Influence of Dentin on the Effectiveness of Antibacterial Agents
Zeynep Ergücü, DDS, PhD, Karl-Anton Hiller, PhD, and Gottfried Schmalz, DDS, DMD, PhD
The influence of dentin on the effectiveness of three antibacterial agents (triclosan, glutaraldehyde, NaOCl) on Streptococcus mutans, S. sobrinus, and Lactobacillus acidophiluswas tested using the agar diffusion method with and without bovine dentin discs (200 µm and 500 µm thickness) placed between bacteria and test substances. The effect of 0.3% triclosan on all tester strains (100%) was reduced after passage through 500 _m dentin discs to 0% ( L. acidophilus) and to 22% and 28% ( S. mutans and S. sobrinus). Seal&Protect (Dentsply, Konstanz, Germany), a triclosan containing dental bonding agent, produced inhibition zones only against S. mutans, but no zone when applied on 200 µm dentin discs. The inhibition zones for 1% NaOCl and 5% glutaraldehyde against all tester strains were significantly increased up to 230% (glutaraldehyde) and 236% (NaOCl) when applied on dentin discs, compared to direct application (100%). Dentin may either decrease or increase the inhibitory effect of antibacterial agents.
Chemical Differences Between White and Gray Mineral Trioxide Aggregate
Saeed Asgary, DDS, MSc, Masoud Parirokh, DDS, MSc, Mohammad Jafar Eghbal, DDS, MSc, and Frank Brink, BAppSc, MSc
The purpose of this research was to determine and compare the composition of white mineral trioxide aggregate and gray mineral trioxide aggregate. Electron probe microanalysis results indicated that lime (CaO), silica (SiO₂), and bismuth oxide (Bi₂O₃) were the dominant compounds in each case and were present at comparable levels in either of the types of mineral trioxide aggregate analyzed. It was concluded that the most significant differences observed were between the measured concentrations of Al₂O₃ (+122%), MgO (+130%), and especially FeO (+1000%) when gray mineral trioxide aggregate was compared with white mineral trioxide aggregate.
Microhardness of Composites in Simulated Root Canals Cured with Light Transmitting Posts and Glass-Fiber Reinforced Composite Posts
Oguz Yoldas, DDS, PhD, and Tayfun Alaçam, DDS, PhD
The aim of this study was to evaluate the depth of cure of composite resin cured within simulated root canals by means of light-transmitting plastic posts, glassfiber–reinforced composite posts, and conventional light curing method. Thirty black plastic cylinders measuring 15 mm in length and 4 mm in internal diameter were divided into three groups. The composite resin was packed into simulated canals. The light-transmitting plastic posts and glass-fiber–reinforced composite posts were inserted into simulated canals and light cured for 90 seconds. The control group was light cured directly. To ensure continual change of material properties by increasing the length of material, a surface microhardness test was done 2 mm, 4 mm, 6 mm, 8 mm, 10 mm, 12 mm, and 14 mm from the light exposure surface. The results showed a significant increase in microhardness of composite resin (depth of cure) for both light-transmitting plastic posts and glassfiber–reinforced composite posts compared with the control group. The microhardness of composite resin was also significantly higher with light-transmitting plastic posts than glass-fiber–reinforced composite posts after 8 mm.
Periapical Inflammation after Coronal Microbial Inoculation of Dog Roots Filled with Gutta-Percha or Resilon
Guy Shipper, BDS, MDent, MS, Fabricio B. Teixeira, DDS, MSc, PhD, Roland R. Arnold, PhD, and Martin Trope, BDS, DMD
A dog model was used to assess and compare in vivo the efficacy of gutta-percha and AH26 sealer versus Resilon with Epiphany primer and sealer [Resilon “Monoblock” System (RMS)] filled roots in preventing apical periodontitis subsequent to coronal inoculation with oral microorganisms. There were 56 vital roots in the premolars of seven adult beagle dogs aseptically instrumented, filled, and temporized. The roots were randomly divided into four experimental groups (Coronal Leakage Model) and one negative control group and filled as follows: group 1—lateral condensation of gutta-percha and AH26 sealer ( n= 12); group 2—vertical condensation of gutta-percha and AH26 sealer ( n= 12); group 3—lateral condensation of RMS ( n=12); group 4 —vertical condensation of RMS ( n= 10); negative control ( n = 10)—gutta-percha and AH26 sealer or RMS root fillings using lateral or vertical condensation techniques as in groups 1 to 4. Positive control—57 additional premolar roots were instrumented, infected and not filled (beginning of the Entombment Model experiment). The premolars in groups 1 to 4 were accessed again, inoculated with dental plaque scaled from the dog’s teeth, and temporized. This fresh innoculum of microorganisms was repeated on two more occasions at monthly intervals. The teeth in the negative control group were not accessed again and remained undisturbed. On the 14-wk postcoronal inoculation, dogs were euthanized, and jaw blocks prepared for histologic evaluation under a light microcope. Mild inflammation was observed in 82% (18 of 22) of roots filled with gutta-percha and AH26 sealer that was stastistically more than roots filled with RMS (19% or 4 of 21) and roots in the negative control (22% or 2 of 9) (McNemar paired analysis, p < 0.05). The Resilon “Monoblock” System was associated with less apical periodontitis, which may be because of its superior resistance to coronal microleakage.
Physicochemical Basis of the Biologic Properties of Mineral Trioxide Aggregate
N. K. Sarkar, R. Caicedo, P. Ritwik, R. Moiseyeva, and I. Kawashima
This study characterized the interactions of mineral trioxide aggregate with a synthetic tissue fluid composed of a neutral phosphate buffer saline solution and root canal dentin in extracted human teeth using inductively coupled plasma—atomic emission spectroscopy, scanning electron microscopy, energy dispersive X-ray analysis, and X-ray diffraction. Mineral trioxide aggregate exposed to synthetic tissue fluid at 37°C released its metallic constituents and produced precipitates with a composition and structure similar to that of hydroxyapatite [Ca₁₀(PO4)₆(OH)₂–HA]. Endodontically prepared teeth filled with mineral trioxide aggregate and stored in synthetic tissue fluid at 37°C for 2 months produced at the dentin wall an adherent interfacial layer that resembled hydroxyapatite in composition. The authors conclude that Ca, the dominant ion released from mineral trioxide aggregate, reacts with phosphates in synthetic tissue fluid, yielding hydroxyapatite. The dentin—mineral trioxide aggregate interfacial layer results from a similar reaction. The sealing ability, biocompatibility, and dentinogenic activity of mineral trioxide aggregate is attributed to these physicochemical reactions.
The Effect of Mesio-Distal Chamber Dimension on Access Preparation in Mandibular Incisors
Christen John Nielsen DMD, MS, and Kianor Shahmohammadi, BS
Because the pulp chamber of a young mandibular incisor flares coronally in a mesio-distal dimension, the access form pictured by a number of authors is triangular in shape. As a person ages, the chamber recedes and the access shape becomes oval in form consistent with a canal system that is primarily bucco-lingual in orientation. Endodontic literature generally recommends either the triangular or oval access shape without acknowledging that both are appropriate at a given time in the life of the individual. The question addressed by this study is when does the pulp chamber loose its coronal flare to become primarily oval in shape, and as a consequence of this change, when should the access form go from triangular to oval. It was concluded that by the age of 40 the canal has decreased in size sufficiently to justify in routine cases an oval preparation of less than 2 mm mesio-distal width.
Endodontic Therapy Associated with Calcium Hydroxide As an Intracanal Dressing: Microbiologic Evaluation by the Checkerboard DNA-DNA Hybridization Technique
Carlos Alberto Soriano de Souza, DDS, MSc, Ricardo Palmier Teles, DDS, PhD, Renata Souto, MSc, Mario Augusto Escobar Chaves, DDS, and Ana Paula Vieira Colombo, DDS, PhD
This study evaluated the predominant microbiota of infected necrotic pulps and the effects of calcium hydroxide therapy on these microorganisms by the checkerboard DNA-DNA hybridization technique. Conventional endodontic therapy associated with calcium hydroxide as intracanal dressing was performed in 12 single-rooted teeth with pulp necrosis and periradicular bone lesion. Samples were collected from the canal at baseline and 14 days after therapy, and the presence of 44 bacterial species was determined by the checkerboard method. Significant differences in the microbiota from baseline to post-therapy were sought by the paired-samples t test. The most prevalent species included F. nucleatum ss. vincentii, C. sputigena, C. ochracea, S. constellatus, V. parvula, P. gingivalis, P. melaninogenica, and S. sanguis. Most of the microorganisms were reduced after treatment, particularly A. gerencseriae, A. israelii, A. naeslundii, C. gingivalis, C. ochracea, P. gingivalis, S. noxia, S. sanguis, and S. oralis (p < 0.05). Conversely, A. actinomycetemcomitans, C. sputigena, and E. corrodens increased in numbers after therapy. These results indicate that conventional endodontic therapy with calcium hydroxide results in the reduction of pathogenic species associated with pulp necrosis. However, its use is limited, because it did not eliminate the whole spectrum of microorganisms.
Expression of Macrophage Inflammatory Protein 3α in Human Inflamed Dental Pulp Tissue
Tadashi Nakanishi, DDS, PhD, Kanako Takahashi, DDS, Yoshitaka Hosokawa, DDS, PhD, Tomohiko Adachi, DDS, Hideaki Nakae, DDS, PhD, and Takashi Matsuo, DDS, PhD
Severe pulpitis resulting from dental caries is characterized by marked inflammatory infiltrate such as lymphocytes. Little is known about the recruitment of these cells into the dental pulp lesions of carious teeth. Macrophage inflammatory protein-3α (MIP-3α), a CC chemokine attracts CC chemokine receptor 6 (CCR6)-expressing T cells. We examined the distribution of MIP-3α-positive and/or CCR6-positive cells in human inflamed and normal dental pulp by immunohistochemistry. MIP-3α was observed in all inflamed pulp sections, and was mostly distributed in macrophages that had accumulated in the area adjacent to carious lesions. Furthermore, CCR6 expression was also observed in the infiltrating lymphocytes. In contrast, MIP-3α and CCR6 were rarely detected in normal pulp. These findings suggest that MIP-3α plays a role in the advancement of pulpal inflammation via the recruitment of CCR6-expressing lymphocytes.
Conventional Treatment of Dens Invaginatus in Maxillary Lateral Incisor with Sinus Tract: One Year Follow-Up
Heike Steffen and Christian Splieth
Endodontic treatment of a maxillary lateral incisor with dens invaginatus in association with sinus tract and lateroradicular lesion is reported. Invaginated teeth present technical difficulties with respect to their management because of complicated canal morphology. This case was treated by conventional root canal treatment. At follow up examination after one year the tooth was asymptomatic and radiographically showed repair of the lesion.
Quality of Gutta-Percha Root Canal Fillings Using Differently Tapered Gutta-Percha Master Points
Juan Camilo Villegas, BDS, Takatomo Yoshioka, DDS, PhD, Chihiro Kobayashi, DDS, PhD, and Hideaki Suda, DDS, PhD
The aim of this study was to evaluate the quality and adaptability of gutta-percha root canal fillings to the root canal walls when two different tapered gutta-percha master points (GPMP) were used to fill a splittooth model. A maxillary central incisor was prepared for the split-tooth model and 10 fillings for group A (ISO .02 GPMP) and group B (ISO .10 GPMP) were carried out. The System B and the Obtura II were used to fill the split-tooth model and replication of round artificial depressions, voids within the gutta-percha (GP) and spaces between the GP and the root canal walls were evaluated and scored. Individual scores of each parameter evaluated were compared between the two groups and statistically analyzed using the Mann-Whitney U test. Group A showed statistically significant better scores (p < 0.05) for the replication of the artificial round depressions and spaces between the GP and the root canal walls. No statistically significant differences were found between the two groups for internal voids. It is concluded that the location of the GPMP binding point and the greater mass of the .10-Tapered GPMP may affect the quality and adaptation of the root canal filling in the important apical part of the canal.
Effect of EDTA and Citric Acid Solutions on the Microhardness and the Roughness of Human Root Canal Dentin
Ayce Unverdi Eldeniz, DDS, PhD, Ali Erdemir, DDS, PhD, and Sema Belli, DDS, PhD
The purpose of this study was to evaluate the effect of citric acid and EDTA solutions on the microhardness and the roughness of human root canal dentin. Forty five human teeth sectioned longitudinally were used. Specimens were randomly divided into three groups of 30 teeth each and were treated as follows: (a) one molar (19%) citric acid (C₆H₈O₇) for 150 s followed by 5.25% NaOCl; (b) 17% EDTA for 150 s and rinsed with 5.25% NaOCl; (c) rinsed with distilled water and served as control. Three groups were then divided into two subgroups of 15 specimens each. The specimens, in first subgroup were subjected to Vicker’s testing whereas the second subgroup underwent surface roughness testing. The results were analyzed using one-way ANOVA and Tukey tests. Significant differences were observed in microhardness among the test groups, citric acid group being the least hard (p 0.05). Also, citric acid significantly increased surface roughness.
The Influence of a Manual Glide Path on the Separation Rate of NiTi Rotary Instruments
Purificación Varela Patiño, DDS, MSc, PhD, Benjamín Martín Biedma, DDS, MSc, PhD, Carmen Rodríguez Liébana, MSc, Giuseppe Cantatore, DDS, MSc, PhD, and José González Bahillo, DDS, MSc, PhD
The dual purpose of this study was, to evaluate the fracture rate of Ni-Ti rotary instruments when following a manual glide path and using stainless steel hand files before carrying out instrumentation by means of rotary files and, to compare the results in this study with those obtained in two previous analyses, in which the glide path technique was not used. A total of 208 canals obtained from a pool of freshly extracted human mandibular and maxillary molars was divided into three groups corresponding to; K3, ProFile and ProTaper. The coronal 2/3 of each tooth were used. In all three groups the apical portion of the samples was prepared with size 10-20 stainless steel K-type hand files. The apical stops were prepared using K3, ProFile and ProTaper rotary instruments. Logistic regression model analysis indicated that breakage was significantly associated with the angle of curvature of the canal (OR = 1.078; 95% CI = 1.032–1.12; p = 0.001), and with the number of clinical uses (files used more than eight times broke more frequently that those used 1 or 2 times; OR: 22.686; 95% CI: 2.6 –191.3; p = 0.004). The breakage rate obtained in the present study is significantly lower than in our previous studies, in which the angle of curvature was also greater than 30° and rotational speed a constant 350 rpm, but in which the canals were not first prepared with hand files (25/ 205 = 12% versus 16/61 = 26%, p = 0.007). Based on the results of this study, we recommend the use of stainless steel hand files to prepare the apical 1/3 of curved canals before introducing rotary files.
In-Vitro Evaluation of Microleakage of an Orthograde Apical Plug of Mineral Trioxide Aggregate in Permanent Teeth with Simulated Immature Apices
Ahmed Al-Kahtani, BDS, MS, Sandra Shostad, DMD, MS, Robert Schifferle, DDS, PhD, and Satish Bhambhani, BDS, DDS, MS
This in vitro study evaluated the seal created by varying depths of mineral trioxide aggregate (MTA) plugs placed in an orthograde fashion in five groups of 10 teeth. One group received a 2 mm thick orthograde apical plug of MTA, the second group a 5 mm apical MTA plug, and the third group a 2 mm apical MTA plug with a second 2 mm increment, 24 h later. The remaining portion of the canal in these groups was left unfilled. Group four received a 2 mm MTA plug that set for 24 h and the canal was then back-filled with gutta-percha and eugenol based sealer. Group five was a positive control without an MTA plug. The apical seal was tested using a bacterial leakage model of Actinomyces viscosus. Results showed a statistically significant difference in only the 5 mm apical plug, which completely prevented bacterial leakage.
Analysis of Torque and Force with Differently Tapered Rotary Endodontic Instruments In Vitro
Charlotte Schrader, Dr Med Dent, and Ove A. Peters, PD, Dr Med Dent, MS, FICD
The aim of this study was to compare torques and forces developed by two sequences of nickel-titanium rotary instruments, using only .04 taper instruments or a combination of .04 and .06 tapers, respectively. Curved canals in plastic blocks were shaped in a torque-testing device; torque, force, contact areas and numbers of working rotations were determined. Analysis of variance and Pearson correlation coefficients were used to compare the two sequences. Mean torque ranged from 0.2 ± 0.03 to 3.19 ± 0.28 Ncm and was higher for instrument sizes 25 to 45 in group A. Mean vertical forces ranged from 1.49 ± 0.54 to 12.0 ± 3.5 N; there were significant correlations between torque and force as well as between torque and contact areas. Numbers of rotations were lower in the combined .04 and .06 sequence. An instrumentation sequence encompassing various tapers seems to be safer regarding torsional and fatigue failure compared to a sequence that used one single taper. However, the former sequence requires the use of more instruments.