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Ridge Preservation

Preventing alveolar bone resorption: Possibilities and limitations

Osseointegration is no longer the only criteria for implant success. Sufficient peri-implant bone volume also plays a decisive role in maintaining long-term stability and esthetics. Thus, prevention of alveolar bone resorption has become a lively topic.

Spontaneous socket healing vs. immediate implant placement 

Alveolar ridge dimensional changes following spontaneous socket healing have been investigated in a series of clinical studies. In the first year following tooth extraction, alveolar ridge resorption results in 2.6-4.5 mm loss of width (about 50%) and 0.4-3.9 mm loss of height.1

The protocol for placing implants immediately in fresh sockets was introduced in 1978.2 Several studies have demonstrated that the timing of implant placement does not infl uence socket remodeling. Similar alveolar width reduction (up to 56%) was reported following immediate implant placement (IIP).3,4 In these studies, all implants were placed in the center of the socket without any bone grafting procedures. In other words, IIP alone does not interfere with sequential socket healing but also does not prevent ridge resorption.

Alveolar ridge preservation vs. immediate implant placement with gap grafting 

Alveolar ridge preservation (ARP) is one of the best documented technologies for preventing alveolar bone resorption and compensating for socket remodeling.5 A recent meta-analysis reported that ARP, as compared to spontaneous socket healing, can prevent 1.99 mm horizontal, 1.72 mm vertical mid-buccal, and 1.16 mm vertical mid-lingual bone resorption.6 Another study has demonstrated that ARP can prevent about 15-25% horizontal bone resorption compared with spontaneous socket healing and allows implant placement into the prosthetically driven position without further bone augmentation procedures in 90.1% of the ARP sites but only 79.2% of the control sites.7

We have already demonstrated that IIP alone can’t prevent resorption of the alveolar ridge; however, results can be totally diff erent when guided bone regeneration (GBR) procedures are used.
A previous prospective study reported that Geistlich Bio-Oss® can significantly reduce horizontal resorption of buccal bone following IIP (Geistlich Bio-Oss® group: 15.8±16.9% resorption, Geistlich Bio-Oss® + Geistlich Bio-Gide® group: 20.0±16.9% resorption, control group: 48.3±9.5% resorption).4 A recent review also concluded that the original shape of the ridge can be maintained by placing implants palatally and filling gaps with grafting materials.8 In our center IIP is a routine treatment option for replacement of single teeth in the anterior region with limited buccal bone dehiscences (less than 20%). The resorption rate of buccal bone ranges from 18% to 25%, and advanced recession of mid-facial mucosal is rare (<5%).

A case for flapless immediate implant placement: stable mid-facial mucosal level, buccal bone plate resorption 21%.

| A-C Before surgery. | D-F Immediately after surgery and At crown delivery. | G-I 1-year examination.

The resorption rate of buccal bone (15-20%) following IIP combined with GBR is similar to ARP. Theoretically, healing processes of ARP and IIP combined with GBR are similar, since the implant itself will not interfere with socket remodeling. So it makes sense that IIP combined with GBR procedures can achieve similar outcomes preventing alveolar bone resorption, as long as implants are placed in an optimal 3D position, which is a challenging surgical procedure. It will be interesting to examine in experimental animal models whether sockets with ARP and IIP combined with GBR show any diff erences in sequential healing.

Limitations for immediate implant placement

It must be noted that, compared with early implant placement, several studies have concluded that IIP increases esthetic risk.9,10 Although some clinicians advocate a fl apless procedure, palatally-positioned implants, narrow-diameter implants, gap filling with grafting materials, augmentation of soft tissue at implant surgery and socket shield procedures when implants are placed in fresh sockets,11 excellent esthetic outcomes can only be achieved in strictly-selected cases.12 Another important concern is the slightly higher early implant failure for IIP compared with delayed implant placement (5.1% vs. 1.1%),13 especially when prophylactic antibiotics are not used.
In conclusion, compared with spontaneous socket healing, both alveolar ridge preservation and immediate implant placement combined with guided bone regeneration procedures can reduce alveolar ridge resorption rates (15-25%). However, strict indications and a potentially higher early failure rate must be taken into consideration before making clinical decisions.

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