| 1. |
- Chowdhary, Ramesh
(författare)
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On efficacy of implant thread design for bone stimulation
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Introduction – The mechanism and efficiency of force transfer by dental implants to surrounding biologic tissues are important determinants in the development of the implant-to-bone/tissue interface and implant longevity. Threads are used to improve the initial stability by maximizing bone contact through an enlarged implant surface area and thereby favor distribution of interfacial stresses. However, knowledge about optimal thread design for an enhanced implant integration in bone tissue is still lacking. Aim – The aim of this thesis was to evaluate the efficacy of implant micro thread design when combined with macro threads, for bone stimulation. The hypothesis is that the short threads will contribute with compression forces that may stimulate bone healing, while the larger threads will provide with primary stability necessary during the healing process. A further aim was to use an FEA model to describe the optimal thread form for reduced stress concentration immediately after implant insertion as well as after completed bone healing. Materials and methods – In study 1, Two-dimensional finite element models were made from 8 different thread designs. The crest module and apex of the implants were removed from the implant models, in order to enhance the effect of the thread designs only. Thus, the suprastructures and microstructures of the implants were not considered. All the eight implant models were assumed to be embedded in cortical bone. In addition, a 3D model was used to evaluate stress in the bone generated by 6 different thread designed implants when the implant models included the entire implant. In the In vivo studies 2 and 3, experimental turned implants with a diameter of 4mm and 8mm in length were prepared with micro threads in between macro threads along the body of the implants. These were used as test implants. Implants without micro-threads were used as controls. In study 4, similar implants were made but with alteration in depth of the macro-thread to improve the possibility for bone stimulation by compression during healing. Insertion and removal torque analysis along with histomophometric analyses were done to evaluate the bone response. Results – In study 1, stresses were calculated using von Mises stress analysis. The stress levels in the bone were in the range of 5-13 MPa in osseointegrated model and 14-107 MPa in immediate 2D models. 3D Analysis results showed the von Mises stress in the range of 4.8-30.9 MPa, when a load of 100N was applied vertically. In Study 4 FEA demonstrated stress levels in the range of 0.28 MPa to 62MPa for the control implant model designs, whereas the test implant models displayed a range of 0.28 MPa to 31Mpa. In study 2, the mean values of the ITQ for the control and test groups in the tibia were 15 and 20 Ncm respectively, and in the femur, the values were 11 and 12 Ncm, respectively. In study 4, the ITQ values were 11Ncm and 14 Ncm respectively in the tibia, and in the femur 13 Ncm and 19 Ncm respectively. The RTQ values for the control and test groups in tibia was 11Ncm and 17Ncm, respectively and in the femur, 13Ncm and 23Ncm, respectively. The histomorphometric analysis of study 3, showed the mean total bone area, BA% (SD) to be higher in the test implants, when compared to the control implants in both the tibia 24 (4), and 21(4), the femoral bone 29 (5), and 25 (7), respectively with no statistical significance. In study 4, the total bone area BA% was higher for the test implants with a mean value of 72% compared to 48% for the control group in tibial bone. In femural bone, the bone area was 63% for the test and 38 % for the control group implants with p value of 0.10 for both tibia and femur. Bone to implant contact showed significantly higher value for the test implants in the femur, p= 0.04. Conclusion – The impact of different thread designs, with respect to the magnitude of the transferred stress peak in the bone, was higher for the immediately inserted implants than for the osseointegrated implant model. The stress distribution was more effective in experimental micro-thread implant models, when compared to the non-micro thread models. The addition of pitch shortened threads in the test implant, did significantly improve the primary and secondary stability of the test implants, when mechanically evaluated with ITQ and RTQ analysis in corticular or trabecular bone rabbit bone. Histomophometrical analysis showed that the addition of the pitch shortened threads in between the macro threads did have a bone stimulatory effect in the femur of the rabbits.
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| 2. |
- Dorkhan, Marjan
(författare)
-
Effect of surface characteristics on cellular adherence and activity
- 2014
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Ersättning av förlorade tänder med tandimplantat är numera en vanlig behandlingsmetod med generellt goda resultat. Antalet implantatsystem på den internationella marknaden har ökat kraftigt under senare år. Stora forskningsinsatser har lagts på att utveckla nya modifierade titanmaterial med ytegenskaper som påskyndar integreringen av implantat i benvävnad. Exempel på sådana modifieringar är hög ytråhet och kemiska ytförändringar som förstärker bioaktiva karaktärsdrag hos titan. Vissa modifieringar har visat sig kunna stimulera benceller att bilda benvävnad och därmed skapa bättre förutsättningar för inläkning av implantat. Klinisk forskning pekar på att även mjukvävnad runt tandimplantat, liksom slemhinnan runt naturliga tänder, har avgörande betydelse för skydd mot mikrobiella angrepp. En funktionell mjukvävnadsbarriär anses vara nödvändig för att tandimplantat skall fungera livet ut. Emellertid är kunskapen enbart sporadisk om hur celltyper såsom mjukvävnads- celler och orala bakterier, reagerar när de kommer i kontakt med modifierade titanytor i munhålan.På tandimplantat i den orala miljön, liksom på naturliga tänder, finns salivproteiner (pellikel) och sådana munhålebakterier som har förmåga att kolonisera fasta ytor som titan. Bakterier som fäster till implantat bildar med tiden komplexa bakteriesamhällen som är inbäddade i en matrix, en så kallad biofilm. Under vissa förhållanden kan dessa mikrobiella biofilmer ge upphov till kroniska infektioner. Flera kliniska uppföljningsstudier pekar på att kroniska infektioner i anslutning till tandimplantat är vanligare än man tidigare trott. Sådana infektioner kan vara svåra att behandla och leda till så omfattande benförlust att tandimplantat förloras. Syftet med denna avhandling var att förbättra förståelsen för hur orala streptokocker, fibroblaster och keratinocyter påverkas då de kommer i kontakt med moderna tandimplantat som har modifierade ytstrukturer.Resultaten i denna avhandling visade att titanytor med skrovliga strukturer på mikrometernivå, framtagna för bättre benläkning, främjade även adhesion av orala streptokocker vilket kan tolkas som att biofilmer lättare ackumuleras på sådana ytor. Vidare framkom det att streptokockers vidhäftningsförmåga och metabola aktivitet ökade avsevärt när en naturlig salivfilm fanns på plats på titanytan vilket ytterligare skulle påskynda bilningen av biofilmer på tandimplantat. Karaktärisering av proteinsammansättningen i salivfilmen på titan visade att sekretoriskt IgA, amylas, cystatin och prolactin-inducible protein var de dominerande proteinerna. S. oralis är en bakterie som ofta förekommer i samband med kroniska infektioner runt tandimplantat. Denna bakterie visade sig ha ett adhesin som interagerade speciellt bra med salivproteiner på titan. Detta var första gången som detta adhesin identifierades.Vad gäller adhesion av mjukvävnadsceller som fibroblaster och keratinocyter visade det sig att dessa celler kunde fästa väl till en titanyta som modifierats med hjälp av anodisk oxidering. Vid en karaktärisering av ytan framkom det att den var rik på anataskristaller och hade också nanoporösa strukturer. Orala streptokocker visade sig binda sämre till den anatasrika ytan än till kommersiellt rent titan. Sammantaget förefaller denna ytmodifikation vara en lämplig kandidat för nya implantat då den minskar inbindningen av streptokocker samtidigt som den tillåter fibroblaster och keratinocyter att växa på ytan.Sammanfattningsvis visar resultaten i denna avhandling att ytmodi- fierat titan påverkar såväl adhesion av mjukvävnadsceller som bakterie- celler och deras aktivitet. Studierna visar också att salivpellikeln på implantat spelar en viktig roll för bakteriernas kolonisation och metabolism. Vi föreslår därför att beroende på tillämpningsområde i praktiken, experimentell utvärdering av nya implantatytor ska i så stor sträckning som möjligt innefatta granskning av effekten av ytornas egenskaper på olika vävnadsceller såväl som bakterier i närvaro av vävnadsvätskor.
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| 3. |
- Edman Tynelius, Gudrun
(författare)
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Orthodontic retention : studies of retention capacity, cost-effectiveness and long-term stability
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Retention strategies, cost-effectiveness and long-term stability oftreatment outcome are essential aspects of orthodontic treatmentplanning.The overall aim of this thesis was to compare and evaluate threedifferent retention strategies, with special reference to short- andlong-term clinical stability and cost-effectiveness. The approach wasevidence-based, hence randomized controlled methodology was usedin order to generate high levels of evidence.This thesis is based on four studies:Papers I and II are based on randomized controlled trials, evaluatingthe stability of treatment outcome after one and two years of retention,using three different retention strategies: a maxillary vacuum-formedretainer combined with a mandibular canine-to-canine retainer; amaxillary vacuum-formed retainer combined with stripping of themandibular anterior teeth and a prefabricated positioner.Paper III presents a cost-minimization analysis of two years ofretention treatment.Paper IV is based on a randomized controlled trial documentingthe results five years post-retention.The following conclusions were drawn:Papers I and II• From a clinical perspective, asssessment after one year ofretention disclosed that the three retention methods weresuccessful in retaining the orthodontic treatment results.• After two years of retention, all three retention methods wereequally effective in controlling relapse at a clinically acceptablelevel.• Most of the relapse occurred during the first year of retention;only minor or negligible changes were found during the secondyear.• The subjects were grouped according to the level ofcompliance (excellent or good). After two years of retentionthere was a negative correlation between growth in bodyheight and relapse of mandibular LII in the group of subjectswith excellent compliance. The group with good complianceshowed a positive correlation (Paper II, Figure 3).• After two years of retention, growth in body height, initialcrowding and gender had no significant influence onmandibular LII (Paper II, Figure 4 and Table 4).Paper III• The cost minimization analysis disclosed that although thethree retention methods achieved clinically similar results, theassociated societal costs differed.• After two years of retention, the vacuum-formed retainer(VFR) in combination with a canine-to-canine retainer (CTC)was the least cost-effective retention appliance.Paper IV• After five years or more out of retention, the three retentionmethods had achieved equally favourable clinical results.Key conclusionsand clinical implicationsThis study compared the short- and long-term outcomes of orthodonticretention by three different methods: a maxillary vacuum-formedretainer combined with a mandibular canine-to-canine retainer;a maxillary vacuum-formed retainer combined with stripping ofthe mandibular anterior teeth and a prefabricated positioner. Allmethods gave equally positive clinical results in both the short-term,i.e. after one and two years of retention, and in the long-term, fiveyears or more post-retention. After two years of retention, the level of compliance affected theretention treatment result. However, no such effect was shown forbody height, the severity of initial crowding or gender.Today, there is increasing emphasis on the importance of economicaspects of healthcare. Of the three methods evaluated in this study,the least cost-effective, after two years of retention, was a vacuumformedretainer combined with a bonded canine-to-canine retainer.The clinical implication of this finding is that in patients meetingthe inclusion criteria, interproximal stripping of the mandibularanterior teeth, or the use of a prefabricated positioner, are highlyappropriate alternatives to a mandibular bonded canine-to-canineretainer.The overall conclusions are that there are a number of effectiveretention methods available and the clinician is not limited to routineuse of a bonded mandibular canine-to-canine retainer. The mostappropriate retention method should be selected on an individual,case to case basis, taking into account such variables as orthodonticdiagnosis, the expected level of patient compliance, patient preferencesand financial considerations.
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| 4. |
- Finnbogadóttir, Hafrún
(författare)
-
Exposure to domestic violence during pregnancy : impact on outcome, midwives’ awareness, women´sexperience and prevalence in the south of Sweden
- 2014
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Objective: The overall aim of this thesis was to investigate pregnant women’shistory of violence and experiences of domestic violence during pregnancy andto explore the possible association between such violence and various outcomemeasures as well as background factors. A further aim was to elucidate midwives’awareness of domestic violence among pregnant women as well as women’sexperiences and management of domestic violence during pregnancy.Design/Setting/Population: Paper I utilised material derived from a populationbasedmulti-centre cohort study. A total of 2652 nulliparous women at nineobstetric departments in Denmark answered a self-administrated questionnaireat 37 weeks of gestation. Among the total sample, 37.1% (985) women met theprotocol criteria for labour dystocia. In Paper II an inductive qualitative methodwas used, based on focus group interviews with sixteen midwives working inantenatal care in southern Sweden who were divided into four focus groups. InPaper III a grounded theory approach was used to develop a theoretical modelof ten women’s experiences of intimate partner violence during pregnancy. PaperIV was a cross-sectional study including a cohort of 1939 pregnant women whoanswered a self-administered questionnaire at their first visit to seventeen ANCsin south-west Scania in Sweden.Results: In paper I, 35.4 % (n = 940) of the total cohort of women reportedhistory of violence, and among these, 2.5 % (n = 66) reported exposure toviolence during their first pregnancy. Further, 39.5% (n = 26) of those had neverbeen exposed to violence before. No associations were found between historyof violence or experienced violence during pregnancy and labour dystocia atterm. However, among those women consuming alcoholic beverages during latepregnancy, women exposed to violence had increased odds of labour dystocia(crude OR 1.49, CI: 1.07 – 2.07) compared to women who were unexposedto violence. In Paper II, an overarching category ‘Failing both mother and theunborn baby’ highlighted the vulnerability of the unborn baby and the needto provide protection for the unborn baby by means of adequate care to thepregnant woman. Also, the analysis yielded five categories: 1) ‘Knowledge about‘the different faces’ of violence’ 2) ‘Identified and visible vulnerable groups’, 3)‘Barriers towards asking the right questions’, 4) ‘Handling the delicate situation’and 5) ‘The crucial role of the midwife’. In Paper III, the analysis of the empiricaldata formed a theoretical model, and the core category, ‘Struggling to survivefor the sake of the unborn baby’, constituted the main concerns of women whowere exposed to IPV during pregnancy. The core category also demonstratedhow the survivors handled their situation. Three sub-core categories wereidentified that were properties of the core category; these were: ‘Trapped inthe situation’, ‘Exposed to mastery’ and ‘Degradation processes’. In Paper IV,‘history of violence’ was reported by 39.5% (n = 761) of the women. Prevalenceof experience of domestic violence during pregnancy, regardless of type or levelof abuse, was 1.0 % (n = 18), and prevalence of history of physical abuse byactual intimate partner was 2.2 % (n = 42). The strongest factor associated withdomestic violence during pregnancy was history of violence (p < 0.001). Thepresence of several symptoms of depression was associated with a 7-fold risk ofdomestic violence during pregnancy (OR 7.0; 95% CI: 1.9-26.3).Conclusions: Our findings indicated that nulliparous women who have ahistory of violence or experienced violence during pregnancy do not appearto have a higher risk of labour dystocia at term, according to the definitionof labour dystocia used in this study. Additional research on this topic wouldbe beneficial, including further evaluation of the criteria for labour dystocia(Paper I). Avoidance of questions concerning the experience of violence duringpregnancy may be regarded as failing not only the pregnant woman but also theunprotected and unborn baby. Still, certain hindrances must be overcome beforethe implementation of routine enquiry concerning pregnant women’s experiencesof violence (Paper II). The theoretical model “Struggling to survive for the sakeof the unborn baby” highlights survival as the pregnant women’s main concernand explains their strategies for dealing with experiences of violence duringpregnancy. The findings may provide a deeper understanding of this complexmatter for midwives and other health care professionals (Paper III). The reportedprevalence of domestic violence during pregnancy in southwest Scania in Swedenis low. Both history of violence and the presence of several depressive symptomsdetected in early pregnancy may indicate that the woman also is exposed todomestic violence during pregnancy (Paper IV).
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| 5. |
- Hedenbjörk Lager, Anders
(författare)
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Dentine caries : acid tolerant microorganisms and aspects on collagen degradation
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Karies är en stor folksjukdom, trots att den både kan förebyggas och behandlas effektivt. Om man inte ingriper preventivt och låter det naturliga förloppet råda, kommer kariesangreppet till slut att bryta igenom emaljen och involvera även den underliggande dentinvävnaden. Kariessjukdomen orsakas av orala mikroorganismer, som en konsekvens av dessas nedbrytning av kostrelaterade kolhydrater. Som en biprodukt bildas då syror som löser upp (demineraliserar tandvävnaden), så att synliga hål till slut bildas. Syran kan lösa upp mineralfasen i tanden, men dentin består även till stor del av kollagen, vilket inte kan lösas upp av enbart syror. Man hänförde länge detta till proteinnedbrytande bakterier, men det har visat sig att munhålebakterierna inte har förmågan att lösa upp kollagen, och man tror nu att denna nedbrytning sker med hjälp av kroppsegna enzymer, bland annat matrix metalloproteinaser (MMP). De biologiska mekanismerna bakom kollagennedbrytning vid dentinkaries är emellertid dåligt undersökta, och delar av denna rapport (Studie III och IV) inriktar sig därför på detta område. Syran som bakterierna bildar skapar också en sur närmiljö för dem själva, vilket gör det svårt för dem att överleva, särskilt i ett begränsat utrymme som ett kariesangrepp. Man har länge ansett att endast vissa specifika bakterier har förmågan att leva och trivas i sura miljöer, men nya studier har ifrågasatt detta. I denna rapport (Studie II) undersöks även förekomsten av syratåliga bakterier på olika nivåer i dentinkariesangrepp med hjälp av en ny metod. Målet vid avlägsnande av karies är att ta bort fullständigt förstörd tandvävnad, men att försöka spara så mycket som möjligt av den delvis skadade vävnaden, vilken kan återställas. Detta har också aktualiserats då nya operativa principer och material lanserats under den senaste tioårsperioden. Det är emellertid svårt att avgöra var gränsen går kliniskt, och ett sätt att mäta dentinets ”friskhet” kan vara att mäta antalet bakterier i vävnaden. I den första rapporten (Studie I) undersöks den kvarvarande bakterieförekomsten efter kariesborttagning med två olika operativa metoder. Avhandlingen söker svar på följande frågeställningar: Studie I. Finns det några skillnader vad gäller antal kvarvarande bakterier efter dentinkariesavlägsnande med mekanisk (vanligt borr) eller kemo-mekanisk (Carisolv) metod? Studie II. Hur ser sammansättningen av den syratåliga bakteriefloran ut på tre olika nivåer i olika dentinkariesangrepp? Studie III. Finns det något samband mellan förekomsten av etablerade kariesangrepp och nivåerna av enzymet MMP-8 och dess nedreglerande protein TIMP-1 i saliv? Studie IV. Kan man framställa demineraliserat dentinmatrix med bibehållen biologisk aktivitet inför framtida studier av mekanismerna bakom nedbrytning av kollagen vid dentinkaries? Vad händer spontant med detta demineraliserade dentinmatrix över tid? Huvudfynden i studierna är: 1. Båda metoderna för att avlägsna dentinkaries minskade bakterieantalet radikalt. Det finns dock alltid kvar små mängder av bakterier i kaviteten. 2. Alla de undersökta kaviteterna hade en unik sammansättning av syratåliga bakterier, både till typ och antal, vilket indikerar att ett flertal olika bakterier har förmågan att anpassa sig till sura miljöer och potentiellt bidra till kariesutvecklingen. Vidare, fungerade de pH-specifika odlingsmedierna väl för att få fram de syratåliga bakterierna, något som är svårt med konventionella metoder. 3. Försökspersoner med etablerade dentinkariesangrepp uppvisade mycket högre förekomst av MMP-8 i saliven jämfört med kariesfria försökspersoner. Det nedreglerande proteinet TIMP-1 uppvisade inga samband alls. 4. Dentinmatrix framställt med båda testmetoderna uppvisade förekomst av intakt kollagen, samt aktivt MMP-8. Vidare så uppvisades en spontan nedbrytning av kollagen över tid, vilket tolkades som mestadels ett resultat av det aktiva MMP-8 enzymet. De nyvunna grundkunskaperna bildar underlag för nya studier inom forskningsområdet, samt för nya behandlingsmetoder, framför allt sådana som skulle kunna moderera eller förhindra dentinkariesprogression.
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| 6. |
- Leisnert, Leif
(författare)
-
Self-directed learning, teamwork, holistic view and oral health
- 2014
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The dental program at the Malmö dental school, the so called Malmö-model, is guided by four linked principles: self-directed learning, teamwork, a holistic view of patient care, and oral health (Fig.1). Figure 1. The four guiding principles of problem based learning at TVH, Malmö.Self-assessment ability is a critical competence for healthcare professionals, necessary for the successful adaptation to the modern life-long learning environment. Educational research seems to point out two critical factors for the development of such skills, continuous practice of self-assessment (1) and constructive feedback (2). The first study (3) presented in this publication assessed students’ self-assessment ability by means of the Interactive Examination in a cohort of senior dental students, who had gone through an identical assessment procedure during their second year of studies (4). The results indicated that self-assessment ability was not directly relevant to subject knowledge. Upon graduation, there were a number of students (10%) with significant self-assessment difficulties. Early detection of students with weak self-assessment abilities appears possible to achieve. The aim of the second study, concerning teamwork and holistic view (5), was to investigate if highlighting teamwork between dental and dental hygienist students could improve the students’ holistic view on patients, as well as their knowledge of, and insight into, each other's future professions. Thus, this project showed that by initiating teamwork between dental and dental hygienist students, it was possible to increase students’ knowledge on dental hygienists competence, develop students’ perceived holistic view on patients, and prepare students for teamwork. The third study explored findings clinicians use when diagnosing chronic periodontitis. A questionnaire was distributed to students, dental teachers and clinical supervisors in the Public Dental Services. Within all categories of clinicians, the majority of the clinicians used deepened pocket, bone loss on x-rays, and bleeding. There were differences in the use of findings between the categories of clinicians. None of the supervisors used attachment loss as a finding, while 13% to 27% of the other categories of clinicians used this finding. A higher frequency of dental hygienist students used plaque, calculus and pus, compared to the other categories.Dental hygienist students used more findings as compared to the other categories of clinicians. Fifty-eight of the 76 clinicians used each finding solitarily, i.e. one at a time, and not in combination to diagnose chronic periodontitis. However, about a third of the dental students and the supervisors only used findings either from the soft tissue inflammation subgroup or the loss of supporting tissue subgroup. With the exception of the dental teachers, the majority of clinicians within each category used irrelevant findings. The third study (6) gave valuable information when designing the fourth study (7). The In the fourth study, a questionnaire was distributed to 2,440 professional clinicians, i.e. dentists and dental hygienists in public and private activity, and dental students at the Dental school in Malmö. The results showed that two groups, representing dentists and dental hygienists delivering basic periodontal care in Sweden, were to a significant degree not sharing the knowledge basis for diagnosis and treatment planning. This may result in a less optimal utilization of resources in Swedish dentistry. The delivery of basic periodontal care was not in line with the severity of disease and too much attention was paid to the needs of relatively healthy persons. To change this pattern, the incentives in, and structure of, the national assurance system need to be adapted in order to stimulate a better inter-collegial cooperation between dentists and dental hygienists in basic periodontal care.
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| 7. |
- Papia, Evaggelia
(författare)
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Micromechanical retention and chemical bonding to polycrystalline dental ceramics : studies on aluminum oxide and stabilized zirconium dioxide
- 2014
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Det pågår en ständig utveckling av olika dentala material avsedda föratt ersätta förlorad tandsubstans. En materialgrupp som är särskiltintressant är höghållfasta keramiska material, oxidkeramer så somyttriumdioxidstabiliserad tetragonal polykristallin zirkoniumdioxid(Y-TZP). Förutom utveckling av material, är en av de störreutmaningarna att få tandersättningar att sitta fast i munnen på ettvävnadsbesparande sätt.Vid traditionell cementeringsteknik, fästs tandstödda ersättningarmed vattenbaserade cement, vars vidhäftning dels är beroendeav att tänderna slipas i syfte att skapa en geometrisk form för attåstadkomma makromekanisk retention och dels av ytstrukturenpå tand och tandersättning som skapas under processen och utgörmikromekanisk retention. I kliniska situationer med otillräckligmakromekanisk retention kan det vara nödvändigt att användaadhesiv cementeringsteknik. En förutsättning för en tillförlitligadhesiv bindning mellan tandersättning, cement och befintligtand är mikromekanisk retention och resinbaserade cement sommöjliggör en kemisk bindning. Det senare har visat sig vara svårtoch oförutsägbart att uppnå för oxidkeramer. Olika tekniker förmodifiering av oxidkeramers cementeringsyta har föreslagits för attmöjliggöra adhesiv cementeringsteknik.Övergripande mål med föreliggande avhandlingsarbete var attutveckla och utvärdera metoder för att modifiera polykristallinakeramers yta och därigenom möjliggöra kombinerad mekanisk ochkemisk bindning mellan oxidkeramer och adhesiva cementsystem. I delarbete I utvärderades bindningsstyrkan mellan olika adhesivacementsystem och en tätsintrad aluminiumoxidbaserad keram. Tvåav sex undersökta cementsystem uppvisade acceptabel bindning tillaluminiumoxid. Valet av ytbehandling på oxidkeramen bör baseraspå vilket cementsystem som ska användas.I delarbete II presenterades och utvärderades en ny framställningsteknikför ytmodifierad Y-TZP, lämpad för adhesivcementeringsteknik. Ytmodifieringen visade ökad mikrostruktur ochhögre bindningsstyrka jämfört med obehandlad Y-TZP. Uppföljninggjordes i delarbete IV med ytterligare ytanalyser och hållfasthetstest.En kemisk sammansättning med glas och monoklin fas identifieradesmed ökad ytråhet. Ytmodifieringen med glasmedium resulterade ilägre hållfasthet som dock ökade i samband med cementering.Delarbete III var en systematisk litteraturöversikt med syfteatt inventera olika metoder för ytbehandling/modifiering avoxidkeramer och utvärdera vilka av dessa som ger kliniskt relevantbindningsstyrka. Indelningen av de olika ytbehandlingarna var:fabriksproducerad, slipad/polerad, sandblästrad, ytmodifierad medolika typer av täckande lager, laser-, syra- och primerbehandlad.Sandblästring eller kiseltäckning av cementeringsytan kombineratmed primer utmärkte sig med högre värden på bindningsstyrkan,något som dock ännu inte blivit bekräftat i kliniska studier. Detfinns ingen universell ytbehandling. Valet av ytbehandlingar börbaseras på vilket material som ska användas.Sammanfattningsvis visar resultaten i avhandlingen att olikaytbehandlingar av oxidkeramer, i synnerlighet ytmodifieringmed glasmedium, kan öka bindningsstyrkan mellan keram ochadhesivt cementsystem. All ytbehandling påverkar dock materialetsegenskaper och slutligen tandersättningen. Valet av ytbehandlingbör göras utifrån specifika materialval, avseende både keram ochrespektive cementsystem.
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| 8. |
- Truedsson, Anna
(författare)
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An injectable biphasic bone substitute in sinus augmentation
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis concerns a new synthetic, injectable bone substitute, Cerament™, primarily developed for treatment of vertebral fractures. The purpose of the thesis was to investigate the properties of the newbone substitute, that is, whether it can contribute to the generation of new bone formation needed for placement of future dental implants. When the amount of bone in the upper jaw is insufficient, primary stability of dental implants cannot be achieved. Sinus augmentationis a well-established method for increasing the bone volume. This technique can be performed with autologous bone graft and/or bone substitute. Autologous bone graft can be harvested either from a local source in the oral cavity or from an extra oral source. The iliac crest is a common donor site for bone grafts when large quantities are needed, but bone harvesting from the iliac crest require surgery under general anesthesia resulting in an increased morbidity and higher costs.The thesis is based on study I-IV, both animal experimental studies and clinical applications. The question is what gains can be achievedwith the use of a bone substitute. Therefore, to start with, study I analyzed and compared the costs of local bone grafts from the oral cavity and extra-oral bone grafts from the iliac crest. In addition, post-operative health parameters were analyzed for those patients who underwent sinus augmentation, performed under general anesthesia, with bone graft from the iliac crest. Finally, the total cost of sinus augmentation, performed under general anesthesia, with iliac bone graft was calculated and analyzed with respect to the cost of surgery, anesthesia, hospitalization and sick leave. To achieve a broader understanding of the properties of the bone substitute study II and III were performed. Firstly, an animal experimental study in rats, with the intention to investigate if and to what extent Cerament™ onlay is able to stimulate new bone growth on a cortical bone surface. Secondly, an animal experimental rat study that analyzed and estimated to what extent Cerament™, in an onlay application, adds strength to the osseointegration of a titanium screw, measured as removal torque resistance. Further, to investigate the effect of a titanium screw without any bone substitute on a corticalbone surface analyzed with regard to bone remodeling. Finally, as a clinical application (study IV), sinus augmentation with Cerament™ was performed in four patients. The patients received either pure Cerament™ or Cerament™ mixed with autologous bone chips. The studies resulted in the following: Costs for sinus augmentation with iliac graft are several times larger than those for policlinic procedures. Most patients, who received iliac graft surgery, had recovered after 14 days. LoP (loss of production) constituted 41% of the total cost for sinus augmentation with iliac bone graft. Cerament™ guided bone generation from a cortical surface on rats’ tibia. The second animal study displayed no difference in torque resistance between screws embedded in Cerament™ and controls. Sinus augmentation in a mixture of bone chips and 50-75% Cerament™ rendered new bone formation after 6-11 months. Conclusion: There are gains to be made, in both economic and morbidity terms, by using Cerament™. When applied as an onlay, Cerament™ is capable of guiding and generating new bone formationon rats’ tibia. In sinus augmentation, Cerament™ has been proven to generate new bone without any adverse reactions. Future research should clarify how the clinical findings made in this thesis can be applied in the orofacial environment.
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