Structure Of Human Teeth Research Articles

Comparative Study on the Effect of Calcium Carbonate and Covarine on the Enamel Structure of Human Teeth (in Vitro Study)

Comparative Study on the Effect of Calcium Carbonate and Covarine on the Enamel Structure of Human Teeth (in Vitro Study)

Evaluation of the efficiency, trueness, and clinical application of novel artificial intelligence design for dental crown prostheses

ObjectiveThe unique structure of human teeth limits dental repair to custom-made solutions. The production process requires a lot of time and manpower. At present, artificial intelligence (AI) has begun to be used in the medical field and improve efficiency. This study attempted to design a variety of dental restorations using AI and evaluate their clinical applicability. MethodsUsing inlay and crown restoration types commonly used in dental standard models, we compared differences in artificial wax-up carving (wax-up), artificial digital designs (digital) and AI designs (AI). The AI system was designed using computer calculations, and the other two methods were designed by humans. Restorations were made by 3D printing resin material. Image evaluations were compared with cone beam computed tomography (CBCT) by calculating the root mean squared error. ResultsSurface truth results showed that AI (68.4 µm) and digital-designed crowns (51.0 µm) had better reproducibility. Using AI for the crown reduced the time spent by 400% (compared to digital) and 900% (compared to wax-up). Optical microscopic and CBCT images showed that AI and digital designs had close margin gaps (p < 0.05). The margin gap of the crown showed that the wax-up group was 4.1 and 4.3 times greater than those of the AI and digital crowns, respectively. Therefore, the utilization of artificial intelligence can assist in the production of dental restorations, thereby enhancing both production efficiency and accuracy. SignificanceIt is expected that the development of AI can contribute to the reproducibility, efficiency, and goodness of fit of dental restorations.

Dependence of Pit Formation in Hard Tissue of Human Teeth on Free Electron Laser Pulse Structures

The purpose of this study was to compare and clarify the differences in pit formation between two modes of free-electron laser（FEL）irradiation with different beam cur rents and pulse structures and how the effects of these modes vary with the tissue structure of human teeth. FEL irradiation using the full-bunch mode（Fm）and burst mode（Bm）. The beam current was carried out at 200 mA for Fm and 2 A for Bm. The micro-pulse interval within the macro-pulse structure was 350 ps for Fm and 22.4 ns for Bm. The wavelength of the FEL was adjusted to 2.94 µm, and macro-pulse energy was adjusted to 6.0 mJ/macro-pulse by polarizing plate. The macro-pulse irradiation was set to 1 or 5 times for both modes. As the number of macro-pulse irradiations increased, the pits became deeper in Fm than in Bm, regardless of the site on the tooth. On the other hand, the bulge height was lower for Bm than for Fm, regardless of the site on the tooth or the number of macro-pulse irradiations. No scorch marks were observed in the pits for either mode. It was concluded that the differences in the pit including bulge formation were the macro-pulse structure between Fm and Bm. The intensity of the FEL irradiation caused plasma evaporation in the tooth hard tissue, and the tooth substance was ablated before thermal conduction occurred. The relation with the thermal relaxation time also confirmed that pits were formed without visible scorch marks.

INVESTIGATION OF FRACTURE-RESISTANCE OF HUMAN TEETH AT THE DENTIN–ENAMEL JUNCTION USING THE J-INTEGRAL CALCULATION OF FINITE ELEMENT ANALYSIS

Most human teeth have an exposed surface layer of calcified enamel, which is harder than the inner layer of dentin. The interface between the enamel and dentin is called the dentin–enamel junction (DEJ), which ensures that teeth do not collapse and fall off. The purpose of this study was to use finite element analysis software through the [Formula: see text]-integral method and the extended finite element method (XFEM) to simulate three models of DEJ structures: (i) wavy DEJ with no thickness, (ii) rectangle DEJ with a thickness of 0.3[Formula: see text]mm, and (iii) wavy DEJ with a thickness of 0.3[Formula: see text]mm. This paper demonstrates that the layered structure of human teeth plays a positive role in enhancing the fracture strength and preventing the crack from spreading to the depths of teeth. At the same time, we also justify of the scalloped structure and concave orientation of the DEJ interface. The residual stresses in DEJ and its adjacent dentin region are also an important factor of tooth resistance to crack propagation. In addition, the configuration of the DEJ interface and residual stresses in DEJ and dentin areas are further justified by means of XFEM method. The findings in this study provide potential inspiration for the biomimetic design toward strengthening the dentin and dentin-like materials.

THE USE OF BIOMIMETIC NANOCRYSTALS ZN-CARBONATE HYDROXYAPATITE IN THE TREATMENT OF LOCALIZED HYPERSENSITIVITY OF HARD TISSUES OF TEETH

Abstract: The problem of hypersensitivity of hard tissues of teeth remains relevant in modern dentistry to this day. Despite the fact that the market of dental products is saturated with ultramodern means to reduce the sensitivity of hard tissues of teeth, the issue associated with the relief of pain remains open. To develop a new approach to solving this problem, localized hypersensitivity of the 2nd degree of hard dental tissues was treated in 40 patients aged 20 to 45 years of both sexes. According to the concept of biomimetic/bioemulation, which became the scientific basis for the study, a toothpaste containing a mixture of bioactive microparticles of carbonate hydroxyapatite with zinc-substituted, similar to the structure of human teeth (biomimetic nanocrystals microRepair®) was used. There was a statistically significant prolonged decrease in the sensitivity of hard tooth tissues when using professional toothpaste with bioactive microparticles, provided its combined use in clinical conditions and at home, with daily use in the form of brushing teeth, compared with its single-component application at a specialist's appointment.

Bionic design perspectives based on the formation mechanism of dental anti-wear function

Abstract Human teeth are the important masticatory organ and therefore are subjected to friction and wear everyday. Both the loading condition and the environment are relatively complex in the mouth, however, normally human teeth can serve in mouth all their time with excellent wear resistance in most people. Obviously, through the process of human evolution, human teeth have become a natural anti-wear system that far outclasses the best engineering anti-wear systems at present. To understand the excellent anti-wear properties of human teeth, we need to look into what act as the wear resisting elements of human teeth. In this paper, based on the results obtained by the authors and from literatures, the formation mechanism of dental anti-wear function was summarized. Particular attention was paid to the multi-scale anti-wear mechanism caused by the unique hierarchical structure of human teeth, the self-repair mechanism by tooth remineralization, and the cooperating lubrication mechanism of salivary pellicle upon tooth surface and the hydration proteins within the tooth. Based on the formation mechanism of dental anti-wear function, some bionic design perspectives were discussed and future research directions are recommended.

Non-destructive Microstructural Evaluation of Intact and Restored Human Teeth Using Tabletop X-Ray $$\upmu $$ μ CT System

This study explores the feasibility of a micro-focus based tabletop X-ray $$\upmu $$ CT system for the micro-structural characterization of human teeth and later its application to the non-destructive evaluation of teeth restored with different composite resin for their interface integrity and micro-imperfections. In the first part of this study, extracted human primary and permanent molar teeth were used to explore potential of micro-focus based tomography setup for their micro-structural characterization. The details of root canal structure of human teeth were visualized and quantified with polychromatic $$\upmu $$ CT. In the second part identification and comparison of defects in a set of six human teeth samples, which were restored with two different composite resins, was carried out. Group ‘A’ samples were restored using a submicron hybrid composite material and Group ‘B’ were restored with a Nano-hybrid restorative composite material. The quantitative analysis of $$\upmu $$ CT data for composite resin restored teeth showed more number of voids or defects in Group ‘A’ restorations compared to Group ‘B’. A comparative evaluation of $$\upmu $$ CT techniques based on synchrotron source and micro-focus source is also illustrated to show their respective merits and limitations.

Minimally Invasive Dentistry Approach Benefits of Using Laser

The preservation of healthy human body and function for every patient should be the goal of all health practitioners. Dentistry is not an exception to this philosophy. The loss of human tooth structure should be regarded as a serious injury and never to be considered lightly, therefore it is imperative to provide the most comprehensive and conservative care to all teeth. In past few decades, the improvements of scientific method and technology has led to a better understanding of oral micro flora and dental materials resulted in the shifting of caries management method from G.V. Black’s “Extension for prevention” to the modern “Minimally invasive” approach in dentistry. The minimally invasive approach to dental caries encompasses the science of detection, diagnosis and treatment on the microscopic level. The approach also establishes a proper doctor-patient relationship thus empowering and educating the patient to take responsibility for their own dental health. It has been widely accepted that the restorative materials and preparation designs are not the cure for caries. The dentist must recognize that the caries is a bacterial disease and the elimination of disease should be the priority before initiating any restorations. The proper sequence of caries management should be the introduction of preventive strategies such as oral hygiene instructions, remineralisation regiments, and risk assessments followed by minimal surgical interventions. Using the laser technology in the aspect of surgical intervention has many clinical advantages. Some of the clinical benefits include its selectivity for carious tissue, reduction of needs for local anaesthesia, decontamination effect of preparation surfaces, minimal thermal stimulus to pulp chamber, increase surface adhesion for composite materials, and other soft tissue applications. A critical evaluation of disadvantages on laser should also be considered when implementing its use in the clinical practice. The combination of caries prevention program, disease control, risk assessment and laser technology application on the surgical intervention significantly reduce the long term restorative needs thus preserve more healthy natural tooth structures, which complimenting the concept of minimally invasive dentistry. This presentation summarized various articles within the past 15 years regarding to topics of minimal invasive dentistry and laser technology usage in dentistry.

Роль углеводно-белковых биополимеров и гиалуроновой кислоты в формировании резистентности твердых тканей зуба от патологических процессов кариозного и некариозного генеза

At the series of histochemical studies hypothesis of existence of a &amp;#34;cationic protein&amp;#34; in human tooth structure and set of its amino acids components and hyaluronic acid has been checked. Taking into account histogenesis and cytogeny of tooth structure and the earlier results received from the epidermis and multilayer partly keratinous epithelium of the oral mucosa, special studies had been created, based on the original equipment preparation of paraffin sections, and thin sections of the whole teeth and modified histochemical identification technology of carbohydrate-protein biopolymers in hard dental tissues. Histological slides are prepared from extracted for orthodontic indications teeth. Sectioned and examined thin sections of teeth has investigated in transmitted light for issues related to topochemistry of carbohydrate-protein biopolymers and hyaluronic acid concerning the distribution in structures of enamel, dentin, predentin, cellular and acellular cement. Identified carbohydrate-protein biopolymers and substances of protein nature objectively fill inter prismatic enamel areas, dentin tubules and their walls, localized in the cement structure of tooth and its soft tissues forming a physiologi-cal barrier to microorganisms and their metabolic products as in the demineralizing processes as for the mechan-ical interventions during the vital activity and medical interventions.

Scanning Electron Microscopy of the Apical Structure of Human Teeth

The objective of this research was to evaluate, by scanning electron microscopy, the apical structure of extracted human permanent teeth with different degrees of pulp and periapical pathology. A total of 25 teeth were extracted: 5 teeth with vital pulp (group I); 10 teeth with pulp necrosis without radiographically visible periapical lesion (group II); 10 teeth with pulp necrosis with radiographically visible periapical lesion (group III). The root apex was sectioned and processed for scanning electron microscopy. In groups I and II, fibers covered the root cementum and there was no cementum resorption or microorganisms. There were areas of cementum resorption in group III with microorganisms on the root apex surface (biofilm) and no fibers. The authors conclude that the presence of chronic periapical lesions causes severe changes in the apical structure with a destruction of fibers and different degrees of cementum resorption forming lacunae in which bacterial biofilm persisted.

High-resolution imaging of proteins in human teeth by scanning probe microscopy

High-resolution studies of dental tissues are of considerable interest for biomedical engineering and clinical applications. In this paper, we demonstrate the application of piezoresponse force microscopy (PFM) to nanoscale imaging of internal structure of human teeth by monitoring the local mechanical response to an electrical bias applied via a conductive tip. It is shown that PFM is capable of detecting dissimilar components of dental tissues, namely, proteins and calcified matrix, which have resembling morphology but different piezoelectric properties. It is demonstrated that collagen fibrils revealed in chemically treated intertubular dentin exhibit high piezoelectric activity and can be visualized in PFM with spatial resolution of 10 nm. Evidence of the presence of protein inclusions of 100–200 nm wide and several micrometers long in tooth enamel has been obtained. Furthermore, it is found that the peritubular dentin and intertubular dentin exhibit different piezoelectric behavior suggesting different concentration of collagen fibrils. The obtained results demonstrate a high potential of PFM in providing an additional insight into the structure of dental tissues. It is suggested that the PFM approach can be used to study the structure of a wide range of biological materials by monitoring their electromechanical behavior at the nanoscale.

Radiopacity of calcium hydroxide cement compared with human tooth structure

All materials added to teeth should present an adequate radiopacity to allow the detection of secondary caries. Usually, in extensive cavities, base materials like calcium hydroxide cement are used for the purpose of protecting the pulp. In an attempt to improve the efficiency of radiographic detection of this material, this study aimed to determine the radiopacity of three calcium hydroxide cements and to compare the radiopacity of these materials with dentin and enamel. Radiographs were taken of 1-mm thick specimens of three calcium hydroxide cements: Hydro-C, Dycal and Life, an aluminium stepwedge, a lead foil, and one 1-mm thick human tooth slice. Densitometric measurements were obtained after radiographic processing. The radiopacity values of the calcium hydroxide cements, dentin and enamel were expressed in terms of the equivalent thickness of aluminium. The analysis of variance indicated statistically significant difference only for Life, which presented the lowest radiopacity when compared to the other cements. However, all cements and enamel possessed a radiopacity equivalent to 2mm Al, while dentin presented a radiopacity equivalent to 1mm Al. All tested cements presented a similar radiopacity to that of enamel and they meet the ISO 4049 specifications.

Application of high resolution microfocus X-ray CT for the observation of human tooth.

The calcification degree of extracted human teeth was observed by using high resolution microfocus X-ray CT. As samples, upper and lower first premolars extracted from a 21-year-old female were used. The computed tomograms were produced by high resolution microfocus X-ray CT with a open vacuum X-ray source, rotating sample stage, and image sensor. The distinction between enamel and dentin was very clear, and the shape of the pulp cavity was also clearly identified. The secondary dentin was visible in the circumpulpal dentin. The color map displays showed the heterogeneity of the calcification degree not only in the dentin but also in the enamel. The enamel was divided into three layers according to the calcification degree. High resolution microfocus X-ray CT was very useful for the observation of the internal structure of human teeth without destroying the samples.

In vitro investigation of the wear of human enamel by dental porcelain

Statement of problem. Metal ceramic systems are advocated when both esthetics and strength are required. A major drawback to many porcelains is their wear and destruction of opposing natural dentition. Purpose. This study evaluated the wear of enamel opposing 1 traditional and 2 recently introduced low-fusing feldspathic dental porcelains. Material and methods. Six blocks of Ceramco II, Finesse, and Omega 900 feldspathic porcelain materials were fabricated and fired according to manufacturer recommendations. Porcelain blocks were polished through 0.25 μm diamond polishing paste. Thirty-six enamel specimens were obtained and milled to a 2 mm (+0.5 mm) diameter. Enamel specimens were attached to an offset cam motor operating at 60 Hz. Enamel specimens were in constant contact with the stationary porcelain blocks under a load of 600 g and traversed a distance of 8 mm. Diameter and height of enamel specimens were measured at times of 0, 6, 12, 24, and 48 hours and subsequent determination of enamel volume loss recorded. Profilometric surface roughness of the ceramic blocks was also measured for the corresponding times. Results. Statistical analysis revealed that both Finesse and Omega 900 feldspathic porcelains caused significantly less enamel volume loss when compared with Ceramco II porcelain at all time intervals. Surface roughness revealed no consistent significant differences among porcelains. Conclusion. Both Finesse and Omega 900 porcelains were not as destructive to human tooth structure as Ceramco II porcelain. These results suggest an advantage of the new, lower-fusing porcelains in conditions where natural dentition wear is a concern. (J Prosthet Dent 1999;81:356-64.)

Evaluation of human tooth structure with the ultrasonic imaging technique.

In recent years, ultrasonic waves have been an interesting subject for studies due to their wide range of applications in medical diagnoses. In this study, the acoustic properties of the structure of human teeth was determined with the ultrasonic imaging technique. This study may offer some fundamental findings related to the clinical application of the ultrasonic imaging technique in the further development of a virtual system for dental education and research. Twenty freshly-extracted permanent human teeth (10 molars and 10 premolars) were used to investigate their acoustic velocity and impedance by the ultrasonic image analyzing system with a high-resolution focusing probe. Additionally, the relationship between the acoustic properties and the hardness of the teeth was evaluated. It was found that the acoustic properties of the human teeth were influenced by factors related to their structure, such as degree of calcification, distribution of dentinal tubules, and volume of the dentin matrix. The acoustic velocity and impedance showed an apparent correspondence to the hardness of tooth. This analyzing system provides visual information related to tooth structure that can easily quantitatively evaluate their acoustic properties. It is expected that this system will have a wide range of applications and be further developed for clinical uses.

Observation of Structure of Human Teeth during Immersing in Liquid by Atomic Force Microscopy

Observation of Structure of Human Teeth during Immersing in Liquid by Atomic Force Microscopy

Erbium:YAG (2.94 mum) laser effects on dental tissues.

Past trials with soft and calcified tissues have demonstrated that long pulse train (2.5 mus) Er:YAG (2.94 mum) laser may be used to ablate tooth structure of human teeth. Determination of physical and thermal damage to surrounding tissue during removal of enamel and dentin is a primary objective of this study. Extracted human teeth with thermal probes imbedded in the pulp chambers were submitted to cavity preparation using an Erbium YAG laser with water mist. Wavelength selection as well as use of a water mist during the procedure resulted in efficient tissue removal without significant surrounding damage. Ground sections and SEM sections of teeth showed little or no melting or ash formation in adjacent dentin and enamel and no visible change in the pulp chamber. The surfaces produced by laser ablation were rough and irregular with craters and grooves. Average temperature change in the pulp chamber monitored during tooth preparation was 2.2 degrees Centigrade. These findings suggest that constantly available water aids vaporization and microexplosions, increasing the efficiency of tooth structure removal, and aids in cooling of the tooth structures. The long pulse Er:YAG (2.94 mum) laser may be an effective method for tooth reduction applications when used with a water mist.

Measurement of absorbed doses near metal and dental material interfaces irradiated by X- and gamma-ray therapy beams

Soft-tissue damage adjacent to dental restorations is a deleterious side effect of radiation therapy which is associated with low-energy electron scatter from dental materials of high electron density. This study was designed to investigate the enhancement of dose to soft tissue (or water) close to high electron-density materials and to measure the detailed lateral and depth-dose profiles in soft-tissue-simulating polymer adjacent to planar interfaces of several higher atomic-number materials: 18-carat gold dental casting alloy; Ag-Hg dental amalgam alloy; Ni-Cr dental casting alloy; and natural human tooth structure. Assemblies of polymer-dosemeter stacks on both sides of the dental materials were irradiated in one fixed direction by collimated 60Co gamma-ray or 10 MV X-ray beams. In another test, designed to simulate more closely therapeutic treatment conditions, a phantom constructed on both sides of a row of restored and unrestored whole teeth was irradiated in one fixed direction by the collimated photon beams. Results indicate that the dose-enhancement in 'tissue' is as great as a factor of 2 on the backscatter side adjacent to gold and a factor of 1.2 adjacent to tooth tissue, but is insignificant on the forward-scatter side because of the predominant effect of attenuation by the high-density, high atomic-number absorbing material.

Visualization of human predentin and hypomineralized areas of dentin by silver methenamine staining

The light microscopic structure of human teeth was studied following silver methenamine staining, with and without previous oxidation in periodic acid. Predentin, hypomineralized dentin and carious dentin stained intensely, whereas highly mineralized dentin and calcospherites at the predentin-dentin junction did not show any reactivity when observed in the light microscope, even following demineralization in strong acid or in EDTA. The reactive sites of the pulp were confined to nuclei, nucleoli and a few thin fibers. This distribution of reactive sites is different from the distribution which is seen following von Kossa's silver stain, and from the distribution seen following silver stain methods for reticular fibers.

Radiographic evidence of tin uptake by human tooth structure

Extracted human teeth with approximal caries have been treated with topical applications of distilled water, sodium and stannous fluoride solutions, with radiographs taken before and after treatment under standard conditions for position, exposure, and film processing. Treatment with distilled water or 4% sodium fluoride solution produced no changes in the radiographic appearance of carious lesions in treated teeth. Treatment with 8% stannous fluoride solution resulted in increases in radiopacity of carious lesions so treated, indicating deposition of tin in or on carious tooth structure. This increase in radiopacity of carious lesions may be related to the high number of reversals in diagnosis of caries reported in clinical trials of stannous fluoride.