Management of Periodontal Tissues for Restorative Dentistry
Management of Periodontal Tissues for Restorative Dentistry Cliflord B . Starr, Lt Col, USAF, DC'
Proper management of periodontal tissues is required to achieve predictable long-term success with restorative dental procedures. Forced eruption as well as several surgical techniques may be used to achieve and maintain adequate biologic width during restorative and esthetic dental procedures. The technique that will yield optimal results depends on the relationshipbetween the restoration's margins and the surrounding periodontium. A classiflcation system that describes these interrelationships and provides treatment recommendations is included.
0
ne of the primary goals of restorative dentistry is to replace form, function,and esthetics lost due to trauma or disease. An equally important goal is to do no harm when placing these restorations. The improper control or management of the periodontium during restorative procedures is a common cause of failure that is often overlooked. According to Maynard and Wilson,' "The preservation of a healthy periodontal attachment is the most significantfactor in the long-term prognosis of a restored tooth." The fact that restorations with overhanging margins, open margins, improper interproximalcontacts, poor contours, inadequate embrasures, plunger cusps, and uneven marginal ridges can trap bacterial plaque and cause gingival inflammation and loss of alveolar bone is well documented."' Predictable long-term restorative success therefore requires a blending of restorative principles with those concerningthe management of supporting periodontal tissues so that iatrogenic defects will not compromise the final result. If the tissues are not healthy, then periodontal disease must Arst be adequately controlled before Mtiating surgical and/or definitiverestorative procedures. For patients with healthy periodontal tissues, there are two separate clinical situations that require periodontal tissue management. The first occurs when the zone of biologic width is inadequate. This can be caused by h c t u r e lines or other lesions, such as caries. internal or external resorption, or pin/post perforations, that involve the extemal tooth surface subghgbdly within 3-4 mm of the alveolar crest.?. '-I8 A second clinical situation that requiresperiodontalmanagement occurs when there isinadequate clinical crown length available
to obtain the esthetic results required.IgThfssituation usually occurs in patients with a high lip line, and the result is an excessive gingival display. In both of these clinical situations, the appropriate periodontal and restorative treatment must be accomplished if a successful result is to be obtained.
BIOLOGIC WIDTH
The concept of a minimumdimension of tissue from the alveolar crest to the bottom of the gingival sulcus is based on the study by Garguilo et They examined 30 cadavers and found that the average dimension of connective tissue fibers was 1.07 mm and that the average dimension of junctional epithelium was 0.97 mm (Fig. 1).The total of these two tissues averaged 2.04 mm. Cohenzl is credited with originating the widely used term 'biologic width', although Ingber et a18 and have also received redi it.?^.?^ Nevins and Skur0w2~ Maynard and Wilson1 further describe the inviolate nature of this tissue, which they term the 'physiologic dimension.' They describe the destruction of periodontal tissues that occurs if restorations and/or defects inMnge upon this area. Currently there is no evidence that, in the absence of jnflammation, restorations that violate the biologic width will cause periodontal breakdown. However, there is ample proof that in the presence of inflammation tooth preparations and/or restorations that impinge on the biologicwidth trap bacterial plaque, induce inflammation, and increase both the likelihood and severity of periodontal b r e a k d o ~ n ~ - ~ - ~ ~ - ~ wig. 2). Universal agreement does not exist regarding the minimum amount of sound tooth structure coronal to the alveolar crest that is necessary to ensure periodontal health. Ramqordz3feelsthat no minimum distance is required as long as inflammationis adequately controlled. Wagenberg et als recommends that margins be
Chatrmaa Departmmt of General Dentbfq and Assistant Director, Residency. U W Medical Center/SGD. WrIght-Patterson
General Dentishy
AFB.Ohio Address reprint requeststo. Clifford Starr. D.M.D.. 4.062 QuatlBush Dr.. Dayton. OH 45424
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JOURNAL OF ESTHETIC DENlISTRY VOLUME 3.NUMBER 6 November/December 1991
treatment used to exposeadequate tooth structure. 1 4 3 35 Several different techniques are available depending upon the proposed location of the restoration margin, the location of the alveolar crest and gingival margin, the width ofattached keratinized tissue, and the amount of exposed tooth structure available. A classification system that describes these interrelationships and provides treatment recommendations is summarized in Table 1. Class 1 cases have all supragingival margins and no periodontal management is needed. Class 2 cases occur when the defect to be treated is apical to the gingival margin, the amount of attached gingiva is adequate, and the amount of sound tooth structure coronal to the alveolar crest is adequate. Access to the subgingival defect or margin for this common clinical situation may be managed in a variety of ways. Often a rubber dam alone or in combination with a rubber dam clamp may provide sufficient access. In other cases, a miniflap made with two vertical incisions at the line angles may be used to provide sufficient
Of the connective The b'ologlc width is tissue fibers and junctional epithelium. The figure on the left shows the ffssue relationships found with atered passive eruption.The figure on the rightshows the relationshipspresent after completion of crown lengthening.
Figure 3. A, Tooth No. 2 1 with a subgingival carlous lesionin an area of minimal keratintzed tissue. Hgare 2. Inflammaton of the periodontal tissues resulting froma restoraffon that implngesi on the biologic width.
placed no closer than 5.25 mm from the bone ifperiodontaI health is to be maintained. However, most authors recommend that when supragingival margins are not feasible, restoration margins should be placed at least 3-4 mm from the alveolar crest.14s15.2837 This addit.€od1-2 mm allow room for a healthy gin$val s d m s and the margin of the restoration.
SURGICAL TREATMENT APPROACHES For patients wHh healthy periodontal tissues, SUrgkd Crrmrm llengthentngIs the t r a d f t o d method of
FYguce 3. B,Mwflap incisions to faditate acce89. 196
Management of Periodontal Tissues for Restorative Dentistry
Tabte 1. Pwbdontal-Restoralive Interrelationships and Treatmenl Recommendations
Sound Gingival Bond
rooft,out of Bone
Lesion/ Restoration Location
Treatment Indicated
Class 1
Adequate
Adequate
Supragingival
None
Class 2
Adequate
Adequate
Subgingival
Rubber dam Rubber dam clamp Retraction cord Minlflap Envelope Flap
Class 3
Wide
Adequate
Subgingival
Gingivectomy
Class 4
Narrow
Adequate
Subgingival
Apically positioned flap without bone removal
Class 5
Either
Inadequate
Subgingival
Apically positioned flap with bone removal
Inadequate
Mucogingival surgery
access while minimizing trauma to the soft tissue3*(Fig. 3).Xhonga30 evaluated four different flap designs for access to subgingivallesions. She found that a miniflap made with two small incisions at the line angles of the tooth provided adequate access, produced the least postoperative inflammation, had the least postoperative recession, and did not require sutures or packing. Larger access flaps can be u s e l l if multiple adjacent teeth are i n ~ o l v e d . ~ ~ ~ Class 3 cases involve a wide band of attached gbgiva, adequate sound tooth structure coronal to the alveolar crest, but inadequate tooth structure coronalto the gingival margin. A gingivectomy may be used to expose sufficient tooth structure for restorative denustry (Fig. 4). Class 4 cases are similar to class 3 cases, except that there is a minimal band of keratinized tissue. A full
Figure 3. C.Access to full extent of the lesion
Figure 4. A. Hyperplastic gingtva is impeding access to distobuccal carious lesion.
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JOURNAL OF ESIHFnC DENTISTRY VOLUME 3,NUMBER 6 Novernber/December 1991
Figure 4. 8.After surgical removal of the excessive gtngival tissue. a rubber dam is used to control bleeding during the restoram procedure.
Figure 1. C, Control of caries and temporization after placement of rubber dam.
-8. A IntraaralviearofapatlQltwithmultiplemb@WJd carious lesions.
Figare 1. D, The periodontal flap is repositioned apically and sutured in place.
R B.Afull Wckncas flapisrdlectedtoprovide acmes to arks and gpoae aound tooth s t r u m for resbratiw
lrlepe 1. E, Afta 2 weeks it can be seen that adequate tooth structure is available for the placement of restorative margins
on sound enamd. 198
Management of Periodontal Tissues for Restorative Dentistry
thickness flap may be used to expose additional tooth structure, and the flap can then be positioned apically and sutured in place. This preserves the entire band of keratinized tissue and prevents the development of a mucogingival defect (Fig. 5). Class 5 cases have insufficient tooth structure coronal to either the alveolar crest or the gingival margin. As long as there is at least a minimum band of gingival tissue present, an apically positioned full thickness flap with ostectomy and osteoplasly is the surgical procedure that should be used to obtain sufficient sound tooth structure for restorative dentistry (Fig. 6). The minimum amount of keratinized attached tissue that is required for the maintenance of periodontal health has not been determined. Maynard and Wilson' feel that there should be 5 mm of keratinized tissue, at least 3 mm ofwhich is attached. Others feel that in areas of health, no specific minimum amount of attached gingiva is needed and that mucogingival surgery should only be performed if problems such as progressive tissue loss are 0 ~ c u r r L n g . ~ ~ ~ ~
Figure 6. C. Two-weekhealingrevealsthe availabilityof sound tooth structure for margin placement.
The timing of the treatment is also important. Most surgical procedures should be performed before the restorative phase is begun so that adequate tissue ~* achealing and maturation can O C C U ~ . ' * ~ .However, cess to the defect can sometimes best be obtained during the surgical procedure, when the flaps are reflected and complete access to the remaining tooth structure is available (Figs. 7 and 8).29-33
FORCED ERUPTION
Flgum 6. A, L m g d view of tooth No. 30 with insufilciemt crown length for restoratrve dentistry.
6.
B, No. 30 after ostectomy and osteophty.
Forced eruption is another treatment technique that exposes inaccessible tooth structure and provides access to subglngival lesions that may extend apical to the alveolar crest. This orthodontic approach was first in 1973,who utilized it to described by Heither~ay3~ gain access to transverse root fractures below the alveolar crest. Since that time forced eruption has been used to gain access to endodontic, restorative, and prosthodontic perforations, internal/extemd resorption
Flgum 6. D, Final restoration.
JOURNAL OF ESTHETlC DENTISTRY VOLUME 3.NUMBER 6 November/December 1991
Figam 7. A. Tooth No. 14 with lingual cusps fractured to the aiveolar crest. Surgical crown lengthening has already been performed and the results are inadequate.
7.
B.
flW provides access forlingualmargins.
eigara 7. D. The flap is replaced after completion of the restorative procedure.
Flgura 8. A, Palatal view of tooth No. 3 with defective MODFL amalgam restoration. palatal margins are subgingival and inaccessible.
Management of Periodontal Tissues for Restorative Dentistry
Table 2. Advantages d Forced Eruption versus Surgical Crown Lengthening improved crown-root ratio No increase in clinical crown length Improved esthetics of the final restoration possible Supportingbone of adjacent teeth not sacrificed Surgical treatment phase may be reduced or eliminated.
is performed during the extrusion process, the gingiva
Figure 8. D, Two-weekhealing response.
should not erupt with the tooth, and the need for periodontal surgery may be e l i m i ~ ~ a t e d . ~ ~ . ~ There are several advantages that forced eruption provides relative to surgical crown lengthening that may be sigmficant in certain clinical situations (Table 2).In the maxillary anterior segment, where esthetics is of paramount importance, the opportunity to obtain an esthetically superior restoration makes forced eruption the treatment of choice. Teeth treated with surgical crown lengthening exhibit increased clinical crown .~~ an improved length that is often ~ n e s t h e t i cHowever, esthetic result is possible with forced eruption, since the crown length of the final restoration is the Same as the original crown length (Fig. 9). While enhanced esthetics is important, the other advantagesof forced eruption should not be overlooked. The final crown-root ratio of the extruded tooth is superior to that obtained with surgical crown lengthening (see Fig. 9). If full thickness flap surgery is used to return the gingiva to its original location, little or no supportingbone needs to be removed from the extruded tooth or the adjacent teeth, and the crown-rootratio for all three teeth is therefore improved. Alternatively, if a supramstal fibemtomy is performed during the extrusion phase, the need for periodontal surgery may be reduced or eliminated.
defects, subgingival caries, and crown and root fi-acWes. 15.24,26.27.40-48 Light orthodontic forces can be used to generate slow tooth movement. The tension transmitted to the alveolar bone is thought to stimulate the deposition of new bone, which has proved to be useful in the ellmination or reduction of periodontal d e f e ~ t s . ~Moderate ~*~' orthodontic forces of 25 to 30 g generate faster tooth movement that allows for tooth extrusion without the accompaniment of alveolar bone.ms"4***50 In c h i & situations where there is insumdent tooth structure coronal to the alveolar crest. either forced eruption or surgical crown lengthening with ostectomy/osteoplasty can be used to expose additional tooth structure. The traditional forced eruption technique causes the gingival tissues to erupt with the tooth and a mir~orperiodontal Procedure is necessary to return the gingtval margin to its proper location.43However.ifagingivdsupracrestalfiberotomy
Figure 9. Crown length comparisonafter forced eruption and surgfcal crown lengthening. Note the improved esthetics and crown-root ratio O b m e d with forced eruption.
Figure 8. C. The flap is sutured in place aftercompletion of the restoration.
JOL‘RVAL OF ESTHETIC DENTlSTRY VOLUME 3.NUMBER 6 November/December 1991
advantages. The direct bonding of the archwire to the tooth makes it easier to ensure that the archwire is passively attached to the abutment teeth. The probabilThere are many techniques available using flxed or ity of undesirable tooth movement is therefore deremovable a p p l i a n c e s . ’ S ~ 2 4 ~ 2 7 . 3 9 ~ 4The 0 ~ 4most 2 ~ ~ ~ 7 ~ 5creased. ~ The case may also become less expensive to common approach uses bands or direct bonded bracktreat, The use of relatively expensive bands and brackets on the abutment teeth. A round or rectangular ets is eliminated. Therefore it is not necessary to mainsegmental archwire is then ligated to the brackets. tain an expensive inventory of bands and brackets to At Various loop designs and elastomeric materials have each tooth. Also, less chairside time is required, since been used to apply the extrusive force to the tooth. This precise bonding of brackets and complex wire bends technique requires the ability to bend a segmental needed to fit the wire passively into the brackets are archwire that will be completely passive when seated eliminated. into the brackets on the abutment teeth. If any deflecSeveraldifferent attachments may be applied to the tion of the archwire occurs when it is seated into the tooth to be extruded (Fig. 11). If the clinical crown or a brackets, active forces will be placed on the abutment temporary crown is present, then an orthodontic button teeth and unintended tooth movement may occur. or threaded pin can be attached. Another option is to An alternative technique that decreases the possifabricate a custom hook made from .018 orthodontic bility of undesirable abutment tooth movement uses a round wire that is bonded directly to the crown. If the rectangular -018x .025 segmental archwire bonded tooth has been endodontically treated and there is no directly to the abutment teeth (Fig. 10).Care must still clinical crown available, a hook made from orthodontic be used to ensure that the wire is bonded passively in round wire may be cemented into the canal with tempoplace. However, the use of this technique offers several
FORCED ERUPTION TECHNIQUES
F@m 10. Bonded directly to the abutment teeth is the . O M
Figure 11. B, An orthodontic button bonded directly to the
x .025 al-hvke.
tooth.
11. AAthreadcdpinplacedintoatempo+arycrown
pioruS11. CUseofacustornhookmadefrom.018roundwire.
202
Management of Periodontal Tissues for Restorative Dentistry
Figure 11. D, A hook made from orthodontic round wire temporarily cemented into the root canal.
Figure 13. Extrusion complete: compare with Figure 11D.
rary cement. The segmental archwire that is bonded to the abutment teeth must have an offset bend so that the wire passes directly over the canal of the tooth to be extruded (Fig. l2LZ7Otherwise, undesirable buccal or lingual tooth movement will occur as the root erupts. With either treatment approach. it is important to ensure that the distance between the bottom of the segmental archwire to the top of the attachment on the tooth to be extruded equals the desired extrusion distance (e.g.. 3 mm) (seeFig. 11D). If the attachment and segmental archwire are properly designed and applied, the desired extrusionwill have been obtained when the attachment touches the segmental wlre (Fig. 13). The extrusion force can be applied by tying elastomericthread, chain, ortubing around the archwire and the attachment. If .025 tubing is used, the recommended 25-30 g of force can be easily obtained. The appliance should be reactivated weekly. Extrusion rates reported in the literature vary from 0.2 to 2 mm per
~ e e k . ~ Cases ~ . ~using ~ . ~.025" ~ . tubing ~ ~ usually exhibit approximately 1 mm of extrusion each week. Therefore, the average case requires only three to four weeks of active movement before the desired result is obtained. The extruded tooth must be stabilized to prevent relapse. This can easily be done by attaching the tooth to the archwire with composite resin mg. 14). It is not known what minimum retention period is required to found that the periodontal prevent relapse. Simon et alse ligament of extruded teeth in dogs returned to normal within 7 weeks of stabilization. However, Bielak et a159 reported relapse of one case after 7 weeks of retention. recommends one month of stabilization for each millimeter that the tooth was extruded. Guilford et alWrecommend a 3 to 6 month stabilization period. Levhesoand IngbeP' reported on several cases using 2 months stabilization without relapse. Kozlovsky et also recently proposed that a 4-week stabilization period may be sufficientfor teeth erupted in conjunction with weekly supracrestal flberotomy procedures. If periodontal surgery is to be performed, adequate healing must be allowed to occur before the gingival tissues are invaded by the restorative procedures. A minimum of 6 weeks healing time prior to restorative therapy is recommended.1a~96*98*61 One successful regimen includes a total stabilization period of 10 weeks h m the time that tooth movement is complete until the orthodontic appliance and attachments are removed and restorative procedures arebegun.If the periodontal flap procedure that allows replacement of the gingival margin (and osseous surgery if necessary)is performed after 4 weeks of stabilization,then 6 weeks of periodontalheallngwllloccurprior to the end of stabilizationand the start of restorative procedures.
ESTHETIC PROBLEMS Figure l2. An offset bend allows the archwire to pass directly overthecanalofthetoothtobeextrudedandpreventsunwanted buccal movement.
As previously stated, anothercljnicalsituationwhere periodontal tissues must be controlled in conjunction 203
Figure 15. B, A wide band of gingiva is present, and the proposed restorative margin will be at least 3 mm from the alveolar crest.
Figure 14. Composite resin is used to attach the tooth to the archwire during the stabillzation phase.
with restorative dentistry occurs when there is inadequate tooth structure available for esthetics (Fig. 15A). These patients often have short clinical crowns and a high lip line that exposes an excessive amount of gingival tissue when smiling. The result is a ‘gummy smile” that may be objectionable to the patient. In addition to cmwn lengthening. many of these patients r e q m crowns or veneer restorations to improve the esthetics of their smile. Before developing a treatment plan, the periodontal tissue relationships and the proposed restoration margin locations need to be determined. The classification system used to describe periodontal-restorativeinterrelationships in Table 1can be used to describe esthetic case management also.
Class 1 and 2 cases have adequate tooth structure and attached gingiva. The restorations have margins that are either supragingival (Class 1) or slightly
15. c.*ginglvectomW used to lengthen the teeth and h~rove the esthetic potential ofthe case.
ra A. -view of a patlent with teeth that to be too wide because of the& short Weal crowns.
Figure 15. D, Teeth No. 5-12 are prepared for porcelain laminate veneers after sufficient healing. The teeth have darkly banded tetracyclinestain.
204
Management of Periodontal Tissues for Restorative Dentistry
subgingival (Class 2). Retraction cord is usually the only soft tissue management required (Fig. 16). Class 3 cases have alveolar bone at least 3 mm apical to the proposed restoration margin. a wide band of attached tissue, clinical crowns that appear too short, and a n excessivedisplay of gingiva. Agingivectomy may be used to decrease or eliminate the amount of gingiva displayed when smiling and to lengthen the clinical crowns so that the esthetic restorations placed will be properly proportioned (see Fig. 15). Class 4 cases also have alveolar bone at least 3 mm apical to the proposed restoration, short clinicalcrowns, and an extreme display of gingiva. However, there is only a narrow band of attached gingiva, and a gingivectomyis contraindicated. An apically positioned flap may be used to expose additional tooth structure while p r e s e m g the entire width of attached tissue present (Fig. 17). Class 5 cases have alveolar bone that is near the proposed restoration margin. To create room for the biologic width and gingival sulcus, the surgical procedure must remove sufficient bone so that 3-4 mm of tooth structure apical to the proposed restoration margin is exposed. This requires an apically positioned flap with bone removal (Fig. 18).
Figure IS. E. Final result: note the improvement in tooth width-length proporttons made possibleby the crown lengthening
SUMMARY The health of periodontal tissues is often determined by the quality of the restorative procedures performed. Only through an understanding of periodontal tissue management can an uncompromised final result be achieved. A classification system of periodontal-restorative interrelationships when inadequate tooth structure is available for restorations and esthetics is described. Periodontal tissue management recommendations for each clinical situation are provided. The advantages of forced eruption techniques are included in the discussion of surgical treatment alternatives.
Figure 16. Retraction cord is placed prior to impression making.
The opinions expressed herein are those of the authorand do not necesar@ reflect the opinions of the DOD. the USAF, or of other federal agencies.The author above is responsible for the contents of this paper.
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Figure 17. A. Defective restoration No. 8 and endodontically NO.9. m e u t e r p m m m W tissue between Nos. 8 and 9 reaches almost to the indsal edge and makes closure of the diastema impossible.
JOURNAL OF ESTHETlC DENnSIRY VOLUME 3, NUMBER 6 Novemkr/Decemkr 1991
Flgaue 17. B. Four weeks after minimal repositioning of the tissue. The entire band of gingiva was preserved. but sumdent interproxfmal tissue was removed to allow for diastema closure.
Figure 18. B. Periodontal flap positioned apically and sutured inplace after removal of 1.5 to 2 mm of marginal alveolar bone.
Fi@m17. C. Final restorations: No. 8 was restored with an
Figure 18. C. Increased clinical crown length is evident after 4 weeks of healing.
M[FLcomposite resin restorationand No. 9 witha ceramo-metal
crown.
Ffomr, 18. D, Final resulk properly proportioned lamjnate veneers would not have been possible without crown lengthening-
18. A h k n t ~ 4 t short h cllnicalm; the alveolar aestwaswithtn 1 m m o f t h e w m m k m m d f u n c t l o n .
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Management of PeriodontalTissues for Restorative Dentistry
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JOURNAL OF ESTHETIC DENTISTRY VOLUME 3. NUMBER 6 November/December 1991
57. Ingber JS. Forced eruption: Part 1. A method of treating isolated one and two wall infrabony osseous defects -rationale and case report. J Periodontol 1974; 45: 199-206. 58. Simon JS. Lythgoe JB, Torabingard M. Clinical and histological evaluation of endodontically treated teeth in dogs. Oral SWg 1980; 50:361-371. 59. Bielak S, Bimstein E, Eiderman E. Forced eruption: the treatment of choice for subgingivally fractured permanent incisors. J Dent Child 1982: 49:18&190. 60. kvine RA. Forced eruption. Part 1. Periodontal and orthodontic considerations for the treatment of an isolated periodontal angular infrabony defect. Compend Contin Educ Gen Dent 1988; 9:lO-18. 61. Lubow RM, Cooley RL. Surgical retraction for subgingival class V restorations. Gen Dent 1985: 33:332-335.
51. Simon JHS. Root extrusion - rationale and techniques. Dent Clln North Am 1984; 28909-921. 52. Murchison DF, Schwartz RS.The use of removable appliances for forced eruption of teeth. Quintessence Int 1986: 17:497-5O 1. 53. Guilford HJ. Grubb TA, Pence DL. Vertical extrusion: a standardized technique. Compend Contin Educ Gen Dent 1984; 5562-567. 54. Simon J H . Kelly WH, Gordon DG. et al. Extrusion of endodonticallytreated teeth. JAmDentAssoc 1978;97:1723. 55. Lythgoe JR. Torabinejad M, Simon JHS. Extrusion techniques for the general dentist. Gen Dent 1980 28:4249. 56. Palomo F. Kopayk RA. Rationale and methods for crown lengthening. J Am Dent Assoc 1978: 96:257-260.
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Management of Periodontal Tissues for Restorative Dentistry Cliflord B . Starr, Lt Col, USAF, DC'
Proper management of periodontal tissues is required to achieve predictable long-term success with restorative dental procedures. Forced eruption as well as several surgical techniques may be used to achieve and maintain adequate biologic width during restorative and esthetic dental procedures. The technique that will yield optimal results depends on the relationshipbetween the restoration's margins and the surrounding periodontium. A classiflcation system that describes these interrelationships and provides treatment recommendations is included.
0
ne of the primary goals of restorative dentistry is to replace form, function,and esthetics lost due to trauma or disease. An equally important goal is to do no harm when placing these restorations. The improper control or management of the periodontium during restorative procedures is a common cause of failure that is often overlooked. According to Maynard and Wilson,' "The preservation of a healthy periodontal attachment is the most significantfactor in the long-term prognosis of a restored tooth." The fact that restorations with overhanging margins, open margins, improper interproximalcontacts, poor contours, inadequate embrasures, plunger cusps, and uneven marginal ridges can trap bacterial plaque and cause gingival inflammation and loss of alveolar bone is well documented."' Predictable long-term restorative success therefore requires a blending of restorative principles with those concerningthe management of supporting periodontal tissues so that iatrogenic defects will not compromise the final result. If the tissues are not healthy, then periodontal disease must Arst be adequately controlled before Mtiating surgical and/or definitiverestorative procedures. For patients with healthy periodontal tissues, there are two separate clinical situations that require periodontal tissue management. The first occurs when the zone of biologic width is inadequate. This can be caused by h c t u r e lines or other lesions, such as caries. internal or external resorption, or pin/post perforations, that involve the extemal tooth surface subghgbdly within 3-4 mm of the alveolar crest.?. '-I8 A second clinical situation that requiresperiodontalmanagement occurs when there isinadequate clinical crown length available
to obtain the esthetic results required.IgThfssituation usually occurs in patients with a high lip line, and the result is an excessive gingival display. In both of these clinical situations, the appropriate periodontal and restorative treatment must be accomplished if a successful result is to be obtained.
BIOLOGIC WIDTH
The concept of a minimumdimension of tissue from the alveolar crest to the bottom of the gingival sulcus is based on the study by Garguilo et They examined 30 cadavers and found that the average dimension of connective tissue fibers was 1.07 mm and that the average dimension of junctional epithelium was 0.97 mm (Fig. 1).The total of these two tissues averaged 2.04 mm. Cohenzl is credited with originating the widely used term 'biologic width', although Ingber et a18 and have also received redi it.?^.?^ Nevins and Skur0w2~ Maynard and Wilson1 further describe the inviolate nature of this tissue, which they term the 'physiologic dimension.' They describe the destruction of periodontal tissues that occurs if restorations and/or defects inMnge upon this area. Currently there is no evidence that, in the absence of jnflammation, restorations that violate the biologic width will cause periodontal breakdown. However, there is ample proof that in the presence of inflammation tooth preparations and/or restorations that impinge on the biologicwidth trap bacterial plaque, induce inflammation, and increase both the likelihood and severity of periodontal b r e a k d o ~ n ~ - ~ - ~ ~ - ~ wig. 2). Universal agreement does not exist regarding the minimum amount of sound tooth structure coronal to the alveolar crest that is necessary to ensure periodontal health. Ramqordz3feelsthat no minimum distance is required as long as inflammationis adequately controlled. Wagenberg et als recommends that margins be
Chatrmaa Departmmt of General Dentbfq and Assistant Director, Residency. U W Medical Center/SGD. WrIght-Patterson
General Dentishy
AFB.Ohio Address reprint requeststo. Clifford Starr. D.M.D.. 4.062 QuatlBush Dr.. Dayton. OH 45424
195
JOURNAL OF ESTHETIC DENlISTRY VOLUME 3.NUMBER 6 November/December 1991
treatment used to exposeadequate tooth structure. 1 4 3 35 Several different techniques are available depending upon the proposed location of the restoration margin, the location of the alveolar crest and gingival margin, the width ofattached keratinized tissue, and the amount of exposed tooth structure available. A classification system that describes these interrelationships and provides treatment recommendations is summarized in Table 1. Class 1 cases have all supragingival margins and no periodontal management is needed. Class 2 cases occur when the defect to be treated is apical to the gingival margin, the amount of attached gingiva is adequate, and the amount of sound tooth structure coronal to the alveolar crest is adequate. Access to the subgingival defect or margin for this common clinical situation may be managed in a variety of ways. Often a rubber dam alone or in combination with a rubber dam clamp may provide sufficient access. In other cases, a miniflap made with two vertical incisions at the line angles may be used to provide sufficient
Of the connective The b'ologlc width is tissue fibers and junctional epithelium. The figure on the left shows the ffssue relationships found with atered passive eruption.The figure on the rightshows the relationshipspresent after completion of crown lengthening.
Figure 3. A, Tooth No. 2 1 with a subgingival carlous lesionin an area of minimal keratintzed tissue. Hgare 2. Inflammaton of the periodontal tissues resulting froma restoraffon that implngesi on the biologic width.
placed no closer than 5.25 mm from the bone ifperiodontaI health is to be maintained. However, most authors recommend that when supragingival margins are not feasible, restoration margins should be placed at least 3-4 mm from the alveolar crest.14s15.2837 This addit.€od1-2 mm allow room for a healthy gin$val s d m s and the margin of the restoration.
SURGICAL TREATMENT APPROACHES For patients wHh healthy periodontal tissues, SUrgkd Crrmrm llengthentngIs the t r a d f t o d method of
FYguce 3. B,Mwflap incisions to faditate acce89. 196
Management of Periodontal Tissues for Restorative Dentistry
Tabte 1. Pwbdontal-Restoralive Interrelationships and Treatmenl Recommendations
Sound Gingival Bond
rooft,out of Bone
Lesion/ Restoration Location
Treatment Indicated
Class 1
Adequate
Adequate
Supragingival
None
Class 2
Adequate
Adequate
Subgingival
Rubber dam Rubber dam clamp Retraction cord Minlflap Envelope Flap
Class 3
Wide
Adequate
Subgingival
Gingivectomy
Class 4
Narrow
Adequate
Subgingival
Apically positioned flap without bone removal
Class 5
Either
Inadequate
Subgingival
Apically positioned flap with bone removal
Inadequate
Mucogingival surgery
access while minimizing trauma to the soft tissue3*(Fig. 3).Xhonga30 evaluated four different flap designs for access to subgingivallesions. She found that a miniflap made with two small incisions at the line angles of the tooth provided adequate access, produced the least postoperative inflammation, had the least postoperative recession, and did not require sutures or packing. Larger access flaps can be u s e l l if multiple adjacent teeth are i n ~ o l v e d . ~ ~ ~ Class 3 cases involve a wide band of attached gbgiva, adequate sound tooth structure coronal to the alveolar crest, but inadequate tooth structure coronalto the gingival margin. A gingivectomy may be used to expose sufficient tooth structure for restorative denustry (Fig. 4). Class 4 cases are similar to class 3 cases, except that there is a minimal band of keratinized tissue. A full
Figure 3. C.Access to full extent of the lesion
Figure 4. A. Hyperplastic gingtva is impeding access to distobuccal carious lesion.
197
JOURNAL OF ESIHFnC DENTISTRY VOLUME 3,NUMBER 6 Novernber/December 1991
Figure 4. 8.After surgical removal of the excessive gtngival tissue. a rubber dam is used to control bleeding during the restoram procedure.
Figure 1. C, Control of caries and temporization after placement of rubber dam.
-8. A IntraaralviearofapatlQltwithmultiplemb@WJd carious lesions.
Figare 1. D, The periodontal flap is repositioned apically and sutured in place.
R B.Afull Wckncas flapisrdlectedtoprovide acmes to arks and gpoae aound tooth s t r u m for resbratiw
lrlepe 1. E, Afta 2 weeks it can be seen that adequate tooth structure is available for the placement of restorative margins
on sound enamd. 198
Management of Periodontal Tissues for Restorative Dentistry
thickness flap may be used to expose additional tooth structure, and the flap can then be positioned apically and sutured in place. This preserves the entire band of keratinized tissue and prevents the development of a mucogingival defect (Fig. 5). Class 5 cases have insufficient tooth structure coronal to either the alveolar crest or the gingival margin. As long as there is at least a minimum band of gingival tissue present, an apically positioned full thickness flap with ostectomy and osteoplasly is the surgical procedure that should be used to obtain sufficient sound tooth structure for restorative dentistry (Fig. 6). The minimum amount of keratinized attached tissue that is required for the maintenance of periodontal health has not been determined. Maynard and Wilson' feel that there should be 5 mm of keratinized tissue, at least 3 mm ofwhich is attached. Others feel that in areas of health, no specific minimum amount of attached gingiva is needed and that mucogingival surgery should only be performed if problems such as progressive tissue loss are 0 ~ c u r r L n g . ~ ~ ~ ~
Figure 6. C. Two-weekhealingrevealsthe availabilityof sound tooth structure for margin placement.
The timing of the treatment is also important. Most surgical procedures should be performed before the restorative phase is begun so that adequate tissue ~* achealing and maturation can O C C U ~ . ' * ~ .However, cess to the defect can sometimes best be obtained during the surgical procedure, when the flaps are reflected and complete access to the remaining tooth structure is available (Figs. 7 and 8).29-33
FORCED ERUPTION
Flgum 6. A, L m g d view of tooth No. 30 with insufilciemt crown length for restoratrve dentistry.
6.
B, No. 30 after ostectomy and osteophty.
Forced eruption is another treatment technique that exposes inaccessible tooth structure and provides access to subglngival lesions that may extend apical to the alveolar crest. This orthodontic approach was first in 1973,who utilized it to described by Heither~ay3~ gain access to transverse root fractures below the alveolar crest. Since that time forced eruption has been used to gain access to endodontic, restorative, and prosthodontic perforations, internal/extemd resorption
Flgum 6. D, Final restoration.
JOURNAL OF ESTHETlC DENTISTRY VOLUME 3.NUMBER 6 November/December 1991
Figam 7. A. Tooth No. 14 with lingual cusps fractured to the aiveolar crest. Surgical crown lengthening has already been performed and the results are inadequate.
7.
B.
flW provides access forlingualmargins.
eigara 7. D. The flap is replaced after completion of the restorative procedure.
Flgura 8. A, Palatal view of tooth No. 3 with defective MODFL amalgam restoration. palatal margins are subgingival and inaccessible.
Management of Periodontal Tissues for Restorative Dentistry
Table 2. Advantages d Forced Eruption versus Surgical Crown Lengthening improved crown-root ratio No increase in clinical crown length Improved esthetics of the final restoration possible Supportingbone of adjacent teeth not sacrificed Surgical treatment phase may be reduced or eliminated.
is performed during the extrusion process, the gingiva
Figure 8. D, Two-weekhealing response.
should not erupt with the tooth, and the need for periodontal surgery may be e l i m i ~ ~ a t e d . ~ ~ . ~ There are several advantages that forced eruption provides relative to surgical crown lengthening that may be sigmficant in certain clinical situations (Table 2).In the maxillary anterior segment, where esthetics is of paramount importance, the opportunity to obtain an esthetically superior restoration makes forced eruption the treatment of choice. Teeth treated with surgical crown lengthening exhibit increased clinical crown .~~ an improved length that is often ~ n e s t h e t i cHowever, esthetic result is possible with forced eruption, since the crown length of the final restoration is the Same as the original crown length (Fig. 9). While enhanced esthetics is important, the other advantagesof forced eruption should not be overlooked. The final crown-root ratio of the extruded tooth is superior to that obtained with surgical crown lengthening (see Fig. 9). If full thickness flap surgery is used to return the gingiva to its original location, little or no supportingbone needs to be removed from the extruded tooth or the adjacent teeth, and the crown-rootratio for all three teeth is therefore improved. Alternatively, if a supramstal fibemtomy is performed during the extrusion phase, the need for periodontal surgery may be reduced or eliminated.
defects, subgingival caries, and crown and root fi-acWes. 15.24,26.27.40-48 Light orthodontic forces can be used to generate slow tooth movement. The tension transmitted to the alveolar bone is thought to stimulate the deposition of new bone, which has proved to be useful in the ellmination or reduction of periodontal d e f e ~ t s . ~Moderate ~*~' orthodontic forces of 25 to 30 g generate faster tooth movement that allows for tooth extrusion without the accompaniment of alveolar bone.ms"4***50 In c h i & situations where there is insumdent tooth structure coronal to the alveolar crest. either forced eruption or surgical crown lengthening with ostectomy/osteoplasty can be used to expose additional tooth structure. The traditional forced eruption technique causes the gingival tissues to erupt with the tooth and a mir~orperiodontal Procedure is necessary to return the gingtval margin to its proper location.43However.ifagingivdsupracrestalfiberotomy
Figure 9. Crown length comparisonafter forced eruption and surgfcal crown lengthening. Note the improved esthetics and crown-root ratio O b m e d with forced eruption.
Figure 8. C. The flap is sutured in place aftercompletion of the restoration.
JOL‘RVAL OF ESTHETIC DENTlSTRY VOLUME 3.NUMBER 6 November/December 1991
advantages. The direct bonding of the archwire to the tooth makes it easier to ensure that the archwire is passively attached to the abutment teeth. The probabilThere are many techniques available using flxed or ity of undesirable tooth movement is therefore deremovable a p p l i a n c e s . ’ S ~ 2 4 ~ 2 7 . 3 9 ~ 4The 0 ~ 4most 2 ~ ~ ~ 7 ~ 5creased. ~ The case may also become less expensive to common approach uses bands or direct bonded bracktreat, The use of relatively expensive bands and brackets on the abutment teeth. A round or rectangular ets is eliminated. Therefore it is not necessary to mainsegmental archwire is then ligated to the brackets. tain an expensive inventory of bands and brackets to At Various loop designs and elastomeric materials have each tooth. Also, less chairside time is required, since been used to apply the extrusive force to the tooth. This precise bonding of brackets and complex wire bends technique requires the ability to bend a segmental needed to fit the wire passively into the brackets are archwire that will be completely passive when seated eliminated. into the brackets on the abutment teeth. If any deflecSeveraldifferent attachments may be applied to the tion of the archwire occurs when it is seated into the tooth to be extruded (Fig. 11). If the clinical crown or a brackets, active forces will be placed on the abutment temporary crown is present, then an orthodontic button teeth and unintended tooth movement may occur. or threaded pin can be attached. Another option is to An alternative technique that decreases the possifabricate a custom hook made from .018 orthodontic bility of undesirable abutment tooth movement uses a round wire that is bonded directly to the crown. If the rectangular -018x .025 segmental archwire bonded tooth has been endodontically treated and there is no directly to the abutment teeth (Fig. 10).Care must still clinical crown available, a hook made from orthodontic be used to ensure that the wire is bonded passively in round wire may be cemented into the canal with tempoplace. However, the use of this technique offers several
FORCED ERUPTION TECHNIQUES
F@m 10. Bonded directly to the abutment teeth is the . O M
Figure 11. B, An orthodontic button bonded directly to the
x .025 al-hvke.
tooth.
11. AAthreadcdpinplacedintoatempo+arycrown
pioruS11. CUseofacustornhookmadefrom.018roundwire.
202
Management of Periodontal Tissues for Restorative Dentistry
Figure 11. D, A hook made from orthodontic round wire temporarily cemented into the root canal.
Figure 13. Extrusion complete: compare with Figure 11D.
rary cement. The segmental archwire that is bonded to the abutment teeth must have an offset bend so that the wire passes directly over the canal of the tooth to be extruded (Fig. l2LZ7Otherwise, undesirable buccal or lingual tooth movement will occur as the root erupts. With either treatment approach. it is important to ensure that the distance between the bottom of the segmental archwire to the top of the attachment on the tooth to be extruded equals the desired extrusion distance (e.g.. 3 mm) (seeFig. 11D). If the attachment and segmental archwire are properly designed and applied, the desired extrusionwill have been obtained when the attachment touches the segmental wlre (Fig. 13). The extrusion force can be applied by tying elastomericthread, chain, ortubing around the archwire and the attachment. If .025 tubing is used, the recommended 25-30 g of force can be easily obtained. The appliance should be reactivated weekly. Extrusion rates reported in the literature vary from 0.2 to 2 mm per
~ e e k . ~ Cases ~ . ~using ~ . ~.025" ~ . tubing ~ ~ usually exhibit approximately 1 mm of extrusion each week. Therefore, the average case requires only three to four weeks of active movement before the desired result is obtained. The extruded tooth must be stabilized to prevent relapse. This can easily be done by attaching the tooth to the archwire with composite resin mg. 14). It is not known what minimum retention period is required to found that the periodontal prevent relapse. Simon et alse ligament of extruded teeth in dogs returned to normal within 7 weeks of stabilization. However, Bielak et a159 reported relapse of one case after 7 weeks of retention. recommends one month of stabilization for each millimeter that the tooth was extruded. Guilford et alWrecommend a 3 to 6 month stabilization period. Levhesoand IngbeP' reported on several cases using 2 months stabilization without relapse. Kozlovsky et also recently proposed that a 4-week stabilization period may be sufficientfor teeth erupted in conjunction with weekly supracrestal flberotomy procedures. If periodontal surgery is to be performed, adequate healing must be allowed to occur before the gingival tissues are invaded by the restorative procedures. A minimum of 6 weeks healing time prior to restorative therapy is recommended.1a~96*98*61 One successful regimen includes a total stabilization period of 10 weeks h m the time that tooth movement is complete until the orthodontic appliance and attachments are removed and restorative procedures arebegun.If the periodontal flap procedure that allows replacement of the gingival margin (and osseous surgery if necessary)is performed after 4 weeks of stabilization,then 6 weeks of periodontalheallngwllloccurprior to the end of stabilizationand the start of restorative procedures.
ESTHETIC PROBLEMS Figure l2. An offset bend allows the archwire to pass directly overthecanalofthetoothtobeextrudedandpreventsunwanted buccal movement.
As previously stated, anothercljnicalsituationwhere periodontal tissues must be controlled in conjunction 203
Figure 15. B, A wide band of gingiva is present, and the proposed restorative margin will be at least 3 mm from the alveolar crest.
Figure 14. Composite resin is used to attach the tooth to the archwire during the stabillzation phase.
with restorative dentistry occurs when there is inadequate tooth structure available for esthetics (Fig. 15A). These patients often have short clinical crowns and a high lip line that exposes an excessive amount of gingival tissue when smiling. The result is a ‘gummy smile” that may be objectionable to the patient. In addition to cmwn lengthening. many of these patients r e q m crowns or veneer restorations to improve the esthetics of their smile. Before developing a treatment plan, the periodontal tissue relationships and the proposed restoration margin locations need to be determined. The classification system used to describe periodontal-restorativeinterrelationships in Table 1can be used to describe esthetic case management also.
Class 1 and 2 cases have adequate tooth structure and attached gingiva. The restorations have margins that are either supragingival (Class 1) or slightly
15. c.*ginglvectomW used to lengthen the teeth and h~rove the esthetic potential ofthe case.
ra A. -view of a patlent with teeth that to be too wide because of the& short Weal crowns.
Figure 15. D, Teeth No. 5-12 are prepared for porcelain laminate veneers after sufficient healing. The teeth have darkly banded tetracyclinestain.
204
Management of Periodontal Tissues for Restorative Dentistry
subgingival (Class 2). Retraction cord is usually the only soft tissue management required (Fig. 16). Class 3 cases have alveolar bone at least 3 mm apical to the proposed restoration margin. a wide band of attached tissue, clinical crowns that appear too short, and a n excessivedisplay of gingiva. Agingivectomy may be used to decrease or eliminate the amount of gingiva displayed when smiling and to lengthen the clinical crowns so that the esthetic restorations placed will be properly proportioned (see Fig. 15). Class 4 cases also have alveolar bone at least 3 mm apical to the proposed restoration, short clinicalcrowns, and an extreme display of gingiva. However, there is only a narrow band of attached gingiva, and a gingivectomyis contraindicated. An apically positioned flap may be used to expose additional tooth structure while p r e s e m g the entire width of attached tissue present (Fig. 17). Class 5 cases have alveolar bone that is near the proposed restoration margin. To create room for the biologic width and gingival sulcus, the surgical procedure must remove sufficient bone so that 3-4 mm of tooth structure apical to the proposed restoration margin is exposed. This requires an apically positioned flap with bone removal (Fig. 18).
Figure IS. E. Final result: note the improvement in tooth width-length proporttons made possibleby the crown lengthening
SUMMARY The health of periodontal tissues is often determined by the quality of the restorative procedures performed. Only through an understanding of periodontal tissue management can an uncompromised final result be achieved. A classification system of periodontal-restorative interrelationships when inadequate tooth structure is available for restorations and esthetics is described. Periodontal tissue management recommendations for each clinical situation are provided. The advantages of forced eruption techniques are included in the discussion of surgical treatment alternatives.
Figure 16. Retraction cord is placed prior to impression making.
The opinions expressed herein are those of the authorand do not necesar@ reflect the opinions of the DOD. the USAF, or of other federal agencies.The author above is responsible for the contents of this paper.
REFERENCES 1. Maynard JG. Wilson RDK Physiologic dimensions of the pericdontium s i g d k a n t to the restorative dentist. J Periodontol1979: *17&174. 2. LangNp.KidRA,hd~~hldenK CWcalandm.tdiOl@cal &ecta of Subginghral restorationswith overhangingor [email protected]; 10563578. 3. BJomAL, B j w H.GrkcwiC Bfit Ofrestora~Om and its relation to periodontal bonelevelI: Metal fiIlings. Odontologisk Revy 1969 20:311-321.
205
Figure 17. A. Defective restoration No. 8 and endodontically NO.9. m e u t e r p m m m W tissue between Nos. 8 and 9 reaches almost to the indsal edge and makes closure of the diastema impossible.
JOURNAL OF ESTHETlC DENnSIRY VOLUME 3, NUMBER 6 Novemkr/Decemkr 1991
Flgaue 17. B. Four weeks after minimal repositioning of the tissue. The entire band of gingiva was preserved. but sumdent interproxfmal tissue was removed to allow for diastema closure.
Figure 18. B. Periodontal flap positioned apically and sutured inplace after removal of 1.5 to 2 mm of marginal alveolar bone.
Fi@m17. C. Final restorations: No. 8 was restored with an
Figure 18. C. Increased clinical crown length is evident after 4 weeks of healing.
M[FLcomposite resin restorationand No. 9 witha ceramo-metal
crown.
Ffomr, 18. D, Final resulk properly proportioned lamjnate veneers would not have been possible without crown lengthening-
18. A h k n t ~ 4 t short h cllnicalm; the alveolar aestwaswithtn 1 m m o f t h e w m m k m m d f u n c t l o n .
206
Management of PeriodontalTissues for Restorative Dentistry
4. Jeffcoat M, Howell T. Alveolar bone destruction due to overhanging amalgamsin periodontal disease.J Periodontol 1980:51:599-602. 5. Sachs RI.Restorative dentistry and the periodontium. Dent C h North Am 1985: 29261-278. 6. Gilmore N. Sheiham A. Overhanging dental restorations and periodontal disease. J Periodontol 1971;42:8-12. 7. Eid M. Relationshipbetween overhangingamalgam restorations and periodontal disease. Quintessence lnt 1987; 18:775-781. 8. Ingber JS. Rose LF. Coslet JG. The 'biologic width': a concept in periodontics and restorative dentistry. Alpha Omegan 1977: 10:62-65. 9. Fugazzotto PA. Periodontal restorative interrelationships: the isolated restoration. J Am Dent Assoc 1985;110:915917. 10. Silness J. Periodontal conditions in patients treated with dental bridges. I, 11, and 111. J Periodont Res 1970:5:60-68, 219-224,225229. 11. Renggli HH, Regolati B. Gingival inflammation and plaque accumulationby well adapted supragingival and subgingival proximal restorations. Helv OdontolActa 1972:1699-101. 12. Newcomb GM. The relationship between the location of subgingival crown margins and gingival inflammation. J Periodontol 1974: 45151-154. 13. Stetler KJ, Bissada NF. Significance of the width of keratinized gingiva on the periodontal status of teeth with submarginalrestorations.J Periodontol1987:58:69&700. 14. Meister F Jr. Gerstein H. Sigarmudi K, et al. Periodontal considerations in clinical crown lengthening procedures. Gen Dent 1981;29401405. 15. Shiloah J. Clinical crown lengthening by vertical root movement. J Prosthet Dent 1981;45602-605. 16. Stem N, Becber A. Forced eruption: biologic and clinical considerations.J Oral Rehabil1980; 7:395-402. 17. Potashnick SR Rosenberg ES.Forced eruption: principles in periodontics and restorative dentistry. J Prosthet Dent 1982;48:141-148. 18. Parma-BenfenatiS,FugazzottoPA, Ruben MP. The effect of restorative m a r e on the postsurgical development and nature of the periodontium. Part I. Int J Periodont Restor Dent 1985:5:31-51. 19. Kohlavi D. Stem N. Crown lengthening procedure. part I. Clinical aspects. Compend contin Educ Gen Dent 1983: 4347-354. 20. Garguilo AW, Wentz FM, Orban B. Dimensions and relationsofthedentoginghmljunctioninhumans. JPeriodontol 1961:32:261-267. 21. Cohen DW. Biologic width. (Lecture).Washington. DC. Walter Reed Army Medical Center, June 3.1962. 22. Nevfns M. Skurow HM. The intracawhdar restorative margin, the biologic width, and the maintenance of the gingivalmargin.IntJPerLod0ntRestorDent1984:4:3049. 23. w o r d SP. Periodontal considerations of operative dentistry. Oper Dent 1988:13:144-159. 24. Bales DJ. 'hurmond JW.Forced eruption in restorative dentistry. J IndianaDent Assoc 1980 59:19-22. 25. Wagenberg BD. Eskow RN. Ianger B. Exposing adequate tooth structure for restorative dentistry. Int J Periodont Restor Dent 1989 9323-331. 26. Levtne RA. Forced eruption. part 2 esthetic treatment of nonrestorable teeth. Compend Contin Educ Gen Dent 1988:9 1 s 1 4 0 . 27. Johnson GK.Sivers JE. Forced a p t i o n in crown-lengthenfngprocedures. J progthet Dent 1986: 563424427.
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