Surgery

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The dentist sometimes faces clinical situations where bony defects left by trauma, infection, or resorptive patterns compromise the prosthetic treatment plan. For some situations, implants are rapidly becoming a standard of care. When planned by the prosthodontist in an ideal location, prosethes anchored by implants can offer excellent form, function, and esthetics. In the past, implants were placed wherever there was adequate available bone, and the final prosethes was sometimes compromised. Today, surgeons can place bone where the prosthodontic treatment plan indicates the implants should be placed. This article will focus on the most common surgical techniques that compensate the quality and quantity bony deficiencies.

Monocortical bone block graftingAutogneous bone block grafts are versatile in that they are able to augment the bone of both jaws in either vertical or lateral dimension or a combination of both. Small grafts may be harvested from intraoral donor sites, mostly the chin or retromolar area (9) (fig.1). Larger cortico-cancellous grafts are usually taken from extraoral donor site, most commonly the iliac crest (fig.2). After enough exposure of the defect site, the host bed is perforated with a small bur to allow blood clot to form between the two bone surfaces to allow communication with the cancellous bone that contains osteoprogenitor cells. Grafts are secured to the recipient bed using miniscrews (fig.3). Any voids may be

An Overview of the Advanced Surgical Techniques

to Enhance the Implant Site

(Figure 1). (a) Schematic diagram of intraoral donor sites. (b) Chin graft. (c) Retromolar graft.

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Dr. Samer Kasabah

Dr. Dr. Ali Gbara

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(Figure 2)(a) Schematic

diagram of iliac crest graft. (b)

Iliac crest graft.

(Figure 3)(a) Schematic

diagram of onlay autogenous bone

graft. (b) Small graft from chin donor site. (c)

Bigger graft from iliac crest.

(Figure 4)(a) Schematic

diagram of bone splitting technique.

(b,c,d) clinical procedure of bone

splitting.

(Figure 5)(a) Schematic

diagram of bone expansion

technique. (b) clinical case shows

an osteotome and implants were

placed using bone cndensing

technique.

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packed with cancellous bone chips to maximize the healing potential. Implant can be placed after a healing period of three months.

Alveolar bone splittingThis surgical approach allows moving the external cortical plate in a labial direction to gain an increase in width to introduce implants of appropriate diameter (6, 11). Bone splitting in the maxilla and mandible is performed using specially developed instruments (fig.4).

Alveolar bone expansionRidge expansion is an option, introducing a range of instruments (osteotomes) into the bone by use of a mallet of increasing size. The technique is designed to widen the maxillary ridge using osteotomes and allow simultaneous placement of implants into the socket that is created. At the same time, the labial cortical plate can be recontoured providing the additional benefit of improved esthetics, particularly in those situations where single teeth may need to be replaced. The ridge that needs to be expanded using this technique must have adequate height, because an increase in ridge height cannot be achieved (Fig. 5). The ridge must have labial and palatal cortical plates that are not fused and are separated by intervening cancellous bone to facilitate the introduction of instruments for expansion of the ridge (4).

Alveolar distraction osteogenesis This technique has its origin in orthopedic surgery, and in the last few years, several authors have proposed applying this

(Figure 6)(a) clinical case shows a big bony defect in the anterior segment of the mandibule as a result of car accident. (b) The distraction process involves creating an osteotomy at a distance from the site of pathology, the ridge crest. (c) the distraction device is in place. (d,e) Under the control of the distraction device, the mobilized alveolar segment is transported coronally in a slow, incremental manner. Bone forms within the distraction zone. (f) the final fixed prosthesis.

method in the maxillofacial area and to augment the severely resorbed alveolar bone to allow dental implant placement (10). Distraction osteogenesis devices have many classifications, most importantly intra-osseous (Fig. 6) or extra-osseous devices. Under local anesthesia, a full thickness mucoperiosteal flap is conservatively elevated on the buccal side with maintenance of the lingual mucoperiosteum. A horizontal osteotomy is made apically and two vertical osteotomies parallel to each other or slightly divergent are made mesial and distal to the defect site to connect the horizontal osteotomy. A chamber between the two bone segments is present after the distraction device application. Following a 7 days rest period, the distractor is activated. After the desired location is achieved, the device is left in place for 8 weeks for maturation of the new bone regenerate. The distractor is then removed and screw-type endosseous dental implants are inserted at the same time. The final construction is performed four months after the operation (fig.7).

Sinus floor elevation, closed and open techniquesMaxillary sinus elevation (sinus lift procedure) has become a well-accepted technique for increasing height of the bone in the posterior maxilla when inadequate bone exists for the placement of dental implants (12). It is a procedure that can be performed under local anesthesia and involves carefully cutting a window in the lateral sinus wall using surgical burs but retaining the integrity of

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the sinus mucosa. The window may then be in-fractured to create a discrete cavity on the superior aspect of the residual alveolus. Graft material may then be inserted that can also serve to keep the bone “rap door” in its elevated position (Fig. 8). Dental implants can be placed into the grafted sinus in one-stage or two-stage surgical procedure (8). Mostly, the determining factor depends on ensuring primary stability of the implants. In one-stage procedure, implant can be placed simultaneously with a sinus graft if adequate alveolar bone is available to stabilize the implant (Fig. 9). In two-stage procedure, a graft is placed first and requires certain time to mature, after this time, the implants are placed. (Fig. 8)

(Figure 7)(a,b,c) Osteotomy of

the segment up to the periodontal ligament

of the neighboring teeth is carried out and

a distractor device is fixed according to the

planned distraction vector. (d) The vector is

visible after flap suturing that will be used for the

distractor activation.(e,f ) At the second

stage surgery the distraction device

was removed and the implants were inserted

simultaneously.

(Figure 8)Two-stage surgical procedure. (a) The

size and shape of the osteotomy should

follow the contours of the maxillary sinus.

(b,c,d,e) sinus mucosa was elevated from different directions to create a cavity

under the elevated sinus mucosa. (f) The

selected augmentation material was placed in the created cavity. The implants will be placed

after the graft healing period and will be given additional enough time

for osseointegration.

(Figure 9)One-stage surgical procedure. (a) The sinus mucosa was

elevated after the bony window preparation, and the implant sites

were prepared. (b) The implants were

inserted in the created cavity and they were

surrounded by the augmentation material

to fill the entire cavity.

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maxilla in the reselected position, it is fixed in the new position with miniature plates. Implants can be placed simultaneously or after 6 months of grafting procedure, and then implant-supported prosthesis can be performed (Fig. 10).

Osseointegration of implants in zygomatic boneThe Brånemark System® Zygoma implant (Nobel Biocare, GÖetbogr, Sweden) concept presents a non-grafting alternative for the treatment of patients with extreme resorption of the maxillary bone with only one surgical procedure and without the need for grafting (3). Zygomatic implants have been designed specially to engage another midfacial bone, the zygoma, yet enter the oral cavity in the second premolar/first molar region to provide stabilization prosthesis. They are available in lengths of 30, 35, 40, 45, and 50 mm. The apical two thirds of the implant has a diameter of 4.0 mm, and the alveolar one third widens to a diameter of 5.0 mm. The zygomatic implant has an angulated head. This 45-degree angulation allows for the platform of the implant to be in the same plane as the conventional implants in the premaxilla. To facilitate implant placement, premounted implant carriers allow for easy handling of the implant with the straight hand piece.The dentist makes a first examination and takes x-rays. Although the operation can be carried out under local anesthesia, for the patient’s comfort, it has been done up to now under general anesthesia or neuroleptic deconnection (7). Preparation

A wide variety of grafting materials have been used to augment bone volume within the sinus including both the block and particulate autografts, demineralized lyophilized human bone, xenografts, and resorbable and nonresorbable alloplast grafts. These materials can be used alone or in combination.

Maxillary interpositional graft combined with Le Fort I osteotomyWhen residual ridge atrophy of edentulous maxilla is accompanied by a skeletal Class III jaw relation, surgical correction is necessary for optimal functional, phonetic, and esthetic results whenever implant-supported prostheses are to be placed (5). In Le Fort I osteotomy, in which the maxilla is repositioned forward and downward and corticocancellous bone grafts are placed in the floor of the maxillary sinus and nasal floor, to correct the inter-maxillary relationship and increase the vertical dimensions at the same time while leaving the alveolar crest form unchanged. Dental implants are placed either simultaneously with a vestibuloplasty performed during one surgical procedure or a two-stage technique is proposed, where the patients are treated with an inter-positional bone graft and Le Fort I osteotomy and the endosteal implants are placed six months after the osteotomy. Vestibular Le Fort I surgical incision and reflection of the mucoperiosteal flap are followed by horizontal osteotomy, down-fracture, and mobilization of the maxilla. Autogenous bone blocks placed in maxillary sinuses and nasal floor are fixed using miniature screws. After placing the

(Figure 10)Schematic diagram of maxillary interpositional graft combined with Le Fort I osteotomy. (b) Clinical case shows the operation. (c) Panoramic x-ray shows 6 implants were placed in the grafted maxilla and connected with a bar. (d,e) The final removable prosthesis.

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allowed before the implants are loaded.

Mandibular nerve repositionIn the posterior parts of the mandible, where the mandibular canal is positioned close to the superior cortical bone as the result of resoprtion, mandibular nerve repositioning technique is indicated (1). Perfect radiographic study for the concretion of the surgical maneuver, taking in consideration all the details of the localization of lower alveolar bundle and its anatomical relations. The surgical procedure begins with crestal horizontal incision with short relief incisions at both ends. After flap elevation, the fibers of the mental nerve are gently separated from the adjacent soft tissue sufficiently to allow the release of the bone surrounding the mental nerve.The size and the localization of the osteotomies will depend on the adopted technique. The transposition of the lower alveolar nervous bundle consists of an osteotomy of the mental foramen, removing it and, to follow, the confection of a posterior bone window that follows the passage of the mandibular canal. Partial transpositioning, requiring no inferior alveolar nerve displacement when entering the mental foramen, involves a simple, rectangular osteotomy placed behind the mental foramen and turning back following the inferior

of the implant site utilizes a modified Le Fort I osteotomy incision, which expose the entire maxillary alveolar process from zygomatic buttress to zygomatic buttress. A window is then made by drilling at the upper limit between the zygoma and the sinus to determine the orientation of the zygoma and to reflect the Schneidarian membrane. This window will also be helpful during the surgical procedure for cooling the drills to avoid overheating. A series of long drills are used to prepare the osteotomy. The preparations extend through the residual alveolus laterally and superiorly, through the anterior position of the maxillary sinus, and through the body of the zygoma. The zygomatic implant engages bone for osseointegration in both the zygoma and the maxillary alveolus. Successful use of the zygomatic implants for prosthetic rehabilitation of the atrophic maxilla requires at least 2 to 4 additional implants in the premaxillary region. Ideally, these are located in the available bone at the junction of the piriform nasal rim and anterior wall of the maxillary sinus (Fig. 11). Prior to closure of the surgical site, implant-level impressions are made. The resultant soft tissue model allows for fabrication of a rigid bar, which must be placed at stage 2 surgery. Relief of the denture base over the zygomatic implants is completed and the patient is discharged. A standard osseointegration time of 6 months is

(Figure 11)(a) Insertion with a low

speed motor of the zygomatic implant. The

head of the implant is seen at the top of

the zygoma. (b,c) clinical and Schematic diagram of zygomatic

implants and additional four anterior implants in

anterior maxilla.

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alveolar nerve course into the mandibular canal. The bone window size is dependent on the number of implants to be placed beyond the mental foramen. A slightly different osteotomy design is required by inferior alveolar nerve total transpositioning. As the inferior alveolar nerve is to be loosened as it exits the mental foramen, the bone surrounding the foramen can be removed en block through a circumferential osteotomy all around the foramen. Small holes are drilled through the cortex along the expected nerve position and then these holes are connected with a fissure bur. Using an elevator, the entire outer rectangular window can be removed, the outer cancellous bone covering the canal is gently removed with the small curet and the nerve is exposed. By using a nerve retractor, the inferior alveolar nerve is mobilized from its position in the canal during implant site preparation. After implant

placement, the nerve is then repositioned over the lateral aspect of the implants. There is no thermal conduction from the implants to the nerve. The neurovascular bundle is allowed to lie passively on the implant/s and the flap is sutured (Fig. 12).

ConclusionIt can be seen that many advanced surgical techniques exist to overcome the expected anatomical difficulties during implantation. It is important however to remember the desired treatment outcome and to explore all the possible solutions. Even in compromised situation, by good evalution of both patient’s desires and the available possibilities and by choosing the suitable technique, keeping the technique as simple and as predictable as possible, the likelihood of success increases greatly.

Figure 12. (a) Panoramic x-ray shows insufficient available bone height superior to the Inferior alveolar nerve. (b,c,d) Buccal bone removed and neurovascular bundle removed from the mandibular canal. (e,f) Implant is placed. (g,h,i) Postoperative panoramic x-ray and the final prosthesis in place. (j) The inferior alveolar nerve is to be loosened as it exits the mental foramen.

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ReferencesBabbush, C. A. Transposition and repositioning the inferior 1.

alveolar and mental nerves in conjunction with endosteal

implant reconstruction. Periodontol. 2000. 1998;(17):183-90.

Barone A, Covani U. Maxillary alveolar ridge reconstruction with 2.

nonvascularized autogenous block bone: clinical results. J Oral

Maxillofac Surg. 2007 Oct;65(10):2039-46.

Brånemark P-I, Svensson B, van Steenberghe D. Ten-year 3.

survival rates of fixed prostheses on four or six implants ad

modum Brånemark in full edentulism. Clin Oral Implants Res

1995;6:227–231

Bravi F, Bruschi GB, Ferrini F. A 10-year multicenter retrospective 4.

clinical study of 1715 implants placed with the edentulous

ridge expansion technique. Int J Periodontics Restorative Dent.

2007 Dec;27(6):557-65

Chiapasco M, Brusati R, Ronchi P. Le Fort I osteotomy with 5.

interpositional bone grafts and delayed oral implants for the

rehabilitation of extremely atrophied maxillae: a 1-9-year

clinical follow-up study on humans. Clin Oral Implants Res. 2007

Feb;18(1):74-85.

Guirado JL, Yuguero MR, Carrión del Valle MJ, Zamora GP. 6.

A maxillary ridge-splitting technique followed by immediate

placement of implants: a case report. Implant Dent. 2005

Mar;14(1):14-20.

Higuchi KW. The zygomaticus fixture: an alternative approach 7.

for implant anchorage in the posterior maxilla. Ann R Australas

Coll Dent Surg 2000;15:28–33.

Kasabah S, Simůnek A, Krug J, Cevallos Lecaro M. Maxillary 8.

sinus augmentation using deproteinized bovine bone (Bio-Oss)

and Impladent Dental Implant System. Part I. Comparison

between one-stage and two-stage procedure. Acta Medica

(Hradec Kralove) 2002;45(3):115-8.

Montazem, A., Varauri, D.V., St-Hilaire, H. & Buchbinder, DThe 9.

mandibular symphysis as a donor site in maxillofacial bone

grafting: a quantitative anatomic study. Journal of Oral and

Maxillofacial Surgery 2000;58:1368–1371.

Saulacic N, Iizuka T, Martin MS, Garcia AG. Alveolar distraction 10.

osteogenesis: a systematic review. Int J Oral Maxillofac Surg

2008;37(1):1-7.

Shimoyama T, Kaneko T, Shimizu S, Kasai D, Tojo T, Horie N. 11.

Ridge widening and immediate implant placement: a case

report. Implant Dent 2001;10(2):108-12

Wallace SS. Maxillary sinus augmentation: evidence-based 12.

decision making with a biological surgical approach.

Compend Contin Educ Dent 2006 Dec;27(12):662-8.

(D.D.S., Dip., OMFS., Ph.D.)Doctor Dental Surgery, Oral & Maxillofacial Surgeon, Doctorate in Dental Implantology & Bone Augmentation. Assistant Professor, Department Oral & Maxillofacial Surgery/Dental Implantology Unit, Damascus University, Syria

(D.D.S., M.D., OMFS., Ph.D.)Doctor Dental Surgery, Doctorate in Oral & Maxillofacial Surgery. Assistant Professor, Department Oral & Maxillofacial Surgery, Damascus/Hamburg University

Author: Dr. Samer Kasabah Author: Dr. Dr. Ali Gbara