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Program Director and Maxillofacial Prosthodontist, Post-Graduate Prosthodontics, School of Dental Medicine, University of Connecticut, Farmington, Conn
Immediately loaded complete-arch fixed implant-supported prostheses have become a popular approach to the treatment of patients with edentulism. In the past 10 years, popular treatment concepts such as All-on-Four (Nobel Biocare) have streamlined the rehabilitation of the edentulous maxilla and mandible, with high implant and prosthetic survival rates.
Creation of a 3-dimensional virtual dental patient for computer-guided surgery and CAD-CAM interim complete removable and fixed dental prostheses: a clinical report.
The chairside conversion of an immediate or conventional denture to an immediately loaded complete-arch fixed implant-supported prosthesis is popular because of its simplicity, adaptability to changes in planned implant positions, and reduced treatment cost. Nevertheless, this is a multistep, technique-sensitive process.
One of the key steps in the conversion process requires the practitioner to accurately determine the position of the implants or abutments before creating access holes to lute it to the titanium cylinders.
Conventionally, fast-setting polyvinyl siloxane (PVS) occlusal registration material has been used inside the denture to capture the positions of the healing abutments. The PVS material is injected onto the intaglio surface of the denture and is seated over the implants or abutments until the material polymerizes. The implant positions are then imprinted in the PVS material, and access holes are drilled in this region with tungsten carbide burs. Although this technique effectively records the location of the implants, clinical risk is present even with adequate suture lubrication. For example, dislodgement of residual PVS into a freshly sutured surgical site is possible (Fig. 1). If the PVS material is not completely removed, inflammation or infection can occur, precluding complete hard and soft tissue healing. Another adverse consequence is that the PVS material may penetrate beneath the sutures and prevent denture removal. In this situation, the sutures need to be cut and new sutures placed. This causes unnecessary irritation to the freshly sutured surgical area and potential loss of primary hemostasis. Finally, the access holes are often large, compromising denture strength and occlusal anatomy.
Figure 1Residual polyvinyl siloxane material, used to record healing abutment positions, dislodged into freshly sutured surgical site, showing adverse consequence of this popular technique for recording implant positions for immediate loading.
The purpose of this article is to present a straightforward, quick, and safe technique using a clear vacuum-formed matrix of the complete maxillary or mandibular denture to record accurate implant/abutment positions and angulations when a conversion prosthesis for immediate loading is fabricated. An advantage of this technique is the exclusion of any material that may become displaced within the freshly sutured surgical site. In addition, excessive trimming and enlargement of access holes that may compromise the strength of the denture or damage the occlusion is prevented because the implant/abutment positions and angulations are seen easily. Moreover, the clear matrix aids in determining and trimming the exact height of the titanium cylinders needed.
A disadvantage of this technique is the requirement of an additional step to fabricate the clear vacuum-formed matrix over the complete denture. This technique can be used for complete or partial arch situations with immediate or delayed loading. With advances in computer-aided engineering, it is expected that the location of the implant positions can be predetermined or the prosthesis fabricated in advance in a more predictable manner in the future.
Creation of a 3-dimensional virtual dental patient for computer-guided surgery and CAD-CAM interim complete removable and fixed dental prostheses: a clinical report.
Before implant surgery, fabricate a clear vacuum-formed matrix using a 0.010-inch thickness of thermoplastic material (Clear Temporary Splint Sheets; Patterson Dental) over the cameo surface of the maxillary or mandibular denture. Ensure that the matrix covers the entire extensions of the denture to allow proper alignment in the mouth.
2.
After implant surgery, suture the buccal and palatal flaps and place healing caps on the implants and/or abutments.
3.
Insert the clear matrix in the mouth until proper alignment is confirmed. In the maxilla, use the palate as a reference. In the mandible, use the border extensions as a reference (Fig. 2).
Figure 2Placement of clear matrix in mandibular arch allows visualization of healing abutment positions. These positions can be marked on clear matrix with indelible marker.
Examine the implant/abutment healing caps through the clear matrix and record their positions with an indelible marker (Expo; Sanford Ink Co).
5.
Trim a small hole in the clear matrix with a no. 8 round tungsten carbide bur (Brasseler) to correspond to the positions of the healing abutments.
6.
Remove the healing abutments and insert titanium cylinders over the implants or abutments.
7.
Replace the clear matrix over the titanium cylinders and trim the titanium cylinders extraorally to the appropriate height. Also trim the clear matrix to record the proper trajectory of the titanium cylinders.
8.
Replace the clear matrix over the complete denture and drill a hole into the denture through the access hole previously recorded in the clear matrix (Fig. 3).
Figure 3Holes drilled into denture at accurate positions using clear matrix as guide.
Once the required access holes are drilled in the denture, confirm passive seating of the denture intraorally (Fig. 4).
Figure 4Mandibular complete denture after drilling 4 access holes using clear matrix technique. Notice that diameters of access holes only slightly larger than diameter of titanium cylinders to provide space for luting resin material, preserving strength of denture and occlusal anatomy of denture teeth.
Creation of a 3-dimensional virtual dental patient for computer-guided surgery and CAD-CAM interim complete removable and fixed dental prostheses: a clinical report.
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