This blog illustrates the use of optical scanning and digital work flow in providing an immediate denture for a patient due to the catastrophic failure of a bridge.
A patient attended a practice on a Wednesday afternoon. The patients main complaint was of a fracture of an old long span bridge which had two pier abutments with recurrent un-restorable caries (Figure 1). To further compound the problem the patient had a speaking engagement in the coming days.
The patient was keen on obtaining a suitable interim replacement for the now defunct bridge. Once appropriate consent was obtained the clinician discussed the case with technical colleagues and it was decided to take a digital impression of the the maxillary arch with the bridge in-situ and of the opposing arch (Fig. 2 & 3). A digital occlusal record was also obtained (Fig 4.). Colour data was also obtained for appropriate colour matching of the planned prosthesis.
The above scans were then ‘digitally poured’ up at the clinic and converted to a stereolithography (STL) file using Autodesk Meshmixer 3D modelling software, the resulting data was emailed to the lab illustrated in Figures 5 & 6.
Laboratory ConstructionThe technician printed the 3D models using SLA technology (Stereolithography printing using an UV laser with a wavelength of 405nm). The optical impression bite scan and the STL file generated was used to get the vertical, horizontal and translational occlusal movements dialled in electronically into the models before printing. Digital extraction of the broken roots and the bridge was also done in the CAD software (computer aided design).
Once the models were 3D printed a conventional PMMA acrylic immediate denture was constructed to mimi as closely as possible the previous bridge. This was delivered the next day.
Once the carious roots had been extracted the immediate denture was fitted Friday morning. A limited amount of adjustment was required and a good colour match was evident. A follow up appointment two weeks later revealed no concerns-the extraction sockets were healing well with no complaints relating to the denture. The patient subsequently returned for discussions with regards to the definitive prosthesis.
This case illustrates the use of digital technology in aiding the provision of a commonly provided treatment plan where fixed prosthodontics has failed and a patient requires an immediate denture. It could be argued that the treatment could have been easily provided with some alginate impressions and a shade with an occlusal registration in the conventional manner. This is true but some consideration for the urgency of the problem, the reduction in turnaround as the impressions did not need to be delivered, accuracy of the shade and the scan which does not ‘deform’ in transit resulting in inaccuracies are all noteworthy considerations.
R.N.Nair, BDS, MDentSci , MFDSRCSEdin, MFDRCSIrel Postgraduate Tutor
Midland West Postgrad Dental Foundation