ABSTRACT
In vitro studies are essential to predict the clinical performance of ceramic widely used as restorative materials. Traditional experiments such as fracture toughness and flexural strength have been used to evaluate the properties of brittle ceramics. However, these experiments have a limitation that the load conditions, failure patterns, and load values at which failure occurs are not similar to human occlusal force ranges or clinical failures. On the other hand, the edge chipping test (ECT), which was recently introduced to study chipping fracture of ceramics, has similar failure patterns to clinical trials. In addition, the failure loads from ECT were similar to human occlusal force. ECT can be usefully used in the study of ceramic properties. In this literature review, a more clinically meaningful experimental study of ceramics by examining the meaning and limitations of traditional ceramic failure tests and comparing them with ECT.
ABSTRACT
In mammalian species, females are born with a number of oocytes exceeding what they release via ovulation. In humans, an average girl is born with over a thousand times more oocytes than she will ovulate in her lifetime. The reason for having such an excessive number of oocytes in a neonatal female ovary is currently unknown. However, it is well established that the oocyte number decreases throughout the entire lifetime until the ovary loses them all. In this review, data published in the past 80 years were used to assess the current knowledge regarding the changing number of oocytes in humans and mice, as well as the reported factors that contribute to the decline of oocyte numbers. Briefly, a collective estimation indicates that an average girl is born with approximately 600,000 oocytes, which is 2,000 times more than the number of oocytes that she will ovulate in her lifetime. The oocyte number begins to decrease immediately after birth and is reduced to half of the initial number by puberty and almost zero by age 50 years. Multiple factors that are either intrinsic or extrinsic to the ovary contribute to the decline of the oocyte number. The inflammation caused by the ovulatory luteinizing hormone surge is discussed as a potential contributing factor to the decline of the oocyte pool during the reproductive lifespan.
ABSTRACT
Loss of posterior bite support might cause unstable occlusal relationship and when the mandible slides forward in the centric or habitual occlusion, excessive load is applied to the anterior region followed by causing the occlusal plane to collapse or leading to a decrease in occlusal vertical dimension. In addition, disorder of temporomandibular joint function may occur. The inter-dental arch discrepancy causes a mismatch in the vertical and horizontal overlap of the anterior and posterior regions. The deep bite in the anterior region and the scissor bite in the posterior region cause unstable occlusal contact and insufficient occlusal contact area. This report was to rehabilitate a patient with above-mentioned complex problems. Physiologic adaptation to increased vertical dimension and new occlusal plane were evaluated using provisional prostheses, and definitive prostheses was fabricated using cross-mounting technique. Stable occlusion, harmonious teeth overlap and adequate occlusal plane were established, so functionally and aesthetically satisfactory results are obtained.
ABSTRACT
Additive manufacturing (AM) for dental materials can produce more complex forms than conventional manufacturing methods.Compared to milling processing, AM consumes less equipment and materials, making sustainability an advantage. AM can be categorized into 7 types. Polymers made by vat polymerization are the most suitable material for AM due to superior mechanical properties and internal fit compared to conventional self-polymerizing methods. However, polymers are mainly used as provisional restoration due to their relatively low mechanical strength. Metal AM uses powder bed fusion methods and has higher fracture toughness and density than castings, but has higher residual stress, which requires research on post-processing methods to remove them. AM for ceramic use vat polymerization of materials mixed with ceramic powder and resin polymer. The ceramic materials for AM needs complex post-processing such as debinding of polymer and sintering. The low mechanical strength and volumetric accuracy of the products made by AM must be improved to be commercialized. AM requires more research to find the most suitable fabrication process conditions, as the mechanical properties and surface of any material will vary depending on the processing condition.
ABSTRACT
Clinical applications of translucent zirconia as well as traditional zirconia (3 mol% yttria stabilized tetragonal zirconia polycrystal, 3Y-TZP) are increasing. For this reason, studies on factors affecting the optical properties of dental zirconia have been continuously reported. The optical effect of dental zirconia may vary depending on the yttria content, the thickness of the prosthesis, the sintering process, polishing, glazing and cementation in laboratory and clinical procedures. Increasing the yttria concentration can reduce the masking effect. Translucency decreases as the thickness of the restoration increases, but the required thickness may vary depending on the properties of the zirconia block. The high-speed sintering method can shorten the manufacturing time, but in some cases, the translucency of the prosthesis may decrease. In addition, the optical properties can be affected by the surface roughness of zirconia and the polishing process. The use of an appropriate colored cement can help with the masking effect of zirconia and can be useful for color matching for more esthetic results.
ABSTRACT
There are very few reports of the restoration of tooth loss using dental implants in patients with diffuse sclerosing osteomyelitis (DSO). Because the patients with DSO have unfavorable bone quality for osseointegration of dental implants, additional considerations such as surgical trauma, infection control, and an extended healing period are essential when placing dental implants. The purpose of this study is to report on the success of osseointegration of a dental implant in the patient with DSO.
ABSTRACT
Implant prostheses and removable partial dentures are mainly used as treatment methods for partial edentulous patients who have lost a number of teeth. The implant-assisted removable partial denture (IARPD) is strategically selected. The defect in maxillofacial structure due to osteomyelitis, a type of facial bone infection, causes dysfunction such as mastication, swallowing, and pronunciation, as well as social and psychological effects, so a removable restoration is required to restore the supporting tissue. Design of abutment and partial dentures is an essential factor in the success of treatment. In this case, IARPD, which has superior retention and stability compared to traditional removable partial dentures, can have a good prognosis. In a partial edentulous patient with bone defects due to osteomyelitis treatment, the stability of the denture was secured with IARPD restoration. Moreover, maintenance problem that may occur in the future was minimized by providing an appropriate denture design and occlusal scheme through several provisional restorations. This case can be expected to have a favorable prognosis in the long term.
ABSTRACT
Congenital tooth agenesis is the most common developmental dental anomaly, of which oligodontia is defined as the absence of six or more permanent teeth, except the third molars. Tooth agenesis causes malocclusion, alveolar atrophy, aesthetic and psychosocial problems. This clinical report describes a multidisciplinary treatment for a patient diagnosed as oligodontia, who exhibited absence of 14 permanent teeth, atrophy of maxillary alveolar bone, and mandibular protrusion. Restoration space was secured and tooth axis was improved by the extraction of deciduous teeth and orthodontic treatment. However, edge-to-edge bite of posterior teeth and arch dimension discrepancy due to atrophic maxilla was remained. To restore the aesthetics and functionality, implant retained prosthesis was planned. Considering minimal bone grafts, location and number of dental implants and prostheses design were determined. Through the gradual adjustment of provisional restoration, the appropriate centric and eccentric occlusion was reflected into a definitive prosthesis. Currently, stable functional results were attained, however, regular follow up and maintenance care over lifetimes should be performed.
ABSTRACT
Purpose@#The aim of this study is to compare the hardness according to the conditions of metal alloys. Moreover, the correlation between the cast crown hardness before and after wear testing and the degree of wear for each dental alloy was assessed. @*Materials and Methods@#Cast crowns of three metal alloys (Co-Cr, gold, and Ni-Cr alloys) opposing smooth-surface monolithic zirconia were used. The Vickers microhardness of the ingot (which did not undergo wear testing) and the cast crown before and after wear testing were measured for each alloy. Two-way ANOVA and Scheffé tests were used to compare the measured hardness values. Moreover, the Pearson correlation coefficient was used to evaluate the relationship between the surface hardness and the wear of the cast crown (α=.05). @*Results@#There was no significant difference in the hardness before and after wear testing for the gold alloy (P >.05); however, the hardness of the worn surface of the cast crown increased compared to that of the cast crown before the wear tests of Ni-Cr and Co-Cr alloys (P .05). @*Conclusion@#There was a significant difference in hardness between dental alloys under the same conditions. No correlation existed between the surface hardness of the cast crown before and after wear testing and the wear of the cast crown.
ABSTRACT
There are very few reports of the restoration of tooth loss using dental implants in patients with diffuse sclerosing osteomyelitis (DSO). Because the patients with DSO have unfavorable bone quality for osseointegration of dental implants, additional considerations such as surgical trauma, infection control, and an extended healing period are essential when placing dental implants. The purpose of this study is to report on the success of osseointegration of a dental implant in the patient with DSO.
ABSTRACT
Implant prostheses and removable partial dentures are mainly used as treatment methods for partial edentulous patients who have lost a number of teeth. The implant-assisted removable partial denture (IARPD) is strategically selected. The defect in maxillofacial structure due to osteomyelitis, a type of facial bone infection, causes dysfunction such as mastication, swallowing, and pronunciation, as well as social and psychological effects, so a removable restoration is required to restore the supporting tissue. Design of abutment and partial dentures is an essential factor in the success of treatment. In this case, IARPD, which has superior retention and stability compared to traditional removable partial dentures, can have a good prognosis. In a partial edentulous patient with bone defects due to osteomyelitis treatment, the stability of the denture was secured with IARPD restoration. Moreover, maintenance problem that may occur in the future was minimized by providing an appropriate denture design and occlusal scheme through several provisional restorations. This case can be expected to have a favorable prognosis in the long term.
ABSTRACT
Congenital tooth agenesis is the most common developmental dental anomaly, of which oligodontia is defined as the absence of six or more permanent teeth, except the third molars. Tooth agenesis causes malocclusion, alveolar atrophy, aesthetic and psychosocial problems. This clinical report describes a multidisciplinary treatment for a patient diagnosed as oligodontia, who exhibited absence of 14 permanent teeth, atrophy of maxillary alveolar bone, and mandibular protrusion. Restoration space was secured and tooth axis was improved by the extraction of deciduous teeth and orthodontic treatment. However, edge-to-edge bite of posterior teeth and arch dimension discrepancy due to atrophic maxilla was remained. To restore the aesthetics and functionality, implant retained prosthesis was planned. Considering minimal bone grafts, location and number of dental implants and prostheses design were determined. Through the gradual adjustment of provisional restoration, the appropriate centric and eccentric occlusion was reflected into a definitive prosthesis. Currently, stable functional results were attained, however, regular follow up and maintenance care over lifetimes should be performed.
ABSTRACT
Purpose@#The aim of this study is to compare the hardness according to the conditions of metal alloys. Moreover, the correlation between the cast crown hardness before and after wear testing and the degree of wear for each dental alloy was assessed. @*Materials and Methods@#Cast crowns of three metal alloys (Co-Cr, gold, and Ni-Cr alloys) opposing smooth-surface monolithic zirconia were used. The Vickers microhardness of the ingot (which did not undergo wear testing) and the cast crown before and after wear testing were measured for each alloy. Two-way ANOVA and Scheffé tests were used to compare the measured hardness values. Moreover, the Pearson correlation coefficient was used to evaluate the relationship between the surface hardness and the wear of the cast crown (α=.05). @*Results@#There was no significant difference in the hardness before and after wear testing for the gold alloy (P >.05); however, the hardness of the worn surface of the cast crown increased compared to that of the cast crown before the wear tests of Ni-Cr and Co-Cr alloys (P .05). @*Conclusion@#There was a significant difference in hardness between dental alloys under the same conditions. No correlation existed between the surface hardness of the cast crown before and after wear testing and the wear of the cast crown.
ABSTRACT
Clinical remounting of complete denture is performed to refine occlusal harmony in maxillo-mandibular relation. It has been reported that patients who used adjusted dentures with clinical remounting felt less complications such as pain and discomfort in mastication. The purpose of this study was to assess effects of clinical remounting with case series. Seven patients with existing complete prosthesis were included. Clinical remounting procedure was done through interocclusal relation recording. In addition, occlusal force was measured with pressure indicating sensor and occlusal contact areas were evaluated with photo occlusion analysis. Occlusal contact areas of prosthesis were enlarged, while bite pressure was not increased. Hit and slide phenomenon of prosthesis was reduced concurrently. Clinical remounting procedure improved denture stability and increased occlusal contact area. Therefore, clinical remounting should be considered.
ABSTRACT
Denture adhesive is a material used to improve the retention and stability of the denture. And denture adhesive is divided into soluble and insoluble type. It improves the retention, stability of dentures, and masticatory functions of patients. Maintenance like cleansing and periodic follow up is essential. Almost of dental clinicians are only simply aware of the effects of denture adhesives and often rely on the manufacturer's instructions on precautions and maintenance. The purpose of this study is to examine the properties, effects, and precautions of denture adhesives, and to present clinical guidelines for patients and professionals.
ABSTRACT
Although not all kinds of deep bite occlusions are considered pathological states, they can cause persistent wear and eruption of the anterior mandibular teeth if the anteriorocclusal contact is unstable or accompanied by an occlusal disharmony. The patient was a 72-year-old man with no occlusal contact of the remaining anterior teeth in the centricrelation position because of a skeletal class II malocclusion and loss of occlusal support. If the vertical dimension needs to be increased for prosthetic restoration in apatient with a deep bite, the amount of vertical dimension increase must be determined through precise diagnosis. This is because the overjet may increase and cause anunstable occlusion. In this review, we report the case of a patient with a stable occlusion and good treatment results achieved by using a removable partial denture prosthesisand applying the Dahl concept. (J Korean Acad Prosthodont 2020;58:110-20)
ABSTRACT
. The effect of core design on the fracture resistance of zirconia-lithium disilicate (LS2) bilayered crowns for anterior teeth is evaluated by comparing with that of metal-ceramic crowns. MATERIALS AND METHODS. Forty customized titanium abutments for maxillary central incisor were prepared. Each group of 10 units was constructed using the same veneer form of designs A and B, which covered labial surface to approximately one third of the incisal and cervical palatal surface, respectively. LS2 pressed-on-zirconia (POZ)and porcelain-fused-to-metal (PFM) crowns were divided into “POZ_A,” “POZ_B,” “PFM_A,” and “PFM_B”groups, and 6000 thermal cycles (5/55 °C) were performed after 24 h storage in distilled water at 37 °C. All specimens were prepared using a single type of self-adhesive resin cement. The fracture resistance was measured using a universal testing machine. Failure mode and elemental analyses of the bonding interface were performed.The data were analyzed using Welch’s t-test and the Games-Howell exact test. RESULTS. The PFM_B (1376. 8 ±93.3 N) group demonstrated significantly higher fracture strength than the PFM_A (915.8 ± 206.3 N) and POZ_B (963.8 ± 316.2 N) groups (P.05). Regardless of the design differences of the zirconiacores, fractures involving cores occurred in all specimens of the POZ groups. CONCLUSION. The bilayered anterior POZ crowns showed different fracture resistance and fracture pattern according to the core design compared to PFM.
ABSTRACT
Purpose@#The purpose of this study was to compare the axial displacement of the hexagonal and conical abutment in internal conical connection implant after screw tightening and cyclic loading. @*Materials and Methods@#Internal conical connection implants were divided into two groups (n = 10): group HEX, hexagonal abutment; and group CON, conical 2-piece abutments. The axial displacement and removal torque values were measured after 30 Ncm torque tightening and 250N loading test of 100,000 cycles. The Student t test with 5% significance level was used to evaluate the data. @*Results@#HEX group demonstrated significantly higher axial displacement values after 30 Ncm tightening in comparison to the CON group (P < 0.05). No significant difference was found in axial displacement after cyclic loading (P = 0.052). Removal torque loss before and after the cyclic loading both revealed no significant difference between groups (P = 0.057 and P = 0.138). Removal torque value decreased after cyclic loading in both groups (P < 0.05). @*Conclusion@#Overall, both abutment with or without hexagon index presented similar biomechanical performance except HEX group demonstrated significantly more axial displacement after applying tightening torque.
ABSTRACT
The typical biomechanical properties of an internal conical connection (ICC) are axial displacement and loss of preload. The axial displacement of an ICC without a vertical stop can cause the loss of preload and a lowered occlusion. The stress of an ICC is concentrated on the contact interface of the abutment and not on the screw, and during placement, it is important to choose a wider coronal wall thickness as much as possible. The ICC should also be placed below the level of the bone crest. During the restoration of an ICC, care should be taken to ensure an appropriate abutment shape and an accurate connection. To get the best clinical results, it is important to select its wall thickness and place it in the appropriate position to restore it adequately.
ABSTRACT
To use the external connection implant (EXT) appropriately, the inter-implant distance should be carefully considered during placement, and the bones raised above the implants should be trimmed during the second surgery. The hex abutment is more useful than the non-hex abutment. EXT is particularly useful when the inter-arch space is limited. The tissue level (TL, internal butt connection) implant has a biomechanical advantage of coronal wall thickness and a biological advantage of an inherent transmucosal smooth surface. During TL implant restoration, an abutment can be selected using the abutment and fixture margins with considerations for the inter-arch space. Since no single type of implant can satisfy all the cases, it is necessary to select the appropriate type, considering the occlusal force and the bone condition.