Space Maintenance Using Tenting Screws in Atrophic Extraction Sockets

The alveolar process is a tooth dependent tissue that develops with tooth eruption. The volume of the alveolar process is dependent on the shape, size, inclination of the tooth, and its eruption pattern. The tooth is anchored by bundle bone, which is invaded by periodontal fibers.¹ 

Following tooth extraction, the bundle bone is rapidly resorbed resulting in loss of height and width.²  The loss of width of alveolar bone is the major concern and is approximately 3 times greater than the loss of height.^4,5  The buccal plate resorbs more because it is thinner, averaging about 0.8mm in the anterior teeth region and 1.1mm at the premolar sites.⁶ 

Approximately 50% of the alveolar ridge width is lost after tooth extraction, most of which occurs during the first 3 months.⁷ 

The rationale for socket grafting is to have bone available to place implants in proper position for a successful implant prosthesis⁸  and studies have stated that the survival rate of implants placed in grafted bone is similar to those in native bone.⁹ 

Extraction sockets with deficient buccal bone that are classified as Funato's Class III and IV types,¹⁰  or Elian's Type III¹¹  are difficult to predictably graft.

Treatment options include guided bone regeneration (GBR) vs titanium reinforced membrane, a titanium mesh, or a high-density polytetrafluoroethylene (PTFE) membrane, or block auto/allogenous grafts.

The tenting screw technique (TST) is an alternative to these procedures and is as effective in promoting new bone formation, localized to the site that is highly predictable, time efficient, cost effective, with less patient morbidity.

TST is based on the basic principles of GBR utilizing resorbable barrier membranes. This technique provides and maintains space, allowing stabilization of the blood clot during healing.

This article illustrates 3 clinical case reports utilizing the tenting screw technique to facilitate GBR in atrophic extraction sockets.

A standard surgical protocol was followed. Patients were locally anesthetized using 2% lidocaine with 1:100 000 epinephrine. A crestal incision was made slightly toward the lingual/palatal in an attempt to preserve keratinized gingiva and limit secondary intention healing over the site. A full-thickness flap was elevated. The tooth was extracted using periotomes. Sockets were degranulated using curettes.

A tenting screw osteotomy was created with the tenting screw kit drill. The tenting screw was placed vertically, horizontally, or diagonally depending on where augmentation was needed.

Salvin bone fixation screw kit was used, which contains 2 latch type or straight handpiece drills of different sizes, self-tapping titanium screws, and a locking tip screw driver. Titanium tenting screws are available in different sizes of 4mm, 6mm, 8mm, 10mm, 12mm, and 15mm in length and 1.5mm to 2mm in diameter. If primary stability is difficult, a longer screw can be used. The lingual/buccal plate can be perforated to get bicortical stabilization.

The vertical height of the screw is determined by proximal height of the adjacent bone. The screw head can be placed 1–2mm above this height if required (Figure 1a and b). Single or multiple screws can be used based on the size of defect.

The buccal vestibular periosteum is scored, and, if necessary, horizontal cut back incisions are made to achieve tension-free primary closure. A membrane template is fabricated prior to membrane placement, extending at least 3mm onto the sound buccal and palatal/lingual bone.

The extraction socket is decorticated to create the necessary heme for osteogenesis. Particulate allograft condensed into the socket and followed by placement of the membrane. Membrane-tacking screws are recommended only with multiple-site socket preservation or in conjunction with ridge augmentation. Tension-free primary closure is desired whenever possible.

Postoperatively, all patients were placed on antibiotics, chlorhexidine rinse, and antiinflammatories. A methylprednisolone dose pack was given only with multiple site augmentation or ridge augmentation.

After 3 months sites were reentered for placement of the implant. Tenting screws were removed by gently unscrewing in a counterclockwise direction. Implant placement was then carried out in the usual manner.

With GBR, the mucogingival junction shifts coronally in an attempt to achieve primary closure. Hence, we apically positioned the flap during uncovery to eliminate the need for additional soft tissue grafting.

A 51-year-old male, with nonsignificant medical history, presented with pain and mobility of his right central incisor. Clinical and radiographic exam revealed a hopeless right central incisor (#8), with a hemi-septal defect on the mesial and a compromised buccal plate of bone (Figure 2a). Although teeth #7 and #9 were treatment planned for full coverage restorations, the patient preferred 3 individual restorations rather than a fixed partial denture option. The patient was treatment planned for extraction of tooth #8, with tenting screw GBR.

After flap reflection and extraction of the tooth, significant loss of facial and mesial bone were noted (Figure 2b). After degranulation of the defect, the tenting screw was placed in the center of the alveolus, angled buccally at the level of the adjacent interproximal bone heights. (Figures 2c and d). Decortication was done to obtain the necessary bleeding for angiogenesis followed by condensation of cancellous allograft (Maxxeus Dental, Kettering, Ohio) of particle size 0.25–1mm (Figure 2e). Resorbable bilayer collagen membrane (Geistlich Bio-Gide, Princeton, NJ) was placed buccal to palatal. Tension-free primary closure was obtained, and the area was fixed provisional to prevent premature loading of the graft site (Figure 2f). At 4 months, a follow-up radiograph was taken, showing radiographic bone fill to the level of the screw head (Figure 2g). Adequate bone formation for implant placement occurs as early as 12 weeks following tooth extraction, with insignificant changes in alveolar ridge dimensions.¹² 

A 67-year-old male with a noncontributory medical history presented for comprehensive dental care. The mandibular right first molar was deemed hopeless due to an endo-perio lesion (Figure 3a). The area was treatment planned for implant crowns in areas #29 and #30. Upon reflection and extraction of the tooth, it was found that both the buccal and interradicular bone was compromised. The tenting screw was placed buccally in the defect (Figure 3b). Particulate cancellous bone graft (Maxxeus) of size 0.25–1mm and resorbable collagen membrane (Geistlich Bio-Gide) were placed and tension-free primary closure was achieved (Figures 3c–e). At 4 months, 2 platform-switched 3i/Biomet fixtures were placed (Figure 3f). The final restorations were placed with sufficient embrasure spacing as well as an adequate band of attached keratinized tissue (Figure 3g).

A 41-year-old healthy female presented with a chief complaint of wanting “implants to replace her missing teeth.” Tooth #4 revealed an endodontically hopeless tooth. The tooth was treatment planned for tenting screw GBR and implant placement. Upon flap reflection and extraction of the tooth, significant loss of vertical bone was noted, and a tenting screw was placed vertically in the center of the defect with the screw slightly coronal to the adjacent interproximal bone heights. Cancellous bone allograft (Maxxeus) of particle size 0.25–1mm was used to fill the socket and regenerate the missing buccal plate. Resorbable collagen membrane (Geistlich Bio-Gide) was trimmed to the desired size and placed from buccal to palatal.

Figure 4a–d shows the radiographic sequence of the preop radiograph, tenting screw placement, immediate grafting with the screw, and 4 months postoperative healing after tenting screw GBR.

Figure 4e shows the radiographic progression of implant placement at the time of surgery, parallel pin, test body implant, and placement of a tapered implant (4/3mm × 11.5mm Biomet 3i implant). The implant was placed at crest in the ridge area (Figure 4f and g). Although no histology was done, clinical impression was of Type III bone. Figure 4h and i shows good crestal bone level at 3 years postoperatively.

Implant surgery is a restoratively driven procedure. Atrophic extraction sockets with defects need to be grafted in order to have a successful esthetic, functional, and restorative outcome. A common problem encountered in the regeneration of these defects is membrane collapse resulting in the loss of graft volume. Various surgical procedures including autogenous/allogenic block grafts and titanium mesh with or without growth factors have been used successfully in the past.

The advantage of the tenting screw technique is its space-making ability. During the healing period, the diagonally placed tenting screws provide a tenting effect and resist the collapse of the membrane, thus maintaining the volume and geometry of the space. This allows for the stabilization of the blood clot, which is fundamental for success.

Some advantages of the tenting screw technique include the following:

• 1.

  Relatively easy to perform

• 2.

  Provides space for the ingrowth of osteogenic cells

• 3.

  Low morbidity

• 4.

  Shorter healing time

• 5.

  Economical

The overall success of this procedure depends on proper design and reflection of tissue flaps, meticulous degranulation, and tension-free primary closure. Although many clinicians advocate flap less extractions, large defects with severe buccal bone discrepancy need to be flapped and thoroughly degranulated for successful regeneration.

Tension-free primary closure is obtained by scoring of the periosteum, which also promotes angiogenesis by causing bleeding into the graft material.¹³ 

Extraction results in significant horizontal and vertical bone resorption. The horizontal bone loss is much higher than the vertical bone loss. The resorption of the buccal plate is more than that of the lingual plate due to a more rapid resorption rate during the first 3–6 months after tooth extraction.

Various socket preservation techniques can be successfully employed to minimize the extent of bone resorption, although bone loss cannot be prevented completely.

GBR using tenting screws is an alternative method to the gold standard of block grafting. It can be used successfully in the regeneration of atrophic extraction sockets.

It is a highly predictable, cost-effective procedure with less healing time and patient morbidity. It should be considered as one of the treatment options in the management of atrophic extraction socket.

Abbreviations

GBR

guided bone regeneration

TST

tenting screw technique