Split Crest
What it is
Split crest (ridge expansion) is a surgical technique that divides the thin alveolar bone ridge longitudinally to increase its thickness, creating a controlled fracture between the two cortices like an opening book. The space is filled with a bone graft or with the implant itself.
Split crest (or ridge expansion) is a reconstructive surgical procedure of the alveolar bone ridge. It consists of making a longitudinal cut (osteotomy) on the ridge, followed by a controlled fracture that separates the two cortices (vestibular and palatal/lingual) like an opening book.
The space thus created is filled with graft material (autologous bone, heterologous or bone substitute) or with the implant itself. The technique uses the flexibility of the bone (in particular of the vestibular cortex) to increase the transverse diameter of the ridge.
Indications
Split crest is indicated for thin alveolar ridges with bone thickness between 3 and 5 mm, knife-edge ridges, replacement of single elements in aesthetic areas and rehabilitation of short edentulous spans of 2-4 elements, where the bone width is insufficient for traditional cylindrical implants.
- Thin alveolar ridge: bone thickness between 3 and 5 mm, insufficient for traditional cylindrical implants (which require at least 5-6 mm)
- Knife-edge ridge: residual bone morphology with minimum thickness in the crestal portion
- Single element: replacement of a single tooth in an aesthetic area with thin bone
- Multiple elements: rehabilitation of short edentulous spans (2-4 elements) with a narrow ridge
Procedure
The procedure involves incision and flap elevation, sagittal osteotomy at the centre of the ridge with a drill or piezoelectric scalpel, controlled fracture with progressively increasing osteotomes, implant placement that keeps the space open, possible filling of the gap with a graft and suturing, with loading postponed to 4-6 months.
- Incision and flap elevation: exposure of the bone ridge
- Sagittal osteotomy: longitudinal cut with a drill or piezoelectric scalpel at the centre of the ridge, along the whole length of the span to be expanded
- Controlled fracture: use of progressively increasing osteotomes to separate and spread the two cortices, creating the necessary space
- Implant placement: preparation of the implant site and placement of the implant, which keeps the space between the cortices open
- Filling: if necessary, filling of the gap with graft material
- Suturing: closure of the flap without tension
Loading is generally postponed to 4-6 months to allow bone healing and osseointegration.
Comparison with blade implants
Split crest is a reconstructive approach that increases bone thickness but requires 4-6 months before loading, while blade implants adapt to the existing thickness with possible immediate loading. Split crest has greater morbidity and often requires grafting, unlike blade implants that fully use the basal bone.
Split crest and blade implants are two different approaches to the same problem: the thin bone ridge. They differ in philosophy and indications:
| Characteristic | Split crest | Blade implant |
|---|---|---|
| Approach | Reconstructive (increases the thickness) | Adaptive (uses the existing thickness) |
| Immediate loading | Generally no | Yes, if primary stability is sufficient |
| Morbidity | Greater (flap + osteotomy) | Minimal (flapless possible) |
| Graft | Often necessary | Not necessary |
| Times | 4-6 months before loading | Immediate loading possible |
| Basal bone | Partially used | Fully used |
Limits
The limits of split crest include the risk of fracture of the already thin vestibular cortex during spreading, possible necrosis due to excessive flap elevation, inadequacy for very thin ridges below 3 mm or long edentulous spans, and the need for grafting for gaps above 2-3 mm which increases costs and times.
- Fracture risk: the vestibular cortex, already thin, can fracture during spreading, compromising the result
- Failed vascularisation: if the flap is excessively elevated, the vestibular cortex can undergo necrosis
- Not suitable for large extensions: for very thin ridges (<3 mm) or long edentulous spans, the failure risk increases
- Need for grafting: for gaps above 2-3 mm, the space must be filled with graft material, increasing costs and times
In the Bilateral Sinus Solution™ (BSS), split crest is generally not necessary because the implants are placed in the basal bone, completely bypassing the thin alveolar ridge. For more information, visit the page on blade implants.
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