Stress analysis of mandibular implant overdenture with locator and bar/clip attachment: Comparative study with differences in the denture base length

PURPOSE: The design of the attachment must provide an optimum stress distribution around the implant. In this study, for implant overdentures with a bar/clip attachment or a locator attachment, the stress transmitted to the implant in accordance with the change in the denture base length and the vertical pressure was measured and analyzed. MATERIALS AND METHODS: Test model was created with epoxy resin. The strain gauges made a tight contact with implant surfaces. A universal testing machine was used to exert a vertical pressure on the mandibular implant overdenture and the strain rate of the implants was measured. RESULTS: Means and standard deviations of the maximum micro-deformation rates were determined. 1) Locator attachment: The implants on the working side generally showed higher strain than those on the non-working side. Tensile force was observed on the mesial surface of the implant on the working side, and the compressive force was applied to the buccal surface and on the surfaces of the implant on the non-working side. 2) Bar/clip attachment: The implants on the both non-working and working sides showed high strain; all surfaces except the mesial surface of the implant on the non-working side showed a compressive force. CONCLUSION: To minimize the strain on implants in mandibular implant overdentures, the attachment of the implant should be carefully selected and the denture base should be extended as much as possible.

Cerebello-Pontine Angle Lipoma: Case Report and Review of the Literature

Intracranial lipomas located in the cerebellopontine angle are extremely rare. These tumors are maldevelopmental lesions which can cause slowly progessive neurological symptoms. The clinical management of these tumours differs significantly from other lesions in this region. A 45 year old man presented with a 3-month history of vertigo and tinnitus in the left ear. In T1-weighted magnetic resonance imaging, the lesion was hyperintense and did not enhance after application of gadolinium. The patient was treated with medical therapy with good response. We present a review of the literature, with particular regard to management. Conservative treatment is recommended and limited surgery is usually indicated if the patients suffer from disabling neurological symptoms and signs e.g., vertigo, nausea, trigeminal neuralgia, facial weakness or facial spasm.

Results of Vestibular Function Tests in Patients with Cerebello-Pontine Aangle Tumors

BACKGROUND AND OBJECTIVES: Acoustic neuroma (AN) is commonly encountered in the cerebello-pontine angle (CPA) and AN arises principally from the vestibular division of the nerve, which can show not only hearing disturbance but also various vestibular symptoms and laboratory findings by affecting central and peripheral vestibular system. Vestibular testing is reported not to be a useful screening test for AN, but can be helpful in defining whether the tumor arises from the superior or inferior division and identifying the cause of dizziness or vertigo. MATERIALS AND METHOD: We are presenting four patients with CPA tumors accompanied by various abnormal findings of vestibular function tests including head-shaking nystagmus, vibration-induced nystagmus, hyperventilation- induced nystagmus and vestibular evoked myogenic potential and subjective visual vertical, which can enable us to understand the pathomechanism of the abnormal results. RESULTS: All patients presented hearing loss and mild dizziness. Caloric test, head thrust test and vibration-induced nystagmus was helpful in localizing the disease, but head-shaking nystagmus and hyperventilation-induced nystagmus was less helpful. Otolith tests did not always show abnormal results. CONCLUSION: We should consider abnormal results of the vestibular function tests in a whole to estimate the status of vestibular compensation in patients with CPA tumors.