3D PRINTED PATTERN : AN IN VITRO STUDY
A Diss ertation sub mitted
in parti al fulfil men t of th e requirements for the degree of
MASTE R O F DENT AL SURGE RY
BRANCH – I
PROSTHO DO NTICS AND CROWN & BRIDGE
THE TAMIL NADU DR.M.G.R. ME DICAL UNI VERS ITY CHENNAI- 600032
2014 – 2017
DE PART MENT O F PROSTHO DO NTICS AND CROWN &
BRIDGE
CERTI FICATE
This is to certi f y that Dr.I.EDILBERT RAJA, Post Graduat e student (2014 -2017) in the Departm ent of Prosthodonti cs and crown &
bridge , Adhiparasakthi Dent al Coll ege and Hos pital, M elm aruvathur – 603319, has done this dissertation titled “ ACCURACY O F FIT O F
SCREW RETAINE D IMPLANT SUPE R STRUCT URE CAST FRO M CONVENT IONAL VS 3D PRINT ED PATTE RN : AN I N VI TRO STUDY" under our di rect gui dance and supervi sion in part ial ful film ent of the regul ations laid down by the Tamilnadu Dr.M.G.R Medi cal Universit y, Chennai – 600032 for M DS., (Branch - I) (PROS THODONTIC S AND CR OWN & BR IDGE ) degree exam inati on.
Dr.S.THILL AINAYAGAM MDS., Principal
Guide
Dr.A.S.RAMESH MDS., Professor & H ead
d Co-Guide
Dr.K.PRABHU MDS., Reader
ACKNOWLE DGE MENT
I am extremel y grat eful to Dr.A.S.Ramesh MDS., Guide, Professor and Head, Departm ent of Prosthodontics, Adhiparas akthi Dental College and Hospital, Mel maruvathur. Words cannot expres s m y gratitude for his quiet confi dence in m y abilit y to do the stud y, hi s willingness to help t o clear the stum bling blocks along the wa y and hi s tremendous pat ience till the end of t he st ud y.
It is m y dut y t o express m y t hanks to m y Co -Guid e Dr.K.Prabhu MDS., R eader for his expert gui dance and moral support duri ng t he com plet ion of t his st ud y. I consider m ys e lf privil eged, to have studi ed, worked and com plet ed m y diss ert ation under them in the departm ent.
M y sincere thanks t o Dr.S.Thill aina yagam MDS. , our beloved Principal, Adhiparas akt hi Dent al Col lege and Hos pit al, M elm aruvathur for providing m e wi th the opport unit y t o utiliz e t he faciliti es of the coll ege.
I thank our Corres pondent Dr.T .Ramesh MD., for his vital encouragem ent and s upport .
I am extrem el y thankful t o m y t eachers Dr.N.Venkatesan MDS., Professor, Dr.Arun ku mar MDS., S eni or l ecturer, for thei r valuable suggesti ons , const ant encouragem ent and ti mel y help rendered throughout this study.
I am t hankful and express m y gratitude to m y previous t eachers Dr.Ri jesh MDS., R eader, Dr.Laks mid evi MDS ., Reader, for their immense help and support for t he initi ati on of t his stud y.
I am extrem el y grat eful to Dr.Shi vaSh ankar MDS., Di rector, Confi dent al l aborat or y,Bengaluru, for grant ing me permission to conduct the s tud y i n his departm ent and helping m e to bri ng out m y stud y.
I thank Dr.Shyam MDS ., S ri venkat eshwara Dental College and hospi tal ,Chennai , for helping m e with the stati sti cs i n the study.
I thank AL MI GHTY GO D for ans weri ng m y pra yers and m aking me what I am toda y.
I owe m y grati tude to m y fat her Mr.K.Iru thayaraj and m y mother Mrs.M.Theresammal who stood besi de wit h st aunch fai th and sacri fi ced s o much t o make m e what I am toda y. I also t ha nk m y l ovi ng sister Dr.I .Geraldin a BDS., for her constant help and encouragem ent throughout m y career.
Dr.I.EDILBERT RAJA
TIT LE OF THE DIS SERTATION “Accuracy of fi t of screw retained i mplan t su per stru ctu re cas t f rom conven tional vs 3D printed pattern - An in vi tro study”
P LACE OF THE S TUDY Adhi paras akt hi Dent al C oll ege and Hospital, M elm aruvathur – 603319 DUR AT ION OF THE COURSE 3 years
NAM E OF THE GUIDE Dr.A.S .Ramesh MDS ., NAM E OF C O-GU ID E Dr.K.P rabhu M DS.,
I hereb y decl are that no part of the di ss ert ati on will be uti li zed for gai ning financial assist ance or an y promoti on wit hout obt aining prior permi ssion of the Pri nci pal, Adhiparas akthi Dent al C ol lege and Hospital, Mel maruvathur – 603319. In addition, I declare t hat no part of this work wil l be published eit her in print or in el ect ronic medi a without t he gui des who has been acti vel y invol ved i n dis sert ation. The aut hor has the ri ght to res erve for publis h work sol el y with the permiss ion of the Princi pal , Adhi parasakthi Dent al College and Hospital, M elm aruvathur – 603319
Co- G ui de Gui d e & H ead of depart m ent Si gnature of candi dat e
BACKGRO UND:
Accurat e fit of dent al prostheses is thought t o be crit ical to the long - term succes s of t he supporti ng st ruct ures whether thos e st ructures be teeth, mucos a, or i mplants. It had been stated that a passi ve fit of a reconst ruction is im port ant for a ph ys iol og i c tiss ue res ponse and long term os seoint egration of impl ants. Due t o the ank yl oti c charact er of the implants, stres s induced b y a mi sfi t of the s uperstruct ures persist s . Therefore, a pas sive fit of the supers truc tures is des irabl e t o prevent uncont roll ed st ress not onl y i n t he adjacent bone but als o in t he reconst ruction its el f. It has been cl aim ed that s uper s truct ures with a poor fit m a y l ead t o prost heti c compli cations such as looseni ng or fracture of screws, as well as fracture of fram eworks or veneering cerami c and even fractures of abutment s or im pl ant s. During conventional desi gning of patt ern using pat tern wax, stress concent rations occur whi ch lead to dist orted castings. A new method of desi gni ng and m aki ng patt ern using 3D printi ng technology w here thes e stress will be mini mal. M argi nal discrepanc y has been rel at ed to t he preparati on of wax patt ern and defect i n the cas ting process so t he misfit has t o evaluat e using RVG.
AI M:
The purpos e of this stud y is to assess the accurac y of fit of cas ting obt ained b y t wo m ethods of pattern m aki ng viz, Conventi onal wax patt ern and 3D pri nt ed pattern.
stud y.
Sel ecti on of experim ent al mo del -com plet el y edent ulous Mandibl e. (1no )
Placem ent of im pl ant s -A B D E positions (from m esi al t o di stal)
Im pression m aki ng.
Fabricati on of m ast er cast .
Wax patt ern of s uperstructure (Convent ional and 3D pri nti ng methods ).
Casti ng of impl ant s uperst ruct ure (C onventional and 3D print ing methods ).
Fabricati on of R adiographi c parall eli ng devi ce .
X-ra ys ( IOP A -Radiovisiograph y) of impl ants with superst ruct ure using radiographi c parall eli ng devi ce .
Evaluat e the standardized radi ographs for pres ence of mi sfit .
Maki ng the m easurement on the radiographs.
Statist ical anal ysi s is used to eval uat e the fit ting of superstruct ure .
RESULTS :
It was found that t he misfit for the conventi onal wax technique in the various regi ons was with a mean val ue of 0.1436 and for t he 3D pri nt ed wax t echnique m ean val ue is 0.1358. These val ues were st atisti call y
CONCLUS ION:
The pres ent invit ro stud y was undert aken t o compare t he cast of conventional t echnique and 3D print ed t echni que for the m arginal fit with radi ograph using RVG. On t he basis of the res ults obt ained i n th e pres ent stud y, it was concluded t hat margi nal fit i n 3D P rint ed techni que is bett er compared to conventi onal t echnique.
S.NO TITLE
PAGE No.
1 INTRODUC TION 1
2 AIM AND OBJ EC TIVES 6
3 REV IEW OF LITER ATURE 7
4 MATER IA LS AND METHODS 35
5 RESULTS 51
6 DISC USS ION 62
7 CONC LUS ION 88
8 REFERENCES 89
9 ANNEXUR E 97
FIG.
NO TITLE PAGE No.
1 EXPER IM ENTA L M ODEL-COMP LETE LY
EDENTULOUS M AND IB LE 44
2 EXPER IM ENTA L M ODEL W ITH SURG ICAL
ACRY LIC GUIDE 44
3 IM P LANT KIT 44
4 IN IT IA L LANCE DR ILL 44
5 CHEC KING FOR PARALLE LIS M 44
6 IM P LANT 44
7 IM P LANT 45
8 P ILOT DR ILL US ING GU IDE 45
9 HAND T IGHTEN ING OF IMP LANT 45
10 P LACEMENTS OF IMP LANTS IN A B D E
POS IT IONS 45
11 IM P LANT W ITH IM PRESS ION P OST 45
12 MAK ING OF PR IMARY IMPR ESS ION OF M ODEL 45
13 PUTTY IMPR ESS IO N OF THE MODE L 46
14 PR IMAR Y C AST 46
15 FABR IC AT ION OF SPEC IA L TRAY 46
16 OPEN TR AY W ITH SPACER 46
17 OPEN TR AY IN THE M ODEL 46
18 MAK ING IMPR ESS ION W ITH M ED IUM BODY 46
19 SP LIN T ING TO C ONNECT THE P OST 47
20 RES IN TO S TAB ILIZE THE POS T 47
21 MAK ING OF F INAL IMPR ESS ION 47
23 MASTER C AST W ITH C ASTABLE S LE EVE S 47
24 MASTER C AST W ITH W AX P ATTER N 47
25 MASTER C AST W ITH SPR UE 48
26 MOUNT ING IN C AS TING R ING 48
27 MASTER FR AME WORK 48
28 FR AME WORK IN DUP LIC AT ING BOX 48
29 DUP LIC AT ING S ILICONE W ITH IMPR ESS ION 48
30 DUP LIC ATED W AX PATTER NS 48
31 3D PR INTING M AC HINE 49
32 CAD DATA 49
33 3-D PR INTED RES IN PATTERN 49
34
3D PR INTED P ATTERN IN EXPER IM ENTAL MODEL
49
35 FR AME WORK IN EXPER IMENTAL MODEL 49
36 FR AMEW ORKS 49
37
MAK ING OF X R AY W ITH P ARA LLE LING DEVIC E
50
38 RVG IM AGE 50
39 RVG IM AGE W ITH MIS FIT M EAS UREMENTS 50
40 RVG IM AGE W ITH MIS FIT M EAS UREMENTS 50
41 RVG IMAGE W ITH MIS FIT MEAS UREMENTS 50
42 RVG IM AGE W ITH MIS FIT MEAS UREMENTS 50
TABLE.
NO
TITLE
PAGE No.
1 M IS FIT M EAS UREMENT OF GR OUP I 53
2 M IS FIT M EAS UREMENT OF GR OUP II 54
3
STAT IST IC AL ANALYS IS IS US ED TO EVALUATE THE F ITTING OF
SUPERSTR UCTURE IN POS IT ION A
55
4
STAT IST IC AL ANALYS IS IS US ED TO EVALUATE THE F ITTING OF
SUPERSTR UCTURE IN POS IT ION B
56
5
STAT IST IC AL ANALYS IS IS US ED TO EVALUATE THE F ITTING OF
SUPERSTR UCTURE IN POS IT ION D
57
6
STAT IST IC AL ANALYS IS IS US ED TO EVALUATE THE F ITTING OF
SUPERSTR UCTURE IN POS IT ION E
58
7 OVERA LL MEAN VALUES 59
8 GROUP STAT IST IC S 59
GRAPH.NO TITLE PAGE No.
1 THE MEASURED DIS CREP ANC Y
VA LUES
60
2 COMPAR IS ON OF MEAN
61
LIST OF FLOW CHARTS
CHART.NO TITLE PAGE No.
1
B IO LOGIC AND MECHANIC AL IM P LA NT COMP LIC AT IONS
63
2
THE D ISTORT ION EQUATION AND IT S RELAT IONSH IP TO THE M IS F IT
73
RVG-R adiovisi ograph y RP- R api d prot ot ypi ng PU – Pol y uret hane W/P – Wat er/Power ratio
KA L - kulzer Abut m ent Lut ing
CAD-CAM – comput er aided desi gn – comput er ai ded m anufacturing 3D- print ing – Three dim ensi onal pri nting
UC LA abut ments – Universit y of C ali fornia abutm ent s EDM –El ect rical dis charge m achine
IOP A- Intra oral peri api cal radoi graph
INTRODUCTION
Treatment options for repl acem ent of missing t eeth have trul y evolved from anci ent tr ans plant to modern da y impl ants -The Thi rd Dentition. Impl ant s have revolut ioniz ed dental practi ce and have hel ped to overcom e m an y of the li mitati ons encount ered wit h conventional fixed or removabl e prosthesis and is considered as an aestheti c, functional restoration wit h l ong -term predictabilit y.1
The impl ant -abutment connection is a joint c onsi sting of 2 part s hel d together wit h a screw. The function of the s crew is to creat e a cl amping force bet ween the impl ant and abutment suffi ci ent t o withs tand external loads .1 Screw retenti on in impl ant -support ed prosthesis was devel oped in response to t he need for ret ri evabilit y even though occl usion and aestheti cs were s acri fi ced. There is almost no tolerance for error i n the fabri cation of the screw ret ained prost hesis becaus e a di rect m etal -to -m etal connecti on exists and there are man y vari abl es not in t he control of the doct or.2 Becaus e t here is no space bet ween the coping and impl ant abutment , the cas ting must fi t com plet el y pas sivel y and accurat el y before the screw is ins ert ed wit h a considerable torque force.1
Accurat e fit of dent al prosthesi s is ess ential for the long -t erm success of t he supporting st ructures whet her those structures be t eeth, mucosa, or im pl ant s. It had been st ated that a passive fit of a restoration is i mport ant for a ph ysiol ogi c tissue response and long -t erm
oss eoint egration o f implants. Due t o the ank yl oti c charact er of the implants, st ress i nduced b y a mi sfi t of t he super st ructures persist s.3
In im plant s upport ed prosthes is, mi nim izing st ress along t he implant and surrounding bone is a desired feature. Thi s could be possi ble t hrough a passi ve fit of the prosthesis ’ superst ructure on the implant abutm ents .
A fram ework i s considered passi ve when there is simultaneous circular cont act of all the prostheti c cyl i nders with thei r respective implant abutm ents .4 Therefore, a passiv e fit of the s uperst ructures is desi rabl e t o prevent uncont rol led st ress not onl y i n the adj acent bone but als o in the restoration its el f.5 , 6
A passi vel y fitti ng superstructure was fi rst cham pioned b y Branemark and col l eagues to m eet concerns surrounding t he unique qualit y of bone im plant anchorage. An oss eoint egrated i mplant has extremel y lim ited movement withi n the range of 10 µm whereas a nat ural tooth can m ove up to 100µm within its periodont al ligam ent , thus compens ati ng for a cert ain degree of inaccu rac y i n the fitting of a fixed parti al denture. This l ack of flexibilit y i n the bone -i mpl ant interface m eans that an y t ensil e, compressi ve, or bending forces introduced into an implant -support ed restoration through misfitt ing superstruct ures l acking passiv e fit will alm ost cert ainl y remain and result in problems ranging from screw loosening t o loss of osseoint egration.7
Achieving a pas si ve fit between im plant frameworks and underl yi ng st ruct ures is ess ential for s uccess ful long t erm oss eoint egration.8 If a pas sive fit i s not achi eved,
1. Il l fitting implant fram ework ma y caus e mechani cal fail ures of the prosthes es , impl ant s yst ems, or biologi c compli cations of the surroundi ng t issue.
2. Mechani cal com pli cations m a y include loosening of the prosthethesi s and abutment screws or fract ure of vari ous com ponent s in the s ystem .
3. Biologi c com pli cat i ons m a y i ncl ude advers e tis sue reacti ons, pai n, t endernes s, m arginal bone los s, and loss of integrati on.8
Stefania C. Kano et al. proposed a cl as sifi cation for the implant -abutm ent i nterface includes both horizont al and verti cal
com ponent s.9
T ype I: No horizontal or verti cal gap could be m easured (horizontal -A = 0 and verti cal -B = 0). Thi s cl ass was considered ideal.
T ype II: Onl y horiz ont al mis fit was obs erved; t he abutm ent was either undercontoured (B < 0) or over contoured (B > 0).
T ype III: Onl y verti cal mi sfi t (A > 0) was obs erved.
T ype IV: Bot h horiz ont al and vertical mi sfit were observed.
As in convent ional fixed rest orations , the caus e o f fi xed implant -support ed fram ework misfit is usuall y multifactoral . Distorti ons can occur in the x -, y- and z -axis and ma y be i ntroduced b y one or more of t he foll owi ng fact ors: impl ant ali gnm ent s , cast ing accurac y im press ion techniques and mat eria l s us ed, process of fram ework fabri cati on, fram ework design and confi gurat ion, and clini ci an/ techni cian experi ence.4 , 8 Moreover, distortions tend to increase wit h increasing prosthesi s span length. One -pi ece casti ngs of multipl e -uni t conventional fixed par ti al dent ures are t echni que sensitive and a certain degree of di st orti on (100 µm ) is accept ed.
Therefore t he us e of different impression techniques , verifi cation ji gs, low fusi ng m etal casts , casti ng fram eworks in secti ons, and m ast er reference casts have been suggest ed to mi nimize mis fit s duri ng fram ework fabricati on. S ectioning and soldering the fram ework can improve som e dis crepanci es , but still may not creat e an absolute fit .8 Some clinici ans have s uggest ed usi ng the KA L t echni que (kulz er Abutm ent Lut in g) in whi ch a cem ent m edium is us ed t o compens at e for an y mis fits.1 0 R ecent laborator y st udi es had shown that intraoral cementation of fram eworks ma y decrease the strains produced in the bone around im plant s; however, there is no docum ent ation of long -t erm success for s uch t reatment s. In s crew retained prost hesis preload s tress is on im plant -support ed superst ructure is t he st ress generat ed b y ti ght eni ng torque prior functi on and is infl uenced b y superst ructure misfit .1 1 Therefore the final cli ni cal fit of a fram ework depends on t he methods us ed and experi ence of the technic i an/cl ini ci an team .
Sci enti fi c evidence is l acki ng t o demonst rat e the need of a pas sive-fitti ng prost hesi s for long -t erm osseoint egration.1 2
During conventional desi gning of patt ern using patt ern wax, stress concent rations occur whi ch l ead to distort ed cas tings .1 3 , 1 4 Inherent i n l aborator y cast ing procedures are dis torti ons and irregul ari ties that ma y affect the fit and functi on of t he impl ant restoration. Inves ti gators have studi ed the impact of thes e casti ng errors on screw j oint int egrit y. C ast i ng procedures decrease t he percentage of appli cation torque and that machined abutm ent s retai ned si gni fi cantl y great er det orque values com pared t o cast abutments.1 3
A new method of desi gning and m aking patt ern using 3D print technology where t hes e stres s woul d be minim al was st udi ed. 3D printing is an addi tive met hod of manufacturing objects in which mat eri al s, s uch as pl asti c or m et al are deposit ed in l a yers to produce a three di mensional object. In t he past few decades t he y have qui ckl y devel oped into a new paradi gm call ed additi ve m anufact uring. 3D printing t echnology is bas ed on ink -j et princi ple and can print with a vari et y of materi als . The technology uses opti cal scanner to get a com put er ai ded desi gn (CAD) file whi ch i s process ed throug h speci aliz ed s oftware and s pli ced into a s eri es of two -di mens ional la yers. The print er produces t he object la yer -b y l a yer wit h support from a water -sol ubl e m at erial .1 5 3D printing is us ed for wax/resi n patt ern i n dentist r y.
AIM AND OBJECTIVES
The purpos e of this stud y is to asses s the accurac y of fit of casting obt ai ned b y 2 met hods of pattern maki ng viz, C onventional wax patt ern and 3D pri nt ed pattern .
REVIEW OF LITERATURE
Bran emark et al (1985 )1 0 st at ed that Trul y pas sive screw -ret ained pros thes is are virt ual l y im possi bl e to fabri cat e
Branemark to be ideall y in the 10 µm range. Becaus e there i s no space bet ween the coping and impl ant abutment , the cas ting must fi t com plet el y pas sivel y and accurat el y before the screw is ins ert ed wit h a considerable torque force.
R.A. E rikss on et al (1986 )1 7 stat ed that t he t em peratures eli ci ted duri ng drilling accordi ng to t he osseoint egrat ion technique wer e measured in vivo i n five edentul ous hum an m andibl es. The temperature changes were meas ured b y a therm ocoupl e, the tip of whi ch was situated 0.5 mm form the dril l surface and s eparat ed from it by a corti cal wall. Ei ghteen m easurem ent s showed a mean initi al temperature of 29.2°C before drilli ng and a mean maximum temperature of 30.3° C duri ng dri lling. The maximum temperature recorded was 33.8°C . The duration of t he maximum temperatures neve r exceeded 5 seconds. All temperat ures recorded were below the l evel for im paired bone regenerat ion. It was concl uded that drilling according t o th e oss eoint egration t echnique does not caus e an y impai red bone regenerati on becaus e of excessive heat producti on.
Patri ck J. Hen ry et al (1987 )2 8 st at ed t hat The precis ion of fit achi eved wit h the doubl e -check impression procedure ensures that the laborato r y fit of the prosthesi s superst ructure will be identical with that i n the m outh. A hi gh degree of accurac y is necessar y to properl y
distribut e functional stress es over the indi vidual impl ant s over the long term. This is parti cularl y im portant in t he m axil lar y prosthesi s where a proper st ress dist ribution i s criti cal to avoid t he ris k of dest ro yi ng an est abli shed oss eoi nt egration of the fixtures. Ext rem e requi rement s for the fit ting of t he prosthesis to t he abutm ents must be mai nt ai ned at all times , and the occlusion must be carefull y adjus ted: “Atraum ati c surger y must be foll owed b y at raum ati c prosthodont ics. ”
Mark R. Sp ector et al (1990 )5 2 s tat ed t hat M easurable distortions resulted from t he t rans fer of impl ant positions as recorded with three im pres s ion techniques. (technique I, gui de pi n -ret ai ned trans fer copings were united with aut o pol ym erizi ng acr yl ic resin and dental floss . t echnique II, a pol yvi n yl sil oxane impressi on was m ade in a stock tra y over h ydrocol loid t ransfer copings. In the thi rd t echni que, a condens ation sili cone impression was made in a stock t ra y over h ydrocoll oid t rans fer copi ngs)The magnitude of the dist orti ons were similar wi th all three techniques evaluat ed. In addit ion to di mens ional changes in the m at erials us ed, positi onal errors were al so att ribut ed t o the m echani cal com ponents used in t he trans fer process . Alt hough the errors m easured are rel ativel y sm all, the s tud y demons trates the pot enti al for distorti ons with the t rans fer techniques us ed.
Phi lippe Mojon et al (1990)5 0 stated that Acr yl ic res ins marketed as i ndex and patt ern mat erials have a pol ymerizati on shri nkage of 6.5% to 7.9%. Ei ght y percent of the ch ange appears before 17 minut es at room t emperat ure. Alt ering the powder -to -li qui d ratio b y
adding m ore li qui d s igni ficantl y i ncreases the shrinkage. When us ed as indexes, thes e m at erials coul d also be di stort ed duri ng pol ymerizati on in addition to dimensio nal change. This i s becaus e of unequal thickness along the index as well as the shrinkage “lakes”. Consequently, it mi ght be advis abl e to rel ine indexes when almos t all pol ymerizati on shri nkage has occurred. The use of a m ix as thi ck as possibl e will al so minimize the worst effects of pol ym eriz at ion.
Tors ten Jemt et al (1991 )2 5 stat ed that The cast framework was carefull y s eat ed on the impl ant s b y firs t ti ght ening down one of the terminal gold s crews com pl etel y. A poor fit was reveal ed as a gap opening bet ween the fram ework and t he terminal impl ant on the ot her side. The fi rst gold screw was uns crewed i f the fram ework s eat ed pas sivel y and t hen t he procedure was repeated at t he other term inal implant. A further as ses s ment of fram ework fit was m ade b y ti ght ening the gol d s crews , one b y one, starti ng with one of the i nt erm ediate implants on one side of the midli ne. The first s crew was brought down until t he fi rst resist ance was observed. At this point , the posit ion of t he screwdriver was identifi ed before the screw was com plet el y ti ght ened.
The dentists had been instruct ed to use a tightening force bet ween 10 to 15 Ncm . A m aximum of half a turn (180°) was allowed for fi nal ti ght eni ng. When m ore t han hal f a t urn was neede d to com plet el y s eat the s crew, the fram ework was considered to have a poor fit . A poor fi t result ed i n the fram ework being sect ioned and a soldering index made.
Fol lowing reassem bl y, a new tr y -i n was then made. Otherwis e, the prosthesis was com plet ed at t he l aborator y when the fram ework was
deem ed to have a passi ve fit on al l indivi dual impl ants. This ret rospective st ud y has shown a wi de range of probl ems and com plicati ons occurring during prost heti c treatm ent and the first year of function. Most of the pr obl em s have been obs erved in maxilla, but few of the problems have jeopardized t he conti nuous st abil it y of the fixed prosthes es . Most probl ems were eas y t o res olve, and thei r rel ati vel y simpl e m anagem ent was facili tat ed b y the ret rievabili t y of the impl ant s ys tem.
Chii-Chih Hsu et al (1993)5 1 stated that Int ensi ve st ud y of the avail abl e li terature, in additi on to clinical experi ence, emphasiz es t he importance of a precis e though passi ve fit of a s uperstruct ure on multipl e im plant abutments. The cons equenc es of im precision ma y be mani fest ed b y fail ure attribut able to undue s tress es on t he s everal constituents that m ake up the tot al prost hesi s, not the l east of which is the alveol ar bone that invests and support s the impl ant itself. Under the conditions of t his st ud y t he following conclusi ons can be drawn wit h respect to di stortion of abut ment positions on t he master cas t: 1. The bulk volum e of Dural a y acr yl ic resi n used to s plint or joi n impl ant trans fer copi ngs is an insi gni ficant factor in impres sion trans fer accurac y. 2. There i s no si gnifi cant difference in impressi on trans fer accurac y between splinted or non splint ed implant copi ngs. 3. With the Zei ser s ys t em it was pos sibl e t o achi eve reduced int er abut ment error in the pos terior regi on of master casts when compared with a solid cast s yst em.
Keion B . Tan et al (1993)3 3 st ated that S igni ficant di fferences i n transl ational and rot ational dis placement s were found bet ween c yli nders i n the s am e casting t ype. C yli nder location within the arch was associ at ed wit h a s peci fi c direction and m agni tude of translational and rotat ional displ acements. Even sm all rot ati onal di spl acement s m a y mani fest l arge gap appearances wit h the one -s crew t est because of t he
"m oment arm " effect . However, other rot ational di spl acem ent s ma y be hidden de pending on the direction and t he mom ent.
Russ ell A. Wi cks et al (1994)3 6 s tat ed that Three di fferent torque deliver y devi ces were evaluat ed: a hand -held screwdriver (D IB 048; Nobelpharm aUSA , Chi cago, IL), a manual torque wrench (D IA 250; NobelpharmaUSA), and an el ect ronic Torque Controll er (DEA 020; NobelpharmaUSA), using a calibrat ed torque meas uri n g d ynamom et er (M agtrol , Inc, Buffalo, NY). Each ass embl y was subj ected to six tri als, ti ghten ing t o recommended torque. This stud y suggest s t hat s crew positi on can be an indicator of fit i n dent al i mpl ant prosthesis i f the end point of screw rotation is adequatel y indexed, speci fi c to each ass embl y and screw.
Thomas Kallus et et al (1994)2 3 stat ed that The fit of the fram ework was rel ated t o the i mpressi on m at eri al us ed. S oft ti ssue com plicati ons were rel ated t o the t ype of impression m at eri al us ed and to the prosthodont ist who perform ed the treatm ent. R egis tered abutment-screw ti ghtness was rel at e d to the ti ght ness of the corresponding gold screws and t o those team m embers who perform ed
the ini tial t reat ment . Since it appears t o be di fficult to predi ct the em ergence of full -arch fixed pros thesis mobilit y, prevent ion can onl y be achi eved b y regular examination that incl udes reti ghtening of gol d and abut ment screws . It is suggest ed that this be done ever y fifth year.
However, to li mit recurrent mai ntenance costs , it is desi rabl e that the endurance of the s crew j oints be i mproved to avoid more s eri ous, ti me- consumi ng cli nical compli cations.
Nei l D. Millingl on et al (1995 )2 7 st ated t hat st ress es were evaluat ed wit h a photo el asti c coati ng. Stress es were induced on the cast superst ructure with fit dis crepanci es as sm all as 6 µm. For a fit discrepanc y l ocat ed at an i nterm edi at e abutm ent, the m aximum rat e of increase i n stres s on the s uperst ructure o ccurred withi n 40 µm. The screw joint fail ed t o clos e when the fi t discrepanc y reached 55 µm.
When the fit di screpanc y was situat ed at the end abutm ent , surface stress conti nued to ris e with increasing discrepanc y of fit up to the largest gap siz e test ed. Stress l evels were hi gher when the fit error was locat ed at an int erm edi at e abutm ent com pared to a simil ar si zed error at t he end abutm ent. The sit e of m aximum s urface stres s on the superstruct ure was al wa ys found t o be above t he intermedi ate abutment, reg ardl es s of the location of fit dis crepanc y. This sit e experi enced compres sive s tresses when t he gap was at the int erm ediate abutment whereas tensil e st resses were recorded for a gap at the end abutment.
Nan cy L. Clel land et al (1995)2 6 stated that Photoel asti c resin was cast di rectl y to two 3.75 × 13 -mm Branem ark fixtures (Nobelpharm a US A Inc, Chi cago, IL) situated 20 mm apart in a silicone mold of an edentul ous m andibl e. Two st rain -gauge ros ett es were also incorporat ed i n the resin to al low precis e det ermi nati on of princi pal st ress es at two locat ions. Four groups of three overdenture bars with 0, 180, 360, and 500μm vertical gaps were fabricated. These bars were s equenti al l y s ecured to the abutments wit h gol d sl ot screws ti ght ened t o 10 Ncm. Strain i ndi cator readings were recorded at a standardized tim e followi ng the initi al fast eni ng of each bar. The t est was repeat ed three times for each overdent ure bar. St rains are trans ferred to the bone when misfitting prost hesis were s ecured. Some of the st rain s m esi al to the fixture appeared to be unfavourabl e for regions of lower bone densit y when the groups with desi gned gaps were secured.
David As sif et al (1996 )4 9 stat ed that factor di scovered was that the m ast er fram ework, when connect ed t o the m ast er cas t, was st ress ed even though it was designed to have a “perfect passive fit” Possible reas ons for thes e st ress es could be att ri but ed to (1) movem ent of t he stai nless st eel anal ogs i n the m ast er model becaus e of t he s ett ing distortion of the Loctit e epox y re sin; and (2) ti ght eni ng of t he superstruct ure to t he anal ogs, becaus e the analog positioning was not carri ed out wit h the torque cont rol unit at 10 Ncm. An i mpressi on techni que usi ng ri gidl y int erconnect ed impressi on copi ngs via an aut opol ym eriz ed acr yli c resin splint is the preferred m ethod of
impress ion m aki ng for im pl ant -supported fixed rest orati ons. The techni que for achi eving a ri gid connecti on using copi ngs s pli nted to an acr yl ic resin custom tra y shoul d be improved so as t o creat e a st abl e bond bet we en t he autopol ym erizing resi n and the cust om tra y, thus ens uri ng ri gid spl inting and fixati on similar to the interconnected techni que.
Kenneth B . May et al (1996 )3 7 stated t hat P eriot est ins trument
was used to m easure t he preci sion of fit bet ween cast hi g h nobl e-met al frameworks and the supporting im pl ants in a pati ent -
simul ation model . Three fram ework conditi ons and three implant - location vari abl es were us ed t o evaluat e the ri gidit y of the as sembl y as measured b y t he P eriotest met hod. The fram ework variabl es were (1) one-pi ece castings (OPC); (2) s ectioned -sol dered inaccurat e casti ngs
(SS IC ); and (3) s ectioned-soldered accurate castings (SSAC). The implant -location vari abl es were ri ght ant erior (RA), cente r (C ), and left
ant erior (LA). The Peri ot est i nst rum ent quanti fi ed differences in th e precision of fit between t hree framework condi tions. The SSAC assemblies were si gnificant l y more ri gi d than the OPC and SS IC assemblies. The OP C and SS IC assem blies ' mean PTVs were not si gni fi cantl y di fferent. The m ean PTVs for the C impl ant location and the R A and LA impl ant locations were si gnificant l y di fferent (p < .01).
The m ean PTVs of the RA and LA implant locations were not si gni fi cantl y different. The im plant -loca tion PTVs followed the sam e rank order for all three fram ework condi tions. The procedures used t o
fabri cat e a m ore precis e fit between the fram ework and the s upporti ng implants is i nfl uenced b y the s kill of the clini ci an and technician.
Tors ten Jemt et al (1996 )2 1 stat ed that prost hesis routi nel y connect ed to os seoi ntegrat ed impl ant s could demons trat e distortion bet ween the fram ework and indivi dual impl ant s of up t o s everal hundred mi crons. When m as ter casts were us ed as a reference, the mean 3-D(photogram met ric t echnique) di stort ion of the cent er point of gold c yl inders was 37 µm and 75 µm for m andi bul ar and maxillar y prosthesis , respectivel y. The correspondi ng mean dis pl acement was 90 µm and 111 µm , respecti vel y, when t he intraoral im plants were us ed as references . Furtherm ore, the overall distorti on was si gnifi cantl y hi gher for the m axillar y prosthesis when the m as ter casts were used as the reference. In thi s stud y None of measured im plant sit es showed a perfect fit wit hout an y di spl acem ent.
Declan Byrne, et al (1998 )5 6 stat ed that prem achined abutm ents, incl uding thos e that are cast onto and are subj ect ed t o porcelain fi ring, are s uperi or i n adaptati on to those cast from burnout pat terns and laborator y finis hed. The result s ma y have both biol ogi c and m echani cal impli cat ions , alt hough controll ed cl ini cal tri als are still lacking.
Although the prem achi ned abutm ent s, onto which a casti ng can be made, m a y ful fil appearance requi rem ents whil e not com prom ising adapt ati on bet ween com ponent s, it is apparent fro m clini cal practice that the patt ern t ype abutm ent will still be requi red i n some situations.
From the res ults of this stud y, further development of the system are
requi red, i ncl udi ng i mprovements in patt ern desi gn and refinem ent of casting and fi nishing p rocedures.
Begoñ a O rmaech ea et al (1999)3 0 st at ed t hat When the x -ra y tube is properl y pl aced, radiographs can confirm the cl os ure of an implant -abutm ent int erface. X -ra y tube angul ation should not exceed 5 degrees. The use of an x -ra y tube posi tioner is recomm ended. The correct fit between i mplant and abut ment is a ke y factor in ensuri ng the success of implant -s upport ed rest orations. One radiograph per impl ant shoul d be taken at the tim e of abutment connection. A radiograph t aken with the film paralle l to t he impl ant and with t he x -ra y tub e perpendicular t o it is a reli abl e m ethod of veri f yi ng fit . With this techni que, one can obs erve openings of at least 21 µm. More than 5 degrees of angul ation of the x -ra y tube with respect to the I -A interface makes for s ubj ective int erpret ation of radi ographs when tr ying t o identif y gaps equal t o or l ess than 50 µm.
Wee, Alvin G et al (1999 )2 8 stat ed that Revi ewed arti cles were limited to thos e that addressed advanced strategi es to im prove fit . All of the s ci ent ifi c st udi es included in t his review us ed an in vit ro experim ent al desi gn. The advanced st rat egi es were cat egorized into methods that address intraoral indexing and m ethods t hat use the implant m ast er cast. Relativel y few m et hods have been s ci entifi call y proven to improve fit in impl ant prost hodonti cs. M ost of the t est ed strat egi es still resul ted i n a sli ght mi sfit of the fram eworks to the implant abutm ents/ analogues. Multi pl e factors preclude that the
concept of "pass ive fit " can be achieved i n implant prost h odonti cs, even with t he us e of advanced st rat egies. The us e of m eticul ous , accurat e im pl ant prosthodonti c procedures and t he appropri ate us e of advanced strat egi es continue t o be t he recomm ended means of achi eving preci se fit of t he impl ant prosthesis to t he intraoral abutments.
Jos eph Y. K. Ka et al (1999 )8 stat ed that The suggest ed l evels of pas sive fit are em piri cal. Num erous techniques have been advocat ed to evaluat e the prosthesis -impl ant int erface, but none individual l y provides obj ecti ve results . It i s suggest ed t hat cli nicians use a com bination of t he avail abl e m e thods t o minimize mi sfits. On the basi s of what i s known, t he rel ative mi sfit wi th the avail abl e fit evaluati on methods cannot be accurat el y as sessed and det erm ined. In the abs ence of such quantit ative fit guideli nes, achi evi ng pas sive fit m a y be of emoti onal reasons rather than of evidence -based s cience. The level of this mis fit has yet to be det ermi ned. Therefore improvi ng cli ni cal techni ques s uch as t he us e of ri gi d impressi on m at erials, cus tom t ra ys , cementabl e s upers truct ure, and a combination of t he a vail able evaluati on m et hods descri bed i n this revi ew ma y be reli ed on to optimiz e fit or compens at e for mi sfi t.
Marian a pi men tel gui marães et al (2001 )6 st at ed that the ti ght eni ng torque is an im portant fact or to im prove m echanical and biological properties of the int erface between impl ant and abutment.
Despit e of that, t he use of t he t orque recomm ended from th e
manufacturer m a y potenti all y reduce t he advers e effects of microl eakage although microbi al and fluid penetration occur on implant/ abutment interface even if a good margi nal fi t between com ponent s exist. This mi crobi al col oni zation w as not obs erved on subm erged im plants. Among the m et hods to anal yz e the adjustm ent bet ween im plant and abutment, the scanni ng el ectron m icros cop y showed a m arginal gap on impl ant/ abutment int erface that vari ed bet ween 5µm and 45µm, reveali ng itsel f as an effi ci ent m ethod for this king of anal ysi s.
Firas Daoudi et al (2001 )4 5 stat ed t hat The repositi oni ng impress ion technique at the implant l evel showed more variati on in the positi on of an abut ment/ impl ant anal ogue ass em bl y i n the resulti ng casts. The pi ckup impressi on t echni que at the abutm ent l evel can be more predi ct abl e to use than t he repositi oning impression t echnique at the im plant level. No si gnificant differences were found between President and Impregum F im pression m at eri als for impressi ons of the t ypes t est ed. The discrepanci es obs erved would, if produced i n a clini cal s etting, res ult in a need for adjustment, or in som e cas es wit h the impl ant -l evel technique, even rem aki ng of t he final restoration.
Jason Bu rns et al (2003 )4 3 stat ed that as measured b y vertical fit discrepanc y, ri gid cust om clos e -fi t trays and s paced cust om tra ys produce si gni fi cant l y more accurat e impressions than fl e xibl e pol ycarbonat e stock tra ys . Also, for anal ogs with a 20m m separation,
there was a di fference i n medi ans of 10mm in accurac y bet ween the stock and cust om t rays , as measured b y vert ical fit dis crepancy.
Manoj Rajan et al (2004 )2 0 stat ed t hat Pl acem ent of the hexagonal screwdri ver s crew i n access channel will ai d in proper wax patt ern m aking. The retrievabl e cement/ screw -ret ai ned impl ant - support ed prost hesis com bines t he advantages of a cement ret ained and screw -ret ained prost hesi s . R et ri evabil it y of the cem ent ed restoration rem ai ns debat abl e. In the prost hes is des cri bed in this art icl e, the abutment and prost hesi s could be easi l y removed from the impl ant without t he us e of a crown rem over. The pres ence of an open abutment screw acc ess channel all ows the prost hesis to serve as an abutm ent - reposi tioni ng device. The di sadvant ages of t his t echni que are that it ma y be cont raindi cat ed for pati ents with l imited int er occlus al dist ance and a cus tom waxing of the abutment m a y be requi red. Fu rt her long - term studies are needed to evaluat e its appli cat ion i n mult ipl e impl ant support ed rest orati ons..
Matthi as Karl et al (2004 )7 stat ed that As an absolut e pass ive fit of superst ruct ures is not possibl e us ing conventi onal cli nical and laborator y procedures, and as clini cal fit -evaluation methods often do not detect “hidden” inaccuracies, the more sensitive strain gauge techni que should be utilized for an obj ective accurac y t es t . Reference strain val ues from implant -support ed prosthesis t hat have s erved without complications could help define a “biologically acceptable fit.”
It must be assum ed t hat passivel y fitti ng restorations reduce t he risk of
biologic as well as mechani cal fail ures . As bondi ng the superst ructure at l east compens at es for the ina ccuraci es res ulting from i mpressi on maki ng and laborat or y procedures, it more clos el y approximated a pas sivel y fit ting rest oration in thi s invest igati on.
Ki van c ak ca et al (2004 )4 6 stat ed that the outcomes achi eved with the direct and indi rect impressi on techniques were si milar. As were the out com es using pol y eit her and vin yl pol y sili cone i mpressi on mat eri al s. The positional and angul ar accurac y of IT I snap -on impress ion technique usi ng a stock tra y VPS impression was accept able, and this methods was f ound to be conveni ent for multiple implant i n this m odel seri es.
W. Ch ee et al (2006 )4 0 stat ed that When impressi ons are requi red for multi i mplant restorati ons t he precision of the i mpressi on is even more criti cal . This is becaus e frame works will be constructed from the m ast er cast and mis -fit in t he fram eworks can l ead to st ress applied to the impl ants on s crewing down the fram ework. Bone l oss and even loss of integrati on has been att ribut ed to t hi s misfi t.
Manufacturers have developed impression copings with metal wings’
that can be connect ed wit h acr yl ic resi n t o reduce t he bulk of shri n king acr yl ic to further i mprove di mensional stabilit y of the im pressi on in order to obt ain a passive fram ework. Another met hod of trans ferring soft tis sue inform ati on is incorporat ing t he provi sional res toration into the im pres sion. When screw retained res torations are used, the provisional restorati on it sel f can be used as a pi ck up t ype impress ion
coping. Using t he modifi ed impressi on techniques , information regarding soft ti ssues can be t rans ferred t o the m ast er cast.
Stefani a C. Kan o et al (2006 )5 5 stat ed that The component interface geom et r y, amount of machi ning tolerance provided, and com ponent passi vit y can impact t he potenti al for s crew loosening.
Machined tit anium abutm ent s retai ned a si gni ficantl y great er percentage of the 30 Ncm appl ied torq ue t han cas t abutm ents . No si gni fi cant di fference of detorque val ues was noti ced among cast abutments.
Sunjai ki m et al (2006)2 2 st at ed t hat the amount of displ acem ent of impression copi ngs or im plant replica that occurred duri ng com ponent connect ion was as great as 3D dimensional li near displ acem ent int roduced whil e m aki ng impress ion or fabrication of definit ive cast. The nons plin t ing group s howed sm all er dist orti on com pare t o li ght cure res in splinted during impressi on making. The li ght cure resi n spli nted group showed small er distorti on compare to non spli nting group duri ng fabri cat ion of definitive m at er cas t.
Ji-Yung Kwon et a l (2007 )5 stat ed t hat Gap di stance was measured at t he ri ght impl ant abutm ent repli ca -gol d c ylinder interface.
A mean gap di stance was calculated b y m eas uring t he gap at the buccal, di stal, and lingual aspects wit h non -cont act PMM for each specim en. The m e an gap distance found after casti ng was 106.3 μm for buccal side, 122.1 μm for distal side and 117.1 μm for the lingual side.
Even though the techniques used in this stud y st ri ctl y fol lowed the
guidelines establis hed i n the l iterature, t he 30 cast im plant bars evaluat ed all yi elded gap di stances t hat were be yond acceptabl e accurac y. There was a s tati sti call y si gni ficant di f ference bet ween pre - casting and post -cas ting bar l engt h (P <0.01). There was a decreasing tendenc y i n bar lengt h aft er cas ting procedure. It was necess ar y to correct t his dim ensi onal change from l aborator y procedure b y som e corrective met hods.
Stefani a C. Kano et al (2007 )9 stated t hat A l arge mi crogap at the im plant -abutm ent interface has been reported to res ult i n advers e effects, i ncl ud i ng s crew loosening, abutment rotati on, and abutment fracture. However, a st andardiz ed cl assi fi cation of the implant - abutment i nterface has not been est abl ished. The purpos es of thi s investi gati on were (1) to propose a clas sifi cation s yst em based on the horizont al and vertical mi crogap of t he i mplant -abutm ent i nt erface and (2) to compare the im plant -abutm ent int erface in 4 groups of abutments. The propos ed impl ant -abutment classi ficati on s yst em dem onst rated a wa y to characteriz e and com pare the mi crogap at the implant -abutm ent i nterface. Thi s stud y results shows no si gni fi cant difference bet ween groups wit h respect to verti cal misfit. For horizont al mi sfit , m achined tit anium abutment s pres ent ed si gnifi cantl y hi gher horizont al m isfit compared t o other gro ups and Premachined cast-on abutm ents had si gnifi cantl y hi gher horizont al mi sfit than cast NiCr abutm ents.
Stefani a C. Kano et al (2007)1 3 stat ed that the prem achi ned pall adi um cast -on abutm ents and the pl asti c burnout abutm ents cast with NiC r had l ess th an 2 degrees of rotational mi sfit and can att ai n optim al rot ational s crew joint stabilit y. The pl asti c burnout abutments cast with CoC r exceeded 2 degrees of rotational mis fit . C asti ng plas tic burnout abut ments with CoC r is cont raindi cat ed i f optim al rotat i onal screw j oint st abilit y is t o be att ained. All of the cast abutment s dem onst rated great er rot ati onal mi sfi t than the m achined tit anium abutment however, t he result s obtained in this stud y showed that the rot ational stabilit y achi eved with pl asti c burn out abutm ents cast wit h NiCr was equival ent to that achieved with machi ned component s.
Casti ng procedures can affect rot ati onal misfit .
Heather J. Con rad et al (2007 )4 4 st at ed t hat The combined interact ion of impression technique, im plant angulation, and impl ant number, had no effect on the accurac y of the dupl icat e cast s compared to the defi nitive casts. The average angl e errors for t he open t ra y techni que were not s ign i ficantl y di fferent from t he average angl e errors for the clos ed tra y t echni que. There were si gni ficant di fferences when isol ating the mai n effect for impl ant angulati on and i mpl ant number as wel l as t he combi ned int eraction of i mplant angul ation and im pla nt number The interaction result s had no int erpret abl e pattern. The interact ion of impression t echni que wit h either t he i mpl ant angul ation or t he implant number was not si gnificant.
Heeje lee et al (2008 )4 2 stated that there was no effect on implant dept h on dimensional accurac y of putt y and l ight bod y com bination with VPS impression either verti call y or hori zontall y.
However, for pol yet her m at eri al , the im pressi on of an im plant pl aced 4mm sub gingi vall y showed a greater horizontal distorti on compared to the im plant pl aced more coronall y. Adding ext ensi on to the ret ent ive part of the im press ion copi ng elimi nated t he difference.
Heeje l ee et al (2008)4 7 st ated that abutment or impl ant l evel internal connection i mplants revealed t hat most st udi es report ed great er accurac y of impl ant impress ions with t he splint t echni que than w ith the non spli nting t echni que . For situati ons i n whi ch t here were 3 or fewer implants s tudi es showed no di fference between the t ransfer and pi ck up techni que, whereas for s ituations i n whi c h t here were 4 or more implants, more st udi es showed m ore accurat e impressi ons wi th pi ck up techni que t han t rans fer t echnique.
Gus tavo au gus to s eabra b arb osa et al (2010 )4 st ated that To provide passive fit or a s train free supers tructure, a framework should, theoreti call y, i nduce absolut e zero st rai n on the supporting implant com ponent s and the surrounding bone i n the abs ence of an appli ed extern al load. when com pared with CP Ti and Ni -C r-Ti all o y, pres ent ed the worst resul ts for pas sive fit , in acco rdance with ot her study results . But , for vert ical fit, Co -C r allo y was st at isticall y simil ar to C P Ti and Ni-C r-Ti al lo y. However, Co -Cr fram eworks c ast in two pieces and laser welded s howed si gni fi cantl y bett er accurac y in com pari son to CP
Ti cast in a single piece. Furt her res earch is necess ar y t o revi ew t he use of Co -Cr all o y as an alt ernat ive for fabri cating implant fram eworks.
Rob erto Sorren tino et al (2010 )4 1 stat ed that The pres ence of undercuts negati vel y affect ed t he preci sion of the impress ions. The angul ation of the im plants ma y caus e strains of impressions, probabl y becaus e of the hi gher forces required for the im press ion removal. In the pres ence of nonp arall el implants, the us e of additi on silicons result ed in more accurat e casts , parti cul arl y toget her wit h a s hort ened length of the connect ion part of t he copi ngs. In the pres ence of paral lel implants or when the pol yether was used, a st andard l ength conn ection of t he copi ngs produced m ore accurat e casts.
Ilser Tu rkyi l ma et al (2011)2 stated that CAD/CAM t echnol ogy has revoluti onized t he fi eld of impl ant dentist r y. surgi cal guides have greatl y im proved t he predi ct abil it y of im plant surger y. CAD/ CAM bars and fram ework have proven more accurat e, l ess expensive, and l es s time-cons uming t o produce. All of this resul ts in improved experi ence for the pati ent, decreas ed t reatm ent ti me, and great er accessibilit y.
Di git al impressi on s ys tem s and CAM models for tooth born restorations are rapi dl y expandi ng in the market . Virtual toot h libraries allow CAD/C AM of both provisi onal and final tooth -born res torations.
J ust on the horiz on is virt ual arti cul ation and virtual toot h arrangem ent , thus compl eti ng the virtual approach of dental technology. It is cl ear that CAD/CAM t echnology has transform ed al l
aspects of denti str y, not just im plant dentist r y. Framework fit can be assess ed b y a vari et y of m ethods. Cl inical met hods for ass es sing fram ework fit i ncl ude finger pres sure, visual i nspection, radiographs , tactil e s ensat ion. S heffi el d t est , disclosing ma t eri als, and the s crew resist ance t est.
Jung-H an Choi et al (2011 )1 1 stat ed t hat strains were produced b y connecti on of t he superst ructure, regardl ess of s crew -ti ght eni ng sequence, torque, and met hod. No st atis t icall y s i gni fi cant differences in superstructure s trains were found bas ed on s crew -ti ght eni ng sequences wit hin the limit ations of t his i n vit ro stud y, screw -ti ght eni ng sequence, torque, and met hod were not cri tical factors for t he st rain generated on a well -fi tting int ernal -connection implant s upers tructure b y the splint ed im pression technique. Further studi es are needed to evaluat e the effect of s crew -t i ght ening techniques on t he prel oad st ress in various di fferent clinical sit uations. Al though the four im pl ants were positi oned parall el to each ot he r in the pres ent stud y, lack of parallel ism between implants is comm onl y encountered i n clini cal implant prosthodont ics. The l ack of paral lel ism m a y exaggerat e t he misfit between a framework and im plant s, especi all y wi th an internal - connecti on impl ant . In other words , for an equall y distorted fram ework, t he prel oad st resses on the fram ework will be great er for nonparallel implants than for parall el im plants. Additi onal st udi es are necessar y to evaluat e the effect of screw -ti ght eni ng t echniques on the preload st ress using fram eworks wit h various degrees of fit t hat can be obt ained cli ni call y w ith nonparal lel impl ants.
Ali T ah mas eb et al (2011 )3 5 st ated that t wo m ethods of measurement of fi t (opti cal s canni ng and strai n gauge as sess ment).
Bot h cl earl y identified a known mis fit that was created t hrough a com put er -aided desi gn/ comput er -assis ted manufacture fram e fabri cation met hod. Given its sim pli c it y, the opti cal method ma y have val ue as a qualit y control m easure i n the dent al laborat ory. Opti cal scanni ng dem onst rat ed an accurac y of 10 µm for t he cont rol fram e, whil e t he mis fit frame dem onst rat ed great er dis crepancies, both at t he intentional l y mi s fit connecti on and at t he other connecti ons al though the l att er connecti ons showed les s misfit. Opti cal scan anal ys is was abl e to det ect the mi sfit in the t est superstruct ure and the manipul at ed implant. The st rain gauge m easurem ents confirm ed thes e findin gs, indi cat ing that both methods of asses si ng inaccurac y are effective.
Opti cal scan anal ys is ma y be used as a simpli fi ed and clini call y applicable method to det ect mi nor misfits i n im plant -s upport ed superstruct ures .
Marian e mi yashi ro et al (2011 )1 6 stat ed that In vit ro s tudies requi re isotropi c s pecim ens wit h elasti c charact eristi cs simil ar to thos e found in t he t arget m andibul ar regi on. The hom ogeneit y of pol yurethane (P U) could favour its use in biomechanical s tudi es of force dist ribution on i mpl an t support ed prost hes es aim ed at est abli shing correl at ions bet ween strai ns generated in the periimpl ant region and physiological strains as proposed by Frost’s theory. Based on these grounds, t he purpose of t his stud y was to val idate t he use of an experim en t al pol yurethane m odel in in vit ro bi omechanical studi es
of i mpl ant -support ed prosthes es. P U has best m echani cal and handli ng charact eri sti cs, and shoul d be t he concentration of choice 1: 1 (pol yol : di isoc yanat e)- pol yurethane reagent for buildi ng of expe ri ment al models to be us ed in upcomi ng bi om echani cal studies of impl ant support ed prost heses in t he mandi bul ar regi on.
Pri thvi raj et al (2011 )1 9 stat ed that accurac y of impl ant impress ion t echniques revealed that more studi es reported great er accurac y of impl ant impress ions with t he splint t echni que than with the non spli nt t echni que. For sit uations in whi ch there were 3 or fewer implants, m ost studi es showed no difference bet ween the pi ck -up and trans fer t echniques , whereas for situati ons i n whi ch t here were 4 or more impl ants , more studi es showed m ore accurat e impres sions wi th the pick-up t echnique (open t ra y) than t he t rans fer t echnique (cl os ed tra y). P ol yet her and VPS were the recomm ended m at erials for the implant im pressi ons . Results indi cat ed that the 2 -st ep VPS i mpressi on was si gni fi cantl y less accurat e than the 1 -step putt y and li ght -bod y VPS combinati on i mpressi on, t he medium bod y VPS monophas e impress ion, and the medi um -bod y pol yet her monophas e impressi on.
Jian Sun et al (2012)1 5 st at ed that Dent al prosthesi s can be fabri cat ed l a yer b y la yer directl y from a comput er model easil y and rapidl y b y various Rapi d prot ot yping (RP) t echni ques wit hout part - speci fi c tool ing and hum an i nt ervention. Thi s techni que i s a revolutionar y change fo r dent al prost hesi s fabri cation. With the devel opm ent and res earch of the diversit y for RP s yst ems and
corres pondingl y bui lt mat eri als , it is possibl e to generat e different kinds of dent al prost hesi s for different applicati ons . These applicati ons incl ude dent al prost hesi s wax patt ern, dent al (facial ) prost hesis m old (shell ) dental metal prosthesis, and zi rconia prosthesi s. RP technology, a new approach i s possi ble for aut omatic wax -up fabri cati on. This approach simpl ifi es the tradi tional fabri cation process and accel erat es the production turnaround period b y using 3D im aging, C AD(com put er aided desi gn), and R P.
Hesham Ibrahi m O th man et al (2012)3 stat ed that A cust om desi gn, a perfect fit and a hi gher resis tance are the main characterist ics of CAD/CAM impl ant abutments. Fut ure developm ents of CAD/C AM will m ake it pos si ble to produce m ore resist ant abut ment s and restorations wit h hi gher qualit y and l ower fabri cation tim e and costs. a pas sive fit of a reconst ruction is important for a ph ys iologic tissue respo ns e and long -t erm oss eointegrati on of impl ant s. Alt hough more recent fi ndi ngs suggest that stress i n t he bone adjacent to impl ant s induces bone form at ion. But because of the ank ylot ic character of the implants, st ress induced b y a mis fit of the s uper structures persists fore, a passive fit of the s uper st ruct ures is des irabl e to prevent uncontroll ed stress not onl y i n the adj acent bone but als o in the reconstruction itsel f. Nam el y, it has been cl aimed t hat supra -st ructures with a poor fit ma y lead to pros thet ic com pli cations such as l oos eni ng or fracture of screws, as well as fract ure of frameworks or veneering cerami c and even fract ures of abutment s or i mpl ants.
Tuncer Burak O zcelik et al (2012 )1 8 st ated that S everal im pl ant impress ion t echni ques with di ffer ent m aterial s have been described in the lit erature. Generall y, border mol ding, functional, and final impress ions have been m ade with 3 di fferent mater i als, whi ch m akes the procedure techni que -s ensitive and ti me -consuming. A combination of open -t ra y and functi onal im press ion t echni ques is des cri bed i n thi s techni cal report. Border mol ding and functional impressi on procedures are m ade at the s ame tim e using a vin yl pol ys il oxane impressi on mat eri al , whi ch m akes this t echnique a si mpl e and tim e effi ci ent alt ernat ive for cli nici ans. The funct ional impres sion with open techni que records the m ucos a in a functional fashion and simult aneousl y records the im pl ant com ponents along wit h the alveol ar tissues. i t provi des an accurat e rel ati on of the impl ant components and the supporting tis sues.
Siddharth shah et al (2012 )3 4 stat ed t hat . There are t wo im pl ant fram ework fabri cati on t echni ques t hat are currentl y us ed i n a major situations one invol ves cop y milli ng sections i n tit anium and l as er wel ding the secti ons together. The ot her i s convent ional lost wax techni que, whi ch i s us ed to cast one - piece full arch implant fram ework. Al l EDM (El ectri c discharge machine)process ed superstruct ure, showed positive one screw test i.e. the y fitt ed passi vel y on abutm ent head. Stud y results show t hat nickel -chromi um allo y can be used for fabrication of implant superst ruct ure wit h EDM as programm ed refini ng procedure to achi eve passive fit.
Stefan Hols t et al (2012 )3 9 stated that R ecent advances in indus tri al non -contact s canners offer unprecedented opport unities for qualit y ass es sment of dent al restorat ions. The m aj orit y of investi gati ons publi s hed t o date are limi ted to l ocal t wo -di mens ional results . A tri pl e -s can prot ocol for vi rtual fit ass essm ent of multi -unit screw -ret ained impl ant restorations i s pres ent ed in t his technical report. The advant ages for appli cation in bi om echani cal research incl ude det ail ed three -dim ensi onal i nformation on internal component congruence in impl ant superst ruct ures to be us ed in m at hem ati cal mod els. appl icati on of tripl e scan protocol technique is an eas y-to-use method facili tati ng t he 3D int ernal fit and precis ion m easurem ents of implant restorations It can be used t o provi de valuabl e dat a on manufacturing di stortion and mis fit of im plant -retained restorations.
V. N. V. Madhav et al (2013 )5 4 stat ed that In m anufact uring rapid prot ot yping, onl y non existi ng models are usuall y virtuall y desi gned on the comput er screen and then convert ed to ph ys ical models. Rapid prot ot ypi ng, additi ve manufacturing, 3 dimensional printing t echnology is becoming a com mon appl i cation wi t hin m an y indus tri es s uch as manufacturing and medi cine. As m ore research is bei ng t o devel op 3D pri nting is rapidl y becoming an affordabl e technology that has the pot enti al to change not onl y t he future of fabri cating m edi cal models and protot yp ing but als o soci et y. M ain advantages is Possi bilit y t o obt ai n more realist ic l ooki ng prosthesis becaus e t he model is form ed from nature tissues.
