Clinical and Esthetic Outcomes of the Surgical Veneer Grafting Protocol in the Anterior Maxilla: A Five-Year Retrospective Analysis

Clinical and Esthetic Outcomes of the Surgical Veneer Grafting Protocol in the Anterior Maxilla

Abstract

A multicenter cohort clinical investigation evaluated the change in horizontal ridge dimension associated with immediate implant placement and provisionalization in anterior extraction sockets. Following the surgical veneer grafting (SVG) protocol, a combination of a bone and connective tissue graft (CTG) was performed in 37 patients to compensate for the natural hard and soft tissue remodeling to achieve a sustainable and predictable esthetic outcome in patients with a thin gingival phenotype. The patients were followed for an average of 39 months (range of 10 to 58 months). At the four-year recall, 61% of the fixtures were evaluated. All 37 implants were successfully integrated, demonstrating stable and healthy peri-implant soft tissues as documented by standard clinical parameters. The results showed an average volume gain of 0.68 mm in the tissue zone, compared to the initial situation.

Key Words: anterior area, critical interface, transition zone, immediate implant, surgical veneer grafting, free gingival margin, Type 1 socket, thin gingival phenotype

Clinical and Esthetic Outcomes - Imagen introducción

«One of the greatest challenges clinicians encounter when extracting a tooth and placing an implant into an extraction socket is what to do with the residual gap between the implant’s facial surface and the labial bone plate.»

Introduction

Contemporary implant therapy seeks to provide highly esthetic and predictable treatment outcomes while decreasing treatment time and morbidity. To help achieve optimal results for implant patients, clinicians need to have a solid understanding of the techniques and protocols that predispose esthetic outcomes during the planning phase. This is especially true when it comes to single-implant treatment, an increasingly popular option that has been found to ensure highly predictable results in terms of implant survival, and hard and soft tissue remodeling.1-4

Successful outcomes seem minimally affected by the timing of implant placement (i.e., immediately post-extraction or delayed post-extraction)5-8 or variations in the surgical9 and restorative procedures.10-12 Placing implants immediately into extraction sockets has proven as predictable as placing implants into healed sites.13,14 To reduce the length of patients’ surgical phases, post-extractive implants are used and treatment procedures are condensed into fewer patient appointments, all of which have the added benefit of also increasing patient comfort and convenience.15

Given its advantages, the implant placement technique is becoming more frequently employed to replace teeth in the visually prominent maxillary anterior region.16-19 The esthetic ramifications of an immediate implant—especially for a single tooth—in the anterior zone are also growing increasingly significant,20 with the primary focus being on achieving an attractive, natural-looking balance between the white esthetic (i.e., crown shape and shade) and the pink esthetic (i.e., soft tissue color and volume).

Esthetic Considerations and Challenges

Although less concerning in areas of low esthetic value (e.g., molars and premolars), recession and discoloration in areas such as the anterior maxilla can pose substantial esthetic concerns. For instance, it may be possible to compensate for compromised esthetics when treating single-tooth cases in which the patient has a low smile line and thick gingival phenotype. However, the risk for esthetic failure rises exponentially when implant therapy is provided to patients with high esthetic risk profiles, high esthetic demands, and thin gingival phenotypes.

Challenges

One of the greatest challenges clinicians encounter when extracting a tooth and placing an implant into an extraction socket is what to do with the residual gap between the implant’s facial surface and the labial bone plate. The determination to place a bone graft, a connective tissue graft (CTG), or a combination of both is made primarily to obtain long-term esthetic results. This is true even when primary stability is key to improving implant survival rates and osseointegration. In fact, while tooth replacement with immediate implant placement and provisionalization (IIPP) has been shown to be a successful procedure in terms of implant survival rates, slight facial gingival recession and buccolingual contour shrinkage have been reported following the first year of prosthetic function.21 Since the buccal bone plate resorbs after tooth extraction, even when an implant is immediately placed, many patients, especially those with thin gingival phenotypes, may exhibit compromised esthetics.22 Not surprisingly, such recession, shrinkage, and resorption issues—and their adverse effect on esthetics—have posed a challenge to patient acceptance of these types of implant therapy alternatives.

Tissue discoloration is another challenge that must be taken into account when considering unesthetic outcomes in implant therapy. Several studies have examined the threshold of color perception for both clinical crown (white) and gingival (pink) colors.23,24 More than a decade ago, Park and colleagues noticed this phenomenon with tissue level implants with a trumpet-shaped neck, reporting an incidence of 100% pink color changes.23 More recently, Benic and colleagues retrospectively reported a 60% gingival discoloration rate associated with single-tooth implants.25

Several studies have documented the biologic and esthetic benefits of bone graft containment with either a custom healing abutment or a provisional restoration.26 The resorption of a post-extraction socket is the direct result of trauma to the bone-periodontal ligament (PDL)-tooth complex. Bundle bone born from a functionally loaded PDL is lost following extraction and leads to an almost certain remodeling of residual buccofacial tissues.27 Moreover, it still is not possible to predict the primary effectiveness of preservation techniques using currently available materials to completely maintain ridge volume after tooth extraction.28

There are three different types of sockets present after tooth extraction and each has prospective risks. However, of these three, Type 1 sockets are the most ideal and predictable clinical situations (i.e., the labial bone plate and associated soft tissues are intact and present prior to tooth extraction) to treat. A study examining 92 cases found that 87% had a buccal plate thinner than 1 mm.29

It has been stated that at least 1 mm shrinkage of the buccal gingiva can be expected following immediate implant placement, and that this situation can possibly worsen in thin gingival phenotypes.30,31 (In cases involving thin phenotype patients, the esthetic outcome of an implant-supported restoration is mainly dependent on the soft tissue, both in terms of volume and being in harmony with the adjacent dentition.)32 Therefore, the question is whether it is possible to compensate for and maintain over time the loss of bone volume in the labial area by thickening the soft tissue with a soft tissue graft.

All these considerations show clearly that the thickness of peri-implant mucosal tissues affects abutment material selection in relation to the gingival color and soft tissue stability over time, all of which must be in balance to achieve a predictable and sustainable esthetic outcome.30-32

Clinical Study

The purpose of this retrospective clinical study was to evaluate the crestal ridge width and thickness changes after post-extraction implants, utilizing the surgical veneer grafting procedure (SVG),33  a technique that combines dual-zone bone grafting34 with a CTG, the goal being to compensate the natural bone remodeling of the socket.

Methods

Thirty-seven patients (22 males, 15 females) ranging in age from 39 to 74 years old (mean age of 52.7 years) were enrolled in the study. All patients were informed of the study specifics, which were in full accordance with the ethical principles of the 2000 Revision of the Declaration of Helsinki of 1975. All participants signed a consent form that outlined the study protocol and completed questionnaires. The study was approved by the Ethics Committee of the University of Milan.

At the patient screening session, clinicians verified the inclusion and exclusion criteria.

Inclusion criteria were as follows:

  • male and female subjects 35 years or older
  • absence of periodontal disease
  • adequate native bone to achieve implant primary stability
  • tissue phenotype evaluation by means of a color-coded periodontal probe
  • facial keratinized mucosa (KM) width of at least 2 mm
  • soft tissue level matching the level of the contralateral tooth
  • need for a single-tooth replacement in the anterior maxilla subsequent to an inevitable tooth

Exclusion criteria were as follows:

  • systemic diseases that could alter the tissue integration of dental implants35
  • pregnancy
  • smoking (>10 cigarettes per day)
  • bruxism (Figs 1a-2b).

A total of 37 implants (19 central incisors, 6 lateral incisors, 6 canines, and 6 first premolars) were placed in 37 patients with Type 1 socket and thin gingival phenotype. The implants were immediately placed and provisionalized in extraction sockets following the SVG protocol. Provisional screw-retained prostheses were inserted at the time of the surgical procedure. Digital measurements overlapping intraoral scanner files of the horizontal ridge dimension level changes were recorded.

Clinical and Esthetic Outcomes - Figure 1a
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Clinical and Esthetic Outcomes - Figure 1b
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Clinical and Esthetic Outcomes - Figure 1c
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Figures 1a-1c: Teeth showing crowned maxillary left incisors with a root palatal fracture, as evidenced by the periapical radiograph and the CBCT scan.

Clinical and Esthetic Outcomes - Figure 2a
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Clinical and Esthetic Outcomes - Figure 2b
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Figures 2a & 2b: The patient presented with high esthetic risk profile (i.e., a high smile line). Tissue phenotype, assessed with a color-coded periodontal probe, is indicative of the marginal tissues and is another crucial parameter to evaluate.

Study Protocol Procedures

Preoperative and clinical procedures: Preoperative antibiotics (amoxicillin, 2 g) were given orally one hour prior to surgery together with a one-minute rinse (0.2% chlorhexidine). A digital intraoral impression scan was taken before starting the procedures.

After administration of local anesthesia, the supracrestal fibers were dissected and the root was removed atraumatically with a dedicated periotome (S.V.G. Kit – Agnini Brothers, Omnia; Fidenza, Italy) and extraction forceps using rotational movements (Figs 3a-3c).

Implant placement: After a thorough socket debridement with a surgical excavator, a proper diameter-tapered design and textured surface implant was placed. In keeping with the indications given by the cone-beam computed tomography (CBCT) evaluation and the surgical guide, placement was toward the palatal aspect of the extraction socket to a final depth of approximately 4 mm from the free gingival margin (FGM) so that a minimum primary stability of 35 Ncm was obtained (Figs 4a-4c).

Clinical and Esthetic Outcomes - Figure 3a
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Clinical and Esthetic Outcomes - Figure 3b
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Clinical and Esthetic Outcomes - Figure 3c
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Figures 3a-3c: Minimally invasive extraction of the maxillary left central incisor root involved avoiding raising a flap and preserving as much of the surrounding hard and soft tissues as possible. A sharp-tipped dedicated periotome was used to cut the periodontal fibers and loosen the root. The socket was then carefully debrided before implant placement.

Clinical and Esthetic Outcomes - Figure 4a
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Clinical and Esthetic Outcomes - Figure 4b
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Clinical and Esthetic Outcomes - Figure 4c
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Figures 4a-4c: A conical connection tapered implant was placed with the implant shoulder 4 mm apical to the FGM. Once the implant was positioned, the marginal residual gap measured 4 mm. The implant b position was centered in the extraction socket site, 1.5 mm from the distal and mesial teeth with the axis along the cingulum.

Provisional restoration: A prefabricated acrylic provisional was sandblasted and given a saline treatment; the titanium cylinder was tightened with a screwdriver and the mouth of the screw was sealed with blue wax (Fig 5a). The provisional was filled with acrylic resins (Palavit and Paladur, Kulzer; South Bend, IN), seated passively into the abutment after protecting the socket with a rubber dam, and allowed to set prior to removal (Fig 5b).

The relined provisional restoration was then disinfected and screwed into a laboratory analog, the proximal contact areas were marked with a pencil, and the subgingival contours were recreated with flowable composite resin (Fig 5c). The concave contour of the provisional restoration was shaped with burs in a low-speed straight handpiece. Finally, the provisional restoration was smoothed and polished with rubber-polishing instruments mounted on a straight handpiece and a pumice stone (Fig 5d). Note that the provisional restoration must first be fabricated before placing the bone and CTG material in the gap; this ensures that the graft material remains intact and uncontaminated during the procedure.

Clinical and Esthetic Outcomes - Figure 5a
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Clinical and Esthetic Outcomes - Figure 5b
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Clinical and Esthetic Outcomes - Figure 5c
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Clinical and Esthetic Outcomes - Figure 5d
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Figures 5a-5d: A prefabricated provisional was adapted to the edentulous and interocclusal space according to the incisal plane. The occlusal surface was opened to check for passive fit with the temporary titanium abutment and to allow unscrewing following set of the acrylic resin. The subgingival contours of the provisional crown were reestablished using a flowable composite resin. Note that the provisional crown’s subgingival contour is concave to provide space for the connective tissue, while the area in contact with the gingival margin is made flat to avoid putting pressure on the facial gingival support.

CTG procedure: The first step was to evaluate the dimension needed for the recipient site, followed by determining the palatal tissue thickness and quality (Fig 6a). Considering that the root profile is a curve and the measurement is done with a straight instrument, it is highly recommended to add 1 mm to the measured length in order to be in the safe zone. Then, the epithelial connective tissue was harvested using a 15C blade, 2 mm apical to the palatal gingival margins of the first and second molars.

During the first incision, the blade had to penetrate 1.5 mm (the blade’s working tip was used as a reference). This incision needed to be horizontal, the most cranial one being 10 mm long (Fig 6b). Two 6-mm long vertical incisions were then made. Before making the last caudal horizontal incision, the graft had to be prepared with a uniform partial thickness incision starting from the mesiocoronal angle, leaving the submucosa to protect the bone.

The palate was managed with two cross-stitch nonabsorbable surgical sutures (PTFE, Omnia) and a collagen sponge (NovaTape, NovaBone; Alachua, FL). Note that the starting cross-stitch suture is the most distal and the end knots need to be in the most apical palatal position in order to block the initial bleeding (Fig 6c).

The epithelial CTG was then approximately 1.5 mm thick, 10 mm long, and 6 mm high (which will decrease to 5 mm after removal of the beveled epithelium). Next, a new 15C blade, oriented to the support plan, was used chairside to remove the epithelial tissue and the fatty glandular soft tissue in order to obtain a white, dense, 1-mm thick CTG (Fig 6d).

On the recipient site, a dedicated spoon-shaped  blade (S.V.G. Kit – Agnini Brothers) was used to create a partial thickness envelope, 3 mm apical to the  mucogingival  junction toward the adjacent teeth (Fig 6e). The graft was stitched intramurally with a resorbable suture (PGA  6/0,  Omnia)  so that it would stabilize and properly adapt. It was positioned 1 mm below the gingival margin, thus minimizing the thickness of the blood clot. Due to this approach, the CTG gains blood supply from both the flap and the periosteum (Figs 6f-6h).

Clinical and Esthetic Outcomes - Figure 6a
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Clinical and Esthetic Outcomes - Figure 6b
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Clinical and Esthetic Outcomes - Figure 6c
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Clinical and Esthetic Outcomes - Figure 6d
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Clinical and Esthetic Outcomes - Figure 6e
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Clinical and Esthetic Outcomes - Figure 6f
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Clinical and Esthetic Outcomes - Figure 6g
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Clinical and Esthetic Outcomes - Figure 6h
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Figures 6a-6h: Before harvesting the graft, it is necessary to assess the thickness of the palatal donor site. The amount of tissue to be harvested, which is related to the root profile of the site to be augmented, must be evaluated. In this case, the tissue was harvested with a 15C blade. After being deepithelialized chairside, the connective tissue was allocated inside the partial thickness envelope flap and fixed intramurally with three single suture points using a resorbable suture.

Dual-zone bone grafting procedure: The final phase was to pack the bone graft material into the remaining gap. To accomplish this, a narrow, flat, contoured healing abutment was screwed into the implant. A slow resorbable xenograft material (OsteoBiol, Tecnoss Dental; Torino, Italy) was used to pack the bone particles in the bone zone and a synthetic fast resorbable (Alloplast, NovaBone) was used to pack the gap to the gingival margin, giving the blood time to incorporate within the particles. The healing abutment should be tall and narrow enough to allow the bone graft to be placed and packed against it with a dedicated instrument (SVG Carrier and Plug, Omnia) to the most coronal aspect of the gingival margin, thus maximizing the amount of graft material that can be placed into the labial gap (Figs 7a & 7b).

The flat profile-healing abutment was then removed, leaving the bone graft material undisturbed; the provisional restoration was repositioned and tightened with 30 Ncm torque. The provisional restoration has subgingival contours that enable it to support the soft tissue profile and helps protect the blood clot, as well as the bone and CTGs. While screwing in the provisional restoration, cleared of dynamic and static occlusion (Figs 8a-8c), excess bone graft material was removed with a periodontal probe to the level of the gingival margin, and a postoperative X-ray and a digital impression scan were taken.

Clinical and Esthetic Outcomes - Figure 7a
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Clinical and Esthetic Outcomes - Figure 7b
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Figures 7a & 7b: With a tall and narrow healing abutment in place, the marginal gap is filled with small-particle bone graft. The dual-zone bone grafting (i.e., placement of the bone graft in the gap between the implant and the labial bony plate, as well as in the zone above the implant-abutment junction) provides support and volume to the hard and soft tissues. The bone graft is carried by the SVG carrier.

Clinical and Esthetic Outcomes - Figure 8a
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Clinical and Esthetic Outcomes - Figure 8b
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Clinical and Esthetic Outcomes - Figure 8c
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Figures 8a-8c: Occlusal, frontal, and profile views of the screw-retained provisional restoration in place the day of surgery. Note the overbuilding of the socket site. The provisional restoration was cleared of dynamic and static occlusion.

Postoperative procedure: All patients were instructed to rinse three times a day for one minute with chlorhexidine digluconate (0.12%) and to avoid removing plaque by mechanical means at the surgical sites for three weeks. Silk sutures from the palate were removed at one week; sutures in the implant site were removed three weeks postoperatively. Patients were asked to start removing plaque on the provisional with a soft-bristled toothbrush and to rinse twice a day for one minute for an additional month. They also were instructed to follow a semi-liquid diet for the first week, followed by soft foods for the next two months, and not to touch or play with the tongue or the provisional restoration.

At the six-month recall visit, each patient underwent a digital X-ray and a digital intraoral scan to verify healing and check for changes to the buccal palatal volume. The provisional restoration was removed, and healthy prosthetic running rooms were noted (Figs 9a-9c). Subsequently, an optical digital impression was taken, capturing the subgingival soft tissue profile by scanning the provisional restoration contour chairside.

Digital impressions were taken using an intraoral scanner (iTero Element 5D, Align Technology; San Jose, CA). The scanning procedure, which averaged 17 minutes, consisted of the following:

  • maxilla scan with provisional restoration in place
  • mandible scan
  • bite registration
  • maxilla scan with scan body in position
  • scan body high-resolution scan
  • provisional restoration chairside scan (Figs 10a-10d).

Final restoration procedure: Employing computer-aided design/computer-aided manufacturing (CAD/CAM) technology (Figs 10e-10g), the dental laboratory designed and fabricated a screw-retained layered zirconia crown on a titanium base (Figs 11a-11e). Intraoral scans were taken at 12- 24-, 36-, 48-, and 60-month intervals to measure the buccal palatal volume changes (Fig 12). Bone sounding was done prior to restoration delivery.

At each patient’s 12-month visit, a CBCT scan was taken to evaluate the bone levels and thickness around the implant, especially in the facial plate interface. At each follow-up appointment, the periodontal health surrounding the restoration was controlled using probing depth evaluation.

Clinical and Esthetic Outcomes - Figure 9a
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Clinical and Esthetic Outcomes - Figure 9b
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Figures 9a & 9b: Clinical situation after four months of healing following the first removal of the provisional restoration. Note the excellent preservation of tissue volume and the proper balance between white and pink esthetics.

Clinical and Esthetic Outcomes - Figure 9c
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Figure 9c: Four-month periapical X-ray control image.

Clinical and Esthetic Outcomes - Figure 10a
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Clinical and Esthetic Outcomes - Figure 10b
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Clinical and Esthetic Outcomes - Figure 10c
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Clinical and Esthetic Outcomes - Figure 10d
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Clinical and Esthetic Outcomes - Figure 10e
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Clinical and Esthetic Outcomes - Figure 10f
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Clinical and Esthetic Outcomes - Figure 10g
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Figures 10a-10g: CAD/CAM technology was employed to duplicate the prosthetic running room in the design and production of the zirconia substructure on a titanium base. CAD software ensured total control during the prosthetic design. Opposing dentition, restorative volume, soft tissue contour, and screw-hole axis were all shown in the same image, permitting precise design of the zirconia abutment.

Clinical and Esthetic Outcomes - Figure 11a
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Clinical and Esthetic Outcomes - Figure 11b
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Clinical and Esthetic Outcomes - Figure 11c
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Clinical and Esthetic Outcomes - Figure 11d
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Clinical and Esthetic Outcomes - Figure 11e
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Figures 11a-11e: Views of the final prosthetic restoration: The definitive crown is screw-retained. Intraoral views at 18 months show not only integration of the facial contour of the implant site compared with the adjacent teeth, but also the stability of the ridge contour over time. CBCT scans taken 24 months after surgery demonstrate the successful overbuilding of the socket. The amount and stability of the peri-implant marginal bone are optimal.

Clinical and Esthetic Outcomes - Figure 12
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Figure 12: Intraoral scans, taken at different stages of the healing phase, were superimposed to measure the buccal palatal volume changes.

«The risk for esthetic failure rises exponentially when implant
therapy is provided to patients with high esthetic risk profiles, high esthetic demands, and thin gingival phenotypes.
»

Tools and Methodology for Patient Monitoring

For research purposes, tissue augmentation typically is assessed with a periodontal probe or analogic calipers clinically, or on stone models, which are operator-dependent.32

Becoming increasingly common in dental practices, intraoral scanners present a highly effective alternative for patient monitoring. Advantages include the following:

  • enable higher accuracy than conventional impressions for almost all clinical applications
  • allow patients’ oral conditions to be easily recorded over time
  • offer a biosafe, easy, comfortable, and noninvasive option for use during various time periods.36

Analysis method: The present study’s analysis method employed a series of scans that were automatically aligned and superimposed, utilizing tooth morphology algorithms, and morphology differences between scans. These scans were subsequently quantified and visualized in various ways.37 Unfortunately, none of the traditional methods of evaluation are completely free of inaccuracies or of posing technical difficulties. For instance, three-dimensional (3D) technology using superimposition of images obtained from scanned stone casts has been proposed for volumetric evaluation of gingival recession in vitro and for tissue maintenance.38 However, the inherent distortion of conventional impressions, intrinsic of the material, and the pouring phase may result in errors, as can pressure on soft tissues caused by elastomeric material. And, while CBCT is a popular method with good precision to document dimensional changes in bone,39 it does necessitate that patients be exposed to this X-ray exam at every step of the evaluation period.

Periodontal probe: Considering the various advantages and disadvantages of the different evaluation methods, the present study opted to determine tissue phenotype with a color-coded periodontal probe,34 which was also used for bone sounding to gauge the socket type based on the sulcus depth and bone crest location according to the CBCT evaluation.

Intraoral scanner: An intraoral scanner with an adequate superimposing algorithms protocol (iTero Time Lapse) and software (Exocad Dental CAD, Exocad America; Woburn, MA) was used to allow for precise volumetric analysis; acquired data described exact changes in buccal palatal contour, permitting monitoring and evaluation of the overall volume changes over time.

Patients were recalled for follow-up data collection at specific time points, as follows:

  • baseline (immediately before tooth extraction)
  • surgery (immediately after implant insertion procedure with provisional restoration)
  • bone insertion (final restoration insertion six months after surgery)
  • one-year follow-up after CI
  • two-year follow-up after CI
  • three-year follow-up after CI
  • four-year follow-up after CI
  • five-year follow-up after

Periapical X-rays were taken at each time point. CBCT evaluations were taken at baseline, surgery, one year, and five years. An implant was considered a failure when it showed individually checked mobility, persistent infection, caused pain, or required removal.

In addition, a pink esthetic score (PES) was calculated for all patients at baseline and at every time point by two independent evaluator-blinded observers for the duration of the study (i.e., the five-year visit).

Intraoral scanning evaluation was done at every time point and overlapped with dedicated software (Geomagix, Interpex; Golden, CO) and quantified using colored bars and digital measurements.

Buccal palatal contour change was measured both in the tissue zone, at 0, 1, 2, and 3 mm, and in the bone zone, at 5, 7, and 9 mm from the gingival margin. The volume was measured at baseline and at every time point.

Thirty-seven patients (22 males and 15 females) were followed for an average of 39 months (range 10 to 58 months). The reasons for tooth extraction were categorized as follows:

  • crown/root fractures of previously restored teeth (64.1%)
  • external root resorption (7.6%)
  • endodontic failure (8.6%)
  • palatal vertical root fracture (13.5%)
  • trauma (7.1%).

Results

The 37 patients in this study were followed for an average of 39 months (range of 10 to 58 months). Of the 37 implants placed, 22 were evaluated at the four-year recall. The buccal plate was found to be intact in all 37 sites. Analysis revealed a mean PES score of 11.24. Overall, the esthetic outcomes were favorable. Using the PES index, 29 sites (78.3%) achieved scores of 10 or more, indicating optimum soft tissue esthetic outcomes. Scores of 9, indicating good esthetic results, were assigned to five sites (13.6%). Scores of 8, indicating sufficient esthetic results, were assigned to three sites (8.1%). No sites reported suboptimal esthetic results.

Buccal palatal volume values showed an interesting global increase after baseline up to five years in the tested group compared with contralateral tooth with higher values observed over time, particularly at the tissue zone level. Specifically, it has been observed that creeping of the CTG over time may be responsible for an average volume gain of 0.68 mm in the tissue zone area, with an average follow-up of 39 months, compared to the initial situation (Table 1).

Table 1. Buccal Palatal Volume (Tissue Zone & Bone Zone) Over Time

T0 T1 T2 T3 T4 +/-
Tissue Zone
0 8.06 8.74 8.70 8.65 8.59 +0.50
1 mm 8.45 9.46 9.40 9.35 9.27 +0.82
3 mm 10.19 11.43 11.32 11.13 10.91 +0.72
Bone Zone
5 mm 11.54 11.59 11.55 11.43 11.35 -0.19
7 mm 12.80 12.77 12.75 12.71 12.55 -0.25
9 mm 13.90 13.84 13.61 13.21 13.10 -0.82

Discussion

Single-implant treatment has been found to be highly predictable in terms of implant survival rates, specifically when sufficient primary stability was achieved.1,2,4 These rates seem minimally affected in managing the immediate implant extraction socket sites and its variations in the surgical8 and restorative procedures.11,40

Dual-Zone Concept

In 2012, Chu and colleagues32 evaluated the buccolingual contour change in immediate implant placement and provisionalization cases. Subsequently, the dual-zone concept was introduced.

Dual-zone socket management refers to the two zones that can be affected when an immediate implant is placed into an extraction socket. These two zones are the bone zone, which is apical to the implant head, and the tissue zone, which is coronal to the implant head.

The dual-zone concept, linked to achieving esthetic success, demonstrates why it is critical in the early phases to take images of both buccal and occlusal views. These photographic references are crucial to initially evaluate what must be done to achieve a definitive restoration that best complements adjacent teeth.

The dual-zone protocol advocates bone grafting the residual gap up to the gingival margin at the time of placement to limit the changes in the buccal contour and enhance the thickness of the peri-implant soft tissue, thereby improving the overall esthetics of the final restoration.40

This study concluded that placing a bone graft into the residual labial gap around an anterior implant in a post-extraction socket aids in limiting the amount of faciopalatal contour change. The study’s authors postulated that to achieve predictable esthetic success, certain critical clinical keys must be respected. They are as follows:

  • atraumatic tooth removal without flap elevation
  • placement of a dual-zone (i.e., bone and tissue) bone graft in the residual gap around an immediate fresh extraction socket implant
  • a screw-retained provisional restoration acting as a prosthetic socket seal device and a mechanical support of the peri-implant tissue
  • achieve sufficient primary stability (> 35 Ncm).

Buccolingual Gingival Dimension

Buccolingual gingival thickness is important for masking the color of different substrate materials and the  abutment.  A study by Jung and colleagues4 found that a minimum of 2.0 mm is required to mask the color of the underlying abutment and perhaps the implant neck as well.

In this regard, Chu and colleagues32 also investigated buccolingual dimension changes and evaluated the soft tissue thickness. The dimension of the free gingiva was measured at three different sites and levels, as follows:

  • The gingival third, which was approximately 3.0 mm from the FGM adjacent to the implant abutment interface.
  • The middle third, which was approximately 0 mm from the FGM.
  • The incisal third, which was approximately 0 mm from the FGM.

The incisal third is always thin because it converges to an apex, but the middle and gingival thirds should be of sufficient thickness to mask the darkness of the underlying metal implant abutment. The best combination resulted in bone grafting with a provisional restoration to anatomically contain the graft material, which ultimately thickens the peri-implant soft tissues.

Araújo and colleagues41 showed that xenograft particulate material can be incorporated and encapsulated into the peri-implant mucosal tissues with bone grafting and immediate implant placement. These particles may act as benign foreign bodies when a localized inflammatory response is absent. This increased volume can create a masking effect that would overcome gray-colored abutments and enhance the esthetic outcome.

Chu and colleagues32 stated that esthetic complications increase in patients with a thin periodontal phenotype. Therefore, an additional surgical intervention may be required to improve the surrounding soft tissue architecture before, during, or after implant placement.

Socket-Shield Technique

The socket-shield technique is another established option that has been widely described based on 10 years of worldwide clinical application. Carrying out this approach requires detailed knowledge of the procedure, as well as of the possible pitfalls, anticipated complications, and instruments required. Five-year volumetric data have confirmed the technique’s value in preventing facial ridge collapse in immediate implant placement.28 Four-year results have reported the implant survival rate to be comparable to conventional immediate and early/delayed implant placement.42 These studies provided detailed reporting of the possible complications and their likelihood of occurring. They also helped advance the understanding that, contrary to what the pioneers of the technique proposed, it is not necessary to apply an enamel matrix derivative to the inner dentin surface of the shield.43

Additionally, it is now established that preparing the socket shield to above bone crest as per the original proof-of-principle technique,44 as well as the similar variation later reported by Siormpas,45 may lead to exposure of the root portion through the overlying soft tissue (for both of these approaches). From animal and human histology, it also is now known that bone can grow between the implant and the shield.44

Relying on the decade’s worth of knowledge and experience as summarized above, the single-implant placement technique has become an established procedure that—when properly performed and local factors and favorable healing coincide— can achieve highly positive outcomes, even in the most challenging of clinical scenarios (e.g., the maxillary central and lateral incisors as adjacent implants).46

Bone Graft Alone, or with CTG?

The question that remains is whether it is necessary to place a bone graft and a CTG in association with a provisional restoration at the time of implant placement. In some cases (i.e., for patients with a thick biotype), a bone graft alone may suffice (with the understanding that not all procedures will be 100% successful; some may involve risks such as loss or infection of the graft).

The use of CTGs from the palate or tuberosity has been employed since the 1980s. Initially, they were used for ridge augmentation, around tooth root coverage, and to improve edentulous ridge anatomy for prosthetic reasons. As the dental implant procedure became more popular and common, so too did the use of autogenous grafts to help increase not only the zone of attached and keratinized gingiva around implants but also its thickness.

Advantages and Disadvantages of CTGs

The primary advantage of CTG is that it harvests the patient’s own tissue so there is no immune response to the graft. These grafts are also vital tissue and therefore do not always have to be completely covered to be successful. Other advantages include biocompatibility and no additional clinical expenses.

The main disadvantage of autogenous CTG is that it requires a donor site. If not done properly, the grafting procedure may lead to increased risk of bleeding and greater postoperative discomfort during the healing phase. Additionally, without a standardized grafting protocol that effectively addresses variations in palatal thickness, clinicians may encounter difficulties with the amount of graft material available.

Factors Affecting Outcomes of CTGs: Contour Changes, Tissue Thickness, and Bone Issues

Contour changes: A study by Grunder47 comparing 3D contour change without CTG in 12 patients and with CTG in 12 patients showed that a 1.1-mm loss of facial tissue occurred without the graft and a 0.3-mm gain of facial tissue occurred with the graft (measured at 3 mm from the FGM) if an implant was placed with only a healing abutment and without flap elevation. (Neither a bone graft nor a provisional restoration was placed in this group of patients.) This is considerably less change than was presented in several classic studies with flap elevation and intact sockets.48

Tissue thickness: Linkevicius and colleagues49,50 affirmed that tissue thickness was shown to affect crestal bone stability around implants, indicating that initially thin mucosal tissues can cause crestal bone loss after implant placement at one year in situ. It also has been proposed that a minimum of 3 mm of peri-implant mucosa is required for a stable epithelial connective tissue attachment to form. This soft tissue extension, usually referred to as the biologic width around implants, serves as a protective mechanism for the underlying bone.

Kan and colleagues13 implied that bilaminar subepithelial CTG (SCTG), in conjunction with immediate tooth replacement procedures, is a technique-sensitive procedure with inherent risks (i.e., inadvertent thinning or perforation of the flap or partial exposure of the SCTG can result in partial or complete necrosis of the SCTG). In this study, 2 of 10 patients experienced CTG necrosis. However, the authors also stated that IIPP in conjunction with a CTG is more likely to result in sufficient peri-implant tissue thickness to conceal underlying restorative materials than when performed without a CTG. The key of the SVG protocol presented in this article is likely the partial-thickness approach, which may help the CTG receive a higher percentage of blood supply from the periosteum, thus avoiding the potential risk of necrosis.

A pivotal role is played by the tissue graft thickness: 1 mm of white, dense connective tissue is required to achieve less shrinkage over time, compensate the coronal bone crest remodeling, and obtain an optimal esthetic integration linked not only to the thickness, but also to the surface and the color of the adjacent tissues. The authors strongly recommend the Zucchelli approach to harvest the CTG in the palatal area between the first and second molars. Moreover, the quality of the CTG positively influenced the creeping of the tissue over time, which clearly compensated, as shown in the present study, the natural buccal palatal contour shrinkage linked to the bone remodeling.51

Bone issues: In a two-year randomized clinical trial,52 47 participants were randomly assigned to the test group (i.e., immediate load post-extractive implant treated with SCTG placed using the tunnel technique in the labial area)51,53  and the control group (i.e., immediate load post-extractive implant treated without the CTG) with an allocation ratio of 1:1. Both groups received deproteinized bovine bone mineral in the gap. The bone graft was placed only in the bone zone, not in the tissue zone. Patients were observed at baseline, crown insertion, one-year follow-up, and two-year follow-up. A statistically significant difference was reported when comparing different gingival phenotypes. Thick phenotypes showed minor soft tissue shrinkage and recession with respect to thin phenotypes. The analysis showed a direct correlation between gingival thickness and the pink esthetic score, highlighting the importance of thickening soft tissues to obtain more predictable esthetic results. (Small soft tissue changes were observed, but since these were within the clinical threshold for detectable change, they did not have esthetic implications.)

PES values: To assess esthetic outcomes, one clinical index and the midfacial mucosal margin level in relation to contralateral natural teeth were investigated. Using the PES, in the control group, a significant proportion of sites failed to achieve good esthetic outcomes, whereas the entire test group obtained sufficient esthetic results (100% PES > 6), and 80% had good results. However, one consideration must be noted: All test group thin biotypes resulted in a sufficient PES value, whereas the control group obtained only 75%; PES values corresponding to good esthetic outcomes (PES >7) were found in 57% (test) and 0% (control) thin biotypes subgroups. This result underlines CTG’s effectiveness, especially when treating thin phenotypes subjects in esthetic areas. Analyzing single mean PES parameters, it was observed that root convexity and gingival texture, facial mucosa level, and facial mucosa curvature were the values to show the biggest differences between control and test groups (1.04 versus 1.48; 1.22 versus 1.74; 0.91 versus 1.30, respectively). Hence, tissue grafts by thickening KM lessened the possibility of unesthetic gingiva transparencies, compensated for the shrinkage from tooth extraction and controlled the consequent physiologic contour change.

In this last study, the final outcomes were encouraging. However, the bone graft in both groups was incorporated only on the labial aspect of the bone zone, whereas, in the SVG protocol presented in this retrospective study, the bone graft was packed up to the gingival margin, including in the tissue zone area.

Importance of material selection: It is critical to use the correct bone graft material (in terms of particle size and type) because improper material selection can potentially irritate the peri-implant soft tissue. The use of small (0.25 to 1 mm) particle mineralized xenograft (OsteoBiol; Torino, Italy) is suggested in the bone zone area and not in the tissue zone, where it is preferable to use the fast resorbable synthetic (Alloplast). The slow resorbable particles will be able to maintain the ridge volume as filler and the fast resorbable one will thicken the tissue without causing irritation because they will resorb in a timely manner.

Summary

Based on the results of the multicenter cohort clinical study discussed in this article, it is the authors’ opinion that the SVG procedure enhances the final esthetic outcome, especially in patients with a thin biotype and scalloped architecture in the esthetic area. The use of a connective tissue graft combined with duel-socket bone grafting—following the surgical veneer grafting protocol guidelines—at the time of immediate implant insertion in the esthetic zone has proven an effective treatment option to compensate for the expected loss of labial soft tissue volume and to maintain natural esthetic results over time.

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