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.

Different Brain Responses to Pain and Its Expectation in the Dental Chair.

A dental appointment commonly prompts fear of a painful experience, yet we have never fully understood how our brains react to the expectation of imminent tooth pain once in a dental chair. In our study, 21 patients with hypersensitive teeth were tested using nonpainful and painful stimuli in a clinical setting. Subjects were tested in a dental chair using functional near-infrared spectroscopy to measure cortical activity during a stepwise cold stimulation of a hypersensitive tooth, as well as nonpainful control stimulation on the same tooth. Patients' sensory-discriminative and emotional-cognitive cortical regions were studied through the transition of a neutral to a painful stimulation. In the putative somatosensory cortex contralateral to the stimulus, 2 well-defined hemodynamic peaks were detected in the homuncular orofacial region: the first peak during the nonpainful phase and a second peak after the pain threshold was reached. Moreover, in the upper-left and lower-right prefrontal cortices, there was a significant active hemodynamic response in only the first phase, before the pain. Subsequently, the same prefrontal cortical areas deactivated after a painful experience had been reached. Our study indicates for the first time that pain perception and expectation elicit different hemodynamic cortical responses in a dental clinical setting.

How is research publishing going to progress in the next 20 years? Transcription of session for editors, associate editors, publishers and others with an interest in scientific publishing held at IADR meeting in Seattle on Wednesday, 20 March 2013.

On March 20th 2013, a one-hour session for Editors, Associate Editors, Publishers and others with an interest in scientific publishing was held at the IADR International Session in Seattle. Organised by Kenneth Eaton and Chris Lynch (Chair and Secretary, respectively, of the British Dental Editors Forum), the meeting sought to bring together leading international experts in dental publishing, as well as authors, reviewers and students engaged in research. The meeting was an overwhelming success, with more than 100 attendees. A panel involving four leading dental editors led a discussion on anticipated developments in publishing dental research with much involvement and contribution from audience members. This was the third such meeting held at the IADR for Editors, Associate Editors, Publishers and others with an interest in scientific publishing. A follow up session will take place in Cape Town on 25 June 2014 as part of the annual IADR meeting. The transcript of the meeting is reproduced in this article. Where possible speakers are identified by name. At the first time of mention their role/ position is also stated, thereafter only their name appears. We are grateful to Stephen Hancocks Ltd for their generous sponsorship of this event. For those who were not able to attend the authors hope this article gives a flavour of the discussions and will encourage colleagues to attend future events. Involvement is open to Editors, Associate Editors, Publishers and others with an interest in scientific publishing. It is a very open group and all those with an interest will be welcome to join in.

Identify and define all diagnostic terms for pulpal health and disease states.

INTRODUCTION: Consensus Conference Subcommittee 2 was charged with the identification and definition of all diagnostic terms for pulpal health and disease states by using a systematic review of the literature. METHODS: Eight databases were searched, and numerous widely recognized endodontic texts were consulted. For each reference the level of evidence was determined, and the findings were summarized by members of the subcommittee. Highest levels of evidence were always included when available. Areas of inquiry included quantification of pulpal pain, the designation of conditions that can be identified in the dental pulp, diagnostic terms that can best represent pulpal health and disease, and metrics used to arrive at such designations. RESULTS AND CONCLUSIONS: On the basis of the findings of this inquiry, specific diagnostic terms for pulpal health and disease are suggested. In addition, numerous areas for further study were identified.

Effects of VEGF and FGF2 on the revascularization of severed human dental pulps.

The long-term outcome of replanted avulsed permanent teeth is frequently compromised by lack of revascularization, resulting in pulp necrosis. The purpose of this study was to evaluate the effects of vascular endothelial growth factor (VEGF) and fibroblast growth factor (FGF-2) on the revascularization of severed human dental pulps. Tooth slices were prepared from non-carious human molars and treated with 0-50 ng/mL rhVEGF(165) or rhFGF-2 for 7 days in vitro. Both angiogenic factors enhanced pulp microvessel density compared with untreated controls (p < 0.05). Tooth slices were also treated with 0 or 50 ng/mL rhVEGF(165) for one hour prior to implantation into the subcutaneous space of immunodeficient mice. Treatment with rhVEGF(165) increased pulp microvessel density in vivo (p < 0.05). These results demonstrate that rhVEGF(165) enhanced neovascularization of severed human dental pulps and suggest that topical application of an angiogenic factor prior to replantation might be beneficial for the treatment of avulsed teeth.

Prostaglandin E production and viability of cells cultured in contact with freshly mixed endodontic materials.

AIM: To determine whether commonly used endodontic sealers could either induce or increase the release of prostaglandin E2 (PGE2) when in contact with cell types found in the periapical tissues. METHODOLOGY: Freshly mixed samples of Roth 801 sealer, Sealapex and ProRoot mineral trioxide aggregate (MTA) were placed in contact with cultured macrophages and fibroblasts for 24 h. The supernatant from the cultures was assayed for PGE2 using enzyme-linked immunosorbent assay. Cell viability counts were made. As a positive control, similar cultures were also exposed to lipopolysaccharide and the supernatant analysed for PGE2. Data were compared by anova. RESULTS: The three materials examined in these experiments did not stimulate increased PGE2 release from either of the cell lines. In control cultures, lipopolysaccharide increased PGE2 release from macrophages but not from fibroblasts. Viability counts revealed that, whilst Roth 801 sealer caused some cell death in both fibroblasts and macrophages, Sealapex led to cell death only in the macrophage cultures. ProRoot MTA did not lead to statistically significant cell death in either culture. CONCLUSIONS: Under 24-h culture conditions, the three freshly mixed test materials did not increase directly either production or release of PGE2 from either macrophages or gingival fibroblasts. Roth 801 decreased cell viability counts for both fibroblasts and macrophages. Sealapex decreases macrophage viability. ProRoot MTA did not affect viability in either cell line.

Is pulpitis painful?

AIM: To determine whether inflamed dental pulps progress to necrosis without pain. METHODOLOGY: Records of 2,202 maxillary anterior teeth endodontically treated at the University of Michigan were collected. Records of teeth presenting with periapical radiolucencies but no response to vitality tests were examined further to determine, from the history, whether the patient had experienced pain or no pain from the involved tooth. RESULTS: Approximately 40% of the teeth included gave no history of spontaneous or prolonged pain to a thermal stimulus. No statistically significant differences in the incidence of 'painless pulpitis' were related to either gender or tooth type. Patients aged >53 years experienced 'painless pulpitis' more often than patients <33 years. CONCLUSIONS: Many teeth appear to progress to pulpal necrosis without the patient experiencing pain attributable to the pulp.

Phosphoprotein analysis of sequential extracts of human dentin and the determination of the subsequent remineralization potential of these dentin matrices.

Phosphoprotein appears to play an important role in the mineralization of dentin during tooth development and remineralization after demineralization by dental caries. To better understand this role, we describe the extraction and characterization of phosphoprotein from immature, human root apex dentin during and after EDTA demineralization. The extraction procedure included dissociation of the demineralized dentin matrix by guanidine hydrochloride (Gdn.HCl) followed by subsequent digestion with cyanogen bromide (CNBr) and collagenase. Characterization of these extracts included 'Stains-All' staining of SDS polyacrylamide gels (SDS-PAGE) and amino acid, protein and phosphorus analyses. The ability of these matrices to remineralize was determined by TEM and measuring calcium levels in the remineralized tissue by atomic absorption spectroscopy. The staining of SDS-PAGE gels and amino acid analysis showed that an intact phosphophoryn was extracted from the dentin of the immature apices during EDTA demineralization and that it had an apparent Mr approximately 140,000. In the subsequent extracts and digests, the phosphoprotein has a range of molecular weights, some of which may have been degraded products of the intact phosphoprotein. A greater quantity of phosphoprotein was found in the EDTA-demineralized dentin matrices than in dentin after Gdn.HCl, CNBr and collagenase digests. These EDTA-demineralized matrices also remineralized to a greater extent than those dissociated with Gdn.HCl. The differences in both the quantity and the quality, as defined by the amino acid residue profile, of the phosphoprotein in the sequential extracts of the root apex dentin may be important in affecting the ability of this tissue to remineralize.

Guidelines for the design and conduct of clinical trials on dentine hypersensitivity.

Clinical trials on dentine hypersensitivity have been numerous and protocols varied. To date there is little consensus as to the conduct of studies on this poorly-understood yet common and painful dental condition. A committee of interested persons from academia and industry was convened to discuss the subject of clinical trials on dentine hypersensitivity and a consensus report is presented. A double-blind randomized parallel groups design is recommended, although cross-over designs may be used for the preliminary screening of agents. Subjects may have multiple sites scored. Sample size will be determined by estimating the variability in the study population, the effect to be detected and the power of the statistical test to be used. Subject selection is based on a clinical diagnosis of dentine hypersensitivity, excluding those with conflicting characteristics such as currently-active medical or dental therapy. The vestibular surfaces of incisors, cuspids and bicuspids are preferred as sites to be tested. A range of sensitivity levels should be included. Tactile, cold and evaporative air stimuli should be applied. Negative and benchmark controls should be incorporated. Most trials should last 8 weeks. Sensitivity may be assessed either in terms of the stimulus intensity required to evoke pain or the subjective evaluation of pain produced by a stimulus using a visual analog or other appropriate scale. The subject's overall assessment may be determined by questionnaire. Outcomes should be expressed in terms of clinically significant changes in symptoms. Follow-up evaluation is required to determine the persistence of changes. At least 2 independent trials should be conducted before a product receives approval.

Steroids reduce the periapical inflammatory and neural changes after pulpectomy.

Root canal treatment, including obturation with gutta-percha and a zinc oxide and eugenol sealer, was conducted, under general anesthesia, on the canine teeth of 12 young ferrets. Six of the ferrets were given 0.5 mg/kg dexamethasone daily. Three months after the root canal treatment, under general anesthesia, the animals were perfused with fixative and the canine periapical tissues prepared for histological examination. The extent of periapical inflammation was measured and the degree of neural sprouting in the periodontal and subapical regions estimated. Periapical lesions in steroid-treated animals were 30% of the size of those in untreated animals. Innervation density in the subapical region of the steroid-treated animals was lower than that in the animals who did not receive steroids and not significantly different from controls. Reduction in periapical inflammation induced by systemic steroids is accompanied by a reduction in neural sprouting.

Periapical changes after orthodontic movement of root-filled ferret canines.

The effectiveness of orthodontic forces in moving root-filled teeth and the degree of apical resorption it causes have been observed in an animal model. Under general anesthesia, root canal therapy was performed on the mandibular canines on one side of 12 young male ferrets. Bilateral movement of the canines was induced with an orthodontic spring (150 to 175 g). Procion red dye was injected 1 wk presurgically to mark bone and cementum deposition. Three months later, tooth movement was assessed from pre- and posttreatment mandibular casts and by fluorescence microscopy from labeled bone deposition. Vital and nonvital teeth moved similar distances when subjected to the same forces. Root-filled teeth showed greater loss of cementum after tooth movement than vital teeth (p < 0.05), but without significant differences in radiographic root length.

A quantitative morphological study of the recovery of cat lingual nerves after transection or crushing.

The morphological changes were examined proximal and distal to crush and transection injuries of the lingual/chorda tympani nerve. Under general anaesthesia the nerve was transected unilaterally in 6 adult cats and crushed with watchmakers forceps in 6 others. After 12 wk, again under general anaesthesia, the injured and contralateral (control) nerves were removed, fixed and embedded for histological examination. Sections were cut from sites proximal and distal to the injury and from a site equivalent to that of the injury on the control side. Using systematic randomised sampling techniques the number of nonmyelinated axons and the number and size of myelinated axons in each nerve at each location was estimated. In addition, the mean number of nonmyelinated axons in each Schwann cell unit was determined. The only significant difference between control and injured nerves proximal to either injury was a reduction in the number of myelinated axons in the chorda tympani after transection, and an increase in their mean size. This indicates a selective loss of smaller fibres and is consistent with the poor recovery of gustatory and thermosensitive fibres previously reported (Robinson, 1989). Distal to both types of injury there was an increase in the number of fascicles. The mean number of myelinated axons was reduced distal to a crush injury but unchanged distal to transection. The number of nonmyelinated axons distal to a transection injury was 5 times control counts and after a crush injury double. These findings suggest that sprouting persists 12 wk after both injuries but is much greater after transection.

A quantitative morphological comparison of cat lingual nerve repair using epineurial sutures or entubulation.

Since lingual nerves may be transected during a variety of oral surgical procedures, including third molar removal, we have investigated two possible methods of repair. Quantitative morphological observations were made on feline chorda tympani and lingual nerves proximal and distal to transection injuries repaired either by epineurial suturing or by insertion of the cut ends into a perforated silicon tube. Proximal to the repair, the most prominent difference was an increase in the number of myelinated axons in the lingual nerve following epineurial suturing but not entubulation. Proximal to the repair site, the number of nonmyelinated axons increased in comparison with controls in both chorda tympani and lingual nerves after both procedures, though the difference was statistically significant only in the lingual nerve proximal to entubulation. Distal to the injury, both types of repair showed a reduction in the number, size, and sheath thickness of myelinated axons in comparison with unoperated controls, but the difference in numbers was statistically signIficant only distal to repair by entubulation. The number of non-myelinated axons distal to the repair sites was much higher than that in controls, the difference being greater distal to entubulation repair. There were more axons per Remak bundle distal to entubulation repair than to epineurial suturing, suggesting, perhaps, that fewer axons would ultimately become myelinated. Though the morphological differences between the two repair techniques are not as striking as the parallel electrophysiological differences reported previously (Smith and Robinson, 1995a,b), they are consistent with them and support the conclusion that, for transected lingual and chorda tympani nerves, epineurial suturing is the preferred approach.

Experimental trigeminal nerve injury.

The successful reinnervation of peripheral targets after injury varies with the axonal population of the nerve that is injured and the extent of the dislocation of its central component from the peripheral endoneurial tube. Larger-diameter axons such as those supplying mechanoreceptors recover more readily than narrower axons such as those supplying taste. A complex, bi-directional interaction between lingual epithelium and sprouting nerve results in the redifferentiation of taste buds after denervation. Dentin and the dental pulp provide a strong attraction to sprouting nerves and will become reinnervated from collateral sources if recovery of the original innervation is blocked. The most effective repair technique for transected lingual nerves is one which brings the cut ends together rather than one that provides a temporary bridge. Injuries can result in cell death in the trigeminal ganglion but only if the injury is severe and recovery is prevented. Lesser damage results in chromatolysis and the increased expression of neuropeptides. All nerve injuries bring about changes in the trigeminal nucleus. These occur as changes in receptive field and the incidence of spontaneously active neurons, effects which are consistent with the unmasking of existing afferents. These functional changes are short-lived and reversible. Morphologically, nerve injury results in terminal degeneration in the nuclei and an increased expression of the c-Fos gene and some neuropeptides. Only a chronic constriction injury induces behavioral changes. The adult trigeminal system retains considerable plasticity that permits it to respond successfully to nerve injury. Much remains to be learned about this response, particularly of the trophic factors that control peripheral recovery and the central response to more severe injuries.

Periapical neural changes after pulpectomy.

Pulpectomy and pulpal necrosis result in severance of the nerves that supply the pulp as well as loss of their target organ. Inflammatory changes commonly extend into the periapical region to involve those nerves. The neural response to pulpal loss combined with periapical inflammation is a derangement of the periodontal plexus normally located in the center of the periodontal space around the apical third of the root; the result is the formation of a disorganized group of sprouting and branching axons that have some features in common with neuromas. The inflammatory and neural responses continue for at least a year even when pulpectomy is followed by canal debridement and obturation. Then the responses are reduced but not eliminated by steroids. Root canal therapy with techniques that do not leave residual inflammation still results in increased periapical innervation; the increase seems to be an organized addition to the normal periradicular plexus.

A histological comparison of periapical inflammatory and neural responses to two endodontic sealers in the ferret.

Previous studies have shown that there is a proliferation of nerves beneath the apices of pulpectomized teeth. This may be due to the inflammation induced after the procedure, resulting, perhaps, from the irritant nature of the materials used to fill the root canal. The experiment reported here was conducted to determine whether this inflammation was induced by the sealer rather than arising as a result of tissue damage and whether, if inflammation is eliminated or reduced, the neural changes are also reduced. In 12 young adult ferrets under general anaesthesia the pulps of the lower canine teeth were removed and replaced with gutta percha and sealer. A sealer of Grossman's formulation with eugenol as the liquid phase was used on one side and a calcium hydroxide sealer that contained no eugenol on the other. Three months later the animals were, again under general anaesthesia, perfused with a fixative mixture. The mandibles were removed and the presence and size of any periapical inflammatory lesions and the density of periapical innervation determined histologically. All 12 teeth sealed with the Grossman's sealer had inflammatory lesions at their apices. Three of the 12 teeth treated with the calcium hydroxide sealer showed similar lesions. In all the teeth with inflammatory lesions the normal arrangement of nerves in a periodontal 'plexus' was disrupted but there was no statistically significant difference between the overall innervation density in inflamed and non-inflamed periapical areas nor between areas beneath teeth sealed with Grossman's sealer and with calcium hydroxide. The incidence of periapical inflammation is related to the nature of endodontic sealer used.(ABSTRACT TRUNCATED AT 250 WORDS)

Morphological features of dentine and pulp related to dentine sensitivity.

This review considers those structural features of the pulp and dentine relevant to an understanding of dentine sensitivity. It does not discuss innervation, or microvasculature, which are covered in other contributions. The sensitivity of dentine is directly related to the size and patency of the dentinal tubules. Tubular occlusion by peritubular dentine deposition or the formation of other intratubular material would reduce the flow of fluid and diffusion of molecules through dentine. Irregular (reparative) secondary dentine would, because its tubules are not continuous with those of primary dentine, be expected to reduce permeability and fluid flow and decrease sensitivity. Regular secondary dentine would have little or no effect other than by increasing diffusion distances. The odontoblast layer is of limited permeability and could restrict the access of materials diffusing through the dentinal tubules to pulpal axons. Odontoblasts are not involved in the sensory process as special sensory receptors but may, by modifying the local ionic environment, alter the threshold of intradentinal nerves.

The distribution and morphological characteristics of axons innervating the periodontal ligament of reimplanted teeth in cats.

Twelve weeks after reimplanting lower canines the distribution and characteristics of myelinated and non-myelinated axons within the periodontal ligament were investigated by light and electron microscopy. The ligament was examined at 2-mm intervals along the length of the root of four reimplanted teeth and of the contralateral canines, which served as controls. In each case the periodontal ligament was reinnervated. In two of the teeth, which showed extensive apical resorption, the innervation was much less than in control teeth. In two teeth showing minimal or no apical resorption the degree of innervation at the most apical level did not differ significantly from controls.