• Restorative Dentistry and Endodontics
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• v.24 no.1
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• pp.129-135
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• 1999

In this review article, in vivo and in vitro wear test methods which measure the wear of tooth and restorative material were discribed. In vivo test, the criteria of each test were reviewed. The merits and limitations were also commented. In vitro tests, three dimensional scanning methods which scan the occlusal tooth surface three dimensionally were described. Profilometer method, Pin on disk method, laser scanner method were reviewed and the limitations of each test were commented. Additionally, the structer of the three dimensional scanner which has been developed in Zurich university and has been reputated as the most accurate one was described. This study was partly supported by 1997 post-doctoral foreign study program.

• The Journal of Advanced Prosthodontics
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• v.16 no.1
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• pp.12-24
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• 2024

PURPOSE. This study aimed to evaluate the maximum vertical wear, volume wear, and surface characteristic of antagonist enamel, opposing monolithic zirconia or lithium disilicate crowns. MATERIALS AND METHODS. The study comprised 24 participants (n = 12), who were randomly allocated to receive either a 5 mol% Y-TZP or a lithium disilicate crown in positions which would oppose the natural first molar tooth. The contralateral first molar along with its antagonist was considered as the enamel opposing natural enamel control. Data collection was performed using an intraoral scanner and polyvinylsiloxane impression. The means of the maximum vertical loss and the volume loss at the occlusal contact areas of the crowns and the various natural antagonists were measured by 3D comparison software. A scanning electron microscope was subsequently used to assess the wear characteristics. RESULTS. The one-year results from 22 participants (n = 11) indicated no significant differences when comparing the zirconia crown's antagonist enamel (40.28 ± 9.11 ㎛, 0.04 ± 0.02 mm³) and the natural enamel wear (38.91 ± 7.09 ㎛, 0.04 ± 0.02 mm³) (P > .05). Also, there is no significant differences between lithium disilicate crown's antagonist enamel (47.81 ± 9.41 ㎛, 0.04 ± 0.02 mm³) and the natural enamel wear (39.11 ± 7.90 ㎛, 0.04 ± 0.02 mm³) (P > .05). CONCLUSION. While some studies suggested that monolithic zirconia caused less wear on opposing enamel than lithium disilicate, this study found similar wear levels to enamel for both materials compared to natural teeth.

• The Journal of Korean Academy of Prosthodontics
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• v.61 no.3
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• pp.234-244
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• 2023

Tooth wear refers to the loss of dental hard tissue caused by various physiological and pathological causes, and excessive pathological wear can cause complications such as pathological changes in dimensions, occlusal disharmony, loss of function, and aesthetic problems. The cause of tooth wear can be caused by attrition, abrasion, corrosion and abfraction, and it is known to act in a multifactorial etiology in interocclusal activity. In patients with excessive pathological wear, it is important to determine whether or not the vertical dimension of occlusion is reduced, and complete oral rehabilitation should be achieved with the adaptation of the neuromuscular and temporomandibular joint through accurate diagnosis and analysis. The patient in this case was a 63-year-old male patient, who presented discomfort to cold beverage due to severe tooth wear. After analysis of the patient's vertical dimension of occlusion, a full mouth rehabilitation was performed with increasing vertical dimension of occlusion. The goal of treatment was to improve the occlusal plane with the equal-intensity contact of all teeth, harmonious anterior guidance and immediate disclusion of all posterior contacts. After rehabilitation, the patient was satisfied with function and esthetic appearance.

• The Journal of Korean Academy of Prosthodontics
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• v.60 no.1
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• pp.80-90
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• 2022

With the development of digital dentistry, it is being applied in various ways of dental treatment. This case report presents the definitive prosthesis designed in advance with a re-established vertical dimension and the digital technology, which determined the amount of tooth preparation, in order to preserve as much tooth structure as possible in a patient with pathological wear of the posterior teeth and loss of vertical dimension. For accurate tooth preparation, the guides of the occlusal and axial surfaces were digitally and additively manufactured. Then, aesthetics and anterior guidance were established at the provisional stage. The information of the provisional restoration was delivered to the definitive stage by double scanning. The digital technology, including the virtual planning and the guided tooth removal, produced the definitive restorations satisfactory to both the patient and clinician.

• The Journal of Korean Academy of Prosthodontics
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• v.57 no.3
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• pp.280-287
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• 2019

In the oral cavity, the teeth undergo wear and corrosion throughout their lives. Progressive and constant tooth wear is a natural phenomenon of aging, but wear and corrosion due to specific factors are pathological factors. It can cause pathological damage of the occlusal surface, aesthetic problems, dimensional loss and jaw joint disorders. This case is a 26-year-old female patient with general tooth abrasion and erosion on the entire dentition. Diagnostic wax-up was fabricated based on the information including digital facial analysis, physiological stabilization, and evaluation of anterior crown length. Through the digital analysis, the necessary guides for crown lengthening were prepared and the mastication function and esthetics were evaluated by using temporary crowns. Definitive prosthesis was fabricated with the zirconia restorations. The results were satisfactory when they were observed 3 months of follow-up.

• The Journal of Korean Academy of Prosthodontics
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• v.58 no.4
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• pp.369-377
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• 2020

Gradual teeth wear is normal physiological progress, severe tooth wear can causes dysfunction, occlusal plane disharmony and esthetic problems. If additional space is needed for prosthetic restoration due to severe attrition, full mouth rehabilitation with increase of occlusal vertical dimension may be considered. In this case, 72 year old male patient with severe worn dentition, irregular gingival zenith and deep anterior bite was treated by full mouth rehabilitation for regaining the space for restoration, improving relationship and esthetic of anterior teeth. Provisional restoration obtained by systemic analysis, diagnosis and re-evaluation for a sufficient time was replicated to final restorations through double scanning technique using monolithic zirconia blocks. Satisfactory functional and esthetic outcomes were obtained.

• Tribology and Lubricants
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• v.7 no.2
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• pp.67-74
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• 1991

The contact characteristics of gear tooth surface were studied by using the gear test rig of power circulation type. The effect of surface treatment conditions and revolutions on the tooth surface roughness parameters, and the relations between the lubrication conditions and tooth surface conditions, in spur gear sets wear considered. The result show that heat treatment of gear have an important effect upon fatigue strength and tooth surface conditions, and surface asperities undergo a circulating process of creation and destruction because of the influnce of plastic deformation. And surface roughness conditions at the tooth tips accompany a great deal of variation in running-in stage. According to the lubrication analysis and the study the tooth surface have a greater effect on surface demage than lubrication conditions, in mixed-lubrication condition.

• The Journal of Korean Academy of Prosthodontics
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• v.50 no.4
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• pp.324-329
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• 2012

Excessive tooth wear causes loss of tooth structure, disharmony of occlusal plane, functional and esthetic problems. Although the decrease of occlusal vertical dimension may be compensated by growth of alveolar bone, if the length of tooth is not enough for the retention of restoration, minimum increase of occlusal vertical dimension is required without discomfort of the patient. In this case, 33-year-old woman drinks more than 1 liter of soft drinks a day and has bruxism in night time, visited in Seoul National University Dental Hospital with chief complaint of generalized tooth wear and related esthetic and functional problems. It was considered as a loss of occlusal vertical dimension based on the accelerated tooth wear caused by erosion and bruxism and facial appearance, phonetic, esthetic, functional evaluations. It was planned to raise occlusal vertical dimension by provisional restoration two times for patient's adaptation, 3 mm and 2 mm each, total 5 mm. Confirming no discomfort and clinical symptom during total 16 weeks after restoration with provisional fixed restoration, it was restored with porcelain fused to gold crown and bridge. Because the patient was young woman, anterior teeth were restored with collarless porcelain fused to gold crown. This case presents that satisfactory esthetic and functional result by full mouth rehabilitation with increase of occlusal vertical dimension.

• The Journal of Korean Academy of Prosthodontics
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• v.61 no.1
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• pp.33-43
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• 2023

Pathological wear across the entire dentition causes problems such as collapsed occlusal plane, reduced vertical dimension, anterior premature contact, inadequate anterior guidance, and tooth migration, thereby induce symptoms such as temporomandibular joint disorder, reduced masticatory efficiency, and tooth hypersensitivity. For the treatment of patients with excessive wear, evaluation of vertical dimension should be preceded along with analysis of the cause. The patient in this case was a 45-year-old female with a history of orthognathic surgery. Through clinical examination, radiographic examination, and model analysis, overall tooth wear, interdental spacing in the anterior maxillary region, retruded condylar position, and insufficient interocclusal space for prosthetic restoration were confirmed. Full mouth rehabilitation with increased vertical dimension was planned, the patient's adaptation to the new vertical dimension was evaluated with a removable occlusal splint and temporary prosthesis, and cross-mounting was performed based on the temporary restoration to fabricate the definitive zirconia prosthesis, maintaining the adjusted vertical dimension. It showed satisfactory functional and esthetic results through stable restoration of the occlusal relationship.

• Transactions of Materials Processing
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• v.28 no.4
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• pp.183-189
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• 2019

Cylindrical worm reducers are generally used in various fields and forms throughout the industry, and demand is increasing due to their role as an integral part of the industry. Market trends require high-load, high-precision components, and small-sized reducers with large loads. When using a cylindrical worm reducer, a reducer designed with a reduced center distance while maintaining the same output torque results in gear wear. To overcome this difficulty, an enveloping worm gear reducer is introduced and studied. In this paper, three types of end mill tools are used to evaluate the tooth profile accuracy for each tool shape during machining of the tooth profile for a non-developed surface worm thread. The effect of the endmill shape on the accuracy of the tooth profile was analyzed by performing 3D modeling of the surrounding worm tooth profile based on the Hindley method. In this study, we analyzed tooth profile accuracy, tooth surface roughness, and tooth surface machining time, etc. Through the study, efficient machining conditions for the enveloping worm gears and the influence of parameters on the process were presented.