Reconstruction of the extremely resorbed mandible with interposed bone grafts and placement of endosseous implants

0 1998 The British Association of Oral and Maxilofacial Surgeons

Reconstruction of the extremely resorbedmandible with interposedbone grafts and placement of endosseousimplants A preliminary report on outcome of treatment and patients’ satisfaction C. Stellingsma, G. M. Raghoebar, H. J. A. Meijer, R. H. K. Batenburg Department of Oral and Maxillofacial Groningen, The Netherlands

Surgery and Maxillofacial

Prosthodontics, University Hospital,

SUMMARY During recent decades many surgical techniques have been developed to enlarge the denture-bearing area of the mandible. Most of these techniques improved retention and stability of the lower dentures only temporarily. Since the advent of endosseous implants to stabilize overdentures, combinations of augmentation procedures and placement of endosseous implants have been introduced to restore the severely resorbed mandible. In this study we describe the preliminary results of such a combined approach using sandwich osteotomy with an autogenous bone graft (iliac crest) followed by placement of four endosseous implants in the interforaminal region in 10 women. After a mean follow-up period of 31 months (range 19-57) several variables were measured including condition of the peri-implant tissues, radiographic bone changes and patient satisfaction. The first results indicate that the technique described offers a solid base for implant-stabilized overdentures: no implants were lost, the periimplant tissues were in good condition, bone loss was limited, and patients were satisfied. Future studies will evaluate the permanence of these results.

outcome of treatment and satisfaction of patients after prosthetic rehabilitation following sandwich osteotomy, placement of endosseous implants, and fabrication of an implant-stabilized lower denture in patients with severely resorbed mandibles.

INTRODUCTION Loss of teeth results in resorption of the bone of the alveolar process.‘x2 In more advanced stages, resorption of the basal bone of the mandible may occur as well.3 Many patients with atrophic mandibles become dental cripples unless special precautions are taken. In many instances substantial improvement in function, lip competence, and facial support can be achieved by prosthetic rehabilitation. The success of such treatment depends on factors such as tolerance and motivation of the patient, residual anatomical contours, and quality of the oral tissues. In recent years many surgical techniques have been developed to improve the denture-bearing area, ranging from a relatively simple vestibuloplasty to complex augmentation procedures with alloplastic materials4 Implant-retained dentures are the treatment of choice if sufticient height and width of bone is available for placement of endosseous implants.5,6 The failure rate of short implants is higher than that of longer implants’ and complications are more common.8~9 Possibly because of unfavourable interarch relationships, which result in overloading of the implants. If the bone volume is insufficient it can be augmented with autogenous grafts (such as rib or iliac crest), bone substitutes (hydroxy-lapatite granules and blocks), and combinations of both. A major drawback of these techniques is the substantial reduction in bone height within a few years, nerve disturbances, and donor area morbidity.“) A combination of the described treatments may give better results, as the placement of endosseous implants diminishes the bone loss in the augmented mandible.” In this study we describe the

PATIENTS

AND METHODS

Ten edentulous female patients (mean age 50 years, range 37-66) with severely resorbed mandibles (Cawood & Howell class VI),i2 and persistent problems with retention and stability of their conventional lower dentures, were treated by a sandwich osteotomy followed by installation of four endosseous implants. The preoperative height was measured in the midline region on the cephalometric radiograph. This was done by measuring the distance between the lowest point of the symphysis and the alveolar ridge in the midline. Surgical and prosthetic procedure Patients were operated on under general anaesthesia. The residual mandibular ridge between the mental foramina was exposed by an interforaminal incision in the buccal fold and raising of the mucoperiosteal flap. The mental foramina area was carefully dissected to allow retraction of the mucoperiosteal flap without tension on the mental nerves. Posteriorly, from the mental foramina to the retromolar region, a subperiosteal tunnel was created between the external oblique ridge and the mylohyoid ridge. Again, care 290

Reconstruction

was taken to protect the mental nerve. Subsequently, on each side vertical cuts were made in the upper third of the mandibular bone with a fissure burr just anteriorly to the mental foramina. These cuts were connected horizontally with an oscillating saw. The osteotomy lines may be inclined slighty downward towards the lingual soft tissues. After all cuts for this anterior segmental osteotomy were completed, the segment was raised 10 mm superiorly. Care was taken to maintain the soft-tissue pedicle on the lingual surface. In this 10 mm upward position the upper segment was fixed using 2.0 mm miniplates (Leibinger, Freiburg, Germany). Simultaneously, a monocortical iliac crest bone graft was taken from the medial surface of the anterior ilium.li The corticocancellous graft was contoured and positioned between upper and lower part of the sectioned mandible. The remaining cancellous bone was applied posteriorly into the subperiosteal tunnel using a disposable syringe. On top of this onlay a monocortical bone block was placed to establish a smooth contour between the frontal and lateral parts of the augmented mandible. Finally, the remaining dead spaces were filled with bone grafts and the wounds were closed with polyglactin 910 (VicryP) sutures (Figs. 2a & 2b). The patient was not allowed to wear a lower denture. Three months later, under local anaesthesia, the miniplates were removed and four Branemark implants (B&remark System, Nobel Biocare, Giiteborg, Sweden) were inserted in the interforaminal region. A total of 40 endosseous implants were placed, four in each patient. Again the patient was not allowed to wear a lower denture. Twelve weeks after implantation the abutment operation took place and the prosthodontic treatment started. All patients received a new upper, conventional prosthesis and an implant stabilized overdenture

of resorbed

mandible

with

bone grafts

and endosseous

implants

for the mandible, according to a standardized prosthetic procedure.14 A bar clip attachment was used to stabilise the overdenture (Figs 3a & 3b). After the abutment connection a standardized oral hygiene programme was started with frequent recall visits during the first 6 months. Thereafter, the patients were recalled for a control visit every 6 months to evaluate the peri-implant tissues, the prosthesis, and oral hygiene. Evaluation procedure and data collection

At the time of evaluation a clinical and radiographic examination was carried out. The patients were asked to till in a questionnaire about their satisfaction. The examination was made by one observer to prevent inter-observer variation. Clinical analysis

Loss of implants, plaque index,15 bleeding index,15 and gingiva index,r6 were recorded. The pocket depth was measured with a periodontal probe (Merrit-B, Hu-Friedy, USA) at four sites around the abutment after the bar had been removed. The probing depth was defined as the distance between the marginal border of the soft tissue and the top of the periodontal probe. Lip and chin dysaesthesia were evaluated by carefully touching these areas of skin with a cotton pellet.

b Fig. 2 ~ (A) Panoramic

Fig. 1 ~ Preoperative

cephalometric

radiograph

291

radiograph before connection of the abutments. (B) Diagram of the augmented mandible with the implants: 1 = upper part of the mandible; 2 = interpositioned bone graft: 3 = lower part of the mandible; 4 = cancellous bone and monocortical bone block in posterior region.

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Fig. 3 - (A) Panoramic

of Oral and Maxillofacial

radiograph

taken

Surgery

at the evaluation

visit.

(B) Clinical

view

of the superstructure.

Radiographical analysis

RESULTS

Detailed quantification of peri-implant bone loss cannot be done with a panoramic radiograph.” However a standardized intra-oral long cone technique is difficult to carry out in patients with a severely resorbed mandible and a relatively high floor of the mouth.r8 The panoramic radiographic technique was therefore chosen despite its lack of sharpness, distortion of images, and superimposition of the bony structures. The radiograph taken during the evaluation visit was compared with the radiograph taken before the connection of the abutments. Peri-implant bone loss (vertical bone loss) was classified according to a four-point rating scale”: 0 = no apparent bone loss; 1 = reduction of the bone level not exceeding more than one third of the implant length; 2 = reduction of the bone level exceeding one third of the implant length but not exceeding a half of the implant length; and 3 = reduction of the bone level exceeding half of the implant length. Diminution of height of the augmented part of the mandible (horizontal bone loss) was measured on panoramic radiographs at five sites: in the midline (site l), between the central and lateral implants (sites 2 and 3), and 10 mm distal to the lateral implants (sites 4 and 5). The magnification factor of each radiograph at each area was calculated using the known length of the adjacent implant, a method similar to that used in other studies.19J0 The panoramic radiograph made before connection of the abutments was compared with the radiograph taken during the evaluation visit. Because the follow-up period was not the same for all the patients, bone loss in patients followed up for more than 30 months was compared with the bone loss of patients who had been followed up for 30 months or less.

The mean preoperative height of the mandible in the midline was 11.7 mm (range 8.7-14.3, Fig. 1). In one patient a small dehiscence of the mucosa was observed at the site of the bone graft. This defect healed uneventfully after local debridement and removal of a few sequestra under local anaesthesia. In all cases there was sufficient bone in the grafted area to insert four endosseous implants in the interforaminal area. None of the patients had any subjective or objective signs of disturbed sensitivity of the lip or chin region postoperatively. At the time of evaluation the mean period the implants had been loaded prosthetically was 31 months (range 19-57). Neither during the healing period before connection of the abutments nor during the evaluation period were any implants lost. The mean plaque index, bleeding index, gingiva index, and pocket depth are shown in Table 1. No abundant amount of plaque (score 3, plaque index) was found in any patient. There was no confluent line of blood or heavy or profuse bleeding after probing (score 2 and 3, bleeding index). Severe inflammation of the gingiva (score 3, gingiva index) was not detected. The pocket depth varied from 1 to 6 mm (mean 2.7 mm, SD 0.88 mm). The possible peri-implant bone loss (vertical bone loss) was judged at the mesial and distal side of each implant on the panoramic radiographs. No apparent bone loss was observed at 48 sites (score 0, 60%). Slight bone loss was seen at 24 sites (score 1, 30%), and serious bone loss was seen at 8 sites (score 2, 10%). No severe bone loss (score 3) was detected. Mean changes in bone height (horizontal bone loss) after loading of the implants in the augmented mandible are shown in Table 2. The difference in bone height after prosthetic loading of the augmented

Satisfaction with the denture Satisfaction with the denture was assessed using a validated self-administered questionnaire*l consisting of items that focused on the upper and lower denture separately, and on specific features related to aesthetics, retention, and functional comfort. Each item was presented on a five-point rating scale on which the patient had to indicate to what extent she was satisfied with the new dentures.

Table 1 ~ Mean (SD) values of plaque index, gingiva index (possible scores 0, 1,2, 3) and pocket

Plaque index Bleeding index Gingiva index Pocket depth

bleeding index, depth (mm)

Mean

(SD)

0.65 0.25 0.45 2.7

(0.8) (0.4) (0.8) (0.9)

Reconstruction

of resorbed

mandible

with bone

grafts

and endosseous

implants

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Table 2 - Mean (SD) bone height changes in mm (horizontal) after augmenting the mandible measured at five sites: Site 1 = midline; Site 2, 3 = between central and lateral implants; Site 4, 5 = 10 mm distal to the lateral implants Site

Preoperative

Preload

2

11.7 1.7* -**

3

-**

4

-**

5

-**

21.6 4.3 21.1 4.8 20.6 4.8 19.6 3.3 18.3 3.3

1

*The preoperative bone height in radiograph corrected for possible **On the preoperative panoramic the sites of the measuring points

Evaluation 20.9 4.2 20.3 4.9 19.8 4.3 18.4 3.0 17.6 3.2

Table 3 - Percentage satisfaction with dentures in general questionnaire after treatment with dental implants in combination with augmentation of the mandible Score

Percentage patients

How satisfied are you in general with your dentures?

I 2 3

100

How satisfied are you with your upper denture?

1 2 3

70 30

How satisfied are you with lower denture‘?

1 2 3

100

How satisfied are you with the appearance of your dentures?

1 2 3

90 10

How satisfied are you with the retention of your dentures?

I 2 3

90 10

How satisfied are you with the functional comfort of your lower dentures?

1 2 3

80 20

How satisfied are you about with your dentures?

I 2 3

100

1 2 3

90 10

your

eating

How satisfied are you about speaking with your dentures? 1 = (very)

satisfied;

2 = neutral;

and 3 = (very)

dissatisfied.

in height 0.7 0.8 0.8 0.5 0.8 0.8 1.2 1.2 0.7 0.8

the symphyseal area was measured on a lateral magnification. radiograph implants are still absent, so finding was not reliable and so not done.

mandible (site l-5) was minimal. Five of the patients had been followed up for more than 30 months (mean 38), and live for 30 months or less (24 months). Bone loss in the first group was more (mean bone loss at sites 1-5 = 0.9 mm) than that in the second group (mean bone loss at sites l-5 = 0.7 mm) but these differences were not significant (t-test, P < 0.05)for any site. The results of the satisfaction questionnaire are shown in Table 3. In this table the live-point scale has been reduced to a three-point scale: (very) satisfied, neutral, (very) dissatisfied.

Question

Change

of

DISCUSSION

The survival rate of the implants in this study is simular to results of endosseous implants placed as a solitary procedureZ2 and results of implants in combination with a ridge augmentation.23,24 The scores for plaque, bleeding, gingiva index and pocket depth are comparable to the results reported by Batenburg rt ~1.‘~Their study comprised a group of edentulous patients with a mandibular bone height of between 12 and 18 mm and treatment with two endosseous implants without an augmentation procedure. No lip and chin dysaesthesia was observed postoperatively, which is contrary to other studies that have reported considerable dysaesthesia of the mental nerve after augmentation procedures.” An explanation for this could be the 5 mm distance between the mental foramen and the vertical cut of the osteotomy. This is used as a safety margin to protect the mental nerve. Peri-implant bone loss (vertical bone loss) is very moderate which suggests that the resorption is corresponding to that of implants placed in edentulous mandibles that are not augmented.i7 Studies describing augmentation procedures using onlay techniques report more peri-implant bone 10ss,?~possibly because our interposition of the bone graft leaves the upper part attached to the periosteum, so securing the blood supply. Comparison of loss of bone height (horizontal bone loss) of the augmented mandible shows fewer changes than augmentation studies without endosseous implants.” There is also less bone loss than reported by McGrath et al. ‘I in which augmentation (onlay technique) was combined with implants. A reason for this could be the 3-month period between the first operation (augmenting the mandible) and the insertion of the implants. During this period part of the initial resorption of the augmented mandible takes place. In this study this resorption is not considered, while in other studies,“,?” in which simultaneous insertion of the implants takes place, this resorption is included in the evaluation. The follow-up period at this moment is still limited and future evaluation of the surgical technique will teach us to what extent this amount of bone loss continues.

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The results show that patients are well satisfied after treatment with dental implants and satisfaction is comparable with earlier studies.28 Disadvantages of this procedure include the three interventions and the morbidity of the donor area. From a larger survey, analysing the effects of taking a bone graft from the iliac crest,29 we conclude that long-term morbidity of the donor area is low. Four endosseous implants placed in an augmented mandible provide a solid base for the support of an overdenture. The method described combines the benefits of two techniques: providing sufficient bone volume and inserting endosseous implants of maximal length to provide retention and stability for the lower denture. Short-term evaluation shows that conservation of bone height gained seems possible. Long-term results and comparison with other techniques such as the insertion of short implants30 or placement of a transmandibular implant31 must lead to it being the treatment of choice for severely resorbed mandibles. Use of short implants, combined with an implant retained overdenture, seems to be promising30 but long-term follow-up studies are still not available. A prospective, clinical trial of these three techniques (short implants, augmentation combined with implants, and transmandibular implant) in which not only clinical performance but morbidity, satisfaction of patients, and cost effectiveness as well will be carried out in our department. In addition, reIinement of measuring techniques with regard to bone remodelling processes should be one of the research targets in the near future. References 1. Atwood DA. Reduction of residual ridges: a major oral disease entity. J Prosthet Dent 1971; 26: 266-279. 2. von Wowern N. Bone mineral content of mandibles: normal reference values- rate of age related bone loss. Calcif Tissue Int 1988; 43: 1933198. 3. Tallgren A. The continuing reduction of the residual alveolar ridge in complete denture wearers; a mixed longitudinal study covering 25 years. J Prosthet Dent 1972;27:120-132. 4. McCord JF, Grant AA, Quayle AA. Treatment options for the edentulous mandible. Eur J Prosthodont Restor Dent 1992; 1: 19-23. 5. Naert EG, de Clercq M, Theuniers G, Schepers E. Overdentures supported by osseointegrated fixtures for the edentulous mandible: a 2.5-year report. Int J Oral Maxillofac Imp1 1988; 3: 191-196. 6. Johns RB, Jemt T, Heath MR, Hutton JE. A multicenter study of overdentures supported by Branemark implants. Int J Oral Maxillofac Imp1 1992; 7: 5 13-522. 7. Friberg B, Jemt T, Lekholm U. Early failures in 4,641 consecutively placed Branemark dental implants: a study from stage 1 surgery to the connection of completed prostheses. Int J &al Maxillbfac Imp1 1991; 6: 142-146.. 8. Tolman DE. Keller EE. Management of mandibular fractures in patients with endosseous implants. Int J Oral Maxillofac Imp1 1991; 6: 427436. 9. Mason ME, Triplett RG, Van Sickels JE, Pare1 SM. Mandibular fractures through endosseous cylinder implants:report of cases and review. J Oral Maxillofac Surg 1990; 48: 311-317. 10. De Koomen HA, Stoelinga PJW, Tideman H. Interposed bone graft augmentation of the atrophic mandible. A progress report. J Maxillofac Surg 1979; 7: 129-135.

11. McGrath CJR, Schepers SHW, Blijdorp PA, Hoppenreijs TJM, Erbe M. Simultaneous placement of endosteal implants and mandibular onlay grafting for treatment of the atrophic mandible. Int J Oral Maxillofac Surg 1996; 25: 184188. 12. Cawood JI, Howell RA. A classification of the edentulous jaws. Int J Oral Maxillofac Surg 1988; 17: 232-236. 13. Van der Wal KGH, Visscher JGAM, Stoelinga PJW. The autogenous inner table iliac bone graft. J Maxillofac Surg 1986; 14: 22-5. 14. Batenburg RHK, Reintsema H, van Oort RP. Use of the final denture base for the intermaxillary registration in an implant supported overdenture. Int J Oral Maxillofac Imp1 1993; 8: 205-207. 15. Mombelli A, van Oosten MAC, Schtirch E, Lang NP The microbiota associated with succesful or failing osseointegrated titanium implants. Oral Microb Immun 1987; 2: 1455151, 16. Silness J, Lo& H. Periodontal disease in pregnancy.11. Correlation between oral hygiene and periodontal condition. Acta Odont Stand 1964; 22: 121-135. 17. Geertman ME, Boerrigter EM, Van Waas MAJ, van Oort RP. Clinical aspects of a multicenter clinical trial of implantretained mandibular overdentures in patients with severely resorbed mandibles. J Prosthet Dent 1996; 75: 194204. 18. Meijer HJA, Steen WHA, Bosman F. Standardized radiographs of the alveolar crest around dental implants in the mandible. J Prosthet Dent 1992; 68: 3 18-321. 19. Kwakman JM, Van Waas MAJ, Hagens M, Voorsmit RACA. Bone level changes in patients with transmandibular implants. J Oral Maxillofac Surg 1997; 55: 15-18. 20. Powers MP. Bosker H. Van Pelt AWJ. Dunbar N. The transmandibular implant: from progressive bone loss to controlled bone growth. J Oral Maxillofac Surg 1994; 52: 904910. 21. Vervoorn JM, Duinkerke ASH, Luteijn F, and Van de Poe1 ACM. Assessment of denture satisfaction. Community Dent Oral Epidemiol 1988; 1636416367. 22. Chao L, Meijer HJA, van Oort RP, Versteegh PAM. The incomprehensible successof the implant stabilised overdenture in the edentulous mandible: a literature review on transfer of chewing forces to bone surrounding implants. Eur J Prosthodont Restor Dent 1995; 325553261. 23. Gratz KW. Sailer HF. Oechslin CK. Results after interforaminal mandibular sandwich procedure in combination with titanium screw implants. Oral Maxillofac Surg North Am 1994; 6: 689-698. 24. Keller EE. Tolman DE. Mandibular ridee auementation with simultaneous onlay iliac bone graft and endosseous implants: A preliminary report. Int J Oral Maxillofac Imp1 1992; 7: 176-184. 25. Batenburg RHK, van Oort RP, Reintsema H, Brouwer TJ, Raghoebar GM, Boering G. Overdentures supported by two IMZ implants in the lower jaw. A retrospective study of periimplant tissues. Clin Oral Imp1 Res 1994; 5: 207-212. 26. Vermeeren JIJF, Wismeijer D, Van Waas MAJ. One-step reconstruction of the severely resorbed mandible with onlay bone grafts and endosteal implants. Int J Oral Maxillofac Surg 1996;25: 112-115. 27. Meijer HJA, Steen WHA, Bosman F, Wittkampf ARM. Radiographic evaluation of mandibular augmentation with prefabricated hydroxylapatite/tibrin glue implants. J Oral Maxillofac Surg 1997; 55: 1388144. 28. Boerrigter EM, Stegenga B, Raghoebar GM, Boering G. Patient satisfaction and chewing ability with implant-retained mandibular overdentures: a comparison with new complete dentures with or without preprosthetic surgery. J Oral Maxillofac Sure 1995: 53: 1167-l 173. 29. Kalk WI, Raghiebar GM, Jansma J, Boering G. Morbidity from iliac crest bone harvesting. J Oral Maxillofac Surg 1996; 54: 14241429. 30. Triplett RG, Mason ME, Alfonso WF, McAnear JT. Endosseous cylinder implants in severely atrophic mandibles. Int Oral Maxillofac Imp1 1991; 6: 264269. 31. Bosker H, Van Dijk L. The transmandibular implant: a 12-year follow-up study. J Oral Maxillofac Surg 1989; 47: 442450.

Reconstruction

The Authors C. Stellingsma DDS H. J. A. Meijer DDS, PhD Maxillofacial Prosthodontists G. M. Raghoehar MD, DDS, PhD R. H. K. Batenhurg DDS Oral and Maxillofacial Surgeons Department of Oral and Maxillofacial Maxillofacial Prosthodontics

of resorbed

mandible

University Hospital PO Box 30.001 9700 RB Groningen The Netherlands Correspondence Surgery

and

with

bone grafts

and endosseous

implants

Groningen

and requests

Paper received 3 February Accepted 1 April 1997

for offprints

1997

to Dr C. Stellingsma

295