Alveolar distraction before insertion of dental implants in the posterior mandible

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Abstract

We investigated the efficacy of alveolar distraction for reducing crown height:implant length ratio in the posterior mandible. Ten alveolar distractions were done in seven patients. The pre-distraction ratio of required crown height to bone height available for implantation was in all cases ≥1. Two implants were placed in each distracted area (total 20 implants). Before distraction, the mean (SD) predicted crown height was 12.8 (2.1) mm; mean bone height available for implantation was 7.8 (1.5) mm. After distraction and insertion of implants, mean crown height was 8.1 (1.9) mm, and mean implant length was 11.3 (1.9) mm. Before distraction, the mean required crown height:available bone height ratio was 1.7 (0.3); after distraction and insertion of implants, the mean crown:implant ratio was 0.7 (0.2) (P<0.0005). Alveolar distraction is effective for increasing the height of the alveolar ridge in the posterior mandibular region, and should be considered when the height of the predicted crown that is required is greater than or equal to the maximum height of bone available for implantation.

Section snippets

INTRODUCTION

One of the most common problems in oral implantology is insufficient bone height between the alveolar ridge and the dental canal, as a result of mandibular atrophy from edentulism. The edentulous mandible atrophies progressively, losing up to 50% of its original volume,1 and in severe cases this atrophy affects both the alveolar ridge and the mandibular basal bone.2 Ulm et al.3 reported that the mandible loses 60% of its bone volume during progressive atrophy, and that most is lost in the early

PATIENTS AND METHODS

Seven patients (5 men and 2 women; mean age (SD) 43 (7) years) were studied. All patients had unilateral (n=4) or bilateral (n=3) partial edentulism in the posterior mandible, with varying degrees of alveolar atrophy. None of the patients had teeth missing from the anterior mandible, or teeth remaining posterior to the edentulous sites. A total of 10 alveolar distractions were done, and 20 implants inserted (16 International Team for Implantology Straumann, Switzerland, and 4 Frialoc, Friadent,

RESULTS

The mean predicted height of crown required (as estimated before distraction) was 12.8 (2.1) mm. The mean available height of bone was 7.8 (1.5) mm. After distraction and implantation, the mean height of the crown was 8.1 (1.9) mm, while the length of the implant was 11.3 (1.9) mm. The mean ratio of predicted crown height to bone available before distraction was 1.7 (0.3) (Index A), and the mean ratio of crown height to length of implant after distraction was 0.7 (0.1) (Index B). These two

DISCUSSION

We used two measurements of available bone. Before distraction we used CT to measure the height available between the alveolar ridge and the dental canal. This measurement is obtained routinely in all patients who are being considered for dental implants. After distraction, however, we used panoramic radiography to calculate implant length (total bone height minus 1 mm), because of the high cost of a second CT and the higher dose of radiation it would entail. We consider that the two

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