Daniel Buser,* Vivianne Chappuis,* Michael M. Bornstein,* Julia-Gabriela Wittneben, Marc Frei,* and Urs C. Belser

Transcription

1 Long-Term Stability of Contour Augmentation With Early Implant Placement Following Single Tooth Extraction in the Esthetic Zone: A Prospective, Cross-Sectional Study in 41 Patients With a 5- to 9-Year Follow-Up Daniel Buser,* Vivianne Chappuis,* Michael M. Bornstein,* Julia-Gabriela Wittneben, Marc Frei,* and Urs C. Belser Background: Early implant placement with simultaneous contour augmentation is documented with short- and medium-term studies. The long-term stability of contour augmentation is uncertain. Methods: In this prospective, cross-sectional study, 41 patients with an implant-borne single crown were examined twice, in 2006 and Clinical, radiologic, and esthetic parameters were assessed at both examinations. In addition, a cone beam computed tomographic (CBCT) image was obtained during the second examination to assess the dimensions of the facial bone wall. Results: All 41 implants demonstrated ankylotic stability without signs of peri-implant infection at both examinations. The clinical parameters remained stable over time. Satisfactory esthetic outcomes were noted, as assessed by the pink and white esthetic score (PES/WES) indices. Overall, the PES scores were slightly higher than the WES scores. None of the implants developed mucosal recession over time, as confirmed by values of the distance between implant shoulder and mucosal margin and cast measurements. The periapical radiographs yielded stable peri-implant bone levels, with a mean distance between implant shoulder and first visible bone-implant contact value of 2.18 mm. The CBCT analysis demonstrated a mean thickness of the facial bone wall 2.2 mm. In two implants (4.9%) no facial bone wall was detectable radiographically. Conclusions: This prospective cross-sectional study demonstrates stable peri-implant hard and soft tissues for all 41 implants examined and satisfactory esthetic outcomes overall. The follow-up of 5 to 9 years confirmed again that the risk for mucosal recession is low with early implant placement. In addition, contour augmentation with guided bone regeneration was able to establish and maintain a facial bone wall in 95% of patients. J Periodontol 2013;84: KEY WORDS Alveolar ridge augmentation; bone grafting; bone regeneration; clinical trial; radiology. * Department of Oral Surgery and Stomatology, School of Dental Medicine, University of Bern, Bern, Switzerland. Department of Fixed Prosthodontics, School of Dental Medicine, University of Bern. Department of Fixed Prosthodontics and Occlusion, School of Dental Medicine, University of Geneva, Geneva, Switzerland. doi: /jop

2 Long-Term Stability of Contour Augmentation With GBR Volume 84 Number 11 Implant placement in post-extraction sites in the esthetic zone is a challenge for clinicians and is rated as either advanced or complex difficulty level according to the straightforward, advanced, complex (SAC) classification established by the International Team of Implantology (ITI). 1 The clinician can choose from different timing options as defined by two ITI Consensus Conferences in 2003 and ,3 These options include: 1) immediate implant placement (type 1) on the day of extraction; 2) early implant placement after 4 to 8 weeks of soft tissue healing (type 2); 3) early implant placement after 12 to 16 weeks of partial bone healing (type 3); and 4) late implant placement after complete bone healing of at least 6 months (type 4). Each treatment approach has indications that depend on the clinical situation. 4 In selecting the appropriate option, the clinician has to consider well-defined parameters to achieve the desired treatment outcome. The two primary objectives of implant therapy in the anterior maxilla are successful esthetic outcomes with high predictability and a low risk of complications. 4 In 2009, a literature review concluded that immediate implant placement in the anterior maxilla is associated with a significant risk of esthetic complications, mainly in the form of recession of the facial mucosa. 5 Various clinical studies demonstrated that 20% to 30% of immediate implants yielded mucosal recession of 1 mm Such recession is caused either by the lack of a facial bone wall to support the facial mucosa, by a facial malposition of the implant, or by a combination of the two. 11 Two recent studies using cone beam computed tomography (CBCT) with immediately placed implants and simultaneous guided bone regeneration (GBR) demonstrated a high percentage of implant sites without a facial bone. 12,13 An alternative to reduce the overall treatment time of implant therapy following tooth extraction is the concept of early implant placement following a soft tissue healing period of 4 to 8 weeks. 14 An important aspect of this approach is local contour augmentation using GBR to compensate for ridge alterations through bundle bone resorption occurring following extraction. 15,16 They often result in a crater-like bone defect on the facial aspect because this bone wall is either thin or missing in the anterior maxilla at the time of extraction in >90% of cases. 17,18 Early implant placement is well documented today with midterm clinical studies A prospective case series study with 20 consecutively treated patients reported measurable mucosal recession (0.5 to 1.0 mm) in only one patient (5%) at the 3-year follow-up examination. 22 The purpose of the present study is to analyze the stability of esthetic treatment outcomes in 41 patients following single tooth replacement in the anterior maxilla using the concept of early implant placement with simultaneous contour augmentation. These 41 patients were examined twice, once in 2006, as part of the already mentioned retrospective study, 19 and again in 2010, allowing a direct comparison between the two cross-sectional examinations. Special emphasis was put on assessing the stability of the facial mucosa because it depends directly on the stability of successful contour augmentation using GBR. MATERIALS AND METHODS Patient Selection and Data Set The 45 implant patients who served as a patient cohort for the retrospective cross-sectional study on early implant placement 19 were recalled in 2010 for a second cross-sectional examination. The study protocol, including clinical and radiographic parameters, was approved by the Ethical Committee of the State of Bern. Of the 45 original patients, 41 accepted the invitation and signed a written consent for a second examination; thus, two data sets of 41 patients were available for a prospective comparison of the peri-implant hard and soft tissue conditions at single-tooth implants in the anterior maxilla. The 41 patients (25 males and 16 females, aged 17 to 66 years; mean age: 38.8 years) required a single tooth extraction in the anterior maxilla. The treatment sites included 25 central incisors, 11 lateral incisors, one canine, and four first premolars. All patients were free of systemic diseases that could have compromised wound healing following surgery. 23 Concerning the risk factor smoking, 30 patients were non-smokers, seven light smokers ( 10 cigarettes/day), three heavy smokers (>10 cigarettes/day), and one was a pipe smoker. Surgical and Restorative Treatment The surgical procedure has been described in detail previously. 14 In brief, the surgical technique is characterized by a low-trauma tooth extraction without flap elevation, a 4- to 8-week soft tissue healing period, and implant placement in a correct three-dimensional (3D) position, placing the implant shoulder inside the so-called comfort zones in all three dimensions. 24 For this study, screw-type dental implants comprising 10 standard and 31 taperedeffect implants with a sandblasted and acid-etched (SLA) surface in the endosseous portion and a regular neck with a diameter of 4.8 mm were used. Because these implants were placed in the anterior maxilla, implant types with a short 1.8-mm machined Straumann Dental Implant System, Institute Straumann, Basel, Switzerland. 1518

3 Buser, Chappuis, Bornstein, Wittneben, Frei, Belser neck were chosen. Implant placement was combined with a simultaneous contour augmentation on the facial aspect with the GBR technique using a bioresorbable collagen membrane. i This membrane was combined with two bone fillers to perform local contour augmentation: as a first layer, locally harvested autogenous bone chips were used to cover the exposed implant surface; second, a superficial layer of deproteinized bovine bone mineral (DBBM) was used. Following incision of the periosteum, the collagen membrane was applied to serve as a temporary barrier, and the surgeries were completed with a tension-free primary wound closure. For all implant surgeries, perioperative antibiotic prophylaxis was initiated 2 hours prior to surgery and maintained for 3 days post-surgically (oral amoxicillin 2 1 g/day). Following a healing period of 8 to 12 weeks, a small additional surgery was performed without flap elevation to gain access to the osseointegrated implant and to initiate the phase of soft tissue conditioning. Most patients were then sent back to their referring dentists for implant restoration with a ceramo-metal crown. Following completion of therapy, the patients were enrolled in a routine recall program, either with their referring dentist or at the University of Bern s School of Dental Medicine. Follow-Up Examinations in 2006 and 2010 The 41 patients were recalled twice for a clinical and radiographic examination using a protocol that has been routinely applied in long-term implant studies for >20 years. 22,25-28 The first cross-sectional examination included implants with a 2- to 4-year follow-up period. During the second cross-sectional examination in 2010, these implants had a 5- to 9-year follow-up (average 7 years). The following clinical parameters were assessed by an experienced examiner (UCB): 1) modified plaque index (mpi) and modified sulcus bleeding index (msbi) at four aspects around the implant; 29 2) probing depth (PD; in mm) at four aspects around the implant (recordings made to the nearest millimeter); 3) the distance between the implant shoulder and the mucosal margin (DIM, in mm) at four aspects around the implant 25 (of the 41 implants examined, the crown could be removed in only 33 patients for various reasons; consequently, this value could be measured only around these 33 screw-retained single crowns); 4) cast analysis (impressions were taken at both examinations to produce study casts of the maxilla, which were photographed using a standardized technique with a millimeter grid as reference; 20 on these digital pictures, the midfacial height of the implant crown [IC] and the corresponding height of the contralateral tooth crown [TC] were both measured to identify potential changes in crown height); and 5) esthetic parameters. To examine the esthetic outcomes of the implant crowns objectively at both examinations, the respective casts and intraoral pictures were analyzed critically and compared by two examiners (JW and UB) assessing the pink esthetic score (PES) and the white esthetic score (WES). 30 To assess the stability of the peri-implant bone structure, the following radiographic examinations were used: 1) The distance between the implant shoulder and the first visible bone-implant contact (DIB) was measured (in mm) at the mesial and distal aspects of each implant using periapical radiographs with the long-cone technique. 25,26 All radiographs were read by an experienced examiner (VC). For each implant, one DIB value was calculated at both time points as the average of the obtained mesial and distal values. In addition, a frequency analysis of the difference between DIB values of both examinations was made (DDIB 2006 to 2010 ). 27 A negative DDIB indicated bone loss between the two examinations. 2) In addition to this standard radiographic examination, an additional 3D radiographic analysis was approved by the ethical committee for the second examination (2010) using CBCT with a 4 4 cm field of view. # For each implant, the thickness of the facial bone wall was measured at three different levels: 2, 4, and 6 mm apical to the implant shoulder (Fig. 1). Statistical Analyses First, all data were analyzed with descriptive methods using box plots. To analyze potential differences in the gingival parameters and radiographic findings over the time period, the Wilcoxon signed-rank test was used. To compensate for multiple testing situations, the P values were adjusted according to the method of Holm, 31 which allowed them to be compared with the usual a level of Data sets of the cast analysis were evaluated descriptively, and the difference between IC and TC was calculated for the two time points separately. To detect statistically significant differences between the IC and TC values, the Wilcoxon signed-rank test was used. The level of significance for all tests was P <0.05. All analyses were performed using a computer software program.** The P value adjustment was done using an Internet-based program. i Bio-Gide Membrane, Geistlich Pharma, Wolhusen, Switzerland. Bio-Oss Granulate, Geistlich Pharma. # 3D Accuitomo 80, J. Morita, Kyoto, Japan. ** SAS 9.1.3, SAS Institute, Cary, NC. R for Windows, Institute for Statistics and Mathematics, Vienna, Austria. 1519

4 Long-Term Stability of Contour Augmentation With GBR Volume 84 Number 11 the first examination (mean DIM value of mm). None of the measured peri-implant soft tissue parameters showed a statistically significant difference between the two examinations, however. Cast Analyses IC and TC values were similar at the two examinations (Table 3). The mean IC at the second examination was 9.47 mm (SD 1.22 mm), and the mean TC was 9.87 mm (SD 1.37 mm). The differences between IC and TC values at both time points were not statistically significant (P = 0.30 for IC values). Esthetic Parameters: PES/WES Values The results of the esthetic parameters PES and WES at both examinations are depicted in Table 4. At the second examination in 2010, the analyses revealed a mean PES value of 7.49 and a mean WES value of 6.88, resulting in a total mean score of Compared with the first examination, the mean PES score was slightly reduced by 0.3 units, whereas the mean WES score was more or less stable. Figure 1. Illustration showing how the thickness of the facial bone wall was measured on CBCT images at three different levels: 2, 4, and 6 mm apical to the implant shoulder. RESULTS Clinical Findings Detailed results of all clinical parameters are listed in Table 1. At the second examinations, all implants were still firmly integrated, demonstrating ankylotic stability. None of the patients presented with a suppuration in the peri-implant sulcus. Overall, the patients exhibited good to sufficient oral hygiene, documented by a mean mpi of The peri-implant soft tissues appeared healthy, which corresponded well to a low mean msbi of The mean PD was 4.26 mm. At the second examination, only 33 crowns could be removed, allowing a direct measurement of the DIM value to the nearest millimeter. Due to the submucosal position of the implant shoulder in the anterior maxilla, DIM values were all in the negative range, with a mean DIM of mm. From an esthetic point of view, a detailed analysis of DIM values is of interest, in particular the facial DIM value, which was on average mm at the second examination (Table 2). Thus, the implant shoulders were slightly more submucosally located compared with Radiographic Findings None of the 41 implants revealed continuous periimplant radiolucency, whereas all implants showed semilunar crestal bone saucers on the mesial and distal aspects, which is typical for this tissue level implant type (Fig. 2A). A typical CBCT image is shown in Figure 2B. The mean DIB value for the first examination (2006) was 2.09 mm (SD 0.60 mm; Table 1). The measured DIB values at the second examination (2010) ranged from 1.30 mm to 3.87 mm, with a mean DIB of 2.18 mm (SD 0.72 mm). The difference between the DIB values for the two time points analyzed was not statistically significant (P = 0.324). The frequency analysis of the 41 implants evaluated at both time points demonstrated that 85% of the implants exhibited either a slight bone gain or bone loss within -0.8 and 0.8 mm (Fig. 3). Six implants exhibited a bone loss of >0.8 mm from the first to the second examination. The maximum bone loss was mm. Examination of the facial bone wall with CBCT demonstrated a mean thickness from 1.58 mm (SD 1.00 mm) to 2.33 mm (SD 1.14 mm) at the three levels of measurement (Table 5). The frequency analysis showed that at the 2-mm level, representing roughly the beginning of the microrough SLA implant surface, 8 of 41 implants showed no facial bone wall (Fig. 4). At the 4- and 6-mm levels, no facial bone wall was detectable for two implants (= 4.9%; Fig. 5A). One of them was clearly malpositioned in an orofacial direction (Fig. 5B). 1520

5 Buser, Chappuis, Bornstein, Wittneben, Frei, Belser Table 1. Comparison of the Clinical and Radiologic Parameters at the Two Time Points Analyzed Time Point 1 (2006) Time Point 2 (2010) Parameter mpi msbi PD (mm) DIM (mm) DIB (mm) mpi msbi PD (mm) DIM (mm) DIB (mm) n Minimum Maximum Mean SD P values Table 2. Detailed Analysis of the Peri-Implant DIM Values Time Point 1 (2006) Time Point 2 (2010) Parameter DIM mesial DIM facial DIM distal DIM oral DIM mesial DIM facial DIM distal DIM oral n Minimum (mm) Maximum (mm) Mean (mm) SD (mm) P values Table 3. Cast Analysis Regarding the Length of the Implant Crown and the Contralateral Tooth Crown (in mm) Time Point 1 (2006) Time Point 2 (2010) Parameter IC TC IC TC Mean Maximum Minimum SD

6 Long-Term Stability of Contour Augmentation With GBR Volume 84 Number 11 Table 4. PES and WES Values of the Implant-Supported Single Crowns at the Two Time Points Analyzed (mean values) PES WES Total PES & WES Mean WES Surface Texture Translucency Tooth Volume / Outline Color Tooth Form Mean PES Root Convexity / Soft Tissue Color and Texture Facial Mucosal Level Facial Mucosa Curvature Distal Papilla Mesial Papilla Time Point Mean values are in bold. Figure 2. Periapical radiograph of an implant at the 6.5-year follow-up (A).Note the typical bone saucer around the osseointegrated implant with a DIB value 2 mm. The corresponding CBCT image (B) shows an intact facial bone wall with a thickness of >2mm. DISCUSSION The results of this prospective cross-sectional study confirm favorable clinical and radiographic 1- and 3- year results for implant-borne single-tooth crowns in the anterior maxilla. 20,22 The examined 41 implants had been placed according to the concept of early implant placement post-extraction, that is, after 8 weeks of soft tissue healing. The prospective comparison between the two time points demonstrated that all 41 implants maintained successful tissue integration up to a 5- to 9-year follow-up, documented by clinical and radiographic parameters. The standard clinical parameters, such as mpi and msbi as well as PD values, indicated healthy periimplant soft tissues. None of the parameters showed a significant change between the two examinations. The mean values obtained were all in line with previous prospective studies using identical parameters. 27,28,32 The obtained DIB values indicated overall stable peri-implant bone crest levels on the mesial and distal aspects of the implants, and the mean DIB values did not change over time either (2.18 mm versus 2.09 mm). However, mean DIB values alone are not indicative of the stability of peri-implant bone crest levels of the whole patient cohort because some implants will lose and some will gain bone over time. Thus, a frequency analysis of the DDIB 2006 to 2010 values must be used. 33 In the present study, 35 of 41 implants (85%) show minimal changes in bone crest levels, whereas six implants (15%) displayed >0.8 mm bone loss during the 4 years between the two examinations. This is in accordance with previous 1522

7 Buser, Chappuis, Bornstein, Wittneben, Frei, Belser Figure 3. Frequency analysis of ΔDIB 2006 to 2010 (in mm). A negative value indicates bone loss between the time points. Table 5. Thickness of the Facial Bone Wall at Three Different Levels Measured on Orofacial CBCT Images (in mm) Parameter At 2-mm Level At 4-mm Level At 6-mm Level Mean Maximum Minimum SD Figure 4. Frequency analysis of the facial bone wall thickness (in mm) at three different levels. A total of 39 of 41 implants (95%) had a detectable facial bone wall. long-term studies presenting a frequency analysis of DDIB values. 27,28 The main focus of this study is to determine the long-term stability of contour augmentation using the GBR technique. The goal of contour augmentation is the establishment of a facial bone wall of sufficient height and thickness to serve as support for esthetic soft tissues. 14 Contour augmentation is needed in most implant sites located in the anterior maxilla because the facial bone wall at extraction sites is often resorbed within a few weeks. 15 A facial bone wall of sufficient dimensions is today considered a prerequisite for esthetic soft tissue contours on the facial aspect 24 because peri-implant soft tissues have a rather constant dimension, often called biologic width. 34,35 The dimensions of the facial bone wall can be examined only with a 3D radiograph. Today, the new CBCT technology offers excellent image quality with a clearly reduced radiation exposure for the patient when compared with dental CT scans, in particular when a small 4 4 cm CBCT field of view is used, as in the present study. 36,37 The analysis of the CBCT images demonstrated a mean thickness of the facial bone wall from 1.6 to 2.3 mm at various levels. At the 2-mm level, where the micro-rough SLA surface starts for this implant type, eight implants had no detectable facial bone wall. This finding is not surprising because the tissue level implants that were used are characterized by a circular bone saucer. This bone resorption develops following implant restoration, is a biologically driven bone remodeling process, and has a dimension of 2.0 mm in a vertical direction. 24,38 At the 4- and 6-mm levels, only two implants did not show a facial bone wall, which corresponds to 4.9% of the examined implants. The mean bone wall thicknesses were 2.2 and 2.3 mm, respectively. It can be concluded that contour augmentation with GBR successfully established a facial 1523

8 Long-Term Stability of Contour Augmentation With GBR Volume 84 Number 11 Figure 5. A) One of the two implants without a detectable facial bone wall analyzed with an orofacial CBCT image. B) The horizontal CBCT image indicates that the implant is located in a facial malposition. bone wall in roughly 95% of patients, and that this bone wall was maintained for a 5- to 9-year follow-up period (average follow-up of 7 years). This is in contrast to two follow-up studies on immediate implants and GBR with a CBCT examination, in which the percentage of a missing facial bone wall was much higher: 57% in the first study 12 and 36% in the second, a 7-year follow-up study. 13 It must be mentioned, however, that the sample size was rather limited in both studies. The lack of a facial bone wall is often combined with a recession of the facial mucosa. An increased rate of mucosal recession has been reported in several studies on immediate implants, 5 and it can be speculated that many of these immediate implants with recession would have no facial bone wall in the long-term follow-up. Thus, additional studies on immediate implants with long-term 3D radiographic imaging using CBCT and larger sample sizes are urgently needed to clarify this hypothesis. It is interesting to note that the two implants without facial bone wall also showed a DDIB of and mm, meaning that both implants lost bone on the mesial and distal aspects as well. Such bone loss can be caused by a peri-implant infection with suppuration. 39 However, given that both implants were free of peri-implant infection at both examinations, other factors must have caused this bone loss. Due to the lack of a facial bone wall, both implants have no osseointegration on the facial aspect. Thus, under functional load, the stress at the bone implant interface was concentrated at the mesial, distal, and palatal aspects of the implants. Hence, the observed bone loss could also have been caused by mechanical overload due to excessive strain. This biomechanical phenomenon is another factor that is not well understood today and needs further clarification. 40,41 In the present study, both implants without facial bone wall must be considered to be at increased risk of a continuation of progressive bone loss. The esthetic outcomes of the 41 single crowns were assessed with the PES/WES indices. 30 The mean total PES/WES value of 14.3 indicated a satisfactory esthetic outcome overall, with a slight reduction of 0.36 when compared with the first examination in This reduction was mainly observed for the PES index, whereas the mean WES score remained stable. As in 2006, the PES values (mean score of 7.5) were still clearly higher than the corresponding WES values (mean score of 6.9). This is not surprising because the PES values are influenced mainly by the local anatomy, the surgical skills and experience of the clinician inserting the implant and augmenting the implant site, and the bone remodeling events in the periimplant bone. In the present study, an experienced implant surgeon (DB) was involved in all implant surgeries. The applied contour augmentation with GBR mainly influences the PES variables facial mucosa curvature and level of facial mucosa. The high scores for both variables (mean scores of 1.8 and 1.7, respectively) confirm the favorable findings of the CBCT examination concerning the facial bone wall. Slightly less favorable were the scores for the mesial and distal papillae (mean 1524

9 Buser, Chappuis, Bornstein, Wittneben, Frei, Belser scores of 1.5 and 1.3, respectively). However, the height of peri-implant papillae depends primarily on the bone level height at adjacent root surfaces. 42 The present patient cohort had a mean age of 39 years at implant surgery, and 13 of 41 patients were aged 50 years. Hence, several of these patients already had a compromised dentition with a reduced vertical bone height at adjacent teeth prior to implant placement. As stated, the WES values were clearly less favorable than the PES values, which is documented by the fact that seven of 41 crowns (18%) scored below the threshold of 6, defined as being the level of clinical acceptability from the examiner s point of view. The main contributing factor for these less favorable WES values is the fact that most implants were restored by the referring practitioners, involving 20 different dental technicians. Thus, it is quite likely that not all of them offered the same level of quality from an esthetic point of view. In another prospective case series by the same group, the mean WES value at 3 years of follow-up had a clearly higher score of In this cohort of 20 patients, all single crowns were fabricated by the same dental technician. The favorable PES variables facial mucosa curvature (mean score 1.8) and level of facial mucosa (mean score 1.7) indicate that the facial mucosa remained stable between the two examinations. This is supported by the measurement of the casts because the mean IC values were 9.47 mm, more or less identical to the mean IC values in This is also confirmed by the facial DIM values, which were obtained for the 33 implant sites restored with screwretained crowns that could be removed for a direct measurement with a periodontal probe. The DIM values represent the position of the implant shoulder in relation to the mucosal margin, a negative value indicating a submucosal implant position, which is a prerequisite for an esthetic implant outcome. The mean facial DIM value was -2.2 mm. Tissue level implants, as used in the present study, were always positioned with the implant shoulder 2 mm below the future mucosal margin on the facial aspect to optimize esthetic outcomes. 24 The mean facial DIM value of -2.2 mm at the 5- to 9-year follow-up confirms that no significant mucosal recession was encountered in the present study. The results of this study confirm favorable data of a previously reported prospective case series study using the same surgical approach. 20,22 That study with 20 patients also showed a remarkably low risk of facial recession after 1 and 3 years of follow-up. The stability of the facial mucosal margin is attributed mainly to the stability of the underlying contour augmentation with GBR. Here, two factors are decisive: 1) the applied treatment quality by the involved surgeon and 2) the characteristics of the biomaterials used for contour augmentation. Based on the promising results of the present study, evidence is increasing that a resorbable collagen membrane, in combination with autogenous bone chips and DBBM granules, is able to provide successful contour augmentation on the facial aspect of the implants. The use of DBBM granules seems important for the long-term stability of a facial bone wall of sufficient height and thickness because DBBM granules have a low substitution rate It can be speculated that these bone fillers will not be resorbed during the natural bone remodeling process and thus will help maintain the dimensions of the facial bone wall over time. This hypothesis is supported by the favorable CBCT data of the present study. Definitive proof can be obtained only through histomorphometric analysis of biopsies harvested from patients in areas of contour augmentation. Results of an ongoing histomorphometric study will be reported soon. CONCLUSIONS The present study allows the following conclusions: 1) After a follow-up period of 5 to 9 years, contour augmentation with GBR is successful in establishing and maintaining a facial bone wall, as documented by 3D CBCT images; 2) of the 41 examined implants, 39 show mean facial bone wall thicknesses of 1.6 to 2.3 mm at the three levels measured on their CBCT images; 3) the concept of early implant placement with simultaneous GBR 8 weeks after tooth extraction results in positive esthetic outcomes with a low risk of recession of the facial mucosa; 4) the two implants without a detectable facial bone wall (4.9%) also demonstrate interproximal radiographic bone loss of 1 mm over the time of observation; and 5) the clinical, radiographic, and esthetic parameters remain stable overall throughout the observation period. ACKNOWLEDGMENTS The study was supported solely by departmental funds of the Universities of Bern and Geneva. The authors thank Mrs. Claudia Moser and Mrs. Olivia Bucher, both dental nurses at the University of Bern, for the organization of all follow-up examinations. The authors report no conflicts of interest related to this study. REFERENCES 1. Dawson T, Chen ST. The SAC Classification in Implant Dentistry. Berlin: Quintessence Publishing; Hämmerle CH, Chen ST, Wilson TG Jr. Consensus statements and recommended clinical procedures regarding the placement of implants in extraction sockets. Int J Oral Maxillofac Implants 2004;19(Suppl.):

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Aesthetic outcome of singletooth 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: Buser D, Wittneben J, Bornstein MM, Grütter L, Chappuis V, Belser UC. Stability of contour augmentation 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: Buser D, von Arx T. Surgical procedures in partially edentulous patients with ITI implants. Clin Oral Implants Res 2000;11(Suppl. 1): Buser D, Martin W, Belser UC. Optimizing esthetics for implant restorations in the anterior maxilla: Anatomic and surgical considerations. Int J Oral Maxillofac Implants 2004;19(Suppl.): Buser D, Weber HP, Lang NP. Tissue integration of nonsubmerged implants. 1-year results of a prospective study with 100 ITI hollow-cylinder and hollow-screw implants. Clin Oral Implants Res 1990;1: Weber HP, Buser D, Fiorellini JP, Williams RC. Radiographic evaluation of crestal bone levels adjacent to nonsubmerged titanium implants. Clin Oral Implants Res 1992;3: Buser D, Mericske-Stern R, Dula K, Lang NP. Clinical experience with one-stage, non-submerged dental implants. Adv Dent Res 1999;13: Bornstein MM, Schmid B, Belser UC, Lussi A, Buser D. Early loading of non-submerged titanium implants with a sandblasted and acid-etched surface. 5-year results of a prospective study in partially edentulous patients. Clin Oral Implants Res 2005;16: Mombelli A, van Oosten MA, Schurch E Jr., Land NP. The microbiota associated with successful or failing osseointegrated titanium implants. Oral Microbiol Immunol 1987;2: Belser UC, Grütter L, Vailati F, Bornstein MM, Weber HP, Buser D. Outcome evaluation of early placed maxillary anterior single-tooth implants using objective esthetic criteria: A cross-sectional, retrospective study in 45 patients with a 2- to 4-year follow-up using pink and white esthetic scores. J Periodontol 2009;80: Holm S. A simple sequentially rejective multiple test procedure. Scand J Stat 1979;6: Weber HP, Crohin CC, Fiorellini JP. A 5-year prospective clinical and radiographic study of non-submerged dental implants. Clin Oral Implants Res 2000; 11: Brägger U. Use of radiographs in evaluating success, stability and failure in implant dentistry. Periodontol ;17:

11 Buser, Chappuis, Bornstein, Wittneben, Frei, Belser 34. Cochran DL, Hermann JS, Schenk RK, Higginbottom FL, Buser D. Biologic width around titanium implants. A histometric analysis of the implanto-gingival junction around unloaded and loaded nonsubmerged implants in the canine mandible. J Periodontol 1997;68: Kan JY, Rungcharassaeng K, Umezu K, Kois JC. Dimensions of peri-implant mucosa: An evaluation of maxillary anterior single implants in humans. J Periodontol 2003;74: Loubele M, Bogaerts R, Van Dijck E, et al. Comparison between effective radiation dose of CBCT and MSCT scanners for dentomaxillofacial applications. Eur J Radiol 2009;71: Pauwels R, Beinsberger J, Collaert B, et al; SEDEN- TEXCT Project Consortium. Effective dose range for dental cone beam computed tomography scanners. Eur J Radiol 2012;81: Esposito M, Ekestubbe A, Gröndahl K. Radiological evaluation of marginal bone loss at tooth surfaces facing single Brånemark implants. Clin Oral Implants Res 1993;4: Heitz-Mayfield LJA. Peri-implant diseases: Diagnosis and risk indicators. J Clin Periodontol 2008;35(Suppl. 8): Albrektsson T, Buser D, Sennerby L. On crestal/ marginal bone loss around dental implants. Int J Oral Maxillofac Implants 2012;27: Albrektsson T, Buser D, Sennerby L. Crestal bone loss and oral implants. Clin Implant Dent Relat Res 2012; 14: Choquet V, Hermans M, Adriaenssens P, Daelemans P, Tarnow DP, Malevez C. Clinical and radiographic evaluation of the papilla level adjacent to singletooth dental implants. A retrospective study in the maxillary anterior region. J Periodontol 2001;72: Jensen SS, Broggini N, Hjørting-Hansen E, Schenk R, Buser D. Bone healing and graft resorption of autograft, anorganic bovine bone and beta-tricalcium phosphate. A histologic and histomorphometric study in the mandibles of minipigs. Clin Oral Implants Res 2006;17: Jensen SS, Yeo A, Dard M, Hunziker E, Schenk R, Buser D. Evaluation of a novel biphasic calcium phosphate in standardized bone defects: A histologic and histomorphometric study in the mandibles of minipigs. Clin Oral Implants Res 2007;18: Jensen SS, Bornstein MM, Dard M, Bosshardt DD, Buser D. Comparative study of biphasic calcium phosphates with different HA/TCP ratios in mandibular bone defects. A long-term histomorphometric study in minipigs. J Biomed Mater Res B Appl Biomater 2009;90: Correspondence: Dr. Daniel Buser, Department of Oral Surgery and Stomatology, Freiburgstrasse 7, CH-3010 Bern, Switzerland. Fax: ; daniel. buser@zmk.unibe.ch. Submitted October 22, 2012; accepted for publication November 22,