Wear resistance of indirect composite resins used for provisional restorations supported by implants

PURPOSE: The aim of this study was to investigate simulated localized and generalized wear of indirect composite resins used for implant supported provisional restorations. MATERIALS AND METHODS: The study investigated ten indirect composite resins. Two kinds of wear were simulated by 400,000 cycles in a Leinfelder-Suzuki (Alabama) machine. Localized wear was simulated with a stainless-steel ball bearing antagonist and generalized with a flat-ended stainless-steel cylinder antagonist. The tests were carried out in water slurry of polymethyl methacrylate beads. Wear was measured using a Proscan 2100 noncontact profilometer in conjunction with Proscan and AnSur 3D software. RESULTS: Both localized and generalized wear were significantly different (P<.05) among the indirect composite resins. SR Nexco and Gradia Plus showed significantly less wear than the other indirect composite resins. The rank order of wear was same in both types of wear simulation. CONCLUSION: Indirect composite resins are recommended when a provisional implant-supported restoration is required to function in place over a long period. Although only some indirect composite resins showed similar wear resistance to CAD/CAM composite resins, the wear resistance of all the indirect composite resins was higher than that of bis-acryl base provisional and polymethyl methacrylate resins.

Analysis of the Relationship between Hypertrophy of the Ligamentum Flavum and Lumbar Segmental Motion with Aging Process

STUDY DESIGN: Retrospective cross-sectional study. PURPOSE: To investigate the relationship between ligamentum flavum (LF) hypertrophy and lumbar segmental motion. OVERVIEW OF LITERATURE: The pathogenesis of LF thickening is unclear and whether the thickening results from tissue hypertrophy or buckling remains controversial. METHODS: 296 consecutive patients underwent assessment of the lumbar spine by radiographic and magnetic resonance imaging (MRI). Of these patients, 39 with normal L4-L5 disc height were selected to exclude LF buckling as one component of LF hypertrophy. The study group included 27 men and 12 women, with an average age of 61.2 years (range, 23-81 years). Disc degeneration and LF thickness were quantified on MRI. Lumbar segmental spine instability and presence of a vacuum phenomenon were identified on radiographic images. RESULTS: The distribution of disc degeneration and LF thickness included grade II degeneration in 4 patients, with a mean LF thickness of 2.43±0.20 mm; grade III in 10 patients, 3.01±0.41 mm; and grade IV in 25 patients, 4.16±1.12 mm. LF thickness significantly increased with grade of disc degeneration and was significantly correlated with age (r=0.55, p<0.01). Logistic regression analysis identified predictive effects of segmental angulation (odds ratio [OR]=1.55, p=0.014) and age (OR=1.16, p=0.008). CONCLUSIONS: Age-related increases in disc degeneration, combined with continuous lumbar segmental flexion-extension motion, leads to the development of LF hypertrophy.

Analysis of the Relationship between Ligamentum Flavum Thickening and Lumbar Segmental Instability, Disc Degeneration, and Facet Joint Osteoarthritis in Lumbar Spinal Stenosis

STUDY DESIGN: Cross-sectional study. PURPOSE: To investigate the relationship between ligamentum flavum (LF) thickening and lumbar segmental instability and disc degeneration and facet joint osteoarthritis. OVERVIEW OF LITERATURE: Posterior spinal structures, including LF thickness, play a major role in lumbar spinal canal stenosis pathogenesis. The cause of LF thickening is multifactorial and includes activity level, age, and mechanical stress. LF thickening pathogenesis is unknown. METHODS: We examined 419 patients who underwent computed tomography (CT) myelography and magnetic resonance imaging after complaints of clinical symptoms. To investigate LF hypertrophy, 57 patients whose lumbar vertebra had normal disc heights at L4–5 were selected to exclude LF buckling as a hypertrophy component. LF thickness, disc space widening angulation in flexion, segmental angulation, presence of a vacuum phenomenon, and lumbar lordosis at T12–S1 were investigated. Disc and facet degeneration were also evaluated. Facet joint orientation was measured via an axial CT scan. RESULTS: The mean LF thickness in all patients was 4.4±1.0 mm at L4–5. There was a significant correlation between LF thickness and disc degeneration; LF thickness significantly increased with severe disc degeneration and facet joint osteoarthritis. There was a tendency toward increased LF thickness in more sagittalized facet joints than in coronalized facet joints. Logistic regression analysis showed that LF thickening was influenced by segmental angulation and facet joint osteoarthritis. Patient age was associated with LF thickening. CONCLUSIONS: LF hypertrophy development was associated with segmental instability and severe disc degeneration, severe facet joint osteoarthritis, and a sagittalized facet joint orientation.

Prevalence and Distribution of Thoracic and Lumbar Compressive Lesions in Cervical Spondylotic Myelopathy

STUDY DESIGN: Retrospective cross-sectional study. PURPOSE: This study analyzed the prevalence and distribution of horacic and lumbar compressive lesions in cervical spondylotic myelopathy as well as their relationships with cervical developmental spinal canal stenosis (DCS) by using whole-spine postmyelographic computed tomography. OVERVIEW OF LITERATURE: There are few studies on missed compressive lesions of the spinal cord or cauda equina at the thoracolumbar level in cervical spondylotic myelopathy. Furthermore, the relationships between DCS, and the prevalence and distribution of thoracic and lumbar compressive lesions are unknown. METHODS: Eighty patients with symptomatic cervical spondylotic myelopathy were evaluated. Preoperative image data were obtained. Patients were classified as DCS or non-DCS (n=40 each) if their spinal canal longitudinal diameter was or =12 mm at all levels, respectively. Compressive lesions in the anterior and anteroposterior parts, ligamentum flavum ossification, posterior longitudinal ligament ossification, and spinal cord tumors at the thoracolumbar levels were analyzed. RESULTS: Compressive lesions in the anterior and anteroposterior parts were observed in 13 (16.3%) and 45 (56.3%) patients, respectively. Ligamentum flavum and posterior longitudinal ligament ossification were observed in 19 (23.8%) and 3 (3.8%) patients, respectively. No spinal cord tumors were observed. Thoracic and lumbar compressive lesions of various causes tended to be more common in DCS patients than non-DCS patients, although the difference was statistically insignificant. CONCLUSIONS: Surveying compressive lesions and considering the thoracic and lumbar level in cervical spondylotic myelopathy in DCS patients are important for preventing unexpected neurological deterioration and predicting accurate neurological condition after cervical surgery.

Analysis of the Prevalence and Distribution of Cervical and Thoracic Compressive Lesions of the Spinal Cord in Lumbar Degenerative Disease

STUDY DESIGN: Retrospective study. PURPOSE: The aim of the present study is to analyze the prevalence and distribution of cervical and thoracic compressive lesions of the spinal cord in lumbar degenerative disease, using whole-spine postmyelographic computed tomography. OVERVIEW OF LITERATURE: Of the various complications resulting from spinal surgery, unexpected neurological deterioration is the most undesired. There are reports of missed compressive lesions of the spinal cord at the cervical or thoracic level in lumbar degenerative disease. METHODS: There were 145 consecutive patients with symptomatic lumbar degenerative disease evaluated. Before the lumbar surgery, image data were obtained. The following parameters at the cervical and thoracic levels were analyzed: compressive lesions from the anterior parts; compressive lesions from the anterior and posterior parts; ossification of the ligamentum flavum; ossification of the posterior longitudinal ligament; and spinal cord tumor. RESULTS: Compressive lesions from the anterior parts were observed in 34 cases (23.4%). Compressive lesions from the anterior and posterior parts were observed in 34 cases (23.4%). Lesions of ossification of the ligamentum flavum were observed in 45 cases (31.0%). Lesions of ossification of the posterior longitudinal ligament were observed in 15 cases (10.3%). Spinal cord tumor was not observed. CONCLUSIONS: A survey of compressive lesions at the cervical or thoracic level in lumbar degenerative disease is important in preventing unexpected neurological deterioration after the lumbar surgery.

Predictable Imaging Signs of Cauda Equina Entrapment in Thoracolumbar and Lumbar Burst Fractures with Greenstick Lamina Fractures

STUDY DESIGN: A retrospective study. PURPOSE: The aim of present study was to investigate imaging findings suggestive of cauda equina entrapment in thoracolumbar and lumbar burst fractures. OVERVIEW OF LITERATURE: Burst fractures with cauda equina entrapment can cause neurologic deterioration during surgery. However, dural tears and cauda equina entrapment are very difficult to diagnose clinically or radiographically before surgery. METHODS: Twenty-three patients who underwent spinal surgery for thoracolumbar or lumbar burst fractures were enrolled in this study. In magnetic resonance imaging T2-weighted images of the transverse plane, we defined cauda equina notch sign (CENS) as a v-shaped image that entrapped cauda equina gathers between lamina fractures. We evaluated the fractured spine by using CENS and lamina fractures and the rate of available space for the spinal canal at the narrowest portion of the burst fracture level. We classified patients into entrapment group or non-entrapment group, based on whether cauda equina entrapment existed. RESULTS: Lamina fractures were detected in 18 (78.3%) and CENS were detected in 6 (26.1%) of 23 burst-fracture patients. Cauda equina entrapment existed in all the patients with CENS. In addition, the rate of available space for the spinal canal increased according to logistic regression. The size of the retropulsed fragment in the spinal canal was the most reliable of all the factors, suggesting cauda equina entrapment. CONCLUSIONS: CENS was the most predictable sign of cauda equina entrapment associated with burst fractures.

Effect of lumbar angular motion on central canal diameter: positional MRI study in 491 cases / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Lumbar spinal stenosis is a common problem that is receiving attention with the advent of novel treatment procedures. Prior positional MRI studies demonstrated lumbar canal diameter changes with flexion and extension. There have not been any studies to examine the amount of spinal canal diameter change relative to the amount of angular motion. The purpose of this study was to evaluate the correlation between the lumbar canal diameter change and the angular motion quantitatively.</p><p><b>METHODS</b>Positional MRI (pMRI) images for 491 patients, including 310 males and 181 females (16 years-85 years of age), were obtained with the subjects in sitting flexion 40 degree, upright, and with extension of 10 degrees within a 0.6 T Positional MRI scanner. Quantitative measurements of the canal diameter and segmental angle of each level in the sagittal midline plane were obtained for each position. Then the diameter change and angular motion were examined for correlation during flexion and extension with linear regression analysis.</p><p><b>RESULTS</b>The lumbar segmental angles were lordotic in all positions except L1-2 in flexion. The changes of canal diameters were statistically correlated with the segmental angular motions during flexion and extension (P < 0.001). The amount of canal diameter change correlated with the amount of angular change and was expressed as a ratio.</p><p><b>CONCLUSIONS</b>Positional MRI demonstrated the amount of spinal canal diameter change that was statistically correlated with the segmental angular motion of the spine during flexion and extension. These results may be used to predict the extent of canal diameter change when interspinous devices or positional changes are used to treat spinal stenosis and the amount of increased canal space may be predicted with the amount of angular or positional change of the spine. This may correlate with symptomatic relief and allow for improved success in the treatment of spinal stenosis.</p>

Rabbit Model for in vivo Study of Intervertebral Disc Degeneration and Regeneration

OBJECTIVE: The purpose of this study is to verify the usefulness of the rabbit model for disc degeneration study. MATERIALS: The L1-L2, L2-L3, L3-L4, or L4-L5 lumbar intervertebral disc (IVD) of 9 mature male New Zealand White rabbits were injured by inserting a 16-gauge needle to a depth of 5 mm in the left anterolateral annulus fibrosus while leaving L5-L6 IVD uninjured. Three other rabbits also received intradiscal injections of rabbit disc cells transfected with adenovirus and bone morphogenetic protein-2 (ad-BMP-2) at L4-L5 in addition to injury by 16-gauge needle at the L1-L2 level. Using digitized radiographs, measurements of IVD height were made and analyzed by using the disc height index (DHI). Magnetic resonance imaging (MRI) scans of the injured discs, injected discs, and uninjured L5-L6 discs were performed at 15 weeks post surgery and compared with preoperative MRI scans. RESULTS: All twelve rabbits showed consistent results of disc degeneration within 15 weeks following annular puncture. DHIs of injured discs were significantly lower than that of the uninjured L5-L6 discs (p<0.05). The mean value of disc degeneration grade of injured discs was significantly higher than that of uninjured discs (p<0.05). The injection of disc cell transfected with ad-BMP-2 did not induce disc regeneration at 15 weeks after injection. CONCLUSION: This study showed that the injured disc had a significant change in DHI on simple lateral radiograph and disc degeneration grade on MRI scans within 15 weeks in all rabbits. Rabbit annular puncture model can be useful as a disc degeneration model in vivo.

Effect of Coix Seed Extract on Muscle Cramps in Patients under Hemodialysis / 日本東洋医学雑誌

Leg cramps are frequently seen in patients who are undergoing hemodialysis. Syakuyaku-kanzo-to is usually effective against leg cramps, but not for all patients. On the other hand, Yokuinin, coix seed, has been known to restrain spasms of the frame muscle. This paper reports on the effectiveness of Yokuinin in controlling leg cramps during hemodialysis-especially when Shakuyaku-kanzo-to is not effective. Tests were performed on nine patients who have had maintenance hemodialysis in our hospital, and whose leg cramps were not responsive to Syakuyaku-kanzo-to. The patients were provided with three to six tablets of Yokuinin (Yokuinin extract tablet “Kotaro”) a day, and the effect on their leg cramps was measured after three weeks. Yokuinin was effective on five patients, whose leg cramps disappeared (an efficacy rate of 55.6%). Side effects were not observed. These results suggest that Yokuinin is a useful medicine (as part of a treatment regimen of traditional medicine) for leg cramps that result from hemodialysis-especially with patients for whom Shakuyaku-kanzo-to is not effective.

Therapeutic Effect of Coix Seed Extract Drug on Hydrathrosis in Patients under Hemodialysis / 日本東洋医学雑誌

Yokuinin, coix seed extract, has been used to regulate gastric functions and to reduce pathological water retention. This paper reports the effect of Yokuinin on controlling hydrarthrosis for patients with arthralgia. Seventeen patients who have had maintenance hemodialisis for an average of 12.7 years and who have suffered hydrarthrosis with arthralgia have been tested. There are 7 male and 10 female patients, with an average of age of 63.4. The hydrarthrosis of the patients resulted from dialysis arthropathy and gonarthrosis. The patients were provided with 3 to 6 tablets of Yokuinin (Yokuinin extract tablet “Kotaro”) a day, and the effect on hydrarthrosis was measured after 3 weeks. The dosage of Yokuinin was 0.33g in 3 tablets. Yokuinin was effective on 14 patients (hydrarthrosis was reduced), relatively effective on 2 patients, and not effective on one patient. This shows an efficacy rate of 82.8%. Arthralgia was reduced for 12 patients, and analgesia was seen in 3 patients. Effective reduction of hydrarthrosis by this medicine was observed: 5 cases out of 6 for patients with dialysis arthropathy (83.3%); 6 cases out of 7 for gonarthrosis (85.7%); and 3 cases of 4 for other diseases (75.0%)—a total of 82.8%. The patient for whom the drug was not effective was suffering from acute hydrarthrosis. Side effects were not observed except for indigestion and cramps. These results suggest that Yokuinin is an effective medicine to control hydrarthrosis with arthralgia for patients under hemodialysis.