A Composite of Overdenture Applications
The overdenture treatment is a good alternative to a fixed, bone-anchored prosthesis. This treatment modality offers distinct advantages to many patients who would benefit from two or three carefully placed implants. Where an unstable full denture is converted to, or replaced by, an implant-supported overdenture, function, fit and stability can be greatly improved. When two or more implants are placed, bone resorption is decreased significantly.
Esthetics can be improved when soft and/or hard tissue defects exist by modifying the dimensions of the acrylic resin. Facial and lip support can be improved by these changes in the design of the prosthesis.
Often, economics dictate a patient's choice of treatment. Since the overdenture prosthesis requires a minimum of two implants, surgical and hardware costs are reduced.
With fewer abutments and increased access, the overdenture works well for patients with limited hygiene maintenance ability. In some cases, phonetics and speech are impaired by the space between the alveolar ridge and the fixed bone-anchored bridge. The overdenture is a good alternative when these problems are present.
In a situation where six fixtures are placed and three fail to osseointegrate, the remaining three can support an overdenture. This can work' as a permanent solution or as an interim prosthesis while new implants are placed.
Hader Retained Maxillary Overdenture Supported by Core-Vent Implants
The Core-Vent implant-supported Hader bar (APM, Stern Gold) offers many alternatives in treatment planning. It is clearly indicated where the patient does not want a fixed implant-supported bridge and feels comfortable with a clip-secured removable overdenture. The Hader system is a cost-effective treatment modality. This plan requires a minimum of two implants, in contrast to the suggested five or six implants for the traditional fixed bone-anchored bridge.
The finished Hader bar weighs approximately six to ten penny weight (Troy weight), while the traditional fixed frame is usually 20 to 30 penny weight. This system offers the option of rotation of the overdenture when the bar is fabricated straight (Figs. 5-1 and 5-2).
With more than two implants and a bar that is not continuously straight, there is minimal movement, increased lateral stability and no rotation of the overdenture. The latter, however, does apply added stress to the implants and remodeling bone. The minimal vertical requirement (3.5 mm), and the fact that Core-Vent sleeves and Hader bar patterns are castable, make this com-bination very compatible.
This master cast shows three Core-Vent brass replicas in the anterior of the maxilla.
Casts are mounted on a semi-adjustable articulator using conventional procedures.
Core-Vent components include: the brass replica (# BTF), plastic castable sleeve (# PSG), and titanium prosthetic screw (# TSF).
The plastic sleeve is secured in place with titanium screw. DO NOT overtighten, as the plastic sleeves will crack.
The Hader clip bar ensemble consists of a plastic castable rider bar, plastic clips, and metal clips.
Using the articulated counter cast as a guide, the bar is cut to the vertical height with a thin disc. The bar must not interfere with the setup or the arrangement of teeth if at all possible.
Any irregularities at the tissue level can be scalloped with a bur.
The sized bar is placed between the plastic sleeves and held in place with utility wax. The plastic bar should be kept parallel with the ridge.
Small increments of DuraLay are painted around the plastic sleeve incorporating the plastic bar. DO NOT allow DuraLay resin to flow beyond the margin of the plastic sleeve. After resin has polymerized, it should be smooth-finished to a thickness of 1.5 mm.
Any portion of the sleeve which now rises above the plastic Hader bar pattern should be cut level with the bar.
Thin areas and voids are thickened and smoothed using crown and bridge wax. When the bar-sleeve pattern is complete, it should be checked for a perfect passive fit. If each plastic sleeve does not fit with total accuracy, the offending area must be sectioned and re-attached.
The pattern can now be sprued and readied for investing. One twelve gauge sprue between each section and an eighteen gauge closed vent sprue at each distal are adequate for successful casting. The plastic bar is now invested following recommended manufacturer's instructions for base alloy metals (Rexillium III, Jeneric Pentron).
After casting and cooling, the bar is retrieved and sandblasted. The metal is finished and polished according to standard crown and bridge procedures.
It is recommended that brass replicas be used to protect the margins on the casting.
Prosthetic screws are placed through the sleeves and secured to the cast. Using an ultra thin disc, the screws are lightly scored at the height of the sleeve. The screw is removed from the cast and cut through at this height. Since the slot for the screwdriver has been cut off, a new slot must be cut in.
This is a view of the base alloy Core-Vent-supported Hader bar with two plastic clips.
NOTE: Sometimes the space between screws will not accommodate a full clip. The plastic clips can be cut to size.
This Hader bar has plastic riders blocked out for the fabrication of a pink Triad material baseplate. The base is light cured and finished to proper peripheral borders.
Teeth (Bioform lPN, Dentsply) are set and tried in for esthetics and occlusal harmony. The Hader bar is checked for accuracy.
After verification of casting fit and denture setup, the restoration is flasked and boiled out in the normal manner.
Metal riders are chosen for the finished restoration, and two are placed in the large area of the bar. Since the metal riders cannot be shortened, no rider is placed in the smaller section.
NOTE: Plastic riders are easier to replace chairside and can be cut for smaller areas, but are not adjustable. Metal riders can be adjusted and have a longer life, but they are more difficult to replace due to their means of retention.
Since the bar on the cast causes many undercuts, it is necessary to block out at this time. A mixture of one-half plaster and one-half ordinary pumice is used to facilitate an easy breakout. The plaster/pumice mix is brought at least half way up the Hader clip. This extra room will allow the clinician the needed space to adjust the clip as necessary. The cast and prepared bar are painted with a separating medium and packed in the conventional manner using Lucitone 199 and cured at 1650 F for nine hours.
After curing, the restoration is retrieved and remounted on the articulator to refine occlusion and eliminate processing errors.
The Hader bar is carefully removed from the tissue side of the denture, and the restoration is finished and polished.
The tissue side of the denture shows two acrylic-retained metal Hader riders. Note the edge of the metal riders. The retention can be increased or reduced by adjustment with a thin instrument.
The finished Hader-retained Core-Vent implant-supported overdenture ready for delivery.
The Branemark System Clip Bar Kit follows the same protocol as the Core- Vent System with the exception that gold cylinders are used in place of the castable sleeves and the alloy of choice must have a melting temperature below 2350° F.