Full mouth rehabilitation utilizing traditional fixed and removable prostheses

Discussion

The 45-degree bevels were chosen to enhance the overall aesthetic appearance of the future restorations. Studies have shown that a bevel that brings metal and porcelain to the margin aides in good fit, contour, and color⁸. This type of margin also results in less plaque accumulation as well as creates less recession at the gingival-restoration interface. If the construction of a provisional restoration is hastily performed, it will not afford adequate protection and/or can result in damage to the prepared teeth and the supporting tissues⁹. The goal of these restorations was to restore satisfactory gingival adaptation, proper contours, cleansable embrasures, acceptable contacts, canine protected occlusal scheme, provision of space for pontics, and provision for acceptable phonetics. The concept of biologically acceptable provisional restorations demands that the prepared teeth be protected and the treatment restorations resemble the form and function of the final restorations. Henderson and Steffel stated: “Retainers for distal extension removable partial dentures, while retaining the appliance, must also act as stress breakers – they must be able to flex or disengage when the denture base moves tissue ward under functional stress”¹⁰. It is important to remember that when fabricating removable prostheses with distal extensions, there is the potential for the prostheses to become Class I cantilevers, especially when circumferential clasps are utilized for retainers¹¹. A distal-extension prosthesis has multi-directional rotation, particularly when masticatory forces are applied to the distal-extension. These multi-directional rotations create damaging cantilever forces to the abutment teeth. Nonlocking, semi-precision rests permit prosthesis rotation and thereby reduce the torquing stresses transmitted to the abutment teeth. The most widely used non-locking intra-coronal attachment is the Thompson dowel rest, which contains two parts: a tapering recess and a well. The lingual surface of the crown is made flat and parallel with both the lingual surface of the opposite-side abutment casting and the lingual wall of the rest seat. The retaining metal projections that fit into the recesses will then be on the axis of rotation, so that they, and the two dowel rests, may rotate without any displacement of the retentive dimples. Lateral force transmission is provided by contact of the sides of the rest with buccal and lingual walls of the rest seat and by the rigid portion of the lingual clasp arm. When distal-extension ridges are present, a non-locking deep rest must be used to overcome the cantilever action which develops in a Class I lever system¹¹. The try-in visit of both the fixed partial denture and removal partial denture setup is a crucial visit that provides valuable information concerning the placement of the restorations. The position of the anterior teeth controls not only the support of the lips, the visibility of the teeth, and anatomic harmony, but also provides definite guides (anterior guidance) for establishing jaw relations⁹. These crucial areas are essential to producing speech and are ones that patients will be most critical of, especially if they are missed. The patient is encouraged to pronounce “f” and “s” words¹². Words with “f” are used to verify the position of the maxillary anterior teeth as they contact the vermillion border of the lower lip, aka the wet-dry lip line. Words with “s” (sibilants) are then used to match the lower anterior teeth to the maxillary anterior teeth. This step helps to identify and verify tooth position when anterior restorations are being fabricated. Loss of posterior teeth may result in the loss of neuromuscular stability of the mandible, reduced masticatory efficiency, loss of the vertical dimension of occlusion, and attrition of the anterior teeth¹³. It can also cause secondary occlusal trauma to the anterior teeth and worsen the integrity of the periodontal condition. Most of all, appearance and aesthetics are compromised. The traditional treatment modalities, including removable and fixed partial dentures, are commonly indicated for restoring vertical dimension and increasing occlusal contact in the posterior region. These treatment modalities also are less invasive and less costly in comparison to implant supported prostheses. If the removable partial denture is carefully implemented to the design principles and enhanced by the attachment system within the fixed partial denture, the patient acceptance of these prostheses is high. Long term care is compromised by prosthetic mechanical failures including tooth fracture, periodontal breakdown, and root caries^14,15. The motivation of the patient to change one’s oral hygiene behavior in order to maintain the newly restored dentition is essential for the longevity of any prostheses. The biological price can be detrimental depending on the patient’s compliance.