MARGINAL FIT OF METAL CERAMIC AND METAL FREE CERAMIC CROWN

Date:

Share post:

ABSTRACT: 

An esthetically pleasing appearance of teeth is the best asset for a good smile. Ceramic restorations because of their natural translucency and tooth like color provide excellent esthetics and are virtually indistinguishable from the adjacent natural dentition. The absence of metal layer in all ceramic restorations helps in transmission of light through the full depth of the restoration there by enhancing the translucency creating a life like appearance. Depending upon the clinical demand, both all ceramic and porcelain fused to metal can be used for full veneer crowns. This study is performed to analyze the marginal fit of heat pressed all ceramic crowns and metal ceramic crowns. 

INTRODUCTION

 Full veneer ceramic crowns are very successful in covering the entire tooth; they can totally mask the previous condition to create a new appearance. Since then various types of metal-ceramic restorations have been developed with advancements being made in both the type of the metal and the porcelain for an effective metal ceramic bond. The porcelain fused metal restorations have a long proven record of success but the esthetic limitations like lack of metal translucency ,exposure of metal collar in the anterior region, paved way for all ceramic metal free restorations. Here ceramic substructure(ceramic core) is made by pressing the ceramic ingots into a refractory mold made by the lost wax technique.

Earlier studies have reported the marginal fit of all ceramic crowns to be inferior to that of the traditional metal ceramic crowns. But of late, the heat pressed ceramic restorations provide a better marginal fit because of the leucite reinforcement in them which imparts more strength to the core ceramic. This study is performed to analyze the marginal fit of the metal copings made by induction casting with that of the ceramic copings made by heat pressing and also assess the marginal fit occurring after porcelain application in both the groups. 

Metal-ceramic dental crowns:

Metal-ceramic dental crowns are the most commonly used crowns in the modern era. They have a frame that’s metallic and it is lined with ceramic. In comparison to plastic or metal  ceramic crown, are much more durable and aesthetic. They also possess a “natural transparency”.

But just like the proverbial fly in the ointment, metal-ceramic crowns have their own disadvantages.

They are insignificant, but do need to be mentioned. Over time, the tooth under a metal-ceramic crown undergoes decay and so, the average lifespan of such procedures is about five years. And when the gum sags over time, the metal edge of the crown becomes visible, which doesn’t look very aesthetically pleasing, especially when a person smiles. But if the dentist and the technicians involved perform the installation correctly and ensure that all requisite care is taken, then the crown could last a very long time and offer immense satisfaction to the patient with its attractive and fresh look/appearance

MATERIAL AND METHODS: 

 The accurate marginal fit of the metal ceramic and pressed ceramic jacket crowns over the prepared tooth. This study also involved to evaluate the distortion of metal and ceramic copings due to repeated heating during the processing procedure. A typhodont maxillary right central incisor was prepared for a jacket crown. Labial and axial reduction of 1.5 mm was made along with a 2 mm incisal reduction and an uniform shoulder of 1.5mm. The height of the preparation was 7mm with the convergence angle of 6°. 20 Impression of the prepared tooth were made in light body impression material, cast made with die stone.  The materials used are diestone, bellavest, addition silicone , inlay wax, ceramic ingots, and ceramic veneering. Equipment used are casting machine, ceramic furnace, vacuum mixer and sectioning machine. 

FABRICATION OF PRESSABLE CERAMIC COPINGS:

In this die spacer applied and thickness of 30-40 µm. Wax pattern of .7mm thickness and investing and burnout done as the routine procedure. And the pellet of pressable ceramic is placed in the mould, Multimat touch and press is used. 

MEASUREMENT OF INITIAL MARGINAL FIT OF THE COPINGS: 

Marginal fit was measured using the video measuring system. The measurements were made at the following 6 points around the circumference of the crowns. 1 point- mid facially, 1 point- mid palatally, 2-points on the mesial side, 2 points on the distal side. The mean of all the 6 values measured is the initial marginal fit of the coping. The measurement sites were marked for reproducible identification by scoring the die with a sharp blade. 

Porcelain build up on the metal coping by layering 

It is done by the layering technique after degassing the opaque porcelain, boy porcelain and finally glazing at the particular temperature as per the manufacture instruction . 

SECTIONING OF THE FINAL SAMPLES: 

The crowns were cemented to the dies with Zn PO4 cement using finger pressure. The samples were then sectioned faciolingually and mesiodistally using diamond sectioning saw, following the guide marks on the dies. There are 2 interfaces for each point if sectioning so measurement can be made at 8 points around the crown. Mean vertical and horizontal marginal discrepancies were calculated from the values obtained. 

LEAVE A REPLY

Please enter your comment!
Please enter your name here

spot_img

Related articles

Trends: Medical Doctor Immigration to New Zealand on the Rise

New Zealand (NZ) has been witnessing a notable surge in the immigration of medical doctors in recent years....

Innovations in Beadlock Rim Technology: What to Expect in 2024 and Beyond

Beadlock rims have long been essential for off-road enthusiasts and competitive racers, offering the security of keeping tires...

Angular in 2024: New Features and Enhancements

Introduction As one of the premier frameworks for building dynamic web applications, Angular continues to evolve, introducing new features...

Exciting Ideas for Going Out in Madison, Alabama

When it comes to going out in Madison, Alabama, the options are endless. Whether you're planning a night...