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
I
i
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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