Case Study 1
This patient was referred to the Practice by Dr Dave Simmons (Chevron Island). Just over thirty years ago he had a hemi maxillectomy and his existing obturator was leaking, the chrome clasps had also broken away. The laboratory work was carried out by Steve Griffin (Apex Dental Laboratory) and was technically difficult as the bulb needed to be hollow to significantly reduce weight. We had a very appreciative patient after the appliance was fitted.
He had managed with his old obturator reasonably well for many years but over the last six months there was loss of the seal between the bulb and surrounding soft tissues which lead to problems when eating and drinking.
Most of this loss of the fit was caused by his aggressive cleaning with regular tooth paste which is far too abrasive for acrylic resin.
When the last chrome clasp fractured off the chrome plate there was no real retention for the prosthesis causing more problems . With an appliance like this the retention is obtained almost completely from clasping on the remaining teeth and a lot of force is put on these teeth. To prevent the future fracturing of the clasp units again it was necessary to reduce the occlusal surfaces inter proximally to allow for quite thick minor connectors.
The impression of the defect was made by progressively adding to the old prosthesis to obtain slight pressure on the displacable tissues and only light contact on the other tissue.
Normally many adjustment appointments are required for these prosthesies but luckily he was very comfortable after two adjustment appointments.
Patients wearing such prosthesies need to be seen every six months and motivated to have above average oral hygiene as loss of the remaining teeth from disease would cause significant difficulties in wearing the prosthesis.
Case Study 2
Implant Supported Bridgework
This patient was referred to the Practice by Dr Peter Barry (Biggera Waters). The patient had failing bridgework from the upper left second pre molar to the upper right second pre molar.
Five teeth supporting this bridgework were extracted and subsequently a ten unit one piece porcelain to metal bridge was fitted.
The work up for placement of the fixtures revealed that it would not be possible to position regular fixtures so that the large fixture screws retaining this bridge would exit through the lingual confines of the anterior teeth.
In the past, I have resorted to using small abutment screws to retain the prosthesis on to various types of abutments which are screwed into the fixtures by the larger screws.
Small abutment screws have caused me many problems over the last twenty five years and I only use them as a last resort.
With the introduction of the co-axis fixtures by Southern Dental, prosthesis such as this one can be retained by large screws which allow for easy and quick removal for maintenance of the bridge over the long term.
Very careful planning and surgical techniques are essential for using these fixtures as it is not only necessary to have the body of the fixture in the pre-planned position but it also has to be rotated so that the access screw alignment is correct.
In this case Dr. Darryl Beresford did the surgery and the result is evidence of his fine work.
Our ceramist, Yasushi Saito did the laboratory work and once again the photos reveal the excellence of his work.
The best choice of material for implant supported long span fixed bridgework is porcelain fused to a gold alloy. No other combination of materials can match the appearance of custom fired porcelain and the long history of success with the use of gold alloys is definitely unsurpassed when compared with other options.
All implant supported crowns and bridges need to be removable. This is required because of the need to maintain the prosthesis as well as the surrounding tissue.
I have fitted many full arch restorations supported by implants over the last twenty five years and using small abutment screws to retain the prosthesis onto abutments on the implants has resulted in may problems with removal and refitting of these bridges.
Abutment screws can:
- Break when refitting the bridgework
- Cause loss of the threading in titanium abutments
- Lock in position and need to be but out
- Cause unacceptable bulkiness in the lingual contours of the crowns
- Contribute to the fracturing of the fine tip of the screw driver
- Distort in the slot or hex so that the screw driver cannot engage
- Cause a frequent concern that such a small object can be dropped and possibly inhaled by the patient.
In short, I don’t like to use them.
For this reason we plan to screw the prosthesis directly to the fixture head and use the larger crew which has a lot fewer problems.