Predictors of Alveolar Process Remodeling Following Ridge Preservation in High-Risk Patients Jan Cosyn, DDS, MSc, PhD;* Roberto Cleymaet, DDS, PhD;† Hugo De Bruyn, DDS, MSc, PhD‡
ABSTRACT Purpose: (1) To clinically evaluate horizontal remodeling of the alveolar process (hard and soft tissues) following ridge preservation in high-risk patients and (2) to identify predictors of such remodeling. Materials and Methods: Periodontally healthy nonsmoking patients with a failing tooth in the anterior maxilla (15–25) were selected for a prospective case series. All were in need of a single implant and demonstrated high risk for aesthetic complications given an incomplete buccal bone wall and/or thin-scalloped gingival biotype. Following flapless tooth extraction, ridge preservation was performed using one or more collagen-enriched, bovine-derived block grafts (Geistlich Bio-Oss® Collagen® 100 mg, Geistlich Pharma AG, Wolhusen, Switzerland) without the additional use of membranes or soft tissue grafts. The change in buccopalatal dimension of the alveolar process between baseline (prior to tooth extraction) and 4 months was assessed on the basis of superimposed occlusal slides. Regression analysis was performed to identify predictors of alveolar process remodeling. Results: Forty-two patients (21 females, 21 males; mean age 38) met the selection criteria and consented to the treatment. Mean alveolar process remodeling was 14% (SD 7, range 4–30) with minimal remodeling (210%) in 16 patients (38%) and advanced remodeling (>20%) in 10 patients (24%). A single implant could be installed in all subjects without additional guided bone regeneration. Connective tissue grafting was performed later on in the treatment for aesthetic purposes, hereby compensating for tissue loss at the buccal aspect. Predictors of alveolar process remodeling were tooth location (central incisors and cuspids > laterals incisors and premolars), tooth abscess (p = .025), and buccal bone loss (p = .035). Conclusion: Alveolar process remodeling seems inevitable yet acceptable following ridge preservation in high-risk patients. Proper case selection may reduce the incidence of advanced remodeling. KEY WORDS: alveolar process, extraction socket, remodeling, ridge preservation, tooth extraction, xenograft
INTRODUCTION An incomplete buccal bone wall is a common finding following tooth extraction. This is traditionally treated by means of guided bone regeneration (GBR) following a postextraction healing period of at least 6 weeks.1–5 GBR is performed in conjunction with implant surgery,
*Associate professor, Faculty of Medicine and Health Sciences, Dental School, Department of Periodontology and Oral Implantology, Ghent University, Ghent, Belgium and professor, Faculty of Medicine and Pharmacy, Dental Medicine, Department of Periodontology and Oral Implantology, Free University of Brussels (VUB), Brussels, Belgium; †professor, Faculty of Medicine and Pharmacy, Dental Medicine, Free University of Brussels (VUB), Brussels, Belgium; ‡ chairman, professor, Faculty of Medicine and Health Sciences, Dental School, Department of Periodontology and Oral Implantology, Ghent University, Ghent, Belgium and professor, Faculty of Odontology, Department of Prosthodontics, Malmö University, Malmö, Sweden
Conflict of interest and source of funding statement The authors declare that they have no conflict of interest. This study was supported by departmental funds of the Free University of Brussels (VUB), and biomaterials were provided by Geistlich Pharma AG (Wolhusen, Switzerland).
Corresponding Author: Prof. Jan Cosyn, Faculty of Medicine and Health Sciences, Dental School, Department of Periodontology and Oral Implantology, University of Ghent, De Pintelaan 185, Ghent B-9000, Belgium; e-mail: [email protected]
© 2014 Wiley Periodicals, Inc. DOI 10.1111/cid.12249
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and implants are usually installed in a two-stage procedure to allow primary wound closure. Complete loss of the buccal bone wall may be considered the worst case scenario as it requires a reconstructive surgery using autogenous bone blocks prior to implant installation.6,7 GBR and bone grafting have been shown to be predictable from a clinical and radiographic point of view; however, postoperative complications are common, and the aesthetic outcome may be suboptimal mostly because of incomplete papillae.8,9 As described in a recent multivariate analysis, this is probably due to multiple papilla opening procedures.9 Also, patients with a thin-scalloped gingival biotype may be considered at risk for aesthetic complications following implant treatment.10 Incomplete papillae and alveolar process deficiency seem common following conventional single implant treatment in these patients.10 In addition, high risk for midfacial recession in the long term has been described following immediate implant treatment.11 These complications should not be surprising as thin soft tissues merely reflect thin underlying bone that is prone to resorption even if the buccal bone wall is intact at the time of tooth extraction.12 Aforementioned findings illustrate that traditional treatment concepts may fall short in high-risk patients when optimal aesthetics are among the primary goals. In order to improve soft tissue aspects of implant treatment in these patients, minimally invasive surgery that allows maximal preservation or reconstruction of the alveolar ridge seems warranted. The moment of tooth extraction appears a suitable time point to preserve or rebuild the alveolar ridge since there is a complete access to the bony architecture without having to raise a flap. Clearly, any other scenario results in additional flap surgery with possible aesthetic consequences. A number of recent systematic reviews have demonstrated the effectiveness of ridge preservation.13–20 Hitherto, however, clinical studies have mainly focused on hard tissue aspects, whereas the complete alveolar process comprising hard as well as soft tissues is obviously more important from an aesthetic point of view. In addition, there are no clinical studies identifying predictors of alveolar process remodeling following ridge preservation. Hence, the objective of the present prospective study was to clinically evaluate horizontal remodeling of the alveolar process following ridge preservation in high-risk patients with an incomplete buccal
bone wall upon tooth extraction and/or a thin-scalloped gingival biotype. Another objective was to identify predictors of such remodeling using a multivariate analysis. MATERIALS AND METHODS Study Group Patients with a failing tooth were enrolled in a private practice in Belgium between April 2011 and December 2012. All patients were in need of a single implant. Inclusion criteria were as follows: • • •
•
At least 18 years old Good oral hygiene defined as full-mouth plaque score 225%21 Presence of a single failing tooth in the anterior maxilla (15–25) with both neighboring teeth present Incomplete buccal bone wall at the time of tooth extraction and/or thin-scalloped gingival biotype as determined by the transparency of a periodontal probe in the buccal sulcus of the contralateral tooth22
Exclusion criteria were as follows: • • • •
Systemic diseases Smoking (History of) Periodontal disease Midfacial recession at the failing tooth in reference to the contralateral tooth
The study was conducted in accordance with the Helsinki declaration of 1975 as revised in 2000, and the study protocol was approved by the ethical committee of the University Hospital in Brussels. Tooth Extraction and Ridge Preservation Antibiotic therapy (amoxicillin 1 g twice daily for 4 days) was started 1 hour preoperatively. In case of a tooth abscess, patients started to take antibiotics 2 days before the intervention. Prior to tooth extraction, patients rinsed with a 0.2% chlorhexidine solution for 1 minute (Corsodyl®, GlaxoSmithKline, Genval, Belgium). Teeth were extracted as atraumatically as possible and without flap elevation. Thereupon, meticulous bone curettage was performed. One or more collagenenriched, bovine-derived xenograft blocks (Geistlich Bio-Oss® Collagen® 100 mg, Geistlich Pharma AG, Wolhusen, Switzerland) were soaked in sterile saline (Figure 1). Blocks were properly individualized with a
Remodeling Following Ridge Preservation
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Figure 1 Collagen-enriched, bovine-derived xenograft block (Geistlich Bio-Oss® Collagen® 100 mg, Geistlich Pharma AG, Wolhusen, Switzerland) as delivered by the manufacturer (left), soaked in sterile saline (middle), and individualized with a surgical blade (right).
surgical blade, applied into the alveolus, and firmly condensed. Each alveolus was filled up to 3 mm below the free gingival margin. The wound was closed with single monofilament sutures (Seralon® 5/0, Serag Wiessner, Naila, Germany). Membranes were never applied, even if the buccal bone wall was damaged. During the first 2 weeks of healing, patients used a 0.2% chlorhexidine spray twice a day for local disinfection and ibuprofen 600 mg when needed. Sutures were removed after 2 weeks. A removable partial denture was used as provisional tooth replacement in all patients. Alveolar Process Remodeling Prior to tooth extraction (baseline) and at 4 months, occlusal digital slides were made by the same clinician. These were superimposed with the best possible fit of both neighboring teeth to ensure identical magnification of the site of interest. On these slides, the buccopalatal dimension of the alveolar process (hard as well as soft tissues) in the center of the failing tooth
(baseline) or edentulous site (4 months) was measured. In case of a tooth abscess, baseline registration was performed at the contralateral tooth for obvious reasons of swelling. The change in buccopalatal dimension of the alveolar process between baseline and 4 months was expressed as a percentage of the baseline value. A positive value corresponded to shrinkage, whereas a negative value corresponded to tissue growth (Figure 2). At 4 months, cone-beam computed tomography was performed to evaluate bone volume for implant surgery. A flapless surgical procedure was chosen a priori. Deviations from the protocol were recorded. This included registration of the number of patients in need of additional bone augmentation/regeneration prior to or during implant installation and registration of the number of patients who were exposed to flap surgery for implant installation. Whenever the implant could not be fully embedded in bone, additional bone augmentation/ regeneration was deemed necessary.
Figure 2 Case with minimal alveolar process remodeling. A reference line (white) connecting the center of both adjacent teeth was constructed. Perpendicular to that line and in the middle of the site of interest, a second line was drawn corresponding to the buccopalatal dimension of the alveolar process at baseline (green, left) and at 4 months (yellow, right).
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Predictors of Alveolar Process Remodeling Tooth location (0 = central incisor; 1 = lateral incisor; 2 = cuspid; 3 = premolar), tooth abscess (0 = no tooth abscess; 1 = tooth abscess), buccal bone loss (mm), and gingival thickness (mm) were included as possible predictors of alveolar process remodeling. Buccal bone loss was measured vertically from the free gingival margin to the first bone contact using a periodontal probe. The total depth was reduced by 3 mm, hereby compensating for biologic width. Gingival thickness was registered using an ultrasonic device (EPOCH 600, Olympus, Aartselaar, Belgium) at the midfacial aspect of the contralateral tooth by the same clinician. This device was used because it produces a reliable and reproducible registration of gingival thickness as recently demonstrated.23 The ultrasonic transducer had a diameter of 4 mm and was moistened with ultrasound gel (Amstel Medical, Megro, Amstelveen, the Netherlands). Its lower border was positioned at the level of the free gingival margin in order to register the average soft tissue thickness at the most coronal part of the gingiva. Statistical Analysis The patient was the statistical unit in all analyses. Descriptive statistics included mean values and standard deviations for continuous variables (age, buccal bone loss, gingival thickness, alveolar process remodeling) and frequency distributions for categorical variables (gender, reason for tooth extraction, tooth location, gingival biotype, tooth abscess). Thinscalloped gingival biotype was compared with thick gingival biotype in terms of ultrasonically assessed gingival thickness using the independent samples t-test. Regression analysis was performed using a general linear model with alveolar process remodeling as the dependent variable. Tooth location and tooth abscess were included as random factors. Buccal bone loss and gingival thickness were included as covariates. A residual analysis on linearity and homoscedasticity was performed to evaluate the model fit. The level of significance was set at 0.05. RESULTS Study Group Forty-two patients (21 females, 21 males; mean age 38, range 19–81) met the selection criteria and consented to the treatment.
Seventeen teeth were extracted because of fracture, 17 because of caries and sequels, seven because of root resorption, and one because of root perforation. Twenty-seven central incisors were extracted, 11 lateral incisors, two cuspids, and two premolars. The vast majority of the cases (n = 36) demonstrated an incomplete buccal bone wall following tooth extraction. Mean buccal bone loss amounted to 6.8 mm (SD 4.5, range 0–15). Fifteen patients had a thin-scalloped gingival biotype. Gingival thickness as ultrasonically assessed was on average 1.00 mm (SD 0.21) in these patients. Twenty-seven patients had a thick gingival biotype and demonstrated mean gingival thickness of 1.32 mm (SD 0.31). The mean difference in gingival thickness of 0.32 mm (95% confidence interval: 0.14–0.50) was significant (p = .001). Four patients had a tooth abscess characterized by swelling, pain, and pus. Alveolar Process Remodeling In none of the patients the original buccopalatal dimension of the ridge could be preserved. Mean alveolar process remodeling was 14% (SD 7, range 4–30). In 16 patients (38%), alveolar process remodeling was minimal (210%) (Figure 2). In another 16 patients (38%), alveolar process remodeling was acceptable (>10% and 220%). In 10 patients (24%), alveolar process remodeling was advanced (>20%) (Figure 3). Despite loss of volume, all 42 patients received a single implant without additional bone augmentation/ regeneration. Note that the latter was deemed necessary only when the implant could not be fully embedded in bone. In 35 patients, the implant could be installed using a flapless surgical approach. Connective tissue grafting was performed later on in the treatment for aesthetic purposes, hereby compensating for tissue loss at the buccal aspect. Predictors of Alveolar Process Remodeling Table 1 shows the alveolar process remodeling per tooth location and the presence or absence of a tooth abscess at the time of extraction. Central incisors and cuspids seemed most prone to remodeling (316% vs 210%) as well as sites with a tooth abscess at the time of extraction (26% vs 13%). Regression analysis confirmed the tooth location and tooth abscess (p = .025) as predictors of alveolar process remodeling (Table 2). Buccal bone loss
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Figure 3 Case with advanced alveolar process remodeling. Baseline (left) and at 4 months (right).
was identified as an another predictor (p = .035) by the regression model. The model quality was satisfying given the linear relationship and homoscedasticity of the residuals (Figure 4). An illustration on the prediction of
TABLE 1 Descriptive Statistics on Alveolar Process Remodeling
Tooth location Central incisor Lateral incisor Cuspid Premolar Tooth abscess No tooth abscess Tooth abscess
n
Mean (%)
Standard Deviation
Range
27 11 2 2
16 10 20 8
8 3 4 4
4–30 5–16 17–22 5–10
38 4
13 26
6 4
4–26 21–30
alveolar process remodeling by the regression model is given in Figure 5. DISCUSSION Ridge preservation following tooth extraction has gained a considerable interest by the scientific community. As the term suggests, the objective is to maintain the original volume of the alveolar process. If this could be fully met, complex hard and soft tissue grafting would become redundant resulting in straightforward implant therapy and pontic-site development. In this respect, ridge preservation has the potential to simplify clinical procedures on one hand and to improve aesthetics on the other. Ample systematic reviews have been published supporting the effectiveness of ridge preservation in limiting horizontal and vertical ridge alterations in postextraction sites.13–20 However, full preservation of
TABLE 2 Regression Analysis with Alveolar Process Remodeling as Dependent Variable Predictor
Tooth location Central incisor versus premolar Lateral incisor versus premolar Cuspid versus premolar Central incisor versus cuspid Lateral incisor versus cuspid Central incisor versus lateral incisor Tooth abscess Buccal bone loss (mm) Gingival thickness (mm)
p Value
Regression Coefficient
Standard Error
95% Confidence Interval
.080 .503 .020 .147 .018 .051 .025 .035 .427
7.371 2.865 13.417 –6.046 –10.552 4.506 7.836 0.480 –2.398
4.091 4.232 5.512 4.076 4.259 2.225 3.351 0.219 2.987
–0.935 to 15.677 –5.726 to 11.456 2.227–24.607 –14.321 to 2.229 –19.197 to –1.906 –0.011 to 9.022 1.034–14.639 0.036–0.925 –8.462 to 3.665
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Figure 4 Scatterplot illustrating the model quality in terms of linearity and homoscedasticity.
the alveolar process does not seem feasible. The fact that all patients in the present study demonstrated reduction in width of the alveolar process may support this. On the other hand, mean alveolar process remodeling was 14%,
and 76% of the cases demonstrated 220% reduction, which is quite acceptable knowing only high-risk patients with an incomplete buccal bone wall upon tooth extraction and/or a thin-scalloped gingival
Figure 5 Scatterplot illustrating the prediction of alveolar process remodeling by the regression model.
Remodeling Following Ridge Preservation
biotype had been included. It is difficult to compare our findings to data in the literature because of these selection criteria and because most studies focused on hard tissue alterations following ridge preservation. Nevertheless, Pietrokovski and Massler24 already demonstrated in 1967 the marked tissue resorption (hard and soft tissues) following single tooth loss. This was supported by a more recent prospective case series using study casts to assess hard and soft tissue changes of the alveolar process following single tooth extraction.25 These investigators demonstrated about 30% width reduction in the first 3 months following tooth extraction. When compared with the results of the present study, ridge preservation seems to reduce the horizontal alveolar process remodeling by half, which is clinically relevant because implant surgery could be performed in all subjects without additional GBR. This is in accordance with Weng and colleagues14 describing five times higher need for GBR at implant placement if no ridge preservation was performed on the day of tooth extraction. It is possible that additional GBR would be the treatment of choice by some clinicians if they were to treat some of the patients included in this study. Given the fact that all implants could be properly embedded in bone, we decided to compensate for tissue loss at the buccal aspect by connective tissue grafting. This decision was mainly based on a systematic review demonstrating there is insufficient evidence to set a threshold for minimal buccal bone thickness around an implant to ensure an optimal aesthetic outcome.26 Ridge preservation can be performed using different biomaterials and surgical techniques. Recent systematic reviews have indicated that recommendations with regard to a specific biomaterial or technique may be premature.13–15,17,18 Especially the need for primary wound closure or soft tissue grafts remains controversial. Given the lack of high-quality evidence on these issues, we mainly selected a biomaterial and surgical technique based on procedural simplicity. We believe the latter is important since ridge preservation is a procedure that should a priori be implemented in general practice. A block graft is easy to individualize and apply into an alveolar socket and does not require – as opposed to granules – coverage with a membrane or soft tissue graft. When interpreting the results of the present study, some limitations should be taken into account. First, results are based on clinical slides that could have been
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taken with some error. Second, we described the clinical outcome of ridge preservation in consecutively treated patients without histological proof of new bone formation. Third, this is not a randomized controlled study, and therefore, one should be careful in comparing the outcome of ridge preservation to alternative techniques. Interestingly, however, Sisti and colleagues27 performed an RCT on ridge preservation versus GBR following a postextraction healing period and concluded that ridge preservation resulted in a better horizontal regeneration of the buccal bone wall. To the best of our knowledge, this is the first clinical study that identified predictors of alveolar process remodeling following ridge preservation. Regression analysis identified tooth location, tooth abscess, and buccal bone loss as significant predictors. The results on tooth location, more specifically cuspids and premolars, should be interpreted with caution given the limited number of such cases (4/42). Tooth abscess was the most important predictor of alveolar process remodeling. In fact, all patients with a tooth abscess demonstrated advanced remodeling (>20%) after 4 months. This observation suggests that inflammation substantially compromises bone healing. Partial or complete loss of the buccal bone wall also increased remodeling whereas gingival thickness did not. CONCLUSION Alveolar process remodeling seems inevitable yet acceptable following ridge preservation in high-risk patients. Tooth location, tooth abscess, and buccal bone loss were significant predictors. Proper case selection may reduce the incidence of advanced remodeling. REFERENCES 1. Buser D, Bornstein MM, Weber HP, Grütter L, Schmid B, Belser UC. Early implant placement with simultaneous guided bone regeneration following single-tooth extraction in the esthetic zone: a cross-sectional, retrospective study in 45 subjects with a 2- to 4-year follow-up. J Periodontol 2008; 79:1773–1781. 2. Buser D, Halbritter S, Hart C, et al. Early implant placement with simultaneous guided bone regeneration following single-tooth extraction in the esthetic zone: 12-month results of a prospective study with 20 consecutive patients. J Periodontol 2009; 80:152–162. 3. Buser D, Wittneben J, Bornstein MM, Grütter L, Chappuis V, Belser UC. Stability of contour augmentation
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and esthetic outcomes of implant-supported single crowns in the esthetic zone: 3-year results of a prospective study with early implant placement postextraction. J Periodontol 2011; 82:342–349. Buser D, Chappuis V, Kuchler U, et al. Long-term stability of early implant placement with contour augmentation. J Dent Res 2013; 92:176S–182S. Cosyn J, De Rouck T. Aesthetic outcome of single-tooth implant restorations following early implant placement and guided bone regeneration: crown and soft tissue dimensions compared with contralateral teeth. Clin Oral Implants Res 2009; 20:1063–1069. Raghoebar GM, Batenburg RH, Vissink A, Reintsema H. Augmentation of localized defects of the anterior maxillary ridge with autogenous bone before insertion of implants. J Oral Maxillofac Surg 1996; 54:1180–1185. von Arx T, Buser D. Horizontal ridge augmentation using autogenous block grafts and the guided bone regeneration technique with collagen membranes: a clinical study with 42 patients. Clin Oral Implants Res 2006; 17:359– 366. Cosyn J, Eghbali A, Hanselaer L, et al. Four modalities of single implant treatment in the anterior maxilla: a clinical, radiographic, and aesthetic evaluation. Clin Implant Dent Relat Res 2013; 15:517–530. Cosyn J, Sabzevar MM, De Bruyn H. Predictors of interproximal and midfacial recession following single implant treatment in the anterior maxilla: a multivariate analysis. J Clin Periodontol 2012; 39:895–903. Cosyn J, Eghbali A, De Bruyn H, Dierens M, De Rouck T. Single implant treatment in healing versus healed sites of the anterior maxilla: an aesthetic evaluation. Clin Implant Dent Relat Res 2012; 14:517–526. Kan JY, Rungcharassaeng K, Lozada JL, Zimmerman G. Facial gingival tissue stability following immediate placement and provisionalization of maxillary anterior single implants: a 2- to 8-year follow-up. Int J Oral Maxillofac Implants 2011; 26:179–187. Lindhe J, Wennström JL, Berglundh T. The mucosa at teeth and implants. Chapter 3. In: Lindhe J, Lang NP, Karring T, eds. Clinical periodontology and implant dentistry. Blackwell Munksgaard, Oxford, UK, 2008:69–85. Darby I, Chen ST, Buser D. Ridge preservation techniques for implant therapy. Int J Oral Maxillofac Implants 2009; 24:260–271. Weng D, Stock V, Schliephake H. Are socket and ridge preservation techniques at the day of tooth extraction efficient in maintaining the tissues of the alveolar ridge? Eur J Oral Implantol 2011; 4:59–66.
15. Horowitz R, Holtzclaw D, Rosen PS. A review on alveolar ridge preservation following tooth extraction. J Evid Based Dent Pract 2012; 12:149–160. 16. Morjaria KR, Wilson R, Palmer RM. Bone healing after tooth extraction with or without an intervention: a systematic review of randomized controlled trials. Clin Implant Dent Relat Res 2014; 16:1–20. 17. Vignoletti F, Matesanz P, Rodrigo D, Figuero E, Martin C, Sanz M. Surgical protocols for ridge preservation after tooth extraction. A systematic review. Clin Oral Implants Res 2012; 23:22–38. 18. Wang RE, Lang NP. Ridge preservation after tooth extraction. Clin Oral Implants Res 2012; 23:147–156. 19. Horváth A, Mardas N, Mezzomo LA, Needleman IG, Donos N. Alveolar ridge preservation. A systematic review. Clin Oral Investig 2013; 17:341–363. 20. Vittorini Orgeas G, Clementini M, De Risi V, de Sanctis M. Surgical techniques for alveolar socket preservation: a systematic review. Int J Oral Maxillofac Implants 2013; 28:1049–1061. 21. O’Leary TJ, Drake RB, Naylor JE. The plaque control record. J Periodontol 1972; 43:38. 22. De Rouck T, Eghbali R, Collys K, De Bruyn H, Cosyn J. The gingival biotype revisited: transparency of the periodontal probe through the gingival margin as a method to discriminate thin from thick gingiva. J Clin Periodontol 2009; 36:428–433. 23. Eghbali A, De Bruyn H, Cosyn J, Kerckaert I, Van Hoof T. Ultrasonic assessment of mucosal thickness around implants: validity, reproducibility and stability of connective tissue grafts at the buccal aspect. Clin Implant Dent Relat Res 2014. [Submitted]. 24. Pietrokovski J, Massler M. Alveolar ridge resorption following tooth extraction. J Prosthet Dent 1967; 17:21–27. 25. Schropp L, Wenzel A, Kostopoulos L, Karring T. Bone healing and soft tissue contour changes following singletooth extraction: a clinical and radiographic 12-month prospective study. Int J Periodontics Restorative Dent 2003; 23:313–323. 26. Teughels W, Merheb J, Quirynen M. Critical horizontal dimensions of interproximal and buccal bone around implants for optimal aesthetic outcomes: a systematic review. Clin Oral Implants Res 2009; 20:134–145. 27. Sisti A, Canullo L, Mottola MP, Covani U, Barone A, Botticelli D. Clinical evaluation of a ridge augmentation procedure for the severely resorbed alveolar socket: multicenter randomized controlled trial, preliminary results. Clin Oral Implants Res 2012; 23:526–535.
ABSTRACT Purpose: (1) To clinically evaluate horizontal remodeling of the alveolar process (hard and soft tissues) following ridge preservation in high-risk patients and (2) to identify predictors of such remodeling. Materials and Methods: Periodontally healthy nonsmoking patients with a failing tooth in the anterior maxilla (15–25) were selected for a prospective case series. All were in need of a single implant and demonstrated high risk for aesthetic complications given an incomplete buccal bone wall and/or thin-scalloped gingival biotype. Following flapless tooth extraction, ridge preservation was performed using one or more collagen-enriched, bovine-derived block grafts (Geistlich Bio-Oss® Collagen® 100 mg, Geistlich Pharma AG, Wolhusen, Switzerland) without the additional use of membranes or soft tissue grafts. The change in buccopalatal dimension of the alveolar process between baseline (prior to tooth extraction) and 4 months was assessed on the basis of superimposed occlusal slides. Regression analysis was performed to identify predictors of alveolar process remodeling. Results: Forty-two patients (21 females, 21 males; mean age 38) met the selection criteria and consented to the treatment. Mean alveolar process remodeling was 14% (SD 7, range 4–30) with minimal remodeling (210%) in 16 patients (38%) and advanced remodeling (>20%) in 10 patients (24%). A single implant could be installed in all subjects without additional guided bone regeneration. Connective tissue grafting was performed later on in the treatment for aesthetic purposes, hereby compensating for tissue loss at the buccal aspect. Predictors of alveolar process remodeling were tooth location (central incisors and cuspids > laterals incisors and premolars), tooth abscess (p = .025), and buccal bone loss (p = .035). Conclusion: Alveolar process remodeling seems inevitable yet acceptable following ridge preservation in high-risk patients. Proper case selection may reduce the incidence of advanced remodeling. KEY WORDS: alveolar process, extraction socket, remodeling, ridge preservation, tooth extraction, xenograft
INTRODUCTION An incomplete buccal bone wall is a common finding following tooth extraction. This is traditionally treated by means of guided bone regeneration (GBR) following a postextraction healing period of at least 6 weeks.1–5 GBR is performed in conjunction with implant surgery,
*Associate professor, Faculty of Medicine and Health Sciences, Dental School, Department of Periodontology and Oral Implantology, Ghent University, Ghent, Belgium and professor, Faculty of Medicine and Pharmacy, Dental Medicine, Department of Periodontology and Oral Implantology, Free University of Brussels (VUB), Brussels, Belgium; †professor, Faculty of Medicine and Pharmacy, Dental Medicine, Free University of Brussels (VUB), Brussels, Belgium; ‡ chairman, professor, Faculty of Medicine and Health Sciences, Dental School, Department of Periodontology and Oral Implantology, Ghent University, Ghent, Belgium and professor, Faculty of Odontology, Department of Prosthodontics, Malmö University, Malmö, Sweden
Conflict of interest and source of funding statement The authors declare that they have no conflict of interest. This study was supported by departmental funds of the Free University of Brussels (VUB), and biomaterials were provided by Geistlich Pharma AG (Wolhusen, Switzerland).
Corresponding Author: Prof. Jan Cosyn, Faculty of Medicine and Health Sciences, Dental School, Department of Periodontology and Oral Implantology, University of Ghent, De Pintelaan 185, Ghent B-9000, Belgium; e-mail: [email protected]
© 2014 Wiley Periodicals, Inc. DOI 10.1111/cid.12249
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and implants are usually installed in a two-stage procedure to allow primary wound closure. Complete loss of the buccal bone wall may be considered the worst case scenario as it requires a reconstructive surgery using autogenous bone blocks prior to implant installation.6,7 GBR and bone grafting have been shown to be predictable from a clinical and radiographic point of view; however, postoperative complications are common, and the aesthetic outcome may be suboptimal mostly because of incomplete papillae.8,9 As described in a recent multivariate analysis, this is probably due to multiple papilla opening procedures.9 Also, patients with a thin-scalloped gingival biotype may be considered at risk for aesthetic complications following implant treatment.10 Incomplete papillae and alveolar process deficiency seem common following conventional single implant treatment in these patients.10 In addition, high risk for midfacial recession in the long term has been described following immediate implant treatment.11 These complications should not be surprising as thin soft tissues merely reflect thin underlying bone that is prone to resorption even if the buccal bone wall is intact at the time of tooth extraction.12 Aforementioned findings illustrate that traditional treatment concepts may fall short in high-risk patients when optimal aesthetics are among the primary goals. In order to improve soft tissue aspects of implant treatment in these patients, minimally invasive surgery that allows maximal preservation or reconstruction of the alveolar ridge seems warranted. The moment of tooth extraction appears a suitable time point to preserve or rebuild the alveolar ridge since there is a complete access to the bony architecture without having to raise a flap. Clearly, any other scenario results in additional flap surgery with possible aesthetic consequences. A number of recent systematic reviews have demonstrated the effectiveness of ridge preservation.13–20 Hitherto, however, clinical studies have mainly focused on hard tissue aspects, whereas the complete alveolar process comprising hard as well as soft tissues is obviously more important from an aesthetic point of view. In addition, there are no clinical studies identifying predictors of alveolar process remodeling following ridge preservation. Hence, the objective of the present prospective study was to clinically evaluate horizontal remodeling of the alveolar process following ridge preservation in high-risk patients with an incomplete buccal
bone wall upon tooth extraction and/or a thin-scalloped gingival biotype. Another objective was to identify predictors of such remodeling using a multivariate analysis. MATERIALS AND METHODS Study Group Patients with a failing tooth were enrolled in a private practice in Belgium between April 2011 and December 2012. All patients were in need of a single implant. Inclusion criteria were as follows: • • •
•
At least 18 years old Good oral hygiene defined as full-mouth plaque score 225%21 Presence of a single failing tooth in the anterior maxilla (15–25) with both neighboring teeth present Incomplete buccal bone wall at the time of tooth extraction and/or thin-scalloped gingival biotype as determined by the transparency of a periodontal probe in the buccal sulcus of the contralateral tooth22
Exclusion criteria were as follows: • • • •
Systemic diseases Smoking (History of) Periodontal disease Midfacial recession at the failing tooth in reference to the contralateral tooth
The study was conducted in accordance with the Helsinki declaration of 1975 as revised in 2000, and the study protocol was approved by the ethical committee of the University Hospital in Brussels. Tooth Extraction and Ridge Preservation Antibiotic therapy (amoxicillin 1 g twice daily for 4 days) was started 1 hour preoperatively. In case of a tooth abscess, patients started to take antibiotics 2 days before the intervention. Prior to tooth extraction, patients rinsed with a 0.2% chlorhexidine solution for 1 minute (Corsodyl®, GlaxoSmithKline, Genval, Belgium). Teeth were extracted as atraumatically as possible and without flap elevation. Thereupon, meticulous bone curettage was performed. One or more collagenenriched, bovine-derived xenograft blocks (Geistlich Bio-Oss® Collagen® 100 mg, Geistlich Pharma AG, Wolhusen, Switzerland) were soaked in sterile saline (Figure 1). Blocks were properly individualized with a
Remodeling Following Ridge Preservation
3
Figure 1 Collagen-enriched, bovine-derived xenograft block (Geistlich Bio-Oss® Collagen® 100 mg, Geistlich Pharma AG, Wolhusen, Switzerland) as delivered by the manufacturer (left), soaked in sterile saline (middle), and individualized with a surgical blade (right).
surgical blade, applied into the alveolus, and firmly condensed. Each alveolus was filled up to 3 mm below the free gingival margin. The wound was closed with single monofilament sutures (Seralon® 5/0, Serag Wiessner, Naila, Germany). Membranes were never applied, even if the buccal bone wall was damaged. During the first 2 weeks of healing, patients used a 0.2% chlorhexidine spray twice a day for local disinfection and ibuprofen 600 mg when needed. Sutures were removed after 2 weeks. A removable partial denture was used as provisional tooth replacement in all patients. Alveolar Process Remodeling Prior to tooth extraction (baseline) and at 4 months, occlusal digital slides were made by the same clinician. These were superimposed with the best possible fit of both neighboring teeth to ensure identical magnification of the site of interest. On these slides, the buccopalatal dimension of the alveolar process (hard as well as soft tissues) in the center of the failing tooth
(baseline) or edentulous site (4 months) was measured. In case of a tooth abscess, baseline registration was performed at the contralateral tooth for obvious reasons of swelling. The change in buccopalatal dimension of the alveolar process between baseline and 4 months was expressed as a percentage of the baseline value. A positive value corresponded to shrinkage, whereas a negative value corresponded to tissue growth (Figure 2). At 4 months, cone-beam computed tomography was performed to evaluate bone volume for implant surgery. A flapless surgical procedure was chosen a priori. Deviations from the protocol were recorded. This included registration of the number of patients in need of additional bone augmentation/regeneration prior to or during implant installation and registration of the number of patients who were exposed to flap surgery for implant installation. Whenever the implant could not be fully embedded in bone, additional bone augmentation/ regeneration was deemed necessary.
Figure 2 Case with minimal alveolar process remodeling. A reference line (white) connecting the center of both adjacent teeth was constructed. Perpendicular to that line and in the middle of the site of interest, a second line was drawn corresponding to the buccopalatal dimension of the alveolar process at baseline (green, left) and at 4 months (yellow, right).
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Predictors of Alveolar Process Remodeling Tooth location (0 = central incisor; 1 = lateral incisor; 2 = cuspid; 3 = premolar), tooth abscess (0 = no tooth abscess; 1 = tooth abscess), buccal bone loss (mm), and gingival thickness (mm) were included as possible predictors of alveolar process remodeling. Buccal bone loss was measured vertically from the free gingival margin to the first bone contact using a periodontal probe. The total depth was reduced by 3 mm, hereby compensating for biologic width. Gingival thickness was registered using an ultrasonic device (EPOCH 600, Olympus, Aartselaar, Belgium) at the midfacial aspect of the contralateral tooth by the same clinician. This device was used because it produces a reliable and reproducible registration of gingival thickness as recently demonstrated.23 The ultrasonic transducer had a diameter of 4 mm and was moistened with ultrasound gel (Amstel Medical, Megro, Amstelveen, the Netherlands). Its lower border was positioned at the level of the free gingival margin in order to register the average soft tissue thickness at the most coronal part of the gingiva. Statistical Analysis The patient was the statistical unit in all analyses. Descriptive statistics included mean values and standard deviations for continuous variables (age, buccal bone loss, gingival thickness, alveolar process remodeling) and frequency distributions for categorical variables (gender, reason for tooth extraction, tooth location, gingival biotype, tooth abscess). Thinscalloped gingival biotype was compared with thick gingival biotype in terms of ultrasonically assessed gingival thickness using the independent samples t-test. Regression analysis was performed using a general linear model with alveolar process remodeling as the dependent variable. Tooth location and tooth abscess were included as random factors. Buccal bone loss and gingival thickness were included as covariates. A residual analysis on linearity and homoscedasticity was performed to evaluate the model fit. The level of significance was set at 0.05. RESULTS Study Group Forty-two patients (21 females, 21 males; mean age 38, range 19–81) met the selection criteria and consented to the treatment.
Seventeen teeth were extracted because of fracture, 17 because of caries and sequels, seven because of root resorption, and one because of root perforation. Twenty-seven central incisors were extracted, 11 lateral incisors, two cuspids, and two premolars. The vast majority of the cases (n = 36) demonstrated an incomplete buccal bone wall following tooth extraction. Mean buccal bone loss amounted to 6.8 mm (SD 4.5, range 0–15). Fifteen patients had a thin-scalloped gingival biotype. Gingival thickness as ultrasonically assessed was on average 1.00 mm (SD 0.21) in these patients. Twenty-seven patients had a thick gingival biotype and demonstrated mean gingival thickness of 1.32 mm (SD 0.31). The mean difference in gingival thickness of 0.32 mm (95% confidence interval: 0.14–0.50) was significant (p = .001). Four patients had a tooth abscess characterized by swelling, pain, and pus. Alveolar Process Remodeling In none of the patients the original buccopalatal dimension of the ridge could be preserved. Mean alveolar process remodeling was 14% (SD 7, range 4–30). In 16 patients (38%), alveolar process remodeling was minimal (210%) (Figure 2). In another 16 patients (38%), alveolar process remodeling was acceptable (>10% and 220%). In 10 patients (24%), alveolar process remodeling was advanced (>20%) (Figure 3). Despite loss of volume, all 42 patients received a single implant without additional bone augmentation/ regeneration. Note that the latter was deemed necessary only when the implant could not be fully embedded in bone. In 35 patients, the implant could be installed using a flapless surgical approach. Connective tissue grafting was performed later on in the treatment for aesthetic purposes, hereby compensating for tissue loss at the buccal aspect. Predictors of Alveolar Process Remodeling Table 1 shows the alveolar process remodeling per tooth location and the presence or absence of a tooth abscess at the time of extraction. Central incisors and cuspids seemed most prone to remodeling (316% vs 210%) as well as sites with a tooth abscess at the time of extraction (26% vs 13%). Regression analysis confirmed the tooth location and tooth abscess (p = .025) as predictors of alveolar process remodeling (Table 2). Buccal bone loss
Remodeling Following Ridge Preservation
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Figure 3 Case with advanced alveolar process remodeling. Baseline (left) and at 4 months (right).
was identified as an another predictor (p = .035) by the regression model. The model quality was satisfying given the linear relationship and homoscedasticity of the residuals (Figure 4). An illustration on the prediction of
TABLE 1 Descriptive Statistics on Alveolar Process Remodeling
Tooth location Central incisor Lateral incisor Cuspid Premolar Tooth abscess No tooth abscess Tooth abscess
n
Mean (%)
Standard Deviation
Range
27 11 2 2
16 10 20 8
8 3 4 4
4–30 5–16 17–22 5–10
38 4
13 26
6 4
4–26 21–30
alveolar process remodeling by the regression model is given in Figure 5. DISCUSSION Ridge preservation following tooth extraction has gained a considerable interest by the scientific community. As the term suggests, the objective is to maintain the original volume of the alveolar process. If this could be fully met, complex hard and soft tissue grafting would become redundant resulting in straightforward implant therapy and pontic-site development. In this respect, ridge preservation has the potential to simplify clinical procedures on one hand and to improve aesthetics on the other. Ample systematic reviews have been published supporting the effectiveness of ridge preservation in limiting horizontal and vertical ridge alterations in postextraction sites.13–20 However, full preservation of
TABLE 2 Regression Analysis with Alveolar Process Remodeling as Dependent Variable Predictor
Tooth location Central incisor versus premolar Lateral incisor versus premolar Cuspid versus premolar Central incisor versus cuspid Lateral incisor versus cuspid Central incisor versus lateral incisor Tooth abscess Buccal bone loss (mm) Gingival thickness (mm)
p Value
Regression Coefficient
Standard Error
95% Confidence Interval
.080 .503 .020 .147 .018 .051 .025 .035 .427
7.371 2.865 13.417 –6.046 –10.552 4.506 7.836 0.480 –2.398
4.091 4.232 5.512 4.076 4.259 2.225 3.351 0.219 2.987
–0.935 to 15.677 –5.726 to 11.456 2.227–24.607 –14.321 to 2.229 –19.197 to –1.906 –0.011 to 9.022 1.034–14.639 0.036–0.925 –8.462 to 3.665
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Figure 4 Scatterplot illustrating the model quality in terms of linearity and homoscedasticity.
the alveolar process does not seem feasible. The fact that all patients in the present study demonstrated reduction in width of the alveolar process may support this. On the other hand, mean alveolar process remodeling was 14%,
and 76% of the cases demonstrated 220% reduction, which is quite acceptable knowing only high-risk patients with an incomplete buccal bone wall upon tooth extraction and/or a thin-scalloped gingival
Figure 5 Scatterplot illustrating the prediction of alveolar process remodeling by the regression model.
Remodeling Following Ridge Preservation
biotype had been included. It is difficult to compare our findings to data in the literature because of these selection criteria and because most studies focused on hard tissue alterations following ridge preservation. Nevertheless, Pietrokovski and Massler24 already demonstrated in 1967 the marked tissue resorption (hard and soft tissues) following single tooth loss. This was supported by a more recent prospective case series using study casts to assess hard and soft tissue changes of the alveolar process following single tooth extraction.25 These investigators demonstrated about 30% width reduction in the first 3 months following tooth extraction. When compared with the results of the present study, ridge preservation seems to reduce the horizontal alveolar process remodeling by half, which is clinically relevant because implant surgery could be performed in all subjects without additional GBR. This is in accordance with Weng and colleagues14 describing five times higher need for GBR at implant placement if no ridge preservation was performed on the day of tooth extraction. It is possible that additional GBR would be the treatment of choice by some clinicians if they were to treat some of the patients included in this study. Given the fact that all implants could be properly embedded in bone, we decided to compensate for tissue loss at the buccal aspect by connective tissue grafting. This decision was mainly based on a systematic review demonstrating there is insufficient evidence to set a threshold for minimal buccal bone thickness around an implant to ensure an optimal aesthetic outcome.26 Ridge preservation can be performed using different biomaterials and surgical techniques. Recent systematic reviews have indicated that recommendations with regard to a specific biomaterial or technique may be premature.13–15,17,18 Especially the need for primary wound closure or soft tissue grafts remains controversial. Given the lack of high-quality evidence on these issues, we mainly selected a biomaterial and surgical technique based on procedural simplicity. We believe the latter is important since ridge preservation is a procedure that should a priori be implemented in general practice. A block graft is easy to individualize and apply into an alveolar socket and does not require – as opposed to granules – coverage with a membrane or soft tissue graft. When interpreting the results of the present study, some limitations should be taken into account. First, results are based on clinical slides that could have been
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taken with some error. Second, we described the clinical outcome of ridge preservation in consecutively treated patients without histological proof of new bone formation. Third, this is not a randomized controlled study, and therefore, one should be careful in comparing the outcome of ridge preservation to alternative techniques. Interestingly, however, Sisti and colleagues27 performed an RCT on ridge preservation versus GBR following a postextraction healing period and concluded that ridge preservation resulted in a better horizontal regeneration of the buccal bone wall. To the best of our knowledge, this is the first clinical study that identified predictors of alveolar process remodeling following ridge preservation. Regression analysis identified tooth location, tooth abscess, and buccal bone loss as significant predictors. The results on tooth location, more specifically cuspids and premolars, should be interpreted with caution given the limited number of such cases (4/42). Tooth abscess was the most important predictor of alveolar process remodeling. In fact, all patients with a tooth abscess demonstrated advanced remodeling (>20%) after 4 months. This observation suggests that inflammation substantially compromises bone healing. Partial or complete loss of the buccal bone wall also increased remodeling whereas gingival thickness did not. CONCLUSION Alveolar process remodeling seems inevitable yet acceptable following ridge preservation in high-risk patients. Tooth location, tooth abscess, and buccal bone loss were significant predictors. Proper case selection may reduce the incidence of advanced remodeling. REFERENCES 1. Buser D, Bornstein MM, Weber HP, Grütter L, Schmid B, Belser UC. Early implant placement with simultaneous guided bone regeneration following single-tooth extraction in the esthetic zone: a cross-sectional, retrospective study in 45 subjects with a 2- to 4-year follow-up. J Periodontol 2008; 79:1773–1781. 2. Buser D, Halbritter S, Hart C, et al. Early implant placement with simultaneous guided bone regeneration following single-tooth extraction in the esthetic zone: 12-month results of a prospective study with 20 consecutive patients. J Periodontol 2009; 80:152–162. 3. Buser D, Wittneben J, Bornstein MM, Grütter L, Chappuis V, Belser UC. Stability of contour augmentation
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