Resistance to fracture of endodontically treated premolars restored with new generation dentine bonding systems

Effect of citric acid versus ethylenediaminetetraacetic acid on radiographic root development in regenerative endodontic treatment: An animal study

INTRODUCTION

Regenerative endodontic treatment was introduced aiming to reinforce the root and enable further root development. In the process of dentin mineralization, bioactive molecules are entrapped in the dentin matrix, which can be later released by rinsing the dentin with chelating agents. This study aimed to compare the effects of citric acid and ethylenediaminetetraacetic acid (EDTA) on radiographic root development in regenerative endodontic treatment in an animal model.

METHODS

Premolars of three beagle dogs were used in this study. The teeth at one side of the jaw were irrigated with EDTA according to the regeneration protocol of the American Association of Endodontists (AAE). The teeth in the other quadrant were irrigated with citric acid in the second treatment session. Follow-up radiographs were obtained at six months, and the primary and final data were analyzed in SPSS using the Analysis of covariance (ANCOVA).

RESULTS

There was no significant difference between the two irrigating solutions regarding the increase in root length (P=0.668); however, EDTA showed significantly superior efficacy in increasing the root dentin thickness compared with citric acid (P=0.022).

CONCLUSIONS

Within the limitations of this study, the use of citric acid versus EDTA was not superior on radiographic root development in regenerative endodontic treatment.

Base Materials' Influence on Fracture Resistance of Molars with MOD Cavities

The aim of this study was to compare fracture resistance of teeth presenting medium-sized mesial-occlusal-distal (MOD) cavities using different base materials. Thirty-six extracted molars were immersed for 48 h in saline solution (0.1% thymol at 4 °C) and divided into six groups. In group A, the molars were untouched, and in group B, cavities were prepared, but not filled. In group C, we used zinc polycarboxylate cement, in group D—conventional glass ionomer cement, in group E—resin modified glass ionomer cement, and in group F—flow composite. Fracture resistance was tested using a universal loading machine (Lloyd Instruments) with a maximum force of 5 kN and a crosshead speed of 1.0 mm/min; we used NEXYGEN Data Analysis Software and ANOVA Method (p < 0.05). The smallest load that determined the sample failure was 2780 N for Group A, 865 N for Group B, 1210 N for Group C, 1340 N for Group D, 1630 N for Group E and 1742 N for Group F. The highest loads were 3050 N (A), 1040 N (B), 1430 N (C), 1500 N (D), 1790 N (E), and 3320 N (F), the mean values being 2902 ± 114 N (A), 972 ± 65 N (B), 1339 ± 84 N (C), 1415 ± 67 N (D), 1712 ± 62 N (E), and 2334 ± 662 N (F). A p = 0.000195 shows a statistically significant difference between groups C, D, E and F. For medium sized mesial-occlusal-distal (MOD) cavities, the best base material regarding fracture resistance was flow composite, followed by glass ionomer modified with resin, conventional glass ionomer cement and zinc polycarboxylate cement. It can be concluded that light-cured base materials are a better option for the analyzed use case, one of the possible reasons being their compatibility with the final restoration material, also light-cured.

Evaluation of fracture resistance of endodontically treated teeth restored with composite resin along with fibre insertion in different positions in vitro

This study was carried out to compare the different techniques of placement of polyethylene fibre (Ribbond) on reinforcement of endodontically treated teeth with MOD cavities in vitro. Forty extracted human premolars were randomly assigned to four groups (n = 10). Teeth in Groups I-IV received root canal treatment and a MOD cavity preparation, with gingival cavosurface margin 1.5 mm in coronal to cementoenamel junction. Group I served as no fibre group, Group II as occlusal fibre group, Group III as base fibre group and Group IV as dual-fibre group (occlusal and base both). Subsequent to restoring with composite resin and thermocycling, a vertical compressive force was applied at a cross-head speed of 0.5 mm min(-1) using universal testing machine until fracture. Data were analysed using one-way analysis of variance and Tukey's post hoc tests. Fracture resistance was significantly highest in dual-fibre group (P < 0.001) as compared with other groups. The highest favourable fracture rate was observed in the base fibre group (70%). This study concluded that the use of polyethylene fibre inserted over or under the restoration significantly increased the fracture strength of the root canal-treated teeth and maximum fracture resistance was observed when cavity was restored using dual-fibre technique.

Effect of novel restorative materials and retention slots on fracture resistance of endodontically-treated teeth

OBJECTIVES

The aim of this study was to evaluate the fracture resistance of endodontically-treated teeth restored with nano-hybrid composite resin, bulk-fill flowable and short fibre-reinforced-composite in the absence/presence of retention slots.

MATERIALS AND METHODS

One hundred and ten extracted non-carious human mandibular molars received endodontic treatment followed by mesio-occlusodistal (MOD) cavities with 3 ± 0.2 mm thicknesses of buccal and lingual walls. Teeth were divided into two main groups according to the retention slot preparation. The dove-tail retention slots were prepared on the middle of opposite buccal and lingual walls to create mechanical interlocking. Each group was further divided into four sub-groups according to restorative material types: control (no restoration), nano-hybrid composite resin (Filtek™ Z550), bulk-fill flowable (Filtek™ Bulk Fill) and short fibre-reinforced-composite (everX Posterior™). Restored teeth were subjected to compressive load at a strain rate of 1 mm/min. The data were statistically analysed using two-way ANOVA and Tukey's test for multiple comparisons.

RESULTS

The fracture resistance was significantly affected by the presence of the retentive slots and restorative material (p < 0.05). Restored teeth with retentive slots significantly increased the fracture resistance compared with restored teeth without retentive slots (p < 0.05). Short fibre-reinforced-composite with retentive slot cavities had significantly higher fracture resistance values compared with the other test groups (p < 0.05).

CONCLUSIONS

The preparation of retention slots may increase the fracture resistance of endodontically-treated teeth, especially, when restored with short fibre-reinforced composite. The use of short fibre-reinforced composite with retentive slots could be an alternative technique to prevent cuspal fracture on endodontically-treated teeth with MOD cavity.

Strain measurements and fracture resistance of endodontically treated premolars restored with all-ceramic restorations

OBJECTIVES

The aim of this study was to investigate the recovery of cuspal stiffness and fracture resistance in endodontically treated maxillary premolars restored with bonded ceramic inlays and onlays of various designs.

METHODS

Seventy intact premolars were selected for this study; six cavity designs were investigated: (i) mesio-occlusal-distal (MOD) inlay (I), (ii) MOD inlay with palatal cusp coverage (IPC), (iii) MOD onlay (O), (iv) MOD inlay with pulp chamber extension (IPE), (v) MOD inlay with palatal cusp coverage and pulp chamber extension (IPCPE), and (vi) MOD onlay with pulp chamber extension (OPE). Intact teeth acted as control. Strain gauges were attached to the buccal and palatal surfaces of the teeth to measure cuspal stiffness under static loading. All specimens were eventually subjected to compressive load to failure. Cuspal stiffness and fracture resistance data were analyzed using ANOVA and Tukey test.

RESULTS

The I and IPE restorations restored cuspal stiffness to 75% of the sound tooth value. The O and OPE restored teeth had stiffness values greater than that of a sound tooth. The I, IPC, O, IPE, IPCPE and OPE restored teeth demonstrated fracture strength values of 938N±113 N (s.d.), 1073N±176 N and 1317N±219 N, 893N±129 N, 1062N±153 N and 1347N±191 N respectively.

CONCLUSIONS

Within the limitations of this study, it was concluded that the all-ceramic onlay or inlay with palatal cusp coverage provided best biomechanical advantage in restoring an endodontically treated maxillary premolar tooth.

CLINICAL SIGNIFICANCE

The onlay approach which is more conservative compared to full coverage restoration is considered an appropriate approach to the restoration of endodontically treated maxillary premolars. The addition of a pulpal extension to the all-ceramic restorations, apart from being technically challenging, was not found to offer any biomechanical advantage to the restored teeth.

Fracture Strength and Fracture Patterns of Root-filled Teeth Restored With Direct Resin Composite Restorations Under Static and Fatigue Loading

Aim

To assess fracture strength and fracture patterns of root-filled teeth with direct resin composite restorations under static and fatigue loading.

Methodology

MOD cavities plus endodontic access were prepared in 48 premolars. Teeth were root filled and divided into three restorative groups, as follows 1) resin composite; 2) glass ionomer cement (GIC) core and resin composite; and 3) open laminate technique with GIC and resin composite. Teeth were loaded in a servohydraulic material test system. Eight samples in each group were subjected to stepped fatigue loading: a preconditioning load of 100 N (5000 cycles) followed by 30,000 cycles each at 200 N and higher loads in 50-N increments until fracture. Noncycled teeth were subjected to a ramped load. Fracture load, number of cycles, and fracture patterns were recorded. Data were analyzed using two-way analysis of variance and Bonferroni tests.

Results

Fatigue cycling reduced fracture strength significantly (p&lt;0.001). Teeth restored with a GIC core and a laminate technique were significantly weaker than the composite group (379±56 N, 352±67 N vs 490±78 N, p=0.001). Initial debonding occurred before the tooth underwent fracture. All failures were predominantly adhesive, with subcrestal fracture of the buccal cusp.

Conclusions

Resin composite restorations had significantly higher fracture strength than did other restorations. Fatigue cycled teeth failed at lower load than did noncycled teeth.

In vitro fracture resistance of mandibular incisors restored with modified partial-coverage ceramic restorations

BACKGROUND/AIM

The aim of this in vitro study was to investigate the impact fracture resistance of anterior teeth that had been fractured and restored with modified partial-coverage ceramics using the edge-up technique.

MATERIAL AND METHODS

A total of 178 extracted human mandibular central and lateral incisors were included in this study. The incisors were randomly divided into two groups. Group 1 (n = 89) teeth were cleaved and restored with modified partial-coverage ceramics using the edge-up technique; Group 2 (n = 89) consisted of intact teeth that served as control. Impact strength was tested in a modified impact testing machine (pendulum type), and the severity of crown fracture after fracture resistance test was registered.

RESULTS

Impact strength was insignificantly lower in restored teeth (median 5.39 and range 0.81-14.12 kJ m(-2) ) than in intact teeth (median 5.45 and range 0.31-16.47 kJ m(-2) ), although no statistically significant differences were observed. Regarding the severity of crown fracture, restored teeth showed a lower rate of severe fractures (20.22%) compared to intact teeth (25.84%), but no statistically significant differences were observed.

CONCLUSIONS

Restoration of cleaved mandibular incisors with modified partial-coverage ceramics using the edge-up technique shows fracture resistance and severity of crown fracture following traumatism similar to intact teeth. In this way, this technique can be used successfully for the treatment of fractured anterior teeth.

Comparative evaluation of the fracture resistance of teeth prepared with rotary system, filled with single cone gutta-percha and laterally condensed with zinc oxide eugenol and resin based (AH26) sealers to that of Resilon

AIM AND OBJECTIVE

To compare the fracture resistance of teeth prepared with rotary system and filled with single cone guttapercha followed by lateral condensation with different sealers like zinc oxide eugenol and resin based (AH26) to that of resilon.

MATERIALS AND METHODS

A total number of 70 extracted intact human permanent maxillary incisors were selected. All prepared samples were divided into one control group (n = 10) and three experimental groups (n = 20 per group). Group 1 control. This group received no obturation; the root canal opening was sealed with a temporary filling material (Cavit, Premier Dental Products, Plymouth Meeting, PA) Group 2: Gutta-Percha and zinc oxide Eugenol sealer. Group 3: Gutta-Percha and AH26 sealer. (DiaDent, Korea) dipped in AH26 sealer. Group 4: Resilon cones and RealSeal Resin Sealer. Obturation was accomplished using a 0.06 taper size 40 gutta-percha master point. All the root samples were stored in 100% humidity at 37 °C for 2 weeks to allow the sealer to set completely. The root samples were then prepared for mechanical testing and the data was recorded and analyzed statistically.

RESULTS

One-way ANOVA and Post hoc test (Duncan Multiple range test) were employed to determine possible statistical variation among the groups tested in this study. The force for group 2 was significantly greater than that for the control group 1 (no obturation).The force for group 3 was significantly greater than that for group 2. The force for group 4 was significantly greater than that for group 3. All other groupwise comparisons were not significant at 5% level. Group 4 seemed to have the greatest force among the three groups of interest in the study.

CONCLUSION

Root canals filled with Resilon increased the in vitro resistance of single canal extracted teeth compared to other experimental groups. The mean fracture resistance value for the experimental groups in ascending order was as follows: Root canals instrumented but not filled, filled with gutta-percha and zinc oxide eugenol sealer, filled with gutta-percha and AH26 sealer and filled with Resilon.

CLINICAL SIGNIFICANCE

Resilon is a promising material for reinforcement of endodontically treated teeth.

Comparing the reinforcing effects of a resin modified glassionomer cement, Flowable compomer, and Flowable composite in the restoration of calcium hydroxide-treated immature roots in vitro

One hundred and sixty human permanent central incisors were enlarged to a 120 file size after crown removal procedure to simulate immature teeth. The root canals were filled with calcium hydroxide and stored for 15 days (phase I), 30 days (phase II), 90 days (phase III), and 180 days (Phase IV). At the end of these selected time periods, calcium hydroxide was cleaned off the root canals of forty teeth that were randomly selected and obturated with gutta-percha points in the apical 2 mm of the root canals with a sealer. The specimens were further equally divided into four groups. Unrestored Group I served as control and the root canals of teeth in the other three group specimens were reinforced with resin modified glassionomer cement (RMGIC) (Group II), Flowable Compomer (Group III), and Flowable Composite (Group IV), respectively, using a translucent curing post. All specimens were subjected to compressive force using an Instron Testing machine, until fracture occurred. All the materials evaluated substantially reinforced the root specimens compared to the control. At the end of 180 days, Flowable composites showed maximum reinforcement compared to the other groups; however, no significant differences were found between the reinforcement capabilities of Flowable Compomer and RMGIC.

Assessment of laminate technique using glass ionomer and resin composite for restoration of root filled teeth

OBJECTIVE

To evaluate the open laminate technique using glass ionomer cements (GIC) in association with a low shrink composite for restoring root filled premolars.

METHODS

Extensive MOD cavities plus endodontic access and root filling were performed in intact extracted maxillary premolars. Three restoration types were evaluated: (1) resin composite alone; (2) resin-modified GIC (RM-GIC) open laminate plus resin composite; (3) conventional GIC open laminate plus resin composite (n=8 for all groups and tests). Three tests were conducted to assess restorations: (A) inward cusp deflection during light curing, using DCDTs; (B) fracture strength using a ramped oblique load at 45° to the long axis in a servohydraulic testing machine in comparison with intact and unrestored teeth; (C) proximal marginal leakage using methylene blue dye and the effect of thermocycling. Data were analysed using 1-way ANOVA for cuspal deflection and fracture strength and Fisher's exact test for leakage.

RESULTS

Laminate restorations resulted in significantly less cuspal deflection compared with resin composite (4.2±1.2 μm for RM-GIC and 5.1±2.3 μm for conventional GIC vs. 12.2±2.6 μm for composite, P<0.001). Fracture strength was not significantly different among all groups. Failure with all restorations was predominantly adhesive at the tooth-restoration interface. The two laminate groups showed significantly better marginal seal than composite alone, but sealing ability of conventional GIC deteriorated after thermocycling.

CONCLUSIONS

Laminate restoration of root filled teeth had beneficial effects in terms of reducing cuspal deflection and marginal seal, with acceptable fracture strength.

Effect of three different core materials on the fracture resistance of endodontically treated deciduous mandibular second molars: an in vitro study

Endodontic treatment makes the tooth brittle due to loss of bulk of tooth structure, decrease in the moisture content of dentin and dentin elasticity. The following study was carried out to evaluate the effect of endodontic treatment on the fracture resistance of the tooth and reinforcing ability of three different core materials. The following study comprised of sample size of 30 deciduous second molars divided into control group (6) and test group (24). Access opening was done in 24 and 18th teeth with access opening were restored with three different core materials namely IRM (6), silver amalgam (6), GIC (6). All the 30 were subjected to fracture test using UTM (Universal testing machine)- Instron 95. Result showed a drastic reduction in the fracture resistance of the tooth on access opening (1/3rd) and out of the three core materials glass ionomer was shown to be the best core material giving the highest fracture registrance followed by silver amalgam and IRM.

An innovative approach for management of vertical coronal fracture in molar: case report

Unlike anterior teeth, acute exogenous trauma is an infrequent cause of posterior coronal vertical tooth fractures. Endodontic and restorative management of such fractures is a great challenge for the clinician. Newer advancements in adhesive techniques can provide successful intracoronal splinting of such teeth to reinforce the remaining tooth structure. This paper describes the diagnosis and management of a case of complicated vertical coronal fracture in mandibular first molar induced by a traffic accident.

Comparison of fracture resistance of endodontically treated teeth using different coronal restorative materials: An in vitro study

AIM/OBJECTIVE

To evaluate the in vitro effect of bonded restorations on the fracture resistance of root canal-treated teeth.

MATERIALS AND METHODS

One hundred twenty extracted, maxillary, permanent premolars were collected. After preparing the access cavity, the teeth were biomechanically prepared and obturated. Samples were divided into six groups based on the type of restorative material used to restore them. Teeth were embedded in acrylic resin and their fracture strength was measured using a Universal Testing Machine. Data were evaluated statistically using one-way ANOVA-F and unpaired t-test.

RESULTS

Teeth restored with bonded amalgam and composite resin showed higher fracture resistance than those restored with conventional amalgam. Fracture strengths of bonded restorations and intact teeth were not statistically different. The results suggested that the group restored with conventional amalgam had the lowest fracture resistance. No statistically significant differences were found between the bonded amalgam and composite resin groups.

CONCLUSION

Conventional amalgam core showed the least fracture resistance whereas; composite resin and bonded amalgam core showed fracture resistance was similar to that of natural tooth.

Influence of cusp coverage on the fracture resistance of premolars with endodontic access cavities

AIM

To assess the influence of cusp reduction and coverage with composite resin on the fracture resistance of premolars with prepared access cavities.

METHODOLOGY

Endodontic access cavities were prepared in 60 premolar teeth that were divided into four test groups: R1, R2, R3 and NR (n=15). In all test groups, MOD cavities were prepared and extended towards one of the cusps. The remaining cusp-wall thickness was: 1-1.5 mm in R1, 1.5-2 mm in R2 and 2-3 mm in both R3 and NR groups. In addition, in group R1, R2 and R3 the same cusp was reduced in height to 3.5 mm. Cuspal coverage and MOD restorations were performed using composite resin. Ten intact premolars served as positive controls and another ten MOD-prepared unrestored premolars as negative controls. Teeth were submitted to cyclic fatigue of 1.2 million cycles. A compressive load was applied 30° to the long axis of the teeth until fracture. Fracture loads were recorded and the means and the Confidence Intervals were compared.

RESULTS

The mean fracture resistance of each of the cusp-reduced groups R1, R2 and R3 (603, 712 and 697 N, respectively) was significantly higher than the non-reduced cusp group (305 N) and was comparable to the intact-premolar group (653 N).

CONCLUSIONS

Cusp reduction and coverage with composite resin significantly increased the fracture resistance of premolar teeth with MOD and endodontic access cavities.

Effect of two types of composite fibers on fracture resistance of endodontically treated maxillary premolars: an in vitro study

AIM

The aim of the present study was to evaluate the effect of the use of composite fibers (glass fiber and polyethylene fiber) at the gingival third of mesio-occlusodistal (MOD) cavities on the fracture resistance of endodontically treated premolars.

MATERIALS AND METHODS

A total of 45 extracted premolars underwent endodontic treatment. MOD cavities, 2.5 ± 0.2 mm thick at the buccal and lingual heights of contour, were prepared, with the gingival cavosurface margin 1.5 mm coronal to the cementoenamel junction. Then the teeth were randomly divided into three groups. In group 1, the cavities were restored with Z250 composite resin without the use of any fibers. In groups 2 and 3, the teeth were restored in the same manner as that in group 1 after placement of glass fiber and polyethylene fiber at the gingival third of the cavities, respectively. Subsequent to thermocycling, fracture resistance of the specimens was measured in Newton (N).

STATISTICAL ANALYSIS

Data were analyzed with one-way ANOVA and a post hoc Tukey test at a significance level of p < 0.05.

RESULTS

There were significant differences in the means of fracture resistance values between the three groups (p = 0.001). Statistically significant differences were observed in the fracture resistance between group 2 and groups 1 and 3 (p < 0.05). However, the differences between groups 1 and 3 were not significant (p = 0.25).

CONCLUSION

The type of fiber influenced the fracture resistance of endodontically treated human premolars.

CLINICAL SIGNIFICANCE

Using glass and/or polyethylene fibers in the gingival third of composite restorations leads to different results in fracture resistance of endodontically treated maxillary premolars.

Influence of sodium hypochlorite and edta on the microtensile bond strength of a self-etching adhesive system

Chemical substances used during biomechanical preparation of root canals can alter the composition of dentin surface and affect the interaction with restorative materials.

Influence of endodontic irrigants on bond strength of a self-etching adhesive

The aim of this in vitro study was to evaluate the bond strength of a self-etching adhesive system to dentine irrigated with sodium hypochlorite (NaOCl), chlorhexidine solution (CX) and ethylene diamine tetra acetic acid (EDTA) by microtensile testing. Sixty human third molars were sectioned 3 mm below the occlusal level and then randomly divided into six groups: G1(control), without irrigant solution; G2, 1% NaOCl; G3, 1% NaOCl followed by the application of 17% EDTA; G4, 2% CX; G5, 2% CX followed by the application of 17% EDTA and G6, 17% EDTA. The specimens received the self-etching adhesive system were restored with composite resin, then sectioned and trimmed to obtain four hourglass-shaped slabs from each tooth. The specimens were submitted to the microtensile test in a Universal Testing Machine at a crosshead speed of 0.5 mm min(-1) until fracture. The results were submitted to statistical analysis by anova /Newman-Keuls. The means and standard deviations (MPa) were: G1, 26.88 (±3.81); G2, 19.08 (±3.89); G3, 18.16 (±2.21); G4, 18.14 (±4.32); G5, 34.30 (±3.32); G6, 13.61 (±1.21). It was concluded that the application of 2% CX followed by the application of 17% EDTA resulted in increasing the bond strength of the self-etching adhesive system to dentine, when compared with the results obtained for the other tested groups.

The effect of three composite fiber insertion techniques on fracture resistance of root-filled teeth

The aim of this study was to evaluate the effect of three methods of fiber insertion on fracture resistance of endodontically treated maxillary premolars in vitro. Sixty extracted human maxillary premolars received endodontic treatment followed by mesioocclusodistal (MOD) cavities with 2.5 +/- 0.2 mm thicknesses of buccal and lingual cusps at height of contour. The gingival cavosurface margin was 1.5 mm coronal to the cementoenamel junction (CEJ). Subsequently, the teeth were randomly divided into four groups. In the no-fiber group, the cavities were restored with composite, and in other groups, composite impregnated glass fibers were placed in the gingival, middle, and occlusal third surfaces of the cavities, respectively, and were restored similar to the no-fiber group. Subsequent to thermocycling and exertion of compressive forces, statistical analysis showed that the fracture resistance in the occlusal fiber group was significantly higher than that in other groups (p < 0.0005). In addition, the highest favorable fracture and the lowest cusp detachment rates were observed in the occlusal fiber group.

The effect of different restoration techniques on the fracture resistance of endodontically-treated molars

AIM

This study compared the fracture resistance of endodontically-treated mandibular molars with mesio-occluso-distal (MOD) cavities restored using different restoration techniques.

METHODOLOGY

Sixty sound extracted mandibular molars were randomly assigned to six groups (n=10). Group 1 did not receive any preparation. The teeth in Groups 2-6 received root canal treatment and a MOD cavity preparation. The teeth in Group 2 were kept unrestored. Group 3 was restored conventionally with amalgam. Group 4 was restored with a dentin bonding system (DBS, Clearfil SE Bond) and resin composite (CR) (Clearfil Photoposterior). Group 5 was restored with indirect hybrid ceramic inlay material (Estenia). In Group 6, polyethylene ribbon fiber (Ribbond) was inserted into cavities in a buccal-to-lingual direction and the teeth were then restored with DBS and CR. After finishing and polishing, the specimens, except for Group 2, were loaded to failure by a chewing simulation device (60,000 cycles x 50 N load, 1.3 Hz frequency) in an artificial environment at 37 degrees C. Each tooth was subjected to compressive loading perpendicular to the occlusal surface at a crosshead speed of 1 mm/minute. The mean loads necessary to fracture were recorded in Newtons and the results were statistically analyzed.

RESULTS

The mean fracture values were as follows: Group 1: 2485.3 +/- 193.98a, Group 2: 533.9 +/- 59.4a, Group 3: 1705.8 +/- 135.7a, Group 4: 2033.3 +/- 137.6cd, Group 5: 2121.3 +/- 156.5d, Group 6: 1908.9 +/- 132.2cd. There were statistically significant differences between the groups annotated with different letters. Thus, Group 1 (intact teeth) had the greatest fracture resistance and Group 2 (non-restored teeth) the poorest. No statistically significant differences were found between Groups 3 (amalgam), 4 (resin composite) and 6 (polyethylene ribbon fiber reinforced composite) (p > 0.05). Group 5 (indirect hybrid ceramic inlay) had greater fracture resistance than Group 3 (p < 0.05).

CONCLUSIONS

Within the limitations of this study, although all of the restoration groups were stronger than the prepared-only group, none of the restoration techniques tested was able to completely restore the fracture resistance lost from MOD cavity preparation. However, use of indirect hybrid inlay restorations in these teeth may be recommended, because this restoration technique indicated more favorable fracture failure modes than other restoration techniques used in this study and particularly greater fracture strength than amalgam restorations. The promising result of indirect hybrid inlay restorations may need to be confirmed by long-term clinical studies.

Influence of restorative technique on the biomechanical behavior of endodontically treated maxillary premolars. Part II: strain measurement and stress distribution

STATEMENT OF PROBLEM

Unresolved controversy exists concerning the preferred cavity design and restorative technique used to restore endodontically treated maxillary premolars to minimize strain and improve stress distribution under occlusal load.

PURPOSE

The purpose of this study was to analyze the influence of cavity design and restorative material on strain measurement and stress distribution in maxillary premolars under occlusal loading conditions, and correlate these influences with the failure modes analyzed in Part I.

MATERIAL AND METHODS

For the strain gauge test, 21 additional specimens were prepared as described in Part 1 of this study (n=3). Two strain gauges were fixed on the buccal (B) and palatal (P) cusps of each specimen with cyanoacrylate adhesive. The specimens were submitted to continuous axial compression loading at a speed of 0.5 mm/min, using a 6-mm sphere, to a maximum limit of 150 N in a universal testing machine. Total strain values were obtained by combining the B and P cusp strain values. These values were submitted to 2-way ANOVA and the Dunnet test (alpha=.05). For finite element analyses, 7 numerical 2-D models were generated: MODd, direct mesio-occlusal-distal preparation; MODi, indirect mesio-occlusal-distal preparation; AM, MODd restored with amalgam; CR, MODd restored with composite resin; LPR, MODi restored with laboratory-processed composite resin; and LGC, MODi restored with leucite-reinforced glass ceramic; each corresponding to 1 of the experimental groups tested in Part I of this study. The models were analyzed with finite element software, using the von Mises criteria for stress distribution analysis.

RESULTS

With the strain gauge test, MODd, MODi, and AM groups showed significantly higher strain values than the CR, LPR, and LGC. Finite element analyses revealed that tooth structure removal and the type of restorative material altered the stress distribution pattern. The MODd, MODi, AM, and LPR models showed higher stress concentration within the tooth structure.

CONCLUSIONS

The specimens with adhesive restorations were shown to behave in a manner similar to the biomechanical behavior of healthy teeth, while the behavior of those restored with amalgam restorations was more like that observed for teeth with nonrestored cavity preparations. These results directly correlate with the fracture mode results obtained in Part I of this study.

Effect of a new restoration technique on fracture resistance of endodontically treated teeth

The aim of the study was to investigate the effect of a new fiber-reinforced composite restoration technique on fracture resistance in endodontically treated premolars. Eighty sound extracted human mandibular premolars were assigned to four groups (n = 20). Group 1 did not receive any treatment. In groups 2, 3 and 4, the teeth received root canal treatment and a mesio-occluso-distal cavity preparation. Group 2 was kept unrestored. Group 3 was restored with a dentin bonding system and composite resin. In group 4, a piece of polyethylene ribbon fiber was inserted into the groove in a buccal to lingual direction during the restoration of teeth with dentin bonding system and composite resin. After finishing and polishing, the specimens were stored in 100% humidity at 37 degrees C for 24 h and placed at an angle of 45 degrees to the long axis of the tooth and subjected to compressive loading in a universal testing machine at a crosshead speed of 0.5 mm min(-1). The load necessary to fracture the samples was recorded in Newton (N) and submitted to Kruskal-Wallis anova and Mann-Whitney U-test. The fracture strength of the teeth reinforced with a combination of polyethylene fiber and composite resin were not significantly different than those that were restored with only composite resin (P > 0.05). However, most of the failure modes of the reinforced teeth were limited to the level of the enamel, while the other three groups showed fractures generally at the level of the dentin, cemento-enamel junction or more below (P < 0.05). Therefore, polyethylene ribbon fiber-reinforced composite resin restorations seemed a more reliable restorative technique than traditional composite restorations for extensive cavities.

Microleakage of self-etch primer/adhesives in endodontically treated teeth

BACKGROUND

The authors evaluated the coronal marginal leakage of endodontically treated teeth bonded with four self-etching adhesives and one total-etch adhesive system.

MATERIALS AND METHODS

The investigators prepared Class II cavities in 60 extracted human premolars. They performed conventional endodontic therapy using a resin-based sealer and gutta-percha points. They randomly assigned each tooth to a group receiving one of the following adhesives: Adper Prompt L-Pop (3M ESPE, Seefeld, Germany), Clearfil SE Bond (Kuraray, Osaka, Japan), FL Bond (Shofu, Kyoto, Japan), Single Bond (3M ESPE) or Xeno III (Dentsply De Trey, Konstanz, Germany). They restored all teeth with resin-based composite material (Z250, 3M ESPE). Specimens underwent thermocycling and dye penetration and were sectioned longitudinally. The authors photographed the sections under a stereomicroscope. They transferred the images to an IBM-compatible personal computer for quantitative assessment of dye penetration using image analysis software. They analyzed data by means of Kruskal-Wallis and Mann-Whitney U tests (P = .05) and evaluated two specimens from each group under scanning electron microscopy.

RESULTS

None of the tested self-etch adhesives completely eliminated microleakage. Dye leakage was restricted to the coronal cavity walls; it did not migrate toward the pulp chamber or toward the root canal. Single Bond and Clearfil SE Bond showed significantly lower dye penetration values at occlusal and gingival margins.

CONCLUSIONS

The coronal sealing performance of the tested self-etch adhesive systems in endodontically treated teeth was material-dependent. The use of Clearfil SE Bond in such teeth can help achieve a marginal seal comparable to that achieved with Single Bond.

Fracture resistance of the buccal cusps of root filled maxillary premolar teeth restored with various techniques

AIM

To compare the cusp fracture resistance of teeth restored with composite resins and two post systems.

METHODOLOGY

Eighty extracted single-rooted human maxillary premolars were randomly assigned to eight groups (n = 10). Group 1 (control) did not receive any preparation. From groups 2 to 8, the teeth were root filled and mesio-occluso-distal (MOD) cavities were prepared. Group 2 remained unrestored. Group 3 was restored with packable resin composite using a single-step adhesive. Group 4 was restored with packable resin composite using a single-step adhesive and a thin layer of flowable resin composite. Group 5 was restored with packable resin composite using a total-etch two-step adhesive. Group 6 was restored with ormocer resin composite using a total-etch two-step adhesive. Group 7 was restored with an endodontic glass fibre post and hybrid resin composite using a total-etch two-step adhesive. Group 8 was restored with an endodontic zirconium post and hybrid resin composite using a total-etch two-step adhesive. The teeth were then mounted in a universal testing machine, the buccal cusp loaded (30 degrees ) until fracture, and the data analysed statistically.

RESULTS

Group 1 had the greatest fracture resistance, and group 2 the poorest. Groups 5-8 had significantly greater (P < 0.05) fracture resistance than groups 3 and 4. No significant differences were found between groups 3 and 4, or amongst groups 5-8 (P > 0.05).

CONCLUSIONS

For root filled maxillary premolars with MOD cavities, adhesive resin composite restorations, with and without glass and zirconium posts, increased the fracture resistance of the buccal cuSPS. A total-etch two-step adhesive increased significantly fracture resistance more than a one-step adhesive. For the one-step adhesive, an additional layer of flowable resin composite did not enhance fracture resistance.

Reattachment of a fractured permanent molar cusp: a 12-month follow-up

A posterior crown fracture due to acute trauma is an uncommon type of dental injury. This case report presents combined endodontic-bioadhesive treatment of a complicated crown fracture of a permanent molar due to a horse riding accident. Endodontic therapy was initiated following surgical removal of the fractured mesiolingual cusp, which was stored frozen until bonding procedures could be carried out. Subgingival and proximal contours of the missing cusp were maintained by an interim glass-ionomer restoration during endodontic therapy. Following root-canal obturation, the fractured cusp was reattached using a total-etch adhesive and composite resin system. The patient was recalled at 1, 3, 6 and 12 months, demonstrating excellent clinical and radiographic findings.

Resistance to fracture of roots filled with three different techniques

AIM

To compare the fracture resistance of roots filled with different materials.

METHODOLOGY

Thirty-four freshly extracted human maxillary central incisor teeth with similar dimension were selected. Crowns were sectioned at the cemento-enamel junction, and the length of the roots were adjusted to 13 mm. Following the preparation of the root canals and final irrigation with EDTA and saline, the 10 root canals in group 1 were filled with Resilon cones and Epiphany sealer, the 10 root canals in group 2 were filled with gutta-percha and AH 26 and the 10 root canals in group 3 were filled with gutta-percha and MCS Canal Sealer. All materials were used with a cold lateral condensation technique. Four root canals remained unfilled and were used as a control group. Tests for fracture strength were performed using a universal testing machine and a round tip that had a diameter of 4 mm. The force was applied vertically with a constant speed of 1 mm min(-1). For each root, the force at the time of fracture was recorded in Newtons. Results were evaluated statistically with ANOVA and Tukey Honestly Significant Difference (HSD) tests.

RESULTS

The mean force of fracture values was 1043 N, 967 N, 859 N and 517.5 N for groups 3, 1 and 2 and the control group, respectively. There was a significant difference (P < 0.01) between the experimental groups and the control group. No significant differences were found between the three experimental groups.

CONCLUSIONS

All the materials used in the present study reinforced the prepared root canals.

The effect of fiber insertion on fracture resistance of endodontically treated molars with MOD cavity and reattached fractured lingual cusps

In this study, the effect of flowable composite reinforced with a leno wave ultra high modulus (LWUHM) polyethylene fiber (Ribbond) on fracture resistance of endodontically treated molars with MOD cavity and lingual cuspal fracture was evaluated. Sixty sound extracted human mandibular molars were randomly assigned to six groups (n = 10). Group 1 served as control. Teeth in groups 2-6 received root canal treatment and a MOD cavity preparation. Teeth in group 2 were kept unrestored. Lingual walls of specimens in groups 3-6 were fractured at the CEJ and reattached (C&B Super-Bond). Group 3 was kept unrestored, and group 4 was restored with a composite resin (CR) (AP-X). In group 5, a flowable resin (FR, Protect Liner F) and in group 6, a Ribbond in combination with FR were inserted inside the cavity before CR restoration. After finishing and polishing, the specimens were subjected to compressive loading perpendicular to the occlusal surface at a crosshead speed of 1 mm/min. The mean load necessary to fracture were recorded in Newton and the results were statistically analyzed. MOD cavity preparation reduced fracture resistance of endodontically treated teeth (p < 0.05). Fracture resistance of rebonded fractured specimens was found to be similar to that of the nonfractured samples (p > 0.05). Use of LWUHM polyethylene fiber Ribbond increased fracture strength of endodontically treated molar teeth with MOD cavity preparation and cuspal fracture (p < 0.05). As a result, it was concluded that the insertion of Ribbond inside the cavity has a positive effect on fracture strength of endodontically treated molar teeth with MOD cavity preparation and cuspal fracture.

Effect of bonded restorations on the fracture resistance of root filled teeth

AIM

To evaluate the fracture resistance of root filled maxillary premolars restored with different techniques.

METHODOLOGY

One hundred and twenty single-rooted maxillary premolar teeth were divided randomly into six groups of 20 teeth and subjected to the following procedures: group 1: intact teeth. Group 2: endodontic access cavities prepared. Group 3: MOD cavities were prepared, root canals were filled and no restoration was placed. Group 4: teeth were prepared as group 3 and restored conventionally with amalgam. Group 5: teeth were prepared as group 3 and restored with amalgam using a bonding material. Group 6: teeth were prepared as group 3 and restored with composite resin using the same bonding material. Teeth were embedded in acrylic resin and the loads for fracture strength were applied vertically with a constant speed of 1 mm min(-1). Data were evaluated statistically with anova and Tukey's tests.

RESULTS

The mean force of fracture values were 1191.41, 599.86, 233.03, 494.72, 962.81 and 856.48 N for groups 1, 2, 3, 4, 5 and 6, respectively. The fracture resistance of group 5 was similar to group 1 (P > 0.05). The mean force at fracture of group 5 and group 6 was not significantly different. The fracture resistance of groups 5 and 6 was significantly higher than group 4 (P < 0.001).

CONCLUSIONS

The group, restored with conventional amalgam, had the weakest resistance to fracture when compared with the bonded restorations. No statistically significant differences were found between the bonded amalgam and composite resin groups.

Reinforcement effect of polyethylene fibre in root-filled teeth: comparison of two restoration techniques

AIM

To compare in vitro two different fibre placement techniques on reinforcement of root-filled molar teeth with mesio-occluso-distal (MOD) cavities.

METHODOLOGY

Fifty sound extracted human mandibular molars were used (n = 10). Group 1 served as control. From group 2-5, endodontic access and standard MOD cavities were prepared. Following root canal treatment, group 2 was kept unrestored. In groups 3 and 4, the teeth were restored with composite resin (AP-X; Kuraray, Japan). A groove was prepared on occlusal surface of the finished restorations in group 4 from buccal to lingual direction. Polyethylene woven fibre (Ribbond; Seattle, WA, USA) was inserted in the groove in combination with flowable resin that was cured for 20 s and covered with composite resin. Cavity surfaces were covered with flowable resin in group 5, and polyethylene fibre was placed into the bed of resin in a buccal to lingual direction before the composite restoration was placed. All specimens were stored in 100% humidity at 37 degrees C for 24 h. Compressive loading of the teeth was performed by a universal testing machine at a crosshead speed of 0.5 mm min(-1) until failure. The data were recorded in Newton and submitted to anova and Tukey post hoc test.

RESULTS

The mean load necessary to fracture the samples in each group was: G1: 1671.57 +/- 131.54(a); G2: 375.21 +/- 34.30(b); G3: 749.47 +/- 124.54(c); G4: 1224.36 +/- 132.17(d); G5: 926.88 +/- 118.28(e). Different superscript letters demonstrate significant difference between groups.

CONCLUSIONS

Polyethylene fibre use over or under MOD composite restorations significantly increased fracture strength. However, when the fibre was placed on the occlusal surface of the restoration in buccal to lingual direction, significantly higher fracture resistance was observed.

Effects of sodium ascorbate on microtensile bond strength of total-etching adhesive system to NaOCl treated dentine

OBJECTIVE

The purpose of this study was to determine the microtensile bond strengths of total etching adhesive systems to pulpal chamber wall dentine after treated with various irrigants.

METHODS

Thirty extracted human third molars were cut horizontally to expose the pulp horn. The roof of the pulp chamber and pulp tissues were removed. The teeth were then divided into five groups of five specimens each to treat with various irrigants. Specimens in each group were treated as follows: group 1, with water for 10 min; group 2, with sodium hypochlorite for 10 min; group 3, with sodium hypochlorite for 10 min and water for 10 min; group 4, with sodium hypochlorite for 10 min and sodium ascorbate for 10 min; group 5, with sodium hypochlorite for 10 min, sodium ascorbate for 10 min and water 10 min. Treated specimens were dried, bonded with a total-etching adhesive system (single bond) and restored with a resin composite (Z250) then kept for 24 h before determination of the microtensile bond strengths.

RESULTS

Group 2 (20.96+/-9.23 MPa) demonstrated significantly lower bond strengths than group 1 (30.06+/-10.44 MPa). No significant differences in bond strengths were found between group 3 (23.08+/-6.94) and group 2. Group 4 (40.55+/-8.99) demonstrated higher bond strengths than group 2. However, there were no significant differences between group 5 (24.55+/-9.73 MPa) and group 2.

CONCLUSIONS

Sodium hypochlorite significantly reduced the bond strengths of the adhesive when a total-etching was applied. The application of sodium ascorbate on sodium hypochlorite treated dentine significantly improved the bond strengths.

The effect of fibre insertion on fracture resistance of root filled molar teeth with MOD preparations restored with composite

AIM

To evaluate the effect of using flowable composite with or without leno woven ultra high modulus polyethylene fibre reinforcement on fracture resistance of root filled mandibular molars with mesio-occlusodistal (MOD) preparations.

METHODOLOGY

Sixty sound extracted human mandibular molars were randomly assigned to five groups (n = 12). Group 1 did not receive any preparation. From groups 2 to 5, the teeth were root filled and MOD preparations were created. Group 2 remained unrestored. Group 3 was restored with a dentine bonding system (DBS; SE Bond, Kuraray, Japan) and composite resin (CR) (AP-X; Kuraray). In group 4, flowable composite resin (Protect Liner F; Kuraray) was used before restoring teeth with CR. In group 5, leno woven ultra high modulus polyethylene ribbon fibre (Ribbond, Seattle, WA, USA) was inserted into the cavities in a buccal to lingual direction and the teeth were then restored with DBS and CR. After finishing and polishing, the specimens were stored in 100% humidity at 37 degrees C for 1 day. Compressive loading of the teeth was performed using a universal testing machine at a crosshead speed of 0.5 mm min(-1). The mean load necessary to fracture the samples were recorded in newtons (N) and were subjected to analysis of variance (ANOVA) and Tukey post-hoc test.

RESULTS

The mean load necessary to fracture the samples in each group were (in N): group 1: 1676.75 +/-154.63(a), group 2: 376.51 +/- 37.36(b), group 3: 733.23 +/- 133.33(c), group 4: 786.48 +/- 145.34(c), group 5: 943.63 +/- 121.15(d). There were statistically significant differences between the groups annotated with different letters.

CONCLUSIONS

(i) Use of flowable composite resin under composite restorations had no effect on fracture resistance of root filled molar teeth with MOD preparations, (ii) use of polyethylene ribbon fibre under composite restorations in root filled teeth with MOD preparations significantly increased fracture strength.

Apexification: a review

This paper reviews the rationale and techniques for treatment of the non-vital immature tooth. The importance of careful case assessment and accurate pulpal diagnosis in the treatment of immature teeth with pulpal injury cannot be overemphasized. The treatment of choice for necrotic teeth is apexification, which is induction of apical closure to produce more favorable conditions for conventional root canal filling. The most commonly advocated medicament is calcium hydroxide, although recently considerable interest has been expressed in the use of mineral trioxide aggregate. Introduction of techniques for one-visit apexification provide an alternative treatment option in these cases. Success rates for calcium hydroxide apexification are high although risks such as reinfection and tooth fracture exist. Prospective clinical trials comparing this and one-visit apexification techniques are required.

In vitro fracture resistance of root-filled teeth using new-generation dentine bonding adhesives

AIM

To compare the fracture resistance of root-filled premolar teeth restored with new-generation dentine bonding adhesives.

METHODOLOGY

Sixty extracted single-rooted human maxillary premolar teeth were used. Access cavities were prepared, and the roots were instrumented with K-files to an apical size 50 using a step-back technique. Root fillings were accomplished using gutta percha (Sure-Endo, Seoul, Korea) and AH Plus root canal sealer (Dentsply DeTrey, Konstanz, Germany) using the lateral condensation technique. The teeth were then randomly divided into six groups of 10 teeth each. A mesiodistocclusal (MOD) cavity was prepared in the teeth to the level of the canal orifices so that the thickness of the buccal wall of the teeth measured 2 mm at the occlusal surface and 3 mm at the cemento-enamel junction. Preparations were restored using the following adhesive systems: Etch & Prime 3.0 (Degussa AG, Hanau, Germany), Clearfil SE Bond (Kuraray, Osaka, Japan), Prompt L-Pop (ESPE, Seefeld, Germany), Panavia F (Kuraray, Osaka, Japan), Optibond Plus (Kerr, Orange, CA, USA) and Admira Bond (Voco, Cuxhaven, Germany); all preparations except those of the Panavia F and Admira Bond groups were further restored with resin composites. The Panavia F group was restored with amalgam and the Admira Bond group with Ormocer (Voco, Cuxhaven, Germany). The teeth were mounted in a Universal Testing Machine (Hounsfield, Surrey, UK), and the buccal walls were subjected to a slowly increasing compressive force until fracture occurred. The force of fracture of the walls of each tooth was recorded and the results in the various groups were compared. Statistical analysis of the data was accomplished using one-way anova.

RESULTS

There was no significant difference in the fracture resistance of any of the test groups.

CONCLUSIONS

In this laboratory study, the type of dentine bonding agents had no influence in the fracture resistance of teeth.

Micro-tensile bond strengths of bonding agents to pulpal floor dentine

AIM

The purpose of this study was to characterize the dentine surface of the pulpal floor and to determine the micro-tensile bond strengths of two dentine adhesive systems used in conjunction with a resin composite core material to pulpal floor dentine.

METHODOLOGY

Thirty-six extracted human molars were cut horizontally with a slow-speed diamond saw to expose the pulp chamber and the pulp tissue was removed. Eight teeth were used to investigate characteristics of untreated and etched dentine surfaces of the pulpal floor using SEM. Twenty-eight teeth were randomly allocated to two groups, each of 14 teeth. In group 1, a 'one-bottle' system (Prime & Bond NT) was used as dentine bonding agent and in group 2, a self-etching-priming system (Clearfil SE Bond) was applied. Pulp chambers of both groups were then filled with resin composite core buildup (FluoroCore) and kept moist in tap water at 37 degrees C for 24 h. Samples were prepared for micro-tensile bond testing by sectioning each tooth vertically in the mid-pulpal floor region and shaped to an hour-glass form of 1 +/- 0.2 mm(2) area at the bonded interface. Micro-tensile bond strengths were determined using a universal testing machine at a crosshead speed of 1 mm min-1. Fractured surfaces were examined by SEM.

RESULTS

The intact pulpal floor showed numerous calcospherites with variable tubule density and few accessory canals. Etching the pulpal floor with 34% phosphoric acid gel resulted in an irregular surface with patent dentinal tubules and the dome-shaped calcospherites mostly lost. With self-etching primer, the superficial dentine surface was less demineralized and little peritubular dentine matrix was removed. Mean bond strength for the self-etching-priming (Clearfil SE Bond) specimens was significantly greater than for 'one-bottle' (Prime & Bond NT) specimens (P< 0.05, Student's t-test). The fracture mode of Clearfil SE Bond specimens was mostly partial cohesive failure within dentine, whilst Prime & Bond NT specimens mostly showed partial cohesive failure in bonding resin/composite.

CONCLUSIONS

Despite an irregular surface morphology and absence of a smear layer, bonding to pulpal floor dentine was weaker than previously reported for cut coronal dentine. The self-etching-priming system bonded more strongly than the 'one-bottle' system.

Fracture resistance of human incisors and premolars: morphological and patho-anatomical factors

305 extracted human front teeth and premolars were investigated for their dynamic resistance to fracture. Morphological factors, such as the anatomical class of tooth and root lengths, and patho-anatomical factors, such as infractions, occlusal and cervical abrasions, composite and amalgam restorations and damage resulting from previous traumatic impacts, were taken into consideration. A comparison of stability after a defined impact stress showed that maxillary canines and premolars had the highest resistance to fracture; this differs significantly from the resistance of maxillary and mandibular incisors. The root length correlates directly with fracture energy and therefore to stability. Composite restorations with an adhesive joint were found to increase the resistance of a tooth to fracture, but amalgam restorations had a weakening effect. Cervical wedge-shaped defects of the tooth cause considerable destabilization, but occlusal abrasion and infractions have only a moderate weakening influence. Previous traumatic stress reduces the resistance to fracture of a tooth by up to 85%. The fracture patterns generated were very similar to clinically observed tooth fractures, indicating the results to be clinically relevant.

Assessment of apical and coronal root canal seals using contemporary endodontic obturation and restorative materials and techniques

AIM

The purpose of this study was to evaluate the sealing ability of two contemporary endodontic obturation and restorative techniques and materials.

METHODOLOGY

Seventy-nine extracted human single-rooted teeth were distributed randomly in two experimental groups of 36 and 37 specimens (groups 1 and 2, respectively), one group of three positive controls and one of three negative controls. The teeth were radiographed preoperatively, accessed, and instrumented. After smear layer removal, the teeth in group 1 were obturated using the System B and Obtura and were restored coronally with Core Paste using Tenure as a bonding agent. The teeth in group 2 were obturated using the Microseal technique and were restored coronally with amalgam using Panavia 21 as a bonding agent. All teeth in groups 1 and 2 were coated with three layers of nail varnish on all of their surfaces apart from the apical 4.0 mm and the coronal area above the cemento-enamel junction. The positive control teeth were obturated, restored coronally and completely coated with varnish, whereas the negative control teeth were not obturated, restored coronally, nor coated with varnish. The teeth were radiographed postoperatively and retained in saline solution for 10 days. For the next 10 days they were submerged in India ink. Subsequently all teeth were demineralized, dehydrated and rendered transparent. Dye penetration was measured using a stereomicroscope.

RESULTS

All materials and techniques provided minimal to zero dye penetration, apart from one specimen in the Core Paste group that showed 4.0 mm of dye penetration. The Wilcoxon rank sum test and t-test showed no statistically significant differences and all materials and techniques tested presented with a high degree of acceptability.

CONCLUSIONS

It was concluded that these contemporary techniques and materials provide equally good results, but long-term studies are needed for outright inferences to be drawn relative to their clinical performance.

Strengthening immature teeth during and after apexification

The purpose of this study was to evaluate the strengthening effect of an internal resin bonding technique. One hundred central incisors were endodontically treated and divided equally into five groups. Group 1, without any cervical preparation and with access repaired with bonded resin, served as the positive control. Teeth in groups 2 to 5 were cervically prepared to simulate the thin dentinal wall of immature teeth, and obturation material was removed to 3 mm below the cementoenamel junction (CEJ). In group 2, the negative control, the access was restored with bonded composite to the level of the CEJ. In group 3, access was restored with composite resin 3 mm apical to the CEJ using a clear post system. Group 4 was treated similarly to group 3, but an opaque post replaced the clear post. Group 5 was treated like group 3, after which a metal post was cemented into the channel left after removal of the clear post. All teeth were subjected to compression testing and the force required to fracture the teeth cervically was recorded for each group and the Kruskal-Wallis analysis performed to detect intergroup differences. All of the bonded resin techniques significantly strengthened the teeth against fracture, compared with the negative control group (p < 0.05). None of the experimental groups (3-5) were significantly different from the positive control group.