1

Master of Medical Science

with a major in Odontology

Institute of Odontology

Stockholm 2008

Effect of crown margin position on

periodontal tissue conditions. A systematic review and clinical interpretations.

Farid Akhlaghi

Tutor: Professor Jan Wennström

Department of Periodontology

University of Gothenburg

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Effect of crown margin position on periodontal tissue conditions.

A systematic review and clinical interpretations.

Abstract:

The present study aimed at determining the effect of crown margin position on surrounding

periodontal tissues. Searches in PubMed and Cochrane libraries from 1965 up to September

2008 were conducted. Additionally, reference lists of selected papers were hand searched for

further relevant articles. All types of studies were included, but priority was given to

randomized controlled trials (RCT). The search was limited to articles in English and

Swedish language. The search identified a total of 392 titles. Titles and abstracts were

independently screened by two reviewers (FA & JD) to identify publications that met the

inclusion criteria. The kappa score for agreement was 77,8%. Twenty-one studies were

included in the review. Study quality was assessed according to the SBU criteria[1]. Studies

varied markedly in the selection of patients and methodology. Intracrevicular depth of crown

margin position was frequently not reported. The results from included studies showed that

placement of crown margins subgingivally increase gingival inflammation (Evidence grade

3). However, relationship between depth of crown margin position and severity of

inflammation could not be confirmed. The scientific evidence for potential effect of

subgingival crown margins on periodontal attachment and bone levels was insufficient for

any conclusion.

Clinical relevance: Based on the reviewed literature, crown margins should preferably be

placed in a supragingival position in order to favour maintenance of periodontal health.

Key words; crowns; gingivitis; alveolar bone loss; periodontal attachment loss; periodontium; prosthodontics; systematic review.

3

Effekten av kronskarvens placering på de

parodontala vävnaderna. En systematisk översiktsartikel med kliniska överväganden.

Sammanfattning:

Syftet med denna systematiska översiktsartikel var att studera effekten av kronskarvens

placering på angränsande parodontala vävnader. Sökningar i PubMed och Cochrane-

biblioteken från 1965 fram till september 2008 genomfördes. Dessutom genomsöktes de

beställda artiklarnas referenslistor för att identifiera ytterligare relevanta artiklar. Alla typer

av studier var inkluderade i granskningen, men randomiserade kontrollerade studier (RCT)

prioriterades. Sökningen var begränsad till artiklar på engelska och svenska. Sammanlagt

identifierades 392 artiklar. Titlar och abstrakt var oberoende granskade av två tandläkare (FA

& JD) för att identifiera publikationer som uppfyllde inklusionskriterierna. Kappa-värdet för

överensstämmelse var 77,8%. 21 artiklar inkluderades i studien. Studiernas kvalitet

bedömdes enligt SBU´s kriterier. Studierna skiljde sig markant åt i urvalet av patienter och

metodik. Ofta rapporterades inte djupet av kronskarvens läge i förhållande till den marginala

gingivan. Resultaten från inkluderade studier visade att subgingivalt placerade kronor ger

upphov till ökad gingival inflammation (Evidensstyrka 3) men förhållandet mellan graden av

inflammation till djupet av kronskarvens placering kunde inte bekräftas. Det vetenskapliga

underlaget avseende potentiell effekt av subgingivalt placerade kronskarvar på parodontal

fästenivå och bennivå var otillräckligt för att konstatera några definitiva slutsatser.

Klinisk relevans: Baserat på genomgången litteratur, bör kronskarvar företrädesvis placeras

supragingivalt för att kunna optimera upprätthållandet av parodontal hälsa.

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1.Introduction:

The goal of all prosthetic treatment is to obtain a satisfying functional and esthetical oral

status. Successful treatment outcome following prosthetic treatment relies on healthy hard

tissues but also on healthy soft tissues. Side effects as a result of the treatment may arise

during the prosthetic rehabilitation, for example because of the preparation and its location[2].

Preparation types may differ in a number of ways, due to factors related to type of tooth,

clinical crown height and position, tooth vitality, the degree of remaining tooth substance and

specific aesthetic needs. Positioning of restorative margins, with relation to both the gingival

and the osseous tissues, has long been a source of controversy in periodontics, and in dentistry

as a whole. Two different principles have been discussed in the literature. The first one

recommended that the preparation should be placed subgingivally [3], and the second one

proposed location of the preparation at or above the gingival crest[4]. G.V.Black [3]

advocated a scientific approach regarding cavity preparation and design. The concept of

"extention for prevention" was one of the principles recommended. As long ago as 1930 this

concept was attacked by Gottlieb & Orban[4]. They argued that the concept of "extention for

prevention" was harmful to the periodontal tissues. This argument was further investigated by

Löe et al[2], who also stated that "the concept of extention for prevention" was wrong and

outdated. In recent years the biological aspects of fixed reconstructions have received a lot of

attention. The concept of biological width was first put forward by Ingber et al.[5], who

defined it as ‘the minimum width at the gingival sulcus required to maintain a normal gingival

attachment. This definition was based on Garguilo’s study [6] of post-mortem specimens.

Their research documented that there is a proportional dimensional relationship within a small

range, ± 0.5 mm, between the dentogingival junction and the other supporting tissues of the

tooth; namely, between the crest of the alveolar bone, the connective tissue attachment, the

junctional epithelium, and sulcus depth. In their study, a total of 325 measurements were

5

taken from clinically normal specimens. The authors noted a great consistency in the

dimensions of the various components: (1) the sulcus depth was 0.69 mm, (2) the junctional

epithelium was 0.97 mm, and (3) the connective tissue attachment averaged 1.07 mm. The

combined dimension of the connective tissue attachment and the junctional epithelium,

therefore, averages 2.04 mm and has been considered as the “biological width”. These two

zones form a biologic seal around the neck of the tooth, that acts as a barrier to help prevent

migration of microorganisms and their products into the underlying gingival connective tissue

and supporting alveolar bone. Eissman et al. [7] recommended that restorations should not be

placed at or near the alveolar crest and that there must be 2 mm of root surface between the

alveolar crest and the restoration to provide for the biologic width. Wilson and Maynard [8]

stated that “… some distance of unprepared tooth structure should remain between the finish

line of the prepared tooth and the junctional epithelium .…. this distance ideally should be 0.5

mm….” .

It has been suggested that extension of tooth preparation apical to the base of the histological

crevice will violate the biologic width, and will disrupt the biologic seal. This extension might

allow bacteria and their products to penetrate the underlying connective tissue and alveolar

bone. The purpose of this systematic review was to study the effect of crown margin

positioning on surrounding periodontal tissues. In addition, some clinical cases illustrating the

issues discussed are presented.

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2- Material and methods:

A literature search for relevant articles was performed, using the PubMed and Cochrane

libraries. Additionally, reference lists of relevant articles were hand searched. All types of

studies were included, but priority was given to randomized controlled trials (RCT). Review

articles were not included, but were used to find further relevant studies. For articles that

explored the same material, the most recent report was used. The results of a study had to be

applicable to the question posed, i.e., appropriate outcome measures, follow-up period and

study design. The outcome measures for various methods reflected changes in the degree of

inflammation, clinical attachment loss and bone loss. Conclusions were based on studies that

were judged to be of moderate or of high value, as described by SBU´s guidelines [1].

2.1. Search strategy and study selection;

A literature search was conducted in MEDLINE (PubMed) and the Cochrane Central Register

of Controlled Trials (CENTERAL) from 1965 up to September 2008. The search was limited

to articles in English and Swedish language. Different combinations of relevant keywords

were used to identify articles. The detailed search strategy with the keywords used was as

follows;

"Crowns"[MeSH] AND "Gingivitis"[MeSH], 160 articles, (97 articles were in English, 1

article in Swedish).

"Crowns"[MeSH] AND "Alveolar Bone Loss"[MeSH], 161 articles, (151 articles were in

English, none were in Swedish).

"Crowns"[MeSH] AND "Periodontal Attachment Loss"[MeSH], 20 articles, (all in English,

no articles in Swedish).

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"Crowns"[MeSH] AND "Periodontium"[MeSH] AND "Periodontal Diseases"[MeSH], 222

articles, (163 articles were in English, none were in Swedish).

"Crowns"[MeSH] AND "Dental Prosthesis"[MeSH] AND "Periodontium"[MeSH] AND

"Tooth Preparation, Prosthodontic"[MeSH] AND "Prosthodontics"[MeSH], 24 articles, (23

articles were in English, none were in Swedish).

The Cochrane Central Register was searched, using the following combinations: “crowns and

periodontal attachment loss”, “crowns and gingivitis”, “crowns and bone loss”, “periodontal

and prosthetic”, “periodontium and crowns”, (34 articles were found, all in English).

Figure 1 describes the process of identifying the included studies from an initial yield of 392

titles. Titles and abstracts were independently screened by two reviewers (Farid Akhlaghi &

Jan Derks) to identify publications that met the inclusion criteria. A total of 45 articles were

identified. Kappa score on agreement was 77.8%. All disagreements were resolved by

consensus discussion after examining the abstracts. The final sample included 38 articles

which were evaluated in full text by one reviewer (FA). Additional searches of reference lists

resulted in 14 articles. These articles were also ordered in full text and were studied, rendering

a total of 52 articles, from which 21 articles were included in the study.

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Figure 1; Search strategy

2.2. Reviewing and Assessing a Study’s Quality:

For assessing the quality of articles, an assessment protocol was used as described in table 4.

Quality assessment of the studies was done using criteria according to SBU [1]. The protocol

formed the basis of compiling data on a study’s design and findings, to assess its quality. The

reviewer (FA) judged the quality of each study as high, moderate or low. The results were

presented in different tables (Table 1 and 2).

Electronic search 392 articles with titles and abstracts

Independent evaluation by 2 screeners 45 articles identified (Kappa score 77.8%)

7 articles discarded after consensus discussion

Included for full text, 38 articles

Total full text, 52 articles

31 articles excluded (Table 3)

Further handsearching, 14 articles

Final number of studies included 21 (Table 1 and 2)

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A study was considered to be of high value if:

¤ RCT with a well-defined study population.

¤ Adequate outcome measures.

¤ Adequate statistical analysis.

¤ Performed and presented test for the reliability of the survey methodology, and evaluators

agreement.

¤ Power calculation.

¤ Adjusted for / discussed confounders.

¤ The outcomes were assessed by blinded evaluators.

¤ Explained / analyzed drop outs.

Moderate value:

A study was considered to have a moderate value if it did not meet all the requirements for a

study of high value but neither had the characteristics of studies with low value.

Low value:

¤ The intervention and control group were not comparable.

¤ Lack of adequate analysis in regard to study aim.

¤ The population was not well defined.

¤ Large number of, or unexplained drop outs.

¤ Further important confounders, other than those reported, were suspected.

¤ Systematic distortion of the results could be suspected.

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2.3. Rating the Report’s Conclusions According to Evidence Grade:

The scientific evidence (evidence grade) for each conclusion was rated as strong (1),

moderately strong (2), limited (3) or insufficient depending on the quality of the studies

assessed.

¤ Strong scientific basis (Evidence grade 1).

At least two studies of high value among the total scientific evidence. If some studies are at

variance with the conclusion, the evidence grade may be lower.

¤ Moderately strong scientific basis (Evidence grade 2).

One study with high value and at least two studies with moderate value among the total

scientific evidence. If some studies are at variance with the conclusion, the evidence grade

may be lower.

¤ Limited scientific basis (Evidence grade 3).

At least two studies with moderate value among the total scientific evidence. If some studies

are at variance with the conclusion, the evidence grade may be lower.

¤ Insufficient scientific basis (Other evidence).

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3- Results:

3.1. Subgingival crown margins increase gingival inflammation (Evidence grade 3).

The literature search resulted in 19 selected studies in which increased gingival inflammation

could be related to the subgingival placement of the crown margin. Four studies were

considered to be of moderate value [9-12] (Table 1) and fifteen studies of low value [13-27]

(Table 2). Sixteen studies showed that there was a greater degree of inflammation around

crowns with subgingival margins [9-12, 14-18, 20-25, 27]. Two studies of low value did not

demonstrate any clear relationship between subgingival placement of the crown margin and

the degree of inflammation [19, 26]. In the first of these two [26] (Table 2), the relationship

between the location of crown margins and gingival inflammation was examined on 12

molars with one half of the facial margin being supragingival and the other half subgingival.

No difference in gingival health was found using Löe’s Gingival Index to assess gingival

tissue reaction. The authors reported no differences in terms of sulcus depth, gingival contour,

or plaque accumulation. It was concluded that fit and finish of full crown restorations may be

more important to gingival health than the location of the finish line. However, the

intracrevicular depth of the preparation was not reported in this study. In the second article of

the two mentioned above [19] (Table 2), forty-six full crown restorations in 28 patients were

evaluated according to gingival margin placement, to determine if there was a difference in

gingival inflammation. In this study, highly motivated patients from a private practice were

selected and the results did not show any difference between supragingival and subgingival

crown margins. Furthermore, in an additional study of low value, crown margins located just

at the gingiva had more inflammation compared to both supra- and subgingival crown

margins [13] (Table 2).

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The scientific evidence grade 3 for the statement “Subgingival crown margins increase

gingival inflammation” is based on four studies of moderate value, according to the previous

description. A short summary of these four studies is as follows:

Studies of moderate value. (Table 1)

Four studies of moderate value [9-12] indicated a greater degree of inflammation around

crowns with subgingival margins. In a randomized 1-year clinical trial by Reitemeier [12]

(Table 1), the impact of posterior crown margin placement on gingival health was

investigated. 10 dentists examined 240 patients with 480 metal ceramic crowns. Results from

this study indicated that supragingival placement significantly lowered, and subgingival

placement significantly increased the probability of bleeding compared with control teeth.

The authors were able to demonstrate that the risk of bleeding around subgingival crown

margins was approximately twice as high compared to similar crowns with supragingival

crown margins (Odds ration 2,2). In a prospective 2-year clinical investigation by Gunay et

al.[11] (Table 1), 116 teeth were followed after crown therapy. Results from this study

showed that PBI (papillary bleeding index) was higher in the group of patients that had crown

margins placed subgingivally, and the authors concluded that the location of the restoration

margins within the zone of biologic width may impair periodontal health. In a 1-year

prospective clinical study by Flores-de-Jacoby et al. [9] (Table 1), the effects of crown margin

location on periodontal health were studied 6–8 weeks and 1 year post insertion. In this study

a total of 693 surfaces of crowned teeth were examined, out of which 135 had the crown

margin at the gingival crest, 415 showed a supragingival and 143 a subgingival margin. The

results from this study showed that subgingival location of crown margins provided the

highest scores of Gingival Index. In a 15-year longitudinal study by Valderhaug et al [10]

(Table 1), a total of 102 patients with 108 fixed bridges were followed over 15 years. Gingival

Index scores 2 and 3 were more frequent in the group that had received crowns. This was

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even more pronounced around crowns with subgingival placement. Valderhaug [28, 29]

reported similar results in previous studies from 1976 and 1980.

3.2. The scientific evidence is insufficient to support the statement “the deeper the

placement of the crown margin, the higher the degree of inflammation”.

Three studies were identified that addressed the question of whether the depth of subgingival

margin placement relates to the degree of gingival inflammation. One study was of moderate

value [11] (Table 1) and two of low value [14, 17] (Table 2). All these three studies indicated

that the deeper the placement of the crown margin, the higher the degree of inflammation.

The only study that could be considered for evidence assessment was an investigation by

Gunay [11]. It was a prospective 2-year clinical trial, in which PBI (Papillary Bleeding Index)

was analyzed before, and 3, 6, 12 and 24 months after crown therapy on 116 teeth. After

preparation, the distance between the restoration margins and the alveolar crest was

registered. Teeth were divided into 3 groups: Group 1, less than 1 mm between crown margin

and alveolar bone, Group 2, 1-2 mm and Group 3, more than 2 mm. The highest PBI increase

was noted in Group 1. The most significant increase in Group 1 was observed between 3 to 6

months after preparation.

The scientific evidence for the statement “The deeper the placement of the crown margin, the

higher the degree of inflammation” is therefore graded as insufficient, because no more than

one study with moderate value was identified.

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3.3. The scientific evidence of the effect of crown margin placement on periodontal

attachment and bone levels is insufficient for any conclusion.

Five studies were identified that described the relationship between crown margin location

and changes in attachment level. Two of these studies were of moderate value [11, 30] (Table

1) and three of low value [21, 25, 31] (Table 2). In one study of moderate value [11] (Table 1)

marked loss of attachment did not occur during a 2-year examination period. A second study

of moderate value [30] (Table 1) showed that intracrevicular crown placement resulted in

attachment loss despite careful supportive therapy. In this study, crowned teeth had an

average of 0.71 mm more attachment loss than control teeth during a 12-month period.

However, the author pointed out that the observed attachment loss at crowned teeth was

probably not of clinical relevance.

In a 26-year longitudinal study by Schatzle [32], the relationship between dental restorations

and periodontal health was investigated in 160 patients. This study suggested that the

increased loss of attachment found in teeth with subgingival restorations started slowly, and

could be detected clinically 1 to 3 years after the fabrication and placement of the restorations.

Since this study included only fillings and not crowns, it was excluded, and could not be

considered for evidence assessment.

Attachment loss in connection with subgingival crown margins was also reported in two

studies by Valderhaug [28, 29]. Both of these studies showed slightly higher attachment loss

around subgingival crown margins after five and ten years when compared to teeth with

margins at or above the gingival crest. Mean differences in clinical attachment levels were

found to be 0.7 mm after ten years [29]. However, the author did not provide significance

testing. In a 15-year follow-up of the same material [10] (Table 1), no analysis was found

regarding changes in attachment level. Because of the inadequate analysis, the studies [28, 29]

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were excluded and could not be considered for evidence assessment of attachment level

changes.

When evaluating changes in bone level, three studies were identified which discussed the

relationship between subgingival crown margins and bone loss [10, 11, 31]. Two studies were

found to be of moderate value [10, 11] (Table 1) and one of low value [31] (Table 2). Based

on histological observations, Tarnow et al. [31] (Table 2) showed a correlation between

subgingival crown margins and bone loss. The two remaining studies failed to show any

relationship using intraoral radiographs [10, 11]. One of them was a 15-year longitudinal

study by Valderhaug [10] (Table 1), in which the bone loss could not be related to the location

of the crown margin at the time of placement. In another study by Gunay [11] (Table 1), no

alterations of bone levels could be diagnosed on radiographs during the 2 years of

investigation. It is important to note that standardized techniques are necessary to guarantee

comparable radiographs, and due to the fact that these studies had different designs, it was

impossible to draw any conclusions regarding the changes in bone level.

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4- Discussion:

The limited number of studies in the analysis, and the diversity of the approach in determining

the influence of crown margins on periodontal tissue health, have made meaningful synthesis

of the evidence difficult. No study of high value could be found. Only a few studies of

moderate value were identified and most studies that could be related to the issue were of low

value (Table 1 and 2). However, several of the selected studies concluded that subgingival

crown margin could contribute to gingival inflammation [9-12, 14-18, 20-25, 27]. Statistically

significant differences in regard to mean Löe and Silness Gingival Index (GI) values between

crowned and control teeth were observed in several patient populations. It is important to note

that GI values are an ordinal value, which means that a greater index value is correlated with

increased inflammation. Since the data is not continuous, a score of 2 does not mean that the

periodontal tissue was twice as inflamed as a score of 1. This must be taken into account in

order to reduce the risk of "bias". In a 15-year longitudinal study by Valderhaug et al. [10]

(Table 1), the authors described the relationship between gingival inflammation and the crown

margin placement by reporting the results in terms of frequencies of index score, and thus

reduced the risk of "bias".

Another consideration is that the term “subgingival” refers to the placement of a restoration

margin between the free gingival margin and the alveolar crest. Wilson and Maynard [8]

created the term “intracrevicular restorative dentistry.” It is defined as placement of

restorative margins within the gingival sulcus and above the junctional epithelium or

epithelial attachment. Because the term “subgingival” often refers to margins extending

beyond the gingival crevice, the term “intracrevicular” is more suitable to use. However, in

most studies factors such as intracrevicular depth of crown margins were frequently not

reported. Only three studies could be identified that investigated the effect of crown margin

depth on periodontal health [11, 14, 17]. In a study by Newcomb [17], 59 patients with 66

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anterior veneer crowns, with subgingival labial margins, were examined. The results from this

study showed that the degree of inflammation was related to the location of the crown margin.

There was a clear negative correlation between gingival inflammation and the distance of the

crown margin from the base of the crevice, and a strong positive correlation between gingival

inflammation and the distance of the crown margin below the gingival crest. Deeper

placement of the crown margin resulted in more gingival inflammation. Since this study was

cross-sectional, it was excluded, and could not be considered for evidence assessment.

When evaluating gingival inflammation and changes in attachment and bone levels, variables

such as initial health of the periodontium, intracrevicular depth of the restoration and

adaptation of the restoration margin are important factors for accurate assessment of the

outcome. Frequently, studies failed to report the exact techniques how these were assessed. In

addition, side effects of the prosthetic treatment per se might have significant influence.

Periodontal tissues may be affected by the preparation of the tooth, impressions,

provisionalization and cementation. It is also important to note that teeth generally have

received extensive direct restorative therapy that may have included intracrevicular

restorations before crown therapy. It is therefore suggested that future clinical investigations

document the tooth´s restorative history and initial periodontal status, so that each crowned

tooth serves as its own control. A further consideration is that a small but statistically

significant difference in terms of clinical attachment and bone levels may be of minor or no

clinical relevance. Some studies [10, 11] have evaluated bone levels based on radiographic

findings. Standardized radiographic methods are a prerequisite to properly assess these, but

were not always used. This may question the validity of the reported results.

The aim of the present study was to evaluate the effect of crown margin positioning on

surrounding periodontal tissues. The situation around implants might be considered as

somewhat similar to crowned teeth. The dimension of the peri-implant mucosa has been

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demonstrated to resemble that of the gingiva around teeth and includes a junctional epithelium

and a connective tissue compartment [33, 34] In so-called 2-part implants, the

abutment/fixture borderline is located in the connective tissue portion, and several studies

have shown that the gap between the intraosseous and transmucosal components have a

detrimental effect on the surrounding connective tissue and marginal bone level [35-39]. The

smaller the gap, the closer the position of the marginal bone to the abutment-implant

interface[40-43]. This condition does not exist around natural teeth and therefore a

comparison is not possible from this point of view between teeth and implants. The conditions

around subgingival crown margins are more comparable to submucosally placed implant

crown margins, because most likely both interface the epithelium. Little is known about the

effect of implant crown margin positioning on surrounding peri-implant tissues. Some studies

have shown that in patients with appropriate oral hygiene, the intracrevicular position of the

restoration margin did not appear to adversely affect peri-implant health [44, 45], while SBI

score (sulcus bleeding index) decreased as the location of a crown margin went from sub- to

supragingival position [46]. In addition, cement-retained crowns revealed a consistently

higher degree of sulcus bleeding than screw-retained crowns [46]. Further research is

necessary to understand the effect of implant crown margins on peri-implant tissues.

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5- Conclusion:

¤ Evidence suggests that subgingival crown margins increase gingival inflammation

(Evidence grade 3).

¤ The scientific evidence is insufficient to support the statement “the deeper the placement of

the crown margin, the higher the degree of inflammation”.

¤ The scientific evidence of the effect of crown margin placement on periodontal attachment

and bone levels is insufficient for any conclusion.

Based on the reviewed literature, crown margins should preferably be placed in a

supragingival position in order to favour maintenance of periodontal health. Subgingival

margin placement, however, may not always be avoided. If this is the case, care must be taken

to involve as little of the periodontium as possible.

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Table 1: Articles of strong and moderate value

Authors

Year

Type,

Duration

Sample Outcome

variables

Results Evidence

Flores-de-

Jacoby et

al.[9]

1989

Prospective

1-year clinical

study

19 pat.

693 teeth

PI

GI

PD

Subgingival crown margins resulted in highest

scores of GI.

GI at margins ending subgingivally > at the gingival

margin> supragingivally

Moderate

Valderhaug

et al.[10]

1993

Longitudinal

study, 15 years

102 pat.

108 bridges

PI

GI

PD

Bone level

GI scores 2 and 3 more frequent in crowned

teeth, mainly when the crown margins are located

subgingivally.

No statistical differences in bone loss between

control and crowned teeth.

Moderate

Changes in

attachment levels

reported in previous

studies in 1976 and

1980.

Gunay

et al.[11]

2000

Prospective

2-year clinical

study

41 pat.

116 prepared

teeth

HI

PBI

PD

PAL

Bone level

PBI higher at subgingival crown margins, the

deeper the placement the higher the increase of

PBI (mainly during first 6 months).

Attachment loss did not occur in any group. No radiographic alterations of bone levels.

Moderate

Reitemeier

et al.[12]

2002

RCT,

1 year

240 pat.

480 metal ceramic

crowns

PI

SBI

Subgingival crown margins increase the

probability of gingival inflammation.

SBI twice as high as at intrasulcular posterior

crown margins compared with supragingival

margins.

Moderate

Koke

et al.[30]

2003

Prospective

1-year clinical

study

11 pat.

44 teeth,

Uncrowned

controls

CAL

Ging.

recession

Crown placement was identified as a major factor

for attachment loss and development of gingival

recession.

Observed attachment loss probably not of clinical

relevance.

Moderate

( PI= Plaque Index, HI=Hygiene Index, GI= Gingival Index, PD= Probing Depth, CAL= Clinical Attachment Level, PBI= Papillary

Bleeding Index, GCF= Gingival Crevicular Fluid)

21

Table 2: Articles of low value

Authors Type,

Duration

Sample Outcome

variables

Results Evidence

Larato[27]

1969

Cross-sectional 268 pat.

546 teeth

Gingivitis More gingivitis around subgingival margins. Low

Marcum

[13]

1967

Histological

animal study,

3 months

66 gold crowns in

6 dogs

Gingival

inflammation

(Different

histological

parameters)

Highest rate of inflammation with margins

located above and below the gingival crest. Least

inflammation with margins located at the gingival

crest.

Low

Karlsen

[14]

1970

Histological

animal study,

2-12 months

2 dogs and

3 monkeys

Gingival

inflammation

Decrease of gingival integrity with subgingival

placement.

More risk for inflammation with deeper

preparation and less accurate fit of crowns.

Similar gingival conditions around supragingval

restorations and unoperated teeth.

Low

Silness[15]

1970

Cross-sectional 385 teeth/

contralateral

PI

GI

PD

GI more frequent in crowned teeth with

subgingival margins.

Low

Bergman

et al.[16]

1971

Longitudinal

2-year clinical

trial.

30 pat.

61 crowns

PI

GI

PD

GI tended to be higher when crown margins were

subgingival.

Low

Richter &

Ueno[26]

1973

Prospective

study,

3 years

12 crowns PI

GI

PD

No differences in gingival health, sulcus-depth,

plaque accumulation between supra- and

subgingival margin placement.

The fit and finish of full crown restorations may

be more significant than the location of crown

margins.

Low

Newcomb

[17]

1974

Cross-sectional 59 pat.

66 crowns with

average age

of 8,23 months/

Uncrowned

controls

PI

GI

PD

When subgingival margins approached the base of

the gingival crevice, more severe gingival

inflammation.

Least inflammation when subgingival crown

margins at gingival crest or just into the gingival

crevice.

Strong negative correlation between gingival

inflammation and distance of crown margin to the

base of crevice.

Low

Janenko &

Smales[18]

1979

Cross-sectional 126 pat.

101 PJC crown

88 PBM crown

PI

GI

Gingivitis higher around crowns than at controls.

Association between gingivitis and subgingival

marginal placement.

Low

( PI= Plaque Index, HI=Hygiene Index, GI= Gingival Index, PD= Probing Depth, CAL= Clinical Attachment Level, PBI= Papillary Bleeding Index, GCF= Gingival Crevicular Fluid)

22

Table 2 continued

Authors Type,

Duration

Sample Outcome

variables

Results Evidence

Koth[19]

1982

Cross-sectional A-38 full crown

restorations in 26

patients.

B-46 full crown

restorations in 28

patients

Crevicular

Fluid,

Gingival

inflammation

Same degree of gingival inflammation around

restored and non-restored teeth.

No differences between supra- and subgingival

placement.

Low

¤ only highly

motivated patients

Grasso

et al[20]

1985

Cross-sectional 291 pat. PI

GI

PD

Crowned and unrestored teeth showed major

differences in PI, GI and PD. The major adverse

effects on the periodontium resulted from the

placement of a crown.

Low

Muller[21]

1986

Cross-sectional 5 pat.

79 teeth

PI

GI

PD

CAL

GI slightly higher at teeth with crown margins at

the gingival margin.

Minor or no clinical signs of inflammation at

supragingival crown margins.

No significant alteration of attachment level.

Low

¤ No subgingivally located margins

Tarnow

et al.[31]

1986

Histological

examination.

2 pat.

13 teeth

Histological

observations,

changes in

bone and

attachment

level.

Reformation of new supracrestal attachment within 1

week after insertion of temporary crowns with finish

line below the base of crevice.

Clinical gingival recession (0,9 mm average with

0,4-1,2 mm range) was observed within 2 weeks, and

an average recession of 1,2 mm was recorded within

8 weeks.

Recession mechanisms were activated within the

first 7 days. Reformation of intracrevicular and

junctional epithelium occurred. The reformed

junctional epithelium was located apical to the finish

line bevel and there was crestal bone resorption.

Low

Orkin

et al.[22]

1987

Cross-sectional 423 pat.

355 subgingival

68 supragingival

Untreated controls

PI

GI

Gingival

recession

Gingival tissues bleed 2.42 times more frequently

with subgingival margins and have a 2.65 times

higher chance of gingival recession. Crowns with

supragingival margins did not differ significantly

compared with contralateral teeth.

Low

Bader

et al.[23]

1991

Cross-sectional 831 pat. PI

GI

PD

Increased GI when subgingival placement of

crown margins.

Low

( PI= Plaque Index, HI=Hygiene Index, GI= Gingival Index, PD= Probing Depth, CAL= Clinical Attachment Level, PBI= Papillary Bleeding Index, GCF= Gingival Crevicular Fluid)

23

Table 2 continued

Authors Type,

Duration

Sample Outcome

variables

Results Evidence

Pippin

et al.[24]

1995

Cross-sectional 60 pat.

120 restorations

60 veneers and 60

PFMs.

GI

GCF

PD

Gingival bleeding index values increased as the

margin index scores increased, with the highest

values recorded for subgingival margin

placement.

(Increased GCF when margins placed closer to

and below the gingiva. Higher GCF scores for the

PFMs than the corresponding values at veneers).

Low

Giollo

et al.[25]

2007

Retrospective

clinical trial,

3-5 years

40 pat.

40 ceramic

crowns

Uncrowned

controls

PI

BI

PPD

CAL

BI significantly higher at crowned teeth, specially

with subgingival placement of margins.

Statistically significant differences were not

observed in CAL between crowned and control

teeth, however more risk for attachment loss with

subgingival crowns.

Low

( PI= Plaque Index, HI=Hygiene Index, GI= Gingival Index, PD= Probing Depth, CAL= Clinical Attachment Level, PBI= Papillary

Bleeding Index, GCF= Gingival Crevicular Fluid)

24

Table 3, Excluded articles

Authors Year Reason

Silness[47, 48] 1970 See later study by Silness[15] 1970 part III.

Renggli & Regolati[49] 1972 Only fillings.

Renggli[50] 1974 Only fillings.

Bellos[51] 1974 General aspects, insufficient analysis.

Silness[52] 1974 Observations on pontics.

Valderhaug & Birkeland

[28]

1976 See later study by Valderhaug[10] 1993.

Valderhaug & Heloe [53] 1977 See later study by Valderhaug[10] 1993.

Valderhaug[29] 1980 See later study by Valderhaug[10] 1993.

Romanelli[54] 1980 General aspects, no individual analysis.

Silness[55] 1980 General aspects, insufficient analysis.

Jenkins[56] 1981 General aspects, no individual analysis.

Dragoo & Williams[57] 1981 Discussion about crown preparation procedure.

Dragoo & Williams[58] 1982 Discussion about temporary crowns.

Rohner et al.[59] 1983 Only radiographic analysis without any information about

restorations type or margin placement.

Carnevale et al.[60] 1983 Discussion about tooth preparation without crown placement.

Behrend[61] 1984 General aspects, no individual analysis.

Nevins & Skurow[62] 1984 General aspects, no individual analysis.

Lesan[63] 1987 Does not address the question, no comparison between

sub/supragingival margins.

Brandau et al.[64] 1988 Does not address the question. Insufficient analysis

Bader et al.[65] 1991 No comparison between subgingival and supragingival margins.

Tiwarri et al.[66] 1992 No comparison between subgingival and supragingival margins.

Wang et al.[67] 1993 No comparison between subgingival and supragingival margins.

Sherif et al.[68] 1993 Does not address the question. Discussion about surface materials.

No comparison between sub/supragingival.

Shavell[69] 1994 Does not address the question. General aspects about preparations

and impression techniques.

25

Table 3 continued

Authors Year Reason

Mojon et al.[70] 1995 No information about crown margin placement.

Kois[71] 1996 General aspects.

Swartz et al[72] 1996 No information about crown margin placement.

Schatzle et al.[32] 2001 Only fillings.

Broadbent et al.[73] 2006 Does not address the question. No information about margin

placement.

De Backer et al.[74] 2007 Does not address the question. No comparison between supra- and

subgingival margins.

26

Clinical considerations and own experience;

1. Working subgingivally means a traumatisation of soft tissues which may be temporary or

permanent. The use of special instruments to protect / keep away the gingiva during preparation

(Zekrya Gingival Protector) can reduce these risks.

2. Working subgingivally means increased difficulty of the preparation procedure, and therefore

automatically a risk of an inadequate fit of the restoration. This, in turn, may lead to increased

possibility of plaque retention around the crown margin, and increased risk of mechanical irritation of

the gingiva.

3. To place crown margins subgingivally means it is more difficult to control the fit of the crown and

detect possible caries lesions.

4. Deeper placement of crown margins with traditional cementation (Phosphate cement/glasionomer

cement) gives a higher degree of inflammation.

5. Very subjectively, I would like to point out the following. Because traditionally cemented crowns

stop the incident light, the area closest to the apical part of the crown margin appears darker. This is

caused by the absence of incident light, which is blocked by the crown. In normal conditions, and

during our daily clinical work, our assessment of a "healthy" gingiva is usually based on the colour of

the gingiva. Brighter gingiva is often considered "healthy" and darker gingiva considered "diseased".

This “dark zone” can be detrimental not only from an aesthetic but also from a diagnostic point of

view, and should be considered during the examination. In the 80`s, several studies showed that Dicor-

crowns had better gingival "health" compared with the traditional crowns. Dicor-crowns were the first

ceramic crowns which were translucent. When translucent cement was used the cervical part of the

crown had a brighter appearance. Was it perhaps this that led to a healthier looking “gingiva”?

Case 1:

The patient is practising good oral hygiene but still the gingiva around the subgingivally placed crown

on 11 shows gingivitis. Soft tissues around the non-treated tooth 21 are perfectly healthy. It is a quite

common clinical finding that soft tissues around subgingivally placed crowns show more gingivitis

than around non-prepared teeth under the same oral hygiene conditions.

¤ Before probing.

Note the colour on 11 cervically.

27

¤ After gentle probing.

Note the bleeding around 11.

Case 2:

Inadequate oral hygiene in combination with bad

fit and deep subgingival placement of the

finishing line results in pronounced gingivitis.

Case 3:

Crowned tooth 21 shows more

gingival inflammation than non-

crowned, neighbouring teeth

even though the finishing line is

supragingival at the time of the

picture. The reason for this is

probably the increased risk for plaque retention

apically to the finishing line.

28

Case 4:

The originally cemented crown was placed subgingivally showing the typical inflammation of

subgingival margin. After an esthetic gingivectomy had been performed a bonded crown was placed

with the finishing line at the gingival level. Healthy gingiva and better esthetics are the result.

The crown on 11 has been treated five times by different

dentists. The colour is acceptable but the crown appears

too short and the gingiva is inflamed.

The crown was lengthened surgically (by Prof. Jan

Wennström). A new 'bonded porcelain crown' was made.

The colour, the length of the crown and gingival health

are improved. The finishing line is at the level of the

gingival crest.

Case 5:

The cemented crown 11, where the gingiva has

receeded, illustrates the darkening effect of the root

surface by the crown´s blocking of incident light. This

also affects the colour of the gingiva since light is not

transmitted through the crown. As a result, the gingiva

looks slightly inflamed. Note that tooth 11 is vital.

This crown was cemented with phosphate cement and the cement has now been washed away in the

margin with a more pronounced plaque accumulation as a result.

Note the healthy gingival and the adequate colour of the

restored tooth after a bonded translucent crown has been

placed slightly supragingivally. The gingiva around 11

looks similar to the gingiva around 21 after the new

restoration was inserted.

Dr. S. Toreskog

Dr. S. Toreskog

29

Case 6:

A 28-year old woman with

discolourations in the upper and

lower front, namely on 11, 21, 31

and 41. According to the patient, the

damage on the tooth surfaces was

due to too high consumption of

citric fruits during long periods of

time.

Previous treatment: 11 and 21 were treated with composite. 31 and 41 were treated with metal-ceramic

crowns. The sole reason for crown therapy on 31 and 41 was the discolouration of these teeth. The

patient was not satisfied with the esthetical result and wanted new restorations. She has a very good

oral hygiene. Visually, the gingiva seems healthy but examination by probing revealed gingivitis

around 31 and 41.

Porcelain veneers on 11 and 21 have been placed slightly

supragingivally. New porcelain crowns have been bonded

on 31 and 41 with subgingival finishing lines due to the

previous treatment.

This case illustrates that the gingiva around subgingivally placed cemented crowns may look

acceptable but there might still be signs of inflammation when the pockets are probed. However, the

bonded porcelain veneers placed deep subgingivally showed no signs of gingivitis after probing.

30

Case 7:

Teased at school because of the yellow colour of 21, which is

seriously affected by 'enamel hypoplasia'. 22, which has been treated

with composite, has also been affected, but not as much.

Note the inflamed gingiva caused by the absence of glossy enamel

and the accumulation of plaque at the rough dentine surface.

Tooth surface prepared subginivally so that the

anatomy of the tooth could be restored with the

bonded porcelain.

The bonded glossy porcelain has repositioned the

gingival to its natural position and the finishing

line is now at the gingival level even if it was

placed subgingivally (the gingiva has intentionally

been repositioned)

This case shows that a rough tooth surface often will result in more plaque accumulation than a

smooth ceramic surface and will thus cause more inflammation. When the surface is restored with

bonded veneers, even though they might be subgingivally placed, the inflammation will recede. This

case also illustrates beautifully that the right anatomy of the buccal veneer will reposition the marginal

gingival to its right place.

Dr. S. Toreskog

Dr. S. Toreskog

Dr. S. Toreskog

31

Case 8:

An interesting aesthetic case, from the standpoint

that the patient lost her centrals when she was 10

years old and the entire quadrant 1 and 2 was moved

orthodontically one step forward.

¤ Before treatment.

¤ Gingivectomy of teeth in position 13 and 23 (teeth

14 and 24) by Prof. Jan Wennström

¤ After treatment.

From the standpoint of the present discussion it is

interesting to compare the colour and texture of the

gingiva around the 6 anterior teeth four years after

bonding. All teeth have been bonded but the bonded

restorations in position 13, 12, 22 and 23 (teeth 14,

13, 23 and 24) have been bonded at the gingival

level and the translucent cervical porcelain is about

0.2 mm thick letting the background colour of the

tooth shine through. The metal ceramic crowns on

the teeth in position 11 and 21 (teeth 12 and 22)

have been bonded subgingivally and the result four

years later is quite dramatic.

This case illustrates that bonded veneers/crowns placed supragingivally or at the gingival level are

superior to subgingivally placed and bonded traditional metal/ceramic crowns when it comes to

gingival response. (A 4-year clinical follow up)

Dr. S. Toreskog

Dr. S. Toreskog

32

General comments on crown margin placement:

What is the reason that we sometimes place the crown margin subgingivally?

The answer to this question is pertinent because the whole above-mentioned discussion would be

unnecessary, if we had been able to place the crown margin supragingivally with all kinds of crown

treatment. So why subgingivally?

1. Traditional crowns (Metal/Ceramic, Procera, Inceram, Lava), which are retained with traditional

cement (phosphate cement, glasionomer cement), stop the incident light so dramatically that the area

apical to the crown margin becomes very dark. Therefore, the margins of these crowns are usually

placed subgingivally for aesthetic reasons. Even if these types of crowns are cemented/bonded with a

translucent composite cement, they will stop incoming light to various degrees due to the different

opacities of their respective cores. Unfortunately, the crown margin becomes visible after a period of

time due to gingival recession, or because of continued tooth eruption which means that the cervical

area will be very unaesthetic.

2. Risk for caries? Yes, this was a big argument 50 years ago, but with today's caries prevention and

increased dental care, this is an outdated argument.

3. Problems with retention? Yes, this was a relevant factor when the crown was manufactured and

cemented traditionally. Today, this argument is not as relevant any more, due to the development of

different bonding agents.

The conclusion is therefore that, if possible, the crown margin should be placed supragingivally (using

a bonded translucent porcelain technique and a translucent cement).

Acknowledgement

I would like to thank Dr. Jan Derks for the assistance regarding the database screening and Dr. Sverker

Toreskog for the clinical pictures.

33

Table 4. Data Extraction Form.

Första författare:

Titel:

Tidskrift:

År/volym/sidor

Beskrivning av studien:

Typ av studie/studiedesign:

Primär frågeställning av studien:

- parodontit

- protetik

- Material

- Estetik

- Annat (namnge)

Underliggande population och vårdmiljö:

- Vårdmiljö

- Typ av vårdgivare

- Årtal för studiens genomförande

- Land/världsdel

- Kommentarer

Patientkarakteristiska:

- Antal individer/tänder (Ålder, mean/range)

- Antal kvinnor (Ålder, mean/range)

- Antal män (Ålder, mean/range)

- Kontrollgrupp

- Bortfall från ursprungpopulationen

- Bortfall av data under studien

- Kommentarer

34

Finns uppgift om:

- Allmän hälsa

- Tobaksbruk

- Övrigt, Kommentarer

Uppföljningstid:

Intervention;

Förbehandling/typ:

Protetisk behandling/ typ:

Material/ typ:

Kommentarer:

Effektmått;

Förändringar i plackförekomst

Gingival inflammation

Förändring i fickdjup

Förändring i fästenivå

35

Förändring av benvävnad

Förändring av mjukvävnadens läge

Tandmobilitet

Förlust av tänder

Inklusionskriterier:

Exklusionskriterier:

Sökstrategi, sökord:

36

Resultat enligt författarna:

Konklusion enligt författarna:

Sammanfattande bevisvärde:

Högt

Medelhögt

Lågt

Sammanfattande kvalitetsomdöme:

Ytterligare kommentarer:

Granskare:

Datum:

37

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40

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