An improved formulation of chloroquine for intramuscular administration: absorption kinetics in rabbits.

Intramuscular chloroquine is rapidly absorbed, even in severe falciparum malaria, and may cause potentially lethal hypotension. Less rapidly absorbed formulations should be safer. A chloroquine phosphate solution containing 2% methylcellulose 1500 released chloroquine 2.6 times more slowly than a commercial aqueous solution in an in-vitro absorption simulator. There was a log linear relationship between viscosity and release rate. The absorption pharmacokinetics of the more viscous chloroquine phosphate solution were then compared with those of a commercial solution after intramuscular injection to eight rabbits in an open cross over comparison. The rate of absorption was over three times slower with the viscous solution; median time to peak whole blood concentration with the commercial aqueous solution was 10 (range 5-20) min compared with 30 (range 10-60) min for the more viscous formulation (P less than 0.05). Peak whole blood concentrations were 66% (95% CI 50-82%) of those with the commercial preparation, but the acute bioavailability of the two solutions was similar. This simple new formulation may be safer than currently available chloroquine preparations and should now be evaluated in man

An Evaluation of Fracture Strength of Zirconium Oxide Posts Fabricated Using CAD-CAM Technology Compared with Prefabricated Glass Fibre Posts

Post and core therapy is regarded as the treatment of choice for restoring severely damaged endodontically treated teeth. Critical control of endodontic materials in the coronal third of the canal and pulp chamber is essential in order to maintain its colour and translucency. In addition to this, the duplication of the optical characteristics of an intact tooth, including shade translucency and fluorescence is often made difficult by the use of metal infrastructures. As a result of this tooth colored posts have gained popularity especially in aesthetic areas. Besides aesthetics, the post is also responsible for transmitting the occlusal forces to the remaining tooth structure making the mechanical properties of the post critical. However, there is no clear consensus regarding an ideal system as far as strength of the post is concerned. Hence this study aims to analyses and compares the fracture strength of traditional prefabricated glass fibre posts with zirconium oxide posts constructed using CAD CAM technology

Ex vivo fracture resistance of direct resin composite complete crowns with and without posts on maxillary premolars.

Contains fulltext : 47466.pdf (publisher's version ) (Closed access)AIM: To investigate ex vivo the fracture resistance and failure mode of direct resin composite complete crowns with and without various root canal posts made on maxillary premolars. METHODOLOGY: The clinical crowns of 40 human extracted single-rooted maxillary premolars were sectioned at the cemento-enamel junction. The canals were prepared with Gates Glidden drills up to size 4. Thirty samples were provided with standardized post spaces in the palatal canal and all roots were embedded in acrylic. Minimal standardized preparations in the canal entrances were made. Groups of 10 samples were treated with (i) prefabricated metal posts, (ii) prefabricated glass fibre posts, (iii) custom-made glass fibre posts, and (iv) no posts (control). Posts were cemented with resin cement and resin composite complete crowns were made. All specimens were thermocycled (6000x, 5-55 degrees C). Static load until fracture was applied using a universal loading device (crosshead speed 5 mm min(-1)) at a loading angle of 30 degrees . Failure modes were categorized as favourable and unfavourable failures. RESULTS: No significant difference was observed between the mean failure loads (group 1: 1386 N, group 2: 1276 N, group 3: 1281 N, and group 4: 1717 N, P > 0.05), nor between frequencies of failure modes (P > 0.05). All failures were fractures of the resin composite crown in combination with tooth material (cohesive failures). CONCLUSIONS: Within the limits of this laboratory investigation it is concluded that severely damaged and root filled maxillary premolars, restored with direct resin composite complete crowns without posts have similar fracture resistances and failure modes compared to those with various posts, which suggest that posts are not necessarily required

Resistance to compression of weakened roots subjected to different root reconstruction protocols

OBJECTIVE: This study evaluated, in vitro, the fracture resistance of human non-vital teeth restored with different reconstruction protocols. MATERIAL AND METHODS: Forty human anterior roots of similar shape and dimensions were assigned to four groups (n=10), according to the root reconstruction protocol: Group I (control): non-weakened roots with glass fiber post; Group II: roots with composite resin by incremental technique and glass fiber post; Group III: roots with accessory glass fiber posts and glass fiber post; and Group IV: roots with anatomic glass fiber post technique. Following post cementation and core reconstruction, the roots were embedded in chemically activated acrylic resin and submitted to fracture resistance testing, with a compressive load at an angle of 45º in relation to the long axis of the root at a speed of 0.5 mm/min until fracture. All data were statistically analyzed with bilateral Dunnett's test (α=0.05). RESULTS: Group I presented higher mean values of fracture resistance when compared with the three experimental groups, which, in turn, presented similar resistance to fracture among each other. None of the techniques of root reconstruction with intraradicular posts improved root strength, and the incremental technique was suggested as being the most recommendable, since the type of fracture that occurred allowed the remaining dental structure to be repaired. CONCLUSION: The results of this in vitro study suggest that the healthy remaining radicular dentin is more important to increase fracture resistance than the root reconstruction protocol

Influence of root embedment material and periodontal ligament simulation on fracture resistance tests Influência do material de inclusão e da simulação do ligamento periodontal nos ensaios de resistência à fratura

The aim of this study was to evaluate the influence of the embedment material and periodontal ligament simulation on fracture resistance of bovine teeth. Eighty bovine incisor teeth were randomized into 8 groups (n = 10), embedded in acrylic or polystyrene resin using 4 types of periodontal ligament simulation: 1 - absence of the ligament; 2 - polyether impression material; 3 - polysulfide impression material; 4 - polyurethane elastomeric material. The specimens were stored at 37°C and 100% humidity for 24 hours. Specimens were submitted to tangential load on the palatal surface at 0.5 mm/minute crosshead speed until fracture. The fracture modes were analyzed as follows: 1 - coronal fracture; 2 - cemento-enamel junction fracture; 3 - partial root fracture; 4 - total root fracture. Statistical analyses by two-way ANOVA and Tukey's test were applied (p < 0.05). The results showed that root embedment method and periodontal ligament simulation have a significant effect on fracture resistance. Artificial periodontal ligament modified the fracture modes.<br>O objetivo deste estudo foi avaliar a influência do material de inclusão e da simulação de ligamento periodontal na resistência à fratura de dentes bovinos. Oitenta incisivos bovinos foram divididos em 8 grupos (n = 10) e, então, incluídos em cilindros com dois materiais, resina acrílica ou resina de poliestireno, usando-se quatro tipos de simulação do ligamento periodontal: 1 - ausência do ligamento; 2 - material de moldagem à base de poliéter; 3 - material de moldagem à base de polissulfeto; e 4 - material elastomérico à base de poliuretano. As amostras foram armazenadas em 100% de umidade a 37°C por 24 horas e então submetidas a carregamento tangencial na superfície palatina com velocidade de 0,5 mm/minuto até a fratura. Os padrões de fratura foram analisados de acordo com: 1 - fraturas coronais; 2 - fratura da junção esmalte-cemento; 3 - fratura parcial da raiz; 4 - fratura radicular total. A análise estatística empregou análise de variância fatorial e teste de Tukey (p < 0,05). Os resultados mostram que o método de inclusão e a simulação do ligamento periodontal tiveram efeito significativo na resistência à fratura. O ligamento periodontal artificial modificou os padrões de fratura