Effect of repair resin type and surface treatment on the repair strength of heat-polymerized denture base resin.

STATEMENT OF PROBLEM: Acrylic resin denture fracture is common in prosthodontic practice. When fractured denture bases are repaired, recurrent fractures frequently occur at the repair surface interface or adjacent areas. PURPOSE: The purpose of this study was to evaluate the effect of different surface treatments on the flexural strength of the acrylic resin denture base repaired with heat-polymerized acrylic resin, autopolymerizing resin, and light-polymerized acrylic resin. MATERIAL AND METHODS: Ninety-six specimens of heat-polymerized acrylic resin were prepared according to the American Dental Association Specification No. 12 (65.0 × 10.0 × 2.5 mm) and sectioned into halves to create a repair gap (3.0 × 10 × 2.5 mm). The sectioned specimens were divided into 3 groups according to their repair materials. The specimens from each group were divided into 4 subgroups according to their surface treatments: a control group without any surface treatment; an experimental group treated with methyl methacrylate monomer (MMA group); an experimental group treated with airborne-particle abrasion with aluminum oxide particles of 250-µm particle size (abrasion group); and an experimental group treated with erbium:yttrium-aluminum-garnet laser (laser group). After the surface treatments, the 3 materials were placed into the repair gaps and then polymerized. After all of the specimens had been ground and polished, they were stored in distilled water at 37°C for 1 week and subjected to a 3-point bend test. Data were analyzed with a 2-way analysis of variance, and the Tukey honestly significant difference test was performed to identify significant differences (α=.05). The effects of the surface treatments and repair resins on the surface of the denture base resin were examined with scanning electron microscopy. RESULTS: Significant differences were found among the groups in terms of repair resin type (P<.001). All surface-treated specimens had higher flexural strength than controls, except the surface treated with the methyl methacrylate in the heat-polymerized group. A significant difference between the control and abrasion groups (P=.013) was found. The scanning electron microscopy observations showed that the application of surface treatments modified the surface of the denture base resin. CONCLUSIONS: The repair procedure with heat-polymerized resin exhibited significantly higher flexural strength than that of the autopolymerized and light-polymerized resins. In addition, the airborne-particle abrasion with aluminum oxide particles of 250-µm particle size improved the flexural strength of the specimens tested.

Provisional repair of a zirconia fixed partial denture with fibre-reinforced restorative composite: a clinical report.

Although all-ceramic restorations have become popular, they present some biomechanical problems. Some technical failures can be repaired intraorally to help maintain the longevity of the restoration. This clinical report describes an intraoral method for repairing a fractured 4-unit posterior zirconia-based ceramic fixed partial denture using fibre-reinforced composite material.

Pulmonary risk of intraoral surface conditioning using crystalline silica.

PURPOSE: This study evaluated the pulmonary risk caused by possible respirable dust of Al2O3 and SiO(x) resulting from chairside tribochemical sandblasting procedures in a dental office. MATERIALS AND METHODS: Dust was collected using a trap near the working field, and quantitative morphologic determination and identification were performed with SEM and EDAX. Forty blasting processes (total time 20 minutes) were aimed at a dummy to obtain maximum pollution of the workplace. Respirable dust fraction was measured using personal air samplers with an 8-microm cellulose-nitrate filter and a volume flow rate of 2 L/min. Mass of the respirable dust fraction was determined, and respirable free crystalline silica was identified with the help of infrared spectroscopy. RESULTS: Blasting of metal or ceramic surfaces with tribochemical agents produces respirable and potentially harmful SiO(x) and Al2O3 particles with a diameter of less than 5 microm, showing a total concentration in the air of less than 0.3 mg/m3. With and without dental suction, the concentration of the respirable free crystalline silica was smaller than 0.02 mg/m3. CONCLUSION: Concern regarding the risk of chairside tribochemical methods and possible impairment of health of patients and dental staff is unfounded, even under extreme conditions or without protective measures, since the concentrations of SiO(x) found in the air of the workplace were far below the current threshold value of 0.15 mg/m3.

Clinical study on the reasons for and location of failures of metal-ceramic restorations and survival of repairs.

PURPOSE: A recently introduced technique, the Cojet system, using SiOx (Al2O3 coated with silisic acid), provides ultrafine mechanical retention by sandblasting, as well as a chemicophysical bond between the metal-ceramic and the composite resin. This study determined the reasons for and locations of failures of metal-ceramic restorations and evaluated the survival of the intraoral silica-coating system used for the repair of failed restorations. MATERIALS AND METHODS: A total of 153 patients possessing 289 fractured crowns were involved in this study; 255 of these fractures were on fixed partial dentures, whereas 34 were on single crowns. The mean observation period was 34.6 months. The materials used for the repair process were ESPE-Sil for silane; Visiogem, Sinfony, and Dentacolor as opaquers; and Pertac II Aplitip, Sinfony, and Charisma as repairing composite resins. RESULTS: The majority of the failures (65%) occurred in the anterior region. Sixty percent of the failures were observed at the labial, 27% at the buccal, 5% at the incisal, and 8% at the occlusal regions. The fractures were mainly in the maxilla (75%), predominantly at the labial surface. The overall cumulative survival rates of the repairs (89%) showed that the first failures happened mostly from 1 week to 3 months after the repair, without any difference between the composite resins. CONCLUSION: The original failures happened mainly during chewing function or because of accidents, iatrogenic factors, and surgical operations, whereas secondary failures after repair using intraoral silica coating and composite resin were due to trauma, chewing function, or lack of rubber dam application.

Intraoral repair of fiber-reinforced composite fixed partial dentures.

STATEMENT OF THE PROBLEM: Fractured composite facings may result in replacement of a fixed partial denture unless a reliable intraoral repair method can be provided. PURPOSE: This in vitro study tested the quality of an intraoral repair method for fractured facings of fixed partial dentures made of a fiber-reinforced composite system. MATERIAL AND METHODS: Shear bond strengths of a light-curing composite to a fiber-reinforced composite material were determined after different mechanical surface treatments. Aluminum oxide air abrading provided the most reliable bond strength values and therefore was used as a pretreatment for the facing repair of three-unit posterior fixed partial dentures. Facing repair was performed with the tested light-curing hybrid composite. Facing fracture strengths of repaired and original fixed partial dentures were determined after thermocycling and mechanical loading. RESULTS: Median facing fracture strength of the original fixed partial dentures was 1450 N after a simulated clinical service of 5 years. Facing fracture strengths of the repaired fixed partial dentures were significantly lower compared with the control group after an additional simulated 2-year interval. However, the median fracture force was still 1000 N. CONCLUSIONS: The facing repair of a fiber-reinforced fixed partial denture with a hybrid composite in combination with aluminum oxide air-abrading pretreatment and silanization provided sufficient fracture strength. Therefore the replacement of the complete restoration may be avoided.

Electroestimulación superficial como coadyuvante en la consolidación de fracturas del maxilar inferior, Hospital Regional de Apartadó (Antioquia), Noviembre 1994 – Mayo 1996 / Superficial electro stimulation as a complementary therapy in the consolidation of mandibular fractures at the Regional Hospital in Apartado, Colombia between November 1994 and May 1996

Con base en estudios sobre las relaciones entre el estrés mecánico y los potenciales eléctricos que éste genera, y en la respuesta del hueso a la corriente eléctrica, se hizo un estudio en 12 de los pacientes del Hospital Regional de Apartadó (Antioquia) que ingresaron entre noviembre de 1994 y mayo de 1996 con fracturas no complicadas del maxilar inferior. A las técnicas convencionales de intervención se adicionó la estimulación eléctrica para producir una "aceleración" biológica de la normalización del hueso afectado. -La estimulación eléctrica se aplicó durante cuatro semanas, durante un mínimo de ocho horas diarias. El proceso de reparación ósea se evaluó clínica y radiográficamente al iniciar el tratamiento, a las cuatro y a las seis semanas.- Todos los pacientes tuvieron consolidación clínica a las cuatro semanas; cinco de ellos no presentaron consolidación radiográfica. A las seis semanas todos registraron consolidación clínica y solamente cuatro no mostraron callo óseo en las radiografías.-Todos tuvieron una evolución muy favorable y se acortó el período de convalecencia de una manera significativa.

Enceramento de diagnóstico para um contorno anatômico / Diagnostic waxing for anatomic contour

Os autores através de uma revisäo da literatura, ressaltam a importância do enceramento de diagnóstico frente ao contorno das restauraçöes protéticas. Tentam deixar claro a importância do enceramento de diagnóstico tanto na fase de planejamento como durante o tratamento. Avaliam as teorias de contorno segundo seus autores, concluindo que devemos evitar o sobrecontorno das regiöes cervicais, através de um preparo adequado e um melhor entrosamento com o técnico de laboratório