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

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On Sep 2018




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Prof. Somashekhar Nimbalkar
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Chairman, Research Group, Charutar Arogya Mandal, Karamsad
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Ex-Member, Governing Body, National Neonatology Forum, New Delhi
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Department of Pediatrics, Pramukhswami Medical College, Karamsad, Anand, Gujarat.
On Sep 2018




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"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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Sri Devaraj Urs Academy of Higher Education and Research , Kolar, Karnataka
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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.
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Professor and Head
Department of Pediatric Dentistry
Saraswati Dental College
Lucknow
On Sep 2018




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




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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 : 2023 | Month : January | Volume : 17 | Issue : 1 | Page : ZC36 - ZC39 Full Version

Translucency and Wear of Pressable Lithium Disilicate and Zirconia-reinforced Lithium Silicate Glass-ceramics: An In-vitro Study


Published: January 1, 2023 | DOI: https://doi.org/10.7860/JCDR/2023/56402.17353
Shruti S Potdukhe, Janani M Iyer, Jyoti B Nadgere

1. Lecturer, Department of Prosthodontics and Crown and Bridge, MGM Dental College, Navi Mumbai, Maharashtra, India. 2. Reader, Department of Prosthodontics and Crown and Bridge, MGM Dental College, Navi Mumbai, Maharashtra, India. 3. Professor and Head, Department of Prosthodontics and Crown and Bridge, MGM Dental College, Navi Mumbai, Maharashtra, India.

Correspondence Address :
Dr. Shruti S Potdukhe,
Lecturer, Department of Prosthodontics and Crown and Bridge, MGM Dental College, Navi Mumbai, Maharashtra, India.
E-mail: shrutipotdukhe@gmail.com

Abstract

Introduction: New ceramic materials have been introduced with less research on their aesthetic outcome and durability for clinical implications. Lithium disilicate is one of the widely used materials for restoration. Recently, Zirconia-reinforced Lithium Silicate (ZLS) glass-ceramic enriched with 10% zirconia in highly dispersed glass phase of ceramic has been introduced.

Aim: To investigate the translucency of pressable Lithium Disilicate (LS2) and ZLS and their effects on wear of opposing enamel.

Materials and Methods: This in-vitro study was carried out at MGM Dental College and Hospital, Mumbai, Maharashtra, India, between January 2017 and January 2020. Twenty disks of 15×3 mm; 10 each of LS2 and ZLS were fabricated by hot pressing method. For translucency Commission Internationale de l’Eclairage (CIE) L*a*b values for each sample were measured against black and white background using a laboratory reflectance spectrophotometer. Translucency was calculated using Translucency Parameter (TP)= {(L*B-L*W)2+(a*B-a*W)2+(b*B-b*W)2}1/2. For wear testing same 20 disks were used as an antagonist. Enamel specimen of 20 maxillary premolar were abraded against each antagonist with two body wear testing machine in rotational motion under a constant load of 20 N at 350 rpm for 5000 cycles. The initial readings and final readings of enamel specimen in μm were measured using contact stylus profilometer. Non parametric Mann-Whitney U test was used to compare the significance of difference between two groups.

Results: The TP values obtained were 23.07 and 24.04 for LS2 and ZLS, respectively (p-value=0.004). The mean wear values obtained were 0.71860 μm and 1.09500 μm for LS2 and ZLS, respectively (p-value=0.049). The difference for both the parameters was statistically significant.

Conclusion: Within the limitation of this study, ZLS showed higher translucency values than LS2. Wear rate of opposing enamel was more with ZLS than LS2. Thus ZLS may provide excellent aesthetics which can be used as an option for rehabilitation in aesthetic zone.

Keywords

Aesthetics, Optical, Rehabilitation, Spectrophotometer

To enhance aesthetic and functional demands of prosthetic restoration various materials have been developed. Metal-free restorations are emerging treatment option in fixed prosthodontics due to superior aesthetic properties and adequate mechanical properties over metal ceramic restorations (1). Lithium disilicate is one of the widely used materials for restoration (2). Before thermal conversion, Lithium disilicate is an amorphous glass matrix that converts into a crystalline material with about 70% of lithium disilicate orthorhombic crystal phase after heat treatment. Lithium disilicate provides good aesthetics but has limited mechanical properties (2).

Recently, Zirconia reinforced Lithium Silicate (ZLS) glass-ceramic enriched with 10% zirconia in highly dispersed glass phase of ceramic has been introduced (3). Removal of silicate molecule and addition of zirconia may enhance the strength of the material but may affect the optical properties and could be detrimental to the opposing to enamel leading to wear (3). ZLS glass-ceramic is a new glass-ceramic which shows combined mechanical characteristics of the zirconia and aesthetic property of glass-ceramic (3).

Translucency is one of the parameter for aesthetics, giving life like appearance to the restoration which is commonly measured by using the contrast ratio and Translucency Parameter (TP) (4). The Commission Internationale de l’Eclairage (CIE) L*a*b* is a nonlinear transformation of the tri stimulus space to agree with Munsell spacing and has been largely used to compare translucency among materials (5).

Wear is a complex phenomenon that occurs when two surfaces are brought into direct contact or indirect contact (6). Restorative dentistry strives to find a suitable and biocompatible alternative for hydroxyapatite so that the property of the material is similar to enamel, which will prevent damage to the opposing tooth structure. No sufficient literature was present on comparison of mechanical and optical properties of pressable lithium disilicate and zirconia-reinforced lithium silicate glass-ceramic. So this present in-vitro study was carried out. The purpose of this study was to evaluate and compare the translucency of pressable lithium disilicate and ZLS and their effect on wear of opposing to enamel giving the clinicians a better choice of material for the restorations which will be more aesthetic and less harmful to the opposing enamel. The null hypotheses were that no difference would be found in the translucency of pressable lithium disilicate and ZLS and their effects on wear of opposing enamel.

Material and Methods

This invitro study was carried out at MGM Dental College and Hospital, Mumbai, Maharashtra, India, between January 2017 and January 2020. Approval was obtained from Institutional Ethical Review Committee held on October 2017 (IERC-MGMDCH reference no.4l/2017 on 9/10/2017).

Inclusion criteria: Pressable lithium disilicate low translucency shade A2; pressable ZLS low translucency shade A2; twenty freshly extracted non carious, non restored, healthy premolars were included in the study.

Exclusion criteria: Ceramic material other than pressable ceramic; high translucency, medium translucency, medium opacity, high opacity of lithium disilicate and high translucency, medium translucency ZLS; other than shade A2 of lithium disilicate and ZLS; Incisors, canines and molars; any decayed, attrited, restored, fractured and desiccated teeth were excluded from the study.

Minimum sample size required for the study was twenty samples. Ten samples of Pressable lithium disilicate low translucency ingot shade A2 {IPS e.max Press (LT), Ivoclar, Vivadent} and ten samples of Pressable ZLS Low Translucency Ingot shade A2 {Celtra Press (LT), Dentsply, Sirona} with 95% confidence interval and 80% power. Sample size estimation was done using Epi software.

Fabrication of silicone laboratory putty mould: Silicone laboratory putty (Zeta plus, Zhermack) mould was fabricated by making an impression of a 15 mm diameter and 3 mm thickness metal disk for fabrication of 20 wax patterns (Renfert, Bego)

Fabrication of lithium disilicate samples and Zirconia reinforced Lithium Silicate (ZLS) samples: The wax patterns were sprued and mounted on the ring base such that the distance between the wax pattern and the silicone ring is atleast 10 mm (7). The phosphate bonded investment material (IPS Press VEST speed Investment material Ivoclar Vivadent) was used to invest the wax pattern. Burnout was done in preheating furnace at 850°C/1562°F temperature for 60 minutes (7). For pressable lithium disilicate (Low Translucency Ingot, shade A2; IPS Emax Press; Ivoclar Vivadent) the pressing was done at 910°C for 45 minutes and for pressable ZLS (Low Translucency ingot, shade A2; Celtra Press; Dentsply Sirona) the pressing was done at 865°C for 30 minutes (7). The pressed disk was then immersed in Invex liquid (IPS Press) containing 1% of hydrofluoric acid for five minutes to remove the reaction layer and then cleaned in an ultrasonic cleaner (8). The above lost wax and hot pressing method were used for fabrication of ten samples of pressable lithium disilicate and ten samples of pressable ZLS which were finished, polished and glazed.

Evaluation of translucency: A dual beam reflectance laboratory spectrophotometer (Agera) with specification of 0°/45°c (circumferential) ASTM E1164 with D65 illumination, was used for measuring the translucency of each samples (Table/Fig 1) (9),(10). The spectrophotometer was standardised against black tile and white tile for eight hours as per the specification given for Agera spectrophotometer. Each sample was placed in the centre of the port plate of size 15 mm in diameter. The portable clamp was then closed, so that it is in close contact with the sample. The even contact of the clamp with the sample was evaluated by inbuilt camera in spectrophotometer. By pressing the start button on the screen, the CIE L*a*b* coordinates of the sample were recorded, displayed and stored by the software (11),

where,

L: represents for lightness (colour coordinate ranges from 0 to 100);
a: represents greenness (positive axis) and redness (negative axis) (colour coordinate ranges from -90 to 70);
b: represents yellowness (positive b*) and blueness (negative b*) (colour coordinate ranges from -80 to 100).

Three readings were taken for each sample on each background and the mean CIE L*a*b* values were recorded for all the twenty samples, ten each of lithium disilicate and ZLS. Translucency was calculated using the TP by using following formula (11):

TP= {(L*B-L*W)2+(a*B-a*W)2+(b*B-b*W)2}1/2

Where,

‘B’ represents colour coordinates on the black background and
‘W’ represents colour coordinates on the white background.

Evaluation of wear of opposing enamel with lithium disilicate and Zirconia Reinforced Lithium Silicate (ZLS) samples: Twenty freshly extracted non carious, healthy, non restored maxillary premolars were selected as enamel specimens (12). The extracted tooth was cleaned; scaling was done and disinfected with 0.05% thymol (13). The entire premolar was then embedded on autopolymerising acrylic resin block of 10X10 mm and 30 mm thickness in the centre and leaving the entire crown structure uncovered with resin; with only buccal cusp undergoing wear testing (14). Before wear testing all samples of 15 mm diameter and 3 mm thickness were stored in distilled water at 37ºC for 24 hours (12). The cusp with resin block was held by holding device on the upper chamber of two body wear testing machine (Table/Fig 2). Every premolar buccal cusp was scanned using a surface profilometer with 20 μm resolution before subjected to wear test to get the initial reading (15). Each sample of 15X3 mm disk was placed in the lower chamber of two body wear testing machine. 5000 cycles of 20 N load was applied from the enamel cusp on to samples at 350 rpm in rotational motion by making a two body contact (16). For every tooth sample a new disk of lithium disilicate and ZLS samples were placed.

Measurement of wear depth by using profilometer: After wear testing the loss of enamel cusp was measured with the surface profilometer (Mitutoyo, Japan; Model: SJ 210). The profilometer consist of stylus profile tip with radius of 2 μm; Tip angle 60° with stylus speed of 0.5 mm/s, cut-off length of 1.25 mm and measuring force of 0.75 mN (17). The sample was fixed in the profilometer and the stylus on vertical arm was positioned on the non abraded portion of the buccal cusp of the premolar (14). The vertical deflection of the stylus was recorded (contact scanning) when premolar was moved horizontally over it. The profilometer connected to an x–y recorder, gives surface profiles of 20×29 magnification. At a parallel line with a distance of 0.1 mm in the mesiodistal direction from midline, the entire process was repeated for three times. The vertical substance loss was measured from the deepest point of the profile. Using the software Leica IM 50, the radius of wear area was directly measured at a 25X magnification (14). The volumetric wear depth was determined by the profilometric software and the difference between the final and initial wear depth determined the wear loss of enamel by the subsequent materials. Wear was calculated using profilometer as difference between final reading and initial reading (18).

Statistical Analysis

Microsoft Excel Spreadsheet was used for data compilation and statistical analysis was done using Statistical Package for the Social Sciences (SPSS) software version 20.0 (IBM, India). The normality of data was determined using Kolmogorov-Smirnov and Shapiro-Wilk test. Data was not meeting the condition of test of normality, so non parametric test was done. Mann-Whitney U test was done to compare the significance of difference between the average translucency and wear value of lithium disilicate group and ZLS group. The value obtained for Mann-Whitney U test for translucency was 12.000 and p-value obtained for Mann-Whitney U test was <0.05 indicates statistically significant difference between two groups.

Results

The TP and wear was evaluated for ten samples of lithium disilicate and ten samples of ZLS and a mean was generated for both parameters (Table/Fig 3).

The TP values obtained were 23.07 and 24.04 for lithium disilicate and ZLS, respectively. The mean wear values obtained were 0.71860 μm and 1.09500 μm for lithium disilicate and ZLS, respectively. The difference in the TP and wear for lithium disilicate and ZLS was statistically significant (p-value=0.004 and p-value=0.049, respectively).

Discussion

Glass-ceramics have been used in aesthetic dentistry due to better mechanical properties and improved aesthetics (1),(18). Approximately, 70% of lithium disilicate crystals of 3-6 μm, embedded in a glassy matrix forms the microstructure of IPS Emax Press. They have improved mechanical properties and optical features, higher than the older glass-ceramics. ZLS is a new glass-ceramics contains lithium silicate (mean size of 0.5-1 μm) which are six times smaller than lithium disilicate crystals as the main crystalline phase in a vitreous matrix reinforced with 10% of zirconium dioxide crystals (19). The mechanical properties of the material are enhanced by presence of 10% zirconium dioxide crystals in the microstructure. Zirconia particles hinder the crystal growth formation and helps in formation of a smaller and finer crystalline phase (19). These new zirconium-reinforced lithium silicate materials provide good optical properties as Compared to the traditional glass-ceramic due to presence of high amount of glass matrix (19).

It was proven that IPS Emax Press has better mechanical properties and optical properties compared to IPS Empress II and pressable lithium disilicate exhibits better mechanical properties compared to the Emax Computer-aided Design (CAD) (20),(21).

Translucency is one of the important parameter for aesthetic purpose indicates the amount of light transmission or diffuse reflection from a substrate through a turbid medium (22). A study carried out by Barizon KT et al., suggested that either constrast ratio or TP can be used to evaluate the relative translucency of ceramic (5). Hence, in the present study, TP was used to measure the translucency. To determine the influence of ceramic thickness on the definitive shade of ceramic restorations, black and white backgrounds have been used. The colour difference of specimens on a black and white background gives TP (23). Hence, in this study white and black backgrounds were used to measure the translucency.

Karamouzos A et al., carried out an in-vivo study to evaluate the precision of a reflectance spectrophotometer during longitudinal assessment of tooth colour and suggested that the repeatability and reproducibility of intraoral spectrophotometric measurements was affected (24). Hence, in this study the Agera® reflectance spectrophotometer which is a contact, full spectrum, balanced Light-emitting Diode (LED) 360-700 nm illumination with Ultraviolet (UV) control, having black and white standardisation tool for error free measurements laboratory spectrophotometer was used (12),(16).

The edge loss phenomenon, occurs when light is scattered to the edges without being reflected, is one of the factor resulting in loss of accuracy in colour measurement. The edge loss was decreased by increasing the window size of the spectrophotometer. The dimension of 15X3 mm was used in accordance to the requirement by the equipments. Translucency is influenced by the thickness of the material so each specimen was measured three times and means were compared (10).

The present study compared the translucency of pressable lithium disilicate and pressable ZLS and observed that the translucency of pressable ZLS was significantly more than that of pressable lithium disilicate which was in accordance to the study done by Sen N and Us YO (25). The difference in translucency between the materials was due to the difference in grain size and crystalline structure. After crystallisation, the crystals of Zirconia-reinforced glass-ceramic had a mean grain size of 500 to 700 nm which were 4-8 times smaller than lithium disilicate crystallites in lithium disilicate ceramic (26),(27). Thus, the better TP values for ZLS were thought to be due to smaller silicate crystals in the lithium silicate glassy matrix with high glass content.

A study carried out by Lawson NC et al., suggested that wear rate was more for glazed porcelain than polished porcelain (28). Hence, in this present study polished and glazed samples were used for wear testing. Sripetchdanond J and Leevailoj C conducted a study using pin-on-disk two body wear tester and the results were statistically significant (29). Hence, this study was carried out using two body wear testing machine which works in rotational motion with 20 N load, 350 rpm and 5000 cycles (30). The wear testing was calculated using a contact stylus profilometer as it has greater acceptance, surface independence, resolution, direct technique, not sensitive to surface reflectance and colour (31). A study carried out by Zandparsa R et al., compared the wear of ceramic systems against human enamel and concluded that all ceramic systems showed higher durability and better wear resistance and no differences were found in the linear and volumetric reduction of enamel cusps abraded against enamel disks and other ceramic specimens (11).

The present study compared the effect of wear on opposing enamel by pressable lithium disilicate and ZLS and observed that there was a significant difference in the wear depth of enamel after wear testing. The present study concluded that the wear of opposing enamel against ZLS was significantly more than that with lithium disilicate.

Limitation(s)

The limitations of this study were that it was a laboratory study, certain errors can occur while fabrication of the samples by hot pressing method such as the temperature difference, amount of polishing and glazing of the samples. Some of the clinical factors like type of the luting cement which could influence the translucency perception of the restoration were not taken into consideration.

Conclusion

Pressable ZLS showed higher translucency values than lithium disilicate thus may provide excellent aesthetic which can be used as an option for rehabilitation in aesthetic zone. Wear was more with pressable ZLS than lithium disilicate which can be used as an option for rehabilitation in the posterior region where the masticatory loads are minimal as in the area of non functional cusp and minimum contact with the functional cusp. However, further in-vivo studies need to be carried out to evaluate the translucency and wear resistance measuring patient satisfaction and longevity of both materials.

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DOI and Others

DOI: 10.7860/JCDR/2023/56402.17353

Date of Submission: Mar 15, 2022
Date of Peer Review: Apr 20, 2022
Date of Acceptance: Aug 18, 2022
Date of Publishing: Jan 01, 2023

AUTHOR DECLARATION:
• Financial or Other Competing Interests: None
• Was Ethics Committee Approval obtained for this study? Yes
• 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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