Osseointegrated implants, either in native bone or in reconstructed bone, have allowed clinicians to provide greater function and esthetics, following treatment of head and neck pathology. The survival of these implants may be in variance with the success and survival we see with osseointegrated implants in conventional, nonablative rehabilitation. This article looks at the survival and complications with using osseointegrated implants in rehabilitation of the maxillofacial region.
Key points
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Planning, from the stage of the original resection surgery to the final installation of implants, is a factor in success of the implants and the prosthesis.
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In the mandible, microvascular free flap rehabilitation is the main stay of implant rehabilitation.
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In the maxilla, zygomatic implants have reduced the need for microvascular procedures for rehabilitation.
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Planning on implant position and management of soft tissue are important considerations in extraoral prosthesis (epithesis).
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Patient-specific implants may be useful in maxillofacial rehabilitation but await refinement and long-term follow-up of survival.
Introduction
Facially disfigured patients with cancer are primarily concerned with survival. Yet, as their survival becomes apparent, they become concerned with their disfigurement.
Rogers and colleagues have shown that following surgery for head and neck cancer, patients are not only concerned about appearance, but more so about speech, swallowing, and chewing function.
Rehabilitation of patients with head and neck cancer, therefore, needs careful planning to restore these functions.
The use of osseointegrated implants (OSIs) has revolutionized the rehabilitation of patients with oral and facial defects. It not only allows the restoration of the dentition but also provides palatal seal and more stable extraoral prostheses such as orbit, nose, and ear, which are almost impossible to restore back to their original appearance otherwise.
However, the use of implants (OSIs) has its limitations and challenges. The long-term survival of implants in many of these situations is not well documented. This review article aims to present the current evidence on the role of implants in maxillofacial rehabilitation prosthetics.
Implant survival versus success
Implant survival in conventional dental rehabilitation in nontumor patients is documented to be 83% to 97%.
The data on implant survival in oncology or tumor patients are, however, confusing.
Success rates of 77% to 99% are reported in various studies. The reason is primarily because implant survival does not mean implant success.
Implant placement in maxillofacial defects is particularly challenging compared to conventional defects for the following reasons.
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Patients compromised health, smoking and lack of oral hygiene
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Volume of residual bone, quality of bone, and its anatomic relationship to the original mandible
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Trismus, limitation of access due to scarring or bulky, mobile soft tissue
Additionally
- 1.
Single implant loss may not mean failure of the prosthesis as many times these patients have additional implants placed
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Implants may have been placed at the time of surgery but not restored due to lack of favorable access for restoration, recurrent tumor, or poor general health
This illustrates the need for careful planning and a multidisciplinary approach to make the rehabilitation of this group of patients successful.
Implants in mandibular rehabilitation
Dental implants can be placed in the native mandible or in reconstructed bone graft. Evidence suggests that patients with remaining existing dentition tend to prefer functioning on the existing natural teeth. All efforts, therefore, during resection and reconstruction should made toward preserving the mandible arch relationships of the presurgical position.
Intermaxillary fixation, virtual surgical planning and reconstruction of the temporomandibular joint are ways of preserving this ( Figs. 1–6 ).
Decision-making in implant rehabilitation of the mandible
Native Mandible or Reconstructed Mandible
Evidence of success/failure of implants in different types of bone is conflicting.
Schliephake reported higher success rate in implants placed into mandible bone grafts, compared to native mandible. It must be noted that the native mandible bone implants were mostly placed 1 year after radiation. The bone grafts were mostly vascular grafts placed after irradiation. Most other studies have shown lower success rate in bone grafts than in native mandible bone.
Native mandible may have better success than bone grafts if the site has not been subjected to radiotherapy. Doses of 60 cGy and above increase the risk of failure. Intensity Modulated Radiotherapy (IMRT) and 3 dimensional (3D) planned radiotherapy allow reference study of the doses to the implant sites to help this decision ( Figs. 7 and 8 ).
Vascularized bone grafts are better than nonvascularized bone. Among various bone flaps, the success in Fibula and Deep Circumflex Iliac Artery flap (DCIA) seems to be the best. Scapula and radial may not have similar success rates. ,
If fibula flaps are used, a number of techniques are used to improve the positioning of the implants to improve prosthetic rehabilitation. These are ( Figs. 9–14 ):
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Double barreling
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Distraction of the fibula
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Positioning the fibula higher in the anterior zone
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Using a patient-specific implant (PSI) to reconstruct the lower border and onlaying fibula above
Radiotherapy and Smoking
Radiotherapy to the site has the following detrimental effects.
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Poor bone vascularity
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Reduced soft tissue vascularity and fibrosis
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Reduced infection resistance, increasing risk of peri-implantitis
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Local inflammation
Statistically, there is a 30% failure rate of implants placed after radiotherapy. Vascularized flaps have a similar risk after radiotherapy. Overengineering, by placing additional implants to plan for failure may be a strategy in these patients.
Many patients who had radiotherapy may be ex-smokers or continue to smoke, which has deleterious effects on the success of implants after radiotherapy.
Primary or Secondary Rehabilitation
Primary implant rehabilitation has its advantages. These are
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Avoid additional surgery
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Reduce cost
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Avoid hyperbaric oxygen/pentoxifylline (Pentoclo) therapy
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Better osseointegration
A number of techniques of primary rehabilitation such as the Rohner technique, Alberta technique, and Sydney technique are described. These are discussed by Gabriela and colleagues.
Secondary implant rehabilitation has certain advantages over primary placement.
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Better assessment of disease status
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Oral function, motivation and ability to maintain oral hygiene
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Allow time for recovery of primary effects of radiotherapy. Evidence suggests that a 12 month waiting period improves the success of implants after radiotherapy
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Tumor recurrence incidence is highest at 8 to 12 months after surgery. Placement after this window may improve the ability to detect early recurrence. Recurrences can sometimes mimic peri-implantitis and peri-implant soft tissue hyperplasia.
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Better prosthetic planning
Soft Tissue Management
Lack of keratinized tissue around implants, lack of prosthetic space for a vestibule, and bulk of soft tissue are some of the challenges in rehabilitation of these patients.
Having fixed keratinized tissue reduces complications and makes maintenance easier.
In our experience, the denture-guided regeneration (DGR) technique creates healthy peri-implant tissue with long-term success ( Figs. 15–18 ).
Removable or Fixed Prosthesis
Evidence suggests that for this group of patients, a removable prosthesis is more favorable over a fixed prosthesis. Implant survival and oral hygiene were significantly better in this group (see Figs. 13 and 14 ).
Patients having mandible rehabilitation have a number of factors making fixed prosthetics undesirable. These factors are
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General factors: radiotherapy, lack of saliva, smoking, and poor oral hygiene
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Unfavorable bone–implant position, poor soft tissue contours, and need for lip support with a flange
However, psychological and functional outcomes may be slightly improved with fixed prosthesis. Where implant position and soft tissue is favorable, a fixed prosthesis may be constructed.
Assessment of patients prior to implant rehabilitation of mandible
The points mentioned earlier illustrate why correct assessment of patients planned for mandible rehabilitation is important ( Fig. 19 ). Extensive resource waste and unnecessary treatment may otherwise result. The following factors are important to assess :
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Adequate motivation and realistic expectations
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Good oral hygiene
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Adequate bone and suitable arch relationship
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Adequate oral function including mouth opening, lip seal, and tongue mobility
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No medical contraindication
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Adequate funding and resources
Implant rehabilitation of maxilla and midface
The challenges of rehabilitation of the maxilla and midface are somewhat different to those of the mandible.
Disability of speech, nasal regurgitation, enophthalmos and loss of facial form are the common problems requiring rehabilitation ( Figs. 20–22 ).
