PERIODONTAL PROSTHESIS:

CREATING SUCCESSFUL RESTORATIONS J O H N C. K O IS ,

ABSTRACT

W hen th e d e n titio n is m u tila te d b y p erio d o n ta l d ise a se , it ’s hard to resto re. T h e au th ors o u tlin e th e m ech a n ica l an d b io lo g ic a l p rob lem s to o v e rc o m e in tr e a tin g a d v a n ce d p erio d o n ta l d ise a se .

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M .S .D .; F R A N K M . S P E A R , D .D .S ., M .S .D .

^ eriodontal prosthesis is defined as those restorative and prosthetic endeavors essential in tre a tin g advanced perioodontal disease.1In restoration, the p ractitioner m u st control the active disease process and work w ith existing anatom ic deform ities. Although the con­ cepts, principles and techniques are often sim ilar to those used in providing restorative care for all patients, we still have m is­ conceptions about successful treatm en t. For example, we have no evidence th a t complex resto ra ­ tive care improves the perioodontal prognosis. Even if we can modify coronal form and rigidly connect m ultiple teeth, th e “h ard w are” alone won’t m ake th e difference. All com­ ponents m ust be identified and m anaged. Periodontitis traditionally has been characterized as slowly and continuously pro­ gressive. B ut recent evidence suggests site-specific compon­ ents in which deep probing depths do not necessarily indicate cu rre n t disease activ­ ity.2 Interestingly, m ost failures are m echanically related, not directly biologically m ediated

problems. For a successful outcome, th ere are five common elem ents to resolve problem s in these patients: "■ Use a facially oriented approach for m igrated, malposed and excessively long te e th to reorient the dentition to the appropriate facial features. *** E xam ine th e dentogingival interface to m anage the peri­ odontal requirem ents of tooth preparation. Address the stru ctu ral comprom ises of long or rootresected teeth. ■■ Choose correct splinting w ith rigid or non-rigid connections. ■■ Study the occlusion in a severely w eakened dentition w ith m ultiple m issing teeth and advanced bone loss. FACIALLY GENERATED ESTHETICS

The m u tilated dentition typically has several esthetic aberrations, including teeth m alpositioned relative to facial tissues, excessively long teeth and lost interproxim al tissues resu ltin g in “black holes.” In general, we use a tre a tm e n t planning approach th a t

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Figure 1. Initial intraoral views.

in teg rates rem ovable and fixed prosthetic principles regarding esthetic tooth positioning. ■■ Place th e m axillary an terio r te e th appropriately, using phonetic and esthetic principles, and evaluate the lower sm ileline.3,4 «■> Position the buccal cusps of the m axillary posterior tee th to provide th e proper sym m etry and balance to the m axillary arch. ■■ Position th e m andibular an terio r te e th using phonetic principles, prim arily th e “S” sound, for correct speech re la ­ tive to th e m axillary incisal edge position and lingual concavity. The exact relation­ ship of th is “an terio r guidance” is worked out clinically w ith provisional restorations to finetu n e th e lingual contours of the m axillary an terio r te e th in harm ony w ith the p a tie n t’s m usculature. ■* Once the anterior guidance is determ ined w ith the m axillary te e th in the esthetically correct position, a lte r the occlusal surfaces of th e posterior teeth, cusp and fossa height, ridge and groove direction to provide im m ediate disclusion w ith m andibular m ovem ent. This facially generated approach is done in th e sam e way as we set a 110

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encountered esthetic problem is denture. th e “black holes” phenom enon “ There are three approaches caused by interproxim al tissue to m anaging excessively long loss. Overcontouring, baking in teeth. F irst, use “illusion” by pink porcelain and constructing creating root areas of lower artificial gingival m asks have color value th a n th e anatom ic been used. The best solution, crown of the restoration and however, m ay be to a lte r the create contours th a t visually root alignm ent of tee th w hen shorten th e te e th ’s appearance. possible, or the ap p a re n t Also consider surgery for alignm ent if we’re discussing coronally positioning th e gin­ gival m argin. This is effective for facial recession areas, b ut it’s difficult if th ere ’s a flat periodontal profile th a t requires coronal m ovem ent of tissue on several teeth. The th ird choice is to erupt the teeth orthodontically, m oving the entire gingival complex, root and bone coronally. At the sam e tim e, shorten the incisal edges as the teeth are moved. ™ The last Figure 2. Dentofacial esthetic appearance at completion. frequently

Figure 3. Tooth preparation at correct vertical dimension and copings.

pontics. The principles are quite simple. Note th a t anterior te e th are alm ost all stra ig h t lines along th e m esial surface from apex to m esioincisal angle. This m eans th a t the m esiodistal inclination of the roots determ ines the size of the gingival em brasure, or black hole. If the apexes of the central incisors are moved a p a rt, the space gets larger. W hen moved together, th e space gets sm aller, and frequently a papilla is formed. B ut th is technique still leaves th e d ark space betw een th e central and late ra l incisors. The solution lies in positioning th e late ra l incisors. Move them lingually and behind the distal corners of th e central incisors to close the space or ro ta te them facially, w ith the m esial surface out. T u rn th e broader buccolingual dim ension sidew ays to fill in space betw een the central incisor and canine. DENTOGINGIVAL INTERFACE

The effect of m argin location and periodontal h ealth is welldocum ented. Simply stated, supragingival is best.20 The restorative d entist h a s a dilem ­ ma. In a p a tie n t w ith periodon­ tium housing the dentition in 112

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th e norm al anatom ic position, conservative m anagem ent is ideal. B ut w hen the entire periodontium has m igrated apically, exposing root surfaces and the furcations of m ulti­ rooted teeth, m u st all m argins term in a te a t th e base of th e gingival sulcus to establish a new clinical crown? We m ust weigh the need to a lte r coronal form and create “biological contours” ag ain st th e potential periodontal compromises. The prevailing approach to the finish line location and configuration alw ays recom­ m ends “barreling in” to exposed furcation involvem ents. This approach m inim izes existing horizontal com ponents created by Class II and III furcation involvem ents. Proponents confirm th a t root resective procedures are necessary to m anage th e resu ltin g osseous deform ities c reated by perio­ dontal diseases, provide p atien t access for plaque m anagem ent and routine debridem ent procedures. It’s wellestablished th a t we can control, via tooth preparation, th e furcation entrance to cover exposed root stru ctu re suscept­ ible to caries and sensitivity and to establish healthy coronal contours by smoothly exiting from the epithelialized

gingival sulcus.56 The periodontium can sup­ port broad contour changes.78 B ut it’s increasingly difficult to consistently generate intracrevicular m argin placem ent circum ferentially in postsurgical patients. A fter surgery for pocket reduction or elim ­ ination, we can’t predict developm ent of th e periodon­ tium and re-establishm ent of th e biologic w idth and sulcus depth. Differences in flap m anagem ent positioning relative to th e osseous crest and th e p a tie n t’s healing response a lte r the short-term results. It can tak e up to th re e years to re-establish norm al supracrestal gingival architecture. U niversally placing m argins below or even above tissue levels too soon after surgery, often jeopardizes a n otherw ise h ealth y periodontium , by encroaching on th e supracrestal gingival attachm ent. Even the m ost m echanically skilled clinician can inadvertently cause violations of biologic w idth w ith th e ir defined sequelae. We m u st consider carefully the intracrevicular m argin placem ent to satisfy m echanical principles, esthetic concerns, coronal form enhancem ent and pre-existing

conditions, b u t not to prevent im pending disease. STRUCTURAL COMPROMISES

Som etimes our efforts to restore compromised te e th do m ore h arm th a n more conservative treatm en t. Often reducing tee th for copings or non-rigid attachm ents, combined w ith excessively long teeth, requires endodontic treatm en t. B ut endodontically treated tee th are w eaker th a n pulpally in tact teeth. In addition, rigidly splinting m ultiple abutm ents w ith compromised osseous support m ay fu rth e r compromise pulpal health. All types of foundation restorations, including th e m ost recent adhesives, won’t adequately reinforce the rem aining tooth stru c tu re .911 L anger’s d a ta show th a t the ultim ate compromise of rootresected or hem isected tee th resu lts more often from m echanical failure ra th e r th an periodontal causes.12 The need to resect roots and hem isect tee th to m anage periodontal problem s h as a point of dim inishing re tu rn w hen we consider the m echanical problem s and loss of overall support.

W hen these procedures are absolutely essential, we m ust determ ine the best foundation restoration. W ith adequate rem aining sound tooth stru ctu re of 1.5 to 2 m illim eters for m argin placem ent and conservative root preparation, all com binations incorporating passive fit are acceptable.13,14 Long full-coverage preparations and teeth , however, pose unique concerns. A nterior tee th have a facial root inclination but require a more vertical coronal tooth preparation orientation to establish a common p a th of insertion w ith posterior teeth. P recast posts w ith a separate m echanically retained core m aterial m ay be inadequate w hen com pared w ith completely cast post cores. W ith th e one-piece cast post core in th e more vertical coronal preparation (relative to the root), it’s easier to m ain ta in the foundation’s integrity. A sep arate core m aterial and precast post won’t have sufficient retention because the p reparation exposes the post and m inim izes core retention. In addition, as tooth preparation extends apically on the narrow ing root, keeping enough core m aterial over the

post is harder. Restoring resected roots poses more difficult problem s. W ith narrow ing and a b erran tly inclined roots and m inim al rem aining dentin, it’s h a rd e r to m aintain the in tegrity of the foundation restoration. W ith m inim al rem aining sound tooth structure, auxiliary pin retention is less effective and even inappropriate in m any situations. The increasing root curvature and narrow canals of posterior tee th increase th e risk of root perforation or fracture. It m ay be im possible to satisfy th e m echanical principles of post design, resulting in an ineffective foundation restoration. We can’t select the best foundation resto ratio n until periodontal procedures are completed. B ut periodontal procedures should never be attem pted w ithout completely understanding prevailing restorative considerations. In this way, we can use a custom ized approach to stru ctu ral compromises. SPLINTING

Splinting is often m isunder­ stood. We suggest th ree needs for splinting w hen tre a tin g advanced periodontal disease:

Figure 4. Structural compromises of endodontically treated teeth.

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adjacent a b u t­ m ents, a semiprecision type of a ttach m en t is used. In more severe mobility, or w ith con­ necting pontics to ab u tm en t teeth, we m ay choose a pre­ cision a tta c h ­ Figure 5. Intraoral view 11 years after treatment. m ent. A contin­ uous, one-piece approach is excessive or uncontrolled m ade w ith severe m obilities or m obility a t such a level th a t th e questionable prognosis of occlusal m anagem ent is not several teeth. For this possible or p atien t comfort is approach, the advantages are affected; rigidity and, when copings are ■■ m issing te e th requiring th a t used, retrievability if th ere is tee th be splinted to serve as subsequent tooth loss. B ut abutm ents; th ere are several disadvant­ *■> unpredictable prognosis of ages. All tee th m ust have the several te e th so th a t splinting sam e p a th of insertion. Sim ul­ provides long-term retrievataneous cem entation to m ulti­ bility of th e restoration in spite ple mobile tee th is difficult. of la te r tooth loss. And one-piece splints are h ard Splints are segm ented—nonto make. rigid connections for splinting Frequently, telescopic betw een segm ents—and contin­ copings are used in periodontal uous—one-piece “horseshoe” prosthesis to circum vent the restorations, often w ith disadvantages of the copings.16 W hen prognosis of all continuous splint.116 Copings rem aining te e th is predictable have some of th eir own after periodontal therapy and liabilities, specifically the mobility is not severe, we necessary degree of tooth choose a segm ented approach. reduction for an extra layer of This is easier to make, requires m etal, th e esthetic problem of p reparing only sm all segm ents two m argins a t the gingival of te e th w ith the same p ath of interface and th eir extra cost insertion and allows a phased and technical difficulty. approach to therapy. B ut it’s In spite of this, for th e tru e not rigid enough if th ere is periodontal prosthetic p atien t severe mobility. In m ost w ith severe m obilities and instances, the segm ented m ultiple tee th w ith a question­ approach is irretrievable if any able prognosis, individual ab u tm en t te e th are lost. copings perm anently cem ented The stresses placed on the to the teeth together w ith a a ttach m en t determ ine its continuous splint rem ain the choice for segm ented splints. best long-term insurance for W ith slight to m oderate success of the dentition and the m obilities and betw een 114

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restoration.1516 The splint can be tem porarily cem ented or removed daily by the patient. O C C L U S IO N

Occlusal goals include th ree m ajor areas: control of tooth loading, control of joint loading and neurom uscular comfort. The p atien t usually has inade­ quate bone support and subse­ quent tooth mobility. W ith a norm al dentition, we m ay equilibrate th e dentition by placing occlusal stresses on the anterior teeth for guidance. In some instances, we can use group function. B ut if all teeth are mobile, any atte m p t to place the discluding contacts on an individual tooth sim ply results in increased mobility. This is, of course, why we include splinting as a n a re a of concern, b ut we m u st consider w hat type of occlusal p a tte rn these splinting restorations require to m eet occlusal goals. Of these goals, the prim ary difference betw een the periodontal prosthetic p atien t and the “norm al” p atien t is the te e th ’s ability to w ithstand late ra l loads based on the dim inished bone support. Con­ trolling jo int loading rem ains the same, as does achieving neurom uscular comfort.17 The real difference becomes m anag­ ing lateral tooth loading. We can C j m inimize loading by controlling as m uch as Dr. Kois is in private possible the prosthodontic practice, Fixed degree of Prosthodontics m uscular con­ Associates, 56115 traction during Valley Ave. E., Tacoma, Wash., lateral 98424. Address m ovements, reprint requests to Dr. Kois. and

m axim izing the m echanical disadvantage of th e angle of tooth contact to m inimize Dr. Spear is in the tran sferred private tooth-to-tooth prosthodontic practice, Fixed load. Prosthodontics In m uscular Associates, Tacoma, Wash. contraction, several studies have looked a t the differing degrees of contraction depending on the presence of canine rise, group function or full-balanced occlusion. We know from the litera tu re th a t canine rise w ith no posterior contact on either side results in the lowest muscle activity of all possible tooth contact schem es.1819 It is also m echanically clear th a t, the steeper the angle of contact, the greater the potential force tran sfer of the contact; con­ versely, the fla tte r the disclusion angle, the lower the force generated on the teeth. For these reasons, the vertical dim ension is frequently altered to flatten th e disclusion angle by decreasing the overbite, th u s m inim izing the load tran sfer on the already compromised anterior teeth. This requires a subsequent flattening of posterior cuspal

form to m aintain adequate guidance w ith full and im m ediate posterior disclusion. C O N C L U S IO N

The periodontal prosthetic patien t rem ains a complex entity who requires procedures sim ilar to any rehabilitation patient, but has distinct problems th a t m ust be dealt w ith in a m ost exacting m anner. We’ve outlined specific techniques to m eet these patien ts’ needs. ■ 1. A m sterdam M. Periodontal prosthesis. Twenty-five years in retrospect. Alpha Omegan 1974;67(3):8-52. 2. Greenwell H., e t al. Periodontics in general practice perspectives on periodontal diagnosis. JADA 1989;119:537-41. 3. Dawson PE. E valuation, diagnosis and tre a tm e n t of occlusal problems. 2nd ed. Chicago: Mosby; 1989:274-97. 4. Lombardi RE. The principles of visual perception and th eir clinical application to denture esthetics. J P ro sthet D ent 1973;29:358-82. 5. Casullo DP, M atarazzo FS. The preparation and restoration of the m ulti­ rooted tooth w ith furcation involvement. C ontinuing Dental Education Quintessence books 1980; Vol. 1. 6. Weisgold A. Coronal forms of the full crown resto ratio n -th eir clinical applications. Continuing D ental Education Quintessence Books 1981; Vol. 4. 7. E hrlich J , Hochman N. A lterations on crown contour—effect on gingival health in man. J P ro sth et D ent 1980;44:523-5. 8. Yuodelis RA, et al. Facial and lingual contours of artificial complete crowns restoration and th eir effect on the periodontium . J P rosthet D ent 1973;29:61-6.

9. Sorenson JA, E nglem an M J. F errule design and fracture resistance of endodontically tre a te d teeth. J P ro sth et D ent 1990;63:529-36. 10. Guzy GE, Nichollas JI. In vitro comparison of intact endodontically treated teeth w ith and w ithout endo-post reinforcem ent. J P rosthet D ent 1979;42:3944. 11. Sorensen JA. P reservation of tooth structure. CDA J 1988;16(ll):15-22. 12. L anger B, et al. An evaluation of root resection, a ten year study. J Periodontal 1982;52( 12):719-22. 13. Hoag PE, Dwyer TG. A com parative evaluation of th ree post and core techniques. J P rosthet D ent 1977;47:177-81. 14. Libm an W, e t al. The effect of ferrule length on the fatigue resistance of teeth restored w ith cast dowel cores and full crown (M aster’s thesis). Seattle: U niversity of W ashington; 1990. 15. F aucher RR, B ryant RA. B ilateral fixed splints. In t J Periodontics R estorative D ent 1983;3(5):9-37. 16. Schluger S, Yuodelis R, and Page R. Periodontal disease: Lea and Febiger: 1988; 657-99. 17. Sm ith DM, McLachlan KR, McCall WD. A num erical model of tem porom andibular joint loading. J D ent Res 1986;65(8):494-501. 18. M anns A, C han C, M iralles R. Influence of group function and canine guidance on electromyographic activity of elevator m uscles. J P ro sth et D ent 1987;57(4):494-501. 19. W illiamson EH, L undquist DO. A nterior guidance: Its effect on th e EMG of muscles. J P ro sth et D ent 1983;49(6):816-23. 20. L avina F-de-J, Zafiropoulos G, Ciancio S. The effect of crown m argin location on plaque and periodontal health. In t J Periodontics R estorative D ent 1989;9(3):197205.

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Periodontal prosthesis: creating successful restorations.

When the dentition is mutilated by periodontal disease, it's hard to restore. The authors outline the mechanical and biological problems to overcome i...
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