DISCUSIÓN
1. WIP COMO MODULADOR DEL CITOESQUELETO DE ACTINA EN ESPINAS DENDRÍTICAS
H.J.A. Meijer
A 63-year-old female patient was referred to the University Medical Center in Groningen, Netherlands, for dental implant treatment. The patient had been edentulous in the upper jaw for 20 years. The remaining teeth in the lower jar had been removed two years before the consultation. The patient was wearing her first maxillary denture and her second mandibular denture; the latter was 1 year old at the time. The conventional upper denture had functioned satisfactorily for many years, but the patient complained about reduced stability and insufficient retention of her lower conventional denture. Her medical history revealed no significant findings. The intraoral examination revealed minor resorption of the maxillary alveolar process and extreme resorption of the mandibular alveolar process. Retention and stability of the maxillary denture were normal, while the mandibular denture exhibited no stability or retention at all, and the occlusion was balanced without anterior contact.
Radiographic diagnosis included a rotational panoramic radiograph and a lateral cephalometric radiograph (Figs 1 and 2).
Fig 1 Baseline rotational panoramic radiograph.
Fig 2 Baseline lateral cephalometric radiograph.
The height of the mandible was 20 mm with a slight knife-edge ridge, as measured in the symphysis region on the lateral cephalometric radiograph (Cawood and Howell class IV). The treatment plan proposed to the patient included two endosseous implants in the interforaminal region of the mandible, a mandibular overdenture supported by a bar attachment system, and a new conventional denture in the maxilla. The patient was informed of the risks and gave her written informed consent.
Procedure
Two Straumann Standard dental implants (Ø 4.1 mm, length 14 mm) were inserted under local anesthesia after the removal of the bony knife-edge ridge aspect. The implants were inserted in the canine region of the mandible, each about 1 cm away from the midline. The procedure was carried out in a one-stage technique. Postoperative analgesics and 0.2% chlorhexidine digluconate mouth rinses were prescribed, but no antibiotics. The patient was not allowed to wear her mandibular denture during the first week after surgery, after which the sutures were removed. A soft liner was applied after selectively relieving the mandibular denture at the implant site. The patient also received oral hygiene instructions. Prosthetic procedures started after a 6-week healing period. The implants were stable and surrounded by healthy peri-implant mucosa (Fig 3).
Fig 3 Two Straumann Standard implants at the end of the 6-week healing period.
The preliminary impression was taken using stock metal trays and alginate (Fig 4). Custom composite trays were fabricated with openings for screw-retained synOcta impression posts. The impression posts were fixed at the implant level (Fig 5).
Fig 4 Preliminary impression for manufacturing the custom tray.
Fig 5 The impression posts mounted on implants.
The tray was placed over the impression posts, and any contact between the post and the tray was avoided to allow the tray to rest firmly on the denture-bearing mucosa. The screw of the post was positioned above the opening of the tray (Fig 6).
Fig 6 Custom impression tray with posts.
The final impression was taken in a hard polyether material. The impression material around the posts was administered by a syringe. The tray was filled and placed on the alveolar process. During setting, the screws had to remain uncovered to facilitate removal of the impression (Fig 7).
Fig 7 Impression taken with a stif polyether impression material. The screws of the impression posts are visible.
The posts were connected to implant analogs in the impression tray, and the master cast was poured (Figs 8 and 9).
Fig 8 Implant analogs connected to the impression posts.
Fig 9 Plaster cast with implant analogs.
In this way, the implant location and the denture-bearing area were reproduced. Before determining the vertical and horizontal dimensions of the new dentures, the bar and the acrylic base of the overdenture were fabricated. A stable and well-retained base made it easier to record the interarch relationship. SynOcta abutments were chosen as connections between implants and titanium copings.
An ovoid titanium bar was connected to the titanium copings, and a gold clip was selected (Fig 10).
Fig 10 Bar with selected length of clip on the master cast.
Requirements for placing the bar include parallelism with the line between the temporomandibular joints, accessibility for oral hygiene, no encroachment on the tongue space, and accommodation of the positions of the artificial teeth. The acrylic denture base was poured and the clip incorporated (Figs 11 and 12).
Fig 11 Final acrylic base of the overdenture.
Fig 12 The clip in the denture base.
An occlusal wax rim was attached to the denture base (Fig 13).
Fig 13 Occlusion wax rim on the denture base.
The synOcta abutments were connected to the implants in the patient’s mouth, and the bar was screwed on the abutments (Figs 14 and 15).
Fig 14 synOcta abutments connected to the implants.
Fig 15 Titanium bar connected to the abutments.
To check the seating of the clip on the bar, a two-component silicone-based disclosing material was inserted in the area of the clip and placed on the bar in the mouth (Fig 16).
Fig 16 Silicone-based disclosing material was inserted in the area of the clip.
After the setting of the disclosing material, the denture base was removed. There was to be a connection between the clip and the bar but no connection between the bar and the acrylic, which was verified (Fig 17).
Fig 17 Checking the connection.
If a connection between the bar and the acrylic had existed, the area would have had to be relieved and the seating rechecked.
Occlusal wax rims on bases were used to determine the vertical dimension and the level of the occlusal plane and to record the maxillomandibular relation (Figs 18 and 19).
Fig 18 Anterior view of the occlusal wax rim.
Fig 19 Dorsal view of the maxillomandibular relationship.
After completion of the tooth set-up, the trial dentures in wax were tried in intraorally and corrections
were made. The lingualized occlusion concept with bilateral balanced guidance and ceramic teeth was used (Figs 20 and 21).
Fig 20 Tooth set-up in the articulator.
Fig 21 Partial view of the tooth set-up with occlusion.
The tooth set-up was approved by both the dentist and the patient, and the conventional upper denture and mandibular overdenture could be finished in the laboratory (Fig 22).
Fig 22 The finished prostheses on the master casts mounted in the articulator.
At the delivery of the prostheses, the synOcta abutments were placed and tightened to 35 Ncm with a
torque controller. The bar was connected and the occlusal screws were tightened to 15 Ncm. After insertion, the adaptation of the base was examined with disclosing material. Once the adaptation had been checked, occlusion and articulation were examined. If necessary, the retention force of the clip can be adjusted at this stage.
The patient was taught to remove the overdenture and to clean the prosthesis and bar. A few days after delivery, the first check-up was performed, and peri-implant radiographs were taken to record peri-implant bone levels at the outset of the functional period (Figs 23 and 24).
Fig 23 Intraoral radiograph at overdenture delivery: right implant.
Fig 24 Intraoral radiograph at overdenture delivery: left implant.
Follow-up
A regular yearly recall system was applied. The status of the alveolar process was checked intraorally together with peri-implant items such as plaque and calculus accumulation, mucosa, sulcus depth, and bleeding. The evaluation of the prosthesis included the fit of the denture base, occlusion and articulation, fracture of denture base or teeth, and clip loosening or fracture. At the 4-year follow-up, the patient presented a satisfactory clinical situation and a favorable peri-implant bone level (Figs 25 to 26).
Fig 25 Bar after 4 years in function.
Fig 26 Rotational panoramic radiograph after 4 years in function.
No complications had occurred during these 4 years and the patient was still very satisfied with the improved function of the mandibular denture.
Acknowledgments
Surgical Procedures
Prof. G.M. Raghoebar – Groningen, Netherlands Laboratory Procedures
Gerrit van Dijk – Groningen, Netherlands