T and B Cells in Periodontal Disease: New Functions in A Complex Scenario.

Periodontal disease is characterised by a dense inflammatory infiltrate in the connective tissue. When the resolution is not achieved, the activation of T and B cells is crucial in controlling chronic inflammation through constitutive cytokine secretion and modulation of osteoclastogenesis. The present narrative review aims to overview the recent findings of the importance of T and B cell subsets, as well as their cytokine expression, in the pathogenesis of the periodontal disease. T regulatory (Treg), CD8+ T, and tissue-resident γδ T cells are important to the maintenance of gingival homeostasis. In inflamed gingiva, however, the secretion of IL-17 and secreted osteoclastogenic factor of activated T cells (SOFAT) by activated T cells is crucial to induce osteoclastogenesis via RANKL activation. Moreover, the capacity of mucosal-associated invariant T cells (MAIT cells) to produce cytokines, such as IFN-γ, TNF-α, and IL-17, might indicate a critical role of such cells in the disease pathogenesis. Regarding B cells, low levels of memory B cells in clinically healthy periodontium seem to be important to avoid bone loss due to the subclinical inflammation that occurs. On the other hand, they can exacerbate alveolar bone loss in a receptor activator of nuclear factor kappa-B ligand (RANKL)-dependent manner and affect the severity of periodontitis. In conclusion, several new functions have been discovered and added to the complex knowledge about T and B cells, such as possible new functions for Tregs, the role of SOFAT, and MAIT cells, as well as B cells activating RANKL. The activation of distinct T and B cell subtypes is decisive in defining whether the inflammatory lesion will stabilise as chronic gingivitis or will progress to a tissue destructive periodontitis.

Collagen-like peptide sequences inhibit bacterial invasion of root dentine.

AIM: To investigate the effects of peptides derived from the sequence of collagen to inhibit penetration of human or bovine dentine by species of streptococci and enterococci. METHODOLOGY: Blocks of human or bovine root dentine were infected for 14 days with bacterial cultures, in the presence or absence of various collagen-like peptide sequences. Invasion of dentinal tubules was determined from microscopic images of histochemically stained dentine thin sections. Extent of invasion was expressed as tubule invasion index (TI), or tubule invasion factor (TIF) which, in addition to the density of invasion, took into account the depth of invasion. Data were analysed by two-way anova. RESULTS: Streptococcus gordonii, Streptococcus mutans and Enterococcus faecalis were associated with heavy invasion (TI >2.5, TIF >4) of human or bovine root dentinal tubules, with E. faecalis being the most penetrative. Incorporation of peptides Gly-Pro-Ala or Gly-Pro-Hyp into the in vitro model system significantly reduced (P < 0.05) dentine invasion by the three species of highly invasive organisms. Inhibition of bacterial invasion by the peptides was dose dependent, and the peptides did not inhibit bacterial growth in culture. CONCLUSION: Specific collagen-like peptide sequences inhibited the invasion of dentine in vitro by a range of oral bacteria. The peptides likely act as competitive inhibitors blocking bacterial collagen receptors and could potentially allow for target-specific control of dentine infections.

Novel keratin preparation supports growth and differentiation of odontoblast-like cells.

AIM: To fabricate a keratin hydrogel, characterize its functionality as a biomaterial and investigate the effects of keratin on growth and differentiation of odontoblast-like cells. METHODOLOGY: Keratins were extracted from sheep wool using a well-established technique. The extracted proteins were purified by dialysis, quantified by gel electrophoresis, mass spectrometry, amino acid analysis and inductively coupled mass spectrometry. The microstructure of the fabricated keratin hydrogels was studied by scanning electron microscopy, flow characteristics by rheometer, hydrolytic stability and cytocompatibility by Live/Dead(®) cell assay. Furthermore, the influence of keratin on odontoblast-like cells (MDPC-23) was assessed to confirm their bioactivity at different dilutions. Cell proliferation was studied using alamarBlue(®) assay and differentiation by alkaline phosphatase enzyme activity, alizarin red staining and calcium quantification, reverse transcription polymerase chain reaction (rt-PCR) and immunocytochemical staining for dentine matrix protein- 1 (DMP-1) expression. anova with Tukey's tests was performed for statistical comparison. RESULTS: The characterized hydrogel was injectable with a highly porous architecture that underwent slow degradation, and its cytocompatibility was statistically equivalent to collagen hydrogel (P > 0.05). Cell proliferation and differentiation were enhanced at the optimal keratin concentration of 0.1 mg mL(-1) . At this concentration, the influence of keratin on cell differentiation was demonstrated by marked elevation in alkaline phosphatase activity (P < 0.05), calcium deposition (P < 0.01), gene expression (P < 0.01) and positive immunostaining for DMP-1. CONCLUSION: The presence of keratin enhanced odontoblast cell behaviour. Keratin hydrogels may be a potential scaffold for pulp-dentine regen-eration.

Oral health of older people admitted to hospital for needs assessment.

OBJECTIVES: To describe the clinical oral health status, treatment needs and oral-health-related quality of life (OHRQoL) of older people admitted to older persons' wards at Dunedin Public Hospital due to a sudden worsening of their general health. Participants and methods: A systematic oral assessment was undertaken for a consecutive case series of 200 patients (59.5% female; mean age 82.6 years, sd 6.6) admitted to older person's wards at Dunedin Public Hospital. The Oral Health Impact Profile-20 (OHIP-20) was used to assess OHRQoL. RESULTS: One in three (36.0%) had been living independently at home prior to admission, and over half (55.0%) had been admitted for a medical reason which required assessment. Half (50.0%) of the participants were dentate (with an average of 16.8 teeth). There was an average of 1.9 decayed teeth present in the dentate group; 70.7% of individuals required restorations or extractions, and about 90% required only simple scaling of the teeth and prophylaxis. A reline or a replacement denture were required by three-quarters of those with dentures. Almost two-thirds of participants did not have a regular dentist, and fewer than one in three had made a dental visit in the previous year. One in six described their oral health as 'fair' or 'poor', and just under one-third reported dry mouth. Dentate participants, those without xerostomia, and those reporting better oral health had better OHRQoL, reflected in lower OHIP-20 scores. Affecting 37.1% of participants, functional limitation was the most commonly experienced of the OHIP-20 domains, followed by physical disability and physical pain (18.0% and 15.6% respectively). CONCLUSIONS: The oral health of medically compromised and functionally dependent but cognitively competent older people in this study is generally poor. If transfer to long-term care is indicated, early and proper preventive measures and appropriate dental contact should be advocated in order to reduce morbidity and improve quality of life for older people.

Expression of Toll-like receptors 2 and 4 and the OPG-RANKL-RANK system in inflammatory external root resorption and external cervical resorption.

AIM: To investigate and compare the expression of the pathogen recognition receptors Toll-like receptor (TLR) 2 and TLR4, and the hard tissue resorption triad osteoprotegerin (OPG)-receptor activator of nuclear factor kappa-B ligand (RANKL)-receptor activator of nuclear factor kappa-B (RANK) in external inflammatory root resorption of endodontic origin (ER) and external cervical root resorption (ECR) by immunohistochemistry. METHODOLOGY: Formalin-fixed, paraffin-embedded archival specimens collected from teeth that were diagnosed clinically, radiographically and histopathologically with either ER (n = 9) or ECR (n = 9) were processed for immunohistochemistry to investigate and compare levels of TLR2, TLR4, OPG, RANKL, RANK, CD3, CD19 and CD83 expression. The histological features were evaluated via haematoxylin and eosin stain. Taylor's modification of the Brown and Brenn Gram stain was used for examining the presence and distribution of bacteria. All stained slides were digitally photographed and qualitatively analysed, and F test and unpaired Student's t-test were used for statistical analysis. RESULTS: Both ER and ECR showed similar immuno-histopathology characteristics of a fibrovascular connective tissue with varying degrees of inflammatory infiltrate consisting of T and B lymphocytes, dendritic cells, polymorphonuclear lymphocytes and plasma cells. Colonies of bacteria were identified in the majority of lesions, and this correlated with the cellular expression of TLR2 and TLR4 in all lesions. Similarly, all lesions showed a significantly higher (P < 0.05) level of cells expressing RANKL than OPG, indicating hard tissue resorption processes where active in the lesions. CONCLUSION: The immunohistopathology patterns of ECR samples were consistent with the bacteria-driven ER specimens, suggesting bacteria-induced inflammation may be involved in ECR.

Toll-like receptor 2 expression in refractory periapical lesions.

AIM: To investigate the expression of TLR2 in refractory periapical lesions. METHODOLOGY: Refractory periapical lesion biopsies were histopathologically and clinically categorized into asymptomatic periapical granuloma (n=10), symptomatic periapical granuloma (n=10) or periapical cyst (n=10) and prepared for immunohistochemical staining using antibodies to TLR2, CD3 and CD19 or staining with methyl green pyronin. Sections were viewed under light microscopy and the presence or absence of the target cells was correlated with the histopathological and clinical data. Additionally, TLR2 expression was quantified by counting TLR(+) cells. RESULTS: Various mononuclear inflammatory cells in the bacteria-induced periapical lesions were reactive to TLR2 antibody, with many showing morphological similarities to lymphocytes and plasma cells. Lymphocytes were the most numerous cells in the inflammatory infiltrate. In refractory periapical granuloma, CD3(+) T cells were more numerous, whereas in periapical cysts, CD19(+) B cells were more numerous. There was a statistically significant (P<0.05) higher expression of TLR2 in symptomatic periapical granuloma than asymptomatic periapical granuloma or periapical cyst. CONCLUSION: The presence of TLR-expressing cells in periapical granulomas and cysts provides further evidence that periapical cysts are likely to be sustained by the immune system via reaction to bacterial antigens.

Antigen recognition and presentation in periapical tissues: a role for TLR expressing cells?

Bacteria are the prime cause of periapical diseases and root canal microbiology is a well-researched area of endodontics. Antigen-presenting cells (APCs) are present in periapical lesions of endodontic origin and play a substantial role in recognizing, processing and presenting pathogenic antigens to the adaptive immune system such as an effective and long-lasting immune response is generated against the specific pathogens. Toll-like receptors (TLRs) are germ-line encoded pathogen recognition receptors (PRR) expressed by various APCs which induce their maturation, lead to gene transcription in the nucleus and the production of several pro- and anti-inflammatory cytokines. Thirteen TLRs have been discovered, 10 of which have been identified in humans so far. Preliminary studies of dental pulp tissue have demonstrated various cell types expressing different TLRs in response to commonly encountered microorganisms. However, there is little information available regarding the expression and function of the various TLRs in human periapical lesions. This review discusses the interactions of various APCs in periapical lesions and the possible roles of different TLRs and APCs in pulp/periapical pathogen recognition and presentation to the adaptive immune system in the initiation and sustaining of periapical diseases.

A Micro CT study of the mesiobuccal root canal morphology of the maxillary first molar tooth.

AIM: To observe the morphology of the root canal system of the maxillary first molar mesiobuccal root using micro computed tomography and compare it to current canal classifications. METHODOLOGY: Twenty mesiobuccal roots were resected from randomly selected extracted human maxillary first molar teeth and prepared for scanning using a SkyScan micro CT scanner (SkyScan 1172 X-ray microtomograph, Antwerp, Belgium) at a slice thickness of 11.6µm. Three-dimensional images were produced and analysed to record the number and configuration of the canals, the presence of accessory canals, connections between the canals and number of canal orifices and foramina. RESULTS: The majority of roots had complex root canal systems with a second mesiobuccal canal present in 90% of the roots examined. Intercanal communications were observed in 55% of the roots. A single apical foramen was found in 15% of roots, two foramina were present in 20% and three or more foramina were present in 65%. In half of the roots, there were two orifices at the furcation level; 40% had one orifice and 10% had three orifices. Accessory canals were present in 85% of the roots. Only 60% of root canals could be classified using the classification of Weine et al. (1969) and 70% using the classification of Vertucci (1984). CONCLUSION: Micro computed tomography offers an ability to examine root canal anatomy in fine detail and confirms that the morphology of the mesiobuccal root of the maxillary first molar teeth is complex and that present morphology classifications do not fully reflect the complexity.

Maxillofacial trauma and the GDP--specialty recognition and patterns of referral.

OBJECTIVE: To investigate New Zealand GDPs' awareness of maxillofacial trauma and to identify their associated referral patterns. DESIGN: Cross-sectional survey of a random sample of GDPs. METHOD: A nationwide postal questionnaire survey was sent to GDPs on the New Zealand Dental Register, maintained by the Dental Council of New Zealand. The questionnaire requested socio-demographic details, together with information on the availability of specialist services and their need for continuing professional development in oral and maxillofacial surgery (OMS). The questionnaire also asked the GDPs to indicate which specialty (plastic surgery, ear nose and throat (ENT) surgery, OMS and Other) they expected to manage--and to which specialty they would refer-seven types of maxillofacial injury. RESULTS: Some 377 GDPs responded (76.6%). The majority of GDPs expected OMS to manage maxillofacial trauma, except for facial lacerations and isolated nasal fractures which were expected to be managed by plastic surgery (83.0%) and ENT surgery (79.7%), respectively. Most GDPs (48.0% to 87.9%) referred maxillofacial trauma to OMS, except for isolated nasal fractures, for which there were similar proportions referred to ENT surgery and OMS (45.8% and 41.4%, respectively). Differences in awareness of and referral patterns for maxillofacial trauma were identified by dentist characteristics. Most GDPs (96.0%) felt there was a need for continuing professional development in OMS, and most (84.1%) preferred this to be in the form of lectures and seminars. CONCLUSION: The first-ever study of GDP referral patterns for maxillofacial trauma in New Zealand has revealed that most GDPs in New Zealand referred maxillofacial trauma appropriately to OMS.

Radiolucent inflammatory jaw lesions: a twenty-year analysis.

AIM: To determine the range and demographic and clinical features of radiolucent inflammatory jaw lesions. METHODOLOGY: Histopathology reports were reviewed to identify radiolucent jaw lesions. There were no clinical exclusive criteria, and the samples represented a wide range of clinical presentation and treatment history from multiple providers. Data were analysed using SPSS. To evaluate concordance of clinical and histological diagnoses, the clinician's provisional diagnosis was compared with the final histopathological diagnosis. RESULTS: A total of 17 038 specimens were reviewed; of these, 4983 (29.2%) were radiolucent jaw lesions, of which inflammatory lesions accounted for 72.8% (n = 3626). Periapical granulomas (59.7%) were the largest group followed by radicular cysts (29.2%). The mean age was 44 years (range 2-100 years), men and women were equally represented and the anterior maxilla was the most common site for the biopsied lesions. A provisional diagnosis was correct for only 48.3% of periapical granulomas and 36% of radicular cysts. CONCLUSIONS: This study included all presentations of periapical radiolucent lesions and showed that the incidence of cystic change in periapical lesions of endodontic origin is high at approximately 30% of all inflammatory lesions. Notwithstanding the relative frequencies, demographics and location of radiolucent inflammatory lesions presenting in the New Zealand population are comparable to that of other populations. No inflammatory radiolucent lesion can be reliably accurately diagnosed from clinical presentation and/or radiographic appearance alone.

Dental stem cells and their potential role in apexogenesis and apexification.

Injury to an immature permanent tooth may result in cessation of dentine deposition and root maturation leaving an open root apex and thin dentinal walls that are prone to fracture. Endodontic treatment is often complicated and protracted with an uncertain prognosis frequently resulting in premature tooth loss. Postnatal stem cells, which are capable of self-renewal, proliferation and differentiation into multiple specialized cell lineages have been isolated and identified within the dental pulp, apical papilla and periodontal ligament. The ability of these cells to produce pulp-dentine and cementum-periodontal ligament complexes in vivo suggest potential applications involving stem cells, growth factors and scaffolds for apexification or apexogenesis. Similar protein expression amongst dental stem cells possibly implicates a common origin; however, the dominant cells to repopulate an open apex will be directed by local environmental cues. A greater understanding of the structure and function of cells within their environment is necessary to regulate and facilitate cellular differentiation along a certain developmental path with subsequent tissue regeneration. This review focuses on development of the apical tissues, dental stem cells and their possible involvement clinically in closing the open root apex. MEDLINE and EMBASE computer databases were searched up to January 2009. Abstracts of all potentially relevant articles were scanned and their contents identified before retrieval of full articles. A manual search of article reference lists as well as a forward search on selected authors of these articles was undertaken. It appears that dental stem cells have the potential for continued cell division and regeneration to replace dental tissues lost through trauma or disease. Clinical applications using these cells for apexogenesis and apexification will be dependent on a greater understanding of the environment at the immature root end and what stimulates dental stem cells to begin dividing and then express a certain phenotype.

Histopathological profile of surgically removed persistent periapical radiolucent lesions of endodontic origin.

AIM: To determine the types of periapical lesions associated with root filled teeth with persistent periapical pathosis that required surgical treatment based on specific inclusion and exclusion criteria. METHODOLOGY: Periapical lesions from a consecutive clinical sample of 100 patients were examined histopathologically to determine a definitive diagnosis. RESULTS: Females were more represented (n = 56), the average age was 46.5 years and there were no age differences between gender or lesion type. A diagnosis of periapical granuloma was the most common finding with a similar number present in females (n = 40) and males (n = 37). A cyst was present in 18% of the cases with a majority of females (n = 12) represented in the sample. Evidence of foreign material, with an appearance consistent with endodontic sealer materials, was seen in 25 periapical granulomas, two cysts and one scar. Two periapical scars were seen, one had a history of apicectomy and amalgam root-end filling while the other was associated with extruded root filling material. CONCLUSIONS: By using defined clinical inclusion and exclusion criteria a predictable clinical diagnosis of a persistent periapical lesion due to endodontic origin can be reliably made. Periapical granulomas and cysts were the most common periapical lesions of endodontic origin associated with persistent periapical pathosis with the overall incidence of periapical cysts similar to previous studies. The presence of endodontic material in a high proportion of periapical lesions suggests a cause-effect association with the inference that clinicians should employ canal preparation techniques that limit apical extrusion of material.

Hemin nutritional stress inhibits bacterial invasion of radicular dentine by two endodontic anaerobes.

AIM: To determine if anaerobic bacteria routinely found in infected dentine and root canals require the presence of heme in the environment in order for them to invade dentinal tubules. METHODOLOGY: Noncarious, unrestored human teeth with single root canals were prepared for invasion experiments and soaked in either TSB-M supplemented with hemin (5 microg mL(-1)) (n = 12 roots), TSB-M media (n = 12 roots) or TSB-M media followed by hemin soak (n = 12 roots) for 2 days, then inoculated with either Prevotella intermedia ATCC 25611 or Peptostreptococcus micros ATCC 33270 and incubated anaerobically for 14 days. Roots were prepared for light microscopy, stained with Brown and Brenn or antisera raised to the bacteria, and invasion within tubules assessed using a tubule invasion index (TI). Data were analysed using Student's t-test and Mann-Whitney U-test. RESULTS: Prevotella intermedia (TI = 0.7 +/- 0.04) and P. micros (TI = 0.96 +/- 0.08) showed low invasion when grown in the presence of hemin with cells generally restricted to the superficial 20 microm of the tubules, whilst neither bacteria invaded tubules (TI = 0) when hemin was absent from the growth media (P < 0.01). CONCLUSIONS: Hemin was required in the growth medium for P. intermedia and P. micros to invade dentinal tubules.

A finite element analysis of ferrule design on restoration resistance and distribution of stress within a root.

AIM: To analyse the effect of ferrule height upon the mechanical resistance and stress distribution within a root to explain variations in the pattern of root fracture. METHODOLOGY: An extracted, intact, caries free, maxillary right central incisor was scanned by laser and then reconstructed on a computer to produce a model of the tooth and associated periodontal ligament. A simulated post/core/crown restoration was constructed on conventional tooth preparations with various ferrules. The crown was loaded with a simulated 500 N force and the simulated displacement of components and the tensile and compressive stress within the tooth structure were recorded. RESULTS: Without a ferrule preparation, the simulated crown tilted to the labial and rotated distally. With increasing ferrule height the displacement and rotation of the crown reduced in conventional and crown-lengthening models with maximum reduction occurring when the ferrule height reached 1.5 mm. In ferrule models, higher levels of tensile stress developed in internal (by a factor of 8) and mid-root palatal (by a factor of 90) dentine at the cervical margin of the preparation. With an increase in ferrule height, the area of tensile stress within the palatal mid-dentine expanded towards the cervical margin. Similar patterns and stress values were recorded for the crown-lengthening models. CONCLUSION: The study confirms that a ferrule increases the mechanical resistance of a post/core/crown restoration. However a ferrule creates a larger area of palatal dentine under tensile stress that may be a favourable condition for a crack to develop. Crown-lengthening did not alter the levels or pattern of stress within compared with conventional ferrule preparations.

Inflammatory responses to the occupational inhalation of metal fume.

Occupational exposure to metal fume promotes a reversible increase in the risk of pneumonia, but by mechanisms which are unclear. To investigate, the current authors measured various markers of host defence function in welders and nonwelders. Induced sputum and venous blood samples were collected from 27 welders with regular long-term exposure to ferrous metal fume and 31 unexposed matched controls. In sputum, the present authors measured cell counts, the soluble and cellular iron concentration, and levels of interleukin-8, tumour necrosis factor-alpha, myeloperoxidase, matrix metalloproteinase-9, immunoglobulin (Ig)A, alpha(2)-macroglobulin and unsaturated iron-binding capacity. Blood samples were assayed for evidence of neutrophil activation and pneumococcal IgG antibodies. Welders had significantly higher iron levels and a substantially lower unsaturated iron-binding capacity in their sputum, but, despite a high iron challenge, there was a noteworthy absence of an inflammatory response. Only blood counts of eosinophils and basophils were significantly related to the extent of welding. Weak nonsignificant trends were observed for several other measures, consistent with low-grade priming of neutrophils. In conclusion, these data suggest that chronic exposure to metal fume blunts responsiveness to inhaled particulate matter. However, the mechanism behind the lack of detectable local inflammatory response requires further investigation.

An evaluation of .06 tapered gutta-percha cones for filling of .06 taper prepared curved root canals.

AIM: To compare the area occupied by gutta-percha, sealer, or void in standardized .06 tapered prepared simulated curved canals and in mesio-buccal canals of extracted maxillary first molars filled with a single .06 gutta-percha point and sealer or lateral condensation of multiple .02 gutta-percha points and sealer. METHODOLOGY: Simulated canals in resin blocks with either a 30 degrees curve and radius of 10.5 mm (n = 20) or a 58 degrees curve and 4.7 mm radius (n = 20) and curved mesio-buccal canals of extracted maxillary first molars (n = 20) were prepared using .06 ProFiles in a variable tip crown-down sequence to an apical size 35 at 0.5 mm from the canal terminus or apical foramen. Ten 30 degrees and 58 degrees curved resin canals and 10 canals in the extracted teeth group were obturated with .02 taper gutta-percha cones and AH 26 sealer using lateral condensation. The time required to obturate was recorded. The remaining canals were obturated with a single .06 taper gutta-percha cone and AH 26 sealer. Excess gutta-percha was removed from the specimens using heat and the warm mass vertically condensed. Horizontal sections were cut at 0.5, 1.5, 2.5, 4.5, 7.5 and 11.5 mm from the canal terminus or apical foramen. Colour photographs were taken using an Olympus 35 mm camera attached to a stereomicroscope set at x40 magnification, and then digitized using a flatbed scanner. The cross-sectional area of the canal contents was analysed using Adobe PhotoShop. The percentage of gutta-percha, sealer or voids to the total root canal area were derived and data analysed using unpaired Student's t-test and the Mann-Whitney U-test. RESULTS: In the 30 degrees curved canals the levels had between 94 and 100% of the area filled with gutta-percha with no significant difference (P > 0.05) between the lateral condensation and single cone techniques. In the 58 degrees curved canals the levels had 92-99% of the area filled with gutta-percha, with the single cone technique having significantly (P < 0.05) more gutta-percha fill at the 2.5 mm level only. In the mesio-buccal canals of the teeth the levels had between 72 and 96% of the area filled with gutta-percha with no significant difference (P > 0.05) between the lateral condensation and single cone technique. The time for obturation was significantly (P < 0.05) greater for lateral condensation compared with the single cone technique in all groups. CONCLUSIONS: The .06 taper single cone technique was comparable with lateral condensation in the amount of gutta-percha occupying a prepared .06 tapered canal. The .06 single cone technique was faster than lateral condensation.

An in-vitro investigation of the antibacterial effect of nisin in root canals and canal wall radicular dentine.

AIM: To determine whether nisin, a bacteriocin, would be effective at killing Enterococcus faecalis and Streptococcus gordonii cells in solution and within the root canal system. METHODOLOGY: Bacterial isolates of E. faecalis and S. gordonii were grown from glycerol stocks in closed tubes containing BHY broth at 37 degrees C. The minimum bactericidal concentration (MBC) of nisin for both bacterial species was determined by a microdilution method. Extracted human teeth were decoronated to produce roots of equal length with a single canal and divided into six groups of 10 roots. The canals were prepared to a master apical size 30 file using 0.04 taper Ni-Ti rotary instruments. Bacterial samples of each species were inoculated into three groups of prepared roots and incubated in closed tubes at 37 degrees C for 21 days. The root canals in each group were then medicated with water (control), calcium hydroxide powder mixed with sterile water [Ca(OH)2], or nisin and incubated for a further 7 days. Rotary Ni-Ti files were used to take radicular dentine samples from the walls of each canal which were then incubated in BHY broth for 24 h. Optical density (OD600) readings were taken as a measure of bacterial growth. RESULTS: The MBC of nisin for E. faecalis and S. gordonii was 70 and 20 mg mL(-1) respectively. Calcium hydroxide and nisin medication eradicated infection within the root canal while cells remained viable in the control group. Mean optical density (OD600) readings from canal wall dentine shavings infected with E. faecalis were 1.32 +/- 0.98, 0.73 +/- 0.27 and 0.69 +/- 0.38 for the control, Ca(OH)2 and nisin samples respectively. Corresponding mean readings for S. gordonii were 1.19 +/- 0.18, 0.73 +/- 0.15 and 0.60 +/- 0.29. The Ca(OH)2 and nisin group readings were significantly (P < 0.01) lower than the control for each species as tested by Student's t-test and Mann-Whitney U statistical analysis. Values for Ca(OH)2 and nisin were not significantly (P > 0.01) different. CONCLUSION: Nisin was effective at eradicating E. faecalis and S. gordonii cells in pure culture and was comparable with Ca(OH)2 in the elimination of these species from within the root canal system.

Shaping ability of ProFile and K3 rotary Ni-Ti instruments when used in a variable tip sequence in simulated curved root canals.

AIM: To compare the shaping ability of ProFile and K3 rotary Ni-Ti instruments when used in a variable tip sequence in simulated curved root canals with different curvature and radius. METHODOLOGY: ProFile or K3.06 taper instruments were used to prepare simulated canals of 20 degrees curvature and 5 mm radius (n = 10) and 30 degrees curvature and 3 mm radius canals (n = 10) in resin blocks. All canals were prepared to an apical size 40 at 0.5 mm from the canal terminus using a variable tip crown-down sequence. Pre- and postinstrumentation digital images were recorded, and an assessment of the canal shape was determined using a computer image analysis program. The material removal from the inner and outer wall of the canal was measured at 28 measuring points, beginning 0.5 mm from the end-point of the canal and the data compared using the Mann-Whitney U-test. RESULTS: In 20 degrees and 30 degrees canals both instruments significantly removed more (P < 0.05) material on the outer wall than the inner wall in the apical half of the canal. For ProFile files there was no significant difference in the amount of material removed on the outer canal wall between the 20 degrees and 30 degrees canals. However, in the K3 groups significantly more (P < 0.05) outer canal wall was removed in the apical area in 20 degrees canals. When comparing both instruments the results showed that in 20 degrees canals K3 instruments removed more outer and inner canal wall than ProFile instruments (P < 0.05) but that there was no significant difference (P > 0.05) between the instruments in 30 degrees canals. CONCLUSION: Within the limitation of this study, both rotary nickel-titanium instruments prepared a well-shaped root canal with minimal canal transportation.

Clarity and diagnostic quality of digitized conventional intraoral radiographs.

OBJECTIVES: To compare digital images of conventional radiographs with the original radiographs for perceived clarity of endodontic files, periapical lesions and carious lesions, and to establish the diagnostic value of the digital images. METHODS: Four groups of ten radiographs were used: standardized bitewings demonstrating carious lesions, periapical radiographs of apical lesions, periapical radiographs showing endodontic files of various sizes at working length, and standardized periapical radiographs with size 08 files at working length. Radiographs were photographed using an Olympus C 2500-L digital camera and a Nikon D1X digital camera and were scanned using a Nikon Supercoolscan 4000 ED film/slide scanner. The digital images were then transferred to a Toshiba Satellite 2210 laptop. Three general dental practitioners compared each conventional radiograph with the three matching digital images. Images were ranked for clarity and were assessed for diagnostic quality. Data were analysed using General Estimating Equations. RESULTS: The clarity and diagnostic quality of the conventional radiographs were superior to the digital images produced by the three techniques (P < 0.001). No significant difference was found between the Nikon D1X and Camedia 2500-L cameras for clarity or diagnostic quality. The scanner was equivalent to the Camedia 2500-L camera for diagnostic quality, but was otherwise inferior to both cameras. CONCLUSIONS: Digitizing conventional radiographs using current high-grade digital cameras or scanners does not produce images of diagnostic quality. Improved resolution of viewing monitors is necessary to fully harness the potential of digital technology.

Comparison of MicroSeal and System B/Obtura II obturation techniques.

AIM: To compare the proportion of gutta-percha, sealer and voids following the filling of simulated root canals in plastic blocks using two warm gutta-percha techniques. METHODOLOGY: Ten simulated root canals in plastic blocks were prepared using System GT Rotary Files and a.02 taper size 40 Quantec rotary nickel-titanium instrument and then filled with MicroSeal and Kerr EWT sealer. A further 10 simulated canals were prepared solely with System GT Rotary Files and obturated with System B/Obtura II and Kerr EWT sealer. All blocks were sectioned at 1 mm intervals. The sectioned root fillings were photographed through a stereomicroscope and the resultant slides scanned. The images were analysed using adobe photoshop 6.0 to give the proportions of gutta-percha, sealer or void at each level. The data were analysed using unpaired Student's t-test and Mann-Whitney U-test. RESULTS: The MicroSeal technique produced a dense homogeneous gutta-percha fill at the apical 1 and 2 mm levels similar to the System B/Obtura II technique, but further coronally the sealer became mixed into the MicroFlow gutta-percha producing a heterogeneous mass with significantly less (P < 0.05) solid gutta-percha in the root filling compared to System B/Obtura II. The MicroSeal technique generally had more pooling of cement than the System B technique, however, this was only significantly different (P < 0.05) at the 4 mm level. The System B/Obtura II obturation gave an average of 99.27% +/- 1.09 gutta-percha fill at all levels. CONCLUSIONS: The MicroSeal technique produced a heterogeneous fill consisting of the MicroFlow Master Cone and gutta-percha from the MicroFlow Cartridge mixed with sealer. The System B/Obtura II technique produced a homogeneous fill at all levels.