Long Axis Of Tooth Research Articles

A comparative study evaluates the effect of Hydrogen peroxide 38% and Carbamide peroxide 35% bleaching products on enamel microhardness (In vitro study)

The aim of this study was to compare the effect of two professional bleachingproducts (in-office Opalescence Boost hydrogen peroxide 38%) and (home bleachingOpalescence carbamide peroxide 35%) on enamel microhardness.The sample consist of thirty maxillary first premolars teeth (freshly extracted),caries free obtained from children aged 12 years old under routine orthodontictreatment. The teeth were sectioned mesiodistally parallel to the long axis of tooth andmounted on acrylic mold. The specimens were divided into two halves buccal andpalatal as per treatment, the buccal half served as experimental, while the palatal halfserved as control (1) and kept in artificial saliva at 37c0 for two weeks. Microhardnesstest were obtained before and after bleaching.Results indicated that teeth specimens submitted to Opalescence carbamideperoxide 35% showed highly significant reduction in enamel microhardness P<0.01,while no-significant difference in enamel microhardness in specimens submitted toOpalescence Boost 38% hydrogen peroxide P>0.05.In this study Opalescence carbamide peroxide 35% leads to the significantdecrease in enamel microhardness compared to Opalescence Boost hydrogenperoxide 38%.

Comparative Evaluation of Fracture Strength of Different Types of Composite Core Build-up Materials: Anin vitroStudy

The aim of the study was to evaluate the fracture strength of three types of composite core build-up materials. The objectives were to study and evaluate the fracture strength and type of fracture in composite core build-up in restoration of endodonti-cally treated teeth with or without a prefabricated metallic post. A total of 60 freshly extracted mandibular premolars free of caries, cracks, or fractures were end-odontically treated and restored with composite core build-up with prefabricated metallic posts cemented with resin luting cement (group I) and without a post (group II). This was followed by a core build-up of 10 teeth each with three different types of composite materials: Hybrid composite, nanocomposite, and ormocer respectively. The samples were mounted on polyvinyl chloride block and then loaded in the universal load frame at 90° to the long axis of tooth. The fracture strength of the samples was directly obtained from the load indicator attached to the universal load frame. Analysis of variance (ANOVA) test revealed that teeth restored with post exhibited highest fracture strength (1552.32 N) and teeth restored without post exhibited lowest fracture strength (232.20 N). Bonferroni's test revealed that values for hybrid composite (Z-100, 3M ESPE) with post, nanocomposite (Z-350, 3M ESPE) with post, ormocer composite (Admira-VOCO) with post, and nanocomposite (Z-350, 3M ESPE) without post were not significantly different from each other. Teeth restored with post and core using hybrid composite yielded the highest values for fracture strength. Teeth restored with ormocer core without post exhibited the lowest values. Teeth restored with nanocomposite core without post exhibited strength that was comparable with hybrid composite core but higher than that of ormocer. Mutilated endodontically treated teeth can be prosthetically rehabilitated successfully by using adhesive composite core build-up along with post to meet anatomical, functional, and esthetic demands.

DENTIN BOND EFFICACY OF COMPOSITE RESIN RESTORATIONS USING RESIN INFILTRANT

Aim: To evaluate the bond efficacy of direct resin composite restorations bonded by three different dentin adhesives an etch-and-rinse, self-etch and resin infiltrant (ICON) using microtensile bond strength testing and Analyze their failure mode. Methodology: Thirty molar teeth were selected and thoroughly cleaned. Each tooth was vertically embedded into self-curing acrylic resin up to the level of the cervical line. The occlusal enamel of teeth was removed perpendicular to the long axis of teeth to expose flat dentin surface at a standardized depth. The teeth were divided into three main groups of 10 teeth each; using Etch and rinse adhesive system control group A1 (All-bond Universal, Bisco), self-etch adhesive system group A2 (All-bond Universal, Bisco) and resin infiltrant group A3 (Icon). Direct resin composite nano-hybrid universal composite (FiltekTM Z250 XT, 3M ESPE) cores were build up on the flat dentin surfaces treated with different adhesive systems. The restored teeth were subjected to thermo-cycling at 5°C and 55°C for 2000cycle. Then each tooth was mounted on the cutting machine, sectioned into a series of 1 mm thick. The sticks were stressed to failure under tension using Universal Testing Machine to record the microtensile bond strength. The fractured sticks were evaluated for bond failure mode under a stereomicroscope at 40X magnification to detect the mode of failure. The collected data were submitted to ANOVA and Tukey’s test. Results: Etch-and-rinse (A1) control group showed the highest significant mean Microtensile bond strength (MPa) followed by Self-etch adhesive (A2) followed by Resin infiltrant (ICON) (A3) at p≤0.001. The result of the stereomicroscopic examination revealed adhesive and cohesive failure mode in composite. The predominant mode of failure using resin infiltrant group A3 (Icon) and self-etch adhesive system group A2 group was adhesive failure with a higher percentage in resin infiltrant A3 (Icon) group 100%. On the other hand cohesive in composite is the predominant mode of failure using the Etch and rinse adhesive system group A1 80%. Conclusion: The use of resin infiltrant (Icon) as an adhesive material impaired efficacy of the microtensile bond strength of direct resin composite to sound dentin .

Fracture resistance of endodontically treated teeth restored with Zirconia filler containing composite core material and fiber posts

Objectives:To assess the fracture resistance of endodontically treated teeth with a novel Zirconia (Zr) nano-particle filler containing bulk fill resin composite.Methods:Forty-five freshly extracted maxillary central incisors were endodontically treated using conventional step back preparation and warm lateral condensation filling. Post space preparation was performed using drills compatible for fiber posts (Rely X Fiber Post) on all teeth (n=45), and posts were cemented using self etch resin cement (Rely X Unicem). Samples were equally divided into three groups (n=15) based on the type of core materials, ZirconCore (ZC) MulticCore Flow (MC) and Luxacore Dual (LC). All specimens were mounted in acrylic resin and loads were applied (Universal testing machine) at 130° to the long axis of teeth, at a crosshead speed of 0.5 mm/min until failure. The loads and the site at which the failures occurred were recorded. Data obtained was tabulated and analyzed using a statistical program. The means and standard deviations were compared using ANOVA and Multiple comparisons test.Results:The lowest and highest failure loads were shown by groups LC (18.741±3.02) and MC (25.16±3.30) respectively. Group LC (18.741±3.02) showed significantly lower failure loads compared to groups ZC (23.02±4.21) and MC (25.16±3.30) (p<0.01). However groups ZC (23.02±4.21) and MC (25.16±3.30) showed comparable failure loads (p=0.23).Conclusions:Fracture resistance of endodontically treated teeth restored with Zr filler containing bulk fill composite cores was comparable to teeth restored with conventional Zr free bulk fill composites. Zr filled bulk fill composites are recommended for restoration of endodontically treated teeth as they show comparable fracture resistance to conventional composite materials with less catastrophic failures.

Analysis of facial bone wall dimensions and sagittal root position in the maxillary esthetic zone: a retrospective study using cone beam computed tomography.

To determine the thickness of the facial bone wall and the sagittal angulation between the long axis of the teeth and the long axis of the associated alveolar bone in the maxillary esthetic zone using cone beam computed tomography (CBCT). A retrospective radiographic study of CBCT images was conducted in 300 patients. The distance between the cementoenamel junction (CEJ) and the facial bone crest, the thickness of the facial bone wall (4 mm apical to the CEJ and midroot), and the sagittal angle between the long axis of teeth and the long axis of the respective alveolar bone were measured. Descriptive statistics and frequency analyses were performed. The sample included 133 men and 167 women (mean age, 36.9 years; range, 18 to 60 years). The distance between the CEJ and the facial bone crest varied between 0.1 and 4 mm and showed an overall tendency to increase with age. Almost 80% of anterior teeth and 40% of premolars exhibited a thin facial bone wall (< 1 mm), and nearly 30% of sites had a bone wall thinner than 0.5 mm. The sagittal angle at approximately 80% of central incisor and second premolar sites was < 20 degrees, but the angle at more than 40% of canine sites was ≥ 30 degrees. There was a significant decrease in facial bone wall thickness from premolars to anterior teeth. The facial bone wall in most maxillary anterior teeth was very thin. There was a substantial sagittal angulation between the long axes of teeth and those of their respective alveolar bone in most esthetic zone positions. CBCT analyses of the facial bone wall and the sagittal angle are recommended to ensure the most appropriate dental implant treatment approach.

Effects of conventional and laser activated intracoronal bleaching agents on ultrastructure and mineral content of dentin

Aims and Objectives: The purpose of this in vitro study was to evaluate the ultra structural changes induced in dentin after exposure to different conventiona and laser-activated intracoronal bleaching agents . Materials and Methods: Forty human maxillary teeth were taken and were decoronated through the cemento-enamel junction (CEJ) perpendicular to the long axis of tooth, the crown part was then cut parallel to long axis dividing the tooth into mesial and distal half. Experimental specimen were then divided into two groups (n = 20) in which group 1-35% hydrogen peroxide (Pola office SDI limited Australia) Group 2-30% hydrogen peroxide (J White Heydent GmbH Germany), the groups were further sub-divided into sub-group A - conventional application and Subgroup B - laser activation (Nd: Yag laser Fotona Fidellis III). The specimens were then evaluated under scanning electron microscope (FEI quanta 200 North America) to determine diameter of dentinal tubules and chemical analysis of the same was done. Results : Within the limits of this in vitro study, higher concentration of hydrogen peroxide used as intracoronal bleaching agent: (1) increases dentinal tubule diameter. (2) And also promote alteration in organic and inorganic components of dentin with reduction in calcium/phosphorous ratio leading to demineralization with insignificant difference between conventional application and laser activation. Conclusion : Laser activation of hydrogen peroxide bleaching agent can be added to the present treatment modalities for intracoronal bleaching techniques for faster and more accurate results.

Three-dimensional analyses of the mandible and the occlusal architecture of mandibular dentition

Introduction The position and inclination of the long axis of teeth in the human dentition can be described by a set of rules. The purpose of this study was to analyze the architecture of the mandibular dentition of adult Caucasians using virtual three-dimensional (3D) reconstruction of skulls and mandibles.

In vitro evaluation of the effect of post system and length on the fracture resistance of endodontically treated human anterior teeth

The aim of this study was to evaluate the effect of post system and length on the fracture resistance of endodontically treated human anterior teeth. Seventy-five extracted human incisors were endodontically treated, out of which 60 were decoronated 2mm above the cementoenamel junction and divided into two experimental groups based on the type of post system to be used: glass fiber post (GFP) and Ribbond fiber post groups (RFP). Endodontically treated human anterior teeth in which no post was placed served as control group. Each group was divided into two subgroups according to the length of post space: 5 and 10mm and all the samples were restored with metal crowns. The fracture resistance was measured by applying loads at an angle of 130° to the long axis of teeth in an Instron universal testing machine. The results revealed that GFP group at 10-mm post space length showed the significantly highest fracture resistance (740.2133N) among all groups and subgroups. Decrease in post length resulted in the decrease in fracture resistance in GFP group (425.1867N), whereas in group RFP 5-mm subgroup (299.6200N) showed significantly higher fracture resistance than 10-mm subgroup (216.9300N) but lesser than the control (437.8733N) in both the subgroups. Glass fiber posts efficiently increase the fracture resistance of an endodontically treated tooth but the determination of optimal post length is also essential. The present investigation highlights the significance of using glass fiber posts in the restoration of endodontically treated teeth. Endodontically treated teeth restored with glass fiber posts showed increased fracture strength and favorable mode of fracture, and are therefore highly recommended to achieve better clinical outcomes.

In vitro evaluation of glass fiber post

Statement of problem: Techniques and recommendations for the restoration of endodontically treated teeth have changed from the use of custom cast metal post and core system to glass fiber-reinforced (GFRC) post and composite core system. Has this latest prefabricated glass fiber reinforced post and composite core system increased the fracture resistance of teeth and reduced the incidence of unrestorable root fractures. Purpose: The purpose of this study was to evaluate the incidence of root fracture and mode of failure of endodontically treated teeth restored with two different post and core systems. Material and Methods: Forty maxillary central incisors were randomly divided into two groups. (n=20). All teeth received endodontic treatment. First group was restored with custom cast post and core system. Second group was restored with glass fiber post and composite core system. In Both the groups posts were cemented with adhesive resin cement. Compressive load was applied at an angle of 130 to the long axis of teeth at a cross head speed of 1 mm/min until fracture occurred. Data were analyzed with student “t” test P<.001. Results: The mean value for fracture resistance was (331.4025) N in Group -I Custom cast Ni-Cr post and core and (237.0625) N in Group -II Glass fiber reinforced post and composite core system. Students “t” test shows the significant difference in fracture resistance of two groups. Conclusion: This study showed that the incidence of root fracture was significantly higher in custom cast Ni-Cr post and core system than glass fiber post and composite core system. A more favourable mode of failure was observed in teeth restored with Group II glass fiber post system. Key words:Post-and-core technique, glass fiber post, cast post and-core system, fracture resistance, endodontically treated teeth.

Evaluation of the integrity of dental sealants by optical coherence tomography

Objectives The purpose of the present research was to demonstrate images of failures into the structure of pit and fissure sealants using optical coherence tomography (OCT). Methods Five human third molars were selected and the sealant ALPHA SEAL LIGHT/DFL was applied according to the manufacturer instructions. For evaluation of the structure of pit and fissure sealants, twenty OCT images of each tooth were performed before and after application of sealant. A total of 200 images were evaluated. A home built spectral OCT system used was operating in spectral domain (SD-OCT), at 840 nm and a measured spatial resolution of 10 μm. The system is based on the Michelson interferometer set-up and is controlled by the software OCT 800 – Complex Square/LabView, that collects data and generates the image. The occlusal surfaces were scanned in a bucco-lingual direction and tomographic images parallel to long axis of tooth were obtained. After the achievement of the images by OCT, the crown of each tooth was sectioned in a occlusogingival direction (buccolingually). Images from each section were obtained and evaluated by an optical microscope. OCT and microscopic images were compared. Results Representative images showed that OCT image provides the insight into sealant material. It was possible to clearly identify the internal structure of sealant and the subjacent enamel. Sealant and enamel are very well distinguished, and failures at the interior and at surface are well detected. Significance OCT could generate images of the features of fissures, bubbles and failures in the adaptation of sealants, opening up possibilities in the future to monitoring sealant application and retention in short and long term.

In Vitro Tomographic Image of Human Pulp-Dentin Complex: Optical Coherence Tomography and Histology

Introduction Optical coherence tomography (OCT), a noninvasive imaging method, was used in this work to image the pulp-dentin complex. Pulp and dentin are integrally connected in the sense that physiologic and pathologic reactions in one of the tissues will also affect the other. Methods An OCT system with 6-μm spatial resolution at 800 nm was used to image the pulp-dentin complex of in vitro samples. Five intact human maxillary premolars scheduled for surgical extraction were used in this in vitro study. The occlusal surfaces of teeth were polished with wet 600-, 1,000-, and 1,200-grit aluminum oxide abrasive paper perpendicular to the long axis of teeth, producing a plane on that surface. The images of pulp-dentin complex were taken by scanning the occlusal surface in a mesiodistal direction. The laser penetrated into the teeth structure and a tomographic image of pulp-dentin complex, parallel to the long axis of teeth, was obtained. Histological and OCT images were analyzed and compared. Results The results showed the capability of the OCT technique to generate images of the boundaries of pulp and its relation to the dentin. It could be clearly seen that the OCT image provided the insight into dentinal substrate about 0.65-mm deep (corrected for the dentin refractive index). Conclusion OCT can be used in the future to prevent iatrogenic exposures of the pulp, complementing other existing methods, and will permit a more predictive prognosis of treatments.

Evaluation of interdental space of the maxillary posterior area for orthodontic mini-implants with cone-beam computed tomography

Our objectives in this study were to measure in a group of patients the interradicular spaces between the maxillary second premolar and first molar, which is often used as placement sites for mini-implants, and to suggest simple guidelines for safe placement. Cone-beam computed tomography was used in 35 patients to measure interdental spaces and distances between the surface of the cortical bone and the closest interradicular area apically in 1-mm intervals in 9 axial images from the cementoenamel junction (CEJ). The cone-beam computed tomography data were analyzed by using anlaysis of variance (ANOVA) to evaluate the differences in interradicular distances, cortical bone surfaces, and narrowest interradicular spaces. A t test was also performed to evaluate sex and placement side differences. Interradicular space became wider toward the apical area; several axial planes showed statistically nonsignificant differences from the CEJ to the root, and the average distance from the surface of the cortical bone to the area of the closest interradicular space was over 5 mm in the most sections. Guidelines for safe placement are as follows: the initial point for mini-implant placement is near the mucogingival line (2-4 mm from the CEJ) and less than a 45 degrees apical angulation to the long axis of tooth, with a mini-implant diameter of 1.4 to 1.8 mm and length of about 6 mm (bone contact). A larger placement angle would increase the cortical bone contact; however, it is difficult to apply various traction materials and might increase the danger of maxillary sinus perforation.

Influence of remaining coronal tooth structure location on the fracture resistance of restored endodontically treated anterior teeth

A restored endodontically treated tooth is less likely to fracture when there is axial tooth structure between the core base and preparation finish line. However, an accurate prognosis requires knowing whether fracture resistance depends on a complete circumferential distribution of tooth structure or tooth structure in a specific location related to the applied force. This in vitro study investigated the fracture resistance of restored endodontically treated teeth when residual axial tooth structure was limited to one half the circumference of the crown preparation. Fifty extracted maxillary anterior teeth were sectioned 18 mm from their apices, endodontically treated, and divided into 5 groups of 10 teeth each. Four groups were prepared with full shoulder crown preparations having axial wall heights of 2 mm around the preparation circumferences. In 3 of the groups with axial tooth structure, one half of the axial tooth structure was removed, palatally, labially, or proximally, and groups were identified according to the site of retained coronal tooth structure. For the fifth group, all axial tooth structure was removed to the level of the preparation shoulder. Thus, in 1 group the axial walls were circumferential, 360 degrees around the preparations (Complete group), in 3 groups the axial walls were continuous for 180 degrees (Palatal, Labial, and Proximal groups), and the last group had no retained coronal tooth structure incisal to the finish line (Level group). All 50 prepared teeth were then restored with quartz fiber posts (Bisco), composite resin (Bisco) cores, and metal crowns. A universal testing machine compressively loaded the tooth specimens from the palatal at a crosshead speed of 0.5 cm/min at an angle of 135 degrees to the long axis of teeth until failure occurred. A survival analysis was conducted using a log-rank test followed by Holm-Sidak pairwise tests (alpha=.05) to detect significant differences in median failure load between groups. The mode of failure was determined by visual inspection of all specimens. The median failure load (P<.001) was 607 N, 782 N, 358 N, 375 N, and 172 N for the Complete, Palatal, Labial, Proximal, and Level groups, respectively. The predominant mode of failure was an oblique palatal to facial root fracture for the groups with remaining coronal tooth structure. In the Level group, post debonding was the predominant mode of failure. For restored endodontically treated teeth that do not have complete circumferential tooth structure between the core and preparation finish line, the location of the remaining coronal tooth structure may affect their fracture resistance.

Comparative evaluation of micro-shear bond strength of adhesive resins to coronal dentin versus dentin at floor of pulp chamber - An Invitro Study

<b>Background and Objectives: </b> To compare the micro shear bond strengths of coronal dentin and pulp chamber dentin using two bonding systems namely Clearfil SE bond and Single bond.<br><b> Methods: </b> Thirty molar teeth were collected for the study out of which sixty samples were prepared. Thirty, 2 mm thick slabs of coronal dentin were prepared from each tooth by removing occlusal enamel perpendicular to the long axis of tooth with low speed diamond disc to expose a flat mid coronal dentin and then thirty pulpal floor dentin samples were prepared by sectioning at mid point between floor of pulp chamber and root furcation. These sixty samples were divided into two major groups depending upon dentin location. GROUP I: 30 samples of coronal dentin. GROUP II: 30 samples of dentin at floor of the pulp chamber. Each group was subdivided into two subgroups depending upon the bonding agent used. Subgroup Ia. IIa: Clearfil SE bond. Sub group Ib, IIb: Single bond).<br><b> Results: </b> Micro shear bond strength showed higher values to coronal dentin compared to dentin at floor of the pulp chamber and Clearfil SE bond showed higher values compared to Single bond in coronal and dentin at floor of the pulp chamber, but statistically insignificant.<br><b> Interpretation and conclusion: </b> Clearfil SE bond showed higher values compared to Single bond in both coronal dentin and dentin at floor of pulp chamber.

Effect of increasing application time of single bottle adhesives to microtensile bond strength of dried dentin

The purpose of this study was to evaluate the effect of increasing application time of single bottle adhesives (SBA) to microtensile bond strength (MTBS) of dried dentin. To expose the superficial dentin surfaces, human molars were sectioned perpendicular to the long axis of tooth. phosphoric acid gels were applied for 15s and rinsed. The teeth were randomly assigned to 3 groups ; S group (Single Bond), O group (One-Step), P group (Prime & Bond NT). Each group was divided to 3 subgroups (W: dentin wipe with wet gauge and light cured immediately, D, dentin dried for 30s and light cured immediately, 30: dentin dried for 30s and light cured after applying SBA for 30s). Composite resin was built up on the dentin surface and sectioned to obtain 20 specimens with cross sectional area and the MTBS was measured. For Single Bond, the mean MTBS of S-W and S-30 group were higher than that of S-D group statistically (P

Effect of Smear Layer and Direction of Dentinal Tubules on Osteoblast Adhesion to Human Dentin Tissue

The purpose of this study was to investigate the effect of smear layer and direction of dentinal tubules on osteoblast adhesion to human dentin tissue in vitro. Dentin disks were made from human premolars extracted for orthodontic reasons. Dentin disks were cut either perpendicularly to the long axis of the tooth or at 45 degrees to the long axis of tooth. The smear layer was removed by 34% phosphoric acid gel from half of the dentin disk surface. Human osteoblast-like Saos-2 cells were grown in RPMI medium with 10% fetal bovine serum and 1% antibiotic/antimycotic cocktail under standard cell culture conditions. Cells were seeded into Nunc four-well culture plates at 1.5 x 10(5) cells per well with dentin disks in the bottom of each well. After 1 day in culture the dentin disks along with cells grown on their surface were examined with a scanning electron microscopy. Osteoblasts attached and spread on the dentin surface and formed a monolayer in the presence and absence of a smear layer. Cells spread over the dentinal tubules despite their direction. These results suggest that cell adhesion and spreading of osteoblasts is not influenced either by the existence of a smear layer or the direction of the dentinal tubules on the dentin surface.

The effect of water pressure on physiological property of gingiva by water pik (author's transl)

This study was made of the strain of gingiva on physiological property of free gingival surface according to the Pias 49 Water Pik.The dog was subject to this experiment and the strain gauge M-101 (Shinkoh Co.) was adhered to the free gingival surface of maxillary cuspid with alpha cyano acrylate and parallel to the long axis of tooth. The tip of the handpiece was 10mm at the distance and the directions were in vertical and forty five degree against the gingival surface. The strain of gingival caused by stream of water pressure on each dial number setting on the Water Pik were record.As the result, the free gingival surface was subject to a tensile strain on each dial number of the Water Pik. The degree of strain were determined by the force of water pressure but this trend appeare more clearly on the dial number three. In the direction of forty five degree the spike of gingival strain showed more than in the vertical direction.