The effect of different ferrule heights and crown-to-root ratios on fracture resistance of endodontically-treated mandibular premolars restored with fiber post or cast metal post system: an in vitro study.

BACKGROUND: This study aimed to investigate the effects of different ferrule heights and crown-to-root ratios on the fracture resistance of endodontically-treated premolars restored with fiber post or cast metal post system. METHODS: Eighty extracted human mandibular first premolars with single root canal were treated endodontically and cut from 2.0 mm above the buccal cemento-enamel junction, to create horizontal residual roots. The roots were randomly divided into two groups. The roots in group FP were restored with a fiber post-and-core system, while the roots in group MP were restored with a cast metal post-and-core system. Each group was divided into five subgroups with different ferrule heights (0: no ferrule; 1: 1.0 mm ferrule; 2: 2.0 mm ferrule; 3: 3.0 mm ferrule; 4: 4.0 mm ferrule). All specimens were subsequently restored with metal crowns and embedded in acrylic resin blocks. The crown-to-root ratios of the specimens were controlled at approximately 0.6, 0.8, 0.9, 1.1, and 1.3 of the five subgroups, respectively. Fracture strengths and fracture patterns of the specimens were tested and recorded by a universal mechanical machine. RESULTS: Mean fracture strengths (mean ± standard deviation (kN)) of FP/0 to FP/4 and MP/0 to MP/4 were: 0.54 ± 0.09, 1.03 ± 0.11, 1.06 ± 0.17, 0.85 ± 0.11; 0.57 ± 0.10, 0.55 ± 0.09, 0.88 ± 0.13, 1.08 ± 0.17, 1.05 ± 0.18 and 0.49 ± 0.09, respectively. Two-way ANOVA revealed significant effects of different ferrule heights and crown-to-root ratios on the fracture resistance (P < 0.001), but no difference in fracture resistance between two post-and-core systems (P = 0.973). The highest fracture strengths of the specimen were found with the ferrule length of 1.92 mm in group FP and 2.07 mm in group MP, the crown-to-root ratio of which in 0.90 and 0.92 respectively., there is a significant difference in fracture patterns among the groups(P < 0.05). CONCLUSIONS: When a certain height of ferrule is prepared and a cast metal or fiber post-and-core system is restored for the residual root, the clinical crown-to-root ratio of the tooth after restoration should be kept within 0.90 to 0.92, so as to improve the fracture resistance of endodontically-treated mandibular first premolars.

Effect of Er:YAG laser irrigation with different etching modes on the push-out bond strength of fiber posts to the root dentine.

The objective of this study was to evaluate the effect of Er:YAG laser irrigation on the push-out bond strength of fiber posts to the root dentine. Sixty extracted human mandibular first premolars were collected and decoronated. The residual roots received endodontic treatment. The treated roots were randomly divided into three groups according to different irrigation protocols: group LAI (Er:YAG laser-activated irrigation), group PUI (passive ultrasonic irrigation, positive control), and group CSI (conventional syringe irrigation, negative control) (n = 20). Each group was divided into two subgroups, either total-etching modes or self-etching modes (n = 10). After fiber post restoration, all roots were sectioned into seven 1.0-mm-thick slices. The slices received a push-out test by a universal test machine. The resin tag on the segments' bonding interfaces was observed by scanning electron microscope. There were significant differences in the effects of the irrigation method, bonding modes, and root regions on the push-out bond strength among the groups (p < 0.05). The specimens with Er:YAG laser-activated irrigation and self-etching mode showed significantly the highest bonding strength (p < 0.001). The lengths and densities of resin tags in group PUI or group LAI with self-etching modes were longer than those in group CSI with total-etching modes. The laser-activated irrigation with self-etching modes improved the bond strength of fiber post to root dentine compared to the passive ultrasonic irrigation or conventional syringe irrigation with total or self-etching modes.

An in vitro study evaluating the effect of ferrule design on the fracture resistance of endodontically treated mandibular premolars after simulated crown lengthening or forced eruption methods.

BACKGROUND: The purpose of this study was to evaluate the effect of ferrule design on the fracture resistance of endodontically treated mandibular first premolars after simulated crown lengthening and orthodontic forced eruption methods restored with a fiber post-and-core system. METHODS: Forty extracted and endodontically treated mandibular first premolars were decoronated to create lingual-to-buccal oblique residual root models, with a 2.0 mm height of the lingual dentine wall coronal to the cemento-enamel junction, and the height of buccal surface at the cemento-enamel junction. The roots were divided randomly into five equal groups. The control group had undergone incomplete ferrule preparation in the cervical root, with 0.0 mm buccal and 2.0 mm lingual ferrule lengths (Group F0). Simulated surgical crown lengthening method provided ferrule preparation of 1.0 mm (Group CL/F1) and 2.0 mm (Group CL/F2) on the buccal surface, with ferrule lengths of 3.0 mm and 4.0 mm on the lingual surface, respectively. Simulated orthodontic forced eruption method provided ferrule preparation of 1.0 mm (Group OE/F1) and 2.0 mm (Group OE/F2) on the buccal surface and ferrule lengths of 3.0 mm and 4.0 mm on the lingual surface, respectively. After restoration with a glass fiber post-and-core system and a cast Co-Cr alloy crown, each specimen was embedded in an acrylic resin block to a height on the root 2.0 mm from the apical surface of the crown margin and loaded to fracture at a 135° angle to its long axis in a universal testing machine. Data were analyzed statistically using two-way ANOVA with Tukey HSD tests and Fisher's test, with α = 0.05. RESULTS: Mean fracture loads (kN) for groups F0, CL/F1, CL/F2, OE/F1 and OE/F2 were as follows: 1.01 (S.D. = 0.26), 0.91 (0.29), 0.73 (0.19), 0.96 (0.25) and 0.76 (0.20), respectively. Two-way ANOVA revealed significant differences for the effect of ferrule lengths (P = 0.012) but no differences for the effect of cervical treatment methods (P = 0.699). The teeth with no buccal ferrule preparation in control group F0 had the highest fracture resistance. In contrast, the mean fracture loads for group CL/F2 with a 2.0-mm buccal and 4.0-mm lingual ferrule created by simulated crown lengthening method were lowest (P = 0.036). CONCLUSIONS: Increased apically complete ferrule preparation resulted in decreased fracture resistance of endodontically treated mandibular first premolars, regardless of whether surgical crown lengthening or orthodontic forced eruption methods been used.

The effect of combined use of resin infiltration with different bioactive calcium phosphate-based approaches on enamel white spot lesions: An in vitro study.

OBJECTIVES: This in vitro study aimed to evaluate the effect of resin infiltration combined with casein phosphopeptide-amorphous calcium phosphate with fluoride (CPP-ACPF) or bioactive glass (BAG) on the stability of enamel white spot lesions (WSLs) treatment. MATERIALS AND METHODS: Eighty-four enamel blocks were prepared from the buccal surfaces of sound human premolars. All enamel blocks were placed in a demineralisation solution for 3 days to establish the artificial enamel WSLs. Enamel blocks with WSLs were randomly divided into three groups (n = 28 each group): RI/B: one-off resin infiltration followed by twice daily BAG treatment; RI/C: one-off resin infiltration followed by twice daily CPP-ACPF treatment; RI: one-off resin infiltration treatment only (as control) and subjected to pH cycling for 7 days. Surface morphology, elemental analysis, crystal characteristics, surface roughness and microhardness of enamel surfaces were investigated by scanning electron microscopy and energy-dispersive spectrometry observation, X-ray diffraction (XRD), atomic force microscope and Vickers' hardness testing, respectively. RESULTS: Mean values of the surface roughness (mean±standard deviation (nm)) were 24.52±5.07, 27.39±5.87 and 34.36±4.55 for groups RI/B, RI/C and RI respectively (p = 0.003). The calcium to phosphate ratios were 1.32±0.16, 1.22±0.26 and 0.69±0.24 for groups RI/B, RI/C and RI respectively (p < 0.001). XRD revealed apatite formation in all three groups. The mean enamel surface microhardness (kg/mm2) of the groups were 353.93±28.49, 339.00±27.32 and 330.38±22.55 for groups RI/B, RI/C and RI respectively (p = 0.216). CONCLUSIONS: Resin infiltration combined with CPP-ACPF or BAG remineralisation appears to improve the surface properties of WSLs. CLINICAL SIGNIFICANCE: The combination of resin infiltration and CPP-ACPF/BAG remineralisation may be a potential treatment for the management of the WSLs.

Minimally invasive esthetic management of dental fluorosis: a case report.

Dental fluorosis is a dental condition caused by excessive intake of fluoride during enamel formation, which can lead to color abnormalities or defects on the tooth surface. The resultant abnormal appearance ranges in severity from mildly white and opaque to dark brown, which substantially affects patients' esthetic characteristics and self-confidence. Treatment methods include tooth whitening or restoration. This clinical report describes the use of a minimally invasive esthetic technique in a 22-year-old woman with moderate dental fluorosis. The treatment plan included enamel microabrasion, at-home bleaching for 2 weeks, and subsequent resin infiltration for each tooth under a rubber dam. After 2 years of follow-up, evaluation of the patient's esthetic appearance revealed that teeth affected by dental fluorosis could be successfully treated with a minimally invasive technique involving microabrasion, at-home bleaching, and resin infiltration.

Fracture resistance after simulated crown lengthening and forced tooth eruption of endodontically-treated teeth restored with a fiber post-and-core system.

PURPOSE: To evaluate the effect of ferrule preparation length on the fracture resistance after simulated surgical crown lengthening and after forced tooth eruption of endodontically-treated teeth restored with a carbon fiber-reinforced post-and-core system. METHODS: 40 extracted endodontically-treated mandibular first premolars were decoronated 1.0 mm coronal to the buccal cemento-enamel junction. The teeth were divided randomly into five equal groups. The control group had no ferrule preparation (Group A). Simulated crown lengthening provided ferrule preparations of 1.0 mm (Group B) and 2.0 mm (Group C). Simulated forced tooth eruption provided ferrule preparations of 1.0 mm (Group D) and 2.0 mm (Group E). After restoration with a carbon fiber post-and-core system, each root was embedded in an acrylic resin block from 2.0 mm apical to the margins of a cast Ni-Cr alloy crown, and loaded at 150 degrees from the long axis in a universal testing machine at a crosshead speed of 1.0 mm/minute until fracture. Data were analyzed using ANOVA with Tukey HSD tests, and Fisher's exact test, with alpha = 0.05. RESULTS: Mean failure loads (kN) for Groups A, B, C, D and E were: 1.13 (SD = 0.15), 1.27 (0.18), 1.02 (0.11), 1.63 (0.14) and 1.92 (0.19), respectively. Significant differences were shown for the effects of treatment method and ferrule length, with significant interaction between these two sources of variation (P < 0.0001). Increased apical ferrule preparation lengths resulted in significantly increased fracture resistance for simulated forced tooth eruption (P < 0.0001), but not for simulated crown lengthening (P > or = 0.24).

[Clinical evaluation of prosthesis-like applicators with radioactive seeds for treatment of eleven palatal glandular malignancies].

PRUPOSE: To evaluate the clinical efficacy of prosthesis-like applicators with radioactive seeds in treatment of palatal glandular malignancy. METHODS: Eleven patients with palatal glandular malignant tumors were treated with surgical resection and postoperative 125I radioactive seed brachytherapy. After resection of the palatal tumors, a prosthesis denture was fabricated for each patient. According to the design of treatment plan system, several 125I radioactive seeds were embedded in the tissue surface of the prosthesis at the same time. All the patients were followed-up for 6 to 24 months and the results were evaluated. SPSS 21.0 software package was used for statistical analysis. RESULTS: Eleven patients could wear prosthesis-like applicators all the time and neither tumor recurrence nor metastasis were found around the target area during the follow-up period. Furthermore, significant improvement was shown in terms of speech, mastication and facial appearance for all patients after prosthesis-like applicator restorations. CONCLUSIONS: For patients with palatal glandular malignant tumors, prosthesis-like applicators with 125I radioactive seed brachytherapy may be effective for preventing recurrence and metastasis of the malignancies and improving the patients'quality of life.

The influence of RGD addition on the gene transfer characteristics of disulfide-containing polyethyleneimine/DNA complexes.

Arginine-glycine-aspartic acid (RGD) ligand is often chemically attached to polycation vector to improve the transfection efficiency. However, the chemical reaction may reduce or even inactivate the biological activities of peptides. In order to retain the targeting ability and biological activities, the RGD peptide was noncovalently introduced into polycations as gene delivery systems. In this paper, the tripeptide sequence RGD was added to disulfide-containing polyethyleneimine (SS-PEI)/DNA binary complexes to evaluate the influence of RGD addition for the particle size, zeta potential, morphology, and transfection efficiency. GelRed was used as a molecular probe to show the effect of RGD addition on the cellular uptake of complexes. In vitro transfection experiments showed that SS-PEI exhibited comparable transfection efficiency, but lower cytotoxicity in comparison with 25kDa PEI. The transfection efficiency of complexes with RGD in HeLa cells was reduced statistically significantly with the increasing content of RGD peptide, but that in 293T cells was not altered significantly with the increasing content of RGD peptide. The reduced transfection efficiency of SS-PEI/DNA complexes with RGD in HeLa cells was attributed to the targeted binding interactions between the surplus RGD and the alpha(nu)beta(3) and alpha(nu)beta(5) integrins in HeLa cells, which would prevent the binding between RGD in complexes and integrin receptor on the surface of cells as well as nonspecific endocytosis of SS-PEI/DNA complexes mediated by proteoglycan in HeLa cells.

Effect of two fiber post types and two luting cement systems on regional post retention using the push-out test.

OBJECTIVE: To investigate regional root canal push-out bond strengths for two fiber-reinforced post types using two adhesive systems. METHODS: The crowns of 24 recently extracted sound maxillary central incisors were sectioned transversely 2 mm coronal to the labial cemento-enamel junction, and the roots treated endodontically. Following standardized post space preparations, fiber-reinforced posts (C-POST; AESTHETI-PLUS) were placed using two adhesive systems (acid-etch ONE-STEP PLUS/C&B CEMENT; self-adhesive RelyX Unicem), in four equal groups. Push-out bond strength tests were performed at four sites in each root. Results were analyzed using split-plot ANOVA, with a=0.05 for statistical significance. RESULTS: AESTHETI-PLUS quartz fiber-reinforced posts showed significantly higher push-out strengths than C-POST carbon fiber-reinforced posts (P<0.0001). The separate acid-etch adhesive system resulted in significantly higher bond strengths than the self-etch self-adhesive system (P<0.0001). Bond strengths decreased significantly from coronal to apical root canal regions (P<0.0001). SIGNIFICANCE: The quartz fiber-reinforced post placed using the separate acid-etch adhesive system provided significantly better post retention than the carbon fiber-reinforced post placed using the self-etch self-adhesive system.

Effect of a ferrule and increased clinical crown length on the in vitro fracture resistance of premolars restored using two dowel-and-core systems.

This study investigated the effect of a crown-lengthening ferrule on the fracture resistance of endodontically-treated teeth restored with two dowel-core systems. Thirty-two extracted mandibular first premolars were sectioned perpendicular to the long axis at a point 1.0 mm occlusal to the buccal cementoenamel junction. Following endodontic treatment, the teeth were randomly assigned to four groups: cast Ni-Cr alloy dowel-core with no ferrule (Group A1), cast Ni-Cr alloy dowel-core with 2.0 mm ferrule (Group A2), prefabricated carbon fiber-reinforced dowel-resin core with no ferrule (Group B1) and carbon fiber-reinforced dowel-resin core with 2.0 mm ferrule (Group B2). Each specimen was embedded in a self-cured acrylic resin block from 2.0 mm apical to the margins of a cast Ni-Cr alloy crown, then loaded at 150 degrees from the long axis in a universal testing machine at a crosshead speed of 1.0 mm/minute until fracture. The data were recorded and analyzed using ANOVA and Fisher's exact tests, with alpha = 0.05. Mean failure loads (kN) for the A1, A2, B1 and B2 Groups were: 1.46 (S.D. 0.45), 1.07 (0.21), 1.13 (0.30) and 1.02 (0.27). The teeth restored with cast Ni-Cr dowel-cores and 2.0 mm ferrules demonstrated significantly lower fracture strengths, p = 0.04. There were significant differences in the root fracture patterns between the two dowel systems, with the carbon fiber-reinforced dowel-resin core system, being the less severe p < 0.05. Crown lengthening with a 2.0 mm apical extended ferrule resulted in reduced fracture strengths for endodontically-treated teeth restored using two dowel-core systems and cast metal crowns. The carbon fiber-reinforced dowel-resin core system reduced the severity of the root fractures.

Comparison of in vitro dentinal tubule occluding efficacy of two different methods using a nano-scaled bioactive glass-containing desensitising agent.

OBJECTIVE: This study aimed to compare the in vitro dentinal tubule occluding efficacy of two different methods using a nano-scaled bioactive glass (BG)-containing desensitising agent. METHODS: Citric acid treated dentine discs were randomly divided into 7 groups (n=8). Group A1, A2 and A3: dentine discs coated with BG desensitising paste; Group B1, B2 and B3: dentine discs coated with BG desensitising paste and covered with matched transparent trays; and control group (GroupC): dentine discs treated with deionised water. Field Emission Scanning Electron Microscopy (FE-SEM) was used to capture topographical images of each dentine discs after they were immersed in artificial saliva for corresponding treatment time and dentinal tubules exposure rates were thus measured. Elemental compositions of dentine discs were identified using Energy-Dispersive X-ray Spectroscopy (EDX). RESULTS: FE-SEM revealed better tubule occluding effects in Group B. Dentinal tubules in Group B3 were totally occluded with continuous homogeneous minerals to a depth of 20.6-24.7µm. Dentinal tubule exposure rates in Group B1, Group B2 and Group B3 were lower than that in Group A1, Group A2 and Group A3. EDX indicated that occluding deposits observed in each group were calcium-deficient hydroxyapatite. CONCLUSIONS: The application of transparent trays in combination with nano-scaled BG-containing desensitising paste could increase the dentinal tubule occluding effectiveness of the latter one and shorten the treatment time. CLINICAL RELEVANCE: Transparent trays could be used in combination with BGs-containing desensitising paste as the containers of the latter one in order to increase the dentinal tubule occluding effectiveness. This could lead to the development of a new therapeutic technique for treating dentine hypersensitivity.

[In vitro study evaluating the effect of different subgingival root exposure methods and ferrule designs on fracture resistance of residual root].

OBJECTIVE: To evaluate the effect of different subgingival root exposure methods, namely, crown lengthening or forced eruption, and different ferrule lengths on fracture resistance of a residual root restored with a carbon fiber post-and-core system. METHODS: Fifty-six extracted endodontically-treated mandibular first premolars were sectioned 1.0 mm coronal to the buccal cementoenamel junction. All the models were divided randomly into seven groups that each consist of eight roots. Group A was given non-ferrule as control. Simulated crown lengthening was performed for the dentin ferrule design in the cervical tooth structure for Groups B, C, and D with a ferrule length of 1.0, 2.0, and 3.0 mm, respectively. Simulated forced eruption was performed with a ferrule length of 1.0, 2.0, and 3.0 mm in the cervical tooth structure for Groups E, F, and G, respectively. After restoration with prefabricated carbon fiber post-and-core system, each specimen was embedded in a self-cured acrylic resin block from 2.0 mm apical to the margins of a cast Ni-Cr alloy crown, then loaded at 150 degrees from the long axis in a universal testing machine at a crosshead speed of 1.0 mm min(-1) until fracture. Data of failure loads and fracture mode were recorded and analyzed. RESULTS: Mean failure loads for Groups A to G were (1.13 +/- 0.15), (1.27 +/- 0.18), (1.02 +/- 0.11), (1.05 +/- 0.12), (1.63 +/- 0.14), (1.92 +/- 0.19), and (1.93 +/- 0.15) kN, respectively. The effects of root exposure method and ferrule design differed significantly, and two factors exhibited significant interaction (F=33.396, P<0.0001). When the ferrule lengths were the same, fracture loads in the simulated forced eruption groups were significantly higher than those of the simulated crown lengthening groups (P<0.001). No statistical differences in fracture mode were observed among all groups (P=1.00). CONCLUSION: More than 1.0 mm ferrule placement on the apical crown margin by using forced eruption significantly increases fracture resistance.

Radioactive seed implantation combined with prosthesis denture in treatment of oral and maxillofacial malignancy.

We sought to evaluate the effect of (125)I radioactive seed implantation combined with prosthesis denture on the treatment of oral and maxillofacial malignancy. For this purpose, 10 patients with glandule palatine malignancy were selected and subjected to the treatment plan of radioactive seed implantation during CT examination. All patients were treated as follow. The tumor tissues were extracted first. After 2 weeks, radioactive seeds were implanted in the palatine tissue and the prosthesis denture was made and worn for the tissue defect. Several radioactive seeds were still embedded in the tissue surface of the prosthesis at the same time; 24-36 seeds (average: 28) were used for each patient. All patients were followed up for 3-16 months and the results were evaluated. We found no tumor recurrence or metastasis around the target area in all patients. Significant improvement was shown in terms of speech, mastication, and facial appearance in all cases. Therefore, we concluded that in patients with glandule palatine malignancy, tumorectomy followed by radioactive seed implantation and prosthesis denture are effective for preventing the recurrence and metastasis of malignancy and improving the quality of life.