Dental implants have been in service for almost 3 decades now. Offering many obvious advantages in terms of chewing efficiency and esthetics over their counterparts, namely dentures and fixed bridges, they have been the workhorse for replacing missing teeth in patients for dental professionals across the globe now.
The global dental implants market was estimated to be $3.74 billion in 2021 and is expected to reach $5.71 billion in 2028 at a CAGR of 6.2% in forecast period, 2021-2028.(1)
However there are multiple scenarios where straightforward routine dental implant placement is precluded by patient conditions like less than ideal bone conditions, proximity to anatomical landmarks, etc. This is where adjuvant procedures for implants come in in ensuring long term success of the treatment and patient satisfaction.
Based on clinical experience, the minimum dimensions in the maxilla to insert a dental implant are an alveolar ridge width of 5 mm and a bone height of 10 mm. Any deficit in these dimensions predisposes the risk of placement in anatomically unfavorable positions and thus leading to implant failure. Therefore, various surgical techniques have been employed to augment the bone volume. Ridge augmentation techniques include the use of bone grafts, guided bone regeneration with bio-resorbable or non-resorbable membrane, alveolar distraction osteogenesis and ridge splitting.
In this article we will overview the 2 most commonly used procedures:-
- Guided bone regeneration
- Chin graft
Guided bone regeneration (GBR):
GBR’s main use belongs in periodontology for gingival grafts and wall defects of tooth socket. It is extended in implants to cover up for the lost gingival wall, most commonly being the labial wall.
Bone width being inadequate, GBR addresses to increase it by adding a bone graft material directly over the host bone, then covering it with a barrier membrane. This is done to prevent soft tissue ingrowth over the bone graft added over the site.
Before the bone graft is added, small bur holes are made over the host bone to make it bleed and rough, to increase surface area and increase wound healing speed, called as “Regional acceleretory phenomenon”.
The important determinants of the success of the procedure is
- absence of mobility of the barrier membrane
- good closure with a hermetic seal
- infection control
1. Recipient site usually is the anterior maxilla in which labial plate shows deficient width with implant exposure. (Figure 1)
Figure 1: Recipient site showing exposure of implant threads due to inadequate bone thickness
2. A 8 no round diamond bur or 703 carbide bur is used to make small punches in the host wall proportional to the area to be grafted.
It is important to observe bleeding at this stage: LESS OR ABSENCE OF BLEEDING points to necrotic bone (osteomyelitis, long term bisphosphonate therapy) and can indicate poor prognosis or failure.
3. Once the host bone is prepared, demineralized freeze dried-bone (DFDB) or particulate bone matter is applied over the area to achieve desired thickness (Figure 2).
Figure 2: DFDB applied over exposed implant surfaces
It is at this stage that overpacking is done to counter graft shrinkage (2) when using cancellous type of particulate bone. Another study says overpacking is needed only for particulate bone and not the cortical bone (3)
Important Tip>>> After incision, proper underming and exposure of the soft tissue to desired vestibular depth is done to ensure adequate movement of the soft tissue. This is important to accommodate the additional dimension of the graft later.
4. To make the bone graft homogenous and easier to handle, various substances are used like PRF membrane and or direct use of commercially available calcium phosphosilicate (CPS) (Novabone) particles in a bimodal size distribution combined with a polyethylene glycol and glycerine binder.
5. Once this is done, a collagen membrane is placed over the graft and carried to the depth of the gingival flap.
It is secured to the depth with horizontal mattress suture taking the bite from the depth of the soft tissue, passing it through the membrane, bringing back to the coronal side and closing (Figure 3) before final closure with non-resorbable suture (prolene 3-0).(Figure 4)
Figure 3 :Horizontal mattress suture over the collagen sheet
Figure 4: Soft tissue closure with Prolene 3-0
2. Chin graft
Chin graft is one of the most trusted amongst block grafts. It offers various advantages over ramal and other sites such as:
- Easy accessibility
- It is harvested under direct vision unlike ramal graft, which is a somewhat blind procedure in terms that the lingual nerve cannot be seen at that time. So chances of nerve paraethesia can be lessoned with confidence as mental foramen can be intentionally retracted away from the surgical site.
Rule of 5: (Figure 5) (4)
Figure 5: Rule of 5:- Minimum Distance to be kept from mental foramen, midsymphysis on each medial side of the blocks. Root of mandibular canine tooth above and from the inferior border of mandible below is 5mm.
Initially bur holes are prepared with carbide round bur no 8 on the marking of the desired block graft borders.
1. A typical recipient site shows deficient labial plate with inadequate width.(Figure 6).
Figure 6:Recipient Upper anterior region with deficient labial plate
2. Block scoring is done with a bone measuring caliper as shown in Figure 7
Figure 7: Scoring of the grafts with bone caliper
3. Then with piezosurgery unit or chisel and mallet, the holes are connected WITHOUT breaching the lingual cortical plate. Just with the minimal amount of thickness required, the blocks are teased out with the chisel. (Figure 8)
Figure 8: Harvesting chin block from right side mandible
4. The donor site is checked for haemorrage and if any, is packed with Gelfoam or similar local hemostatic agent.
5. The grafts are then stored in saline bowl, and should be placed over the recipient site as early as possible to avoid graft necrosis and improve successful uptake.
Important Tip>>> A gutta percha point may be placed at the superior osteotomy site of the block graft to access the comparative position of the cut and the teeth roots to avoid paraesthesia.(Figure 9)
Figure 9: Placing a gutta percha over the mark and comparing the root levels over RVG to avoid injury to the teeth
6. Grafts are secured in place with 2mmx 6/8mm titanium screws.(Figure 10)
Figure 10:-Grafts are secured with titanium screws to the recipient site
Figure 11: – Result after 6 months of Grafting. (Screws removed)
A thickness of 5mm was obtained in this case after grafting, approximately 3 mm was lost due to the initial graft resorption.
Various techniques and materials for ridge augmentation are available, but it is most appropriate to use an evidence- based approach for treatment planning. Adjuvant surgical modalities like GBR membrane and autogenous chin graft are beneficial for the treatment of localized anterior alveolar ridge defects.(6)
- The global dental implants market is $3.74 billion in 2021 and is expected to reach $5.71 billion in 2028 at a CAGR of 6.2% in forecast period, 2021-2028. Read More at:-https://www.fortunebusinessinsights.com/industry-reports/dental-implants-market-100443
- Alterations in Bone Quality After Socket Preservation with Grafting Materials: A Systematic Review
- Hsun-Liang Chan, DDS, MS/Guo-Hao Lin, DDS/Jia-Hui Fu, BDS, MS/Hom-Lay Wang, DDS, MSD, PhD
- Comparison of allogeneic and autogenous bone grafts for augmentation of alveolar ridge defects—A 12‐month retrospective radiographic evaluation
- Mandibular block grafts:Carl Misch
- Deepa D et al. Autogenous chin graft and guided bone regeneration (GBR) in localized ridge augmentation. International Journal of Periodontology and Implantology, July-September 2017;2(3):91-94 91