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, Belgium

2Malmö University, Department of Prosthetic Dentistry, Carl Gustafsväg, SE-20506 Malmö, Sweden

3Clinic for Prosthodontics, Centre of Dental Specialist Care, Spårvägsgatan 12, SE-21427 Malmö, Sweden

4Free 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

E-mail:

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.

Abstract

Purpose: 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 baselineclinical 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.

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 relevance

Scientific 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.

Introduction

Implant 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, HenrikssonJemt 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 protocolin well-selected patients has been evaluated in a prospective study andmay 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.

Material and methods

Patient selection

This retrospective case serieswas 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 than3 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 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 CeraOneTMabutments. 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 parameterswere 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-examinationthe 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 linesat 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.
  • 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 animage 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 midfacialrecession 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 & 2PLEASE)

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 0representing 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 premolarfor 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 WESis 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.

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 (LoëSilness 1963) and plaque index (SillnessLoë 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 ofsoft 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

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 groupcan 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 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 implantsonly 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.