Characterization of the mineral trioxide aggregate-resin modified glass ionomer cement interface in different setting conditions

INTRODUCTION

Mineral trioxide aggregate (MTA) has been used successfully for perforation repair, vital pulpotomies, and direct pulp capping. However, little is known about the interactions between MTA and glass ionomer cement (GIC) in final restorations. In this study, 2 null hypotheses were tested: (1) GIC placement time does not affect the MTA-GIC structural interface and hardness and (2) moisture does not affect the MTA-GIC structural interface and hardness.

METHODS

Fifty cylinders were half filled with MTA and divided into 5 groups. The other half was filled with resin-modified GIC either immediately after MTA placement or after 1 or 7 days of temporization in the presence or absence of a wet cotton pellet. The specimens were then sectioned, carbon coated, and examined using a scanning electron microscope and an electron probe microanalyzer (SEM-EPMA) for interfacial adaptation, gap formation, and elemental analysis. The Vickers hardness numbers of the interfacial MTA were recorded 24 hours after GIC placement and 8 days after MTA placement and analyzed using the analysis of variance test.

RESULTS

Hardness testing 24 hours after GIC placement revealed a significant increase in hardness with an increase of temporization time but not with a change of moisture conditions (P < .05). Hardness testing 8 days after MTA placement indicated no significant differences among groups. SEM-EPMA showed interfacial adaptation to improve with temporization time and moisture. Observed changes were limited to the outermost layer of MTA. The 2 null hypotheses were not rejected.

CONCLUSIONS

GIC can be applied over freshly mixed MTA with minimal effects on the MTA, which seemed to decrease with time.

In vitro evaluation of dentinal tubule penetration and biomineralization ability of a new root-end filling material

INTRODUCTION

Capasio is being developed as a new generation of endodontic material with potential use as a root-end filling material. The aim of this study was to compare the ability of Capasio and mineral trioxide aggregate (MTA) to penetrate human dentinal tubules and examine the interaction of Capasio and MTA with a synthetic tissue fluid (STF) and root canal walls in extracted human teeth.

METHODS

Root-end preparations were filled with Capasio or MTA, allowed to set for 4 weeks in STF, and then sectioned at 1, 2, and 3 mm from resected surface. Depth of penetration was evaluated by using scanning electron microscopy (SEM). Next, Capasio and MTA samples were prepared both in 1-g pellets and in root-end preparations. Samples were placed in STF, allowed to set, and then characterized by using SEM, energy dispersive x-ray analysis (EDXA), and x-ray diffraction (XRD) techniques.

RESULTS

Penetration of Capasio into dentinal tubules was observed at all levels. No penetration of MTA into dentinal tubules was observed at any level. Both Capasio and MTA formed apatite crystals in the supernatant, on their exposed surfaces, and in the interfacial layers that were similar in structure and elemental composition when evaluated by using SEM and EDXA. XRD analysis of these crystals corresponds with those reported for hydroxyapatite.

CONCLUSIONS

When used as a root-end filling material, Capasio is more likely to penetrate dentinal tubules. Both Capasio and MTA promote apatite deposition when exposed to STF.

Concrescence of permanent maxillary second and third molars: case report of non-surgical root canal treatment

Concrescence is a rare developmental anomaly with an overall incidence of 0.8% in the permanent dentition. While many case reports describe the treatment of concrescence with extraction, there are few reports of non-surgical root canal treatment (NSRCT), due to the atypical root form, canal morphology, and technical difficulties involved in concrescence. This unique case report describes a technical modification of NSRCT that can retain joined posterior maxillary teeth to maintain natural posterior occlusion without surgical intervention or dental implants, thereby avoiding the risk of damage to a large portion of the alveolar bone near the maxillary sinus.

Graduate and undergraduate geriatric dentistry education in a selected dental school in Japan

Geriatric dentistry and its instruction are critical in a rapidly ageing population. Japan is the world's fastest-ageing society, and thus, geriatric dentistry education in Japan can serve as a global model for other countries that will soon encounter the issues that Japan has already confronted. This study aimed at evaluating geriatric dental education with respect to the overall dental education system, undergraduate geriatric dentistry curricula, mandatory internships, and graduate geriatric education of a selected dental school in Japan. Bibliographical data and local information were collected. Descriptive and statistical analyses (Fisher and chi-squared test) were conducted. Japanese dental schools teach geriatric dentistry in 10 geriatric dentistry departments as well as in prosthodontic departments. There were no significant differences found between the number of public and private dental schools with geriatric dentistry departments (P = 0.615). At Showa University School of Dentistry, there are more didactic hours than practical training hours; however, there is no significant didactic/practical hour distribution difference between the overall dental curriculum and fourth-year dental students' geriatric dental education curriculum (P = 0.077). Graduate geriatric education is unique because it is a 4-year PhD course of study; there is neither a master's degree programme nor a certificate programme in geriatric dentistry. Overall, both undergraduate and graduate geriatric dentistry curricula are multidisciplinary. This study contributes to a better understanding of geriatric dental education in Japan; the implications of this study include developing a clinical/didactic curriculum, designing new national/international dental public health policies, and calibrating the competency of dentists in geriatric dentistry.

Cemento-osseous dysplasia in an elderly Asian male: a case report

Cemento-osseous dysplasia is a disorder typically found in middle-aged black women. However, the present report describes a case in a 61-year-old Vietnamese male. Without proper pulp testing and diagnosis, the radiographic presentation can easily be misdiagnosed as periapical periodontitis. On the basis of pulp vitality, lack of clinical symptoms and radiographic features, the diagnosis in this case was periapical cemento-osseous dysplasia at the mixed stage, which generally requires no treatment. At the 18-month follow-up, the patient was still asymptomatic and none of the clinical signs had changed. This case highlights the importance of careful clinical examination, including a pulp vitality test, and of having an unbiased view of age, gender, and ethnicity when diagnosing this condition.

Cytotoxicity evaluation of Gutta Flow and Endo Sequence BC sealers

OBJECTIVE

This study evaluated the cytotoxicity of GuttaFlow and EndoSequence BC sealers and compared them with AH Plus and Tubli-Seal sealers.

STUDY DESIGN

Samples (0.5 mg) of freshly mixed or set BC, GuttaFlow, AH Plus, and Tubli-Seal sealers were eluted with 300, 600, and 1,000 μL cell culture medium for 24 and 72 hours. L929 cells were seeded into 96-well plates at 3 × 10(4) cells/well and cultured with 100 μL eluate from each eluate group. Cells cultured only with culture medium served as control. After 24 hours' incubation, the cytotoxicity was evaluated by MTT assay. Cell viability was calculated as the percentage of the control group, and the results were analyzed with a one-way analysis of variance.

RESULTS

For the freshly mixed sealer, cell viability in the AH Plus group was less than in all of the other 3 sealer groups. The Tubli-Seal sealer group had less cell viability than the EndoSequence BC and GuttaFlow sealer groups. For the set sealer, the Tubli-Seal and AH Plus groups had less cell viability than the EndoSequence BC and GuttaFlow sealer groups. There was no cell viability difference between the EndoSequence BC and GuttaFlow sealer groups in the either freshly mixed or set sealer group.

CONCLUSIONS

The GuttaFlow and EndoSequence BC sealers have lower cytotoxicity than the AH Plus and Tubli-Seal sealers.

Effect of exercise training on the density of endothelial cells in the white adipose tissue of rats

We examined the effects of a 9-week exercise training (TR) in Wistar male rats, beginning at 4 weeks of age, on the density of endothelial cells (ECs) in epididymal white adipose tissue (WAT) and the mRNA expression of angiogenic factors in adipose tissue stromal vascular fraction (SVF) cells. The number of ECs and mRNA expressions were assessed by lectin staining and real-time reverse transcriptase-polymerase chain reaction, respectively. Compared with control (CR) rats, TR rats gained weight more slowly and had significantly lower final weight of WAT due to the reduction in the size and the number of adipocytes. TR significantly increased the number of ECs per square millimeter and per adipocyte (1.37- and 1.23-fold, respectively) in WAT. This is probably because the number of adipocytes is fewer while the number of ECs is constant in the WAT of TR rats, because the regression line of TR rats for adipocyte number-dependent EC number was shifted toward the left without significant differences in the slopes between groups. TR also induced the upregulation of mRNA expression of vascular endothelial growth factor (Vegf)-A and Vegf-receptor-2 in SVF cells, thereby retaining a constant number of ECs in the WAT.

Innovative endodontic therapy for anti-inflammatory direct pulp capping of permanent teeth with a mature apex

Direct pulp capping is treatment of an exposed vital pulp with a dental material to facilitate the formation of reparative dentin and maintenance of vital pulp. It has been studied as an alternate way to avoid vital pulp extirpation. However, the success rate of pulp capping is much lower than that of vital pulp extirpation. Therefore, direct pulp capping is currently considered controversial by many clinicians. To increase the success rate, a critical need exists to develop new biologically based therapeutics that reduce pulp inflammation, promote the continued formation of new dentin-pulp complex, and restore vitality by stimulating the regrowth of pulpal tissue. Bioengineered anti-inflammatory direct pulp-capping materials, together with adhesive materials for leakage prevention, have great potential to improve the condition of the existing pulp from an inflamed to a noninflamed status and lead to a high rate of long-term success.

Dentin permeability reduction by a sequential application of calcium and fluoride-phosphate solutions

OBJECTIVE

A sequential topical application of calcium and fluoride-phosphate solutions was reported to occlude open dentin tubules, mainly with fluoroapatite precipitates by a rapid ionic reaction, and to be effective at treating dentin hypersensitivity. However, its ability to reduce dentin permeability (Lp) is unknown. The aim of this in vitro study was to evaluate the effect of this treatment on Lp.

METHODS

Nine extracted human third molars were sectioned transversely to obtain 0.5 mm-thick discs, which were then etched and rinsed. Aqueous solutions of 5% (w/w) disodium phosphate containing 0.3% (w/w) sodium fluoride (A) and 10% (w/w) calcium chloride (B) were prepared. The sequential application of the A&B solutions was repeated three times on each disc, which was then rinsed with distilled water. The Lp of the discs was measured before and after the application using a modified Pashley's fluid flow measuring system. The differences in the Lp values between the conditions before and after the solution applications were analysed using a generalized estimating equation method and paired t-test. Scanning Electron Microscopy (SEM) was used to observe the dentin surfaces.

RESULTS

All nine discs consistently indicated reduced Lp following the application of the A&B solutions. There was a significant decrease in the mean Lp [microL/(cm(2) s cm H(2)O)] from baseline (-0.27+/-0.25, p=0.011). Overall, an average decrease of 34% Lp occurred after the application of the A&B solutions. SEM observation indicated that the reaction products covered the entire dentin disc surface.

CONCLUSION

The application of the A&B solutions was effective at reducing the Lp of the dentin discs.

PRECEDE-PROCEED model modification in community-based oral health promotion by using the linear structural relations programme

PURPOSE

The PRECEDE-PROCEED (P-P) model is a framework for designing health education/promotion programmes. While the P-P model has been used to design community-based oral health programmes, outcome assessments of the model are seldom reported. The aim of the present study was to explore whether pathways in the P-P model accurately reflect the current status of environmental/behavioural assessment in a Japanese community and to examine whether using the linear structural relations (LISREL) programme would improve the model.

MATERIALS AND METHODS

In a community health centre in Japan, a questionnaire with 29 items regarding oral health was distributed to 824 mothers with 3-year-old children. The items were compiled into eight variables that were tested using the LISREL programme. Goodness-of-fit index (GFI), adjusted goodness-of-fit index (AGFI) and root mean square error of approximation (RMSEA) were statistically analysed before and after P-P model modification.

RESULTS

The GFI, AGFI and RMSEA were 0.913, 0.776 and 0.161 before, and 0.975, 0.939 and 0.075 after P-P model modification, respectively. Indirect effects on the quality of life from the predisposing, reinforcing and enabling factors became stronger than those in the initial P-P model. The overall fit of the modified P-P model was significantly better than that of the P-P model without modification, which did not accurately reflect the status of environmental/behavioural assessment in the community.

CONCLUSIONS

The modified P-P model reflected the current status of environmental/behavioural assessment in the community. Health education models should be tested rigorously to ensure that they fit the reality of people's behaviour.

Chronologic comparison of root dentin moisture in extracted human teeth stored in formalin, sodium azide, and distilled water

This study quantified in vitro the root dentin moisture when 10% formalin (group A), 3% sodium azide (group B), and distilled water (group C) were used as teeth storage media. The root dentin moisture of 66 extracted human mandibular single-rooted teeth was measured at baseline (day 0) and at 1, 3, 7, and 14 days using a digital grain moisture meter. The baseline dentin moisture value was used as covariate in the generalized estimating equation (GEE) analysis. The mean dentin moisture values (%) +/- SD on days 0, 1, 3, 7, and 14 were, respectively: 10.6 +/- 0.64, 14.3 +/- 0.71, 14.6 +/- 0.84, 14.4 +/- 0.64, and 14.7 +/- 0.75 in group A; 11.4 +/- 0.94, 14.6 +/- 0.95, 14.6 +/- 0.76, 14.6 +/- 0.93, and 14.8 +/- 0.81 in group B; and 10.2 +/- 0.95, 12.8 +/- 0.90, 13.3 +/- 0.95, 13.0 +/- 0.91, and 13.2 +/- 0.89 in group C. The dentin moisture increased in all 3 groups; however, there was no overall significant difference in moisture between the formalin and sodium azide groups.

Polypeptide-catalyzed Biosilicification of Dentin Surfaces

In situ formation of mineral particles by biocatalysis would be advantageous for occluding dentin tubules to reduce permeability or for sealing of material-tooth interfaces. One approach would require that the peptide-catalyst remain functional on the dentin surface. Based on recent observations of retained activity on other surfaces, we hypothesized that poly(L-lysine) (PLL), an analog of the protein catalyst responsible for silica formation in primitive marine species, would remain functional on dentin. PLL was applied to dentin discs along with a pre-hydrolyzed silica precursor, tetramethyl orthosilicate (TMOS). Discs were analyzed microscopically (scanning electron microscopy, SEM) and chemically (x-ray photoelectron spectroscopy, XPS). The treated discs, but not the negative controls, exhibited partial distinct coating whose XPS survey was consistent with that of silica, demonstrating that the polypeptide was required and retained its mediating activity. Peptide-catalysts that mediate mineral formation can retain functionality on dentin, suggesting a wide range of preventive and treatment strategies.

Root dentin body moisture changes caused by ascorbic acid

OBJECTIVES

To quantify in vitro the root dentin moisture (DM) when soaked in 10% ascorbic acid solution (Group A) and distilled water (Group B) for up to 14 days.

METHODS

Forty-four extracted human mandibular single-rooted teeth were sectioned perpendicular to the long axis at the CEJ to access the root dentin. The samples were divided into Groups A and B. Baseline (day 0) DM was measured using a digital grain moisture meter. One sample was placed in each tube, which was then filled with solution. All tubes were kept at 37 degrees C and 100% humidity. DM was measured after 1, 3, 7, and 14 days. The baseline DM value was used as a covariate in the generalized estimating equation (GEE) analysis to account for the difference in the baseline DM between the two groups.

RESULTS

The mean DM (%) values+/-standard deviation on days 0, 1, 3, 7, and 14 were 11.4+/-1.08, 17.1+/-0.87, 18.2+/-0.76, 18.4+/-0.77, and 17.9+/-0.90 in Group A, and 10.2+/-0.95, 12.8+/-0.90, 13.3+/-0.95, 13.0+/-0.91, and 13.2+/-0.89 in Group B, respectively. Group A had significantly higher baseline DM than Group B (p=0.006). After adjusting for differences in the baseline, the GEE analysis indicated that, on average, Group A had a significantly higher increase in DM than Group B, with means+/-standard deviation of 4.35+/-0.26.

CONCLUSIONS

The moisture increase in the ascorbic acid group was greater than that in the distilled water group. Soaking root dentin in the unreplenished ascorbic acid solution or distilled water beyond 3 days did not further increase DM.

A rapid nondestructive method for root dentin moisture measurements: in vitro pilot study

Dentin moisture content is important in adhesive bonding and structural strength research; however, there is no rapid method available to assess dentin moisture without sample destruction. This study examined the use of a digital grain moisture meter to measure root dentin moisture in vitro. Extracted mandibular single-rooted teeth were sectioned at the CEJ. The moisture of the root dentin was measured at 6 measuring modes for different grains and repeated 5 times. Dentin weight changes before and after drying were measured to obtain control values. The control values were compared with machine readings. In conclusion, (1) each nondestructive measurement took less than 30 seconds, (2) 24 hours of storage at 37 degrees C and 100% humidity did not restore dentin moisture, and (3) 5 grain modes had a high validity and could be used for dentin moisture measurements.

Dental education in Peru

This paper provides information about Peru's dental history and dental school system, including the curriculum and dental licensure. With the increase in the number of dental schools in Peru, the number of dentists is also increasing. Until 1965, Peru had only three dental schools; currently, there are 14. Four of these dental schools are public, and ten are private. A five- or six-year dental program leads to the B.D.S. degree. After successful completion of a thesis defense or competency examination, the D.D.S. degree is awarded. The D.D.S. is mandatory for practicing dentistry in Peru. Currently, there are approximately 14,000 active dentists, with a dentist-patient ratio of approximately 1:2,000.

Dentin tubule numerical density variations below the CEJ

AIM

To evaluate dentin tubule numerical density variations below the CEJ.

METHODOLOGY

Three human non-carious permanent canines were sectioned parallel to the CEJ to obtain dentin disks 1mm thick whose surfaces were 1mm and 2mm below the CEJ. Each disk was sectioned into quarters resulting in four segment locations: facial, lingual, mesial, and distal. The outer (PDL side) and inner (pulp side) surfaces of the specimens were shaped to expose dentin with SiC papers and polished. Numerical tubule density was determined from SEM images. All data were statistically analyzed using a three-way ANOVA.

RESULTS

The dentin tubule density (number/mm(2)) ranged from 13,700 to 32,300. Dentin tubule density was relatively uniform at 1mm and 2mm below the CEJ and increased by a factor of about two from the outer to the inner surface, which was significantly different (P<0.0001).

CONCLUSIONS

The tubule density variations at the cervical root did not present marked.

Dental education in Malaysia

There was only one dental school in Malaysia until 1997 but five new schools have been established since 1998. This review provides information about dental education in Malaysia including; the history of dental education, the current dental school system and curriculum, and dental licensure. There are four public and two private dental schools in Malaysia. High school graduates are required to take the nationwide matriculation entrance examination or the Higher School Certificate (HSC) to apply for a dental degree programme. A five-year dental programme leads to the BDS or the DDS degree. National or state examinations are not required to practise dentistry. Currently, there are approximately 2,500 dentists, with a ratio of 1 dentist for every 10,000 people.

Comparative analysis of the particle size and shape of commercially available mineral trioxide aggregates and Portland cement: a study with a flow particle image analyzer

The aim of this study is to characterize the particle size distribution and circularity of various Mineral Trioxide Aggregates (MTA) (ProRoot MTA/ MTA Angelus/Gray and White) and Portland cements with effective size ranges of 1.5-160 microm using a flow particle analyzer (Sysmex FPIA-3000, Kobe, Japan). Cumulative percentage of particles between 6 and 10 microm were, 65, 73, 48, 53, and 70 %, for Gray ProRoot MTA, White ProRoot MTA, Gray MTA Angelus, White MTA Angelus, and Portland cement, respectively. ProRoot MTA contains fewer large particles than MTA Angelus. MTA Angelus contains a higher number of small particles than ProRoot MTA. White MTA contains smaller particles with a narrower range of size distribution than Gray MTA. MTA Angelus particles have relatively low circularity and wide size distribution and are less homogeneous than ProRoot MTA.

Dental education in Norway

Our review of dental education in Norway will address the following topics: the history of dental education, the dental school admission process, dental school curriculum, student evaluation, post-graduation and the number of dentists in Norway relative to dental education.

Education of dentists in Thailand

Thailand is geographically located in southeast Asia and its population is 63 million. Little has been published on dental education in Thailand. This paper provides information about Thailand regarding its dental history, dental school system including curriculum and dental licensure. There are eight public and one private dental school in Thailand. A six-year dental education leads to the DDS degree. On graduation from the public dental schools, dentists are required to work in the public system for three years. Currently, there are approximately 8000 active dentists, with a dentist: population ratio of approximately 1:7000.