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Medicina Oral, Patología Oral y Cirugía Bucal (Ed. impresa)

versión impresa ISSN 1698-4447

Med. oral patol. oral cir. bucal (Ed.impr.) v.10 n.4 Valencia ago.-oct. 2005

 

Preprosthetic and implantological surgery in patients with severe maxillary atrophy
Cirugía preprotésica e implantológica en pacientes con atrofia maxilar severa

 

Raúl González García (1), Luís Naval Gías (2), Mario Fernando Muñoz Guerra (2), Jesús Sastre Pérez (2)
Francisco José Rodríguez Campo (2), José Luís Gil-Díez Usandizaga (3)

(1) Médico Residente
(2) Cirujano Adjunto
(3) Jefe de Sección. Servicio de Cirugía Oral y Maxilofacial
(Jefe de Servicio: Francisco J. Díaz González)
Hospital Universitario de La Princesa (Universidad Autónoma) - Madrid

Address:
Raúl González García
C/ Los Yébenes nº 35, 8º C
28047 - Madrid
ESPAÑA
teléfono- + (48%) 917191259
Fax- + (48%) 914702259
E-mail: raugg@mixmail.com

Received: 28-05-2004 Accepted: 10-10-2004

González-García R, Naval-Gías L, Muñoz-Guerra MF, Sastre-Pérez J, Rodríguez-Campo FJ, Gil-Díez-Usandizaga JL. Preprosthetic and implantological surgery in patients with severe maxillary atrophy. Med Oral Patol Oral Cir Bucal 2005;10:343-54.
© Medicina Oral S. L. C.I.F. B 96689336 - ISSN 1698-4447

 

ABSTRACT

Aims. To evaluate the success of the osseointegration of dental implants in patients with severe maxillary atrophy after sinus lift augmentation and onlay graft surgery with autologous bone grafts.
Design.
A descriptive and analytic study of 27 patients with severe maxillary atrophy and partial or total edentulism, after 4 years follow-up. All cases underwent to autologous bone graft sinus lift augmentation with or without onlay grafts in the anterior maxillae. After this, reconstruction with osseointegrated implants was performed.
Results.
After the follow-up period, 89.1% of implants were osseointegrated and loaded. Anterior iliac crest bone graft provides good results with respect to implant osseointegration. The achievement of two surgical procedures for bone grafts surgery and implants surgery, separated 2 or more months, provides better results for osseointegration in comparison to a sole surgical procedure (p<0.01).
Conclusions.
Implants survival predictability is greater when a second surgical procedure is performed, once bone grafts have experimented an appropriate consolidation. The use of onlay graft and sinus lift augmentation techniques is useful in the resolution of complex problems such as the severe maxillary atrophy.

Key words: autologous bone graft, osseointegration, dental implant, sinus lift, onlay graft, severe maxillary atrophy.

 

RESUMEN

Objetivos. Valoración del éxito en la osteointegración de los implantes dentales en pacientes con atrofia maxilar severa sometidos a cirugía de elevación de seno maxilar y técnica por aposición mediante el uso de injertos de hueso autólogo.
Diseño del estudio.
Se realiza estudio descriptivo y analítico de 27 pacientes con atrofia maxilar severa y edentulismo parcial o total, durante 4 años de seguimiento. Todos los casos fueron tratados mediante cirugía con utilización de injertos óseos autólogos para la elevación de seno maxilar unida o no a injerto óseo por aposición para el tratamiento del maxilar anterior, con posterior colocación de implantes osteointegrados.
Resultados.
Al final del periodo de seguimiento un 89,1% de los implantes se encuentra osteointegrado y cargado. El injerto óseo de cresta ilíaca anterior aporta unos resultados óptimos en cuanto a osteointegración implantaria. La realización de dos tiempos quirúrgicos separados entre sí 2 o más meses para la cirugía de injertos óseos y para la cirugía implantológica aporta un mayor porcentaje de osteointegración de los implantes en comparación con la realización de un único tiempo quirúrgico (p<0,01).
Conclusiones.
El grado de predictibilidad en la supervivencia de los implantes es mayor cuando se colocan en un segundo tiempo quirúrgico, una vez que se ha producido la correcta consolidación de los injertos óseos. El empleo de las técnicas de injerto óseo autólogo por aposición y elevación de seno maxilar y posterior colocación de implantes se muestra eficaz en la resolución de problemas complejos como la atrofia maxilar severa.

Palabras clave: Injerto óseo autólogo, osteointegración, implante dental, elevación de seno, injerto onlay, atrofia maxilar severa.

 

INTRODUCTION

Pathological situations with important loss of bone support have been observed in relation with bone jaws, which can develop a functional and aesthetical handicap to the patient. These alterations may limit masticatory, deglutory and phonatory ability, with subsequent psychological implications. Patients with severe maxillary atrophy are clear examples of this condition, and constitute an important group candidate for reconstructive treatment.

The introduction of osseointegrated implants for the rehabilitation of edentulism makes possible the integral treatment of the patient in a practical manner. However, those patients with severe atrophy of maxillary alveolar process or excessive neumatized maxillary sinus, present difficulties for implants anchorage, due to the absence of bone enough. (1,2,3)

For time, several techniques for the treatment of maxillary atrophy with bone grafts together with osseointegrated dental implants have been used. In 1980, Breine and Brånemark (3) developed first clinical and experimental studies about implants in bone grafts. These authors used tibia trabecullar bone graft in combination with titanium fixtures, the implants were placed in the remainder alveolar bone and apically covered by particulate bone. The percentage of osseointegration was low, with only 25% of implants osseointegrated and most of bone grafts experimented resorption after a year. In another work, the same authors placed implants in the tibia proximal metaphysis and, after 3 to 6 months, they obtained tibia bone grafts with osseointegrated implants and placed them on the atrophic maxilla with additional long implants. With this second surgical procedure, 60% of implants remained osteointegrated after a year when they used onlay bone grafts, whereas only 50% of the initial volume of bone graft was preserved.

Brånemark (4) in 1985 and Keller (5) in 1987 developed and extended a technique combining the use of iliac crest bone grafts fixed with implants to the atrophic alveolar bone. In the Keller´s work, 24 of 28 implants were osseointegrated. This author studied the use of implants in iliac crest bone grafts placed after Le Fort I osteotomy of the atrophic alveolar bone, with the result of 16 of 21 implants osseointegrated after the follow-up. (5)

In 1980 Boyne and James (6) described the procedure of maxillary sinus lift augmentation with interposition of bone grafts between the floor of the sinus and the alveolar process, with the purpose of augmenting the height available for implants in the posterior sector. In 1980, Sailer (7) described the implant insertion in the atrophic maxilla with the interposition of autologous bone graft obtained from the iliac crest combined to a Le Fort I osteotomy fixed to the maxilla with micro-screws, and with the use of miniplates for the osteotomy fixation. After this, the use of bone grafts and the placement of implants have been developed to elevate the maxillary sinus and the floor of the nasal cavity, in order to obtain functional rehabilitation of the atrophic alveolar process. (8)

In the present work, we have designed an observational retrospective study to evaluate the success rate in the osseointegration of dental implants. We analysed a series of 27 patients with severe maxillary atrophy and partial or total edentulism, with a follow-up of 4 years. All patients were managed with preprosthetic surgery, with autologous bone grafts for the sinus lift augmentation with or without onlay grafts for the rehabilitation of the anterior sector of the maxilla, and subsequent osseointegrated implants placement.

MATERIALS AND METHODS

In the period 2001-2004, we treated 27 patients with severe maxillary atrophy (classes V and VI in the Cawood and Howell classification (9)) in our Department using onlay bone grafts and sinus lift surgery, 23 cases were female and four were male. Of these twenty-seven patients, 10 were partially edentulous and 17 completely edentulous. We selected patients by clinical and radiological examination, using panoramic radiography and dental computerized tomography (TC). According with other authors, (10) alveolar height lower to 7 mm and alveolar width lower to 4 mm were considered abnormal dimensions. As exclusion factors for surgical intervention, the next were considered: important smokers, recent radiotherapy treatment to the maxillary bone (less than a year), sinusitis, diabetes mellitus non-controlled and very poor oral hygiene.

Surgical treatment was performed under general anaesthesia and nasal endotracheal intubation. The increase of maxillary dimensions was obtained by onlay bone graft and sinus lift augmentation techniques with particulate corticocancellous bone and additional cancellous bone. Autologous bone grafts were obtained from several donor sites, such as anterior iliac crest, posterior iliac crest, calvarian bone, maxillary tuberosity and mandibular ramus. Anterior iliac crest were obtained from the medial side. Corticocancellous bone graft and additionally cancellous bone was obtained with the purpose of filling the floor of the maxillary sinus. Also calvarian bone, maxillary tuberosity and mandibular ramus were obtained in the same manner. Careful haemostasia of the donor site was performed, and drainages to avoid haematic collections and to control eventual bleeding were disposed in cases in which iliac crest and calvarian bone grafts were obtained.

We performed an incision on the border of the alveolar crest to place onlay grafts. According with other authors, (11) we think that this technique decrease ischaemic risks of the flap edges. Discharge incisions were performed both sides to configure the flap, allowing an adequate mobilization and a direct closure without tension. Bone grafts were used to increase the horizontal and vertical dimensions of the alveolar crest, according to the particular necessity of each patient. We stabilized them with 1.5 to 2 mm titanium micro-screws, with rigid fixation to bone graft and basal bone (Fig.1). Bone perforations were performed in order to improve the osseogenesis process. Residual defects after corticocancellous bone graft were filled with particulated cancellous bone. No membranes were used to cover the graft, and all cases were treated with a direct closure without tension.

Sinus lift augmentation was performed to increase the quantity and height of the posterior maxillae. We consider that an alveolar height less than 7 mm in this site is an indication for bone graft and sinus lift augmentation. A mucoperiostic release after an incision on the border of the crest from the canine to the maxillary tuberosity region was performed. The flap was elevated to the infraorbital foramen or to 2 cm upper than the floor of the sinus. A bone window was designed on the lateral wall of the maxillary sinus and, once the osteotomy was finished, a careful release of the sinus membrane was performed with membrane dissectors. Once the mucosa was lifted, the new formed cavity was filled up with bone grafts (Fig.2). In cases in which a mucosal perforation was achieved, it was used a commercial preparation of fibrin together with autologous bone grafts in blocks. In these cases, we do not placed cancellous bone in order to avoid the lost of material through this perforation.

All cases in which the use of onlay grafts for anterior maxillae were performed together with sinus lift augmentation for the posterior maxillae; the implant surgery was achieved in a second surgical time. In this time, micro-screws from the bone grafts were retired (Fig.3).

Posterior follow-up was performed by physical exploration and radiological study with panoramic radiography and dental CT. The success of the viability of bone graft was judged in relation to the conservation of alveolar height obtained after the surgery and considering the existence of a stable osseous pattern. The success in implant osseointegration was established in relation with the absence of radiolucent images round the implants and the absence of pain, mobility and peri-implantitis signs.

For the acceptance and follow-up of patient candidate to surgery, we make a retrospective data study. We registered personal disease history, pre-surgical oral hygiene, reason for treatment, type of bone graft used for the onlay technique and donor site, type of graft fixation, tri-dimensional structure of the defect and date of different surgical times. Also, we registered if bilateral or unilateral sinus lift augmentation was performed, type of bone graft used for the sinus lift and donor site, material of bone graft and existence of perforation of the sinus membrane during surgical management. Moreover, some other registered data were: immediate implant placement, number, type and location of implants per patient, quality of bone, date of implants surgery, complications during the implants follow-up, situation of implants at final revision, lost of bone graft height during the postoperatory follow-up, type of dental prostheses used and definitive aesthetic-functional result.

-Statistical study

For the statistical study it was used the SPSS 6.1 statistical software. Firstly, we achieved a descriptive study of our series and later an analytic study was performed. We used measurement of frequencies for the different variables (cited in previous paragraph) and Χ2 test for univariante analysis of qualitative variables. It was consider a value of p<0.05 as statistically significant. Lost of cases (patients or implants), due to lack of follow-up or data missing in some of the descriptive studies, were in all cases less than 12%.

RESULTS

For 4 years, we treated 27 patients with severe maxillary atrophy, with sinus lift augmentation as a unique treatment modality in 11 (40.7%) patients, and together with onlay graft technique in the other 16 (59.3%). Twenty-three (85.2%) patients were female and 4 (14.8%) male. We classified oral hygiene as good in 82.6% of the cases, regular in 13% and bad in 4.3%.

In 16 cases in which sinus lift augmentation and onlay graft for anterior maxillae were combined, bone graft used for this last technique was bone in blocks for 13 (81,3%) cases and bone in blocks together with particulate bone in the other 3 (18,8%) cases. The bone grafts were fixed with titanium micro-screws in 100% of cases. In the study before surgery, a lost of alveolar bone height and width was observed in 50% of 27 cases, whereas a lost of height dimension without simultaneous lost of width dimension was observed in the remaining 50%.

All patients were managed with sinus lift augmentation. Seventeen (63%) cases were bilateral, 5 (18.5%) from right maxillary sinus, and other 5 (18.5%) from left maxillary sinus, with a total number of 44 sinus lifts. Autologous particulate bone for sinus lift augmentation was used in all 27 patients. Anterior iliac crest bone graft was used in 19 (43.1%) patients, calvarian bone in 14 (31.8%), posterior iliac crest in 8 (18.1%), mandibular ramus in 2 (4.5%) and maxillary tuberosity in 1 (2.2%).

During the sinus lift surgical procedure, a perforation of the membrane was achieved in 2 (4.5%) cases, but no reparative techniques with membranes were necessary. Implant surgery was performed at the same time as bone grafts surgery in 8 (29.6%) patients, and it was delayed to a second surgical time in the other 19 (70.4%) patients. Implant surgery was performed as the same time as bone grafts surgery in those cases with enough alveolar width and primary stability, with at least 4 mm high. All patients that required additional onlay bone graft and those who do not fulfil the anterior criteria, were managed with implants placement in a second surgical time. Simultaneous nasal cavity lift was performed in 6 (22.2%) of the cases.

Average time between bone graft surgery and implants surgery was 3 months. Follow-up after bone graft placement and previous to implant placement was performed with dental scan, which was compared with pre-surgical CT. Lost upper than 2 mm were observed in 7 (25.9%) cases, whereas bone graft height do not experimented any variation in 17 (63%) cases. Three (11.1%) cases were not registered due to lost of follow-up. Discarding lost patients, percentage of patients who do not experimented variation of bone height upper than 2 mm was 70,8% of cases.

A hundred and forty-eight dental implants were placed in 27 patients. In relation with implants, average time between bone graft surgery and implants surgery was 3 months. In anterior maxillae, 48.6% of implants were placed, while 51.4% of implants were placed in posterior maxilla.

Implants used were titanium screw type, alloy of titanium screw type, titanium cylindrical type and alloy of titanium cylindrical type in different proportions and with different length and width. The most frequently used (43.4%) was the 13 mm length and 3.75 mm width titanium screw type, followed by the 15 mm length and 3.75 mm width titanium screw type (27.9%). The other were used in lower proportions with similar frequencies between them.

At the end of the follow-up, a great proportion of implants were osseointegrated (90.1%). We do not considered patients who had not completed the treatment (36 implants) or those in whom follow-up was lost (11 implants).

In the ten cases with partial edentulism we placed partial fixed implant-supported prostheses. We used complete fixed implant-supported prostheses in 7 (41.2%) of 17 patients with complete edentulism, Brånemark prostheses in 5 (29.4%) and overdenture in 1 (5.8%). Four of our patients with complete edentulism do not wear prostheses because post-surgical treatment has not already finished.

At the end of the follow-up, aesthetic results were good in 93.75% and regular in 6.25% of cases. This evaluation was subjective, in relation to surgeon (the same in all cases) and degree of patient’s satisfaction. Four cases are waiting for evaluation because they have not finished prosthetic treatment.

In the analytic study, we tried to demonstrate any significant statistically association between different variables in relation with final situation of implants (osteointegrated or non-osteointegrated) and aesthetic results (good, regular or bad results). In relation with this, significant statistical association with p<0.01 was demonstrated between implant situation at the end of the follow-up and different variables, such as: type of implant, bone graft donor site, bone graft lost of height after the bone graft surgery, time between both surgical procedures. In the same manner, a significant statistical association was demonstrated between final aesthetic results and the variables: type of implant and type of prostheses used.

These associations provides an advantage to screw type implants in relation with osseointegration (93.1% of screw type implants in contrast with 66.6% of cylindrical type implants). Results were better when we used anterior iliac crest (table 1). Preservation of bone graft height after the first surgical time improves implant osseointegration. In relation with time between both surgical procedures, we observed less osseointegration rate in those cases in which we placed implants in the same surgical procedure as bone graft (table 2). Screw type implants provides better aesthetic results than cylindrical type implants.

 

 

Some variables of interest that do not demonstrated significant association (p>0.05) were increase of maxillary bone defect (horizontal, vertical or both), placement of implants (anterior or posterior maxillary) and type of bone graft used (in block versus in block together with particulated bone).

DISCUSSION

It has been termed osseointegration as the direct structural and functional connection between bone alive and implant surface. (4) The osseointegrated implants loaded maintain appropriate bone graft dimensions. In relation with this subject, we have overcome classical resorptions of onlay bone grafts, which may support unfavourable external forces, coming from dental prostheses directly supported over soft tissue. (12) The existence of these unfavourable forces over the bone graft disappears with the use of osseointegrated implants. New bone around an implant has an adequate density in relation to direction and intensity of charges; if surgical process has been very aggressive, or applied forces are very intense, the osseointegration process stop and soft tissue is developed. (4)

There are some principles, which are necessary to consider in the treatment of the atrophic maxilla. These principles are the elimination of a minimal volume of the residual bone and the conservation of maxillary topography. Finally, if osseointegration is not possible, it is important that the patient preserves the original maxilla in order to use conventional dental prostheses. (4)

In our series, we used onlay bone grafts to restore height and width of the atrophic maxillae. According with other authors, (11) we think that this technique is indicated when there is an inadequate height and width of the alveolar process that makes non-possible to support dental prostheses. In addition, this technique is indicated when there is a defect in bone contour, which makes difficult a correct placement of implants or it was aesthetically unacceptable. Finally, the existence of a partial maxillary atrophy constitutes an indication for this technique.

Iliac crest bone graft in block has some characteristics in relation with its curvature. In our experience and according with other authors, (13) it is more suitable for reconstruction of the upper anterior maxillae than calvarian bone graft. We have obtained good results with anterior iliac crest and calvarian bone, with a favourable disposition to use iliac crest, due to its easier adaptability to the anterior maxillary curvature. Our experience with posterior iliac crest is lower and, although there are clear inconvenient in relation with change of position in the surgical room, it seems to report a lower incidence of pain in the donor site. This aspect may be considered in future studies with a greater number of patients and a specific design for that purposes.

In relation with influence of the donor site in implant osseointegration, we observed (once lost patients were not considered) 96.6% implant osseointegration rate by anterior iliac crest, 82.35% implant osseointegration rate by posterior iliac crest, 100% implant osseointegration rate by mandibular ramus, 100% implant osseointegration rate by calvarian bone and 20% implant osseointegration rate by maxillary tuberosity. We only placed 6 implants in mandibular ramus bone graft and 6 implants in maxillary tuberosity bone graft. Moreover, the percentage of patients who had received calvarian bone graft and was waiting for evaluation was 47.2%, so we have to be very careful in considering data from these bone grafts. However, data from posterior iliac crest and anterior iliac crest show optimal success for implant osseointegration. These results reassert our conviction about these bone grafts suitability.

Results obtained about implant placement over bone grafts advocate for an implant surgery in a second surgical procedure, a few months after the bone graft surgery. In relation with it, results obtained with implant placement in the same time as bone graft placement show definitive results. Thirty-three per cent of patients were managed with bone graft and implant placement in a single surgical procedure. In relation with percentage of implants, it accounted for 31.7%. Disregarding patients non evaluated or lost, failure in osseointegration of implants was 31.25%, whereas 68.75% of them were osseointegrated. When we placed implants just only 2 months after the bone graft surgery, failure of osseointegration decreased to 13.1%, with an osseointegration rate of 86.9%. If we analyze what happened when implants were placed 3, 4 and 5 months after the bone graft surgery, we observed success rates of 100%, 90.9% and 100%, respectively. These data agree with data referred by other authors. (14,15) We conclude that the use of two surgical procedures separated 3 or more months provides greater implant osseointegration rates and so better results, in comparison with both surgical procedures performed simultaneously. Other works have shown similar results. (16,17,18,19)

In the other side, it is interesting that the use of autologous bone graft is actually a method that provides a greater survival rate of implants. Occasionally, it may be indicated the use of allograft and alloplastic materials, (20) but autologous bone grafts constitute the ideal material. Our group shares this opinion, and we only used autologous bone grafts. It is known that the use of allografts together with autologous bone graft reduces implant survival to 79%, in comparison with the use of autologous bone graft alone (79%). (21,22)

In relation with the preparation of bone graft, we were not able to demonstrate a significant statistical association between osseointegration and the use of bone grafts in blocks or bone grafts in blocks together with particulate bone. Some authors (7) advocate that probably the most important prognostic factor in maxillary bone osseointegration is that cancellous bone has lower support ability than cortical bone. In our study, we do not consider this aspect. In fact, we did not design the work with the intention of comparing cancellous bone versus cortical bone. In the surgical procedure, cortical bone graft with or without cancellous bone was added to the receptor site, with the particularity that, in some cases, we used bone grafts in blocks and, in other cases, we used bone grafts in blocks together with particulate bone.

Finally, it is important to emphasize that the implants with better results were titanium screw type implants, specifically those of 13 and 15 mm length and 3.75 mm width. This is referred to the implant osseointegration rate achieved. In our series, these implants were the most frequently used, due to our good clinical experience with them.

With the techniques described above, we obtained predictable results, with an elevated success rate in relation with implant osseointegration, aesthetic and functional results, with a low number of complications.

CONCLUSIONS

The use of autologous bone graft is useful providing a support base that allows us to place osseointegrated dental implants.

It is necessary to remark that the surgical process requires the adhesion to basic principles of rigid osseous fixation and primary closure of soft tissues without tension. A careful technique and a trained surgeon are the best warranties to obtain success, which is no other than the correct implant osseointegration and good aesthetical and functional results.

The implant survival predictability is greater when they are placed in a second surgical time, once correct bone graft osseointegration has been obtained.

The use of onlay bone grafts and maxillary sinus lift augmentation with subsequent implant placement, provides a great predictability in relation to solve complex problems in severe maxillary atrophy.

It would be desirable the development of studies attending follow-up with more patients and during a greater period, to determine implant survival rate. In addition, it would be interesting the development of works that value specifically some aspects, such as utility of different bone grafts, resorption degree evaluated by dental scan, functional results and patient’s satisfaction degree.

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