Written by Samuel M. Strong, DDS Thursday, 30 April 2009 19:00
The totally edentulous patient has several options for implant treatment today, including both fixed and removable solutions. While fixed prostheses may appear more attractive by restoring the patient closer to a truly “dentate” status, many patients are also favorable to receiving a removable appliance.1-4 This removable choice has become increasingly popular during the recent global financial downturn.
BACKGROUND: REMOVABLE VERSUS FIXED OVERDENTURES
In most instances, the removable implant retained overdenture can be done for significantly less expense than a comparable fixed restoration with a metal framework that bolts directly into the implants, or is cemented to implant abutments.5 Fabrication and fitting such a metal framework, in addition to the cost factor also adds a layer of significantly greater technical expertise required for successful case completion.6
The long-term repairability and replacement issues associated with a removable overdenture are more easily accomplished than those associated with a fixed appliance. The most common repair needed for the overdenture is that of replacing a denture tooth. This can typically be done in the dentist’s office, or by the commercial lab, with a minimum of turn-around time. Repairing a fixed PFM or acrylic-to-metal prosthesis generally requires more lab time and expense compared to the implant overdenture.
Replacement of an attachment-retained implant overdenture (not bar-retained) usually allows preservation of the existing abutments used in the original overdenture. This has the added convenience of allowing the patient to continue the use of the original overdenture while the replacement is being fabricated. In contrast, the replacement of a PFM or acrylic-fused-to-metal fixed prosthesis typically requires sending the original metal framework to the lab for several days, or longer, if it is to be used in a new appliance. Or, the framework is completely replaced in the replacement appliance which adds more to the patient’s costs.
There are now refined techniques and products enabling the clinician to produce attachment-retained overdentures with greater predictability and success than previously available. These include, but are not limited to, impression trays, impression materials, and techniques in addition to jaw relation record products that greatly increase the accuracy of centric relation registration. The following case report illustrates these items.
|Figure 1. Preoperative view of the patient’s maxillary edentulous arch.||Figure 2. Preoperative view of the patient’s mandibular edentulous arch. Full-mouth extractions and immediate dentures had been placed 6 years prior to presenting to our office.|
|Figure 3. Panoramic x-ray prior to grafting and placement of implants.||
Figure 4. Healing abutments were placed in Replace Groovy (Nobel Biocare) maxillary implants.
|Figure 5. Mandibular healing abutments were placed into the implants providing a measure of retention for the soft lined existing dentures during the implant integration period.||Figure 6. The clear heat-moldable Strong-Massad DenPlant impression trays (gdit.us) come in 3 sizes for each arch.|
Figure 7. Tray stops were established utilizing placement of a rigid polyvinylsiloxane (PVS) impression material (Aquasil Ultra Heavy Rigid [DENTSPLY Caulk]). This prevents over-seating of the impression tray in subsequent steps.
|Figure 8. Border molding with a heavy body PVS impression material (Aquasil Heavy [DENTSPLY Caulk]).|
|Figure 9. Maxillary master impression with impression copings and implant analogs.||Figure 10. Mandibular master impression with impression copings and implant analogs.|
Figure 11. The Jaw Relation Recorder (Great Lakes Orthodontics) consists of 2 sizes for a maxillary striking plate, mandibular pin holder, and a pivoting nut and pin.
Due to the degree of bone grafting anticipated to place implants in desirable positions, the patient was referred to an oral surgeon for further evaluation. The panoramic radiograph and a written request for an implant evaluation were sent to the surgical office prior to the patient’s appointment there. The surgical evaluation confirmed our initial exam opinion regarding the need for bone grafting. Sinus lift and buccal onlay grafting were recommended by the oral surgeon in order to provide sufficient bone for either fixed or removable implant options.
The patient returned to our office for a consultation at which all of these options were discussed in detail. After careful consideration, she chose to pursue a removable implant option using 4 implants in each arch to support attachment-retained overdentures.
A surgical hip graft was performed by the oral surgeon to produce sufficient osseous bulk and height to house the proposed 4 maxillary and 4 mandibular implants. The patient’s existing dentures were relined (Visco-gel [DENTSPLY Caulk]) immediately following the surgery to reduce micromovement and trauma to the new graft while continuing to use her existing prostheses. The graft was allowed to mature for a period of 5 months prior to placement of the implants.
The patient’s existing dentures were duplicated (Lang Denture Duplicator [Lang Dental]) in clear acrylic to use as surgical templates. In each template, 4 holes, 3 mm in diameter, were drilled by the author through these templates for use at the time of implant placements. The purpose of the template was to use as a guide for the implant sites and angulations during placement by the surgical dentist. The 3 mm hole size allows a 2 to 2.5 mm pilot drill to be used without impingement—an important point that in order to encourage the surgical use of the template.
Under the guidance of the template, 8-4.3 mm diameter implants (Replace Groovy [Nobel Biocare]) were placed (4 in each arch). Healing abutments with sufficient height to extend slightly supragingivally were threaded into each implant (Figures 4 and 5). The patient’s existing dentures were then relined again with a soft-lining material (Visco-gel) over the newly placed healing abutments. The slight protrusion of these healing abutments through the soft tissue provided some additional stability and retention of the soft lined dentures. A 3-month integration period was then observed prior to beginning prosthetic appointments to fabricate the maxillary and mandibular overdentures.
Prosthetic Phase: Four Appointments are Needed
The sequence of appointments to complete the prosthetic phase of treatment was as follows:
- Appt 1—Implant level master impression.
- Appt 2—Face-bow transfer and Jaw Relation Recording.
- Appt 3—Wax try-in.
- Appt 4—Delivery.
(Additional appointments may be required in order to gain approval of the overdenture setups by the patient and dentist at the wax try-in appointment.)
Prosthetic Phase: First Appointment (Master Impression)
For the maxillary and mandibular master impressions, impression copings were connected into the implants and radiographed to confirm complete seating. Next, clear heat-moldable trays (Strong-Massad DenPlant [Global Dental Impression Trays]), designed for all implant overdenture and dentate impressions, were sized and selected (Figure 6). The trays were customized by heating specific areas with a Blazer Torch (Leemark Dental Products) to create a well-fitting impression tray that would be comfortable to the patient. Since the impression trays are clear, it was easy to confirm that the impression copings did not touch the trough area of the impression tray, providing at least 1.0 mm of impression material between the copings and tray. The rigidity of these polystyrene material trays provides a greater degree of accuracy than seen with other disposable impression trays.7
Figure 12. The patient: closed with the mandibular pin against the maxillary striking plate at the proper vertical dimension of occlusion.
Figure 13. The patient’s scribed arrow from the Jaw Relation Recorder. The tip of this arrow represents centric relation.
Figure 14. Upper and lower baseplates were locked together with a PVS bite registration material (Regisil Rigid [DENTSPLY Caulk]) for mounting the lower cast in centric relation.
Figure 15. The maxillary and mandibular prostheses (VITA Physiodens denture teeth [Vident]) were returned in wax for the try-in appointment.
Figure 16. The processed overdentures, ready for delivery to the patient.
|Figure 17. Maxillary posterior housings and gaskets ready for intraoral pickup in the overdentures.|
Figure 18. Two blue (1 lb retention) attachments in the maxillary anterior and 2 black attachments provided sufficient retention for an acclimation period after delivery.
|Figure 19. The final mandibular attachments consisted of 3 blue-studded and one red-studless attachment.|
Figure 20. The processed overdentures in centric occlusion.
Figure 21. Note the palateless design of the maxillary overdenture.
Figure 22. The completed mandibular overdenture with metal reinforcement.
|Figure 23. The patient exhibited excellent aesthetics following delivery of the overdentures.|
Figure 24. Full-face portrait revealed a pleasant smile.
The master impression was done in 3 steps.8 The first of these included tray stops utilizing placement of a rigid polyvinylsiloxane (PVS) impression material (Aquasil Ultra Heavy Rigid [DENTSPLY Caulk]) (Figure 7). PVS or polyether impression materials are the preferred impression materials for this procedure.9 The second phase of the impression included border molding using a heavy bodied PVS (Aquasil Ultra Heavy [DENTSPLY Caulk]). For the maxillary arch, the border-trimmed tray was inserted into the mouth. The anterior frenum and buccal vestibule was border molded by grasping and moving the lips in a traditional border molding technique. The patient was then instructed to open widely which resulted in translating the mandibular coronoid process and registering the hamular frenum. Next, the patient performed a “pooch and smile” movement to capture the border molding of the impression. Then the patient’s nostrils were occluded while the patient coughed forcefully. This action caused the soft palate to depress into the border molding impression material and register the post dam (Figure 8). The mandibular border molding process was completed in the same fashion as the maxillary with the addition of having the patient move her tongue forward and side-to-side while holding the tray intraorally.
The third and final part of the master impression was the wash portion. The border molded impression material was cut back about 1 to 2 mm from its periphery. Any areas of the impression tray that protruded through the border were reduced about 1 mm using a lab carbide bur. An extra light PVS (AquaSil Ultra Extra Light Viscosity [DENTSPLY Caulk]) impression material was injected around the impression copings and tray periphery. A medium viscosity PVS impression material (Aquasil Ultra Monophase [DENTSPLY Caulk]) was placed into the tray interior to provide rigidity adjacent to the impression copings. After insertion of the impression tray into the mouth, the border molding movements were performed again (ie, anterior frenum, buccal vestibule, “pooch and smile,” opening widely, and occluding the nostrils while coughing). This technique produces a routinely exquisite impression with excellent reproduction of all the tissue surfaces and border areas. The impression copings were removed from the implants, joined to implant replicas, and returned to the impression (Figures 9 and 10). The impressions were then ready to send to the dental laboratory.
Measurements were then taken by inserting a ruler (Lip Ruler [GDIT]) under the upper lip and allowing it to rest on the incisive papilla. The first measurement was made with the lip “at rest.” The incisal edges of the central incisors are generally expected to extend 1 to 2 mm beyond this resting lip position. The second measurement (with the lip ruler in place) was made with the patient exhibiting a full smile. This resultant superiorly positioned upper lip position generally is expected to be about 1 to 2 mm short of the central incisors’ gingival zenith. Therefore, the length of the central incisor is usually about 2 to 4 mm greater than the distance between the resting and high smile measurement. The impressions were poured at the dental laboratory.
Prosthetic Phase: Second Appointment (Jaw relations)
For the second appointment, the following items were returned to our office with the maxillary and mandibular master casts:
- Maxillary aesthetic control base built 1.0 mm longer than the resting lip ruler measurement.
- Maxillary baseplate with a striking plate fixed into the palatal area.
- Mandibular baseplate with a bite registration pin inserted.
- Mandibular neutral zone baseplate and impression compound rim.
The maxillary aesthetic control base (ACB) was inserted intraorally and contoured for the proper facial contour, occlusal plane, and incisal length to simulate the positions for the incisal edges of the anterior denture teeth. The midline was marked into the wax rim portion of the ACB, in addition to the ala of the nose. A horizontal line representing the upper lip line at a high smile was also marked into the wax rim. These markings aid the denture setup artist in positioning the anterior teeth incisal edges and selecting a mold size. The ACB was then attached to a bite fork to obtain a face-bow transfer for mounting the maxillary master cast to the upper member of the SAM 3 articulator (Great Lakes Orthodontics).
The centric bite registration was obtained using the Jaw Relation Recorder (Global Dental Impressions), which is a tracing device (Figure 11). With both the maxillary striking plate and mandibular pin inserted into the mouth, the patient’s occlusal vertical dimension (OVD) was recorded. This is found by closing the vertical dimension 1 to 4 mm within the patient’s physiologic resting position. This 1 to 4 mm zone can also be referred to as the patient’s freeway space. With the mandibular pin contacting the maxillary striking plate upon patient closure at the designated OVD, the patient was then instructed to slide the mandible “forward and back, forward and back”, then “side to side” (Figure 12). The motion of the pin against the striking plate in these movements scribed an arrow on the colored portion of the plate. The tip of this arrow identified the patient’s centric relation position (Figure 13).
With the patient locked into this centric position, bite registration material (Regisil Rigid [DENTSPLY Caulk]) was injected between the 2 baseplates and around the striking pin. Removal of the bite registration (locked onto the baseplates) provided the jaw relation record to mount the mandibular cast in centric relation (Figure 14). The mandibular master cast was mounted on the lower member of the articulator using the Jaw Relation Recorder registration.
The neutral zone rim (baseplate with an impression compound rim) was heated in a water bath to 120˚F and then inserted into the mouth. The patient then swallowed several sips of warm water with the neutral zone in place. This swallowing action produced an impression compound rim that followed the lower lip line. The tongue and lip indentations were clearly seen forming a “zone” to be used for setting the occlusal and incisal edge positions of the mandibular denture teeth.
The mounted models were sent back to the dental laboratory technician. Mold selections from the Lingoform denture teeth (Vident) were used for the denture teeth setups in wax. Due to the patient’s petite arch size, small denture teeth from this selection were made. Locator abutments and attachments (Zest) were selected to provide a 1.5 mm retention area for the attachments supragingivally. The attachments and metal housings were luted into the denture baseplate intaglia. The setups were then returned to our office for the try-in appointment (Figure 15).
Prosthetic Phase: Third Appointment (Try-in)
At the patient’s try-in appointment, all implant healing abutments were removed and replaced with the appropriate Locator abutments. The maxillary and mandibular baseplates/setups were then seated with the attachments providing stability and retention during the evaluation process. The patient and doctor (author) then approved the denture teeth arrangement for aesthetics, phonetics, and proper occlusion. The patient was instructed to read aloud and to pronounce the classic f, v, s, and th sounds to confirm that her speech was favorably comparative to a dentate patient; that being an important preprocessing test. The patient then signed a Processing Approval Form (Leemark Dental) prior to returning the case to the laboratory for completion. The maxillary and mandibular implant overdentures were processed by the dental laboratory and returned to our office for delivery to the patient (Figure 16).
Prosthetic Phase: Third Appointment (Delivery)
All Locator abutments were threaded into their appropriate positions and torqued to 20 NCm force using the Nobel Biocare torque wrench and Locator insert. The 2 anterior implant positions had the Locator metal housings and attachments processed into the overdentures at the lab. The 2 posterior positions were then “customized” by being picked up intraorally. This pick up procedure was accomplished by applying ERA bonding agent and PickUp resin (Sterngold) to the intaglia of the overdentures where the attachments were to be positioned. The metal housings and black processing attachments were placed onto the Locator abutments in the mouth. A white block-out gasket was positioned apical to the retentive portion of each Locator abutment to prevent engagement of any undercut by the resin material (Figure 17). The overdentures were then seated intraorally over the metal housings/attachments and the patient was instructed to close gently into complete occlusion. The resin was then cured through the buccal and lingual aspects of the denture base by using a standard light-curing wand. Removal of the prostheses from the mouth confirmed that the housings and attachments were then luted into the intaglia of the overdentures.
A lingualized occlusal pattern for the overdenture teeth setups was used.10 In this format; the palatal cusps of the maxillary denture teeth are set directly into the central fossae of the mandibular denture teeth. The maxillary buccal cusps are set in a slightly more bucco-apical position or “up and out” in order to avoid any contact or interference when the mandible moves laterally or protrusively.
The patient was instructed on how to insert and remove the maxillary and mandibular overdentures. For the initial acclimation period with these appliances, we utilized blue (1 lb retention) attachments in the 2 anterior positions with the black processing attachments in the 2 posterior sites (Figure 18). The patient confirmed that this combination of attachments was fully satisfactory for retention of both appliances. Approximately 2 months later, the black processing attachments were replaced with blue (1 lb) attachments providing sufficient retention of the maxillary overdenture for use with an unlimited diet regimen. The mandibular overdenture was secured with 3 blue (1 lb) attachments and one red studless attachment to accommodate an implant that was divergent in angulation from the others (Figure 19). Only one postoperative appointment for sore spot adjustment was needed. After that time the patient was able to continue her usage of the overdentures in complete comfort.
At 6 months post-insertion the patient returned to the office for a follow-up appointment. Occlusion, phonetics, and aesthetics were again approved by the patient and the author (Figures 20 to 24). It was at this appointment that we asked the patient to answer several questions regarding her motivation to seek implant treatment, and to assess her opinion of the overdentures fabricated for her. She stated emphatically that—despite the costs incurred to have bone grafting, implants placed, and prostheses completed—she was entirely satisfied. She said that the treatment “was worth every penny and more.”
The effects of edentulism are often misunderstood even by clinicians who work with these patients. Our patient’s inability to go out in public, enjoy a normal diet at a restaurant, or even smile and laugh without embarrassment are beyond calculation. To have her self-worth restored exclusively due to dental therapy should be motivation enough for clinicians and prospective patients alike to seek out implant options.
The patient noted that her previous dentist had mentioned implants as an option to rectify the problems she experienced with her conventional dentures. However, according to her, this dentist effectively talked her out of the implant option by telling her that implants were prohibitively expensive and more time consuming to accomplish than she would want to consider. Again in her words, “neither of these obstacles proved to be true. The treatment was costly, yes, but nothing that I wouldn’t pay for again now that I know how great my implant appliances are compared to what I had before. Now I have the real me back!” There is no better testimonial than that.
- Malo P, Rangert B, Nobre M. All-on-4 immediate-function concept with Bränemark System implants for completely edentulous maxillae: a 1-year retrospective clinical study. Clin Implant Dent Relat Res. 2005;7(suppl):88-94.
- Strong SM, Callan DP. Restoration of the resorbed maxilla: a multidisciplinary approach. Pract Periodontics Aesthet Dent. 1993;5:45-52.
- Karabuda C, Yaltirik M, Bayraktar M. A clinical comparison of prosthetic complications of implant-supported overdentures with different attachment systems. Implant Dent. 2008;17:74-81.
- Wismeijer D, Van Waas MA, Vermeeren JI, et al. Patient satisfaction with implant-supported mandibular overdentures. A comparison of three treatment strategies with ITI-dental implants. Int J Oral Maxillofac Surg. 1997;26:263-267.
- Zitzmann NU, Marinello CP. Treatment outcomes of fixed or removable implant-supported prostheses in the edentulous maxilla. Part I: patients’ assessments. J Prosthet Dent. 2000;83:424-433.
- Leopardi A. Fixed restorative options for the edentulous maxilla. Functional Esthetics & Restorative Dentistry. 2008;Series 2:44-56.
- Burns J, Palmer R, Howe L, et al. Accuracy of open tray implant impressions: an in vitro comparison of stock versus custom trays. J Prosthet Dent. 2003;89:250-255.
- Strong S. Removable implant overdentures: growth area in the restorative practice. Dental Econ. 2008;98:44-46.
- Lee H, So JS, Hochstedler JL, et al. The accuracy of implant impressions: a
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