Total Hip Arthroplasty (THA) is an orthopaedic procedure that is performed to reduce pain and restore the functionality of hip joints that are affected by degenerative diseases. The outcomes of THA are generally good. However, the stress shielding of the periprosthetic femur is a factor that can contribute towards the premature loosening of the femoral stem. In order to improve the stress shielding characteristics of metallic femoral stems, stiffness configurations that offer more flexibility should be considered. This research has investigated the potential of more flexible and lightweight cobalt chromium molybdenum (CoCrMo) femoral stems that can be manufactured using Selective Laser Melting (SLM). Square pore cellular structures with compressive properties that are similar to human bone have been presented and incorporated into femoral stems by utilising fully porous and functionally graded designs. A three dimensional finite element model has been developed to investigate and compare the load transfer to the periprosthetic femur when implanted with femoral stems offering different stiffness configurations. It was shown that the load transfer was improved when the properties of the square pore cellular structures were incorporated into the femoral stem designs. Factors affecting the manufacturability and production of laser melted femoral stems have been investigated. A femoral stem design has been proposed for cemented or cementless fixation. Physical testing has shown that a functionally graded stem can be repeatedly manufactured using SLM, which was 48% lighter and 60% more flexible than a traditional CoCrMo prosthesis. The research presented in this thesis has provided an early indication of utilising SLM to manufacture lightweight CoCrMo femoral stems with levels of flexibility that have the potential to reduce stress shielding in the periprosthetic femur.

Syftet: Utvärdera produktionstolerans av objekt som producerats genom additiv framställningsteknik (AF) för användning inom tandvård, samt att jämföra denna teknik med subtraktiv framställningsteknik (SF) genom reverse engineering.Material och metod: Tio exemplar av två olika geometriska objekt framställdes från fem olika AF maskiner och en SF maskin. Objekt A efterliknar ett inlay, medan objekt B återspeglar en modell av en fyrledsbro. Alla objekt delades in i olika mätled; X, Y och Z. Mätningarna utfördes med validerade och kalibrerade instrument. Linjära avstånd mättes med ett digitalt skjutmått och hörnradie samt vinklar mättes med ett digitalt mikroskop.Resultat: Vare sig additiv eller subtraktiv framställning uppvisade en perfekt matchning till CAD-filen med hänsyn till de parametrar som utvärderades i denna studie. Standardavvikelsen gällande linjära mätningar för subtraktiv framställning uppvisade konsekventa resultat i alla led, med undantag för X- och Y-led för objektet A och i Y-led för objekt B. Samtliga additiva tillverkningsgrupper hade en konsekvent standardavvikelse i X- och Y-led, men inte i Z-led. Med avseende på hörnradiemätningar, hade SF gruppen i överlag bättre produktionsnoggrannhet för både objekt A och B medan AM grupperna var mindre noggranna.Konklusion: Med hänsyn till begränsningarna med denna in vitro studie, stödjer resultat hypotesen, med hänsyn till att AF hade en bättre förmåga att återskapa komplexa och små geometrier jämfört med SF. Samtidigt identifierades en bättre reproducerbarhet hos SF gällande enkla geometrier och linjära avstånd. Vidare studier krävs för att bekräfta dessa resultat. / Purpose: To evaluate the production tolerance of objects produced by additive manufacturing systems (AM) for usage in dentistry and to compare with subtractive manufacturing system (SM) through reverse engineering. Materials and methods: Ten specimens of two geometrical objects were produced by five different AM machines and one SM machine. Object A mimics an inlay-shaped object, meanwhile object B reflects a four-unit bridge model. All the objects were divided into different measuring-axis; X, Y and Z. Measurements were performed with validated and calibrated equipment. Linear distances were measured with a digital calliper while corner radius and angle were measured with a digital microscope. Results: None of the additive manufacturing or subtractive manufacturing groups presented a perfect match to the CAD-file regarding all parameters included in present study. Considering linear measurements, the standard deviation for subtractive manufacturing group were consistent in all axis, except for X- and Y-axis in object A and Y-axis for object B. Meanwhile additive manufacturing groups had a consistent standard deviation in X- and Y- axis but not in Z-axis. Regarding corner radius measurements, SM group overall had the best accuracy for both object A and B comparing to AM groups. Conclusion: Within the limitations of this in vitro study, results support the hypothesis, considering AM had preferable capability to re-create complex and small geometry compare to SM. Meanwhile, SM were superior producing simple geometry and linear distances. Further studies are required to confirm these results.

SammanfattningSyfteSyftet med föreliggande studie var att undersöka om olika förbehandlingar av metallens yta påverkar bindningsstyrkan mellan CoCr och porslin.Material och metodSexton metallbasar med totalt 64 porslinscylindrar tillverkades genom gjutning av CoCr och porslinsuppläggning (de olika skikten; bondingagent, opak och dentin). Metallbasarna delades slumpmässigt in i 4 grupper; SB 50 sandblästrade med 50 m Al2O3, SB 250 sandblästrade med 250 m Al2O3, OASB oxiderade med atmosfäriskt tryck och sandblästrade med 250 m Al2O3, samt kontrollgrupp OVSB oxiderade i vakuumtryck och sandblästrade med 250 m Al2O3, samtliga grupper blästrades med 3 bars tryck. Efter glansbränning termocyklades provkropparna i 5000 cykler, förvarades fuktigt i 36o C och testades enligt ISO/TS11405:2016. Resultaten analyserades med one-way ANOVA, Tukey´s test. Signifikansnivån sattes till  = 0,05. Brottytorna analyserades visuellt och fotograferades i mikroskop. ResultatMedelvärdet för samtliga grupper var likvärdiga men med stor skillnad i spridning inom grupperna. Brotten delades in i tre grupper, adhesiv-, kohesiv- och blandfraktur.Slutsats Med reservation för de begränsningar som finns inom föreliggande studie kan följande slutsatser dras:•De olika förbehandlingsmetoderna, oxidering med vakuum eller atmosfäriskt tryck följt av sandblästring eller enbart sandblästring med olika kornstorlekar, ger ingen specifik skillnad vad gäller bindningsstyrkan mellan metall och porslin.•Oxidering med vakuum har ingen negativ inverkan på bindningsstyrkan mellan metall och porslin. De-gasing av metallen kan utföras.•Sandblästring med 50 μm hade större spridning inom gruppen än de övriga tre grupperna. •Studiens nollhypotes kan bekräftas. / Abstract PurposeThe purpose of the present study was to investigate whether various pretreatments affect the bond strength between CoCr and porcelain.Material and method64 porcelain cylinders were manufactured (bonding agent, opaque, dentin) divided on sixteen metal bases. The metal bases were randomly divided into 4 groups; SB 50 sandblasted with 50 m Al2O3, SB 250 sandblasted with 250 m Al2O3, OASB oxidized with atmospheric pressure and then sandblasted with 250 m Al2O3 and control group OVSB oxidized in vacuum and then sandblasted with 250 m Al2O3. All groups were sandblasted with 3 bars pressure. After glazefiring, the specimens were thermocycled 5000 cycles, stored in moist at 36o C and tested according to ISO / TS11405: 2016. The results were analyzed with one-way ANOVA, Tukey's test with significance level  = 0.05. The fracture surfaces were analyzed visually and photographed in microscope.ResultsThe mean values in all groups were equivalent but with large difference in standard deviation within the groups. The fractures were divided into three groups, adhesive-, cohesive and mixed fractures.ConclusionWithin the limitations of the study, the following conclusions can be drawn: •The different pretreatment methods, vacuum or atmospheric pressure, oxidation with or without sandblasting do not affect the bond strength between metal and porcelain.•Oxidation with vacuum does not adversely affect the bonding strength between metal and porcelain. De-gasing of the metal can be performed.•Sandblasting with 50 μm had a greater deviation within the group than the other groups•The study's null-hypothesis can be confirmed

The purpose of this study was to evaluate the incidence of corrosion and fretting in 48 retrieved titanium-6aluminum-4vanadium and/or cobalt-chromium-molybdenum modular total hip prosthesis with respect to alloy material microstructure and design parameters. The results revealed vastly different performance results for the wide array of microstructures examined. Severe corrosion/fretting was seen in 100% of as-cast, 24% of low carbon wrought, 9% of high carbon wrought and 5% of solution heat treated cobalt-chrome. Severe corrosion/fretting was observed in 60% of Ti-6Al-4V components. Design features which allow for fluid entry and stagnation, amplification of contact pressure and/or increased micromotion were also shown to play a role. 75% of prosthesis with high femoral head-trunnion offset exhibited poor performance compared to 15% with a low offset. Large femoral heads (>32mm) did not exhibit poor corrosion or fretting. Implantation time was not sufficient to cause poor performance; 54% of prosthesis with greater than 10 years in-vivo demonstrated none or mild corrosion/fretting.