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Chapter 4120Surgical risks and operation timeThe immediate advantage of a patient-fitted prosthesis is that it requires no alteration of the patient’s anatomy. The total contact surface between the mandibular component and the mandible is optimal for improved osseointegration and stability.(2) In contrast, when using a stock implant, either the bony surface has to be fitted to the implant, or the implant must be bent or grinded down. This increases the total operation time and puts the materials at risk for fatigue and micromotions, which can lead to implant failure.(2,11,12,24,37) Zhoa et al.(37) set out to evaluate the amount of bone that needed to be removed or grafted to achieve a good fit for the stock Biomet system in 63 joints they had treated between 2010 and 2016. Computer simulation revealed that a medium amount of bone trimming was needed (150-300 mm³ bone) in 46% of skull bases, and in 33% a large volume (>300 mm³) of bone trimming was necessary. The mandibular bone required medium and large amounts of trimming in 27% and 29% of all cases, respectively. Furthermore, in 44% of all cases a medium bone graft was needed elsewhere on the fossa to achieve a good fit, while in 35% a large amount was needed. They concluded that a patient-fitted implant required less adaptation, which decreases surgery time and the risk of injury to the skull base and alveolar nerve.(37) Similarly, Abramowicz et al.(38) set out to evaluate the necessity of the use of a patient-fitted implant in 22 cases by evaluating if a stock Biomet implant could be fitted to the stereolithographic models of patients who were treated with an TMJ Concepts device. They found that in 23% of all sites, no fit could be achieved by means of a stock implant. In an additional 27% of all sites, significant alterations had to be performed to either the skull base or condylar bone with a minimum of 3 mm of bone that needed to be removed. They concluded that in more complex cases, such as patients who underwent multiple operations or who have more severe anatomical abnormalities, the use of a patient-fitted solution should be preferred over a stock implant. However, for more straightforward and simple cases, they found that a stock implant was a more cost-effective solution.(38)Nikolas de Meurechy NW.indd 120 05-06-2024 10:14