• Journal of Periodontal and Implant Science
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• v.47 no.4
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• pp.211-218
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• 2017

Purpose: The purpose of the present study was to perform a pattern analysis in patients with temporomandibular disorder (TMD) resulting from unilateral mastication due to chronic periodontitis. Methods: Thirty participants with signs or symptoms of TMD who engaged in unilateral mastication due to periodontitis-related discomfort (test group) were selected. Another 30 subjects exhibiting signs or symptoms of TMD resulting from unilateral mastication not due to chronic periodontitis (control group) were also recruited. An interview-based questionnaire was administered, and an examination of the temporomandibular joint (TMJ) with determination of periodontal status was performed. Results: The duration of unilateral mastication was significantly longer in the control group than in the test group. There was a significant negative correlation between the duration of unilateral mastication and the Community Periodontal Index score. Using the Research Diagnostic Criteria for TMD (RDC/TMD) axis I algorithms, all the subjects were assigned to 3 main groups. The test group exhibited significantly a higher diagnostic distribution of group III (arthralgia, osteoarthritis, or osteoarthrosis), and in both the test and control groups, the number of diagnoses was larger for the non-chewing side. The control group showed a significantly higher diagnostic distribution of group I (myofacial pain), and in both the test and control groups, the number of diagnoses was larger for the chewing side. Conclusions: The results of the present study indicate that unilateral mastication due to chronic periodontitis could induce not only pain but also structural TMJ changes if adequate treatment is not administered and supported within a short time from the onset of the condition. Therefore, immediate treatment of chronic periodontitis is recommended to prevent not only the primary progress of periodontal disease, but also secondary TMJ-related problems. Furthermore, subjects who have suffered chronic long-term periodontitis without treatment should be urged to undergo a TMJ examination.

• Journal of the korean academy of Pediatric Dentistry
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• v.35 no.4
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• pp.607-618
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• 2008

This study three-dimensionally and histologically assessed the effect of Emdogain$^{(R)}$ on periodontal healing in replanted teeth in three beagle dogs which were 1 to 2 years old, weighing from 10 to 13 ㎏. Twelve maxillary and mandibular incisors were intentionally extracted and replanted after 15(Group I), 30(Group II) and 60(Group III) minutes of air dry storage with and without the application of Emdogain$^{(R)}$. The following conclusions could be drawn from the present investigation. 1. Increased incidence of inflammatory healing response in periodontal tissue was proportional to air dry time in Both control and experimental group(P<0.001). 2. Treatment Group showed lower inflammatory root resorption, especially there were statically significant in Group I, III(P<0.001, Group II : P=0.093). 3. Inflammatory root resorption were mainly occurred in apical third(14, 15-16 section)(P<0.05, 0.001), and cervical third(1 section)(P<0.05). 4. In view of horizontal section of long tooth axis, Main root resorption area were 1, 4, 5 line area(bucco-lingual area)(p<0.01).

• The Journal of Korean Academy of Prosthodontics
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• v.38 no.2
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• pp.200-213
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• 2000

Lasers have given dentistry a new rapid, economic, and accurate technique for metal joining. Although laser welding has been recommended as an accurate technique, there are some limitations with this technique. For example, the two joining surfaces must have a tight-fitting contact, which may be difficult to achieve in some situations. The tensile samples used for this study were made from a custom-made pure titanium and type III gold alloy plates. 27 of 33 specimens were sectioned perpendicular to their long axis with a carborundum disk and water coolant. Six specimens remained and served as the control group. A group of 6 specimens was posed as butt joints in custom parallel positioning device with a feeler gauge at each of three gaps : 0.00, 0.25. and 0.50mm. All specimens were then machined to produce a uniform cross-sectional dimension, none of the specimens was subjected to any subsequent form of heat treatment. Scanning electron microscopy was performed on representative tested specimens at fractured surfaces in both the parent metal and the weld. Vickers hardness was measured at the center of the welds with a micropenetrometer using a force of 300gm for 15 seconds. Measurement was made at approximately $200{\mu}m\;and\;500{\mu}m$ deep from each surface. One-way analysis of variance (ANOVA) and Scheffe's test was calculated to detect differences between groups. The purpose of this study is to compare the strength and properties of the joint achieved at various butt Joint gaps by the laser welding of type III gold alloy and pure titanium tensile specimens in an argon atmosphere. The results of this study were as follows : 1. When indexing and welding pure titanium, there was no decrease in ultimate tensile strength as compared with the unsectioned alloys for indexing gaps of 0.00 to 0.50mm, although with increasing gap size may come increased distortion (p>0.05). 2. When indexing and welding type III gold alloy, there were significant differences in ultimate tensile strength among groups with weld gaps of 0.00mm, 0.25 and 0.50mm, and the control group. Group with butt contact without weld gap demonstrated a significant higher ultimate tensile strength than groups with weld gaps of 0.25 and 0.50mm (p<0.05). 3. When indexing and welding the different metal combination of type III gold alloy and pure titanium, there were significant differences in ultimate tensile strength between groups with weld gaps of 0.00, 0.25, and 0.50mm. However, the mechanical properties of the welded joint would become too brittle to be acceptable clinically (p<0.05). 4. The presence of large pores in the laser welded joint appears to be the most important factor in controlling the tensile strength of the weld in both pure titanium and type III gold alloy.

• The korean journal of orthodontics
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• v.28 no.3 s.68
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• pp.453-459
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• 1998

The dental implants for edentulous Patients have been used for more than 20 years. After the introduction of osseointegration by $Br{\aa}nemark$, the commercially pure titanium implants were accepted by most practitioners. Recently dental implants are used for orthodontic anchorages as well as prosthetic abutment. Many researchers have reported implants as a good orthodontic anchorage through basic research and clinical evaluation. But previous researches were done after the healing time for osseointegration of inserted implants. If dental implants are to be used for prosthetic abutment the healing time for osseointegration is necessary, but orthodontic forces to implants are different from bite force regarding its amount of force, duration and direction. The authors evaluated the effect of orthopedic force to implants on bone tissue before osseointegration. 48 implants were placed at 12 rabbits. 2 implants into left side and 2 implants into right side were inserted along the long axis of femur respectively 2 weeks (2 weeks group), 4 weeks (4 weeks group) and 6 weeks (6 weeks group) after implants placement, 300g force had been applied to the implants at left side femur by Ni-Ti close coil spring for 4 weeks (experimental group) and no force applied to implants at right side femur (control group). After the force application for 4weeks, rabbits were sacrificed and microscopic evaluation was done by hematoxylin-eosin stain and Masson trichrome stain. The result3 were followed. 1. All implants in experimental group remained rigid after the force application for 4 weeks. 2. More fibrous tissue between bone and implants were noticed at 2 weeks experimental group than 2 weeks control group 3. More bone remodeling was noticed at 4weeks group than 2 weeks group and it was difficult to find out fibrous tissue between bone and implants at both experimental and control group of 4 weeks group. 4. It was hard to distinguish experimental group from control group at 6 weeks group. Therefore if initial stability can be obtained on implant insertion, it can be possible to use implants as a orthodontic anchorage before the healing time for osseointegration.

• Journal of the Korean Geotechnical Society
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• v.16 no.1
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• pp.31-42
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• 2000

Consolidation and permeability are major engineering properties of soil. In clay, coefficient of permeability and consolidation can be calculated by incremental loading consolidation test. However, it is known that the incremental loading test has several deficiencies including long testing time, non-uniform stress state, very soft clay and problem of back pressure saturation. Specially, it is not performed with horizontal consolidation test. Several methods have been proposed for obtaining reliable values of $C_v$. Among these, the square root of time-fitting method proposed by Taylor(1948) and logarithm of time-fitting method, also called Casagrande's method, are used extensively in soil engineering practice. But these methods are not amenable for the absence of initial linear portion and have the difficulties involved in distinguishing secondary compression from primary compression. Rowecell consolidation tests were carried out in this study with different trimming axis and sample size. The results were compared with those of other methods; Casagrande,$Taylor,\; Casagrande,\; Hyperbolic,\; \delta/t-logt$. From the results, we explained a relationship between horizontal coefficient of permeability and void ratio was obtained. Finally, the directly measured horizontal coefficient of permeability obtained by using the Rowecell was compared with the permeability derived indirectly from the consolidation test result.

• Journal of the Korean Geotechnical Society
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• v.19 no.6
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• pp.127-149
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• 2003

The bridge tested was 3 spans 90m-long PSC beam concrete bridge with a stub-type abutment which had a skew of 60$^{\circ}$ about the axis of bridge. A cement concrete was placed at the superstructural slab of the bridge. Inclinometers and straingauges were installed at piles as well. During 7 days-curing of superstructural slab, the pile behavior in response to hydration heat and drying shrinkage of the slab was monitored. Then monitored values were compared with the horizontal movement obtained from the HACOM program and the calculated lateral behavior obtained from the nonlinear p-y curves of pile. As a result, lateral behavior of H-piles by the field measurement occurred due to the influence of hydration heat and drying shrinkage obtained during curing of superstructural concrete. The lateral displacements by hydration heat and drying shrinkage were 2.2mmand 1.4mm respectively. It was observed as well that the inflection point of lateral displacement of pile was shown at 1.3m down from footing base. It means that the horizontal movement of stub abutment did not behave as the fixed head condition of a pile but behave as a similar condition. The measured bending stress did not show the same behavior as the fixed head condition of pile but showed a similar condition. The increment of maximum bending stress obtained from the nonlinear p-y curves of pile was about 300(kgf/$\textrm{km}^2$) and was 2 times larger than measured values regardless of installation places of straingauges. Meanwhile, lateral load, maximum lateral displacement, maximum bending stress and maximum bending moment of pile showed a linear behavior as curing of superstructural concrete slab.

• Journal of Dental Rehabilitation and Applied Science
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• v.19 no.4
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• pp.257-268
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• 2003

The purpose of this study was to assess the loading distributing characteristics of implant prosthesis according to position and direction of load, under vertical and inclined loading using FEA analysis. The finite element model was designed according to standard fixture (4.1mm restorative component x 11.5mm length). The crown for mandibular first molar was made using UCLA abutment. Each three-dimensional finite element model was created with the physical properties of the implant and surrounding bone. This study simulated loads of 200N at the central fossa in a vertical direction (loading condition A), 200N at the outside point of the central fossa with resin filling into screw hole in a vertical direction (loading condition B), 200N at the centric usp in a $15^{\circ}$ inward oblique direction (loading condition C), 200N at the in a $30^{\circ}$ inward oblique direction (loading condition D) or 200N at the centric cusp in a $30^{\circ}$ outward oblique direction (loading condition E) individually. Von Mises stresses were recorded and compared in the supporting bone, fixture, and abutment screw. The following results have been made based on this study: 1. Stresses were concentrated mainly at the ridge crest around implant in both vertical and oblique loading but stresses in the cancellous bone were low in both vertical and oblique loading. 2. Bending moments resulting from non-axial loading of dental implants caused stress concentrations on cortical bone. The magnitude of the stress was greater with the oblique loading than with the vertical loading. 3. An offset of the vertical occlusal force in the buccolingual direction relative to the implant axis gave rise to increased bending of the implant. 4. The relative positions of the resultant line of force from occlusal contact and the center of rotation seems to be more important. 5. The magnitude of the stress in the supporting bone, fixture and abutment screw was greater with the outward oblique loading than with the inward oblique loading and was the greatest under loading at the centric cusp in a $30^{\circ}$ outward oblique direction. Conclusively, this study provides evidence that bending moments resulting from non-axial loading of dental implants caused stress concentrations on cortical bone. But it seems to be more important that how long is the distance from center of rotation of the implant itself to the resultant line of force from occlusal contact(leverage). The goal of improving implants should be to avoid bending of the implant.

• Journal of Dental Rehabilitation and Applied Science
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• v.21 no.1
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• pp.1-14
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• 2005

The purpose of this study was to assess the loading distributing characteristics of implant prosthesis of internal connection system(ITI system) according to position and direction of load, under vertical and inclined loading using finite element analysis (FEA). The finite element model of a synOcta implant and a solid abutment with $8^{\circ}$ internal conical joint used by the ITI implant was constructed. The gold crown for mandibular first molar was made on solid abutment. Each three-dimensional finite element model was created with the physical properties of the implant and surrounding bone. This study simulated loads of 200N at the central fossa in a vertical direction (loading condition A), 200N at the outside point of the central fossa with resin filling into screw hole in a vertical direction (loading condition B), 200N at the centric cusp in a $15^{\circ}$ inward oblique direction (loading condition C), 200N at the in a $30^{\circ}$ inward oblique direction (loading condition D) or 200N at the centric cusp in a $30^{\circ}$ outward oblique direction (loading condition E) individually. Von Mises stresses were recorded and compared in the supporting bone, fixture, and abutment. The following results have been made based on this study: 1. Stresses were concentrated mainly at the ridge crest around implant under both vertical and oblique loading but stresses in the cancellous bone were low under both vertical and oblique loading. 2. Bending moments resulting from non-axial loading of dental implants caused stress concentrations on cortical bone. The magnitude of the stress was greater with the oblique loading than with the vertical loading. 3. An offset of the vertical occlusal force in the buccolingual direction relative to the implant axis gave rise to increased bending of the implant. So, the relative positions of the resultant line of force from occlusal contact and the center of rotation seems to be more important. 4. In this internal conical joint, vertical and oblique loads were resisted mainly by the implant-abutment joint at the screw level and by the implant collar. Conclusively, It seems to be more important that how long the distance is from center of rotation of the implant itself to the resultant line of force from occlusal contact (leverage). In a morse taper implant, vertical and oblique loads are resisted mainly by the implant-abutment joint at the screw level and by the implant collar. This type of implant-abutment connection can also distribute forces deeper within the implant and shield the retention screw from excessive loading. Lateral forces are transmitted directly to the walls of the implant and the implant abutment mating bevels, providing greater resistance to interface opening.

• Journal of Dental Rehabilitation and Applied Science
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• v.25 no.3
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• pp.255-265
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• 2009

Recently many studies have been published on application of immediate loaded implants. However, the immediate loading protocol has not been well documented. The purpose of the present study was to evaluate the stress distribution between bone-implant interfaces and the effect of implant length in the anterior maxilla using 3 dimensional finite element analyses. The diameter 4.0 mm threaded type implants with different length(8.5 mm, 10.0 mm, 11.5 mm, 13.0 mm, 15.0 mm) were used in this study. The bone quality of anterior maxillary bone block was assumed to D3 bone. Bone-implant interfaces of immediately loaded implant were constructed using a contact element for simulating the non osseointegration status. For simplification of all the processing procedures, all of the material assumed to be homogenous, isotropic, and linearly elastic. The 178 N of static force was applied on the middle of the palatoincisal line angle of the abutment with $120^{\circ}$ angle to the long axis of abutment. Maximum von Mises stress were concentrated on the labial cortical bone of the implant neck area, especially at the cortical-cancellous bone interfaces. Compared the different length, highest peak stress value was observed at the 8.5 mm implants and the results indicated a tendency towards favorable stress distribution on the bone, when the length was increased. Presence of cortical bone was very important to immediate loading, and it appears that implants of a length more than 13 mm are preferable for immediate loading at the anterior maxilla.

• Journal of Periodontal and Implant Science
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• v.25 no.3
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• pp.557-567
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• 1995

The purpose of this study was to investigated the effect of root planing and decalcified freeze dried allografts on the resorption of transplanted roots and the healing of preveously diseased recipient extraction sockets. The experimental chronic periodontitis was induced by elastic ligatures on the 2nd and 3rd mandibular premolars of 4 adult dogs, and after 8 weeks, crowns were removed and the teeth extracted. The extracted roots were split in half along the long-axis, and the extednt of plaque exposure was morked on the root surfaces with burs. The roots were either root-planed(Test group), or left uninstrumented(Control group), and transplanted in the extraction sockets with decalcified freeze-dried allografts filling the void. The flaps were sutured to cover the sockets completely. The animals were sacrificed after 12 weeks of healing, and the specimens were examined histologically. The results were as follows : 1. No signs of inflammation or disease activity were observed in either groups. 2. Replacement root resorption was observed in both groups. 3. More connective tissue attachments and less ankylosis were observed in the test groups compared to the control. 4. The unresorbed remains of DFDB particles were observed in both groups. 5. DFDB particles in the apical portion of the alveolar sockets were encased in newly-formed bone, while those in the coronal areas were seen encapsulated with connective tissue. 6. No significant difference was found between root-planed and uninstrumented roots relative to the healing and the bone fromation in the recipient extraction sockdets. From the present study, there seemed to be no significant benefits in root planing the transplanted roots or grafting the sockets with DFDB in order to curve the replacement resorption, although the root-planed roots showed more connective tissue attachments. There was also no significant benefits in root transplantation and DFDB for and enhanced healing and bone formation in alveolar extraction sockets.