relationship between crowns and gum

VOLUME 41 NUMBER 2 FEBRUARY 2010 109

QUINTESSENCE INTERNATIONAL

The question of whether crowns have an

effect upon the condition of periodontal tis-

sues has been the subject of numerous stud-

ies in dental literature for many years.118

Particular interest has been paid to the rela-

tionship between periodontal health and the

location of the crown margin, the marginal fit

of the crown, the crown material, and the

crown contour (Figs 1 and 2). These key fac-

tors, unless appropriately managed, may cre-

ate niches for plaque growth,19 thus providing

a protected environment in which the indige-

nous microbial population may mature into

an even more pathogenic and virulent

flora.9,20,21 Under such circumstances, initia-

tion or progression of periodontal disease is

certain.

With respect to the gingival crest, four

options for positioning the crown margin are

described in the literature: the supragingival

location; the equigingival location, or location

at the gingival margin; the intracrevicular or

slightly subgingival location, in which the

margin is confined within the gingival

crevice2227; and the subgingival location.

Originally, the term subgingival location

referred to the location of the margin posi-

tioned somewhere between the free gingival

margin and the alveolar crest,17 implying a

possible impingement upon the junctional

epithelium or the connective tissue.28 More

recent studies have used the term intra-

crevicular location, which describes a crown

margin placed and confined within the gingi-

val sulcus.2227

Relationship between crowns and the periodontium: A literature updatePanagiota Kosyfaki, DDS1/Maria del Pilar Pinilla Martn, DDS1/

Jrg Rudolf Strub, DDS, Dr Med Dent, Dr hc, PhD2

Location of the crown margin, marginal fit, crown material, and crown contour all impact

periodontal tissues. This literature review evaluated available data on their relationship with

the periodontium and also examines whether any changes in established knowledge

and/or perspectives have been published during the past 30 years. Electronic and manual

searches conducted for in vivo investigations in the English and German literature for

1953 to 2009 provided 64 studies. Findings indicate that the supragingival location

remains the most advantageous from the periodontal point of view; esthetic demands,

however, dictated an intracrevicular location of the margin in the anterior zone. Metal-

ceramic and all-ceramic crowns show a clinically acceptable marginal fit. Ceramic materi-

als have the lowest plaque-retaining capacity, and a normal crown contour guarantees

satisfactory periodontal health and esthetics. The accompanying data confirm the results

reported in the literature, revealing that nothing has substantially changed, thereby sup-

porting current approaches. (Quintessence Int 2010;41:109122)

Key words: crown contour, crown material, crowns, location of the crown margin, marginal

fit, periodontium

1Postgraduate Student, Department of Prosthodontics, School

of Dentistry, Albert-Ludwigs University, Freiburg, Germany.

2Professor and Chair, Department of Prosthodontics, School of

Dentistry, Albert-Ludwigs University, Freiburg, Germany.

Correspondence: Dr Panagiota Kosyfaki, Department of

Prosthodontics, School of Dentistry, Hugstetter Strasse 55, 79106,

Freiburg, Germany. Fax: 49 (761) 270 4824. Email: panagiota.

[email protected]

109_Kosyfaki_ref_Arcari 1/25/10 10:38 AM Page 109

2009 BY QUINTESSENCE PUBLISHING CO, INC. PRINTING OF THIS DOCUMENT IS RESTRICTED TO PERSONAL USE ONLY. NO PART OF THIS ARTICLE MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM WITHOUT WRITTEN PERMISSION FROM THE PUBLISHER.

110 VOLUME 41 NUMBER 2 FERUARY 2010


Kosyfaki et a l

Marginal fit is valued as an essential factor

for the long-term success and overall accept-

ability of the restoration.1,3,4,7,2935 However,

despite careful attention to waxing and casting

procedures, marginal discrepancies, including

the marginal gap, overextension, and under-

extension,36 do occur3739 and have been

directly implicated in producing strong adverse

inflammatory responses in the periodon-

tium.9,29,33,4042

Every material in the oral cavitymetal,

ceramic, or acrylic resinhas the potential to

retain plaque deposits.43 However, because of

the chemical and physical properties of each

material,3,43,44 the composition and retention of

built-up plaque and the subsequent periodon-

tal response will vary from material to material.

For example, acrylic resin, because of its

porosity, shows the highest plaque-retaining

capacity and is associated with chronic inflam-

mation of the gingival tissues.44,45 For this rea-

son, its use has been limited to the fabrication

of provisional restorations.46 On the contrary,

porcelain, owing to its chemical composition,

is a highly biocompatible material that displays

a low affinity to soft debris accumulation.44,45,47

Emulating the contour of the natural tooth,7

thus avoiding overcontouring or undercon-

touring the crown, is essential for supporting

the surrounding soft tissues, optimal

hygiene,22,37,4851 and a natural-looking restora-

tion.52 Natural teeth exhibit straight emergence

profiles in the gingival third, with an emer-

gence angle of 15 degrees in relation to the

long axis of the tooth.49,53 The contact areas

are high, 4 to 5 mm above the interproximal

bone in patients with normal periodontium,54

while the triangular embrasure to the contact

area is filled with the interdental papilla.13

The first critical review, which extensively

examined the relationship between restora-

tive procedures and the periodontium, was

published in 1977.3 Since then, numerous

studies on novel materials and techniques

have been conducted, providing various

observations and results about the close

interaction between crowns and periodon-

tium. However, no literature review has been

undertaken to present the new data and

summarize the current scientific knowledge

on crowns and periodontal health until now.

The aim of this review was to evaluate

available literature on the impact of a crown

its margin location, marginal fit, material, and

contouron the periodontium and also to

determine if any significant change in estab-

lished knowledge or perspectives during the

past 30 years has been recorded.

Fig 2 All-ceramic crowns on the maxillary central incisorswith intracrevicular margins, clinically acceptable fit, and anormal tooth contour: good result.

Fig 1 Acrylic resinveneered crowns on the maxillary central andright lateral incisor(s) with overcontoured, insufficient, subgingivalmargins: bad result.





Kosyfaki et a l

LITERATURE SEARCH

On the basis of specific inclusion and exclu-

sion criteria, a detailed search protocol was

designed to identify studies examining the

relationship between crowns and the peri-

odontium.

Inclusion criteriaStudies considered for this review were in

vivo studiesprospective, retrospective, ran-

domized controlled trials, controlled clinical

trials, or comparative studiesconducted on

either human or animal subjects, focusing

mainly on crowns and examining at least one

of the following featureslocation of the

crown margin, marginal fit, crown material,

crown contourand its impact on the peri-

odontium. For the purposes of this review,

review articles were also included.

Exclusion criteriaStudies considered ineligible were in vitro

studies, case reports, and studies focusing

on restorations other than crowns, such as

fixed partial dentures, inlays, onlays, direct

restorations, veneers, or implant-supported

restorations. However, several articles report-

ing on crowns and fixed partial den-

tures,41,5561 direct restorations,30 onlays,20 and

inlays62 were included because of the difficul-

ty of extracting data exclusively concerning

crowns.

Search strategyThe Medline (PubMed) electronic database

was explored for dental articles published

between 1953 and 2009. Language restric-

tions were applied, and only relevant articles

written in English or German were included.

The search used a combination of key words

and search terms: periodontium, crown, loca-

tion of the crown margin, marginal fit, crown

material, and crown contour. In addition,

hand searches were performed on books

and high-yield journals. The final electronic

search was conducted in May 2009.

Study selectionThe obtained titles, abstracts, and texts, iden-

tified through the electronic and manual

searches, were scanned and evaluated for

appropriateness by the two review authors

(P.K. and J.R.S.) independently according to

the defined criteria. Studies that did not meet

the inclusion criteria were excluded from fur-

ther evaluation. Subsequently, the full reports

of the studies that appeared to fulfill the inclu-

sion criteria were retrieved and assessed. At

that stage, the search was narrowed using

the following terms: supragingival, equigin -

gival, intracrevicular, subgingival, marginal

gap, overextension, underextension, metal-

ceramics, all-ceramics, gold, acrylic resin,

surface roughness, normal contour, overcon-

tour, and undercontour. The bibliographies of

all pertinent articles were further checked

and reviewed using the defined inclusion and

exclusion criteria. Any discrepancies were

resolved by discussion between the two

reviewers.

FINDINGS

The initial search yielded 1,138 titles. After

screening by the two reviewers and applica-

tion of the set inclusion and exclusion crite-

ria, 130 pertinent articles were selected. Of

the 130, 64 were identified as in vivo investi-

gations (Table 1) and incorporated in the

body of the review because of their clinical

relevance to the topic. Of the 64, 56 in vivo

investigations could be further classified into

7 tables, each table examining the relation-

ship between the periodontium and location

of the crown margin in humans (19 studies,

Table 2) and in animals (2 studies, Table 3);

marginal fit in humans, whereby the meas-

ured marginal discrepancy is reported (12

studies, Table 4); crown material in humans

(17 studies, Table 5) and in animals (1 study,

Table 6); and crown contour in humans (4

studies, Table 7) and in animals (2 studies,

Table 8).

One study63 has been included in both

Tables 2 and 5. The results of another study

were published in German in 199864 and in

English in 2000.65 Due to the heterogeneity

in the basic components of the study design,

eg, population, intervention, and outcome,

a statistical analysis of the data was not pos-

sible.




Kosyfaki et a l

The outcomes of the selected studies

were categorized into the following four sub-

sections: relationship between location of the

crown margin and the periodontium; margin-

al fit and the periodontium; crown material

and the periodontium; and crown contour

and the periodontium.

Location of the crown margin and the periodontiumThe literature search identified 21 in vivo

studies (Tables 2 and 3). Of these studies,

821,55,56,60,63,6668 assessed whether clinical

differences with respect to the periodontium

were present with supragingival, equigingival,

and subgingival margins. Five studies59,6972

compared supragingival to subgingival mar-

gins and seven studies dealt with the place-

ment of the margin at different levels in the

gingival crevice.26,64,65,7376 The overwhelming

majority of human studies21,55,56,5961,66,70,71,73,74,76

implemented a retrospective design. A

prospective design was employed in four

studies.26,64,65,67 One study was identified as a

controlled clinical trial.63

A comparison of earlier studies showed

several authors held diametrically opposed

opinions. On one hand, it was claimed that

gingival inflammation is completely irrespec-

tive of the position of the crown margin, pro-

vided the patient participates in a personalized

prophylactic dental care program.66 On the

other hand, it was suggested that even

among highly motivated patients with regular

plaque control, supragingival margins, as

well as subgingival margins, would adversely

affect periodontal tissues.4,71

112 VOLUME 41 NUMBER 2 FEBRUARY 2010

19531959 19601969 19701979 19801989 19901999 20002009

Waerhaug 195342 Marcum 196768 Karlsen 197072 Ehrlich and Adamczyk and Boening et al 200089

Hochman 1980130 Spiechowicz 199044

Waerhaug 1956107 Perel 1971116 Keenan et al 1980112 Carnevale et al 199060 Gnay et al 200065

McLean and Valderhaug 198056 Jensen et al 1990101 Lvgren et al 200057

von Fraunhofer 197162

Jones 197296 Marxkors 198091 Bader et al 199171 Gnay et al 200126

Richter and Koth 198266 Felton et al 199134 Kancyper and Ueno 197369 Koka 200176

Newcomb 197474 Lang et al 198320 Ferrari 199195 Bindl and Mrmann 2002100

Larato 197573 Lindhe et al 198380 Tarnow et al 199254 Gemalmaz et al 200263

Wise and Riley et al 1983106 Karlsson 199388 Reitemeier et al 200267

Dykema 197547

Sackett and Belser et al 198586 Castellani et al 1996104 Sundh and Khler Gildenhuys 1976113 2002115

Valderhaug and Diedrich and Seeger et al 199864 Kohal et al 2003117

Birkeland 197655 Erpenstein 198592

Parkinson 1976114 Fransson et al 198587 Sjgren et al 1999102 Kokubo et al 200590

Strub and Belser Chan and Weber Sjgren et al 1999103 Ohlmann et al 200697

197859 198645

Mller 198661 Davidi et al 200746

Shafagh 1986111 Weishaupt et al 200798

Spiekermann 198641 Quante et al 200835

Tarnow et al 198675

Jger and Besimo 198793

Orkin et al 198770

Bieniek and Kpper 198894

Flores-de-Jacoby et al 198921

Kpper and Bieniek 1989105

Simonis et al 198999

Table 1 In vivo studies in humans and animals on the relationship between crowns and the periodontium from 1953 to 2009





Kosyfaki et a l

However, the outcomes of a 10-year longi-

tudinal investigation55,56 showed that while

about 60% of the crown margins were origi-

nally located subgingivally, a little more than

half of those (or about 36% of the original

crown margins) remained subgingival after

10 years. Disease had taken its toll, obvious-

ly initiated by the subgingival margins.

Generally, when comparing supragingival

to subgingival margins, subgingival margins

are associated with increased plaque accu-

mulation, gingival inflammation,55,56,63,67,71,75

deep gingival pocket formation,55,56,71,73

greater attachment loss,55,56 and gingival

recession70 as demonstrated by clinical

parameters, namely, the higher Plaque Index,

Gingival Index, and crevicular fluid flow

rates,21,59 compared with those of supragingi-

val margins.

When comparing supragingival to equi -

gingival margins, equigingival margins tend

to show a slight increase in gingival inflam-

mation and probing depths and slightly more

attachment loss than supragingival mar-

gins.55,56,61

As a matter of fact, restorations terminat-

ing at the gingival margin or intracrevicularly

show more similarities with subgingival

restorations than with supragingival ones.21

Therefore, despite appearing less injurious

than subgingival margins,76 intracrevicular

and equigingival margins may cause inflam-

mation.

In contrast, one retrospective study60

demonstrated that a crown margin placed in

a gingival or slightly subgingival location is

not detrimental to periodontal health. It must

be stressed, however, that a highly precise

prosthetic margin was given and that effec-

tive plaque control in patients was achieved

through an intensive oral hygiene program,

conducted by professionals in the field.

Moreover, when atraumatic preparation tech-

niques are used,25,26 it is possible to maintain

periodontal health even with intracrevicular

margins.26

Compared to intracrevicular margins,

margins placed within the zone of the bio-

logic width were found to exhibit increased

pocket depths and loss of attachment.64,65

Note worthy was the absence of alteration of

bone levels 2 years after insertion as diag-

nosed by means of intraoral radiographs.

Nonetheless, it was indirectly implied that a

possible three-dimensional change of the

bony profile may have occurred, though not

successfully depicted.

As a rule, the deeper the margin is placed

within the gingival crevice, the greater the

severity of gingival inflammation65,74,77 and

also the greater the danger of violating the

biologic width.48,77,78 Subgingival margins cre-

ate a sheltered environment, inaccessible for

effective plaque removal by means of oral

hygiene procedures.9 Thus, the subgingival

extension may dynamically modify the distri-

bution pattern of bacterial plaque and favor

the establishment of gram-negative anaero-

bic microbiota.20,21,27,79 This shift in the

subgingival microflora toward a more peri-

odontopathic microflora represents a high

risk for periodontal breakdown.80 This may

result in epithelial proliferation (gingivitis)

and, if unaffected by treatment, may lead to

apical migration of the junctional epitheli-

um75 and bone loss (periodontitis).78,81,82

Simultaneously, when the margin of the

restoration is positioned subgingivally, it is

possible that the epithelial attachment or the

connective tissue fibers will become irre-

versibly inflamed.64,65 In an attempt by the

periodontal structures to recreate the space

between the alveolar crest and the crown

margin,48 apical migration of the epithelium

occurs.75 This results in an increase in gingi-

val inflammation64,65 and deepened peri-

odontal pockets in the case of thick biotype,

or gingival recession75 in the case of thin bio-

type.83,84 Interproximally, loss of crestal bone

might22,23,75,83,85 or might not64,65 be observed.

In any case, the violation of the biologic width

will certainly facilitate the development of the

aforementioned plaque-related inflammatory

process.9,65,85

Marginal fit and the periodontiumThe literature search yielded 12 in vivo inves-

tigations reporting on the measured margin-

al discrepancy of crowns (Table 4). Six

studies35,8690 evaluated the fit by means of

replica technique before cementation of the

crowns in patients. Of the six, four stud-

ies35,8688 reported on the marginal fit of

metal-ceramic crowns and two studies89,90





Kosyfaki et a l

No. of examined Location ofrestorations/ crown margin/

No. of patients/ No. of examined Parameters Observation Author(s) No. of dropouts restorations assessed period Results/observations

Larato 197573 111 crowns/111 Subgingival/111 PD NR 55% of the subgingival marginsshowed increased pocket depthscompared to natural teeth.

Richter and Ueno 197369 12 crowns/12 Supragingival/12 GI, PD, 3 y Precision of fit is more important Subgingival/12 absence than location of the margin.

of plaque However, supragingival margins are better than subgingival.

Newcomb 197474 66 crowns/59 Subgingival location GI, PI 8.23 mo The deeper the margin is placedat different levels within into the crevice, the more severethe gingival crevice the gingival inflammation.

Strub and Belser 197859 315 crowns Supragingival/37 PI, PD, 1 y Supragingival margins showed and FPDs/24 Subgingival/278 TM, WAG less inflammation than

subgingival margins.Valderhaug and 357 crown Supragingival/30% GI, PI, 5 y Compared to supragingival Birkeland 197655 and FPDs/114/98 Equigingival/29% PD, AL margins, equigingival margins

Subgingival/41% showed an increase in gingivalinflammation and in pocketdepths. Additionally subgingivalmargins showed increase in loss ofattachment.

Valderhaug 198056 357 crowns Supragingival/37% GI, PI, 10 y Compared to equigingival and and FPDs/114/82 Equigingival/28% PD, AL supragingival margins, subgingival

Subgingival/36% margins showed higher gingivalinflammation. Compared tosupragingival location, equigingi-val margins showed increase inpocket depth, and a little moreloss of attachment.

Koth 198266 46 crowns/28 Supragingival and GCF 19 y Gingival inflammation is irrespectiveEquigingival/41.3% (mean: either of a supragingival, Subgingival/58.7% 3.5 y) equigingival, or subgingival mar-

gin, when the patient attends astrict recall program.

Mller 198661 47 crowns Supragingival/25 PI, GI, 1 y Equigingival margins show little and FPDs/5 Equigingival/22 PD, AL, GF, inflammation in contrast to supra-

composition gingival margins that showedof microflora minor signs of inflammation.

Tarnow et al 198675 13 provisional crowns/2 Subgingival location, Histologic 2 mo Gingival recession, migration of halfway between the examination the junctional epithelium, and gingival margin and of the PDL resorption of crestal bone were bone crest observed.

Orkin et al 198770 423 crowns/423 Supragingival/68 GI, PI, R 2 y (supra) Gingival tissues tended to bleed Subgingival/355 4 y (sub) 2.42 times more frequently with

subgingival margins and have a2.65 times higher chance of gin-gival recession.

Flores-de-Jacoby 693 TS of crowns/19 Supragingival/415 TS GI, PI, PD, 1 y The supragingival location is the et al 198921 Equigingival/135 TS CFFR, least detrimental to the peri

Subgingival/143 TS composition odontium. Subgingival margins of microflora show the highest values for GI, PI,

PD, and CFFR. Equigingivalmargins show more similarities tosubgingival margins.

Table 2 In vivo studies in humans on the relationship between location of the crown margin and the periodontium





Kosyfaki et a l

No. of examined Location of crown crowns/No. of margin/No. of Observation

Author(s) animal subjects examined crowns period Results/observations

Marcum 196768 12 crowns/6 Supragingival/4 13 mo Equigingival margins caused the leastEquigingival/4 inflammatory response.Subgingival/4

Karlsen 197072 27 crowns/5 Supragingival/9 212 mo Subgingival margins show more pronounced Subgingival/18 signs of inflammation than supragingival margins.

Table 3 In vivo studies in animals on the relationship between location of the crown margin and the periodontium

No. of examined Location ofrestorations/ crown margin/

No. of patients/ No. of examined Parameters Observation Author(s) No. of dropouts restorations assessed period Results/observations

Carnevale et al 510 crowns Supragingival/56 PI, GI, PD 13 y An equigingival or slightly subgingival199060 and FPDs/109 Equigingival/123 35 y but precise margin is not prejudicial

Slightly subgingival/331 69 y to periodontal health in patients with effective plaque control.

Bader et al 199171 599 crowns/367 Supragingival/90 PI, CI, 5 y Supragingival and subgingival Subgingival/509 GI, PD margins show higher inflammation

and deeper probing depths com-pared to natural teeth even amongregularly attending patients.

Gnay et al 200065 116 crowns/41 Intracrevicularly/25 HI, PBI, 2 y Margins placed within the zone of Seeger et al 199864 In junctional PD, PAL biologic width result in increased

epithelium/59 In pocket depths and gingival inflam-connective tissue/32 mation and clinical attachment loss

No change in bone levels was noted.Kancyper 30 crowns/30/0 Intracrevicular/30 Gingival redness, 6 mo Gingival redness, plaque, swelling,and Koka 200176 plaque, swelling, and bleeding scores were low, and no

bleeding scores, pathogenic bacteria were detectedcomposition of with intracrevicular margins.microflora

Gnay et al 200126 66 crowns/34/0 Intracrevicular/66 HI, BOP, 1 y There was no statistically significantPPD, PAL, difference between the HI, BOP, FGM PPD, PAL, and FGM of the intra-

crevicular margin and natural teeth. Teeth had been prepared using an atraumatic preparation diamond.25,26

Gemalmaz et al 37 crowns/20 Supragingival/20% PI, GI 24.56 mo Subgingival margins showed higher200263 Equigingival/25% values for PI and GI compared to

Subgingival/55% natural teeth. Supragingival and equi-gingival margins showed similar values to the natural teeth.

Reitemeier et al 480 crowns/240 Supragingival/NR PI, SBI 1 y Subgingival margins showed the200267 Equigingival/NR greatest inflammation followed by

Subgingival/NR the equigingival and then the supra-gingival margins. The risk of bleeding with subgingival margins is double compared to supragingival margins.

(FPD) Fixed partial dentures; (TS) tooth surface; (PD/PPD) probing depth; (GI) Gingival Index; (PI) Plaque Index; (TM) tooth mobility; (WAG) width ofattached gingiva; (AL/PAL) clinical attachment level; (GCF) gingival crevicular fluid; (GF) gingival fluid flow; (PDL) periodontal ligament; (R) recession;(CFFR) crevicular fluid flow rate; (CI) Calculus Index; (HI) Hygiene Index; (PBI) Papillary Bleeding Index; (SBI) sulcular bleeding index; (BOP) bleeding onprobing; (FGM) level from the free gingival margin; (NR) not reported. Aside from Valderhaug and Birkeland55 and Valderhaug,56 the number of dropoutsfrom all other studies was zero.

Table 2 In vivo studies in humans on the relationship between location of the crown margin and the periodontium (continued)





Kosyfaki et a l

Study Mean marginal Wear time Author(s) No. of crowns subjects Method gap (m) of crowns Results/observations

(RT) Replica technique; (SEM) scanning electron microscope; (LM) light microscope; (HA) histologic analysis; (CPM) computerized picture microscope;(SM) stereomicroscope; (NR) not reported.

Table 4 In vivo studies in humans on the relationship between marginal fit and the periodontium

Marxkors 198091

Belser et al 198586

Fransson et al198587

Diedrich andErpenstein 198592

Spiekermann198641

Jger and Besimo198793

Bieniek and Kpper198894

Ferrari 199195

Karlsson 199388

Boening et al200089

Kokubo et al 200590

Quante et al200835

Over 100 goldcrowns

36 metal-ceramic crowns27 (beveledmetal margin,metal butt mar-gin, porcelainbutt margin)55 metal-ceramiccrowns (38 highgold crowns, 17gold palladiumcrowns)3 gold crowns

142 gold crowns(63 single crowns,35 FPDs)6 all-ceramiccrowns (3Cerestore crowns,3 Dicor* crowns)80 crowns (70 Hi-Ceram, 10 gold)

15 crowns (14Dicor, 1 metal-ceramic)

12 Procera titani-um crowns

80 ProceraAllCeram crowns

90 ProceraAllCeram/53

28 metal-ceramiccrowns fabricatedwith laser meltingtechnology28 (base alloy,precious alloy

Clinicalevaluation

RT + SEManalysis

RT + LManalysis

SEManalysis

HA

HA + CPManalysis

HA + SEManalysis

SM + SEManalysis

RT + LManalysis

RT + LManalysis

RT + LManalysis

RT + LManalysis

110270 (featheredge)70160 (distinguish-able margin finish line)< 50

100

142.40

382 (80.3% feather-edge margins)

< 50

68.9 7.5 (HA ofHi-Ceram crowns)2.7 5.8 (SEM ofHi-Ceram crowns)59.1 6.1 (HA of goldcrowns)50100 (for Dicorcrowns)

70

8095 (anterior teeth)90145 (posterior teeth)

36 36 (anterior teeth)32 32 (premolar teeth)35 33 (molar teeth)7499 for both alloys

The marginal gap of featheredge margins wa greater thanthat of margins with distinguish-able finish lines.The marginal fit of the threedesigns is clinically acceptable.Porcelain butt margins 50 mare feasible.

Metal-ceramic crowns have a clin-ically acceptable fit ( 120 m).62

Gold-palladium crowns show abetter fit than high-gold crowns.

The marginal gap is over theclinically acceptable value(>50 m).40

The marginal gap is over theclinically acceptable value(50100 m).40

The mean marginal discrepancyfor both systems is under 50 m.

The accuracy of fit of Hi-Ceram isin the range of clinical acceptance(50100 m).40

Metal-ceramic crowns have bettermarginal adaptation than Dicorcrowns. However, the marginal fitof Dicor crowns is clinically accept-able.The accuracy of fit is in the rangeof clinical acceptance ( 120 m).62

The accuracy of fit is in the range ofclinical acceptance (100150 m).62

The accuracy of fit is in the rangeof clinical acceptance ( 120 m).62

The accuracy of fit for bothalloys is in the range of clinicalacceptance ( 120 m).62

NR

5 y

NR

3 mo

3 mo

47mo

Extracted teethof humanpatients (no.ofpatients NR)27 humanpatients

Humanpatients (no.ofpatients NR)

Extracted teethof humanpatients81 human jawspecimens

Extracted teethof 1 patient

Extracted teethof humanpatients

Extracted teethof 6 humanpatients

Humanpatients (no.ofpatients NR)Humanpatients (no.ofpatients NR)53 humanpatients

28 humanpatients





Kosyfaki et a l

reported on the marginal fit of all-ceramic

crowns, whereby slightly different fit values

were provided. However, based on the six

studies, both systems demonstrated the

accuracy of fit to be within the limits of clini-

cal acceptance ( 120 m).62

In addition, six retrospective studies inves-

tigated the marginal fit of crowns on extract-

ed human teeth.41,9195 Sufficient clinical fit

was found to be feasible with Cerestore

(Johnson & Johnson), Dicor (Dentsply), and

Hi-Ceram (Vita Zahnfabrik) crowns.9395 In

contrast, large marginal discrepancies of 110

to 160 m,91 142.40 m,92 and 384 m41

were registered with gold cast crowns.

Feather-edge margins could account for

these results.41,91

Moreover, it was found in one of these

studies that 41.5% of the crown margins

were overextended and 33% underextended,

which explained the presence of calculus

deposits under most of the examined crown

margins (75%).41 Overextending or overhang-

ing margins constitute iatrogenic factors

responsible for strong gingival inflamma-

tion96 due to the plaque-retentive capacity of

the crown material1,3,47 and alterations in the

subgingival microflora,20,34 as well as changes

in the epithelial and connective tissues.42 One

study20 found overhanging margins caused

no loss of attachment, yet another study30

reported a compromised interproximal bone

height around defective crowns. On the other

hand, a short underextended margin exhibits

an emergence profile incompatible with nat-

ural tooth morphology. This factor, in combi-

nation with the roughness of the exposed

prepared tooth structure, contributes largely

to plaque retention and chronic inflammation

of the periodontium.34

Between the marginal discrepancy and

inflammation of periodontal tissues, a signifi-

cant quantitative relationship for subgingival-

ly located crowns has also been document-

ed.34 More specifically, a strong correlation

was found between marginal discrepancy

and Gingival Index and also between mar-

ginal discrepancy and crevicular fluid volume

values, although no significant correlation

was established between marginal discrep-

ancy and pocket depth.

Crown material and the periodontiumThrough the literature search, 18 in vivo stud-

ies were found providing information on

plaque growth and accumulation relative to

crown material (Tables 5 and 6). Three stud-

ies employed a prospective design,57,97,98 two

of which were also identified as randomized

controlled studies.97,98 The rest of the studies

presented a retrospective design.

The first randomized clinical trial98 evaluat-

ed the performance of galvanoceramic

crowns placed in 52 patients with regard to

periodontal conditions. Scores for Plaque

Index, Gingival Index, gingival crevicular fluid

flow rate, and immunoglobulin G were signifi-

cantly lower for gingival tissues adjacent to

galvanoceramic crowns than metal-ceramic

crowns. More pronounced plaque accumula-

tion was also observed on metal-ceramic

surfaces compared with galvanoceramic sur-

faces during a period of 4 months to 4 years.99

In the second randomized clinical trial,97

conventional metal-ceramic crowns and

metal-free polymer crowns with or without a

glass-fiber framework were compared. After

1 year, polymer crowns with a fiber frame-

work showed a significantly higher plaque

accumulation and Gingival Index than metal-

ceramic crowns, a fact that points to the

drawbacks of fiber reinforcement. In con-

trast, no significant differences could be

observed between polymer crowns without

fiber reinforcement and metal-ceramic

crowns. However, with the polymer crowns,

the need for endodontic treatment and rece-

mentation was evident.

Disagreement exists in the literature over

whether metal-ceramic and all-ceramic

crowns elicit a more inflammatory response

from the periodontium than natural teeth.

Procera titanium crowns (Nobel Biocare),57

In-Ceram Spinell (Vita Zahnfabrik) and In-

Ceram Alumina crowns (Vita Zahnfabrik),100

IPS-Empress crowns (Ivoclar Vivadent),63 and

Dicor crowns (Dentsply)101 reportedly provide

lower scores for Plaque Index compared with

natural teeth. Still, in other studies,102,103 no

difference in plaque accumulation and

bleeding on probing between natural teeth

and Empress crowns or between natural

teeth and Dicor crowns could be observed.





Kosyfaki et a l

Crown material/(No. of crowns/ Observation Author(s) No. of patients) period Results/observations

Wise and Dykema (40 disks/10); Type III gold (10/10) 48 h Porcelain and acrylic resin have a lower plaque-197547 Gold alloy for veneering retaining capacity than type III gold. No statistically

with porcelain (10/10) significant difference was observed between the Porcelain (10/10),Acrylic resin (10/10) plaque-retaining capacity of acrylic resin and

porcelain. However, these conclusions may be valid for only the particular experimental conditions

Keenan et al 1980112 Gold (carborundum disk rubber 72 h Polished gold surfaces retained lower amountswheel, tripoli, rouge, sandblasting) of plaque than less well-finished gold surfaces.

Chan and Weber All-ceramics (50/19) 4 wk All ceramic crowns had the lowest plaque retention198645 Metal-ceramics (68/19) (lowest PI).

Cast gold (13/19) Acrylic resin veneer crowns had the highest plaqueAcrylic resinveneered crowns (19/19) retention (highest PI).Natural teeth

Shafagh 1986111 Gold (green stones, rubber wheels, bristle 72 h Highly polished crowns showed under a microscope brushes, tripoli, rouge) less plaque accumulation than hastily polished crowns.

Kpper and Bieniek Hi-Ceram crowns, version I (43/37) 21 mo Compared to metal-ceramic crowns, Hi-Ceram crown1989105 Hi-Ceram crowns, version II (89/37) margins (version I) showed increased porosity and

Metal-ceramic crowns (132/37) plaque accumulation, while Hi-Ceram margins (version II) showed less plaque accumulation.

Simonis et al 198999 (377/48); Resin-veneered (32/48) 4 mo to 4 y Galvanoceramic crowns showed the least plaque Metal-ceramics (104/48) accumulation (lowest PI) compared to natural teeth andAll-ceramics (14/48); Galvanoceramics (169/48) the other restorative materials. The PBI values of galvano-Cast gold (58/48); Natural teeth (465/48) ceramic crowns were higher than those of natural teethPontics (39/48) but lower than those of the other restorative materials.

Adamczyk and (17/10); Metal 24 h The largest amounts of plaque were found on metal, Spiechowicz 199044 Acrylic resin; Glazed porcelain a large amount of plaque was found on acrylic resin,

and a very low amount of plaque was found on porcelain.Jensen et al 1990101 Dicor (77/77); Natural teeth 4 y Dicor crowns showed less plaque accumulation and a

decrease in the mean PI compared to natural teeth.There was no statistically significant difference in BI andGI between Dicor crowns and natural teeth.

Castellani et al (disks/10); Dicor (shaded vs nonshaded) 48 h No statistically significant difference was observed1996104 Metal-ceramics (glazed vs nonglazed) between the plaque-retaining capacity of all-ceramic

and metal-ceramic surfaces. Glazed surfaces showed less plaque accumulation than nonglazed surfaces.

Sjgren et al 1999102 Empress (110/29); Natural teeth 3.6 to 3.9 y No significant difference was observed between Empress crowns and natural teeth with regard to the occurrence of plaque and bleeding on probing.

Sjgren et al 1999103 Dicor (98/46); Natural teeth 5.8 to 6.1 y No significant difference was observed between Dicor crowns and natural teeth with regard to the occurrence of plaque and bleeding on probing.

Lvgren et al Procera ceramicveneered titanium 5 y There was less plaque accumulation on the teeth with200057 crowns (242 single crowns and 91 FPDs/260) Procera titanium crowns than on the control teeth.

Natural teethBindl and Mrmann In-Ceram Spinell (19/21) 39 11 mo In-Ceram Spinell and In-Ceram Alumina showed lower 2002100 In-Ceram Alumina (24/21); Natural teeth plaque (PI) and bleeding scores (BI) than natural teeth.Gemalmaz et al IPS-Empress (37/20); Natural teeth 24.56 mo IPS-Empress showed less plaque growth (lower PI)200263 than natural teeth.Ohlmann et al (120/66); Polymer crowns 12 mo Polymer crowns with glass-fiber framework exhibited 200697 with glass-fiber framework (40/66) significantly higher plaque accumulation (higher PI) and

Polymer crowns without glass-fiber Gingival Index (GI) than metal-ceramic crowns. Betweenframework (40/66); Metal-ceramics (40/66) polymer crowns without fiber reinforcement and metal-

ceramic crowns there were no significant differences in PI and GI.

Table 5 In vivo studies in humans on the relationship between crown material and the periodontium





Kosyfaki et a l

Several studies comparing the plaque-

retaining capacity of metal-ceramics and all-

ceramics proved contradictory. While in one

study no statistically significant difference

was clinically found,104 in another study Hi-

Ceram margins were reported to be porous

and more plaque retentive than metal-ceram-

ic margins.105 In the absence of meticulous

oral hygiene, it was shown in an animal

model that more plaque accumulates on

metal-ceramic crowns than on all-ceramic

ones.106

Just as important as the material is the

surface roughness. Surface roughness does

not in itself exert irritant effects on the peri-

odontal tissues; rather, it influences the

amount of adhesion of plaque compo-

nents.1,3,5,42,107 It has been documented that

glazed porcelain provides a smooth, glossy,

and dense, well-wetted surface108,109 with low

plaque-retaining capacity. As an alternative to

glazing, polishing has also been proposed

because it produces an equally smooth sur-

face and better-controlled surface luster.109,110

Apart from porcelain, polished gold surfaces

retain lower amounts of plaque than less

well-finished gold surfaces.111,112

Crown contour and the periodontiumThe literature review revealed six in vivo stud-

ies reporting on external crown morphology

(Tables 7 and 8). All the studies gave evi-

dence that overcontouring may produce an

adverse effect on the periodontal tissues.

Overcontouring the buccal and lingual sur-

faces of a crown113117 is associated with

increased plaque accumulation at the gingi-

val margin,116,118 increased scores for the

Plaque Index and Gingival Index, as well as

increased gingival crevicular fluid flow and

pocket probing depths. In addition, an

increased loss of clinical attachment levels

might be observed, indicating the coronal

migration of the periodontal attachment.117

Nonetheless, with professional oral hygiene,

periodontal health may be only slightly

affected by overcontoured crowns.117

Crown material/(No. of crowns/ Observation Author(s) No. of patients) period Results/observations

Davidi et al 200746 (26/1); Self-cured acrylic resin (polished, 12 h Significantly less biofilm was observed on the crownspolished and coated with bonding agent, coated with bonding agent, whereas no biofilm waspolished and coated with light cured observed on the crowns coated with liquid polish. liquid polish) Bonding resin or liquid polish coatings significantly

reduce early biofilm formation, which in turn might influence the overall plaque accumulation on provisional restorations.

Weishaupt et al (104/52); Metal-ceramics (52/52) 24 mo Gingival tissues adjacent to galvanoceramic crowns200798 Galvanoceramics (52/52) showed significantly less pronounced clinical and inflam-

matory reaction as shown by their lower PI, GI, Rec,CFFR, and IgG values, compared to metal-ceramic crowns.

(PI) Plaque Index; (PBI) papillary bleeding index; (BI) Bleeding Index; (GI) Gingival Index; (Rec) recession; (CFFR) crevicular fluid flow rate; (IgG)immunoglobulin G.

Table 5 In vivo studies in humans on the relationship between crown material and the periodontium (continued)

Crown material/ ObservationAuthor(s) (No. of crowns/No. of animals) period Results/observations

Riley et al 1983106 All-ceramic crowns (20/4) 6 mo In the absence of oral hygiene, the plaque accumulation wasMetal-ceramic crowns (20/4) greater for the metal-ceramic crowns than for the all-ceramic ones.

Table 6 In vivo studies in animals on the relationship between crown material and the periodontium





Kosyfaki et a l

Overcontouring the interproximal areas of a

crown results in localized inflammation of the

interdental gingival papillae,2,13,37,119 which nor-

mally protrude from the buccal and lingual

sides into the interdental spaces.120 Acces -

sibility to oral hygiene measures6,13,113,115,120 under

such conditions is, of course, extremely limited.

Overcontouring occurs mainly because of

inadequate tooth preparation2,9,22,48 buccally,

lingually, and interproximally.50 Overcontouring

may also occur with overbuilding10 of the

restoration because the gingival tissues near

the margin were removed in trimming the dies

to better finish the margin.2,37

Conversely, undercontouring may favor

periodontal health,114,116 compared with over-

contouring,1 because neither clinical nor

microscopic alterations in the gingival area

have been noted with undercontoured buc-

cal and lingual surfaces of crowns. Indeed a

slightly larger-than-normal interproximal

embrasure may be desirable because it

ensures sufficient space for the papilla and

simultaneously facilitates effective plaque

control.1,121 However, excessively open inter-

dental contacts are responsible for food

impaction or phonetic and esthetic prob-

lems.12,50,120

Crown contourObservation

Author(s) No. of crowns/No. of patients Alteration in contour period Results/observations

Sackett and Natural teeth Overcontouring of axial and buccal 4249 Overcontoured teeth showed gingival Gildenhuys 1976113 (42 pairs/12) third facings made of acrylic resin d inflammation and greater production of

No overcontouring gingival sulcular fluid than natural teeth.Ehrlich and Provisional Overcontouring: +1 mm 4 mo A variation in contour in the range of Hochman 1980130 splinted Undercontouring: 1 mm 1 mm is tolerated by the gingival tissues.

crowns (8/4)Parkinson 1976114 Cast metal (25/NR) Overcontouring: 0.31.1 mm NR Overcontoured cast metal and metal-

Metal-ceramics (25/NR) Overcontouring: 0.21.6 mm -ceramic crowns exhibited greater meanNatural teeth No overcontouring plaque accumulation than natural teeth.

Sundh and Khler Procera titanium crowns Emergence profile angle: 9 d An emergence profile of 10 degrees is2002115 (7/6) 10 degrees more accessible to oral hygiene than

Emergence profile angle: 20 degrees emergence profiles of 20 degrees and Emergence profile angle: 40 degrees. However, even a 40-degree 40 degrees emergence profile formed less plaque

Natural teeth No overcontouring than natural teeth.

(NR) Not reported.

Table 7 In vivo studies in humans on the relationship between crown contour and the periodontium

Crown contourObservation

Author(s) No. of crowns/No. of patients Alteration in contour period Results/observations

Perel 1971116 Natural teeth/ Overcontouring by applying 9 wk Overcontoured teeth showed gingival 6 mongrel dogs cold-cured acrylic resin hyperplastic inflammatory changes.

Undercontouring by removing Undercontoured teeth showed no signs oftooth structure inflammation.

Kohal et al 2003117 24 cast crowns made of Overcontouring: 50 degrees 5 mo The 30-degree and 50-degree over-high-noble alloy/ Overcontouring: 30 degrees contour groups provided higher values for4 beagle dogs PI, GI, GCFF, PD, and CAL. For the normalNatural teeth Normal contour contour and control group only minor

No overcontouring changes were recorded.

(PI) Plaque Index; (GI) Gingival Index; (GCFF) gingival crevicular fluid flow; (CAL) clinical attachment level; (PD) probing depth.

Table 8 In vivo studies in animals on the relationship between crown contour and the periodontium





Kosyfaki et a l

DISCUSSION

The purpose of the present literature review

was to critically evaluate and present up-to-

date data on crowns and periodontal tissues.

The search process revealed 64 in vivo inves-

tigations conducted on human and animal

subjects, dealing with the location of the

crown margin, marginal fit, crown material,

and crown contourfactors closely interrelat-

ed to one another and to periodontal health,

as well. Despite the large number of identi-

fied studies and the significant new develop-

ments in materials and techniques, it can be

concluded that well-established knowledge

and/or perspectives, and consequently the

clinical approach and orientation, remained

unchanged over a long period of time.

Most studies21,55,56,59,61,63,67,69,70 demonstrate

clearly the advantage of the supragingival

location of the margin, which enables not

only the validation of accuracy of fit but also

the future evaluation of marginal deteriora-

tion.91 Surprisingly, only one study in the ani-

mal model describes unfavorable histologic

conditions with supragingival margins.68

However, it is not mentioned if the crowns

before insertion were clinically or radiograph-

ically controlled with respect to their fit.

Of particular importance is the intracrevic-

ular placement of the crown margin27,77,79 in

the anterior esthetic zone (maxillary incisors

up to the first premolar).122 This can success-

fully mask the visible marginal transition

between crown and tooth, achieving opti-

mum esthetics.123 For the posterior region,

where esthetics do not play a predominant

role, a supragingival margin should be pre-

ferred to an intracrevicular margin.67,77

Nonetheless, it must be taken into consider-

ation that, in most of the cases of intracrevic-

ularly placed margins, proper finishing of the

margin,9,48 adequate impression making,27

accurate fabrication of the provisional

restoration, thorough removal of all cement

remnants, or even moisture control during

cementation123 are difficult to attain.8,9,24,73

Therefore, even given a highly precise fitting

of the crown,60,69 an intensive oral hygiene

regimen must also be executed in the case

of an intracrevicular margin to control

prospective gingival inflammation.4,58,60,66,74

Moreover, the available tooth structure is

often compromised due to caries, insufficient

preexisting restorations, fractures, cervical

abrasion, or attrition.8,1012,17,18,37,48,79,85 To obtain

adequate abutment height, many clinicians

extend the margin below the free gingival

crest. To avoid the subgingival extension and

consequently a possible impingement on the

biologic width, crown lengthening proce-

dures, involving gingivectomy, osseous sur-

gery with surgical removal of supporting alve-

olar bone, and forced orthodontic eruption,

are recommended.1012,14,18,84,85,124,125

The marginal fit of a crown has long been

a controversial topic. Apart from the theoreti-

cal requirements of cementation lines rang-

ing between 25 and 40 m,126 which are sel-

dom fulfilled clinically, the minimum detec -

table gap for a crown margin has been

proposed to be 20 m,31 50 m,127 or in a

range between 50 m and 100 m.40,41

Further more, a 5-year clinical study62 of more

than 1,000 restorations indicated that a gap of

120 m or less can be clinically acceptable.

According to the review results, metal-

ceramics and all-ceramics exhibit sufficient

accuracy of fit.89,90,9395 It is remarkable, how-

ever, that no in vivo investigations have been

identified through the review process that give

exact measurements in micrometers of the

marginal fit of contemporary ceramic materi-

als.128 In fact, two studies89,90 reported on

Procera AllCeram (Nobel Biocare), and three

studies9395 provided data concerning ceram-

ic systems that appeared on the market 20

years ago but are no longer in clinical use.

Many studies44,45,57,63,100104 came to the

conclusion that ceramic materials offer the

benefits of proven biocompatibility and

reduced propensity for retaining bacterial

plaque. Therefore, apart from the optical and

physical properties of porcelain materials

guaranteeing good esthetics and function,

their low plaque-retaining capacity makes

them to this day the material of choice as

both veneering and core ceramics.

Crown contour may clinically compensate

for an undesirable soft tissue deficiency. In

patients in need of prosthetic rehabilitation

but with a history of advanced periodontal

disease, the distance between the bone level

and the approximal contact point is larger





Kosyfaki et a l

than 5 mm, which means that the gingival

papillae do not completely fill the interdental

space below the approximal contact point.54

Consequently, visible triangular spacesthe

so-called black triangles117,124 emerge, com-

promising esthetics of the smile.129 In this

case, always respecting the emergence pro-

file, a slight extension of ceramic can be

made.48,51 To avoid the appearance of an

overbulked, rounded tooth,10,51 porcelain of

higher chroma should be used. The proximal

contact point becomes an interdental con-

tact line while the shape of the crown

remains unchanged. As a matter of fact, only

a slight variation in crown contour of less

than 1 mm of the original contour may be tol-

erated well by the periodontal apparatus.130

CONCLUSIONS

The data presented confirm results already

known from the literature and reveal that noth-

ing in essence has changed. The supragingi-

val location of the crown margin is the most

advantageous from the periodontal point of

view. The intracrevicular location is indicated

in the anterior zone for esthetic reasons.

Metal-ceramic and all-ceramic crowns show a

clinically acceptable marginal fit. Ceramic

materials have the lowest plaque-retaining

capacity. A normal contour of the crown con-

tributes significantly to establishing and main-

taining favorable periodontal conditions.

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