ABSTRACT
Abstract Polymer-based composite materials have been proposed as an alternative for single unit restorations, due to their resilient and shock absorbing behavior, in contrast to the brittleness of ceramic materials that could result in failure by fracture. Objective: To evaluate the fatigue strength and damage modes of monolithic posterior resin nanoceramic and lithium disilicate glass ceramic crowns. Methodology: Twenty-six resin nanoceramic (RNC) and lithium disilicate glass ceramic (LD) 2 mm monolithic crowns (n=13) were cemented on composite resin replicas of a prepared tooth and subjected to cyclic load with lithium disilicate indenters for 2 million cycles. Specimens and indenters were inspected every 500,000 cycles and suspended when presenting fractures or debonding. Surviving specimens were embedded in epoxy resin, polished and subsurface damage was analyzed. Specimens presenting fractures or severe subsurface damage were considered as failures. Survival data was subjected to Fisher's exact test; damage modes were subjected to Mann-Whitney test (p<0.05). Results: There were no debonding, cohesive or catastrophic failures. Considering subsurface damage, 53.8% of RNC and 46.2% of LD crowns survived the fatigue test, presenting no statistical difference. Chief damage modes were radial cracks for RNC and inner cone cracks for LD, presenting no statistical difference. Conclusions: The results suggest that if debonding issues can be resolved, resin nanoceramic figures can be an alternative to posterior crowns. Although distinct, damage modes revealed potential to cause bulk fracture in both glass ceramic and resin nanoceramic crowns.
Subject(s)
Humans , Ceramics/chemistry , Resin Cements/chemistry , Crowns , Dental Porcelain/chemistry , Surface Properties , Time Factors , Materials Testing , Reproducibility of Results , Dental Prosthesis Design , Computer-Aided Design , Statistics, Nonparametric , Dental Restoration Failure , Dental Restoration Wear , Dental Restoration, Permanent/methods , Dental Stress AnalysisABSTRACT
Appropriate hygiene of dentures contributes to the maintenance of oral and systemic health. However, most of denture wearers had never been instructed on how to perform daily oral/denture care. The purpose of this study is to investigate the influence of a guidance material associated or not to the provision of hygiene devices and its effect on the habits of denture wearers. Forty- eight complete denture wearers were randomly divided into three groups. Group N received no guidance on how to clean and wear their dentures, group G received an illustrated leaflet and verbal complementary instructions and group GK received the same guidance as group G and a hygiene kit for denture cleaning. After a six to ten week period they responded to a 'hygiene and wearing habits' questionnaire. Chi-square test was used for statistical analysis considering p < 0.05. Brushing was the most frequent cleaning method, the majority of groups N and G used toothpaste. Participants of group G and GK presented low percentages of individuals with hygiene and wearing routine considered improper. The differences between groups in hygiene and wearing routine were statistically significant (p < 0.001). The proposed guidance material yielded better results when associated to provision of hygiene devices for denture cleaning.
O objetivo deste estudo é investigar a influência de um material de orientação de higiene, associado ou não à distribuição de dispositivos de higiene, nos hábitos de portadores de próteses totais. Quarenta e oito voluntários foram divididos em três grupos. O grupo N não recebeu orientação sobre higienização de próteses. O grupo G recebeu um folheto ilustrado e orientações verbais. O grupo GK recebeu orientações similares as do grupo G e um conjunto de dispositivos para higiene de próteses. Após seis a dez semanas, os voluntários responderam um questionário sobre hábitos de higiene e uso das próteses. A análise estatística foi realizada através do teste qui- quadrado, considerando p < 0.05. A escovação foi o método de higienização mais utilizado, e a maioria dos voluntários dos grupos N e G utilizaram creme dental. Um baixo percentual de participantes do grupo G e GK apresentaram uma rotina de higienização e uso considerada imprópria. Houve diferença estatisticamente significante entre os grupos para a rotina de higienização e uso (p < 0,001). O material de orientação de higiene proposto neste estudo apresentou melhores resultados quando associado à distribuição de dispositivos de higiene.