Case Presentation

The involvement of dental and alveolar trauma in accidents and assaults is not uncommon. The predisposition of the jaws to trauma often presents the restorative dentist with many problems as multiple teeth may be avulsed and require replacement. Restoration by means of conventional fixed bridgework and/or removable partial dentures often provide acceptable results. However it is to the patient's advantage that implants be considered in a comparable light with conventional restorations.

Following through the premise set in chapter 4, that the Ideal restoration should not be compromised by the cause of tooth loss and should itself not compromise general dental health, it is possible that conventional prostheses may themselves be contraindicated. Typically, in a young patient with unrestored abutment teeth, a conventional fixed bridge would be ill-advised. In the case presented in this chapter, the patient suffered parasymphyseal mandibular fracture, loss of alveolus, and avulsion of four anterior teeth 3 2 1 | 1 (43 42 41 31), with associated fracture of adjacent crowns on 5 4 | 2 3 (45 44 32 33). There was a through and through horizontal split of the lip, associated with the direct trauma from hitting the steering wheel in a road traffic accident.

It was apparent that substantial bone loss and scarring were likely to

Fig 6-3 Loss of teeth and alveolus, in combination with intra- and extra-oral scarring, has resulted in loss of lip contour The labiomental groove has deepened, with subsequent trapping of the lower lip behind the upper central incisor.

compromise the construction of an aesthetic conventional fixed bridge, which the patient would have been unable to clean and may have inadequately restored lip support {Fig 6-3). Furthermore the patient presented with a heavy bite, which would easily destabilise a removable partial denture.

A decision was taken to restore the patient with a hybrid prosthesis supported by means of implants placed in the residual alveolus (Fig 64). A diagnostic wax set up clearly indicates the poor position of the implants in relation to the arch line

(Fig 6 - 5), as dictated by the residual ridge morphology.

A cast substructure (Fig 6-6) was constructed on precision fit cylinders and screw retained to the implants, splinting them according to the principles set out by Lothigius et al.1-2 Two Mini Conex (Cendres et Metaux SA Biel, Switzerland) attachments were cantilevered labially, the patrix parts being located within the Co/Cr framework of the partial overdenture (Fig 6-7).

When activated, the precision attachments provide the essential retention required for the prosthesis

Fig 6-4 The master cast demonstrates the position of implants, placed in the residual alveolus after removal of bone plates used to reduce the fracture.

Mini Implant Retained Partial

Fig 6-5 As a result of residual ridge morphology implants can be seen to be lingually placed in relation to the wax set-up. which represents the ideal position for dental and soft tissue rehabilitation. It was on this basis, that the decision was taken to fabricate a hybrid prosthesis.

Conex Attachment

Fig 6-6 The milled substructure varies from the conventional design in shape and in the choice of precision attachment. In this case two Mini Conex attachments (Cendres et Metaux SA Biel, Switzerland) are iabially cantilevered to provide retention under the incisal table.

Overdenture Fitting Surface

Fig 6-7 The lilting surface of this partial overdenture demonstrates the close fitting Cobalt/Chromium framework, which incorporates the male components of the Mini Conex attachments.

Fig 6-8 The hybrid prosthesis in situ demonstrates a high degree of retention and stability. Occlusal balance is restored, though a right sided cross bite and lack of maxillary symmetry complicate the occlusion.

and the close adaptation of the Co/Cr framework to the milled substructure provides the lateral stabilisation (Fig 6-8).

The advantage of the overdenture is clearly demonstrated in the restoration of lip support by the provision of a labial flange (Figs 6-9 and 6-10), Being removable, greater opportunity is also afforded the patient with respect to access for oral hygiene maintenance.

In essence the combination of replacement of lost tissues by means of a denture, with the support and retention of a fixed prosthesis are the qualities afforded by the provision of a hybrid fixed-detachable prosthesis, retained by precision attachments to a splinted implant substructure.

Fig 6-9 The advantage of the hybrid prosthesis is clearly seen, with the labial flange providing the necessary soft tissue support to correct the lower lip trapping seen in figure 6-3.

Fig 6-10 The patient's confidence is restored. Implant maintenance is facilitated by the removable nature of the prosthesis.

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