University of Groningen
Soft tissue grafting and single implant treatment in the aesthetic region
Zuiderveld, Elise
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Publication date: 2018
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Zuiderveld, E. (2018). Soft tissue grafting and single implant treatment in the aesthetic region. Rijksuniversiteit Groningen.
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This chapter is an edited version of the manuscript:
Zuiderveld, E.G., den Hartog, L., Vissink, A., Raghoebar, G.M., Meijer, H.J.A. Significance of Buccopalatal Implant Position, Biotype, Platform Switching, and
Pre-im-plant Bone Augmentation on the Level of the Midbuccal Mucosa.
The International Journal of Prosthodontics 2014; 27: 477-479.
CHAPTER 2
Significance of bucco-palatal
implant position, gingival biotype,
platform-switching and pre-implant
bone augmentation on the level of the
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Abstract
Aim:
To assess whether bucco-palatal implant position, gingival biotype, platform-switching and pre-implant bone augmentation affects the level of the mid-buccal mucosa (MBML).
Materials & Methods:
90 patients with a single-tooth implant in the aesthetic zone were included. The MBML was measured on photographs taken one year after crown placement.
Results:
The factors analysed explained 22% of the variance of the MBML. The more an implant was placed to the buccal, the more the MBML was positioned apically. A comparable phenome-non was observed in cases with a thick biotype and cases that underwent pre-implant bone augmentation. Platform-switching did not affect the level of the MBML.
Conclusion:
The factors analysed in this study account for only a small portion of the variance of the MBML.
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Introduction
Hitherto, only few studies have focused on factors influencing the level of the mid-buccal mucosa (MBML). It has been suggested that implants placed too far to the buccal and cases with a thin gingival biotype show more mid-buccal recession (Evans & Chen 2008, Cosyn et al. 2012a). Furthermore, it has been shown that pre-implant bone augmentation is associated with less satisfactory overall soft tissue aesthetics (Cosyn et al. 2012a), but its effect on the posi-tion of the MBML has not been considered yet.The same holds true for the effect of using implants with a non-matching implant abutment diameter (i.e., platform-switching). Although implants with platform-switching show less marginal peri-implant bone loss (Al-Nsour et al. 2012), the effect of platform-switching on the position of the MBML is debatable. Therefore, by means of a multivariate analysis, we assessed the significance of bucco-palatal implant position, gingival biotype, platform-switching, and pre-implant bone augmentation on the mid-buccal mucosal level for single-tooth implants in the aesthetic zone.
Materials & Methods
Ninety patients (53.3% male; mean age: 36.5 years; range: 18-71 years) with a single-tooth implant replacing a central (75.6%) or lateral incisor (24.4%) were included. Patients partici- pated in clinical trials of different implant types and received an implant depending on the study they were enrolled: NobelReplace Groovy and NobelReplace Select (Nobel Biocare AB, Gothenburg) without platform-switching (45 patients) or Straumann Bone Level (Wolhusen, Switzerland) with platform-switching (45 patients). Implants were inserted in healed sites (45.6% with pre-implant bone augmentation) and restored after three months.
Implant position, i.e., its distance from the buccal contour of the alveolar crest, was measured on the definitive crown casts with a digital caliper (Fig. 1). The vertical position of the MBML was measured on photographs taken one year after placement of the implant crown, using the GNU Image Manipulation Program (http://www.gimp.org/; Fig. 2). Negative values, which indicated a more coronally positioned mucosal level compared to the contralateral tooth, were considered as no difference in mucosa position. Measurements were done to the nearest 0.1 mm. Gingival biotype was rated visually on the same photographs based on specific features according to De Rouck et al. (2009)by two examiners independently. Data were analysed using IBM SPSS Statistics (version 20.0, SPSS Inc, Chicago, IL, USA). Univariate analyses were performed for each predictor variable. Predictors with a p-value ≤0.2 were entered into a multivariate linear regression model using a stepwise entry procedure. A significance level of 0.05 was chosen.
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Fig. 1 – Measurement of the bucco-palatal implant position
A reference line was drawn between the cervical edges of the neighbouring teeth. The distance of the buccal aspect of the implant to this line was measured with a digital caliper.
Fig. 2 – Measurement of the position of the MBML
After calibration with a periodontal probe, the length of the clinical implant crown along the vertical axis (i.e., distance between incisal edge and mucosal margin) was measured and subtracted from the length of the crown of the contralateral tooth.
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Results
On average, the MBML was located 0.55±0.72 mm more apically compared to the gingival level of the contralateral tooth. Of the total number of implants, 94.4% of the implants were placed at least 1.0 mm palatal to the reference line. 53.3% of the cases were screened as a thin gingival biotype. Multivariate linear regression analysis showed that the factors implant position, gingival biotype, and pre-implant bone augmentation together explained 22% of the variance of the level of the mid-buccal mucosa. Platform-switching provided no contribution to this variance. The more the implant was positioned to the buccal, the more the MBML was situated apically. The same was found for a thick gingival biotype and pre-implant bone augmentation. Results of the analysis are shown in Table 1.
Table 1 – Results of the multiple linear regression analysis.
Variable β p-value R Square
Pre-implant bone augmentation Thick gingival biotype
Implant position .29 .28 -.24 0.005 0.005 0.015 0.086 0.166 0.222
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Discussion
The factors analysed in this study only explained 22% of the variance of the MBML, mean-ing that there are more factors influencmean-ing this position. It might be that the soft and hard tissue levels before implant placement play a dominant role for the final position of the MBML. According to the literature, an intact buccal bone wall is associated with little risk of recession for immediate implant cases (Cosyn et al. 2012b). Although implants in our study were conventionally placed, we hypothesize that a favourable pre-operative situation with little resorption of the buccal bone wall, will lead to a more favourable final position of the MBML, also in conventional cases. This hypothesis might be supported by the finding that in our study a pre-implant bone augmentation contributed most to the variance of the vertical position of the MBML. The fact that a pre-implant bone augmentation is needed implies that the pre-existing architecture is already compromised. Of course, the augmentation procedure itself might also lead to a more apically located MBML.
We found a more apically situated MBML in cases with a thick gingival biotype. This is in contrast with the study by Evans and Chen (2008), showing more mid-buccal recession in cases with a thin gingival biotype. It should be noted, however, that this study only included immediate implant cases. Furthermore, as stated in a recent systematic review (Cosyn et al. 2012b), evidence to support increased risk for mid-buccal recession in patients with a thin gingival biotype is limited. To what extent gingival biotype is of significance, also in conven-tional cases, needs further investigation.
In conclusion, the factors analysed in this study account for only a small portion of the vari-ance of the MBML. The more an implant was placed to the buccal, the more the MBML was positioned apically. A comparable phenomenon was observed in cases with a thick gingival biotype and in cases in which pre-implant bone augmentation was performed, whereas plat-form-switching did not affect the level of the mid-buccal mucosa.
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References
Al-Nsour, M.M., Chan, H.-L. & Wang, H.-L. (2012) Effect of the platform-switching technique on preservation of peri-implant marginal bone: a systematic review. The International journal of oral & maxillofacial implants 27, 138–145.
Cosyn, J., Sabzevar, M.M. & De Bruyn, H. (2012a) Predictors of inter-proximal and midfacial recession following single implant treatment in the anterior maxilla: a multivariate analysis. Journal of clinical periodontology 39, 895–903. Cosyn, J., Hooghe, N. & De Bruyn, H. (2012b) A systematic review on the frequency of advanced recession following
single immediate implant treatment. Journal of clinical periodontology 39, 582–589.
Evans, C.D. & Chen, S.T. (2008) Esthetic outcomes of immediate implant placements. Clinical oral implants research 19, 73–80.
De Rouck, T., Eghbali, R., Collys, K., De Bruyn, H. & Cosyn, J. (2009) The gingival biotype revisited: transparency of the periodontal probe through the gingival margin as a method to discriminate thin from thick gingiva.
