Supervisors info:
Κωνσταντίνος-Νικόλαος Σπυρόπουλος, Επίκουρος Καθηγητής, Τμήμα Οδοντικής Τεχνολογίας, Σχολή Επαγγελμάτων Υγείας και Πρόνοιας
Νικόλαος Πολυχρονάκης, Επίκουρος Καθηγητής, Τμήμα Οδοντιατρικής, Σχολή Επιστημών Υγείας, ΕΚΠΑ
Ασπασία Σαραφιανού, Επίκουρη Καθηγήτρια, Τμήμα Οδοντιατρικής, Σχολή Επιστημών Υγείας, ΕΚΠΑ
Translated title:
Comparative study of the durability of the metal-ceramic bond between the porcelain and the metal substrate feldspar cobalt alloys - chromium (Co-Cr), generated by four different manufacturing methods.
Summary:
Introduction
New technologies aim to simplify the laboratory stages, aiming to offer fast construction, high dimensional accuracy, high precision in application and low cost. The metal-ceramic prosthetic work still remains the most popular prosthetic work these days. The advantages of these structures are aesthetics and durability, which ensures the longevity of these works under the chewing forces and is directly related to the strength of the metallocceral bond. Metallic substrates are manufactured by casting dental alloys, but in recent years, new technologies have provided alternatives using subtraction or prosthetic techniques (cutting or fusion) driven by computer programs. The introduction of these techniques into daily laboratory and clinical practice has led to researches on the strength of the metalloceramic bond. Many researchers published articles on the application of these techniques where mainly cobalt chromium alloys are used and various factors relating to the metalloceramic bond are examined. Results have been published that investigate the strength of this bond by looking at various parameters such as changes in the microstructure of the alloys used under different heat treatments, The use of different techniques such as cutting, sintering and sintering leads to the construction of dental prosthetic restorations with the same good results and advantages of casting, but simplifying the intermediate stages and technique. The lack of sufficient documentation for the effectiveness of these applications compared to the casting method, the strength of the metalloceramic bond led to the completion of this research.
Purpose
The purpose of this research is to investigate the strength of the metalloceramic bond between Co-Cr dental alloy and dental porcelain, when M, SM and DMLS techniques are used for the construction of the metal substrate as opposed to the traditional casting technique.
Materials and methods
In order to control the metalloceramic bond, 40 metal substrates were constructed, according to the specifications defined by ISO 9693, which were divided into four groups: the reference group, the metal substrates of which were made by the basic metal alloy casting technique Co-Cr and control groups, the metal substrates of which were made by the technique of Milling, Soft Milling and DMLS from a base metal alloy Co-Cr. Based on the same specification, 4 metal substrates were manufactured from each manufacturing technique in order to check their elastic modulus. The ceramic mass placed on the metal substrates according to the dimensions defined by ISO 9693 was Noritake, EX-3. Subsequently, after radiographic testing of the metal substrates of each group for the determination of the internal porosity, the three-point bending test was followed both for controlling the elastic modulus of the metal substrates and for controlling the metalloceramic bond, by means of a mechanical device (Ten-someter10, Monsanto, Akron, Ohio, USA). After the completion of the three-point bend test, to determine the type of failure of the metal-ceramic tests, the fractured specimens were tested in an optical stereomicroscope (Nickon Eclipse ME600, Japan) in magnification x5. For the elemental characterization of the type of metalloceramic bond failure, the fractured surfaces of the specimens were checked at the middle and at the edges in a SEM scanning electron microscope. The concept of cohesive failure type includes the presence on the broken surfaces of the components of the adhesive agent and the ceramic mass, while the concept of adhesive-type failure includes the retention of the metal substrate elements. For statistical processing, oneway ANOVA and Tukey's post-hoc were used where P <.05 is considered statistically significant.
Results
From the radiographic control of the metal substrates, the specimens prepared by the casting technique exhibit an internal microporous. The results of the three-point bending test for determining the metalloceramic bond strength did not show a statistically significant difference between the values of the groups. Testing of specimens in stereoscopic microscopy and electron microscopy showed that all specimens had a coherent type of failure.
Conclusions
The results showed that metal substrates construction techniques meet the 25 MPa metalloceramic bond tolerance limits defined in ISO 9693 and do not show a statistically significant difference in bond strength with a higher value for the casting technique. The type of failure for the techniques was of a coherent type.
Keywords:
Metal-ceramic bond strength, Co-Cr, Metal substrates, Casting, Soft milling, Milling, DMLS