170,026 research outputs found
Precisión y estabilidad dimensional de poliéteres y siliconas utilizados para la toma de impresiones en prótesis fija
No full textFil: Albera, Hugo Alejandro. Universidad Nacional de Córdoba. Facultad de Odontología; Argentina.Uno de los problemas que afectan y pueden determinar el fracaso de las prótesis fijas es la falta de adaptación o ajuste marginal de las restauraciones finales sobre pilares dentarios convenientemente preparados. Entre los factores que tienen incidencia en estos problemas se pueden mencionar:
1- Incorrecta selección o manipulación de los materiales de impresión. 2- Inapropiada selección de la cubeta, ya sea por: a) la falta de rigidez, pues una cubeta flexible puede ser deformada elásticamente en la zona de las paredes, particularmente si se ejerce indebida presión durante la toma de la impresión. b) la presencia de perforaciones en la cubeta que afecten la recuperación elástica del material utilizado, particularmente cuando esta característica se asocia a flexibilidad (de la cubeta) e inadecuada adhesión del material de impresión a sus paredes. C) el tamaño de la cubeta, ya que los elastómeros no deberian comprimirse más de un 30%, ya que si esto ocurre el material no podrá recuperar su volumen original; por ello es conveniente calcular un margen de seguridad. El espesor de material debería ser 3 a 4 veces mayor que la zona retentiva del maxilar o área a impresionar. d) la ausencia de dispositivos de retención del material o no utilización de adhesivo adecuado, pues puede producirse un desprendimiento parcial o total del material de impresión de las paredes de la cubeta con consecuentes deformaciones. 4- La utilización de una técnica inadecuada, ya sea en: a) la mezcla del material b) el llenado de la cubeta c) la ubicación de la cubeta con material de impresión d) la presencia de humedad excesiva. e) el retiro de la impresión. 5- El inapropiado almacenamiento de la impresión, en cuanto a: a) tiempos sugeridos por el fabricante a) temperatura c) metodología de desinfección 6- La incorrecta confección del modelo en lo que respecta a: a) selección del material de vaciado incompatible con el material de impresión (tipos de yeso, resinas epóxicas, resinas poliuretánicas, troqueles galvanoplásticos) b) proporción indebida de la relación entre los componentes conque se vaciará el modelo (por ejemplo si el material a emplear es yeso densita, la proporción yeso/agua) C) técnica de mezclado, ya sea manual o mecánico d) técnica de llenado e) tiempo de fraguado insuficiente f) elaboración de troqueles individuales ) delimitación del margen protético h) aplicación indebida de laca espaciadora si la estructura a confeccionar es colada
7- Errores durante el cierre del margen cervical del encerado 8- Errores en el procedimiento de investido
9- Imprecisiones durante la colada de las estructuras metálicas 10- Deformación por tracción de los metales inadecuadamente preparados durante la cocción de sobreestructuras cerámicas. Las estructuras o copings obtenidos vía CAD/CAM no eliminan las falencias descriptas anteriormente entre los factores enunciados relativos a la toma de impresiones y obtención de modelos de trabajo, ya que para su
obtención el escaneo o lectura se hace, en la mayoría de los sistemas actuales, sobre modelos o troqueles individuales.Fil: Albera, Hugo Alejandro. Universidad Nacional de Córdoba. Facultad de Odontología; Argentina
Menieres' disease symptomatology in relation to the AAO-HNS 1995 guidelines
No full textAim. Meniere's disease (MD) is a complex progressive disorders of the inner ear characterized by sensorineural hearing loss, episodic vertigo, tinnitus and aural fullness. MD diagnosis is essentially clinical and specialized test equipment should not be required. In 1995 the Committee on Hearing and Equilibrium of the American Academy of Otolaryngology - Head and Neck Surgery published recommended guidelines for the diagnosis of the MD (3) classifying it in certain, definite, probable and possible. It was the aim of this paper to determine, in a large series of subjects affected by MD according to the AAO-HNS 1995 criteria, the distribution of the different forms, their relationship with clinical paramters and the aspects of the evolution of the disease over time. Methods. The study group consisted of 384 consecutive subjects affected by MD according to the AAO-HNS 1995 guidelines. In each case we have carried out an exhaustive anamnesis regarding all the aspects of the disease and audiometric threshold. Results. According to AAO-HNS classification 228 subjects (59%) at the moment of the first control in our department were affected by definite MD, 30 (8%) by probable MD and 126 (33%) by possible MD. In this sample, among the 129 subjects of this group 90 (73%) were affected only by hearing loss and 36 (27%) only by vertigo. Age at the beginning of the disease was not different among definite, probable and possible forms while subjects affected by the certain MD were older and presented a longer duration of the disease. Disability level was lesser in the possible forms, condition in which the lower degrees are more represented. Among the 228 definite forms, MD appeared with both vertigo and hearing loss together (temporal delay less than 24 hours) in 79 cases (35%), with hearing loss alone in 96 cases (42%) and with vertigo alone in 53 cases (23%). PTA mean threshold at 0.5-1-2-3 kHz at the first control in the 228 cases of definite MD is worse than in the 90 subjects subjects affected by possible MD in its cochlear form. Conclusion. In conclusion definite form represents the most common form of MD at diagnosis and comprises the most disabling cases. However in the larger part of cases it begin as possible and transforms in definite later, normally within 5 years
Ossicular Chain Lesions in Tympanic Perforations and Chronic Otitis Media without Cholesteatoma
No full textOBJECTIVE: The first aim was to determine the prevalence, kind, and functional effects on hearing of ossicular chain suffering (OCS) in chronic otitis without cholesteatoma (NCOM) and tympanic perforations (TP). The second aim was to correlate the findings with clinical parameters and hearing level.MATERIALS AND METHODS: The study group comprised 250 consecutive patients affected by NCOM and who were subjected to tympanoplasty and never operated on before. Each patient underwent preoperative pure tone audiometry. Ossicles were evaluated during surgery. The incidence of OCS in NCOM was reported in 15-62% of the patients.RESULTS: Ossicular chain suffering was found in 26 out of the 250 patients included in the overall sample (10%). It was found in 7% of the patients affected by TP without otorrhea and in 19% of the patients affected by chronic ear discharge with drum perforation. OCS was found most frequently in posterior eardrum perforations and in patients with bilateral disease. The incus was the ossicle most frequently interested by resorption (92% of the patients). The air conduction threshold and air bone gap were more impaired in NCOM than in TP.CONCLUSION: Ossicular chain damages in patients with non-cholesteatomatous middle ear pathologies are not frequent and are present in no more than 10% of the patients, but lesions found were similar to those reported in patients with cholesteatoma. Otorrhea, posterior perforation, and bilateral disease can be considered as good predictors of OCS
Hearing loss in Ménière disease
No full textBACKGROUND: Hearing loss in the unilateral form of Ménière disease (MD) is described as a low-frequency sensorineural deficit that has to be greater than 30 dB at least at two contiguous frequencies below 2000 Hz. The aim of the present study was to determine whether the audio metric pattern of the hearing loss in a large series of definite MD patients correlates with parameters proposed by the Barany Society consensus paper. METHODS: The study group was composed by 275 patients suffering from episodes of typical MD vertigo and unilateral low-frequency fluc tuating hearing loss. RESULTS: According to the Barany Society criteria, 133 (48%) patients presented a hearing threshold difference greater than 30 dB between the two ears at least at two contiguous frequencies. In particular, the hearing threshold difference between was greater than 30 dB in 50% of cases at 250 Hz, in 53% of cases at 500 Hz and in 41% of cases at 1 kHz. According to the updated 2015 Barany Society criteria, only 48% of diseases which were previously claimed "definite MD"on the basis of the 1995 AAO guidelines can be really considered definite MD. CONCLUSIONS: Our study suggests that the limit of 30 dB of differential hearing threshold between the two ears seems too large, possibly leading to high rates of misdiagnosis
Clinical features and long-term outcome of ipsilateral delayed endolymphatic hydrops
No full textBACKGROUND: Ipsilateral delayed endolymphatic hydrops (IDEH) is a disease characterized by recurrent acute vertigo that manifests after the appearance of a severe sensorineural non-hydropic hearing loss without symptomatology at the other ear. The cause of hearing loss can be congenital or acquired and, in the latter group, the hearing loss is usually sudden or secondary to head or acoustic trauma, ear surgery, viral infection, otitis media, streptomycin, meningitis, inner ear abnormality or idiopathic. METHODS: Data from 37 IDEH patients, who account for 3.4% of the overall sample of menieric patients at our institution, were analyzed in this retrospective study. RESULTLTS: The mean age of the sample was 58 years. Mean duration of the disease at the moment of diagnosis was 57 months. Follow-up ranged from 24 to 180 months (average: 87 months). Hearing loss at the ear cause of IDEH was due to sudden hearing loss in 23 cases (62%), chronic otitis operated on in five cases (14%) and congenital in one case (3%); in eight cases (21%) the cause of hearing loss was unknown. Mean age of appearance of IDEH was 54 years, mean interval between the appearance of HL and IDEH was 82 months and mean duration of the disease at the time of diagnosis was 57 months. Mean PTATA threshold at the affected ear was 88 dB. After dietetic and medical treatment, with a follow-up of 24 to 180 months (average: 87 months), we have obtained the resolution of vertigo crisis, or an acceptable reduction in crisis intensity and/or frequency, in 50 patients (88%). In the remaining seven patients intratympanic gentamicin, following the titration method, was applied, with the resolution of vertigo in six of them (88%); in one cases we have carried out the labyrinthectomy, that solved vertigo crisis. CONCLUSIONS: In conclusion IDEH is a not frequent form of Ménière's disease with good long-term prognosis and in case on vertigo not responsive to medical therapy intratympanic gentamicin labyrinthectomy can solve symptomatology
Management of acoustic neuroma: A retrospective study
No full textBACKGROUND: Acoustic neuromas (AN) are benign tumors of the vestibulocochlear nerve with classic symptomatology that include unilateral sensorineural hearing loss, tinnitus, dizziness, facial and/or trigeminal neuropathy. There are different treatment options of AN: watchful waiting, microsurgical resection, stereotactic radiation and the choice depends by many variables such age, health and hearing of patients as size, location and growing status of tumor. The objective of this retrospective study is to better understand the differences in demographic, hearing status, symptoms, tumor characteristics in patients affected by AN presenting at our clinic and analyze the factors that influence the therapeutic choice. METHODS: One hundred and three patients affected by AN were included in the study. All subjects underwent a detailed clinical interview and audio-vestibular examination, and magnetic resonance imaging (MRI). Tumor status, growing or stable, was estimated comparing new size to any previous MRI with at least a 6-month interval. Descriptive statistics were used for clinical and demographic features of patients. Therapeutic choices related to subjective symptoms were assessed with the chi-square test. RESULTS: Treatment options in our sample included watchful waiting, surgical resection and stereotactic radiosurgery. Overall, 17 patients (16.5%) pursued surgical resection via the retrosigmoid approach, 3 patients (2.9%) were treated with gamma knife stereotactic radiosurgery and 83 patients (80.6%) underwent watchful waiting. The decision-making process for AN treatment was based on size of tumor, age, and hearing loss; a statistically significant difference was found between the size of tumor and PTA of patients that underwent retrosigmoid surgery. No statistically significant difference was found at chi-square test between the type of treatment and symptoms (P=0.719). The analysis of the data showed that the main elements taken into consideration for surgery were the size of tumor (P<0.000004) and, secondly, the PTA threshold; the latter may be due to the fact that patients with bigger tumors had greater hearing impairment (P<0.001). Disease progression influenced the therapeutic decision making with a positive correlation between tumor progression and surgery (P<0.001). CONCLUSIONS: In our sample active surveillance was the most adopted option for small tumor, slow growth and old age. Microsurgical resection was the preferred treatment in patients with large tumors, hearing deterioration and rapid growth. Stereotactic radiation has been proposed in a few cases of elderly patients with slow growing tumor and mild hearing loss
A case of extensive squamous cell carcinoma of the external auditory canal with multiple negative biopsies
No full textWe present the case of a squamous cell carcinoma of the external auditory canal, with double negative biopsy and an imaging before surgery non indicative. The histological examination of the surgical piece did not found any cellular atypies, and the diagnosis was made based upon the clinical and the postsurgical radiological findings
Short-term result of mannitol administration on hearing loss improvement in Menière's disease and in sensorineural low-frequency fluctuating hearing loss without vertigo
No full textIn 1995 Menière's disease has been classified by an international guideline, on the basis of auditory and vestibular symptoms, in four different forms: certain, definite, probable and possible. According to this guideline fluctuating low frequency hearing loss was considered as possible Menière's disease. Since the administration of osmotic diuretic, such as mannitol, has been proposed in diagnosis and therapy it is the aim of this paper to evaluate if there are some differences is the hearing threshold modification after mannitol administration in two groups of patients affected by possible and definite Menière's disease. The study was carried out on 137 patients affected by definite (39%) and possible (61%) Menière's disease, according to 1995 guidelines, and submitted to 18% (intravenous) IV mannitol therapy. After therapy we have found in both groups a significant improvement of hearing threshold in about 30% of cases. Improvement was not related with sex, age and age of appearance of symptomatology while it was related with the duration of the disease that was significantly shorter in subjects who showed a significant hearing improvement. In conclusion IV mannitol administration is a reliable therapy in improving acute hearing loss in possible and definite Menière's disease
Underlay or overlay myringoplasty in children: Which approach is better?
No full textBACKGROUND: Bilateral tympanic membrane perforation may cause a loss of hearing resulting in impaired social interactions and academic performance, delayed language and cognitive development, and lower learning abilities in children, the overlay and the underlay techniques are the two standard methods for perforation repair, with much debate between which of the two is better, especially from the functional point of view. We compared the perforation closure rates and hearing improvement after surgery with the overlay and the underlay techniques to determine which of the two is preferable for tympanic membrane perforation repair in children. METHODS: This retrospective study involved 149 patients who had undergone myringoplasty. Pure tone audiometry was conducted before and after surgery and functional results were defined considering the air bone gap. RESULTS: The overall perforation closure rate was 91.9% in underlay and 90% in overlay technique and the air-bone gap <10 dB was respectively 60.6% and 38%. CONCLUSIONS: In conclusion, myringoplasty may be safe even in younger children and both techniques can achieve high rates of anatomical success. The optimal results after the underlay technique suggest that it should be more widely used and that it should be the first option when considering repair of tympanic membrane perforation
Relationship between hearing threshold at the affected and unaffected ear in unilateral Meniere’s disease
No full textHearing loss in Menière’s disease has been described to affect above all low frequencies (upward curve) with a tendency to become irreversible and non-fluctuating at the higher frequencies (peaked curve) over time. The aim of the study was to determine the effects of MD on hearing function on the basis of differences existing between the affected and the unaffected ear in a group of patients affected by definite unilateral MD and whose contralateral ear was not affected by any disease other than age-related hearing loss (ARHL). Following this procedure we have also evaluated the possible effects of age and disease duration on hearing loss in MD. The study group consisted of 86 subjects affected by definite unilateral MD. In our sample a peaked audiometric curve characterized the affected ears; however, the result after subtracting the normal ear hearing threshold was an upward sloping curve, which highlighted the greater suffering at the lower frequencies. On the basis of differences existing between affected and unaffected ear, our data suggest that threshold evolution is more related to disease duration rather than to age
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