Facial Gingival Changes With and Without Socket Gap Grafting Following Single Maxillary Anterior Immediate Tooth Replacement: One-Year Results

Immediate tooth replacement or immediate implant placement and provisionalization (IIPP) has been a viable and successful method for replacing failing maxillary anterior teeth.^1–8  Not only does it shorten the treatment time, it eliminates the need for a removable prosthesis. However, buccal bone remodeling after IIPP, is still inevitable, and often leads to facial gingival recession and or facial gingival profile (FGP) changes. This remodeling is partly due to the disappearance of the bundle bone as a result of the buccal bony plate resorption after tooth removal.⁶  Clinicians have, over the years, advocated various methods to minimize or compensate for this buccal plate loss, thereby mitigating potential esthetic issues.

The effect of placing bone graft material (BGM) into the implant socket gap (ISG) after IIPP is controversial. Some believed BGM in ISG may retard the healing process.⁹  Tarnow et al, in a histologic report, showed bone fill up to 4 mm in the ISG without BGM.⁹  On the other hand, when BGM was not used, a significantly lower bone-implant contact in ISG of 1.5 mm or greater was observed in other histomorphometric studies.^10,11 

The purpose of this prospective study was to compare the facial gingival level and facial gingival profile changes after IIPP procedures with and without BGM in the ISG. The null hypothesis, which stated that the effects of BGM in the ISG on the peri-implant tissue response were not significant, was also tested. All variables were measured on the ratio scale.

This study was approved by the Institutional Review Board of Loma Linda University, which follows the guideline of the World Medical Association Declaration of Helsinki, and was conducted at the Center for Implant Dentistry, Loma Linda University School of Dentistry. Subjects were explained about the nature of the study and required to read, understand, and sign the consent form before being enrolled in the study. Hard copies were retained following the standard protocol set by the Institutional Review Board of Loma Linda University.

To be included in this study, the patient must: (1) be 18 years or older and a healthy individual (ASA 1 and ASA 2 according to the American Society of Anesthesiologists classification) with good oral hygiene, (2) have a single failing maxillary tooth with intact buccal bone, adjacent natural dentition, and without active infection, and (3) have sufficient bone volume to accommodate placement of a single implant with a minimum dimension of 3.4 mm × 12 mm. The patients (1) with a history of smoking, head and neck radiation treatment, bruxism, and parafunctional habits, (2) without stable posterior occlusion, and (3) in whom primary implant stability could not be achieved were excluded from the study.

To avoid selection bias, all participants were randomly assigned to 2 groups by using a randomization software (QuickCalc software, GraphPad Software Inc, La Jolla, Calif); IIPP without BGM in the ISG (NG), and IIPP with BGM in the ISG (G).

An acrylic resin provisional restoration was prepared prior to the implant surgery.

After administering of local anesthetic, the failing tooth (Figures 1 and 2) was removed and an implant (SuperLine fixture, Dentium, Cypress, Calif) was placed immediately without flap reflection (Figures 3 and 4) by engaging the palatal wall and the bone 4 to 5 mm beyond the apex of the extraction socket. The implant platform was placed 3 mm apical to the predetermined gingival margin.⁴  Primary implant stability was achieved with a minimum insertion torque of 25 Ncm (manufacturer's recommendation). The provisional restoration was relined with flowable composite resin (Perma Flo, Ultradent Products Inc, South Jordan, Utah) onto the temporary abutment (Temporary Abutment, Dentium, Cypress, Calif). Screw-retained provisional restoration was fabricated regardless of implant angulation and was adjusted to clear all centric/eccentric contacts and hand tightened onto the implant (Figure 5).

For the G group, prior to the provisional restoration placement, BGM (Bio-Oss, Geistlich, NJ) was placed into the ISG above the implant platform.

Antibiotics (amoxicillin, 500 mg; 20 capsules) and analgesics (ibuprofen, 400 mg; 10 tablets) were prescribed and the patients were instructed to rinse with a 0.12% chlorhexidine gluconate solution (Peridex, Zila Pharmaceuticals Inc, Phoenix, Ariz), twice a day, for 2 weeks. A liquid diet was suggested for 1 week after the surgery, transitioning to a soft diet over the next 3 months.

The final implant-level impression was made (Aquasil Monophase, Dentsply, York, Pa) after approximately 9 months (Figure 6). A customized gold alloy abutment (Direct-casting Abutment, G/H 1.0, hex, Dentium) was fabricated (Figure 7), torqued to 25 Ncm (manufacturer's recommendation, Dentium) and the definitive metal ceramic restoration (Vita VM 13, Vita Zahnfabrik, Bad Säckingen, Germany) was cemented with resin cement (Figures 8 through 10; Rely-X Unicem, 3M ESPE, St Paul, Minn).

All examinations and data collections were performed by 2 examiners (P.Y. and H.M.). The following data, when indicated, were collected and compared between each follow-up time interval: pre-surgery (T_pre), immediately after implant placement (T_sx), 3 months (T_3m), 6 months (T_6m), 9 months (T_9m), and 12 months (T_12m) after surgery:

The implants were evaluated according to the criteria proposed by Smith and Zarb, where applicable.¹² 

The implant stability was evaluated using Resonance Frequency Analysis (Integration Diagnostics, Savedalen, Sweden)^13,14  at T_sx and T_9m.

The facial gingival tissue thickness (FGTT) of the failing tooth was evaluated subjectively at T_sx and objectively at T_sx and T_9m. The subjective gingival thickness was evaluated using a periodontal probe (15 UNC Color-coded probe, Hu-Friedy, Chicago, Ill) and were categorized as thin or thick according to visibility of the underlying periodontal probe through the facial gingival tissue (visible = thin, not visible = thick).^15,16  The objective FGTT was measured directly with a tension free caliper (Wax Caliper, Pearson, Sylmar, Calif) 2 mm apical to the mid facial aspect of free gingival margin.¹⁷  The measurements were made 3 times, and average of values were recorded.

The ISG dimension was evaluated following implant placement with a periodontal probe (15 UNC Color-coded probe, Hu-Friedy) to the nearest 0.5 mm.

The presence of plaque and the incidence of bleeding were assessed at the mesiolabial, labial, distolabial, mesiolingual, lingual, and distolingual surfaces of the implant provisional and definitive restorations according to the modified Plaque Index¹⁸  and modified Bleeding Index¹⁹  at T_Pre, T_3m, T_6m, T_9m and T_12m.

Marginal bone level was measured at T_sx, T_6m, and T_12m with sequential periapical radiographs using long cone paralleling technique²⁰  with a customized occlusal jig attached to a film-holder (Rinn XCP, Dentsply, Elgin, Ill). The apical corner of implant shoulder was used as reference point. The distance between the reference point and the most coronal implant-bone contact point was measured and compared between each designated time interval. The value was zero when implant-bone contact point was at or more coronal to the reference point, and negative when implant-bone contact point was more apical.

The casts fabricated from the impressions made at T_pre, T_3m, and T_12m were scanned (Ortho Insight 3D, Motion View Software, LLC, Chattanooga, Tenn) and the 3D images obtained at different time points were superimposed (Netfabb software, Netfabb GmbH, Eichenbühl 10, Lupburg, Germany). A superimposed sagittal image made along the long axis of the implant restoration at T_12m was used for measurement of FGL and FGP changes. A 12.5×12.5×12.5 mm³ cube was then scanned and the sagittal image created and imported to the same platform as the superimposed sagittal image of the casts. This was used as the reference dimension.

The sagittal superimposed image [T_pre (Outline 1), T_3m (Outline 2), and T_12m (Outline 3)] and the reference image (Figure 11) were screen captured and imported into a presentation program (Keynote 6.2, Apple) at 1920 × 1080 resolution. A vertical line was created along the long axis of crown at 1-year follow-up using a drawing tool (Shapes) and bisected the crown. Horizontal lines (perpendicular to the vertical line) across the FGL at T_pre (Line A), T_3m (Line B), and T_12m (Line C) were drawn. The FGL changes among different time intervals were calculated from the perpendicular distance between Lines A, B, and C (Figure 12).

The FGP changes among different time intervals were the horizontal distance between Facial Outlines 1, 2, and 3 (Figure 13). Changes in FGP were measured at 7 levels, starting at Line A (or H₀: horizontal line at 0 mm) and progressed apically at 1 mm increments (H₁ to H₆; Figure 12).

The intra- and inter-observer reliability for the radiographic and photographic assessments were expressed by utilizing Kappa statistic. The methodology and results of the study were reviewed by an independent statistician (Udochukwu Oyoyo, MPH). The data was analyzed using Friedman, Wilcoxon signed-rank and Mann-Whitney U tests at the significance level of α = .05 (IBM SPSS Statistics 24, IBM Corp, Armonk, NY).

Twenty-four patients were enrolled for this study. Four patients were excluded due to active infection (2) and insufficient bone volume to accommodate implant placement (2). Twenty patients with a mean age of 65.4 (range = 41–83) years underwent IIPP procedure. A total of 20 implants, 7 on central incisors and 13 on lateral incisors, were placed. Tooth failures were attributed to unrestorable tooth (n = 16), root fracture (n = 3), and periodontitis (n = 1) (Table 1). One implant in the G group failed 3 weeks after placement resulting in an overall implant success rate of 95% (19/20). The mean implant stability quotient (ISQ) value at T_9m was statistically significantly greater than that at T_sx in both group (P < .05; Table 2). The means ISG dimension in NG and G groups were 1.45 mm (range: 0.5–2 mm) and 1.50 mm (range: 0.5–2 mm), respectively.

The intra-observer agreement expressed as kappa value ranged from 0.86–0.95 for P.Y. and 0.87–0.94 for H.M. The inter-observer agreement expressed as kappa value ranged from 0.75 to 0.80 for radiographic and photographic assessments.

No statistically significant differences were noted in the mean facial gingival tissue thickness between two groups at different time intervals (P > .05; Table 3). However, the mean facial gingival tissue thickness at T_9m was significantly greater than that at T_sx in both groups (P < .05; Table 3).

There were no statistically significant differences in mBI and mPI between both groups and at different time intervals (P > .05; Tables 4 and 5).

There were no significant differences in MBL changes between both groups at different time intervals (P > .05; Table 6). After 12 months follow up, the mean of MBL changes in NG and G group was 0.50 and 0.41 mm, respectively (P = .67).

There were no statistically significant differences in FGL changes between both groups from T_pre – T_3m and T_3m – T_12m (P > .05; Table 7). However, at 12-month follow-up, the mean FGL change (T_pre – T_12m) in G group (0.77 mm) was statistically significant less than that of NG group (1.35 mm) (P < .05; Table 7). There were no statistically significant differences in FGL changes within groups between 2 different gingival phenotypes (P > .05; Table 8).

At the same time interval, there were no statistically significant differences in FGP changes within group at different distances from free gingival level (H_0–H₆) and there were no statistically significant differences in FGP changes between both groups at each horizontal line level (P > .05; Tables 9 through 11). Within group, FGP changes in both groups from T_pre – T_3m were not statistically significantly different to those from T_3m – T_12m and T_pre – T_12m (P > .05; Tables 12 and 13). However, there were statistically significant differences in FGP changes between T_3m – T_12m and T_pre – T_12m in both groups (P < .05; Tables 12 and 13).

Four prosthetic complications were observed in this study. Three patients had screw loosening of the provisional 5 to 6 months after IIPP procedure, and were resolved by retightening the screw. One patient presented with broken provisional restoration at 5 months and was repaired without further complication.

The success rate after single immediate implant replacement and provisionalization was 95% (19/20) after 1 year of follow-up. Other studies had demonstrated comparable success rates with either immediate loading protocol (100%)^21–24  or delayed loading approach (97%).^25–27  This suggests that placement of BGM into the ISG and immediate implant placement are not variables that affect implant success. For the one implant failed in the G group, it was later noted that the patient wore the pre-extraction occlusal splint during the healing phase and the nonpassive fit might have contributed to the failure. This patient was excluded from data analysis.

The ISQ value of 55 or greater has been suggested as an objective guideline for immediate loading.^28–30  In this study, ISQ values of greater than 55 were registered for all implants at time of placement. Statistically significant greater mean ISQ value was observed at T_9m in both groups, compared to T_sx, suggesting osseointegration is a dynamic process and the implants had become more stable over time.

In this study, at T_9m, the FGTT (1.55–1.68 mm; Table 3) is in accordance with the results from other studies (1.8–2.0 mm) where implant were placed without gingival graft.^19,31  The statistically insignificant differences in the mean FGTT between 2 groups at different time intervals (P > .05; Table 3) in this study implies that placement of biomaterial into ISG does not affect the FGTT. Majority of the patients (18/19) showed greater FGTT at T_9m compared to T_Sx and can be explained by the fact that the implants in this study were positioned palatally, thereby increasing the space between the implant restoration and gingival tissue, which might have contributed to the thickening of the facial gingival tissue.³²  Furthermore, the emergence profile of implant restoration could also have an effect on the facial gingival tissue thickness.³³  Over-contouring facial gingival profile of implant restoration had been shown to cause horizontal and vertical gingival tissue loss.³³  On the other hand, horizontal and vertical facial gingival tissues are generally well preserved in implant restoration with under-contoured emergence profile.³³ 

It was widely agreed that plaque accumulation may induce a negative mucosal response.⁴  The mPI and mBI scores observed at T_12m, with the majority scores either 0 or 1, implied that patients had been able to maintain a good level of oral hygiene over the course of this study.

This study has shown similar MBL changes after 1 year (−0.45 mm) compared with other studies on conventional delayed implant placement procedure (−0.4 to −1.6 mm)^25–27  and immediate tooth replacement procedure (−0.2 to −1 mm).^2–5  Furthermore, an absence of statistically significant difference in MBL changes between 2 groups after 1 year of function indicates that ISG grafting or lack thereof does not affect peri-implant bone changes.

The mean FGL change after 12 months in G group (0.77 mm) was statistically significantly less than that of NG group (1.35 mm) (P < .05; Table 7) suggesting that placement of BGM into the ISG can minimize, but not prevent, FGL change. It has been documented that thin gingival phenotype around natural tooth may increase a risk of gingival recession following surgical, restorative, or mechanical trauma.^34,35  This phenomenon has also been observed on the peri-implant mucosa.^36,37  Though not statistically significantly different, the mean FGL change of thin gingival phenotype (−1.25 mm) is almost double that of thick gingival phenotype (−0.72 mm) in this study. This in part might be due to the small sample size. Regardless, a study by Kan et al³⁸  demonstrated similar results where a thicker gingival phenotype exhibited significantly smaller changes in FGL than with a thin gingival phenotype (−0.56 vs −1.50 mm).

A study has shown marked buccal hard tissue alteration occurs within 3 months after tooth extraction and immediate implant placement.³⁶  Similar findings were noted in this study where the majority of FGP changes occurred within the first 3 months after IIPP in both groups (Tables 12 and 13). Furthermore, at 1 year, the largest FGP changes occurred at the H₀ level in both G (−1.34 mm) and NG (−1.75 mm) groups (Table 11) with the FGP change progressively decreasing in the apical direction. These changes are comparable to the reported average horizontal labial tissue dimension change of −1.063 mm after 6 months of immediate implant placement without hard and soft tissue augmentation.³⁹ 

Greater FGP changes at all levels and at all times were observed in NG group (Tables 9 through 11). At T_12m, the difference in FGP change ranged from 0.26 to 0.41 mm between the 2 groups, which translated to a 31%–52% difference in percentage changes (Table 11). Nevertheless, these differences were not statistically significant (Table 11; P > .05). Again, this lack of statistically significant difference might be attributed to the small sample size. A larger sample size and long-term follow-up will provide more insightful evidence on the peri-implant tissue response. Standardized/matched ISG and or soft tissue thickness for all participants in both groups will provide more precise results. This would be possible only with a much larger sample size. Increased sample size would also allow comparison of another augmentation technique, such as connective tissue graft in conjunction with IIPP with BGM in the ISG, with the original 2 groups. A recent study has shown that one-time abutment protocol (no disconnected/reconnected manipulation) can minimize marginal bone loss and promote better peri-implant tissue response.⁴⁰  These could also be included in future studies to elucidate the importance of appropriate surgical and prosthetic protocol for IIPP procedure.

The use of bone graft material in the ISG can lead to less FGL losses, but not the FGP losses. Esthetically compromised result in terms of FGP can be observed in both groups. Although favorable results were achieved in this short-term follow-up, future long-term studies, with larger sample sizes, are needed to validate the efficacy of such procedures.

Abbreviations

BGM:

bone graft material

FGL:

facial gingival level

FGP:

facial gingival profile

FGTT:

facial gingival tissue thickness

IIPP:

immediate implant placement and provisionalization

ISG:

implant socket gap

ISQ:

implant stability quotient

mBI:

modified bleeding index

MBL:

marginal bone level

mPI:

modified plaque index

The authors would like to thank Mr Udochukwu Oyoyo for his assistance in the statistical analysis.

The authors have no affiliation with any organization with a direct or indirect financial interest in the subject matter discussed in the manuscript.