Dentin Area Research Articles

Effects of Nd:YAG Laser Irradiation on Root Canal Dentin Wall: A Scanning Electron Microscopic Study

The purpose of this study was to evaluate, by scanning electron microscopy (SEM), the effects of Nd:YAG laser irradiation applied perpendicular or parallel to the root canal dentin wall. Thirty human teeth were divided into two groups: Group A (20 roots), laser application with circular movements, parallel to the dentin root surface; and Group B (10 roots), roots cut longitudinally and laser applied perpendicular to the root surface. Group A was subdivided into A1 (10 roots), laser application with 100 mJ, 15 Hz and 1.5 W; and A2 (10 roots) with 160 mJ, 15 Hz, and 2.4 W. Group B was subdivided into B1 (10 hemisections) and B2 (10 hemi-sections) with parameters similar to A1 and A2. Four applications of 7-sec duration were performed, with a total exposure of 28 sec. SEM evaluations were made in the cervical, middle, and apical thirds, with 500x and 2000x magnifications. Morphological changes scores were attributed, and the results were submitted to Kruskal Wallis statistical test (5%). Significant statistical differences were found between groups Aand B (p = 0.001). In groups A1 and A2, few areas of dentin melting were observed. In groups B1 and B2, areas of melting dentin covering dentin surface were observed. It was concluded that intracanal laser application with circular movements (parallel to the surface) produces limited morphological changes in root canal dentin wall.

Effect of temporary cements on the bond strength of ceramic luted to dentin

The purpose of this study was to evaluate the effect of either eugenol-containing or eugenol-free temporary cement removal by excavator or sandblasting on the shear bond strength of ceramic luted to dentin. A self-etching primer system, Panavia F 2.0, Kuraray Medical (PF2), and a total-etch bonding system, Excite/Variolink II, Vivadent (EXV), were used. One hundred and forty human molars, ground to expose dentin surfaces, were divided into 14 groups (seven groups for each adhesive system). For each adhesive system, either a eugenol-containing (Temp bond) or a eugenol-free (Temp bond NE) temporary cement was applied to the dentin surface for 7 days, then removed by an excavator or sandblasting (four groups). Three control groups were studied where fresh dentin was either scratched by excavator or sandblasted, or underwent no surface treatment. After application of the adhesives, ceramic cones (Cerafil inserts) were adhesively luted to standardized dentin areas. After 24 h storage in distilled water, the shear bond strengths were determined at a cross-head speed of 0.75 mm/min. For each adhesive system, neither the method of temporary cement removal nor the type of temporary cement affected the bond strength significantly (P<or=0.05). EXV showed statistically higher bond strengths (26.6-31.6 MPa) than PF2 (8.6-12.9 MPa) within all groups. The use of temporary cements, either containing eugenol or not, does not alter the retentive strength of ceramic restorations luted to dentin using the tested adhesive systems, whether the temporary cements are removed by excavator or sandblasting.

Microhardness of dentine underlying ART restorations in primary molars: an in vivo pilot study

To evaluate the microhardness of dentine underlying glass ionomer restorations made with Atraumatic Restorative Treatment. An experimental single-centre study. University Department, Brazil, 2001. Sixteen children were selected showing primary molars containing carious cavities (n = 29), which were restored using Fugi IX. Subsequently, some teeth were extracted respecting Nolla stage 7 or 8 of the permanent successor, and categorised according to the post-restoration time in the mouth: G1 (baseline, immediate extraction), G2 (30 days), G3 (90 days) and G4 (180 days). Four teeth were excluded because they were not in time of normal exfoliation. The 25 extracted teeth were resin embedded, sectioned mesiodistally and prepared metallographically. Knoop microhardness analysis (Micromet 2003; 10g for 1.5 sec.) produced identations in three areas of dentine: Zone 1 (just below the restoration), Zone 3 (as close as possible to the pulp) and Zone 2 (intermediate region between 1 and 3). Non-parametric statistical tests were done--at a significance level of 5%. Four teeth were excluded. No significant difference was noted among the zones, inside the groups. Zones 1 and 2 showed a considerable increase of microhardness according to the time, except for Group 3 (p > 0.05). Although microhardness had increased, it was not sufficiently equal to the microhardness of the healthy dentine, regardless of the depth evaluated.

Shear Bond Strengths of Two Composite Core Materials After Using All‐in‐One and Single‐Bottle Dentin Adhesives

The purpose of this study was to compare the shear bond strengths of 2 composite core materials after using all-in-one and single-bottle dentin bonding materials. The occlusal surfaces of 100 extracted, intact human third molars were ground to expose a flattened area of dentin and polished with 600-grit silicon carbide paper. Specimens were divided into 5 main groups (n= 20). Three all-in-one (AQ Bond, One-Up Bond, Xeno-CF Bond) and 2 single-bottle adhesives (Single Bond, One-Step Plus) were used. Each group was further divided into 2 subgroups. Ti-Core and Built-it F.R. core materials were applied using a translucent plastic ring (diameter: 3 mm, height: 5 mm). After storage in 37 degrees C water for 24 hours, shear bond strengths were measured using a Universal testing machine with a crosshead speed of 0.5 mm/min. Debonded dentin surfaces were examined with SEM. Two-way analysis of variance (ANOVA) and multiple comparison (Tukey) tests were used for statistical analysis of data. Two-way ANOVA revealed that the type of core material did not significantly influence the shear bond strength (p > 0.05), whereas there were significant differences in shear bond strength among the types of bonding agents (p < 0.0001). Shear bond strengths for single-bottle adhesive systems were significantly higher than those for all-in-one adhesive systems (p < 0.05). Furthermore, the interaction of these 2 parameters was not significant (p > 0.05). The fracture modes were predominantly adhesive for all-in-one adhesives and cohesive for single-bottle adhesives. Bonding of composite core materials with the newly developed all-in-one dentin adhesives produced lower shear bond strengths as compared with single-bottle adhesives.

In vitro evaluation of probiotics microorganisms adhesion to an artificial caries model

This in vitro study compared the adhesion of two probiotics microorganisms (Lactobacillus casei Shirota and Lactobacillus acidophilus) to an artificial caries model. In total, 30 bovine teeth were longitudinally sectioned, excluding the lingual half surface. The specimens were covered with nail varnish, except for an area of 3 by 5 mm in dentin, suspended in an artificial caries solution promoted by Streptococcus mutans, and incubated at 37 degrees C. After 14 days, the specimens were separated equally into two groups and transferred to a brain heart infusion culture media containing L. acidophilus (group A) and L. casei Shirota (group S), at 37 degrees C. After 48 h, the exposed area of dentin was washed with 1 ml of distilled water and the caries dentin was removed and dispersed in 1 ml of saline solution. The samples of distilled water and caries dentin were diluted and inoculated in Rogosa selective Lactobacillus agar. The results in CFU/ml were analysed by the Mann-Whitney test. There was no significant difference between Groups A and S for the lactobacilli count in samples of distilled water (P = 0.237). The amount of L. acidophilus in the artificially caries dentin was significantly superior compared to L. casei Shirota (P = 0.047), suggesting an inferior adhesion potential for this microorganism.

Dental phenotype of the col1a2oim mutation: DI is present in both homozygotes and heterozygotes

Dentinogenesis imperfecta (DI) is a common but variable feature of osteogenesis imperfecta (OI). The Col1a2 oim mutation ( oim) is a well-studied mouse model of chain deficiency OI. Heterozygous oim/+ mice have subtle skeletal fragility, while homozygous oim/ oim mice have marked skeletal fragility. To further define the consequences of oim mutation, we examined teeth by light and scanning electron microscopy (SEM). The dental phenotype in Col1a2 oim ( oim) mice is more severe in incisors than in molars and includes changes in pulp chamber size, tooth shape, and dentin ultrastructure. Teeth in oim/ oim animals are clinically fragile, while oim/+ teeth are grossly normal. Incisor pulp chamber areas (in μm 2) are: upper +/+ = 358 ± 75, lower +/+ = 671 ± 162, upper oim/+ = 161 ± 54, lower oim/+ = 156 ± 19, upper oim/ oim = 6900 ± 1040, and lower oim/ oim = 66 ± 62 ( P < 10 −5). Incisor non-pulp chamber cross-sectional areas (in μm 2), reflecting dentin areas, are: upper +/+ = 39,000 ± 1670, lower +/+ = 35,600 ± 1980, upper oim/+ = 47,500 ± 2510, lower oim/+ = 26,000 ± 1830, upper oim/ oim = 29,800 + 315, and lower oim/ oim = 36,800 ± 3450 ( P < 10 −5). Ultrastructural abnormalities are more pronounced in incisors than in molars and depend on dosage of the mutant allele. These include reduction in the number and regularity of spacing of the dentinal tubules, lesser mineralization, and blurring of the boundary between peritubular and intertubular dentin. Our findings demonstrate that both oim/ oim and oim/+ mice suffer from DI. The more severe incisor phenotype may reflect incisors' continuous growth.

The sealing ability of an epoxy resin root canal sealer after Nd:YAG laser irradiation of the root canal

To evaluate ex vivo the effect of Nd:YAG laser irradiation with and without black ink on instrumented root canal walls, and the degree of both coronal and apical microleakage of filled root canals. Seventy-two single-rooted teeth were instrumented up to a size 40 K-file, and then divided into six groups of 10 teeth: groups 1 and 4 remained unlased and acted as control groups, groups 2 and 5 were treated with a Nd:YAG laser (Fidelis Plus, Herzele, Belgium), groups 3 and 6 were treated with a laser and black ink; the remaining 12 teeth served as positive and negative controls. The laser was operated at 1.5 W, 15 Hz, four times for 5 s with a 20-s interval. Groups 4-6 were filled using cold lateral condensation of gutta-percha and AH26. After storage in water for 48 h at 37 degrees C, through-and-through leakage (L in microL day-1) was measured for 48 h under a pressure of 1.2 atm using a fluid transport model and recorded as L=0 (L1), 0<L<or=10 (L2), L>10 (L3). After the assessment of leakage with the fluid transport model, the teeth were immersed in rhodamine B solution for 48 h at 37 degrees C. Apical and coronal dye leakage was scored after longitudinal splitting of these teeth. All teeth of groups 1-3 were split longitudinally and observed under SEM for evaluation of remaining smear layer. Through-and-through leakage was only observed in the group lased with black ink (two samples-L2). Apical and coronal dye leakage was observed in all groups; there were no statistically significant differences amongst the three experimental groups. The through-and-through leakage, measured with the fluid transport model in two teeth of group 6, was confirmed in the dye leakage test (rhodamine B dye was observed along the total length of the root filling). There was evidence of melted and ablated root canal dentine in the laser-treated groups. These findings were more obvious in root canals lased in association with black ink. All apical foramina in the lased group remained patent. Nd:YAG laser irradiation with black ink increased the amount of melted and ablated dentine areas compared with that without black ink. Nd:YAG lasing in association with black ink did not result in a reduction of either coronal or apical microleakage in root filled teeth.

Variation in hominoid molar enamel thickness

Enamel thickness has figured prominently in discussions of hominid origins for nearly a century, although little is known about its intra-taxon variation. It has been suggested that enamel thickness increases from first to third molars, perhaps due to varying functional demands or developmental constraints, but this has not been tested with appropriate statistical methods. We quantified enamel cap area (c), dentine area (b), and enamel-dentine junction length (e) in coronal planes of sections through the mesial and distal cusps in 57 permanent molars of Pan and 59 of Pongo, and calculated average (c/e) and relative enamel thickness (([c/e]/√b) * 100). Posteriorly increasing or decreasing trends in each variable and average (AET) and relative enamel thickness (RET) were tested among molars in the same row. Differences between maxillary and mandibular analogues and between mesial and distal sections of the same tooth were also examined. In mesial sections of both genera, enamel cap area significantly increased posteriorly, except in Pan maxillary sections. In distal sections of maxillary teeth, trends of decreasing dentine area were significant in both taxa, possibly due to hypocone reduction. Significant increases in AET and RET posteriorly were found in all comparisons, except for AET in Pongo distal maxillary sections. Several significant differences were found between maxillary and mandibular analogues in both taxa. Relative to their mesial counterparts, distal sections showed increased enamel cap area and/or decreased dentine area, and thus increased AET and RET. This study indicates that when AET and RET are calculated from samples of mixed molars, variability is exaggerated due to the lumping of tooth types. To maximize taxonomic discrimination using enamel thickness, tooth type and section plane should be taken into account. Nonetheless, previous findings that African apes have relatively thinner enamel than Pongo is supported for certain molar positions.

Non-rigid connectors in fixed prosthodontics: Current concepts with a case report

The occlusal forces applied to a fixed partial denture (FPD) are transmitted to the supporting structures through the pontic, connectors, and retainers. Variables that may influence the longevity of an FPD and its abutment include occlusion, span length, bone loss, and quality of periodontium. The excessive flexing of the long-span FPD, which varies with the cube of the length of span, can lead to material failure of prosthesis or to an unfavorable response. Biomechanical factors such as overload, leverage, torque and flexing, induce abnormal stress concentration in an FPD. Stress concentration is found in the connectors of the prosthesis and in the cervical dentin area near the edentulous ridge. This factor plays an important role in the potential for failure in long-span FPD. The conventional use of a nonrigid connector (NRC) aids in compensating for the difference in the resistance and retention form between the abutments. The design and passive fit of NRC is critical to the success of a long-span FPD. This paper presents the current concepts in the design of an NRC and a case report of Pier abutment treated with FPD having Tenon-Mortise Connector.

Chemical analysis and surface morphology of enamel and dentin following 9.6μ CO2 laser irradiation versus high speed drilling

The purpose of the present in vitro study was to determine whether there is a change in the chemical composition and surface morphology of enamel and dentin following 9.6mu CO2 laser irradiation and high-speed drilling. Ten permanent, non-carious, young premolars, extracted for orthodontic reasons, were selected. The crowns were separated longitudinally into two equal parts at their mesiodistal axis. Two areas on the inner enamel surface of each specimen and two on the dentinal surface were selected. A high-speed drill and 9.6mu CO2 laser irradiation were applied to the selected enamel and dentinal areas. A random area on the unlased enamel and on the unlased dentin of each specimen served as controls. The morphology of the specimens was evaluated using scanning electron microscopy. Calcium, phosphorus and oxygen levels were measured using an energy dispersive spectrometer. Mineral analysis revealed no significant difference in the mineral content of the enamel and dentin after laser irradiation or high speed drilling versus the control. Use of the high-speed drill on enamel and dentin resulted in very clear cavity margins, with characteristic grooves, whereas laser irradiation of enamel and dentin did not produce clear margins and the floor of the cavity displayed an irregular surface. The 9.6mu CO2 laser appears to be a promising tool in the clinical setting. However, further investigation is indicated to ensure maximum effectiveness.

Effects of protein deficiency induced by raw soy with and without sucrose on dentine formation and dentinal caries in young rats

The effects of protein deficiency and sucrose on formation and mineralization of dentine and dental caries in the molars of young rats were investigated. Two groups of weaning Wistar rats received raw soy flour to induce protein deficiency with sucrose or starch as the carbohydrate source; the other two groups received skim milk powder as the protein source with sucrose or starch as the carbohydrate source. At the onset, tetracycline was injected to mark the dentine formed at that moment. After 6 weeks, lower molars were sectioned sagittally, and the areas of dentine formation and dentinal caries developed during the experiment were quantified separately in the first and second molars. Dental caries was also classified according to Schiff's reaction. Calcium (Ca), phosphorus (P) and total mineral elements were analyzed using an electron probe microanalyzer. Rats in both protein-deficient groups and normal protein sucrose group had significantly larger areas of dentine formed compared with rats fed with normal protein starch diet. Ca, P and total mineral elements in dentine were significantly reduced by normal protein sucrose diet. P content was significantly reduced in dentine of rats in protein-deficient sucrose group. Rats in normal protein sucrose group had significantly more and larger dentinal caries lesions than in any other group. This study suggests that protein deficiency induced by soy prevents the progression of dental caries even in highly cariogenic environment.

A three-year clinical evaluation of two dentin bonding agents

A new restorative called a "giomer composite" has been introduced. The authors conducted a study to determine retention, anatomical form, caries, staining, marginal discoloration, marginal adaptation, surface roughness and sensitivity of giomer compared with those of a microfilled composite. The authors placed 40 sets of restorations randomly in canines and premolars in vivo. They used a giomer composite and a microfilled composite in erosion/abrasion/abfraction Class V lesions that were not altered with rotary instruments. They placed the restorations according to manufacturer's recommendations, and two calibrated examiners evaluated the restorations independently using modified U.S. Public Health Service criteria at baseline and at six, 18 and 36 months. The lesions receiving the restorations did not differ from each other in the amount of circumferential enamel present, the percentage of the surface area of dentin or lesion type. There were no differences in the restorations at baseline, an evaluation made two weeks after placement. At 36 months, the giomer and microfilled composite restorations were not significantly different from one another in any of the eight criteria evaluated. The percentage agreement between examiners was at least 83 percent for each criterion in each evaluation period. Both the giomer and the microfilled composite used in this study meet the clinical portion of the Acceptance Program Guidelines for Dentin and Enamel Adhesives Materials established by the American Dental Association. Both the giomer and the microfilled composite used in this study can be used with confidence in Class V lesions.

Surface debris of canal walls after post space preparation in endodontically treated teeth: a scanning electron microscopic study

Purpose To evaluate surface cleanliness of root canal walls along post space after endodontic treatment using 2 different irrigant regimens, obturation techniques, and post space preparation for adhesive bonding. Study design Forty teeth, divided into 4 groups, were instrumented, using Ni-Ti rotary files, irrigated with NaOCl or NaOCl + EDTA and obturated with cold lateral condensation (CLC) or warm vertical condensation (WVC) of gutta-percha. After post space preparation, etching, and washing procedure, canal walls were observed using a scanning electron microscope (SEM). Amount of debris, smear layer, sealer/gutta-percha remnants, and visibility of open tubules were rated. Results Higher amounts of rough debris, large sealer/gutta-percha remnants, thick smear layer, and no visibility of tubule orifices were recorded in all the groups at apical level of post space. At middle and coronal levels areas of clean dentin, alternating with areas covered by thin smear layer, smaller debris, gutta-percha remnants, and orifices of tubules partially or totally occluded by plugs were frequently observed. Conclusions After endodontic treatment, obturation, and post space preparation SEM analysis of canal walls along post space shows large areas (covered by smear layer, debris, and sealer/gutta-percha remnants) not available for adhesive bonding and resin cementation of fiber posts.

Evaluation of canal preparation with Ni-Ti rotary files by micro computed tomography

The purpose of this study was to compare the effects of preparation with GT files and profiles .04 in shaping of root canals and reconstruct the three-dimensional root canal system using micro computed tomography 40 canals of the extracted human mandibular molars were used, and randomly distributed into two experimental groups. In group 1, canals were prepared by GT files. In group 2, Profiles .04. were used. Apical preparation size was #30. For each tooth pre and post operative cross-sectional images were obtained by the micro CT at 50 micron intervals. Pre and post operative cross-sectional images of 1, 2, 3, 5, and 8mm from the apex were compared. For each section, canal area and centering ratio were determined. For each tooth pre- and post-operative root canal volume from the furcation to the apex of the roots was calculated by three-dimensional image software. Following results were obtained: 1. At 8mm from the apex, area of dentin removed by GT rotary file was significantly larger than that by Profile .04. And at the other levels there was not a significant difference. 2. There was a trend for GT rotary file to remain more centered in the canals than Profile .04 at all levels. But at 3mm level, there was a statistically significant difference. 3. In root canal volume increments after instrumentation, there was no significant difference between two

Association of photoactivation methods and low modulus liners on marginal adaptation of composite restorations

The aim of this study was to evaluate the effect of photoactivation methods, resin liners, and the association of these techniques on the marginal adaptation of composite restorations. One‐hundred‐and‐twenty bovine incisors were selected. A circular cavity was prepared in a flat dentin area on the buccal surface and the Scotchbond Multi Purpose system was applied. These teeth were assigned to four groups in accordance with lining technique: control (one adhesive layer), three adhesive layers individually photoactivated, Filtek Flow, and Protect Liner F. Each group was subdivided depending on the photoactivation method: continuous light, soft‐start, or intermittent light. All cavities were restored with Filtek Z250 and then polished. Caries detector was applied on each specimen for 5 s in order to verify marginal adaptation through dye‐staining of the gaps formed on the outer margins. Images of the stained gaps were observed under the stereomicroscope, and transferred to a computer measurement program in order to determine gap length. Data were submitted to ANOVA and Tukey's test (P < 0.05). Significant differences among the lining techniques were only observed using the photoactivation method with continuous light. In this case, the lining technique with Filtek Flow significantly increased marginal adaptation of the composite to the outer dentin margins compared with the results of the control group. The other lining techniques showed intermediate values and no statistical difference from the other groups. For the photoactivation methods, intermittent light showed the best marginal quality of all the methods. This was statistically significant only for the control lining technique.

Morphological analysis and chemical content of natural dentin carious lesion zones

Dentin is one of the earliest bio-mineralization products to appear in the evolution of vertebrates. Dentin reactions to infection mimic earlier phylogenetic patterns, and carious lesions are divided into different zones which reflect the natural patho-morphological reaction of dentin to the carious attack. It was the aim of this study to investigate deep dentin carious lesions of human molars with combined polarization light microscopy, scanning electron microscopy and energy dispersive X-ray element analysis (EDX) for the determination of different zones of the carious lesions, their extent and the chemical content. Sixteen extracted teeth with deep dentin carious lesions were embedded in Technovit 9100 (Kulzer) and serial sections of 80 microm thickness were made. These sections were then examined with polarized light microscopy to identify the different zones of the lesions. The outlines of the zones were traced consecutively and 3D-reconstructions were made for the determination of the extent and calculation of the volumes of the different zones. From the volumes of the demineralizing dentin and the translucent zone a Dentin Demineralization Index (DDI) was calculated. Three sections of each lesion were then coated with carbon and studied with a scanning electron microscope. 3D-reconstruction of the teeth showed the rather stable translucent zone, interrupted by remnants of dead tracts, and very different volumes of demineralizing dentin. Therefore, with increasing size of the demineralizing dentin, the DDI increased. The chemical content was measured using energy dispersive X-ray analysis (EDX) in areas of intertubular dentin. The content of Ca, P, and C was significantly different in all zones. The Ca/P ratio was significantly different between sound dentin and demineralizing dentin. From the results we conclude that the mineral content of intertubular dentin of the translucent zone and demineralizing dentin is different from that of sound dentin, and the unique mineralization pattern of the translucent zone is a biological reaction to the carious attack. Because active dentin lesions exhibit many non-occluded open dentin tubules, further bacterial invasion or, in case of dentin treatment, the penetration of bonding agents towards the pulp is morphologically not prevented and therefore of clinical importance.

Density of dentinal tubules affects the tensile strength of root dentin

Objectives. The aim of this study is to count the dentinal tubules in the coronal and middle-apical third of root dentin of teeth extracted due to the progression of periodontal disease, and to compare the Ultimate Tensile Strength (UTS) of the same areas. The research hypothesis was that root dentin areas with different densities of dentinal tubules would also show different UTS values. Methods. From 10 caries free maxillary central, lateral incisors and canines, extracted for periodontal reasons from three patients, cylindrical specimens approximately 10 mm long were prepared parallel to the long axis of the root and then divided into two parts using a low speed diamond saw one from the coronal third of the root, (Group 1) and one from the middle-apical third of the root (Group 2). The density of the dentinal tubules of the specimens of the two groups was measured by means of a scanning electron microscope and the UTS of the specimens was measured by a microtensile test. One way ANOVA was used to assess the effect of specimen location (coronal specimens vs. middle-apical specimens) on UTS. The differences in the density of dentinal tubules between coronal and middle-apical specimens were also subjected to statistical analysis using one-way ANOVA. Results. UTS values of middle-apical specimens were found to be significantly ( p<0.05) higher than those of coronal specimens. The results of the one-way analysis of variance showed that the number of dentinal tubules of the samples from the coronal part of the root groups was significantly higher than that of samples from the middle-apical part ( p<0.05). Significance. These results suggest that high values of tensile strength of the dentin are associated with low densities of dentinal tubules and that apical areas of root dentin are more resistant to tension than coronal ones.

Three dimensional reconstruction of teeth using x-ray microtomography

Complete understanding of the exterior and interior structure of the tooth would be prerequisite to the successful clinical results, especially in the restorative and endodontic treatment. Although three-dimensional reconstruction method using x-ray microtomography could not be used in clinical cases, it may be the best way to reconstruct the morphologic characteristics of the tooth structure in detail without destructing the tooth itself. This study was done to three dimensionally reconstruct every teeth in the arch in order to increase the understanding about the endodontic treatment and to promote the effective restorative treatment by upgrading the knowledge of the tooth morphology. After placing tooth between the microfocus x-ray tube and the image intensifier to obtain two-dimensional images of each level. scanning was done under the condition of 80 keV, , 16.8 magnification with the spot size of . Cross-section pixel size of and 48.83 cross-section to cross-section distance were also used. From the results of this study, precise three dimensional reconstructed images of every teeth could be obtained. Furthermore, it was possible to see image that showed interested area only, for example. enamel portion only, pulp and dentin area without enamel structure, pulp only, combination image of enamel and pulp, etc. It was also possible to see transparent image without some part of tooth structure. This image might be used as a guide when restoring and preparing the full and partial crown by showing the positional and morphological relationship between the pulp and the outer tooth structure. Another profit may be related with the fact that it would promote the understanding of the interior structure by making observation of the auto-rotating image of AVI file from the various direction possible.

Odontoblast morphology and dental repair

Objectives. To investigate the changes in morphology and activity of pulp odontoblasts in response to cavity restoration variables and patient factors. Methods. Class V non exposed cavities were prepared in the intact 1st or 2nd premolar teeth of 27 patients, aged between 9 and 17 years-old. Following tooth extraction, the area of reactionary dentine and the area of the odontoblasts were measured using computerised histomorphometry. Results. The cytoplasm to nucleus ratio of the odontoblasts was found to increase beneath cut dentinal tubules, following the secretion of reactionary dentine. However, none of the patient or preparation variables were found to be correlated with changes in the odontoblast cytoplasm to nucleus ratio. Conclusions. Morphological changes in human odontoblasts is directly related to their capacity to repair dentine injuries and provide pulp protection. Changes in odontoblast morphology reflect secretory activity.

PERBEDAAN SHEAR BOND STRENGTH DUA MACAM KOMPOSIT RESIN PADA DENTIN DENGAN DUA BAHAN BONDING YANG BERBEDA

The aim of this in vitro study was to evaluate the shear bond strength of resin composite materials to dentin by using different bonding agents. Forty human premolars were selected for the study, and cylindrical posts of either Spectrum TPH and Charisma were bonded vertically to a standard flat dentinal area, prepared on the buccal surface. A chisel-shaped shearing blade, attached to the crosshead of a universal mechanical testing machine. The shear bond strength to dentin of 10 resin composite-dentin adhesive combinations were measured. The results showed that the bond strength values of dentin bonding agents were not significant (p>0.05). It seems important for clinicians to use the combination of resin composite and dentin bonding agent recommended by the manufacturer.