This paper proposes a new method for estimating the word probabilities in latent Dirichlet allocation (LDA). LDA uses a Dirichlet distribution as the prior for the per-document topic discrete distributions. While another Dirichlet prior can be introduced for the per-topic word discrete distributions, point estimations may lead to a better evaluation result, e.g. in terms of test perplexity. This paper proposes a method for the point estimation of the per-topic word probabilities in LDA by using multilayer perceptron (MLP). Our point estimation is performed in an online manner by mini-batch gradient ascent. We compared our method to the baseline method using a perceptron with no hidden layers and also to the collapsed Gibbs sampling (CGS). The evaluation experiment showed that the test perplexity of CGS could not be improved in almost all cases. However, there certainly were situations where our method achieved a better perplexity than the baseline. We also discuss a usage of our method as word embedding.