Selecting drill size for post space preparation based on final endodontic radiographs: An in vitro study

BACKGROUND

For placement of intraradicular posts the intracanal filling material has to be removed. If drills are employed for this purpose, extra widening of the canal, incomplete cracks or root perforation are probable when inappropriate size of drill is used.

OBJECTIVE

This in vitro study assessed the efficacy of radiographs taken after completion of root canal therapy in selecting the appropriate-sized Peeso reamer for post space preparation.

METHODS

Canals of 53 extracted maxillary and mandibular teeth of different types were cleaned and shaped. Then with acrylic resin 3-dimensional model of the intracanal space of each tooth was fabricated. Next, all canals were filled with gutta-percha and teeth were radiographed buccolingually. Based on these radiographs two observers selected a Peeso reamer that best matched each canal's diameter. The diameter of the selected Peeso reamer was compared to the diameter of the corresponding resin model of each canal by two independent observers and the difference was measured. The data were analyzed by paired sample t-test using SPSS version 22.

RESULTS

The diameter of the selected Peeso reamers ranged from 0.21 mm smaller to 0.12 mm larger than the diameter of intracanal spaces. The difference between reamer and resin model was less than 0.1 mm in 75% of the cases.

CONCLUSION

The result of this study suggests that post-operation endodontic radiographs are reliable means for selecting a size of Peeso reamer that does not encroach on dentinal wall during removal of intracanal filling material and post space preparation.

Effect of Die Materials on Marginal and Internal Adaptation of Zirconia Copings: An In Vitro Study

Aim:

Close adaptation of cemented CAD/CAM restorations to their abutments is highly dependent on precise impressions and accurate replicas of teeth and adjacent oral tissues. This in-vitro study compared the effect of two die materials, as physical replicas of prepared teeth, on internal and marginal adaptations of zirconia copings to their corresponding abutments.

Materials and Methods:

A virtual model simulating a prepared premolar was designed and used for the milling of thirty identical metal models. Impression was taken of all models by Polyvinyl siloxane material. Fifteen impressions were poured in with Type IV stone and the other fifteen with polyurethane resin to make dies. All dies were scanned, and for each of them, zirconia coping was designed and milled. The copings were cemented to their corresponding metal models. Marginal gap between each coping and its metal model was measured at 20 points with a stereomicroscope (×60). Then the specimens were sectioned into two halves, and the internal gap was measured at seven points, including right and left cervico-axial, mid-axial, occluso-axial, and mid-occlusal. The data were analyzed with an independent T-test and repeated measure ANOVA at a 95% confidence level (p<0.05).

Results:

Mean value of marginal gap for Type IV stone and Exakto-Form groups were 54.31 ± 4.11 μm and 56.25 ± 4.24 μm, respectively. Mean values of the internal gaps for both groups ranged from 48 μm to 120 μm.

Conclusion:

Based on the results of this study, an internal and marginal adaptation of zirconia copings designed on digitized polyurethane and Type IV stone dies are clinically acceptable.

Effect of cement type and thickness on push-out bond strength of fiber posts

Background. This study investigated the effect of the thickness of two resin cements on push-out bond strength of fiber posts to root dentin.

Methods. Sixty decoronated single-rooted teeth were endodontically treated. The specimens were then randomly allocated to two groups (n=30); group 1: drill size 90 w, matching the size of fiber posts used; group 2: drill size 110, larger than the posts. The specimens in each group were divided into 2 subgroups (n=15); subgroup SE, in which the posts were cemented with self-etch Panavia F2.0 and subgroup SA, in which self-adhesive Panavia cement was used. After 72 hours, 2 slices with 1 mm of thickness were prepared from the mid-root of each specimen. Push-out bond strength test was performed in a universal testing machine at a crosshead speed of 1 mm/min. Data were analyzed with two-way ANOVA and t-test.

Results. The mean bond strengths of the posts cemented in matched-size spaces for SE and SA groups were 4.02±1.6 and 4.12±2.3 MPa, respectively. For posts cemented in oversized spaces, the values were 4.9±2.3 and 2.8±1.3 MPa, respectively. In matched-size spaces, there was no significant difference between the two groups.

Conclusion. The results of this study suggested that increasing the cement thickness would reduce the bond strength of fiber posts to root dentin when self-adhesive cements are used; however, self-etch adhesives were not affected.

Effect of Different Irrigants Applied After Post Space Preparation on Push-Out Bond Strength of a Self-Etch Resin Cement

OBJECTIVES

The aim was to investigate the effect of intracanal irrigants and agents on the bond strength of intraradicular fiber posts to dentin.

MATERIALS AND METHODS

Root canals of 72 decoronated single-rooted premolars were cleaned, shaped, and obturated with gutta-percha and AH26. The specimens were incubated at 37°C and 100% humidity for seven days. Next, the coronal 10 mm of the canals were prepared to receive size 2 D.T. Light fiber post, and the specimens were randomly allocated into six groups according to the irrigants used after post space preparation: normal saline (control group), 5.25% sodium hypochlorite (NaOCl)/15 seconds, 17% ethylenediaminetetraacetic acid (EDTA)/60 seconds, 2% chlorhexidine (CHX)/5 minutes, MTAD/5 minutes, and acid-etching/15 seconds. All canals were rinsed with normal saline and dried. Fiber posts were cemented using Panavia F2.0. After 24 hours, two mid-root slices of 1mm thickness were obtained from each specimen. Push-out bond strength test was performed in a universal testing machine at 0.5mm/minute. The maximum applied load was recorded, and the bond strength was calculated in megapascal (MPa). Data were analyzed by one-way analysis of variance (ANOVA) and Tukey's test.

RESULTS

The mean shear bond strengths of etched (53.21±12.11 MPa), MTAD (52.47±14.75 MPa) and EDTA (49.08±10.19 MPa) groups were significantly higher than that of the control group (39.82±10.04 MPa). The difference was marginally significant for CHX group (49.8±13.57 MPa) and not significant for NaOCl group (47.15±17.64 MPa).

CONCLUSIONS

Etching or irrigating the root canals with MTAD or EDTA after post space preparation increases the bond strength of Panavia F2.0 to dentin.

The Effect of BC Sealer, AH-Plus and Dorifill on Push-out Bond Strength of Fiber Post

Introduction:

Dentinal canal walls are in direct contact with endodontic sealers prior to post space preparation and luting cements after post space preparation. This direct contact may affect the bond strength of intraradicular posts to root dentin. This study aimed to assess the effect of three different sealers on the bond strength of fiber posts to root dentin.

Methods and Materials:

The canals of 56 extracted single-rooted human premolars after selection and decoronation were prepared. For obturation of the canals, specimens were randomly divided into four groups (n=14) according to the type of sealer used in conjunction with gutta-percha: group 1 (control) without any sealer; group 2 with AH-Plus sealer (resin based); group 3 with Dorifill sealer (ZOE-based); and group 4 with BC Sealer (calcium silicate-based). Nine mm-deep post space was prepared in the canal of each specimen. Intraradicular fiber posts were cemented using dual-cure resin cement (Panavia F2.0). Sections of 1 mm thickness were made at the coronal, middle and apical thirds of the post space of each specimen. The push-out bond strength of post to root dentin was measured in a universal testing machine. The data were analyzed using one-way ANOVA and post-hoc Tukey’s test.

Results:

The mean push-out bond strength in the coronal third was significantly lower in Dorifill group compared to AH-Plus (P=0.004). This value was significantly lower in BC Sealer group than AH-Plus (P=0.000) and control group (P=0.03). In middle and apical thirds, the mean push-out bond strength was not significantly different among the four groups (P=0.407, P=0.065, respectively). The mean push-out bond strength was significantly lower in apical than coronal third in AH-Plus group (P=0.001).

Conclusion:

Application of BC Sealer and Dorifill decreased the mean push-out bond strength of intracanal post to root dentin in the coronal third in comparison to AH-Plus.

Computer-Based Technologies in Dentistry: Types and Applications

During dental education, dental students learn how to examine patients, make diagnosis, plan treatment and perform dental procedures perfectly and efficiently. However, progresses in computer-based technologies including virtual reality (VR) simulators, augmented reality (AR) and computer aided design/computer aided manufacturing (CAD/CAM) systems have resulted in new modalities for instruction and practice of dentistry. Virtual reality dental simulators enable repeated, objective and assessable practice in various controlled situations. Superimposition of three-dimensional (3D) virtual images on actual images in AR allows surgeons to simultaneously visualize the surgical site and superimpose informative 3D images of invisible regions on the surgical site to serve as a guide. The use of CAD/CAM systems for designing and manufacturing of dental appliances and prostheses has been well established. This article reviews computer-based technologies, their application in dentistry and their potentials and limitations in promoting dental education, training and practice. Practitioners will be able to choose from a broader spectrum of options in their field of practice by becoming familiar with new modalities of training and practice.

Single Tooth Replacement Using InCeram Resin Bonded Fixed Partial Denture: A Clinical Report

This clinical report describes a treatment option for replacement of a missing mandibular anterior tooth using InCeram resin bonded fixed partial denture (RBFPD). The conventional approach for replacing mandibular incisors dictates the placement of either a conventional porcelain-fused-to-metal (PFM) bridge, Maryland bridge, or fiber-reinforced composite veneer bridge and several appearance-related disadvantages have been reported in the use of a prosthesis that incorporates a metal substructure. The InCeram bridge is a minimally invasive restoration and eliminates undesirable incisal graying frequently observed in metal RBFPDs. This method was successfully clinically applied to overcome shortcomings of other approaches that may require a minimal invasive technique to preserve lasting sound tooth structure.

Association between Serum 25 (OH) Vitamin D Concentrations and Inflammatory Bowel Diseases (IBDs) Activity

Inflammatory bowel diseases (IBDs) are immune mediated diseases affecting the gastrointestinal tract. Several environmental factors in concert with genetic susceptibilities can trigger IBDs. Recently, one of the important environmental factors contributing to the development of autoimmune diseases is vitamin D (VitD) deficiency. Furthermore, some new evidence points to VitD deficiency and its receptor dysfunction as an underlying factor for the emergence experimental IBDs. The aim of the current study was to evaluate the correlation between serum 25(OH)D concentrations and IBD activity in patients with ulcerative colitis or Crohn's disease. Sixty patients with confirmed diagnosis of IBD were recruited for a cross sectional study. Most of the identified confounders affecting serum VitD concentrations were excluded. Disease activity was assessed using validated questionnaires, including Truelove for Ulcerative Colitis and Crohn Disease Activity Index (CDAI) for Crohn disease. Serum 25(OH)D concentrations were determined by chemiluminescent assay. Serum 25(OH)D≤10 (ng/ml) was considered as VitD deficiency and 11≤25(OH)D<29(ng/ml) as VitD insufficiency. Mean serum 25(OH)D value was 13.1 ± 11.1(ng/ml) in IBD patients. Almost 95% of patients were vitamin D insufficient or deficient. Forty one percent of IBD patients had active disease. VitD deficiency was not associated with IBD activity (p=0.23). However, VitD deficiency was significantly associated with a history of IBD related intestinal surgery (p=0.001). In conclusion, this cross-sectional prospective study suggested that there is no association between vitamin D deficiency and disease activity in a relatively small number of IBD patients in a short period of time.

The effect of multiple firings on microtensile bond strength of core-veneer zirconia-based all-ceramic restorations

PURPOSE

Differences in core and veneer coefficients of thermal expansion, firing shrinkage, and speed of increasing and decreasing the temperature may generate stress in veneered all-ceramic restorations. Given the necessity of performing multiple firing cycles to achieve improved contour, color, and esthetics, the purpose of this study was to determine the effect of multiple firing cycles on the microtensile bond strength (MTBS) of zirconia core to the porcelain veneer in zirconia-based all-ceramic restorations.

MATERIALS AND METHODS

Thirty blocks (12 × 12 × 4 mm(3)) of semi-sintered zirconia were machined and sintered according to manufacturer's instruction. Specimens were placed in three groups based on the number of firing cycles (4, 6, 8) for the veneering process. After veneering, the specimens were sectioned into microbars with 8 mm length and 1 mm cross-section. Twenty sound microbars in each group were stressed to failure in a microtensile tester machine at 1 mm/min. Fractured specimens were surveyed under a scanning electron microscope and classified as cohesive in core, cohesive in veneer, and mixed. MTBS data were analyzed using one-way ANOVA and Tukey test (p < 0.05).

RESULTS

The mean MTBS (MPa) after 4, 6, and 8 firing cycles were 30.33 ± 2.13, 27.43 ± 1.79, and 25.06 ± 1.76, respectively. There was a statistically significant difference between the bond strengths of each of the three groups (p < 0.001).

CONCLUSION

Increase in firing cycles decreased MTBS. Most of the failures (90-95%) in all three groups were cohesive in the veneering porcelain and did not change as the number of firing cycles increased.

In vitro evaluation of the effect of core thickness and fabrication stages on the marginal accuracy of an all-ceramic system

OBJECTIVE

To evaluate the influence of core thickness and fabrication stages on the marginal accuracy of IPS e.max Press crowns.

MATERIALS AND METHODS

Twenty IPS e.max Press crowns, 1.5mm thick, were fabricated on metal dies. The crowns had two different core thicknesses, 0.8mm for group A and 1mm for group B, ten for each group. Marginal gap was measured after each stage of core fabrication, veneering and glaze firing. The specimens were not cemented and the measurements were made at four points on metal dies using a stereomicroscope (×120). Data were analyzed by SPSS software and independent t-test.

RESULTS

Mean marginal gaps measured after each stage for group A were 13.5 (±1.4) μm, 33.9 (±2.3) μm and 40.5(±1.7) μm, and for group B these figures were 14.9(±2.0) μm, 35.5(±2.2) μm and 41.3(±2.0) μm. There were no statistically significant differences in marginal gap values between the two groups (p>0.1). Significant increase in gap was observed after the veneering stage in both groups (p<0.05). After glazing, no significant increase in gap was detected.

CONCLUSION

IPS e.max Press crowns have an acceptable marginal fit. Increasing thickness of core does not increase marginal fitness.

The quality of reporting of randomised controlled trials in dental public health

OBJECTIVE

To assess the quality of the reporting of randomised controlled trials (RCTs) in dental public health journals.

METHOD

Electronic and hand searches were used to search for RCTs published in the following three journals over the period 1993 - 2008: Community Dental Health, Community Dentistry & Oral Epidemiology and the Journal of Public Health Dentistry. Exclusion criteria were applied. Each of the resulting papers was reviewed and scored, according to 56 criteria, based on the CONSORT statement.

RESULTS

The search identified 48 papers. The average number of criteria present per article was 27.0 (SD = 6.9), with variation between journals as follows: Community Dental Health (27.7); Community Dentistry & Oral Epidemiology (27.4); Journal of Public Health Dentistry (23.2). The average number of criteria present per article increased over the time period used.

CONCLUSION

There were inadequacies in the reporting of trials in dental public health journals. The quality of the reporting could be improved if the CONSORT statement was followed more closely.

Pycnogenol((R)) in the Management of Asthma

Asthma is characterized as a chronic inflammatory process. Pycnogenol((R)), a bioflavonoid mixture extracted from Pinus maritima, is known to scavenge free radicals while possessing antioxidant and antiinflammatory properties. The objective of this study was to evaluate the efficiency of this agent in a randomized, double-blinded, placebo-controlled, crossover study in patients with varying asthma severity. Twenty-six patients who fulfilled the American Thoracic Society criteria for asthma were enrolled in the study. Medical history, physical examination, blood sample analyses, and spirometric values were obtained at baseline, 4 weeks, and 8 weeks. The patients were randomly assigned to receive either 1 mg/lb/day (maximum 200 mg/day) Pycnogenol or placebo for the first period of 4 weeks and then crossed over to the alternate regimen for the next 4 weeks. No adverse effects were observed related to the study drug. Within the contingent of 22 patients who completed the study, almost all responded favorably to Pycnogenol in contrast to placebo. Pycnogenol treatment also significantly reduced serum leukotrienes compared with placebo. The results of this pilot study indicate that Pycnogenol may be a valuable nutraceutical in the management of chronic asthma. We recommend that further clinical trials be conducted in larger groups of asthmatics to establish its efficacy.

Acute glomerulonephritis with bacteriuria: a probable etiologic relationship

Twenty-one cases of acute glomerulonephritis in children with no previous history of renal disease were studied. Urinary infection with a rising titre of serum agglutinins against the organisms isolated from urine was found in 5 cases. No evidence of previous streptococcal infection was found in these cases. In the meantime all 8 cases with post-streptococcal glomerulonephritis remained without bacteriuria. In one case acute glomerulonephritis followed virus hepatitis, and in the remaining 7 cases the cause of glomerulonephritis was unknown. It is suggested that in predisposed patients the bacteria present in urinary infections might act as antigens starting immunologic reactions in the glomeruli, leading to glomerulonephritis. The final proof of this theory awaits immunofluorescence identification of these antigens in the glomeruli.