The aim of this study was to evaluate the mechanical strength properties of a poly-L-lactide (PLLA) bioresorbable osteosynthesis system (Neofix^®) that was bent in a staircase pattern and to compare the mechanical strength of this system with the mechanical strengths of conventional titanium osteosynthesis systems (Modus^® 1.5 and Modus^® 2.0) that were bent in the same way.
A straight 4-hole plate of Neofix^® was bent in a staircase pattern with step height of 5mm using a heated bender and fixed to artificial bones with 8-mmlong screws. Straight 4-hole titanium plates were bent in the same pattern and fixed to artificial bones with 8-mmlong screws. Plate thicknesses of Modus^® 1.5 and Modus^® 2.0 were 0.6mm and 1.0mm, respectively. Artificial bones were mounted in a mechanical testing machine (Autograph, Shimadzu Corporation) and forces were applied at a rate of 2mm/min to determine tensile strengths, bending strengths and shear strengths. Eachtest was repeated three times, and critical forces and patterns of hardware failure were recorded.
Mean tensile strength of Neofix^® was 19.1±2.0 kgf, which was about half the value of Modus^® 1.5 (38.2±0.6 kgf). Mean bending strength of Neofix^®, which was bent more than 45 degrees, was 1.56±0.08kgf, which was slightly higher than that (1.39±0.11kgf) of Modus^® 1.5 and 43% of that (3.63±0.24kgf) of Modus^® 2.0. Mean shear strength of Neofix^® was 19.9±0.8kgf, which was 38% of that (52.8±1.5kgf) of Modus^® 1.5 and 14% of that (142.0±3.8kgf) of Modus^® 2.0.
Neofix^® bent in a staircase pattern showed lower tensile strength and lower shear strength than those of the two types of titanium plates bent in the same way, although the bending strength of Neofix^® was similar to that of the titanium plates.

View full abstract

The skeletal stability after Le Fort I osteotomy and bilateral sagittal split osteotomy was evaluated on lateral cephalograms in 108 patients with mandibular prognathism with/without facial asymmetry. The subjects were divided into two groups based on the types of used osteosynthesis systems and the usefulness of a resorbable poly-L-lactide (PLLA) osteosynthesis system for bone fixation in orthognathic surgery was examined. Group A consisted of 37 patients in whom the titanium osteosynthesis system was used for bone fixation and group B consisted of 71 patients in whom the PLLA osteosynthesis system was used for bone fixation at the bilateral border of piriform aperture and the titanium osteosynthesis system was used at the zygomatic process of maxilla. Lateral cephalograms were taken before surgery, immediately after surgery, and at least six months after surgery. Changes in the positions ofpoint A, the incisal edge of the upper central incisor (U1), the incisal edge of the lower central incisor (L1), and point B were examined. The postoperative changes of the maxilla and mandible were less than 1mm on cephalograms except the vertical change at L1 in group B. There was no statistical difference in the postoperative skeletal stability between the two groups. In both groups, the tendency to relapse was greater in cases in which large movements of maxilla and/or mandible occurred during surgery. It can be concluded that the PLLA osteosynthesis system is considered to be clinically useful since the system does not have to be removed and maintains the postoperative skeletal stability.

View full abstract

It is not always simple to treat maxillary protrusion cases with marked labially inclined mandibular incisors and mandibular retrognathia. Optimal front teeth inclination, along with a proper maxillo-mandibular relation is a key factor in obtaining postsurgical longterm stability. When treating such cases, mandibular advancement only by sagittal ramus osteotomy does not lead to pertinent incisor angle at all, and hence it is crucial to improve incisor angle by other means. On such occasions, especially in narrow mandibular symphysis, the root exposes from the surface of the alveolar bone following axial improvements by ordinary orthodontic treatment. Meanwhile, anterior subapical alveolar osteotomy results in no bone contact to the basal stump of the segment, leading to poor alveolar segment stability. Therefore, we considered various treatment modalities of such condition, and finally used the following strategy. Namely, we performed genioplasty in the early stage of the presurgical orthodontic treatment to lay the infrastructure for the subsequent forward root movement. Following bone union at the osteotomy site, we secondarily carried out mandibular anterior subapical alveolar osteotomy to improve the axis of the incisors. After completing the presurgical orthodontic treatment, we performed Le Fort I and sagittal split ramus osteotomies to achieve a functional maxillo-mandibular relation. Improvements in angle measurements before presurgical and after postsurgical orthodontic treatment were: L1-Mn 92.0 improved to 81.5 degrees; L1-Oc 32.5 to 19.5; and interincisal angle improved from 111.0 to 131.5. We consider this method to be fascinating and outline of the representative case in this report.

View full abstract

Schizophrenia is an inherent disease that causes disruption of thinking patterns, sensing, self-esteem, will and emotions, resulting in mental disorder involving hallucinations and other mental symptoms.
The major complaint of this 21-year-old female patient with skeletal mandibular protrusion was thought to be pain of the temporomandibular region. However, upon careful analysis based on Narrative Based Medicine, the primary concern was the mandibular protrusion with asymmetry inducing multiple psychological symptoms. Combined ortho-surgical intervention was performed to resolve this patient's problem. Although increased antidepressant intake was noted prior to the surgery, once the treatment had been performed, resulting in major improvements of the profile and appearance, dramatic mental and psychological changes for the better were noted, allowing this patient's return to a healthy and normal social life along with decreased dependency on anti-depressant drugs.

View full abstract