Alterations of surface hardness with gypsum die hardeners

STATEMENT OF PROBLEM: Die stones require abrasion resistance, dimensional stability with time, and high surface wettability material properties. PURPOSE: The purpose of this study was to compare the surface microhardness (Knoop) of 4 contemporary gypsum materials with and without surface die hardener. MATERIAL AND METHODS: Materials used were a Type III stone (Microstone) and 3 die stones (Die-Keen, Silky-Rock, and ResinRock). Die hardener was cyanoacrylate (Permabond 910) or Clear Coat. Specimens of stone were hand mixed with distilled room temperature water and vacuum spatulated according to manufacturer's directions. Five cylinders (15 x 15 mm) per group were poured, using vibration, into phenolic ring molds positioned on top of a glass slide. The face of each specimen was polished with 2400-grit Al2O sandpaper. One face of each of 5 specimens/material was coated with cyanoacrylate; 5 specimens/material were coated with Clear Coat, air thinned and dried; and 5 specimens/material had no treatment (control). Knoop hardness (kg/mm2) readings were made on each face (5 readings/time point) 3, 12, and 24 hours after pouring. An ANOVA procedure with post hoc Tukey tests were performed (alpha=.05). RESULTS: Microhardness did not vary between 3 and 24 hours for any material (P>.05). Microstone had significantly lower surface hardness (P<.0001) than the die stones. Specimens coated with die hardener had lower hardness values (P<.001 in all cases) CONCLUSIONS: The 3 types of die stones evaluated in this study did not differ significantly in surface microhardness. Under these conditions, die hardener coatings reduced the surface hardness of the gypsum material.     

Oncocytoid artifact of the parotid gland: A newly reported artifact

Electrocautery can induce significant alterations in the connective tissues and epithelium of specimens removed for diagnostic or therapeutic purposes. When electrocautery is used during parotid surgery, it can cause an oncocytoid artifact. The alterations described in this article are enlarged, tightly packed serous acinar cells with coarse to granular eosinophilic cytoplasm, distinct cell borders, and round basal nuclei that on cursory microscopic examination resemble oncocytes with respect to morphology. These changes are seen in conjunction with other, more recognized changes secondary to electrocautery and are believed to occur as a consequence of the electrothermal discharge. On the basis of our findings, this artifact is common in parotid surgical specimens and was misdiagnosed as benign oncocytic lesions in 5 cases.     

Australian Dental Research Fund Trebitsch Scholarship* Efficacy of antifungal prophylaxis in bone marrow transplantation

Oral candidal infection is a common problem in bone marrow transplantation. This prospective study compared the effectiveness of antifungal prophylaxis with topical antifungals (nystatin and amphotericin B suspensions) versus oral fluconazole in 196 patients undergoing bone marrow transplantation. Oral candidosis occurred frequently in the group receiving topical antifungals (61/113, 54%), but was rare in the group receiving fluconazole (6/83, 7%). The difference in efficacy between the two groups was highly significant (p<0.00001). There was no difference in the incidence of suspected systemic fungal infection between the two groups. While nausea was a problem with antifungal suspensions, no significant adverse reactions to fluconazole occurred. Because of greater efficacy in preventing oral candidosis and better patient tolerance, oral fluconazole is preferred to antifungal suspensions for prophylactic use in patients undergoing bone marrow transplantation.     

Clinical and microbiological effects of localized ligature-induced periodontitis on non-ligated sites in the cynomolgus monkey

The purpose of this study was to examine the clinical and microbiological effects of localized ligature-induced periodontitis on non-ligated sites in a monkey model system. Ligature-induced periodontitis was produced in one quadrant in each of four Macaca fascicularis monkeys. Two additional monkeys without any ligatures served as control. The clinical condition and subgingival microflora of ligated, non-ligated, and control sites were monitored for 8–11 weeks. Ligated sites demonstrated an initial (1–2 weeks post-ligation) increase in inflammation, Gram-negative surface translocating bacteria (STB), and motile rods. Clinical and radiographic evidence of loss of attachment associated with increased proportions of Bacteroides gingivalis was evident 4–6 weeks post-ligation. No clinical changes were demonstrated in non-ligated and control sites throughout the experimental period. Non-ligated sites, however, demonstrated an increase from 4.6% to 13.7% in Gram-negative STB and motile rods by 4–6 weeks which continued to increase to 20.3%, by 8–11 weeks. Control sites showed no microbiological changes during the experimental period. In a second experiment pure cultures of B. gingivalis were implanted subgingivally at various times in non-ligated sites. It was only possible to recover increased proportions of B. gingivalis from non-ligated sites when implantation occurred while proportions of Gram-negative STB and motile rods were elevated. Loss of attachment in infected non-ligated sites was not seen within four weeks of implantation.     

Preventive Behaviors as Correlates of Periodontal Health Status

Objectives: This investigation examined current practices of brushing, flossing, and periodic dental visits and their association with periodontal health status. Methods : Data were collected using face-to-face interviews and 40-minute in-home dental examinations with a probability sample of adults 18 years of age or older, having at least one tooth, and living in housing units in the Detroit tricounty area. Complete examinations were performed on 319 individuals. Results : On average, subjects reported brushing their teeth about twice a day. About one-third of the population reported flossing at least once a day. Loss of periodontal attachment was related to frequency of brushing while subjects who exhibited acceptable flossing ability had less plaque and calculus, shallower pocket depths, and less attachment loss. Subjects reporting a periodic dental visit at least once a year had less plaque, gingivitis, and calculus than subjects reporting less frequent visits. In regression analyses, brushing thoroughness, flossing ability and frequency, and dental visit frequency were predictors of lower plaque, gingivitis, and calculus scores. In turn, these scores were predictors of shallower pocket depths and less attachment loss. Conclusions : Brushing, flossing, and periodic dental visits were correlated with better periodontal health. The behaviors appeared to be indirectly related to pocket depth and attachment loss through their associations with plaque, gingivitis, and calculus levels.     

Upper removable appliance or Jones Jig for distalizing first molars? A randomized clinical trial

Aim – To compare the effectiveness of two intra‐oral methods of distalizing upper first permanent molars: an upper removable appliance (URA) and a Jones Jig. Sample – Twelve patients were randomly allocated to URA treatment and 11 patients to a Jones Jig. Methods – Upper study models were collected at the start of treatment and after 6 months of appliance wear. The amount of distal movement, tipping and rotation of the upper first permanent molars and mesial movement of the upper first permanent premolars was measured using a reflex metrograph. Results – There were no statistically significant differences between the two treatment methods for any of the outcome measures (P < 0.05). Distal movement obtained by both appliances was approximately 1 mm. Conclusions – The amount of distal movement obtained with both appliances was small and no differences were shown in the amount of molar tooth movement. It is suggested that there is no advantage in using the Jones Jig as a non‐compliance appliance.     

Craniectomy and noggin application in an infant model.

INTRODUCTION: Noggin is an antagonist of bone morphogenetic proteins (BMP)-2, -4 and -7. Little data are available regarding its clinical utility. Two hypotheses were put forward: firstly, that spontaneous regeneration of calvarial defects with noggin protein would result in diminished bone volume when compared with calvarial defects not so treated. Secondly, that centrifugal cranial expansion would remain undisturbed whether noggin was applied or not. MATERIAL AND METHODS: A unilateral defect of the frontal and parietal bones (2x4cm) was generated by excising the right coronal suture in 2-month-old minipigs (n=10) and in group 1 (n=5) no further intervention was undertaken. In the second group (n=5), a collagen type I tissue fleece and noggin protein (1.05mg/ml) were applied. After 4 months the coronal suture regions of frontal sides were examined in each animal by computed tomography and non-decalcified histology. RESULTS: Bony gaps of equivalent size remained in animals of both groups. The differences in bone volumes of the experimental sides of group 1 were not statistically significantly different (p=0.117) when compared with those of group 2. A significant difference in the bone volumes of the experimental versus control (unoperated) sides was found in both group 1 (p=0.043) and group 2 (p=0.043). Internal skull diameters increased by 16.4% in both groups but the physiological centrifugal cranial expansion remained undisturbed. Bone densities of the experimental and control sides of groups 1 and 2 were not statistically significantly different (both p>0.05). CONCLUSIONS: The first hypothesis was contradicted: the quantity and quality of spontaneous bone regenerates was not altered by application of noggin protein. The second hypothesis was confirmed: no disruption of subsequent cranial development was seen. It may be that a single application of noggin protein in this study was insufficient. However, it may well be suggested that the continuous supplementation of noggin, for example by adenoviral noggin gene transfer may significantly reduce the quantity of spontaneous bone regeneration in a similar experiment.     

Parental satisfaction with preveneered stainless steel crowns for primary anterior teeth

PURPOSE: The purpose of this study was to evaluate parental satisfaction with preveneered stainless steel crowns placed on their child. METHODS: A questionnaire using a 5-point Likert-type scale was administered by a trained assistant to a convenience sample of 58 parents at recall of their child at least 6 months after placement of preveneered stainless steel crowns (PVSSCs; NuSmile). The questionnaire asked about: (1) durability; (2) color; (3) size; and (4) shape. Fifty-eight children ranged in age from 18 months to 12 years were approached for participation. Crowns were placed by pediatric dental residents or private practice pediatric dentists. RESULTS: Fifty-four of 58 parent questionnaires were usable. The average age of the children was 5 years, 2 months at recall. The children had crowns present an overage of 13 months at evaluation. Overall, parental acceptance of NuSmile PVSSCs was very high at 93% (N=50). Parents were most satisfied with the crown's: (1) size (N=52; 97%); (2) shape (N=51; 94%); (3) shade and retention (N=48; 89%); (4) metal visibility (N=40; 74%); and (5) durability (N=38; 70%). Forty-three parents (80%) stated that their children were satisfied with the crowns. CONCLUSIONS: Parent satisfaction with the NuSmile preveneered stainless steel crowns was very high.     

Bonding to ground versus unground enamel in fluorosed teeth.

OBJECTIVES: To determine the effect of grinding on the bonding effectiveness of a self-etch and an etch-and-rinse adhesive to fluorosed enamel. METHODS: The teeth were classified using the Thylstrup and Fejerskov index (TFI). Fluorosed teeth (TFI=5) obtained from Isparta (Turkey) and control teeth (TFI=0) obtained from Leuven (Belgium) were used. Using a depth-marking diamond bur, 0.3mm of enamel was removed from mid-buccal and mid-palatal/lingual surfaces of the teeth, whereas the area adjacent to the ground area was left unprepared. A two-step self-etch (Clearfil Protect Bond, Kuraray) and a three-step etch-and-rinse adhesive (Optibond FL, Kerr) were used to bond the resin composite to the ground and unground enamel. Rectangular micro-specimens were prepared using the slow-speed diamond saw and tested in tensile to determine the micro-tensile bond strength (microTBS). RESULTS: The microTBS to unground fluorosed enamel was significantly lower than to ground fluorosed enamel for Clearfil Protect Bond (15.8+/-15.2 and 45.0+/-12.4MPa, p<0.0001) and for Optibond FL (35.5+/-21.4 and 50.5+/-12.3MPa, p<0.05), respectively. In control teeth, Clearfil Protect Bond bonded better to ground enamel (p<0.01), whereas OptiBond FL exhibited a similar bonding effectiveness to ground and unground enamel (p=0.0634). SIGNIFICANCE: Preparation of enamel improved the resin-enamel bond strength in fluorosed teeth. The bonding effectiveness to unground enamel was lower in fluorosed teeth than in control teeth for the self-etch adhesive tested.