Skeletal changes in patients with mandibular prognathism after mandibular set back and bimaxillary surgery: A comparative cephalometric study

Abstract

Bacground/Aim. Recently, maxillary and bimaxillary surgery gained the primacy in the surgical correction of class III deformities. The aim of this investigation was to compare the changes in the skeletal relationships in patients with mandibular prognathism after bimaxillary surgery. Methods. The study included 70 subjects divided into three groups. Twenty class III patients of the experimental group 1 underwent bilateral sagittal ramus osteotomy and twenty patients of the experimental group 2 were subjected to bimaxillary surgery. The control group consisted of 30 subjects with skeletal class I and physiological occlusion. Cephalometric research was conducted on 110 lateral cephalometric radiographs made in subjects of the experimental groups 1 and 2 before and after surgery and in subjects of the control group. Using the computer program "Dr. Ceph", 30 linear and angular skeletal variables were analyzed on each radiograph. Results. Bimaxillary osteotomies changed most of variables that characterize the mandibular prognathism. The changes in the sagittal plane included the significant increase of sella-nasion to the A point (SNA) angle (by 4º on the average) and the A point to B point (ANB) angle (6°), and significant reduction in angles sellanasion to the B point (SNB) (3º), gonial angle (ArGoMe) (8°), gonial angle inferior (NGoMe) (6.2º), and Björks sum (7°). The vertical relationships were normalized by significant reduction in overall anterior face height N-Me (by 5 mm on the average), the lower anterior face height ANS-Me (4 mm), significant increase in the total posterior face height S-Go (2.5-3 mm), lower posterior face height PNS-Go (4 mm), and significant reduction of the basal and mandibular plane angles. Conclusion. Compared to the isolated mandibular operations, bimaxillary surgery changes more efficiently the sagittal and vertical skeletal relations in patients with class III deformities and harmonizes more successfully the entire skeletal facial profile.

Uvod/Cilj. Maksilarna i bimaksilarna hirurgija dobila je nedavno primat u hirurškim korekcijama deformiteta klase III. Cilj ovog istraživanja je bio da se uporede promene u skeletnim odnosima kod bolesnika sa mandibularnim prognatizmom posle bimaksilarne operacije. Metode. Ispitivanjem je obuhvaćeno 70 ispitanika podeljenih u tri grupe. Dvadeset ispitanika klase III eksperimentalne grupe 1 podvrgnuto je bilateralnoj sagitalnoj ramus osteotomiji, a dvadeset ispitanika eksperimentalne grupe 2 podvrgnuto je bimaksilarnoj operaciji. Kontrolnu grupu činilo je 30 ispitanika sa skeletnom klasom I i fiziološkom okluzijom. Rendgen-kraniometrijsko istraživanje obavljeno je na 110 bočnih telerendgen snimaka urađenih kod ispitanika u eksperimentalnim grupama 1 i 2 pre i posle operacije i ispitanika kontrolne grupe. Koristeći kompjuterski program "Dr.Ceph", na svakom telerendgenu analizirano je 30 linearnih i ugaonih skeletnih varijabli. Rezultati. Bimaksilarna osteotomija promenila je većinu varijabli koje karakterišu mandibularni prognatizam. Promene u sagitalnoj ravni uključuju značajan porast ugla maksilarnog prognatizma (SNA) (od 4º u proseku) i ugla gagitalnog odnosa tela gornje i donje vilice (ANB) ugla (6°), značajno smanjenje uglova ugao mandibularnog prognatizma (SNB) (3º), ganialnog ugla (ArGoMe) (8°), donjeg gonialnog ugla (NGoMe) (6,2º), i Bjorkovog poligona (7°). Vertikalni odnosi su normalizovani značajnim smanjenjem ukupne prednje visine lica NMe (od 5 mm u proseku), prednje donje visine lica (ANBMe) (4 mm), povećanjem ukupne zadnje visine lica M-Go (2,5-3 mm), zadnje donje visine lice PNS-Go (4 mm), i značajnim smanjenjem mandibularnih uglova. Zaključak. U poređenju sa izolovanom mandibularnom operacijom bimaksilarna hirurgija menja efikasnije sagitalne i vertikalne skeletne odnose kod bolesnik sa deformitetima klase III i uspešnije harmonizuje ceo skeletni profil lica.