U-Shaped Bone Splitting and Osteotome Techniques for Narrow Alveolar Ridge in Implant Surgery

Abstract

Purpose: 

Bone splitting and osteotome are common ridge expansion choices for patients with a narrow alveolar ridge requiring dental implant restoration. Despite the effectiveness of the 2 techniques in horizontal ridge augmentation, they could also result in severe complications, which is thus considered a contraindication.

Materials and Methods: 

A modification of the bone splitting and the osteotome techniques is proposed hereby as an alternative.

Results: 

The modified procedure reduces the tension of labial bone plate by creating a partial bone fracture at the most depressed area of labial defect where the thinner bone exists.

Conclusions: 

This technique is primarily useful for cases with a facial concavity. The modification could prevent iatrogenic labial bone defect during the surgery, and compared with onlay bone grafting, it may shorten the overall treatment time and avoid traumatizing the bone donor site.

The lack of alveolar bone width is common in dental implant surgeries, especially at the anterior labial side after tooth loss and alveolar remodeling. This greatly complicates the operation, subjects the patient to greater trauma, increases the risk of failure, and compromises the aesthetics of the definitive restoration.^1,2 Ridge augmentation techniques to gain sufficient bone mass, and specifically for patients with horizontally atrophic maxilla, include the following: alveolar ridge split (ARS) and osteotome techniques combined with artificial or autologous bone grafts, guided bone regeneration (GBR), block bone grafting, and titanium mesh reportedly improve the success rate and aesthetics of implant-supported prosthesis.^3–8

Conventional ARS and osteotome techniques involve the splitting of alveolar ridge longitudinally and the subsequent expanding of the bone slit plates, which widens the narrow alveolar ridge for implant placement.^9,10 However, for cases with a facial concavity at anterior alveolar bone, especially when the bone width is less than 4 mm, the application of ARS puts labial bone plate at a higher risk of fracture due to the tension created by osteotome. If major bone plate fractures occur, it can cause significant bone loss and considerably complicate the surgical process.¹¹ In this situation, onlay bone grafting technique is usually adopted, although this brings about extra injury to the bone donor site and prolongs the operation.¹²

In this case, a U-shaped bone split and osteotome techniques aiming at reducing the tension of labial bone plate was proposed. This could be an alternative in some cases to onlay bone grafting for the patient with extremely narrow alveolar ridge at the anterior teeth area (Table 1).

Table 1: A General Comparison of Bone Augmentation Techniques for Dental Implantation

Technique

1. Make an incision through the mucoperiosteum along the crest of the alveolar ridge and 2 vertical incisions on the labial side extending the mesial and distal end of the first incision (Fig. 1, A and B).
2. Make 1 horizontal and 2 vertical osteotomies by ultrasonic osteotome (Surgybone; Silfradent, Santa Sofia, Italy) at the labial bone concave to produce a square-shaped bone plate with 3 free edges. The size of the bone plate is 4 × 4 mm, and the depth of the grooves is 1.5 mm (Fig. 1, D). Greenstick fracture of the labial bone plate made with spreading instrument #D2005 (Split-Control; Meisinger, Neuss, Germany).
3. Horizontally split the alveolar bone at the crest using a bone osteotome #XBC60 (Dentium RS Kit; Dentium, Seoul, Korea) (Fig. 1, E).
4. Insert a tapered implant of which the diameter is 3.5 mm at the center of the prepared crestal osteotomy (Fig. 1, F).
5. Apply particulate bone graft (Bio-Oss; Geistlich Pharma, Wolhusen, Switzerland) to the implant site and cover it with barrier membranes (Bio-Gide; Geistlich Pharma) for GBR (Fig. 1, G).
6. Close the soft tissue (Fig. 1, H).
7. Examine the inserted implant and surrounding bone with CBCT (Fig. 2, B). (Note: In a regular case, the postoperative CBCT is not necessary for this technique. In this case, the patient has problem with another tooth which need a CBCT.) After 6 months, the implant was uncovered for 1 month. Then the final restoration was presented (Fig. 3, A and B).

Fig. 1: A and B, Significant defect of labial bone. C and D, Make 2 vertical osteotomies and 1 horizontal osteotomy at the bottom of labial bone depression. E and F, Bone split and osteotome on the crest of alveolar ridge and implant insertion. G and H, Apply particulate bone graft and barrier membrane for GBR before closing soft tissue.

Fig. 2: CBCT images before (I) and after the surgery (J). I, The middle 1/3 of the ridge was narrow with a large risk of implant exposure. J, After splitting and osteotome, the whole ridge was augmented and the implant was placed in a suitable position.

Fig. 3: K and L, The final restoration appearance showed the patient acquired a beautiful smile with proper white and pink aesthetics.

The whole procedure and reformed instrument had been shown in the sketches (Fig. 4, A–D).

Fig. 4: A protocol of U-shaped bone splitting and osteotome techniques. M, Prepare a trapezoidal flap in the surgical area. N, Make a “U” shaped osteotomy on the middle of labial ridge by ultrasonic osteotome (Surgybone; Silfradent). Then split the alveolar bone horizontally at the crest using a bone osteotome #XBC60 (Dentium RS Kit; Dentium). O, Use a reformed instrument (named split expander) to press the labial bone plate to make greenstick fracture. P, The side view of the labial bone plate after osteotome. The bone plate rose from the bottom of labial concave to increase the width of alveolar bone.

Discussion

The rationale of the modified procedure is that the U-shaped window opening on the labial bone plate releases the pressure built up by osteotome between labial and palatal bone plate. The length of the transverse osteotomy should be larger than the diameter of the planned implant. When using splitting and expanding, a vertical fracture line might appear and stopped at the transverse osteotomy. Then after continuous expansion, the partially fractured bone plate would be propped up and thus stopped the transmission of stress, leaving other parts of the labial bone plate intact. As this modified method reduces the tension of labial bone plate, complete fracture could be avoided, thus preventing iatrogenic labial bone defect during the surgery.

Generally, for an insufficient bone condition, the most common augmentation method is GBR technique.¹³ However, GBR is considered most suitable for a 3-wall defect. The bone substitute materials will be partly lost especially when used alone, and the osteogenic effect is limited.¹³ In that case, either space maintenance procedures or additional bone augmentation procedure is needed.¹⁴ The space maintenance procedures include titanium membrane and titanium alloy screw tent technology.^15,16,17 Titanium reinforced membranes have a long history with GBR application since 1999.^15,16 However, the membrane also owns an high exposure rate,¹⁸ which largely limited its application. Recently, the titanium alloy screw tent technique came into sight.¹⁶ The principle of tent technology is using a titanium alloy screws to support the GBR membrane and form a stable osteogenesis space. However, this technique only gains limited new bone formation. More importantly, the alloy screws would impact the implant to be put at a suitable place, so this procedure usually take place before implant placement and lead a second surgery for implant placement.

Our U-shaped bone split technique takes advantages of the basic principle of the tent technique. We use the partially fractured bone plate to support the space. In this procedure, no secondary surgery would be needed, and the placement of implant would not be affected by a tent screw.

Bone augmentation techniques as onlay bone graft, ARS techniques are also frequently used in bone defect cases.^8,19 The amount of bone gained by onlay grafting is abundant.⁸ However, onlay bone graft needs a donation bone area, which leads a secondary injury for the patient. The donation area has complications like facial hematoma, pain, tooth root damage, and even fractures. To overcome such disadvantages, our U-shaped bone split technique does not have other surgical site. The greenstick fracture of the labial bone plate takes place of the onlay bone plate and it still has enough blood supply.

For cases with bone defect at the labial middle or root 1/3, our technique has unique advantages comparing with regular ARS. Simultaneous implantation with regular ARS has a risk of buccal wall fracture at the thinnest bone area and leads the loss of buccal bone plate.²⁰ Our vertical and horizontal osteotomies stop the force delivery and protected the thin bone plate. In addition, the bone plate act as a shell to hold the GBR bone substitute materials. The disadvantage of this approach is that the implant parallels the palatal wall and may well require angle correction. Also, this technique requires careful selection of suitable gingiva biotype. Gingival retraction is prone to occur in patients whose gums are of a thin biotype. It is recommended to choose the medium-thickness gingiva biotype or choose soft tissue transplantation.

Conclusion

Taken together, this modified procedure decreases the risk of fracture of the outer cortex of split area. In contrast to onlay bone grafting, the surgical procedure is much simpler and less time-consuming, and it also avoids the extra requirement of a bone donor site. Also, it is better than the stage split technique for cases with bone defect at the labial middle or root 1/3. We recommend this technique particularly for bone type III and type IV as these types of bone possess the most controllable dilatation of horizontally absorbed bone, especially labial defect, so that they can provide the minimally invasive alternative for the application of bone osteotomes in implant surgery.

In the clinic, patients with very narrow anterior maxillary alveolar ridge usually require onlay bone grafting to gain sufficient bone width for implant insertion. The present study proposes an alternative method modified from ARS technique and osteotome technique, which reduces the tension of labial bone plate and thus prevents significant fracture. This method provides an effective but simple way to achieve GBR and simultaneously insert the implant without increasing the risk of fracture of the outer cortex for patients with extremely narrow anterior maxillary alveolar ridge.

Disclosure

The authors claim to have no financial interest, either directly or indirectly, in the products or information listed in the article.

Approval

The West China Hospital of Stomatology Institute Review Board (WCSHIRB) approved the research protocol of bone splitting modification under protocol number 2009034.

Roles/Contributions by Authors

Y. Yao: article writing. K. He: drawer of the diagrams. P. Gong: critical review of the manuscript. H. Tang: method maker and case provider.

Acknowledgments

This work was supported by ITI Research Grant (no. 973_2014) and National Natural Science Foundation of China (81700941).