Periodontal considerations in restorative and implant therapy

Periodontology 2000, Vol. 25, 2001, 100–109 Copyright C Munksgaard 2001Printed in Denmark ¡ All rights reserved

PERIODONTOLOGY 2000ISSN 0906-6713

Periodontal considerations inrestorative and implant therapyPERRY V. GOLDBERG, FRANK L. HIGGINBOTTOM & THOMAS G. WILSON, JR.

Successful restorative dentistry can be best accom-plished when healthy and stable tissues surroundthe teeth or their implant replacements. This chapteraddresses the interactions between periodontaltissues and restorative procedures. Close attention toboth soft and hard tissues around teeth and im-plants before, during, and after restorative pro-

Fig. 1. A minimal band of keratinized gingiva was associ-ated with recession following placement of restorationsapproaching the free gingival margin.

Fig. 2. Two retraction cords have been placed to ensureadequate coverage of the margins by the impression ma-terial.

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cedures will greatly increase the probability of a suc-cessful outcome.

Mucogingival considerations

While the need for attached and keratinized gingivain maintaining health around the natural dentitionand dental implants can be debated, the importanceof these tissues adjacent to restorative margins isclear. Specifically, attached gingiva is needed to re-duce the probability of gingival recession in areas ofaesthetic margin placement, to facilitate im-pressions, and in some cases, to increase patientcomfort.

The margins of some restorations must be ex-tended slightly into the gingival sulcus. The exten-sion of any restorative margin into the gingival sul-cus should be considered a compromise (29–32), butaesthetic or retentive demands often make it necess-ary. Because margins in aesthetic areas must becamouflaged or concealed, any gingival recessionthat occurs following final placement of the restora-tion can compromise aesthetics (Fig. 1). To minimizethe probability of recession, the gingival tissuesshould be clinically healthy before beginning re-storative procedures. In addition, there should be an‘‘adequate’’ band of keratinized and attached gingiva(34). The important question then becomes what is‘‘adequate’’? While there is no universal answer,thicker tissues with 2 mm of keratinized gingiva and1 mm of attached gingiva have been found by theauthors to provide adequate protection against re-cession. This assumes that: 1) the health of thetissues is maintained, 2) restorative margins do notextend into the sulcus more than 0.5 mm, 3) atraum-atic retraction and impression procedures are used,and 4) the final restoration has optimal contours andmarginal fit (Fig. 2, 3).

The accuracy of subgingival impressions dependson exposure of tooth preparation margins. This is

Periodontal considerations in restorative and implant therapy

best achieved when the soft tissues can be gentlyand atraumatically retracted and allowed to reboundafter these procedures. An adequate band of kera-tinized and attached gingiva will increase the prob-ability of this tissue rebound.

Some patients with dental implants experiencegingival tenderness and food impaction where thereis inadequate attached gingiva. This problem can beeliminated by surgical gingival augmentation. Aug-mentation can take several forms and is beyond thescope of this chapter. The reader is referred to othersources for a discussion on this topic (35). Theauthors have found that subepithelial connectivetissue grafts in aesthetic areas satisfy functional andaesthetic demands more predictably than other pro-cedures.

Tooth/implant preparation –margin placement

As previously stated, subgingival margins should beconsidered a compromise (1, 18, 28, 22–25), andsupragingival margins are preferred (13, 19). Whereaesthetics are not a concern and adequate toothstructure exists, supragingival margins (for both thenatural dentition and dental implants) are rec-ommended (Fig. 4). In areas where inadequate toothstructure is present coronal to the soft tissues, crownlengthening (see Wang & Greenwell in this volume)or orthodontic extrusion can be used to increaseclinical crown length.

For both the natural teeth and dental implants,several principles should be taken into considerationwhen subgingival margin placement is necessary.First, the marginal fit should be optimal becauserough restorations or open margins lead to an ac-cumulation of bacterial pathogens that are associ-ated with inflammatory periodontal diseases (10).Second, the margins of restorations around naturalteeth should extend only slightly into the gingivalsulcus. This is to facilitates oral hygiene and avoidsencroachment on the ‘‘biological width’’ (see below).Third, materials used for the restoration should becompatible with the soft tissues and lend themselvesto the precise interface needed to minimize marginaldiscrepancies that encourage retention of bacterialplaque.

In areas of aesthetic concern, the connection ofthe implant and the prosthetic element is locatedbelow the soft tissue margin. To minimize the effectof the bacterial trap at this implant/restorative junc-tion, the clinician should consider selection of an

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Fig. 3. The impression from the case seen in Fig. 2.

Fig. 4. The margin of this restoration is located just co-ronal to the free gingival margin. This allows the patientto clean the interface where there are no aesthetic con-cerns.

implant system that: 1) has this interface coronal tothe facial and lingual bone, 2) provides the closestpossible implant/abutment interface, and 3) allowsscrew-retained restorations (as opposed to ce-mented) (9) (Fig. 5, 6). Although more techniquesensitive in achieving passively fitting prostheses,screw-retained restorations that use machined com-ponents result in smaller implant/restorative discre-pancies, and therefore, minimize accumulation ofsubgingival bacterial plaque.

Crown lengthening andbiological width

Crown lengthening or the increasing exposure of co-ronal tooth structure is a valuable adjunctive pro-cedure in restorative dentistry that may be indicatedfor a number of reasons. The first of these is where

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Fig. 7. The biological width is the di-Fig. 6. Transverse section of cement-mension of the soft tissue from the al-retained specimen of an ITI implantFig. 5. Transverse section of a screw-veolar bone to the apical extent of the(in vitro) (original ¿40). Courtesy ofretained specimen of an ITI implant.junctional epithelium. In the averageScott E. Keith.Compare the space between the im-patient, this 2- to 3-mm distance re-plant and the crown with that seen inmains constant in health and disease.Fig. 4 in which the crown is cementedEncroachment on the biological width(in vitro) (original ¿40). Courtesy ofby restorations often leads to a seriesScott E. Keith.of events that result in the formationof periodontal pockets.

previous restorations, caries, fractures, etc. haveencroached on the biological width. The gingivaltissues must attach to the tooth coronal to the al-veolar bone and, in general, 2–3 mm of clean,healthy tooth surface is needed for this attachment.This gingival attachment is usually constant at all

Fig. 8. This patient was referred to expose caries that ex-tended close to the alveolar bone on the facial surface ofthe lateral incisor.

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levels of probing depth, and has been termed thebiological width (6) (Fig. 7). Encroachment on thebiological width by tooth preparation, caries, frac-ture, restorative materials or orthodontic devices canlead to bacterial accumulation, inflammation, in-creased probing depths, gingival recession or a com-bination of these problems. To avoid encroachmenton the biological width, the restorative dentistshould measure probing depths before preparing theteeth. In normal (2–3 mm), healthy sulci with ade-quate bands of gingiva, margins can be placed 0.5mm into the sulcus. In areas where there is insuf-ficient tooth structure to allow adequate soft tissueattachment, crown lengthening may be necessary.This can be accomplished surgically (4, 8) or by or-thodontic extrusion (Fig. 8–10). The surgical aspectsof this procedure are covered by Wang & Greenwellin this volume.

A second indication for crown lengthening is insituations when short clinical crowns must be re-stored. This may require exposure of additionaltooth structure for adequate retention of the fixedrestoration. Short clinical crowns can be due to ex-cessive coverage of the coronal portion of the tooth


Fig. 9. Radiograph of tooth in Fig. 6 showing sufficienttooth length to allow orthodontic extrusion of the lateralincisor

by the soft tissues or may be associated with pos-terior bite collapse or excessive parafunctional pat-terns (bruxism, etc.) that have resulted in a reducedtooth height. In either instance, apical positioning ofthe gingival margin is usually accompanied by oss-eous resection to ensure a stable tissue level afterhealing.

Endodontically treated teeth often require full-coverage restorations. Regardless of the type of corebuild-up or reinforcement, whether it be preformedor custom post, bonded or cemented, forces may beimparted to the tooth that predispose it to fracture.To avoid or minimize this potential problem, crownpreparations should extend apically beyond themargin of the core and engage approximately 2 to 3mm of sound tooth structure. If there is less than 2mm of sound clinical tooth beyond the post or core,then either surgical crown lengthening or orthodon-tic super-eruption is indicated so the requiredamount of tooth structure may be engaged by therestoration.

Crown lengthening may also be done for aestheticreasons. This may sometimes be associated with theso-called gummy smile or excessive display of gingi-val tissue (see Wang & Greenwell in this volume).Wear patterns, restorations that have been artificiallywidened to close diastemas or tissue levels that arein an abnormal coronal position may create a situ-ation in which teeth are disproportionately widerelative to their height. The ‘‘golden proportion’’ has

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been recommended as a guide for an aesthetictooth/restoration: the mesial-distal width of a toothis approximately 75% of its height (20). Even in anatural dentition where no restoration is planned,crown lengthening may be indicated to establish thisproportion. Where excessive suprabony gingivaltissue is present (more than 3 mm during soundingwith a periodontal probe following local anesthesia);gingivoplasty of up to 1.5 mm can be performed.Following normal tooth eruption, excessive gingivaltissues in aesthetic areas are uncommon. Reflectionof a full-thickness mucoperiosteal flap followed byjudicious bone removal and apically positioning ofthe flap is often required (Fig. 11–15).

Several months of healing are necessary to re-es-tablish a normal sulcular depth after crown-length-

Fig. 10. To preserve the aesthetics of the area, orthodonticextrusion was chosen over crown lengthening surgery.This moved the soft tissues coronally allowing an apicallypositioned flap (performed after this photograph wastaken) to move the tissues into a normal relation withtissues on the contiguous teeth.

Fig. 11. This patient had worn away her anterior dentitionthrough years of bruxing.

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Fig. 12. After placing provisional restorations, it was deter-mined that crown lengthening was needed to establishimproved aesthetics by increasing the length of the clin-ical crowns.

Fig. 13. A surgical template was constructed to guideplacement of the soft tissues.

ening procedures. It is, therefore, suggested that finaltooth preparation and restoration be delayed untiladequate time for healing has occurred. On average,this takes about 90 days (2). The use of provisionalrestorations that mimic the proposed shape of thefinal restorations allows the clinician to preview theresponse of the soft tissues to subgingival marginsand the contours of the restoration. It also providesan optimal environment for performing proceduressuch as surgical tissue modification prior to fabricat-ing the final restoration.

Crown contour and emergenceprofile

Crown contours are normally determined by toothanatomy, periodontal condition, margin placement,

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and access for oral hygiene. However, compromisesmust occasionally be made in the interest of aesthet-ics or to reduce food retention. Proper restorativecontours require adequate tooth reduction to allowproper thickness of restorative materials, whileallowing easy access for personal oral hygiene.

The emergence profile of a restoration is the shapeof the restoration in relation to the gingival tissues.The emergence profile of a restoration in aestheticareas has two aspects: subgingival form and supra-gingival form. The subgingival form should followthe contours of the cementoenamel junction andsupport the gingival tissues. Within limits, increasedthickness of interproximal subgingival contoursleads to increased papillary height, while increasedfacial contours lead to apical positioning of the gin-gival tissues.

Fig. 14. The area 3 months after periodontal surgery

Fig. 15. The final clinical appearance following an apicallypositioned flap. Bone removal was needed to establish anadequate biological width (compare with Fig. 11).


Tissue retraction for impressions:displacement versus resectiveprocedures

The extension of preparations below the free gingivalmargin and the use of elastic impression materialsnecessitate the exposure of gingival margins of prep-arations to allow for their accurate duplication (11).Gingival retraction may take one of two forms. Thefirst involves the displacement of the gingival tissues(such as retraction cords, copper bands, etc.). A two-cord technique is an effective way of providing gingi-val retraction. The initial tooth preparation is com-pleted to the level of the free gingival margin. A smalldiameter cord (lightly braided with minimal memoryand usually impregnated with a chemical agent) isgently placed slightly below gingival level circumfer-entially around the tooth. The preparation is thenrefined and, where dictated by aesthetics or the needfor additional retention, the margins of the prepara-tion are extended approximately 0.5 mm below thetissue level. A second and larger diameter cord isthen gently packed over the first cord to expose themargins. An impression can then be taken after re-moval of only the larger diameter cord. The use ofbands as a displacement technique, whether withimpression compound or elastic materials, is an ac-curate and effective method of gingival retraction.However, trimming and fitting of such bands mustbe done with great care because excessive pressureor extension of the band may sever or traumatize thegingival attachment and lead to irreversible gingivalrecession.

The second major method of gingival retractioninvolves the surgical removal of tissue to form atrough around the preparation, thereby exposing themargins for the impression material. This is mostcommonly accomplished with electrosurgery orlasers. While recognized as an effective method ofretraction, injudicious use of either of these instru-ments can cause excessive necrosis of the gingivaand, in extreme cases, the underlying bone. Elec-trosurgery works by concentrating an electrical cur-rent at the tip of the electrode, thus generatingenough heat to volatize the tissues. If care is nottaken to keep the electrode in constant motion andto allow recovery time between passes, irreversibledamage may occur (33). The same is true for the useof the laser for retraction. Therefore, tissue resectionhas the potential of reducing soft tissue height andcausing bone destruction. This may lead to exposureof margins or compromised aesthetics and resectiveprocedures should be avoided in areas where the

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gingival architecture is thin or over prominent teethsuch as in anterior segments of the mouth.

Prosthetic design

As is the case with natural teeth, implants functionbest and withstand occlusal forces optimally whenloaded in a vertical direction. This is especially truein the posterior regions of the mouth, where the po-tential forces are increased in relation to the proxim-ity of the temporomandibular joints and muscu-lature. For this reason, planning and placement ofimplants with proper angulation is critical. In pos-terior partially edentulous situations, where three ormore implants are placed, an attempt to keep im-plants from being in a straight line (that is, tripodiz-ation) is recommended for one style of implant (17).This establishes a more optimum foundation tobetter withstand subsequent loading for this particu-lar system.

In fully edentulous patients, an attempt should bemade to extend the implants over as large an arc aspossible. If possible, a straight-line arrangement ofimplants in the anterior region should be avoidedbecause it results in excessive and unfavorabletorque when loaded with prosthesis. Such a pros-thesis will transmit forces that may ultimately resultin loosening or breakage of implant components.The forces may even jeopardize osseointegration ofthe implants themselves. Proprioception is greateraround natural teeth than around implants. Conse-quently, whenever possible, in partially edentulouspatients, it is suggested that natural teeth be used toguide the occlusion. If natural canine guidance inexcursive movements cannot be achieved, groupfunction of splinted implants should be consideredin order to maximize support.

Cantilevers incorporated in restorations placed onnatural teeth, while often eliminating the need forremovable prostheses, are fraught with potentialproblems. As a result of pressure being placed on alargely unsupported restoration (the pontic), it is notuncommon to see complications such as fractures ofsolder joints or porcelain, cement washout andcaries of the adjacent retainers, breakdown of theperiodontium (in the presence of inflammation) orfracture of roots. Cantilevered implant restorationsare subjected to similar loads. Therefore, the de-cision to use cantilevered pontics with implantsshould be made only after a careful consideration offorces that are associated with their use. In general,in patients with a history of parafunctional habits,

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cantilevers in posterior segments should be usedsparingly and, if used, should be suspended onlyfrom multiple-splinted implant restorations. The oc-clusal contacts of cantilevers should be light and tominimize the chance of occlusal overload, canti-levered units can even be modified to consist of afacial aspect with little or no occlusal surface. As amatter of course, these restorations should be pro-tected with a physiological bite appliance.

The role of occlusion in periodontaldisease

Bacterial plaque is necessary for the initiating andsustaining marginal periodontal inflammation (12)and the clinical course of the periodontal diseasecan be influenced by risk factors such as genetic in-fluences, smoking, and diabetes. The location andcomposition of bacterial pathogens are importantlocal factors that can be affected by compliance withsuggested oral hygiene procedures and periodontalmaintenance. Some have downplayed the role of oc-clusion as a risk factor for patients with periodontitis(16), but the opposite view can also be supported.Pihlstrom et al. showed that teeth exhibiting move-ment in function (fremitus) have less bone supportthan teeth without fremitus, even when matched forcomparable levels of inflammation and clinicalattachment loss (15). Other work has related in-creased tooth mobility to increased loss of peri-odontal support (5). Still other studies have shown apositive relation between tooth movement and in-creased levels of interleukin-1 (7). Interleukin-1 is aninflammatory mediator that is found in higher levelsin inflamed than noninflamed gingiva.

The role of occlusion inimplant failure

Implants and the prostheses they support are vul-nerable to excessive forces. The design of an individ-ual implant may influence its long-term success.Overloading, often from occlusal forces, can result inloosening or breakage of implant components and,in extreme cases, of the implants themselves. How-ever, the judicious selection of appropriate implants,proper treatment planning, careful implant place-ment and prosthetic reconstruction can virtuallyeliminate breakage. The use of narrow implantsshould be restricted to areas of minimal loading(usually in anterior segments), and increased use of

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wide-bodied implants in posterior areas can helpavoid these problems.

The role of occlusion in the failure of implantswithout fracture is more controversial. Bone lossaround failing implants has been blamed on trau-matic forces of occlusion, improperly fitting restora-tions, bacterially induced inflammation, or a combi-nation of these factors (14). The use of more andlarger diameter implants, offset placement (17), orstructurally stronger implants with greater bone af-finity (3) have been suggested as possible ways toreduce the probability of implant failure from oc-clusal trauma.

Splinting teeth can increase patient comfort andimprove mastication. It can also be indicated in pa-tients with increasing tooth mobility (26). In mostcases with early to moderate tooth mobility, the de-cision to splint should be made following resolutionof inflammation, fabrication of occlusal guards, andocclusal adjustment. In some advanced cases, splint-ing may be needed early in treatment to improvefunction or enhance aesthetics or to allow place-ment of implants under provisional restorations.Splinting has not been shown to reduce tooth mo-bility once the splint is removed (21). Implants maybe splinted to provide additional stability to theprosthesis and increase support. Cross-arch stabil-ization has been suggested for immediately loadedfull arch implants (27). The relative contraindi-cations to splinting implants include reduced accessfor oral hygiene or possible aesthetic compromises.

Temporization

Temporization (Fig. 12, 16, 17) provides a templatefor tissue healing and a diagnostic tool for successfulrestorations. Fabrication of a fixed provisional res-toration, whether it be for a single unit restorationor full-mouth rehabilitation, and whether for naturalteeth or implants, is a critical phase of restorativedentistry. The provisional restoration serves as a di-agnostic tool and is essential in establishing a pre-cursor to the permanent restoration. By using pro-visional restorations, an evaluation of the proposedfinal restorations can be done in the early stages oftreatment. Corrections or alterations can then beperformed prior to making a commitment to the fi-nal restoration. The following are some of the func-tions of provisional restorations.

O They maintain space and protect the teeth whilea final restoration is being fabricated.


O They facilitate elimination of caries and faulty res-torations as well as facilitate healing and oral hy-giene.

O They provide improved access and visibility forperiodontal surgical procedures or implant place-ment.

O They serve as a trial method for re-establishingvertical dimension and occlusal schemes in casesof posterior bite collapse or tooth migration. Assuch, they allow the practitioner to evaluatewhether or not prosthetics alone will be sufficientor whether other treatment such as pre-prostheticsurgery, dental implants or orthodontics will beneeded to achieve the desired outcome.

O They can provide anchorage for orthodontic toothmovement.

O They may be used to stabilize mobile teeth andto evaluate the periodontal and pulpal status ofindividual teeth.

O They serve as a template to evaluate aestheticsand phonetics, as well as to assess the form andfunction of the final restoration.

O Provisional restorations provide patients with apreview of the end result. This can have tremen-dous psychological benefits and build patientconfidence in the dentist. It also helps patients tobecome more comfortable with plans for futuretreatment. This may be especially true for patientswho are new to a dental practice or for those whoare having complex treatment because the finalrestoration may be months or even sometimes,years away.

O In implant dentistry, the provisional restorationcan be used to facilitate and guide soft tissue heal-ing by establishing ideal contours.

O The provisional restoration can be utilized to fa-cilitate the transition from a tooth-supportedprosthesis to one that is implant-borne.

O Provisional restorations can be used to avoid re-movable appliances during the osseointegrationphase of implant placement, and thus eliminatepremature loading of the fixtures.

There are numerous methods of fabricating pro-visional restorations. They can be made by using di-rect intraoral procedures, by utilizing an impressionand a vacuum formed shell from the existing den-tition or by a diagnostic wax-up. Provisional restora-tions may also be prefabricated as a heat-processedshell in the laboratory prior to tooth preparation.The heat-processed provisional, whether for thesingle tooth or full arch, has the advantages of im-proved aesthetics and durability. When teeth with

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Fig. 16. Provisional restorations in place following initialstabilization of implants that replace the maxillary centralincisors

Fig. 17. Care was taken to provide supragingival and sub-gingival contours that would support and shape the gingi-val tissues seen around natural teeth.

questionable prognoses or excessive mobility arebeing maintained, or when a minimal number ofteeth are being utilized to support a provisional res-toration during osseointegration, the incorporationof metal reinforcement for extra strength is advis-able.

The importance of the temporization phase can-not be overemphasized. It provides both the dentistand the patient with a preview of the end result. Italso serves as a trial and error method of evaluationthat is often necessary to create a successful andlong lasting restoration. If a satisfactory provisionalrestoration cannot be fabricated, the practitionershould not expect the final restoration to magicallyeliminate any unresolved difficulties.

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Summary

The successful integration of periodontal and re-storative dentistry for both natural teeth and im-plants requires knowledge and application of bothmechanical and biological principles. In areas of aes-thetic concern, an adequate band of attached gin-giva can increase patient comfort, reduce the prob-ability of gingival recession following tooth prepara-tion and simplify restorative procedures. While somerestorative margins need to be placed at or belowthe margin of the free gingiva, this should be con-sidered to be a compromise, and margins should notbe placed more than 0.5 mm into a healthy gingivalsulcus. Approximately 2–3 mm of healthy, natural su-pra-alveolar tooth surface is needed for attachmentof the gingival tissues to the tooth. This dimensionis called the biological width. If adequate biologicalwidth does not exist, surgical or orthodontic pro-cedures to expose healthy tooth structure are rec-ommended before final restorations are placed. Re-traction of soft tissues for impressions is best accom-plished with mechanical methods rather than lasersor electosurgery because of the potentially harmfuleffects of these devices to the cementum, bone andsoft tissues surrounding the teeth. Implants functionbest and withstand occlusal forces optimally whenloaded in a vertical direction. Therefore, planningimplant placement is critical for success. Because ofincreased proprioception, it is suggested that naturalteeth be used to guide the occlusion in partiallyedentulous patients. Cantilevers should be used withcaution and with appropriate attention to occlusalforces. While occlusal trauma does not cause peri-odontal disease, it may contribute to bone lossaround teeth and implants. In the opinion of theauthors, provisional restorations are an integral partof dental and periodontal therapy. They can be usedto establish aesthetic and physiological contoursthat can be easily cleaned by patients and they canalso be used as a guide for any needed surgical tissuemodification.

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Periodontal considerations in restorative and implant therapy