Scalp-Split Technique: A Concept of Bone Splitting and Expansion for Thin Alveolar Ridges to Place Dental Implants

Introduction

Implant-retained or implant-supported prostheses have become the most popular and ideal treatment modality for rehabilitating edentulous arches. The quality and quantity of the available alveolar bone play significant roles in the success of implant osseointegration. However, the favorable implant positioning and prosthetic outcomes may be considerably affected by buccolingual deficiency in edentulous alveolar ridges due to atrophic bone resorption, trauma, or bone pathologies.¹ Various augmentation methods are available to gain enough bone volume to overcome the lack of bone quantity in atrophic alveolar ridges. The main techniques, including guided bone regeneration, ridge splitting, distraction osteogenesis, and autogenous block bone grafting, have successful outcomes in reconstructing bone thickness.²

The selection of appropriate bone-expansion techniques is based on individual assessment of bone quality, including bone density and bone flexibility. When the alveolar ridge is slim bucco-lingually, preparing an osteotomy seems impossible with twist drills. In addition, bone harvesting from another site is also only feasible sometimes. In such instances, dealing with the amount of bone available in the desired implant site/s must be the ultimate challenge implantologists face in day-to-day practice. The remaining possible solution is to place the implants in such places as doing bone expansion before making the osteotomy.

Ridge augmentation with an autogenous bone graft combined with a guided tissue membrane has shown successful results over significantly atrophic ridges.³ However, to gain predictable results along the horizontal dimension, the clinician and the patient must accept the following challenges and risks: invasiveness, additional donor site/s, resorption of grafting materials, membrane collapse or exposure to infection, and delaying of implant placement until the maturation of grafting.² On the other hand, employing such a traumatic technique in ultrathin ridges is an additional risk. Thus, a minimally invasive ridge augmentation procedure involving ridge splitting and expansion can be performed effortlessly without compromising or harming the surrounding bone tissue.

Splitting the ridge and expanding the bone presents a feasible choice when the bucco-lingual bone width ranges from 3 mm to less than 6 mm, indicating suitability for implant placement.² The reasoning lies in the fact that, within the 3 mm of bone, at least 1 mm of trabecular bone is sandwiched between the cortical plates. This configuration ensures the preservation of 1.5 mm of cortical and cancellous bone on each split side, facilitating bone spreading and ensuring adequate blood supply around the implant. Numerous authors have proposed many bone-expansion techniques and adaptations to densify the peri-implant bone, aiming to attain superior primary stability while preserving bone integrity.^4–6

This article introduces a novel concept of bone expansion for the ultrathin alveolar ridges to place dental implants with zero wastage of existing natural bone in long-time edentulous arches that were not restored with any prosthesis. Instead of using twist drills and piezo surgery kits, the bone is split with a surgical scalpel blade and expanded with bone expanders to prevent natural bone wastage.

Procedure

Local anesthesia, containing 2% lignocaine with 1:80 000 adrenaline, was administered. An incision was then made along the crest of the mandibular ridge, extending from the canine to the canine region, and a full-thickness flap was reflected. With a good understanding of bone availability after performing a thorough clinical assessment and evaluating the cone beam computerized tomography (CBCT) radiograph (Figure 1), desired implant sites were marked with the help of a surgical guide over the exposed alveolar bone. To alleviate the pressures on the crestal bone and mitigate the risk of vertical fracture in the buccal bone plate, the incision was extended slightly mesially and distally beyond the intended osteotomy site (Figure 2). The precise positioning of the implant along the ridge was determined by a notch made with the scalpel blade. The alternate use of a surgical blade and bone expanders allowed the creation of the osteotomy without any cracking of the bone on either side (Figure 3). Both surgical blades (blade No. 11 and/or No. 15) and ridge expanders from 2 mm diameter onward were used in the surgery. Depending on the flexibility and the alveolar bone’s toughness, the ostomy’s diameter is judged with the help of CBCT evaluation. If the bone density belongs to either type III or IV, according to Lekholm and Zarb’s classification, it would be more flexible and easier to use expanders without vertical fracture. Apart from bone expanders, the surgical blade was utilized through gentle tapping facilitated by a mallet (Figure 4).

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The initial use of a scalpel blade penetrated the cortical bone to access the cancellous bone. Despite the substantial thickness of the crestal cortical bone, which makes perforation challenging, it is advised against utilizing a round bur to create an indentation for initiating the osteotomy because it will lead to the propagation of vertical cracks and bone loss in the buccolingual dimension.

The scalpel splitting and 2-mm initial expander were used alternately to create the desired osteotomy length. Once the osteotomy reached the desired length, scalpel cuts extended 3–5 mm mesial and distal to the osteotomy before introducing the next diameter (2.5 mm) expander (Figure 5). After using every other expander except the last expander, the surgical split should be patent by inserting the scalpel blade and making a mesiodistal motion along the split. It minimizes the lateral and horizontal stress on the wall of the osteotomy to prevent vertical cracks during implant installation (Figure 6). Furthermore, it helps to accumulate blood and form a coagulum within the osteotomy and bone split (Figure 5). This promotes accelerated (jumped) healing along the split bone and around the implant, eliminating the need for bone graft placements.

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Satisfactory primary stability was achieved with a 25–30 Ncm insertion torque, and implants were placed at the crestal level in a nonsubmerged manner. The flap was repositioned and sutured using nonresorbable 3-0 suture material in a continuous suturing technique. Figure 7 demonstrates the scalp-split technique step by step in sketch diagrams.

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The following postoperative medication regimen was prescribed: ibuprofen (400–600 mg every 6–8 hours for 3–5 days) for pain management and a combination of amoxicillin (500 mg) and metronidazole (400 mg), both taken every 8 hours for 5–7 days, for infection prevention. Additionally, a 0.2% chlorhexidine gluconate rinse (15 ml twice daily for 1–2 weeks) was recommended to reduce bacterial load in the mouth. Patients were also given the following postoperative instructions: maintain excellent oral hygiene while avoiding direct brushing at the surgical site, follow a soft food diet for the first few days to prevent trauma to the implant site, avoid strenuous activities for a few days to minimize the risk of bleeding or swelling, and attend regular follow-up appointments to monitor the healing process and ensure there are no complications. The first review was conducted after 1 week with suture removal performed after 2 weeks. It is strongly emphasized not to use healing abutments immediately after implant placement using the scalp-split technique to avoid premature loading of the implants.

The implant-supported overdenture was delivered 4 months after successful osteointegration (Figure 8). Four months after implant placement, no significant marginal bone loss was observed. Postloading follow-ups are planned every 6 months until 3 years have passed, followed by annual recalls thereafter.

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Discussion

A diameter of 3.5 mm and larger is considered a conventional implant, and narrow diameter implants of 3.3–3.5 mm are well-documented in all indications, including load-bearing posterior regions.⁷ Mini-implants <3.0 mm in diameter are only documented for the edentulous arch and single-tooth non–load-bearing regions, and success rates are not available.⁷ Therefore, we do not recommend using mini-implants in this particular technique. At the same time, 1.5–2.0 mm healthy bone should be available right around the implant to achieve the proper osteointegration.⁸ According to these norms, to receive the minor diameter conventional endosseous implant, there should be a minimum of 6 mm bone on either mesiodistal or buccolingual sides. Therefore, it is well-established that alveolar ridges <5 mm require a bone augmentation procedure before placing the conventional regular implants. As per Goyal et al,⁹ insufficient bone width of less than 1–1.5 mm around the implant can increase the risk of peri-implantitis. This condition may result in the unsightly exposure of metal, thinning of the labial plate, subsequent mucosal recession, and eventual implant exposure.

Several options have been implemented in clinical implant dentistry to minimize or overcome the issues associated with atrophic alveolar ridges. The primary techniques for successfully reconstructing bone thickness include distraction osteogenesis, ridge splitting, guided bone regeneration, and autogenous block bone grafting.² Each has its pros and cons.

Ridge augmentation using bone block and guided bone regeneration methods involves an extra donor site, a prolonged waiting period ranging from 6 to 12 months, infection, potential risks of membrane exposure, and heightened financial burden for the patient, which are considered disadvantages of those methods.^10–12 Distraction osteogenesis can result in discomfort and be cumbersome for the patient.^13,14

Despite appearing to be technique-sensitive, ridge splitting and bone expansion offer numerous benefits.¹⁵ One significant advantage is their ability to preserve the patient’s bone, a benefit not typically achievable through drilling procedures. In addition, it allows for manipulation of the bone by slow compaction and corticalization to improve the bone density and the width of the desired implant site. The efficacy of this method is also contingent upon preserving the integrity of the labial bone, a condition ensured by the intact periosteum. The elastic quality of the periosteum facilitates bone expansion and manipulation while serving as a barrier membrane. This membrane aids in effectively healing microfractures due to its ability to maintain an intact blood supply. Further, it takes advantage of the inherent quality of flexibility of cancellous bone.²

One limitation of the scalp-split technique is its dependence on meticulous surgical skill and precise instrumentation, which may pose challenges for less experienced practitioners. Additionally, individual variations in bone density and flexibility could influence the procedure’s success, requiring thorough preoperative assessment. Further clinical studies are needed to evaluate its long-term outcomes and compare them with alternative techniques.

Considering the pros and cons of all the other ridge-splitting and bone-expansion techniques, such as piezo surgery, the scalp-spilt technique is a promising technique for providing implant-retained or implant-supported prostheses over the ultrathin edentulous alveolar ridges while preserving natural bone to maintain sustainable osteointegration.

Conclusion

Ridge splitting and expansion is an effective technique for expanding ultrathin alveolar ridges with minimal natural bone wastage. The technique has advantages over other augmentation methods, such as guided bone regeneration or block grafting, including patient comfort, time savings, and less invasiveness with reasonable predictability. The scalp-spilt technique is a promising ridge-splitting and expansion technique for providing implant-retained or implant-supported prostheses over ultrathin edentulous alveolar ridges.