Oral Prosthetics and Dental Materials Science
Short description
Oral prosthodontics and dental materials science is a research area with a wide scope that includes research question on all aspects within prosthetic rehabilitations and dental biomaterials. Our projects involve dental implants- and implant supported prosthodontics, as well as investigations of tooth supported prostheses. We collaborate with national and international research laboratories and clinics. An area of special interest is related to tissue reactions to dental implants and implant protheses as well as clinical studies of dental implant supported constructions. Surface morphology analyses of various biomaterials and is another prominent research area as well as biomechanical investigations of new dental materials.
Biodegradable metallic implants
Metals such as titanium and titanium alloys have since long been used in surgery to stabilize and assure a correct position in ortopaedic-, cranio-facial- and trauma applications. Titanium and its alloys are biocompatible with very good mechanical properties and they integrates well in the bone. The latter may be a disadvantage when the stabilizing element is to be removed, a second operation is needed and new damage to the new bone may occur. If biodegradable materials could be used, these disadvantages can be prevented. Magnesium and magnesium alloys are promising biodegradable materials. However, so far the mechanical properties have been inferior to those of titanium and titanium alloys. Further, the degradation process has been difficult to steer. Ideally the degradation of the implant should go hand in hand with the healing process, thus the newly formed bone should gradually replace the implant.
Aims
- To evaluate degradation properties (rate, speed, homogeneity) in vivo at different time points and how these factors correlate with the material properties (macrostructure, chemical composition, intermetallic phases).
- To evaluate the tissue response around the implants in terms of bone structure, bone quality, vascularization, and chemical composition.
- To measure the biomechanical properties of the bone-implant interface under loading up to failure, to predict failure mechanisms under function and to further tailor their properties.
Material and Methods
By comparing Mg-alloys to well-known implant materials, such as Ti and PEEK, we could deduce how different implant materials stimulate the formation of bone at the interface and how they dissipate stresses when loaded. Our hypothesis was that Mg alloys, due to the release of Mg ions and of alloying elements, as well as the changes in the local environment due to degradation, could influence the composition and quality of the bone at the interface. We aimed to evaluate the interface, employing histology, absorption and scattering based tomography, scattering and diffraction techniques (SAXS/WAXS) and chemical analyses (XRF).
Project Facts
Project Manager
Ann Wennerberg
Factors related to clinical outcome of oral implant treatment
To replace lost teeth, oral implants are today a well documented treatment, generally with a very good prognosis. However, failures occur, some of those due to loss of bone support. To be able to select the best treatment for the patients factors important for failures need to be identified as well as more research on the osseointegration process and its complicated immunological response.
Aims
The major aim with this clinical and in vivo experimental project was to analyze clinical data and evaluate molecular mechanisms of implant/host interactions. The project has in a series of systematic reviews, retrospective and prospective clinical trials evaluated the reasons for dental implant failures, reasons for marginal bone resorption around the implants and in addition, reasons for post operative infections. Further, in experimental animal models the project has evaluated the immunological response towards the foreign body that an implant represents. Different materials have been evaluated for comparison with titanium which often is claimed to be inert. The immunological action that takes place in bone healing without the presence of an implant, through so called sham sites, has been studied as well.
Material and Methods
Evaluation methods have included clinical examinations, literature reviews, PROMS, X-rays, biopsies, light microscopy, interferometry, XPS, SEM, qRT-PCR for gene expression analysis and mRNA isolation.
Projects Facts
Project Manager
Ann Wennerberg
New biomaterials-a clinical improvement or an increased risk?
Hip and knee joint replacements are treatment with a very high cost-benefit through the increase in patient mobility and increased quality of life, after a successful surgery. The materials that are being used in the clinic for this purpose are not always fully evaluated from all aspects, and theoretically side effects could therefore arise. A common material used in in hip/knee arthroplasty is Zirconia (ZrO2) also used in dental implant treatment. In the area of disc regeneration and oral surgery, PEEK is often used, which has worked satisfactorily clinically, but without the material having been tested for possible side effects. Results from published in vivo analyzes performed within our research group indicate that PEEK induces strong immunological reaction and that fat cell degeneration occurred during a 28-day test period.
Oral implants, similarly to hip and knee implants, have provided good long-term clinical results, but factors related to the patient, treating team, and implant can affect the degree of bone loss around the implants and the frequency of implant loss over time. One contributing factor to complications can be particle release from the implant structures. In particular, Zirconia in contact with titanium appears to be able to give rise to large particle release due to wear during load. An additional risk is that the use of new implant materials such as Zirconia with different hardness and titanium/zirconia (TiZr) alloys increases, even though there is too little knowledge about their clinical effects after a longer follow-up period.
Purpose
The project studies clinical effects of oral biomaterials materials. Specifically, cellular, immunological and molecular response to new prosthetic materials and combinations of materials.
Material och Metod
Retrospective studies of the clinical outcome when using new implant and prostheses materials. Also we aim to investigate the molecular and immunological response in the peri-implant soft tissue around implants with abutment of zirconia or titanium/zirconium as compared to titanium. The presence of wear particles in the tissues will be analyzed as well as molecular analyses of the immunological and inflammatory expression using quantitative real-time PCR, scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS).
Project Facts
Project Manager
Victoria Franke Stenport
New dental ceramics- on the effect of the chemical composition and manufacturing technique
Dental ceramics have become a frequently used treatment alternative to metal-based dentures. Within the dental ceramic field, there are several different material subgroups, where the strength of the crystalline zirconia materials has widened the indication range for ceramics produced for crowns and bridges in dentistry. Zirconia has also been used for hip prostheses in orthopedics since the 1980s and to a small extent for the dental implant application since 2015. During the last ten years, digital development has made it possible to design and manufacture all-ceramic constructions completely digitally, which has further increased the interest in this material.
The traditional composition of zirconia-based ceramics has shown beneficial properties in both clinical and preclinical studies. The two most common complications are loss of retention of the crowns and chip fractures of the surface porcelain. New zirconia materials with improved esthetics are now available that allow usage without porcelain veneers. These new materials have a modified chemical composition compared to the previous zirconia materials and are now manufactured to an increased extent by additive techniques compared to the previous manufacturing which was mainly milling-based. The new zirconia materials are incompletely explored and there is a lack of information on how they function in the oral environment after a longer period of time and how variations in the chemical composition affect the strength. Furthermore, there is a lack of research on how the new manufacturing technique affects the material properties.
Purpose
To explore how modifications to the composition and manufacturing technology of new zirconia materials affect mechanical properties, surface structure, and functional longevity in the oral environment, as well as the cement bonding strength and aging to the material.
Material and method
Monolithic translucent crowns cemented with different cement types will be studied with computer simulation (finite element analysis) to visualize the stress distribution of the material, underlying cement and in the tooth. Furthermore, the bonding potential of different zirconia materials with a 10-methacryloyloxydecyl dihydrogen phosphate-based composite cement will be studied using different spectroscopic techniques. The crystallographic structure and surface morphology will be analyzed. Specimens of different chemical compositions and manufacturing techniques will receive different surface treatments and cementation procedures. Thermocycling will be carried out corresponding to mimic aging for one year. Evaluation of the materials' hardness, fracture toughness, load strength and bond strength between cement and ceramic will be explored.
Project Facts
Project Manager
Victoria Franke Stenport
Dental constructions - new materials and manufacturing techniques and design
Tooth loss may lead to both a physiological and social handicap. Dental restorations such as crowns and bridges on teeth or implants are common solutions to restore lost teeth or parts of teeth. Dentists and dental technicians often discuss patient conditions to decide the most suitable material for a certain patient. In the last ten years, there has been a rapid development of production techniques and dental materials. Mainly seen in dental laboratories where the production techniques are changing from lost wax to CAD/CAM such as subtractive and additive techniques. The last ten years have been marked by the rapid development of production technology and materials. This development is mainly taking place in dental laboratories, from casting technology to milling and to additive manufacturing, where a majority of the designs are now produced using CAD/CAM technology. With the use of CAD/CAM the materials used have been developed further and there have been more material groups and more variants of previous materials introduced to dentistry. The restorations can be produced in a variety of materials, including alloys such as cobalt chromium and titanium, as well as ceramics such as lithium disilicate and zirconia. Zirconia is an oxide ceramic that has seen major development and is now available in various strengths and translucence. Production of the restorations can be done with industrial control via large production centers with central manufacturing or directly at the dental laboratories with smaller desktop milling machines. To create a more tooth-like and aesthetic appearance of the restoration, dental technicians veneer the alloy or ceramic substructure with surface porcelain. When firing the surface porcelain, the differences in thermal expansion between the alloy or ceramic substructure and the porcelain can adversely affect the fit. Also, the preparation of the alloy or ceramic substructure may cause internal tension in the substructure that may affect the fit at the high temperatures the bridge is exposed to during the process.
Purpose
The overall aim of the project is to evaluate dental and implant-supported dental restorations in different materials produced with digital technology based on design, fit and strength.
Materials and Method
Specimens of various materials, designs and manufacturing techniques will be evaluated for fit and strength and porcelain bond strength. The fit will be studied using various available techniques (coordinate measurement technology, scanning electron microscopy, optical microscopy, 3D scanning or silicone replica technology). The strength of the materials will be characterized by load testing, fracture test, and Vickers hardness test. Fracture analyses will be done using light microscopy and scanning electron microscopy.
Project Facts
Project Manager
Per Svanborg