Classification based on the positions of the screw assembly.
Screw assemblies in two adjacent abutments
This method may be used to connect two cast crowns, two roots or a cast crown and a root.
Screw assemblies in the removable section of a combined prosthesis
The fixed part of the prosthesis is cemented in the usual manner and the removable part is then screwed to the fixed component. In this way it is possible to construct a prosthesis on divergent abutments.
Screw assemblies in the removable section of a combined prosthesis.
Classification based on location of the screws.
The dental screws may be placed in the following locations
3. Cast Crown.
Inner coping of implants where the outer section of prosthetic component will be attached.
Screws are placed in metal structures when insertion and removal will be required.
Screws are inserted within the crown contour using the correct reaming or tapping instruments. Once they are in place, the screws may provide retention for a restorative material which in turn may become a core. Of the various types of screw used in this way, the following are the examples:
– TMS pin
– Reten pin
Occasionally, screws are used to add to the retention of a casting. The divergent screws pass through threads in the Casting into the underlying dentin. A screw may act as a retainer for a resin veneer cast crown.
Intra root screws
A screw is inserted into the root preparation to retain a prosthesis such as a cast crown; a retaining device covers the screw. The following systems are among those that are available.
Kurer Crown anchor system
Post and core system
Kurer press stud
The Kurer press stud has a male part on its head. The female part may be simply placed over the male after the stud shaped projection has been screwed into the prepared root.
In addition to the classification I mentioned in the first post about Dental Screws in Prosthodontics and Dental Implant Prosthodontics, here is the second classification of Dental Screws that may be inserted in the oral cavity.
Classification based on methods of machining the internal thread.
There are two ways of machining the internal thread. The internal thread may be cut in the internal surface of a tube, and the external thread fits this precisely. Alternatively, the internal thread may be cut in the internal surface of a metal part of the prosthetic component of dental implants.
Screw retained outer structure where the prosthetic component of dental implants will attach.
Dental screws are used to attach abutments to implants and prostheses to abutments. Screws designed for abutment to implant attachment have different mechanical properties compared to screws used to attach prosthesis to abutment. The following is a general description of dental screws.
There are four divisions of available bone based on width, height, length, angulation and crown height in the edentulous site.
1. Division A edentulous ridge offer abundant bone in all dimensions.
2. Division B bone may provide adequate width for narrower, small diameter root form endosteal implants.
3. Division C edentulous ridge exhibits moderate resorption and presents more limiting factors for predictable endosteal implants.
4. Division D edentulous ridge basal bone loss and severe atrophy, resulting in dehiscent mandibular canals or a completely flat maxilla.
Misch CE: Dental Implant Prosthetics, Mosby Inc 2005
Angulated Abutment is an innovative component designed to adjust access hole position, prosthetic screw angulation and improve cosmetics. Before the development of Angled Abutments, if screws and access holes were positioned jutting through the labial aspect of an anterior tooth, there were basically three options:
1. The double casting technique.
2. Unsightly patch marks which closed the access holes after final insertion.
3. The combination of implant supported posts securing a crown and bridge type prosthesis.
Implant Angulated Abutments
Factors to Consider in Dental Implant Treatment
1. How does the patient feel about surgery?
2. Is the patient prepared to pay the costs involved in implant theraphy?
3. Does the patient have sufficient bone to place dental implants? Bone grafting may be required and this could be a barrier to treatment.
4. If bone grafting is required, is the patient prepared to accept this?
5. Is the patient prepared to accept the burden of maintenance associated with implant retained prosthesis?
Implant Analog for Impression
Tools for titanium machining are used for drilling of titanium abutment. The fixture must be well fixed and correct RPM must also be checked before drilling. There must be adequate cooling so that overheating of abutments is prevented.
Titanium Implant Abutment Component
Torque wrench was used to to achieve the desired dental implant bone contact and avoid too much compression on the bone that may lead to necrosis of the implant bed.
Implant was placed mesial to tooth number 22 (FDI Two-Digit Notation).
Following dental implant surgical sequences and protocols, drilling should follow the desired RPM with copious irrigation preferably with an NSS refrigerated the night before surgery.