Implant Esthetics: Form Meeting Function 55) of the cases studied were identified as requiring grafting procedures. This may be due to the pre-exist- ing anatomy and ridge resorption pattern in the maxillary anterior area (13, 14). However, deformities in the anterior part of the maxilla may be related to the tooth biotype, genetic disorders, trauma, iatrogenic damage of the bone, or other reasons independent of the maxillary resorption. The limited number of cases present in our study that did not require graft procedures with the 3.25 mm diameter template may be of importance for clinicians placing implants in the maxillary anterior area. Moreover, the use of con - ventional diameter implants would have resulted in a greater number of ridge defects and complications than that reported in the present study population. In addition this may have increased the number of patients with more advanced classifications of deformities. Based on the number of ridge deformity com- plications documented in the present study, a knowledge and training in procedures for ridge augmenta- tion may be necessary for clinicians to obtain predictable results and manage surgical complications. CONCLUSION T he present report proposed a new classification system for maxillary alveolar ridge deformities based on CAT-scan implant simulation as a useful concept in order to more precisely predict treatment out- comes and the necessity for ridge augmentation prior to implant placement. The results indicate that a high number of cases in the maxillary anterior area would require augmentation procedures in order to achieve ideal implant placement and restoration. T he ultimate goal of implant treatment is to surgically place implants in the most desirable posi- tion compatible with esthetics, phonetics, and function. Identification of the “optimal final tooth position” allows the restorative dentist and surgeon to analyze the impact of pathologic alterations and to determine if soft or hard tissues need to be reconstructed to maximize function and esthetics (9). To achieve a long-lasting, ideal esthetic result with implants, in light of circumferential bone resorption that usually occurs as part of the healing response around the implant head, the thickness of the bone on the buccal side of an implant should be at least 2mm (8). The new method of classification presented in the current study can identify this parameter. Using the proposed new classification system, ridge classification of the bone defects may be identified and complications avoided due to more accurate treatment planning of implant size and position. The rela - tionship between the adjacent teeth and bone can also be observed by utilizing the radiographic template, which was worn by the patient when taking the CAT-scan. The advantages of this new Implant Oriented Classification System (IOCS) include: 1) more accurate eval- uation of the clinical situation prior to surgery to determine treatment options. 2) the ability to evaluate the need for hard tissue augmentation and simulate the necessary augmentation prior to surgery. 3) allowing selection of appropriate implant type and size before surgery. 4) using the radiographic template as a sur- gical guide. 5) ability to communicate with restorative dentists and patients concerning treatment proce - dures and the expected outcomes. A 3.25x10mm implant was selected as a guide implant for the new IOCS because, according to the liter - ature, this is the smallest permanent implant with a high success rate (10, 11). The ideal implant position in this study was based on the radiographic template. The simulated implants were placed 3mm below the ideal CEJ as a determined from the wax-up and radiographic template in order to provide enough apico- coronal room for esthetic prosthetic replacement (12). The results reported in the present study revealed that 29.8% of the deformities were classified as Class I. Almost 66% of Class I deformities were classified as Class I-A. The remaining 34% of the Class I defects would require some form of bone augmentation procedure for a successful long term prognosis. On the other hand 30% of the deformities were classified as Class IV according to the CAT-scan simulation. This high number of Class IV deformities may be due to the fact that when these patients were evaluated at the time of intra-oral examination the treating clinician, noting the ridge defect, subsequently sent the patient for CAT-scan evaluation. Nevertheless, these findings indicate that a significant number of implant cases would require ridge augmentation for implant placement or a modification in the treatment plan which may preclude the use of an implant in these sites. According to our IDD CAT-scan data, 81% (116 of the total 144) of the implant sites and 92.7% (51 of Depth: The implants were placed 3mm below the buccal cemento-enamel junction (CEJ) of the tooth posi- tion outlined by the radiographic template. Proposal of a new classification system of ridge deformities: In the new proposed classification system ridges were categorized into seven different classes as follows: Class I: The implant is completely surrounded by bone; no dehiscence or fenestration present Class I-A : >= 2mm of facial plate of thickness Class I-B : < 2mm of facial plate of thickness Class II: Dehiscences are detected but no fenestrations are present Class II-A: only buccal or palatal dehiscence is present Class II-B: both buccal and palatal dehiscences are present Class III: Fenestrations are detected but no dehiscence is present Class III-A: only buccal or palatal fenestration is present Class III-B: both buccal and palatal fenestrations are present Class IV: Both dehiscences and fenestrations are present RESULTS T he following represents the findings in our study utilizing 144 CAT-scan images to classify maxillary anterior ridge deformities: 19.4% (28) of our locations were classified as Class I-A ridge deformities; 10.4% (15) were Class I-B; 20.8% (30) were Class II-A alveolar defects; Class II-B were present on 12.5% (18) of our samples; 6.3% (9) of sites were fenestrations without dehiscences (Class III), and all were in the Class III-A category (buc- cal or palatal fenestration). Finally, 30.6% (44) of the potential implant site showed both dehiscences and fenestrations(Class IV). Class IV ridge deformities had the highest incidence followed by Class II- A, Class I-A, II-B, I-B, and Class III. Other findings showed that 28 Class I-A deformities were in 17 cases; 15 Class I-B deformities were in 14 cases; 30 Class II-A deformities presented in 21 cases; 18 Class II-B deformities were found in 9 cases; 9 Class III deformities were observed in 5 cases, and 44 Class IV deformities were noted in 18 cases. Class II-A was the most common ridge deformities followed by Class IV, Class I-A, Class I-B, Class II-B and Class III. There were 34 patients (61.8%) with more than one class of ridge deformities present and the remaining 21 patients (38.2%) showed only one class of deformity. DISCUSSION Ridge Classification According to Ideal Implant Restorative Position Ridge Classification According to Ideal Implant Restorative Position as Determined by CT Analysis with Radiographic Templates as Determined by CT Analysis with Radiographic Templates Park, Young Sang; Lee, Cheng-Hsun; Jalbout, Ziad; Cho, Sang-Choon; Froum, Stuart; Elian, Nicolas; Tarnow, Dennis. Ashman Department of Periodontology and Implant Dentistry, New York University Author Year Classification Siebert 1983 Class I: buccolingual loss of tissue with normal apicocoronal ridge height Class II: apicocoronal loss of tissue with normal buccolingual ridge width Class III: combination-type defects (loss of both height and width) Allen et al 1985 A: Apicocornal loss of tissue B: Buccolingual loss of tissue C: Combination Mild: <3mm; Medium:3-6mm; Severe:>6mm Lekholm and Zarb 1985 virtually intact alveolar ridge minor resorption of alveolar ridge advanced resorption of alveolar ridge to base of dental arch initial resorption of base of dental arch extreme resorption to base of dental arch Misch and Judy 1987 abundant bone barely sufficient bone compromised bone C-h: compromised height; C-w: compromised width deficient width Defect Type Classification Detailed Description Extraction wounds Class I the envelope of bone is intact Class II the envelope of bone is not intact Fenestrations Class I the implant surface penetrates the wall of bone by an insignificant amount and located within the envelope of bone Class II there is a convexity and a significant portion of the implant is exposed outside the envelope of bone for reasons of restorability Dehiscence Class I the implant surface resides within the envelope of bone Class II the implant surface resides outside the envelope of bone Horizontal ridge deficiencies (HRD) Class I the exposed implant surface resides within the envelope of bone Class II the exposed implant surface resides outside the envelope of bone Vertical ridge deficiencies (VRD) Class I the vertical insufficiency is < 3 mm Class II the vertical insufficiency is > 3 mm Classification Suggested Treatment Options Class I Class I-A Implant placement in ideal restorative position Class I-B Implant placement without dehiscence or fenestration Class II Class II-A Staged GBR; Simultaneously GBR and implant placement; Ridge expansion; Ridge splitting Class II-B Staged GBR; Simultaneously GBR and implant placement; inlay/onlay block graft; distraction osteogenesis Class III Staged GBR; Simultaneously GBR and implant placement; inlay/onlay block graft, Taper implants; Shorter implants Class IV Distraction osteogenesis + Staged GBR or onlay graft; block graft Fig 6. Class II-A Fig 7. Class II-B Fig 8. Class III Fig 9. Class IV REFERENCES 1. Abrams H, Kopczyk RA, Kaplan A. Incidence of anterior ridge deformities in par- tially edentulous patients. J Prosthet Dent 1987;57:191-194. 2. Tinti C, Benfenati SP. Clinical Classification of Bone Defects Concerning the Placement of Dental Implants. Int J Peri Resto Dent 2003;23:147-155. 3. Seibert JS. Reconstruction of deformed, par- tially edentulous ridges, using full thickness onlay grafts. Part I. Technique and wound healing. Compend Contin Educ Dent 1983;4:437-453. 4. Wang HL, Shammari KA.. HVC Ridge Deficiency Classification: A Therapeutically Oriented Classfication. Int J Peri Resto Dent 2002;22:335-343. 5. Lekholm U, Zarb GA. Patient selection and preparation. Tissue Integrated Prosthesis 1985;1:199-209. 6. Misch CE. Maxillary sinus augmentation for endosteal implants: Organized alternative treatment plans. Int J Oral Implantol 1987;4:49-58. 7. Spray J, Black V, Morris H, Ochi S. The influence of bone thickness on facial margin- al bone response stage 1 placement through stage 2 uncovering. Ann Periodontolgy 2000;5:119-128. 8. Grunder U, Gracis S, Capelli M. Influence of the 3-D bone-to-implant relationship on esthetics+. Int J Peri Resto Dent 2005;25:113-119. 9. Mecall RA, Rosenfeld AL. Influence of Residual Ridge Resorption Patterns on Fixture Placement and Tooth Position, Part3: Presurgical Assessment of Ridge Augmentation Requirements. Int J Peri Resto Dent 1996;16:323-337. 10. Andersen E, Saxegaard E, Knutsen BM, Haanæs HR. A Prospective Clinical Study Evaluating the Safety and Effectiveness of Narrow-Diameter Threaded Implants in the Anterior Region of the Maxilla. Int J Oral Maxillofac Implants 2001;16:217-224. 11. Lekholm U, Gunne J, Henry P, Higuchi K, Linden U, Bergstrom C, Van Steenberghe D. Survival of the Branemark implant in partial- ly edentulous jaws: A 10-year prospective multicenter study. Int J Oral Maxillofac Implants 1999;14:639-645. 12. Buser D, Martin W, Belser U. Optimizing Esthetics for Implant Restorations in the Anterior Maxilla: Anatomic and Surgical Considerations. Int J Oral Maxillofac Implants 2004;19:43-61. 13. Atwood DA. Reduction of residual ridges: A major oral disease entity. J Prosthet Dent 1971;26:266-279. 14. Atwood DA, Coy W. Clinical, cephalomet- ric, and densitometric study of reduction of residual ridges. J Prosthet Dent 1971;26:280- 295. Fig 1. Vertical and horizontal defects Fig 2. Edentulous ridge “...the results indicate that a high number of cases in the maxillary anterior area would require augmentation procedures in order to achieve ideal implant placement and restoration...” D eformed partially edentulous ridges may compromise ideal implant placement and implant sur - vival. Deformities of the alveolar ridge may be caused by traumatic extraction, facial trauma, clefts from birth defects, endodontic surgeries, removal of teeth with advanced periodontal disease, or implant failures (1). Several published reports classified ridge defects to help plan the treatment regimen for clinical correction (2). Seibert classified ridge deformities into three broad categories which are buccolingual tissue loss, apicocoronal tissue loss, and a combination of both (3). Recently, Wang and Al-Shammari described a new system, HVC classification, which is a modification of Seibert’s classification (4). These H (horizon- tal), V (vertical), and C (combination) defects were subdivided into S (small), M (medium), and L (large) subcategories. They also described treatment options based on this HVC classification. The advent and widespread use of dental implants mandated careful evaluation of available bony ridge volume and dimensions. Lekholm and Zarb’s classification includes five stages of bone resorption, from minimal to severe (5). Misch and Judy’s classification describes four divisions of available bone with treatment options based on the amount of available bone height, width, and angulation (6). Tinti and Parma- Benfenati introduced a clinical classification of bone defects. They categorized “the envelope of bone” into five categories: extraction wounds, fenestrations, dehiscences, horizontal ridge deficiencies, and ver- tical ridge deficiencies (2). They also proposed treatment based on this classification. To date, no published report has classified ridge deformities according to the position of the projected implant restoration. Currently, 3-dimensional radiographic images are available to evaluate hard tissue and to plan implant placement prior to surgery. Clinicians must focus on the 3-D bone-to-implant rela - tionship to establish the basis for an ideal and harmonic soft tissue situation that is stable over a long peri- od. Furthermore, many authors discussed the importance of at least 2mm of facial plate thickness (7, 8). When the facial plate is less than this critical thickness, the clinician may expect frequent and greater loss of vertical height of the facial plate. The purpose of present study was to classify ridge deformities utilizing Computerized Axial Tomographic (CAT) scan images based on the ideal implant restorative position as determined by implant simulation. MATERIALS AND METHODS C linical and CAT-scan data in this study were obtained from the Implant Dentistry Database (IDD) established at the Department of Periodontology and Implant Dentistry at New York University College of Dentistry (NYUCD) Kriser Dental Center. This data set was extracted as de-identified information from the routine treatment of patients. The IDD was certified by the Office of Quality Assurance at NYUCD. This study is in compliance with the Health Insurance Portability and Accountability Act (HIPAA) requirements and was approved by the IRBA. CAT-scans were selected with the following criteria: -Only maxillary anterior missing teeth were included. -At least two consecutive missing teeth were required. -Images had to show at least one remaining anterior tooth, which was used as a guide for angula - tion. -Radiographic templates used during taking of the CAT-scan were a prerequisite for this study. -Unclear CAT-scan images were excluded from this study One thousand and five hundred CAT-scans were screened from the NYUCD Department of Periodontology and Implant Dentistry IDD. Fifty five cases satisfied the selection criteria. In these 55 sub- jects, 144 implant sites were evaluated. Characteristics of the measurements: -All the measurements were performed and documented using CAT-scan software(SimPlant 8.0, Materialize, Glen Burnie, MD, USA) in a IDD by two independent investigators -In all CAT-scan images, one 3.25x10mm parallel side simulated implant was positioned for every single edentulous area. -Every simulated implant was placed in the ideal tooth position according to following protocol: Position: The implants were placed according to the tooth position outlined by the radiographic tem- plate. Angulation: The implants were placed according to the angulation of the adjacent existing tooth. Inclination: The implants were placed using the adjacent existing tooth/teeth and the tooth position outlined by the radiographic template as guides. Table 1. Classifications of ridge defects Table 2. Tinti’s clinical classification Table 3. New classification and treatment options Fig 3. Metal exposure due to insufficient facial bone Fig 4. Class I-A Fig 5. Class I-B This Presentation was Sponsored by New York University Department of Implant Dentistry Alumni Association (NYUDIDAA) and the Office for International Program