Facial Mucosal Level Change Following Maxillary Anterior Single Immediate Tooth Replacement in Extraction Sockets With Facial Bone Wall Defects: A 4- to 15-Year Retrospective Study

The purpose of this retrospective study was to evaluate long-term facial mucosal stability following IIPP in extraction sockets with a facial bone wall defect in the esthetic zone.

Materials and Methods

This study was approved by the Institutional Review Board of Loma Linda University and conducted at the Center for Implant Dentistry, Loma Linda, California. Treatment records were evaluated for single maxillary anterior (teeth Nos. 6 through 11) IIPP with contour bone graft (C-BG) and contour connective tissue graft (C-CTG) in extraction sockets with facial bone wall defects with or without flap reflection. Inclusion criteria were as follows: The facial gingival zenith of the failing tooth had to be within 1 mm compared to the facial gingival zenith of the contralateral corresponding tooth; the mesiodistal extent of the facial bone wall defect of the extraction socket must not extend to the interproximal bone of the adjacent teeth (ie, V- or U-shaped defect only)⁶ and the defect length must be ≥5 mm; and all immediate implants placed must have initial primary stability (>25 Ncm).¹¹ Only cases with applicable data at preoperative stage (T₀), tooth extraction and IIPP (T₁), final prosthesis placement (T₂), and the latest follow-up (T₃) were included in the study (Figure 1).

Facial Bone Wall Defect Assessment and Measurement

At T₀, the facial bone wall defect of the failing tooth was assessed by bone sounding the facial and proximal line angles of the failing tooth, as well as the interproximal bone of the adjacent teeth. Only extraction sockets with either V-shaped defects (ie, facial bone wall defect did not extend to the proximal line angle) or U-shaped defects (ie, facial bone wall defect extended to the proximal line angle but not to the proximal bone of adjacent teeth) were included. At T₁, immediately following tooth extraction, a periodontal probe was used to measure the vertical bone wall defect depth by midfacial bone sounding (MFBS) the socket from the free mucosal margin to the most apical point of the facial bone wall defect. At T₃, MFBS was performed again after the final prosthesis was placed.

Implant Success Rate

Implant success was evaluated based on guidelines from Smith and Zarb wherever applicable.¹²

Marginal Bone Level (MBL)

Marginal bone level (MBL) was measured at T₁ and T₃ with sequential periapical radiographs using the long cone parallel technique, and the MBL change was calculated. The coronal corner of the implant platform was used as the reference point. The distance between the reference point and the most coronal implant-bone contact point was measured and compared between the two time intervals (T₁ and T₃). The value was positive when the implant-bone contact point was more coronal to the reference point, and negative when the implant-bone contact point was more apical.

CBCT Facial Marginal Bone Level (CBCT-FMBL)

A cone-beam computed tomography (CBCT) scan was taken at T₃ and the data was transferred to and opened in an implant planning software (Invivo^™6, Anatomage, anatomage.com), in which the midsagittal image of the implant was identified. The image with the vertical and horizontal scale bars was then screen-captured and transferred to a presentation program (Keynote, Apple, apple.com) for evaluation. The facial coronal corner of the implant platform was used as the reference point. The facial marginal bone level (CBCT-FMBL) is the perpendicular distance from the implant platform to the most coronal point of the facial bone. The value was positive when the implant-bone contact point was more coronal to the reference point, and negative when the implant-bone contact point was more apical.

CBCT Facial Horizontal Bone Thickness (CBCT-FHBT)

At the sagittal view of the CBCT, lines parallel to the implant platform (horizontal implant lines) were placed at 0 mm (implant platform), 1 mm, 2 mm, 3 mm, 5 mm, and 7 mm apical to the implant platform. The facial horizontal bone thickness (CBCT-FHBT) at each designated level, including the implant platform level, was measured on the corresponding horizontal implant lines from the facial implant surface extending to the outline of the facial bone.

Facial Implant Mucosal Thickness (FIMT)

The facial implant mucosal thickness (FIMT) was evaluated at T₁ (after extraction) and T₂(at definitive prosthesis placement) by direct measurement using a tension-free caliper to the nearest 0.1 mm at approximately 2 mm apical from the free mucosal margin on the midfacial aspect of the extraction socket,¹³ and the changes were calculated. The soft-tissue phenotype was considered thin if the T₁ measurement was ≤1.1 mm, and thick if the T₁ measurement was >1.1 mm.¹³

Facial Implant Mucosal Level (FIML)

The facial implant mucosal level (FIML) was recorded at T₀ (pretreatment) and T₃ (latest follow-up) using casts and photographs taken at 1:1 magnification at a right angle to the failing tooth or implant prosthesis, and the changes were calculated. The measurement was made from the midfacial gingival margin of the failing tooth to the line connecting the facial gingival zenith of the two adjacent teeth (reference line) at 10x magnification to the nearest 0.1 mm.¹⁴ The value was positive/negative when the facial mucosal level was more coronal/apical, respectively, to the reference line. The changes in the FIML of the implant crown were evaluated by measuring the distance from the midfacial mucosal margin of the implant crown to the reference line at the respective time interval.

Calibration and Statistical Analysis

The intra-examiner reliability of measurement was determined by repeated measurements of MBL, FIML, CBCT-FMBL, and CBCT-FHBT 3 weeks apart and was expressed as the intraclass correlation coefficient.

Wilcoxon signed-rank test was used to compare measurements at different timepoints, and Mann-Whitney U test was used to compare changes between different groups. All statistical analyses were conducted at a significance level of α = 0.05.

Case Presentation: Surgical Phase

In a representative case, a 32-year-old female patient presented with a failing maxillary central incisor (tooth No. 8) (Figure 2 and Figure 3). Clinical evaluation showed harmonious gingival architecture and good oral hygiene. Radiographic examination, including periapical radiographs and CBCT, indicated periapical radiolucency and absence of facial bone around the failing tooth No. 8 (Figure 4 and Figure 5). Further examination through bone sounding on the facial aspect of tooth No. 8 revealed a U-shaped bone wall defect (Figure 6 through Figure 8). After treatment options were presented, the patient elected to replace the failing tooth No. 8 with IIPP in conjunction with C-BG and C-CTG.

A provisional shell restoration (TempShell, Nobel Biocare, nobelbiocare.com) was fabricated prior to the surgery. After anesthesia was administered, the failing tooth was extracted and a full-thickness flap was reflected. The facial bone wall defect was evaluated with a periodontal probe (Figure 9 and Figure 10). After degranulation, an implant was immediately placed (Figure 11) according to the following guidelines¹⁵ for 3-dimensional implant positioning:

Apicocoronal implant position: The implant platform was positioned 3 mm to 4 mm apically from the predetermined facial mucosal margin of the definitive crown.

Buccolingual implant position: The implant was placed palatally with the center of the implant being 1 mm to 2 mm palatal to an imaginary horizontal line bisecting the facial and palatal halves of the corresponding tooth (No. 9) (Figure 12).

Sagittal implant position: The implant was placed aiming at the incisal edge of the definitive crown.

The prefabricated provisional shell was relined (Protemp^™, 3M Oral Care, 3m.com) onto the prepared temporary abutment (Temporary Snap Abutment, Nobel Biocare). The emergence profile of the provisional crown was then refined (Vit-l-escence^™, Ultradent, ultradent.com), polished, and hand-tightened onto the implant (Figure 13).

Particulate autogenous bone was harvested using a bone scraper (Henry Schein Dental, henryschein.com) from areas surrounding the surgical site and layered around the exposed implant surface. Subsequently, xenograft (Bio-Oss^®, Geistlich, geistlich-pharma.com) was used as the C-BG, overlaying the particulate autogenous bone and implant (Figure 13). A resorbable collagen membrane (Bio-Gide^®, Geistlich) was used to contain the bone graft material. A C-CTG was then harvested from the lateral palate and sutured onto the cervical-facial aspect of the C-BG around the provisional (Figure 14). A periosteal releasing incision was made to ensure flap passivity, and polypropylene sutures (Hu-Friedy, hufriedygroup.com) were used to achieve primary closure (Figure 15).

Case Presentation: Immediate Postoperative Phase

Appropriate antibiotics and analgesics were prescribed for postoperative use. The patient was instructed not to brush the surgical site for 2 weeks, but to rinse gently with 0.12% chlorhexidine gluconate solution (Peridex^™, 3M Oral Care) and was placed on a liquid diet for 2 to 3 days. A soft diet was recommended for the entire healing phase (3 months), and the patient was advised against functioning on the surgical site.

Case Presentation: Definitive Prosthetic Phase

The definitive implant impression was made 10 months after IIPP. At 1 year, a screw-retained definitive prosthesis (with angulated screw channel abutment, Nobel Biocare) was placed and torqued to 35 Ncm according to the manufacturer's recommendation (Figure 16 through Figure 18). Clinical and radiographic follow-up at 6 years showed that the facial mucosal contour was well-maintained with IIPP, C-BG, and C-CTG (Figure 19 through Figure 22).

Results

In this study, 16 patients (11 female, 5 male) with a mean age of 49.8 (28 to 80) years underwent IIPP in extraction sockets with facial bone wall defects (six V-shaped, 10 U-shaped) with a mean midfacial bone sounding (MFBS) of 9.6 mm (8 mm to 12 mm). Tooth failures were attributed to fracture (n = 5), endodontic failure (n = 4), periodontal disease (n = 3), and root resorption (n = 4). Eleven sites were considered thin, while five sites possessed thick phenotype.

A total of 16 implants (14 NobelActive^® [Nobel Biocare] [four 3.5 mm x 13 mm, nine 3.5 mm x 15 mm, one 4.3 mm x 15 mm], one NobelReplace^® [Nobel Biocare] [4.3 mm x 15 mm], and one Straumann BLT [Straumann, straumann.com] [4.1 mm x 14 mm]) were evaluated, which included 14 central incisors and two canines. Full-thickness flap was reflected during IIPP surgery on nine sites, while flapless surgery was performed at seven sites. Particulate autogenous bone, xenograft, and connective tissue grafts were applied at all surgical sites. At T₃, after a mean follow-up time of 6 years (4.1 to 15.4), implant success rate was 100% (16/16). The intraclass correlation coefficient was greater than 0.95 for all measurements, indicating that the measurement methods were highly reliable and reproducible.¹⁶

At T₃, the mean radiographic marginal bone level (MBL) change of -0.3 ± 0.3 (-0.7 to 0) mm was noted on the mesial aspect of the implant, while -0.5 ± 0.5 (-2.0 to 0) mm was noted on the distal aspect of the implant, yielding an overall average MBL change of -0.4 ± 0.3 (-1.0 to 0) mm. There was no statistically significant difference in the mean MBL between the U-shaped (-0.6 mm) and V-shaped (-0.4) groups (P = .79). At T₃, CBCT evaluation showed a mean facial marginal bone level (FMBL) of -0.6 ± 0.8 (-2.1 to 0.5) mm in relation to the implant platform. Except for a single site at the 2 mm level, facial horizontal bone thickness (CBCT-FHBT) at all sites in all levels was ≥1.5 mm (Table 1).

The mean overall changes of facial implant mucosal thickness (FIMT) from T1 to T2, facial implant mucosal level (FIML) from T0 to T3, and midfacial bone sounding (MFBS) from T1 to T3 were 1.2 ± 0.5 (1.6 to 2.9) mm, -0.4 ± 0.4 (-1.6 to 1.0) mm, and 6.0 ± 1.4 (4.0 to 8.5) mm, respectively (Table 2 through Table 4). Comparisons of tissue changes between different parameters (thick vs thin phenotype, V- vs U-shaped facial bone wall defect, and surgery with vs without full-thickness flap reflection) also are presented in Table 2 and Table 3. Regardless of phenotype, defect shape, or surgical technique, the mean FIMT values at T2 were comparable (2.3 mm to 2.4 mm), and all MFBS measurements at T3 were between 3 mm and 4 mm (Table 2 and Table 4). The mean FIML change of -0.4 mm and MFBS change of 6.0 mm translates to a mean vertical facial hard tissue gain of 5.6 mm.

Discussion

The present retrospective study demonstrated the effectiveness in terms of hard- and soft-tissue stability of IIPP simultaneous with hard- and soft-tissue contour augmentation in compromised defects exhibiting a deficient facial bone wall. The implant success rate in this study (mean = 100%) was comparable to previous reports published elsewhere identifying IIPP in extraction sites with (94% to 100%)^7,10 and without (96.7% to 100%)^17-20 facial bone wall defects. Moreover, in this study, the mean overall MBL change of -0.4 mm (T₃) showed that the grafted bone remained stable over a mean period of 6 years, and the results are comparable to MBL changes (-0.4 to -0.1 mm)^8,21 reported by other IIPP studies with intact extraction sockets.

The factors that affect FIML change following IIPP in extraction sockets with a facial bone wall defect are the facial bone wall thickness, facial-palatal implant position, and facial mucosa thickness. An intact anterior extraction socket has long been considered one of the prerequisites for IIPP due to the belief that facial bone is needed to provide support to the overlying FIML.⁶ Moreover, a 3 mm distance from the facial free mucosal margin to the underlying facial bone wall has been considered necessary to provide mucosal support and stability.²² In other words, it is speculated that the presence of a facial bone wall defect on an extraction socket may increase the risk of facial mucosal recession.

However, despite the fact that all extraction sockets included in the present study lacked an intact facial bone wall (mean MFBS = 9.5 mm), none of the sites displayed facial mucosal recession. This finding suggests that the scenarios exhibiting a deficient facial bone are not prone to show deleterious outcomes. Nevertheless, this only applies to cases in which the facial bone wall defect does not extend to the interproximal bone of adjacent teeth (ie, V- or U-shaped defect). The presence of intact interproximal bone of a failing tooth and/or adjacent teeth seems to be instrumental in dictating the FIML.⁶ The question remains as to whether severing the supracrestal fibers during tooth extraction and implant placement affects facial mucosal stability in the absence of facial bone. In this study, after a mean follow-up time of 6 years, it was shown that the mean FIML can be maintained (mean -0.4 mm) with IIPP in V- and U-shaped facial bone wall defects.

The significance of a C-BG at the time of IIPP in maintaining facial mucosal level in the presence of a facial bone wall defect is also a point of discussion. Typically, it takes months for bone cells to migrate from the surrounding socket walls to encase or replace the grafted bone material within the extraction socket.²³ Therefore, the initially grafted bone only serves as a matrix to support the soft tissue until vital bone formation occurs. During the early healing time, the most coronal portion of the bone at the facial entrance of the extraction socket will serve to maintain the FIML until grafted bone matures. In this study, facial contour bone grafting over the implant and facial bone wall defect (T₁) resulted in a mean MFBS change of 3.5 mm ± 0.4 mm (T₃), suggesting that the particulate bone graft material turned into solid, stable bone over time. It is interesting to note that regardless of tissue phenotype, defect shape, or whether the surgical procedure was done with or without flap reflection, all of the MFBS measurements at T₃in all sites were between 3 mm and 4 mm (Table 3), indicating that the technique performed in this study could yield a predictable result. Moreover, because the platforms of the implants in this study were placed about 3 mm apical from the facial mucosal margin, the radiographic bone measurement from the implant platform (mean CBCT-FMBL [-0.7 mm]) and the bone sounding measurement (mean MFBS [3.5 mm]) confirmed that the facial bone was regenerated almost to the level of the implant platform. At T₃, the mean FIML change of -0.4 mm and mean MFBS change of 6.0 mm also translate to the mean vertical facial hard tissue gain of 5.6 mm.

The importance of the facial-palatal implant position on the FIML cannot be overstated. A facially positioned implant can exhibit gingival recession three times greater than that of a palatally positioned implant.²⁴ In general, from an incisal view, the implant should be placed palatally (engaging palatal bone) and within the confines of the extraction socket aligned with the arch form. Especially in situations where a facial bone wall defect is present, a palatally positioned implant allows for facial bone grafting to achieve appropriate vertical and horizontal underlying bone support for optimal peri-implant soft-tissue architecture. In the present study, CBCT assessment showed a mean FHBT of 0.6 mm, 1.5 mm, 1.9 mm, 2.5 mm, 2.7 mm, and 2.9 mm at 0 mm, 1 mm, 2 mm, 3 mm, 5 mm, and 7 mm apical to the implant platform, respectively. Creating an adequate bone thickness with a contour bone graft over the facial aspect of the implant is significant, as Monje et al reported that the chances of implant marginal bone loss were significantly reduced with a minimal facial bone thickness of 1.5 mm,²⁵ thereby lessening the risk of surface contamination and peri-implantitis.^26,27

A thin soft-tissue phenotype has been associated with an increased risk of facial implant mucosal dehiscence (ie, recession).^19,24,28 Numerous studies have shown the benefits of C-CTG simultaneous with IIPP.^{17,21,23,29,30} Thickening the FIMT not only can minimize facial mucosal recession, but it may also conceal the underlying implant and/or implant restorative materials. Moreover, thickening the facial mucosa may override the need for underlying facial bone support. A 1-year follow-up study on IIPP and C-CTG on maxillary anterior implants showed an average increase in FIMT of 1.4 mm (0.4 mm to 2.7 mm).²⁹ In the present study, a comparable mean FIMT gain of 1.2 ± 0.5 (0.3 to 2.0) mm with C-CTG grafting was noted after a mean follow-up time of 8.9 (6 to 15) months. Irrespective of initial (T₁) soft-tissue phenotype, the average resulting (T₂) FIMT of both thick-tissue and thin-tissue phenotype groups was similar (2.3 ± 0.4 mm; Table 2), indicating that thin soft-tissue phenotype is likely to benefit more from this phenotype modification procedure. The changes in FIML and MFBS were comparable between thick and thin phenotype groups (Table 3 and Table 4).

Conclusion

Immediate implant placement in fresh extraction sockets exhibiting facial bone wall defects can be managed by means of simultaneous hard- and soft-tissue contour augmentation. This protocol proved long-term effectiveness in terms of marginal bone/mucosal level stability and gain in contour that favored the esthetic outcomes in the maxillary anterior region.

About the Authors

Joseph Y. K. Kan, DDS, MS
Professor, Department of Implantology, Loma Linda University School of Dentistry, Loma Linda, California

Kitichai Rungcharassaeng, DDS, MS
Private Practice in Orthodontics, Claremont, California

Shi Yin, DDS, MS
Assistant Professor, Advanced Education in Periodontics and Implant Dentistry, Loma Linda University School of Dentistry, Loma Linda, California

Qiao Fang, DDS, MSD
Clinical Assistant Professor, Department of Restorative Dentistry, University of Illinois at Chicago College of Dentistry, Chicago, Illinois

Istvan A. Urban, DMD, MD, PhD
Director, Urban Regeneration Institute, Budapest, Hungary; Adjunct Clinical Associate Professor, Department of Periodontics and Oral Medicine, University of Michigan School of Dentistry, Ann Arbor, Michigan; Visiting Faculty, Harvard School of Dental Medicine, Boston, Massachusetts

Alberto Monje, DDS, MS, PhD
Head, Division of Periodontology, CICOM, Badajoz, Spain;Adjunct Clinical Professor, Department of Periodontology, Universitat Internacional de Catalunya, Spain; Adjunct Clinical Professor, Department of Periodontology, University of Michigan, Ann Arbor, Michigan; Visiting Professor, Department of Periodontics, ZMK Universitat Bern, Bern, Switzerland

Lorenzo Tavelli, DDS, MS, PhD
Assistant Professor, Department of Oral Medicine, Infection, and Immunity, Division of Periodontology, Harvard School of Dental Medicine, Boston, Massachusetts

Shayan Barootchi, DMD, MS
Adjunct Clinical Assistant Professor, Department of Periodontics and Oral Medicine, University of Michigan School of Dentistry, Ann Arbor, Michigan

Ji Yeon Chung, DDS
Resident, Advanced Education in Implant Dentistry, Loma Linda University School of Dentistry, Loma Linda, California

Jaime L. Lozada, DDS
Program Director, Advanced Education in Implant Dentistry, Loma Linda University School of Dentistry, Loma Linda, California