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Compare the Translucency of Zirconia Based Ceramics with Different Core and Veneer Thickness Combination: An In Vitro Study

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TO COMPARE THE TRANSLUCENCY OF ZIRCONIA BASED

CERAMICS WITH DIFFERENT CORE AND VENEER

THICKNESS COMBINATION – AN IN VITRO

STUDY

A Di ss ertat ion su bm itted to

THE TAMIL NADU DR.M.G.R. ME DICAL UNI VERS ITY

CHENNAI - 600032

In parti al fulfil men t for the degree of MASTE R O F DENT AL SURGE RY

BRANCH – I

DE PART MENT O F PROSTHO DO NTICS & CRO WN AND B RIDGE

2016 – 2019

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CERTIFICATE

This is to certify that the Dissertation entitled “TO CO MPARE

THE TRANSLUCE NCY O F ZIRCO NI A B ASED CERAMI CS WITH DI FFERE NT CORE AND VE NEER TH ICKNESS CO MBI NATIO N – AN I N VI TRO STUDY" b y Dr.KARTH ICK P. A P ost Graduat e st udent MDS P rosthodontics & Crown And Bridge, M adha Dent al C ollege &

Hospital-C hennai – 69 Submitt ed to The Tam ilnadu Dr. M.G.R . Medi cal Universit y the M DS Degree Examination April 2019 is

bonafi de research work carried out b y him under m y supervision and guidance

Guid ed B y

Dr. SH ARMIL A H USSAIN, M.D.S .,Ph .D Professor and Head

Departm ent of P rost hodonti cs and C rown and Bridge Madha Dent al Coll ege & Hospit al, Chennai - 600 069

MADH A DE NT AL COLLE GE AND H OSPITAL

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CERTIFICATE - II PLAGIARISM

This is to certi f y that this dis sertation work ti tled

"TO COMPARE T HE T RANSLUCE NCY O F ZIRCONIA BASE D

CERAMICS WIT H DIFF E RENT CORE AND VENEE R

THICKNESS CO MBINAT ION - AN IN VI TRO ST UDY" of the

candi dat e Dr.KART HICK P.A wit h R egi strati on Number 241611502

for the award of ……… in the branch of Prosthodontics

& Crown and Bridge. I personall y veri fi ed the urkund.com websi te for the purpos e of pl agi ari sm Check. I found that the upl oaded t hesi s fi le

contai ns from i ntroducti on to conclusion pages and res ult shows 2%

percentage of pl agiarism in the diss ertat ion.

Guide & Supervi sor si gn wit h S eal .

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ENDORSEMENT BY HEAD OF THE DEPARTMENT

/ HEAD OF THE INSTITUTION

This is t o cert if y that the Diss ert ati on entitl ed “TO

COMPARE THE TRANSLUCENCY O F ZI RCO NI A B ASE D

CERAMICS WIT H DIFFE RENT CORE AND VENEE R

THICKNESS COMBINAT ION – AN IN VI TRO STUDY” is a

bonafi de work done b y Dr. KARTHICK P A, Post Graduate student

(2016 -2019) i n t he Departm ent of P rost hodonti cs & C rown and Bridge,

under the guidance of Dr. SHARMI LA HUSS AIN, MDS, Ph.D.,

Professor, Departm ent of Prosthodonti cs & C rown and Bridge, M adha Dental Col lege and Hospital, C hennai – 600 069.

Dr. SHARMILA HUSSAIN, MDS, Ph.D., Professor, Head and guide

Department of Prosthodontics

& Crown and Bridge

Madha Dental College & Hospital,

Chennai – 600 069

Dr. M.C.SAINATH, MDS, MBA., PGDCR. Principal

Madha Demtal College & Hospital,

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DECLARATION OF THE CANDIDATE

I, Dr. KARTHICK P A hereb y decl are that t his di ss ert at ion

titled “TO COMPARE THE TRANSLUCE NCY O F ZIRCO NI A

BASED CE RAMI CS WITH DIFFE RENT CORE AND VENE ER THICKNESS COMBINAT ION – AN IN VI TRO ST UDY” is a bonafide

and genuine res earch work carried out b y me under t he guidance of

Dr.SHARMILA HUSSAIN, MDS, PhD. Professor & Head, Department of P ros thodonti cs & Crown and Bridge, Madha Dental Col lege and Hospital, C hennai -600069.

Dr.KARTHI CK. P.A Post Graduat e S tudent

Departm ent of P rost hodonti cs & Crown and Bridge,

Madha Dent al Coll ege and Hospi tal , Kundrat hur, Chennai.

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TRIPARTITE AGREEMENT

This agreement herein after the “Agreement” is entered into 9th of Februar y 2019 between the Madha Dental C oll ege and Hospit al

repres ent ed b y it s Prin cipal having address at M adha Dent al Coll ege

and Hospit al , Chenna i-69, (hereaft er referred to as , ‘the col lege’)

And Dr. SH ARMIL A HUSS AIN M .D.S , Ph .D aged 46 years worki ng as Profes sor and HOD at t he College, having residence address at 7F, Rear block, S ai s uboda ya apartment , 66, ECR Thi ruvanmi yur , Chennai -600041, Tamilnadu (Herein after referred to as the ‘Principal Author’)

And Dr.KARTHI CK. P. A aged 28 years currentl y stud ying as post graduat e s tudent in Departm ent of Prost hodonti cs & C rown and Bridge i n Madha Dental C oll ege and Hospit al (Herein after referred t o as the ‘PG/Research student and Co - Author’).

Whereas the ‘PG/Research student as part of his curriculum undertakes

to res earch "TO CO MPARE THE T RANSLUCENCY O F ZIRCO NI A

BASED CE RAMI CS WITH DI FFE RENT CORE AND VENE ER THICKNESS CO MBINAT ION - AN I N VI TR O STUDY" for whi ch purpos e t he PG/P ri ncipal author s hall act as principal aut hor and t he coll ege shall provi de t he requisit e infrastruct ure based on avail abi lit y and also provide facilit y t o t he P G/R esearch st udent as t o the extent possi ble as a C o -Aut hor.

Whereas t he parti es , b y t his agreem ent have m utuall y agreed t o the various i ssues including i n parti cul ar t he cop yri ght and confidenti alit y issues t hat ari se in t his regard.

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Now thi s agreem ent witness es as foll ows:

1. The parties agree t hat all the R esearch m ateri al and ownershi p therein shall becom e the vested ri ght of the coll ege, incl uding i n parti cul ar all t he cop yri ght in the lit erat ure i ncludi ng t he stud y, research and all othe r rel at ed papers.

2. To the ext ent that the coll ege has legal ri ght t o do go, shal l grant to licens e or assi gn the cop yri ght do vest ed with it for m edi cal and/or comm ercial usage of int erest ed persons/entiti es subject to a reasonable terms/ conditions i ncl u ding ro yalt y as deemed b y the coll ege.

3. The ro yalt y so received b y the coll ege shal l be shared equal l y b y all the parti es

4. The PG/R es earch st udent and P G/Pri nci pal Aut hor shall under no circumst ances deal with the cop yri ght , Confi denti al inform ation and know – how generat ed duri ng t he course of research/st ud y in an y manner whats oever, whil e shall sol e vest wit h t he m anner whats oever and for an y purpose without t he express writ ten consent of the coll ege. 5. All expens es pert aini ng to t he research shal l be deci ded upon b y the princi pal investi gat or/Co -Author or borne s ol e b y t he P G/res earch student (C o-Aut hor).

6. The coll ege shal l provide all infras tructure and access facilit ies withi n and i n other inst itut es to the extent poss ibl e. This includes pati ent i nt eractions, int roductor y l ett ers, recomm endation l ett ers and such ot her acts requi red in thi s regard.

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9. If an y disput e ari ses as to the m att ers rel at ed or connect ed to t his agreem ent herein, it shal l be referred to arbit rat ion i n accordance wit h the provi sions of t he Arbit ration and C oncili ation Act , 1996.

In wi t ness wher eof t he par t i es herei nabo ve ment i oned ha ve on t hi s t he

day mont h and year he r ei n abo ve ment i oned set t hei r hands t o t hi s agree ment

i n t he presence of t he f ol l owi ng t wo wi t ness es.

Col l ege represent ed b y i t s

Prin cipal PG Stud en t

Witn ess es Studen t Guid e

1.

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ACKNOWLEDGEMENT

I offer m y fervent pra yers and grat itude t o Almi ght y God for the

bles sings s howered on m e and gui ding through ever y st ep.

I, woul d li ke to extend m y s incere grat itude and t hanks to our

bel oved C hai rm an - Dr. Li on. S. Peter, Managi ng Di rect or - Mr. Ajay

Ravind ra Ku mar and Vice Chairperson - Mrs . P. Mercy Floren ce

Peter of M adha Dental Coll ege and Hospit al, Kundrat hur, Chennai -69 for their cont inuous support, help and encouragem ent duri ng m y

post graduation to accom plish m y academ ic carri er.

I ex press m y humble gratit ude, sinceri t y and respect to m y

est eemed profess or Dr.M.C.Sainath M. D.S, Pri nci pal, Madha Dent al

College & hospital , kundrathur, C hennai. I am thankful to hi m for his

guidance, const ructi ve criti cism, pati ent hearing and m oral support throughout m y post graduat e cours e and without whi ch this proj ect woul d not have been possi ble.

I would like to express m y sincere gratit ude towards m y

profess or and guide, Dr. Sharmil a Hussain, M. D.S, PhD., H ead of t he

departm ent , Depart ment o f P rost hodontics , a great t eacher who has

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val uable guidance i n all m y endeavou rs, bringing out the best in m y work. I thank her, for her rel entl ess support and dedicati on.

M y sincere thanks t o Dr. Gajend ran, M D, Dean, M adha M edical

College, C hairm an of ethical commit tee for approving m y thesis to be conduct ed.

M y si ncere thanks to Dr. Kamatchi K, M DS, R eader ,

Dr. Krishnameera N M DS, Reader and Dr. Prathyusha K MDS .,

Reader, Depart ment of P rosthodonti cs, M adha dental col lege and hospi tal , for t heir inval uable guidance and s ugges tions throughout this proj ect.

I rem ain thankful to Dr. Su ji D, MDS, S eni or Lecturer,

Dr.Fai z Mohammed tanveer MDS, Senior Lect urer, Dr.Sou mo Ghoshal, M DS, Senior Lecturer, Dr.Praveen Peru mal , M DS, S enior

Lecturer , Dr. Vi jay Krishna K, BDS Lecturer and Dr. Sin dhu , BDS

Lecturer , Depart m ent of prosthodontics, M adha dent al college and hospi tal for thei r constan t support and academi c i nputs.

I am extremel y thankful t o m y co pos t graduat e Dr. Aarthy P and

seni ors Dr.A.Rames h, and Dr.K.B.Prak ash J uniors Dr. M. Raja Chi tra

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I ex pres s m y profound sens e of gratitude t o m y Fat her Dr.P.As okan and m y m other Mrs. C.Indu mathy and m y brot her

Mr.P.A.S ath eesh B abu for t hei r encouragem ent , love, great s a cri fi ces, innate confidence, without which I wouldn’t have been where I am

toda y. I am eternall y grat eful to them for all that the y have done for me.

Words are inadequat e to m enti on t he support , encouragem ent and

inspi ration from m y wife, Dr. K.M.S Ragha vi BDS ., who i s ever yt hi ng

to m e.

I am extrem el y fort unate to have an ever encouraging sm il e of

m y Son A.K.Kavin, which const antl y e ncouraged m e to succes sfull y

com plet e this work.

Finall y I woul d like to thank ever ybod y who was import ant to the success ful realiz ation of t his dissert ation and I si ncerel y apologiz e

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ABSTRACT

TO PIC O F THE S TUDY: TO CO MPARE THE T RANS LUCE NCY O F ZI RCO NI A B ASED CERAMICS WITH DI FFERE NT CO RE AND VENEE R T HICKNESS COMB INAT ION – AN I N VI TR O

STUDY

Objectives

* To stud y the i nfluence of core & veneer t hi cknes s on the transl ucenc y of zirconia bas ed cerami cs.

* To stud y the effect of core & veneer t hicknes s on col or m at ching of

zirconi a bas ed ceram ics.

Materi als and Meth ods :

In thi s stud y a t ot al of 45 zi rconi a dis c specim en (n=15) were fabri cat ed wit h di fferent core and veneer thickness and eval uat ed the

transl ucenc y of zirconi a di sc, with vit a eas y shade s pect rophotom et er. To st ud y the trans lucenc y of these zi rconia dis c on stained t eeth with

different t est sol ution , six groups of t est sol ution was us ed. The need for great er t ransluce nc y or m aski ng abili t y was id enti fi ed accordi ng to the thi cknes s of t he core foundation m aterial .

Results : The transl ucenc y of t he restoration is best when t here i s a

minimum t hickness of (0.5mm+1.00mm ) core and veneer i s used. The col or m asking abil it y of t he zi rconi a disc is superi or for Orange II test

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Con clusion : The t ranslucenc y of zi rconi a cerami cs i s det ermined b y the speci fi c mi crost ruct ure of the m at eri al. For an overall restorati on

thickness of 1.5mm , the change in t he thi ckness of zirconia based cerami c veneer is a major fact or i n det ermining the translucenc y of the

restoration.

The opti cal propert y of zirconi a restorations helps cli ni cians to achi eve bet ter estheti c t han wit h m et al -ceram ic res torat i ons . Thi s

opti cal propert y of t he restoration m ateri al is compromi sed when us ed for met al post and core, a dis col ored substrat e, or a tit anium implant

abutment, to avoid this com promised esthetic sit uati on the zirconi a coping or a suffi cient veneered porcel a in can be us ed.

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TABLE OF CONTENT

S.No TITLE Page No

1. INTRODUCTI ON 1

2. AI M & OBJE CTI VES 6

3. REVIE W O F LITE RAT URE 7

4. MATE RI ALS AND METHO D S 24

5. RESULT S 37

6. DISCUSSIO N 41

7. SUMMARY 56

8. CONCLUS ION 57

9. BIBILIO GRAPHY 58

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LIST OF FIGURES

Figu re No TITLE

1. Dis c s amples

2. Groupi ng of s ampl e disc

3. Stainl es s st eel m old

4. Rhodamine B Test solution

5. Alizarin Red Test solution

6. Orange II Test s oluti on

7. Stained teet h

8.

Readings obtained from s pect rophot om eter for

sample in tested solution

9. VITA Eas y shade spectrophotom et er

10. Anal ysi s of t eeth

11.

Reading Obt ained from spect rophotom et er for

core specim en

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LIST OF TABLES

Table No TITLE

1. Shows ∆E value of three thickness groups of

zirconi a disc

2. Mean and standard deviation of the ∆E value

and t ransl ucenc y param et er of three groups of

zirconi a disc wi th di fferent t hickness

3. Compari son bet ween all t hree groups of

zirconi a disc wi th di fferent t hickness

4. Mean and st andard deviati on of all groups of

test sol ution among t he three groups of di sc

5. Comparison of ∆E values of all six groups of

test sol ution among t he three groups of di sc

6. Compari son tran slucenc y param et er for t he six

groups of t est sol uti on among the three groups of dis cs

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LIST OF CHARTS

CHART NO TITLE

1. Chart represents m ean and st andard deviation of zirconia core dis c wit h di fferent thi cknes s com bination

2. Chart represents t he core t ranslucenc y for six groups of

test sol ution in three groups

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LIST OF ABBREVATION

CIE - Int ernational Commi ssion on Il luminati on

Co Cr - Cobalt chromi um

LV - La yered Veneering

DV - Di git al Veneeri ng

OV - Overpress ed Veneeri ng

+ve - Positive

-v e - Negat ive

% - Percent age

> - Greater than

< - less than

CAD/CAM - Comput er-aided desi gn & Computer -aided m anufact uri ng

CR - Contras t rati o

MPa - Mega pascal s

TP - Transl ucenc y P aram eter

SR - Spectroradiom et ric

Y2O3 - Yttrium h ydroxide

Mg-PS Z - Zirconia m agnesi a

TZP - Titanium st abiliz ed Zirconia Porcel ain

g - Gram

mg - Milli gram

ml - Millilit er

mm - Millim eter

p-valu e - Probabi lit y value

sig - Signi ficant

NS - Non Si gni fi cant

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Introduction

1

INTRODUCTION

The face and the t eeth are the most im port ant indi vidual charact eri sti c of a man, and the t eeth along with its hard and soft

tissue com ponents contribut es to two t hi rds of faci al st ructure. The dentist should creat e, preserve and enhance the sm il e of the pati ent without impai ring i ts funct ion. There are s everal factors whi ch

det ermine the dental est heti cs , among which t he primar y fact ors are the translucenc y of t he core and the sel ection of materi als.

The fi rst priorit y for pati ents s eeki ng prosthodontic t reatm ent

is the estheti cs . The appearance of the maxillar y anterior t eeth i s more im port ant for faci al and dent al est heti cs , the dent al es theti cs in turn depends on t he t ransl ucenc y of the t eet h, nat ural col or of t he

teeth and optim al hard and soft ti ssue relationshi p whi ch should be

in harmon y with the faci al appearance( 1 )

Shade s el ection i s one of t he m ost im port ant crit eria for a restoration especi all y in restoring a anterior teet h. All cerami c

crowns offer the best pos sibl e opti on when compared t o other mat eri al for a dis colored toot h to m aintain its est hetic, functi on,

durabi lit y and l ongevit y of t he restoration. ( 2 ) Final s hade of an

estheti c restoration depends on several factors such as translucenc y, opacit y, shade of t he porcel ain, the com bination of ceramic la yers,

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Introduction

2

The restoration of ant erior and post eri or teet h are bett er alt ered with zi rconia -bas ed rest orati ons, due to t hei r superior

mechani cal properti es and excell ent esthetics . ( 3 )

A zi rconi a copi ng provi des hi gh strengt h, whi le a veneering

porcel ain creat es a natural appearance for t hes e restorati ons. ( 4 )

Addit ionall y, a zirconi a coping m ani fests a nonmet all ic margin

becaus e of the natural whi te color of zi rconia bas ed cerami c. ( 5 , 6 )

A 1-mm -t hick zirconia cerami c as a coping m at eri al dem onst rates an approximatel y. 37% visible li ght t ransmit tance, and

therefore zi rconi a cerami c is call ed a s emi translucent mat eri al .( 7 )

This opti cal propert y of zi rconi a res torations helps cli ni ci ans t o

achi eve bett er esthetic resul ts t han with met al -cerami c

restorations.( 8 ) In patient s with hi gh estheti c dem ands, t he ceram ic

with good ph ys ical and opti cal properti es is the m at eri al of choi ce whi ch matches t he nat ural dentiti on. The t ypi cal thi cknes s of no

preparati on veneers is st at ed to be 0.3mm, a mi nim all y invasi ve soluti on for cert ain estheti c s ituations . The m anufacturer have

introduced t he new cerami c s yst ems in dentist r y, whi ch has improved m echani cal and t ranslucent propert y compared wi th the

conventional fel dspathic porcelai ns . ( 9 )

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Introduction

3

Compared to ot her mat eri al s, all cerami c veneers have bet ter estheti cs . Studies have shown that t he opacit y of core specimens

enhances the est het i cs of the restoration. Therefore, t he opaci t y can be increas ed b y i ncreasi ng t he specim en thi ckness , increasi ng the

struct ure of the veneering porcel ai n, refl ect ance at t he interface bet ween the core and the veneering porcelai n, the pres ence of porositi es between t he l a yers and an y changes in the constituents of

the core m at erial wit h additi onal fi ring cycl es.

To achi eve the optim al est hetics, t he t rans lucenc y of t he core and veneer s ys tem pla ys t he maj or rol e. The cerami c t ransl ucenc y can be affect ed b y t hickness of the core, core cr ys talline st ruct ure

and the num ber of fi rings. The pres ence of reduce d cr ystalli ne struct ure and the refracti ve index of t he cr yst als whi ch i s cl ose to

that of the matrix wi ll cause less s catt eri ng of t he li ght. Leucite and lithium di sili cate have refractive indi ces cl os e t o that of the porcel ain m atrix. The color repli cati on process of dent al porcelai n

consists of t wo phases nam el y shade s el ect ion phase and shade dupli cation phase.

The thi ckness of the Core required for the lit hium dis ilicat e restoration reinforced wi th ceramic s hould be 0.8 m m and the

veneering materi al s hould be as thin as 0.7 mm. The IPS e m ax cerami c veneering m at eri al consists of m icro fl uorapat ite and nano

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Introduction

4

It is hi ghl y translucent due t o it s opti cal com pati bilit y pres ent bet ween t he gl ass y mat rix and t he cr yst alline p hase. Thi s mi nimizes

the int ernal s catt ering of the li ght as it passes t hrough it . The oxides of Zirconium are us uall y added as t he opaci fiers . The var yi ng color

differences bet ween the groups and the var yi ng shade reproducti on among them are res ulted from the addit ion of thes e opacifi ers i n different percent ages .

The translucenc y, color, outl ine form and the surface are the

important factors which have to be considered whil e dealing wit h the patient s ati sfacti on for an est het ic restoration. There are s ome disadvant ages wi th porcelai n fused to m etal restor ations such as the

chi pping of veneering cerami c, exposure of the m et al, and t he lack of t ransl ucenc y, s om e m et als t hat are us ed for the restorations have

the abilit y t o promote carci nogenic acti vit y. ( 1 0 ) Thes e met als are

known to cause “graying” in the g ingival margin that reduces their

usage. (1 1 ) Evolution of all ceramic m at erial is a boon to the field of

cosm eti c dentist r y. ( 1 2 )

Heat press ed ceram i c res torati ons are us ed for the fabri cation of fram eworks on vit al as well as for t he discolored tooth or even as a tit anium abutm ent to have bett er esthetic res ults . The good

estheti c res ult of heat pressed cerami c res toration i s due to its color rendering and opti cal properti es whi ch could sim ulate t he nat ural

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Introduction

5

biocompati bilit y, s trength, and surface texture. The heat press ed cerami c restorat ion yi el ds an appearance of a vi tal tooth b y

providi ng the rest oration whi ch could perm it the li ght t rans mission to the underl yi ng tooth st ructure, b y mi nimizing gi ngi val

shadow.( 1 3 )

However, predomi nantl y t he core m ateri al contribut es for the

col or of an all cerami c restoration. Lifelike restorations are

fabri cat ed b y m as ki ng the substructure b y using opaque cores.( 1 4 )

Hence, it coul d be presum ed that the shade of the st ained t ooth is masked b y di fferent opaciti es of the core of al l cerami c s ys t em. In this stud y the thi ckness of the veneer and core and its influence on

the t ransl ucenc y of zirconi a bas ed ceram ics was i nvesti gat ed. Further the effect of core thickness on t he color m aski ng abilit y of

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Aim and Objectives

6

AIM AND OBJECTIVES

Ai m:

To stud y the effect of veneer thicknes s of zirconia bas ed

cerami cs on t rans lucenc y.

Objectives :

 To st ud y the influence of core & veneer thi ckness on the

transl ucenc y of zirconia bas ed cerami cs .

 To st ud y the effect of core & veneer thickness on co lor

masking abilit y of zi rconi a based cerami cs.

Scop e of study:

The need for greater translucenc y or m as king abili t y shoul d be identi fi ed accordi ng t o the shade of the remai ning tooth st ruct ure

or the core foundation materi al. With the int roduction of new cerami c s yst ems , clini ci ans m ust becom e famili ar wit h the transl ucenc y of di fferent porcel ain s ys tems to ens ure the choice of

an appropri ate rest oration m at eri al .

Null Hypothesis : The t hickness and the t ranslucenc y of zi rconi a bas ed ceramics is not affect ed b y core or veneer thi ckness.

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Review of Literature

7

REVIEW OF LITERATURE

Zircon has been known as a gem si nce anci ent tim es. The name zirconium comes from the Arabic “Zargun” (golden in color) which in turn comes from the two Persian words “Zar” (Gold) and

“Gun” (Color). Zirconia is a crystalline dioxide of zirconium. In

1776, porcel ain m aki ng was the topi c of a revi ew paper gi ven at the Academ y of S ci ences in P aris. In 1770 another apot hecar y, worki ng

with porcel ai n form ulati ons and then hi gh t echnology kilns of the Guehard Porcelai n Factor y, the y succeeded b y 1774 i n fabricati ng a

com plet e dent ure for Duchat eau. In 1808 anot her Parisi an denti st, Gius eppangelo Fonzi, si gni fi cantl y i m proved the versatil it y of cerami cs b y firing individual denture teeth, each cont ai ning a

plati num pi n. This invention all owed t eeth to be fixed to m etal fram eworks enabling: (1) partial dent ure fabri cation (2) reparabili t y and (3) i ncreased aestheti cs . Pl atinum had onl y been known to

Europeans si nce around 1741 and given its extrem el y hi gh melti ng point (1769 ֯C) was generall y onl y worked i nto sm all w ires and

crucibl es b y hamm eri ng indivi dual red -hot nuggets. One m ajor advance i n porcelain itself cam e in 1962 with the developm ent of a formul ation that could be fi red on com mon dent al cas ting allo ys .

This i nventi on built on a paper publis hed in t he J ourn al of t he Ameri can C erami cs Soci et y (JACS) dem onst rating an oddit y in the

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8

due to the form ation of a new cr yst all ine component not in the ori ginal rock, called leucit e Due to an i ncreasing i nt erest i n

estheti cs and concerns about toxi c and allergi c reactions t o cert ain allo ys , pati ents and dentists have been looking f or m et alfree tooth

-col ored rest orati ons.

Therefore, t he devel opm ent of new hi gh strength dental

cerami cs, whi ch appear to be less brittl e, l ess limit ed in t hei r tens ile strength, and less subj ect to tim e dependent st res s fail ure, has

dominat ed i n the lat er part of 20th cent ur y. Thes e capabiliti es are hi ghl y att racti ve i n pros theti c dentis tr y, where st rengt h and estheti cs are of paramount import ance.

Quant if yi ng t he color of t eeth is highl y diffi cult according to

the aestheti c aspect s . Color perception vari es from person t o person and is hi ghl y subjective and it depends on indivi dual variation. Modern cerami c s ys t ems rel y on rel ativel y opaque core m aterials to

provide st rengt h. M an y s yst em s have overl yi ng veneer porcelai ns for est hetic s, but t he core mat eri al cont ributes t o t he overal l color

of t he res torati on, as well as its t rans lucenc y.

To utilize t he favorabl e qualit ies of cerami c m at eri al , a new technique was developed, the “porcelain press technique.” Using

this simpl i fi ed suppl ement ar y t echni que in whi ch al umina

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9

com press ed in t he furnace, an y t ype of i nla y, crown or bridge (fixed parti al denture), can be reproduced enhanci ng the qualiti es , dense,

strength and accurac y. S everal res earchers developed di fferent techni ques t o achi eve the m aximum est heti cs b y producing

difference i n t ransl ucenc y of core and veneer. There are li mit ed data avail abl e on t he t ranslucenc y of t he shaded zi rconi a cores.

The estheti c out come of all ceram ic res torat ions can be affected b y the cli nical sit uati on and Laborator y factors . The

clini cal s ituation such as color s cal e, s ource of li ght during the tim e of color eval uation, charact eri sti c of t he core m at erial , color of the adj acent teet h, t ype of luti ng cem ent us ed and pres ence of t he root

post are s ome of the clini cal situati ons that could affect the es theti c out com e of t he all ceram ic rest orati ons.

The l aborator y factors such as t emperat ure duri ng t he fabri cation, thicknes s of the di sc, ceramic condens ation, and the

number of firing c ycl es also det erm ine color of all cerami c restoration. The opaque core will suffici entl y m as k the subs t ructure

and enabl e the fabrication of li felike restorations. Therefore, it could be h ypothesiz ed that di fferent opaciti es of the core of all cerami c s ys t em m as k the color of st ained tooth.

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10

The t ypical thi cknes s of no preparati on veneers is st ated t o be 0.3mm , a m inim all y invasive solution for certain est hetic sit uations.

New ceram ic s ys t ems, for whi ch the m anufacturers cl aim transl ucent properti es comparable wi th felds pathi c porcel ains al ong

with improved m echanical resi stance have been i ntroduced in dentist r y.

The tooth specimen was divided into t hree areas: e nam el, out er dent in (j ust i nside the dentinoenam el juncti on), and inner

dentin (j ust lat eral t o the pul p chamber). Three points without li ght refl ection were chosen in each area for color evaluation. Subs equent l y, the i mage of the t ooth s pecim en was trans f ormed t o

derive a s et of numerical values i n t erm s of t he Int ernational Commissi on on Il lumination (C IE) Lab s ys tem wi th image

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Review of Literature

11

Mi cheal et al (2002) ( 1 5 ) eval uat ed the contrast rati o from lum inous refl ectance b y pl acing the specim en on a bl ack and white

background and obtained Yb/Yw value under C IE ill uminant D6 5 on

2-degree obs erver function. In t his st ud y the y fabricat ed Core

specim ens of Empress denti n, Empress 2 dentin, In ceram al umina, Inceram spi nel l, In Ceram Zi rconia and Procera All ceram compared with veneered vitadur Alpha opaque dent in, a cl ear gl ass dis c and a

hi gh nobl e m et al cerami c allo y veneered with vit adur omega dentin. Resul t obt ained in this stud y shown decreas e opacit y of all

mat eri al s ot her t han in zirco ni a and metal cerami c specimens.

Yunlong Zhan g et al (2004) ( 1 6 ) Thi s stud y was t o access the

infl uence of powder/liquid mixing ratio on poros i t y and

transl ucenc y of dent al porcel ains . Duceram LFC dentin, Duceram

LFC incis al , IPS Eris dent in & IPS Eris incis al porcelai ns were studi ed. The appearent densit y of each specim en were m easured using Archim edes method and the porosit y cal cul at ed, each

specim ens was coupl ed to standard ceram ic ti les us ing an imm ersion liquid and the color shade was meas ured in C IE Y x y coordinates

using a t ris timul us col orim et er, Trans lucenc y was ass ess ed b y calculating t he contrast rati o of shade value in front of bl ack versus whit e backgrounds. The powder/li quid ratio di d not s i gni fi cantl y

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Alvin G. Wee et al (2005) ( 1 7 ) This stud y was evaluated that the col or formul ation and reproducti on of opaque dent al cerami c A t ot al

of 25 opaque felds pathi c dent al cerami c speci mens were fabricat ed b y mixing s ix di fferent shades i n different concent rations. The

refl ectance spect ra were m easured and the act ual C IE LAB coordi nates were obtained. The CA LAB and C AK/S method were used to predi ct t he L*A*B* values with reference t o the

concent ration of t he pur e shade, bot h m et hods produced m ean DE*s bet ween t he actual and predi ct ed m ethods. The s impl er C ALAB

method can be us ed to det ermine the opaque cerami c mixt ure for speci fi c s hades with accurac y.

Moon soo et al (2006) ( 1 8 ) The purpose of t his stud y e valuated the changes in opt ical properti es of enam el porcel ai n aft er repeat ed

external st aining. Enam el porcel ain disks of 1 shade were prepared and 1 of 4 t ypes of external stains was applied over the specim ens and fi red. Fi ring was repeated three ti m es a ft er appli cation of the

sam e st ains. Col or of the specim ens before and aft er st aini ng was measured wi th a refl ection spect rophotom eter. Two fact ors of

repeat ed m easure anal ys is of vari ance wi th fixed factors of the s tai n t ype and num ber of staining c ycl e f or t he change in C IE L*A*B* col or and chrom a aft er repeated staining was perform ed. Color

difference and li ghtness increases si gnificant l y aft er repeated stai ning c ycl e, but chrom a changes was small after repeat ed staini ng

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Review of Literature

13

Tamer E. Shok ry et al (2006) ( 1 2 ) The purpos e of t his stud y evaluat ed t he effect of core and veneer thickness es on the color

paramet ers of t wo all -ceramic s ys tems. Dis k s pecim ens 16mm in diam et er wi th core/ veneer thi ckness of 0.8/ 0.2 were made with

leucit e reinforced ceram ics a nd thi ckness of 0.5/0.5 were made from gl as s i nfiltrat ed s pinell cerami c. Col or param et er L*A*B* of C IE LAB color s pace were m easured agai nst a neutral gra y

background with a tristimul us colorim eter. The color of t he cerami c disk s pecim ens is strongl y infl uenced b y the core thi ckness, veneer

thickness and als o by thei r interact ion.

Fred eri ck et al (2007) ( 1 9 ) Thi s st ud y eval uat ed the Contras t ratio

and m as king abili ties of three t ypes of ceram ic veneers. Disk shaped specim ens of s hade A2 of 3 t ypes of all ceram ic s ys t ems was

fabri cat ed. The contrast rati o i s ass es sed on black background to the illuminance of t he sam e mat eri al when it is pl aced over a whit e background was determined, it i s the rati o of illuminance of t he t est

mat eri al . Vi tadur Al pha had s i gn i fi cantl y lower contrast rat io and poor masking abilit y com pared to P rocera, Empress 2 & Vit adur

alpha. P rocera veneers had a si gnifi cantl y hi gher cont rast ratio com pared t o Empres s 2 vit adur alpha.

Jin Soo et al (2008) ( 2 0 ) This stud y eval uat ed the transl ucenc y propert y in t he different cerami cs m aterial. The A2 corres ponding

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14

as a reference were prepared in clini call y rel evant t hi cknes s. The A2 and A3 cor responding shades of each recomm ended veneer

cerami cs were fabricated s o that the thi cknes s of t he la yered specim en over t he white and t he bl ack background.

The color of core, veneer & l a yered specim ens was meas ured

over whi te and bl ack backgrounds rel ati ve t o t he illuminants -D6 5, A

and F2 wi th a reflecti on spectrophot omet er. Under dayl i ght condition t rans lucenc y of all ceramic m at eri als is lower than thos e

under incandes cent or fluorescent l am ps . Therefore, t he di fference shoul d be consi dered when shade m atching t ranslucent shades of all cerami cs.

Ni coleta Ili e et al (2008) ( 2 1 ) Thi s stud y has evaluat ed the

Correl ati on between ceramic translucenc y and pol ym eri zation effi ci enc y through cerami cs. All thes e effect s were expressed in terms of Vi ckers hardnes s m easured wit h an aut om ati c micro

hardnes s indent er on thin luti ng com posit e fil ms stored for 24 hrs in distill ed wat er at 37c. The effect on l uting composit e hardness

without an addit i onal chemi cal cat al ys t and the fol lowing paramet er: curing ti me , cerami c t hi cknes s and cerami c t ransl ucenc y, measured using a refl ectance spectrophotom et er. With m inimal

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Review of Literature

15

Bor-Shiunn Lee et al (2008) ( 2 2 ) The purpos e of the s tud y was to evaluat e the development of reproduci ble i n vit ro tooth s taini ng

model to simulat e t he i nt rinsi c discol oration of t eeth and eval uat e the abilit y of t wo cat al ys t to enhance t he bleaching activit y of H2O2

, Rhodam ine B , Orang e II, Fe( III) phthal oc yanine and t ea were used to s tai n the tooth speci mens for 4 -72h and s ubs equentl y bleached b y H2O2 for 4 - 72 h. The process was phot ographed using

a di git al st ereos copi c mi croscope and di gi tal cam era the im age was trans form ed t o get L *A*B* val ues of C IE L a b s ys t em w ith image

processi ng s oft ware. The catal yti c abilit y of li ght i rradi ati on plus addition of Fe/Sodi um -Y for specim ens stained b y orange II was evaluat ed in t es t tubes and i n extract ed t ooth model. Orange II was

the m ost appropri at e d ye for tooth st ai ni ng am ong the d ye for tooth stai ning among d yes us ed in t his stud y, addition of Fe/ sodi um -Y or

Mn/ sodium -Y and for the specim ens s tained b y Orange II, li ght irradiat ion could elevat e t he bl eaching efficac y of H2O2.

Ho-Nam Li m et al (2010) ( 2 3 ) The purpose of the stud y was t o evaluat e t he Spectroradiom et ri c m easurement s s howed si gni ficantl y

different t ransl ucenc y for different t ypes of cl ini call y sim ulat ed cerami c specim ens . Seven A2 shade core cerami cs (Slip cast block - In ceram Spi nell Bl anks, In ceram Al umi na bl anks, Zi rconi a Block,

Felds pathi c Vit a block, Heat press ed IP S Empress 2, Si nteri ng VM 7) and A2 and A3 shade veneer cerami cs has a thi ckness of 1.5 mm.

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16

measured over whit e and bl ack backgrounds by an

spect roradiom et ri c with 2 m easuring apertures of 2.63 and diamet er

is 5.25. The differences i n s pect roradiomet ri c (5.25) -bas ed Transl ucenc y param et er values of t he la yered cerami cs are

evaluat ed wi th 2 -wa y ANOVA with the help of fixed factors of shade designation and type of ceramic core (α=.05). Translucency

paramet er values measured b y t he s pect roradiom et ric and the

spect rophot ometri c were si gni fi cant l y di fferent but hi ghl y

correl at ed.

Isab elle Den ry et al (2010) ( 9 ) The t echnologi cal evol uti on of cerami cs for dent al appl icati ons has been remarkabl e, as new

mat eri al s and processin g techniques are steadi l y being introduced the improvem ent in both st rength and toughnes s as m ade it possibl e

to expand the range of indi cations t o long span fixed parti al prosthesis , im plant abutm ents and impl ants.

Hui Wang et al (2011) ( 2 4 ) The purpos e o f t he st ud y was to eval uat e the i nfl uence of vari ed s urface t exture of dentin porcel ain on opti cal

properti es . Ei ght y dentin porcel ai n (ShoFu Vint age Halo, s hade A2) disks (1.0 x 10.0 m m) were fabri cated and assi gned to 10 groups . The specimens whi ch is denti n porcelai n are made up of d i fferent

surface t extures wi th modi fi ed roughness i n surface (R a) and different level s of waviness (W a). Using spect rophotomet er

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Review of Literature

17

(PR-650) aft er st andard fi nishi ng of the enam el -denti n porcelai n com plex. Surface texture of dentine porcel ain si gnifi cantl y

infl uenced the opti cal properti es of enam el - denti n porcelai n specim ens, and s urface wavi ness had hi gher correlat ion coeffi ci ent

with opti cal param et ers than di d roughness.

Bogna stawarczyk et al (2011) ( 2 5 ) The purpos e of the stud y was to

evaluat e the l oad beari ng capacit y and t he t ypes of fail ures in t he ant erior zirconi a crowns i n whi ch t he veneer has been fabri cat ed b y

over pressi ng and l a yeri ng t echni que. St andardiz ed zi rconi a fram ework were fabricat ed and randoml y divided i nto 8 groups , Four groups were veneered with one of t he l a yered veneering

porcel ains: Zi rox, GC Initial ZR , VITA VM9 or IPS e.m ax Ceram and the other four were veneered wit h over press ed veneeri ng

porcel ains: Pres sX Zr , GC Initi al LF, V ITA PM 9 or IPS .E.m ax ZirP ress. The crowns were cem ented on thei r corresponding Co -C r abutment and t he s pecimens were loaded at an angl e of 45degree in

a universal t esti ng machi ne to determine the fracture load. Veneering Porcel ain for zi r coni a fram eworks have good fracture

load res ist ance compared wi th l a yered porcel ain.

Motoaki Ishib e et al (2011) ( 2 6 ) Conduct ed a st ud y to evaluate the

shear bond strength bet ween pressed and la yered veneeri ng ceram ics fabri cat ed i n hi gh nobl e allo y and cores of zi rconi a. The result

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18

pressi ng and l a yering ce rami cs. For shear bond st rengt h of veneering ceramic t o zirconia there was no si gni ficant di fference

bet ween the pres sed and l a yered groups.

Wei-Sh ao Lin et al (2012) ( 2 7 ) Conduct ed a stud y t o evaluate t he Fl exural st rength of core and veneeri ng porcelai n and fabri cation techni que b y W eibul l anal ys is t est on the s el ect ed dent al cerami cs.

Leucit e -rei nforced glass -cerami c cores have l ower fl exural s t rength than l ithium disili cat e ones, w hil e fabricati on t echni ques (heat

-press ed or C AD/C AM) and specim en thicknes ses do not affect the flexural st rength of all gl ass ceramics. The powder/li quid veneering techni que showed lower flexural strength and has increased

rel iabilit y, with a hi gher Wei b ull modulus for zirconia bila yer specim ens when com pared t o heat – press ed veneering t echni que.

Lisa S. Spink et al (2013) ( 2 8 ) Conduct ed a comparative stud y

bet ween absolut e and surrogat e m easures of rel ative t ransl ucenc y in

cerami cs b y s pect rophot om eter us ing14 di sk of cerami cs with different thi cknes s and chrom a. This study res ulted that the contras t

rat io i s not a di rect measure of translucenc y and cannot be used bel ow t he 50% of t ransm issi on. Non –li near regressi on was used to com pare m easurem ents of abs olut e versus rel ati ve val ue for each of

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Review of Literature

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Fu Wan g et al (2013) ( 2 9 ) This st ud y concluded t hat t he t hicknes s of the zirconia is invers el y proporti onal t o the trans lucenc y of the

mat eri al used. The y have also st at ed that for an improved es t heti c, the t rans lucent charact eri sti c of the ceramic m at erial should be well

known al ong with it s compositi on and t hickness. The t ransl ucenc y paramet ers (TP ) val ue for a gl ass ceramic ranges fro m 2.0 to 0.6 mm, and for zi rconi a ceramics it ranges from 1.0 to 0.4 mm which is

measured b y using s pect rophotom et er.

Bara Bagis et al (2013) ( 3 0 ) Conduct ed a stud y to eval uat e the opti cal properti es of various ceram ic s ys t em. It has revealed t hat the none of t he full ceramic s ys tems were able to m at ch the color of the

shade guide, each s pecimen was m easured before and after to obtain the L, A, B coordinates and t o m easure t he translucenc y paramet er.

As cerami cs becomes more opaque, darker, reddi sh and yel lowis h due to agi ng. This stud y result also reveal ed that the chemi cal struct ure of cerami c s ys tem i s m ore im port ant i s determi ni ng the

opti cal param et ers.

Rich ard Ans ong et al (2013) ( 3 1 ) The y conducted a stud y t o evaluat e the fract ure t oughness of Heat press ed and l a yered cerami cs. The aut hors have used bar speci mens t o fabri cate 8

different t ypes of ceram ics and us ed si ngl e edge notch beam t est method with a uni vers al t esti ng m achi ne to record t he fracture force

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Review of Literature

20

val ues ranges from 1.20 MP a to 1.74 MPa and it could relate prim aril y to t he processi ng t echnique.

Bari zon et al (2013) ( 3 2 ) C onducted a st ud y to evaluat e t he

correl ation of cont rast ratio and t ransl ucenc y paramet er. They have concl uded t hat t here is a si gni fi cant correl ati on between contrast rat io and translucenc y parameter. Disks of about 13mm i n di am eter

and 0.7mm in t hi ckness were fabri cat ed using several m at eri als li ke VITAVM9, V ITA P M9, IPS Em press C AD, IPS e.m ax CAD, IPS

e.m axPress and Lava Zi rconi a, V ITA VM 9, Lava zirconi a.

Ku rsoglu et al (2014) ( 3 3 ) This stud y conduct ed usi ng a 56 cerami c

disc of var yi ng thi cknes s and 7 different groups with a var ying veneer thickness (0.2, 0.5, 0.7mm ) t o i nvesti gat e t he t ransl ucenc y

paramet er of core veneer thi ckne s s. Translucenc y param eter decreas es when the cerami c t hi ckness increas e. Hence, t ot al cerami c thickness affects the translucenc y. If thickness decreas es as per

paramet er values t he translucenc y of core materi al has m ore effect than that of veneer mat eri al .

Bari zon et al (2014) ( 3 4 ) This st ud y evaluat ed the degree of transl ucenc y wit h di fferent cerami c s yst ems des i gned for porcel ain

veneers. The transl ucenc y of a restoration is affected by both thickness and s hade of lithi um di sili cat e cerami c. S hade affects

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21

differences in the transl ucenc y paramet er were found among porcel ains . VM9 greater than PM9, Em press estheti c great er t han

Empres s C AD great er t han M arkII, Everest, e.max C AD great er t han e. m ax pres s great er t han Lava. Si gni fi cant di fference was not ed

when different shades and t hi cknes s were confi rm ed.

Neelam Pande et al (2015) ( 3 5 ) The press abl e all -cerami c s yst em

was us ed in this stud y for shade reproduction using a color measurement s pect rophot om eter on uns tained and st ai ned nat ural

maxillar y cent ral inci sor. Com paring shade reproducti on in unst ained t eeth with low -translucenc y and m edi um opacit y; m edi um transl ucenc y and hi gh opacit y on st ained tooth. Fabri cation of the

restoration for unstai ned nat ural tooth produces best shade reproducti on using All -cerami c l ow t ranslucenc y m at eri al . For a

bett er estheti cs medium opacit y is an i mportant m at eri al for t he fabri cation of restorat ion on bot h unst ained and s tai ned nat ural teeth. In cli ni call y using a hi gh op acit y m at eri al is diffi cult on

stai ned tooth as it gi ves di fferent shade reproduction.

Jeong et al (2015) ( 3 6 ) Conducted an in vitro stud y to evaluate the transl ucenc y of pres sabl e cerami cs with different core and veneer thickness es , Specim ens were grouped bas ed on core + veneer

thickness i nto three groups; 1+0.5mm, 0.7+0.8 m m and 0.5 + 1mm, Studi es have shown that l uminous t ransmittance value of pressabl e

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22

stati sti cal l y s i gni fi cant dependence on both t ype. The y concluded that m ajor fact or i n det ermini ng the t ranslucenc y of zi rconi a is the

thickness o f the rest oration.

Ahed Al -Wah adni et al (2016) ( 2 ) Condu ct ed an in vit ro study that evaluat ed the shade reproduci bilit y of veneered zirconia rest orat ion in arti fi ci al t ooth. In thi s st ud y CAD/C AM t echnology was used to

scan the prepared t ooth for 45 cobal t chromi um di es. They used onl y one C o-C r di e for scanning an d all 45 zirconia coping was

milled and di vided i nto 15 speci mens for each group according t o the veneeri ng t echnique t he y are di gi tal veneeri ng, l ayering veneering and over pressi ng veneering . The y us ed A2 shade for al l

three groups . The s pecim ens were c em ent ed onto the dies usi ng gl as s ionomer cement. The color shade for Vit a A2 shade t ab was

measured usi ng a s pectrophotom et er. As per s hade reproducibilit y la yered veneering group is superior to other groups in each specim en.

Farh ad T abatabai an et al (2017) ( 3 7 ) conduct ed an in vitro st ud y

that evaluat ed the effect of thickness of zi rconi a on its m aski ng abili t y and t o defi ne a correct t hicknes s of zi rconi a cerami c as a coping mat eri al. Nine groups of following thi ckness of zi rconia dis c

specim ens were us ed in thi s st ud y such as 0.4 m m, 0.6 mm, 0.8 mm , 1 mm, 1.2 mm, 1.4 mm, 1.6 mm, 1.8 m m, and 2 mm each cont aining

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These dis c s pecim ens were placed i n whi te and bl ack subst rat e and anal yzed usi ng spectrophotom et ri c m easurement s.

The y concluded that idea l m asking abilit y of zi rconi a cerami cs was obt ained wit h a mini mum t hickness of 1.6mm and clinical m aski ng

abili t y was obt ained with 1mm.

Esra Al juaila et al (2018) ( 3 8 ) Conduct ed an invi tro st ud y t o

com pare t ranslucency of estheti c zi rconi a cerami c wit h conventional cerami cs. Us ing 6 different t ypes of ceram ics with t hree var yi ng

thickness . In thi s st ud y 144 zi rconi a s amples were prepared and divided int o 6 m ai n groups ba sed on mat eri als, and bas ed on thickness the y are sub grouped int o 3. Us ing spectrophot omet er

each dis c has been test ed. The y concluded t hat gl ass ceram ics showed hi gher Trans lucenc y Param eter value t han cr yst alli ne based

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Materials and Methods

24

MATERIALS AND METHODS

The pres ent in -vit ro stud y is conduct ed for t he evaluation of masking abilit y of z irconi a based cerami cs with different core and

veneer thi ckness.

The following m at erials , instrum ents and equipm ent are us ed

for the stud y.

MATE RI ALS USED

1. Zirconia bl ank (Zenostar, Ivoclar Vivadent, US A)

2. Press abl e gl ass ceramics - IPS Em ax i ngot (Ivocl ar Vivadent ,

USA)

3. Felds pathi c Porcelai n (Vit a VMK m ast er)

4. Rhodamine B st ain (Sigma Al dri ch Co., St Louis, US A)

5. Orange II s tai n (Si gma Aldri ch C o., St Louis, US A)

6. Alizarine red st ain

7. Povidone

8. Tea

9. Distill ed wat er

EQUI PME NTS USE D I N THIS STUDY

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Materials and Methods

25

METHO DOLO GY Sampl e size:

Tot al number of s am ple were 45

Sampl es were divi ded int o three experi ment al groups with 15

samples

Three groups wi th di fferent t hickness cat egoriz ed Group 1 = 0.5 + 1m m

Group 2 = 0.6 + 0.9mm

Group 3= 0.7 + 0.8m m wit h variant col or groups

Six Groups of Test S olution : Group A - R hodami ne B

Group B- Orange II Group C - Alizarin R ed

Group D - Tea

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Materials and Methods

26

FAB RICATIO N O F ALL CERAMI C CORES

A Tot al of 45 ceramic dis k specim en (N=15) was prepared

that are zirconi a core wit h a ceramic veneer. Specim ens are grouped bas ed on thei r core + veneer t hickness es: 0.5+1 mm , 0.6+0.9mm

and 0.7+0.8 mm is shown in Fi gure 1 and 2. Al l speci mens were undergone surface grinding, polis hing to obt ai n proper t hi cknes s and t ransl ucenc y before evaluati on. Two s pecim ens t aken without

unveneered surface wit h zi rconi a core and veneered porcel ain without zi rconi a core where t aken as control for the st ud y .

To achi eve the required cons ist enc y and t o elimi nate the vari ant degree of roughnes s on t he translucenc y, scanning profil er

was us ed to anal yz e the surface roughnes s of each speci men t o make all specim ens in a uniform surface and t he cons ist enc y was verified

through st atis tical anal ys is. Spectrophot omet er is the devi ce t hat was us ed t o determine t he luminous of t ransmitt ance of the

specim ens.( 3 9 ) It was us ed to access the t hickness of the core veneer

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Materials and Methods

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To produce t he s pecim en, a zi rconia blank was m ill ed using

com put er -aided desi gn and com puter -aided m anufacturi ng

(CAD/C AM) and the mill ed zirconia core was t hen fi red accordi ng to the manufacturer’s instructions. To apply the veneer on the

zirconi a core, a wax bl ock was mill ed using CAD/C AM and a wax veneer was subs equentl y attached to the zirconi a core before it was invest ed and elimi nated. The all ceramic s yst em wit h the var ying in

thickness of core lithium di sili cate reinforced cerami c ( 2 0 )

SAMPLE COLLE CTION & EVAL UAT ION O F CE RAMI C DIS C ON TEETH

The s urfaces of the specim ens were ground whil e wet on 240 -,

400 -, 600-, 800 -, and 1200-gri t sili con carbi de paper. While the specim ens were bei ng ground, thei r thicknes ses were m easured

frequentl y wi t h a di git al m icrom et er and the y were ul ti mat el y ground t o a thi cknes s of 1.5 ±0.01 mm. All the produced s pecim ens were cl eaned i n an ultrasonic cl eaner for 180 s econds to remove an y

residue.

To meas ure the surface roughness of each specim en, a scanni ng profil er with a st yl us was used. The st yl us was pl aced at the center of the specimen s urface and the average roughness was

calculated b y meas uring the roughness across a 5 -mm l engt h at a speed of 0.1 mm/s. For the quant itative anal ysis of t he luminous

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Materials and Methods

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used. M easurem ents were perform ed i n the V ITA eas y shade com pact dent al s pectrophot ometer i s shown i n fi g 9 with day li ght

source ( 3 6 )

The extracted maxillar y cent ral incisor nat ural t ooth with all the s urface int act is used for the evaluation of ceram ic dis cs. The

teeth were preserved i n 5% norm al sali ne solut ion at room temperature prior t o the st aini ng process. ISO St andard ization IS O NO: 7491: 1983 (Det erm ination of col or s tabil it y).

STAINING THE TE ETH

Staining the natural t eeth b y imm ersing it in cool drinks for up to 72 hrs (GROUP -E).Imm ersing it in Povidone Iodine and evaluat ed

(GR OUP –F). Boil ed 2gm of t ea i n 100ml of distill ed wat er for 5min then imm ersed t eeth (GR OUP -D) for 72 hrs s tai ns are up

taken. St ai n proces s was m onit ored at 4, 24, 48, 72 hrs aft er immersion and t he color of the t oot h specim ens was sim ult aneousl y evaluat ed at the s am e tim e peri od.

1 gm of R hodami ne d ye (GR OUP -A) was diluted in 10 ml of distill ed wat er and teeth were immersed in it for 72 Hrs . Stains were up t aken and st ain process was monitored at 4, 24, 48, 72 hrs

aft er imm ersion and the color of the tooth s pecim ens was simult aneousl y eval uat ed is shown i n Figure 7.Teeth are im mersed

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Materials and Methods

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MOUNTI NG THE T EETH IN ACRYLI C BLO CK

The s el ected nat ural t eeth have been st ored in sal ine for 24

hrs pri or to procedure t o rem ove all the debris, cal cul us and extrinsic st ains. The teet h are then rem oved from t he s ali ne washed

thoroughl y in running t ap wat er, poli shed with polishi n g brush and

polis hing past e using cont rangl e hand piece.( 4 0) Unst ained norm al

nat ural t eeth with zi rconi a veneered wit h cerami c was t aken as the

control.

The t reat ed ext ract ed natural t eet h are dri ed and t hen m ount ed on a wax sheet to prepare a wax patt ern for the fabri cat ion of acr yl ic block to m ount the nat ural t eeth, wax patt ern is then flasked,

dewaxing procedure is done and then packed with s el f -cure acr yl ic resin (DP I) b y pl aci ng the long axis of the tooth perpendicular t o

the horizont al pl ane.

The t eeth are then mount ed on t he acryl i c bl ock, in such a

wa y that t he portion of t he teet h above cement -enam el j unct ion is expos ed for the preparat i on of the l abial surface of both uns tained

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Materials and Methods

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PRE PARATI ON O F TOOTH FO R RECEIVI NG ALL CE RAMIC

PRESSABLE LITH I UM DIS ILICATE DISCS

During evaluation of the s pecim en b y usi ng

spect rophot ometer, whi ch has a sm all aperture usuall y res ults in

inadequate reading of the li ght ness. The inadequate reading of t he li ghtnes s i s due to the reduct ion in the ill umination and the coll ection of li ght source. The Edge l oss effect p res ent i n the

nat ural t eeth will have a negative im pact on the refl ect ed li ght from the spectrophotom et er. To avoid such errors ceramic dis cs should be

flat. The l abi al surface of bot h unstai ned and s tai ned tooth shoul d

be prepared up t o 1 mm for pl acing t he discs. ( 4 1 )

PRE PARATI ON O F MOLD FO R STANDARDI ZATIO N O F THE

ALL CERAMIC DI SCS

Fabricati on of Zirconia di scs usi ng Ceramil l CAD/CAM machine:

In the pres ent stud y, the Zi rconi a dis cs are fabricat ed usi ng

the C erami ll s yst em (AM ANN G IRR BACH, C eramill MOTION 2). It consis ts of a s canning s ys t em (C erami ll m ap 300 work st at ion), a

CAD soft ware (C eramill mind CAD), a C AM m achini ng s yst em (Ceramill C AM ) and a sint ering furnace (Sint ering furnace C eramil l Therm furnace).

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Materials and Methods

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The m at eri al us ed i n the present stud y is parti all y sint ered Zirconia (zenost ar) whi ch has got hi gh strength and ri gi dit y. The

process of obtaining the Zi rconi a dis cs i s des cribed in det ail below.

a) Stainl es s s teel mol d -Model t rans fer: Before t he m old is

scanned, it is ess ent ial t hat proper orientation of the m old is shown in Fi gure 3 and the scanner is achi eved i n order t o

capture all t he det ail s of the preparation.

b) Scanni ng the di e: C eramil l m ap 300 work st ation is us ed for

scanni ng the m old. The s canni ng process is then activat ed. The s can det ails are fed into the C erami ll mind software for further desi gning of the dis cs. The ti me t aken t o s can each di e

is approxim atel y 4m i nut es.

c) Desi gni ng of Zi rconi a dis cs: The Ceramil l m ind C AD

soft ware is us ed for the virtual desi gni ng of the dis cs . The scanned im age of the disc is vi sualized on the screen of the Ceramil l work st ati on and t he dis c is des igned t o adapt t o the

contours of the s canned im age. Us uall y a Zi rconi a onl a y desi gn i s s el ected from t he librar y of predesi gned form ats

avail abl e i n the soft ware. This predesi gned patt ern is alt ered virt ual l y on the screen to m at ch the coordinates on the scanned i mage s o t hat an a ccurat el y fitting di sc for that

parti cul ar mold space i s obt ained. The thickness of t he Zirconia disc is set uniforml y as 2mm t hroughout. This desi gn

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Materials and Methods

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using a speci al s oft ware called as C eramill m atc h. S uccess i ve Zirconia dis cs are t hus desi gned and st ored. The num ber of

Zirconia dis c that can be mi lled from a s ingl e bl ank depends on the size of the bl ank and t he number of desi gned Zi rconi a

discs t o be fed for milling in a singl e bat ch is det ermined accordingl y. The whole process of desi gning of each Zi rconi a disc t akes approximat el y 15mi n. The order button integrat ed

in t he program transfers the const ruction data from the

desi gni ng unit to t he milling unit (CAM).( 4 2 )

d) Comput er aided machi ning (C AM ) of zirconi a discs: The

Zirconia m ateri al used in t he present stud y is Zenos tar Zi whi ch features hi gh strength, ri gi dit y and biocompati bilit y.

These pre-sint ered Zirconi a bl anks can be easil y proces sed as the y do not splitt er and provi de opti mum edge st abilit y. The

milling process begi ns with t he sel ect ion of appropri at e s ize of the blank. In thi s st ud y two 14mm blanks are us ed. The blank is s crewed to a ret ai ning pl at e and the ret aini ng plate i s

mount ed int o t he m illing machine (Ceramill moti on). Each Zenost a r Zi blank i s provided wit h a bat ch -specifi c coding

whi ch has a m at chi ng enl argement fact or. This com pens at es for the volumet ri c shrinkage that occurs during si nt eri ng. The milling of each Zirconia dis c t akes approxim atel y 15 to 16

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Materials and Methods

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e) Sintering of Zirconi a dis cs: The Sinteri ng furnace C eram ill

Therm (Am anngi rrbach) furnace is used for t he si nt eri ng the

zirconium dis c. The mil led Zi rconia discs are pl aced for sint eri ng i nto t he si ntering bowl fill ed wi th si ntering pearls.

To ensure proper support , the disc were placed wit h the sli ght press ure on to the si ntering pearls and fi nal sintering i s perform ed

b y heating the furnace from room t em perat u re to final t emperat ure

of 14500C at a heati ng rate of 5 -10 k/ mi n. The dwell tim e at final

temperature i s 2hrs and the bl anks are cooled from final t em perat ure

of 14500C to room tem perature (at l east <2000C) at a rat e of

approxim at el y 5k/mi nut e over a period of 5hrs. Aft er final si nterin g

the Zi rconi a dis c are reworked wit h water cool ed l ab t urbi ne and

ground using di amond points ( 4 3 ). The cores are fabri cated from the

cerami c ingots , two veneering m at erial as per the i nst ruction gi ven in the manufacturer’s description.

SPE CT RO PHOT O METRIC EVALUATION

The difference in the col or is us uall y evaluat ed b y t he t wo

methods: namel y the percept ional m et hod and the instrument al measuring m ethod. Among these two m ethods the perceptional is most frequentl y us ed m ethod for t he fabri cati on of t he indirect

restoration. The perception m ethod depends on the presence of cones in the hum an e ye for the color perception. The hum an col or

Figure

Figure 1: Sample Disc
Figure 3: Metal mold
Figure 7: Stained teeth
Figure 9: Vita easy shade guide
+6

References

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