Submission to Journal of Clinical Periodontology (accepted version)

TITLE

Alterations in soft tissue levels and aesthetics over a 16 to 22 year period following single

implant treatment in periodontally-healthy patients: a retrospective case series

RUNNING TITLE

Long term soft tissue alterations

KEY WORDS

Dental implant, single tooth, soft tissue, recession, infra-position, eruption, aesthetics, long

term

AUTHORS

Dierens, M., De Bruecker, E., Vandeweghe, S., Kisch, J., De Bruyn, H., Cosyn, J.

AFFILIATIONS AND INSTITUTIONS

Melissa Dierens1, Evelyn De Bruecker1, Stefan Vandeweghe1,2, Jëno Kisch3, Hugo De Bruyn1,2,

Jan Cosyn1,4

1University of Ghent, Faculty of Medicine and Health Sciences, Dental School, Department of

Periodontology and Oral Implantology, De Pintelaan 185, B-9000 Ghent, Belgium2Malmö University, Department of Prosthetic Dentistry, Carl Gustafsväg, SE-20506 Malmö,

Sweden3Clinic for Prosthodontics, Centre of Dental Specialist Care, Spårvägsgatan 12, SE-21427

Malmö, Sweden4Free University of Brussels (VUB), Faculty of Medicine and Pharmacy, Dental Medicine,

Laarbeeklaan 103, B-1090 Brussels, Belgium

CONTACT ADDRESS CORRESPONDING AUTHOR

Jan Cosyn

University of Ghent, Faculty of Medicine and Health Sciences, Dental School, Department of

Periodontology and Oral Implantology, De Pintelaan 185, B-9000 Ghent, Belgium

1

E-mail: jan.cosyn@ugent.be

WORD COUNT

3920

CONFLICT OF INTERESTS AND SOURCE OF FUNDING

The authors declare they have no conflict of interests. The study was supported by the

Department of Periodontology and Oral Implantology of the University in Ghent and

Folktandvården, Region Skåne, Sweden.

AbstractPurpose: Long term studies on single implants are scarce and merely focus on clinical

response parameters, complications and bone remodelling. The objective of this

retrospective case series was to assess alterations in soft tissue levels and aesthetics over a

16 to 22 year period in periodontally-healthy patients.

Material and methods: Patients who had received a single turned implant in the anterior

maxilla/mandible at the Dental Specialist Clinic in Malmö between 1987 and 1993 were

invited for a re-examination on the basis of a number of inclusion criteria. Both neighbouring

teeth had to be present at re-examination and baseline clinical photographs (within the first

year of function) had to be available for soft tissue evaluation. These photographs were

superimposed onto final clinical photographs to assess longitudinal soft tissue alterations.

Results: Twenty-one patients (9 females; mean age 23, range 16-41) treated with 24 single

implants met the criteria for soft tissue evaluation. Peri-implant soft tissue levels (papillae,

midfacial level) remained stable over a 16 to 22 year observation period (p ≥ 0.372).

However, neighbouring teeth demonstrated midfacial recession and eruption pointing to a

major distortion with the implant crown (> 1 mm) in 5/24 (21 %) and 10/24 (42 %) of the

cases, respectively. Baseline aesthetics was considered poor (mean Pink Esthetic Score 7.42,

mean White Esthetic Score 5.43), yet a significant time effect could not be demonstrated (p

≥ 0.552). Implant and tooth bone loss was low (mean 0.6 mm and 0.4 mm, respectively) over

a 16 to 22 year period.

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Conclusions: This limited case series demonstrated stable peri-implant soft tissue levels and

aesthetics in the long term following single implant treatment in periodontally-healthy

patients. However, midfacial recession and eruption may be expected at neighbouring teeth.

Clinical relevanceScientific rationale: There are no long term studies on single implant treatment with

longitudinal data on soft tissue levels and aesthetics.

Principal findings: This limited case series of 21 patients demonstrated stable peri-implant

soft tissue levels and aesthetics over a 16 to 22 year period following single implant

treatment in periodontally-healthy patients. However, midfacial recession and eruption may

be expected at neighbouring teeth.

Practical implications: In the long term disparities between implant restorations and

neighbouring teeth may be expected in terms of soft tissue and incisal levels.

3

IntroductionImplant treatment has become a viable option in contemporary practice to restore a single

tooth gap (Cosyn et al. 2012b). According to a number of systematic reviews this concept is

predictable and successful (Creugers et al. 2000, Berglundh et al. 2002, den Hartog et al.

2008, Jung et al. 2008). However, this statement should be interpreted in the context of

important limitations relating to study duration and registered parameters. In this respect,

clinical studies on single implants with observation periods of 15 years or longer are scarce

and merely focus on clinical response parameters, complications and bone remodelling

(Jemt 2008, Bergenblock et al. 2010, Dierens et al. 2012). Still, contemporary practice shows

that patients mainly judge the outcome of a single implant on aesthetic aspects. This

evolution may explain the growing interest by scientists for soft tissue dynamics, objective

aesthetic ratings and patient-reported outcomes in the last 5 years. At least in the short

term, ample studies have shown that midfacial recession may be expected following single

implant treatment, whereas papillae tend to regrow usually filling up the embrasure space

to an acceptable extent (Grunder 2000, Henriksson & Jemt 2004, Cardaropoli et al. 2006,

Juodzbalys & Wang 2007, Lai et al. 2008, Chen et al. 2009, Cosyn et al. 2011, Buser et al.

2011, den Hartog et al. 2011, Gallucci et al. 2011a, Raes et al. 2011). Albeit midfacial soft

tissue level and papillae are key factors for aesthetic success, the latter is influenced by many

other parameters of which most are probably taken into account in novel indices (Fürhauser

et al. 2005, Meijer et al. 2005, Belser et al. 2009). On the basis of these objective scoring

methods, it seems that the aesthetic outcome of single implant treatment lacks

predictability given aesthetic failure rates up to about one third of the cases (Juodzbalys &

Wang 2007, Meijndert et al. 2007, Lai et al. 2008, Belser et al. 2009, Chen et al. 2009, Cosyn

et al. 2010, 2011, 2012a, Buser et al. 2011, den Hartog et al. 2011, Gallucci et al. 2011b, Raes

et al. 2011). A demanding protocol in well-selected patients has been evaluated in a

prospective study and may overcome this (Cosyn et al. 2012a), yet such protocols may

probably not reflect daily clinical practice. In this respect, retrospective studies may add

relevant information to what can be expected on a routine basis. The objective of this

retrospective case series was to document alterations in soft tissue levels and aesthetics

over a 16 to 22 year period following single implant treatment in periodontally-healthy

patients.

4

Material and methodsPatient selection

This retrospective case series was based on data from periodontally-healthy patients who

were clinically re-examined 16 to 22 years following single implant treatment at the Centre

of Dental Specialist Care, Malmö, Sweden. Patients were invited for a re-examination if they

met the following inclusion criteria according to their records:

Single implant treatment in the anterior maxilla (15-25) or mandible (45-35) using the

Brånemark Implant System (Nobelpharma AB, Göteborg, Sweden) with a turned

surface and externally hexed implant-abutment connection between 1987 and 1993.

Presence of both neighbouring teeth.

Availability of peri-apical radiographs.

At least one control visit following crown installation.

The clinical and radiographic outcome of this case series can be found in a recent paper

(Dierens et al. 2012). Given the objective of this study focusing on soft tissue aspects of

treatment outcome, the following inclusion criteria had to be additionally fulfilled:

Presence of both neighbouring teeth and the contra-lateral tooth in case of incisor or

cuspid replacements at re-examination.

Availability of baseline clinical photographs (within the first year of function) of the

implant restoration.

The protocol was approved by the Regional Ethical Review Board in Lund and all patients

signed an informed consent.

Surgical and restorative procedures

At least 6 months following tooth removal, implants were placed according to a classical

two-stage procedure (Brånemark et al. 1977, Adell et al. 1981, Jemt et al. 1986). This

included standard flap elevation, bone preparation including countersinking, implant

installation in a strict palatal position, application of a cover screw and primary wound

closure. Abutment connection was performed after no less than 3 months of

osseointegration. Bone augmentation was never performed nor before implant surgery,

neither at the time of implant placement. Given the developmental stage of implant

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prosthetics in the eighties, several prosthetic designs requiring various technical procedures

were included. Impression taking was performed at implant level or abutment level for

customized or CeraOneTM abutments, respectively. Customized abutments were fixed with a

titanium screw, whereas CeraOneTM abutments were fixed with a gold screw. Implant crowns

were placed in occlusal contact, but out of articulation to prevent overload. Full-ceramic or

acrylic/porcelain-fused-to-metal gold crowns were cemented onto individually customized

abutments or CeraOneTM abutments. The initial follow-up was performed in the Dental

Specialist Clinic.

Examination criteria

The clinical and radiographic outcome of this case series can be found in a recent paper

(Dierens et al. 2012). The present report adds new information on this patient sample

focusing on soft tissue aspects of treatment outcome. Alterations over time in soft tissue

levels and aesthetic parameters were considered primary outcome variables. Clinical and

radiographic parameters were considered secondary outcome variables.

Soft tissue levels

Baseline clinical photographs were digitized using designated software (Super Coolscan 4000

ED, Nikon, Tokyo, Japan; Photo Station, Albumprinter, Amsterdam, The Netherlands). These

were superimposed onto the final digital photographs using photo-editing software

(Photoshop, version CS5, San Jose, California, USA) based on the best fit of the implant

crown. During the clinical re-examination the clinical crown length of the implant

restoration, i.e. the total length of the restoration visible in the mouth including possible

recession, was measured intra-orally using a calliper. This distance was used to calibrate

both photographs. First, horizontal parallel lines at the level of the incisal plane and midfacial

soft tissue level were drawn onto the final clinical photograph (fig. 1). Then, these lines were

projected onto the baseline clinical photograph after superimposing both photographs.

Given the known distance between the horizontal lines, the following linear measurements

could be recorded:

Clinical implant crown length at baseline and at re-examination.

Clinical tooth crown length at baseline and re-examination for the best visible

neighbouring tooth.

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Mesial papilla height at baseline and re-examination.

Distal papilla height at baseline and re-examination.

Aforementioned measurements were performed by one clinician (EDB) using an image

processing program (Image J, Bethesda, Maryland, USA). Recordings were repeated by the

same clinician after an interval of 6 weeks in order to evaluate intra-assessor reliability.

At the best visible neighbouring tooth midfacial recession and eruption were assessed giving

a score of 0, 1 or 2 with 0 representing no change, 1 representing minor change (≤ 1mm) and

2 representing major change (> 1mm) between baseline and re-examination. The gingival

horizontal line for calibration was used as a reference for recession evaluation, whereas the

incisal plane of the implant crown was used as a reference for evaluating eruption of the

neighbouring tooth. For the latter it was assumed that the incisal plane of the implant crown

remained unchanged over a 16 to 22 year period.

(HERE APPROXIMATELY FIGURE 1 & 2 PLEASE)

Aesthetic parameters

The aesthetic outcome was assessed at baseline and re-examination on the basis of the Pink

Esthetic Score (Fürhauser et al. 2005) and White Esthetic Score (Belser et al. 2009). The PES

is based on 7 criteria: mesial papilla, distal papilla, soft tissue level, contour, alveolar process

deficiency, colour and texture. Each of these parameters is assessed giving a score of 0, 1 or

2 with 0 representing the poorest outcome and 2 representing a perfect outcome. Papillae

are evaluated for completeness whereas the other variables are scored by comparing with a

reference tooth, which is the contralateral tooth for incisor and cuspid replacements and the

neighbouring premolar for premolar replacements. As proposed by Cosyn et al. (2010) a

total score ≤ 7 was considered aesthetic failure, whereas a total score ≥ 12 was considered

(almost) perfect outcome.

The WES is based on 5 criteria focusing on the visible part of the restoration. Tooth form,

volume, colour, texture and translucency are scored in a similar way as the criteria of the

PES. As proposed by Cosyn et al. (2010) a total score ≤ 5 was considered aesthetic failure,

whereas a total score ≥ 9 was considered (almost) perfect outcome. All clinical photographs

were scored twice by the same clinician (EDB) with an interval of 6 weeks in order to

evaluate intra-assessor reliability.

7

Clinical and radiographic parameters

At re-examination a peri-apical radiograph was taken using the long cone parallel technique

to evaluate implant bone level using the implant-abutment interface as a reference point.

The distance between this point and the first visible bone-to-implant contact was measured

at both sides of the implant. Baseline radiographs taken within 6 months after abutment

connection were digitized and analysed likewise by an independent examiner (RP) calibrating

on the known distance between the implant threads. Implant bone loss was calculated as

the difference between implant bone level at re-examination and baseline.

Tooth bone level was also registered at re-examination and baseline and was defined as the

distance between the cemento-enamel junction and the tooth bone crest. Tooth bone loss

was calculated as the difference between tooth bone level at re-examination and baseline.

Probing depth was registered at 6 sites per implant and contralateral tooth and gingival

index (Loë & Silness 1963) and plaque index (Sillness & Loë 1964) were scored at four sites

per implant.

Statistical analysis

Mean values and standard deviations were calculated for all continuous variables (soft tissue

levels, total PES, total WES, implant bone loss, tooth bone loss, implant probing depth,

contralateral tooth probing depth, implant gingival index, implant plaque index), whereas

frequency distributions were given for categorical variables (PES and WES criteria, recession

at the neighbouring tooth, infra-position of the implant crown). Alterations over time in soft

tissue levels and aesthetic parameters were evaluated using the Wilcoxon signed ranks test.

Comparison between cases with full documentation and cases lacking baseline clinical

photographs was performed by means of the Mann-Whitney-U test. Intra-assessor reliability

of soft tissue levels was evaluated using the intra-class correlation coefficient. Kappa

statistics were used to assess intra-assessor reliability of aesthetic ratings. The level of

significance was set at 0.05.

Results

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One hundred and one patients who had been treated with a single implant between 1987

and 1993 at the Centre of Dental Specialist Care, were possible candidates for a clinical

inspection. Fifty-three of them agreed to attend such examination, however 3 patients did

not show up at the scheduled visit. Hence, 50 patients who received 62 single implants were

originally included. Three of these implants failed in the early healing phase, resulting in a

sample of 59 clinically-evaluable single implants. The clinical and radiographic outcome of

this patient group can be found in a recent paper (Dierens et al. 2012). Twenty-nine patients

did not meet the additional inclusion criteria for soft tissue evaluation. Nine of the 21

remaining patients were female and mean age was 23 years (SD 6, range 16-41) and 41 years

(SD 7, range 33-58) at implant placement and re-examination, respectively. Thus, the mean

follow-up was 18 years (SD 1, range 16-22). None of the patients had been suffering from

systemic disease or had been taking medication that could induce gingival overgrowth. One

patient was a smoker. All patients were periodontally-healthy at implant placement and

remained periodontally-healthy during follow-up as based on the definition described by

Page and Eke (2007). Nineteen patients had received 1 single implant, 1 patient had received

2 single implants and 1 patient had received 3 single implants. Thus, in total 24 single

implants had been installed of which 10 in a lateral incisor position, 8 in a central incisor

position, 4 in a premolar position and 2 in a canine position. In the 16 to 22 year period, only

one patient received a crown on a natural tooth neighbouring the implant restoration.

Neighbouring teeth were not additionally restored in any other patient and surgical

procedures were never performed adjacent to the implant restoration.

Soft tissue levels

The intra-class correlation coefficient on duplicate soft tissue measurements was 0.725 (p <

0.001) indicative of substantial intra-assessor reliability. Table 1 shows soft tissue levels at

baseline and at re-examination. Peri-implant levels remained stable over a 16 to 22 year

observation period (p ≥ 0.372). However, clinical tooth crown length showed a significant

increase of 0.5 mm on average (p = 0.039). About half of the cases (13/24, 54 %)

demonstrated midfacial recession after 16 to 22 years of function. Minor recession was

found in 8/24 (33 %) cases, whereas 5/24 (21 %) cases showed major midfacial recession.

The vast majority of the cases (17/24, 71 %) demonstrated infra-position of the implant

9

crown after 16 to 22 years of function. Minor infra-position was found in 7/24 (29 %) cases,

whereas 10/24 (42 %) cases showed major infra-position.

(HERE APPROXIMATELY TABLE 1 PLEASE)

Aesthetic parameters

The kappa value on duplicate registration of the PES criteria was ≥ 0.797 (p < 0.001)

indicative of substantial intra-assessor reliability. Table 2 shows the results of the PES and its

7 criteria sorted per time point. There was no significant difference in the PES or the 7

criteria between baseline and re-examination (p ≥ 0.132). Alveolar process deficiency and

papillae scored worst at both time points with an unfavourable outcome in 7/24 (29 %)

cases. Most satisfying at both time points was soft tissue contour. The mean PES at baseline

was 7.42 with aesthetic failure in 10/24 (42 %) of the cases and (almost) perfect outcome in

1 case (4 %). After 16 to 22 years of function the mean PES was 7.71 with aesthetic failure in

9/24 cases (38 %) and (almost) perfect outcome in 1 case (4 %).

The kappa value on duplicate registration of the WES criteria was ≥ 0.851 (p < 0.001)

indicative of almost perfect intra-assessor reliability. Table 2 shows the results of the WES

and its 5 criteria sorted per time point. There was no significant difference in the WES or the

5 criteria between baseline and re-examination (p ≥ 0.153). The mean WES at baseline was

5.43 with aesthetic failure in 11/24 (46 %) of the cases and (almost) perfect outcome in 3/24

(13 %) of the cases. After 16 to 22 years of function the mean WES was 5.33 with aesthetic

failure in 10/24 (42 %) of the cases and (almost) perfect outcome in 6/24 (25 %) of the cases.

Of the 59 clinically-evaluable single implants only 24 met the additional inclusion criteria for

longitudinal aesthetic evaluation. Eighteen of the remainder could also be aesthetically

evaluated, yet only after 16 to 22 years of function given the lack of baseline clinical

photographs on these cases. Table 2 shows the results on the PES and WES of these 18 single

implants. There was no significant difference for any of the parameters after 16 to 22 years

of function between the 24 cases with full documentation and the 18 cases lacking baseline

clinical photographs.

(HERE APPROXIMATELY TABLE 2 PLEASE)

10

Clinical and radiographic parameters

Table 3 shows the clinical and radiographic outcome of the 24 cases with full documentation

and the 18 cases lacking baseline clinical photographs. There was no significant difference in

any of the parameters between these patient groups. Implant and tooth bone loss were

limited in the long term with mean values below 1 mm (fig. 2).

(HERE APPROXIMATELY TABLE 3 PLEASE)

DiscussionTo the best of our knowledge this is the first longitudinal study with long term data on soft

tissue levels and aesthetics following single implant treatment.

In this study peri-implant soft tissue levels remained stable over a 16 to 22 year period,

which could be considered remarkable, especially since several studies have demonstrated

significant short-term alterations in soft tissue levels (Grunder 2000, Henriksson & Jemt

2004, Cardaropoli et al. 2006, Juodzbalys & Wang 2007, Lai et al. 2008, Chen et al. 2009,

Cosyn et al. 2011, Buser et al. 2011, den Hartog et al. 2011, Gallucci et al. 2011a, Raes et al.

2011). The latter may not necessarily contrast with our findings since baseline clinical

photographs pertained to the first year of function in our patient sample. This time frame

may not enable to detect early soft tissue changes, yet these may contribute most to soft

tissue dynamics. The latter may be illustrated by recently published one- and three-year data

on immediate implant treatment (De Rouck et al. 2008, Cosyn et al. 2011). De Rouck and co-

workers (2008) demonstrated significant papilla reduction and midfacial recession in the

early stages of healing following such treatment. Yet, after 3 years of function the same

patient group showed full papilla regeneration and some reduction in midfacial recession

(Cosyn et al. 2011). The present long term study failed to demonstrate significant midfacial

recession at the implant restoration, which could be a reflection of the fact that in the early

days turned implants were used in a strict palatal position. Such position could be confirmed

by clinical evaluation in the vast majority of the cases and ensures a thick buccal bone wall

supporting soft tissue stability.

In contrast to peri-implant soft tissue levels, gingival levels at adjacent natural teeth

demonstrated significant recession in the 16 to 22 year period. In fact, over one fifth of the

11

cases (21 %) showed major midfacial recession. These findings may suggest that peri-implant

soft tissues show more resistance to recession than gingival tissues. We believe that

quantitative rather than qualitative disparities may explain this phenomenon. At least in the

short term, soft tissues are thicker at the buccal aspect of implants than teeth (Henriksson &

Jemt 2004, Cardaropoli et al. 2006), which may be explained by a palatal implant position in

relation to the neighbouring teeth on one hand, and a buccal repositioning of the peri-

implant mucosa at second stage surgery on the other hand. Moreover, the abutment

diameters used in the developmental phase of single implant restorations in the late

eighties, can be considered smaller than the root diameters of the replaced or neighbouring

teeth, possible leaving more space for surrounding tissues. The risk for soft tissue recession

mainly relates to its thickness, as shown around teeth (Melsen and Allais 2005, Yared et al.

2006) and implants (Kan et al. 2011).

A particularly interesting finding was that the vast majority of the cases (71 %) demonstrated

infra-position of the implant crown after 16 to 22 years of function. In nearly half of them

(42 %) a major distortion was found indicating substantial eruption of the neighbouring

teeth. Interestingly, Bernard and co-workers (2004) demonstrated infra-position of the

implant crown in all treated cases after on average 4.2 years of function irrespective of age,

gender and implant position. Recently, Chang and Wennström (2012) showed an increase in

the vertical position of neighbouring teeth in relation to the implant in 58 % of the cases

after 8 years of function. With an observation period of more than 15 years Jemt et al.

(2007) showed infra-occlusion of the implant crown in 60 % of the cases. Our observations

seem to be in line with these investigations and point to an important aspect of treatment

outcome with possible aesthetic consequences.

Another primary goal of this study was to objectively assess the aesthetic outcome of single

implant treatment and to evaluate possible time effects. Hitherto, a number of studies have

been published on the aesthetic outcome of single implant restorations using the PES and/or

WES (Juodzbalys & Wang 2007, Lai et al. 2008, Belser et al. 2009, Chen et al. 2009, Cosyn et

al. 2010, 2011, 2012a, Buser et al. 2011, den Hartog et al. 2011, Gallucci et al. 2011b, Raes et

al. 2011). When compared to these studies it is clear that the aesthetic outcome of single

implant treatment was poor in the late eighties and early nineties given a mean PES of 7.42

and a mean WES of 5.43 at baseline. Given that, it should not be surprising that only very

few cases demonstrated (almost) perfect aesthetic outcome based on arbitrarily chosen

12

thresholds by Cosyn et al. (2010). When interpreting these results, one should take into

account that at the time implant therapy was in a developmental stage in terms of implant

surface topography and prosthetic components, mainly focusing on functional rehabilitation.

In contemporary practice more attention is paid to an optimal three-dimensional implant

position and the use of biomaterials, provisional restorations and connective tissue grafts

have become common. It seems that these aspects have substantially improved the

aesthetic outcome of single implant treatment over the years (Juodzbalys & Wang 2007, Lai

et al. 2008, Belser et al. 2009, Chen et al. 2009, Cosyn et al. 2010, 2011, 2012a, Buser et al.

2011, den Hartog et al. 2011, Gallucci et al. 2011b, Raes et al. 2011), yet they also drastically

increased its complexity. In addition, these treatment concepts still need to withstand the

test of time given the relatively short time frame in which they were studied. On the other

hand, the present study did not show significant differences in the PES or WES between

baseline and re-examination, indicating stable aesthetics over a 16 to 22 year period for

conventional single implant treatment.

For a number of reasons aforementioned results should be interpreted with caution,

especially in terms of generalizability. First, important information may not be available in a

retrospective study. Intra-surgical data on the thickness of the buccal bone wall upon

implant installation would have been valuable since the buccal bone wall possibly affects

midfacial recession. Cone beam CT could be used to overcome this, yet technology was not

yet available in the late eighties and is still lacking accuracy (Raes et al. 2011). Other relevant

parameters that could not be thoroughly assessed given the retrospective study design

include restoration materials, prosthetic design and oral hygiene. Apart from the study

design, a second limitation relates to the small study sample. One could question whether

the sample size was sufficient to demonstrate significant peri-implant soft tissue alterations.

Post factum calculations based on a change of 0.4 mm (e.g. mesial papilla), SD of 1.7, an

alpha error of 0.05 and statistical power of 0.80 resulted in a required sample size of 12.

Thus, the present case series including 24 single implants was not underpowered to show a

significant time effect. On the other hand, 186 single implants would be needed in order to

demonstrate a 0.1 mm significant change (e.g. clinical implant crown length). Theoretically,

our sample was underpowered to show this time effect, yet one could question the clinical

relevance of a 0.1 mm difference. A third limitation refers to the methodology. Albeit clinical

photographs were superimposed based on the best fit of the implant crown, they were

13

possibly taken from different angles. This could have an impact on accuracy. On the other

hand, registration of soft tissue data demonstrated high precision given substantial intra-

assessor reliability on duplicate measurements. A final concern could relate to selection bias

as it is conceivable that only baseline clinical photographs had been taken from the best

cases. We consider this unlikely and the reason for that may be threefold. First, baseline PES

and WES were 7.42 and 5.43, respectively. These data reflect a rather poor outcome instead

of a favourable outcome. Second, final PES and WES were also calculated for 18 cases

without baseline clinical photographs and these were not significantly different from the 24

cases with full documentation, at least not after 16 to 22 years of function. Third, clinical and

radiographic parameters on the same 18 cases without baseline clinical photographs were

also not significantly different from the 24 cases with full documentation.

In conclusion, this retrospective case series demonstrated stable peri-implant soft tissue

levels over a 16 to 22 year period following single implant treatment in periodontally-healthy

patients. On the other hand, neighbouring teeth showed significant midfacial recession and

eruption. Based on objective parameters baseline aesthetics was considered poor, yet a

significant time effect could not be demonstrated, indicating long term stability.

AcknowledgementsThe authors express their gratitude to Ulf Lindén who initiated this study, to Rigmor Persson

for analysing all radiographs and to all co-workers at the Centre of Dental Specialist Care in

Malmö for supporting the clinical part of this project.

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