Use of biomodels to prefabricate templates and splints.

Case courtesy of Dr. John Arvier, Brisbane, Australia. These techniques were pioneered by Dr. Arvier.

Biomodels may be used to plan endosseous surgery and to create customised drill guide templates (figures 1 & 2).

Figure 1: Mandibular biomodel with drill guide template.

Figure 2: Mandibular biomodel with template used to guide the drill so as to avoid the course of the mandibular nerve, marked by red wire.

Edentulous patients may have teeth restored by mounting them on titanium pins which are implanted into the jaw. The implantation of the titanium pins however can be difficult and complicated by damage to the underlying dental nerve. Mandibular biomodels accurately replicate the neurovascular canal through which the mandibular nerve travels. The course of this nerve may easily be displayed by passing a malleable coloured wire along the neurovascular canal (figure 2) or replicated in a second colour. The biomodel can then be used to determine and rehearse the positioning and depth of the holes required to receive the titanium mounting pins. The pins can then be inserted into position and acrylic moulded around them and the mandibular contour to form a relocatable drill guide (figure 2). The depth of each hole can also be determined relative to the drill guide and recorded. During the surgery the mucosa is stripped from the mandible and the drill guide matched using the reciprocal contours. Whilst firmly held in place the guide can be used to drill the holes with the correct positioning and depth as pre planned in the biomodel without risk of injury to the underlying mandibular nerve.

Another example of the use of splints was the case of a 24 year old New Guinean man who sustained a major middle face deficit from necrotising infection after a motor vehicle accident. The articulated biomodel clearly demonstrated the loss of maxillary bone (figure 3 ). It was used to study the capacity of the remaining bony architecture to support reconstruction. A template was fashioned to trace the resection margin of a bone graft from the mandible that was fastened with screws to the maxilla. Restorative dental implants were incorporated by using a second template created on the reconstructed biomodel. The surgeons found the biomodel particularly useful for planning the reconstruction and were impressed with the precision of biomodel surgery.

Figure 3: Biomodel of 24 year old male with a severe mid-face deficit after a motor vehicle accident.

Dental splints may also be prefabricated using articulated biomodels of the teeth and jaws. Such splints may be useful to maintain the relative position of the dental arches after osteotomy surgery. If the surgery is rehearsed on the biomodel and the relative position of the bones determined and set, a splint may be moulded to fit to the biomodel (figure 4). At the end of surgery, which closely replicates the surgical plan simulated on the biomodel, the splint may then be used to maintain positioning (figure 5) This can save the time taken at the end of the procedure to mould such a splint intraoperatively. The risk of bony movements whilst moulding such a splint directly is also avoided with this technique.

Figure 4: Splint fashioned to biomodel.

Figure 5: Splint in patient's mouth after surgery.

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