Comparison between two Procion dyes and Alizarin Red to assess marginal leakage in resin restorations. A laboratory study

To assess the width of the gaps that may occur in resin restorations bonded to dentine, buccal and lingual cavities were prepared in 18 caries- and restoration-free extracted molar teeth. All teeth were restored with composite resin. Nine of the teeth were then thermocycled for five hours. All teeth were stained with 0.5 per cent, 1.0 per cent or 1.5 per cent solutions of chloro-s-triazinyl dyes (Reactive Red and Reactive Orange 14) or Alizarin Red in order to assess the effectiveness of each stain in detecting marginal leakage. Quantitative assessment indicated that Reactive Orange 14 was superior to the other two stains as it more clearly defined the marginal gaps of the restorations. This superiority was evident for both thermocycled and nonthermocycled teeth.     

Conservative approach to unerupted teeth within cystic lesions in Gorlin's syndrome

The unerupted maxillary canine is the tooth that most commonly requires surgical exposure and guided eruption. The orthodontic specialist must be aware that delayed eruption is caused, sometimes, by serious pathologic conditions such as cystic or neoplastic malformation. A case of a 12-year-old girl who suffered from Gorlin's syndrome (nevoid basal cell carcinoma syndrome) is presented. Her symptoms were multiple jaw keratocysts, skeletal anomalies, and cleft lip and palate. Some authors advocate an aggressive surgical approach to jaw keratocysts because of their tendency to recur, thus sacrificing those teeth associated with them. Our view is that in young patients with Gorlin's syndrome, an attempt should be made to preserve permanent teeth, especially those vital for a normal growth pattern of the jaws. Therefore we recommend a conservative surgical approach, enabling guided eruption of unerupted teeth associated with cystic lesions in patients with Gorlin's syndrome.     

Resin-bonded fixed partial dentures: A recall study

A clinical recall program was initiated at the University of Minnesota to evaluate the longevity and factors affecting longevity of resin-bonded fixed partial dentures (FPDs). Of the 49 resin-bonded FPDs evaluated in the clinic, 43 were acid-etched metal, resin-bonded FPDs, four were combinations of resin-bonded and conventional FPDs, and two were composite resin pontics. None of the combination FPDs and one of the two composite resin pontics were judged as failed at the examination. Of the 43 acid-etched metal resin-bonded FPDs, 15 were found to be debonded (failure rate = 34.9%). The average length of service for the 43 FPDs was 47.3 months. The average time of placement to debondment was 33 months for the 15 debonded FPDs. The failure rate for maxillary FPDs and FPDs with two retainers were significantly lower than the failure rate for mandibular FPDs and FPDs with more than two retainers (p greater than 0.05). The clinical significance of the present study was discussed.     

Ultrasound observations of tongue motor behavior

In this investigation of motor skills of the tongue and age-related changes in motor behavior, upward and downward tongue movements with the teeth in centric occlusion and regulated by a metronome were recorded. The recordings were made by use of ultrasound diagnostic equipment with a 5 MHz electronic convex section scanning probe and a physiologic signal unit connected to a heart sound microphone in a group of young subjects and a group of older subjects. The results were as follows. (1) The system provided a useful method to evaluate motor skills of the tongue with sound signals showing clear images of the tongue surface and its movements. (2) The rhythm of tongue movements in older persons varied more than in younger persons. (3) The velocity in the upward and downward movements decreased and were statistically significant (p less than 0.01) in the older group. (4) The time lag between the sound signal and the start of touching the palate and floor of the mouth was longer (p less than 0.01) and the variations were greater in the older group. (5) The study showed age-related changes in motor behavior of the tongue.     

Ovarian hormones and gingivitis

Elevated plasma concentrations of the ovarian hormones--estrogen and progestins--during pregnancy, puberty, the menstrual cycle, and oral contraceptive (OC) use are associated with an increased incidence of gingival inflammation and exudate. Gingivitis is induced by the micro- organisms that compose subgingival plaque, particularly anaerobic organisms. The ovarian hormones both stimulate bacterial growth and promote the inflammatory process. In the presence of sex hormones, the metabolic breakdown of folate is increased, leading to a folate deficiency that enhances the inflammatory destruction of oral tissue. Gingivitis occurs in an estimated 60-75% of pregnancy women, but the numbers of gingivitis-producing bacteria decrease toward the end of pregnancy and the gingival tissues return to their previous state. In OC users, on the other hand, inflammation of the gingiva is chronic and may increase over time. If gingivitis is already present at the onset of pregnancy or OC use, the inflammation will become progressively more severe. Although these effects cannot be avoided, ovarian hormone- induced gingivitis can be substantially minimized of low plaque levels exist at the beginning of pregnancy or pill initiation.     

Evaluation of shear strength at the cement-endodontic post interface

The strength characteristics of the cement-implant interface were evaluated for smooth-tapered, threaded, and porous-surfaced endodontic implants with the use of different cements. Specifically, tensile and torsional shear strengths were measured for zinc phosphate, polycarboxylate, glass-ionomer, silicophosphate, and AH-26 cements. The results indicated superior shear strength characteristics for threaded endodontic implants on axial loading. However, this strength was diminished when torsional forces were applied. Porous-surfaced endodontic implants showed strong resistance to both axial and torsional loading.     

Water Fluoridation: a Response to Critics in Australia and New Zealand

Recent questions about the effectiveness of water fluoridation have come from Diesendorf in Australia and Colquhoun in New Zealand. This report examines the arguments of both authors in detail and finds errors in each. Diesendorf employed an outdated view of how fluoride exerts its anticariogenic action and took a number of quotations out of context. Colquhoun's data are questionable. Neither author has produced evidence to challenge the established safety and effectiveness of water fluoridation.     

Blood group substances as differentiation markers in human dento-gingival epithelium

The level of cellular differentiation of human oral, sulcular, and junctional epithelium was compared by immunohistochemical analysis of cell membrane-associated blood group-specific carbohydrates. Identification of the blood group A-specific carbohydrate and its two immediate precursor substances, type 2 chain H and N-acetyllactosamine, was accomplished by an indirect immunofluorescence technique. Murine monoclonal antibodies reacting specifically with the antigenic determinants of the blood group substances were used as markers. The blood group A substance, indicating the highest level of cellular differentiation, was demonstrated on the cells in the upper layers of the oral epithelium. In the sulcular epithelium, the A substance was present on a few cells only, while type 2 chain H was observed frequently. This indicates an intermediate differentiation level of sulcular epithelium. The type 2 chain H precursor, N-acetyllactosamine, the indicator of the lowest level of cell differentiation among the tested substances, was the only blood group substance detected on the junctional epithelial cells and on the basal cells of the sulcular and oral epithelium. Based upon previous studies of cell renewal and differentiation in oral epithelium, the present results indicate that the variations in distribution of the different blood group substances correspond with the regional rates of cell division and the levels of cellular differentiation. The findings also suggest that the cells in the junctional epithelium differentiate to a level similar to that of basal cells in the oral epithelium.