Authors of section

Authors

Alexander Schramm, Marc Metzger, Nils Gellrich, Bradley Strong

General Editor

Daniel Buchbinder

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CAS: Prostodontic-driven maxillary reconstruction

1. Introduction

Pre-operative staging in malignancies involving the maxilla includes preoperative 3D scanning. Whether the patient is dentate or not the reconstruction of the maxilla has to be backwards-planned prior to resection of the maxilla. There are different options for reconstruction (see section of postablative reconstruction) which can be applied primarily, delayed primarily (ie. within weeks) or secondarily (ie. after 6-12 months eg. following radiotherapy).

In the case of delayed reconstruction of the maxilla, temporary closure of the palatal defect can be performed with the help of a thermoplastic temporary splint.

Whatever reconstructive strategy is applied, a prosthodontic-driven backwards-planned digital workflow should be advocated. A stereolithographic (STL) model of an ideal reconstruction is made. This allows for preoperative adaptation of bone plates of to replace resected midfacial buttresses and reconstruct the original contours.

Furthermore, dental implant position can be virtually planned ensuring placement in sufficient bone stock (existent or to be reconstructed). A drill guide is then produced to ensure correct bone augmentation and simultaneously/secondary implant position.

The following clinical cases demonstrates examples of this digital workflow step by step.

2. Case 1 – Diagnostic imaging

A 3D-scan is made to diagnose the extent of the defect.

The Brown type II defect shown on the left will be used to illustrate the digital workflow for maxillary reconstruction.

cas prostodontic driven maxillary reconstruction

This axial CT slice shows the right maxillary defect.

cas prostodontic driven maxillary reconstruction

3. Case 1 - Virtual reconstruction

Ideal location of dental implants

In this case, the patient is partially dentate (3 teeth) on the contralateral side. Implant placement is simulated in red.

Note: In the case of a complete alveolar resection or an edentulous maxilla, the Atlas function of the software would be used to virtually reconstruct the ideal hard tissue anatomy based on the 3D-CT scan of a normal adult skull without any artifacts.

This virtual reconstruction would then serve as a base for the planning of dental implants without the need of any dental impressions or casts.

cas prostodontic driven maxillary reconstruction

Bone stock needed for each implant

The red cylinders show the amount of vital bone needed around the dental implants.

midface brown ii

Reconstruction volume needed

The shape and volume of the needed bone graft (yellow) is dictated by the shape of the bone necessary for successful insertion of implants (red cylinders).

cas prostodontic driven maxillary reconstruction

4. Case 1 – Preparation of drill guide

A physical model of the maxilla is made and used to prefabricate a drill guide by a dental technician to define:

  • The position of the required bone graft
  • The position of the dental implants
cas prostodontic driven maxillary reconstruction

Alternatively, the drill guide can be made virtually and fabricated with a 3D printer.

cas prostodontic driven maxillary reconstruction

5. Case 1 - Reconstruction

Exposure of the defect

This picture show the right maxillary defect after the fasciocutaneous flap has been dissected.

cas prostodontic driven maxillary reconstruction

Bone grafting

The drill guide is inserted and used as an aid to place the bone grafts. Care is taken that adequate bone volume (red cylinders in the virtual planning) is added for each planned implant.

cas prostodontic driven maxillary reconstruction

Each bone graft is adequately stabilized with either lag screws and/or plates.

cas prostodontic driven maxillary reconstruction

Insertion of dental implants

After the bone has matured (min 12 weeks) the plates and screws are removed.

cas prostodontic driven maxillary reconstruction

In the same surgery, the original drill guide is used to insert the dental implants.

cas prostodontic driven maxillary reconstruction

Postoperative assessment

Postoperative validation of the correct implant position by comparing the virtually-planned (red lower picture) and the final implant position (upper picture).

cas prostodontic driven maxillary reconstruction

6. Case 2 – Diagnostic imaging

A 3D-CT scan is made to diagnose the extent of the defect.

In cases were the general health status of the patient does not allow for bony reconstruction of the maxillary defect, alternative techniques might help to rehabilitate the patient in terms of dentation, lip support and competence, speech etc.

The Brown type II defect shown on the left will be used to illustrate the digital workflow for maxillary reconstruction when bony reconstruction is not possible.

cas prostodontic driven maxillary reconstruction

7. Case 2 – Virtual reconstruction

Ideal location of dental implants

If the malar bone provides sufficient bone stock, prosthodontic-driven backwards-planning helps to virtually position one or two zygomatic fixtures (blue and pink).

cas prostodontic driven maxillary reconstruction

This picture shows the virtual position of the two implants to assure that the position meets prosthodontic requirements.

cas prostodontic driven maxillary reconstruction

The exact trajectory of the drill is planned.

cas prostodontic driven maxillary reconstruction

Intraoperative navigation is used to precisely position the implants.

cas prostodontic driven maxillary reconstruction

Intraoral view after implant placement.

cas prostodontic driven maxillary reconstruction

Postoperative cone beam scan in the coronal plane demonstrates the parallel position of the two zygomatic fixtures on the right side.

cas prostodontic driven maxillary reconstruction

Three years follow up showing the screw-retained bar on the two zygomatic fixtures together with 5 conventional implants.

cas prostodontic driven maxillary reconstruction

This picture shows the final prosthesis.

cas prostodontic driven maxillary reconstruction