Mechanical evaluation of six techniques for stable fixation of the sagittal split osteotomy after counterclockwise mandibular advancement

Abstract

We have evaluated the resistance to displacement of six stable methods of fixation of a sagittal split ramus osteotomy (SSRO) in the mandibular advancement with counterclockwise rotation. We tested 60 synthetic hemimandibles in six groups of 10 each: Group I - fixation with a straight four-hole 2.0mm miniplate; Group II - a straight six-hole 2.0mm miniplate; Group III - two straight 2.0mm four-hole miniplates; Group IV - an eight-hole 2.0mm (grid plate); Group V - a 2.0mm four-hole straight miniplate and 2.0×12mm bicortical screw; and Group VI - a straight four-hole 2.0mm locking miniplate. We applied a linear force in the region between the canine and the first premolar using a universal testing machine (EMIC- DL2000) with a loading cell of 10 KN. The loads at 1, 3, and 5mm displacement were recorded (N) and the data transmitted from the load cell to a computer. Results were analysed using analysis of variance (ANOVA) (p<0.001) and the Tukey post-test for comparison of the significance of the differences between the groups. For the three degrees of displacement, fixation with two straight 2.0mm plates and with the grid plate gave higher load values.

Stability of fixation methods in large mandibular advancements after sagittal split ramus osteotomy: an in vitro biomechanical study

“…This accords with other studies on mandibular advancements of 10 mm. 8,9 However, regarding stability, in two studies with minor advancement (5 mm) after SSRO the hybrid method performed better than two miniplates. 14,15 The amount of advancement may be an important factor in the rigidity gained with the hybrid method.…”

“…Other biomechanical studies have also shown that the addition of another miniplate resulted in more than double the strength of a single miniplate. 7,8,14,17 Although adding a second miniplate results in more mechanical resistance with an extra point of fixation, this does not explain why the strength of a single miniplate is more than doubled. The phenomenon may well be related to the vertical distance between the two miniplates, and according to Ellis, a larger distance will result in more rigidity.…”

“…6 However, thus far, we know of only a few biomechanical studies that have assessed the stability of fixation methods for larger advancements after SSRO. [7][8][9] One of them compared three bicortical screws with two miniplates and observed comparable stability. 9 With the lack of research regarding the stability of fixation methods beyond 10 mm, it could be hypothesised that fixation with three bicortical screws is also (in these cases) the gold standard for the most rigid fixation.…”

Investigation of a Modified Novel Technique in Bilateral Sagittal Splitting Osteotomy Fixation: Finite Element Analysis and In Vitro Biomechanical Test

“…FEA has become a popular and essential approach employed broadly in biomechanical research [ 24 – 26 ]. Owing to the scarcity of cadaveric samples and different properties of animal mandibles [ 19 , 23 , 27 ], artificial mandible bones are used [ 6 , 28 ]. Using the synthetic bones can eliminate the variables associated with animal or cadaveric bone [ 18 ], minimize interspecimen variability and variations in mandibular size, shape, bone properties, and bite forced associated with sex, age, and size [ 14 ].…”

The effect of botulinum toxin-A injection into the masseter muscles on prevention of plate fracture and post-operative relapse in patients receiving orthognathic surgery

“…Two four-hole plates are more stable than a single four-hole plate for the fixation of the mandibular ramus [ 15 ]. The stress on the condyle is less in a single four-hole plate system than two two-hole plate systems [ 16 ]. As absorbable plates are weaker than titanium plates, a longer intermaxillary fixation period is required [ 17 ].…”