Peter Briggs Arijit Ry-Chudhuri nd Kewl Shh Avoiding nd Mnging the Filure of Conventionl Crowns nd Bridges Astrt: The replement of rowns nd ridges is ommon proedure for mny dentl prtitioners. When orretly plnned nd exeuted, fixed prostheses will provide preditle funtion, esthetis nd vlue for money. However, when done poorly, they re more likely to fil premturely nd led to irreversile dmge to the teeth nd supporting strutures eneth. Sound dignosis, ssessment nd tehnil skills re essentil when deling with filed or filing fixed restortions. These skills re essentil for the 21st entury dentist. This pper, with treted linil exmples, illustrtes the res of tehnil skill nd linil deisions needed for this type of work. It lso provides dvie on how the risk of premture filure n, in generl, e further redued. The rtile lso onfirms the very rel risk in the UK of dento-legl prolems when ptients experiene unexpeted prolems with their rowns nd ridges. Clinil Relevne: This pper outlines linil implitions of filed fixed prosthodontis to the dentl surgeon. It lso disusses ftors tht we n ll use to predit nd redue the risk of premture restortion filure. Restortion design, linil exeution nd ptient ftors re the most frequent resons for premture prolems. It is worth rememering (nd informing ptients) tht the helth of the underlying supporting dentl tissue is often irreversily ompromised t the time of fixed restortion filure. Dent Updte 2012; 39: 78 84 The provision of onventionl rowns nd ridges is ommon proedure for most generl nd speilist dentl prtitioners. It is estimted tht more thn one million rowns re pled per yer under the NHS Generl Peter Briggs, BDS(Hons), MS, MRD, FDS RCS(Eng), Consultnt in Restortive nd Implnt Dentistry, Mxillofil Unit, St George s Hospitl, London, SW17 OQT, Speilist Prtitioner, Hodsoll House Speilist Referrl Prtie, Frninghm, Kent DA4 0DH nd BSSPD ounil memer, Arijit Ry-Chudhuri, BDS, MFDS RCS(Ed), MJDF RCS(Eng), LLM, Speilist Registrr in Restortive Dentistry, St George s Hospitl, London, SW17 OQT nd King s College Dentl Hospitl, London, SE5 9RW nd Kewl Shh, BDS MFDS RCS(Eng), Speilty Dentist in Restortive Dentistry, St George s Hospitl, London, SW17 OQT. Dentl Servies (GDS) in Englnd nd Wles ontrt with n unknown numer pled independently of this. 1 This represents yerly spend of 117.5 million under the GDS ontrt lone in the yer ending Mrh 2005. It is likely tht the totl numer of rowns pled (NHS, insurne nd self-funded) is doule tht figure. All qulified dentists will hve enountered the filure of rowns nd ridges (Figure 1). The most reent Adult Dentl Survey 2 onfirmed tht 37% of dults hve one rown or more (men = 3) nd 7% of dults hve ridge (3% ged 16 44 yers nd 14% ged 55 74 yers). Unfortuntely, the numer of resin-onded ridges still remins disppointingly low. 3 Brtlett nd o-workers hve previously ommented tht prtitioners re more likely to presrie onventionl ridges thn dhesive lterntives. 4 If onventionl rowns nd ridges re presried nd mintined well they re likely to provide good linil servie nd vlue for money. However, unless the restortions Figure 1. A ptient with likely prfuntion showing evidene of filure of oth dhesive ermi nd onventionl fixed restortions. outlive the ptient, they will eventully fil. The ommonest use of rown nd ridge filure is ries 5 8 (Figure 2). Mny restortions will lso fil s result of de-ementtion, or prtil de-ementtion in the se of ridges. For mny ridge filures it is diffiult to know whether de-ementtion of n utment preeded the ries or not. The uthors onsider tht prtil de-ementtion nd the 78 DentlUpdte Mrh 2012
d e f Figure 2. Gross seondry ries evident fter removl of onventionl rowns t UR1, UR2 nd UL1. The ptient will need different restortive strtegy to restore these teeth suessfully. g Figure 3. () Cse 1: A frontl view of the ptient desried in Cse 1 whih illustrtes frturing of the veneering ermi of UR1, UR2 nd UL1. () Applition of Sinfony TM Opquer (3M ESPE) to the metl su-struture of the ridge fter intr-orl sndlsting. () Post-opertive review of diret Grdi omposite (GC) to msk the frtured ermi. reking of the retiner sel is ommon use of tstrophi ries eneth ridges. Pulpl nd endodonti prolems eneth otherwise well-funtioning rowns nd ridges re ommon. 6,9 13 This mens tht dentists will often e required to undertke endodonti ess through existing rowns or ridges or fter they hve een removed. Tn et l found mehnil frture to ffet 3.2% of their reviewed fixed prostheses. 9 It must lso not e forgotten tht some ptients re unhppy with the Figure 4. () Cse 2: Mxillry olusl view. The 3-unit fixed-fixed onventionl porelin fused to the metl ridge in the upper left qudrnt repled UL5 with frture of the ermi on the ponti. The 4-unit fixed-fixed onventionl ridge of the upper right qudrnt repled missing UR56. The right ridge displyed ermi frture on the lil spets of the UR56 pontis. () Bul spets of the UR56 pontis. Existing ermi frture likely to reflet prfuntion nd indequte metl support. () Clinil view of the ridge of the upper left qudrnt fter setioning nd prior to removl nd investigtion of UL46. Olusl nd pltl setioning of retiners ws hieved with dimond ur for the porelin nd new fluted tungsten ride ur for the metl. The uthors never reommend tpping off onventionl ridges s this is likely to led to signifint irreversile dmge to the teeth nd ores eneth. (d) The ridge in the upper right qudrnt hs een removed ut olusl ontt etween the UR7 nd LR7 remins. The prolem ws resolved y further olusl djustment of UR7 nd presription of metl for the olusl spet of the future retiner (gold rown with pre-ermi solder to UR6 ponti). Note some over-eruption ssoited with the LR6. (e) The sme ptient s ove fter ementtion of the new posterior ridge in the upper right qudrnt. Note tht the ridge hs een re-designed to inorporte full veneer preious metl rown whih hs een soldered to the PFM elements of the ridge. This design llowed less tooth redution on olusl nd ul spet UR7. Current evidene onfirms tht tooth preprtion for posterior PFM ounts for pproximtely 76% of the oronl tooth struture. 26 (f) Cementtion of the replement ridge in the upper left qudrnt. Note tht the ridge hs een re-designed to inorporte movle joint etween the ponti nd the mesil utment. The uthors reommend n F/M joint where there is signifint differene in the likely retention offered y the mjor nd minor utments. The femle slot should e pled within the distl spet of the minor retiner nd the mle portion integrl to the mesil spet of the ponti. Metl ICP stops on metl surfes of ridges nd ul ermi re ppropritely supported y underlying metl. (g) Bul view fter ementtion of the ridge in the upper right qudrnt. Note tht the ptient greed to hve metl mrgin t the ollr of the UR5 retiner (fvourle lip line) whih llowed the liniin to remove less tooth tissue in the ervil re. Metl ollrs on PFM rowns/retiners outside the estheti zone re eptle to ll ut the most esthetilly wre ptients. finl estheti result of their rowns nd ridges. 11,14 16 Poor ptient seletion together with the su-optiml linil exeution of tooth ore uild-up, tooth preprtion(s), impressiontking, jw registrtion nd ementtion will inrese the risk of erly restortion filure. Unfortuntely, the long-term prognosis of nturl teeth eneth filed restortions will e detrimentlly ffeted y these linil Mrh 2012 DentlUpdte 79
d e g h f i Figure 5. () Cse 3: Upper olusl view showing two posterior PFM ridges in the upper rh. () Lower olusl view the lower left qudrnt restored with 3-unit fixed-fixed onventionl ridge. The lower right qudrnt ws restored with 4-unit onventionl ridge. () A right ul view illustrting lk of olusion nd posterior funtion of the upper nd lower PFM onventionl ridges on the right-hnd side. The ptient hs n endodonti sinus from the filed RCT of the UR5. There ws rrested uo-ervil ries on the LR3 nd res of lolized plque-indued gingivitis. (d) Olusl view fter removl of the ridge in the upper right qudrnt to llow investigtion of UR56. Note gingivl inflmmtion round the UR56 nd the lk of olusl height with UR5. (e) Olusl view fter rown lengthening surgery nd temporiztion of UR56. The UR5 lso required pil surgery. Note tht the UR3 is unrestored nd therefore menle to t s n utment tooth for preditle dhesive ridge. (f) Full ontour dignosti wx-up reted prior to removl of ridges. Also used to onstrut indiret provisionl restortions. (g) Right ul view fter investigtion nd restortion of the utment teeth. The ptient hd temporry ridges in situ for three months to mke the est ssessment of the modified olusl sheme. Definitive ridges were pled on the right side first. An interolusl reord ws tken with Miro-Beuty Wx (Moyo, USA) whih ws only supported y the prepred posterior teeth on the right side. The nterior nturl teeth nd the left provisionl ridges stilized other res of the olusion during the right jw registrtion, whih ws further refined y reline with TempBond (Kerr Dentl, UK). (h) Upper olusl view of the fit nd djustment of the restortions in the URQ. Note the distl ntilever dhesive ridge repling the UR4. The olusl spets of UR45 will e polished one the olusion is pproprite. The UR4 hs een restored with distl dhesive ridge from UR3 whih llows the root-filled UR5 to e restored s n individul rown. Upper left qudrnt hs een redesigned with fixed-movle restortion. The ottomed-out femle portion of the joint is pled within the distl spet of the minor retiner (UL5) nd the mle omponent is prt of the nterior spet of the ponti. (i) Lower olusl view fter finl ementtion of the definitive ridges. (j) Anterior view fter review of replement rowns nd ridges. Note tht the sinus hs heled t UR5. Preopertive disussions onfirmed tht lip line llowed ptient to ept metl ollrs. j Generl Dentl Counil (GDC). The ommonest re of omplint ws tretment relted to rowns (196) followed y ridges (116). 16 This rtile highlights the importnt res of linil risk nd how they n e voided t the time of initil restortion presription. With the id of linil exmples, the rtile will lso offer tehnil nd linil dvie tht n e used t the time of filure. shortomings. Dentists working in the UK re now mong the most likely in the world to e exposed to dento-legl prolems. Between 2009/10 there were 1180 omplints reeived y the Dentl Complints Servie t the Clinil exmples of filed onventionl fixed restortions Cse 1 (Figure 3 ) This 67-yer-old mle ptient 80 DentlUpdte Mrh 2012
presented with frtured 10 unit PFM ridge extending from the UR4 to the UL6. The frture ws limited to the veneering ermi of UR1, UR2 nd UL1. The dmge ws used y fll nd there ws no evidene of dmge to the rest of the restortion. The utments were helthy with no evidene of de-ementtion. The ptient s mjor onern ws the estheti impt of the dmge. Following disussions with the ptient, whih inluded n explntion of ll tretment options, it ws deided to ept the existing fixed restortion nd ttempt repir of the frtured ermi with diret resin. The ptient relized tht, if this tretment proved unsuessful, the mxillry nterior ridge would need to e removed to llow reful investigtion of the utments to pln for future tretment. e f d Cse 2 (Figure 4 g) A 40-yer-old femle ptient presented with two mxillry posterior PFM ridges tht displyed ermi frture. She ws unhppy with the resultnt osmeti impirment nd the visile drk res of the underlying metl. The ridges hd een in situ for pproximtely 10 yers nd hd lwys een slightly unomfortle sine ementtion. She gve history of possile prfuntion. There ws no evidene of de-ementtion or pthology ssoited with the four utment teeth. The thought proesses of the treting liniin inluded: Why hs the ermi frtured nd wht m I going to do differently to ensure tht similr prolem does not hppen with new restortion? How m I going to remove the restortions sfely nd ensure tht I n mke nd fit good qulity provisionl restortions? Wht future designs will I use for the replement ridges nd will the ptient ept ervil metl ollrs nd metl olusl surfes? Cse 3 (Figure 5 j) This femle ptient ws referred with pin nd infetion under her onventionl ridge in the upper right qudrnt nd n inility to mke olusl ontt nd funtion with her posterior ridges. The ptient ws medilly well 50-yer-old. Figures 5 ( j) outline the prtil steps of investigting the sttus of underlying tooth tissues nd improving Figure 6. () Cse 4: Anterior view the ptient hd prtil overge splint tht extended from UR2 to UL2 nd ws worn onstntly. The ptient presented with n nterior open ite nd ontt on her posterior teeth nd temporry posterior restortions only in her inter-uspl position (ICP). Thin unrelile provisionl restortions were in situ on the LR4567 nd LL457. () The lower posterior temporry restortions were removed to llow ontt etween the nterior teeth t redued vertil dimension. At this vertil dimension the ptient ws omfortle nd le to disply lterl nd protrusive guidne on the nturl nterior teeth. It ws lso felt tht this reltionship would id the frition of the posterior restortions. () Olusl view showing the LR4567 fter rown lengthening surgery whih ws needed to improve their linil rown height. Note tht the root-filling of LR5 ws exposed to orl fluids. (d) Cut-k wx-ups for the metl sustrutures of new PFMs for LR4567. A pink putty mtrix ws tken of the full ontour wx-ups. This ensures optimum design, thikness of metl nd support of future ermi. (e) Lower olusl view fter ementtion of definitive restortions. The ptient requested tooth-oloured olusl surfes where possile. Individul PFM rowns were pled on LL4 nd LR4567. The ridge in the lower left qudrnt ws redesigned to inorporte movle joint into the posterior prt of the LL5 with PFM full overge minor retiner nd pre-ermi soldered full veneer preious metl rown s the distl mjor retiner. (f) Anterior view t 24 months fter plement of her definitive mndiulr restortions. The ptient ws le to ontt her nterior nd posterior teeth in her ICP. (with the id of rown lengthening surgery nd endodonti revision) the qulity of the support for replement restortions. The suess of this se relied on the orret plnning nd exeution of stti jw registrtion. Cse 4 (Figure 6 f) This se represents prolems tht n flow from over zelous tehnil tretment of temporo-mndiulr dysfuntion (TMD). The questions sked y the treting liniin inluded: Is the TMD under ontrol? At wht vertil dimension will I e le to get nterior tooth ontt nd how muh olusl spe will there e for the posterior fixed restortions? Will there e enough remining tooth tissue to provide preditle fixed mndiulr restortions? I will e short of olusl height t LL7 n I get the ptient to ept metl olusl surfe on this tooth? Does the ptient relize the diffiulty of her tretment nd the time nd effort tht will e involved in improving her sitution? Is the ptient hppy to wer splint fter ompletion of tretment? 82 DentlUpdte Mrh 2012
Risk ftors ssoited with filure of rowns nd ridges Ptient issues Otining thorough ptient history is lwys essentil prior to the presription of de novo or replement onventionl fixed prosthesis. The history should fous on the ptient-driver(s) for the rowns/ridges, s opposed to epting the spe or using n dhesive ridge, denture or implnt(s). The uthors sk ptients open questions designed to enourge two-wy disussion. Exmples of suh questions inlude: How muh does the spe worry you? Wht re the min resons for you wnting fixed rowns or ridges? Would you onsider wering denture nd, if not, why not? How long re you expeting these new restortions to lst? Unfortuntely your ridge hs filed nd the supporting teeth re very ompromised. How do you feel out the support teeth eing restored with single rowns nd either epting your spe or restoring it with denture or implnt? Wht estheti prolems do you hve with your existing teeth? How do you think tht rown nd ridge work n help? If ptient is wering denture it is importnt to onfirm whether it hs flnge nd, if so, whether it is essentil for the mintenne of fil/lip support. A fixed onventionl or implnt restortion is unlikely to e good restortive option where the ptient needs dditionl fil support following post-extrtion lveolr resorption. In suh irumstne, flngeless denture tryin is the only wy to onfirm the fesiility of using fixed restortion. It is essentil tht the ptient knows, t the outset, tht pulpl deth is potentil omplition of rowns nd ridges. They should lso understnd tht this risk is greter with ridge utments nd for teeth with signifint restortions in situ. 17 Ptients should lso hve n understnding of the following: The numer of ppointments; The likely period of temporiztion; The likely iologil dmge delivered to the prepred teeth; nd The prole survivl time of the plnned restortion(s). The uthors find tht fullyinformed ptient will lwys ope etter with pre-wrned omplitions ompred to unpredited prolems. Any explntion of the ltter will lwys sound like n exuse for poor tretment to the ptient. When deling with filed onventionl indiret restortions the ptient should lwys e dvised, t the outset, tht n urte finnil quote my not e possile until thorough linil investigtion hs een undertken. The uthors would lso suggest tht ll ptients ept nd understnd tht the initil phse of deling with filed restortions is n investigtion of the supporting teeth. This will involve initil removl of the filed restortion(s), ssessment of the qulity nd quntity of remining tooth tissue (together with n indition for endodonti tretment or rown lengthening) nd suggestion of pproprite long-term tretment options. At the time of filure ptient should e wre of wht they ring-tothe-tle in terms of the risk of future replement restortions. They should e wre of the importne of home plque ontrol, future hygiene rell, smoking esstion, ontrol of dietry intke of sugrs nd the use of fluoride prevention. The uthors dvie is tht it is lwys est to refuse tretment t the onset if it is felt tht it is not in the ptient s est interest. Erly pre-tretment referrl to n pproprite hospitl or prtie-sed speilist will dd further ressurne where there re diffiult issues. Orl hygiene One of the most importnt ftors tht ffets the likely performne of replement fixed restortions is the ptient s ility to len nd mintin his/ her dentition. Ptients should understnd tht plque ontrol round fixed restortions will e more diffiult thn for nturl teeth. Unwillingness or n inility to ffet pproprite hygiene will not ode well for ny replement rowns nd ridges (Figures 3 5). Ptients should e enourged to use interdentl nd eneththe-ponti lening ids on dily sis. If ptient is suseptile to ries, then they should supplement their lening regime with fluoride supplement nd thorough dietry nlysis should e undertken nd reorded prior to ny tretment. Smoking Although smoking is not ontrindition to the repir or replement of filing rowns nd ridges, the ptient should e wre tht the hit will undermine the survivl time of ny replement restortions. All ptients who smoke should e offered smoking esstion dvie 18 nd enhned prevention mesures (eg fluoride supplements nd more regulr hygiene rell). Crown nd ridge ftors Design Gold rowns hve een shown to survive etter thn porelin fused to metl rowns. Single unit restortions hve lso een shown to survive etter, nd dmge fewer teeth on filure, when ompred to fixed ridges. The ermi must lwys e used ppropritely supported y ny underlying metl. Cntilever ridges Trditionl wisdom suggested tht pontis should hve support y utments on eh side of the spn. This view is no longer held, s onventionl single unit ntilever ridges n perform well. Idelly, the utment tooth should e sustntil in omprison to the ponti spe, eg first molr supporting missing seond premolr or nine repling missing lterl inisor. Conventionl doule nd distl ntilever ridges should e used with more ution s oth designs re ssoited with higher filure rtes thn single mesil ntilevers nd teeth with distl utment. 19 Position of proposed ridge More onventionl ridges re pled, nd therefore likely to fil, in the nterior zone of the mxill. Both nterior nd posterior ound onventionl ridges show preditle long-term survivl (estimted t pproximtely 90% t 10 yers). 20 Unfortuntely, ridges tht omine nterior nd posterior teeth (ie extend in front of nd ehind nine) tend to hve less good outlook. Suh ridges re often used to reple missing nines. Numer of units within ridge Unfortuntely, some dentists nnot resist the inlusion of multiple (more thn two) utments within the ridge design. Mrh 2012 DentlUpdte 83
Unfortuntely this loks-in sound teeth to other ompromised utments. The survivl of ny ridge will lwys e ditted y the most ompromised tooth. In generl, if the two teeth next to ponti spe re unle to support ridge preditly, then nother restortive option should e onsidered. In generl, ridge of more thn four units is high risk. 21,22 Four missing inisors n e restored preditly with six-unit onventionl ridge, with full overge rowns pled on the nine teeth. This my e eptle s long s the ptient hs rejeted denture or implnts/dhesive ridge following unised tretment plnning disussions. Eventully suh ridge will fil, whih will use ompromise to t lest one of the supporting nines. Design of retiner The uthors usully use full overge rowns for nterior onventionl ridges with no movle joints. For posterior teeth the presription of hoie would e oth full nd ¾ overge retiners, s these demonstrte preditle survivl s mjor retiners. 23 A ¾ rown or only n e used preditly s posterior minor retiner. It should e ppreited tht endodontillytreted teeth mke poorer utments thn vitl teeth nd, when restored with post, they re high risk eneth ridges. This is espeilly the se in ntilevered ridges nd ridges with more thn three units. 24,25 Mteril Porelin fused to metl rowns re the most ommon type of full overge restortion presried in the GDS (pproximtely 80%), followed y full overge metl rowns nd ll ermi rowns. PFMs hve een shown y Burke nd Lurotti 1 to hve lower 10-yer survivl thn full metl rowns (48% vs 68%) used within the NHS GDS servie. A ommon use for re-intervention of PFM rowns nd ridges is frturing of the veneering ermi, whih is estimted to use 2 3% of ll filures. 25 With modern dhesive tehnology it is often possile to ttempt repir with omposite resin, lthough the long-term performne of suh repirs is unknown. Rdiogrphi ssessment Bitewing rdiogrphs re often underused in the ssessment nd mngement of filing posterior rowns nd ridges. They provide ner prllel imge of the utment teeth (unlike peripil rdiogrphs tht re often ompromised y the ntomy of the floor of the mouth or plte). Bitewings re exellent for dignosing reurrent ries, erly one loss (up to 5 mm) nd ssessing the mount of likely sound tooth tissue ove the lveolr rest. Conlusion The ses used in this pulition illustrte the hllenges present when deling with filing indiret restortions. Mngement should lwys inlude n initil investigtion, whih will then e followed y repir, removl with replement, or use of different form of restortion. Referenes 1. Burke FJT, Lurotti PSK. Ten-yer outome of rowns pled within the Generl Dentl Servies in Englnd nd Wles. J Dentistry 2009; 37: 12 24. 2. Adult Dentl Helth Survey 2009. Summry report nd themti series. 3. Steele JG, Tresure E, Pitts NB. Totl tooth loss in the United Kingdom in 1998 nd implitions for the future. Br Dent J 2000 189: 589 603. 4. Brtlett D, Preiskel A, Shh P et l. An udit of prosthodontis undertken in generl dentl prtie in the South Est of Englnd. Br Dent J 2009; 207: E17. 5. Goodre CJ, Bernl G, Runghrsseng K et l. Clinil omplitions in fixed prosthodontis. J Prosthet Dent 2003; 90(1): 31 41. 6. Holm C, Tidehq P, Tillerg A et l. Longevity nd qulity of FPDs: retrospetive study of restortions 30, 20, nd 10 yers fter insertion. Int J Prosthodont 2003; 16: 283 289. 7. Krlsson S. A linil evlution of fixed ridges, 10 yers following insertion. J Orl Rehil 1986; 13: 423 432. 8. Leempeol PJB, Eshen S, De Hnn AFJ et l. An evlution of rowns nd ridges in generl dentl prtie. J Orl Rehil 1985; 12: 515 528. 9. Tn K, Pjetursson B, Lng N et l. A systemti review of the survivl nd omplition rtes of fixed prtil dentures (FPDs) fter n oservtion period of t lest 5 yers III. Conventionl FPDs. Clin Orl Implnts Res 2004; 15: 654 666. 10. Clrk-Holke D, Drke D, Wlton R. Bteril penetrtion through nls of endodontilly treted teeth in the presene or sene of the smer lyer. J Dentistry 2003; 31: 275 281. 11. Cpln DJ, Kolker J, River EM et l. Reltionship etween numer of proximl ontts nd survivl of root nl treted teeth. Int Endodont J 2002; 35: 193 199. 12. Chilertvnitkul P, Sunders WP, Sunders EM et l. An evlution of miroil oronl lekge in the restored pulp hmer of root-nl treted multirooted teeth. Int Endodont J 1997; 30: 318 322. 13. Bergenholtz G, Nymn S. Endodonti omplitions following periodontl nd prostheti tretment of ptients with dvned periodontl disese. J Periodont 1984; 55: 63 68. 14. Wlton TR. A 10-yer longitudinl study of fixed prosthodontis: linil hrteristis nd outome of single-unit metl-ermi rowns. Int J Prosthodont 1999; 12: 519 526. 15. Plmqvist S, Swrtz B. Artifiil rowns nd fixed prtil dentures 18 to 23 yers fter plement. Int J Prosthodont 1993; 6: 279 285. 16. Helping You Put Things Right. Dentl Complints Servie Annul review 2009/10. 17. Cheung GSP, Li SCN, Ng RPY. Fte of vitl pulps eneth metl-ermi rown or ridge retiner. Int Endodont J 2005; 38: 521 530. 18. Wtt RG, Dly B (Series Editor Ky EJ). Prevention. Prt 1: Smoking esstion dvie within the generl dentl prtie. Br Dent J 2003; 194: 665 668. 19. Rndow K, Glntz P, Zoger B. Tehnil filures nd some relted linil omplitions in extensive fixed prosthodontis: n epidemiologil study of long-term linil qulity. At Odont Snd 1986: 44: 241 255. 20. Surri M, Bder JD, Shugrs DA. Met-nlysis of fixed prtil denture survivl: prostheses nd utments. J Prosthet Dent 1998; 79: 459 464. 21. Reuter JE, Brose MO. Filures in full rown retined dentl ridges. Br Dent J 1984; 157: 61 63. 22. Foster LV. The reltionship etween filure nd design in onventionl ridgework from generl dentl prtie. J Orl Rehil 1991; 18: 491 495. 23. Roerts DH. The filure of retiners in ridge prostheses. An nlysis of 2,000 retiners. Br Dent J 1970; 128: 117 124. 24. De Bker H, Vn Mele G, De Moor N et l. A 20-yer retrospetive survivl study of fixed prtil dentures. Int J Prosthodont 2006; 19: 143 153. 25. De Bker H, Vn Mele G, De Moor N et l. Long-term survivl of omplete rowns, fixed dentl prostheses, nd ntilever fixed dentl prostheses with posts nd ores on root nl-treted teeth. Int J Prosthodont 2007; 20: 229 234. 26. Edelhoff D, Sorensen JA. Tooth struture removl ssoited with vrious preprtion designs for nterior teeth. J Prosthet Dent 2002; 87: 503 509. 84 DentlUpdte Mrh 2012