Artificial Caries Resistance in Enamel after Topical Fluoride Treatment and 445 nm Laser Irradiation.

OBJECTIVE: This in vitro study is aimed at investigating the caries preventive effectiveness of 445 nm diode laser in combination with topical fluoridation. MATERIALS AND METHODS: A total of 30 caries-free bovine teeth were used in this study. Eighteen teeth were covered with nail varnish except four windows on the labial surface. The windows were assigned to no treatment/control (C), laser (L) (0.3 W, 60 s, and 90 J/cm2), fluoride (F), and fluoride followed by laser (FL) treatment groups. Artificial caries lesions were created, and the teeth were sectioned and investigated under polarized light microscopy for quantitative measurement of the resulted lesion depth. Ten teeth were used for surface temperature measurement and two teeth for scanning electron microscopy (SEM). Extra twelve human molars were used for the intrapulpal temperature measurement. The absorbance of fluoride at 445 nm was measured. RESULTS: The means of lesion depth for the C, L, F, and FL groups were 123.48 (±21.93), 112.33 (±20.42), 99.58 (±30.68), and 89.03 (±30.38) µm, respectively. The pairwise differences of the L, F, and FL groups compared with the C group were significant (p < 0.05). The differences between groups were tested: FL versus L p=0.02, F versus L p=0.16, and FL versus F p=0.91, and the difference of the F versus FL was not significant (p=0.91). Temperature increment at the enamel surface and pulp roof were ∆T = 16.67 (±4.11) and 2.12 (±0.66)°C, respectively. The topical fluoride absorbance at 445 nm is five orders higher than that at 810 nm. SEM shows that after laser irradiation the enamel surface was intact and without thermal damage. CONCLUSIONS: The 445 nm laser irradiation may be useful for caries prevention, and its effectiveness is lower than those previously achieved using the argon ion laser.

The evaluation of the effect of carbon dioxide laser radiation on dentine tissue.

of this study was to analyze the effects of carbon dioxide (CO2) laser light on the structure and elemental composition of dentine. METHODS: The evaluation was conducted on samples from extracted teeth. The surface of the dentine was exposed to the radiation from a CTL 1401 CO2 laser (Centre of Laser Technology, Poland). The radiation and frequency parameters were as follows: group I with 5 W and 1 Hz, group II with 10 W and 1 Hz, group III with 5 W and 5 Hz, and group IV with 10 W and 5 Hz. The altered dentine structure was macroscopically and microscopically evaluated using a Nova NanoSEM 200 Scanning Electron Microscope (FEI Europe) with integrated microanalysis X-ray system for elemental analysis in points. RESULTS: There were significant differences between groups in the macro- and microstructure of laser defects. CONCLUSIONS: CO2 laser radiation causes irreversible, destructive changes in dentine. The structural dentine lesions developed under the influence of the CO2 laser radiation may hinder proper adhesion of bonding systems with the damaged tissue. Laser defects in the structure should be treated like defects of noncarious origin requiring preparation and filling with composite materials in accordance with the procedures.

Effects of cell-mediated osteoprotegerin gene transfer and mesenchymal stem cell applications on orthodontically induced root resorption of rat teeth.

Aim: The aim of this study is to evaluate and compare therapeutic effects of mesenchymal stem cell (MSCs) and osteoprotegerin (OPG) gene transfer applications on inhibition and/or repair of orthodontically induced inflammatory root resorption (OIIRR). Materials and methods: Thirty Wistar rats were divided into four groups as untreated group (negative control), treated with orthodontic appliance group (positive control), MSCs injection group, and OPG transfected MSCs [gene therapy (GT) group]. About 100g of orthodontic force was applied to upper first molar teeth of rats for 14 days. MSCs and transfected MSC injections were performed at 1st, 6th, and 11th days to the MSC and GT group rats. At the end of experiment, upper first molar teeth were prepared for genetical, scanning electron microscopy (SEM), fluorescent microscopy, and haematoxylin eosin-tartrate resistant acid phosphatase staining histological analyses. Number of total cells, number of osteoclastic cells, number of resorption lacunae, resorption area ratio, SEM resorption ratio, OPG, RANKL, Cox-2 gene expression levels at the periodontal ligament (PDL) were calculated. Paired t-test, Kruskal-Wallis, and chi-square tests were performed. Results: Transferred MSCs showed marked fluorescence in PDL. The results revealed that number of osteoclastic cells, resorption lacunae, resorption area ratio, RANKL, and Cox-2 were reduced after single MSC injections significantly (P < 0.05). GT group showed the lowest number of osteoclastic cells (P < 0.01), number of resorption lacunae, resorption area ratio, and highest OPG expression (P < 0.001). Conclusions: Taken together all these results, MSCs and GT showed marked inhibition and/or repair effects on OIIRR during orthodontic treatment on rats.

Evaluation of a novel repetitive gas-enhanced permeation test for restoration leakage determination after thermo-mechanical loading.

OBJECTIVES: To assess leakage of class-I restorations using a gas-enhanced permeation test (GEPT) as compared with conventional SEM or dye analysis. MATERIALS AND METHODS: Pressure differences over time and penetrating water volumes were measured simultaneously in a two-chamber system (GEPT) before and after class I cavity preparation in 30 molars. Ten teeth were restored with a composite restoration without bonding (A1), a composite restoration with bonding (A2) or a ceramic indirect restoration (B). Five intact teeth served as controls (C). Another GEPT measurement was performed and impressions were taken. Teeth were subjected to thermodynamic loading (1 200 000 cycles) and final GEPT measurements and impressions were made. SEM evaluation of the marginal continuity was performed and teeth were subjected to a Fuchsin dye penetration test. Spearman's rank test was used to compare results from different tests. RESULTS: The GEPT and SEM values did not correlate before loading (0.359, p = 0.051), but significantly correlated afterwards (0.662, p < 0.0001). The correlations between the Fuchsin dye penetration test and GEPT and SEM surface marginal analysis were significant (0.777 and 0.534, p-values < 0.0001 and 0.002, respectively). CONCLUSIONS: SEM marginal analysis was mainly limited in reflecting the surface restoration integrity. GEPT evaluation may, therefore, serve as a tool to non-destructively assess restoration sub-surface integrity over time. CLINICAL RELEVANCE: The current study provided proof that restoration margin quality does not necessarily reflect its leakage behaviour.

The appearance of root canal surfaces in teeth previously treated using resorcinol-formaldehyde resin: a preliminary SEM investigation.

OBJECTIVE: To evaluate the root canal surfaces in teeth previously treated using RF resin by SEM. MATERIAL AND METHODS: 20 distal roots of mandibular molars with typical discoloration of tooth crown were used in this study: 10 brownish - red and 10 non-colored roots. The roots were removed from the crowns, splinted longitudinally and subjected to SEM in a back-scattered electron mode. RESULTS: In discolored root samples canal walls appeared without smear layer and varying amount of remaining debris, the observed morphology of dentine was ordinary. In the non-colored root samples the dentin profile revealed: in coronal third of the root just few open dentinal tubules were detected, while in the middle and apical thirds no open dentinal tubules were observed, dentin profile was similar to sclerotic dentin. The multiple dentinal defects were detected in all samples, however significantly more dentinal defects were found in the colored roots. The RF paste was well adhered to the root canal dentine and multiple tags of RF resin penetrating deeply into the dentinal tubules were detected. CONCLUSIONS: The surfaces of the root canal walls of the teeth treated using RF paste exhibits usual appearance and ordinary dentin morphology in colored roots while the dentin of non-colored samples has the profile of sclerotic dentin. Multiple dentinal defects could be determined by damaging effect of RF resin on dentin. The adaptation and adhesion of RF paste to the dentin, capability to penetrate into dentinal tubules is comparable with the modern resin based sealers.

Pit and Fissure Sealant Retention Following Air Abrasion Preparation with Bioactive Glass and Aluminum Oxide Particles.

PURPOSE: Alumina air abrasion is an alternative for acid-etch technique for tooth preparation before placement of a fissure sealant. The aim of this study was to compare the retention of sealants placed subsequent to air abrasion with alumina and bioactive glass (BAG) particles. METHODS: Sixty-two 6-12 year old children were included in this study. Using a halfmouth design, the fissures were prepared using air abrasion with alumina particles on randomly assigned permanent mandibular or/and maxillary first molars on one side of the mouth (Group 1) and air abrasion with BAG on the contralateral side of the mouth (Group 2). Sealants were applied on 180 teeth, and were scored as missing, partially retained, and completely retained after three, six, nine and 12 months. Data were analyzed using Friedman and Wilcoxon tests (α=0.05). RESULTS: Sealant retention rates in the alumina group were higher than those in the BAG group at all time periods (P<0.001). CONCLUSIONS: Sealant retention after air abrasion with alumina particles was higher than BAG over 12 months.

Acción de los agentes blanqueadores sobre materiales de restauración / Action of bleaching agents on restorative materials

El propósito del trabajo será analizar comparativamente los diversos efectos que producen sobre las restauraciones dentales agentes blanqueadores.El objetivo será valorar los cambios que experimentan en la superficie los materiales de restauración, sometidos a la acción de un agente blanqueador. La metodología utilizada será visualización microscópica electrónica de barrido ambiental. Los resultados obtenidos tendrán transferencia relevante a Insti-tuciones formadoras de recursos humanos en Salud Bucal, al campo profesional odontológico y a empresas o fabricantes para el mejoramiento de su producto...

Effect of super short pulse Er:YAG laser on human dentin--Scanning electron microscopy analysis.

This study evaluated the effect of different pulse widths in the morphological characteristics of human dentin irradiated with Er:YAG in cavity preparation protocols and dentin pretreatment. Dentin discs with 2 mm thickness were obtained from 18 human molars. The experimental groups were composed from two variables: (1) clinical protocol-cavity preparation (E = 200 mJ/20 Hz)-and pretreatment (E = 80 mJ/2 Hz); and (2) pulse duration-50, 300, and 600 µs. This formed six experimental groups (n = 3): G1 (E = 200 mJ/20 Hz/50 µs); G2 (E = 200 mJ/20 Hz/300 µs); G3 (E = 200 mJ/20 Hz/600 µs); G4 (E = 80 mJ/2 Hz/50 µs); G5 (E = 80 mJ/2 Hz/300 µs); G6 (E = 80 mJ/2 Hz/600 µs). The samples were irradiated with the Er:YAG laser by noncontact mode at a focal distance of 7 mm from the target point under continuous water spray (60% water and 40% air). After the irradiation, they were processed for scanning electron microscopy (SEM). Morphological analysis showed an irregular dentin surface, absence of smear layer with opening of the exposure of dentinal tubules and protruding peritubular dentin-without indications of changes for all protocols used. Regardless of the analyzed experimental group, the dentin surface showed a microretentive morphology characteristic of ablation. The G1 and G4 showed a rougher surface when compared to other groups. Finally, we concluded that the pulse width can influence the morphological characteristics of the irradiated dentin tested in different clinical indications. The larger surface irregularity caused by regulation with less pulse width (50 µs) seems more appropriate to get a microretentive pattern necessary for successful adhesives restoration procedures.

Microscopic analysis of molar--incisor malformation.

OBJECTIVE: Molar-incisor malformation (MIM) is a newly discovered type of dental anomaly that involves a characteristic root malformation of the permanent first molars. The aim of this study was to reveal the microstructure of MIM teeth in order to determine their origin. STUDY DESIGN: Four MIM teeth were extracted from a 9-year-old girl due to severe mobility. The detailed microstructure of the teeth was determined by examinations with micro-computed tomography (micro-CT), hematoxylin and eosin (H&E) staining, immunohistochemical staining, and scanning electron microscopy to reveal the detailed microstructure. RESULTS: Micro-CT and H&E staining revealed the pulpal floor comprising three layers: upper, middle, and lower. Amorphous hard tissues and hyperactive cells were observed in the middle layer of the pulpal floor, and the cells stained positively for dentin sialoprotein and osteocalcin, but not for collagen XII. CONCLUSION: The results of the present study imply that MIM-affected molars probably result from inappropriate differentiation of the apical pulp and dental follicle.

Ultrastructure of the surface of dental enamel with molar incisor hypomineralization (MIH) with and without acid etching / Ultraestructura de la superficie del esmalte dental con hipomineralización molar incisiva (mih) con y sin grabado ácido

El objetivo del presente trabajo fue analizar la ultraestructura y composición mineral de la superficie del esmalte de un molar con MIH, con y sin tratamiento de grabado ácido. Se analizaron una pieza dentaria permanente sin lesiones clínicas de MIH (controles) y una pieza con diagnóstico clínico de MIH leve y moderada, con indicación de extracción con y sin grabado acido (H3PO4 37 por ciento, 20”). Fueron procesadas para su observación con microscopio electrónico de barrido (SEM) ZEISS (Supra 40) y análisis de la composición mineral con detector EDS (Oxford Instruments). El esmalte del control mostró superficie prismática y patrón de grabado normales. El esmalte clínicamente sano en la pieza con MIH reveló una pérdida parcial del patrón prismático. La lesión leve se presentó porosa con ocasional esgrietas. La moderada presentó mayor porosidad, con grietas de mayor tamaño y presencia de gran cantidad de escamas. La composición mineral de las superficies afectadas mostró menor contenido de Ca y P y aumento de O y C. En la muestra con MIH, inclusive con aspecto normal, las desmineralizaciones no responden a un patrón de grabado, mostrando exposición de cristales con redondeamiento en los extremos de las varillas y menor desmineralización en los espacios interprismáticos. El grabado ácido incrementó la aparición de grietas y profundos poros en la estructura adamantina del esmalte con lesión. La composición mineral mostró en las lesiones moderadas una mayor disminución del contenido de Ca, P y Cl.El esmalte con MIH, inclusive en la superficie adamantina clínicamente intacta, presenta severas alteraciones ultraestructurales y cambios en la composición iónica afectando el patrónde grabado ácido, que podría interferir con los mecanismos de adhesión.

The aim of the present work was to analyze the ultrastructure and mineral composition of the surface of the enamel on amolar with MIH, with and without acid etching. A permanent tooth without clinical MIH lesions (control) and a tooth with clinical diagnosis of mild and moderate MIH, with indication for extraction, were processed with and without acid etching(H3PO437%, 20”) for observation with scanning electron microscope (SEM) ZEISS (Supra 40) and mineral composition analysis with an EDS detector (Oxford Instruments). The control enamel showed normal prismatic surface and etching pattern. The clinically health y enamel on the tooth with MIH revealed partial loss of prismatic pattern. The mild lesion wasporous with occasional cracks. The moderate lesion was moreporous, with larger cracks and many scales. The mineral composition of the affected surfaces had lower Ca and Pcontent and higher O and C. On the tooth with MIH, even on normal looking enamel, the demineralization does not correspond to an etching pattern, and exhibits exposure of crystals with rods with rounded ends and less demineralization in the inter-prismatic spaces. Acid etching increased the presence of cracks and deep pores in the adamantine structure of the enamel with lesion. In moderate lesions, the mineral composition had higher content of Ca, P and Cl. Enamel with MIH, even on clinically intact adamantine surfaces, shows severe alterations in the ultrastructure and changes in ionic composition, which affect the acid etching pattern and may interfere with adhesion.

Radiation therapy alters microhardness and microstructure of enamel and dentin of permanent human teeth.

OBJECTIVES: To evaluate, in vitro, the effects of ionizing radiation on the mechanical and micro-morphological properties of enamel and dentin of permanent teeth. METHODS: Enamel and dentin microhardness (n=12 hemi-sections) was evaluated at three depths (superficial, middle and deep) prior to (control) and after every 10Gy radiation dose up to a cumulative dose of 60Gy by means of longitudinal microhardness. Data were analyzed using two-way analysis of variance and Tukey's test at a significance level of 5%. Enamel and dentin morphology was assessed by scanning electron microscopy (SEM) for semi-quantitative analysis (n=8 hemi-sections). Data were analyzed using Kruskal-Wallis and Dunn's or Fisher exact tests at a significance level of 5%. RESULTS: The application of ionizing radiation did not change the overall enamel microhardness, although an increase in superficial enamel microhardness was observed. The micro-morphological analysis of enamel revealed that irradiation did not influence rod structure but interprismatic structure became more evident. Dentin microhardness decreased after 10, 20, 30, 50 and 60Gy cumulative doses (p<0.05) compared with non-irradiated dentin, mainly in the middle portion of the tissue. The micro-morphological analysis revealed fissures in the dentin structure, obliterated dentinal tubules and fragmentation of collagen fibers after 30 and 60Gy cumulative doses. CONCLUSIONS: Although ionizing radiation did not affect the enamel microhardness of permanent teeth as a whole, an increase in superficial enamel microhardness was observed. Dentin microhardness decreased after almost all radiation doses compared with the control, with the greatest reduction of microhardness in the middle depth region. The morphological alterations on enamel and dentin structures increased with the increase of the radiation dose, with a more evident interprismatic portion, presence of fissures and obliterated dentinal tubules, and progressive fragmentation of the collagen fibers. CLINICAL SIGNIFICANCE: This study shows that irradiation affects microhardness and micro-morphology of enamel and dentin of permanent teeth. The effects of gamma irradiation on dental substrate might contribute to increased risk of radiation tooth decay associated with salivary changes, microbiota shift and high soft and carbohydrate-rich food intake.

The distribution and ultrastructure of the forming blood capillaries and the effect of apoptosis on vascularization in mouse embryonic molar mesenchyme.

Vascularization is essential for organ and tissue development. Teeth develop through interactions between epithelium and mesenchyme. The developing capillaries in the enamel organ, the dental epithelial structure, occur simultaneously by mechanisms of vasculogenesis and angiogenesis at the onset of dentinogenesis. The vascular neoformation in the dental mesenchyme has been reported to start from the cap stage. However, the mechanisms of vascularization in the dental mesenchyme remain unknown. In the hope of understanding the mechanisms of the formation of dental mesenchymal vasculature, mouse lower molar germs from embryonic day (E) 13.5 to E16.5 were processed for immunostaining of CD31 and CD34, terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling (TUNEL) and transmission electron microscopy (TEM). In addition, the role of apoptosis for the vascularization in dental mesenchyme was examined by in vitro culture of E14.0 lower molars in the presence of the apoptosis inhibitor (z-VAD-fmk) and a subsequent subrenal culture. Our results showed that CD31- and CD34-positive cells progressively entered the central part of the dental papilla from the peridental mesenchyme. For TEM, angioblasts, young capillaries with thick endothelium and endothelial cells containing vacuoles were observed in peripheral dental mesenchyme, suggesting vasculogenesis was taking place. The presence of lateral sprouting, cytoplasmic filopodia and transluminal bridges in the dental papilla suggested angiogenesis was also occurring. Inhibition of apoptosis delayed the angiogenic vascularization of the dental papilla. Therefore, these data demonstrated that molar mesenchyme is progressively vascularized by mechanisms of both vasculogenesis and angiogenesis and apoptosis partially contributes to the vascularization of the dental papilla.

Effect of caries removal techniques on the bond strength of adhesives to caries-affected primary dentin in vitro.

AIM: The aim of this in vitro study is to evaluate the effects of three different caries removal techniques on the microtensile bond strength of adhesive materials to caries-affected dentin. MATERIALS AND METHODS: Thirty primary molar teeth were used. The teeth were randomly divided into three groups according to the caries removal technique employed: conventional steel bur (group 1); Er:YAG laser (group 2); chemomechanical method (group 3). Each group was divided into two subgroups according to bonding agents: one-step self-etch adhesive and etch-and-rinse adhesive. The teeth were restored with composite resin. Vertical sticks were obtained and subjected to tensile stress. Data were analyzed by two-way analysis of variance (ANOVA), Tukey's test and an independent samples t-test. RESULTS: The values for the laser groups were significantly lower than those of the bur groups for both bonding agents (p<0.05). There were no significant differences between the bur and chemomechanical groups (p > 0.05). CONCLUSION: Bur and chemomechanical techniques in primary teeth were found more successful. Similar results were found according to the adhesives used for each caries removal techniques.

Temperature changes in the pulpal chamber and the sealing performance of various methods of direct pulp capping of primary teeth.

AIM: To compare changes in pulpal chamber temperature during the visible-light curing of direct pulp capping compounds and various modes of diode laser irradiation without prior placement of a pulp capping compound and the resultant seals. MATERIALS AND METHODS: Pulp exposure holes were made in 100 extracted human primary first molars, which were randomly assigned to ten equal groups. The holes were sealed by (a= Group 1, 2, 3, 4, 5, 6 and 7) different pulp capping compounds which were cured using various types of visible-light curing units or (b=Group 8, 9 and 10) diode laser irradiation without prior application of a pulp capping compound. Pulpal chamber temperatures were recorded during the procedure, and the resultant seals were examined under a scanning electron microscope. RESULTS: Visible-light curing of the pulp capping compounds and diode laser irradiation at a 0.7 W output power can cause non-injurious temperature rises in the pulpal chamber. At higher output powers of the diode laser, the temperature rises are sufficient to cause thermal injury. The seals were complete when pulp capping compounds were used for direct pulp capping, but were incomplete when laser irradiation without prior placement of a pulp capping compound was used for the identical purpose. CONCLUSION: The visible-light curing of pulp capping compounds is not harmful to vital pulp, and provides an effective seal of the pulp exposure hole. Laser irradiation is not an effective sealant, and can cause thermal injury to vital pulp at high output powers.

Ameloblastin modulates osteoclastogenesis through the integrin/ERK pathway.

Proteins of the extracellular matrix often have multiple functions to facilitate complex tasks ranging from signaling to structural support. Here we have focused on the function of one of the matrix proteins expressed in bones and teeth, the matrix adhesion protein ameloblastin (AMBN). Transgenic mice with 5-fold elevated AMBN levels in mandibles suffered from root cementum resorption, delamination, and reduced alveolar bone thickness. AMBN gain of function also resulted in a significant reduction in trabecular bone volume and bone mass dentistry in 42 days postnatal mouse jaws. In an in vitro model of osteoclastogenesis, AMBN modulated osteoclast differentiation from bone marrow derived monocytes (BMMCs), and dramatically increased osteoclast numbers and resorption pits. Furthermore, AMBN more than doubled BMMC adhesion, accelerated cell spreading, and promoted podosome belt and actin ring formation. These effects were associated with elevated ERK1/2 and AKT phosphorylation as well as higher expression of osteoclast activation related genes. Blocking integrin α2ß1 and ERK 1/2 pathways alleviated the effects of AMBN on osteoclast differentiation. Together, our data indicate that AMBN increases osteoclast number and differentiation as well as mineralized tissue resorption by regulating cell adhesion and actin cytoskeleton polymerization, initiating integrin-dependent extracellular matrix signaling cascades and enhancing osteoclastogenesis.

Comparison of influence of different manufacturing methods on the cleaning efficiency of rotary nickel-titanium files.

The purpose of this study was to evaluate and compare cleaning effectiveness of TwistedFile, GT series X, Revo-S, RaCe, Mtwo, and ProTaper Universal rotary files in curved canals. Seventy mesiobuccal canals of extracted human first maxillary molars were divided into seven groups of 10 samples each. Canals were prepared with six nickel-titanium (NiTi) rotary systems and manual K-Flexofile. Irrigation was performed with 2 mL 2.5% NaOCl solution after each file, and 5 mL 2.5% NaOCl was used for the final flush. After the roots were split longitudinally, the presence of debris and smear layer was visualized using scanning electron microscopic photomicrographs taken at coronal, middle, and apical third. Mean scores for debris and the smear layer were calculated and statistically analyzed for significance between groups using the Kruskal-Wallis nonparametric analysis of variance (P < 0.05) and Mann-Whitney U test (P < 0.001). There was no significant difference among the groups in terms of debris and smear layer scores (P > 0.05). Without considering the preparation method used, while no statistically significant difference was found between the coronal third and the middle third (P > 0.05), higher amount of debris and smear layer were found in apical third (P = 0.001). The new generation of NiTi rotary files including the Twisted File and GT Series X presented similar cleaning effectiveness compared with traditionally ground NiTi rotary files.

Deficiency in acellular cementum and periodontal attachment in bsp null mice.

Bone sialoprotein (BSP) is an extracellular matrix protein found in mineralized tissues of the skeleton and dentition. BSP is multifunctional, affecting cell attachment and signaling through an RGD integrin-binding region, and acting as a positive regulator for mineral precipitation by nucleating hydroxyapatite crystals. BSP is present in cementum, the hard tissue covering the tooth root that anchors periodontal ligament (PDL) attachment. To test our hypothesis that BSP plays an important role in cementogenesis, we analyzed tooth development in a Bsp null ((-/-)) mouse model. Developmental analysis by histology, histochemistry, and SEM revealed a significant reduction in acellular cementum formation on Bsp (-/-) mouse molar and incisor roots, and the cementum deposited appeared hypomineralized. Structural defects in cementum-PDL interfaces in Bsp (-/-) mice caused PDL detachment, likely contributing to the high incidence of incisor malocclusion. Loss of BSP caused progressively disorganized PDL and significantly increased epithelial down-growth with aging. Bsp (-/-) mice displayed extensive root and alveolar bone resorption, mediated by increased RANKL and the presence of osteoclasts. Results collected here suggest that BSP plays a non-redundant role in acellular cementum formation, likely involved in initiating mineralization on the root surface. Through its importance to cementum integrity, BSP is essential for periodontal function.

[Enamel structure of atypically formed human teeth].

Using light and scanning electron microscopy thin epoxide processed sections of 12 impacted third molars, one molar developed in odontogenic follicular cyst and one tooth-like teratoma were studied. It was established that the 4 impacted teeth and the tooth developed in odontogenic follicular cyst had obvious signs of enamel damage in the form of erosion in the crown fissures. The features of enamel alteration make it possible to interpret the changes as carious process which apparently has endogenous origin. Tooth-like teratoma extracted from ovarian dermoid cyst looked like canine and incisor "hybrid" coronal portion of which is covered with thin enamel layer, marked by obvious signs of multiple erosive lesions of endogenous nature. But unlike alterations in impacted teeth it resembles either fluorosis or enamel hypoplasia.

Changes in centring and shaping ability using three nickel­titanium instrumentation techniques analysed by micro-computed tomography (µCT).

AIM: To compare the centring ability and the shaping ability of ProTaper (PT) files used in reciprocating motion and PT and Twisted Files (TF) used in continuous rotary motion, and to compare the volume changes obtained with the different instrumentation techniques using micro-computed tomography. Methodology Sixty mesial canals of thirty mandibular molars were randomly assigned to three instrumentation techniques: group 1, canals prepared with the PT series (up to F2) (n = 20); group 2, canals prepared with the F2 PT in reciprocating motion (n = 20); group 3 canals prepared with the TF series (size 25) (n = 20). Teeth were scanned pre- and postoperatively using micro-computed tomography to measure volume and shaping changes, and the obtained results were statistically analysed using parametric tests. Results The increase in canal volume obtained with the three instrumentation techniques was not significantly different. Canals were transported mostly towards the mesial aspect in the apical- and mid-third of the roots, and towards the furcal aspect coronally. No difference in the transportation and centring ratio was found between the techniques. There was no significant difference between the times of instrumentation (TF: 62.5 ± 5.4 s; PT: 60.6 ± 3.9 s; and F2 PT file in reciprocating motion: 51.0 ± 3.3 s). Conclusions ProTaper files used in reciprocating motion and PT and TF used in continuous rotary motion were capable of producing centred preparations with no substantial procedural errors.

Influence of effective number of pulses on the morphological structure of teeth and bovine femur after femtosecond laser ablation.

Femtosecond lasers have been widely used in laser surgery as an instrument for contact-free tissue removal of hard dental, restorative materials, and osseous tissues, complementing conventional drilling or cutting tools. In order to obtain a laser system that provides an ablation efficiency comparable to mechanical instruments, the laser pulse rate must be maximal without causing thermal damage. The aim of this study was to compare the different morphological characteristics of the hard tissue after exposure to lasers operating in the femtosecond pulse regime. Two different kinds of samples were irradiated: dentin from human extracted teeth and bovine femur samples. Different procedures were applied, while paying special care to preserving the structures. The incubation factor S was calculated to be 0.788±0.004 for the bovine femur bone. These results indicate that the incubation effect is still substantial during the femtosecond laser ablation of hard tissues. The plasma-induced ablation has reduced side effects, i.e., we observe less thermal and mechanical damage when using a superficial femtosecond laser irradiation close to the threshold conditions. In the femtosecond regime, the morphology characteristics of the cavity were strongly influenced by the change of the effective number of pulses.