• Journal of Technologic Dentistry
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• v.31 no.3
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• pp.35-45
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• 2009

This survey study was conducted on dental technician school students in April 2008 to investigate the effects of smoking on oral health. 110 male and 39 female students were surveyed and cross analysis was performed to examine the relationship between oral health status and smoking-related and oral health maintenance characteristics of smoking and non-smoking group. T-test and one-way ANAVA was used to analyze the average difference verification of two independent samples(smoking group and non-smoking group) and followings are the results. In general characteristics, 74 male students(74.7%) and 25 female(25.3%) students smoked and the percentage of male students were higher in smoking group. Regarding class grade, 2nd-year students(37 students, 37.4%) and 1st-year students(18 students, 36.0%) took the highest percentage of smoking and non-smoking group, respectively. Concerning the experience of drinking, smoking group consumed more alcoholic beverages(94 students, 94.9%) With respect to the frequency of between-meal consumption, respondents who eat between-meal once or twice smoked more. Respecting preferences of sweet food, respondents who enjoyed sweet food smoked more. Concerning smoking characteristics, many of smoking group had been smoked fo a long time(two to five years) and it was worrisome. About the amounts of smoking, 50 respondents(52.6%) of smoking group smoked 20 cigarettes a day with the highest proportion. With regard to the awareness of harmfulness, 70 respondents(70.7%) considered smoking as very harmful and showed that smoking group were aware of its harmfulness but it was habitualized. Respecting smokers in family members, father was more common as smokers(58 respondents, 58.6%) in family and showed that the influence of father. Main reasons of poor periodontal health were alchoholic consumption, smoking, and oral parafunctional habit(57 respondents, 56.7%) in smoking group and neglect of oral hygiene(21 respondents, 42.0%) in non-smoking group. With regard to the scaling, 80 respondents of smoking group(80.8%) didn't received scaling and showed that more oral health education was required. Regarding the periodontal status, non-smoking group was $1.26{\pm}0.44$, respondents who received scaling was $1.43{\pm}0.50$, respondents who regularly floss was $1.50{\pm}0.52$, respondents who brush more than three times a day was $1.38{\pm}0.49$ and had better periodontal health. Bleeding during tooth brushing was more frequent in smoking group ($1.51{\pm}0.70$). Regarding mouth order, non-smoking group was $2.34{\pm}0.62$, after scaling was $2.02{\pm}0.76$, patients who regularly floss was $1.50{\pm}0.52$, patients who brush more than three times a day was $1.81{\pm}0.87$. Concerning the experience of dental caries treatment, smoking group was $1.20{\pm}0.40$, patients who do not floss was $1.30{\pm}0.46$, patients who brush once a day was $1.29{\pm}0.45$. With regard to dental prosthesis, non-smoking group was $3.78{\pm}1.62$, patients who received scaling was $1.43{\pm}0.50$, patients who regularly floss was $1.40{\pm}0.51$, patients who brush more than three times a day was $1.24{\pm}0.43$. From these results, oral health education and smoking has correlation and more oral health education needs to be carried out to educate students with non-health related majors about harmfulness of smoking on oral health. Also more study are required.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.32 no.3
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• pp.218-228
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• 2010

Components of dental resin-based restorative materials are reported to leach from the filling materials even after polymerization. Hydroquinone (HQ) is one of the major monomers used in the dental resin and is known as a carcinogen. Thus, carcinogenic risk of HQ leaching from the dental resin becomes a public health concern. The present study attempted to examine the carcinogenic potentials of HQ on the human epithelial cell, which is the target cell origin of the most of oral cancers. Cytotoxicity of HQ was observed above 50${\mu}M$ as measured by LDH assay, indicating a relatively low toxicity of this substance in human epithelial cells. The parameters of neoplastic cellular transformation such as cell saturation density, soft agar colony formation and cell aggregation were analyzed to examine the carcinogenic potential of HQ. The study showed that 2-week exposure of HQ showed the tendency of increase in the saturation density and the significant enhancement of soft agar colony formation at the highest dose, 50 ${\mu}M$ only. It is suggested that HQ has a weak potential of carcinogenicity. When cells were treated with HQ and TPA, a well-known tumor promoter, the parameters of neoplastic cellular transformation was significantly increased. This result indicates that the potential risk of carcinogenicity from HQ is largely dependent upon the presence of promoter. Exposure of 50 ${\mu}M$ HQ increased the time-dependent apoptosis as measured by the ELISA kit. This concentration coincides with a dose of neoplastic transformation, indicating a possible link between apoptosis and HQ-induced cellular transformation. Hydroquinone generated Reactive Oxygen Species (ROS) which was evidenced by the treatment of antioxidants such as trolox and N-acetyl cysteine and the GSH depleting agent, BSO. Antioxidants blocked the generation of ROS and the GSH depleting agent, BSO dramatically increased the ROS production. Since HQ is known to increase ROS production thru activation of transcriptional factor such as c-Myb and Pim-1, it is speculated that ROS generation by HQ plays a role in the activation of oncogene, which may lead to neoplastic transformation. In addition, ROS is involved in the alteration of signal transduction, which regulates the apoptosis in many cellular systems. Thus, ROS-mediated apoptosis may be involved in the HQ-induced carcinogenic processes. Protein kinase C (PKC) is known to play pivotal roles in neoplastic transformation of cells and its high expression is often found in a variety of types of tumors including oral cancer. PKC translocation of PKC-${\alpha}$ was observed following HQ exposure. Altered signaling system may also play a role in the transformation process. Taken together, HQ leached from the dental resin does not pose a significant threat as a cancer causing agent, but its carcinogenic potential can be significantly elevated in the presence of promoter. The mechanism of HQ-induced carcinogenesis involved ROS generation, apoptosis and altered signaling pathway. The present study will provide a valuable data to estimate the potential risk of HQ as a carcinogen and understand mechanism of HQ-induced carcinogenesis in human epithelial cells.

• The korean journal of orthodontics
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• v.25 no.4
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• pp.497-509
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• 1995

With socioeconomic development and change of esthetic recognition, the demand for orthodontic treatment and number of orthodontic patients has been increasing so rapidly. And frequency of malocclusion was changed. So this study was done in an attempt to provide an epidemiologic study so that we can accomodate their orthodontic needs adequately and to obtain the reliable quantitative information regarding the characteristics of orthodontic patients who visited Department of Orthodontics, Seoul National University Hospital from 1985 to 1994. Following results were obtained. 1. The total number of orthodontic patients of SNUDH during 1990-1994 increased in comparing with that of 1985-1989. And it showed that the number of annual patients was increasing trend. 2. The total number of female patients was 1.59 times as high as that of male. It showed that the annual percentage of female patients has been increasing and that of male patients has been decreasing. So demands for orthodontic treatment of malocclusion of female patients were higher than that of male patients. 3. Each total percentage of class I, class II div.1, class II div. 2 and class III was 35.98%, 14.00%, 1.74% and 48.28%. The annual percentage of class I group had been decreasing but it has increased at 1994. However that of Class III group had been increasing until 1991 but it has been decreasing. 4. Each percentage of less than 6 year-old group, D to 8 year-old group, 8 to 12 year-old group, 12 to 18 year-old group and more than 18 year-old group was 2.65%, 8.63%, 32.50%, 27.74% and 28.48%. Annual percentage of 12 to 18 year-old group ( middle & high school students group ) had been decreasing but it has been increasing. However 18 year-old group had been increasing but it has been decreasing. So entrance examination for college and university is an important factor to distribution of age group.

• The Journal of Korean Academy of Prosthodontics
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• v.49 no.1
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• pp.16-21
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• 2011

Purpose: The purpose of this study was to investigate the bioactivity of precalcified nanotubular $TiO_2$ layer on Ti-6Al-7Nb alloy. Materials and methods: Anodic oxidation was carried out at a potential of 20 V and current density of 20 mA/$cm^2$ for 1 hour. The glycerol solution containing 1 wt% $NH_4F$ and 20 wt% deionized water was used as an electrolyte. Precalcification treatment was obtained by soaking in $Na_2HPO_4$ solution at $80^{\circ}C$ for 30 minutes followed by soaking in saturated $Ca(OH)_2$ solution at $100^{\circ}C$ for 30 minutes, followed by heat treatment at $500^{\circ}C$ for 2 hours. To evaluate the activity of precalcified nanotubular $TiO_2$ layer, specimens were immersed in a simulated body fluid with pH 7.4 at $36.5^{\circ}C$ for 10 days. Results: 1. Nanotubular $TiO_2$ layer showed the highly ordered dense structure by interposing small diameter nanotubes between large ones, the shape of nanotubes was enlarged as going down. 2. The mean length of nanotubes was $517.0{\pm}23.2\;nm$ innm glycerol solution containing 1 wt% $NH_4F$ and 20 wt% $H_2O$ at 20 V for 1 hour. 3. The bioactivity of Ti-6Al-7Nb alloy was improved with formation of nanotubular $TiO_2$ layer and precalcification treatment in $80^{\circ}C$ 0.5 M $Na_2HPO_4$ and saturated $100^{\circ}C$ $Ca(OH)_2$ solution. Conclusion: Bioactivity of precalcified nanotubular $TiO_2$ layer on Ti-6Al-7Nb alloy was improved.

• Journal of the Korean Society of Radiology
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• v.6 no.2
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• pp.93-98
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• 2012

Micro-computed tomography (microCT) is an important tool for preclinical vascular imaging, with micron-level resolution. This non-destructive means of imaging allows for rapid collection of 2D and 3D reconstructions to visualize specimens prior to destructive analysis such as pathological analysis. Objectives. The aim of this study was to suggest a method for ex vivo, postmortem examination of stented arterial segments with microCT. And ex vivo evaluation of stents such as bare metal or drug eluting stents on in-stent restenosis (ISR) in rabbit model was performed. The bare metal stent (BMS) and drug eluting stent (DES, paclitaxel) were implanted in the left or right iliac arteries alternatively in eight New Zealand white rabbits. After 4 weeks of post-implantation, the part of iliac arteries surrounding the stent were removed carefully and processed for microCT. Prior to microCT analysis, a contrast medium was loaded to lumen of stents. All samples were subjected to an X-ray source operating at 50 kV and 200 ${\mu}A$ by using a 3D isotropic resolution. The region of interest was traced and measured by CTAN analytical software. Objects being exposed to radiation had different Hounsfield unit each other with values of approximately 1.2 at stent area, 0.12 ~ 0.17 at a contrast medium and 0 ~ 0.06 at outer area of stent. Based on above, further analyses were performed. As a result, the difference of lengths and volumes between expanded stents, which may relate to injury score in pathological analysis, was not different significantly. Moreover, ISR area of BMS was 1.6 times higher than that of DES, indicating that paclitaxel has inhibitory effect on cell proliferation and prevent infiltration of restenosis into lumen of stent. And ISR area of BMS was higher ($1.52{\pm}0.48mm^2$) than that of DES ($0.94{\pm}0.42mm^2$), indicating that paclitaxel has inhibitory effect on cell proliferation and prevent infiltration of restenosis into lumen of stent. Though it was not statistically significant, it showed that the extent of neointema of mid-region of stents was relatively higher than that of anterior and posterior region in parts of BMS as showing cross-sectional 2-D image. suggest that microCT can be utilized as an accessorial tool for pathological analysis.

• Journal of agricultural medicine and community health
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• v.21 no.1
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• pp.75-84
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• 1996

This study was conducted to reveal the relationship between the oral health status and their Knowledges about the oral health of the freshman of colleges in Taegu city. The evaluation for the oral health status through the oral examinations and their analysis of their knowledges on the periodontal disease were done on 216 males and 205 females from 1st to 30th April, 1993. The obtained results were as follows: The oral health status of 421 subject showed that 35.7% was good, 59.1% fair, and 6.2% poor, respectively. In case of the oral health status of females, 41.9% was good and 4.4% poor, and then in males 27.8% was good, 7.8% poor. The oral health status of the females was better than that of the males(p=0.006). The 52.1% among the good oral health status group answered that the dental plaque is the bacterial membrane causing dental disease, and the 23.1% among the poor oral health status group answered same as the above. The 91.8% among the good oral health status group answered that the periodontal diseases can be prevented, and the same answer came out from 15.4% of the poor group. It was found that the better oral health status group had the better knowledges about periodontal disease(p=0.001). For the question about their experiences in scaling the 30.1% of good oral health status group and the 23.1% of poor group answered that scaling is very helpful to periodontal health(p=0.001). About the experience of the education for tooth brushing, the 53.2% of good oral health status group and the 7.6% of poor group had the experiences to receive the education for tooth brushing(p=0.001). About the frequency and the time of tooth brushing, the 53.4% of good oral health status group brushed their teeth more then 3 times a day and 41.8% of good group brushed their teeth after every meal(p=0.001). The result of multiple regression analysis according to the simplified oral health index indicated that the variable having an effect on the oral health status was the tooth brushing frequency, knowledge of periodontal disease prevention, experience in education of tooth brushing and time of tooth brushing(p=0.001).

• Journal of Embryo Transfer
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• v.22 no.1
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• pp.69-74
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• 2007

This study was performed to determine the estrous cycles by macroscopic observation of the ovarian changes using the laparoscopy and to make use of these results for embryo transfer in Korean black goat (Copra hircus aegagrus). Laparoscopic examinations of the ovaries were performed from 2 days after $CIDR^(R)$ removal to 22 days after ovulation. The serial morphological changes of follicles and corpus luteum (CL) were observed. CL was classified corpus hemorrhagicum(CH), corpus luteum (CL) and corpus albicans (CA) by its maturation and regression. On the day before ovulation (Day 0), Graafian follicles (GF) were found on one or both ovaries. On the day (Day 1) and $2^{nd}$day (Day 2) of ovulation, and ovulation depression (OD) and an early stage corpus hemorrhagicum $(CH_1)$ were observed at the site of GF, respectively. On Days 3 to 4, more developed and enlarged corpus hemorrhagicum $(CH_2\;and\;CH_3)$ arised from the ovulation of the GF with well vascularization. On Days 5 to 6, it was identified that mature corpus luteum $(CL_3)$ was grown on the ovary, and fully developed CL with adjacent follicles were occupied most part of the ovary on Days 17 and 18. Then the size of CL was diminished, and completely luteal regression $(CL_1\;or\;CA)$ with new large follicle was identified on Days 20 and 22. From these results, the 4 stages of the estrous cycle in Korean black goats were 1) estrus (Day 0) for 1 day, 2) metestrus $(Day\;1{\sim}4)$ for 4 days (stage of CH development), 3) diestrus $(Day\;5{\sim}16/17)$ for 12 or 13 days (luteal stage), and 4) proestrus $(Day\;17/18{\sim}20/22)$ for 4 or 5 days (stage of luteal regression and follicular growing). Laparoscopy for observation of ovarian changes was invasive than laparotomy. Additionally, it had advantages of reduced adhesion and quick operation time. It was considered that laparoscopic examination of ovarian changes will be useful for embryo transfer in the Korean black goats.

• 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.

• Journal of Technologic Dentistry
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• v.29 no.2
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• pp.151-161
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• 2007

To obtain the information of dental arch size and the distance from one tooth center to adjacent tooth center of occlusal surface of each tooth which is perforated by Pindex system on working cast for removable die system, 600 dental casts in Busan were examined. The distance of center of occlusal surface of each tooth and dental arch size were digitized. The results were as follows; 1. Mean values of the distance from center of maxillary central incisor to maxillary lateral incisor(tooth number 11$\sim$12, 21$\sim$22) is 5,7 mm, 12$\sim$13(22$\sim$23) is 5.9 mm, 13$\sim$14(23$\sim$24) is 6.9 mm, 14$\sim$15(24$\sim$25) is 7.1 mm, 15$\sim$16(25$\sim$26) is 8.4 mm, 16$\sim$17(26$\sim$27) is 10.2 mm, 11$\sim$21 is 7.30 mm. Mean values of the distance from center of mandibular central incisor to mandibular lateral incisor(tooth number 31$\sim$32, 41$\sim$42) is 4.5 mm, 32$\sim$33(42$\sim$43) is 4.8 mm, 33$\sim$34(43$\sim$44) is 6.3 mm, 34$\sim$35(44$\sim$45) is 7.2 mm, 35$\sim$36(45$\sim$46) is 9.2 mm, 36$\sim$37(46$\sim$47) is 10.7 mm, 31$\sim$41 is 4.7 mm. 2. Mean values of the distance from the center of maxillary right central incisor to the center of maxillary left central incisor(11$\sim$21) is 7.3 mm, 12$\sim$22 is 18.2 mm, 13$\sim$23 is 26.9 mm, 14$\sim$24 is 37.2 mm, 15$\sim$25 is 43.2 mm, 16$\sim$26 is 48.5 mm, 17$\sim$27 is 53.5 mm. Mean values of the distance from the center of mandibular right central incisor to the center of mandibular left central incisor(31$\sim$41) is 4.7 mm, 32$\sim$42 is 13.3 mm, 33$\sim$43 is 21.7 mm, 34$\sim$44 is 31.9 mm, 35$\sim$45 is 38.2 mm, 36$\sim$46 is 44.8 mm, 37$\sim$47 is 50.7 mm. 3. Mean values of the distance from the line of between 11$\sim$21 to 12$\sim$22 is 10.9 mm, 12$\sim$22 to 13$\sim$23 is 8.7 mm, 13$\sim$23 to 14$\sim$24 is 10.3 mm, 14$\sim$24 to 15$\sim$25 is 6.0 mm, 15$\sim$25 to 16$\sim$26 is 5.3 mm, 16$\sim$26 to 17$\sim$27 is 5.0 mm. 31$\sim$41 to 32$\sim$42 is 8.6 mm, 32$\sim$42 to 33$\sim$43 is 8.4 mm, 33$\sim$43 to 34$\sim$44 is 10.2 mm, 34$\sim$44 to 35$\sim$45 is 6.3 mm, 35$\sim$45 to 36$\sim$46 is 6.6 mm, 36$\sim$46 to 37$\sim$47 is 5.9 mm. 4. We checked the bottom side of cast to verify the position of dowel pin. There is no difference upper side and lower side.

• The Journal of Korean Academy of Prosthodontics
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• v.52 no.1
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• pp.34-41
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• 2014

Purpose: In this study, the diameter of each implant driver was measured and compared to find out the compatibility of implant drivers. Materials and methods: Drivers from 12 implant systems being used in Dankook University Dental Hospital were included in this study. The shapes of the implant drivers were segregated, and the effective length and the diameter of upper, middle, lower part of driver tips were measured (n=10). The measured data were mathematically analyzed for its compatibility. Results: A driver with the smallest diameter (1.17 mm) had the highest compatibility at the upper part of driver tip. This driver could be used for a bigger driver up to 1.35 mm in diameter. There were several driver groups which had the same diameter so as to be interchangeable each other. In the middle part, the smallest diameter measured was 1.2 mm and this was able to replace a driver up to 1.40 mm diameter. Since the diameter generally became thicker from upper part (the tip of driver) to the lower part (the shank of driver), some drivers with bigger diameter at the upper part so which was failed to show any compatibility became compatible with a driver which had smaller diameter at the upper part but wider in the middle part. The compatibility of torx shape drivers were affected by the inner diameter of the drivers not only by the outer diameter. Furthermore, the inner diameter of torx drivers decided the compatibility between torx and hex drivers. Conclusion: From the study it was found that compatibility in drivers existed among certain implant systems and to check its compatibility the diameter at a certain effective length should be measured. However, there has been not enough studies about long-term use of compatible drivers, so effects of using compatible drivers on drivers and implants are unknown. Therefore, usage in inevitable cases only is recommended and further study is needed.