IN THE NAME OF GOD m.akouchekian

Implant body size: A biomechanical and esthetic rationale Presented by:Dr.m.akouchakian Supervised by: Dr. Mansour Rismanchian And Dr.saied Nosouhian Dental of implantology Dental implants research center Isfahan university of mediacal science   m.akouchekian

Implant body size: A biomechanical and esthetic rationale m.akouchekian

Introduction The initial treatment plan for implan dentistry: include the ideal implant size(based primarily on biomechanic and esthetic considerationse) primarily:existing bone volume in height, width and length determined The size of implant m.akouchekian

Ideal treatment plan sequence The prothesis first is planned The patient force factors are considered to evaluated the magnitude and type of force The bone density is evaluated in the regions of the potential implant sites The key implant positions and the implant number are selected The next consideration is the implant size m.akouchekian

Biomechanical load management based on: The character of the applied forces The functional surface area over which the load is dissipated The implant size directly affects the functional surface area m.akouchekian

Character of forces applied to implant Stress and strain Although several conditions may cause crestal bone loss, one of these may be prosthetic overload. Excessive loads on an osteointegrated implant may result in mobility of the supporting device, even after a favorable bone-implant interface has been obtained. m.akouchekian

Character of forces applied to implant Stress and strain Excessive loads on the implant result in increased strain in the bone Microstrains on the bone may affect the bone remodeling rate ,which result in bone loss The amount of bone strain is directly related to the amount of stress applied to the implant-bone interface m.akouchekian

Five distinct forces factors Type Magnitude Duration Direction Magnification m.akouchekian

Force magnitude The magnitude of bite force varies as a function of anatomical region and state of dentition(10 to 350 Ib) The magnitude of force is greater in molar region, less in canine area and least in incisor region The average bite forces increase with parafunction (approach 1000 Ib) m.akouchekian

Force duration Under ideal condition, the teeth come together during swallowing and eating ( less than 30 minutes) In parafunctional habits, teeth may be in contacts in several hours each day Increase in force duration directly increases the risk of fatigue damage to cortical bone (e.g, shin splints in runners) m.akouchekian

Force duration Although fatigue damage to alveolar bone has not yet been reported in the literature. Roberts et al. Report: the bone around an implant may be remodeled at a rate of 500% each year after loading, compared with normal trabecular physiologic remodeling around a tooth of 20% to 40% per year The dramatic increase in remodeling rates may eventually lead to fatigue damage and resultant bone IOSS. m.akouchekian

Force type Three type of forces may be imposed on dental implants: compression tension shear m.akouchekian

Force type Bone is strongest when loaded in compression, 30% weaker when subjected to tensile and 65% weaker when loaded in shear m.akouchekian

Force type An attempt should be made to limit shear forces on bone Increased width of implant: decrease offset loads and Increase the amount of the implant-bone interface m.akouchekian

Force direction The forces to an implant body are typically greatest at the crestal bone interface Angled loads to the implant produce angled loads to the crest module of the implant the direction of the load has a significant effect on the magnitude of compressive and lateral load components. m.akouchekian

Force direction By increasing the angle of the load by only 6 degrees , the lateral load is increased by 233% m.akouchekian

Force direction Angled loads increase the amount of shear loads to the bone The implant should be inserted perpendicular to the curve of wilson and spee The anatomy of the mandible and maxilla places significant constraints Bone undercuts further constrain implant placement and thus load direction imposed on the implant The premaxilla is 12 to 15 degrees off the long axis of load To decrease the effect of angled load on the implant , the implant may be increased in diameter m.akouchekian

Force magnification Cantilevered prosthesis Crown height greater than normal Parafunction Force magnification increases the stress m.akouchekian

Force magnification D4 bone may be more than 10 times weaker than D1, and 70% weaker than D2 bone Implant failure rates are 35% in D4 bone The most important factor to decrease stress: increase in implant number=> increases the effective surface area=> decreases stress increase implant size m.akouchekian

Surface area Stress = Force / Surface area To decrease stress: the force must decrease surface area must increase Increase in implant size is beneficial to decrease stress m.akouchekian

Rationale for longer implant length The length of the implant is directly related to the overall implant surface area A 10 mm cylinder implant: increases surface area 30%> 7 mm implant 20%< 13 mm long implant m.akouchekian

Rationale for longer implant length A common axiom has been to place an implant as long as possible The length of implant corresponds to the height of available bone The available in the anterior mandible: bone height is greater Bite forces are lower bone density is greater The posterior have less bone height and the implant cannot engage the dense opposing cortical plate ThePosterior maxilla associated with the highest failure rate because less height and less dense m.akouchekian

Rationale for longer implant length Implants longer than 15 mm provide greater stability under lateral loading Increasing the length beyond a certain dimension may not reduce force transfer proportionately. m.akouchekian

Rationale for longer implant length The length of the implant in favorable bone quality and crown height may range from 10 to 15 mm,and 12 is usually ideal length of 12 mm:usually ideal under most patient force and bone density conditions 15 mm :suggested in softer bone types m.akouchekian

Rationale for longer implant length All implant lengths exhibited 80% to 100% of the stress in the crestal 40% of the implant length m.akouchekian

Disadvantages of longer implants Overheating because preparation a longer osteotomy(D1,D2) Threaded implant may not readily engage the denser bone of the apical cortical plate(D3,D4) Implant threads may strip along the rest of osteotomy especially in D3 or D4 bone Excessively long implants do not transfer stress to the apical region (most of the stresses are transmitted within the crestal 7 to 9 mm of bone ) Advanced surgical procedures may be needed (nerve repositioning and sinus graft) The apical end of implant will not benefit from the sinus bone graft m.akouchekian

Rationale for shorter implant length The posterior region of jaws usually have the least height of existing bone and have higher bite forces Under some clinical conditions, stress transfer patterns may be similar between a short and a longer implant m.akouchekian

Advantages of short implants Less bone grafting in height Less time for treatment Less cost for treatment Less discomfort Less surgical risk of : Sinus perforation Paresthesia Osteotomy trauma from heat Damage to adjacent tooth root Surgical ease: decreased inter arch spaces Less inventory/ cost m.akouchekian

Disadvantage of short implants In the majority of articles, implants 10 mm or smaller have increased failure rates Implants shorter than 10 mm had a survival rate of 81.5% whereas longer implants had higher than 95% m.akouchekian

Disadvantage of short implants The failures associated with short implants, often occurred after prosthetic loading (especially within the first 12 to 18 months) the surgical success was not affected by implant length m.akouchekian

Why the posterior short implants have higher failure rate Higher bite forces Low bone density in the region Increased crown height Implant design considerations m.akouchekian

IDEAL IMPLANT SIZE The softer the bone: the greater the implant body length and diameter suggested m.akouchekian

m.akouchekian

Implant diameter Over several decades, implants have gradually increased in wide(scialom were less than 2 mm wide) Branemark first introduced an implant body diameter of 3.75 mm The larger diameter implants were primarily used to improve emergence profile The wide diameter implant presents surgical, loading and prosthetic advantages m.akouchekian

Surgical advantages Surgical rescue implant Failed implant /immediate Tooth extraction/immediate m.akouchekian

Loading advantages Because occlusal stress to the implant interfere at concentrated at the crest of ridge , width appears more important than height Increased surface area Compensate unfavorable patient force factors In cantilevers , reduce the risk of overload Compensate for poor bone density Enhance surface for short implants m.akouchekian

Prosthetic advantages Improve emergence profile Decrease screw loosening Minimize component fracture Facilitate oral hygiene(decrease interproximal space) m.akouchekian

Disadvantages of wide diameter implants Bone trauma- drill sequence Decreased facial bone thickness may lead to recession (Because closer than 1.5mm to the adjacent teeth or facial or palatal bone ) Increased surgical failure rate May too close to adjacent tooth, PDL encroachment Stress shielding: the implant is so wide that strain may be too low to maintain bone m.akouchekian

In anterior:implant should not be wider than 5 mm in the posterior:implant should not be greater than 6 mm(when adequate mesiodistal space is present and force magnitude is also observed) When larger diameter implants can not be used in the molar region , two 4 mm implants for each molar should be considered m.akouchekian

Natural teeth PDL complex is a very effective organ that distributes occlusal loads along the entire root surface The smallest diameter roots are in the mandibular anterior region The canines have a greater surface area than premolars, because they receive a lateral loads more than premolars m.akouchekian

Natural teeth The maxillary molars have more roots than mandibular molars (because the maxillary posterior region has the least bone density) m.akouchekian

Natural teeth indicator for width implant m.akouchekian The natural tooth roots indicator for width implant m.akouchekian

Anterior tooth replacement The diameter of natural teeth in 2 mm below the CEJ. the implant body should not be as wide as the natural tooth or clinical crown it replaces =>The emergence contour and interdental papilla can not be established properly Implant should be at least 1.5mm from the adjacent teeth When in doubt, smaller size diameter implant should be selected m.akouchekian

Multiple anterior implants When implants are adjacent to each other, a minimum distance of 3mm is suggested The size dimension of two adjacent anterior implants should most often be reduced compared with single implant m.akouchekian

Implant size selection criteria in posterior maxilla The implant dimension should correspond to the natural tooth(2mm below the CEJ) The implant should be at least 1.5 mm from the adjacent teeth The implant should be at least 3 mm from adjacent implant The implant should be at least 4 mm in diameter m.akouchekian

The molars:5- or 6-mm diameter the mandibular incisors and the maxillary lateral incisor: 3- to 3.5-mm diameter the maxillary anteriors, premolars in both arches,and canine:4-mm diameter implants The molars:5- or 6-mm diameter The implant dimension in question is the size of the crest module, not the implant body dimension m.akouchekian

The number of implants should be increased : When the diameters of molar implants do not provide sufficient surface area Very soft bone types Unfavorable force factors (i.e, parafunction) Multiple adjacent posterior teeth are missing m.akouchekian

For You’r Attention m.akouchekian