Orala implantat används för att skapa käkbensförankrade ersättningar i partiellt eller helt tandlösa käkar. Denna möjlighet att återställa bettfunktionen bygger på konceptet om osseointegration, där en främmande kropp i form av ett implantat accepteras och integreras i benvävnaden, för att senare utgöra plattformen för den fortsatta bettrekonstruktionen. Implantatbehandling har visat långsiktigt hög överlevnad och lyckandefrekvens med stor patienttillfredsställelse, men brister i osseointegration och implantatförluster uppstår fortfarande. En av riskfaktorerna för misslyckande vid implantatbehandling är olämpligt kirurgiskt tillvägagångssätt. Vid implantatoperation är fixeringen av implantatet i käkbenet en viktig faktor så kallat implantatets primärstabilitet. Denna variabel kan mätas kliniskt och är ett momentvärde vid insättande av implantat (Insertion Torque Value; ITV).
Att modifiera borrprotokollet där det borras ett mindre (underpreparation) säte i benet (osteotomi) än implantatets diameter är en vanlig metod för att öka implantatets primärstabilitet. Denna teknik skapar en tätare kontakt i gränsytan mellan ben och implantat med en ökad kompression. Antagandet är att för hög kompression vid implantatinstallationen även genererar benskada och att det därmed skapas negativa konsekvenser på implantatbehandlingen. Även om underpreparation av implantatsätet är en vanligt förekommande metod så finns det ingen vetenskaplig evidens för denna metodik. Den här avhandlingen har som övergripande syfte att utvärdera effekterna av ett modifierat borrprotokoll för att uppnå bättre primärstabilitet.
Delarbete I var en systematisk litteraturöversikt om biomekaniska, biologiska och kliniska effekter där modifierat och konventionellt borrprotokoll jämfördes. Det visade sig att implantat som installerades i en modifierad osteotomi nådde betydligt högre ITV än vid konventionell osteotomi i käkben med låg densitet. Den biologiska reaktionen i ben i kontakt med implantat var likartad mellan modifierad och konventionell osteotomi efter fullständig läkning. Litteraturöversikten visade att den kliniska evidensen var sparsam.
Delarbete II var en retrospektiv studie som utvärderar resultatet av implantat som installerades efter modifierat borrprotokoll enligt operatörens egen uppfattning om käkbenets kvalitet. ITV påverkades mest av benkvalitet och diametern på implantatet. Signifikant högre benresorption upptäcktes runt implantaten som installerades efter modifierat borrprotokoll. Marginal benförlust (runt kragen på implantatet) påverkades av benkvalitet, implantatdiameter, ITV och interaktion mellan benkvalitet och ITV. Den marginala benförlusten visade sig vara större med öka bendensitet i kombination med högre ITV.
Delarbete III syftade till att in vivo (i levande vävnad) utvärdera benets biologiska respons vid implantatinstallation i käkben på får efter modifierat och konventionellt borrprotokoll. Modifierat borrprotokoll säkerställde högre rotationsstabilitet men orsakade samtidigt mindre nybildning av ben vid implantatens gränsyta till ben. En tre- och tvådimensionell analys av benvävnaden visade en lägre mängd mineraliserat ben med många kaviteter runt de underpreparerade osteotomierna. Dessa skillnader mellan de två grupperna observerades efter 5 veckors inläkning av implantaten, medan inga skillnader noterades efter 10 veckors inläkning.
Syftet med delarbete IV var att bedöma käkbenets egenskaper och att förutsäga mekaniskt reaktionssätt vid funktionell belastning i en datasimulerad modell. Två typer av benstrukturer i underkäken simulerades: en modell med benkaviteter och en modell utan benkaviteter i likhet med benvävnad där implantatinstallationer utförts i modifierat respektive konventionellt borrprotokoll. Studien visade att kaviteterna avsevärt försämrade benets mekaniska egenskaper. I modellen för underpreparerade osteotomier, uppmättes högre spänning vid kragen på implantatet och vid benkaviteterna.
Sammanfattningsvis indikerar denna avhandling att modifierat borrprotokoll med underpreparerade osteotomier kan orsaka negativa effekter i benet. Den underpreparerade osteotomin genererar en intensiv benresorptionsaktivitet i det omgivande benet kring implantatet under den tidiga fasen av benläkningen. Porositeter i ben på grund av kaviteter och marginal benförlust bidrar till försämrade mekaniska egenskaper och en fördröjd läkningsprocess i käkbenet. Nuvarande klinisk evidens bör förbättras genom framtida kliniska studier för att bekräfta de föreliggande resultaten.
AKNOWLEDGEMENTS
Writing this thesis was the final step of an intense experience that changed my life. It is with some sadness that I conclude this 4-year journey full of indelible memories of happiness, joy, enthusiasm, struggle and commitment. This experience would have been so empty without meeting many people from all over the world. Everyone has left his/her mark on me, but I would like to express my deepest gratitude in particular to:
Associate Professor Jonas Peter Becktor, my main supervisor. Thank you for your endless support to my work, for your energetic enthusiasm and determination in the research, thank you for having sustained me in the time of need. And of course thank you for all the fun we had and all the numerous instruments we played.
Dr. Ryo Jimbo, my co-supervisor. I cannot forget how you always supported me. You taught me more than you may know, probably. Recollecting the years in which we worked together, I believe that you were one of the most talented minds in research that I have known. I wish you all the best.
Professor Ann Wennerberg, my co-supervisor. I would like to thank you with profound gratitude for the most inspiring person you have been during these years. Thank you for your kindness, your good advices and your sincere support. I consider myself fortunate being one of your team.
Professor Tomas Albrektsson. Thank you for your precious notes and for the proof reading of my thesis. My deepest gratitude is for your endless passion for research. Studying your work and having the chance to meet you was really motivating. I feel so lucky to have you in the faculty.
Associate Professor Satoshi Yamaguchi. I feel thankfulness for having worked with you. Thank you for accepting me in Osaka, and making my experience memorable there. I cannot forget how you supported me with your dedication, your serious commitment to the work and your always-quick reply to my questions. Arigato gozaimashita. I am looking forward to future collaborations with you.
Professor Eriberto Bressan. You were the one who convinced me to enter into the research work, the one who incited me to go abroad, the one who always supported me even when not in Padova. I will always be grateful for your support.
Dr. Denis Cecchinato for your valuable input and for letting me start the PhD on the right foot. Thank you for sharing your knowledge with me.
Dr. Stig Hansson for supporting my projects. I was honored to share with you the early results of my thesis.
Associate Professor Cristiano Tomasi for being an example to me. You once told me that writing a Swedish doctoral thesis is time- consuming. You were more than right. It was indeed.
All my colleagues that I had the luck to meet at the Department of Prosthodontics, Malmö University. In particular, I want to thank Dr. Silvia Galli for everything you taught me. You have been an example of what a good researcher should be, and a good friend always available for help. Thank you for your super effort with front- page image as well. I am so grateful for having worked with you, and our collaboration has just started!
My dear friend Dr. Francesca Cecchinato, for all the good time we shared in Malmö. We met when you were almost at the beginning of your PhD and I can testify how you have changed your way of thinking through those years. I agree with you that we have had a remarkable journey that has changed how we are thinking and who we are. I am so glad for being your friend.
Dr. Anders Halldin for your priceless collaboration and for sharing your knowledge with your countless trips to Malmö. I learned a lot from your enthusiastic approach to research.
Ricardo Trindade, for all the discussions we had in our past, and will have at present and in the future, on our aspirations, on our values. I believe we always had a special understanding between us. You are a free thinker and I wish you all the best.
Dr. Ramesh Chowdhary, for all the funny moments we shared in Malmö and to all our unexpected meetings around the world. Dr. Ali Alenezi for all the discussions we had and the nice time in Nösund. Dr. Pär Johansson, for all the fruitful discussions we had. Dr. Bruno Chrcanovic, for your precious support in the last period.
Smiling Dr. Lisa Papia for your continuous optimism and for your sensitive words of support when I was worried and tired. Dr. Zdenka Prgomet and Dr. Anna Trudesson for the nights out. Anna Klinge for the time we shared and your help when I broke my tooth; that was fun to remember. Marianne Ahmad for your generous help during the last months of my thesis work.
All the people at the Department of Oral Surgery, Malmö University for the kind support you gave me in the last three years: Amjad, Eva, Fredrik, Krister, Lars, Magda, Monika, Nathalie, Samra, Selma and Yvonne.
The administrators for their outstanding job: Monica Lotfinia, Christina Stenervik, Helén Åkesson. Thank you for having taken care of innumerable issues, requests, forms, questions, invoices that I sent you.
The people I had the chance to meet during my two trips to Japan. Dr. Yoshihito Naito and your wonderful family, for the happy moments and all the ramen we shared; to Henmichan for your joyful guidance in my first-shocking experience in the far East; to Lily for our interesting discussions: I am glad for having met you and hope you can realize your dreams. To all other people I met in Japan: otsukaresama desu!
All the Padova crew: Sivo and Bru, for your sincere friendship; Sara, Ricky and Luca for all the fun time we shared; Ciccio Saverio, Maddi and Marika for the late night discussions.
My flat mates in Malmö: Guillaume, Johan, Nacho, Camilla, Hanna and Tove. I recall happy memories in Sweden. Thank you for letting me playing the drums.
The dearest friends in Valdagno: Gaspa, Paolo, Andrea, Carlo, Fede, Davide, Chiara and Tomi. The thought that you will always be there for me even in the most difficult moments is blissful.
During the past years I achieved many gratifications, however the most precious gift was having met you, Marco and Yohei. You have been the pillars of my doctorate; for all these years, you have always been ready to support me.
Marco Toia, my bigger brother, thank you for everything you did, I really mean it. It is almost impossible to list all the ways you supported my research work and my everyday life. You helped me with your determination, sensitivity, passion and blind trust. Always ready for a good advice. You know that I believe that you are one of the most talented persons I ever met and I am so glad to having had the chance to work with you and being your friend.
Dr. Yohei Jinno, my senpai, for all our work together. It is almost impossible to quantify how hard we worked, how far we traveled, how many troubles we encountered and finally resolved. Thank you for all the fun we had, the beers we drank, the jokes we made, for our long talks, confiding our problems. All those moments are life-
long memories. I’m sad that we may not be able to meet as often as previously, but you deserve all the best for your future. I am glad to call you best friend.
My family, for your endless love. Paolo, thank you for always being an example to me since I was a kid, being my calmer, gentler and more profound part. And I am so happy that Monica has joined the family.
Mum and Dad. This journey would not have been possible if it was not for you. You accepted my choices, even though they sometimes were the most difficult ones. I feel so grateful thinking how much you supported me in my endless trips, my confusing schedule, my deadlines and even during my bad moods.
Marta for being my soul mate. You alone know how much I sacrificed during these years. How many weekends working at home, how many nights I stayed up, and how much free time I lost. You only know because you always stayed with me, no matter what. Thank you. I love you.
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