Comparison of two techniques for removing fiber posts.

The purpose of this study was to evaluate the time needed to remove several types of fiber posts using two different bur kits. Estimates refer to the time needed to pass the fiber post until arriving at the gutta-percha. Sixty extracted anterior teeth were treated endodontically. A post space with a standard depth of 10 mm was prepared in each root canal. The sample was randomly divided into 3 groups of 20 specimens each. Three different types of posts were cemented: group 1, Conic 6% tapered fiber posts (Ghimas); group 2, FRC Poster fiber posts (Ivoclar-Vivadent); and group 3, Composipost carbon fiber posts (RTD). To remove the post, for half of each group's specimens the burs from the RTD fiber posts removal kit were used (subgroup A). From the other half of the teeth in each group (subgroup B), posts were removed by using a diamond bur and a Largo bur. Composipost carbon fiber posts (group 3) took significantly less time to remove than the other two types of posts (p < 0.05). For the bur kits, the procedure involving the use of a diamond and a Largo bur (subgroup B) was significantly faster (p < 0.05). The interaction between the type of post and the type of bur kit used was not significant (p > 0.05).

Preliminary report of an experimental design for in vivo testing of bonded restorations applied to a new enamel-dentinal bonding agent.

Because of inconsistency often found between in vitro testing and in vivo performance, a new restorative bonding system was evaluated by the placement of restorations in vivo in teeth to be extracted. The microleakage was determined following extraction after 3 months of clinical service. In each of the sample teeth, two restorations were placed on the labial surface, one in the middle of the enamel portion and the other extending over the cementoenamel portion. The results of this pilot study indicated that bonding to conditioned enamel with the new adhesive material is effective, and bonding to conditioned dentin appears to be clinically adequate.

Long-term training, transfer, and retention in learning to lipread.

A long-term training paradigm in lipreading was used to test the fuzzy logical model of perception (FLMP). This model has been used successfully to describe the joint contribution of audible and visible speech in bimodal speech perception. Tests of the model were extended in the present experiment to include the prediction of confusion matrices, as well as performance at several different levels of skill. The predictions of the FLMP were contrasted with the predictions of a prelabeling integration model (PRLM). Subjects were taught to lipread 22 initial consonants in three different vowel contexts. Training involved a variety of discrimination and identification lessons with the consonant-vowel syllables. Repeated testing was given on syllables, words, and sentences. The test items were presented visually, auditorily, and bimodally, at normal rate or three times normal rate. The subjects improved in their lipreading ability across all three types of test items. Replicating previous results, the present study illustrates that substantial gains in lipreading performance are possible. Relative to the PRLM, the FLMP gave a better description of the confusion matrices at both the beginning and the end of practice. One new finding from the present study is that the FLMP can account for the gains in bimodal speech perception as subjects improve their lipreading and listening abilities.

Discovery and expository methods in teaching visual consonant and word identification.

An experiment was conducted to examine the processes involved in lipreading as well as to investigate an optimal approach to teaching lipreading skill. We compared discovery and expository methods of learning to lip-read. Twenty-six college students with normal hearing were trained over 3 days to lip-read consonant-vowel (CV) syllables. The training material consisted of a prerecorded videotape of four different talkers. The task was a forced-choice procedure with feedback. Subjects learned with training, but there was no difference between the two learning methods. As a retention measure, subjects returned 4 weeks later and repeated the training. There were significant savings of the original learning. Three weeks after the retention phase, subjects were tested with a 10-item forced-choice monosyllabic word task. Those subjects who had extensive training on CV syllables did no better on identifying the monosyllabic words than did a control group of 9 subjects with no training. Nevertheless, performance for all three groups (discovery, expository, and no training) improved during training in the word identification task.

Marginal leakage of a new adhesive restorative system: a preliminary in vivo investigation.

The efficacy of newly developed adhesive restorative materials is commonly described by in vitro test results such as bond strength and microleakage data. Due to the inconsistency often found between in vitro testing and in vivo performance, the purpose of the present investigation was to restore teeth scheduled for extraction in vivo with an experimental restorative bonding system and to evaluate the microleakage of the restorations by common laboratory techniques following extraction after 3 months of clinical service. Two restorations were placed in each of seven anterior teeth, one in the middle of the labial enamel portion and the other labially extending over the cementoenamel junction (CEJ). Six of the seven fillings completely surrounded by enamel showed no microleakage. However, two of the restorations crossing the CEJ revealed microleakage originating from the cervical margins. In spite of the small number of fillings assessed, the experimental enamel-dentin adhesive compound tested is preliminarily considered a promising new system.