The design of a two-part acid-etched resin-bonded fixed partial denture.

A new framework design is presented for resin-bonded, acid-etched, fixed partial dentures. This innovative design divided the restoration into two parts, each with a separate path of insertion. The preparation of abutment teeth required minimal reduction and the pontic could not be displaced during function. Thirty-five patients with missing posterior teeth have been treated with this imaginative approach and after approximately 2 years, there have been no debonding failures.     

Intrapocket chemotherapy in adult periodontitis using a new controlled-release insert containing ofloxacin (PT-01).

PT-01 is a newly developed water-soluble controlled-release insert containing ofloxacin (OFLX) as an antibacterial agent. The effect of PT-01 was evaluated by split-mouth application after oral hygiene instruction. No mechanical debridement was carried out during the experiment. PT-01 was applied once a week for 4 weeks in the periodontal pockets of 46 patients with adult periodontitis. The control insert without any antibacterial agent was applied in a selected pocket in a different quadrant for each patient. Clinical findings plaque index, PI; gingival index, GI; bleeding on probing, BOP; pus discharge, pus; and probing depth, PD at both PT-01 and control sites were measured at every visit for 4 weeks. Clinical findings were improved at both PT-01 and control sites, but the improvements were much more significant at PT-01 sites, in particular BOP and PD, than at control sites. PI was also significantly reduced at PT-01 sites. These results suggest that weekly application of PT-01 in the periodontal pocket has a significant effect on the resolution of periodontal inflammation and has an inhibitory effect on supragingival plaque deposition.     

Crouzon twins with cloverleaf skull malformations.

We describe unique monozygotic twins with Crouzon's disease and cloverleaf-shaped skull deformities who have been closely followed since birth. Their abnormal skull shapes were identified during antenatal ultrasound examination. The twins had gross exophthalmos and hydrocephalus with papilledema, so early calvarial decompression surgery was required. Although born to healthy parents of normal appearance, a third cousin of the twins had a milder form of Crouzon's disease, and there was a family history of high-arched palate on the twins' paternal side. Because Crouzon's disease is an uncommon condition and the cloverleaf skull shape is unusual in patients with Crouzon's disease, identical twins with this constellation of deformities must be exceptionally rare.     

The carcinostatic effects of 1-(2-tetrahydrofuryl)-5-fluorouracil and uracil (UFT) on tongue carcinoma induced by 4-nitroquinoline 1-oxide (4NQO) in rats.

UFT is a carcinostatic agent used in adjuvant chemotherapy for head and neck cancer. In the present study. UFT was given orally to treat tongue carcinoma in rats induced by 4-nitroquinoline 1-oxide. The antitumor effects of UFT were studied macroscopically and histologically. In addition, the antitumor effects of UFT were evaluated in relationship to lesions of the clinical and, invasive types, and to there vascular structure. In clinical lesions, the antitumor effect of UFT was higher in extrovert tumor-mass lesions and lower in ulcerous lesions. With regard to vascular structure, the effect was higher in cases demonstrating irregular net-like patterns and branch-like patterns and lower in cases in which the pattern had been destroyed. There was a correlation between antitumor effect and invasive type. As invasive tendency the 3H-thymidine labeling index, and mitotic index increased, antitumor effect and degree of tumor cell degeneration decreased.     

Parental attitudes toward behavior management techniques used in pediatric dentistry

Previous studies evaluating parents' attitudes toward behavior management techniques used in pediatric dentistry suggest that parental attitudes are generally negative. The purpose of this study was to reexamine this issue by comparing the effect of prior explanation on parental acceptance of eight behavior management techniques. Videotaped segments were made of children's dental appointments containing examples of eight behavior management techniques. One group of 40 parents viewed a videotape which provided no explanation for each technique before it was shown. Another group of 40 parents viewed a videotape which provided no explanation of the techniques. The parents then were asked to rate the acceptability of each technique using a visual analogue scale. Results indicated that the informed parents were significantly more accepting of behavior management techniques than the uninformed parents but both groups were generally positive about the techniques studied. Further, parents reporting greater stress were less accepting of the techniques studied.     

Measuring dental drift and orthodontic tooth movement in response to various initial forces in adult rats

A method for the quantification of orthodontic tooth movement in the rat is presented. Reliability, sensitivity, and validity were assessed and tooth movement kinetics were determined for initial forces of 20, 40, and 60 gm. The appliance consisted of a 9 mm length of closed coil spring suspended between a cleat and bonded to the occlusal surface of the maxillary first molars and the maxillary incisors. Initial tipping forces were placed by suspending known weights from the anterior end of these coils before fixation to the incisors. Tooth movement was quantified from enlarged cephalograms by measuring the position of a reproducible landmark on the molar cleat with respect to either zygomatic amalgam implants or a barbed broach placed submucosally on the palate. All measurements were made along the molar-incisor vector by projecting at 90 degrees to this line. Validity and sensitivity were assessed by quantifying molar distal drift and comparing these results with reports of bone turnover rates adjacent to distally drifting adult rat molars. Reliability was obtained by estimating the error of a single measurement in a longitudinal study of 12 adult male Sprague-Dawley rats (180 to 200 days) receiving both amalgam and broach implants and a cross-sectional study of 72 animals divided equally into six groups to be killed at 1, 3, 5, 7, 10, and 14 days. No orthodontic forces were used in this portion of the study. Implant stability within the craniofacial complex was assessed by measuring bilateral broaches as a function of time with respect to each other. There were no systematic errors between replicate films for either the amalgam or the broach method. The 95% confidence limit for a single determination of molar position was 62 microns using the amalgams and 47 microns for the broach (p less than 0.001). The latter could be reduced to 23 microns when the average of four independent determinations was used. Homologous implants did not differ with respect to each other in the sagittal plane but did in the transverse plane (p less than 0.01), migrating laterally 9 microns/day. Linear regression analysis of molar distal movement over time predicted 7.7 microns/day distal drift (p less than 0.01), which compared favorably with reports of 6.7 microns/day of alveolar bone turnover during this drifting process. Characteristic three-part cumulative tooth movement kinetics were obtained for the 40 and 60 gm initial force groups. No individual time point at 60 gm differed from its counterpart at 40 gm.(ABSTRACT TRUNCATED AT 400 WORDS)     

Ultrastructural differentiation in the distal ends of ameloblasts from the presecretory zone to the early secretory zone

Morphological differentiation of the distal ends of ameloblasts (AMs) from the late presecretory to early secretory zones of the rat upper incisor was studied by electron microscopy. Preameloblasts (PAs) showed a high columnar shape, with the nucleus located in the basal portion. The Golgi apparatus occupied the supranuclear region with type-1 vesicles, and microvilli were present at the distal cell membrane. Coarse-textured material was observed inside the type-1 vesicles and in the lateral intercellular spaces as well as along the distal cell membrane, whereas fine-textured material was found along the distal cell membrane. Near the region of initial enamel formation, large matrix islands were found in the lateral intercellular space. A thin electron-dense layer was observed on the dentin surface. This layer might have occurred as a result of diffusion after degradation of the coarse- or fine-textured material into a finer substance in the extracellular spaces. In the region of initial enamel formation, the distal cell membrane of AMs was flat, but shallow and narrow membrane invaginations were associated with the cell membrane close to the matrix islands. In the region of inner enamel formation, a cone-shaped Tomes' process was formed between large matrix islands which had developed in the intercellular spaces between the lateral portions of the distal ends of AMs. It was considered that the membrane invaginations which had existed at the distal end of PAs moved lower toward the distal terminal bar, thereafter becoming microvilli.     

The current for a two-electron reaction is not necessarily twice that of a one-electron reaction

Two-setp oxidation or reduction of a molecule is considered for the case where removal (or addition) of the second electron is more difficult than that of the first. In such cases, the comproportionation reaction between the final product and the original reactant to give two molecules of the one-electron intermediate is favored and can occur in the diffusion-reaction layer. When the diffusion coefficients of the three species differ, the current seen at potentials where the two-electron reaction occurs will not be twice that seen at potentials where the one-electron reaction occurs, i.e. n_app does not equal 2. For chronoamperometry, digital simulations have been employed to predict the dependence of n_app on the relative diffusion coefficients. It has been shown that equality of the diffusion coefficients of the reactant and the one-electron product is sufficient to guarantee that n_app will be 2. Diffusion coefficients of neutral tetracyanoquinodimethane (TCNQ), its radical anion and the dianion have been meaured in acetonitrile. It is predicted that n_app will be 1.98 for reduction of neutral TCNQ and 2.18 for oxidation of TCNQ^2?. Within experimental error, these values were found experimentally using normal pulse voltammetry. The effect of unequal diffusion coefficients was also observed in cyclic voltammetry and confirmed by simulation.