• The Journal of Korean Academy of Prosthodontics
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• v.51 no.3
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• pp.190-198
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• 2013

Purpose: The purposes of this study were to investigate osseointegration around zirconia implants which had machined or alumina sandblasted surface, and to compare the results with titanium implants. Materials and methods: The study was performed on the tibia of 6 pigs. Three types of implants were investigated: group T-titanium implant, group Z-machined zirconia implant, group ZS-alumina sandblasting treated zirconia implant. Zirconia implants were manufactured from yttria-stabilized tetragonal zirconia polycrystalline (Acucera Inc., Pocheon, Korea). A total of 36 implants were installed in pigs' tibias. After 1, 4 and 12 weeks of healing period, the periotest and the histomorphometric analysis were performed. The data were analyzed using one-way ANOVA and significance was assessed by the Scheffe test (${\alpha}=.05$). Results: In the measurement of surface roughness, highest Ra value was measured in group T with significant difference. No significant differences were found among groups regarding Periotest values. After 1 week, in comparison of bone to implant contact (BIC), group Z showed higher value with significant difference. In comparison of bone area (BA), group T and group Z showed higher value with significant difference than group ZS. After 4 weeks, in comparison of BIC, group T showed higher value with significant difference. Comparison of BA showed no significant difference among each implant. After 12 weeks, the highest mean BIC values were found in group T with significant difference. Group ZS showed higher BIC value with significant difference than group Z. In comparison of BA, group T and group ZS showed higher value with significant difference than group Z. Conclusion: Zirconia implant showed low levels of osseointegration in this experiment. Modification of surface structure should be taken into consideration in designing zirconia implants to improve the success rate.

• The Journal of Korean Academy of Prosthodontics
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• v.51 no.3
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• pp.199-207
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• 2013

Purpose: The importance of occlusal contacts of the natural dentition for durability of teeth, mandibular stabilization, and restorative dentistry is well known. The purpose of this study is to analyze the occlusal contact and guidance pattern of Koreans by evaluating the static occlusion on maximal intercuspal position and measuring dynamic occlusion during straight protrusion. Materials and methods: The occlusal contacts at maximal interincisal position and the occlusal guidance pattern during straight protrusion of 29 subjects were recorded with shimstock foil (Whaledent, Langenau, Germany), T-Scan III (Tekscan Inc., Boston, MA, USA), polyvinylsiloxane registration material (Genie Bite, Sultan Healthcare, Hackensack, NJ, USA) and compared. Occlusal registration procedures were repeated 3 times. The position was fixed to an upright position and the head position was fixed with the Frankfurt horizontal plane paralleling the horizontal plane. Fisher's Exact Test (R-General Public License, ver. 2.14.1) and Pearson's Test were used to assess the significance level of the differences between the experimental groups (${\alpha}=.05$). Results: When using shimstock foil, T-Scan III system, and polyvinylsiloxane registration material, most of the patients showed contact on anterior, premolar, and molar teeth during maximal intercuspal position. Approximately 51% of maximal intercuspal position showed anterior contact using shimstock foil. When examining the protrusive movement using shimstock foil and T-Scan III system, guidance pattern with the central incisor was the most common. Conclusion: During maximal intercuspal position, there were cases in which not all of the teeth showed occlusal contact. During mandibular protrusive movements, one or more maxillary central incisors frequently joined in straight protrusion and the posterior teeth were disoccluded. Therefore, the anterior teeth protect the posterior teeth, and vice versa. Thus, mutually protected occlusion should be applied when reconstructing occlusion.

• The Journal of Korean Academy of Prosthodontics
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• v.51 no.3
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• pp.183-189
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• 2013

Purpose: The aim of this study was to evaluate clinical outcomes of implant supported fixed-hybrid prostheses (FHP) in the fully edentulous arches. Materials and methods: Patients in this retrospective study were restored with fixed-hybrid prostheses supported by 4 to 6 implants and functioned more than 1 year of loading. Outcome measures were marginal bone change of implant related with sex, anatomical location (maxilla vs. mandible), opposing teeth, loading time of patients, tilting of posterior implant by Mann- Whitney U test and cantilever length of superstructure by regression analysis, and complication rates. Significance level was set P<.05. Results: A total number of 84 implants (16 restorations) placed in 16 patients were observed for 28 months and mean marginal bone loss was $0.53{\pm}0.39mm$. There were no differences of marginal bone loss according to sex, anatomical location (maxilla vs. mandible), opposing teeth, loading time of patients (P>.05), and cantilever length was not significantly related with a marginal bone loss of implant next to cantilever (P>.05). Complication was shown in 11 patients and veneer fracture and dislodging of artificial teeth were most prevalent. Conclusion: Within the limitations of this study, although marginal bone loss of FHP was very little, complication rates were high. Irrespective of tilting of most posterior implants, marginal bone loss of most posterior implants next to cantilever was less than those of the other implants positioned anteriorly. Cantilever length (<17 mm) did not affect a marginal bone loss of most posterior implants.

• The Journal of Korean Academy of Prosthodontics
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• v.51 no.3
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• pp.147-152
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• 2013

Purpose: The aim of this study was to propose the position of maxillary anterior teeth and intercanine width measurements based on the incisive papilla in accordance with the cephalic type and gender of dentate Korean adult with normal teeth alignment. Materials and methods: 42 students with Class I normal occlusion, without crowding or spacing, were selected from the Chonnam National University School of Dentistry. The lateral skull radiographs of the subjects were taken and were classified as different cephalic types, based on their PFH / AFH ratios. 42 casts of their maxilla were prepared and both the distance between the upper central incisors and the middle of the incisor papilla was measured with a vernier caliper (A) and the distance between the maxillary canine cusp tips (B) were measured. Statistical analysis was performed using SPSS version 15 and their significance was investigated. Results: For dolichocephalic group, the mean values for A and B were 8.43 (SD: 0.61) and 36.73 (SD: 2.17), respectively. The mean value for A was 8.51 (SD: 1.27) for the mesocephalic group and 8.76 (SD 1.03) for the brachycephalic group. The mean value for B was 35.91 (SD: 1.86) for the mesocephalic group and 37.34 (SD: 2.23) for the brachycephalic group. For the male group, the mean A value was 8.86 (SD: 1.04) and the mean B value was 37.60 (SD: 0.24). For the female group, the mean A value was 8.41 (SD: 0.93) and the mean B value was 36.18 (SD: 2.01). The difference between male and female group in A values were not statistically significant (P>.05). The B values of the male subjects were greater than those of the female subjects and was statistically significant (P<.05). Conclusion: 42 students with normal dentition and occlusion in korea, the distance from the incisive papilla and the incisal edge of maxillary central incisors had no difference in cephalic type or gender. However, the distance between the cusp tip of both canines had significant difference in gender where the male showed higher values than the female, while having no difference in cephalic types.

• The Journal of Korean Academy of Prosthodontics
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• v.58 no.2
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• pp.77-85
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• 2020

Purpose: The aim of the present study was to investigate the effects of N-acetyl cysteine (NAC) loading on the bone formation surrounding sandblasted, large-grit and acid-etched (SLA) implants. Materials and methods: Implantation of NAC loaded SLA implants (NSI group) and SLA implants (SI group) was performed bilaterally in the mandible of 4 adult beagle dogs (each group, n = 8). The animals were sacrificed after a healing period of 3 and 6 weeks, respectively (n = 2 animal each). Dissected blocks were processed for histomorphometrical analysis. Bone to implant contact percentage (BIC%) and bone volume (BV%) were assessed histomorphometrically. Results: BIC% of NAC loaded SLA implants were about 50% higher than that of SLA implants at 3 weeks of bone healing, but not significantly (51.79 vs 35.43%; P=.185). BV% of NAC loaded SLA implants were significantly higher than that of SLA implants at 3 weeks of bone healing (45.09 vs 37.57 %; P=.044). At 6 weeks of bone healing, BIC% and BV% of two experimental groups were similar (P>.05). Conclusion: Within the limits of the present study, NAC loading have a positive effects on the early bone formation surrounding SLA implants. So, it might be concluded that NAC loading enhance the osseointegration and shorten the healing time after implantation of the SLA implants.

• The Journal of Korean Academy of Prosthodontics
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• v.58 no.1
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• pp.1-6
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• 2020

Purpose: This study evaluated color stability of Dentca 3D-printed denture teeth, in comparison to color stabilities of four conventional types of denture teeth, upon being immersed in various colorants. Materials and methods: Four types of conventional prefabricated denture teeth (Surpass, GC, Artic 6, Heraeus Kulzer, Premium 6, Heraeus Kulzer, Preference, Candulor), 3D-printed denture teeth (Dentca); and Z250 (Filtek Z250, 3M ESPE) were prepared for testing. The samples were immersed in erythrosine 3%, coffee, cola, and distilled water (DW) at 37℃. Color change (ΔE) was measured by spectrophotometer before immersion and at 7, 14, and 21 days after immersion. One-way analysis of variance was performed along with Tukey's honestly significant difference multiple comparisons test (P<.05). Results: No great difference was observed between the color change of Dentca denture teeth and that of conventional denture teeth in most cases (P>.05). The color change of Dentca denture teeth immersed in erythrosine 3% was greater than that of Surpass (ΔE = 0.67 ± 0.25) after 1 week; Artic 6 (ΔE = 1.44 ± 0.38) and Premium 6 (ΔE = 1.69 ± 0.35) after 2 weeks; and Surpass (ΔE = 1.79 ± 0.49), Artic 6 (ΔE = 2.07 ± 0.21), Premium 6 (ΔE = 2.03 ± 0.75), and Preference (ΔE = 2.01 ± 0.75) after 3 weeks (P<.05). Conclusion: A color change was observed in Dentca denture teeth when immersed in some colorants; however, the maximum value of ΔE for Dentca denture teeth was within the clinically acceptable range.

• Journal of Gastric Cancer
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• v.5 no.2
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• pp.101-105
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• 2005

Purpose: Some gastric cancer patients in whom the cancer has infiltrated up to the muscularis propria (mp) have a good postoperative course similar to that of early gastric cancer (EGC) patients (this does not match the general classification of gastric cancer). Therefore, we performed a retrospective analysis of 125 patients with mp gastric cancer based on the degree of mp invasion. Materials and Methods: The clinicopathologic features of 125 cases of mp gastric cancer were subdivided according to depth of invasion, and were retrospectively reviewed and compared with the surgical features of 222 patients with gastric cancer invading the submucosa (sm). For each tumor, using the section that showed the greatest extent of invasion, we evaluated the degree of tumor invasion into the mp layer at a magnification of $\times$100. The patients were classified into 2 groups: mp1, the tumor was limited to the first of the 3 mp layers, and mp2, the tumor had expanded beyond the first layer. Results: Patients with mp1 (n=50) had a significantly lower incidence of lymph node metastasis, and a smaller tumor size than patients with mp2 (n=75) (P=0.01 and P=0.029, respectively). The 5-year survival rate of mp1 patients was significantly better than that of mp2 patients ($95.3\%\;vs.\;77.6\%$, P=0.0282), but was similar to that ($91.2\%$) of the 222 sm patients. The 5-year survival rate of mp patients without lymph node metastasis (n=55) was significantly better than that of those with lymph node metastasis (n=70)($93.3\%\;vs.\;78.2\%$, P=0.0192). Patients with mp1 had a significantly higher incidence of lymph node metastasis ($42.5\%\;vs\;23\%$, P=0.006) than patients with sm. Conclusion: There were clear differences in clinical features between the mp1 and the mp2 patients. Subdivision of mp gastric cancer according to the depth of invasion may enable a more precise prognosis and a more pertinent treatment plan for mp patients. In particular, as the clinicopathological findings and surgical outcomes for mp1 patients were akin to those of the sm patients, mp1 patients may require treatment analogous to that administered to patients with sm gastric cancer. (J Korean Gastric Cancer Assoc 2005;5:101-105)

• Journal of Gastric Cancer
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• v.5 no.4 s.20
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• pp.273-280
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• 2005

Purpose: Cyclin G2 has been reported to be a negative cell-cycle regulator in various cancer tissues. However, the pattern of cyclin G2 expression in gastric cancer is relatively unknown. We investigated the expression of cyclin G2 in gastric cancer tissues and evaluated the clinical significance of its expression. Materials and Methods: Well-preserved gastric cancer tissues were consecutively obtained from 172 patients who underwent gastric cancer operations at Samsung Medical Center between November 1994 and December 1997. Cyclin G2 expression in the tissues was examined immunohistochemically, and the clinicopathological features and prognostic significance according to the expression were analyzed. Results: Of the 172 gastric cancer tissues, cyclin G2 expression was positive in 43 tissues (25.0%). According to the stage, cyclin G2 expression was lower in more advanced stages (P<0.001). Negative expression of cyclin G2 was positively correlated with more advanced depth of tumor invasion (P<0.05), presence of lymph-node metastasis (P<0.05) and presence of lymphatic invasion (P<0.05). The prognosis of the cyclin G2(+) group was significantly better than that of the cyclin G2(-) group (P<0.001). Multivariate analysis revealed that T stage, lymph-node metastasis, distant metastasis, and lymphatic invasion were independent prognostic factors, but the expression of cyclin G2 was not. Conclusion: Cyclin G2 was expressed in 25% of the gastric cancer tissues, and negative expression of cyclin G2 was associated with more advanced tumor progression. Cyclin G2 may be a negative cell-cycle regulator in gastric cancer, and further studies are necessary to elucidate its exact role in the mechanism of carcinogenesis.

• Journal of Gastric Cancer
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• v.5 no.4 s.20
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• pp.228-237
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• 2005

Purpose: We investigated the impacts of the methylation states of the P16 and the hMLH1 genes on pathogenesis and genetic expression of stomach cancer and their relationships with Helicobater pylori infection, and with other clinico-pathologic factors. Material and Methods: In our study, to detect protein expression and methylation status of the P16 and the hMLH1 genes in 100 advanced gastric adenocarcinomas, used immunohistochemical staining and methylation-specific PCR (MSP) and direct automatic genetic sequencing analysis. Results: Methylation of the P16 gene was observed in 19 out of 100 cases (19%) and in the 18 of those cases (94.7%) loss of protein expression was seen. We were sble to show that loss of P16 gene expression was related to methylation of the P16 gene (kappa coefficient=0.317, p=0.0011). Methylation of the hMLH1 gene was observed in 27 cases (27%), and in 24 cases of those 27 cases (88.8%), loss of protein expression was seen, which suggested that loss of protein expression in the hMLH1 gene is related to methylation of hMLH1 gene (kappa coefficient=0.675, P<0.0001). Also methylation of the hMLH1 gene was related to age, size of the mass, and lauren's classification. Conclusion: We found that methylation of DNA plays an important role in inactivation of the P16 and the hMLH1 genes. The methylation of the hMLH1 genes is significantly related to age, size of the mass, and lauren's classification.

• Journal of Gastric Cancer
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• v.6 no.2
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• pp.109-113
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• 2006

Purpose: Various minimally invasive surgical techniques, such as an endoscopic mucosal resection and a laparoscopic gastrectomy, are becoming common practice for some cases of early gastric cancer (EGC) defined in terms of the depth of invasion being limited to the mucosa or submucosa. However, there are rare cases of early gastric cancer with massive lymph-node metastasis. Materials and Methods: From 6 university hospitals of Korea, 2,772 EGC cases were resected during the various period of analysis (1,432 cases of mucosal cancer and 1,340 of submucosal cancer). Results: As control data, we used the data from a single institute, CHA University Hospital. There were nine cases of early gastric cancer (9/2,772, 0.32%) with N3 lymph node metastasis defined by more than 15 lymph nodes being metastasized according to the UICC-TNM classification (pT1N3, stage IV). Two cases were mucosal cancer (2/1,432, 0.1 4%), and seven cases were submucosal cancer (7/1,340, 0.52%). Metastasized lymph nodes varied in number from 18 to 52. There were three male and six female patients with a mean age of 57. This is a totally reversed sex ratio compared to the usual gastric cancer or EGC. Among the total of 9 EGC patients, there were 5 who had superficial spreading carcinomas with surface areas larger than $25\;cm^2$. This is a significantly higher proportion compared to the general EGC population. When we compared the tumor size according to the LN status, the N3 group was definitely larger than the other groups. 78% of the pT1N3 cases showed lymphatic invasion, which is very high compared to the 4.7% in general EGC cases. Among the 9 cases, 6 patients had too short a follow-up period to evaluate the correct prognosis, but there was one patient with a non-curative resection and two patients with early recurrence. Although the sample size is small and the follow-up period is short, we can expect a very poor prognosis when we consider the common prognosis of EGC that is widely known and accepted. Conclusion: From these results, we can a conclude that the risk factors for pT1N3 gastric cancer are female patients, submucosal invasion, larger tumor size, and lymphatic invasion. However rare, the existence of pT1N3 gastric cancer needs to be taken into consideration, especially during the diagnosis. Furthermore, minimally invasive treatment for EGC needs to be chosen with great precaution. Since the prognosis of pT1N3 gastric cancer is expected to be poor, aggressive adjuvant chemotherapy may be necessary. (J Korean Gastric Cancer Assoc 2006;6:109-113)