DR : HAMED BAKRI

Ridge Augmentation Procedures

Principles in alveolar bone regeneration

Treatment objectives

Diagnosis and treatment planning

Biologic principles of guided bone regeneration

Regenerative materials

Evidence‐based results for ridge augmentation procedures

Emerging technologies

Conclusion

CHAPTER OUTLINE

Ridge Augmentation Procedures

• approximately 25% bone loss after the first year of the bone and 40–60% loss of alveolar volume during the first 3 years after a tooth is lost. The resulting ridge deficiency is primarily the result of the gradual loss of the horizontal dimension accompanied by a rapid loss of bone height (Carlsson et al. 1967).

• alveolar bone loss can be congenital, trauma, pathology, infection, or a consequence of periodontal disease and tooth extraction

Introduction:

Promoting primary wound closurepassive and tension‐free wound closure . To reduce the risk of membrane exposure, wound contraction, patient discomfort.

Factors Assist in proper wound healing

Enhancing cell proliferation and differentiationprovides blood, oxygen, and nutrients to the tissues also acts as a source of angiogenic and osteogenic cells

Protecting initial wound stability and integrity

The placement of bone grafting materials to favor healing in osseous defects or to augment edentulous ridges to allow dental implant installation become a gold standard treatment in implant dentistry

*

Principles in alveolar bone regeneration

Cell Exclusion used to prevent gingival fibroblasts and / or epithelial cells from gaining access to the wound site

Space is created beneath the membrane, completely isolating the defect to be regenerated from the overlying soft tissue.

Scaffolding : space initially becomes occupied by a fibrin clot, which serves as a scaffold for the bone cells.

protect the clot is important for the formation of granulation tissue and subsequent formation of bone (Schenk et al. 1994).

Treatment Objectives*

The rationale behind any crestal bone augmentation procedure is to establish sufficient bone availability for safe and predictable dental implant therapy , as well as for getting adequate bone thickness around the installed implant.

To achieve long‐term stability of peri‐implant health and good esthetics and avoid complications around functional implants by get at least 2 mm of bone on the buccal side

*Diagnosis and Treatment Planning

There are some relative contraindications that need to be taken into consideration:

medical conditions that may impair normal bone healing as diabetes mellitus

(Colombo et al. 2011; Schlegel et al. 2013). when compared between controls diabetic to healthy pt. in osseointegration was achieved in both groups(Retzepi et al. 2010). The uncontrolled diabetes showed an increased rate of infection complications and a less predictable outcome

Smoking has also been found to negatively affect the long‐term prognosis of Osseointegration Clinical studies have reported that in smokers• higher rates of implant failure• Great numbers of complications around successfully integrated implants (Roos‐Jansaker et al. 2006),• higher incidence of peri‐implant mucositis and periimplantitis (Heitz‐Mayfield 2008)

(Bain &Moy 1993). non‐smokers, the augmentation procedure was successful in 95% of the cases, whereas in smokers it was successful in only 63%

*Defect classification

•Class 1 defects: when the bone deficiency is predominantly in the horizontal dimension

•Class 2 defects: when the bone deficiency is predominantly in the vertical dimension

•Class 3 defects: when the bone deficiency affects both the vertical and horizontal dimensions.

According to Seibert (1983), alveolar crest defects

Hämmerle and Jung have classified crest defects in fresh extraction sockets:

•Class I: extraction socket that has intact bone walls after tooth extraction

•Class II: extraction socket that has a marginal dehiscence fenestration of the buccal bone wall after tooth extraction

•Class III: extraction socket that has a large dehiscence of the buccal bone wall after tooth extraction.

Defect classification

Bone Augmentation Therapies

Melcher (1976), who developed the concept of using barrier membranes to “guide” the biologic process of wound healing.

early experimental studies demonstrated that the exclusion of soft tissue invasion of the defect by means of a barrier membrane, allowed the cells with regenerative potential to migrate to the site (derived from the periodontal ligament or bone marrow) and promoted periodontal regeneration (Nyman et al. 1982).

Rege

nera

tive

mat

eria

ls Barrier membranes

Bone grafts and bone substitutes

Regenerative materials

Barrier membranes

Purpose:membrane is to prohibit the penetration of cells, primarily epithelial, through its structure .

There are five criteria which are considered to be important in the design of barrier membranes used for GBR1. biocompatibility, 2. cell occlusion properties, 3. integration by the host tissue, 4. Space making capacity.5. clinical manageability

Types of membranes :Barrier membranes have been derived to two principal varieties:1- Non resorbable As e-PTFEnon‐degradable barrier membranes require a secondsurgical intervention to remove them.

The choice of membrane material usually depends on the amount of bone regeneration needed, mainly in the vertical dimension. e‐PTFE barrier membranes have demonstrated more favorable results when compared with resorbable devices, mainly due to their better space‐making capacity, longer barrier function lack of a resorption process that may negatively affect bone formation

)Hämmerle & Jung 2003.(

Bone grafts and bone substitutes

Type

s of B

one

Gra

fts Autograft

Allograft

Xenograft

alloplast

Types of Bone Grafts

Autogenous• Max.

tuberosity• Ramus• chin

Intraoral

• rib• tibia• Iliac crestExrtaoral

AutogenousConsidered the “ gold standard ” by which other materials are Osteoinductive, osteoconductive, and osteogenic properties No risk of infection

Disadvantages

Low availability of bone volume Require a second operative site Morbidity associated with their harvesting, mainly from the chin particulate autografts, resorption rate is high

Allograft Allografts are bone grafts harvested from cadaver donors and processed by freezing or demineralization and freezing.

These allografts are usually used in combination with barrier membranes following the principles of GBR.

DisadvantagesPossible infections, and antigenicity risks

Xenograft

biomaterials of animal origin, mainly bovine and equine. These graft materials are deproteinized in order to completely remove the organic component and thus avoid any immunogenic reaction.

alloplast

Cancellous Bone Coralline hydroxyapatite

are synthetic bone substitutes that include different combinations of calcium phosphates fabricated under different conditions, which yields different physical properties and resorption rates

This choice should be based on the clinical indication . For small bone defects requiring mainly horizontal bone augmentation, the use of xenografts and

alloplasts has demonstrated excellent results.

use of xenografts with a much slower resorption rate demonstrated significantly better preservation of the socket walls than the non‐grafted sites.

In large crestal defects for which the aim is both horizontal and vertical bone augmentation, the use of autogenous block grafts is recommended.

Choice of material

Ridge Augmentation Procedures 1. ridge preservation, 2. bone regeneration in fresh extraction sockets, 3. horizontal bone augmentation, 4. ridge splitting/expansion, 5. vertical ridge augmentation

Ridge preservation

These ridge preservation approaches have utilized GBR principles using the following regenerative

•Resorbable and non‐ resorbable barrier membranes alone •Resorbable barrier membranes in combination with bone substitutes

•Bone substitutes alone •Bone substitutes in combination with soft tissue grafts technologies:

“Any therapeutic approach carried out immediately after tooth extraction aimed to preserve the alveolar socket architecture and to provide the maximum bone availability for implant placement” (Vignoletti et al. 2012).

hard and soft tissue changes occurring 6 months after tooth extraction in humans and demonstrated a horizontal bone loss 29–63%

vertical bone loss 11–22% )Tan et al. 2012.(

immediate and early implant placement (type 1 and 2) protocols have been indicated as the most suitable for implant placement following tooth extraction.

Bone regeneration in fresh extraction sockets

Horizontal ridge augmentation

Horizontal ridge augmentation can be performed using particulate or block grafts with or without barrier membranes

Ridge splitting/expansion

Another technique used in the maxilla to augment bone width through bone condensation is ridge splitting or ridge expansion osteotomy.

Ridge splitting and/or expansion are frequently described together because of their common treatment outcome: increase in lateral bone width. Ridge splitting is essentially the fracture of the buccal cortical plate and its displacement laterally to accommodate implant placement.

Vertical ridge augmentation

augmentation techniques:)1 (GBR

)2 (onlay bone‐block grafting )3 (distraction osteogenesis

)Class 3 defect (Seibert). Implant placement and vertical GBR with an ePTFE membrane and autologous bone. (d) Re‐entry 1Y. (Courtesy .)

Emerging technologies

1 -growth factorsto increase bone volume have significantly advancedthe field of periodontal regenerative medicine. like PDGF and BMPs

2-Cell therapyCell delivery approaches are used to accelerate edentulous ridge regeneration through two primary mechanisms:(1)use of cells as carriers to deliver growth or cellular signals(2)provision of cells which are able to differentiate into multiple cell types to promote regeneration

4-Computer‐based applications in scaffold design and fabrication

3-Scaffolding matrices to deliver cells and genesScaffolding matrices are used in tissue engineering to provide an environment where space is created and maintained over a period of time for cellular growth and tissue in‐growth.

In general, ridge augmentation procedures have become increasingly predictable .The correct selection and application of the available techniques and biomaterials are key

determinants of implant survival/success rates .Currently, research in the field of advanced bone grafting is directed at overcoming the technical and biologic limitations that continue to challenge implant dentistry.

Conclusion