Assessment of compression and strength of divergent screws mounted on miniplates for fixation of mandibular fractures: an in vitro experimental study.
An efficient band of tension is critical for the adequate fixation of mandibular fractures, so fixation devices that compress are helpful. We aimed to evaluate the possibility of creating compression using screws inserted divergently into miniplates placed in the tension zone of mandibular fractures and record the effects on the strength of fixation. For this in vitro experimental study we prepared 20 sheep hemimandibles. After angle fractures had been created, the specimens were divided into standard and study groups (n=10 in each). In the standard group the tension zones were fixed in the standard manner with 4-hole miniplates and 4 parallel screws. Those in the study group were fixed as for the standard group but with 4×45° divergent screws. The differences in the gap in the fracture line before and after fixation were measured as indicators of compression. The strength of fixation was also assessed with a universal testing machine in vitro. The amount of compression was significant only in the study group (p<0.001), and there was no difference in the strength of fixation between the two groups (p=0.7). We conclude that divergent drilling and insertion of screws creates more horizontal force when miniplates are used, and results in reduction in the size of the probable gap in the fracture line. Insertion of divergent screws in miniplates may create compression between fractured segments without jeopardising the strength of fixation.
Associate professor, Department of Oral and Maxillofacial Surgery, Dental school, Dental Research Center, Taleghani Hospital, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
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Jafarian
Associate professor, Department of Oral and Maxillofacial Surgery, Dental school, Taleghani Hospital, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
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Pourdanesh
Resident, Department of Oral and Maxillofacial Surgery, Dental school, Taleghani Hospital, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
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Esmaeelinejad
Resident, Department of Oral and Maxillofacial Surgery, Dental school, Taleghani Hospital, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
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Dehghani
Resident, Department of Oral and Maxillofacial Surgery, Dental school, Taleghani Hospital, Shahid Beheshti University of Medical Sciences, Tehran, Iran. Electronic address: Fal2zad@gmail.com.
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Aghdashi
Assistant Professor, Department of Oral and Maxillofacial Surgery, Dental school, Taleghani Hospital, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
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Tabrizi
D000818:Animals; D001672:Biocompatible Materials / Q000737:chemistry; D001696:Biomechanical Phenomena; D001860:Bone Plates; D001863:Bone Screws; D004867:Equipment Design; D005593:Fracture Fixation, Internal / Q000295:instrumentation*; D008337:Mandibular Fractures / Q000473:pathology / Q000601:surgery*; D008422:Materials Testing; D008904:Miniaturization; D012756:Sheep; D013314:Stress, Mechanical; D014025:Titanium / Q000737:chemistry
D001672:Biocompatible Materials; D014025:Titanium
Bone plates; Fracture fixation; Mandibular fractures