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Periodontal considerations for overdentures
J /O A A R T I C L E S
Overdentures can offer an alternative to regular dentures w ith the correct factors. T his paper discusses proper abutm ent selection an d preparation coupled w ith a p propriate periodontal m aintenance and caries control to assure the success o f overdentures.
Periodontal considerations for overdentures G eo rg ia K. J o h n so n , DDS, MS J o a n E. Sivers, DDS
hen com plete dentures are in cluded in the treatm ent plan fo r a p a tie n t, o v erd e n tu re s should be considered as a possible altern a tive. An overdenture is a com plete or p a r tial rem ovable denture constructed over retained teeth w hich have been dram ati cally reduced in height. Preservation of alveolar bone is the chief advantage of the overdenture, a lth o u g h other advantages include m aintenance of proprioceptive sen sation an d psychological benefits to the patient. T h e concept of the overdenture is not new to dentistry. Ledger1 advocated leav ing root “ stum ps” under artificial teeth. O th er au th o rs2-4 have encouraged the re ten tio n of n atu ra l roots for denture su p port. O verdentures have recently become p o p u la r, p rim arily as a result of the sim p li fication of techniques and reduction of cost to the p atient. T h e use of overdentures has drastically decreased the n um ber of patients w h o are totally edentulous. T h is article discusses from a periodontal standpoint indications, contraindications, abutm ent tooth selection and preparation, and p eri odontal therapy before an d after overden ture construction.
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Indications and contraindications An overdenture may be indicated in situ a tions in w hich existing teeth can no longer 468 ■ JADA, Vol. 114, A pril 1987
su p p o rt a rem ovable or fixed partial den ture.5 O verdentures are m ore beneficial in the m andibular arch because bone loss in the m andible is greater th an th at in the m axilla after to o th loss. T allg re n 6observed th a t after teeth were removed an d dentures were placed, the m andible lost four times m ore ridge heig h t th an the m axilla d u rin g a period of 7 years. T h e fact th at the pres ence of teeth aids in retention of alveolar bone height is illustrated in Figure 1. T h e value of overdentures as a means of preserv in g alveolar bone has been show n in a study by C rum an d R ooney,7 w ho m ea
sured vertical alveolar bone loss in two g ro u p s of patients: one gro u p w ith conven tio n al m axillary and m an d ib u lar dentures, an d the other gro u p w ith conventional m axillary dentures an d m an d ib u lar over dentures. M andibular vertical bone loss after 5 years was m ore th an eight times greater in the patients in the conventional denture g ro u p th an in the p atients in the o verdenture g ro u p . Bone loss in ihe m ax il lary arch was sim ilar for both groups. A lth o u g h overdentures are indicated more freq u en tly in the m an d ib u lar arch, there are selected instances in w hich a m axillary
F ig 1 ■ T h is p a n o ra m ic radiograph show s th a t alve o lar bone height is better m ain tain ed w here teeth are present. N otice the d ram at ic loss of p o sterior alveolar bone heig h t as contrasted to the bone level in the canine and p re m o la r regions.
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overdenture is beneficial. T hese include situations that can generate greater than n o rm al occlusal forces to the m axillary an terio r ridge, w hen a Class III m alocclu sion is present or only the natu ral m an d ib u la r an terio r teeth rem ain. Use of an over denture can help prevent the developm ent of the “co m b in atio n syndrom e,” w hich is characterized by loss of the anterior p a rt of the m axilla, overgrow th of the tuberosities, inflam m atory p apillary hyperplasia, extru sion of the m an d ib u lar anterior teeth, and loss of bone u nder the distal extension bases.8T h e overdenture concept m ight also be used in the distal extension p o rtio n of a a rem ovable p artial denture (Fig 2). In this m anner, a tooth unsuitable for clasping may be used to provide vertical support and aid in bone preservation. O verdentures are contraindicated if bone loss is extremely severe, so that all teeth are u n su itab le choices for abutm ents. T hey are also n ot indicated in situations in w hich sufficient su p p o rt rem ains for fixed or rem ovable partial dentures.9 Insufficient interridge distance m ig h t also preclude the use of overdentures unless corrected by alveoloplasty or odontoplasty.10 P oor oral hygiene has often been cited as a co n tra in dication, as it can lead to caries and p eri o d o n tal disease w ith resultant abutm ent loss. P oor oral hygiene should n o t be con sidered as an absolute co ntraindication as the p atien t may be m otivated to change these habits. Even if the abutm ents are lost eventually, patients will have had the ad vantage of the bone-retaining properties w hile present; the necessary denture m odi fications are relatively sim ple after ab u t m ent extraction.
Selection of abutment teeth T reatm en t p la n n in g begins w ith the selec tio n of ab u tm en t teeth and is based largely
Fig 2 ■ T his first molar was hemisected, retaining the distal root as an overdenture abutment for a removable partial denture. T h is abutment w ill be valuable as a means of preserving alveolar bone height in the posterior region o f the alveolar ridge (photograph courtesy o f Dr. David Okano, Rock Springs, WY).
on periodontal considerations. T h e p eri odontal exam ination includes an assess m ent of the follow ing factors: rem aining osseous support, p ro b in g depths, inflam m ation, w idth of attached gingiva, tooth m obility, and consideration of root an at om y an d the p o sitio n of the teeth in the arch.
th o u g h keratinized tissue m ay be present. In such cases, a soft tissue g raft is indicated to increase the w id th of attached gingiva. If this aspect of treatm ent p la n n in g is over looked, traum a or pressure to the gingival region m ig h t cause loss of attachm ent, resu ltin g in soft tissue clefting. M obility should also be evaluated, keep-
Jreatment planning begins with the selection of abutment teeth and is based largely on periodontal considerations.
It has been suggested that an overdenture ab u tm en t should have a m in im u m of 5 to 6 m m of rem ain in g bone s u p p o rt.11 R adio graphs are necessary to assess the rem ain in g osseous heig h t a n d also serve as a good prelim inary screening to elim inate u n su it able teeth. However, they do n ot show periodontal pockets, or accurately depict soft to hard tissue relationships or struc tures on the buccal an d lin g u al aspects of the teeth.12 Therefore, the inform ation gained from periodontal p ro b in g m ust be used w ith the radiographs. T h e gingival tissues m ig h t ap p ear healthy and the g in gival m argin m ig h t be at its norm al level, b u t careful circum ferential p ro b in g is necessary to identify increased probing depths. If the gingiva bleeds w hen probed, the in flam m atio n should be reduced by oral hygiene instructions an d periodontal scaling before ab u tm en t p reparation. A relatively shallow gingival crevice is desir able, and if deep p ro b in g d epths exist, they should be appropriately treated. R ecent research has indicated th at the w idth of attached gingiva is n o t a critical factor w hen a w ell-m aintained natural tooth is present.13 However, the su rro u n d ing tissues of overdenture abutm ents are subjected to greater m echanical stresses and m ore bacterial p la q u e tends to accum ulate. Therefore, a greater w idth of a t tached gingiva is necessary when the tissue is covered than w hen it is n o t covered.14 T he dim ensions of attached gingiva sh o u ld be evaluated on the buccal surfaces of the m axillary teeth an d on the buccal an d lin gual aspects of the m andible, as the latter is an often overlooked area. T o determ ine the dim ension of the attached gingiva, the m ucogingival ju n c tio n sh o u ld be located. T h e w idth of keratinized gingiva is then m easured, and the p ro b in g d epth is sub tracted from this m easurem ent to give the w idth of attached gingiva. If the pro b in g d epth extends beyond the m ucogingival ju n c tio n there is no attached gingiva al
in g in m in d th a t the crow n-to-root ratio w ill be greatly im proved d u rin g a b u tm en t reduction, thereby im p ro v in g the to o th ’s stability. A clinically m obile tooth should n o t be elim inated as a p o ten tial ab u tm en t u n til a total periodontal assessment has been made. C onsideration of root anatom y is essen tial in the selection process. Deep root co n cavities or grooves such as those fo u n d on m axillary first prem olars are d ifficult to clean, m aking these teeth p o o r ab u tm en t choices. M olars or m axillary prem olars w ith furcation involvem ent are n o t su it able choices as ab u tm en t teeth because of difficult access to the furcal region. If the fu rcatio n can be elim in ated by a hem isectio n or bicuspidization procedure (divid in g a m o lar in to tw o prem olars) an d there is sufficient bone su p p o rt rem ain in g , re sected teeth m ay serve as valuable a b u t ments. R oot anatom y should also be consid ered from an endodontic stan d p o in t, as m ost ab u tm en ts w ill req u ire endodontic treatm ent and m ust be am enable to such therapy. T eeth should be retained in areas in w hich fu nctional stresses are the greatest. E dentulous an terio r segments th a t oppose n atu ra l teeth are p articu larly susceptible to bone resorption; therefore, incisors, ca nines, or prem olars (or all three) are likely candidates for retention.4 It has been su g gested that four widely separated teeth offer the ideal situ atio n ,14 a lth o u g h fewer ab u t m ent teeth m ig h t be used. Even one tooth can be a valuable a b u tm en t w hen teeth are n ot available on b oth sides of the arch .4 T h e retained teeth sh o u ld be separated suf ficiently to allow for adequate oral hygiene procedures. D iagonal fulcrum lines should be avoided to prevent problem s m a in ta in in g d en tu re stability. A fu lcru m lin e th a t is perp en d icu lar to the sagittal p lan e seems to result in a m ore stable prosthesis.14 T eeth in extrem e labial p o sitio n w ith soft tissue undercuts can pose a problem to the p ath of
Johnson-S ivers : P E R IO D O N T A L C O N SID E R A T IO N S FO R O V E R D E N T U R E S ■ 469
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Periodontal therapy
Fig 3 ■ C row n le n g th e n in g has been done o n m ax illary a n te rio r teeth to allow p ro p e r c o n to u rin g of the o verdentu re a b u tm en ts. T o p , p resurgical m od els. M iddle, overdenture a b u tm e n t p re p a ra tio n of m ax illary rig h t central incisor after h e alin g (note, 2 to 3 m m height). B ottom , dom e-shaped contour.
insertion. Also, a tooth that is p rom inent m ig h t n ot have cortical bone over the facial surface an d may be m ore susceptible to g ingival recession.15 A ngulation of the to o th is another consideration. T o distrib ute occlusal forces m ost effectively, the root sho u ld be in an axial positio n w ith the forces directed alo n g its lo n g axis. An adequate assessm ent of the factors discussed is crucial to the success of the overall treatm ent. T h e elim ination of hope less teeth d uring treatm ent p la n n in g should m inim ize p o tential periodontal problem s. 470 ■ JADA, Vol. 114, A pril 1987
T h e prim ary objectives of periodontal p rep aration are the achievem ent of m inim al p ro b in g depths an d an ad equate zone of healthy attached gingiva. T herefore, surgi cal pocket elim in atio n an d soft tissue grafts are the m ost com m only used surgical proce dures in abutm ent preparation. T o accom plish pocket elim ination, the gingivectom y or apically po sitioned flap w ith osseous surgery may be used. T h e gingivectom y can be used if there are no infrabony pockets present an d if an ad equate zone of attached gingiva w ill rem ain after surgery. More often, as a resu lt of the need for osse ous recontouring an d conservation of at tached gingiva, the apically positioned flap is indicated. T h is procedure allow s access to elim inate osseous defects, and the apical placem ent of the flap at or near the crestal bone w ill result in h ea lin g w ith a shallow sulcus. T h e apically positioned flap w ith osseous surgery is also indicated w here crow n height is in adequate to allow proper abutm en t p rep aratio n (Fig 3) or w here isolated occlusal p lan e problem s exist. If esthetic appearance is n ot affected or if posterior su p p o rt w ill n o t be lost, it is advisable to remove hopeless teeth as early as possible in the treatm ent. T h is allow s for h ealing of the ridges w hile periodontal therapy is being done, and pocket elim in a tion procedures are m ore easily perform ed around isolated abutm ents.5 M olars w ith furcation involvem ents may be candidates for hem isection or bicuspidization procedures to elim inate the furca tion. T hese treatm ents are m ore likely to be indicated in the m an d ib u lar arch resulting from its greater propensity for postextraction resorption. R etention of a posterior root in the tissue-supported region of a m andibular removable partial denture w ith distal extensions m ay be especially v alu able to prevent further bone loss. H em isec tion is an o p tio n if one root is more involved w ith adequate su p p o rt on the rem ain in g root. If adequate bone rem ains on both roots and if the roots are well separated to allow for cleaning, bicuspidization procedures can be considered. If the abutm en t is surrounded by an inadequate zone of attached gingiva or if the vestibule requires deepening, these d i m ensions should be augm ented before den ture fabrication. T h e autogenous free g in gival graft is a relatively sim ple an d predict able means of increasing the w idth of attached gingiva.16 O ther less often used m ethods of g ain in g an adequate zone of attached gingiva include an apically posi tioned flap at the tim e of ex tractio n ,4 the
pedicle fla p ,17 or the horizontally reposi tioned flap .18
Abutment preparation A dom e-shaped ab u tm ent p rep aratio n is com m only used w ith the retained tooth, reduced to 2 to S m m above the crestal ridge.14 Care sh o u ld be taken n ot to over shorten the tooth, as the gingiva w ill tend to creep occlusal ly over the m argins of the overprepared tooth, leading to gingival irritatio n (Fig 4). W hen an ad equate occlu sal h eig h t is m aintained, a w ell-polished am algam placed in the endodontic access o p en in g can serve as the final restoration. If less th an 2 m m of h eig h t exists, it may be necessary to place a gold co p in g to restore heig h t an d contours of the ab u tm ent. C op in g m argins m ust often be placed subgingivally, leading to periodontal com plica tions. O nly the occlusal surface ol the ab u tm en t sh o u ld be in contact w ith the overdenture d u rin g function. W hen ihe den tu re is n o t in function, there should be no contact on the retained to o th because of tissue resiliency.4 At no tim e sh o u ld there be lateral im p in g em en t on the crestal or sulcular gingiva.
Maintenance M aintenance of p eriodontal h ealth is p ara m o u n t to the long-term success of overden tures. T h is responsibility is shared by the d entist an d patient. T h e d en tist is resp o n sible for establishing an ap p ro p riate recall interval an d for p ro p er therapy at these ap p o in tm en ts, as well as for education of patients. T h e patien ts’ responsibility is com pliance w ith these program s. L o n g i tu d in a l studies19'20 have show n th a t a 3m o n th interval allow s m ost periodontal patients to be m ain tain ed w ith o u t sig n ifi cant attach m en t loss a lth o u g h the recall
F ig 4 ■ O verreduction of these a b u tm e n t teeth has led to m a rg in a l gingival in flam m a tio n . Ideally, the teeth sh o u ld be reduced to a level 2 to 3 m m above the crestal tissues w ith a dom e-shaped p re p a ra tio n .
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interval w ill vary depending on the needs of the patient. The following procedures should be done during recall appointments: caries exam i nation, record of probing depths and reces sion, assessment of plaque and inflamma tion, oral hygiene reinforcement, evalua tion of the denture’s fit and occlusion, and cleaning of the prosthesis, if necessary. Plaque control is the biggest challenge the dentist faces with patients w ho have over dentures. Therefore, oral hygiene proce dures should be individualized and can include the use of such adjuncts as an endtufted toothbrush. The daily use of a topi cal 0.4% stannous fluoride gel is recom mended primarily for caries prevention,21 but this preparation also has an antibacte rial effect that has been shown to reduce gingivitis.22 Patients at high-risk for caries can brush with the gel in the evening in addition to filling the denture abutment indentations with the gel in the morning before denture insertion. Studies of overdenture patients have shown that these patients universally expe rience an increase in gingivitis around abutment teeth and that patients with poor recall compliance have the highest increase in caries and periodontal disease. Even so, overdentures can be considered successful if success is based on tooth retention. Re tention has been reported to be as high as 96% in a 5-year period.23
Summary An overdenture is a preferable alternative
to a conventional denture. Clinically the major advantage of the overdenture is pres ervation of alveolar bone. T he most impor tant factors to be evaluated during abut ment selection include the amount of re m aining bone support, probing depth, and the width of attached gingiva. T he goals of periodontal therapy before overdenture construction are the establishment of a shallow, healthy, gingival crevice with an adequate zone of attached gingiva. Proper abutment selection and preparation cou pled with appropriate periodontal main tenance and caries control w ill assure the success of overdenture treatment.
------------------- JiiO A ------------------Dr. Johnson is assistant professor, department of periodontology, and Dr. Sivers is assistant professor, department o f adult restorative dentistry, University of Nebraska Medical Center, 40th and Holdrege, Lincoln, 68583-0740. Address requests for reprints to Dr. Johnson.
1. Ledger, E. On preparing the m outh for the recep tion o f a full m outh set of artificial teeth. Br J Dent Sci 1:909, 1856. 2. Miller, P. A. Complete dentures supported by nat ural teeth. J Prosthet D ent 8(6):924-928,1958. 3. Morrow, R.M., and others. Tooth-supported com plete dentures: an approach to preventive prosthodontics. J Prosthet Dent 21(5):513-522, 1969. 4. Becker, C.M., and Kaldahl, W.B. An overdenture technique designed to protect the rem aining periodon tium. Int J Periodont Rest Dent (4):29-41, 1984. 5. Brewer, A. A., and Morrow, R.M. Overdentures, ed 2. St. Louis, C. V. Mosby Co, 1980, pp 50-64. 6. Tallgren, H. T he continuing reduction of the residual alveolar ridges in complete denture wearers. A m ixed longitudinal study covering 25 years. J Prosthet Dent 27(2): 120-132, 1972. 7. Crum, R. J., and R ooney, G.E. Alveolar bone loss
in overdentures: five-year study. J Prosthet Dent 40(6): 610-613, 1978. 8. Kelly, E. Changes caused by a mandibular remov able partial denture opp osin g a m axillary complete denture. J Prosthet Dent 27(2):140-150, 1972. 9. Leuck, M .H., and LaVelle, W.E. Preservation of the mandibular ridge through root retention. J Acad Gen Dent 21(4):29-32, 1973. 10. Jones, P.A.; Peterson, R.J.; and Taintor, J.F. Indications, advantages, and clinical procedures for overdentures. J Nebr Dent Assoc 55(1):8-10, 1978. 11. Zamikoff, 1.1. Overdentures— theory and tech nique. JADA 86(4):853-857, 1973. 12. Prichard, J.F. Advanced periodontal disease/ surgical and prosthetic m anagem ent, ed 2. Philadel phia, W. B. Saunders Co, 1972, p 142. 13. Trey, E.D., and Bernim oulin, J.P. Influence of free gingival grafts on the health of the marginal g in giva. J Clin Periodontol 7(5):381-393, 1980. 14. Bates, J.F.; N eill, D.J.; and Preiskel, H.W . R esto ration of the partially dentate mouth. Chicago, Q uin tessence Publishing Co, Inc, 1984, p p 132-141. 15. Clarke, M.A., and Bueltm ann, K.W. Anatomical considerations in periodontal surgery. J Periodontol 42(9):610-625, 1971. 16. Sullivan, H.C., and Atkins, J.H. Free autogenous gingival grafts. Principles of successful grafting. Perio dontics 6(3):121-129,1968. 17. Corn, H. Edentulous area pedicle grafts in mucogingival surgery. Periodontics 2(6):229-242, 1964. 18. Grupe, H.E. Horizontal slidin g flap operation. Dent Clin North Am 43-46, 1960. 19. Ramfjord, S.P., and others. L ongitudinal study of periodontal therapy. J Periodontol 44(2):66-77,1973. 20. Ramfjord, S.P., and others. Oral hygiene and maintenance of periodontal support. J Periodontol 53(l):26-30, 1982. 21. Key, M. T opical fluoride treatment o f overden ture abutments. Gen Dent 28:5-8, 1980. 22. Derkson, G .D., and MacEntee, M.M. Effect of 0.4% stannous fluoride gel on the gingival health of overdenture abutments. J Prosthet Dent 48(l):23-26, 1982. 23. Ettinger, R.L.; T aylor, T.D.; and Scandrett, F.R. Treatment needs of overdenture patients in a longitud inal study: five year results. J Prosthet Dent 52(4):532537, 1984.
Johnson-Sivers : PERIODONTAL CONSIDERATIONS FOR OVERDENTURES ■ 471
Overdentures can offer an alternative to regular dentures w ith the correct factors. T his paper discusses proper abutm ent selection an d preparation coupled w ith a p propriate periodontal m aintenance and caries control to assure the success o f overdentures.
Periodontal considerations for overdentures G eo rg ia K. J o h n so n , DDS, MS J o a n E. Sivers, DDS
hen com plete dentures are in cluded in the treatm ent plan fo r a p a tie n t, o v erd e n tu re s should be considered as a possible altern a tive. An overdenture is a com plete or p a r tial rem ovable denture constructed over retained teeth w hich have been dram ati cally reduced in height. Preservation of alveolar bone is the chief advantage of the overdenture, a lth o u g h other advantages include m aintenance of proprioceptive sen sation an d psychological benefits to the patient. T h e concept of the overdenture is not new to dentistry. Ledger1 advocated leav ing root “ stum ps” under artificial teeth. O th er au th o rs2-4 have encouraged the re ten tio n of n atu ra l roots for denture su p port. O verdentures have recently become p o p u la r, p rim arily as a result of the sim p li fication of techniques and reduction of cost to the p atient. T h e use of overdentures has drastically decreased the n um ber of patients w h o are totally edentulous. T h is article discusses from a periodontal standpoint indications, contraindications, abutm ent tooth selection and preparation, and p eri odontal therapy before an d after overden ture construction.
W
Indications and contraindications An overdenture may be indicated in situ a tions in w hich existing teeth can no longer 468 ■ JADA, Vol. 114, A pril 1987
su p p o rt a rem ovable or fixed partial den ture.5 O verdentures are m ore beneficial in the m andibular arch because bone loss in the m andible is greater th an th at in the m axilla after to o th loss. T allg re n 6observed th a t after teeth were removed an d dentures were placed, the m andible lost four times m ore ridge heig h t th an the m axilla d u rin g a period of 7 years. T h e fact th at the pres ence of teeth aids in retention of alveolar bone height is illustrated in Figure 1. T h e value of overdentures as a means of preserv in g alveolar bone has been show n in a study by C rum an d R ooney,7 w ho m ea
sured vertical alveolar bone loss in two g ro u p s of patients: one gro u p w ith conven tio n al m axillary and m an d ib u lar dentures, an d the other gro u p w ith conventional m axillary dentures an d m an d ib u lar over dentures. M andibular vertical bone loss after 5 years was m ore th an eight times greater in the patients in the conventional denture g ro u p th an in the p atients in the o verdenture g ro u p . Bone loss in ihe m ax il lary arch was sim ilar for both groups. A lth o u g h overdentures are indicated more freq u en tly in the m an d ib u lar arch, there are selected instances in w hich a m axillary
F ig 1 ■ T h is p a n o ra m ic radiograph show s th a t alve o lar bone height is better m ain tain ed w here teeth are present. N otice the d ram at ic loss of p o sterior alveolar bone heig h t as contrasted to the bone level in the canine and p re m o la r regions.
ARTICLES
overdenture is beneficial. T hese include situations that can generate greater than n o rm al occlusal forces to the m axillary an terio r ridge, w hen a Class III m alocclu sion is present or only the natu ral m an d ib u la r an terio r teeth rem ain. Use of an over denture can help prevent the developm ent of the “co m b in atio n syndrom e,” w hich is characterized by loss of the anterior p a rt of the m axilla, overgrow th of the tuberosities, inflam m atory p apillary hyperplasia, extru sion of the m an d ib u lar anterior teeth, and loss of bone u nder the distal extension bases.8T h e overdenture concept m ight also be used in the distal extension p o rtio n of a a rem ovable p artial denture (Fig 2). In this m anner, a tooth unsuitable for clasping may be used to provide vertical support and aid in bone preservation. O verdentures are contraindicated if bone loss is extremely severe, so that all teeth are u n su itab le choices for abutm ents. T hey are also n ot indicated in situations in w hich sufficient su p p o rt rem ains for fixed or rem ovable partial dentures.9 Insufficient interridge distance m ig h t also preclude the use of overdentures unless corrected by alveoloplasty or odontoplasty.10 P oor oral hygiene has often been cited as a co n tra in dication, as it can lead to caries and p eri o d o n tal disease w ith resultant abutm ent loss. P oor oral hygiene should n o t be con sidered as an absolute co ntraindication as the p atien t may be m otivated to change these habits. Even if the abutm ents are lost eventually, patients will have had the ad vantage of the bone-retaining properties w hile present; the necessary denture m odi fications are relatively sim ple after ab u t m ent extraction.
Selection of abutment teeth T reatm en t p la n n in g begins w ith the selec tio n of ab u tm en t teeth and is based largely
Fig 2 ■ T his first molar was hemisected, retaining the distal root as an overdenture abutment for a removable partial denture. T h is abutment w ill be valuable as a means of preserving alveolar bone height in the posterior region o f the alveolar ridge (photograph courtesy o f Dr. David Okano, Rock Springs, WY).
on periodontal considerations. T h e p eri odontal exam ination includes an assess m ent of the follow ing factors: rem aining osseous support, p ro b in g depths, inflam m ation, w idth of attached gingiva, tooth m obility, and consideration of root an at om y an d the p o sitio n of the teeth in the arch.
th o u g h keratinized tissue m ay be present. In such cases, a soft tissue g raft is indicated to increase the w id th of attached gingiva. If this aspect of treatm ent p la n n in g is over looked, traum a or pressure to the gingival region m ig h t cause loss of attachm ent, resu ltin g in soft tissue clefting. M obility should also be evaluated, keep-
Jreatment planning begins with the selection of abutment teeth and is based largely on periodontal considerations.
It has been suggested that an overdenture ab u tm en t should have a m in im u m of 5 to 6 m m of rem ain in g bone s u p p o rt.11 R adio graphs are necessary to assess the rem ain in g osseous heig h t a n d also serve as a good prelim inary screening to elim inate u n su it able teeth. However, they do n ot show periodontal pockets, or accurately depict soft to hard tissue relationships or struc tures on the buccal an d lin g u al aspects of the teeth.12 Therefore, the inform ation gained from periodontal p ro b in g m ust be used w ith the radiographs. T h e gingival tissues m ig h t ap p ear healthy and the g in gival m argin m ig h t be at its norm al level, b u t careful circum ferential p ro b in g is necessary to identify increased probing depths. If the gingiva bleeds w hen probed, the in flam m atio n should be reduced by oral hygiene instructions an d periodontal scaling before ab u tm en t p reparation. A relatively shallow gingival crevice is desir able, and if deep p ro b in g d epths exist, they should be appropriately treated. R ecent research has indicated th at the w idth of attached gingiva is n o t a critical factor w hen a w ell-m aintained natural tooth is present.13 However, the su rro u n d ing tissues of overdenture abutm ents are subjected to greater m echanical stresses and m ore bacterial p la q u e tends to accum ulate. Therefore, a greater w idth of a t tached gingiva is necessary when the tissue is covered than w hen it is n o t covered.14 T he dim ensions of attached gingiva sh o u ld be evaluated on the buccal surfaces of the m axillary teeth an d on the buccal an d lin gual aspects of the m andible, as the latter is an often overlooked area. T o determ ine the dim ension of the attached gingiva, the m ucogingival ju n c tio n sh o u ld be located. T h e w idth of keratinized gingiva is then m easured, and the p ro b in g d epth is sub tracted from this m easurem ent to give the w idth of attached gingiva. If the pro b in g d epth extends beyond the m ucogingival ju n c tio n there is no attached gingiva al
in g in m in d th a t the crow n-to-root ratio w ill be greatly im proved d u rin g a b u tm en t reduction, thereby im p ro v in g the to o th ’s stability. A clinically m obile tooth should n o t be elim inated as a p o ten tial ab u tm en t u n til a total periodontal assessment has been made. C onsideration of root anatom y is essen tial in the selection process. Deep root co n cavities or grooves such as those fo u n d on m axillary first prem olars are d ifficult to clean, m aking these teeth p o o r ab u tm en t choices. M olars or m axillary prem olars w ith furcation involvem ent are n o t su it able choices as ab u tm en t teeth because of difficult access to the furcal region. If the fu rcatio n can be elim in ated by a hem isectio n or bicuspidization procedure (divid in g a m o lar in to tw o prem olars) an d there is sufficient bone su p p o rt rem ain in g , re sected teeth m ay serve as valuable a b u t ments. R oot anatom y should also be consid ered from an endodontic stan d p o in t, as m ost ab u tm en ts w ill req u ire endodontic treatm ent and m ust be am enable to such therapy. T eeth should be retained in areas in w hich fu nctional stresses are the greatest. E dentulous an terio r segments th a t oppose n atu ra l teeth are p articu larly susceptible to bone resorption; therefore, incisors, ca nines, or prem olars (or all three) are likely candidates for retention.4 It has been su g gested that four widely separated teeth offer the ideal situ atio n ,14 a lth o u g h fewer ab u t m ent teeth m ig h t be used. Even one tooth can be a valuable a b u tm en t w hen teeth are n ot available on b oth sides of the arch .4 T h e retained teeth sh o u ld be separated suf ficiently to allow for adequate oral hygiene procedures. D iagonal fulcrum lines should be avoided to prevent problem s m a in ta in in g d en tu re stability. A fu lcru m lin e th a t is perp en d icu lar to the sagittal p lan e seems to result in a m ore stable prosthesis.14 T eeth in extrem e labial p o sitio n w ith soft tissue undercuts can pose a problem to the p ath of
Johnson-S ivers : P E R IO D O N T A L C O N SID E R A T IO N S FO R O V E R D E N T U R E S ■ 469
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Periodontal therapy
Fig 3 ■ C row n le n g th e n in g has been done o n m ax illary a n te rio r teeth to allow p ro p e r c o n to u rin g of the o verdentu re a b u tm en ts. T o p , p resurgical m od els. M iddle, overdenture a b u tm e n t p re p a ra tio n of m ax illary rig h t central incisor after h e alin g (note, 2 to 3 m m height). B ottom , dom e-shaped contour.
insertion. Also, a tooth that is p rom inent m ig h t n ot have cortical bone over the facial surface an d may be m ore susceptible to g ingival recession.15 A ngulation of the to o th is another consideration. T o distrib ute occlusal forces m ost effectively, the root sho u ld be in an axial positio n w ith the forces directed alo n g its lo n g axis. An adequate assessm ent of the factors discussed is crucial to the success of the overall treatm ent. T h e elim ination of hope less teeth d uring treatm ent p la n n in g should m inim ize p o tential periodontal problem s. 470 ■ JADA, Vol. 114, A pril 1987
T h e prim ary objectives of periodontal p rep aration are the achievem ent of m inim al p ro b in g depths an d an ad equate zone of healthy attached gingiva. T herefore, surgi cal pocket elim in atio n an d soft tissue grafts are the m ost com m only used surgical proce dures in abutm ent preparation. T o accom plish pocket elim ination, the gingivectom y or apically po sitioned flap w ith osseous surgery may be used. T h e gingivectom y can be used if there are no infrabony pockets present an d if an ad equate zone of attached gingiva w ill rem ain after surgery. More often, as a resu lt of the need for osse ous recontouring an d conservation of at tached gingiva, the apically positioned flap is indicated. T h is procedure allow s access to elim inate osseous defects, and the apical placem ent of the flap at or near the crestal bone w ill result in h ea lin g w ith a shallow sulcus. T h e apically positioned flap w ith osseous surgery is also indicated w here crow n height is in adequate to allow proper abutm en t p rep aratio n (Fig 3) or w here isolated occlusal p lan e problem s exist. If esthetic appearance is n ot affected or if posterior su p p o rt w ill n o t be lost, it is advisable to remove hopeless teeth as early as possible in the treatm ent. T h is allow s for h ealing of the ridges w hile periodontal therapy is being done, and pocket elim in a tion procedures are m ore easily perform ed around isolated abutm ents.5 M olars w ith furcation involvem ents may be candidates for hem isection or bicuspidization procedures to elim inate the furca tion. T hese treatm ents are m ore likely to be indicated in the m an d ib u lar arch resulting from its greater propensity for postextraction resorption. R etention of a posterior root in the tissue-supported region of a m andibular removable partial denture w ith distal extensions m ay be especially v alu able to prevent further bone loss. H em isec tion is an o p tio n if one root is more involved w ith adequate su p p o rt on the rem ain in g root. If adequate bone rem ains on both roots and if the roots are well separated to allow for cleaning, bicuspidization procedures can be considered. If the abutm en t is surrounded by an inadequate zone of attached gingiva or if the vestibule requires deepening, these d i m ensions should be augm ented before den ture fabrication. T h e autogenous free g in gival graft is a relatively sim ple an d predict able means of increasing the w idth of attached gingiva.16 O ther less often used m ethods of g ain in g an adequate zone of attached gingiva include an apically posi tioned flap at the tim e of ex tractio n ,4 the
pedicle fla p ,17 or the horizontally reposi tioned flap .18
Abutment preparation A dom e-shaped ab u tm ent p rep aratio n is com m only used w ith the retained tooth, reduced to 2 to S m m above the crestal ridge.14 Care sh o u ld be taken n ot to over shorten the tooth, as the gingiva w ill tend to creep occlusal ly over the m argins of the overprepared tooth, leading to gingival irritatio n (Fig 4). W hen an ad equate occlu sal h eig h t is m aintained, a w ell-polished am algam placed in the endodontic access o p en in g can serve as the final restoration. If less th an 2 m m of h eig h t exists, it may be necessary to place a gold co p in g to restore heig h t an d contours of the ab u tm ent. C op in g m argins m ust often be placed subgingivally, leading to periodontal com plica tions. O nly the occlusal surface ol the ab u tm en t sh o u ld be in contact w ith the overdenture d u rin g function. W hen ihe den tu re is n o t in function, there should be no contact on the retained to o th because of tissue resiliency.4 At no tim e sh o u ld there be lateral im p in g em en t on the crestal or sulcular gingiva.
Maintenance M aintenance of p eriodontal h ealth is p ara m o u n t to the long-term success of overden tures. T h is responsibility is shared by the d entist an d patient. T h e d en tist is resp o n sible for establishing an ap p ro p riate recall interval an d for p ro p er therapy at these ap p o in tm en ts, as well as for education of patients. T h e patien ts’ responsibility is com pliance w ith these program s. L o n g i tu d in a l studies19'20 have show n th a t a 3m o n th interval allow s m ost periodontal patients to be m ain tain ed w ith o u t sig n ifi cant attach m en t loss a lth o u g h the recall
F ig 4 ■ O verreduction of these a b u tm e n t teeth has led to m a rg in a l gingival in flam m a tio n . Ideally, the teeth sh o u ld be reduced to a level 2 to 3 m m above the crestal tissues w ith a dom e-shaped p re p a ra tio n .
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interval w ill vary depending on the needs of the patient. The following procedures should be done during recall appointments: caries exam i nation, record of probing depths and reces sion, assessment of plaque and inflamma tion, oral hygiene reinforcement, evalua tion of the denture’s fit and occlusion, and cleaning of the prosthesis, if necessary. Plaque control is the biggest challenge the dentist faces with patients w ho have over dentures. Therefore, oral hygiene proce dures should be individualized and can include the use of such adjuncts as an endtufted toothbrush. The daily use of a topi cal 0.4% stannous fluoride gel is recom mended primarily for caries prevention,21 but this preparation also has an antibacte rial effect that has been shown to reduce gingivitis.22 Patients at high-risk for caries can brush with the gel in the evening in addition to filling the denture abutment indentations with the gel in the morning before denture insertion. Studies of overdenture patients have shown that these patients universally expe rience an increase in gingivitis around abutment teeth and that patients with poor recall compliance have the highest increase in caries and periodontal disease. Even so, overdentures can be considered successful if success is based on tooth retention. Re tention has been reported to be as high as 96% in a 5-year period.23
Summary An overdenture is a preferable alternative
to a conventional denture. Clinically the major advantage of the overdenture is pres ervation of alveolar bone. T he most impor tant factors to be evaluated during abut ment selection include the amount of re m aining bone support, probing depth, and the width of attached gingiva. T he goals of periodontal therapy before overdenture construction are the establishment of a shallow, healthy, gingival crevice with an adequate zone of attached gingiva. Proper abutment selection and preparation cou pled with appropriate periodontal main tenance and caries control w ill assure the success of overdenture treatment.
------------------- JiiO A ------------------Dr. Johnson is assistant professor, department of periodontology, and Dr. Sivers is assistant professor, department o f adult restorative dentistry, University of Nebraska Medical Center, 40th and Holdrege, Lincoln, 68583-0740. Address requests for reprints to Dr. Johnson.
1. Ledger, E. On preparing the m outh for the recep tion o f a full m outh set of artificial teeth. Br J Dent Sci 1:909, 1856. 2. Miller, P. A. Complete dentures supported by nat ural teeth. J Prosthet D ent 8(6):924-928,1958. 3. Morrow, R.M., and others. Tooth-supported com plete dentures: an approach to preventive prosthodontics. J Prosthet Dent 21(5):513-522, 1969. 4. Becker, C.M., and Kaldahl, W.B. An overdenture technique designed to protect the rem aining periodon tium. Int J Periodont Rest Dent (4):29-41, 1984. 5. Brewer, A. A., and Morrow, R.M. Overdentures, ed 2. St. Louis, C. V. Mosby Co, 1980, pp 50-64. 6. Tallgren, H. T he continuing reduction of the residual alveolar ridges in complete denture wearers. A m ixed longitudinal study covering 25 years. J Prosthet Dent 27(2): 120-132, 1972. 7. Crum, R. J., and R ooney, G.E. Alveolar bone loss
in overdentures: five-year study. J Prosthet Dent 40(6): 610-613, 1978. 8. Kelly, E. Changes caused by a mandibular remov able partial denture opp osin g a m axillary complete denture. J Prosthet Dent 27(2):140-150, 1972. 9. Leuck, M .H., and LaVelle, W.E. Preservation of the mandibular ridge through root retention. J Acad Gen Dent 21(4):29-32, 1973. 10. Jones, P.A.; Peterson, R.J.; and Taintor, J.F. Indications, advantages, and clinical procedures for overdentures. J Nebr Dent Assoc 55(1):8-10, 1978. 11. Zamikoff, 1.1. Overdentures— theory and tech nique. JADA 86(4):853-857, 1973. 12. Prichard, J.F. Advanced periodontal disease/ surgical and prosthetic m anagem ent, ed 2. Philadel phia, W. B. Saunders Co, 1972, p 142. 13. Trey, E.D., and Bernim oulin, J.P. Influence of free gingival grafts on the health of the marginal g in giva. J Clin Periodontol 7(5):381-393, 1980. 14. Bates, J.F.; N eill, D.J.; and Preiskel, H.W . R esto ration of the partially dentate mouth. Chicago, Q uin tessence Publishing Co, Inc, 1984, p p 132-141. 15. Clarke, M.A., and Bueltm ann, K.W. Anatomical considerations in periodontal surgery. J Periodontol 42(9):610-625, 1971. 16. Sullivan, H.C., and Atkins, J.H. Free autogenous gingival grafts. Principles of successful grafting. Perio dontics 6(3):121-129,1968. 17. Corn, H. Edentulous area pedicle grafts in mucogingival surgery. Periodontics 2(6):229-242, 1964. 18. Grupe, H.E. Horizontal slidin g flap operation. Dent Clin North Am 43-46, 1960. 19. Ramfjord, S.P., and others. L ongitudinal study of periodontal therapy. J Periodontol 44(2):66-77,1973. 20. Ramfjord, S.P., and others. Oral hygiene and maintenance of periodontal support. J Periodontol 53(l):26-30, 1982. 21. Key, M. T opical fluoride treatment o f overden ture abutments. Gen Dent 28:5-8, 1980. 22. Derkson, G .D., and MacEntee, M.M. Effect of 0.4% stannous fluoride gel on the gingival health of overdenture abutments. J Prosthet Dent 48(l):23-26, 1982. 23. Ettinger, R.L.; T aylor, T.D.; and Scandrett, F.R. Treatment needs of overdenture patients in a longitud inal study: five year results. J Prosthet Dent 52(4):532537, 1984.
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