Managing bone deficiencies for implant surgery
< ?xml:namespace prefix = "mbp" />Chapter 19 illustrated three cases in which implants were placed in sites with adequate bone volume (i.e., height and width). This chapter discusses the surgical technique most widely recommended for sites where resorption of alveolar ridge after tooth extraction has been significant, leaving insufficient bone width for placement of a dental implant in an ideal prosthetically driven position. Often, there is simply insufficient bone width to even place an implant within the bony housing.
Rebuilding alveolar bone width is more predictable than vertical bone grafting. The focus of this chapter is limited to bone grafting in cases with inadequate bone width.
Generally, two different surgical approaches are indicated in cases with inadequate bone width: simultaneous or staged bone grafting (Table 20.1). As the name implies, simultaneous bone grafting is carried out at the same time the implant is placed, whereas in the staged approach, the ridge is grafted first in a separate surgical procedure. After a healing period of 4–6 months, the implant is placed in a second surgical procedure.
Table 20.1 Advantages and disadvantages of staged and simultaneous bone augmentation
||Staged (block graft)
||Simultaneous (particulate bone)
|No. of surgeries
||Two-stage procedure involving separate grafting and implant placement surgery
||Single procedure in which implant is placed and bone grafted
||Higher because two separate surgical sites, including risk to lower anterior teeth
|Scope of grafting
||Potentially greater than simultaneously using particulate bone
||Predictable in horizontal but unpredictable in vertical augmentation
||Significantly increases treatment time
||Much shorter treatment time
||More cost-effective for the patient
The former technique, also called simultaneous guided bone regeneration (GBR), is carried out using particulate bone, which is protected under a barrier membrane during healing. This is based on similar principles as guided tissue regeneration in periodontal defects, which was discussed in Chapter 12. The most predictable technique in implants involves use of autogenous bone chips collected during the surgical procedure combined with deproteinized bovine bone granules, which are then covered with a resorbable porcine-derived collagen membrane.
On the contrary, if the ridge defect is significant, a staged approach is necessary. This involves grafting with a block of bone of appropriate dimension to rebuild the surgical site. Autogenous bone is still considered to be a gold standard, and this can be harvested from either the mandibular ramus or the symphysial area. The former allows a limited size of bone block, whereas the latter can offer a larger size extending from lower right to left canine.
This chapter discusses two cases illustrating the previously mentioned techniques.
Surgical placement of an implant with simultaneous guided bone regeneration
A 20-year-old female presents with a failing resin-bonded bridge (RBB) replacing the UR1.
The patient is complaining of repeatedly debonding RBB.
History of complaint
The tooth had a previous history of trauma and reimplantation following avulsion, subsequently developed root resorption, and was extracted when the patient was 16 years old.
The patient has been a regular dental attendee and had had several years of endodontic treatment in UR1 before its extraction. The patient is now concerned about the long-term prognosis of UR1 and wishes to have a more predictable solution for the missing tooth. She has lost confidence due to repeated failure of the RBB.
The dentition is minimally restored, with a good level of oral hygiene.
UR1 is missing (Figure 20.1), and the adjacent UR2 and UL1 are unrestored. A class I incisal relationship is noted. She has a high smile line and a thin gingival biotype.
Fig 20.1 A missing UR1 that has been replaced with a resin-bonded cantilever bridge from UL1.
A detailed examination and assessment as discussed in Chapter 17 was carried out. Assessment of alveolar ridge confirmed lack of adequate ridge width (Figure 20.2); however, it was considered feasible to manage implant placement with simultaneous GBR. The patient consented to have this tooth replaced with a dental implant.
Fig 20.2 Alveolar ridge assessment shows lateral ridge resorption.
No abnormality is noted (Figure 20.3).
Fig 20.3 A periapical radiograph confirming satisfactory vertical bone level.
What important factors would you consider when placing implants with simultaneous GBR?
In order to achieve a successful functional and aesthetic result, several surgical factors must be considered:
1. Implant position
It is imperative that the position of the implant is not compromised due to lack of optimal bone volume. For a successful outcome, prosthetically driven ideal three-dimensional position should be the goal.
2. Primary stability
A good primary stability is necessary for this surgical approach.
3. Principles of GBR
Angiogenesis and space maintenance are two important prerequisites for successful GBR. Angiogenesis is promoted by carrying out corticotomy holes. These are holes drilled with a small bur perforating the cortical plate to encourage bleeding from the bone trabeculae. When using particulate bone under a resorbable and malleable membrane, overcontouring with bone graft is recommended to maintain adequate long-term bone volume.
4. Tension-free primary closure
A tension-free primary closure is of significance to ensure the flap remains completely closed during submerged healing. Dehiscence is the most common postoperative complication, which is primarily attributed to forced flap clos/>
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