By Dr C. Sharath Babu
Prosthodontist and Implantologist
Published on 23/08/2022
Maxillofacial prosthetics is a specialty of dentistry that treats congenital and acquired defects of the head and neck (such as traumatic injuries and cancers). It involves the rehabilitation, management, replacement of lost or missing structures and functions of maxillofacial defects or disabilities. The goals of maxillofacial prosthetics include restoring aesthetics or cosmetic appearance, conserving maxillofacial functions and providing psychological therapy.
Prostheses are made to replace broken teeth, lost bone, or soft tissue with a wide range of materials.
Maxillofacial prosthetics might be indicated in the following conditions:
- 1. Congenital problems such as birth defects, anotia (external ear of baby is missing completely at birth), cleft lip and cleft palate.
- 2. Loss of maxillofacial organs due to trauma.
- 3. Lost of maxillofacial organs due to cancers
There are two major types of maxillofacial prostheses based on prosthetic positioning:
- 1. Intraoral prosthesis include artificial soft and hard palates, oral exercisers, assistive speech devices and devices that allow swallowing.
- 2. Extraoral prosthesis include orbital implants and ear, nose, ocular and skull prostheses.
The primary goal of intraoral prosthetics is to restore function and appearance in patients with oral cavity defects. Prostheses are usually made of "acrylic" due to its flexibility and durability.
Several steps are involved in the process, beginning with an impression (a negative imprint of teeth and soft tissues inside and outside the mouth), implant planning, and surgical and prosthetic procedures. Intraoral prosthetic processes are far more sophisticated than extraoral prosthetic processes. Each prosthesis takes about a month to complete.
An extraoral prosthesis functions as a cosmetic bandage, concealing surgical defects. In terms of cosmetic concerns, the most essential aspect of prostheses is their natural appearance (size, shape, and colour), which contributes to the patient's confidence.
The majority of the materials used are "silicone," which has a high degree of flexibility and cosmetic advantages. When compared to intraoral procedures, the assembly process takes 2-4 weeks on average.
Basic steps of Maxillofacial Prosthetics
- 1. A dental impression is used to imprint the missing part of the face or mouth cavity.
- 2. Making a positive reproduction (cast or model) by placing a suitable material in a dental impression tray. Size measurements may be required in some cases.
- 3. Assembly process is made by the prosthodontist to create prostheses with a natural appearance and appropriate size for each patient.
- 4. Positioning and placement of Prosthesis.
Benefits Of Maxillofacial Prosthetics
- Restoring structure and function of organs
- Cosmetic advantages
- Regaining confidence
- Enhancement of quality of life of the patient
Following prosthetic surgery, maintaining good hygiene and following the instructions recommended by the dentist are essential in order to extend the lifespan of prosthesis. Prosthetic dislocation can occur on occasion. Therefore, regular follow-up is advised.
Various alloplastic materials such as silastic sheets and blocks, Polymethylmethacrylate (PMMA), or polyether ether ketone implants are used for 3D correction of maxillofacial defects. Medical grade titanium alloy also has recently been used to fabricate 3D customised implants for the reconstruction of various facial bony defects.
Computed tomography (CT) scan is used for the acquisition of patient data. CT data are sent to the manufacturer for fabrication of the stereolithographic model. The bony defect on the stereolithographic model is reconstructed using modelling wax.
The contours are individually shaped by the doctors themselves. Morphometric measurements of the uninvolved side are duplicated on the defect side. Extension wings are created on the wax model to aid as fixation elements and the waxed-up model will be sent to the engineering lab for implant fabrication.
The wax model is scanned using a visible blue light scanner. The digital data of wax reconstruction obtained in the stereolithography (STL) will be transferred to the control data of the computer numerical control (CNC) milling machine.
The titanium implant is fabricated through this milling process. The final thickness of the implant was fixed at 0.6 mm. Holes are drilled over the surface of the implant to aid in the drainage and to prevent any extradural collection. Holes are also drilled into the extension wings to facilitate screw fixation.
Patient specific implants for oral and maxillofacial reconstruction
- Patient specific implants(PSI) with titanium alloy have revolutionised reconstructive surgeries as well as their outcomes. It is now being used in many medical specialties such as orthopaedics, neurosurgery, and craniomaxillofacial surgery. Its planning and manufacturing require acquiring technical data from the CT scan in a Digital Imaging and Communications in Medicine file format and then the file is converted into a STL file that depicts the dimensions of the implant.
- The STL file is converted into a scalable link interface file format that designs the implants into multiple layered (30 microns approx.) structures. This scalable link interface format file is then sent to the 3D printer that builds the implant by the process of additive (layer-wise) manufacturing.
- After being removed from the 3D printer, the implant is polished, wiped, and sterilised before packaging and delivery. The surgeon is also intricately involved in the designing and approval of the implant.
- Patient specific implants offer high accuracy and adaptation to the defect, enhanced stability, predictable outcomes, and better facial contour refinement.
- Implants are intraoral prostheses used to replace missing teeth. Dental implants are prosthesis used to support crowns that replace single missing teeth, bridges that restore multiple missing teeth, and even dentures in edentulous patients (toothless). Titanium is a metal that is known to be compatible with body tissues and capable of bonding with adjacent bone during healing.
- A dental implant is 4mm to 16mm long titanium screw or cylinder that is inserted into a bony socket inside the jaw and serves as a substitute for the missing tooth. The abutment is a special attachment that is fitted to the top of the dental implant and serves as the external connection to the crown, bridge or denture.
- After placement of the implant in the tooth socket, it needs to heal before the crowns can be attached. During this healing, which can take nearly two and six months, the implant surface fuses with the nearby bone by a process known as osseointegration.
- When this procedure is completed, the implant will be stable enough to support crowns, bridges, or dentures. In some cases, bone grafts are needed to prepare the jawbone to be able to support the implant.