Mineral trioxide aggregate as an alternative treatment for intruded permanent teeth with root resorption and incomplete apex formation

A case of extensive crown fracture associated with intrusion of the permanent maxillary central incisors in an 8-year-old boy is reported. The treatment of both injured teeth included attempts of apexification and arrest of root resorption with calcium hydroxide. After 8 months of the trauma, there was no calcified barrier formation in the apex. Mineral trioxide aggregate (MTA) was then used as a filling material. At 15-month follow up, the teeth were asymptomatic and correctly sealed, the external inflammatory root resorption had stopped, and the radiolucent image had disappeared, which meant the initial healing of the periapical lesion. MTA may be considered as an alternative option for the treatment of traumatized and immature permanent teeth.

Influence of root parallelism on the stability of extraction-site closures

Introduction: In premolar extraction cases, root parallelism is recommended to preserve the stability of space closures. The influence of the degree of root parallelism on relapse of tooth extraction spaces has been a controversial topic in the literature. The aim of this study was to compare the angle between the long axes of the canine and the second premolarin patients with and without stability of extraction-space closures. Methods: A sample of 56 patients, treated with 4 premolar extractions, was divided into 2 groups: group 1, consisting of 25 patients with reopening of extraction spaces; and group 2, consisting of 31 patients without reopening of extraction spaces. Panoramic radiographs of each patient were analyzed at the posttreatment and 1-year posttreatment stages. The data were statistically analyzed by using chi-square tests, t tests, analysis of variance (ANOVA), and Pearson correlation coefficients. Results: The results showed that the groups did not differ regarding the angle between the canine and the second premolar, and there was no correlation between angular changes and reopening of extraction spaces, showing that dental angular changes are not determining factors for relapse, and other factors should be investigated. Conclusions: The final angle and the posttreatment changes observed in the angle between the long axes of the canine and the second premolar showed no influence on the relapse of extraction spaces. (Am J Orthod Dentofacial Orthop 2011; 139: e505-e510)

Effects of accentuated and reversed curve of Spee on apical root resorption

Introduction: In this study, we evaluated the influence of intrusion mechanics with accentuated and reversed curve of Spee on root resorption of the maxillary and mandibular incisors. Methods: A sample of 60 patients with Class I and Class II Division 1 malocclusions having nonextraction treatment was divided into 2 groups with the following characteristics: group 1 comprised 30 deepbite patients, treated with accentuated and reversed curve of Spee intrusion mechanics, with an initial mean age of 12.8 +/- 1.23 years (range, 10.01-15.32 years), and group 2 comprised 30 patients with normal overbite treated without intrusion mechanics, with an initial mean age of 12.87 +/- 1.43 years ( range, 10.02-15.36 years). Pretreatment and posttreatment periapical radiographs were used to evaluate root resorption. The groups were compared by using the Mann-Whitney U test. Correlation between root resorption and tooth movement was investigated with the Spearman correlation coefficient. Results: The deepbite group treated with accentuated and reversed curve of Spee had statistically greater root resorption ( 1.87) than the normal overbite group ( 1.54), at P=.017. Changes in overbite and vertical displacements of the maxillary central incisor apices had significant correlations to root resorption ( r = 0.30, P =.019; r = 0.27, P =.037, respectively). Conclusions: Accentuating and reversing the curve of Spee in the archwires to correct deep overbite causes more root resorption than nonintrusive mechanics.

Effect of oxalate desensitizers and dentin moisture during total-etch bonding

Purpose: To evaluate the effect of oxalate during total-etch bonding, under different dentin moisture conditions, over time. The null hypothesis tested was that microtensile bond strength (mu TBS) was not affected by oxalate treatment and dentin moisture during two evaluation periods. Methods: Extracted human third molars had their mid-coronal dentin exposed flat and polished with 600-grit SiC paper. The surfaces were etched with 35% phosphoric acid for 15 seconds, washed and blot dried. After etching, a 3% potassium oxalate gel was applied for 120 seconds, except for the control group (no desensitizer). The surface was then washed and left moist (Wet bonding) or air-dried for 30 seconds (Dry bonding). The surfaces were bonded with: (I) two 2-step etch-and-rinse adhesives: Single Bond (SB); Prime & Bond NT (PBNT) and (2) one 3-step etch-and-rinse adhesive: Scotchbond Multi Purpose (SBMP). Composite buildups were constructed incrementally with Tetric Ceram resin composite. Each increment was cured for 40 seconds. After storage in water for 24 hours or 1 year at 37 C, the specimens were prepared for mu TBS testing with a cross-sectional area of approximately 1 mm(2). They were then tested in tension in an Instron machine at 0.5 mm/minute. Data were analyzed by ANOVA and Student-Newman-Keuls at alpha = 0.05. Results: Application of potassium oxalate had no significant effect on the bond strengths of SBMP and PBNT, regardless of the surface moisture condition (P > 0.05). Conversely, reduced bond strengths were observed after oxalate treatment for SB in both moisture conditions, that being significantly lower when using a dry-bonding procedure (P < 0.05). Lower bond strength was obtained for PBNT when a dry-bonding technique was used, regardless of the oxalate treatment (P < 0.05). After aging the specimens for 1 year, bond strengths decreased. Smaller reductions were observed for SBMP, regardless of moisture conditions. For the WB technique, smaller reductions after 1 year were observed without oxalate treatment for SB and after oxalate treatment for PBNT. (Am J Dent 2010;23:137-141).

Fracture resistance of endodontically treated teeth with different heights of crown ferrule restored with prefabricated carbon fiber post and composite resin core by intermittent loading

This study evaluated the fracture resistance of endodontically treated teeth restored with prefabricated carbon fiber posts and varying quantities of coronal dentin. Sixty freshly extracted upper canines were randomly divided into groups of 10 teeth each. The specimens were exposed to 250,000 cycles in a controlled chewing simulator. All intact specimens were subjected to a static load (N) in a universal testing machine at 45 degrees to the long axis. Data were analyzed by 1-way analysis of variance and Tukey test (alpha = .05). Significant differences (P < .001) were found among the mean fracture forces of the test groups (positive control, 0 mm, 1 mm, 2 mm, 3 mm, and negative control groups: 1022.82 N, 1008.22 N, 1292.52 N, 1289.19 N, 1255.38 N, and 1582.11, respectively). These results suggested that the amount of coronal dentin did not significantly increase the fracture resistance of endodontically treated teeth restored with prefabricated carbon fiber post and composite resin core. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2008;106:e52-e57)

The requirement of zinc and calcium ions for functional MMP activity in demineralized dentin matrices

The progressive degradation of resin-dentin bonds is due, in part, to the slow degradation of collagen fibrils in the hybrid layer by endogenous matrix metalloproteinases (MMPs) of the dentin matrix. In in vitro durability studies, the storage medium composition might be important because the optimum activity of MMPs requires both zinc and calcium. Objective. This study evaluated the effect of different storage media on changes in matrix stiffness, loss of dry weight or solubilization of collagen from demineralized dentin beams incubated in vitro for up to 60 days. Methods. Dentin beams (1 mm x 2 mm x 6 mm) were completely demineralized in 10% phosphoric acid. After baseline measurements of dry mass and elastic modulus (E) (3-point bending, 15% strain) the beams were divided into 5 groups (n = 11/group) and incubated at 37 degrees C in either media containing both zinc and calcium designated as complete medium (CM), calcium-free medium, zinc-free medium, a doubled-zinc medium or water. Beams were retested at 3, 7, 14, 30, and 60 days of incubation. The incubation media was hydrolyzed with HCl for the quantitation of hydroxyproline (HOP) as an index of solubilization of collagen by MMPs. Data were analyzed using repeated measures of ANOVA. Results. Both the storage medium and the storage time showed significant effects on E, mass loss and HOP release (p < 0.05). The incubation in CM resulted in relatively rapid and significant (p < 0.05) decreases in stiffness, and increasing amounts of mass loss. The HOP content of the experimental media also increased with incubation time but was significantly lower (p < 0.05) than in the control CM medium, the recommended storage medium. Conclusions. The storage solutions used to age resin-dentin bonds should be buffered solutions that contain both calcium and zinc. The common use of water as an aging medium may underestimate the hydrolytic activity of endogenous dentin MMPs. (c) 2010 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Substantivity of chlorhexidine to human dentin

Objectives. To better comprehend the role of CHX in the preservation of resin-dentin bonds, this study investigated the substantivity of CHX to human dentin. Material and methods. Dentin disks (n = 45) were obtained from the mid-coronal portion of human third molars. One-third of dentin disks were kept mineralized (MD), while the other two-thirds had one of the surfaces partially demineralized with 37% phosphoric acid for 15 s (PDD) or they were totally demineralized with 10% phosphoric acid (TDD). Disks of hydroxyapatite (HA) were also prepared. Specimens were treated with: (1) 10 mu L of distilled water (controls), (2) 10 mu L of 0.2% chlorhexidine diacetate (0.2% CHX) or (3) 10 mu L of 2% chlorhexidine diacetate (2% CHX). Then, they were incubated in 1 mL of PBS (pH 7.4, 37 degrees C). Substantivity was evaluated as a function of the CHX-applied dose after: 0.5 h, 1 h, 3 h, 6 h, 24 h, 168 h (1 week), 672 h (4 weeks) and 1344 h (8 weeks) of incubation. CHX concentration in eluates was spectrophotometrically analyzed at 260 nm. Results. Significant amounts of CHX remained retained in dentin substrates (MD, PPD or TDD), independent on the CHX-applied dose or time of incubation (p < 0.05). High amounts of retained CHX onto HA were observed only for specimens treated with the highest concentration of CHX (2%) (p < 0.05). Conclusion. The outstanding substantivity of CHX to dentin and its reported effect on the inhibition of dentinal proteases may explain why CHX can prolong the durability of resin-dentin bonds. (C) 2010 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Resin cement thickness in oval-shaped canals: Oval vs. circular fiber posts in combination with different tips/drills for post space preparation

Purpose: To evaluate the cement thickness around oval and circular posts luted in oval post spaces prepared with different drills/tips. Methods: Extracted premolars were endodontically treated and obturated, then randomly divided into three groups (n = 5) according to the tips/drills used for post-space preparation and to the type of fiber post luted: medium grit oval tip + oval posts, fine grit oval tip + oval posts, Mtwo Post File drill + circular posts. The specimens were sectioned in horizontal slices; one slice per canal third was chosen for each post-space, resulting in three slices for each specimen. The distances between the canal wall and the post perimeter were measured on SEM images of each slice. Results: The fine grit tip + oval post group obtained statistically significant lower cement thicknesses than the other groups (P < 0.05), in particular in the apical third. The MtwoPF + circular post group showed the highest cement thickness, comparable to that of the medium tip + oval post group. A good post fitting in oval-shaped canals can be obtained using a fine grit oval tip combined with oval posts. (Am J Dent 2009;22:290-294).

Effect of 2% Chlorhexidine Digluconate on the Bond Strength to Normal Versus Caries-affected Dentin

This study evaluated the effect of 2% chlorhexidine digluconate (CHX) used as a therapeutic primer on the long-term bond strengths of two etch-and-rinse adhesives to normal (ND) and caries-affected (CAD) dentin. Forty extracted human molars with coronal carious lesions, surrounded by normal dentin, were selected for this study. The flat surfaces of two types of dentin (ND and CAD) were prepared with a water-cooled high-speed diamond disc, then acidetched, rinsed and air-dried. In the control groups, the dentin was re-hydrated with distilled water, blot-dried and bonded with a three-step (Scotchbond Multi-Purpose-MP) or two-step (Single Bond 2-SB) etch-and-rinse adhesive. In the experimental groups, the dentin was rehydrated with 2% CHX (60 seconds), blot-dried and bonded with the same adhesives. Resin composite build-ups were made. The specimens were prepared for microtensile bond testing in accordance with the non-trimming technique, then tested either immediately or after six-months storage in artificial saliva. The data were analyzed by ANOVA/Bonferroni tests (alpha=0.05). CHX did not affect the immediate bond strength to ND or CAD (p>0.05). CHX treatment significantly lowered the loss of bond strength after six months as seen in the control bonds for ND (p<0.05), but it did not alter the bond strength of CAD (p>0.05). The application of NIP on CHX-treated ND or CAD produced bonds that did not change over six months of storage.

Push-out Bond Strength of Fiber Posts Luted with Unfilled Resin Cement

Purpose: The study evaluates the behavior of different adhesive systems and resin cements in fiber post placement, with the intent to clarify the possible role of unfilled resin as a luting material for fiber posts. Materials and Methods: Two luting agents (Dual-Link and Unfilled Resin) for cementing fiber posts into root canals were applied either with All-Bond 2 or One-Step Plus, or without an adhesive system, and challenged with the push-out test. Slices of roots restored with posts were loaded until post segment extrusion in the apical-coronal direction. Failure modes were analyzed under SEM. Results: Push-out strength was significantly influenced by the luting agent (p < 0.05), but not by the bonding strategy (p > 0.05). The best results were obtained in combination with Unfilled Resin with One-Step Plus. Dual-Link groups failed mainly cohesively within the cement, while Unfilled Resin demonstrated more adhesive fracture at the post interface. Conclusion: The results of this study support the hypothesis that adhesive unfilled resin application is essential for achieving high bond strength to radicular dentin.

Influence of occlusal access on demineralized dentin removal in the Atraumatic Restorative Treatment (ART) approach

Purpose: To verify the influence of cavity access diameter on demineralized dentin removal in the ART approach. Methods: 40 non-carious human premolars were randomly divided into four groups. The occlusal surface was ground flat and the teeth were sectioned mesio-distally. The hemi-sections were reassembled and occlusal access preparations were carried out using ball-shaped diamonds. The resulting size of the occlusal opening was 1.0 mm, 1.4 mm, 1.6 mm and 1.8 mm for Groups A, B, C, and D, respectively. Standardized artificial carious lesions were created and demineralized dentin was excavated. After excavation, the cavities were analyzed using: (a) the tactile method, (b) caries-detection dye to stain demineralized dentin, as proposed by Smales & Fang, and (c) Demineralized Tissue Removal index, as proposed in this study. Statistical analysis was performed using Fisher, Spearman correlation coefficient, kappa, Kruskal-Wallis and Miller tests (P < 0.05). Results: The three methods of evaluation showed no significant difference between Groups A vs. B, and C vs. D, while statistically significant differences were observed between Groups A vs. C, A vs. D, B vs. C and B vs. D. Based on the results of this study, the size of occlusal access significantly affected the efficacy of demineralized tissue removal.

Cytotoxic effects and pulpal response caused by a mineral trioxide aggregate formulation and calcium hydroxide

Purpose: To evaluate: the in vivo pulpal response after pulpotomy with different capping agents. In addition, the in vitro cytotoxic effects of both materials were assessed by applying them on culture of pulp cells. Methods: For the in vivo test, the coronal pulp of 28 teeth of dogs was mechanically removed and the root pulps were capped with the following dental materials: Group 1: Pro-Root NITA (PRMTA); and Group 2 (control): calcium hydroxide saline paste (CH). After 60 days, the animals were sacrificed and the teeth processed for histological analysis. In the in vitro test, experimental extracts obtained from both capping agents were applied on the cultured MDPC-23 odontoblast-like cells. Results: In the root pulps capped with PRMTA or CH, coagulation necrosis partially replaced by dystrophic calcification as well as tubular dentin matrix laid down by elongated pulp cells was observed. None or mild inflammatory response occurred beneath the capped pulpal wound. Regarding the pulpal response, PRMTA and CH presented no statistical difference. However, the teeth capped CH presented greater healthy pulp loss which resulted in convex shape of the hard barrier than PRMTA. When applied on the cultured cells, it was demonstrated that PRMTA and CH solutions decreased the cell metabolic activity by 9.9% and 29.4%, respectively. CH caused higher cytotoxic effects to the MDPC-23 cells as well as deeper healthy pulp tissue loss than PRMTA. However, similar sequence of healing occurred after pulpotomy with both dental materials.

Post space debridement in oval-shaped canals: The use of a new ultrasonic tip with oval section

This study evaluates the effect on post space debridement in oval-shaped canals of an experimental ultrasonic tip with oval section (Satelec) compared with a circular ultrasonic tip (KaVo). Thirty teeth with an oval-shaped canal were endodontically treated and obturated and then randomly divided into 3 groups (n = 10) according to the procedure used for post space debridement: Satelec tip, Largo #2 drill + KaVo file, and Largo #2 drill + water. Debris and dentin tubules were evaluated by assigning scores to scanning electron microscope post spaces images; lower scores corresponded to fewer debris and higher number of open tubules. The Satelec group showed significantly lower debris and open tubules scores than KaVo group (p < .05) and control group (p < .05), which differed significantly between each other (p < .05). Also the debris and open tubules scores in different post space regions differed significantly among the experimental groups (p < .001). The oval ultrasonic tip resulted in a better post space debridement than a circular ultrasonic tip in oval-shaped canals.

Post space cleaning using a new nickel titanium endodontic drill combined with different cleaning regimens

This study compared the effect of two drills and five cleaning regimens on post space debridement. One hundred extracted premolars were instrumented and obturated with warm vertical compaction of gutta percha. The teeth were divided into two groups according to the drill used to remove gutta percha/sealer and for post space preparation: a Largo drill (Largo; Dentsply, St Quentin en Yvelines, France) or a MTwo-PF drill (Sweden&Martina, Due Carrare, Padova, Italy). The following cleaning regimens were used: EDTA, ultrasonics, ultrasonics + EDTA, phosphoric acid, and distilled water. Scanning electron microscopic images of the post spaces were taken, and the presence of debris and of open dentin tubules were evaluated. The ultrasonics + EDTA, phosphoric acid, and EDTA groups were comparable in open tubules scores for both drills and in debris scores after the use of MTwo-PF (p > 0.05). The ultrasonics and control groups performed significantly worse (p < 0.05). The MTwo-PF drill resulted as effective as the Largo drill in obtaining a good post space cleaning, especially when followed by ultrasonics + EDTA irrigant regimen.

Evaluation of physicochemical properties of four root canal sealers

P>Aim To assess the physicochemical properties and the surface morphology of AH Plus, GuttaFlow, RoekoSeal and Activ GP root canal sealers. Methodology Five samples of each material were evaluated for setting time, dimensional alteration, solubility and radiopacity tests, according to ANSI/ADA Specification 57. A total of 50 mL of deionized distilled water from the solubility tests were used to measure the metal solubility by atomic absorption spectrometry. The morphologies of the external surface and the cross-section of the samples were analysed by means of a scanning electron microscope (SEM). Statistical analysis was performed by using one-way anova and post hoc Tukey-Kramer tests with the null hypothesis set as 5%. Results AH Plus had the longest setting time (580.6 +/- 3.05 min) (P < 0.05). Activ GP did not have a mean value on the radiopacity and solubility tests (1.31 +/- 0.35 mm and 11.8 +/- 0.43%, respectively) in accordance with ANSI/ADA, being significantly different from the other materials (P < 0.05), which had mean values for these tests in accordance with the ADA`s requirements. GuttaFlow was the only sealer that conformed to the Specification 57 concerning the dimensional alteration test (0.44 +/- 0.16%) (P < 0.05). The spectrometry test revealed significant Ca2+, K+, Zn2+ ion release from Activ GP sealer (32.57 +/- 5.0, 1.57 +/- 0.22 and 8.20 +/- 1.74 mu g mL-1, respectively). In SEM analysis, the loss of matrix was evident and the filler particles were more distinguishable in all groups. Conclusions The setting time of all sealers was in accordance with ANSI/ADA`s requirements. Activ GP did not fulfill ANSI/ADA`s protocols regarding radiopacity, dimensional alteration and solubility. GuttaFlow was the only sealer that conformed to the Specification 57 in all tests. SEM analysis revealed that the surfaces of all sealers had micromorphological changes after the solubility test.