Physiologie Dimensions of thePeriodontium Significant tothe Restorative Dentist*

byJ. Gary Maynard, Jr., d.d.s.|Richard Daniel K. Wilson, d.d.s4There are many components of successful restorativedentistry that require daily consideration by the thera-pist.1 The preservation of a healthy periodontal attach-ment is the most significant factor in the long-termprognosis of a restored tooth. In order to assist therestorative dentist in accomplishing the objective of a

healthy periodontium in the presence of restorative den-tistry, the authors have divided the dentogingival unitand its epithelial and connective tissue covering intothree separate components; these three components allblend together, and distinct lines of separation do notexist. However, if these components are considered dailyby the dentist, and an attempt is made to visualize themduring intracrevicular restorative procedures, the pre-dictability of successful restorative dentistry will bemarkedly improved.

These components have been termed the physiologicdimensions of the periodontium that are fundamental tosuccessful restorative dentistry.2 The word "physiologic"was chosen because it means "consistent with the normalfunctioning of an organism."3 Preservation of an intactdentogingival unit with the gingival margin slightly cor-

onal to the cementoenamel junction in a state of opti-mum health is consistent with the normal functioning ofa tooth. The physiologic dimensions of the periodontiumfor the successful maintenance of a healthy periodontiumhave been classified as follows: I. Superficial PhysiologicDimension, II. Crevicular Physiologic Dimension, III.Subcrevicular Physiologic Dimension (Fig. 1).

This classification serves as a guide and teaching aidto the practitioner. It encompasses previously recognizedlandmarks and structures of the periodontium and at-

tempts to organize them in a fashion that is meaningfulto the restorative dentist.

Intracrevicular Restorative Margins

Intracrevicular restorative margins are defined as

those placed into and confined within the gingival crev-

* Send reprint requests to: J. Gary Maynard, Jr., D.D.S., 4909Grove Ave., Richmond, Va. 23226.

t Clinical Professor, Department of Periodontics, Medical Collegeof Virginia, Virginia Commonwealth University, Richmond, Va.

X Clinical Professor and Director, Periodontal Prosthesis Depart-ment of Periodontics, Medical College of Virginia, Virginia Common-wealth University.

ice. The term is more limiting and descriptive than thephrase "subgingival margin". Subgingival margins oftenextend beyond the gingival crevice into the junctionalepithelium and connective tissue. This causes marginaland papillary gingivitis, which may progress to Perio-dontitis.4"6 Some of the reasons for intracrevicular place-ment of margins are as follows: removal of caries or

faulty restorations, development of adequate retention,prevention of root sensitivity, and satisfaction of theesthetic demands of the patient. The theory that dentalcaries can be prevented by extending the margin of therestoration into the gingival crevice has not been proven.

Superficial Physiologic Dimension

The choice of the word superficial was made becausethis dimension is obvious to the clinician when he ex-

amines the tooth and its surrounding tissue. The super-ficial physiologic dimension extends from the mucogin-gival junction to the gingival margin (Fig. 1). It iscomposed of the attached gingiva and the free gingiva.The keratinized epithelial covering and the underlyingdense connective tissue fibers of the attached gingivadissipate the tensional stress created by the frenulum andmuscle fibers and protect the mobile free gingival marginfrom tension.

If there is insufficient attached gingiva for intracrevi-cular restorative procedures, increasing this superficialphysiologic dimension by a surgical procedure should beconsidered before restorative treatment begins. If restor-ative procedures extend into a crevice and the externalcovering of that crevice is alveolar mucosa or an insuf-ficient amount of gingiva, the result may be apicalmigration of the marginal tissue, the attachment appa-ratus, or both (Figs. 2 and 3). If sufficient attachedgingiva is present, the soft tissue abuse may be reversibleor may not reach the level of clinical significance (Fig.4 and 5). An adequate band of keratinized tissue isfundamental to successful restorative dentistry if themargins of the restorations are extended under the freegingival margin.How Much Gingiva is Adequate for RestorativeProcedures?

If the clinician plans restorative procedures that willenter the gingival crevice, approximately 5 mm of kera-tinized tissue, composed of 2 mm of free gingiva and 3mm of attached gingiva, is necessary to meet the restor-ative objectives. Occasionally restorations may be placedsuccessfully with less, but success is far more predictablewith the above dimensions.

A second dimension of keratinized tissue to be evalu-ated is the thickness. As with all tissue, this varies frompatient to patient, and in the same patient from tooth totooth. The clinician should not take for granted thatsufficient tissue in the vertical dimension necessarilyindicates that the tissue is thick enough to tolerate intra-crevicular restorative procedures. If a periodontal probe

170

Volume 50Number 4 Physiologic Dimensions ofPeriodontium 171

ENAMEL**-

BOTTOMOF CREVICE*

JUNCTIONALEPITHELIUM-

CEMENTO-ENAMEL***-JUNCTION

CONNECTIVE*TISSUEFIBERS

PERIODONTALLIGAMENT**

CREVICULAREPITHELIUM

FREE tGINGIVAE

KERATINIZEDTISSUE

ATTACHEDGINGIVAE

* *MUCOGINGIVALJUNCTION

ALVEOLARPROCESS

Figure 1. Diagram illustrating the concept of the three physiologic dimensions of the periodontium which are significant to therestorative dentist. Superficial physiologic dimension, shaded medium grey. Crevicular physiologic dimension, shaded dark grey.Subcrevicular physiologic dimension, shaded light grey.

Figure 2. Mandibular right canine serving as a retainer for a

fixed prosthesis. The marginal tissue is inflamed and has movedapically from its prerestorative location.

can be seen through the free gingival margin, even

though the superficial aspect of that margin is clinicallydiagnosed as keratinized tissue, the ability of that kera-tinized tissue to support intracrevicular restorative pro-

FlGURE 3. The periodontal probe demonstrates reduced resist-ance to probing and indicates a depth that probes 6 mm. The endof the probe passes beyond the mucogingival junction.

cedures is doubtful. The surgical placement of a thickerand more substantial segment of keratinized tissueshould be considered.

172 Maynard, Wilson

Figure 4. Six maxillary anterior teeth to be restored withcomplete coronal coverage. A sufficient dimension of keratinizedtissue is present.

Figure 5. A 3-year postinsertion view of the teeth restored withporcelain fused to metal crowns with metal intracrevicular mar-

gins. The tissue appears clinically healthy.

Marginal Tissue RecessionWhen there is recession and the soft tissue margin is

alveolar mucosa, it is incorrect to call it "gingival reces-sion". At the time of examination, one cannot be certainwhether the tissue margin was alveolar mucosa when thetooth erupted or whether it had been gingiva (free) whichhad been lost through recession and is presently alveolarmucosa. "Marginal tissue recession" is a more accuratedescription of the process that has occurred.

If marginal tissue recession is present prior to begin-ning restorative procedures, the two-step technique pre-viously described7 should be considered. This includesfirst placing the free graft and, after healing, using asecond procedure to position the grafted marginal tissuecoronally as a pedicle graft. This sequence has a highrate of success, offers a more symmetrical and estheticalignment ofmarginal tissue, and creates an environmentmore capable of withstanding intracrevicular restorativeprocedures.

Crevicular Physiologic DimensionThe gingival crevice extends from the free gingival

margin to the junctional epithelium (Fig. I). Normallyit has depth that measures from 0 to 3 to 4 mm, and it islined with thin crevicular epithelium. In health this thin,

J. Periodontol.April, 1979

fragile epithelium is in contact with the surface of thetooth. These two parts of the crevice (the depth and itscircumference) have been termed the depth and breadthaspects of the crevicular physiologic dimension.

Depth of the crevice can be described as being eitherexcessive or adequate for restorative dentistry. Excessivecrevicular depth is characteristic of periodontal disease.Diagnosis of periodontal disease is made by "

. ..

in-spection, palpation, and probing. The periodontal pocketis pathognomonic of periodontal disease; it is present inno other disease."8 Successful long-term restorative den-tistry depends on a healthy periodontium around thetooth being restored; restorative procedures should notbe done in the presence of disease. Without adequate"inspection, palpation, and probing," periodontal diseasemay be overlooked, and a crown may be fabricated fora tooth with excessive crevicular depth.

To prepare a tooth for an intracrevicular margin, aminimum depth of 1.5 to 2 mm is suggested by theauthors if the margin is to be covered by the free gingiva.If crevice depth is less, the patient and the therapist mustbe content with supragingival margins (Fig. 6). Imme-diately following periodontal surgical procedures, therestorative dentist is often faced with a crevice less than1.5 mm deep. In an attempt to place casting marginsbeneath the gingiva, he "creates" a crevice during toothpreparation. This is done at the expense of an intactdentogingival unit, and there is permanent damage tothe junctional epithelium and underlying supra-alveolarconnective tissue fibers. The significance of this damageis explained in the discussion of the subcrevicular phys-iologic dimension.

Restorative procedures must be delayed until a new

gingival crevice develops after periodontal surgery. Thiswaiting period may be 6 weeks, but it is usually muchlonger. To proceed with the intracrevicular margin prep-aration before the development of a new gingival crevice

Figure 6. A 7-year, postinsertion view of a maxillary left four-unitfixedprosthesis with gold collars partially visible. Where thecrevicular depth is less than 1.5 mm, it becomes necessary toallow some of the collar of the crown to be visible.

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of adequate depth, will cause prolonged marginal inflam-mation and usually pocket formation.

The breadth or circumferential aspect of a crevice alsomust be understood. In health, the epithelial lining ofthe crevice is in direct contact with the tooth surface.There is no significant space separating this crevicularepithelial lining from the tooth surface. In restoring a

tooth with a full coverage restoration with intracrevicularmargins, care must be taken to avoid injury of thecrevicular epithelial lining. This injury may occur byquantitative and qualitative violation of the circumfer-ential aspect of the crevice.

Quantitative violation is defined as excessive materialbeing placed within the crevice. For example, the crownthat restores the tooth is larger than the natural tooththat was previously present. This chronically distendsthe crevicular lining and probably the junctional epithe-lium (Fig. 7). The crevicular lining usually has beeninjured during tooth preparation, impression taking, andplacement of a temporary restoration. When a crownthat is too large is cemented, there is permanent disten-tion and injury to the crevicular lining. The result ofovercrowded embrasure spaces is inflammation of mar-

ginal tissue. This is a common finding after placement ofsuch a restoration.9

The qualitative violation of the circumferential aspectof a crevice is defined as poor adaptation and roughnessof the margin of the restoration (Fig. 8). Such a violationresults in both mechanical irritation of the crevicularepithelium and a harbor for microbial flora. Clinicallythis is demonstrated by chronic inflammation of themarginal tissue and bleeding from the crevicular area,which with time will result in dissolution of the supra-

FlGURE 7. Restorative dentistry inserted 18 months prior to thetaking of this picture. A maxillary rightfour-unitfixedprosthesisis accompanied by a single crown on the maxillary right canine.There is no solder joint between the canine and the premolar.The inflammation and aberrant contour of the interdental tissueis a result of too much restorative material in the crevice on themesial of the premolar and the distal of the canine. This is a

quantitative violation of the crevicular physiologic dimension.

Physiologic Dimensions ofPeriodontium 173

Figure 8. Rough and ill-fitting intracrevicular crown margins.The inflamed and edematous marginal tissues are the result of a

qualitative violation of the crevicular physiologic dimension.

alveolar connective tissue fibers, apical proliferation ofthe junctional epithelium, and pocket formation.

subcrevicular physiologic dimensionThis dimension is defined as the distance from the

base of the gingival crevice to the alveolar crest andincludes the junctional epithelium and the supra-alveolarconnective tissue fibers (Fig. 1).

Gargiulo, Wentz and Orban10 described this dimen-sion. It varies in width because of variation in width ofthe supra-alveolar connective tissue fibers. The connec-

tive tissue component appears to remain constant

through the stage of passive eruption. These authorsfound the average measurement of the epithelial attach-ment to be 0.97 mm with a range of averages of 0.71 to1.35 mm. The connective tissue fiber attachment had an

average measurement of 1.07 mm with a range of aver-

ages of 1.06 to 1.08 mm.

Measurements of this subcrevicular physiologic di-mension may vary from tooth to tooth and from surfaceto surface on the same tooth. However, this dimensionis constant in one respect, that is, its presence on allteeth. Encroachment into this dimension is prevalentamong restorative dentists as they attempt to place a

margin "subgingivally" rather than intracrevicularly.Such violation severs the junctional epithelium and

the supra-alveolar connective tissue fibers. The subse-quent retraction procedures, impression technique, andplacement of a temporary restoration maintain the injuryto the periodontium. A progressive inflammatory processensues.

When the final restoration is placed into this previ-ously injured and inflamed area, continuation of theinflammatory process results. The dentist, in effect, has,inserted permanent calculus beyond the crevice. Inter-proximally, the result is usually loss of eresiai bone.Apical migration of the junctional epithelium occurs,and a periodontal pocket is soon present. Periodontaldisease has been created by restoration of the toothwithout proper consideration for subcrevicular physio-logic dimension.

OcclusionThe role of trauma from occlusion in Periodontitis

continues to be studied. Recent investigations11'12 appear

174 Maynard, Wilson1. Periodontol.

Aprii. 1979

to support the contention that, in a healthy periodontiumand in the absence of inflammation, repeated occlusaltrauma will not increase depth that can be measuredwith a probe. Poison11 comments that although the "sub-crestal periodontal tissues" undergo "resorptive, repara-tion and adaptive reactions" to occlusal trauma, there isno evidence that trauma from occlusion will produceperiodontal pocketing.

In the healthy periodontium, occlusal trauma can

render teeth mobile. As long as the crevicular and sub-crevicular physiologic dimensions remain unaffected byinflammation, this mobility is reversible if the source ofthe trauma is removed. Violation of the crevicular orsubcrevicular physiologic dimension by restorative den-tistry will cause inflammation which, in the presence ofocclusal trauma, will result in more rapid periodontaldestruction. Preservation of an intact crevicular andsubcrevicular physiologic dimension by the restorativedentist will allow traumatic occlusal forces to be cor-rected without permanent damage to the periodontium.

ConclusionWhen treating patients, the objectives of restorative

therapy must be clear. The first and most basic objectiveis preservation of the teeth. The attainment of this objec-tive would be far less complex if it could be consideredindependent of restoration of function, comfort and es-

thetics, but such is not the case. The latter objectivesusually require sophisticated restorative dentistry andoften include restorations with intracrevicular margins.Although it is widely accepted that the best restorativemargin is one that is placed coronal to marginal tissue,most restorations have margins in the gingival crevice,and permanent tissue damage is common. In attempting

to reach his objective, the restorative dentist must re-member the fundamental precept of the health profes-sions, which is: Do no harm. Daily observation of thethree physiologic dimensions permits the therapist torestore teeth with minimal injury to the periodontium.

References1. Amsterdam, M.: Periodontal prosthesis—twenty-five

years in retrospect. Alpha Omegan 13, December 1974.2. Prichard, J. F.: The diagnosis and treatment of perio-

dontal disease. Wilson, R. D., and Maynard, J. G., Jr. (eds),General Dental Practice, Chapter 19, to be published. Philadel-phia, W. B. Saunders Co., 1978.

3. Stein, J. (ed) 77¡e Random House Dictionary of theEnglish Language, p. 1087. New York, Random House, 1967.

4. Silness, J.: Periodontal conditions in patients treatedwith dental bridges I, II and III. J Periodont Res 5: 60, 219, and225, 1970.

5. Renggli, H. H., and Regolati, .: Gingival inflammationand plaque accumulation by well-adapted supra-gingival andsub-gingival proximal restorations. Acta Odontol Oct. 1972.

6. Newcomb, G. M.: The relationship between the locationof subgingival crown margins and gingival inflammation. /Periodontol 45: 3, 1974.

7. Maynard, J. G, Jr.: Coronal positioning of a previouslyplaced autogenous gingival graft. J Periodontol 48: 3, 1977.

8. Prichard, J. F.: Advanced Periodontal Disease, Surgicaland Prosthetic Management, 2nd ed., p. 132. Philadelphia, W.B. Saunders Co., 1972.

9. Skurow, H. M., and Lytle, J. D.: The interproximalembrasure. Dent Clin North Am 15: 641, 1971.

10. Gargiulo, A. W., Wentz, F. M., and Orban, B.: Dimen-sions and relations of the dentogingival junction in humans. JPeriodontol 32: 261, 1961.

11. Poison, A. M., Meitner, S. W., and Zander, . .:Trauma and progression of marginal Periodontitis in squirrelmonkeys. J Periodont Res 11: 279, 1976.

12. Lindhe, J., and Svanberg, G: Influence of trauma fromocclusion in progression of experimental Periodontitis in thebeagle dog. J Clin Periodont 1: 3, 1974.

AnnouncementsPOSTGRADUATE DENTAL PROGRAM

ALBERT EINSTEIN COLLEGE OF MEDICINEPostgraduate Extension Program (Off Campus Courses): Faculty

members of the Postgraduate Dental Program, who are specialists intheir fields, are available for short, intensive courses that can begiven in various cities if a sufficient number of practitioners evinceinterest. If clinical facilities are available, these courses can be acombination of lectures and demonstrations.For further information and application, write to: Dr. Irving Yud-

koff, Director, Postgraduate Dental Program, Albert Einstein Collegeof Medicine, 1165 Morris Park Ave., Bronx, New York 10461.

GEORGETOWN UNIVERSITY SCHOOL OF DENTISTRY

Academic Opportunity. District of Columbia—Georgetown Univer-

sity School of Dentistry is inviting applications for a full-time facultyposition in Periodontics at the level of assistant professor, effectiveAugust 1979. The appointment is available for participation in clinicaland didactic instruction for undergraduate students and for research.Time will be allowed for clinical practice. Graduation from an ac-

credited post doctoral degree or certification program in Periodonticsis required and training and/or experience in teaching is preferred.Interested individuals should send their curriculum vitae to Peter D.Ferrigno, D.D.S., M.S., Chairman, Department of Periodontics andEndodontics, Georgetown University School of Dentistry, 4000 Res-ervoir Rd. NW, Washington, DC 20007.

Georgetown University is an equal opportunity, affirmative actionemployer.