| Abstract | Dentalni implantati služe kao nadomjestak u slučaju dentalne traume, tj. gubitka jednog ili nekoliko zuba kod pacijenta. Budući se implantati postavljaju ručno, a kako bi se smanjio utjecaj ljudskog faktora kod preparacije koštanog ležišta za dentalni implantat (pozicija i nagib), osmišljen je sustav dentalnih vodilica za postavljanje implantata. Osnovna namjena dentalnih vodilica je da na relativno jednostavan način omoguće prijenos plana operacije s računala u koordinatni sustav pacijenta na način da naliježu na odabranu anatomiju pacijenta, pri čemu adekvatno osiguravaju svoj položaj od pomicanja i/ili deformiranja. Dentalne vodilice osiguravaju putanje svrdla za osteotomiju, odnosno za navođenje pri postavljanju implantata. Provedeno istraživanje bavi se problematikom dentalnih vodilica koje se oslanjaju na zube. Naime, iako dentalne vodilice poboljšavaju točnost kod postavljanja implantata, zbog velikog broja utjecajnih parametara još uvijek postoje odstupanja od plana. Disertacija se bavi analizom, primjenom te izradom matematičkih modela stabilnosti vodilica na anatomiji pacijenta, numeričko-eksperimentalnog modela deformiranja dentalnih vodilica pod utjecajem ručnih sila kirurga, a sve uzimajući u obzir utjecaj kvalitete digitalizacije pri akviziciji (snimanju) anatomske građe pacijenta nekom od metoda beskontaktnog mjerenja (3D digitalizacije). Podatci i materijali za istraživanje prikupljeni su tijekom suradnje s nekoliko dentalnih poliklinika koje se bave postupcima ugradnje dentalnih implantata. U prvom dijelu istraživanja provedena je 3D digitalizacija anatomske građe pacijenta i određene su pogreške koje se javljaju. Provedena je analiza digitaliziranih površina te je utvrđeno koje dentalne površine se bolje (točnije) digitaliziraju, a koje lošije. Utvrđeno je da zakrivljenost površine, tj. mjesta gdje postoji nagla promjena geometrije, uski utori i sl. pri digitalizaciji generiraju pogreške koje se kasnije prenose u algoritam izrade dentalnih vodilica. Kao posebnu stavku treba izdvojiti digitalizaciju okluzijskih površina kutnjaka i pretkutnjaka te incizalnog brida kod sjekutića jer su frekvencije pogrešaka tamo najveće. Potrebno je izbjegavati oslanjanje dentalnih vodlica na površine koje se netočno digitaliziraju. U nastavku su analizirani dostupni matematički modeli za predikciju stabilnosti vodilica na anatomiji pacijenta. Stabilnost se u ovom slučaju definira kao svojstvo dentalnih vodilica da za vrijeme oslanjanja onemogući pomak na anatomiji pacijenta. U programskom paketu Matlab (v.R2012.a, The MathWorks, Inc., Natick, MA, USA) implementiran je prilagođeni model stabilnosti koji se temelji na vodilicama u ortopedskoj kirurgiji te su izvršeni izračuni za različite načine oslanjanja (različite površine). Ukupno je analizirano sto različitih površina oslanjanja. Analizom stabilnosti dolazi se do zaključka kako smanjenjem površine oslanjanja translacijska stabilnost raste, dok se rotacijska u isto vrijeme smanjuje te da je moguće definirati smjernice za odabir površina za oslanjanje i oblikovanje dentalnih vodlica s obzirom na stabilnost. U završnom dijelu istraživanja promatran je utjecaj ručnih sila (pridržavanje, osteotomija) kirurga na deformacije dentalnih vodilica. Mjerenjem na eksperimentalnom postavu za četiri različite izvedbe dentalnih vodilica utvrđeni su pomaci na slobodnim krajevima. Upotrebom numeričkog modela istraženi su slučajevi koje nije bilo moguće izmjeriti. Varirani su smjerovi opterećenja (sile) te pozicije oslonaca. Rezultati pokazuju da dimenzije i oblik, te način oslanjanja dentalnih vodilica mogu utjecati na točnost kod postavljanja implantata. Usvajanjem rezultata istraživanja i usporedbom s relevantnim dostupnim studijama, dokazana je njihova primjenjivost u dentalnoj implantološkoj praksi. |
| Abstract (english) | Dental implants serve as a substitute in case of dental trauma, i.e. loss of one or several teeth in the patient. The implants are installed manually, and in order to reduce the influence of the human factor during osteotomy (position and inclination), a system of dental guides for implant placement was designed. The basic purpose of dental guides is to enable the transfer of the surgery plan from the computer to the patient's coordinate system in a relatively simple way in such a way that they lie on the patient's selected anatomy, while adequately securing their position against movement and/or deformation. Dental guides provide paths for osteotomy during surgery and for guidance during implant placement. The research deals with the issue of surgical dental guides that use teeth as a support. Although dental guides improve the accuracy of implant placement, due to a large number of influencing parameters, the deviations from the plan still occur. The dissertation deals with the analysis, application and creation of mathematical models of the stability of the guides on the patient's anatomy, the numerical experimental model of the deformation of the dental guides under the influence of manual forces of the surgeon, all while taking into account the influence of the quality of digitization during the acquisition (recording) of the anatomical structure of the patient using one of the non-contact measurement methods (3D digitization). Data and materials for research were collected during cooperation with several dental polyclinics that deal with dental implant procedures. In the first part of the research, the 3D digitization of the patient's anatomical structure was carried out and the errors that occur have been observed. An analysis of digitized surfaces was carried out and it was determined which dental surfaces are digitized better (more accurately) and which are worse. It was established that curvature of the surface, i.e. places where there is a sudden change in geometry, narrow grooves, etc. during digitalization generate errors that are later transferred to the algorithm for manufacturing dental guides. Digitization of the occlusal surfaces of molars and premolars and the incisal edge of incisors should be singled out as a special item, because the frequency of errors is highest there. It is necessary to avoid resting dental guides on surfaces that are digitized incorrectly. In the next part of the research, the available mathematical models for predicting the stability of the guides on the patient's anatomy were analyzed. In this case, stability is defined as the property of dental guides to prevent displacement of the patient's anatomy during support. The adapted stability model which is derived from orthopaedic drill guides was implemented in the Matlab (v.R2012.a, The MathWorks, Inc., Natick, MA, USA) program package and calculations were performed for different ways of support (different surfaces). A total of one hundred different support surfaces were analyzed. Analysis of stability leads to the conclusion that by reducing the support surface, translational stability increases, while rotational stability decreases at the same time, so it is possible to define guidelines for the selection of surfaces for support and the design of dental guides with regard to stability. In the final part of the research, the impact of the surgeon's manual forces (holding, drilling) on the deformations of the dental guides was observed. Measurements on the experimental setup for four different types of dental guides determined the displacements at the free ends. Cases that could not be measured were investigated using a numerical model. Load directions (forces) and support positions were varied. The results show that the dimensions and shape, as well as the way the dental guides are supported, can affect the accuracy of implant placement. By adopting the research results and comparing them with relevant available studies, their applicability in dental implantology practice has been proven. The research was conducted in several phases, which are listed below. Chapter 1 "Introduction" presents an introduction to dental implantology with reference to surgical dental guides. Based on available and published research, the parameters that affect the precision of implant placement using dental guides are described in detail and listed, as well as an overview of previous research according to the parameter of influence. The rest of the chapter describes the types and work algorithm for making dental guides. Chapter 2 "Research objective and hypotheses" formulates the research objectives, hypotheses, expected scientific contribution and gives the structure of the dissertation. Chapter 3 "Digitalization of the anatomical structures of the patient" shows the problems with 3D digitalization of the anatomical structures of the patient. It describes the materials and methods used in the comparative analysis of four different 3D scanners when digitizing the patient's dental anatomy. Ultimately, on the basis of the collected results, it presents guidelines for the support of dental guides. Chapter 4 "Mathematical stability model" defines stability as a property of dental guides and presents available mathematical models for stability calculation. It shows the selected and adapted mathematical model for calculating the stability of dental guides. Chapter 5 "Simulation of the stability of dental guides" shows how the stability of a dental guide depends on the support surfaces. Calculations were made for six different designs, which show that by reducing the support surface, the translational stability increases, while the rotational stability decreases at the same time. The results suggest that the form "B1" of the dental guides, which satisfies in terms of resistance to translation and rotation, and is more favorable (cheaper) in terms of material consumption, is optimal. Chapter 6 "Influence of the Clinician on the Surgical Guide" looks at the influence of manual and/or drilling forces on the deformations of the dental guide during application. By measuring the deflection at the free ends of the dental guides, it was proven that the surgeon can have a significant influence on the shape of the dental guide during application if the lever is too large. Stresses in dental guides are generally within the acceptable limits of the mechanical properties of the material. Displacement and stress diagrams provide adequate guidelines for the design and selection of dental guide support methods. Chapter 7 "Conclusion" represents the last and at the same time concluding chapter in which the original scientific contribution of the research is presented and a summary of the results is presented. Also, based on the presented results, the areas and possible directions of future research are listed. |
