of several intercritical annealing temperatures on one sample, thereby increasing the efficiency of experimental work. The method is based on data retrieved from thermocouples attached to the specimen during Gleeble trials with the intent to identify the thermal gradient. This data is combined with x-ray diffraction measurements where the retained austenite fraction is measured. Thermodynamic calculations of expected retained austenite fraction following intercritical annealing are performed parallel to experimental work. The results of this work show that it is possible to utilize the thermal gradient to retrieve extensive data regarding the effect of intercritical annealing using only one sample. The results show a distinct thermal gradient and a corresponding gradient of retained austenite fraction along the specimen. The results for retained austenite fraction at room temperature can be rationalized on the basis of computational predictions. These variations potentially arise due to the material not reaching equilibrium within the annealing timeframe. This conclusion is supported by other computational results concerning austenite composition. In summary, the present work illustrates a new approach streamlining experimental work that, with some refinements, has the potential to benefit the broader scienitific community, in addition to providing a powerful new tool for rapid technological advancement in the steel industry / Tredje generationens avancerade höghållfasta stål representerar en möjlighet för dagens stålutveckling där lättare material med bibehållen styrka och seghet efterfrågas. De unika egenskaperna hos dessa material härrör ofta frän en skräddarsydd mikrostruktur. Vid fortsatt utveckling av dessa stål är det önskvärt att minimera användningen av legeringsämnen, vilket betyder att processdesign i form av korrekta värmebehandlingar blir  av  stor  betydelse.  Detta  arbete  fokuserar  på  Medium  Mn  avancerade höghållfasta stål med syftet att undersöka en av dessa värmebehandlingar, interkritisk glödgning,  vilken  har  en  avgörande  betydelse  för  att  uppnå önskad  prestanda. Experimentell  testning  av  glödgningseffekter  anses  vara  en  utmanande  process och avsikten med denna studie är att presentera ett nytt tillvägagångssätt för denna typ av test. Under experimentell utvärdering av glödgningseffekter används ofta det termomekaniska testsystemet  Gleeble  3800.  Provmonteringen  i  Gleeblen  resulterar i en  inhomogen värmefördelning i proverna vilket medför en temperaturgradient. Denna rapport syftar till att använda gradienten som en möjlighet att testa effekten av flera  glödgningstemperaturer  på  ett  enda  prov  och  därigenom  öka  effektiviteten i det  experimentella  arbetet.  Metoden  grundas  på  data  från  termoelement  fästa  på provet under Gleebleförsök, med avsikt att identifiera den termiska gradienten. Denna data kombineras sedan med XRD-mätningar där austenitfraktion efter värmebehandling utvärderas.  Termodynamiska  beräkningar  av  förväntad  austenitfraktion  efter interkritisk glödgning genomförs parallellt med experimentellt arbete. Resultaten  från  detta  arbete  påvisar  att  den  presenterade  metoden  är  genomförbar då omfattande data gällande interkritisk glödgningseffekt grundat på endast ett prov erhålls. Resultaten visar en tydlig termisk gradient och en motsvarande gradient av austenitfraktion längs provet, vilka är i överensstämmelse med tidigare experimentella resultat för samma material. Resultaten för austenitfraktion vid rumstemperatur uppvisar  betydande  likheter  med  de  termodymiska  beräkningarna, med  några  undantag. Orsaken till dessa variationer ¨ar troligen en otillräcklig glödgningstid, vilket gör att  materialet  inte  når  jämvikt.  Denna  hypotes  stöds  av andra  beräkningsresultat gällande austenitens sammansättning. Sammanfattningsvis presenterar denna rapport ett nytt tillvägagångssätt för att effektivisera experimentellt arbete, som med vissa förbättringar har potential att gynna det bredare forskarsamhället.

The share of corporate saving in total saving in South Africa has increased during the past four decades. In this dissertation various economic theories are examined in order to try to explain this change and to determine the possible implications of this change. The conclusion is that the relationship between the investment decision of companies and their savings decision is governed by the determinants of the financing choice of firms. These include cost, risk, control and availability. If, because of these factors, firms prefer to finance investment with retained earnings, there is a relationship between investment and the level of corporate saving. The degree to which the investment decision is dependent on the availability of internal financing will determine the importance of the level of corporate saving in a country. / Oor die afgelope vier dekades het die aandeel van maatskapybesparing in die totale besparing in Suid-Afika toegeneem. In hiersie vehandeling word veskillende ekonomiese teoriee ondersoek ten einde hierdie verandering te probeer veklaar en te probeer vasstel wat die implikasies van hierdie veandering is. Die gevolgtrekking waartoe gekom word, is dat die verband tussen die investeringsbeleid en die maatskappye se besparingsbesluit bepaal word deur faktore wat die finansieringskeuse van die firmas beinvloed, naamlik koste, risiko, beheer en beskikbaarheid. Indien hierdie faktore daartoe lei dat die maatskapye verkies om investering met terruggehoue bespaaring the finansier, is daar 'n verband tussen investering en die vlak van maatskappybesparing. Die mate waarin die investeringsbesluit afhanklik is van die beskikbaarheid van interne finansiering, sal bepaal hoe belangrik die vlak van maatskappybesparing in 'n land is. / Economics and Management Sciences / M.Com.

近年來許多的產險公司因為買不到比例性的天災再保險合約，不得不使用超額賠款再保險方式以規避和轉嫁天災風險，但也因此承擔相當大的天災累積風險。 本文將企業風險管理的概念引進，把保險公司的再保部門模擬成企業的風險管理部門，期能更精確地定位保險公司再保險部門的功能、應該扮演的角色及未來經營策略。 超額賠款再保險之使用與產物保險的經營關聯密切，其最重要關鍵在於風險自行承擔，因此其間的保費收入、再保費成本支出等有關費率釐定計算方式，可說是超額賠款再保險之精華所在，亦為保險相關從業人員必備之專業知識。由於超額賠款再保險運用到許多統計相關的計算說明，本文之論述期能幫助保險相關從業人員找到各方的均衡點，有助於保險事業將資源做最有效率、效能的經營。 本文針對財產保險運用超額賠款再保險經營實務之考量加以介紹，同時強調經營者必須提升專業，包括損防服務、專業化核保、作業流程電腦化、財務風險管理等，尤其在計算天災的累積和購買適當再保險的承保容量方面，這亦有助於保險公司對天災風險的評估與認識。 最後，本文籲請保險公司主管必須重視目前以超額賠款再保險風險自留方式所承保之業務其費率是否適當，尤其是天災風險，所謂多算勝，少算不勝，而況於無算乎？否則會和賭場的賭客一樣， 大部分人是輸光退場的。 / Excess of Loss Reinsurance has become the viable solution in Taiwan’s insurance community, since the constraints were imposed by reinsrers a few years ago that natural catastrophe exposures could not be fully transferred to proportional treaties. But, the insurers also take very large natural risks at the same time. The aforementioned is the key issue to be discussed at the first part of this text, which introduces the concept of “corporate risk management” that Risk Management Department in enterprise is playing a role very similar to Reinsurance Department in an insurance company. We can, from this perspective, easier and clearer identify the functions and business objectives of Reinsurance Department in an insurance company. One distinctive advantage over proportional reinsurance is that, by adopting XOL reinsurance, ceding companies can expect to retain more premiums. Virtually, the performance of XOL operations is directly linked to the level of reinsurance cost, so it is very vital for insurance people to be fully aware of the connections between their insured exposures and reinsurance prices. A number of charts, tables, and cases are illustrated in the text for the calculation of XOL prices, and readers, particularly those who are doing insurance business, of this text are able to fairly locate the equilibrium of reinsurance cost that can be mutually accepted by the insured、brokers、reinsurers and insurers. Actual practices of applying property XOL reinsurance are analyzed in the text, which has also highlighted the importance of upgrading insurers’ professionalism, including loss prevention, underwriting, work-flow computerization, financial risk management, in particular, aggregate control on natural perils and adequate reinsurance protection. My conclusions and recommendations are pinpointing the issues required to be dealt with by the authorities for the adequacy of direct premium rates, particularly for the business with natural perils that are retained under XOL programs. Insurers are destined to be out of the market, sooner or later, if they are unable to charge sufficient premiums to finance their losses in the long run.

Problématique : Les connaissances théoriques et pratiques au sujet de la mise en charge immédiate d’implants non jumelés chez les édentés sont limitées. Objectifs : Cette étude avait pour but de : (1) déterminer le taux de survie implantaire de 2 implants non jumelés supportant une prothèse totale mandibulaire suite à une mise en charge immédiate, (2) évaluer les changements des niveaux osseux et de stabilité implantaire survenus sur ces 2 implants durant une période de 4 mois et les comparer à un implant témoin, et (3) décrire les complications cliniques associées à ce mode de mise en charge. Méthodologie : Chez 18 individus édentés (âge moyen de 62±7 ans), cette étude de phase I avec un design pré/post a évalué les résultats cliniques suivant la mise en charge immédiate (<48 heures) de 2 implants non jumelés par une prothèse totale mandibulaire. À l’aide de radiographies périapicales, de sondages osseux et d’analyses de la fréquence en résonnance, les niveaux osseux péri-implantaires (en mm) et les niveaux de stabilité implantairte (en ISQ) de ces 2 implants insérés dans la région parasymphysaire ont été évalués à la chirurgie (T0) et au suivi de 4 mois (T1). Un implant non submergé et sans mise en charge inséré dans la région de la symphyse mandibulaire a été utilisé comme témoin. Les données ont été analysées avec des modèles mixtes linéaires, la méthode de Tukey ajustée, l’analyse de variance de Friedman et des tests de rang signés de Wilcoxon. Résultats : De T0 à T1, 3 implants mis en charge immédiatement ont échoué chez 2 patients. Le taux de survie implantaire obtenu était donc de 91,7% (33/36) et, par patient, de 88,9% (16/18). Aucun implant témoin n’a échoué. Les changements osseux documentés radiologiquement et par sondage autour des implants mis en charge immédiatement étaient, respectivement, de -0,2 ± 0,3 mm et de -0,5 ± 0,6 mm. Les pertes d’os de support implantaire n’ont pas été démontrées statistiquement différentes entre les implants avec mise en charge immédiate et les témoins. Les niveaux moyens de stabilité implantaire ont augmenté de 5 ISQ indépendamment de la mise en charge. Les niveaux moyens d’ISQ n’ont pas été démontrés statistiquement différents entre les implants avec mise en charge immédiate et les témoins à T0 ou T1. Cinq des 18 patients n’ont expérimenté aucune complication clinique, alors que 9 en ont eu au moins deux. Hormis les échecs implantaires, aucune de ces complications n’a entraîné de changements au protocole. Conclusion : Les résultats à court terme suggèrent que : (1) le taux de survie implantaire suite au protocole immédiat est similaire à ceux rapportés lors d’un protocole de mise en charge conventionnel (2) les changements d’os de support implantaire et de stabilité ne sont pas différents comparativement à ceux d’un implant témoin, (3) un niveau élevé d’expérience clinique et chirurgicale est requis pour effectuer les procédures et pour gérer les complications associées. Ces résultats préliminaires devraient être confirmés dans une étude clinique de phase II. / Problem: There is a theoretical and practice knowledge gap in regard to immediate loading of unsplinted implants in edentulous individuals. Objectives: This study aimed to: (1) determine the implant survival rate of 2 unsplinted implants supporting a mandibular complete overdenture following an immediate loading protocol, (2) assess marginal bone level and implant stability changes of these immediately loaded implants in a 4-month period and compared them to a control implant, and (3) describe the clinical complications associated with this mode of loading. Methods: In 18 edentate individuals (mean age 62±7 years), this phase-I trial with a pre/post design assessed the clinical outcomes following the immediate loading (<48 hours) of 2 unsplinted implants supporting a mandibular overdenture. Periapical radiograhs, bone probing measurements and resonance frequency analysis were used to assess marginal bone losses and implant stability changes of these two implants inserted in the mandibular parasymphyseal region, at baseline (T0) and 4-month follow-up (T1). A non-submerged and non-loaded implant inserted in the mandibular symphysis was used as a control. Data were analyzed using linear mixed models, adjusted Tukey tests, Friedman’s analysis of variance and Wilcoxon signed-ranks tests. Results: From T0 to T1, 3 immediately loaded implants failed in 2 patients. This resulted in an implant survival rate of 91.7% (33/36), and, per patient, of 88.9% (16/18). No control implant failed. The marginal bone losses around loaded implants were -0.2 ± 0.3 mm for radiographic measurements and -0.5 ± 0.6 mm for probing measurements. There was no statistically significant difference between immediately loaded and control implants in regard to the supporting marginal bone losses. The implant stability levels increased of 5 ISQ units regardless of loading. There was no statistically significant difference in the mean ISQ levels between immediately loaded and control implants at T0 or T1. Five out of 18 patients experienced no clinical complication, while 9 of them had at least two. Apart from implant failures, none of these clinical complications led to changes in the protocol. Conclusion: The short-term results suggest that: (1) the implant survival rate following the immediate protocol is similar to those reported during a conventional loading protocol, (2) marginal implant supporting bone and stability changes are not different compared to those of a control implant, (3) a high level of clinical and surgical experience is required to perform the procedures and to manage the associated complications. These preliminary results should be confirmed in a phase II clinical trial.

O presente trabalho avaliou o efeito de tratamentos térmicos ou diferentes graus de deformação plástica na transformação da austenita do microconstituinte AM de uma chapa de aço alta resistência baixa liga (ARBL) classe API 5L X80 usada para gasodutos. A chapa tem espessura de 19 mm e passaria pelo processo de conformação UOE, mas a deformação foi realizada por laminação a frio, a temperatura ambiente, com reduções de 5 a 20%. O propósito foi compreender melhor o microconstituinte AM, explorar a transformação martensítica induzida por deformação (SIMT) e a decomposição austenítica por tratamento térmico, com ênfase em seu comportamento magnético. A transformação da austenita foi acompanhada através de medidas de polarização magnética, comparada com a densidade de massa e difração de raios X. A deformação plástica e os tratamentos térmicos alteraram a polarização magnética de saturação e a densidade de massa da amostra de aço de forma compatível com a eliminação da austenita retida metaestável. O método de densidade hidrostática foi considerado sensível para mensurar transformações de fase. Os dados obtidos revelam expansão volumétrica de aproximadamente 0,13%, correspondendo a 3,2% a quantidade de austenita retida original do material, enquanto os valores obtidos por polarização magnética de saturação são 2,8% pelo histeresígrafo e 2,1% por MAV. A difração de raios X nas amostras sob deformação ou tratamentos térmicos resultaram em queda nos primeiros picos da austenita quando comparadas com a amostra como recebida. / This study evaluated the effect of different degrees of plastic deformation or heat treatment on the transformation of austenite into martensite of an HSLA steel plate API 5L X80 for pipelines. A 19 mm thickness plate would be submitted to UOE forming process, but the cold work instead occurred by cold rolling at room temperature, with reductions of 5 up to 20%. The purpose was to better understand the MA constituent, explore the strain-induced martensitic transformation (SIMT) and austenitic decomposition by heat treatment with emphasis on its magnetic behavior. The transformation was accompanied by saturation magnetization measurements, compared with the mass density and X-ray diffraction. The plastic deformation or the heat treatment altered the saturation magnetization and the mass density in a manner consistent with the elimination of metastable retained austenite. The density method is sensible to measure phase transformations induced by strain. The data obtained shows a volumetric expansion of about 0.13%, corresponding to an amount of retained austenite of the original material of 3.2%, while the values obtained by magnetization saturation are 2.8% by hysteresigraph and 2.1% by VSM. By X-ray diffraction there is a clear drop in first peaks of austenite of the samples under deformation or heat treatment compared with the sample as-received.

Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro / Para reabilitar a ausência de um elemento dentário posterior, as próteses parciais fixas (PPF) com retentores intracoronários são uma alternativa aos implantes osseointegrados. O objetivo deste estudo foi avaliar a distribuição de tensões nessas próteses com três combinações de materiais: cerâmica de zircônia parcialmente estabilizada por ítria (ZPEI) revestida por cerâmica de fluorapatita (&#945;), cerâmica de dissilicato de lítio (&#946;) ou compósito fibrorreforçado (&#947;). Na composição &#945;, foram analisadas a presença ou ausência da cerâmica de revestimento na parede cervical das caixas proximais e três variações na área total da seção transversal dos conectores (4 mm de largura x 3,2, 4,2 ou 5,2 mm de altura). Em 8 modelos bidimensionais de elementos finitos, uma carga vertical de 500 N foi aplicada na fossa central do pôntico e as tensões principais máximas (tração) e mínimas (compressão) foram apontadas em MPa. Inicialmente foram avaliados os 6 modelos com PPF de ZPEI e suas variações. Os maiores valores das tensões de tração foram encontrados no terço cervical dos conectores. Quando presente nestas regiões, a cerâmica de revestimento recebeu tensões acima do limite de sua resistência à flexão. Na comparação entre os modelos sem cerâmica de revestimento na parede cervical das caixas proximais, mesmo aquele com conectores de 3,2 x 4 mm, cuja infraestrutura apresentava 2,5 x 3 mm, poderia ser recomendado para uso clínico. Altos valores de tensões de compressão foram registrados entre o terço oclusal e médio dos conectores, correspondente à união entre as cerâmicas, o que poderia ocasionar, devido à flexão, falhas adesivas. Posteriormente, o modelo de ZPEI com a cerâmica de fluorapatita ausente da parede cervical das caixas proximais e área total dos conectores de 4,2 x 4 mm foi comparado aos dois outros materiais com conectores de mesma área. Na PPF de dissilicato de lítio, os valores representaram uma provável violação do limite de sua resistência à flexão. A PPF de compósito fibrorreforçado apresentou tensões bem abaixo do limite de resistência à flexão de sua infraestrutura, mas, como no modelo de ZPEI, tensões compressivas se concentraram com alto valor entre o terço oclusal e médio dos conectores, local de união entre a resina composta e a infraestrutura de fibras. Os resultados mostraram que a cerâmica de dissilicato de lítio e a presença da cerâmica de fluorapatita na parede cervical das caixas proximais deveriam ser contraindicadas para a condição proposta. Parece viável uma área de conectores na infraestrutura de ZPEI com no mínimo 2,5 x 3 mm. A PPF de compósito fibrorreforçado apresenta resistência estrutural para a situação estudada, mas, como também aquelas compostas de ZPEI, aparenta ter como pontos fracos a adesão entre a infraestrutura e o material de cobertura e a própria resistência deste último. / Inlay-retained fixed partial dentures (IRFPD) are an alternative to osseointegrated implants to replace a single missing posterior tooth. The aim of this study was to evaluate the stress distribution within these prostheses with three material combinations: yttria-tetragonal zirconia polycrystal (Y-TZP) ceramic veneered with fluorapatite ceramic (&#945;), lithium-disilicate ceramic (&#946;) or fiber-reinforced composite (&#947;). In composition &#945;, an analysis was conducted on the presence or absence of the veneering ceramic on the cervical wall of the proximal boxes and three variations in the total area of the connectors cross-section (4 mm in width x 3.2, 4.2 or 5.2 mm in height). In 8 two-dimensional finite element models, a vertical load of 500 N was applied on the central fossa of the pontic. Maximum (tension) and minimum (compression) principal stresses were then shown in MPa. First, the 6 models with Y-TZP fixed partial dentures (FPD) and their variations were evaluated. The highest values of tensile stresses were found at the cervical third of the connectors. When present in these regions, the veneering ceramic received stresses beyond its flexural strength limit. In the comparison among models without veneering ceramic on the cervical wall of the proximal boxes, even the model with connectors of 3.2 x 4 mm, whose framework presented 2.5 x 3 mm, could be recommended for clinical use. High values of compressive stresses were recorded between the middle and occlusal thirds of the connectors, corresponding to the juncture of the ceramics. Owing to flexure, these stresses might lead to adhesive failures. Then, the Y-TZP model without fluorapatite ceramic on the cervical wall of the proximal boxes and total connector area of 4.2 x 4 mm was compared to the other two materials with connectors of the same area. For the lithium-disilicate FPD, the observed values would probably exceed its flexural strength limit. The fiber-reinforced composite FPD presented stresses far below the flexural strength limit of its framework, but, as observed in the Y-TZP model, high values of compressive stresses were concentrated between the middle and occlusal thirds of the connectors, where the juncture of the composite and the fiber framework is located. The results showed that the use of lithium-disilicate ceramics and the presence of fluorapatite ceramics on the cervical wall of the proximal boxes should be contraindicated for the condition proposed. A minimum of 2.5 x 3 mm for the connector area of the Y-TZP framework seems viable. The fiber-reinforced composite FPD presented structural resistance for the situation studied but, as was also the case of the Y-TZP fixed partial dentures, its weak points seem to be the adhesion between the framework and the veneering material, as well as the resistance of the veneering material itself.

Problématique : Les connaissances théoriques et pratiques au sujet de la mise en charge immédiate d’implants non jumelés chez les édentés sont limitées. Objectifs : Cette étude avait pour but de : (1) déterminer le taux de survie implantaire de 2 implants non jumelés supportant une prothèse totale mandibulaire suite à une mise en charge immédiate, (2) évaluer les changements des niveaux osseux et de stabilité implantaire survenus sur ces 2 implants durant une période de 4 mois et les comparer à un implant témoin, et (3) décrire les complications cliniques associées à ce mode de mise en charge. Méthodologie : Chez 18 individus édentés (âge moyen de 62±7 ans), cette étude de phase I avec un design pré/post a évalué les résultats cliniques suivant la mise en charge immédiate (<48 heures) de 2 implants non jumelés par une prothèse totale mandibulaire. À l’aide de radiographies périapicales, de sondages osseux et d’analyses de la fréquence en résonnance, les niveaux osseux péri-implantaires (en mm) et les niveaux de stabilité implantairte (en ISQ) de ces 2 implants insérés dans la région parasymphysaire ont été évalués à la chirurgie (T0) et au suivi de 4 mois (T1). Un implant non submergé et sans mise en charge inséré dans la région de la symphyse mandibulaire a été utilisé comme témoin. Les données ont été analysées avec des modèles mixtes linéaires, la méthode de Tukey ajustée, l’analyse de variance de Friedman et des tests de rang signés de Wilcoxon. Résultats : De T0 à T1, 3 implants mis en charge immédiatement ont échoué chez 2 patients. Le taux de survie implantaire obtenu était donc de 91,7% (33/36) et, par patient, de 88,9% (16/18). Aucun implant témoin n’a échoué. Les changements osseux documentés radiologiquement et par sondage autour des implants mis en charge immédiatement étaient, respectivement, de -0,2 ± 0,3 mm et de -0,5 ± 0,6 mm. Les pertes d’os de support implantaire n’ont pas été démontrées statistiquement différentes entre les implants avec mise en charge immédiate et les témoins. Les niveaux moyens de stabilité implantaire ont augmenté de 5 ISQ indépendamment de la mise en charge. Les niveaux moyens d’ISQ n’ont pas été démontrés statistiquement différents entre les implants avec mise en charge immédiate et les témoins à T0 ou T1. Cinq des 18 patients n’ont expérimenté aucune complication clinique, alors que 9 en ont eu au moins deux. Hormis les échecs implantaires, aucune de ces complications n’a entraîné de changements au protocole. Conclusion : Les résultats à court terme suggèrent que : (1) le taux de survie implantaire suite au protocole immédiat est similaire à ceux rapportés lors d’un protocole de mise en charge conventionnel (2) les changements d’os de support implantaire et de stabilité ne sont pas différents comparativement à ceux d’un implant témoin, (3) un niveau élevé d’expérience clinique et chirurgicale est requis pour effectuer les procédures et pour gérer les complications associées. Ces résultats préliminaires devraient être confirmés dans une étude clinique de phase II. / Problem: There is a theoretical and practice knowledge gap in regard to immediate loading of unsplinted implants in edentulous individuals. Objectives: This study aimed to: (1) determine the implant survival rate of 2 unsplinted implants supporting a mandibular complete overdenture following an immediate loading protocol, (2) assess marginal bone level and implant stability changes of these immediately loaded implants in a 4-month period and compared them to a control implant, and (3) describe the clinical complications associated with this mode of loading. Methods: In 18 edentate individuals (mean age 62±7 years), this phase-I trial with a pre/post design assessed the clinical outcomes following the immediate loading (<48 hours) of 2 unsplinted implants supporting a mandibular overdenture. Periapical radiograhs, bone probing measurements and resonance frequency analysis were used to assess marginal bone losses and implant stability changes of these two implants inserted in the mandibular parasymphyseal region, at baseline (T0) and 4-month follow-up (T1). A non-submerged and non-loaded implant inserted in the mandibular symphysis was used as a control. Data were analyzed using linear mixed models, adjusted Tukey tests, Friedman’s analysis of variance and Wilcoxon signed-ranks tests. Results: From T0 to T1, 3 immediately loaded implants failed in 2 patients. This resulted in an implant survival rate of 91.7% (33/36), and, per patient, of 88.9% (16/18). No control implant failed. The marginal bone losses around loaded implants were -0.2 ± 0.3 mm for radiographic measurements and -0.5 ± 0.6 mm for probing measurements. There was no statistically significant difference between immediately loaded and control implants in regard to the supporting marginal bone losses. The implant stability levels increased of 5 ISQ units regardless of loading. There was no statistically significant difference in the mean ISQ levels between immediately loaded and control implants at T0 or T1. Five out of 18 patients experienced no clinical complication, while 9 of them had at least two. Apart from implant failures, none of these clinical complications led to changes in the protocol. Conclusion: The short-term results suggest that: (1) the implant survival rate following the immediate protocol is similar to those reported during a conventional loading protocol, (2) marginal implant supporting bone and stability changes are not different compared to those of a control implant, (3) a high level of clinical and surgical experience is required to perform the procedures and to manage the associated complications. These preliminary results should be confirmed in a phase II clinical trial.