• Restorative Dentistry and Endodontics
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• v.26 no.6
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• pp.464-484
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• 2001

When restoring a tooth, the dentist tries to choose the ideal material for existing situation. One criterion that is considered is its suitability for restoring coronal strength. As more tooth structure is removed, the cusps are weakened and susceptible to fracture. Further, this increased deformation may cause the formation of intermittent gaps at the margin between the hard tissue and the restoration, facilitating marginal leakage. The improvements in ceramic materials now make it possible for alternatives to amalgams, composites, and cast metal to be of offered for posterior teeth. Of the materials used, ceramics most closely approximates the properties of enamel. The introduction of computer-aided design/computer-aided manufacture(CAD/CAM) systems to restorative dentistry represents a major technological breakthrough. It is possible to design and fabricate ceramic restorations at a single appointment. Additionally, CAD/CAM systems eliminate certain errors and inaccuracies that are inherent to the indirect method and provide an esthetic restoration. The aim of this investigation was to study the loading characteristics of CAD/CAM ceramic inlay and to compare the stress distribution and displacement associated with different designs of cavity(the isthmus width and cavity depth). A human maxillary left first premolar was prepared with standard mesio-occlusal cavity preparation, as recommended by the manufacturer Ceramic inlay was fabricated with CEREC 2 CAD/CIM equipment and cemented into the prepared cavity. Three dimensional model was made by the serial photographic method. The cavity width was varied $\frac{1}{3}$, $\frac{1}{2}$ and $\frac{2}{3}$ of intercuspal distance between buccal and lingual cusp tip. The cavity depth was varied 1.5mm and 2.3mm. So six models were constructed to simulate six conditions. A point load of 500N was applied vertically onto the first node of the lingual slope from the buccal cusp tip. The stress distribution and displacement were solved using ANSYS finite element program(Swanson Analysis System). (omitted)

• Journal of dental hygiene science
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• v.21 no.1
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• pp.38-44
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• 2021

Background: Dental caries and periodontal disease are bacterial infectious disease, mainly caused by plaque, a bacterial colony deposited on the tooth surface and gum tissue. Dental plaque disclosants easily stain the dental plaque, making them effective for scaling and tooth brushing education. As the erythrosine typically contained in dental plaque disclosants is highly cytotoxic, a low toxicity additive is needed. In this study, we aimed to examine the natural pigments with negligible cytotoxicity but can effectively stain the dental plaques for use in dental plaque disclosants. Methods: The pigmentation of eight types of natural pigments was tested on bovine tongue and teeth, as well as on head and neck tissue sections of experimental ICR mice. The cytotoxicity of gingival epithelial cells was measured via MTT assay. Pigmentation was performed on the bovine tongue and tooth surface. Pigmentation in the oral environment was observed in four mandibular incisors. A 2 Tone was used as a control. Results: Of the eight types of natural pigments, purple and blue pigments were effective in coloring dental plaques on the enamel surface as well as in the head and neck tissue sections. Additionally, purple and blue pigments were visible on the surface of the bovine tongue. Red, pink, orange, green, purple, and yellow pigments showed strong cytotoxicity, whereas brown and blue pigments had relatively low cytotoxicity. Blue pigment was effective in staining the dental plaque of four mandibular incisors. Conclusion: We suggest that the blue pigment derived from Gardenia jasminoides Ellis (Rubiaceae), which is effective for coloring dental plaques and has low cytotoxicity, is useful as a naturally derived dental disclosant.

• Restorative Dentistry and Endodontics
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• v.19 no.2
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• pp.345-371
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• 1994

Restorative procedures can lead to weakening tooth due to reduction and alteraton of tooth structure. It is essential to prevent fractures to conserve tooth. Among the several parameters in cavity designs, cavity isthmus and depth are very important. In this study, MO amalgam cavity was prepared on maxillary first premolar. Three dimensional. finite element models were made by serial photographic method and cavity depth(1.7mm, 2.4mm) and isthmus (11 4, 1/3, 1/2 of intercuspal distance) were varied. linear, eight and six-nodal, isoparametric brick elements were used for the three dimensional finite element model. The periodontal ligament and alveolar bone surrounding the tooth were excluded in these models. Three types model(B, G and R model) were developed. B model was assumed perfect bonding between the restoration and cavity wall. Both compressive and tensile forces were distributed directly to the adjacent regions. G model(Gap Distance: 0.000001mm) was assumed the possibility of play at the interface simulated the lack of real bonding between the amalgam and cavity wall (enamel and dentin). When compression occurred along the interface, the forces were transferred to the adjacent regions. However, tensile forces perpendicular to the interface were excluded. R model was assumed non-connection between the restoration and cavity wall. No force was transferred to the adjacent regions. A load of 500N was applied vertically at the first node from the lingual slope of the buccal cusp tip. This study analysed the displacement, von Mises stress, 1 and 2 direction normal stress and strain with FEM software ABAQUS Version 5.2 and hardware IRIS 4D/310 VGX Work-station. The results were as follows: 1. G model showed stress and strain patterns between Band R model. 2. B model and G model showed the bending phenomenon in the displacement. 3. R model showed the greatest amount of the displacement of the buccal cusp followed by G and B model in descending order. G model showed the greatest amount of the displacement of the lingual cusp followed by B and R model in descending order. 4. B model showed no change of the displacement as increasing depth and width of the cavity. G and R model showed greater displacement of the buccal cusp as increasing depth and width of the cavity, but no change in the displacement of the lingual cusp. 5. As increasing of the width of the cavity, stress and strain were not changed in B model. Stress and strain were increased on the distal marginal ridge and buccopulpal line angle in G and R model. The possibility of the tooth fracture was increased. 6. As increasing of the depth of the cavity, stress and strain were not changed in B and G model. Stress and strain were increased on the distal marginal ridge and buccopulpal line angle in R model. The possibility of the tooth fracture was increased.

• The Journal of Advanced Prosthodontics
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• v.1 no.2
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• pp.85-90
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• 2009

STATEMENT OF PROBLEM. Over the years, resin-bonded fixed partial dentures (RBFPDs) have gone through substantial development and refinement. Several studies examined the biomechanics of tooth preparation and framework design in relation to the success rate of RBFPDs and considered retention and resistance form essential for increase of clinical retention. However, these criteria required preparations to be more invasive, which violates not only the original intentions of the RBFPD, but may also have an adverse effect on retention due to loss of enamel, an important factor in bonding. PURPOSE. The object of this in vitro study was to compare the dislodgement resistance of the new types of RBFPDs, the conventional three-unit fixed partial denture, and conventional design of RBFPD (Maryland bridge). MATERIAL AND METHODS. Fifty resin mandibular left second premolars and second molars were prepared on dentiforms, according to the RBFPD design. After model fabrication (five group, n = 10), prostheses were fabricated and cemented with zinc phosphate cement. After cementation, the specimens were subjected to tensile loading at a cross head speed of 4 mm/min in a universal testing machine. The separation load was recorded and analyzed statistically using one-way analysis of variance followed by Duncan's multiple range test. RESULTS. Group V, the pin-retained RBFPDs, had the highest mean dislodgement resistance, whereas specimens of group II, the conventional RBFPDs, exhibited a significantly lower mean dislodgement resistance compared to the other 4 groups (P <.05). There were no significant differences between group I, III, and IV in terms of dislodgement resistance (P>.05). Group V had the highest mean MPa (N/$mm^2$) (P <.05). There was no significant difference between groups I, II, III and IV (P > .05). CONCLUSION. Within the limits of the design of this in vitro study, it was concluded that: 1. The modified RBFPDs which utilizes the original tooth undercuts and requires no tooth preparation, compared with the conventional design of RBFPDs, has significantly high dislodgement resistance (P < .05). 2. The modified RBFPDs which utilizes the original tooth undercuts and requires minimal tooth preparation, compared with the conventional FPDs, has significantly no difference in retention and dislodgement resistance)(P>.05). 3. The pin-retained FPDs showed a high dislodgement resistance compared to the conventional three-unit FPDs (P<.05).

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.22 no.2
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• pp.215-219
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• 1992

The author ovserved a case of dentinogenesis imperfecta in a 8-year-old and a 9-year-old brother with complaints of abnormal morphologic changes of the teeth. 1. Clinically, yellowish brown colored teeth, fractured crown and numerous retained root tips of deciduous teeth with severe attrition were observed in the both deciduous and permanent dentitions. 2 Radiographically, small-sized teeth, partial or complete obliteration of the pulp chambers and pulp canals in the anterior teeth, partial obliteration of the pulp chambers and thin enamel in the permanent tooth germs were observed. 3. The familial history was their father has been lose his teeth early.

• Restorative Dentistry and Endodontics
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• v.13 no.1
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• pp.139-150
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• 1988

The purpose of this study was to evaluate the marginal adaptation of Class V resin restorations by the filling techniques. The cavities were filled with Heliosit$^{(R)}$ light curing composite resin system in accordance with the following three filling techniques - bulk-pack placement technique, apical to occlusal layering placement technique, and buccolingual layering placement technique. And the interface between the restoration and the tooth structure was observed with scanning electron microscope. The following results were obtained. 1. Marginal adaptation of enamel showed excellent irrespective of the filling techniques. 2. Marginal leakage of dentin was observed irrespective of the filling techniques. 3. No difference of marginal adaptation according to the filling techniques was observed in light curing composite resin.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.521-522
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• 2006

Occlusal loading is considered as the main factor of noncarious cervical lesions. The goal of this study is to identify stress distribution using three dimensional finite element analysis, when occlusal loading is applied on the cervical lesion of human tooth. A finite element model was constructed from micro-CT image and three kinds of static force(500 N) were assumed. In all cases stress concentrates on the same area in the cement-enamel junction. This finding is consistent with published experimental results.

• Journal of Food Hygiene and Safety
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• v.14 no.1
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• pp.22-26
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• 1999

The purpose of this experiment was to examine the antimicrobial effect of the natural flavonoid hesperidin on dental caries and alveolar bone resorption in the albinorats. Twenty five day old male rats were fed with the experimental diets for 42 days. At the end of the 42 day experimental period, the molar tooth occlusal surface was examined by a dissecting microscope. The sulcular caries lesions were recorded: the first molar caries incidence was higher than that of the second molar and the third molar. Alvelolar bone resorption was measured on the buccal and lingual aspects of each molars. Three measurements were taken on the first molar (mesialpoint, midpoint, distalpoint). The results of this experiments, showed that hesperidin is effective in reducing dental caries and alveolar bone resorption.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.44 no.4
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• pp.198-203
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• 2018

Dyke-Davidoff-Masson syndrome is a non-inherited rare condition that presents during childhood and is characterized by seizures, hemiplegia, mental retardation, cerebral hemiatrophy, calvarial thickening, and hyperpneumatization of the frontal sinuses. The present article highlights a case of a 12-year-old male child with additional clinical findings of $caf{\acute{e}}$-au-late pigmentation and ocular lipodermoid. This is the first case report of DykeDavidoff-Masson syndrome to describe oral manifestations, such as unilateral delayed eruption of teeth, hypoplasia, and taurodontism, which could be unique and characteristic of this condition. Oral health care providers and physicians should be aware of these oral observations as dental referrals could warrant early dental prophylactic care and can be useful in diagnosing the possible time of injury and type of Dyke-Davidoff-Masson syndrome.

• Current Optics and Photonics
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• v.6 no.1
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• pp.86-91
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• 2022

Two-photon fluorescence microscopy was performed on the enamel-dentin junction area of a human tooth using a femtosecond pulsed laser. We obtained a clear image contrast between the bright dentin and dark tubules with the autofluorescence generated from the endogenous fluorophores in dentin. The autofluorescence shows a broad spectrum due to complex cross links between dentinal collagens, which extend from blue to orange wavelengths (470-590 nm), but a gradual autofluorescence loss in photobleaching was observed for a long-term exposure under strong excitation. For increasing excitation power, we found that two-step decay becomes significant in the spectrally integrated autofluorescence.