Immediate Prosthetic Loading of Implants Placed in Reconstructed Jaws After Hyperbaric Oxygen Therapy

Treatment of facial tumors by mandibulectomy can cause severe esthetic, functional, and psychosocial issues. Reconstruction of facial bone defects is challenging, generally involving multidisciplinary approaches to rehabilitate affected patients. Large reconstructions using free bone grafts are possible; however, some patients require special attention when it comes time to decide which type of reconstruction procedure will be performed, such as cancer patients and patients under bisphosphonate treatment.¹  Additionally, these grafts may present increased difficulty to be incorporated compared with vascularized bone grafts.²  Thus, the use of hyperbaric oxygen therapy (HOT) has been stimulated due to the potential neo-osteogenesis and angiogenesis offered by this technique in accelerating healing of bone grafts.^3–8 

Oral rehabilitation following bone reconstruction is commonly indicated and conducted using different techniques. Implant-supported restorations are the primary restorative option, because dental implants can be successfully installed over grafted areas after the bone maturing period.⁹  However, the ideal loading moment of such implants is still a controversial topic. However, some studies suggest that adequate osseointegration is possible after immediate loading of implants in reconstructed areas.^10–12 

This report describes 3 cases of mandibulectomy followed by reconstruction using free iliac bone grafting associated to HOT and rehabilitation with immediate prosthetic loading of implants.

Three patients diagnosed with odontogenic tumors were submitted to segmental or partial mandibulectomy followed by installation of reconstructive titanium plates for maintaining facial contour and preventing bone fractures. Patient 1 was a 29-year-old woman who presented with an osteoblastoma on the posterior right side of the mandible, which was confirmed with pathologic analysis after the initial biopsy. A partial mandibulectomy was developed, and installation of a reconstruction plate of 2.4 mm (Neoortho, Curitiba, PR, Brazil) was made to prevent bone fractures. After 6 months, the reconstruction procedure was performed using nonvascularized iliac bone graft, which was fixed using 3 titanium miniplates and 4 screws for each one, system 2.0 mm (Neoortho). Patient 2 was a 38-year-old male patient, diagnosed with ameloblastoma on the left body region of the mandible. The treatment consisted of a segmental mandibulectomy of the region and installation of a reconstruction plate of 2.4 mm (Neoortho) to maintain the mandibular perimeter and facial contour. After 5 months, a reconstructive procedure, using the anterior iliac crest as a donor site to the nonvascularized bone graft, was performed. The bone graft was fixed on the reconstructive plate that was previously installed. The third case we report here is a 32-year-old woman who showed volumetric augmentation of the left region of the mandibular body, diagnosed as an ameloblastoma, and treated with partial mandbulectomy and installation of a reconstruction plate of 2.4 mm (Neoortho) to prevent bone fractures. After approximately 6 months, a nonvascularized bone graft removed from the anterior iliac crest was used to reconstruct the defect. It was fixed with 3 miniplates of 2.0 mm (Neoortho) and 4 screws for each miniplate. All patients underwent a protocol of HOT. The HOT protocol consisted of patients inhaling 100% O₂ for 90 minutes at 2.4 atmosphere absolute pressure for 10 sessions prior to reconstructive surgery and 20 sessions afterward.

Surgery for mandibular reconstruction was performed by submandibular access, location of defect, and preparation of the recipient area with small perforations. Then, iliac crest bone blocks were adapted and fixed with plates and screws in the previous prepared area (Figure 1) as reported here. After 6 months, the evaluation of the panoramic radiographies of each patient revealed good adaptation and incorporation of the bone grafts to the recipient area (Figure 2a through c). None of the patients presented with infections or pain after the reconstruction process or during the 6 months following surgery (Figure 3a through c).

Planning for implant placement was initiated with confection of provisional removable partial dentures. After adjustments, impressions of the removable dentures were taken with putty vinyl polysiloxane impression material (Express XT, 3M-ESPE, St. Paul, Minn), and self-curing resin surgical guides were obtained by duplication (Figure 4a through c). Then, conical-shaped Morse taper implants (Drive CM, Neodent) were placed into the grafted areas following the manufacturer's recommendations. All implants reached primary stability above 45 Ncm and were immediately loaded by converting the provisional removable partial dentures into implant-supported fixed partial dentures.

This step was performed by removing the base of the removable partial dentures with diamond discs and perforating the regions corresponding to the position of the implants for capturing the provisional components screwed on conical abutments (CM Mini Conical Abutment, Neodent) with self-curing resin (Dura-Liner II, Reliance Dental Mfg, Worth, Ill) (Figure 5a and b). After filling the remaining spaces between the provisional components with self-curing resin, the provisional implant-supported dentures were finished and polished using carbide (H79E, Komet Dental, Lemgo, Germany) and diamond burs (170-171, Komet Dental) (Figure 6). The provisional dentures were installed and the occlusion was checked and adjusted in centric and eccentric movements, allowing only functional contacts to reach the prostheses (Figure 7a through c).

Six months after implant placement and immediate prosthetic loading, none of the patients presented with pain, inflammation, or infection at the operated sites. Evaluation of panoramic radiographies revealed no radiolucency around the implants (Figure 8a through c). The provisional dentures remained satisfactory and stable without any screw loosening until the last visit.

Oral and maxillofacial rehabilitation of patients with major defects in facial bones is challenging. Facial trauma or treatment of jaw tumors can result in bone loss, affecting facial contour, speech, and chewing. Psychological issues may also affect these patients. The reconstruction of facial bones that undergone resection with bone grafting is commonly indicated in these cases. Patients treated for cancer and patients who received bisphosphonate therapy must be observed separately, because the reconstruction with autogenous nonvascularized free bone graft and even vascularized ones are controversial for the reason of the possibility of side effects on bone healing and the risk of transferring cancer cells.¹  However, when the indication is appropriate, placement of dental implants and the following prosthetic rehabilitation are excellent treatments for recovering masticatory ability and improving function, with better digestion and good diction in the reconstructed areas. Meanwhile, the quality of bone tissue determines the success of implant-based rehabilitations.

The resorption of nonvascularized bone grafts is an important consideration when treatment planning includes reconstruction of hard tissues and placement of dental implants associated with fixed prosthetic restorations. Some authors indicate that nonvascularized onlay iliac bone block grafts may present more resorption than intramembranous bone grafts, such as ramus, symphysis, and calvaria blocks.⁸  As an alternative to nonvascularized bone grafts, there are the vascularized ones, which can be inserted at the same time as the initial surgery with soft tissue supplied simultaneously; also, the graft can be placed in irradiated tissue, and implants can be placed primarily,¹³  all contributing to a lesser bone resorption process. As an auxiliary to the nonvascularized bone grafts is the HOT that favors successful treatment in mandibular bone reconstructions. HOT can stimulate angiogenesis and osteogenesis, thus favoring tissue repair and the overall success of bone reconstructive procedures.^3–8  Therefore, incorporation of bone grafts may be facilitated by stimulation of angiogenesis, because increased vascularization of grafted bone tissues implies decreased resorption of the reconstructed area.^3,4  This provides better preservation of tissues to receive dental implants. HOT also presents bacteriostatic and bactericidal effects, therefore preventing infections in bone-grafted sites.

A limitation for the complete rehabilitation described in this report is the long time taken from the resection of the tumor until the definitive implant-based fixed prosthesis is installed. Trying to overcome this issue, some authors have performed 1-stage procedures by placing endosteal implants during the reconstruction surgery.^14,15  This approach assumes that integration of the bone graft and osseointegration of implants occur simultaneously, becoming an alternative for decreasing treatment time. Others have suggested that a second surgery for placing dental implants after the grafted bone is completely healed would be more predictable.^11,16  Problems such as inadequate position of implants, excessive proximity, and lack of parallelism, among others, can be experienced when the 1-stage surgery approach is performed.¹⁷  On the other hand, it has been shown that waiting for the healing period of the bone graft before placing implants allows adequate revascularization and remodeling to happen, commonly resulting in increased success rates.^11,16,18  The treatment used in the 3 cases presented her is in agreement with this sequence, and the authors considered the healing time of the bone graft before placing the endosteal implants.

Some authors advocate that a waiting period varying from 3 to 6 months is ideal for allowing osseointegration before the prosthesis installation.^19,20  Other investigators have shown good results when performing immediate loading in implants placed in areas previously submitted to reconstruction with autogenous bone grafts.^10–12  When good quality of the grafted bone is observed and primary stability is achieved during implant placement, immediate loading can be performed with a provisional denture,¹⁶  because the functional loading of implants installed in bone grafts has been shown to reduce bone resorption.⁹ 

The work group who treated these cases does not have a microvascular surgery team at their disposal; therefore, because HOT is available and shows good effects, it was the choice to benefit the patients. In the cases reported here, a positive change in bone density was observed during drilling for implant placement in the grafted area compared with the free iliac bone graft of origin. The observation of the bone density was just clinical because no core sample was taken for microscopic analysis and percentage comparison. The good primary stability of the implants allowed the immediate prosthetic loading using fixed provisional dentures, anticipating the return of masticatory function to the patients. Although functional and esthetic recovery have been achieved with these complex treatments, future clinical research should be encouraged to establish the adequate protocol when designing this kind of treatment. The restorative approach described here resulted in improved nutrition capacity, muscular equilibrium, good facial appearance, and a better quality of life for the patients.

Abbreviation

HOT

hyperbaric oxygen therapy