Replacement of a Missing Maxillary Central Incisor with an Astra Tech® Implant, Following a Horizontal Ridge Augmentation, Using a Sympheseal Mandibular Onlay Graft: A Case Report.

Abstract

Background: An 18 year old female patient presented for implant placement at the site of a congenitally missing right maxillary central incisor. The clinical examination revealed an insufficient bucco-lingual width of the edentulous ridge, requiring a horizontal bone augmentation procedure prior to implant placement.

Methods: An autogenous bone block graft was harvested from mandibular symphysis, fixed on buccal aspect of edentulous crest with titanium miniscrews, covered first by autogenous bone chips and xenograft particles, and second with a resorbable barrier membrane. Four months later, an Astra Tech® implant was placed in the grafted site, surrounded by a thick buccal bony wall, demonstrating excellent primary stability and guaranteeing a better esthetic outcome. Impressions for prosthetic work were taken and final restoration cemented 3 months following implant placement.

Discussion: Autogenous bone block grafting is regarded as a predictable procedure, especially in horizontal bone augmentation from intra-oral sites. Many requirements have to be respected however in order to achieve this purpose. In addition, timing of implant placement with autogenous block grafts is a subject of controversy. Finally, implant placement in anterior maxilla has to meet guidelines proposed in the literature to avoid esthetic shortcomings.

Conclusion: This case report describes the successful replacement of an anterior missing tooth with an Astra® implant after a bucco-lingual augmentation of the edentulous ridge.

Introduction

The ability to successfully replace single or multiple missing teeth with osseointegrated dental implants has revolutionized dentistry over the past four decades. Consistent long-term results have been reported in the literature (Adell et al., 1990; Albrektsson et al., 1986; Lekholm et al., 1994). Nevertheless, dental implant therapy can be complicated by numerous local factors, namely the anatomy of the edentulous ridge. An inadequate bone volume, either in height or in width, renders the placement of implants rather difficult, especially in areas of high esthetic demands. Various bone augmentation techniques have been described in the literature in order to reconstruct deficient alveolar ridges such as particulate bone grafting, guided bone regeneration, autogenous bone block graft, ridge expansion, and alveolar distraction osteogenesis (McAllister and Haghighat, 2007; Chiapasco et al., 2006 & 2007; Esposito et al., 2006). The purpose of this clinical report is to describe a case of single implant placement in maxillary right central incisor region following horizontal bone augmentation using an autogenous block graft in a young female patient.

Case Report

An 18 year old female patient was referred by the Department of Orthodontics to the Department of Periodontology (at the Lebanese University School of Dentistry) because of a missing maxillary right central incisor (Fig. 1). The patient had just completed her orthodontic treatment and a removable maxillary retainer was fabricated to maintain the space as well as to temporarily replace the missing tooth (Fig. 2). In addition, the Department of Orthodontics and Dentofacial Orthopedics approved the initiation of surgical procedures after examining a hand wrist radiograph in order to confirm the end of growth. The questionnaire and the patient’s file revealed that this central incisor was congenitally missing. An extra-oral examination was first carried out, demonstrating a low lip line, facial symmetry and a well aligned dental midline. Then, intra-oral examination of the edentulous space showed a well managed space to symmetrically replace the missing right central incisor according to the left central incisor, a narrow alveolar crest indicating a horizontal bone loss at the site of the missing tooth (Fig. 3). A periodontal probe (Michigan probe, Hu-Friedy, IL, USA) was then used under local analgesia to assess bucco-lingual width of bone crest, after subtracting the thicknesses of buccal and lingual soft tissues from total bucco-lingual width of the ridge at top of the crest. These measurements displayed an approximate horizontal bone thickness of 3 mm. However, optimal implant placement required a buccal bone thickness of at least 1 mm to avoid esthetic shortcomings, i.e. gingival recession (Belser et al., 1998; Chiapasco et al., 1999; Buser et al., 2004). Therefore, it was decided to perform a horizontal bone augmentation procedure using an autogenous block graft prior to implant placement in a staged approach. Moreover, a peri-apical radiograph revealed a sufficient height of bone (Fig. 4).

Fig. 1. Extra-oral examination showing smile line, symmetry and missing right central incisor.

Fig. 2. Maxillary retainer in place.

Fig. 3. Insufficient bucco-lingual width of the edentulous ridge.

Fig. 4. Peri-appical radiograph of the edentulous site.

Onlay Bone Block Grafting

Patient was instructed to perform a mouthrinse with a 0.12% solution of chlorhexidine-digluconate for 1 minute with a 10 ml solution immediately prior to surgery. Local analgesia (2% lidocaine with 1:100000 epinephrine) was administered in the area of the maxillary edentulous crest as well as in the interforaminal region of anterior mandible.
Full-thickness buccal and palatal mucoperiosteal flaps with 2 buccal vertical releasing incisions were first raised at the recipient site. The direct measurement using a periodontal probe (Michigan probe, Hu-Friedy, IL, USA) confirmed the pre-operative bucco-lingual width evaluation. Then, a template was used and adjusted at the recipient bed to assess the dimensions of the block graft to be harvested (Fig. 5).

Fig. 5. Adjustment of a template of the graft at the recipient site.

Subsequently, a horizontal incision was made at muco-gingival junction from cuspid to cuspid at mandibular symphysis region and a full-thickness (mucoperiosteal) flap was raised (Fig. 6). Right and left mental nerves were identified and protected and the adjusted template was used to outline the cortico-cancellous block with a fissure bur used on a straight handpiece, under copious irrigation with sterile saline (Fig. 7). Following ostectomy, a 14x6x5 mm bone block was removed with fine straight chisels while preserving the lingual cortex. Further cancellous bone chips were harvested with surgical curettes and the donor site filled with haemostatic material (Cutanplast®, Milan, Italy) (Fig. 8) to minimize hematoma formation. Next, the flap was sutured back to its original position using an interlocked continuous suture technique.

Fig. 6. Incision and flap at mandibular donor site.

Fig. 7. Use of the template to outline the block graft.

Fig. 8. Cancellous bone chips after block harvesting.

At the recipient site, the block graft was adjusted to achieve better adaptability and decrease micro-movements. A round bur was used to perforate the buccal cortex of the recipient bed in order to promote bleeding and the block was fixed with 2 titanium miniscrews (Straumann^®, Switzerland) after smoothening of its sharp edges (Fig. 9). Cancellous bone chips collected from donor site were mixed with xenograft bone particles (Bio-Oss®, Geistlich, Switzerland) and were used to fill the gap around the bone block (Fig. 10). Then, a resorbable membrane (Bio-Gide®, Geistlich, Switzerland) was placed in a double layer technique to cover both the block graft and bone particles (Fig. 11). Periosteal releasing incisions allowed a coronal displacement of the buccal flap enough to close the wound, using mattress and tension-free simple interrupted resorbable sutures (3/0 Vicryl®) (Fig. 12).

Fig. 9. Fixation of the block graft with 2 titanium miniscrews.

Fig. 10. cancellous bone chips and Bio-Oss® particles filling the defects around the bone block.

Fig. 11. Placement of Bio-Gide® membrane (double layer).

Fig. 12. Horizontal mattress and simple interrupted sutures.

Antibiotic (Augmentin® 625mg TID for one week) and anti-inflammatory (Brufen® 400mg TID in case of pain) drugs were administered following surgery. Mouthrinses with a 0.12% solution of chlorhexidine-digluconate were started again 24 hours after surgery and continued for 2 weeks. The maxillary removable retainer was adjusted to avoid pressure over the grafted site and sutures were removed 10 days post-operatively.

Implant Placement

Four months later, patient returned to the Department of Periodontology for implant placement (Figs. 13 & 14).

Fig. 13. Recipient site 4 months after bone grafting (Note that 1 of the miniscrews is showing through the alveolar mucosa).

Fig. 14. Occlusal view of the edentulous crest 4 months after bone grafting.

Immediately prior to starting surgery, patient was asked to use a mouthrinse (Chlorhexidine digluconate 0.12%) for 3 minutes, and local analgesia (2% lidocaine with 1:100000 epinephrine) was administered in the grafted maxillary area. Similar to the previous procedure, crestal, intra-sulcular and vertical releasing incisions were made and full-thickness buccal and palatal mucoperiosteal flaps were raised. The grafted region demonstrated an adequate horizontal bone augmentation of approximately 7 mm with some resorption at coronal level with no considerable effect on the outcome of therapy (Fig. 15). Next, the 2 titanium miniscrews were removed, a 2mm twist drill was then used to the length of 13mm followed by verification with the direction indicator (Fig. 16). Then, the 2.5 mm Tiger drill was used to the length of 13 mm, followed by the intermediate Pilot drill, and finally the 3.2 mm Tiger drill followed by the 3.5mm cortical drill. The Direction Indicator was used at all times to guide implant positioning both mesio-distally and bucco-lingually (Fig. 17). The 3-dimensional implant placement was performed in respect to the guidelines proposed in the literature (Buser et al., 2004). Subsequently, a 3.5 x 13 mm Astra Tech® implant was removed from its sterile container and delivered to the drilling site by first using the Delivery Cap and later the Torque Wrench until its rough surface was fully submerged in bone (Figs. 18 & 19). The implant carrier was released using the Torque Wrench in a counterclockwise direction with the Combination Wrench and a 3.5 mm cover screw placed on top of the implant. Finally, the mucoperiosteal flaps were sutured in their original position (Fig. 20).
Post-operative medications were prescribed similarly to previous surgery and sutures were removed 1 week after.

Fig. 15. Bone resorption at the level of the more coronal miniscrew.

Fig. 16. Direction indicator in place to verify the ideal position.

Fig. 17. Occlusal view of the Direction Indicator.

Fig. 18. Frontal view of the implant showing its corono-apical position.

Fig. 19. Occlusal view of the implant showing the presence of 2mm thickness.

Fig. 20. Flap Closure.

Crown Placement

Three months after implant placement, uncovering of the implant was performed and a healing screw replaced the cover screw. Three weeks later, abutment choice and impressions were made for prosthesis fabrication at the Lebanese University School of Dentistry Department of Prosthodontics. After another 3 weeks, the crown was cemented in place demonstrating an excellent immediate esthetic outcome and after a follow-up period of 1 month and 2 years (Figs 21, 22 & 23).

Fig. 21. Final cemented restoration.

Fig. 22. Peri-apical radiograph of the implant/crown connection.

Fig. 23. Peri-apical radiograph (2 years follow-up).

Discussion

Insufficient width of alveolar crest has led to the application of different grafting techniques. Autogenous block grafting is a well documented procedure, either from intra-or extra-oral sites (McAllister and Haghighat 2007; Chiapasco et al., 2006). Horizontal bone augmentation, in particular, is considered a predictable approach with onlay bone grafts (Buser et al., 1996; Misch, 1997). Available intra-oral donor sites include mandibular symphysis, mandibular ramus and mandibular external oblique ridge (Proussaefs et al., 2002; Misch, 2000). Pre-requisites for the success of this therapy are the intimate contact and stabilization of the block graft to the recipient bed (de Carvalho et al., 2000; Urbani et al., 1998), and the cortical perforation with intra-marrow penetration of the defect site to increase the rate of re-vascularization and remodeling (Majzoub et al., 2000; de Carvalho, 2000). The amount of bone resorption of intra-oral (chin and mandibular ramus) onlay block grafts has been reported to vary between 5 and 10% (Chiapasco et al., 1999; Raghoebar et al., 2000; Jemt and Lekholm, 2003). However, the use of barrier membranes in combination with block grafts seems to minimize the rate of bone resorption (McAllister and Haghighat, 2007; Chiapasco et al., 2006).

The timing of implant placement in grafted sites has been a subject of controversy. Many authors24,25 advocated an immediate implant placement in conjunction with intra-oral onlay grafting procedure in order to reduce the risk of bone resorption that occurs, for the most part, shortly after graft fixation. Other authors22,23 recommended implant placement after a waiting period of 4 to 5 months of the grafting procedure to permit a better primary stability and integration of the implant in a re-vascularized bone and to avoid an implant loss due to exposure or infection of the block graft (Chiapasco et al., 2006). Therefore, in areas of esthetic concern, it would be wiser to place the implants in a delayed approach for more predictable results.

Conclusion

Lateral bone augmentation of a narrow edentulous ridge, using autogenous block grafts, has shown to be a successful technique. Furthermore, if guidelines for implant placement in anterior maxilla are respected, excellent esthetic outcomes can be achieved. This case report demonstrated the ability to replace a congenitally missing tooth using an Astra Tech® implant, 4 months following a ridge augmentation with an onlay block graft from mandibular symphysis.

Authors declare that they do not have financial arrangement or interest in Astra Tech® implant system.

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by Dr. Badry Meouchy, Dr. Fady Abillamaa, Dr. Elie Azar Maalouf, Dr. Fatmé Mouchref Hamasny, Dr. Ramzi Abou Arraj