|Year : 2014 | Volume
| Issue : 1 | Page : 72-77
Osseointegrated supported prosthesis - Surgical techniques for hard and soft tissue grafting
D Krishna Prasad, Divya Mehra, D Anupama Prasad
Department of Prosthodontics and Crown and Bridge, A. B. Shetty Memorial Institute of Dental Sciences, Nitte University, Deralakatte, Mangalore, India
|Date of Web Publication||19-Apr-2014|
D Krishna Prasad
Department of Prosthodontics and Crown and Bridge, A. B. Shetty Memorial Institute of Dental Sciences, Nitte University, Deralakatte, Mangalore - 575 018
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Several techniques have been developed to improve the bone volume for the placement of dental implants in an effort to shorten the length of treatment, avoid a second surgical appointment, reduce the use of additional surgical sites, reduce challenges to the patient and decrease patient morbidity. This article will review these surgical procedures for both hard and soft tissue grafting in the placement of endosseous dental implants.
Keywords: Hard tissue grafting, soft tissue grafting, surgical techniques
|How to cite this article:|
Prasad D K, Mehra D, Prasad D A. Osseointegrated supported prosthesis - Surgical techniques for hard and soft tissue grafting. J Dent Implant 2014;4:72-7
|How to cite this URL:|
Prasad D K, Mehra D, Prasad D A. Osseointegrated supported prosthesis - Surgical techniques for hard and soft tissue grafting. J Dent Implant [serial online] 2014 [cited 2022 Aug 12];4:72-7. Available from: https://www.jdionline.org/text.asp?2014/4/1/72/131010
| Introduction|| |
Alveolar ridge resorption after tooth loss is a common phenomenon. After a tooth is extracted the alveolar ridge decreases in width and height very rapidly, with as much as 50% loss in width during the first year, two-thirds of which occurs in the initial 3 months. Often in clinical practice, the loss of a tooth does not coincide with replacement by osseointegrated supported prosthesis and there is frequently a lag of months to years before an edentulous site presents for therapy. This often calls for augmentation procedures to increase the height and width of the existing bone to facilitate dental implant placement and restoration. Multiple soft and hard tissue grafting techniques have been used to reconstruct the partially dentate and edentulous maxilla and mandible.
This article reviews the various surgical procedures for hard and soft tissue grafting before and after placement of dental implants.
| Surgical Techniques for Hard Tissue Grafting|| |
Adequate bone volume pre-requisites the implant therapy and proper esthetic result. Inadequate alveolar bone height and width often requires bone augmentation procedures either performed prior to, at the time of, or after the implant surgery. Alveolar ridge defects resulting from tooth extraction, trauma or periodontal disease are recommended to have surgical corrections prior to their comprehensive prosthodontic reconstruction, especially in osseointegrated supported prosthesis.
There are several techniques that had been described for ridge augmentation [Figure 1].
Guided bone regeneration
The concept of guided bone regeneration implies the use of cell-occlusive membranes for space provision over a vertical or horizontal defect, promoting the in-growth of osteogenic cells while preventing migration of undesired cells from the overlying soft tissue.  Space maintenance by various particulate graft materials and the use of resorbable, non-resorbable as well as titanium-reinforced membranes has been described. No differences in implant survival rates following guided bone regeneration could be found compared to implants in native jawbone. However, mean increase in horizontal and vertical dimensions of 2.6 mm and 3.6 mm, respectively, has been reported with up to 40% of initial bone gain undergoing resorption thereafter.  The benefit of GBR for correcting dehiscence of alveolar ridge was investigated for the use of GBR in threads exposed implants in deficient ridges and was reported to be successful in treating dehiscence defects. Failures are mainly related to premature membrane exposure that has been seen in up to 38% of cases and may lead to infection and eventually partial or total loss of regenerated bone. 
Onlay block grafts
Onlay bone grafts are used for external augmentation of horizontal (veneer graft) or vertical alveolar ridge deficiencies, as well as combined defects (saddle graft). Compression screws are placed to fix bone blocks to the residual alveolar crest that should be extensively perforated to increase blood supply to the host-graft interface. Autogenous bone grafts may be derived from intraoral or extraoral donor sites. Intra-oral sources for block grafts are symphysis, body and ramus of the mandible with ramus being the preferred site as local consequences of graft harvest are less. Intraoral graft site is preferred when augmenting smaller defects. Allogenic bone may also be used as an onlay graft. If autogenous bone grafts are used, it is highly recommended to use corticocancellous bone blocks. Cancellous bone alone and particulate bone, if not associated with membranes of titanium meshes, do not provide sufficient rigidity to withstand tension from the overlying soft tissues or from the compression by provisional removable dentures, and may undergo almost complete resorption. Implant placement may be immediate or delayed. Simultaneous implant placement can be an option only in vertical grafts, with the implants acting as osteosynthesis screws. 
Barrier membranes are not routinely used with cortical block grafts. It adds unnecessary volume to the graft site increasing the tension on the overlying soft tissue and the risk of incision line opening. However, if the size of the block is inadequate to fill the entire graft site or if the harvest is more particulate or trabecular in nature, a barrier membrane should be used.
- When harvested from the symphysis - can be used for predictable bone augmentation up to 6 mm in horizontal and vertical dimensions. Up to three-teeth edentulous site can be grafted. Bone density of the graft - D1 or D2
- When harvested from ramus - used for horizontal or vertical augmentation of 3 to 4 mm. Bone density of the graft is D1. 
Large volume of bone that can be harvested and carved into various shapes.
- Temporary paresthesia when harvested from chin
- Unpredictable graft resorption
- Higher risk of wound dehiscence and osseointegration failure
- Total graft loss
- Lower values of bone-to-implant contact and compromised implant position, thereby making the one-step procedure undesirable from a prosthetic point of view. 
A mean increase in horizontal and vertical dimension of 4.4 mm and 3.7 mm has been reported. 
Particulate onlay grafts have been used extensively for reconstruction of mandibular alveolar defects. Both autogenous and non-autogenous options can be used. The source of autogenous particulate is the same as has been discussed for block augmentation of the mandibular ridge with calvarial bone and simultaneous implant placement. For small amounts of bone, local sites can be used, including the symphysis, ramus and maxillary tuberosity. The graft is usually harvested using a bone shaver. When greater volumes of bone are required, then distant sites may be employed. Allergenic and xenogenic particulate grafts have been growing in popularity. These grafts are readily available and abundant. They can be used in combination with autogenous bone or alone. Recent studies have shown success with these graft materials for vertical ridge augmentation when protected with a rigid membrane. 
Rapid vascularization, but they must be protected by a membrane to reduce the risk of resorption.
Alveolar ridge expansion
It is also known as bone splitting technique. Following crestal osteotomy, the buccal cortex is gently expanded against the lingual plate using osteotomes of increasing diameters to allow implants to be placed in between. The residual gap created may be filled with graft material. The aim of these expansion techniques is to reduce surgical morbidity and complications associated with grafting procedures while providing similar success rates. Bone splitting of knife-edge ridges is only possible if the buccal and lingual cortices are separated by spongy bone. An average gain of 4 mm is found in horizontal bone width. Due to the lower bone density and thinner cortical plates, success rates may be higher in the maxilla.  The presence of only cortical bone represents a contraindication of the technique. Jong-Jin Suh et al. recommended a new microsaw technique wherein he used microsaws instead of the osteotomes to perform bone splitting in situations when the existing bone was less than 3 mm with more cortical bone and less or insignificant amount of trabecular bone. He concluded that microsaws allowed for expansion of thin alveolar ridges with better control of instrumentation, fewer traumas and lesser risk of bone fracture or perforation. 
When the bucco-lingual bone width is 3 mm or greater but less than 6 mm, to allow implant placement. The existing 3 mm bone should have at least 1 mm of trabecular bone between the cortical plates.
- Simultaneous implant placement and grafting
- Lower cost
- Lower possibility of cross-infection from graft materials and lower morbidity
- Greater predictability, since the area that is grafted is essentially a five-wall bony defect, with excellent blood supply.
- Allows for better implant positioning and avoidance of compromised prosthetic outcomes.
- Cannot increase height, only width
- It is a very difficult and operator dependent technique
- It is more difficult to perform on a single tooth than on entire ridges, where the operator can take advantage of the elasticity of a long ridge of bone. 
The piezoelectric ridge expansion technique described by Vercellotti uses the modulated-frequency piezoelectric energy scalpels, permitting the expansion of the edentulous ridge irrespective of what the quality of bone is, even in the case of the most mineralized bone, allowing the placement of implants in single stage surgery.  This technique significantly reduces the risk of fracture of the bone which is otherwise a common complication with ridge expansion technique.
In this technique, a defect is created when two bone segments are slowly separated under tension. One week after osteotomy and distractor placement (latency period), distraction of segments is advanced at a rate of 0.5-1 mm per day until the desired separation is reached. A consolidation period of 5 days per mm of the space created should be maintained before device removal and implant placement. It allows for a vertical bone gain of 3-20 mm without the use of graft material and additional mucosal grafting is not required as the soft tissue follows bone distraction. 
- Need for daily activation
- Compromised speech
- Eating difficulty
- Partial relapse of initial bone height (8%)
- Change of distraction vector (8%)
- Basal bone or segment fracture (3%)
- Fracture of distraction device (2%)
- Incomplete distraction (2%)
- Transient paresthesia (2%)
- Total failure in 1% of cases on average. 
It is not a recommended technique for correction of narrow ridges as it requires over-distraction, which can result in surrounding tissue tears or ischemia. 
Bone ring augmentation
The implantologist Dr. Bernhard Giesenhagen from Melsungen has developed an augmentation technique, which allows bone transplantation and implantation to be performed on large three-dimensional bone defects in a single operation. Bone is harvested either from the chin, palatal or retromolar pad area. The recipient site is prepared and the transplant removed with special trephine drills.
The following factors require special attention in augmentation with autogenous bone ring transplants:
- The receptor site must contain as many vital cells as possible to ensure optimal revascularization of the transplant
- Sufficient local bone is required to anchor the implant for primary stability
- Immobile positioning of the transplant is essential.
- The transplant must be contoured with slowly resorbable bone regeneration material to combat any volume loss
- Safe and tension-free wound closure is a prerequisite for trouble-free healing.
- Single tooth gap
- Edentulous space
- Severely atrophic ridge
- Sinus floor elevation.
Surgical techniques for soft tissue grafting
Several surgical techniques may be applied to obtain an adequate emergence profile of the restoration with sufficient keratinized gingiva: , [Figure 2].
The "roll flap procedure"
The roll technique, described by Abrams in 1980, involves the preparation of a de-epithelialized connective tissue pedicle graft, which is subsequently placed in a subepithelial pouch. The length of the pedicle should be compatible with the height of the defect on the buccal aspect and similar to the crest in mesiodistal direction. This pedicle is rolled under the buccal mucosa to increase the buccolingual dimension of the edentulous ridge for later fabrication of a fixed prosthesis. The flap is released by two vertical incisions extended beyond the mucogingival junction. It is used in the treatment of small to moderate class I ridge defects, primarily in cases with a single-tooth space. The technique enables the surgeon to augment tissue apically and labially to the cervical area of a pontic and to give the recipient site the appearance of a normal tooth-gingiva interface. Hence, a buccolingual ridge concavity can be converted into a ridge convexity resembling the eminence produced by the roots of the adjacent teeth. 
- Risk of graft necrosis
- Need for a second surgical site
- Pain due to healing by second intention at the donor site.
Barone (1999)  modified the technique suggested by Abrams by using intrasulcular incisions to form a full-thickness 'envelope' on the buccal aspect instead of the two buccal releasing incisions, which would serve to accommodate the roll of connective tissue.
- It requires only one horizontal incision for access and release of the underlying connective tissue
- There is maintenance of proper blood supply to the palatal graft
- Reduced number of sutures
- No need for stents or hemostatic agents at the palatal region
- Healing by first intention at the donor site, which provides more comfort to the patient in the postoperative stage.
The "pouch procedure"
Mainly used in the correction of class I defects. A subepithelial pouch is prepared in the area of the ridge deformity, into which a free graft of connective tissue is placed and molded to create the desired contour of the ridge. The entrance incision and the plane of dissection may be made in different ways:
- Coronal-apically: The horizontal incision is made on the palatal or lingual side of the defect and the plane of dissection carried in an apical direction
- &Apical-coronally: The horizontal incision is made high in the vestibule near the mucobuccal fold and the plane of dissection is carried coronally to the crest of the ridge
- Laterally: One or two vertical entrance incisions are started from either side of the defect. The plane of dissection is made laterally across the span of the deformity.
- To correct class I defects.
- Patients with large-volume defects may have thin palatal tissues, which are insufficient to provide the volume of the donor tissue necessary to fill the deformity. In such cases, various procedures for hard tissue augmentation may be required.
An onlay graft is a full-thickness detached mucosal graft that is shaped to fill in a ridge defect. The technical aspects of this graft are similar to the free gingival graft procedure. The initial step of an onlay graft is to prepare a bed for the soft tissue graft. The bed is firmly attached to the bone and contains vascular elements that seep nutrients into the underside of the soft tissue graft. A large full-thickness tissue graft is obtained from the palate and trimmed, shaped and adapted to fit the defect. The large donor site is usually protected with a surgical stent and heals by second intention. A rather thick graft must be used to compensate for the shrinkage that occurs during healing. A successful onlay graft can increase ridge thickness as well as ridge height. Significant residual ridge defects can be corrected with this technique.
- Color blending with adjacent tissues can be a problem due to color differences between palatal and gingival tissues. 
Interpositional grafts are not completely submerged and covered in the manner that a sub-epithelial connective tissue graft is placed. Therefore, there is no need to remove the epithelium from the surface of the donor tissue. If augmentation is required not only in the buccolingual but also in the apico-coronal direction, a portion of the graft must be positioned above the surface of the tissue surrounding the recipient site. A certain amount of the grafted connective tissue will thus be exposed in the oral cavity.
- Interpositional graft procedures are used to correct class I as well as small and moderate class II defects.
Class III ridge defects pose a major challenge to the clinician since the ridge has to be augmented in both vertical and horizontal dimensions. The combined onlay-interpositional graft procedure may successfully be used in such a situation.  The combined graft procedure may offer the following advantages:
- The submerged connective tissue section of the interpositional graft aids in the revascularization of the onlay section of the graft, thereby gaining a greater percentage acceptance of the overall graft
- A smaller post-operative open wound in the palate donor site
- Faster healing in the palate donor site with less patient discomfort
- Greater latitude or ability to control the degree of bucco-lingual and apico-coronal augmentation within a single procedure
- Vestibular depth is not decreased and the mucogingival junction is not moved coronally, thereby eliminating the need for follow-up corrective procedures.
| Discussion|| |
Alveolar ridge modification is a pre requisite for both the implant and/or fixed prosthesis. It improves both the gingival and the bone architecture for esthetic and functional purposes. Peri-implant plastic surgery focuses on harmonizing peri-implant structures by means of hard tissue engineering and soft tissue engineering. It includes: bone structure enhancement, soft tissue enhancement, precision in implant placement and quality of the prosthetic restoration.
A deform ridge may result from teeth extractions, severe periodontal disease, abscess formations, etc., The deformity that exits in the ridge is directly related to the volume of the root structure and associated bone that is missing or has been destroyed.
Numerous studies demonstrate that peri-implant soft tissue dimensions of 3.0 mm vertical tissue height and 2.0-3.0 mm tissue thickness are necessary in order to satisfy the vertical and lateral biologic width requirements at an implant site. When the peri-implant soft tissues dimensions are less than those described above, the biologic width phenomenon will establish a peri-implant soft tissue seal at the expense of approximately 1.0-2.0 mm of peri-implant crestal bone height, resulting in apical migration of the soft tissue seal, which is often responsible for the exposure or visualization of metal implant components.
Several hard and soft tissue augmentation techniques with their advantages, disadvantages, indications and contraindications have been described in this review article. However, the following factors should be determined prior to the initiation of therapy:
- Volume of tissue required to eliminate the ridge deformity
- Type of graft procedure to be used
- Timing of various treatment procedure
- Problem with tissue discolorations and matching tissue color.
| Conclusion|| |
The availability of the various options to choose from to manage the hard and soft tissue defects at various stages of the treatment makes it possible for the dental specialist to improve the final outcome of any surgical or prosthetic rehabilitation done. However, as rightly said, prevention is better than cure, the best way to treat a ridge deficiency is to prevent it from occurring. Performing extraction site preservation at the time of extraction can minimize the amount of bone loss from an extraction. A thorough knowledge, clinical evaluation of each individual situation and skill on the part of the implantologist will greatly improve the final outcome of the implant therapy.
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[Figure 1], [Figure 2]