RESUMEN
BACKGROUND: The effect of different thread designs and diameters on the all-on-four concept is unclear. OBJECTIVE: The aim of the study was to clarify the differences in stress distribution of dental implants with various thread designs and diameters based on the all-on-four concept with three dimensional (3D) finite element analysis (FEA). METHODS: A 3D model of a totally edentulous mandible was used to perform the FEA. Four different models (M1, M2, M3, and M4) including 3.5 and 4.3 mm diameter dental implants with active and passive threaded designs were generated. The dental implants were positioned according to the all-on-four concept. The Von Mises stresses on dental implants and maximum and minimum principal stresses (Pmax and Pmin) on bony structures were calculated under vertical, oblique and horizontal loads. RESULTS: For Von Mises stresses, the highest stress values were detected on the distal implants for all models. Distal implants had also the highest stress values for vertical loading. The Von Mises stresses were found to be concentrated around the implant's neck. In all models the highest Pmax and Pmin stresses occurred in the bone surrounding the distal implant. It was noted that the active threaded implants showed the highest Pmax and Pmin stress values. CONCLUSION: The implant thread design and diameter might have a strong influence on the stress values in the all-on-four concept.
Asunto(s)
Implantes Dentales , Fenómenos Biomecánicos , Simulación por Computador , Análisis de Elementos Finitos , Humanos , Programas Informáticos , Estrés MecánicoRESUMEN
The relationship between mandibular third molar (M3) angulation and mandibular angle fragility is not well established. The aim of this study was to evaluate the impact of M3 angulation on the mandibular angle fragility when submitted to a trauma to the mandibular body region. A three-dimensional (3D) mandibular model without M3 (Model 0) was obtained by means of finite-element analysis (FEA). Four models were generated from the initial model, representing distoangular (Model D), horizontal (Model H), mesioangular (Model M) and vertical (Model V) angulations. A blunt trauma with a magnitude of 2000 N was applied perpendicularly to the sagittal plane in the mandibular body. Maximum principal stress (Pmax) (tensile stress) values were calculated in the bone. The lowest Pmax stress values were noted in Model 0. When the M3 was present extra stress fields were found around marginal bone of second molar and M3. Comparative analysis of the models with M3 revealed that the highest level of stress was found in Model V, whereas Model D showed the lowest stress values. The angulation of M3 affects the stress levels in the mandibular angle and has an impact on mandibular fragility. The mandibular angle becomes more fragile in case of vertical impaction when submitted to a trauma to the mandibular body region.
Asunto(s)
Análisis de Elementos Finitos , Imagenología Tridimensional , Mandíbula/fisiopatología , Tercer Molar/fisiopatología , Heridas y Lesiones/fisiopatología , Humanos , Estrés Mecánico , Soporte de PesoRESUMEN
To assess the effectiveness of a dental instrument for reduction of isolated zygomatic arch fractures. Two patients were admitted to our clinic representing isolated unilateral zygomatic arch fracture. The common presenting complaints were pain, swelling and difficulty in mouth opening. Fractures were confirmed with plain radiography and computerized tomography. The fractures were reduced with upper buccal sulcus approach by dental instrument. Patients achieved satisfactory maximum mouth opening within 10 days. At follow up after 6 months, there was complete healing without any complication. This procedure is cost effective, time saving, safe and effective to manage isolated zygomatic arch fractures under local anaesthesia with satisfactory outcomes.
Asunto(s)
Reducción Cerrada/métodos , Instrumentos Dentales , Cigoma/cirugía , Fracturas Cigomáticas/cirugía , Reducción Cerrada/instrumentación , Humanos , Radiografía , Tomografía Computarizada por Rayos X , Cigoma/diagnóstico por imagen , Fracturas Cigomáticas/diagnóstico por imagenRESUMEN
BACKGROUND: Preoperative radiographic examination of impacted mandibular third molars (IMTM) is essential to prevent inferior alveolar nerve injury during extraction. The purpose of this study was to evaluate the correlation between cone-beam computed tomography (CBCT) and digital panoramic radiography (DPR) findings in preoperative examination of IMTM. METHODS: This retrospective study included 298 teeth in 191 individuals. The relationship between the inferior alveolar canal (IAC) and the IMTM (buccal, lingual, interradicular or inferior), the position of the IMTM with respect to the IAC (contact, no contact), the morphologic shape of the mandible in the IMTM region (round, lingual extended, lingual concave), the type of IMTM (vertical, horizontal or angular) and the number of roots of the IMTM were evaluated on CBCT images. DPR images were evaluated for the number of roots of the IMTM and for the most common radiographic findings indicating a relationship between the IAC and the IMTM (darkening of the roots, diversion of the IAC, narrowing of the IAC and interruption of the white line). Data were statistically analyzed with Cramer V coefficient, Kappa statistic, chi-square and Fisher's exact test. RESULTS: There was a significant difference in number of roots detected on DPR versus CBCT images. There was a significant association between the type of IMTM and the morphologic shape of the mandible on CBCT images. Darkening of the roots and interruption of the white line on DPR images were significantly associated with the presence of contact between the IMTM and the IAC on CBCT images. CONCLUSIONS: Panoramic radiography is inadequate, whereas CBCT is useful to detect multiple roots of IMTM. When darkening of the roots and interruption of the white line are observed on panoramic images, there is increased likelihood of contact between the IMTM and the IAC. CBCT is required in these cases.
Asunto(s)
Tomografía Computarizada de Haz Cónico/métodos , Mandíbula/diagnóstico por imagen , Tercer Molar/diagnóstico por imagen , Radiografía Dental Digital/métodos , Radiografía Panorámica/métodos , Diente Impactado/diagnóstico por imagen , Adulto , Proceso Alveolar/diagnóstico por imagen , Proceso Alveolar/inervación , Femenino , Humanos , Procesamiento de Imagen Asistido por Computador/métodos , Masculino , Mandíbula/inervación , Nervio Mandibular/diagnóstico por imagen , Persona de Mediana Edad , Cuidados Preoperatorios , Estudios Retrospectivos , Raíz del Diente/diagnóstico por imagen , Diente Impactado/clasificación , Adulto JovenRESUMEN
OBJECTIVE: Pain is the most encountered complication following third molar surgery. Although nonsteroidal anti-inflammatory drugs are often used for pain control, the effect of preemptive lornoxicam has not been detailed. We compare the analgesic efficacy of preemptive lornoxicam versus postoperative lornoxicam. STUDY DESIGN: Forty-three participants aged 18 to 33 years who had bilateral, symmetrical third molars were included in this double-blind, randomized, placebo-controlled study. All participants took part in each of the 2 groups for a 1-month interval (crossover design). Group Pre received lornoxicam 8 mg intravenously 25 minutes before surgery and 2 mL serum saline postoperatively. Group Post was given the opposite protocol. Pain was evaluated by visual analog scale in the first 12 hours. RESULTS: We observed statistically significant differences in the reduction of the pain level in group Pre (P < .05). These participants felt less pain in the first 5 postoperative hours and needed fewer analgesics in the first 12 postoperative hours. CONCLUSIONS: Preemptive lornoxicam is effective for postoperative pain control.