ORIGINAL ARTICLES Crown-lengthening procedures, which include tissue shrinkage, gingivectomy, apical positioning of the flap, osseous surgery, and tooth eruption, are useful in attaining and maintaining periodontal health. However, if the involved tooth has a poor prognosis or the osseous surgical procedure would create a poor crow n-root ratio, furcation involvement, mobility, or esthetic problem, crown-lengthening should be avoided. In these cases, extraction may be indicated.

Rationale and methods for crown lengthening

Francisco Palomo, DDS, G uatem ala City Raymond A. Kopczyk, DDS, MSc, Lexington, KyHi

T o help m ain tain h ealth y p erio d o n tal tissu e s, m argins o f re sto ra tio n s sh o u ld be k e p t co ro n ally to th e free gingival m argin. In som e in stan ces w h ere a c ro w n is sh o rt b e­ cau se o f c a rie s, fra c tu re , e x c e ssiv e w ear, o r d e ­ v elo p m en tal ab n o rm alities, re sto ra tio n s usually are e x te n d e d apically to th e gingival m argin and are difficult to p re p a re an d finish. T h e subgingival p rep a ra tio n as w ell as th e resu ltin g subgingival m argin can c o n trib u te to d e v e lo p m e n t o f p erio d o n tal d isease. R atio n ale an d p ro c e d u re s th a t will en ab le th e clinician to ex p o se th e m ar­ ginal a re a o f re sto ra tio n s an d len g th en cro w n s to help a tta in and m aintain p erio d o n tal h ealth are describ ed . In th is p a p e r, “ clinical c ro w n ” re fe rs to th at p a rt o f the to o th w hich is co ro n ally to the gingival m argin.

R a tio n a le Som e clinicians claim th a t it is n e c e ssa ry to e x ­ te n d cro w n p re p a ra tio n s subgingivally to increase m ech an ical re te n tio n . A lo n g er clinical cro w n in­ c re a se s th e re te n tiv e su rface o f th e p re p a ra tio n .1

C linical and histologic stu d ies2'9 analyzing sev ­ eral ty p es o f resto ratio n s have show n th a t gingival inflam m ation is m ore p ro m inent in are as w here subgingival m argins o f re sto ratio n s are p re se n t, reg ard less o f th e m aterial u sed. Subgingival m arTHE AUTHORS

PALOMO

KOPCZYK

Dr. Palomo, former clinical fellow, department of periodontics, University of Kentucky, cur­ rently is in private practice in Guatemala City. He is also a member of the dental faculty at Univer­ sidad de San Carlos. Dr. Kopczyk is professor and chairman, department of periodontics, Uni­ versity of Kentucky, Lexington, 40506. Address requests for reprints to Dr. Kopczyk.

JADA, Vol. 96, February 1978 ■ 257

C a lc u lu s

gins with marginal deficiencies or overhangs have a deleterious effect, but so do well-adapted mar­ gins.5'9 In patients with advanced caries or fractured teeth, the destruction o f tooth structure may have extended into the subgingival area. Many clini­ cians believe that they have no choice but to place the margin o f these restorations subgingivally. In some instances, surgical crown-lengthening pro­ cedures may be used to increase the length o f the crow n.10 The procedure may allow for increased mechanical retention and exposure o f deep caries or fractures. It also may permit placing margins of restorations coronally to the gingival margin, and allow the clinician to maintain rather than destroy existing attached gingiva. Markley11 suggested that surgical flaps be ele­ vated when carious lesions extend subgingivally. This creates access for placing a rubber dam and clamp and for finishing and restoring the tooth. H e also suggested that in cases o f subgingival caries which approach the alveolar crest, it may be necessary “ to remove a sliver o f alveolar bone for full a ccess.” 11 This, in effect, is a crownlengthening procedure. Extending cavity preparations so that they ap­ proach the crest o f alveolar bone may encroach on the “ biologic width.” This is the area o f tooth surface to which epithelial and connective tissue attachment occur12; it extends about IV2 mm co­ ronally to marginal bone. If the margin o f a resto­ ration infringes on this minimum width, it may become an iatrogenic factor and may result in periodontal disease with resulting bone resorption to create space for an attachment and gingival crevice. H owever, the resulting bone contours may be unfavorable and conducive to further periodontal breakdown.

Fig 1 ■ A: False pocket associated with local irritant. Notice en­ largement of tissue with resultant pocket depth and short clinical crown. B: "Shrinkage” due to elimination of local irritant; notice increase in clinical crown length as result of tissue shrinkage.

Fig 2 ■ A: False pocket associated with enlarged fibrotic tissues; notice englargment of tissue with resultant pocket depth and short clinical crown. B: Gingivectomy eliminates enlarged tissue. C: Ap­ proximate final position of gingival margin, biological width, and bone margin after healing.

Surgical considerations A biologic width of at least IV2 mm between the base o f the sulcus and the crest o f alveolar bone should be surgically created. An additional width o f 1 to 2 mm also should be created for regenera­ tion o f the gingival crevice. If esthetics is a prob­ lem and margins must be placed subgingivally, additional space should be attained to allow the margin to be placed within the crevice without impinging on the soft tissue attachment to the tooth. Surgical crown-lengthening also enables treat­ ment of a periodontal lesion, if one is present. The 258 ■ JADA, Vol. 96, February 1978

Fig 3 ■ A: Pocket and short clinical crown. B: Facial tissue apically positioned. C: Approximate final position of gingival margin, biological width, and bone margin after healing.

procedure may reduce pocket depth, provide ac­ cess for correction of osseous defects, provide access for removal of remaining plaque and cal­ culus, or be used in conjuction with periodontal treatment in adjacent areas. Crown-lengthening procedures include the fol­ lowing: tissue shrinkage (Fig 1), gingivectomy (Fig 2), apical positioning o f flaps (Fig 3), osseous

Fig 4 ■ A: Pocketdepth and short clinical crown; an abnormal soft tissue contour and osseous defect are present. B: Immediately after apically positioned flap and osseous surgery. C: Approximate final position of gingival margin, biological width, and bone margin after healing.

Fig 5 ■ A: Tooth with short clinical crown and osseous lesion; dot­ ted line indicates reduction of occlusal surface to allow eruption. B: Same tooth allowed to erupt or extrude orthodontically; com­ pare final position of cementoenamel junctions, apexes and bone levels.

Fig 6 a Fractured maxillary right central incisor (left); probe indicates distance between gingival margin and edge of fracture. Notice short clinical crown as result of fracture. Clinical crown length has been increased by surgery (middle); probe indicates distance to alveolar crest. Fractured tooth and adjacent incisor restored eight months postoperatively (right).

Fig 7 ■ Maxillary anterior teeth of adult patient (left); notice severe wear resulting in very short crowns. Apically positioned flaps and osseous surgery to increase crown length (middle). Appearance at three-week postopera­ tive appointment; notice increased crown length (right). (Photographs courtesy of Dr. Carl B. Stewart, Richardson, Tex.)

surgery (F ig 4), and in d u cem en t o f to o th eru p tio n (F ig 5). P laq u e c o n tro l and elim ination o f local etiologic fa cto rs m ay red u ce gingival in flam m ation, w hich can resu lt in shrinkage and h ealth ier gingiva (F ig 1). In som e in sta n c e s, enlarged gingiva o r p se u d o p o c k e ts m ay be b e st tre a te d b y surgical resec tio n o f th e en larged soft tissu es. T h u s , a gin­ g ivecto m y as p ro p o se d by G o ld m a n ,13 p ro d u c e s a physiological gingival a rc h ite c tu re a t a m o re ap i­ cal level. T h e new gingival position resu lts in a longer clinical crow n p o sto p e ra tiv e ly (Fig 2). F re q u e n tly , in creasin g th e cro w n length m ay be accom p lish ed by apically positioning fla p s .14 T h is

p ro ce d u re in c re ase s the clinical cro w n length, re ­ d uces p o ck et d ep th , and m aintains ad eq u ate keratin ized gingiva (F ig 3). P ossibly the g re a te st ad v antage o f this m eth o d is th a t it pro v id es acc ess to the underlying o sseo u s stru c tu re s. O sse o u s surgery m ay b e done in co n ju n ctio n w ith apically p o sitio n ed flaps to ach ieve physiological o sse o u s arch ite c tu re and gingival p o sitio n th a t can be m aintained by th e p atien t (Fig 4-7). T h e d etails o f th ese p ro c e d u re s can be found in m o st p erio d o n ­ tal te x tb o o k s .15,16 A n o th e r m eth o d to gain cro w n length is in­ d u c em en t o f to o th e ru p tio n .17 A clinically sh o rt to o th , o r one w ith d eep subgingival fra c tu re o r Palomo— Kopczyk: CROWN LENGTHENING ■ 259

c a rie s, m ay b e allow ed to e ru p t to a p o in t w here th e clinical c ro w n is lo n g er (F ig 5). I t also is p o ssi­ b le to fo rc e e ru p tio n o f a to o th b y ex tru d in g it o rth o d o n tic a lly , achieving th e sam e re su lts. F o r p a tie n ts in w hom th e b o n e also e ru p ts co ronally w ith th e eru p tin g to o th , it m ay b e p o ssib le to elim in ate o sse o u s d efects. F u r th e r p erio d o n tal tre a tm e n t su ch as o sseo u s su rg ery still m ay be n e c e ssa ry as a seco n d -stag e p ro c e d u re , d e p e n d ­ ing on th e b o n y c o n to u rs th a t re su lt a fte r eru p tio n . F in a l p re p a ra tio n s an d finishing p ro c e d u re s are e a sie r w h e n th e clinical c ro w n len g th h as b een in c re a se d . A t tim e s, p re p a ra tio n s a n d p lac em en t o f re sto ra tio n s m ay be d o n e at th e sam e ap p o in t­ m e n t as th e surg ical p ro c e d u re .11 T h e final p o sitio n o f m arginal b o n e , biologic w id th , an d gingival m argin m ay v a r y .18-19 H o w ­ e v e r, th e ir p o sitio n s m ay be a p p ro x im a te d . C lini­ cally , th e ch an g es in p o sitio n th a t o c c u r during healin g m ay b e o f little clinical significance.

Conclusion S urgical c ro w n lengthening sh o u ld n o t be a t­ te m p te d w h en to o th fra c tu re s e x te n d into the m iddle th ird o f th e ro o t. E x c e ssiv e b o n e red u ctio n o n th e fra c tu re d to o th an d n e c e ssa ry blending o f o sse o u s c o n to u rs o v e r a d ja c e n t te e th m ay resu lt in m o bility o r fu rcatio n in v o lv em en t. In addition, th e n e c e ssa ry o sseo u s su rg ery m ay c re a te p re ­ cip ito u s ch an g es in th e b o n y a rc h ite c tu re th a t will b e brid g ed by soft tissu e s. T h is re su lts in in­ c re a se d p o c k e t d ep th an d an u n h e a lth y situation. I f th e to o th in q u e stio n has a h o p e le ss prognosis o r th e o sse o u s surgical p ro c e d u re w o u ld c re a te a p o o r c ro w n -ro o t ratio , fu rc a tio n in v o lv em ent, m o b ility , o r e sth e tic p ro b le m s, c ro w n lengthening

260 ■ JADA, Vol. 96, February 1978

should be av o id ed . In ca se s su ch as th e se , e x tra c ­ tion m ay be in d icated.

1. Willey, R.L. Retention in the preparation of teeth for cast restorations. J Prosthet Dent 35:526 May 1976. 2. Bjorn, A.L., and others. Marginal fit of restorations and its relation to periodontal bone level. Part I. Metal Fillings. Odontol Revy 20:311, 1969. 3. Bjorn, A.L., and others. Marginal fit of restorations and its relation to periodontal bone level. Part II. Crowns. Odontol Revy 21:337, 1970. 4. Christensen, G.J. Marginal fit of gold inlay castings. J Prosthet Dent 16:297 March-April 1966. 5. Gilmore, N., and Sheiham, A. Overhanging dental restorations and periodontal disease. J Periodontol 42:8 Jan 1971. 6. Karlsen, K. Gingival reaction to dental restorations. Acta Odontol Scand 28:895 Dec 1970. 7. Newcomb, G.M. The relationship between the location of subgingival crown margins and gingival Inflammation. J Periodon­ tol 45:151 Feb 1974. 8. Sanchez Sotres, L., and others. A histological study of gingival tissue response to amalgam, silicate and resin restorations. J Periodontol 40:543 Sept 1969. 9. Morman, W., and others. Gingival reaction to well-fitted sub­ gingival proximal gold inlays. J Clin Periodont 1:120 Jan 1974. 10. Burch, J.G. Ten rules for developing crown contours in res­ torations. Dent Clin North Am 15:611 July 1971. 11. Markley, M.R. Amalgam restorations for Class V cavities. JADA 50:301 March 1955. 12. Gargiulo, A.W., and others. Dimensions and relationship of the dento-gingival junction in humans. J Periodontol 32:261 May 1961. 13. Goldman, H.M. Gingivectomy, indications, contraindica­ tions and method. Am J Orthod 32:323 May 1946. 14. Friedman, N. Mucoglngival surgery: the apically reposi­ tioned flap. J Periodontol 33:328 Oct 1962. 15. Goldman, H.M., and Cohen, D.W. Periodontal therapy, ed 5. St. Louis, C.V. Mosby Co., 1973, p 2. 16. Prichard, J.F. Advanced periodontal disease, ed 2. Philadel­ phia, W.B. Saunders, 1972, p 2. 17. Ingber, J.S. Forced eruption: part I. A method of treating isolated one and two wall infrabony defects—rationale and case report. J Periodontol 45:199 Feb 1974. 18. Bergstrom, J. An investigation of gingival topography in man by means of analytical stereophotogrammetry. II. Changes follow­ ing periodontal surgery. Acta Odontol Scand 32:221 July 1974. 19. Rosling, B., and others. The healing potential of the periodontal tissues following different techniques of periodontal surgery in plaque-free dentitions. J Clin Periodont 3:233 Nov 1976.

Rationale and methods for crown lengthening.

ORIGINAL ARTICLES Crown-lengthening procedures, which include tissue shrinkage, gingivectomy, apical positioning of the flap, osseous surgery, and too...
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