The radiographic assessment of dental implant treatments : a pilot study on two-implant supported overdenture cases

Abstract

The introduction of the osseointegrated implant has revolutionised the way in which operators consider treating patients who are completely or partially edentulous, by providing an option which is more stable and less destructive to adjacent teeth than conventional modalities of treatment. In recent years the use of dental implants has become increasingly popular, with practitioners becoming aware of the results which may be achieved. Patients who have had marked resorption of their alveolar processes can be provided with comfortable, secure prostheses, subsequently improving their confidence. Periodic radiographs have been found to be the best non-invasive means of assessing the marginal bone around an implant. In a retrospective pilot study, 24 patients provided with overdentures retained by two Calcitek Integral implants (Calcitek, Carlsbad, CA) had periodic radiographs taken, using a standardised projection technique, over a five year period (placement, six months, one year, two years, three years, four years, five years). These were then digitised through a scanner and imported into an implant analysis programme, the Radiographic Analysis of Dental Implants (RADÐ (Biotek Pty Ltd, Adelaide, Australia). The marginal bone immediately adjacent to the implant on the mesial and distal of the implant was then analysed using this programme. After calibration within the programme (using known dimensions), three components of the 'defect' adjacent to the implant were calculated - horizontal width, vertical height and average area. The patient population was then separated into subgroups according to the type of overdenture retention system provided - ball attachment, O-ring or Dolder bar. The study found that the RADI programme was able to provide measurements and average areas within the same magnitude as other studies have - defect (horizontal) width 0.50 - 1.70 mm, (vertical) height 0.40 - 1.60 mm and average area 0.20 - 1.0 mm2 for the whole group. These are similar to the results of other studies and meet one of the criteria for the clinical success of an implant proposed by Smith and Zarb (1939). Comparisons of the denture retention unit indicated that the ball attachment and O-ring attachment were statistically similar to each other, showing gradual increases in the dimensions of each component of the defect over the five years. These were found to be statistically significantly different to the Dolder Bar (p<0.05), which showed minimal changes to the bone over the five years. However, this differed to the findings of Bergendal and Engquist (1998), who found that ball attachment and bar retained overdentures followed similar patterns of changes in the bone. This study showed that digitised radiographs of dental implants can be used to quantitatively assess the status of the marginal bone around an implant. These images may be obtained by converting plain film radiographs to digital images or by using direct digital imaging radiography. However, in order to gain a more accurate assessment of a patient pool, the population needs to be larger than a pool of 24, The radiographs ideally must be taken at regular intervals, using a standardised, reproducible projection technique.