Ying-Xin Gu* Jun-Yu Shi* Long-Fei Zhuang Shi-Chong Qiao You-You Xu Hong-Chang Lai
Authors’ affiliations: Ying-Xin Gu, Jun-Yu Shi, Long-Fei Zhuang, Shi-Chong Qiao, You-You Xu, Hong-Chang Lai, Department of Oral and Maxillo-facial Implantology, Shanghai Key Laboratory of Stomatology, Shanghai Ninth People’s Hospital, School of Medicine, Shanghai Jiaotong University, Shanghai, China Corresponding author: Hong-Chang Lai Department of Oral and Maxillo-facial Implantology Shanghai Ninth People’s Hospital, School of Medicine Shanghai Jiaotong University 639 Zhizaoju Road, Shanghai, 200011, China Tel.: +86 21 23271699 Fax: +86 21 53073068 e-mail: [email protected]
Esthetic outcome and alterations of soft tissue around single implant crowns: a 2-year prospective study
Key words: dental implants, pink esthetic score/white esthetic score, soft tissue esthetic out-
come, tissue level Abstract Objective: The aim of this prospective study was to assess the esthetic outcome and alterations of peri-implant soft tissue using tissue-level implants. Furthermore, the influencing factors, including grafting and gingival biotype, of esthetic outcome of peri-implant soft tissue were also evaluated. Materials and methods: Of 38 patients with single missing anterior tooth in maxilla were treated with a Straumann
â
Standard Plus SLA implant. Bone augmentation was performed in 24 patients.
Follow-up was conducted at 12 and 24 months after definitive crowns placement. Esthetic outcome using the pink esthetic score/white esthetic score (PES/WES) and clinical parameters were evaluated. Results: The mean PES/WES value at baseline, 1-year, and 2-year examination was 13.79, 14.87, and 14.96. Significant improvement was found between baseline and 1-year examination (P < 0.01). And the improvement between 1-year and 2-year examination was not significant (P = 0.40). The mean PES changing value in patients with thick biotype was significantly higher than those with thin biotype at 2-year after definitive crowns placement (P = 0.03). Graft procedure had an unfavorable effect on mean PES value both at baseline and at follow-up (P < 0.01). No implants were lost at 2-year examination. Three patients experienced peri-implant infection. No significant difference was found with the passage of time in modified plaque index (mPI), probing pocket depth (PPD), and modified bleeding index (mBI). Conclusion: According to the present prospective clinical study, it can be concluded that it is feasible to use tissue-level implant to support single crowns in esthetic area. Favorable short-term esthetic outcome and stability of soft tissue around single implant crowns can be expected in patients with or without graft. However, graft procedures might have an unfavorable effect on the esthetic outcome. Gingival biotype can be considered as prognostic factor for esthetic outcome. RCTs with long-term follow-up are needed to provide evidence for the long-term stability of peri-implant soft tissue using tissue-level implant systems.
*These authors contributed equally to this work. The authors claim that none of the material in the article has been published or is under consideration for publication elsewhere. Date: Accepted 21 March 2014 To cite this article: Gu Y-X, Shi J-Y, Zhuang L-F, Qiao S-C, Xu Y-Y, Lai H-C. Esthetic outcome and alterations of soft tissue around single implant crowns: a 2-year prospective study. Clin. Oral Impl. Res. 00, 2014, 1–6 doi: 10.1111/clr.12408
In recent years, rehabilitation of single-tooth gaps by means of dental implants has become a routine treatment with high survival and success rates (Pjetursson et al. 2007, 2012; Jung et al. 2008). However, the success of implant treatment should not be limited to achieving osseointegration. The esthetic outcome of the reconstruction also becomes an important parameter for clinical success especially for esthetically sensitive cases. For clinical esthetic assessment, both implant crown features and peri-implant soft tissue stability should be taken into consideration (Chang et al. 1999). However, periimplant soft tissue meets most clinical challenges from the esthetic aspect. The most
© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd
common reasons for esthetic failure include disharmonious mucosal color or texture, complete or incomplete loss of interproximal papillae, and recession of soft tissue level. So the soft tissue esthetic outcome is of paramount importance to achieving clinical esthetic success (Belser et al. 2004). Pink esthetic score (PES) (Furhauser et al. 2005) or pink esthetic score/white esthetic score (PES/WES) (Belser et al. 2009) is now adopted by more and more studies to assess esthetic outcome and alterations of periimplant soft tissue. Connective tissue graft might be necessary in about one-third of the patients following type 1 (immediate after tooth extraction) implants placement to
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Gu et al Evaluation of soft tissue alteration
achieve steady improvement in PES score (Cosyn et al. 2013). Following type 2 (4–8 weeks after tooth extraction) and type 3 (12– 16 weeks after tooth extraction) implants placement, spontaneous improvements of PES score might occur in the short-term follow-up, and then the PES score will likely reverse to the baseline level when the observational time was prolonged to at least 3 years after crown installation (Buser et al. 2011, 2013; Weinlander et al. 2011; Pieri et al. 2013). It is worth mentioning that only bone-level implant systems were used in the above studies. Bone-level implant systems were widely used in patients needed implant treatment in esthetic area because of more concise surgical procedures and less bone resportion especially when platform-switching technology was used (Al-Nsour et al. 2012; Annibali et al. 2012). Meanwhile, tissue-level implant systems are also widely used in clinical practices, and few studies have reported the esthetic evaluation using tissue-level implant systems. A previously published study by our group has proved that tissue-level implant systems can also achieve predictable soft tissue appearance on the premise of accurate implant placement depth (Lai et al. 2008). However, the follow-up was relatively short (6–8 months), and patients in need of graft procedures were excluded. To our knowledge, this is the first prospective study reporting the PES index of soft tissue using tissue-level implants in patients with and without bone augmentation. Therefore, the aims of the present study were (i) to assess the esthetic outcome and alterations of peri-implant soft tissue using tissue-level implants after 2-year follow-up and (ii) to study the influencing factors, including grafting and gingival biotype, of esthetic outcome of peri-implant soft tissue.
performed. Fig. 1 shows the flow of clinical procedures. The inclusion criteria were as follows: 1. Patients in need of single-tooth restoration in the anterior maxilla; 2. Tooth extraction at least three months before implant surgery; 3. No severe vertical bone defect and enough primary stability to achieve simultaneous implant placement; 4. Not be heavy smokers (>10 cigarettes/ day); 5. Not require restorative treatment of the adjacent teeth.
Intervention Implant placement
All the implants used in this study were Straumannâ Standard Plus SLA implants (Institut Straumann AG, Waldenburg, Switzerland). The implant placement was planned based on pre-surgical clinical and radiographic assessment. The implants were placed in a three-dimensional position described by Buser and colleagues (Buser et al. 2004). A bone augmentation procedure was carried out if (i) implant neck remained uncovered or (ii) the buccal bone plate was PES ≥ 6), and unfavorable rate (PES < 6) (Belser et al. 2009; Cosyn et al. 2012). Clinical assessment
Material and methods
The survival rate was defined as the percentage of the implants remained in the oral cav-
Study design and patient data
This study was design as a prospective study with 2-year follow-up. The study was conducted at the Department of Oral and Maxillofacial Implant of the Shanghai Ninth People Hospital. From May 2010 to May 2012, 40 generally healthy patients (18 women and 22 men), aged from 19 to 58 years (mean 31.3 years), were included in this study. All patients signed the information consent from and received oral hygiene instructions before the implant surgery was
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Fig. 2. The fabrication of provisional plastic crowns. Fig. 1. Flow chart of clinical procedures.
© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd
Gu et al Evaluation of soft tissue alteration
ity. Both biological and mechanical complications were recorded. In addition, the following clinical variables were assessed: gingival biotype (Muller et al. 2000), modified plaque index (mPI), probing pocket depth (PPD), modified bleeding index (mBI). All the measurements were made by the same dentist using a periodontal probe (15 UNC/CP-11.5B Screening Color-Coded Probe, Hu-Friedy) (Mombelli et al. 1987). Follow-up assessment
Patients were re-called for clinical and esthetic assessment at 1-year and 2-year after crown placement, and the indices of mPI, PPD, mBI, and PES/WES were recorded. Statistical methods
Data analysis was performed using a statistical software package STATA (version 11.0; StataCorp, College Station, TX, USA). Nonnormally distributed data (mBI, mPI, PPD, and PES/WES) were analyzed using Wilcoxon signed-rank test. The intraclass correlation coefficient was used to determine the interexaminer reliability. Wilcoxon rank-sum test was used to analyze the mean PES value and PES changing in patients with different graft procedures and gingival biotypes. The reported P values were two-sided. Statistical significance was set at 5%.
Results After two-year follow-up, two patients were excluded because they declined to come back for the follow-up examination. At last, 38 patients were included in this analysis. Table 1 shows the demographic features of all the subjects. The interclass correlation coefficient of the mean PES/WES value given by two orthodontists was 0.85 at baseline, 0.82 at 1-year follow-up, and 0.82 at 2-year follow-up. Table 2 shows the mean PES/WES value from baseline to 1-year follow-up. PES/WES significantly increased from 13.79 to 14.87 at 1-year follow-up (P < 0.01). In detail, the mean value of mesial and distal papilla, curvature and PES also increased significantly at
Table 1. Summary of patient characteristics Mean age in years Male/female ratio Patient need graft/not graft Implant site location: I1/I2/C Implant diameter: 3.3 mm/4.1 mm Implant length: 10 mm/12 mm
31.3(19–58) 22/16 24/14 12/18/8 20/18 12/26
I1, first incisor; I2, second incisor; C, cannine.
1-year follow-up. The mean value of margin level and root convexity/color/texture slightly increased, but both did not reach statistically significance. Table 3 shows the mean PES/WES value from 1-year follow-up to 2-year follow-up. PES/WES showed steady improvement (from 14.87 to 14.96) at 2-year follow-up (P = 0.40). In detail, the mean value of mesial and distal papilla, curvature, root convexity/color/texture, and PES showed steady improvement at 2-year follow-up. The mean value of margin level decreased slightly. And none parameters showed statistically significantly difference from 1-year follow-up to 2-year follow-up. Fig 3 shows one typical example of all the subjects included in the study. Table 4 shows PES frequency at baseline, 1-year, and 2-year follow-up. The perfect rate (PR) increased from 2.63% to 34.21% after 2year follow-up. The acceptable rate (AR) decreased from 78.95% to 59.21%. The unfavorable rate (UR) decreased from 18.42% to 6.58%. Table 5 shows influence of variables on esthetic outcome of peri-implant soft tissue. Mean PES value did not show significant
difference between patients with thick and thin biotype at baseline (P = 0.27). However, patients with thick biotype could achieve significantly higher mean PES value at followup (P = 0.02). In addition, PES changing value was higher in patients with thick biotype (P = 0.03). Graft procedure had an unfavorable effect on mean PES value both at baseline and at follow-up (P < 0.01). However, similar PES changing value was found in patients with or without graft (P = 0.44). No implants were lost during the observation period, representing the survival rate was 100%. Three patients experienced periimplant infection. All the three patients had undergone guided bone regeneration (GBR) procedure due to the insufficient bone volume. Thus, the biological complication rate was 7.9%. Two patients showed significant improvement after debridement. One patient showed recession of mid-facial mucosa and exposure of neck metal. No mechanical complications have occurred during the observation period. Table 6 shows the change of clinical parameters from baseline to follow-up. No significant difference was found with the
Table 2. Mean pink esthetic score/white esthetic score value from baseline to 1-year follow-up mean (median) SD Baseline(n = 38) Mesial papilla Distal papilla Margin level Curvature Root/color/texture PES Form Outline Color Texture Translucency WES PES/WES *
1.34 (1) 1.03 (1) 1.34 (1) 1.58 (2) 1.16 (1) 6.45 (7) 1.58 (2) 1.34 (1) 1.29 (1) 1.50 (1) 1.63 (2) 7.34 (8) 13.79 (14)
0.48 0.16 0.58 0.50 0.37 1.16 0.50 0.48 0.46 0.51 0.49 1.26 2.25
1-year (n = 38) 1.68 (2) 1.42 (1) 1.39 (1) 1.84 (2) 1.24 (1) 7.58 (8) 1.55 (2) 1.32 (1) 1.28 (1) 1.49 (1) 1.66 (2) 7.29 (8) 14.87 (15)
0.47 0.50 0.68 0.37 0.59 1.51 0.49 0.53 0.45 0.53 0.48 1.11 2.21
P P P P P P P P P P P P P
< < = = = < = = = = = =
7). As the WES score is strongly related to the prosthetic design and quality, we pay more attention to the PES score. In this study, baseline assessment was performed two days later to avoid the interference of pressure caused by immediately crowns placement. Spontaneous improvement in mean PES value was observed after one year follow-up and the slowdown of the improvement was observed at the second year follow-up. Mesial and distal papilla showed significant improvement during the observation period. This observation may be due to the relatively high bone level at the adjacent natural teeth as only patients with single gap were included, for it is strongly believed that the extent of papillae fill surrounding an implant-supported restoration is principally decided by the bone level at the adjacent teeth (Chow & Wang 2010; Singh et al. 2013). The curvature of soft tissue also showed significant improvement during the observation period. It has been proven that periimplant soft tissue is still in remodeling phase after abutment and crown attachment (Priest 2003; Schropp et al. 2005). With the relief of the pressure, the soft tissue may become relatively more mature and healthier with the time. This may probably explain why the soft tissue curvature score increased significantly. The margin level and root convexity/color/ texture of soft tissue did not show significant difference during the observation period. The score of margin level even slightly decreased at 2-year follow-up compared with score at 1year follow-up. This result is a little different from our previous study using the same implant systems (Lai et al. 2008). Only patients with sufficient bone volume were included in that study. Significant improvement in margin-level score was reported after 6–8 months follow-up. Recession of midfacial mucosa caused by peri-implant infection in three subjects may explain the differ-
© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd
Gu et al Evaluation of soft tissue alteration
Table 6. Summary of patient’s gingival biotype and clinical parameters mean (median) SD Biotype: thick/thin
mBI
PPD(mm)
mPI
Baseline (n = 38) 1-year follow-up (n = 38)
28/10 28/10
2-year follow-up (n = 38)
28/10
0.58 (1) 0.50 0.63 (1) 0.67 P = 0.59 0.66 (1) 0.67 P = 0.44
4.16 (4) 0.68 4.32 (4) 0.57 P = 0.11 4.39 (4) 0.70 P = 0.06
0.37 (0) 0.49 0.45 (0) 0.50 P = 0.37 0.47 (0) 0.51 P = 0.25
mPI, modified plaque index; PPD, probing pocket depth; mBI, modified bleeding index.
ence. This agreed with the findings in previous studies that higher biological complication rate was found in patients with grafting (den Hartog et al. 2013; Santing et al. 2013). Among 38 patients in this study, 24 patients experienced grafting procedures combined with implant placement. The mean PES value in patients with grafting was significantly lower in those without grafting both at baseline and at follow-up. This implied that the grafting procedures might have an unfavorable effect on the esthetic outcome of peri-implant soft tissue. The less favorable pre-surgical situation, scar tissue caused by additional surgical procedures, higher complication rate, and resorption of graft materials may be the possible reason for this result. However, similar alterations of mean PES value were found in patients with or without GBR in this study, and the mean PES value increased from 5.92 to 7.31 after 2-year follow-up. This indicated tissue-level implant systems could achieve spontaneous improvement in soft tissue visual appearance also in patients with GBR. It is believed that biologic width around one-piece tissue-level implants was more similar to natural teeth than that around twopiece bone-level implants (Hermann et al.
2001). The disconnections and reconnections of abutments which are necessary in bonelevel implant systems may disturb connective tissue interaction and result a more apically positioned zone of connective tissue (Degidi et al. 2011). In addition, a recent published study showed tissue-level implants may present better long-term results in terms of peri-implant bone maintenance, as compared with bone-level implants (Chiapasco et al. 2014). This may explain the favorable outcome in our study and demonstrate that tissue-level implants are also suitable to support single implant crowns in esthetic area. Several studies have demonstrated that thick gingivae have lower risk of recession of mid-facial margin-level and interdental papilla (Lee et al. 2011; Cabello et al. 2013). In this study, similar mean PES value was found in patients with thick or thin gingival biotype at baseline. After 2-year follow-up, patients with thick gingival biotype achieved more favorable esthetic outcome of peri-implant soft tissue. This means gingival biotype can be considered as prognostic factors for esthetic assessment. Besides the mean value, the existing indices that categorize single features should also be analyzed with frequency analysis (Lang &
Zitzmann 2012). It should be noted that PES/ WES index should be classified as an ordinal data instead of a continuous data. Frequency analysis which reflects the discrete distribution of data is important for ordinal data (Shi et al. 2014). In this study, the perfect rate at 2-year follow-up was almost thirteen times as much as it at baseline. And the unfavorable rate decreased after 2-year follow-up. The result of frequency analysis also confirmed the improvement in esthetic outcome.
Conclusion The results of the present study indicate that it is feasible to use tissue-level implant to support single crowns in esthetic area. Favorable short-term esthetic outcome and stability of soft tissue around single implant crowns can be expected in patients with or without graft. However, graft procedures might have an unfavorable effect on the esthetic outcome. Gingival biotype can be considered as prognostic factor for esthetic outcome. RCTs with long-term follow-up are needed to provide evidence for the long-term stability of peri-implant soft tissue using tissue-level implant systems.
Acknowledgement We would like to thank Sheng-hui Li (Shanghai Jiaotong University, College of Medicine) for statistics consultation.
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Authors’ affiliations: Ying-Xin Gu, Jun-Yu Shi, Long-Fei Zhuang, Shi-Chong Qiao, You-You Xu, Hong-Chang Lai, Department of Oral and Maxillo-facial Implantology, Shanghai Key Laboratory of Stomatology, Shanghai Ninth People’s Hospital, School of Medicine, Shanghai Jiaotong University, Shanghai, China Corresponding author: Hong-Chang Lai Department of Oral and Maxillo-facial Implantology Shanghai Ninth People’s Hospital, School of Medicine Shanghai Jiaotong University 639 Zhizaoju Road, Shanghai, 200011, China Tel.: +86 21 23271699 Fax: +86 21 53073068 e-mail: [email protected]
Esthetic outcome and alterations of soft tissue around single implant crowns: a 2-year prospective study
Key words: dental implants, pink esthetic score/white esthetic score, soft tissue esthetic out-
come, tissue level Abstract Objective: The aim of this prospective study was to assess the esthetic outcome and alterations of peri-implant soft tissue using tissue-level implants. Furthermore, the influencing factors, including grafting and gingival biotype, of esthetic outcome of peri-implant soft tissue were also evaluated. Materials and methods: Of 38 patients with single missing anterior tooth in maxilla were treated with a Straumann
â
Standard Plus SLA implant. Bone augmentation was performed in 24 patients.
Follow-up was conducted at 12 and 24 months after definitive crowns placement. Esthetic outcome using the pink esthetic score/white esthetic score (PES/WES) and clinical parameters were evaluated. Results: The mean PES/WES value at baseline, 1-year, and 2-year examination was 13.79, 14.87, and 14.96. Significant improvement was found between baseline and 1-year examination (P < 0.01). And the improvement between 1-year and 2-year examination was not significant (P = 0.40). The mean PES changing value in patients with thick biotype was significantly higher than those with thin biotype at 2-year after definitive crowns placement (P = 0.03). Graft procedure had an unfavorable effect on mean PES value both at baseline and at follow-up (P < 0.01). No implants were lost at 2-year examination. Three patients experienced peri-implant infection. No significant difference was found with the passage of time in modified plaque index (mPI), probing pocket depth (PPD), and modified bleeding index (mBI). Conclusion: According to the present prospective clinical study, it can be concluded that it is feasible to use tissue-level implant to support single crowns in esthetic area. Favorable short-term esthetic outcome and stability of soft tissue around single implant crowns can be expected in patients with or without graft. However, graft procedures might have an unfavorable effect on the esthetic outcome. Gingival biotype can be considered as prognostic factor for esthetic outcome. RCTs with long-term follow-up are needed to provide evidence for the long-term stability of peri-implant soft tissue using tissue-level implant systems.
*These authors contributed equally to this work. The authors claim that none of the material in the article has been published or is under consideration for publication elsewhere. Date: Accepted 21 March 2014 To cite this article: Gu Y-X, Shi J-Y, Zhuang L-F, Qiao S-C, Xu Y-Y, Lai H-C. Esthetic outcome and alterations of soft tissue around single implant crowns: a 2-year prospective study. Clin. Oral Impl. Res. 00, 2014, 1–6 doi: 10.1111/clr.12408
In recent years, rehabilitation of single-tooth gaps by means of dental implants has become a routine treatment with high survival and success rates (Pjetursson et al. 2007, 2012; Jung et al. 2008). However, the success of implant treatment should not be limited to achieving osseointegration. The esthetic outcome of the reconstruction also becomes an important parameter for clinical success especially for esthetically sensitive cases. For clinical esthetic assessment, both implant crown features and peri-implant soft tissue stability should be taken into consideration (Chang et al. 1999). However, periimplant soft tissue meets most clinical challenges from the esthetic aspect. The most
© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd
common reasons for esthetic failure include disharmonious mucosal color or texture, complete or incomplete loss of interproximal papillae, and recession of soft tissue level. So the soft tissue esthetic outcome is of paramount importance to achieving clinical esthetic success (Belser et al. 2004). Pink esthetic score (PES) (Furhauser et al. 2005) or pink esthetic score/white esthetic score (PES/WES) (Belser et al. 2009) is now adopted by more and more studies to assess esthetic outcome and alterations of periimplant soft tissue. Connective tissue graft might be necessary in about one-third of the patients following type 1 (immediate after tooth extraction) implants placement to
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achieve steady improvement in PES score (Cosyn et al. 2013). Following type 2 (4–8 weeks after tooth extraction) and type 3 (12– 16 weeks after tooth extraction) implants placement, spontaneous improvements of PES score might occur in the short-term follow-up, and then the PES score will likely reverse to the baseline level when the observational time was prolonged to at least 3 years after crown installation (Buser et al. 2011, 2013; Weinlander et al. 2011; Pieri et al. 2013). It is worth mentioning that only bone-level implant systems were used in the above studies. Bone-level implant systems were widely used in patients needed implant treatment in esthetic area because of more concise surgical procedures and less bone resportion especially when platform-switching technology was used (Al-Nsour et al. 2012; Annibali et al. 2012). Meanwhile, tissue-level implant systems are also widely used in clinical practices, and few studies have reported the esthetic evaluation using tissue-level implant systems. A previously published study by our group has proved that tissue-level implant systems can also achieve predictable soft tissue appearance on the premise of accurate implant placement depth (Lai et al. 2008). However, the follow-up was relatively short (6–8 months), and patients in need of graft procedures were excluded. To our knowledge, this is the first prospective study reporting the PES index of soft tissue using tissue-level implants in patients with and without bone augmentation. Therefore, the aims of the present study were (i) to assess the esthetic outcome and alterations of peri-implant soft tissue using tissue-level implants after 2-year follow-up and (ii) to study the influencing factors, including grafting and gingival biotype, of esthetic outcome of peri-implant soft tissue.
performed. Fig. 1 shows the flow of clinical procedures. The inclusion criteria were as follows: 1. Patients in need of single-tooth restoration in the anterior maxilla; 2. Tooth extraction at least three months before implant surgery; 3. No severe vertical bone defect and enough primary stability to achieve simultaneous implant placement; 4. Not be heavy smokers (>10 cigarettes/ day); 5. Not require restorative treatment of the adjacent teeth.
Intervention Implant placement
All the implants used in this study were Straumannâ Standard Plus SLA implants (Institut Straumann AG, Waldenburg, Switzerland). The implant placement was planned based on pre-surgical clinical and radiographic assessment. The implants were placed in a three-dimensional position described by Buser and colleagues (Buser et al. 2004). A bone augmentation procedure was carried out if (i) implant neck remained uncovered or (ii) the buccal bone plate was PES ≥ 6), and unfavorable rate (PES < 6) (Belser et al. 2009; Cosyn et al. 2012). Clinical assessment
Material and methods
The survival rate was defined as the percentage of the implants remained in the oral cav-
Study design and patient data
This study was design as a prospective study with 2-year follow-up. The study was conducted at the Department of Oral and Maxillofacial Implant of the Shanghai Ninth People Hospital. From May 2010 to May 2012, 40 generally healthy patients (18 women and 22 men), aged from 19 to 58 years (mean 31.3 years), were included in this study. All patients signed the information consent from and received oral hygiene instructions before the implant surgery was
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Fig. 2. The fabrication of provisional plastic crowns. Fig. 1. Flow chart of clinical procedures.
© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd
Gu et al Evaluation of soft tissue alteration
ity. Both biological and mechanical complications were recorded. In addition, the following clinical variables were assessed: gingival biotype (Muller et al. 2000), modified plaque index (mPI), probing pocket depth (PPD), modified bleeding index (mBI). All the measurements were made by the same dentist using a periodontal probe (15 UNC/CP-11.5B Screening Color-Coded Probe, Hu-Friedy) (Mombelli et al. 1987). Follow-up assessment
Patients were re-called for clinical and esthetic assessment at 1-year and 2-year after crown placement, and the indices of mPI, PPD, mBI, and PES/WES were recorded. Statistical methods
Data analysis was performed using a statistical software package STATA (version 11.0; StataCorp, College Station, TX, USA). Nonnormally distributed data (mBI, mPI, PPD, and PES/WES) were analyzed using Wilcoxon signed-rank test. The intraclass correlation coefficient was used to determine the interexaminer reliability. Wilcoxon rank-sum test was used to analyze the mean PES value and PES changing in patients with different graft procedures and gingival biotypes. The reported P values were two-sided. Statistical significance was set at 5%.
Results After two-year follow-up, two patients were excluded because they declined to come back for the follow-up examination. At last, 38 patients were included in this analysis. Table 1 shows the demographic features of all the subjects. The interclass correlation coefficient of the mean PES/WES value given by two orthodontists was 0.85 at baseline, 0.82 at 1-year follow-up, and 0.82 at 2-year follow-up. Table 2 shows the mean PES/WES value from baseline to 1-year follow-up. PES/WES significantly increased from 13.79 to 14.87 at 1-year follow-up (P < 0.01). In detail, the mean value of mesial and distal papilla, curvature and PES also increased significantly at
Table 1. Summary of patient characteristics Mean age in years Male/female ratio Patient need graft/not graft Implant site location: I1/I2/C Implant diameter: 3.3 mm/4.1 mm Implant length: 10 mm/12 mm
31.3(19–58) 22/16 24/14 12/18/8 20/18 12/26
I1, first incisor; I2, second incisor; C, cannine.
1-year follow-up. The mean value of margin level and root convexity/color/texture slightly increased, but both did not reach statistically significance. Table 3 shows the mean PES/WES value from 1-year follow-up to 2-year follow-up. PES/WES showed steady improvement (from 14.87 to 14.96) at 2-year follow-up (P = 0.40). In detail, the mean value of mesial and distal papilla, curvature, root convexity/color/texture, and PES showed steady improvement at 2-year follow-up. The mean value of margin level decreased slightly. And none parameters showed statistically significantly difference from 1-year follow-up to 2-year follow-up. Fig 3 shows one typical example of all the subjects included in the study. Table 4 shows PES frequency at baseline, 1-year, and 2-year follow-up. The perfect rate (PR) increased from 2.63% to 34.21% after 2year follow-up. The acceptable rate (AR) decreased from 78.95% to 59.21%. The unfavorable rate (UR) decreased from 18.42% to 6.58%. Table 5 shows influence of variables on esthetic outcome of peri-implant soft tissue. Mean PES value did not show significant
difference between patients with thick and thin biotype at baseline (P = 0.27). However, patients with thick biotype could achieve significantly higher mean PES value at followup (P = 0.02). In addition, PES changing value was higher in patients with thick biotype (P = 0.03). Graft procedure had an unfavorable effect on mean PES value both at baseline and at follow-up (P < 0.01). However, similar PES changing value was found in patients with or without graft (P = 0.44). No implants were lost during the observation period, representing the survival rate was 100%. Three patients experienced periimplant infection. All the three patients had undergone guided bone regeneration (GBR) procedure due to the insufficient bone volume. Thus, the biological complication rate was 7.9%. Two patients showed significant improvement after debridement. One patient showed recession of mid-facial mucosa and exposure of neck metal. No mechanical complications have occurred during the observation period. Table 6 shows the change of clinical parameters from baseline to follow-up. No significant difference was found with the
Table 2. Mean pink esthetic score/white esthetic score value from baseline to 1-year follow-up mean (median) SD Baseline(n = 38) Mesial papilla Distal papilla Margin level Curvature Root/color/texture PES Form Outline Color Texture Translucency WES PES/WES *
1.34 (1) 1.03 (1) 1.34 (1) 1.58 (2) 1.16 (1) 6.45 (7) 1.58 (2) 1.34 (1) 1.29 (1) 1.50 (1) 1.63 (2) 7.34 (8) 13.79 (14)
0.48 0.16 0.58 0.50 0.37 1.16 0.50 0.48 0.46 0.51 0.49 1.26 2.25
1-year (n = 38) 1.68 (2) 1.42 (1) 1.39 (1) 1.84 (2) 1.24 (1) 7.58 (8) 1.55 (2) 1.32 (1) 1.28 (1) 1.49 (1) 1.66 (2) 7.29 (8) 14.87 (15)
0.47 0.50 0.68 0.37 0.59 1.51 0.49 0.53 0.45 0.53 0.48 1.11 2.21
P P P P P P P P P P P P P
< < = = = < = = = = = =
7). As the WES score is strongly related to the prosthetic design and quality, we pay more attention to the PES score. In this study, baseline assessment was performed two days later to avoid the interference of pressure caused by immediately crowns placement. Spontaneous improvement in mean PES value was observed after one year follow-up and the slowdown of the improvement was observed at the second year follow-up. Mesial and distal papilla showed significant improvement during the observation period. This observation may be due to the relatively high bone level at the adjacent natural teeth as only patients with single gap were included, for it is strongly believed that the extent of papillae fill surrounding an implant-supported restoration is principally decided by the bone level at the adjacent teeth (Chow & Wang 2010; Singh et al. 2013). The curvature of soft tissue also showed significant improvement during the observation period. It has been proven that periimplant soft tissue is still in remodeling phase after abutment and crown attachment (Priest 2003; Schropp et al. 2005). With the relief of the pressure, the soft tissue may become relatively more mature and healthier with the time. This may probably explain why the soft tissue curvature score increased significantly. The margin level and root convexity/color/ texture of soft tissue did not show significant difference during the observation period. The score of margin level even slightly decreased at 2-year follow-up compared with score at 1year follow-up. This result is a little different from our previous study using the same implant systems (Lai et al. 2008). Only patients with sufficient bone volume were included in that study. Significant improvement in margin-level score was reported after 6–8 months follow-up. Recession of midfacial mucosa caused by peri-implant infection in three subjects may explain the differ-
© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd
Gu et al Evaluation of soft tissue alteration
Table 6. Summary of patient’s gingival biotype and clinical parameters mean (median) SD Biotype: thick/thin
mBI
PPD(mm)
mPI
Baseline (n = 38) 1-year follow-up (n = 38)
28/10 28/10
2-year follow-up (n = 38)
28/10
0.58 (1) 0.50 0.63 (1) 0.67 P = 0.59 0.66 (1) 0.67 P = 0.44
4.16 (4) 0.68 4.32 (4) 0.57 P = 0.11 4.39 (4) 0.70 P = 0.06
0.37 (0) 0.49 0.45 (0) 0.50 P = 0.37 0.47 (0) 0.51 P = 0.25
mPI, modified plaque index; PPD, probing pocket depth; mBI, modified bleeding index.
ence. This agreed with the findings in previous studies that higher biological complication rate was found in patients with grafting (den Hartog et al. 2013; Santing et al. 2013). Among 38 patients in this study, 24 patients experienced grafting procedures combined with implant placement. The mean PES value in patients with grafting was significantly lower in those without grafting both at baseline and at follow-up. This implied that the grafting procedures might have an unfavorable effect on the esthetic outcome of peri-implant soft tissue. The less favorable pre-surgical situation, scar tissue caused by additional surgical procedures, higher complication rate, and resorption of graft materials may be the possible reason for this result. However, similar alterations of mean PES value were found in patients with or without GBR in this study, and the mean PES value increased from 5.92 to 7.31 after 2-year follow-up. This indicated tissue-level implant systems could achieve spontaneous improvement in soft tissue visual appearance also in patients with GBR. It is believed that biologic width around one-piece tissue-level implants was more similar to natural teeth than that around twopiece bone-level implants (Hermann et al.
2001). The disconnections and reconnections of abutments which are necessary in bonelevel implant systems may disturb connective tissue interaction and result a more apically positioned zone of connective tissue (Degidi et al. 2011). In addition, a recent published study showed tissue-level implants may present better long-term results in terms of peri-implant bone maintenance, as compared with bone-level implants (Chiapasco et al. 2014). This may explain the favorable outcome in our study and demonstrate that tissue-level implants are also suitable to support single implant crowns in esthetic area. Several studies have demonstrated that thick gingivae have lower risk of recession of mid-facial margin-level and interdental papilla (Lee et al. 2011; Cabello et al. 2013). In this study, similar mean PES value was found in patients with thick or thin gingival biotype at baseline. After 2-year follow-up, patients with thick gingival biotype achieved more favorable esthetic outcome of peri-implant soft tissue. This means gingival biotype can be considered as prognostic factors for esthetic assessment. Besides the mean value, the existing indices that categorize single features should also be analyzed with frequency analysis (Lang &
Zitzmann 2012). It should be noted that PES/ WES index should be classified as an ordinal data instead of a continuous data. Frequency analysis which reflects the discrete distribution of data is important for ordinal data (Shi et al. 2014). In this study, the perfect rate at 2-year follow-up was almost thirteen times as much as it at baseline. And the unfavorable rate decreased after 2-year follow-up. The result of frequency analysis also confirmed the improvement in esthetic outcome.
Conclusion The results of the present study indicate that it is feasible to use tissue-level implant to support single crowns in esthetic area. Favorable short-term esthetic outcome and stability of soft tissue around single implant crowns can be expected in patients with or without graft. However, graft procedures might have an unfavorable effect on the esthetic outcome. Gingival biotype can be considered as prognostic factor for esthetic outcome. RCTs with long-term follow-up are needed to provide evidence for the long-term stability of peri-implant soft tissue using tissue-level implant systems.
Acknowledgement We would like to thank Sheng-hui Li (Shanghai Jiaotong University, College of Medicine) for statistics consultation.
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