Fracture of the anterior segment of the atrophic mandible related to dental implants

Abstract

Implant placement in an anterior atrophic mandible is not an uncommon procedure. Fracture secondary to such implant placement is a rare complication. The authors discuss a case referred to their surgical centre and discuss the management approaches found in the English literature.

Patients with atrophic mandible are often elderly with brittle bones and reduced healing capacity of the hard and soft tissues compared to younger individuals. To restore form and function in these edentulous patients, implant supported overdenture has been proposed as a treatment option with a success rate of 80–100% or a bone graft surgical procedure to precede implant placement. Such surgical procedures are predictable but side effects and complications can occur such as neurosensory disturbance, infection, improper placement, haemorrhage, and mandible fracture, which is reported to occur at a rate of 0.2%. The rate of occurrence seems to be low, but it can lead to devastating outcomes such as osteomyelitis, parasthesia, malunion, non-union, and prolonged functional and nutritional disturbances. The authors present the case of a 77-year-old female patient who had five anterior mandibular implants placed to support an overdenture and developed a mandible fracture at the distal implant area of the right mandible first premolar (RMFP). The authors review and discuss the different treatment approaches reported in the English literature to treat similar cases.

Case report

A 77-year-old female patient was referred to the Oral and Maxillofacial Surgery unit in McGill University Health Centre, Montreal General Hospital for a fractured mandible and a loose implant at the RMFP. She had controlled hypothyroidism with replacement therapy and no known drug allergy. The patient reported having five implants placed by her dentist in the edentuolous anterior atrophic mandible. Four days after the surgery, the patient started to use her old relined denture as a provisional prosthesis and 1 week later, she felt a crack in her mouth whilst eating. Her dentist carried out a clinical and radiographic examination which showed a fracture of the RMFP area ( Fig. 1 ) and she was referred for management.

Fig. 1
Preoperative panoramic radiograph showing the mandible fracture at the right premolar area.

At her initial hospital examination, the authors noticed the following positive findings: localized pain on palpation at the fracture site; right inferior alveolar nerve (IAN) parasthesia; the implant at RMFP had grade two mobility; the fractured bone segments were exposed intraorally; and there was minimal echymosis lingual to the fracture site. The working diagnosis was displaced, compound right mandible body fracture at the RMFP implant position that was removed to avoid accidental aspiration or swallowing.

The patient was offered an intraoral open reduction and internal fixation (ORIF) using a 2.4 locking reconstruction plate. The main advantage of using an intraoral rather than an extraoral ORIF in this case is to avoid the risk of injuring the marginal mandibular branch of the facial nerve. It is also a less invasive procedure and it avoids the risk of orocervical communication. The authors anticipated sufficient access for plate fixation at the symphysis/parasymphysis area, and with transbuccal access at the body/angle area. The procedure and the possible surgical complications were discussed thoroughly with the patient, including possible damage to the other implants, non-union, IAN injury, infection, haematoma, fixation failure and the need for the transcervical approach. The patient was admitted and placed on amoxicillin 500 mg p.o. every 8 h.

Under general anaesthesia (orotracheal intubation), the incision was placed at the crest of the mandible with two distal vertical releases to elevate a full thickness flap. The mental nerves were identified and protected throughout the procedure ( Fig. 2 ). After identification of the anatomical structures and exposing the fracture segment, the granulation tissue and necrotic bony specules were curetted and the area copiously irrigated with normal saline. The other implants were checked and found to be stable. Reduction of the bony segments was performed and a plate template was applied and adapted to fit at the inferior mandible border where fixation took place using 2.4 screws placed directly between the implants in the anterior region and indirectly through a transbuccal access to the right mandible body/angle areas. A gap of approximately 4–5 mm was noticed at the fracture segment and immediately grafted using autogenous particulate bone harvested from the external oblique ridge, ramus, and chin areas using a sharp scraper ( Fig. 2 ).

Fig. 2
Postoperative panoramic radiograph at 9 months showing the reduction and fixation using a 2.4 mm reconstruction plate.

To prepare for closure, the flap at the lower lip side was undermined to achieve tension free approximation at the anterior segment. The mentalis muscle was reapproximated using 3-0 Vicryl sutures over the plate and the flap was watertight-sutured using 4-0 Vicryl suture. A chin external dressing was placed and maintained for 2 weeks. The patient was placed on amoxicillin 500 mg p.o. every 8 h and chlorhexidine 0.12% mouthwash every 12 h. On the second postoperative day, mitronidazole 500 mg p.o. every 8 h was added after the patient reported feeling bitter salty taste (as pertaining to purulent discharge) were clearly identified. A series of postoperative mandibular radiographs was taken, which showed adequate plate and screw fixation positioning ( Fig. 2 ). The patient was started on a clear fluid diet and was discharged on the third postoperative day in a stable condition.

A follow up visit, 8 days postoperatively, demonstrated a 4 mm wound dehiscence showing healthy bone at the left anterior mandible that was managed by local wound normal saline irrigation every 6 h, oral hygiene and weekly follow ups. Antibiotics were continued for a total of 15 days postoperatively and the dehisced area showed stable healing by secondary intention. The patient was kept on amoxicillin and mitronidazole for 15 days postoperatively. Follow up visits were continued and showed overall stable wound healing and right IAN parasthesia to be improving slowly. The overdenture bar was inserted 4 months postoperatively.

At 20 postoperative months, the patient shows good wound healing and normal lip sensation (IAN parasthesia has disappeared). The patient is using her implant supported overdenture and is satisfied with the overall results.

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Jan 26, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Fracture of the anterior segment of the atrophic mandible related to dental implants
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