Aspectos clínicos y forenses del color rosa de los dientes: reporte de un caso / Clinical and forensic aspects of the pink color of teeth: report of a case

La coloración rosa de los dientes puede originarse por diferentes factores. En el ámbito forense se ha descrito al fenómeno denominado post mortem pink teeth como un signo asociado a muertes violentas de etiología diversa. En la práctica clínica también es posible observar pacientes con dientes rosados, fre-cuentemente ocasionados por traumatismos o iatro-genia proveniente de ortodoncia, cuyo mecanismo de producción obedece a distintas etiopatogenias, destacándose las reabsorciones dentinarias inter-nas, cemento-dentinarias externas y calcificaciones dentinarias. El presente artículo expone el caso de un individuo adulto con antecedente de trauma óseo-dentario por accidente vial que, luego de un prolon-gado tiempo, asiste al Servicio de Urgencias Odon-tológicas y Orientación de Pacientes de la Facultad de Odontología de la Universidad de Buenos Aires, en donde se le detecta, a modo de hallazgo exploratorio, una ostensible coloración rosada en el canino infe-rior derecho. La situación motivó un pormenorizado abordaje clínico y radiográfico, indagando respecto a los probables factores que intervinieron en su ge-neración y desarrollo (AU)

The pink coloration of the teeth can be caused by dif-ferent factors. In the forensic field, the phenomenon called post mortem pink teeth has been described as a sign associated with violent deaths of various etiology. In clinical practice, it is also possible to ob-serve patients with pink teeth, frequently caused by trauma or iatrogenesis from orthodontics, whose production mechanism is due to different etiopatho-genesis, highlighting internal dentin resorption, ex-ternal cemento-dentinal resorption and dentin calci-fications. This article presents the case of an adult individual with a history of bone-dental trauma due to a road accident who, after a long time, attends the Dental Emergency and Patient Guidance Service of the Faculty of Dentistry of the University of Bue-nos Aires, where an ostensible pink coloration was detected in the lower right canine as an exploratory finding. The situation motivated a detailed clinical and radiographic approach, inquiring about the probable factors that intervened in its generation and development (AU)

Levels of matrix metalloproteinase-8 and cold test in reversible and irreversible pulpitis.

ABSTRACT: Researchers have reported false positive/negative results of the cold test in the diagnosis of pulpitis. Knowledge of the correlation between results of the cold test and proteins could aid in decreasing the frequency of incorrect diagnosis. To associate the levels of matrix metalloproteinase-8 (MMP-8) with the responses (in seconds) to the cold test in teeth diagnosed with reversible and irreversible pulpitis.A cross-sectional study was performed. A total of 150 subjects were evaluated, of which 60 subjects met the selection criteria. The participants were divided into 3 groups: Group 1, healthy pulps, 20 subjects with 20 posterior teeth (premolars) with clinically normal pulp tissue; Group 2, reversible pulpitis, 20 patients with 20 teeth diagnosed with reversible pulpitis; and Group 3, irreversible pulpitis, 20 subjects with 20 teeth diagnosed with irreversible pulpitis. All participants were evaluated based on the following variables: medical and dental history, cold test, and expression of MMP-8 by enzyme-linked immunosorbent assay in dentin samples.Responses to the cold test between 4 to 5 seconds (second evaluation; P < .0001) were associated with high levels of MMP-8 (mean, 0.36 ng/mL) in the reversible pulpitis group. In the irreversible pulpitis group, the responses from 6 to ≥10 seconds (second evaluation; P < .0001) were associated with a higher average of MMP-8 levels (mean, 1.97 ng/mL).We determined that an increase in the duration of response to the cold test was associated with an increase in MMP-8 levels (Rho = 0.81, P < .0001) in teeth with pulpitis. The above correlations can be considered an adjunct to the clinical diagnosis of pulpitis.

Terapia endodóntica en pacientes adultos mayores ¿qué debemos tener en cuenta? / Endodontic therapy in elderly patients, what should we consider?

De acuerdo con la tendencia mundial, el número de personas de 60 años y más va en aumento. Este crecimiento demográfico de la población, el aumento de las expectativas de vida de las personas y la tendencia a la disminución de pacientes edéntulos, produce una mayor demanda de procedimientos endodónticos en la población anciana. Es fundamental que el odontólogo conozca la fisiología del envejecimiento para poder abordar, en forma eficaz, el tratamiento en los pacientes pertenecientes a este grupo etario. Se ha descripto que los tejidos dentales sufren cambios a lo largo de la vida; entre ellos, la reducción del número de fibroblastos, de odontoblastos, de vasos sanguíneos y de fibras nerviosas; el aumento de fibras colágenas, de masas calcificadas, aposición de cemento, de dentina secundaria y de dentina de reparación. El objetivo del presente trabajo es realizar una revisión bibliográfica en relación a los cambios que presentan la pulpa dental, la dentina y el cemento, relacionados con el proceso de envejecimiento y sus posibles dificultades al momento de realizar el tratamiento endodóntico; sin olvidar cómo pueden inferir en el éxito del tratamiento las posibles patologías sistémicas que presentan los pacientes a consecuencia de la edad (AU)

According to the world trend, the number of people aged 60 and over is increasing. This demographic growth of the population, the increase in people's life expectancies and the tendency to decrease edentulous patients, produces a greater demand for endodontic procedures in the elderly population. It is essential that the dentist knows the physiology of aging to be able to effectively address the treatment in patients belonging to this age group. It has been described that dental tissues suffer changes throughout life, including the reduction of the number of fibroblasts, odontoblasts, blood vessels and nerve fibers; the increase of collagen fibers, calcified masses, apposition of cement, secondary dentin and repair dentin. The objective of the present work is to carry out a bibliographic review in relation to the changes that the dental pulp, dentine and cement have in relation to the aging process and its possible consequences in the endodontic treatment; without forgetting how it can infer in the success of the treatment the possible systemic pathologies that patients present as a result of age (AU)

Silver-loaded nanoparticles affect ex-vivo mechanical behavior and mineralization of dentin

Background: The aim was to evaluate the effect of silver loaded nanoparticles (NPs) application on the triboscopic, crystallographic and viscoelastic properties of demineralized dentin. Polymethylmetacrylate-based NPs and Ag loaded NPs were applied on demineralized dentin. Material and Methods: Treated and untreated surfaces were probed by a nanoindenter to test viscoelasticity, and by atomic force microscopy to test nanoroughness and collagen fibril diameter. X-ray diffraction and transmission electron microscopy through selected area diffraction and bright-field imaging were also used. Results: Dentin treated with Ag-NPs attained the lowest complex modulus, and the highest tan delta values after 7 days of storage. Dentin treated with undoped-NPs achieved the lowest nanoroughness and the greatest collagen bandwidths among groups. Crystals were identified as hydroxyapatite with the highest crystallographic maturity and crystallite size in dentin treated with undoped-NPs. Texture increased in all samples from 24 h to 7 d, except in dentin surfaces treated with Ag-NPs at 310 plane. Polyhedral, block-like, hexagonal or plate-like shaped apatite crystals constituted the bulk of minerals in dentin treated with Ag-NPs, after 7 d. Polyhedral or rounded/drop-like, and polymorphic in strata crystal apatite characterized the minerals when undoped-NPs were used, with more crystalline characteristics after 7 d than that found when Ag-NPs were applied. Ag-NPs application did not improve the mechanical performance of dentin and did not produce dentin remineralization. However, energy was dissipated through the dentin without showing stress concentration; contrary was occurring at dentin treated with undoped- NPs, that provoked bridge-like mineral deposits at the dentin surface. Conclusions: Ag-NPs application did not enhance the mechanical properties of cervical dentin, though the energy dissipation did not damage the dentin structure. Remineralization at dentin was not produced after Ag-NPs appli-cation, though improved crystallinity may lead to increase stability of the apatite that was generated at the dentin surface

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Effect of ageing and endodontic treatment on the thermal stability of human dentin.

BACKGROUND: Human dentin is a highly calcified tissue of mesenchymal origin with a heterogeneous structure. Its morphology is constantly remodelled throughout the life span of the tooth, as well as under the influence of external stimuli. OBJECTIVE: The aim of the present study was to obtain information about the thermal changes in the crown and root dentin specimens of vital and devitalized teeth. METHODS: The investigated samples were divided into 6 groups, depending on the patients' age and dentin location (crown, root). An additional group of endodontically treated teeth was created. The methods of choice were were combined thermal analysis (DTA-TG(DTG)-MS and gas chromatography-mass spectrometry. RESULTS: After heating up to 1200 °C, endo- and exothermal effects were observed. The effects' dynamic was the same for all samples. The differences were in the samples' weight after the experiment, with root dentin showing the greatest mass loss percentage. CONCLUSIONS: The observed mass loss differences could be attributed to the presence of impurities in the dentin, as well as alterations in the collagen matrix. Ageing and endodontic treatment could catalyse the accumulation of such changes and affect the microstructure of the mineralized tissue.

Alteraciones de la dentina con el envejecimiento / Dentin alterations with aging

Diferentes estudios han demostrado que después de la tercera década de vida hay una transición en la microestructura de la dentina. Dada la importancia de ésta como sustrato para la adhesión de materiales de restauración utilizados en operatoria y rehabilitación oral, ha sido objetivo de este trabajo realizar una búsqueda bibliográfica de las publicaciones existentes en inglés y español de los últimos 15 años, haciendo uso de buscadores científicos como Pubmed, Google Schoolar y LILACS que permitieran actualizar la información existente ayudando a entender los efectos biológicos del envejecimiento de la dentina, identificando los cambios de mayor relevancia a nivel histológico. De la búsqueda realizada se concluye que el envejecimiento de la dentina está asociado con aumento de dentina secundaria, formación de dentina esclerótica opaca, variaciones en la composición química de la matriz y disminución del número y actividad de los odontoblastos. Los conocimientos sobre el envejecimiento de la dentina deben tenerse en cuenta frente a estudios relacionados con materiales de restauración dental, ya que los cambios en la microestructura y capacidad funcional de la dentina con el envejecimiento requieren que éstos se adapten a dichas variaciones (AU)

Different studies have shown that aafter the third term of life there is a transition in the microstructure of dentin. Given the importance of dentin as a substrate for the adhesion of restorative materials used in operative and oral rehabilitation, the aim of the present work was to conduct a search of the scientific literature in English and Spanish, published in the last 15 years, using search engines such as Pubmed, Google Schoolar and LILACS, for an update on the biological effects of dentin aging, to identify the most relevant age-related histological changes in dentina. The data obtained from the literature review allow concluding that dentin aging is associated with an increase in secondary dentina, opaque sclerotic dentin formation, variations in the chemical composition of the matrix and a decrease in odontoblast number and activity. Updated information on dentin aging should be taken into account in studies on dental restoration materials, since the latter must adapt to aging-related changes in the microstructure and functional capacity of dentin (AU)

Effects of the nitric oxide releasing biomimetic nanomatrix gel on pulp-dentin regeneration: Pilot study.

Successful disinfection alongside complete endodontic tissue regeneration and revascularization are the most desired clinical outcomes of regenerative endodontics. Despite reported clinical successes, significant limitations to the current regenerative endodontic procedure (REP) have been elucidated. To improve the current REP, an antibiotics and nitric oxide (NO) releasing biomimetic nanomatrix gel was developed. The study evaluates antibacterial effects of an antibiotics and NO releasing biomimetic nanomatrix gel on multispecies endodontic bacteria. Antibiotics, ciprofloxacin (CF) and metronidazole (MN) were mixed and encapsulated within the NO releasing biomimetic nanomatrix gel. The gel was synthesized and self-assembled from peptide amphiphiles containing various functional groups. Antibacterial effects of the antibiotics and NO releasing biomimetic nanomatrix gel were evaluated using bacterial viability assays involving endodontic microorganisms including clinical samples. Pulp-dentin regeneration was evaluated via animal-model experiments. The antibiotics and NO releasing biomimetic nanomatrix gel demonstrated a concentration dependent antibacterial effect. In addition, NO alone demonstrated a concentration dependent antibacterial effect on endodontic microorganism. An in vivo analysis demonstrated the antibiotics and NO releasing biomimetic nanomatrix gel promoted tooth revascularization with maturation of root canals. An optimal concentration of and NO releasing nanomatrix gel is suggested for its potential as a root treatment material for REP and an appropriate protocol for human trials. Further investigation is required to obtain a larger sample size and decide upon ideal growth factor incorporation.

Effect of hydration and crack orientation on crack-tip strain, crack opening displacement and crack-tip shielding in elephant dentin.

OBJECTIVES: To quantify the extent of crack-tip plasticity, crack opening displacement (COD) and crack bridging for crack growth perpendicular (HAH) and parallel (RAR) to the tubules in elephant dentin under both hydrated and dry conditions to better understand their influence on intrinsic and extrinsic toughening during crack growth. METHODS: Compact tension test-pieces were prepared from a tusk of African elephant ivory. Crack-tip strain mapping and COD measurements by digital image correlation (DIC) technique were made under incremental loading and unloading of cracks for hydrated and dry dentin of different orientations. RESULTS: For the RAR test-piece the plastic zones were significantly larger in the hydrated condition compared to when dry. By contrast, the plastic strains in the HAH test-piece were negligible in both wet and dry conditions. In the RAR condition the crack front was broken up into overlapping longitudinal 'fingers' with crack bridging regions in between, the ligaments extending 400µm behind the crack front in the dry case. This could only be seen in 3D by X-ray CT. Extrinsic shielding reduces the crack-tip stresses by 52% and 40% for hydrated and dry RAR test-pieces respectively. No significant bridging was found in the HAH case. SIGNIFICANCE: For crack growth parallel to the tubules, collagen plasticity determines the intrinsic toughening, whereas microcracking from the tubules governs extrinsic shielding via ligament bridging, which is maintained further behind the crack in the hydrated case. For cracks grown perpendicular to the tubules, neither toughening mechanisms are significant.

Starch Combined with Sucrose Provokes Greater Root Dentine Demineralization than Sucrose Alone.

Since there is no consensus about whether starch increases the cariogenic potential of sucrose, we used a validated 3-species biofilm model to evaluate if starch combined with sucrose provokes higher root dentine demineralization than sucrose alone. Biofilms (n = 18) composed by Streptococcus mutans (the most cariogenic bacteria), Actinomces naeslundii (which has amylolytic activity), and Streptococcus gordonii (which binds salivary amylase) were formed on root dentine slabs under exposure 8 ×/day to one of the following treatments: 0.9% NaCl, 1% starch, 10% sucrose, or a combination of 1% starch and 10% sucrose. Before each treatment, biofilms were pretreated with human whole saliva for 1 min. The pH of the culture medium was measured daily as an indicator of biofilm acidogenicity. After 96 h of growth, the biofilms were collected, and the biomass, bacteria viability, and polysaccharides were analyzed. Dentine demineralization was assessed by surface hardness loss (% SHL). Biofilm bioarchitecture was analyzed using confocal laser scanning microscopy. Treatment with a starch and sucrose combination provoked higher (p = 0.01) dentine demineralization than sucrose alone (% SHL = 53.2 ± 7.0 vs. 43.2 ± 8.7). This was supported by lower pH values (p = 0.007) of the culture medium after daily exposure to the starch and sucrose combination compared with sucrose (4.89 ± 0.29 vs. 5.19 ± 0.32). Microbiological and biochemical findings did not differ between biofilms treated with the combination of starch and sucrose and sucrose alone (p > 0.05). Our findings give support to the hypothesis that a starch and sucrose combination is more cariogenic for root dentine than sucrose alone.

Dental properties, ultrastructure, and pulp cells associated with a novel DSPP mutation.

OBJECTIVE: To investigate physical characteristics and behaviours of dental pulp cells of teeth isolated from a dentinogenesis imperfecta (DGI) patient with a novel dentin sialophosphoprotein (DSPP) mutation. SUBJECTS AND METHODS: Whole exome and Sanger sequencing were employed to identify mutations. Physical characteristics of the teeth were examined. Pulp cells' behaviours including cell proliferation, colony-forming unit, osteogenic differentiation, pluripotent markers, and mesenchymal stem cell markers were investigated. RESULTS: The proband had opalescent brown primary teeth with extensive loss of enamel. Mutation analysis revealed a novel heterozygous 4-bp deletion, c.1915_1918delAAGT (p.K639QfsX674), in exon 5 of the DSPP associated with DGI. Analysis of the extracted primary incisor demonstrated a decrease in brightness but an increase in yellow and red chroma. The dentin showed reduced mineral density. The dentinal tubules were present in the predentin, but progressively collapsed in the dentin. The pulp cells exhibited markedly reduced CD105 expression, decreased cell proliferation, and smaller colony-forming units. CONCLUSIONS: We identified a novel mutation in the DSPP gene which disturbed dentin characteristics and pulp cells' behaviours. Our study expands the mutation spectrum and understanding of pathologic dentin phenotypes related to the frameshift deletion in the dentin phosphoprotein (DPP) region of the DSPP gene.

Effect of cavity depth on dentine sensitivity in man.

OBJECTIVE: To determine if dentine at the enamel-dentine junction (EDJ) in man is more sensitive to hydrostatic pressure stimuli then deeper dentine. DESIGN: Cavities (1mm diam.) were cut at the tips of the buccal and lingual cusps of 8 premolars in 3 subjects (ages: 22-25 years). Both cavities were initially deepened to expose the EDJ then one (the test cavity) was deepened in steps of 0.5mm to a maximum of 2.0 mm below the EDJ. The cavities were tested at each stage, before and after etching, with 5s, hydrostatic pressure stimuli between 400 mm above, and 400 mm below atmospheric. The intensity of any pain produced was recorded on a VAS scale and electrodes were placed in both cavities in an attempt to monitor any action potentials evoked in intradental nerves. RESULTS: In all the teeth, the intensity of the pain produced by a stimulus tended to increase as the cavity was deepened, as did the number of action potentials recorded (in 6 of the 8 teeth). The responses were greater from etched than unetched dentine, and negative pressures evoked greater responses than the corresponding positive pressures. CONCLUSION: There was no evidence that dentine close to the EDJ was more sensitive to hydrostatic pressure stimuli than deeper dentine. It may however be more sensitive to mechanical stimuli as it is more compliant.

Evaluation of the Effect of Enterococcus faecalis Biofilm on the 2% Chlorhexidine Substantivity: An In Vitro Study.

INTRODUCTION: The aim of this study was to correlate the bacterial viability and the presence of 2% chlorhexidine (CHX) solution on dentin by means of confocal laser scanning microscopy and high-performance liquid chromatography for 48 hours, 7 days, and 30 days. METHODS: One hundred twenty-three extracted human teeth were used. Samples were divided into 4 groups according to the solution (CHX or saline) and the presence of Enterococus faecalis biofilm. Samples were kept in contact with 5 mL of the solution for 5 minutes. Each group was divided into 3 subgroups according to the evaluation period (n = 10). Statistical analysis was performed by using the Kruskal-Wallis test, the Mann-Whitney U test (P < .05), and the Spearman rank correlation coefficient (P < .01). RESULTS: There was a negative correlation between the percentage of live cells and the amount of remaining CHX (P = .000). CHX significantly reduced the percentage of viable cells compared with saline after 48 hours (P = .007). Differences were maintained in the 7-day evaluation period (P = .001). After 30 days, the CHX group presented an increase of viable cells, thereby becoming similar to saline (P = .623). Simultaneously, the remaining CHX was significantly reduced in the 30-day specimens (P = .000). CONCLUSIONS: The results of this study indicate that 2% CHX solution was detected for 48 hours and 7 days with a low percentage of viable cells. The presence of microorganisms on human dentin did not affect 2% CHX maintenance.

Antibacterial Properties Associated with Chitosan Nanoparticle Treatment on Root Dentin and 2 Types of Endodontic Sealers.

INTRODUCTION: The aim of this study was to evaluate the efficacy of carboxymethyl chitosan (CMCS) and chitosan nanoparticles (CNps) to inactivate bacteria and prevent biofilm formation at sealer-dentin interfaces. METHODS: The study was divided into 3 stages: first stage, the experiment was conducted to analyze the antibacterial properties of CMCS in different formulations against biofilms; second stage, direct-contact and membrane-restricted methods were used to evaluate the antibacterial properties of an epoxy resin (ThermaSeal Plus; Dentsply Tulsa Dental, Tulsa, OK) and calcium silicate (MTA Fillapex; Angelus SA, Londrina, PR, Brazil) based-sealers with or without CNps; and third stage, biofilm formation at the sealer dentin interfaces of root dentin treated with CMCS and filled with gutta-percha and CNp incorporated sealer were analyzed after 1- and 4-week aging periods. The samples were treated and filled as follows: (1) distilled water: unaltered sealer (control group), (2) CMCS: sealer+CNps (CMCS group), and (3) CMCS/rose bengal: sealer+CNps (CMCS/RB group). Enterococcus faecalis was used to infect all the samples. Microbiological and microscopic analyses were used to assess the antibacterial characteristics. RESULTS: CMCS-based treatments effectively killed bacteria adherent on root dentin (P < .05). The addition of CNps to ThermaSeal enhanced its antibacterial ability by direct-contact and membrane-restricted tests (P < .05). The CNp incorporation significantly increased the antibacterial efficacy of root canal sealers even after a 4-week aging time (P < .05). CONCLUSIONS: This study highlighted the ability of CMCS to disinfect root canal dentin and inhibit bacterial adhesion. CNps in root canal sealers are capable of maintaining their antibacterial activity even after prolonged aging.

Antimicrobial Effects of Novel Triple Antibiotic Paste-Mimic Scaffolds on Actinomyces naeslundii Biofilm.

INTRODUCTION: Actinomyces naeslundii has been recovered from traumatized permanent teeth diagnosed with necrotic pulps. In this work, a triple antibiotic paste (TAP)-mimic scaffold is proposed as a drug-delivery strategy to eliminate A. naeslundii dentin biofilm. METHODS: Metronidazole, ciprofloxacin, and minocycline were added to a polydioxanone (PDS) polymer solution and spun into fibrous scaffolds. Fiber morphology, mechanical properties, and drug release were investigated by using scanning electron microscopy, microtensile testing, and high-performance liquid chromatography, respectively. Human dentin specimens (4 × 4 × 1 mm(3), n = 4/group) were inoculated with A. naeslundii (ATCC 43146) for 7 days for biofilm formation. The infected dentin specimens were exposed to TAP-mimic scaffolds, TAP solution (positive control), and pure PDS (drug-free scaffold). Dentin infected (7-day biofilm) specimens were used for comparison (negative control). Confocal laser scanning microscopy was done to determine bacterial viability. RESULTS: Scaffolds displayed a submicron mean fiber diameter (PDS = 689 ± 312 nm and TAP-mimic = 718 ± 125 nm). Overall, TAP-mimic scaffolds showed significantly (P ≤ .040) lower mechanical properties than PDS. Within the first 24 hours, a burst release for all drugs was seen. A sustained maintenance of metronidazole and ciprofloxacin was observed over 4 weeks, but not for minocycline. Confocal laser scanning microscopy demonstrated complete elimination of all viable bacteria exposed to the TAP solution. Meanwhile, TAP-mimic scaffolds led to a significant (P < .05) reduction in the percentage of viable bacteria compared with the negative control and PDS. CONCLUSIONS: Our findings suggest that TAP-mimic scaffolds hold significant potential in the eradication/elimination of bacterial biofilm, a critical step in regenerative endodontics.

Periapical microsurgery: the effect of root dentinal defects on short- and long-term outcome.

INTRODUCTION: The purpose of this prospective clinical study was to evaluate the clinical outcome of endodontic microsurgery on roots exhibiting the presence or absence of dentinal defects at 1-year and 3-year follow-up period. METHODS: One hundred fifty-five teeth were treated with periapical microsurgery using a modern microsurgical protocol in a private practice setting. The root apices were resected and inspected for dentinal defects with a surgical operating microscope and a 0.8-mm head diameter light-emitting diode microscope diagnostic probe light. After inspection, root-end preparations were performed using ultrasonic tips, and root-end fillings were placed. Follow-up visits occurred at 1 year and 3 years postoperatively. The primary outcome measure used was the change in the radiographic apical bone density, and the secondary outcome measure used was the absence of clinical symptoms. RESULTS: Of the 155 treated teeth, a total of 134 teeth were assessed at the 1-year follow-up and 127 teeth at the 3-year evaluation. In the "intact" group, 94.8% healed at 1 year, and 97.3% healed at 3 years. In the "dentinal defect" group, 29.8% healed at 1 year, and 31.5% healed at 3 years. The baseline root condition of either "dentinal defect" or "intact" showed a statistical difference in the healing outcome at both 1 and 3 years. CONCLUSIONS: This prospective periapical microsurgery study showed a significant superior clinical outcome for intact roots when compared with roots with dentinal defects at both 1 year and at 3 years postoperatively.

Removal of filling materials from oval-shaped canals using laser irradiation: a micro-computed tomographic study.

INTRODUCTION: The aim of this study was to assess the efficacy of lasers in removing filling remnants from oval-shaped canals after retreatment procedures with rotary instruments using micro-computed tomographic imaging. METHODS: The root canals of 42 mandibular canines were prepared and obturated using the warm vertical compaction technique. Retreatment was performed with rotary instruments, and the specimens were distributed in 3 groups (n = 14) according to the laser device used in a later stage of retreatment procedure: Er:YAG, Er:YAG laser-based photon-induced photoacoustic streaming, and Nd:YAG. The specimens were scanned in a micro-computed tomographic device after root canal filling and each stage of retreatment at a resolution of 13.68 µm. The percentage differences of the remaining filling material before and after laser application within and between groups were statistically compared using the paired sample t test and 1-way analysis of variance test, respectively. Significance level was set at 5%. RESULTS: Overall, filling residues were located mainly in the apical third and into canal irregularities after the retreatment procedures. After using rotary instruments, the mean percentage volume of the filling remnants ranged from 13%-16%, with no statistical significant difference between groups (P > .05). Within groups, additional laser application had a significant reduction in the amount of the remaining filling materials (P < .05). A comparison between groups showed that Er:YAG laser application after the use of rotary instruments had a significantly higher removal of filling remnants (~13%) than Er:YAG laser-based photon-induced photoacoustic streaming (~4%) and Nd:YAG (~3%) (P < .05). CONCLUSIONS: None of the retreatment procedures completely removed the filling materials. The additional use of lasers improved the removal of filling material after the retreatment procedure with rotary instruments.

Dentinal crack formation during root canal preparations by the twisted file adaptive, ProTaper Next, ProTaper Universal, and WaveOne instruments.

INTRODUCTION: The aim of this study was to compare the incidence of root cracks after root canal instrumentation with the TF Adaptive, WaveOne, ProTaper Next, and ProTaper Universal systems. METHODS: Seventy-five extracted mandibular central incisors with mature apices and straight root canals (<5°) were selected and kept in distilled water. The root canals were instrumented by using the ProTaper Universal, ProTaper Next, WaveOne, and TF Adaptive systems. All the roots were horizontally sectioned 3, 6, and 9 mm from the apex with a low-speed saw under water cooling. The slices were then viewed through a stereomicroscope at ×25 magnification. The samples were photographed with a camera to determine the presence of dentinal cracks. RESULTS: The control group had no cracks, and the difference between the control group and the experimental groups was statistically significant (P < .001). The ProTaper Next and TF Adaptive systems produced significantly less cracks than the ProTaper Universal and WaveOne systems in the apical section (3 mm) (P < .05). CONCLUSIONS: Under the study conditions and within the limitations of this study, it can be concluded that the ProTaper Universal, ProTaper Next, WaveOne, and TF Adaptive instruments can result in dentinal cracks.

Effect of the size of the apical enlargement with rotary instruments, single-cone filling, post space preparation with drills, fiber post removal, and root canal filling removal on apical crack initiation and propagation.

INTRODUCTION: The purpose of this study was to investigate the incidence of apical crack initiation and propagation in root dentin after several endodontic procedures. METHODS: Sixty intact mandibular premolars were sectioned perpendicular to the long axis at 1 mm from the apex, and the apical surface was polished. Thirty teeth were left unprepared and served as a control, and the remaining 30 teeth were instrumented with ProTaper Universal instruments (Dentsply Maillefer, Ballaigues, Switzerland) up to size F5. The root canals were filled with the single-cone technique. Gutta-percha was removed with drills of the Rebilda post system (VOCO, Cuxhaven, Germany). Glass fiber-reinforced composite fiber posts were cemented using a dual-cure resin cement. The fiber posts were removed with a drill of the post system. Retreatment was completed after the removal of the gutta-percha. Crack initiation and propagation in the apical surfaces of the samples were examined with a stereomicroscope after each procedure. The absence/presence of cracks was recorded. Logistic regression was performed to analyze statistically the incidence of crack initiation and propagation with each procedure. RESULTS: The initiation of the first crack and crack propagation was associated with F2 and F4 instruments, respectively. The logistic regression analysis revealed that instrumentation and F2 instrument significantly affected apical crack initiation (P < .001). Post space preparation had a significant effect on crack propagation (P = .0004). The other procedures had no significant effects on crack initiation and propagation (P > .05). CONCLUSIONS: Rotary nickel-titanium instrumentation had a significant effect on apical crack initiation, and post space preparation with drills had a significant impact on crack propagation.

Dental wear: a scanning electron microscope study.

Dental wear can be differentiated into different types on the basis of morphological and etiological factors. The present research was carried out on twelve extracted human teeth with dental wear (three teeth showing each type of wear: erosion, attrition, abrasion, and abfraction) studied by scanning electron microscopy (SEM). The study aimed, through analysis of the macro- and micromorphological features of the lesions (considering the enamel, dentin, enamel prisms, dentinal tubules, and pulp), to clarify the different clinical and diagnostic presentations of dental wear and their possible significance. Our results, which confirm current knowledge, provide a complete overview of the distinctive morphology of each lesion type. It is important to identify the type of dental wear lesion in order to recognize the contributing etiological factors and, consequently, identify other more complex, nondental disorders (such as gastroesophageal reflux, eating disorders). It is clear that each type of lesion has a specific morphology and mechanism, and further clinical studies are needed to clarify the etiological processes, particularly those underlying the onset of abfraction.