• The Journal of Korean Academy of Prosthodontics
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• v.37 no.4
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• pp.474-493
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• 1999

According to repeated measurements and correction procedures, the accuracy of the phase-shifting profilometry was developed. At first, after 20 final models for maxillary complete denture were duplicated , the mucosa sur-faces of models were measured with the phase-shifting proflometry and each mirror view of these was calibrated. Maxillary casts were divided into 4 groups of 5 casts per each, and wax dentures with 2 sheets of baseplate wax and artificial teeth were made and then cured according to the curing method of each group. Group I ; quick curing with QC-20 acrylic resin Group II ; 9 hour curing with QC-20 acrylic resin Group III ; SR-Ivocap system Group IV ; metal base and quick curing with QC-20 acrylic resin. After curing, polishing, and storing at $37^{\circ}C$ in saline for 30 days, the forms of the impression surface of the dentures were measured with the phase-shifting profilometry. Then, the impression surface form of each denture was placed in the optimal position of com-parison with the mirror view of the same final cast. The amount and direction of distortion of each denture was analyzed and the effects of polishing and storage in each denture were compared, The obtained results were as follows : 1. In Group I, the denture was observed as the appearance distorted in the opposite direction of the mucosa and the postero-lateral part of palatal portion of the denture was observed as the appearance separated from the mucosa. Also, the buccal flanges of the denture were observed as the appearance distorted in the direction of the mucosa. 2. In Group II, the postero-lateral part of palatal portion of the denture was observed as the appearance separated slightly from the mucosa. The bilateral buccal flanges of denture were observed as the appearance distorted severely in the direction of the mucosa. 3. In Group III the bilateral part of the residual ridge crest portions and the buccal flanges of the denture were observed as the appearance distorted in the direction of the mucosa, and specially, the buccal flanges of the maxillary tuberosities were distorted severely. 4. In Group IV, the acrylic resin base of the buccal portion of the denture was observed as the appearance distorted in the opposite direction of the mucosa. 5. The phase-shifting profilometry, done with repeated measurements and correction procedures, was effective in comparing the amount and direction of distortion at every position after the laboratory work and the delivery of maxillary complete denture.

• Journal of Technologic Dentistry
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• v.27 no.1
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• pp.115-129
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• 2005

The purpose of this study was to identify injury characteristics happened in the college dental laboratory technique classes and to provide the empirical accident findings for safety education development for the college dental technology classes. The research data were collected from a self-administered survey distributed to the conveniently selected college students. The study participants were 476 freshmen, sophomore and junior students whose major was the dental laboratory technology of the 4 colleges in 2 metropolitan cities and 2 medium-size cities. All collected survey responses were encoded and analyzed in SPSS 12.0. The findings were as follows. The accidents happened to the college students during the dental laboratory technology classes: 1. The accident rate was the highest in the sophomore and the freshmen, junior in order. 2. The body parts frequently injured were hands, face, eyes, arms, and legs in order. 3. The frequent injury types were cut, burnt, stuck, wound, and suffocated in order. 4. The treatment methods for their accidents were the simple first-aids, no treatment, and the emergency room visits in order. 5. The laboratory training conditions inducing the accidents were significantly frequent under wire-related, and wax-related, iron-related, alcohol-related jobs in order, but not frequent in investing material-related, porcelain-related, resin-related, and agar-related jobs. Polishing was the most accident-prone job explaining 63% of the laboratory accidents and then, model producing, wax patterning, casting, burning, and investing jobs in order. In summary, the college dental laboratory accidents had the certain patterns by the training level and by the material or machine involved in each class. Thus, the planned and organized safety education programs should be produced and investigated for college students before their major laboratory classes.

• Journal of Technologic Dentistry
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• v.27 no.1
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• pp.131-153
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• 2005

The purpose of this study was to identify the accidents happened in the college dental laboratory technique classes and to realize the level of safety education for the dental laboratory technique major students. The research data were collected from a self-administered survey distributed to the conveniently selected college students whose majors were dental laboratory technology in Suwon, Daejeon, Daegu, Kimcheon, and Icsan. The study participants were 422 freshmen, sophomore and junior students in the selected cities. All collected survey responses were encoded and analyzed in SPSS 12.0. The findings were as follows. 1. The students who had any accidents in their laboratory classes were 36% and the other 64% answered 'no.' 2. Most injuries which the participants had were not significant. 3. The medical treatment periods of most injury cases were less than one week; however, approximately 20% of the self-reported injury cases reported that their treatment periods were longer than one week. 4. The body parts frequently injured from accidents were hands with 84.7% and arms, eyes, face, head, and legs in order. 5. Concerning the materials involved in the laboratory classes, most accidents happened when working with wax in 59.9%, with plaster in 52.3%, with wire in 39.8%, with alcohol in 34.6%, and casting iron in 22.2% in order. 6. The accident-prone laboratory methods were polishing with 53.5%, pickling or sanding with 17.4%, and casting or burning with 5.8% in order. 7. Most students wore their laboratory gowns well; however, few students wore mask before dust-involved jobs. Furthermore, only 57.1% students answered their laboratory fans worked during the polishing job. 8. Approximately 54% participant students answered that they took laboratory safety education when necessary only from the class instructors. 9. The 76.1% students responded that they needed laboratory safety education at least 1-2 times every semester. 10. The survey participants answered that the primary factors for injury prevention in their laboratory were taking safety education, wearing safety equipments, and providing safety-focused facilities. Concludingly, comprehensive evaluation and monitoring for potential risk factors from both the human side and the environment side should be continually provided to minimize the college laboratory accidents.

• Journal of Technologic Dentistry
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• v.28 no.1
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• pp.177-198
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• 2006

This study purposed to offer basic data for safety education of the dental laboratory technology after the investigation of how much the students in the dept. of dental laboratory technology are aware of the danger of each instrument, equipment or laboratory procedure that they use during laboratory and how much they demand safety education for this. The objects for this study were 423 students who were in the dept. of dental laboratory technology. In this regard, four colleges which have the dept. of dental laboratory technology were randomly selected to do a questionnaire survey. SPSS 12.0 was used to analyze the collected data. The results were as follows: As for satisfaction with their major, the respondents answered Satisfied (59.1%), Average (35.5%) and Dissatisfied (5.4%). In terms of the production process of a partial denture, they considered casting, polishing the casting body, polishing denture and burn out were most dangerous in order. As for the production process of a full denture, what they regarded as the most dangerous in order was polishing denture, deflasking and wax wash. Regarding the laboratory procedures of porcelain material, casting, trimming casting body, polishing porcelain material and burn out were the most dangerous procedures that they perceived. With regard to materials for use, alcohol, polishing, metal and wire were the most dangerous ones they thought. As for the handling characteristics of each material, small towns showed a higher demand for safety of the handling characteristics of alcohol. In terms of school year and sex, juniors and girls had higher scores in the demand for safety of the handling characteristics of acid. Regarding the handling characteristics of each equipment and instrument, all of small towns, juniors and girls showed the highest demand for safety of the handling characteristics of alcohol lamps. With regard to scores in the demand for safety of other characteristics, all of small towns, juniors and girls had the highest demand for safety of emergency treatment. Concerning the demand for safety education by the completion of safety education, in terms of each material, highest was the demand for safety of acid from the group which completed safety education. In regard to equipments and instruments, when it came to the demand for safety of the handling characteristics of casting machine, the educated group's demand for safety of acid was higher. Regarding other characteristics, the group which was not educated gained higher scores in the demand for safety of emergency treatment. 11. In all areas(materials, machines and others), small towns, girls and juniors showed higher scores in the demand for safety. Based on the above results, it was found that when students conduct the laboratory of dental technology, they would think that many materials, instruments or equipments for use are very dangerous. However, safety education was not fully given to them. Regarding the scores in the damned for safety education, the highest was 4.16 and the lowest was 3.43, which suggests that the scores were generally very high. In this regard, it is necessary to continue delivering a systematic safety education of materials, equipments or instruments used during the laboratory of dental technology. Therefore, through the analysis of each material, instruments or facility used in every laboratory and each process, safety accident types and accident risk factors should be investigated to develop educational materials for this. Moreover, it is required to open safety education as a single course of study or insert safety contents of all materials and machines into the class of dental laboratory instrument or dental materials for the purpose of a systematic and thorough safety education to prevent a safety accident during laboratory.

• The Journal of Korean Academy of Prosthodontics
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• v.54 no.4
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• pp.445-450
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• 2016

Piezography, prosthetic space recorded by pronunciation, can be used as a reference for arrangement of artificial teeth and polishing surface of a denture. In this case, a 67 year old female patient was presented for new dentures. Old dentures had class II relationship and poor retention. For fabrication of stable dentures, using piezography and lingualized occlusion was planned. After taking impressions with conventional method, conventional denture bases with wax rim were fabricated. Then, additional mandibular denture base was fabricated for piezography. With fast setting silicon impression material, piezography was recorded by using six pronunciations, 'si', 'so', 'me', 'te', 'de', and 'mu'. According to the piezographic space, mandibular artificial teeth were arranged and modified for lingualized occlusion. As a result, the patient was satisfied with new dentures functionally and esthetically.

• Restorative Dentistry and Endodontics
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• v.28 no.5
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• pp.363-368
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• 2003

The purpose of this study is to evaluate the effect of additional enamel etching with phosphoric acid on the microleakage of the adhesion of self-etching primer system. Class V cavity($4mm{\times}3mm{\times}1.5mm$) preparations with all margins in enamel were prepared on buccal surface of 42 extracted human upper central incisor teeth. Prepared teeth were randomly divided into 3 groups. Group 1：no additional pretreatment with 37% phosphoric acid (NE). Group 2：additional pretreatment with 37% phosphoric acid for 10 seconds (E10s). Group 3：additional pretreatment with 37% phosphoric acid for 20 seconds (E20s). The adhesives(Clearfil SE $Bond^{\circledR}$, Kuraray, Osaka, Japan) and composite resins(Clearfil $AP-X^{\circledR}$, Osaka, Kuraray, Japan) were applied following the manufacturer's instructions. All the specimens were finished with the polishing disc(3M dental product, St Paul, MN, USA), thermocycled for 500 cycles between $5^{\circ}C$ and $55^{\circ}C$ and resected apical 3-mm root. 0.028 stainless steel wire was inserted apically into the pulp chamber of each tooth and sealed into position with sticky wax. Surrounding tooth surface was covered with a nail varnish 2 times except areas 1mm far from all the margins. After drying for one day, soaked the samples in the distilled water. Microleakage was assessed by electrochemical method(System 6514, $Electrometer^{\circledR}$), Keithley, USA) in the distilled water. In this study, the microleakage was the lowest in group 1 (NE) and the highest in group 3(E20s)(NE