Victor E. Arana-Chavez

Root Resorptions in Upper First Premolars after Application of Continuous Torque Moment Intra-Individual Study

AbstractMaterial and Method: With the purpose of investigating the occurrence, localization and extension of possible root resorptions after fixed appliance treatment with a continuous torque force, 28 upper first premolars orthodontically indicated for extraction from 14 patients were analyzed by scanning electron microscopy. Tooth movement was carried out with continuous moments of different magnitudes (300 cNmm, and 600 cNmm), using a biomechanical model with superelastic wires (stainless steel-NiTi-SE), which was specially designed and individually calibrated. The teeth were divided into one control group with four premolars (non-moved) from two patients, and two experimental groups (300 cNmm and 600 cNmm respectively) with six patients each. Each group was distributed intra-individually as follows: the right first premolar of six patients was extracted after 1 week of movement, the left first premolars were removed after 2, 3 and 4 weeks. After extraction, teeth were fixed, treated with 2% sodium hypochlorite solution for 6 hours in order to remove the organic tissue components, dehydrated, and metalcoated in a Balzers SCD 050 apparatus. Results: The analysis in a scanning electron microscope (Jeol 6100, at 10–15 kV) revealed many resorption lacunae in the root surface, mainly on the lingual side in the apical third of the roots. Resorption processes were also observed on the buccal root surface in the cervical third. All experimental teeth showed resorption areas. Teeth which had been moved for a longer time period and with a higher magnitude of applied moments showed a higher degree of root resorption in width as well as in depth. Higher magnitude of moments produced exposure of root dentine, evidencing pronounced root resorption.ZusammenfassungMaterial und Methode: 28 erste obere Prämolaren von 14 Patienten, die aus kieferorthopädischen Gründen zur Extraktion vorgesehen waren, wurden rasterelektronenmikroskopisch untersucht, um die Präsenz, die Lage und die Ausdehnung möglicher Wurzelresorptionen während kontinuierlichem Torque zu untersuchen. Das kontinuierliche Moment unterschiedlicher Größe (300 cNmm und 600 cNmm) wurde durchgeführt mit Hilfe einer biomechanischen Apparatur mit superelastischen Drähten (NiTi-SE-Stahl), die individuell entwickelt und kalibriert war. Es erfolgte eine Einteilung der Zähne in eine Kontrollgruppe mit vier Prämolaren (nicht bewegt) von zwei Patienten und zwei experimentelle Gruppen (300 cNmm und 600 cNmm) von jeweils sechs Patienten. Jede Gruppe wurde intraindividuell wie folgt eingeteilt: Die ersten rechten Prämolaren von sechs Patienten wurden, nachdem sie 1 Woche bewegt wurden, extrahiert, die ersten linken Prämolaren wurde jeweils nach 2, 3 und 4 Wochen extrahiert. Nach der Extraktion wurden die Zähne für 6 Stunden in 2% Natriumhypochloritlösung gelegt, um die organischen Teile zu entfernen. Es erfolgte die Trocknung und Metallbeschichtung im Balzers-SCD-050-Gerät. Ergebnisse: Die Untersuchung mit dem Rasterelektronenmikroskop zeigte viele Konkavitäten (Resortionslakunen), die sich hauptsächlich auf der lingualen Fläche des apikalen Wurzeldrittels befanden. Diese fanden sich auch auf der bukkalen Fläche des zervikalen Drittels. Alle bewegten Zähne wiesen resorptive Bereiche auf. Zähne, die über einen längeren Zeitraum mit größeren Momenten bewegt worden waren, zeigten stärkere Resorptionen in Breite und Tiefe. Größere Momente erzeugten eine Freilegung des Dentins und ausgeprägte Wurzelresorptionen.

Effects of ultramorphological changes on adhesion to lased dentin-Scanning electron microscopy and transmission electron microscopy analysis.

Dentin irradiation with erbium lasers has been reported to alter the composite resin bond to this treated surface. There is still a lack of studies reporting the effect of erbium lasers on dentin organic content and elucidating how laser treatment could interfere in the quality of the resin–dentin interface. This study aimed to evaluate the effect of erbium laser irradiation on dentin morphology and microtensile bond strength (μTBS) of an adhesive to dentin. Seventy‐two dentin disks were divided into nine groups (n = 8): G1‐Control (600‐grit SiC paper); Er:YAG groups: G2‐ 250 mJ/4 Hz; G3‐ 200 mJ/4 Hz; G4‐ 180 mJ/10 Hz; G5‐ 160 mJ/10 Hz; Er,Cr:YSGG groups: G6‐ 2 W/20 Hz; G7‐ 2.5 W/20 Hz; G8‐ 3 W/20 Hz; G9‐ 4 W/20 Hz. Specimens were processed for cross‐sectional analysis by scanning electron microscopy (SEM) (n = 3), transmission electron microscopy (TEM) (n = 2), and adhesive interface (n = 3). Forty‐five dentin samples (n = 5) were restored and submitted to μTBS testing. ANOVA (α = 5%) revealed that G1 presented the highest μTBS values and irradiated groups did not differ from each other. TEM micrographs showed a superficial layer of denatured collagen fibrils. For SEM micrographs, it was possible to verify the laser effects extending to dentin subsurface presenting a rough aspect. Cross‐sectional dentin micrographs of this hybridized surface revealed a pattern of modified tags with ringlike structures around it. This in vitro study showed that erbium laser irradiation interacts with the dental hard tissue resulting in a specific morphological pattern of dentin and collagen fibrils that negatively affected the bond strength to composite resin. Microsc. Res. Tech., 2011.

Clastic cells: mineralized tissue resorption in health and disease.

Clastic cells are responsible for mineralized tissue resorption. Bone resorbing cells are called osteoclasts; however, they are able to resorb mineralized dental tissues or calcified cartilage and then they are called odontoclasts and chondroclasts, respectively. They derive from mononuclear precursors of the monocyte-macrophage lineage from hemopoietic tissue, reach target mineralized tissues and degrade them under many different physiologic or pathologic stimuli. Clastic cells play a key role in calcium homeostasis, and participate in skeletal growth, tooth movement, and other physiological and pathological events. They interact tightly with forming cells in bone and dental hard tissues; their unbalance may result in disturbed resorptive activity thus, causing local or systemic diseases.

Root resorptions in upper first premolars after application of continuous intrusive forces

A scanning electron microscopy study of possible root resorptions and their localization after application of continuous forces of different magnitudes was conducted. Twelve upper first premolars, indicated for extraction, were previously intruded with constant forces. The teeth were divided into 3 groups: 1. non-moved control teeth, 2. continuous force application of 50 cN for 4 weeks, 3. continuous force application of 100 cN for 4 weeks. Specially designed NiTi-SE-stainless steel springs were utilized to exert the actual forces. After experimental tooth movement, the extracted teeth were dehydrated, metal-coated and examined by scanning electron microscopy. The intruded teeth showed resorptive areas consisting of lacunae (concavities) in the mineralized root surface. The teeth moved with 50 cN showed in the apical third several, in the medial third few, and in the cervical third no resorptive areas. In the case of the teeth moved with 100 cN, we observed resorptive areas in most of the apical third—including the apex contour—, several in the medial third, and none in the cervical third. In the control group no resorptions were observed. Thus, our results suggest that intrusion of human teeth with continuous forces induces root resorption, depending on the magnitude of force applied.ZusammenfassungEine histologische Studie der möglichen Wurzelresorptionen und ihre Lokalisation bei der Anwendung kontinuierlicher Kräfte unterschiedlicher Größe wurde durchgeführt. Zwölf erste obere Prämolaren, die im Rahmen einer Extraktionstherapie entfernt werden sollten, wurden vorher mit konstanten Kräften intrudiert. Es erfolgte eine Einteilung in drei Gruppen: 1. nichtbewegte Kontrollzähne, 2. kontinuierliche Kraftapplikation mit 50 cN für vier Wochen, 3. kontinuierliche Kraftapplikation von 100 cN für vier Wochen. Zur Anwendung kamen speziell gefertigte NiTi-SE-Stahl-Federn, die die jeweiligen Kräfte ausübten. Die entfernten Zähne wurden nach entsprechender Aufarbeitung metallbeschichtet und in einem Rasterelektronenmikroskop untersucht. Die resorptiven Bereiche zeigten sich in Form von Lakunen (Konkavitäten) im Bereich der mineralisierten Wurzeloberfläche der intrudierten Zähne. Die mit 50 cN bewegten Zähne zeigten im apikalen Drittel mehrere, im medialen Drittel selten und im zervikalen Drittel keine resorptiven Bereiche. Bei den mit 100 cN bewegten Zähnen konnten resorptive Bereiche im überwiegenden Teil des apikalen Drittels-einschließlich der Wurzelspitzenkontur-, im mittleren Drittel nur gelegentlich und im zervikalen Drittel keine resorptiven Bereiche beobachtet werden. Bei der Kontrollgruppe traten keine Resorptionen auf. Eine Intrusion menschlicher Zähne mit kontinuierlichen Kräften verursacht Wurzelresorptionen, die von der angewandten Kraftgröße abhängig sind.

Root resorption on torqued human premolars shown by tartrate-resistant acid phosphatase histochemistry and transmission electron microscopy.

OBJECTIVE To identify clastic cells on the root surfaces of torqued human premolars. MATERIALS AND METHODS A continuous force of 600 cNmm was applied to upper first premolars in patients 13-16 years of age by using a precise biomechanical model with superelastic wires (NiTi-SE). The 28 teeth in 14 patients were divided into five groups (control [nonmoved], and moved for either 1, 2, 3, or 4 weeks) and processed for tartrate-resistant acid phosphatase (TRAP) histochemistry and transmission electron microscopy. RESULTS Mononuclear TRAP-positive cells appeared at 2 weeks, where as large multinucleated TRAP-positive cells were numerous at 3 and 4 weeks. Ultrastructural examination revealed many clastic cells in contact with resorption lacunae. In addition, some cementoblast-like cells appeared secreting new cementum over previously resorbed lacunae. CONCLUSIONS In general, resorption lacunae and the number of clastic cells, which increased with the duration of the applied force, were found on the cementum surface at the pressure areas. Some signs of cementum repair were also noticed, even with the maintenance of the level of the force.

Ultrastructural and immunocytochemical analyses of osteopontin in reactionary and reparative dentine formed after extrusion of upper rat incisors

Reactionary dentine and reparative dentine are two strategies used by the dentine–pulp complex to respond to injury. The reactionary dentine is secreted by original odontoblasts, while the reparative dentine is formed by odontoblast‐like cells. Osteopontin (OPN) is a non‐collagenous protein usually present in the repair of mineralized tissues. It is likely to be present in newly formed dentine but there are no studies attempting to detect it in reactionary and reparative dentine. The aim of the present study was to examine the ultrastructural characteristics, as well as the presence and distribution of OPN in reactionary and reparative dentine by provoking extrusion of the rat incisor. The right upper incisors of 3‐month‐old male rats were extruded 3 mm and then repositioned into their original sockets. At 3, 7, 10, 15, 20, 30 and 60 days after surgery, the incisors were fixed in glutaraldehyde–formaldehyde and then processed for scanning and transmission electron microscopy and for immunocytochemistry for OPN. After extrusive trauma, the dentine–pulp interface showed the presence of reactionary and reparative dentine, which varied in aspect, thickness and related cells. OPN was not detected in the physiological and reactionary dentine, while it was strongly immunoreactive in the matrix that surrounded the entrapped cells of reparative dentine. In addition, original odontoblasts subjacent to the physiological dentine contained OPN in their Golgi region. The present findings showed that reparative dentine shares some structural characteristics with primary bone, especially in relation to its OPN content. The odontoblast‐like cells resemble osteoblasts rather than odontoblasts.

Early alveolar bone regeneration in rats after topical administration of simvastatin

OBJECTIVES The aim of this study was to ultrastructurally examine the influence of simvastatin on bone healing in surgically created defects in rat mandibles. STUDY DESIGN Bone defects 0.8 mm in diameter were created in the buccal aspect of first mandibular molar roots and filled with 2.5% simvastatin gel, while the controls were allowed to heal spontaneously. The rats were humanely killed 7, 9, 11, or 14 days postoperatively, and the specimens were processed for scanning and transmission electron microscopy, as well as for colloidal gold immunolabeling of osteopontin. RESULTS The regenerated alveolar bone in the simvastatin-treated defects presented smaller marrow spaces, and the collagen fibrils were regularly packed exhibiting a lamellar bone aspect. Osteopontin was present through the bone matrix during the wound healing and alveolar bone regeneration. CONCLUSION The present study provides evidence that a single topical application of 2.5% simvastatin gel improves the quality of the new bone and decreases bone resorption.

Immunocytochemical Study of Amelogenin Deposition during the Early Odontogenesis of Molars in Alendronate-treated Newborn Rats

Newborn rats were treated with sodium alendronate to study how enamel is formed and the effect of alendronate during early odontogenesis. Ultrastructural analysis combined with high-resolution immunocytochemistry for amelogenin was carried out. Twelve rats were subjected to daily SC injections of sodium alendronate (2.5 mg/kg/day) for 3 days on their dorsal region, whereas three rats were daily injected with saline solution as a control. Molar tooth germs from 3-day-old rats were fixed under microwave irradiation in 0.1% glutaraldehyde + 4% formaldehyde buffered at pH 7.2 with 0.1 M sodium cacodylate. The specimens were left undecalcified, postfixed with osmium tetroxide, dehydrated, and embedded in LR White resin. Ultrathin sections were incubated with a chicken anti-24-kDa rat amelogenin antibody, a secondary antibody, and finally with a protein A-gold complex. Large patches of amelogenin were present over the unmineralized mantle dentin and at early secretory ameloblasts. At more advanced stages, they were also detected at the enamel matrix, as well as in the mineralized dentin, at the periodontoblastic space of the dentinal tubules, and at the predentin. It is likely that the main effect of alendronate at early stages of odontogenesis is the increase of synthesis/secretion of amelogenin, promoting its deposition within the forming dentin and enamel.

Enoxacin directly inhibits osteoclastogenesis without inducing apoptosis

Background: Enoxacin inhibits vacuolar H+-ATPase binding to microfilaments and bone resorption. Results: Enoxacin inhibits osteoclastogenesis without triggering apoptosis, induces changes in the proteolytic regulation of proteins, and alters the localization of key proteins involved in osteoclast function. Conclusion: Enoxacin inhibits osteoclastogenesis by a mechanism that involves changes in post-translational processing and targeting of proteins. Significance: A new type of direct inhibitor of osteoclasts has been identified. Enoxacin has been identified as a small molecule inhibitor of binding between the B2-subunit of vacuolar H+-ATPase (V-ATPase) and microfilaments. It inhibits bone resorption by calcitriol-stimulated mouse marrow cultures. We hypothesized that enoxacin acts directly and specifically on osteoclasts by disrupting the interaction between plasma membrane-directed V-ATPases, which contain the osteoclast-selective a3-subunit of V-ATPase, and microfilaments. Consistent with this hypothesis, enoxacin dose-dependently reduced the number of multinuclear cells expressing tartrate-resistant acid phosphatase (TRAP) activity produced by RANK-L-stimulated osteoclast precursors. Enoxacin (50 μm) did not induce apoptosis as measured by TUNEL and caspase-3 assays. V-ATPases containing the a3-subunit, but not the “housekeeping” a1-subunit, were isolated bound to actin. Treatment with enoxacin reduced the association of V-ATPase subunits with the detergent-insoluble cytoskeleton. Quantitative PCR revealed that enoxacin triggered significant reductions in several osteoclast-selective mRNAs, but levels of various osteoclast proteins were not reduced, as determined by quantitative immunoblots, even when their mRNA levels were reduced. Immunoblots demonstrated that proteolytic processing of TRAP5b and the cytoskeletal protein l-plastin was altered in cells treated with 50 μm enoxacin. Flow cytometry revealed that enoxacin treatment favored the expression of high levels of DC-STAMP on the surface of osteoclasts. Our data show that enoxacin directly inhibits osteoclast formation without affecting cell viability by a novel mechanism that involves changes in posttranslational processing and trafficking of several proteins with known roles in osteoclast function. We propose that these effects are downstream to blocking the binding interaction between a3-containing V-ATPases and microfilaments.

Bond strength and morphology of enamel using self-etching adhesive systems with different acidities

Objectives: To assess the bond strength and the morphology of enamel after application of self-etching adhesive systems with different acidities. The tested hypothesis was that the performance of the self-etching adhesive systems does not vary for the studied parameters. Material and methods: Composite resin (Filtek Z250) buildups were bonded to untreated (prophylaxis) and treated (burcut or SiC-paper) enamel surfaces of third molars after application of four self-etching and two etch-and-rinse adhesive systems (n=6/condition): Clearfil SE Bond (CSE); OptiBond Solo Plus Self-Etch (OP); AdheSe (AD); Tyrian Self Priming Etching (TY), Adper Scotchbond Multi-Purpose Plus (SBMP) and Adper Single Bond (SB). After storage in water (24 h/37°C), the bonded specimens were sectioned into sticks with 0.8 mm2 cross-sectional area and the microtensile bond strength was tested at a crosshead speed of 0.5 mm/min. The mean bond strength values (MPa) were subjected to two-way ANOVA and Tukeys test (α=0.05). The etching patterns of the adhesive systems were also observed with a scanning electron microscope. Results: The main factor adhesive system was statistically significant (p<0.05). The mean bond strength values (MPa) and standard deviations were: CSE (20.5±3.5), OP (11.3±2.3), AD (11.2±2.8), TY (11.1±3.0), SBMP (21.9±4.0) and SB (24.9±3.0). Different etching patterns were observed for the self-etching primers depending on the enamel treatment and the pH of the adhesive system. Conclusion: Although there is a tendency towards using adhesive systems with simplified application procedures, this may compromise the bonding performance of some systems to enamel, even when the prismless enamel is removed.