Kunio Yoshizawa

Changes in computed tomography values of mandibular condyle and temporomandibular joint disc position after sagittal split ramus osteotomy

PURPOSEnThe purpose of this study was to evaluate change in computed tomography (CT) value of condyle and temporomandibular joint (TMJ) disc position after sagittal split ramus osteotomy (SSRO) setback surgery, retrospectively.nnnSUBJECTS AND METHODSnThe subjects were 76 patients (152 condyles) who underwent bilateral SSRO setback surgery. They were divided into 2 groups (43 symmetric patients and 33 asymmetric patients). CT values (pixel values) of 5 sites of the condyle and condylar width, length, horizontal angle were measured pre-operatively and 1 year post-operatively. Disc position was classified as anterior disc displacement, anterior type, fully covered type and posterior type, preoperatively and postoperatively using magnetic resonance imaging (MRI).nnnRESULTSnIn maximum CT value at the center of the condyle, post-operative value was significantly lower than pre-operative value bilaterally (Deviation side: P = 0.0003, Non-deviation side: P = 0.0003) in asymmetry group. In minimum CT value at the center of the condyle, the post-operative value was significantly lower than the pre-operative value bilaterally (Deviation side: P = 0.0309, Non-deviation side: P = 0.0004) in the symmetry group. With regard to maximum CT value at the lateral site of the condyle in the deviation side, the value for the anterior disc displacement group was significantly larger than that of the posterior type pre-operatively (P = 0.0123). CT value of the anterior disc displacement group was significantly larger than those of some other areas pre- and post-operatively (P < 0.05).nnnCONCLUSIONnThis study suggested that CT value of condylar bone changes after 1 year in SSRO and anterior disc displacement may partially affect the CT value of the condyle in the TMJ in mandibular prognathism patients.

Evaluation of factors affecting recovery period in lower lip hypoesthesia after sagittal split ramus osteotomy in mandibular prognathism patients

PURPOSEnThe purpose of this study was to evaluate the factors affecting the recovery period of lower lip hypoesthesia after sagittal split ramus osteotomy (SSRO) in mandibular prognathism patients using multivariate analysis, retrospectively.nnnSUBJECTS AND METHODSnThe subjects were 222 patients (444 sides) who underwent bilateral SSRO setback surgery with and without Le Fort I osteotomy. Trigeminal nerve hypoesthesia at the region of the lower lip was assessed bilaterally by the trigeminal somatosensory-evoked potential (TSEP) method pre- and post-operatively. Recovery period was determined as the time when TSEP was first measurable post-operatively. Age, sex, presence or absence of third molars, setback amount and osteotomy type and fixation method were selected as covariates in the multivariate analysis. The factor affecting the recovery period in lower lip hypoesthesia was examined with Coxs proportional hazard regression.nnnRESULTSnSex and osteotomy fixation method affected the recovery period in lower lip hypoesthesia significantly (P = 0.0132 and P = 0.0394). However, the other factors did not affect the recovery period.nnnCONCLUSIONnThis study suggested that sex and osteotomy type and fixation method may affect the recovery period in lower lip hypoesthesia after SSRO setback surgery.

Comparison of skeletal stability after sagittal split ramus osteotomy among mono-cortical plate fixation, bi-cortical plate fixation, and hybrid fixation using absorbable plates and screws

PURPOSEnThe purpose of this study was to examine skeletal stability and plate breakage after sagittal split ramus osteotomy (SSRO) with the mono-cortical plate fixation, bi-cortical plate fixation, and hybrid fixation techniques using absorbable plates and screws.nnnMATERIALS AND METHODSnA total of 76 Japanese patients diagnosed with mandibular prognathism with and without maxillary deformity were divided into 3 groups randomly. A total of 28 patients underwent SSRO with mono-cortical plate fixation, 23 underwent SSRO with bi-cortical plate fixation, and 25 underwent SSRO with hybrid fixation. Skeletal stability and horizontal condylar angle were analyzed by axial, frontal, and lateral cephalograms from before the operation to 1 year postoperatively. Breakage of the plate and screws was observed by 3-dimensional computed tomography (3DCT) immediately after surgery and after 1 year.nnnRESULTSnAlthough there was a significant difference between the mono-cortical plate fixation group and hybrid fixation group regarding right MeAg in T1 (Pxa0=xa00.0488) and occlusal plane in T1 (Pxa0=xa00.0346), there were no significant differences between the groups for the other measurements in each time interval. In 2 cases, namely, 6 sides in the mono-cortical plate fixation group, breakage of the absorbable plate was found by 3DCT. However, there was no breakage in the bi-cortical plate fixation group and hybrid fixation group.nnnCONCLUSIONnThis study results suggested that there were no significant differences in the postoperative skeletal stability among the 3 groups, and bi-cortical fixation as well as hybrid fixation was a reliable and useful method to prevent plate breakage even if an absorbable material was used.

Changes in occlusal function after orthognathic surgery in mandibular prognathism with and without asymmetry

This study aimed to evaluate the postoperative changes in masticatory function in patients with jaw deformities with or without asymmetry treated by orthognathic surgery. Thirty female patients who underwent a Le Fort I osteotomy with sagittal split ramus osteotomy (SSRO) were enrolled. The patients were divided into symmetry and asymmetry groups. The bite force, occlusal contact area, and bite force balance were measured before and at 1, 3, and 6 months and 1 year after surgery; these measurements were compared statistically within and between the two groups. In the symmetry group, there was a significant difference in the preoperative bite force and the 1 month postoperative bite force (P=0.0033). In the asymmetry group, the bite force before surgery was significantly different from that at 1 month (P=0.0375) and at 1 year (P=0.0353) after surgery. Significant differences in the bite force were also observed between the following time points: 1 month and 1 year (P=0.0003), 3 months and 1 year (P=0.0034), and 1 month and 6 months (P=0.0486). The occlusal contact area, bite force, and occlusal balance tended to change after Le Fort I osteotomy with SSRO, with a significantly improved bite force in patients with asymmetry before surgery.

Change in mandibular body height at the site of a fixation plate in the advance (lengthening) and setback (shortening) sides after sagittal split ramus osteotomy

PURPOSEnThe purpose of this study was to evaluate changes in mandibular body height at the site of a fixation plate in the advance (lengthening) and setback (shortening) sides after sagittal split ramus osteotomy (SSRO).nnnSUBJECTS AND METHODSnThe subjects were 49 patients (98 sides) who underwent bilateral SSRO surgery. The subjects were divided into 4 groups as follows, setback (shortening) sides in mandibular prognathism (Prog S group; nxa0=xa042), advancement (lengthening) sides in mandibular retrognathism (Retro L group; nxa0=xa024), setback (shortening) sides in mandibular asymmetry (Asym S group; nxa0=xa016) and advancement (lengthening) sides in mandibular asymmetry (Asym L group; nxa0=xa016). Postoperative computed tomography (CT) was analyzed for all patients pre-operatively, and at 1 week and 1 year postoperative. Mandibular body height at the site of the fixation plate, mandibular upper height above the plate and mandibular lower height under the plate were measured by 3-dimensional (3D) CT.nnnRESULTSnThere were no significant differences in mandibular height between the lengthening and shortening sides in mandibular prognathism, retrognathism and asymmetry in the time-course change. Upper mandibular height at the mid-point of the fixation plate after 1 year was significantly smaller than that after 1 week in all sides (Pxa0<xa00.05).nnnCONCLUSIONnThis study suggested that slight bone resorption could occur at the upper site of a fixation plate after set back and advancement SSRO.

Evaluation of bone formation after sagittal split ramus osteotomy using different fixation materials

PURPOSEnThe purpose of this study was to evaluate bony change between the proximal and distal segments after sagittal split ramus osteotomy (SSRO) using different fixation materials.nnnSUBJECTS AND METHODSnThe subjects consisted of 74 patients (21 male and 53 female; 148 sides) who underwent SSRO with and without Le Fort I osteotomy. They were divided into five groups: (1) an MT group, mono-cortical titanium plate fixation (26 sides); (2) an MA group, mono-cortical absorbable plate fixation (48 sides); (3) a BA group, bi-cortical absorbable plate fixation (22 sides); (4) an MAα group, mono-cortical plate absorbable fixation with α-tricalcium phosphate (36 sides); and (5) a BAα group, bi-cortical plate absorbable fixation with α-tricalcium phosphate (16 sides). Ramus square (RmS), ramus width (RmM-RmL) and ramus length (RmA-RmP) at the horizontal plane under the mandibular foramen were assessed pre-operatively, immediately after surgery, and at 1 year after surgery by computed tomography (CT).nnnRESULTSnThere were significant differences among the groups regarding change over time in RmS (pxa0=xa00.0126) and RmM-RmL (pxa0=xa00.0001). However, there was no significant difference among the groups regarding change over time in RmA-RmP.nnnCONCLUSIONnThese results suggest that the use of different fixation materials leads to significant differences in the bone healing process after SSRO.

Comparison of temporomandibular joint and ramus morphology between class II and class III cases before and after bi-maxillary osteotomy

PURPOSEnThe purpose of this study was to compare changes in temporomandibular joint (TMJ) and ramus morphology between class II and III cases before and after sagittal split ramus osteotomy (SSRO) and Le Fort I osteotomy.nnnMATERIALS AND METHODSnThe subjects were 39 patients (78 sides) who underwent bi-maxillary surgery. They consisted of 2 groups (18 class II cases and 21 class III cases), and were selected randomly from among patients who underwent surgery between 2012 and 2016. The TMJ disc tissue and joint effusion were assessed by magnetic resonance imaging (MRI) and the TMJ space, condylar height, ramus height, ramus inclination and condylar square were assessed by computed tomography (CT), pre- and post-operatively.nnnRESULTSnThe number of joints with anterior disc displacement in class II was significantly higher than that in class III (pxa0<xa00.0001). However, there were no significant differences between the two classes regarding ratio of joint symptoms and ratio of joint effusion pre- and post-operatively. Class II was significantly better than class III regarding reduction ratio of condylar height (pxa0<xa00.0001) and square (pxa0=xa00.0005).nnnCONCLUSIONnThe study findings suggest that condylar morphology could change in both class II and III after bi-maxillary surgery. The findings of the numerical analysis also demonstrated that reduction of condylar volume occurred frequently in class II, although TMJ disc position classification did not change significantly, as previously reported.

Comparison of lower lip hypoesthesia between hybrid fixation and conventional fixation following sagittal split ramus osteotomy

PURPOSEnThe purpose of this study was to compare the recovery period of lower lip hypoesthesia between hybrid fixation and conventional fixation using absorbable plates and screw systems following sagittal split ramus osteotomy (SSRO).nnnSUBJECTS AND METHODSnThe subjects were 66 patients (132 sides) who underwent bilateral SSRO setback surgery. They were divided into a hybrid fixation group (66 sides, 1 u-HA/PLLA plate and 4 mono-cortical screws and a bi-cortical screw in each side) and a conventional fixation group (66 sides, 1 u-HA/PLLA plate and 4 mono-cortical screws in each side). Trigeminal nerve hypoesthesia at the region of the lower lip was assessed bilaterally by the trigeminal somatosensory-evoked potential (TSEP) method.nnnRESULTSnThe mean measurable periods were 8.1 ± 10.4 weeks in the hybrid fixation group, 5.1 ± 11.5 weeks in the conventional group with no significant difference. However, the maximum in the hybrid fixation group was 27 sides at 4 weeks postoperative and in the conventional fixation group was 37 sides at 1 week postoperative, and there was significant difference in the distribution of the measurable period (P < 0.0001).nnnCONCLUSIONnThis study suggested that additional bi-cortical screws could affect the recovery of lower lip hypoesthesia after SSRO with bent absorbable plate fixation.

Effect on surface character and mechanical property of unsintered hydroxyapatite/poly‐l‐lactic acid (uHA/PLLA) material by UV treatment

Materials fabricated with unsintered hydroxyapatite/poly-l-lactic acid (uHA/PLLA) exhibit biological activity and biocompatibility, but are also hydrophobic. This hydrophobicity limits the ability of cells or tissues to adhere to the surface of the material and thereby prevents the materials from exhibiting effective biological activity. In this study, we examined the effects of ultraviolet (UV) treatment on the hydrophobicity of uHA/PLLA. We compared the contact angle, mechanical strength, cell attachment, and cell differentiation capacity between untreated uHA/PLLA and uHA/PLLA treated with UV light. The contact angle of UV-treated uHA/PLLA was significantly reduced compared with that of untreated uHA/PLLA. However, there were no differences in mechanical strength between untreated uHA/PLLA and UV-treated uHA/PLLA. Notably, the ability of cells to adhere to UV-treated uHA/PLLA was significantly increased compared with that of untreated uHA/PLLA. Similarly, there were significant differences between UV-treated uHA/PLLA and untreated uHA/PLLA in alkaline phosphatase assays. These findings demonstrated that UV irradiation of uHA/PLLA improved the surface hydrophilicity without changing the mechanical strength of the material; thus, UV treatment of uHA/PLLA may facilitate the use of this material in biomedical applications.

Condylar surface CT value in sagittal plane before and after sagittal split ramus osteotomy

PurposeThe purpose of this study was to evaluate the relationship between computed tomography (CT) values of the condylar surface and temporomandibular joint (TMJ) disc position in the sagittal plane before and after sagittal split ramus osteotomy (SSRO) setback surgery, retrospectively.Materials and methodsThe subjects were 75 patients (150 condyles) who underwent bilateral SSRO setback surgery. They were divided into two groups (42 symmetric patients and 33 asymmetric patients). Maximum CT values (pixel values) of five points of the condylar surface and condylar height, length, fossa height, fossa length, and ramus angle in the sagittal plane were measured preoperatively and 1xa0year postoperatively. Disc position was classified as anterior disc displacement, anterior type, fully covered type, and posterior type, both pre- and postoperatively, using magnetic resonance imaging (MRI).ResultsPostoperative value was significantly higher than preoperative one in CT value of 135° (Pxa0=xa00.0199) and 180° (0.0363), in the non-deviation side in the asymmetry group. The anterior disc displacement group was significantly larger than those of some other areas pre- and postoperatively in the CT value of 0° point (Pxa0<xa00.05).ConclusionsThis study suggested that CT value of the posterior site of the condylar surface could change in the non-deviation side in the asymmetry group after 1xa0year SSRO, and the condyle with anterior displacement showed high CT value at the anterior site of the condyle before and after surgery.