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1 1 Critical Factors in Implant Aesthetics, Immediate Loading and Sinus Lifts Lecturer : Dennis P. Tarnow Immediate loading Definition Stabilization vs. Osseointegration Histological Outcomes Clinical Outcomes Implant Design Transitional Implants Technique Conclusions 2002년 Spain의 Barcelona에서열렸던 Immediate Loading 에관한 Consensus Meeting 에서 Definition 이확정되기전까진미국과유럽의 Immediate load ing 과 immediate function에관한정의는서로완전히상반된것이었다. Consensus 이전 Immediate Loading Immediate Function U.S. In occlusion Out of occlusion Europe Out of occlusion In occlusion Today s Definition of immediate loading after the 2002 consensus : A procedure in which dental implants are subjected to Functional Occlusal Forces / loads coincident with the date on which the surgery to place them was performed. Immediate loading 에관해다음네가지상황을고려 해볼수있다. 1. immediate temporization without occlusion 2. immediate temporization in occlusion 3. immediate socket placement without occlusion 4. immediate socket placement with occlusal loading 표 1-1 은 immediate loading 을위해반드시이해해야만하는도표다. a, b, c 선이 % of osseointegration line 과만나는곳은 initial stabilization이 osseointe gration의힘으로넘어가는지점이다. 여기서 type III bone에주의해야한다. 왜냐하면초기의 biologic width 형성후첫번째 thread 까지 bone 이흡수되면약한 marrow 쪽의 bone 만남기때문이다. 그러므로 type III bone 에서는 supracrestal 로 implant 를위치시키도록해야한다. [ 표 1-1 ] Initial stabilization을높이는 3가지방법은 1)dense bone에심는다, 2)wedging force를위해 tapered implant를심는다. 3) go around the turn

2 2 즉 straight line splint가아니라 U-shaped splint를한다. Straight line splints는 mesiodistal force엔강하나 buccolingual force엔약하다. 약 150 μm 이상의 lateral force 가있을시 osseointegration이일어나지않는다. 그러므로 M/D, B/L force에저항할수있는 U-shaped splint를해준다. Immediate loading 에관한몇가지 literature review 를해보도록한다. 1. The effects of early occlusal loading on Onestage Ti-Alloy implants in beagle dogs: A pilot study Sagara M, JPD 1993; 69: BIC (Bone to Implant Contact) Healing abutment, No loading 40.1 Occlusally loaded 35.5 Submerged 57.4 Submerged case에서더나은 BIC를보여주었다 2. Immediate loading of Ti-plasma-sprayed implants: An Histological Analysis in Monkeys Piattelli A, Scarano M, Paolantonia M J. Periodontol 69; :1998 -monkey study -48 TPS (24 Maxilla, 24 Mandible) -24 test (loaded), 24 control (unloaded) -9 months -Histomorphometric analysis -BIC (bone to implant contact) Test Control Maxilla 67.3 ± ± 3.3 Mandible 73.2 ± ± 6.5 Overall 70.2 ± ± 5.1-1번연구와는달리 loading을가한 test group 에서더나은 BIC를보여주고있다. 3. Histological and Histomorphometrical implant bone subjected to immediate loading : An experi mental study with Macasa fascilularis Romanos GE, Toh CG, Siar C IJOMI 17; 44-51, 2002 BIC 는 immediately loaded case와 delayed case 에서별다른차이를보이지않았으나, BA(bone around implant within the threads) 에서는 immediately loaded case에서더많은 % bone 을보여주었다. 4. Immediate fixed interim prosthesis supported by two-stage threaded implants: Methodology and Results Schnitman P, Wohlre B, Rubenstein J J Oral Implantol 1990; 16; N=7 patients 47 Nobelpharma Implants 26 implants submerged in anterior mandible 4 months submerged period 21 implants loaded to support interim prosthesis 1 immediately loaded molar region fixture failed at 3 months 1 immediately loaded molar region fixture failed at 6 months 1 immediately loaded molar region fixture failed at 21 months Potential cause for immediate implant failure -inadequate implant length -poor bone quality (as per Schnitman) 18 still integrated 위에열거된서로상반된연구결과로본인은자체적

3 3 으로 Immediate loading 에관한다음과같은새로운실험을하게되었다. 1)Immediate loading of threaded implants at stage 1 surgery in edentulous arches: Ten consecutive case reports with 1 to 5 year date Tarnow DP, Emtiaz S, Classi A IJOMI 12; , patients 6 mandibular cases (64) 4 maxillary cases (43) Total loaded: 69 Total submerged: 38 Total # placed: 107 Failed 2 immediate loaded ( 이두 case 모두 interim prosthesis 를한경우임 ) 1 submerged 2)Implant-retained mandibular overdentures with immediate loading: A Retrospective multicenter study on 226 consecutive cases Chiapasco M, Markwalder TH COIR; 8:48-57, patients, 904 Implants (4/implant) 4 systems (TPS, ITI, HA-Ti, NLS) Impression immediately after surgery U-shaped gold bar inserted next day Clips mounted and denture inserted same day Average follow up 6.4 years Implant success 96.9%, Bar success 98.5% 여기서 Dr. Tarnow 는 bar는 class III malocclusion 에서 maxillary case 를제외하고는이제잘쓰지않는다고함. Case # Total placed Immediate loaded Submerged Arch Type Mandible Noble Mandible Noble Mandible Noble Mandible ITI Maxilla Noble Mandible Noble Maxilla Noble Maxilla Astra Mandible Astra Maxilla 3I 본인은 case 가진행됨에따라좀더자신있게 imme diate loading의수를늘리게되었다. 또한 Maxilla의경우도예외가아니며 implant type 에따른차이도없는것을볼수있다. 3)The use of transitional implants for immediate fixed temporary prostheses in cases of implant restorations Froum S, Emtiaz S, Tarnow D Pract Perio Aesthet Dent ; 1998; 10(6) transitional implants in 15 patients 6 failed (3 in one patient) 3 were mobile but remained in function no prostheses were lost failure due to early prosthesis removal 정확한 Surgical Template를만들고 2mm twist drill 로깊이 5mm까지 drilling 한후 drilling 한위치에 attached gigiva 가있을경우 flapless surgery를한다. punch를사용하는경우는일종의 flap이므로 flapless surgery 라할수없다.

4 4 다음과같은경우에 out of occlusion 시켜준다 immediate temporization without occlusion 1)One stage surgery with a healing abutment 2)Single crown 3)Straight line splints Immediate socket placement without occlusion 1)when the socket is filled by the implant (1.5mm rule) 2)full arch case only or 4 on floor splinted Conclusion 1)Full arch cases only for occlusally loaded cases 2)Or 4 on the floor splinted with a bar 3)Non-occlusally loaded with immediate temporization for cases with good initial stabilization (type I & II bone) 4)Immediate socket implants should be utilized with caution for immediate occlusally loaded cases 5)Success will depend on length of implant in bone density of bone width of the implants distribution of the implants (turn in the arch and AP spread) Tips for immediate occlusal loading 1)For Full arch case only 2)Use minimum 10mm implants 3)Use diagnostic wax-up for template and provisional 4)Use rigid metal casting in lingual of provisional (if there are long spans) 5)Use screw retained provisional 6)If cemented, do not remove provisional for 8 + weeks 7)All implants must have high initial stability (tongue, ISQ, periotest) 8)Utilize widest A-P distribution of implants Sinus lift NYU sinus study database Evidence- based decision making Effect of time Effect of graft materials Effect of membranes Effect of implant surface Interactions NYU Sinus Study (1993~July 2003) 797 Sinus lifts (517 patients) 1461implants placed 395 histological cores Effect of time on sinus graft healing 1) Histological evaluation of the sinus elevation procedure : A clinical report Wallace et al Int J Rest Dent 1996; 16; sinus cores from the same subject 80% Osteograf/N, 20% Autogenous Cores at 4, 8, months Histomorphometric analysis done inde - pendently by different university & not supported by any company # months % vital bone 15% 33% 38% 65% 2) Effect of time on graft maturation Froum et al

5 5 Int J periodont Rest Dent 1998; 18: Time # cores Range % Average % 6 ~ 9 months ~ 15 months *cores from the same patient * 여기서 25-30% 의 calcification에주목해야한다. 예를들어같은시기에발치한하악소구치와상악소구치는 1년후분명히다른 calcification 상태를보인다. Genetically coded된발치외벽으로부터새골조직이형성되기때문이다. 그래서만약 sinus가 anterior mandible 에있다면 sinus augmentation 후약 70% 의 calcification 과약 30% 의 marrow를갖게될것이나, posterior maxilla 에있으므로약 25-30% 의 calcification 과 70% 정도의 marrow 를갖게되는것이다. Rate of calcification 은약 1mm/month from the bony wall 예 ) remaining bone 이약 4mm 인경우 sinus augmentation 후 6개월이지난시점에서약 10mm 정도의 solid bone이형성된다. Effect of graft material 1) Human histologic evidence of integration functionally loaded hydroxyapatite-coated implants placed simultaneously with sinus augmen tation: A case report 2.5 years post placement Rosenlicht J, Tarnow D J Oral Implantol 1999; 25: 년후일부 graft material (bovine bone) 은 bone 과완전히 integration된상태로남아있으며 implant 주변엔 bone 과 marrow 만이접해있다 (bovine bone graft material 은주변에접 해남아있지않는다 ) 2) Histologic evaluation of Bio-Oss in a 2 stage sinus floor elevation and implantation procedure: A human case report Valentini P, Abensur D, Densari D COIR 1998; 9:59-64 Area densities of the mineralized bone at 6 month Area density Area density Area density of bone Bio-Oss Bone marrow Non-grafted area Grafted area Area density of bone은어떤 research paper든, 어떤 material 을쓰는가에상관없이일정하게 25-30% 정도로나온다. Grafted area 에서 Bio-Oss 가 bone marrow space를차지하고있는것은좋은점이다. 결론적으로반드시 Mineralized boned을사용해야만한다. (human bone 이나 bovine bone 어느쪽이나무방하다 ) 3) Sinus Grafting with porous bone mineral (Bio- Oss) for implant placement: A 5 year study on 15 patients Valentini P, Abensur D, Schenk R et al Int J Rest Dent 2000; 20: sinuses, 15 patients 100% Bio-Oss 57 implants placed at 6 months stage 2 surgery in 6 months cores at 6 & 12 months in 3 patients cores taken through crest

6 6 N=3 % new bone % Bio-Oss % marrow Grafted area 6 months Non-Grafted area 6 months Grafted area 12 months Non-Grafted area 12 months 시간이지남에따라분명 new bone 은증가하나 non -grafted area의 % 를넘어서지못한다. Results achieved with different grafting materials 1) Sinus floor elevation using anorganic bovine bone matrix (Osteograf/N) with and without autogenous bone Froum S et al Int J Rest Dent 1998; 18: Graft combinations in study With Without Graft material membrane membrane Osteograft alone 11 4 Osteograft + Autogenous bone 30 6 Osteograft + DFDBA 13 9 Osteograft + DFDBA + Autogenous bone Total % vital bone content at 6 month Graft material N Range % Average Osteograft alone Osteograft + Autogenous bone Osteograft + DFDBA Osteograft + DFDBA + Autogenous bone Xenograft + DFDBA 가 Xenograft 단독사용시보다 더많은 vital bone 형성이이루어짐을볼수있다 Implant Survival Graft material Placed Failed % Survival Osteograft alone Osteograft + Autogenous bone Osteograft + DFDBA (Cluster) Osteograft + DFDBA Autogenous bone Osteograft 단독사용시 5% vital bone range 에서도 성공을보여주고있는점은주목할만하다. 2) Clinical and histological evaluation of implant integration after sinus floor augmentation with autogenous bone, bovine HA, or a 20:80 mixture Hallman M, Sennerby L, Lundgren S IJOMI 2002; 17: sinuses, vital bone contents 100% autogenous 37.7 ± 31.3% 20/80 composite 39.9 ± 8% 100% Bio-Oss 41.7 ± 26.6% No statistical difference Then, How about implant survival? 36 sinuses, 111 implants, 1 year loading Overall survival 91.0 % 100% autogenous 82.4 % 100% Bio-Oss 96.0 % 20/80 composite 94.4 % Autogenous bone이 Gold Standard 가아님을보여준다.

7 7 Evidence shows mineralized bone replacement grafts can be used alone with highly predictable results 100% Bio-Oss Hising 2001, Hallman 2002, Valentini % Osteograf/N Froum 1998 Evidence-based literature reviews Wallace, Froum 2003, Del Fabbro, Testori 2004 Effect of autogenous bone, PRP 1) Effect of PRP on bone formation in Xenografts (Bio-Oss) placed in the human Maxillary sinus: A pilot study of 3 bilateral cases Froum S et al Int J Periodontal Rest Dent 2002; 22:45-53 Case Graft Time Platelet gel No platelet # 1 100% Bio-Oss, months 7 15 gel 13 Bioguide 2 95% Bio-Oss, % Autogenous, Bioguide 3 100% Bio-Oss, test implants Mean PRP를사용한경우와그렇지않은경우에통계적으로유의있는차이가없음을알수있다. 2) Implant survival by graft material Del Fabbro, Testori et al, IJPRD accepted Graft material # # # % Studies Implants Failures Survival 100% Autogenous bone Composite % Bovine replacement 여기서자가골에서의 survival rate이더낮은이유가, 초창기엔주로 hip marrow 와 machined Tiimplants 를조로사용하였기때문일수도있다. (Rough surface implant 는더나중에사용되기시작 ) 3) Particulate vs. autogenous block graft Wallace et al, Annals Periodontol 2003; 7 Graft type Mean Standard error Least square mean Iliac block particulate *least square mean include adjustments for other variables Sinus Graft 시의 Membrane 사용 장점 : -excludes non-osteogenic connective tissue from the flap -enhances graft containment 단점 : -removes periosteum from the healing site -inhibits vascularity Patient Maturation time % Vital bone % Vital bone (months) without memb. with memb Average

8 8 1) Effect of membrane on vital bone formation Tarnow et al Int J Rest Dent 2000; 20: Same graft material, same maturation time, membrane on one side only 결과를보면평균적으로 membrane을쓰는쪽이분 명히도움이되고개별적으로보더라도월등히좋거 나차이가없다. 그러므로 Sinus lift 시 membrane 사 용은이제 routine practice가되어야한다. 2) Intrastudy comparison of 3 randomly controlled trials Wallace et al, Annals Periodontol 2003; 7 Study With membrane Without membrane Tarnow (2000) 28 implants, 100% 27 implants, 92.6% Tawil (2001) 29 implants, 93.1% 32 implants, 78.1% Froum 133 implants, 99.2% 82 implants, 96.3% 3) Sinus augmentation using Bio-Oss with various membranes Froum et al, manuscript in preparation Membrane type # Sinuses Range vital bone Average e-ptfe % Collagen % No membrane % e-ptfe와 Collagen membrane 사이에차이가없음 을보여준다. Survival Rate for implants Membrane type # Placed # Failed % Survival e-ptfe % Collagen % Total % Effect of implant surfaces 1) Survival rates of implants with different surface morphologies in grafted sinuses - 6 months post loading data Tarnow et al, manuscript in preparation 517 patient 1461 implants loaded for a minimum of 6 months Surface Acid- HA SLA TiOBlast TPS Machined etched # of implants Survival rates 918/962 20/22 162/169 27/28 152/160 74/105 Average survival rates: 93.7 % (1368/1461) Survival rate of rough surface: 95.4 % Survival rate of smooth surface: 70.4 % 2) Implant survival by surface Del Fabbro, Testori et al IJPRD, Accepted for publication Surface # studies # implants # failures % survival Turned Rough ) Wallace et al, Annals Periodontol 2003:7 surface Mean Machined 82.4 Rough 95.2 In conclusion, Don t place machined surface in sinus Interaction Graft material and Implant surfaces Mean Standard Least square Machined-iliac block Machined-particulate Rough-iliac block Rough-particulate

9 9 Vital bone formation is -time dependent -graft material dependent -enhanced with a barrier membrane Implant survival is -graft material dependent -enhanced with a barrier membrane -enhanced by a rough surface ( 가장중요!!) Biology Rules!!! Aesthetics 3- dimensional placement Occlusal-gigival Facial-lingual Mesial-distal 3- dimensional integration Occlusal- gingival level의고려 1998 년의 concept 은 3mm from the height of soft tissue (apical to adjacent CEJ) 였다. 그러나만약이처럼 implant platform이 crest 에위치하게되면 interdental area 에서는 3mm + 4.5mm (between labial tissue and papilla) 가되어약 7.5 ~ 10mm 의차이가생기며첫번째 thread 까지흡수되는 biologic width 까지고려시약 9mm정도의차이가생긴다 Facial-lingual 의고려 Gingival recession around wide vs. standard diameter implants: A 5-year longitudinal prospective study Small P, Cho S, Tarnow D PPAD 2001; 15: Buccal Recession 전기간에걸쳐 standard diameter의 recession 정도가 wide diameter implant 를사용한경우보다작았다. Standard diameter Wide diameter Prosthesis insertion 0.43 mm (138) 1.15 mm (58) 3 month 0.56 mm (138) 1.41 mm (58) 6 month 0.61 mm (138) 1.45 mm (58) 1 year 0.69 mm (128) 1.48 mm (54) 18 month 0.82 mm (110) 1.55 mm (45) Mesial-distal 의고려 1) Radiological evaluation of marginal bone loss at tooth surfaces facing single Br anemark implants Esposito M et al COIR 4(3); , 1993 The mean bone loss at adjacent tooth surfaces increased with increasing distance fixture-tooth for the time interval between preoperative evaluation and crown installation 2) Influence of flap design on peri-implant interproximal crestal bone loss around single tooth implants Gomez-Roman G IJOMI 16; 61-67, 2001 Adjacent tooth 에약간의 tissue를남겨두는 limited flap design이 0.5mm, wide flap 이 2mm 정도의 bone loss 를보여주었다 3) The effect of the distance from the contact point to the crest of bone on the presence or absence of the interproximal dental papilla Tarnow et al J Periodontol 63; , 1992 Presence of papillae (n=288)

10 10 X-axis: % presence of papillae Y-axis: distance from contact point to crest of bone 결론 : contact point에서 crest of bone 까지의거리가 5mm 또는그이하인경우에 papillae 형성이거의 100% 가된다 4) Regeneration of gingival papilla after singleimplant treatment Jemt T Int J perio Resto Dent 17; , 1997 Papillae index 0 - bad, 1- slight growth of papilla 2 - good, 3- perfect, 4 - overgrowth Papilla index score Mesial papilla Placement Follow up Distal papilla Placement Follow up year F/U 에서 17 papilla 가거의완벽하게자라났음을볼수있으며, implant crown insertion 시환자에게 (contact 이제대로있는한 ) papilla growth 는시간이걸림을주지시킨다! 5) Restoring the gingival contour by means of provisional resin crowns after single-implant treatment Jemt T Int J Perio Resto Dent 19; 21-29, 차수술시 Healing abutment를채우든지, 바로 temporary crown을제작해주든지는 papilla growth 에는큰영향을주지않는다. 술후 2년 follow up 에서 soft tissue volume에차이가없었음 Is the 5mm rule also true for papillae between teeth and implants? Yes 6) Stability of the mucosa: Topography around single-tooth implants and adjacent tooth: 1 year result Grunder U, IJPRD 20; 11-17, 2000 자연치와 implant 사이의 papilla존재여부는 implant 쪽이아니라치아쪽 bone level이결정적인요소다. Contact point 에서 bone level 까지의거리가거의 9mm (max 10.5) 인경우에도자연치쪽이 5mm 이하인경우문제가없었음. 7) clinical and radiographic evaluation of the papilla level adjacent to single-tooth dental implants: A retrospective study in the Maxillary anterior region Choquet V, Hermans M, Tarnow D, Malevez C J Periodontol 72; , patient, 27 Br anemark Implant 17 implant: uncovered with a standard technique 10 implants: generate papilla-like formation

11 11 52 papillae were evaluated clinically and radiographically Immediate implant placement and Immediate provisionalization Immediate vs. delayed placement variables -height of soft tissue -thickness of soft tissue -amount of keratinized tissue -degree of inflammation of buccal tissue -thickness of buccal plate of bone ( 가장중요 ) -are adjacent crowns being placed -histologic vs. clinical success -placement of graft or not? -was flap elevated? -was membrane placed? -was primary closure achieved? -was implant placed facially or palatally -provisionalization -fixed or removable? 2) Evaluation of Ti-implants placed into simulated extraction sockets: A study in dogs Akimoto K, Becker W IJOMI 14; , 1999 Clinically, all control and test sites healed with complete bone fill in the defect. But, histologically there s space. As the gap widened, the amount of bone-to-implant contact decreased, and the point of the highest bone-to-implant contact shifted apically. 3) Dimensions of peri-implant mucosa: An evaluation of maxillary anterior single implants in humans Kan JYK, Rungcharussaeng K, Kois JC J Periodontol 74; , 2003 Bone-sounding measurements of anterior implant single crowns comparing thick and thin biotype Bone sounding depth Site Thick biotype (n=28) Thin biotype (n=17) MI (mesial of implant) 6.54 ± ± 1.40 F (mid facial) 3.79 ± ± 0.91 DI (distal of implant) 6.14 ± ± 1.31 DT (distal of tooth) 4.45 ± ± ) Single tooth replacement in the aesthetic zone with immediate provisionlization; 14 consecutive case reports Wohrle PS PPAD 10; , 1998 Immediate provisionalization은 papilla를위해서는좋지만 midfacial tissue height 에도도움이되는가하는문제는 questionable 하다. <<Ice cream Technique>> Handle - socket 아이스크림 - over the top extraction socket 에 bone material 삽입후 collagen membrane사용 buccal plate missing area에 handle 모양삽입, 아이스크림쪽은 bone material 을덥고 palatal 쪽에서 2~3 suture, buccal 쪽은 suture 안함

12 12 Between adjacent implants Is the 5 mm rule also true for papillae between implants? NO 1) The effect of inter-implant distance on the height of the inter-implant bone crest Tarnow DP, Cho SC, Wallace S J Periodontol 71; l , 2000 Inter-implant distance less than 3mm show increased crestal bone resorption 1) D (distance between the adjacent implant) >3mm (n=11) X (implant shoulder to inter-implant crest peak) = 0.45mm 2) D 3 mm (n=25) X = 1.04mm 2) The vertical distance from the crest of bone to the height of the interproximal papilla between adjacent implants Tarnow et al, J Periodontol 74; , 2003 Height of papilla (mm) Total % % 반이상의 case 가 3mm 이하이므로문제 2 Maxillary incisor missing case -broad contact point를만들어준다 Central and lateral incisor missing case -central 에 implant, lateral에 distal cantilever ovate pontic Lateral and Cuspid missing case -canine에 implant, lateral 에 mesial cantilever ovate pontic 4 Maxillary incisor missing case -2 laterals 에 implant 3-dimensional positioning 1) platform switching : placing a smaller diameter abutment on a larger diameter implant seating surface 3)Scalloped implant의사용 : Nobelbiocare의 Scalloped implant는정확한개념에서출발하였으나 screw type이어서정확히식립하는것이힘들어서성공적이지못했다. Dr.Tarnow s version of Scalloped implant는 Endopore와같은 mallet을이용한식립을하므로식립용이. Golden Rule Do all site development before implant placement into the aesthetic zone Do one miracle at a time Use the KISS principle (Keep It Simple, Stupid!!) Treatment Planning guidelines in the aesthetic zone Do all significant site development before placing implants Place implants 2 to 3 mm apical to desired height of facial tissue Place implants at least 1 to 1.5 mm away from adjacent teeth Position implants palatal to the incisal edge or at the cingulum Use ovate pontic Use papillae saving incisions where possible Avoid adjacent implants if possible Overbuild the inter-implant bone before placing implants adjacent to each other

13 13 Place adjacent implants 3mm apart to preserve the crestal bone Place a scalloped top implant (??) or platform switching Transcriber s note Dr.Tarnow 의강의는언제나그러했듯근거중심 (evidence-based) 이었으며훌륭했습니다. 다만약간아쉬웠던점은이전의그의강의와중복되고, 이미많이알려진내용도있었고대부분의 evidence 가자신과그의동료들의연구에바탕을두었으므로 ( 물론, 그와그의동료들의연구업적은존경받아마땅합니다 ), 좀더제 3 자의연구에근거한강의였으면더욱좋았을거라는생각은해봅니다. 좋은강의를해주신 Dr.Tarnow 께이자리를빌어다시한번감사드리며이 Transcription 이이식학회회원분들께조금이나마도움이되기를바랍니다. 이 transcription 은그가언급한 literature 의요약형식을취하며간혹표, 그림, 사진등은저작권문제등으로모두싣지못하므로이해해주시기바랍니다. Transcriber : 강민석

00)13-3목차1~3

00)13-3목차1~3 An evaluation of marginal bone level change in single short implant : an 1-year follow up Tae-Hoon Lee, Joo-Hyun Kwon, Sunjai Kim, Chong-Hyun Han Department of Prosthodontics, Kangnam Severance hospital,