Bone grafting simultaneous to implant placement. Presentation of a case
Injerto óseo simultáneo a la colocación de implantes. A propósito de un caso

 

Miguel Peñarrocha Diago ⁽¹⁾, Mª Dolores Gómez Adrián ⁽²⁾, Berta García Mira ⁽²⁾, Mariola Ivorra Sais ⁽²⁾

(1) Profesor Titular de Cirugía Bucal. Director del Máster de Cirugía e Implantología Oral
(2) Alumna del Máster de Cirugía e Implantología Oral. Facultad de Medicina y Odontología. Universidad de Valencia.

Address:
Dr. Miguel Peñarrocha Diago
C/ Gascó Oliag, 1
Unidad Médico-Quirúrgica
Clínica Odontológica
46021 Valencia
E-mail: penarroc@uv.es

Received: 21-02-2004 Accepted: 4-06-2004

Peñarrocha-Diago M, Gómez-Adrián MD, García-Mira B, Ivorra-Sais M. Bone grafting simultaneous to implant placement. Presentation of a case. Med Oral Patol Oral Cir Bucal 2005;10:444-7. © Medicina Oral S. L. C.I.F. B 96689336 - ISSN 1698-4447

 

ABSTRACT Bone defects at mandibular alveolar crest level complicate the placement of dental implants in the ideal location. Surgical reconstruction using autologous bone grafts allows implant fixation in an esthetic and functional manner. We describe a patient with large mandibular bone loss secondary to periodontal inflammatory processes. Reconstruction of the mandibular alveolar process was carried out using onlay block bone grafts harvested from the mandible. The grafts were stabilized by positioning the dental implants through them – a procedure that moreover afforded good primary implant fixation. After two years of follow-up the clinical and radiological outcome is good. In the lower jaw, where bone regeneration is complicated, we were able to achieve good results in this patient – minimizing the corresponding waiting time by grafting and placing the implants in the same surgical step. Key words: Autologous grafts, dental implants.

RESUMEN Los defectos óseos a nivel de la cresta alveolar mandibular dificultan la colocación de los implantes dentales en el lugar idóneo. La reconstrucción quirúrgica mediante injertos de hueso autólogo es una opción que permite la fijación de los implantes de manera estética y funcional. Presentamos un paciente con grandes pérdidas óseas mandibulares, secundarias a procesos inflamatorios periodontales. Se realizó la reconstrucción del proceso alveolar mandibular, empleando injertos en bloque, tipo onlay, tomados de la mandíbula. Los injertos fueron estabilizados al colocar los implantes a través de ellos, consiguiéndose además una buena fijación primaria de los mismos. Tras dos años de seguimiento existe éxito clínico y radiológico. En mandíbula, donde es complicada la regeneración ósea, en nuestro caso conseguimos unos buenos resultados, minimizando el tiempo de espera al realizar los injertos y la colocación de los implantes en una cirugía. Palabras clave: Injerto autólogo, implantes dentales.

 

INTRODUCTION

Different alveolar bone augmentation techniques have been developed (1-4). In the case of extensive alveolar defects, or when vertical augmentation is contemplated, onlay block grafting procedures can be used to achieve the required alveolar bone height and thickness, with adequate implant positioning and an acceptable esthetic outcome (5,6).

We present a clinical case involving large mandibular bone defects in which bone regeneration was carried out via onlay block grafting, with the simultaneous placement of 6 dental implants.

CLINICAL CASE

A 57-year-old male with type 2 diabetes mellitus controlled with oral antidiabetic drugs, an upper fixed prosthesis and an edentulous lower jaw presented for implant treatment. One week previously teeth 33, 42 and 43 had been removed. Orthopantomography revealed the presence of important bone defects in the areas where the extractions had been carried out, possibly as a result of the existing periodontal disease (Fig. 1). Treatment was planned in the form of block grafting to fill the defects and position dental implants in the same surgical session.

Surgery was performed under local anesthesia with 2% articaine and 1:100,000 adrenalin. A supracrestal incision was made, with posterior vestibular sectioning and the raising of a full-thickness flap; the inflammatory soft tissue responsible for the bone loss was removed, leaving two large mandibular bone defects (Fig. 2A). In the third quadrant a trephine bur was used to harvest a circular block of mandibular bone (Fig. 2B), and after placing it in the receptor zone of 33, it was perforated with drills to prepare the bed and position the implant through the orifice – thereby fixing grant and implant together. In the fourth quadrant we obtained the graft from the retromolar zone, marking the extent of the graft with a rounded tungsten carbide drill (Fig. 2C). The block was then extracted and placed over the atrophic zone, followed by fixation with an Osteomed^® osteosynthesis screw. The beds were subsequently prepared to receive the implants. In the anterior zone we positioned another two implants, with an additional implant distal to the graft of the third quadrant (Fig. 2D). The implants used were Defon^®(Impladent, Sentmenat, Barcelona, Spain), TSA, measuring 4.2 mm in diameter. The threads were covered with particulate bone obtained from preparation of the implant beds. Suturing was carried out with triple-zero silk, leaving the implants submerged. The radiological control showed alignment of the implants and the mandibular bone height achieved (Fig. 3A). Four months later second step surgery was performed to place the healing posts. After two months, imprints were obtained for construction of a fixed prosthesis over the 6 implants – good tissue regeneration being noted (Fig. 3B and 3C). After two years of follow-up, no complications have been recorded, and the orthopantomographic images show perfect graft integration.

DISCUSSION

Alveolar bone defects can be surgically corrected before or at the time of implant placement (1). The advantage of performing the procedure in a single step is that the number of surgical interventions is reduced, and graft stabilization can be procured by the implant itself. The disadvantages of the combined graft-implant procedure are that graft failure implies also implant failure, and while implant osseointegration may be achieved in the apical zone, there may be no such integration in the bone in the coronal zone (1). We carried out grafting and implantation at the same time, achieving good primary implant fixation and graft stability.

According to Simion et al. (7), the characteristics of regenerated bone are more dependent upon the bone quality of the receptor bed than on quality of the grafted bone, and in the case of simultaneous implant positioning, the achievement of increased percentage bone-implant contact is dependent upon this same factor. Accordingly, when bone of cortical characteristics is obtained, percentage osseointegration after 7-11 months is 67.6%, versus only 39.1% when spongy bone is involved. The results obtained following rehabilitation with implants over regenerated bone tissue over periods of 1-5 years suggest that this procedure can be used with 90%-97.7% implant success in patients with bone defects (8). In our case we obtained a cortical donor bone block, and the receptor bed was spongy and well vascularized – i.e., both characteristics were very suitable for graft success.

The literature presents a number of studies in which grafting and implant placement in a single step is described as a safe and effective technique (9,10). Lekholm et al. (10), in a study involving 781 ITI^® implants, reported greater percentage success with implants placed over mature bone than over grafts – with failure rates of 11% and 25%, respectively. Of 25 mandibular implants positioned over onlay bone grafts in the lower jaw in a single step, the reported success rate was 85%. On the other hand, the implant failure rate was found to be greater on simultaneously positioning grafts and implants versus deferred implantation. An alternative in our case would have been to perform grafting in a first step, followed by implant placement in second-step surgery. However, this would have posed the need and difficulty of fixing the grafts with osteosynthesis screws only, and the important mandibular bone defect would have led to much greater graft instability with the screws than with simultaneous implant placement. Another alternative would have been to apply the guided bone regeneration technique, using a titanium reinforced membrane barrier, since different authors have reported good results with this approach (11,12). Even in the context of vertical augmentation of the lower jaw, Tinti et al. (13) have described vertical alveolar crest increments of 7 mm around 14 implants, after 12 months, when using autologous bone grafts and a titanium reinforced barrier. However, we opted for block grafting (since in our patient the problem was more a matter of mandibular bone defect than a lack of vertical height) without a membrane, in order to reduce the number of interventions and thus the duration of treatment.

The origin of the bone used in grafting is fundamentally dependent on the size of the bone defect involved. In most cases intraoral, chin, mandibular ramus, zygomatic arch, retromolar or maxillary tuberosity grafts are used (1,3,14). In our case we harvested bone from the retromolar region to ensure a sufficiently large monocortical graft to cover the entire defect – using the same surgical field required for implant placement, and thereby minimizing the complexity of the procedure. Furthermore, a trephine bur was used to harvest one of the blocks destined to fill the circular defect, while a fissuring drill was employed to simulate the ovoid shape of the other defect.

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