Title page for ETD etd-12142010-173549
Ehlers, Hendrik Petrus URN
Prof F J Jacobs
biomechanical torsion stability
biomeganiese torsie stabiliteit
In a recent in vitro biomechanical stability study by F.J. Jacobs, a unique, patented
inclined screw insertion (I.S.I.) mandibular angle, intra-oral trauma-plate was evaluated
for torsion and compression stability and compared to conventional plating of simulated
angle fractures in polyurethane mandibular replicas.
This in vitro comparative pilot study is an extension of the above-mentioned study.
Similar I.S.I. mini-plates with 45� inclined screw holes in quadrant 3 (Fig 1), were used
but in the one sample 13mm-long lag screws were used to transect the fracture lines
where in the other group non-lagging screws of similar length were used to fixate
simulated mandibular angle fractures in polyurethane mandible replicas. A uniquely
designed and manufactured jig, incorporated in a Zwick machine, was utilized to apply
torsion forces within clinical relevant load values. The load-displacement values for
torsion forces was determined and compared for the two groups. It was established that 5
lag screws significantly improved the torsion stability of the lag-plate group to that of
the non-lag group.
During the stability testing, two factors were identified, which had a critical influence on
the compression generated by the lag screw between the fracture fragments. An adequate
amount of bone must be maintained between the first screw hole, directly distal to the
fracture line, and the fracture line. All screws must be inserted in the correct sequence in
order to insure sufficient compression between the fracture fragments as a result of the
AFRIKAANS : In `n onlangse in vitro studie deur F.J. Jacobs, is `n gepatenteerde, unieke geanguleerde miniplate, waarvan die skroefgate geanguleer is, die sg. Inklineerde Skroef Inplasing (I.S.I.) kaak-hoek, intra-orale traumaplaat geevalueer vir torsie en kompressie stabiliteit en vergelyk met konvensionele plate op gesimuleerde kaakhoek frakture in poli-uretaan
In hierdie in vitro loodstudie, is I.S.I. miniplate met skroefgate wat teen 45� geanguleer is, gebruik in kombinasie met `n enkele 13mm lange grypskroef (�lag screw�) om
gesimuleerde kaakhoek frakture in poli-uretaan mandibula replikas te fikseer. Deur
gebruik te maak van `n spesiaal ontwerpte en vervaardigde monterings-apparaat wat
binne in `n Zwick masjien ge�nkorporeer word, is die I.S.I gefikseerde replikas onderwerp aan torsie kragte, binne klinies relevante ladingswaardes. Die verplasings en ladingswaardes is geregistreer en vergelyk met identiese I.S.I miniplate sonder `n
Die loodstudie resultate het getoon dat die frakture wat gefikseerd is met die I.S.I.
miniplaat-grypskroef kombinasie betekenisvol beter stabiliteit toon as die frakture wat
met slegs die miniplaat, sonder `n grypskroef, gefikseerd is vir klinies relevante ladingsen
Tydens biomeganiese toetsing van die mandibula replikas, is twee faktore wat `n kardinale rol speel in die stabiliteit wat verkry word deur `n miniplaat grypskroef kombinasie te gebruik, ge�dentifiseer. Voldoende hoeveelheid been tussen die eerste skroefgat, direk distaal van die fraktuurlyn, en die fraktuurlyn asook die korrekte
volgorde waarin die skroewe geplaas word, moet gehandhaaf word om maksimale kompressie van die fragmente deur die grypskroef te verseker.
Deur `n I.S.I miniplaat, met geanguleerde skroefgate van 45�, te kombineer met `n
grypskroef, kan die stabiliteit van die gefikseerde mandibulere kaakhoek betekenisvol
verbeter word en verleen dit meer stabiliteit wanneer vergelyk word met frakture gereduseer met `n I.S.I miniplaat sonder grypskroef plasing.
Ehlers, HP 2010, Lag screw effect on the biomechanical torsion stability in the I.S.L monocortical mandible angle system, MSc dissertation, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-12142010-173549/ >