Rationale for the Application of Immediate Load In Implant Dentistry: Part II Carl E. Misch, DDS, MDS,* Hom-Lay Wang, DDS, MDS,† Craig M. Misch, DDS, MDS,‡ Mohamed Sharawy, BDS, PhD,§ Jack Lemons, PhD, and Kenneth W. M. Judy, DDS¶ I mmediate loading of a dental im- plant loads the implant with a pro- visional restoration at the same ap- pointment or shortly thereafter. Immediate loading was the initial pro- tocol suggested with dental im- plants. 1–5 The patient does not need to wear a removable restoration during initial bone healing, which greatly in- creases comfort, function, speech, and stability and enhances certain psycho- logic factors during the transition pe- riod. 6,7 Over the last few years, several authors have reported on immediate loading in the completely or partially edentulous patient, with 95% to 100% success rates. 8–67 RATIONALE FOR IMPLANT IMMEDIATE LOADING Part I of this article presented a rationale to decrease strain to the im- mediate loaded implant– bone inter- face. This is important because the higher the microstrain in bone, the greater the bone turnover rate. This results in more “reactive” woven bone, which is weaker and has a lower modulus of elasticity (and biome- chanical mismatch to titanium). One method to decrease the strain in the bone is to decrease the stress to the implant and/or prosthesis, because stress and strain are directly related. Stress equals force divided by area. As a result, conditions that increase area of support in the bone or methods to decrease force to the prosthesis are appropriate. Area may be increased by implant number, because a number of implants splinted together may de- crease the risk of overload to each implant as a result of a greater surface area and improved biomechanical dis- tribution. This concept was presented in the previous report. 68 Area of load may also be in- creased by implant size, implant de- sign, and implant surface condition. In addition, stress may be reduced by de- creasing the force applied to the pros- thesis. Forces may be influenced by patient factors, implant position, can- tilever forces, occlusal load direction, occlusal contact positions, and diet. This article correlates these stress- reducing conditions for a rationale for immediate loading using a wide range of clinical experiences and animal studies. Implant Size In the partially edentulous patient, the number of implants is more diffi- cult to dramatically increase, com- pared with the completely edentulous situation. The surface area of implant support may also be increased by the size of the implant. For example, the length of the implant in most systems increases in increments of 2 to 4 mm. Each 3-mm increase in length can in- crease surface area by more than 20% for a cylinder implant design 69 (Fig. 1). Removal torque, pushout force val- ues, and Periotest values have been highly correlated with implant size. 70 –72 Most of the stresses to an implant bone interface are concen- trated at the crestal bone, so the in- creased implant length does little to decrease the stress that occurs at the transosteal region around the im- plant. 73 However, because the imme- diately restored implant loads the in- terface before the establishment of a cellular connection, implant length is more relevant, especially in softer bone types. The benefit of increased length may not be found at the crestal *Adjunct Professor, Department of Periodontics/Geriatrics, University of Michigan; private practice, Beverly Hills, MI. †Professor and Director of Graduate Periodontics, Department of Periodontics/Prevention, Geriatrics, University of Michigan. ‡Associate Professor, Department of Implant Dentistry, New York University; and in private practice, Sarasota, FL. §Professor and Chairman, Department of Biology/Anatomy, University of Georgia. Professor and Chairman, Department of Bioengineering, University of Alabama at Birmingham. ¶Clinical Professor, Department of Implant Dentistry, New York University; and in private practice, New York, NY. ISSN 1056-6163/04/01304-310 Implant Dentistry Volume 13 • Number 4 Copyright © 2004 by Lippincott Williams & Wilkins DOI: 10.1097/01.id.0000148556.73137.24 Immediate loading of an implant interface has been used for com- pletely and partially edentulous pa- tients. A biomechanical rationale to decrease the initial risk of overload is reasonable, because implant fail- ure and overload has been well es- tablished. This article addresses methods to decrease stress to the transitional restoration. Forces may be influenced by patient factors, im- plant position, cantilever forces, oc- clusal load direction, occlusal con tact intensity, and diet. The surface area of load distribution may be in- creased by implant size, implant de- sign, and surface condition of the implant body. A blend of these fac- tors affects the amount of stress to the developing implant interface and hence may affect the risk of immedi- ate occlusal loading for implant prostheses. (Implant Dent 2004;13: 310 –321) Key Words: endosteal implants, im- mediate load, occlusal loading 310 RATIONALE FOR THE APPLICATION OF IMMEDIATE LOAD