Journal of Clinical and Diagnostic Research, ISSN - 0973 - 709X

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Dr Mohan Z Mani

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On Sep 2018




Prof. Somashekhar Nimbalkar

"Over the last few years, we have published our research regularly in Journal of Clinical and Diagnostic Research. Having published in more than 20 high impact journals over the last five years including several high impact ones and reviewing articles for even more journals across my fields of interest, we value our published work in JCDR for their high standards in publishing scientific articles. The ease of submission, the rapid reviews in under a month, the high quality of their reviewers and keen attention to the final process of proofs and publication, ensure that there are no mistakes in the final article. We have been asked clarifications on several occasions and have been happy to provide them and it exemplifies the commitment to quality of the team at JCDR."



Prof. Somashekhar Nimbalkar
Head, Department of Pediatrics, Pramukhswami Medical College, Karamsad
Chairman, Research Group, Charutar Arogya Mandal, Karamsad
National Joint Coordinator - Advanced IAP NNF NRP Program
Ex-Member, Governing Body, National Neonatology Forum, New Delhi
Ex-President - National Neonatology Forum Gujarat State Chapter
Department of Pediatrics, Pramukhswami Medical College, Karamsad, Anand, Gujarat.
On Sep 2018




Dr. Kalyani R

"Journal of Clinical and Diagnostic Research is at present a well-known Indian originated scientific journal which started with a humble beginning. I have been associated with this journal since many years. I appreciate the Editor, Dr. Hemant Jain, for his constant effort in bringing up this journal to the present status right from the scratch. The journal is multidisciplinary. It encourages in publishing the scientific articles from postgraduates and also the beginners who start their career. At the same time the journal also caters for the high quality articles from specialty and super-specialty researchers. Hence it provides a platform for the scientist and researchers to publish. The other aspect of it is, the readers get the information regarding the most recent developments in science which can be used for teaching, research, treating patients and to some extent take preventive measures against certain diseases. The journal is contributing immensely to the society at national and international level."



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Professor and Head
Department of Pathology
Sri Devaraj Urs Medical College
Sri Devaraj Urs Academy of Higher Education and Research , Kolar, Karnataka
On Sep 2018




Dr. Saumya Navit

"As a peer-reviewed journal, the Journal of Clinical and Diagnostic Research provides an opportunity to researchers, scientists and budding professionals to explore the developments in the field of medicine and dentistry and their varied specialities, thus extending our view on biological diversities of living species in relation to medicine.
‘Knowledge is treasure of a wise man.’ The free access of this journal provides an immense scope of learning for the both the old and the young in field of medicine and dentistry as well. The multidisciplinary nature of the journal makes it a better platform to absorb all that is being researched and developed. The publication process is systematic and professional. Online submission, publication and peer reviewing makes it a user-friendly journal.
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Dr Saumya Navit
Professor and Head
Department of Pediatric Dentistry
Saraswati Dental College
Lucknow
On Sep 2018




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Their prompt and timely response to review's query and the manner in which they have set the reviewing process helps in extracting the best possible scientific writings for publication.
It's a honour and pride to be a part of the JCDR team. My very best wishes to JCDR and hope it will sparkle up above the sky as a high indexed journal in near future."



Dr. Arunava Biswas
MD, DM (Clinical Pharmacology)
Assistant Professor
Department of Pharmacology
Calcutta National Medical College & Hospital , Kolkata




Dr. C.S. Ramesh Babu
" Journal of Clinical and Diagnostic Research (JCDR) is a multi-specialty medical and dental journal publishing high quality research articles in almost all branches of medicine. The quality of printing of figures and tables is excellent and comparable to any International journal. An added advantage is nominal publication charges and monthly issue of the journal and more chances of an article being accepted for publication. Moreover being a multi-specialty journal an article concerning a particular specialty has a wider reach of readers of other related specialties also. As an author and reviewer for several years I find this Journal most suitable and highly recommend this Journal."
Best regards,
C.S. Ramesh Babu,
Associate Professor of Anatomy,
Muzaffarnagar Medical College,
Muzaffarnagar.
On Aug 2018




Dr. Arundhathi. S
"Journal of Clinical and Diagnostic Research (JCDR) is a reputed peer reviewed journal and is constantly involved in publishing high quality research articles related to medicine. Its been a great pleasure to be associated with this esteemed journal as a reviewer and as an author for a couple of years. The editorial board consists of many dedicated and reputed experts as its members and they are doing an appreciable work in guiding budding researchers. JCDR is doing a commendable job in scientific research by promoting excellent quality research & review articles and case reports & series. The reviewers provide appropriate suggestions that improve the quality of articles. I strongly recommend my fraternity to encourage JCDR by contributing their valuable research work in this widely accepted, user friendly journal. I hope my collaboration with JCDR will continue for a long time".



Dr. Arundhathi. S
MBBS, MD (Pathology),
Sanjay Gandhi institute of trauma and orthopedics,
Bengaluru.
On Aug 2018




Dr. Mamta Gupta,
"It gives me great pleasure to be associated with JCDR, since last 2-3 years. Since then I have authored, co-authored and reviewed about 25 articles in JCDR. I thank JCDR for giving me an opportunity to improve my own skills as an author and a reviewer.
It 's a multispecialty journal, publishing high quality articles. It gives a platform to the authors to publish their research work which can be available for everyone across the globe to read. The best thing about JCDR is that the full articles of all medical specialties are available as pdf/html for reading free of cost or without institutional subscription, which is not there for other journals. For those who have problem in writing manuscript or do statistical work, JCDR comes for their rescue.
The journal has a monthly publication and the articles are published quite fast. In time compared to other journals. The on-line first publication is also a great advantage and facility to review one's own articles before going to print. The response to any query and permission if required, is quite fast; this is quite commendable. I have a very good experience about seeking quick permission for quoting a photograph (Fig.) from a JCDR article for my chapter authored in an E book. I never thought it would be so easy. No hassles.
Reviewing articles is no less a pain staking process and requires in depth perception, knowledge about the topic for review. It requires time and concentration, yet I enjoy doing it. The JCDR website especially for the reviewers is quite user friendly. My suggestions for improving the journal is, more strict review process, so that only high quality articles are published. I find a a good number of articles in Obst. Gynae, hence, a new journal for this specialty titled JCDR-OG can be started. May be a bimonthly or quarterly publication to begin with. Only selected articles should find a place in it.
An yearly reward for the best article authored can also incentivize the authors. Though the process of finding the best article will be not be very easy. I do not know how reviewing process can be improved. If an article is being reviewed by two reviewers, then opinion of one can be communicated to the other or the final opinion of the editor can be communicated to the reviewer if requested for. This will help one’s reviewing skills.
My best wishes to Dr. Hemant Jain and all the editorial staff of JCDR for their untiring efforts to bring out this journal. I strongly recommend medical fraternity to publish their valuable research work in this esteemed journal, JCDR".



Dr. Mamta Gupta
Consultant
(Ex HOD Obs &Gynae, Hindu Rao Hospital and associated NDMC Medical College, Delhi)
Aug 2018




Dr. Rajendra Kumar Ghritlaharey

"I wish to thank Dr. Hemant Jain, Editor-in-Chief Journal of Clinical and Diagnostic Research (JCDR), for asking me to write up few words.
Writing is the representation of language in a textual medium i e; into the words and sentences on paper. Quality medical manuscript writing in particular, demands not only a high-quality research, but also requires accurate and concise communication of findings and conclusions, with adherence to particular journal guidelines. In medical field whether working in teaching, private, or in corporate institution, everyone wants to excel in his / her own field and get recognised by making manuscripts publication.


Authors are the souls of any journal, and deserve much respect. To publish a journal manuscripts are needed from authors. Authors have a great responsibility for producing facts of their work in terms of number and results truthfully and an individual honesty is expected from authors in this regards. Both ways its true "No authors-No manuscripts-No journals" and "No journals–No manuscripts–No authors". Reviewing a manuscript is also a very responsible and important task of any peer-reviewed journal and to be taken seriously. It needs knowledge on the subject, sincerity, honesty and determination. Although the process of reviewing a manuscript is a time consuming task butit is expected to give one's best remarks within the time frame of the journal.
Salient features of the JCDR: It is a biomedical, multidisciplinary (including all medical and dental specialities), e-journal, with wide scope and extensive author support. At the same time, a free text of manuscript is available in HTML and PDF format. There is fast growing authorship and readership with JCDR as this can be judged by the number of articles published in it i e; in Feb 2007 of its first issue, it contained 5 articles only, and now in its recent volume published in April 2011, it contained 67 manuscripts. This e-journal is fulfilling the commitments and objectives sincerely, (as stated by Editor-in-chief in his preface to first edition) i e; to encourage physicians through the internet, especially from the developing countries who witness a spectrum of disease and acquire a wealth of knowledge to publish their experiences to benefit the medical community in patients care. I also feel that many of us have work of substance, newer ideas, adequate clinical materials but poor in medical writing and hesitation to submit the work and need help. JCDR provides authors help in this regards.
Timely publication of journal: Publication of manuscripts and bringing out the issue in time is one of the positive aspects of JCDR and is possible with strong support team in terms of peer reviewers, proof reading, language check, computer operators, etc. This is one of the great reasons for authors to submit their work with JCDR. Another best part of JCDR is "Online first Publications" facilities available for the authors. This facility not only provides the prompt publications of the manuscripts but at the same time also early availability of the manuscripts for the readers.
Indexation and online availability: Indexation transforms the journal in some sense from its local ownership to the worldwide professional community and to the public.JCDR is indexed with Embase & EMbiology, Google Scholar, Index Copernicus, Chemical Abstracts Service, Journal seek Database, Indian Science Abstracts, to name few of them. Manuscriptspublished in JCDR are available on major search engines ie; google, yahoo, msn.
In the era of fast growing newer technologies, and in computer and internet friendly environment the manuscripts preparation, submission, review, revision, etc and all can be done and checked with a click from all corer of the world, at any time. Of course there is always a scope for improvement in every field and none is perfect. To progress, one needs to identify the areas of one's weakness and to strengthen them.
It is well said that "happy beginning is half done" and it fits perfectly with JCDR. It has grown considerably and I feel it has already grown up from its infancy to adolescence, achieving the status of standard online e-journal form Indian continent since its inception in Feb 2007. This had been made possible due to the efforts and the hard work put in it. The way the JCDR is improving with every new volume, with good quality original manuscripts, makes it a quality journal for readers. I must thank and congratulate Dr Hemant Jain, Editor-in-Chief JCDR and his team for their sincere efforts, dedication, and determination for making JCDR a fast growing journal.
Every one of us: authors, reviewers, editors, and publisher are responsible for enhancing the stature of the journal. I wish for a great success for JCDR."



Thanking you
With sincere regards
Dr. Rajendra Kumar Ghritlaharey, M.S., M. Ch., FAIS
Associate Professor,
Department of Paediatric Surgery, Gandhi Medical College & Associated
Kamla Nehru & Hamidia Hospitals Bhopal, Madhya Pradesh 462 001 (India)
E-mail: drrajendrak1@rediffmail.com
On May 11,2011




Dr. Shankar P.R.

"On looking back through my Gmail archives after being requested by the journal to write a short editorial about my experiences of publishing with the Journal of Clinical and Diagnostic Research (JCDR), I came across an e-mail from Dr. Hemant Jain, Editor, in March 2007, which introduced the new electronic journal. The main features of the journal which were outlined in the e-mail were extensive author support, cash rewards, the peer review process, and other salient features of the journal.
Over a span of over four years, we (I and my colleagues) have published around 25 articles in the journal. In this editorial, I plan to briefly discuss my experiences of publishing with JCDR and the strengths of the journal and to finally address the areas for improvement.
My experiences of publishing with JCDR: Overall, my experiences of publishing withJCDR have been positive. The best point about the journal is that it responds to queries from the author. This may seem to be simple and not too much to ask for, but unfortunately, many journals in the subcontinent and from many developing countries do not respond or they respond with a long delay to the queries from the authors 1. The reasons could be many, including lack of optimal secretarial and other support. Another problem with many journals is the slowness of the review process. Editorial processing and peer review can take anywhere between a year to two years with some journals. Also, some journals do not keep the contributors informed about the progress of the review process. Due to the long review process, the articles can lose their relevance and topicality. A major benefit with JCDR is the timeliness and promptness of its response. In Dr Jain's e-mail which was sent to me in 2007, before the introduction of the Pre-publishing system, he had stated that he had received my submission and that he would get back to me within seven days and he did!
Most of the manuscripts are published within 3 to 4 months of their submission if they are found to be suitable after the review process. JCDR is published bimonthly and the accepted articles were usually published in the next issue. Recently, due to the increased volume of the submissions, the review process has become slower and it ?? Section can take from 4 to 6 months for the articles to be reviewed. The journal has an extensive author support system and it has recently introduced a paid expedited review process. The journal also mentions the average time for processing the manuscript under different submission systems - regular submission and expedited review.
Strengths of the journal: The journal has an online first facility in which the accepted manuscripts may be published on the website before being included in a regular issue of the journal. This cuts down the time between their acceptance and the publication. The journal is indexed in many databases, though not in PubMed. The editorial board should now take steps to index the journal in PubMed. The journal has a system of notifying readers through e-mail when a new issue is released. Also, the articles are available in both the HTML and the PDF formats. I especially like the new and colorful page format of the journal. Also, the access statistics of the articles are available. The prepublication and the manuscript tracking system are also helpful for the authors.
Areas for improvement: In certain cases, I felt that the peer review process of the manuscripts was not up to international standards and that it should be strengthened. Also, the number of manuscripts in an issue is high and it may be difficult for readers to go through all of them. The journal can consider tightening of the peer review process and increasing the quality standards for the acceptance of the manuscripts. I faced occasional problems with the online manuscript submission (Pre-publishing) system, which have to be addressed.
Overall, the publishing process with JCDR has been smooth, quick and relatively hassle free and I can recommend other authors to consider the journal as an outlet for their work."



Dr. P. Ravi Shankar
KIST Medical College, P.O. Box 14142, Kathmandu, Nepal.
E-mail: ravi.dr.shankar@gmail.com
On April 2011
Anuradha

Dear team JCDR, I would like to thank you for the very professional and polite service provided by everyone at JCDR. While i have been in the field of writing and editing for sometime, this has been my first attempt in publishing a scientific paper.Thank you for hand-holding me through the process.


Dr. Anuradha
E-mail: anuradha2nittur@gmail.com
On Jan 2020

Important Notice

Original article / research
Year : 2022 | Month : June | Volume : 16 | Issue : 6 | Page : ZC01 - ZC07 Full Version

Evaluation of Hardness and Fracture Toughness of Feldspathic Porcelain by Various Surface Finishing Techniques


Published: June 1, 2022 | DOI: https://doi.org/10.7860/JCDR/2022/53002.16469
Khalid Ghiaz, Vasanthakumar, Deepak Kamalanathan, T Anjan Kumar, R Akhila, Hariharan Ramakrishnan, NS Azhagarasan

1. Professor and Head, Department of Prosthodontics, Priyadarshini Dental College and Hospital, Chennai, Tamil Nadu, India. 2. Professor Emeritus, Department of Prosthodontics, Ragas Dental College and Hospital, Chennai, Tamil Nadu, India. 3. Reader, Department of Prosthodontics, Chettinad Dental College and Hospital, Chennai, Tamil Nadu, India. 4. Lecturer, Department of Prosthodontics, Priyadarshini Dental College and Hospital, Chennai, Tamil Nadu, India. 5. Consultant Prosthodontist, Private Practice, Chennai, Tamil Nadu, India. 6. Professor, Department of Prosthodontics, Ragas Dental College and Hospital, Chennai, Tamil Nadu, India. 7. Professor and Head, Department of Prosthodontics, Ragas Dental College and Hospital, Chennai, Tamil Nadu, India.

Correspondence Address :
Hariharan Ramakrishnan,
Ragas Dental College and Hospital, East Coast Road, Uthandi, Chennai-600119, Tamil Nadu, India.
E-mail: abcv2005@yahoo.com

Abstract

Introduction: Dental porcelain is fired at a high temperature inside the furnace and subsequently glazed for intraoral use as a restoration. There is no clarity on the correlation between physical properties of porcelain and its surface finishing techniques.

Aim: To evaluate surface hardness and fracture toughness of feldspathic porcelain with different porcelain surface finishing methods.

Materials and Methods: This in-vitro descriptive study was conducted between November 2018 and August 2019 at Department of Prosthodontics, Ragas Dental College and Hospital with 40 samples of Nickel Chrome (Ni Cr) alloy specimens, with addition of porcelain. The sample were divided into four groups S1: Unpolished, S2: Polished, S3: Autoglazed, S4: Add-on glaze according to the finishing procedures used with each group containing ten samples. All samples were tested for surface hardness and Fracture toughness and were subjected to One way ANOVA, Bonferroni posthoc tests and Statistical Package of the Social Sciences (SPSS) California, USA.

Results: Mean value of fracture toughness (in MPa1/2) for 0.2 kg load was 0.729672 for S1, 1.187567 for S2, 0.89482 for S3, 1.324399 for S4. Mean value of surface hardness (in kg/mm2) for 1 kg load was 360.048 for S1, 519.166 for S2, 508.817 for S3, 527.916 for S4. Maximum deviation of 24.752 and error of 7.8273 was found in S4, least deviation of 10.77 and error of 3.4077 was found in S1 group.

Conclusion: The glazed porcelain had the highest micro hardness and fracture toughness followed by polished porcelain and autoglazed porcelain.

Keywords

Dental casting technique, Dental polishing, Dental porcelain, Hardness test, Porcelain metal alloys

Porcelain is widely used in dental practice as material of choice for an individual jacket crown, fixed long span restorations. Effective finishing and polishing of dental restorations provide three benefits of dental care: oral health, function, and esthetics (1). Main advantages of porcelain include biocompatibility, natural appearance and high resistance to wear and chemical inertness. refractive nature, hardness, susceptibility to clinical fracture and chemical inertness (2).

Disadvantages of porcelain include brittleness, lesser edge strength, high hardness resulting in more impact to the opposing teeth during mastication and abrasion of enamel of the natural opposing and adjacent teeth. The finishing and polishing of porcelain restorations are considered as an essential procedure for the final fit (2),(3),(4). Some authors have concluded that finishing and polishing of porcelain restoration is considered satisfactory with usage of conventional polishing systems such as polishing cups, disks and with porcelain polishing pastes (5),(6). However, the usual method of producing the surface gloss is by the application of glazes on the surface of porcelain (4).

Porcelain which is used as metal ceramic restorative material should have adequate strength, hardness, formable to the required shape, biocompatible, resistant to the oral environment, abrasive resistance and should be able to obtain the required colour and translucency (7),(8). For dental application hardness of ceramic, similar to that of enamel is desirable to minimize the wear of the resulting ceramic restoration and reduce the wear damage that can be produced on enamel by the ceramic restoration (8),(9).

It is also considered that the surface flaws induced at the time of surface finish leads to brittleness and reduces the flexural strength, micro hardness and thereby reducing the fracture toughness values. However it is mandatory and essential that high surface finish with an increase in esthetic value is achieved by the method of polishing and glazing (8),(10).

Considering these facts at the background, this study was conducted with the aim to evaluate two important physical properties namely micro hardness and fracture toughness and their relation to various methods of finishing and polishing such as conventional usage of polishing materials on porcelain, glazing with vitreous materials and also auto glazing. Objectives of the study included intra group comparison and inter group comparison of microhardness and fracture hardness of feldspathic porcelain following four different polishing techniques, and identification of the viable and acceptable polishing method.

Material and Methods

This in-vitro descriptive study was conducted between November 2018 and August 2019 at Department of Prosthodontics, Ragas Dental College and Hospital. A sample size of 60 was included in the present study.

Inclusion and Exclusion criteria: The inclusion criteria included uniformly fired casting samples without any distortion, uniformly fired opaque porcelain samples, uniformly fired dentin ceramic samples. Inadequately fired porcelain samples, inadequately polished porcelain samples requiring repolishing were excluded. Twenty samples were discarded from study based on the exclusion criteria through visual inspection. Finally, forty samples were considered and selected and they were further divided into four groups of ten samples each.

Study Procedure

The preparation of specimens for testing and for conducting the study of metal ceramic were made in two stages. The first stage in the preparation of the specimens was the making of the alloy substructure. The second stage was fusion of porcelain to the alloy structure, so the entire unit comprised of porcelain fused to alloy structure, as the final specimen to test the important physical properties.

The Ni Cr alloy samples were made from acrylic resin pattern. A stainless steel die was prepared for the fabrication of resin specimens of equal size and shape of the metal substructure. Sample preparation was done as per American Society for Testing and Materials (ASTM), specifications for materials (11). These acrylic patterns have a better dimensional stability than the wax pattern (11). The dimensions of the patterns were 40 mm length and 10 mm width at one end. Thus a total of 60 resin patterns were fabricated.

Each of the acrylic patterns were attached to a standardized wax sprue former of 5 mm length and diameter of 2.5 mm. The sprue was attached at the narrow portion of each acrylic pattern. Thus group of 10 resin patterns were taken up and sprue formers were attached to each one of the resin pattern at one time for casting purpose. In each group 10 patterns were arranged in circular configuration and all the samples were connected to a conical form to which a crucible former was attached. The crucible former assembled with the sprues with the resin patterns were attached to the casting ring with 100 mm height and 3.5 inch diameter. The patterns were sprayed with debubblizer to improve the wetting of the patterns.

This whole assembly of 10 such sprued plastic patterns were invested in graphite free phosphate bonded precision investment material, Heravest universal N (Heraeus kulzer, Germany) . The ring was preheated and held at the final temperature for 50 minutes for complete burn out. The burnout ring was kept in the induction casting machine and adjusted for alignment with the preheated crucible held in the casting machine. The alloy pellets were kept in the crucible and the weights were balanced. The casting temperature of the alloy was adjusted at 1500C (11). Once the alloy had melted the lever was released to cast the metal in the mold.

The casting ring was allowed to cool to room temperature and divested. The sprues were severed and nodules removed. All the casting specimen were trimmed and finished with a thickness of 2 mm. Ten samples were obtained from each casting. Likewise six castings were made in a phased manner to produce a total of 60 samples made with nickel chromium alloy (Table/Fig 1). The samples were coded for ease of identification. The specimens were held under vacuum for two minutes at 960°C. With temperature increase of 70°C per minute according to the manufacturer instructions to form oxide layer.

A custom mold was fabricated with clear methyl methacrylate. It consisted of a slot of 40 mm × 10 mm × 2 mm, which would facilitate the uniformity in the porcelain buildup. The working end of the metal samples, were grounded to 1 cm×0.5 mm and made to fit into the slot. When metal specimens were placed in the slot a uniform space of 2 mm remained in the slot between the top of the mold and metal and in the test site alone the metal was 0.5 mm (Table/Fig 2). Porcelain powders were to be mixed with the modular liquid and filled in the mold. The mold was then placed on the mechanical vibrator and the porcelain condensed. A glass slab was placed on the mold surface to make the porcelain surface smooth and of uniform thickness.

Specimens were trimmed flush at the top of the mold with a glass slab, which would give the approximate uniform thickness to all the porcelain samples. The thickness was further measured with the micrometer for the uniformity in all samples at nine points and the thickness of ceramic was totally 1.5 mm for all the forty samples and were divided into four groups of ten each as UP-unpolished, P-polished, AG-autoglazed, G-glazed.

The porcelain bearing surface of the alloy specimen was air abraded to simulate standard laboratory procedure. Further all the samples were steam cleaned to remove any surface impurities small amount of opaque porcelain paste was mixed with the special liquid. It was applied on the metal surface with the ceramic brush. Wash opaque was painted on the metal as a thin coating; no attempt was made to completely mask the metal. After firing the wash opaque a second layer of opaque was applied to completely mask the metal. The specimen was gently vibrated to evenly spread the paste. The second firing too was done as per manufacturers instructions. The thickness of opaque layer was found to be 0.3 mm after two firings (Table/Fig 3). The same procedure was follow for the application of opaque layer on all the forty alloy specimens. Following this,dentin porcelain was added and all the 40 specimens and were fired according to the manufacturer's instructions. Total thickness of sample was 2.0 mm (0.5 metal+0.3 opaque+0.8 dentine+0.4 enamel) (Table/Fig 4), (Table/Fig 5), (Table/Fig 6).

Among the 40 specimens , ten specimens were taken for the study group coded as S1:UP unpolished, Ten specimens were taken and coded as S2: P, were polished with conventional polishing system to produce glossy appearance on the surface, by using finishing and polishing kit (Shofu,USA), and diamond polishing paste and finally they were all steam cleansed. Third group of 10 specimens, S3 were taken for study group coded as AG was given a surface finish with auto glazing according to the manufacturer recommended autoglazing firing temperature. The fourth, group of specimens of 10 members, S4 was coded as G and glazing was done by applying add on glazing material and were fired according to the manufacturer's recommended glazing temperature.

Study Parameters

Hardness was measured by indentation method. Hardness was indicated though Vicker’s Hardness Number (VHN) Kg/mm2. In Vicker's hardness test, two different loads of 0.2 kg and 1 kg was used. Diamond in the shape of a square pyramid is used as the indentor. The method of analysis of VHN is the load, divided by the area of indentation. The indentation was square in shape. The length of the diagonals of the indentation (sides of the diamond) are measured and averaged. Vicker’s test is used for brittle materials but not suitable for elastic materials (9),(10),(11),(12),(13),(14).

Fracture toughness or the critical stress intensity is a mechanical property that describes the ability of a material containing crack to resist further propagation and is given in the units of stress times the square root of crack length is MPa.m1/2, Klc - 0.16 ha2 c3/2, where Klc -fracture toughness, h-hardness value, a-radius of impression, c-height of the crack (12),(13),(14),(15),(16).

Statistical Analysis

Statistical analysis was done using One way ANOVA and Posthoc Bonferroni tests (IBM SPSS, Los Angeles, California). A value of p<0.05 was considered significant.

Results

Values of micro hardness in kg/m2 of porcelain, tested under 0.2 kg load, that have been finished using various techniques within the samples tested for S1,mean was 475.064.For S2 group, mean was 662.54.Within the samples tested for S3, mean was 641.224.Within the samples tested for S4, mean was 668.069.

The values of fracture toughness for 0.2 kg load are shown in (Table/Fig 8). The fracture toughness has been shown in Mpa1/2”. The fracture toughness in S1 with a mean value was 0.729672, fracture toughness in S2 ,with mean value was 1.187567. fracture toughness in S3 with a mean value was 0.894827. fracture toughness in S4 with the mean value was 1.324399.

Values of micro hardness of porcelain, tested under 1 kg load that have been finished using various techniques are shown in (Table/Fig 9). Within the samples tested for S1, mean was 360.048. Within the samples tested for S2, mean was 519.166. Within the samples tested for S3, mean was 508.817. Within the samples tested for S4, mean was 527.916.

The values of fracture toughness of porcelain for I kg load. The mean value for S1 was 0.553014 was shown in (Table/Fig 10). Fracture toughness in S2 mean value was 0.930577. In S3 the mean value was 0.710053. in S4 mean value was 1.046556.

There were significant differences in values of surface hardness and fracture toughness between these four groups (p<0.05) (Table/Fig 11). There were significant differences in values of surface hardness and fracture toughness between these four groups (Table/Fig 12).

Intergroup comparison of microhardness and fracture toughness between the four groups at 0.2 kg load has been presented n (Table/Fig 13). When S1 (unpolished) was compared with the rest, it was found to have a significant mean difference with all the other groups. The values of mean difference were all in negative, proving that this group is significantly inferior to the rest. When S2 (polished) was compared with the rest of the groups, it was found to be significantly superior to S1. It's difference with the rest of the groups was not significant. When S3 (autoglazed) was compared with the rest of the groups, it was found to be significantly superior to S1, and significantly inferior to S4. It's difference with S2 was not significant. When S4 (glazed) was compared with the rest of the groups, it was found to be significantly superior to S1 and S3. It's difference with the S2 was not significant.

Intergroup comparison of microhardness and fracture toughness between the four groups at 1 kg load has been presented in (Table/Fig 14). For fracture toughness when S1(unpolished) was compared with the rest, it was found to have a significant difference with all the other groups. When S2 (polished) was compared with the rest of the groups, it was found to be superior to S1. It’s difference with the rest of the groups was insignificant. When S3 (autoglazed) was compared with the rest of the groups, it was found to be significantly superior to S1, and significantly inferior to S4. It's difference with S2 was not significant. When S4 (glazed) was compared with the rest of the groups, it was found to be significantly superior to S1 and S3. It's difference with the S2 was not significant.

Discussion

The outcome of the present study indicated preferential use of glazed porcelain over other types of polishing techniques for porcelain.

Analyzing the results of hardness value obtained showed that glazed material could be considered harder than that of conventional polishing. Anusaivice also mentioned that autoglazed (or) self glazed medium fusing feldspathic porcelain is much stronger than ground and rough, non glazed porcelain (11). If the material was unpolished or if the glaze, was removed by grinding, the hardness and fracture toughness was 25-35% less than that of the porcelain with the glaze layer intact. The glaze is effective in decreasing the crack propagation which in the outer surface because the surface flaws may be bridged and the surface will be under a state of comprehensive stress (11).

Results of this study indicated that porcelain with conventional highly polished surface with Shofu ceramic polishing kit and diamond polishing paste (S2), have comparably higher values of 519.166 as hardness and 0.930577 as fracture toughness value than that of the autoglazed shown in a value of 508.817 as hardness and 0.710053 as fracture toughness under 1 kg load. It is assumed that both type of glazing whether self (or) autoglazing produces smoother surface than any mechanical polishing agents (or) technique. In the case of self glazing a minimum fitted surface could arise due to the mismatch in the thermal coefficient of expansion as surface silica particles a higher temperature flows more than that of inner core of silica. In such conditions if the glaze has lower coefficient of thermal expansion than that of the body porcelain it will be put under compressive stress on cooling. On such occasion tensile stress develop and the tendency is to develop crazing on the surface of the self glaze. Crazing is apparently shown as micro cracks or through conventional mechanical polishing flaws which would expose such cracks. This observation is of clinical importance because after the porcelain fused metal prosthesis is cemented in the mouth, it is a common practice for the operator to adjust the occlusion by grinding the surface of the porcelain with diamond burs and polishing it with a polishing kit (11),(12),(13),(14).

Deleterious effects of the rough and ground porcelain includes increased susceptibility for fracture due to propagation of microcracks, increase in wear of opposing restoration and/or tooth and discoloration due to more plaque accumulation. Increased wear of opposing teeth, loss of vertical dimension and interceptive contacts due to unglazed porcelain teeth induces traumatic occlusion in complete denture (15),(16),(17),(18). Additional firing for glazing may have a deleterious effect on the porcelain itself like devitrification. Moreover, reglazing is more time consuming as the chair side time, transportation, and laboratory time are involved. Grinding process removes glazed superficial surface. Ideally, it is advised to be re-glazed to get the smooth surface (19),(20),(21),(22),(23),(24),(25).

In a previous study, different polishing kits used reduced the average roughness by approximately 77% (20). It was concluded that corrected porcelain surfaces should ideally be reglazed, alternatively, polish the surfaces before final cementation .this study and the current study had utilized Shofu kit for polishing, but hardness and fracture toughness was not included in their study. Sethi S et al., explained that Polishing of feldspathic porcelain surface will lead to a finish similar to a reglazed surface. Therefore chairside polishing can be a good alternative to reglazing for finishing adjusted porcelain surface (26). Manjuran NG et al., concluded that polishing with feldspathic porcelain adjustment kit followed by diamond particle impregnated wax, created surfaces significantly smoother than the glazed specimens (27). Rani V et al., elaborated the fact that after adjustment of ceramic restorations in dental clinics, diamond polishing paste, when used after porcelain adjustment kit, could provide the marked finish equal to glazed or reglazed surface (28). Kalia P et al., concluded abraded specimens of feldspathic ,after polishing using pearl finish polishing paste and soflex disc became smoother than glazed specimens (29). Facts and conclusions derived from these studies are different from current study. This could be attributed due to difference in brands of feldspathic porcelains and their composition used, operator style of polishing. comparison of previous studies had been done in (Table/Fig 15) (20),(26),(27),(28),(29).

Limitation(s)

This study included interpretation of only two mechanical properties of porcelain following finishing methods. More properties including ultimate tensile strength and ductility should be included in future studies. Only one type of porcelain and alloy was used in this study. artificial saliva was not used in this study to simulate clinical situation.

Conclusion

Within the limitations of the study, it can be concluded that glazed porcelain exhibited significant and highest micro-hardness and fracture toughness when compared with other finishing and polishing techniques. Polished porcelain exhibited significant and lesser values for microhardness and fracture toughness, than glazed porcelain and was second best. Glazed porcelain should be used whenever possible for porcelain fused to metal, for fixed single and multiple anterior and posterior long span restorations for greater durability and clinical longevity.

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DOI and Others

DOI: 10.7860/JCDR/2022/53002.16469

Date of Submission: Oct 26, 2021
Date of Peer Review: Jan 07, 2022
Date of Acceptance: Mar 29, 2022
Date of Publishing: Jun 01, 2022

AUTHOR DECLARATION:
• Financial or Other Competing Interests: None
• Was Ethics Committee Approval obtained for this study? NA
• Was informed consent obtained from the subjects involved in the study? NA
• For any images presented appropriate consent has been obtained from the subjects. NA

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