Biological Integration of Aesthetic Restorations Factors In

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Periodontology 2000, Vol. 27, 2001, 2944 Copyright C Munksgaard 2001Printed in Denmark All rights reserved

PERIODONTOLOGY 2000ISSN 0906-6713

Biological integration of aestheticrestorations: factors influencing

appearance and long-termsuccessSTEFANO GRACIS, MAURO FRADEANI, RENATO CELLETTI& GUIDO BRACCHETTI

In the past few years, different authors have madeefforts to improve both techniques and materials tomeet the ever-increasing aesthetic requirements ofour patients. However, too often, the emphasis isplaced on these factors as the only keys to success.It is instead the integration of a natural-looking pros-thesis within a healthy periodontium that shouldrepresent the ultimate goal of every component ofthe dental team: general practitioner, periodontist,hygienist, dental technician and prosthodontist. Thischapter summarizes the current knowledge of pros-thetic materials and clinical procedures that play arole in any clinicians attempt to create biologicallyacceptable and aesthetically pleasing long-lastingrestorations.

Restorative margin location andimplications for soft tissuestability

Preservation of sound tooth structure and tooth vi-

tality is of the utmost importance in tooth prepara-tion. Trauma to the pulp has to be minimized throughthe use of an air and water spray. At the same time,there must be sufficient space: cervically to create thecorrect contour that facilitates plaque removal, oc-clusally to allow the restoration of a proper occlusion,and axially to provide a proper thickness of veneeringmaterial to achieve an aesthetically acceptable result(Fig. 1) (44). Improper preparations may lead to over-contouring of the restoration, poor occlusal design,and poor aesthetics (Fig. 2).

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Fig. 1. Tooth preparation should allow enough space cer-

vically, occlusally and axially to give the technician the

ability to create a mechanically sound and aesthetically

acceptable prosthesis. A shoulder preparation with no

sharp angles is excellent for metal-ceramic crowns with

butt porcelain margins.

However, for a restoration to become integrated inthe mouth, strength and aesthetic appearance alone


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Gracis et al.

Fig. 2. An overcontoured restoration is often the result of

an underprepared abutment. Notice the inflamed gingiva

and the opaque appearance of the ceramometal crowns.

are not sufficient. A critical area is the crowntoothinterface and its relation to the periodontal tissues.Therefore, it is important to understand the necessi-ty for a well-fitting restoration (provisional or defini-tive) and how both the position of the preparationmargin with respect to the gingiva and the pro-cedures necessary to define and record it affect thequality of the final restoration and the health of thesurrounding tissues. Knowledge of the anatomy ofthe periodontal tissues and an awareness of how,under certain conditions, the prosthetic procedurescan lead to gingival inflammation, recession, or

pockets are prerequisites for any clinician doing thiswork.

Anatomic considerations

The relationships among the tooth-supporting softand hard tissues, the junctional epithelium, the con-nective tissue attachment and the bone crest havebeen clarified in histological studies by Gargiulo etal. (21). Even though the connective tissue attach-ment was found to have an average apicocoronal

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width of 1.07 mm and the junctional epithelium awidth of 0.97 mm, a high degree of individual vari-ability was reported. The combined dimensions ofthese two structures represent the biological width.This structure should always be respected (33). How-ever, many authors have highlighted the inevitabilityof penetrating the epithelial attachment during the

prosthetic procedures without this maneuver caus-ing any irreversible damage. Therefore, nowadays,true biological width violation means the place-ment of a restorative margin in the connective tissueattachment.

In health, the gingival margin and the alveolarcrest follow approximately the scallop of thecementoenamel junction except interproximally,

where the soft tissue col is concave and thus doesnot mimic the bone crest, which instead tends to beconvex or flat (41). The height of the interproximalpapilla depends not only on the bone architecture

but also on the relative tooth proximity: the closerthe crowns, the more accentuated is the papilla be-cause the soft tissues tend to be supported by theproximal contours of the crowns. The farther apartthe teeth (that is, in case of a diastema or a missingtooth), the flatter the papilla will be. When preparinga tooth, the tip of the bur should therefore follow thegingival margin or the anatomic configuration of thecementoenamel junction. It is important for the in-terproximal preparation, especially of the front teeth,not to become too flat; otherwise, there is a risk ofviolating the connective tissue attachment andtherefore the biological width (62).

Depending on the thickness of the underlyingbone and the dimension of keratinized gingiva, dif-ferent clinical and histological responses can resultfrom a supracrestal biological width violation.Usually, with a thick periodontium (fairly flat

Fig. 3. Typical appearance of thick periodontium


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Biological integration of aesthetic restorations

Fig. 4. In a patient with a thin periodontium, it is often

wise to select supragingival margin placement.

cementoenamel junction and gingival scallops, thickcortical plates and increased thickness of keratinized

gingiva), little apical migration of the dentogingivalunit and intrabony pocket formation are observed(Fig. 3) (63). In the presence of a thin periodontium(high gingival scallop, thin cortical plates and limitedthickness of keratinized gingiva), gingival recessionand apical migration of the dentogingival unit mayinstead be observed (Fig. 4). This migration is some-times self-limiting, as observed by Tarnow et al. (59).

Prominent roots need to be evaluated to identifyany fenestrations or dehiscences. These conditionsassociated with a thin periodontium contraindicatethe placement of a restorative margin intracrevicul-arly.

Supragingival versus intracrevicularmargins

Regardless of the preparation design and its co-ronoapical position, a precise and well-defined mar-gin should always be achieved. As Richter & Uenostated (51), marginal fit and finish may be more sig-nificant to gingival health than the location of themargin. Ideally, the margin of a prosthetic restora-

tion should be easily accessible for the following rea-sons:

O to facilitate fabrication of the provisional restora-tion;

O to facilitate impression taking;

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Fig. 5. Supragingival margins are easier to prepare and A. Supragingival preparations of lower incisors. B, C. Mag-

record in the impression; furthermore, in conjunction nified views of supragingival preparations. D. Empress

with all ceramic restorations, they can allow a very natu- crowns after final cementation with resin cement.

ral-looking result. In this case, the crowns are in Empress.


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Fig. 6. A shoulder preparation with an intracrevicular

margin. The ceramometal crown has emergence profile

that supports the soft tissues.

O to allow assessment of the fit of the restoration;O to allow margin finishing and burnishing; andO to facilitate plaque removal.

Supragingival margins stay away from the peri-odontal tissues, and thus, they are easier to prepare,record in the impression, and maintain (Fig. 5) (7).This is in contrast to the subgingival margins,

which impinge on the junctional epithelium or eventhe connective tissue attachment. Intracrevicularmargins are defined as those confined within the

gingival crevice (Fig. 6) (6, 33). Different studies (42,60) have demonstrated conclusively that periodontaltissues show more signs of inflammation aroundcrowns with intracrevicular or subgingival marginsthan those with supragingival margins. There may bea number of reasons for this result (17, 26):

O defective margins;O inaccurate fit;O roughness of the toothrestoration interface;O improper crown contour;

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O violation of the connective tissue attachment; andO greater pathogenicity of the subgingival dental

plaque.

However, even if from a periodontal point of view itis preferable to have exposed (supragingival) mar-gins, in clinical practice, the following factors may

force the clinician to place a restoration margin in-tracrevicularly:

O need to improve the resistance and retention formof a short clinical crown;

O presence of caries or restorations extending apicalto the gingival margin;

O modification of the emergence profile; andO aesthetics.

In these cases, the key factors for achieving a healthyand aesthetically pleasing result are proper margin

placement during tooth preparation, gentle tissuemanagement techniques during impression taking,and the fabrication of restorations (both provisionaland definitive) with high-quality margins (25, 26, 51,61).

Initial therapy should always be the first step inthe treatment of patients who need a restorative pro-cedure. Intrasulcular preparations should be per-formed exclusively in presence of a healthy crevice:only when it is inflammation free is the gingival mar-gin stable and less prone to recession and can beprobed and packed more accurately (63). Thehealthy crevice is shallow, generally ranging in depthfrom 0.5 to 1.0 mm on the facial aspect of the an-terior teeth (12, 52). Therefore, an intracrevicularmargin should be placed 0.2 to 0.5 mm apical to thefree gingival margin on the facial side. Interproxim-ally, because the sulcus normally is deeper, the prep-aration can extend more apically to better supportthe soft tissues. Be aware, however, that an increasein gingival inflammation has been reported as therestoration margin approaches the base of the sulcus(42, 61).

Some authors (6, 63) suggest placing a retractioncord in the sulcus before finalizing the preparation.This maneuver has two advantages: it highlights thebase of the sulcus and therefore the ultimate limit ofthe preparation before causing irreversible damage,and it pushes the gingival margin outward and apic-ally to better expose the unprepared tooth structureto be removed (Fig. 7). Margin placement has to re-spect the attachment apparatus and to allow forsome degree of error during the high-speed instru-mentation (6).


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Fig. 7. A thin periodontium is readily displaced vertically

by a retraction cord.

The sequence of clinical steps consists of:

O tooth preparation to the gingival margin;O placement of an extra-thin knitted retraction cord

that displaces the gingiva outward and apically;and

O definitive margin preparation to the top of thecord achieving a new, more apical position.

Role of provisional restorations

Fabrication of a provisional restoration is an ex-tremely important phase of treatment. Provisional

restorations are needed to protect the preparedteeth, to reduce the sensitivity of the vital abut-ments, and to prevent tooth migration. They are alsoinstrumental in developing the correct aesthetics,phonetics and occlusal scheme before fabrication ofthe definitive restoration (65). More importantly,

well-contoured and well-fitting provisional restora-tions allow the periodontal tissues to stay or becomehealthy. Special attention should be dedicated to thedevelopment of the proper emergence profile of theprovisional prosthesis both interproximally and buc-

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colingually to allow the patient access to all areas tomaintain periodontal health (Fig. 8). This prepara-tion depends on the patients periodontium type.Some authors have stressed the importance ofavoiding overcontouring of highly scalloped thintissue; otherwise, recession may occur (62).

Much time and effort should also be dedicated to

assuring an optimal fit of the resin provisional,avoiding open margins and overextension or under-extension. When relining provisionals with the directmethod, a multiple reline technique should be used(6). Alternatively, margins can be checked and final-ized on a stone die poured from an impression ofthe prepared tooth.

Special care should be directed to minimizingmechanical and chemical trauma to the naturaldentition and to the periodontium during pro-visional fabrication. In particular, the potentialtrauma to the pulp of the direct technique caused

by the heat of polymerization and the presence ofthe monomer is significant, especially if the thick-ness of residual dentin is limited (5). To minimizepulpal temperature rise and gingival irritation, it is

Fig. 8. Provisional prosthesis should be fabricated with the

proper contours and emergence profile, both interproxim-

ally and buccolingually, to allow the patient access to all

areas to maintain periodontal health.


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Fig. 9. An ultrathin (000) cord is placed around prepared

teeth. If sulcus is shallow and cord causes sufficient dis-

placement of gingiva, no additional cord is placed.

strongly recommended that an external airwaterspray be used in combination with regular removalfrom the preparation of the setting provisional res-toration (39).

Impression technique

The impression technique can have a negative im-pact on the soft tissues around the abutments,even causing irreversible damage if the techniqueis not properly carried out. Depending on the soft

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tissue type (thick versus thin) and the position ofthe preparation margin (at the gingival margin ver-sus intracrevicular), different tissue managementprocedures are indicated. The objective of tissueretraction is to expose all of the prepared toothstructure and, possibly, a portion of the unpre-pared root beyond the margin by causing a hori-

zontal and vertical displacement of the marginalgingiva. This can be achieved easily by placing in

Fig. 10. Use of double cord technique. The first cord is

ultrathin (000) cord, which will stay in place throughout

impression taking, while the second cord is one size big-

ger and will be removed just before injection of im-

pression material.


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the sulcus one or two knitted cords (Ultrapak; Ul-tradent Products, Salt Lake City, UT) of a suitablesize. A single-cord technique is the least traumaticoption and is normally employed when the sulcusis shallow and the margin is placed only minimallyin the crevice (Fig. 9). The cord is usually impreg-nated in a buffered aluminum chloride solution

(Hemodent; Premier Dental Products, Norristown,PA), and it is removed at the time of impression.The exposure of the tissues to the prolonged pres-ence of an astringent solution is well documentedin the literature (8, 11, 40, 49). A double-cord tech-nique is used when the sulcus is deeper (Fig. 10).From the point of view of prosthetic convenience,it may be desirable to employ this technique be-cause it yields more extensive displacement. How-ever, the soft tissue anatomy on the buccal aspectof the anterior teeth rarely permits two cords to beplaced. In the presence of a limited facial crevice,

a selective double-string technique is better, thesecond cord being placed only interproximally andlingually. The second cord is usually one size big-ger than the first, and it is soaked to control fluidseepage and any slight bleeding. The first cord,

which stays in place throughout the impressionprocedure, is left untreated.

Root proximity may create severe problems in ob-taining good impressions because there will not beenough space to accommodate the retraction cordsand, subsequently, a proper thickness of impressionmaterial. The placement of cords in such restrictedinterproximal spaces may cause irreversible damage.Possible solutions to this problem are:

O partial- instead of full-coverage restorations toavoid preparing and restoring the side of the tooth

with the proximity problem;O more apical placement of the restorative margin if

the root trunk tapers apically or an odontoplasty with a flame-shaped bur to increase the separ-ation;

O orthodontic movement to separate the teeth; and

O strategic extractions.

Choice of restoration andpreparation designs

The selection of the restorative material and the rela-tive tooth preparation design should be performedonly after the clinician has considered the variablesthat play a role in the decision-making process of

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Fig. 11. Cementation of two feldspathic porcelain veneers

allows a high degree of light transmission, which makes

the restorative margin virtually invisible.

any treatment plan that contemplates the placementof one or more prosthetic restorations:

O tissue type;O coronoapical position of the crown margin rela-

tive to the gingival margin and to the need ofmaintaining the tooths vitality;

O tooth vitality;O abutment integrity;O abutment height;O occlusal clearance for proper strength;


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Fig. 12. Color of abutment and presence of metallic or

dark core materials are primary factors that can affect

color of gingiva and aesthetic appearance of prosthesis.

This is particularly true when full ceramic restorations are

planned, as was the case with these two Procera crowns.

O aesthetic needs of the patient; andO parafunctional habits.

Only a careful evaluation of each of these featurescan indicate which preparation design is most suit-able in each particular case.

Full crowns versus porcelain veneers

The successful creation of adhesively luted conserva-tive restorations (porcelain veneers) is challenging

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more and more the traditional approach of fullcrowns. This is especially true when restoring singlevital teeth. In the past few years, clinical evaluationsof porcelain veneers have documented positive re-sults in terms of fracture rate, debonding, microleak-age, soft tissue response, aesthetics and longevity(13, 20, 30, 46, 47). Enamel-supported restorations

have a high light transmission and can be manufac-tured with several porcelain systems (Fig. 11). Forthe sake of this discussion, however, only full-cover-age restorations will be considered, because they stillconstitute the bulk of the prosthetic work performedin a typical dental office and because they are thereal challenge as far as the integration with the sur-rounding soft tissues. At the same time, it is interest-ing to note how, for single teeth, the use of tra-ditional cemented complete-coverage restorationsthat may extend intracrevicularly is increasinglylimited to two situations: 1) restoration of severely

damaged teeth and 2) replacement of existing full-coverage crowns (30).

Appearance and integrity of theabutments

The color of the abutment and the presence of met-allic or dark core materials, especially in endodont-ically treated teeth where posts are often used, areprimary factors affecting the appearance of the pros-thesis. This is particularly true in the cases in whichfull ceramic restorations are planned (Fig. 12).

In order to have a preparation with an adequateretention and resistance form, often, vital teeth andall nonvital abutments need some form of prepros-thetic reconstruction. The choice for a core build-up material was traditionally made among amalgam,glass-ionomer materials and composite resins. Morerecently, the use of amalgam has decreased becauseof biocompatibility issues, poor initial resistance(need to wait 24 hours to finalize the preparation),and fragility if its thickness is 1 mm, among otherreasons. Glassionomer materials, even the re-

inforced ones (such as Ketac-Silver; ESPE, Seefeld,Germany), are usually not recommended becausetheir low tensile strength makes them prone to frac-ture (24, 28, 36), especially if they are used for largebuild-ups not sustained by surrounding dentinal

walls.When only a minimal amount of tooth structure

has been lost, the authors prefer employing a com-posite resin, as it allows a conservative approach andthe possibility of matching the dentins color. How-ever, even when adhesive agents and materials are


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Fig. 13. Examples of aesthetic posts

used, it is a good habit not to rely solely on thechemical adhesives strength for long-term retentionof the core. Because these restored abutments aresubjected to repeated stresses such as tensilestresses when a provisional crown is removed, it ishighly recommended that some sort of mechanicalretention (undercuts, pins) be incorporated (45).

When a great amount of coronal tooth structure ismissing, as is the case with most endodonticallytreated teeth, one of the main problems that needsto be addressed is the retention of the build-up ma-terial. In some cases, an adequate retention is ob-tained by locking the material in the pulp chamber,but very often, a post cemented in one of the canals

is needed (1, 38). There are several post systemsavailable. To choose the ideal post material, it isimportant to consider features such as rigidity (stiff-ness) and color.

Although the clinical effectiveness of rigid metalposts is well established, some clinical reports havelinked a greater likelihood of root fracture to theiruse (4, 37, 50, 57). For this reason, the use of posts

with a modulus of elasticity similar to that of dentinhas been recommended (16). In this study theauthors consider carbon fiber posts a valid alterna-

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tive since, according to the research they carried out,the above-montioned physical property and the abil-ity to be bonded apparently create a homogeneousunit that can reduce stresses to the root and the po-tential for fracture. On the other hand, some authors(32, 55, 58) have highlighted the consequences ofusing such a system in conjunction with a rigid ce-

ramic or metal-ceramic crown. One group (55) con-cluded that the potential for flexure of the carbonfiber post on loading could result in the loss of thecement lute marginal seal with the accompanyingmicroleakage of oral bacteria and fluids.

From an aesthetic point of view, a metal post hasa significant disadvantage in that its presence doesnot allow sufficient light transmission through thecervical portion of the root. Thus, it can affect nega-tively the aesthetic quality of the final restoration.This is particularly true in patients with a thin peri-odontium and a high smile line. As a result, alterna-

tive aesthetic post systems have been developed inthe last few years (Fig. 13) (18). Table 1 summarizesthe indications, advantages, and disadvantages ofthe different aesthetic post systems available.

It is senseless to use the aesthetic post systemsand highly translucent metal-free restorations if thetooths substrate is dark as a result of prior endodon-tic treatments. In these cases, internal bleaching hasbeen suggested before proceeding with the recon-struction of the abutment (Fig. 14). However, thereare reports of external root resorption and decreasedbond strength to resin cements following such pro-cedures when chemicals for chairside bleaching

Fig. 14. Clinical view of dark endodontically treated teeth

before and after walking bleaching procedure


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Table 1. Aesthetic post and core systems

Zirconium post withMetal or carbon fiber post composite core, Cosmopost, Quartz and fiberglass post

Metal-ceramic post and core with composite core In-Ceram post and core with a composite core

IndicationsO To be used in presence of O To be used in presence of O Can be used in presence of O Can be used in presence of

a thick periodontium and a thick periodontium and a thin periodontium and a thin periodontium andlow lip line, as grayness low lip line, as grayness high lip line and in teeth high lip line and in teethcaused by metallic post caused by these posts with no discoloration or with no discoloration orinside root has an impact inside the root has an that have been bleached. that have been bleached.on the final result. impact on the final result. O When the post space has

an adequate diameter.

AdvantagesO Strong and durable O Direct technique: only one O Natural root color. O Natural root color.

material for the core. appointment is required O Direct technique: only oneO Predictability when for the fabrication of the appointment is required

properly used. restoration. for the fabrication of theO Carbon fiber post can post and core.

bond to tooth structure.

DisadvantagesO The stiffness of the post O Carbon post can allow too O No long-term data are O No long-term data are

may cause root fracture. much deformation of the available on the clinical available on the clinicalabutment and therefore performance of this performance of thiscan result in marginal material. material.leakage of the cemented O Stiffness of the post can O These posts can allow too

crown. cause root fracture. much deformation of thecore and therefore canresult in marginal leakageof the cemented crown.

were applied (2, 10). Therefore, it is suggested that awalking bleaching procedure be performed and thatat least 2 weeks then elapse before luting a post. Re-currence of the dark pigments is to be expected inmost cases.

Preparation designs

Preparation designs for full-coverage restorationsmay be classified into four distinct types (Fig. 15):

O feather-edge;O chamfer;O shoulder with bevel; andO shoulder.

A brief description of the salient features and indi-

cations of each type of design follows.

Feather-edge (vertical preparation)

Frequently used for gold cast crowns and porcelainor resin-veneered crowns in periodontally involvedcases, the feather-edge preparation design requiresthe least amount of tooth structure removal. Thefinish line is often hard to read, however, and fin-ishing and polishing can be difficult (64). It yieldslimited resistance to marginal distortion during por-

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celain firings and it can result in overcontouring ofthe final restoration if porcelain is applied close tothe margin. For these reasons, its application is con-fined to those situations where removal of a limitedquantity of tooth structure is of paramount import-ance for the long-term preservation of the abut-ments integrity and where the patient accepts thepresence of a metal collar (44).

Chamfer (hybrid preparation)

Widely used for cast restorations or for ceramometalcrowns with a minimal metal collar, the finish line

Fig. 15. Diagrammatic representation of four types

of preparation design. A. Feather-edge. B. Chamfer.

C. Shoulder with bevel. D. Shoulder.


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of a chamfer preparation is easy for the clinician toprepare and for the technician to read. However, ac-cording to some authors (15, 54), the thin metal col-lar may distort during the firing of porcelain, thusproducing inaccurate margins. A thermal cycle atoxidation temperature immediately after casting ap-parently decreases the likelihood of such distortion,

but there is no agreement among different authorson this issue (9, 23). The visibility of the metal doesnot allow these crowns to be used in areas where theaesthetic demands are high (Fig. 16).

Shoulder with bevel (vertical preparation)

The shoulder with bevel can be used for ceramomet-al crowns, full gold crowns and gold crowns withresin facings. This design was originally advocatedby Rosner (53), who demonstrated how the bevel canimprove fit. Subsequently, this concept was demon-

strated to be effective only above 70 shoulder-to-bevel angles, therefore losing most of its clinical util-ity (35). It is more conservative than a full shoulderpreparation, but the presence of the metal collarnecessitates an intracrevicular preparation in aes-thetic areas (Fig. 17).

Shoulder (horizontal preparation)

The shoulder is probably the most popular designbecause it is very easily read by the technician, andit allows sufficient bulk for porcelain to produce aes-thetically pleasing restorations. It can be used for all-ceramic or metal-ceramic crowns with either a metalcollar or a porcelain butt margin. The preparationshould display internal rounded axial angles (14) todecrease stress concentration and reduce the risk ofporcelain failure. However, castings made for a flatshoulder preparation may display a relatively poorfit, whereas excellent accuracy can be obtained withporcelain margins (48).

Metal-ceramic restorations

Because of their strength, durability and relative sim-plicity of fabrication, metal-ceramic restorations arethe most widely used for both single crowns andfixed partial dentures (6). However, these advantages

were often counterbalanced by a less-than-ideal aes-thetic result when the appearance of both the crown(especially of the cervical one third) and of the sur-rounding soft tissues were analyzed. In recent years,the effort to improve the aesthetic potential ofmetal-ceramic restorations has brought about a

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Fig. 16. The use of ceramometal restorations with por-

celain butt joint has greatly improved aesthetic outcome,

especially in the gingival third.

number of technical improvements and new metalframework designs. The most important develop-ment is without a doubt represented by collarlessmetal frameworks (Fig. 16).

The aesthetic appearance of the traditional apic-ally extended frameworks often leaves much to bedesired because of the lack of brightness and liveli-ness in the marginal soft tissues surrounding theprosthesis. As a consequence, they take on a bluishhue. This is true both in the presence of a vital abut-ment and in case of an endodontically treated tooth


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Fig. 17. Hemisected molar is a typical situation where a

metal-ceramic crown with a metal collar is indicated.

restored with a post and core (Fig. 17). Magne et al.

(30) extended this notion, introducing the conceptof the umbrella effect; that is, the absence of in-direct light penetration into the soft tissues becauseof the shadow cast by the upper lip on the cervicalpart of a restoration with a metal substructure.

To solve these problems, Geller (22) suggested areduction of the metal to provide space between thegingival margin and the most apical border of theframework, allowing room for the application ofshoulder porcelain and the passage of light. An ade-quate reduction of the metal framework and the as-

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sociated use of fluorescent porcelain margins are ef-fective in obtaining a certain degree of brightness inthe root and allowing the illumination of the peri-odontal tissues typical of natural dentition. At thesame time, collarless metal-ceramic restorationshave demonstrated the same resistance to axialpressures as metal-ceramic restorations with a tra-

ditional framework (3, 27, 43).If the tooth to be restored has no discolorationand no previous restoration that extends intracrevic-ularly, the choice of an all-ceramic crown allows theoperator to maintain the prosthetic margin supra-gingivally or at the gingival margin. Thus, it is poss-ible to avoid the time-consuming complications as-sociated with an intracrevicular extension while stillachieving a very aesthetic result.

All-ceramic restorations

The increasing aesthetic awareness of patients hasled to the search for metal-free restorations and tothe development of new ceramic systems that chal-lenge traditional metal-ceramic restorations (34).The improved physical characteristics of these ma-terials and the introduction of a new generation ofdental adhesives and resin cements have in fact re-sulted in predictable and consistent clinical per-formance, especially when they are used for singleanterior restorations (19, 31, 56). The likely expla-nation is that the all-ceramic restoration and the re-sidual tooth structure are mutually reinforced by theadhesive cement (29). On the other hand, multistepcementing procedures are demanding and tech-nique sensitive, cement removal is difficult, and adental technician with adequate experience isneeded. Short-span fixed partial dentures may alsobe fabricated with some of these ceramic systems.However, the standard for fixed partial dentures from

Table 2. Reduction requirements for full crownsand porcelain veneers

Full crownsPorcelain

Metal-ceramic All ceramic Cast veneers

Facial1.31.7 mm 1.21.5 mm 0.51.0 mm 0.51.0 mm

Lingual0.7 mm 1.0 mm 0.51.0 mm (if in metal)

Occlusal or incisal1.52.5 mm 2.0 mm 1.0 mm 1.02.0 mm


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Fig. 18. Two Procera caps being tried to determine color

base (A). B. Finished product.

a structural and biomechanical point of view is stillmetal-ceramic restorations.

An all-ceramic restoration can be selected on thebasis of specific criteria, such as mechanical prop-erties and light transmission. In this context, it isuseful to classify the materials used for single-unitrestorations in two main groups: alumina-based ce-ramics and non-alumina-based (glass) ceramics. Thefirst group encompasses Spinell (Vita Zahnfabrik,Bad Sackingen, Germany), In-Ceram (Vita Zahnfab-rik), and Procera (NobelBiocare, Goteborg, Sweden).In the second group can be included Dicor (Dent-

sply) and Empress and Empress 2 (Ivoclar-Vivadent,Schaan, Liechtenstein). The materials in the formergroup typically display higher strength and limitedtranslucency (alumina is relatively opaque) (Fig. 12,18), whereas those in the latter group show a highertranslucency but more limited strength (Fig. 5). As amatter of fact, so far, only two systems are appar-ently indicated for use as single posterior crowns: In-Ceram and Procera. All new ceramic systems sharea common goal: to limit the occurrence of completefailures caused by fractures that encompass both the

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core and the veneering material. This goal has beenachieved by developing cores strong enough that thefractures are limited to the veneering material, thusapproaching the failure pattern typical of metal-ce-ramic restorations.

The reduction requirements for the two types ofcrowns, metal-ceramic and all-ceramic, are listed in

Table 2.

Conclusions

Recent progress in restorative materials and clin-ical techniques, especially those in the field of ad-hesive dentistry, can indeed make it easier for ageneral practitioner or a prosthodontist to createnatural-looking restorations. However, no matterhow significant new material developments may

be, by themselves, they will never provide the keyto success in prosthodontics. Tissue managementis of utmost importance and the real basis on

which to determine whether a prosthesis has beenproperly fabricated and has been integrated in themouth of a patient. Bringing the periodontaltissues to a state of health and maintaining such astate throughout the therapy and beyond requirescareful planning and execution during all phasesof the restorative treatment (Fig. 19). This can beachieved only through extreme attention to detailand the allowance of an appropriate amount oftime to carry out every single procedure, as it isnecessary to do when relining provisional restora-tions, making impressions and removing excess ce-ment around the restorations.

This chapter reviewed some of the most signifi-cant concepts and clinical considerations relating torestorative procedures in light of recent and olderliterature. The aim is to focus the attention of theclinicians on the aspects that should always be keptin mind when trying to replace missing tooth struc-ture.

Acknowledgments

We thank Silvano Sandrini and Giancarlo Barducci,Master Dental Technicians, for their invaluable ef-forts in always providing restorations that enhancethe clinical work while adding an artistic flare tosomething that otherwise would be a mere toothsubstitute at best.


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