Grand rounds for dental students: an exploration.

Grand Rounds are widely used in medicine for educating students comprehensively about clinical issues. The aim of this study was to explore the value of Grand Rounds for introducing first- (D1) and second-year (D2) dental students to an interdisciplinary approach to dental care. The objectives were to explore how interested students were in various topics, which topics they would like to see addressed in future sessions, which aspects they liked/disliked, how they evaluated the program components, and how they evaluated the outcomes. Data were collected from D1s at the end of the Year 1 fall term and from D1s and D2s at the beginning and end of the Year 1 winter term and at the end of Year 2. Response rates for most of the groups ranged from 88% to 100%, but response rates for surveys at the end of the study period fell to 40% and 32%. The results showed that the students were most interested in clinical topics that were presented in an interdisciplinary way. Their suggested topics ranged from specialty-specific issues to treatment-related topics such as implants and cosmetic dentistry. The open-ended responses showed that students liked learning differing perspectives on these topics, but disliked the course-related assignments and the preparation work in small groups. The closed-ended responses showed that the students appreciated the in-class presentations by experts and evaluated the course as helpful in informing them about the complexity of issues and the importance of the interplay between basic and clinical sciences. Educating future dentists in a way in which they embrace interdisciplinary approaches is challenging. Using the Grand Rounds concept could be one approach to increasing students' awareness of the importance of interdisciplinary work.

Hypertonic sodium bicarbonate versus intravenous lipid emulsion in a rabbit model of intravenous flecainide toxicity: no difference, no sink.

CONTEXT: The use of intravenous lipid emulsion (ILE) as an antidote in non-local, anaesthetic drug toxicity has generated considerable interest. Flecainide is a lipophilic anti-arrhythmic with a significant cardiotoxic profile, with blockade of sodium and potassium channels causing arrhythmias and shock in severe toxicity. ILE has been proposed as a treatment option in severe flecainide toxicity refractory to other modalities. OBJECTIVE: We compared the effects of ILE and hypertonic sodium bicarbonate in a rabbit model of flecainide toxicity. MATERIALS AND METHODS: Twenty sedated and ventilated New Zealand White Rabbits received flecainide infusion titrated to a mean arterial pressure (MAP) of 60% baseline, which was defined as toxicity. The rabbits then received either sodium bicarbonate or ILE, and the flecainide infusion was reduced in an attempt to model ongoing enteric absorption. MAP and heart rate were recorded every minute for 15 min and plasma flecainide concentration was measured at toxicity and 15 min. ECG QRS duration was recorded at baseline, toxicity and at 5, 10 and 15 min post-toxicity. RESULTS: No difference was observed in heart rate (p = 0.2804), MAP (p = 0.1802) or QRS duration (p = 0.7471) between groups. The immediate rate of rise in MAP was greatest in the bicarbonate group in the 5 min immediately post-toxicity. CONCLUSIONS: In this study, no differences were observed between an active control of hypertonic sodium bicarbonate and ILE for the primary endpoint of MAP at 15 min nor for QRS duration at any timepoint. There was a transient rapid increase in blood pressure seen in the sodium bicarbonate group that was not sustained. No increase was seen in blood concentration of flecainide in the ILE group, suggesting no 'lipid sink' for flecainide in this model. More research is warranted to define any role for ILE in flecainide toxicity.

A retrospective analysis of the efficacy and safety of infliximab as rescue therapy in acute severe ulcerative colitis.

BACKGROUND: Forty per cent of patients with acute severe ulcerative colitis will not respond to intravenous corticosteroids and require second-line medical therapy or colectomy. A recent controlled trial has suggested that infliximab may be effective as rescue therapy. AIM: To assess the value of infliximab as rescue therapy for acute severe colitis in a retrospective cohort of ulcerative colitis patients in Scotland. METHODS: All patients satisfied Truelove and Witts criteria on admission, failed to respond to intravenous corticosteroids and received infliximab (5 mg/kg) as rescue therapy. Response was defined as need for colectomy at hospital discharge and by 90 days. RESULTS: A total of 39 patients (median age 31.7 years) were treated. 26/39 (66%) responded, avoiding colectomy during the acute admission, and were followed up for a median of 203 days (Interquartile range = 135.5-328.5). Hypoalbuminaemia was a consistent predictor of non-response on univariate and multivariate analysis. At day 3 of intravenous steroids, 9/18 (50.0%) with serum albumin <34 g/L had urgent colectomy vs. 1/13 (7.7%) >or=34 g/L (P = 0.02, OR = 12.0, C.I. 1.28-112.7). Two serious adverse events occurred - one death due to Pseudomonas pneumonia, and one post-operative fungal septicaemia. CONCLUSIONS: Infliximab represents a moderately effective rescue therapy for patients with acute severe ulcerative colitis. Serious adverse events, including death, do occur and should be discussed with patients prior to therapy.

The effect of pulpal fluid flow on tensile bond strength of a glass-ionomer cement: an in vivo and in vitro comparison.

Previous studies of the bonding capabilities of glass-ionomer cements have concentrated on the use of in vitro testing conditions. Since early moisture contamination appears to have adverse effects on the physical properties of glass-ionomer cements, and with the probability of pulpally derived dentinal fluid being present under in vivo conditions, the objective of this study was to compare in vivo tensile bond strength with in vitro tensile bond strength of a glass-ionomer cement to dentin utilizing the same teeth under similar test conditions. A glass-ionomer lining cement was placed on freshly exposed labial dentin of the maxillary incisor on 10 Rhesus monkeys. Immediately following placement, an orthodontic button was placed over the cement and left undisturbed for 1 hour. The teeth were then extracted and stored in 100% relative humidity for 23 hours. An Instron testing machine was used to register in kilograms the force required to cause tensile bond failure of the cement. Identical methodology was then used on the same teeth for in vitro testing. The concluding results indicate that a statistically significant difference (P < or = 0.05) exists between in vivo and in vitro tensile bond strengths of the glass-ionomer lining cement and that the bond failure was cohesive in character for all cases both in vivo and in vitro. These findings suggest that clinically, tensile bond strengths of glass-ionomer cements to cut dentin can be expected to be weaker in vital teeth than in devital teeth.

Healing of primate dental pulps capped with Teflon.

The pulps of Rhesus monkey teeth were exposed and capped with three materials: Teflon, a commercial hard-set calcium hydroxide (Ca(OH)2) material, and Ca(OH)2 plus saline. Experimental test periods were 3, 10, and 21 days, and 5 and 8 weeks. After treatment, the teeth were removed and processed for routine histologic evaluation. Teeth treated with the two Ca(OH)2 materials showed resolution of the inflammatory response and hard tissue formation at the exposure site as early as 10 days postoperatively, with consistent healing at 21 days and longer. Teflon had a similar soft tissue healing pattern but at a slower rate. Hard tissue formation at the exposure site in the teeth treated with Teflon was infrequent at the early time periods and present in only 20% of the teeth treated for 5 and 8 weeks. By evaluating the soft and hard tissue responses of the Ca(OH)2-capped and Teflon-capped teeth it may be possible, in future studies, to identify events unique to odontoblast differentiation during pulpal healing.

Autoradiographic analysis of odontoblast replacement following pulp exposure in primate teeth.

Cell migration and replication associated with odontoblast replacement occurring soon after pulp exposure in primate teeth were studied. Class 5 cavity preparations resulting in pulp exposures were restored with a calcium hydroxide-containing capping agent and amalgam. Eighty-four and 96 h after this the animals were injected with 0.5 microCi/g body wt tritiated thymidine (sp. act. 6.7 Ci/mM). Teeth were extracted 6, 8, 10 and 12 days after treatment. The number of labelled cells as well as the number of grains per labelled cell were counted for odontoblast-like, fibroblast-like and perivascular cells in three 60 x 260 microns zones. These zones represented the odontoblast and cell-free (zone 1), cell-rich (zone 2) and deep pulp (zone 3) areas of normal pulp tissue. Ten sections centred around the mid-point of the exposure were counted for each tooth. Matrix formation and labelled odontoblast-like cells were observed at the interface between the capping agent and the pulp as early as day 8. Other significant findings were: (1) an increase in labelled odontoblast-like cells in zone 1 over time, suggesting a continual influx of differentiating cells; (2) an increase in labelled cells in zone 1 over time with a concurrent decrease in zone 3, suggesting that the influx of cells in zone 1 was from the deeper pulp; and (3) differences in grain counts between zones, treatment times and cell types, indicating that at least two DNA replications had occurred between initial treatment and final odontoblast-like cell differentiation.

An evaluation of a glass ionomer luting agent: bacterial leakage.

This study quantitatively evaluates the bacterial leakage beneath crowns cemented with a glass ionomer cement compared with those cemented with a polycarboxylate cement or a varnish plus zinc phosphate cement. Bacterial samples were taken from beneath full crowns cemented with the test luting agents 3, 10, and 56 days after cementation. Two-way analysis of variance of the resultant data showed a significant increase in bacterial counts for zinc phosphate, a significant decrease for polycarboxylate, and no change for glass ionomer. These findings suggest that bacterial leakage may not be the reason for the reported poor clinical response associated with glass ionomer luting agents.

An evaluation of a glass ionomer luting agent: pulpal histological response.

Pulpal histological response after crown cementation with a glass ionomer luting agent was evaluated and compared with the response to a polycarboxylate cement or a varnish plus zinc phosphate cement. Pulpal histological response was evaluated on teeth that had full crowns cemented with the test luting agents 3, 10, and 56 days after cementation. No statistically significant differences were found in pulpal histological response between the materials tested during all periods. These findings suggest that factors other than pulpal inflammation are contributing to the reported hypersensitivity after cementation associated with glass ionomer luting agents.

Quality assessment of amalgam and inlay restorations on posterior teeth: a retrospective study.

This study was designed to assess and compare the quality of posterior proximo-occlusal amalgam and inlay restorations relative to type of restoration (material, surfaces involved, and cusp protection) and length of service of the restorations. A clinical evaluation system based on operationally defined and clinically important criteria was used. Clinically and statistically significant differences were found between overall ratings for amalgam and inlay restorations and between small (two-surface) amalgam and inlay restorations, as well as between larger (three-surface) amalgam and inlay restorations. In all cases, inlay restorations were of higher quality. A not acceptable rating for marginal integrity was the most frequent reason for not acceptable overall ratings. There was no difference in satisfactory/not acceptable ratings for inlay restorations with or without protected cusps (p = .95).

Pulp capping of dental pulp mechanically exposed to oral microflora: a 1-2 year observation of wound healing in the monkey.

Four adult Rhesus monkeys provided 120 teeth for buccal Class V cavities. Twenty-nine were non-exposed controls and 91 were exposed for 3 intervals. All 120 teeth were capped with a hard set Ca(OH)2 medicament, restored with amalgam, 57 evaluated after 1 year and 63 after 2 years. Of the 91 exposed pulps, 45 showed complete healing, 25 showed pulpal inflammation varying from acute to chronic, 12 showed severe pulpal breakdown and abscess formation and 9 were necrotic. No difference was observed in the healing response between the 3 exposure times. New hard tissue formed at, or subjacent to, the medicament in 77 of 91 exposed pulps with a tunnel defect frequently present, running from the medicament interface to the pulp. This study demonstrates that recurring pulp inflammation observed after 1 & 2 year direct pulp capping, is associated with bacterial contamination.

Capping of the dental pulp mechanically exposed to the oral microflora -- a 5 week observation of wound healing in the monkey.

The healing capacity of mechanically exposed and bacterially contaminated dental pulps was assessed in monkeys after capping with 2 commercial Ca(OH)2 containing compounds. One hundred eighty teeth in 7 monkeys were employed, 45 as untreated controls and 135 as treated exposures. Class V buccal cavity preparations resulting in pulpal exposure were prepared, left open to the oral cavity for 0, 1, 24 h or 7 days and employed as controls, or debrided, capped, restored with amalgam and left undisturbed for 5 weeks as treated exposures. Zero and 1 h untreated exposures presented damage from the mechanical trauma only, whereas 24 h and 7 day pulp wounds exhibited pronounced infiltrations of polymorphonuclear and mononuclear leukocytes. In addition, the 7 day exposures demonstrated several teeth with partial and total necrosis. Treated 0, 1 and 24 h exposures demonstrated wound healing, minimal pulp tissue inflammation, reorganization of soft tissue and formation of new hard tissue at the exposure site in 86 of 99 teeth. Treated 7 day exposures healed less frequently, showing signs of dentin bridging in 15 of 27 teeth. This study indicated that mechanically exposed and orally contaminated dental pulps in monkeys have a high capacity to resolve inflammation and initiate healing with new dentin formation at the exposure site when treated as described.

Histological considerations of direct pulp capping agents.

The results from this study showed a variety of pulpal responses to various calcium hydroxide materials when placed directly on the dental pulp. Two of the materials proved to be more successful at stimulating reparative dentin bridging and healing of the underlying pulp tissue. The remainder of the pulp capping agents were ineffective at healing the pulp and forming a reparative dentin bridge. When teeth were capped with these other agents, the pulp showed necrosis and chronic inflammation.

The response of four calcium hydroxides on monkey pulps.

Dentinal bridge formation and pulpal responses of four calcium hydroxide materials, pulp capping medicaments, MPC, Experimental MPC-12, Dycal and Pulpdent, were evaluated in primary and permanent monkey teeth. A total of 60 primary and 60 permanent teeth were used with each material placed in a Class V cavity exposure in Rhesus monkey teeth. The materials were placed on the exposed pulp tissue and were histologically evaluated at 3 days, 5 weeks and 8 weeks. After perfusion the teeth were processed using routine histological procedures. The 3-day pulpal responses in both primary and permanent teeth were moderate, characterized by disruption of the pulpal tissue directly beneath the exposure site and a zone of acute inflammation and hemorrhage in the underlying pulp. The 5-week response showed histological differences between the four medicaments, with Dycal producing the least amount of pulpal irritation with reparative dentin bridges occurring in 50% of the permanent teeth. Experimental MPC-12 stimulated one reparative dentin bridge, while Pulpdent and MPC showed no evidence of bridge formation. Pulpal responses to Dycal were moderate and moderate to severe for the other calcium hydroxide compounds. No reparative dentin bridges were seen in the primary teeth at 5 weeks with any of the materials, and the pulpal responses were of a moderate degree at that time. Eight-week responses were similar to the 5-week responses Dycal provoked a slight to moderate pulpal response with 50% success at bridging. Experimental MPC-12 initiated pulpal responses in the moderate to severe range with some bridging evident. Pulpdent incited moderate to severe histological responses with three teeth demonstrating bridge formation, and MPC provoked severe pulpal responses with no bridging. Primary teeth showed some bridging for all compounds except those treated with MPC, in which no evidence of bridging occurred, and moderate to severe pulpal responses were present.

The effect of various restorative materials on the microhardness of reparative dentin.

This study showed a statistically significant difference between the microhardness of reparative and primary dentin at both five-and eight-week intervals. Reparative dentin from occlusal trauma is harder than reparative dentin underlying a cavity preparation at the 99% level. No statistical difference was noted in the hardness of reparative dentin underlying different materials, but trends were observed.

Histopathologic and bacterial evaluation of conventional and new copper amalgams.

In vivo pulpal responses in monkeys and in vitro bacterial inhibition studies were completed on new copper amalgams, Sybraloy, Dispersalloy, Tytin and a conventional Spheraloy amalgam. Amalgams were placed in cavities lined with ZOE and in unlined cavities. Silicate and ZOE were used as controls. A total of 165 adult monkey teeth were evaluated at 3 days, 5 and 8 weeks. At 3 days the pulpal responses elicited by the copper amalgams appeared similar to conventional Spheraloy, all showing a slight to moderate response. At 5 weeks the majority of amalgams exhibited a slight pulpar response with a tubular reparative dentin under each restoration. The 8 week pulpal response showed a reduction of the inflammatory response characterized by a tubular reparative dentin with a uniform zone of predentin. Lined ZOE controls exhibited a slight response while silicate showed a moderate response with some persistent chronic inflammation. In vitro bacterial tests revealed that the various amalgams had little to no inhibitory effect on the three serotypes of S. mutans that are most prominent in humans.

Histopathologic evaluation of three ultraviolet-activated composite resins on monkey pulps.

The pulpal responses of three ultraviolet-activated composite resins, Nuva-Fil, Experimental UV No. 1 and Experimental UV No. 2, were tested on adult monkey teeth using silicate and zinc oxide eugenol (ZOE) as positive and negative controls. All materials were placed in Class V cavity preparations in Rhesus monkey teeth using approximately 48 anterior and 63 posterior teeth of both the maxillary and mandibular arches. A total of 111 teeth were utilized and all materials were evaluated at 3 days, 5 and 8 weeks. Following left ventricular perfusion, the teeth were prepared for microscopic evaluation using routine histological procedures. The 3-day pulpal response of all the ultraviolet-activated composites was slight with some disruption and vacuolization in the odontoblastic layer and a slight inflammatory response. At 5 weeks there was a reduction of the inflammatory response and the formation of reparative dentin was noted for all ultraviolet composites. The 8-week pulp response was slight, characterized by a minimal inflammatory response adjacent to the zone of reparative dentin. Generally, ZOE produced the mildest response while silicate produced the most severe response at the three time intervals.

The histological effects of composite resin materials on the pulps of monkey teeth.

Pulpal response of three bis glycol methacrylate composite resins, Smile, Simulate and Experimental Composite no. 2 were tested on primary and permanent monkey teeth using zinc oxide eugenol (ZOE) and silicate as controls. All materials were placed in Class V cavity preparations in Rhesus monkey teeth and evaluated at 3 days and 5 and 8 weeks. The materials were randomly placed in anterior and posterior teeth utilizing 75 primary and 75 permanent teeth. Following perfusion the teeth were prepared by routine histological procedures. The 3 day response of the composite resins was moderate, characterized by disruption of the odontoblasts, vacuolization and mild inflammatory response underlying the cavity. At 5 weeks the formation of reparative dentin and a decrease in the inflammatory response was similar for all resins observed. At 8 weeks a slight increase in reparative dentin and continued decrease in inflammation was noted when compared to the 5 weeks responses. At all time intervals ZOE produced the least pulpal response while silicate produced the most severe response.

Histopathologic evaluation of the effects of four calcium hydroxide liners on monkey pulps.

Pulpal response of four calcium hydroxide liners, MPC 10, MPC 12, Dycal and Pulpdent were tested on primary and permanent teeth with zinc oxide and eugenol (ZOE) and silicate as controls. Responses of the pulps were evaluatedi in Rhesus monkeys, utilizing Class V cavity preparations at 3 days, 5 and 8 weeks. An equivalent number of anterior and posterior teeth were studied for all compounds. The Ca(OH)2 liners, zinc oxide and eugenol (ZOE) and silicate controls were placed in 80 primary and 80 permanent teeth. Following perfusions the teeth were prepared utilizing routine histological procedures. The 3 day response of the calcium hydroxides was moderate with some disruption in the odontoblasts, vacuolization and mild inflammation underlying the cavity except Pulpdent which was more severe. At 5 weeks a decrease in inflammatory response and the formation of reparative dentin was similar for all calcium hydroxides tested at this time period. At 8 weeks more reparative dentin was noted with slight to moderate pulpal responses. At all time periods ZOE produced the least pulpal response while silicate produced the most severe response at 5 and 8 weeks. This study reports the biological responses of four calcium hydroxide compounds used as cavity liners in non-exposures in a series of primary and permanent teeth of monkeys using ZOE and silicate as controls. Responses to the four Ca(OH)2 compounds were moderate for all the experimental compounds except Pulpdent which was more severe at the early time period tested. ZOE produced a milder and silicate a severe response at all periods. All of these compounds were placed by random selection in anterior and posterior teeth of both arches and five teeth were evaluated in both primary and permanent teeth at 3 days, 5 and 8 weeks.