Bone Manipulation in the Maxilla (not including distraction osteogenesis)

Introduction

Severe alveolar deficiencies in the Maxilla can prevent ideal implant placement in terms of a good aesthetic outcome, and sound biomechanical support for the eventual occlusion. To quote Sethi and Kaus: ‘Predictable methods to treat osseous ridge deficiencies are therefore a necessity to achieve treatment outcomes comparable to the results seen for the uncompromised alveolar ridge. Several ridge augmentation techniques, including bone-spreading, bone grafting, and guided bone regeneration, have been described in the literature’.

This assignment aims to explore the relevance of bone manipulation in increasing width, height and bone density of the maxillary alveolus, and to establish its predictability.

Bone Manipulation to increase width of available bone

Sethi and Kaus1 in a study of 449 implants placed in 150 patients over 93 months, describe a technique for expanding the width of available bone by ridge-splitting. In any situation where the patient has a thin ridge of adequate height and two cortical plates separated by spongy bone, the ridge can be split and expanded using a sequence of round and D-shaped osteotomes. Simultaneous placement of implants between the expanded cortical plates prevents relapse of the achieved expansion. A remote-palatal flap is used to ensure soft-tissue closure over the expanded ridge. Using this technique they demonstrated a predicted 5-year survival of 97%. They concluded that predictable expansion of a thin maxillary ridge with separate cortical plates could be achieved using this method.

Bone Manipulation to increase height of available bone

In 1994, Summers3 described a technique of placing implants in the maxilla using graded osteotomes rather than drills. The reduced density of bone in the maxilla, especially the posterior maxilla makes this possible. The technique has the advantage that bone density around the osteotomy thus formed is increased by compaction. Summers developed this technique to increase available bone height in the posterior maxilla by using osteotomes to elevate the floor of the sinus. In 2004, Toffler2 published a prospective study of 276 osteotome-mediated sinus floor elevations in 167 patients completed between August 1995 and February 2003. Using a well-documented methodology, he achieved a mean increase in the height of available bone at the implant sites of 3.8mm. He was able to demonstrate an overall survival rate of 93.5% over an average loaded period of 27.9 months. He further demonstrated that greater success could be predicted with increased residual bone height before the procedure, as this gave better primary stability to the implant.

Bone Manipulation to increase density of available bone.

As already stated Summers noted that his technique of using graded osteotomes rather than drills had the advantage of compacting bone around the osteotomy. J Hahn4 in his paper on the clinical uses of osteotomes notes that in addition to bone being visco-elastic, and therefore capable of compression; no heat is generated using osteotomes, and therefore the quality of bone surrounding the osteotomy is preserved. A further advantage of using osteotomes is the greater tactility of the technique. This allows the operator to gauge the initial density of the bone, when making the osteotomy. However he publishes no results to back his clinical observations and experience.

Discussion

Bone Manipulation techniques are relatively straight-forward in comparison to bone grafting or guided bone regeneration. Some implant systems including Ankylos have matching osteotomes, which make preparation of osteotomies for specific sizes of implants even easier, and therefore more predictable. Chiapasco et al.5 reviewed three studies between 1997 and 2006 encompassing 392 patients treated with ridge-splitting and bone expansion, and the immediate placement of 753 implants. Restoration with fixed or removable prostheses was started 3-6 months later. Patients were followed up from 6 to 68 months after prosthetic loading. Success rates of the surgical procedures ranged from 98% to 100%. Fracture of the buccal plate was the most common complication. Survival rates of implants ranged from 91% to 97.3%, and success rates from 86.2% to 97.5%.

These figures when taken in conjunction with Sethi and Kaus figures suggest that bone manipulation is a reliable and relatively non-invasive technique for increasing the volume and density of available bone. Success rates of implants placed in expanded bone are similar to those placed in un-reconstructed bone. The success rates of bone-manipulation techniques are much less variable than those of bone-grafting techniques. The degree of surgical intervention is reduced in comparison with other techniques for increasing the volume and density of available bone.

Limitations of the techniques include the need for separate cortical plates when ridge-splitting, (and therefore indicate a CAT scan of the proposed site), and that in the maxilla ridge-splitting may lead to increased buccal inclination of simultaneously placed implants, making restoration more difficult in the aesthetic zone.

References

  1. Sethi A, Kaus T. Maxillary Ridge Expansion with Simultaneous Implant Placement: 5-Year Results of an Ongoing Clinical Study. Int J Oral Maxillofac Implants. 2000;15:491-499.
  2. Toffler M. Osteotome-mediated sinus floor elevation: a clinical report. Int J Oral Maxillofac Implants. 2004;19:266-73.
  3. Summers RB. The Osteotome technique: Part 3 – Less invasive methods of elevating the sinus floor. Compendium. 1994:15:152, 154-156,158.
  4. Hahn J. Clinical Uses of Osteotomes. J Oral Implantology. 1999;25(1):23-9.
  5. Chiapasco M, Zaniboni M, Boisco M. Augmentation procedures for the rehabilitation of deficient edentulous ridges with oral implants. Clin Oral Impl. Res. 17(Suppl. 2), 2006;136-159.