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Divisions of available bone:PRESENTED BY:DR.GLAREH EBLAGHIAN SUPERVISED BY: DR. MANSOUR RISMANCHIAN AND DR.SAIED NOSOUHIAN DENTAL OF IMPLANTOLOGY DENTAL IMPLANTS RESEARCH CENTERISFAHAN UNIVERSITY OF MEDIACAL SCIENCE 

Divisions of available bone:

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DIVIOSION A: Aboundant bone that forms soon after extraction or

a few years after extraction

For group A implant of 12mm or more can be successful without compromise (very long implant is not necessary because of stress to the implant-bone interface

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Implant diametter is at least 4mm at the crest moduleIn the bone width greater than 7mm(A+): 5mm implant may be insertedOsteoplasty may be performedDivision A should not be treated with smaller diametter implant

A patient with division A bone should be notified that this is the ideal time to restore their edentulous condision by implant

Division A:decrease in treatment cost, increase in

benefits

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DIVISION A IMPLANTS ADVANTAGES:

The larger the diameter, the greater surface area and the less stress distributed through the crestal bone region

The larger implant is closer to the lateral cortical plate that increase strengh

The larger diameter implant is less likely to fracture because the strength of the material is increased four times by diameter

The smaller diameter implant are often one piece and require an immediate restoration. So likely loading and micro movement may be occure with the crestal bone loss

The larger diameter teeth can be more esthetically restored with the wider diameter implant

The large implant diameter, the less stress applied to the abutment screw, and screw loosening and fracture are less

The larger diameter make greater cement retention for final restoration

Oral hygiene are more compromised around smaller diameter implant with overcontour restoration

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DIVISION A IMPLANTS ADVANTAGES:

The crestal module of many two piece small diameter implants are smooth metal thus creating shear loads to the crestal bone

Division A root form implants are designed for variable bone density and can provide the greatest range of prosthetic options

Implant cost to patient is related to implant number not diameter

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PROSTHETIC OPTIONS:

FP1 prosthesis requieres division A FP2 prosthesis requiers division A → is most common

posterior restoration in partially edentulous patients FP3 is the option selected in anterior division A bone when

smiling lip line is high for maxilla or low for mandible

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REMOVABLE IMPLANT OVERDENTURE:• The final position of the tooth and suprastructure bar

must be evaluated before surgery• Final RP4 or RP5 may require osteoplasty• division A may have contraindicated for high profile

O-ring attachment or suprastructures placed several mm above tissue

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GROUP B: BARELY SUFFICIENT BONE: As the bone resorbes the wide of available bone decreases at

the expense of the facial cortical plate 25% decrease in bone width at the first yeare and 40%

decrease within 1 to 3 yeares after tooth extraction After these , bone volume may remain for more than 15 yeares

in anterior mandible The posterior maxilla have less available bone height because

of sinus expansion

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THREE TREATMENT OPTIONS:

1) Modify the existing division b to another by osteoplasty to permit placement of root form 4mm implant in width if more than 12mm bone height is available →convert to division A if less than 12mm bone height is available → convert to division C-h

2) Insert narrow division B rootform implant

3) Modify B by augmentation

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To select the proper approach the final prosthesis must first be considerWhen division B changed to A by osteoplasty the final prosthesis has to compensate d for increased CHS

If the ridge is deficientin width for implant , it is not unusual to remove 3mm of crestal bone but it tends to extended tooth(FP2 or FP3)Osteoplasty is less likely treatment of choice for FP1 prosthesis with a B-W ridge because greater bone reduction is requiredThe most common approach is to modify division B to A by osteoplasty when final restoration is implant overdentureIf the ridge height is reduced so that CHS is greater than 15 mm , the bone division changed to C-h( when cantilever or lateral forces are present , is not predictable for endosteal implant placement)RP4 & RP5 most often requires osteoplasty to make adequate CHS

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•The second main treatment option for narrow bone in division B is small diameter root form implant (3 to 3.5mm)

•The implant body must bisect the bone and implant angulation is less flexible•This option is used for single tooth replacement of maxillary lateral incisor and mandibular incisors when mesiodistal width is restricted

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Thirdaltration: grafting the edentulous ridge with outogenous or combination of allograft and alloplast to change division B to A

A healing period of at least 4 to 6 month is neededFP1 restoration most often mandates option

Stress factors may also dictate the surgical approach : in presence of unfavorable stress, the number and width of abutment should be increased without increasing the CHS

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Success of augmentation is correlates with:I. Number of osseous wall in contact with

the graft material(5 wall bony defect as a tooth socket is more predictable than one- wall defects as an onlay graft)

II. Bone augmentation is more predictable when is minimal and for width( 1 to 2mm increase in width may be obtained with an alloplast and GBR , more than 2mm needs autologous block graft)

III.Some regions are better suited(e.g floor of the maxilla ry sinuses)

IV.An alteration for the augmentation ≈ bone speading

( a narrow osteoplasty →bone spreader are tapped in to edentulous site)

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If division B-W ridge contour should be altered an onlay particulate or block graft of outogenous bone is indicated( from symphisis or ramus)The implant placement should be delayed for 4-6 month

The patient delayed treatment with division B bone should be notified if the future bone resorption and so augmentation in height is much less predictable the final prosthesis is dependent on the surgical options:Fixed prosthesis for grafted ridge removable prosthesis for osteoplasty

The treatment option may be influenced by the region:For anterior maxilla→augmentationFor anterior mandible →osteoplastyFor premolar region→division B rootform implants

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DIVISION C (COMPROMISED BONE): Division C is deficient in one or more dimention ( width, length

or angulation) Resorbtion pattern occures first in width and then in height B→ continuse to resorbe in width but height is still present→C-W →available

bone is the reduced in height →C-H posterior region of ridges result with division C-H more rapidly than anterior

region because of maxillary sinus and mandibular canal when anterior mandible is C-H the floor of the mouth is level with the crest

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The fast of resorbtion: C –W to C-H ≈ A to B ≥ B to C-w without implant or bone graft C-h will evolve in to D the division C does not offer as many elements for predictable endosteal implant survival: anatomical landmarks to determine implant angulation or position in relation to incisal edge are not present so more skill in surgary is needed

Division C ridge implant supported prosthesis is more complex and have more complication in healing, design, and long term maintenance

Altered treatment plans that decrease stress can provide predictable long term treatment

Subdivision C-a : adequate bone in height and width but angulated is greater than 30 degree C-a is more in anterior mandible , maxilla with sever facial undercut and second molar with a sever lingual undercut

Root form implant in this category may be positioned within the floor of the mouth

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THERE ARE 7 IMPLANT TREATMENT OPTION:

C-W may be treated by osteoplasty and convert to C –h

the most common available bone alter osteoplasty of C-w is C-h not A because CHS is more than 15mm

The C-w osteoplasty may convert the ridge to division D especially in the posterior mandible or maxilla

Alter division C by grafting for fix prosthesis→autogenous graft prior to to implant

palcement to acquire proper lip support and ideal CHS

the C-h posterior maxilla is a common and unique: because of the initial ridge width dimention a decrease of 60% in dimension still is sdequate for 4mm implant

the maxillary sinus expands after tooth loss

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Sinus graft : elevated the maxillary sinus floor membran and graft the previus sinus floor is most predictable region to augment in exess to 10mm in vertical

Various implant approach in division C-h:1. Shorter implant are the most common(4mm or more in in width

and 10mm or less in height)

several studies indicated implant survival is decrease for implantby 10 mm or less

2. When greater crown height is occure additional impalnt should be placed to increase overal impalnt bone surface

in removable prosthesis should iften reduse cantilever lenght

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Alternative designe in posterior mandible division C-h are subperioseal and disk like design implant especially in mandibular arch the limitation of antomy for root form implants may be :Bone angulation: premucosal posts may be designed with greater latitute than endosteal implantsSquare arches for anterior root form implantsmay have distally cantilever because of poor anteroposterior distance

a fix or RP_4 overdenture prosthesis is contraindicated with anterior root form in square arch form a subperiosteal may provide anteroposterior bone support and RP-4 prosthesis

Surgical risk of nerve repositioning and parasthesia

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Disk designe implant in posterior mandible or premaxilla : engages lateral aspect of cortical bone and may be used in height of 3mm eliminate of cantilever in full arch restoration

prosthetic option for divisionC : removable prosthesis in maxillary arch support the uper lip without hygine compromised in the mandible : soft tissue support for restoration

fix prosthesis in division c with greater than 15mm CHS is hybrid divice

In general: additional impalnts or tooth, cross arch stabilization, soft tissue support, opposing removable prosthesis often need to be considered

an alternative method for maxilla: changing the division with nonresorbable hydroxy apaite

augmentation is only a delayed tactic for bone resorbtion and it doesent stimulate or maintained bone mass

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