oral health and heart

Evidence continues to mount that maintaining good oral hygiene is good for your heart.
It has been apparent for several years that consistent flossing and seeing your dentist regularly can help to prevent heart disease. Flossing and periodic teeth cleaning by a dental professional (to remove the plaque that invariably forms on everyone's teeth) are vital in preventing periodontal disease — gingivitis or periodontitis — which is caused by a chronic bacterial infection of the gums.
 
Periodontal disease can promote inflammation of the blood vessels, an important risk factor for atherosclerosis. People with gum disease are known, for instance, to have elevated levels of C-reactive protein (CRP), a marker for inflammation that is associated with an increased risk of coronary artery disease. More recently, it has been shown that people with periodontal disease also have elevated levels of lipoprotein-associated phospholipase A2, another significant marker for inflammation that increases cardiac risk.
 
Furthermore, there is evidence that when people who have active periodontal disease receive good dental care and improve their own oral hygiene, their vascular function improves. And one small study has even suggested that aggressive treatment of periodontal disease can potentially result in the partial reversal of vascular disease, as determined by the carotid intimal medial thickness test. (This, interestingly, was the same test that failed to improve with Vytorin therapy in the controversial ENHANCE trial, suggesting that simple oral hygiene may be able to accomplish something that even some expensive cholesterol drugs cannot.)
 
Of course, the link between oral hygiene and the prevention of heart disease has not yet been proven definitively with the sort of long-term, randomized clinical trials demanded by evidence-based medical purists. These trials, for instance, would demonstrate that the incidence of heart attacks and/or cardiac death is significantly reduced by good dental care. Perhaps in 10 or 15 years such evidence will be available (if somebody is willing to produce the $20 to $50 million that such a clinical trial would likely cost).
 
In the meantime, though, considering that good oral hygiene is known to produce several other benefits aside from a healthy heart (including the reduction in cavities, the preservation of teeth, the reduced risk of halitosis and — though this has not yet been proven in formal randomized clinical trials either — better sex), it seems advisable, to this cardiologist, for me to strongly recommend good oral hygiene to you.
_Sources:
Mochari H, Grbic JT, Mosca L. Usefulness of self-reported periodontal disease to identify individuals with elevated inflammatory markers at risk of cardiovascular disease. Am J Cardiol 2008; 102:1509-1513.
Tonetti MS, D'Aiuto F, Nibali L, et al. Treatment of periodontitis and endothelial function. N Engl J Med 2007; 356:911-20.
Piconi S, Trabattoni D, Luraghi C et al. Treatment of periodontal disease results in improvements in endothelial dysfunction and reduction of the carotid intima-media thickness. FASEB J 2008; DOI: 10.1096/fj.08-119578.

Chinese-can-now-feel-good-with-Sudarshan-Kriya

Sudarshan Kriya, the famous yoga technique initiated by the Art of Living, has reached China's doorstep. Spiritual leader Sri Sri Ravishankar inaugurated the AoL ashram on the outskirts of Beijing on Sunday. 

"India and China share a long tradition of wisdom and spirituality," Sri Sri said at the inauguration. 

Hundreds of Chinese devotees gathered at the event which was followed by a satsang. Representatives of Chinese Peoples Association of Friendship of Foreign Countries ( CPAFFC), a government-backed organization, attended. 

Thanking the Communist Party of China for its support, Sri Sri said: "Confucianism, Taoism, Buddhism and the Upanishads all point to the fact that peace is within us and we need to share it with everyone. China's contribution to the world has been Kung Fu and Tai Chi which ensured alertness and good health. India has contributed yoga and breathing techniques. The Art of Living's Beijing ashram will not only cater to Chinese, but will draw people from all over the world to experience their hospitality." 

PERIODONTAL ESTHETIC SURGERY

Periodontal Plastic Surgery

Introduction

The mucogingival relationship is important in sustaining the health of the gingival attachment. Mucogingival surgery is a periodontal surgical procedure used to correct defects in the morphology, position, and/or amount of gingiva.

Indications

 Gingival augmentation is used in sites with inadequate width and thickness of attached gingiva that exhibit persistent inflammation (bleeding) or progressive recession and sites with inadequate dimensions of gingiva that have subgingival restorations or orthodontics. In sites where crown margins are to be placed subgingivally, recession with exposure of the crown margins may occur when there is inadequate gingival dimensions. Other indications for mucogingival procedures include 

(1) elimination of frenum and muscle pull at or near the gingival margin (Figure 24-15),

(2) areas in which the base of a periodontal pocket extends to or beyond the mucogingival junction, 

(3) deepening of the buccal vestibule, 

(4) aesthetic reasons (e.g., to cover exposed roots), and 

(5) modifications of edentulous ridges prior to prosthetic reconstruction.

[Figure 24-15. Frenectomy: (a) Note the lack of attached gingiva on the central incisors and the high frenum attachment that was pulling on the gingival margin. (b) A frenectomy using a split-thickness flap was performed. The frenectomy cuts the frenum, allowing it to relocate further apically. (c) One month postoperative.]

Classification of Gingival Recession

The original classification of gingival recession by Sullivan and Atkins (1985) was later expanded by Miller (1985) (Figure 24-16). The Miller classification includes: I: soft tissue recession not extending to the mucogingival junction; II: isolated soft tissue recession that extends to or beyond the mucogingival junction with intact interdental papillae and no bone loss; III: soft tissue recession extending beyond the mucogingival junction with bone or soft tissue loss in the interdental area and; IV: extensive soft tissue recession and bone loss or soft tissue loss in the interdental area with malpositioned teeth.

[Figure 24-16. P. D. Miller's classification of gingival recession.]

Did You Know?

Smokers have less desirable long-term results following periodontal plastic surgery than nonsmokers.

Types of Soft Tissue Grafts

Mucogingival defects are corrected using different types of soft tissue grafts. In addition, guided tissue regeneration procedures also may be used for this purpose.

Pedicle Graft or Laterally Positioned Flap

The pedicle graft, as the name implies, is used to move gingiva from an adjacent tooth or edentulous area to a prepared recipient site on another tooth with an inadequate amount of attached gingiva. The pedicle graft is "freed" on three aspects but retains its attachment (blood supply) from its base. This procedure requires sufficient width and thickness of gingiva to be present in the donor site. There should be no underlying bone dehiscence or fenestration. The pedicle graft is best used for single-site recession for root coverage and augmentation (increasing the amount) of attached gingiva.

Technique   (Figure 24-17) A V-shaped incision is made around the recipient site. Incised tissue is removed, and root planing of the root surface is performed. A full- or split-thickness flap is elevated on the tooth away from the defect and rotated to cover the defect. The flap is sutured, and pressure is applied (this is done with all soft tissue grafts) for about 4 to 5 minutes, ensuring that no blood clot has formed under the graft. A periodontal dressing to protect the flap can be placed. If a periodontal dressing is not used, the patient should not brush the area. Postoperative instructions are given to the patient (see Table 24-1), and the patient returns one to two weeks later. At the first postoperative visit, the sutures and the dressing are removed, and the area either may be left uncovered or may be redressed for an additional week.

Table 24-1. Surgical Care Procedures

Surgical Procedure	Postoperative Care		Reevaluation Procedures
Gingivectomy	1.	Instruct patient not to brush the area where the periodontal dressing is located.	1.	Periodontal probing should not be done until a minimum of six weeks after surgery.
	2.	The area will heal by secondary intention; the wound is open and exposed because there is no flap and no sutures. This area is similar to a scraped knee or pizza burn on the palate. It will be sore.	2.	Final prosthetic restorations should not be completed until six weeks or more after surgery.
	3.	Avoid smoking, if possible.
	4.	At postoperative visit, carefully remove the dressing, irrigate with sterile water or saline and wipe off the white film (this consists of dead epithelial cells).
	5.	Reapply dressing if needed.	3.	Supragingival scaling can be done after one week, but subgingival periodontal debridement should not be performed until six weeks after surgery.
	6.	After the first postoperative visit, the patient may start to brush the teeth around the surgical site gently with a roll technique. Bleeding will occur but will gradually lessen. The patient should continue to brush even if light bleeding is seen.
Flap surgery (with or without osseous resection)	1.	Instruct patient not to brush the area where the periodontal dressing is located.	1.	Periodontal probing should not be done until a minimum of three months after surgery.
	2.	Apply ice pack.
	3.	At postoperative visit, carefully remove the dressing and sutures, irrigate with sterile water or saline and wipe off the white film (this consists of dead epithelial cells).	2.	Final prosthetic restorations should not be completed until a minimum of three months after surgery.
	4.	Reapply dressing if needed; patient may start to brush surgical site gently with a roll technique. Bleeding will occur but will gradually lessen. The patient should continue to brush even if bleeding is seen.	3.	Supragingival scaling can be done after one week, but subgingival periodontal debridement should not be performed until three months after surgery.
	5.	Avoid smoking, if possible.
Mucogingival surgery (soft tissue grafts)	1.	Instruct patient not to brush the area where the periodontal dressing is located.	1.	Gingival grafts with root coverage would be reevaluated a minimum of six months after surgery.
	2.	At postoperative visit, carefully remove the dressing and sutures at the donor site, irrigate with sterile water or saline and wipe off the white film (this consists of dead epithelial cells).	2.	Gingival grafts without root coverage can be reevaluated a minimum of two months after surgery.
	3.	Avoid smoking.
	4.	Reapply dressing if needed; patient may start to brush surgical site gently with a roll technique. Advise the patient not to hit the gums with the toothbrush. The patient should discontinue brushing if bleeding is seen and only rinse the area with warm water.

Healing   Usually, clinical healing occurs in about one month. However, complete maturation can take up to one year.

[Figure 24-17. (a) Lateral incisor with severe gingival recession with root exposure. (b) A laterally positioned flap was used to move gingiva from the right central incisor to the left central incisor. An anchor suture is around the lateral incisor. (c) Two months healing shows good root coverage and increased width of attached gingiva.]

Double Papillae Flap

The double papillae flap is a modification of the laterally positioned flap. The papillae from each side of the tooth with the defect are reflected and rotated over the midfacial aspect of the recipient tooth and sutured.

Free Gingival Soft Tissue Graft

Unlike a pedicle graft, a free gingival graft (FGG) has a donor site located away from the grafted site. Thus, the blood supply is not attached to the graft but depends on the recipient bed. The most common site for donor tissue is the palate, but in many cases, edentulous areas also can be used. Free gingival grafts are more predictable for augmentation of attached gingiva than for root coverage because significant shrinkage of the graft occurs during healing. Thicker free gingival grafts can be used for root coverage because there is less tissue shrinkage. Often, after a frenectomy a free gingival graft is placed at the site to prevent frenum reattachment.

Technique   (Figure 24-18) After local anesthesia is administered on the palate and the recipient area, split-thickness flaps are reflected at the recipient site. A piece of gingiva about 1.5 mm thick is obtained from an intraoral area. Although the most common donor site is the hard palate, edentulous areas also can be used. The donor tissue (graft) is placed on the recipient bed, and the graft is sutured in place, usually with absorbable sutures, making sure that it does not move, since this will interfere with the establishment of a blood supply from the recipient bed and the graft may fail. A periodontal dressing may be applied. Postoperative instructions are given, and the patient returns in one week (see Table 24-1). Smoking is strictly prohibited because soft tissue grafts are more likely to fail if the patient smokes. This was demonstrated by Miller (1987), where he found a 100% correlation between failure to obtain root coverage and heaving smoking. A major disadvantage of free gingival grafts is the poor color match between the graft and the existing gingiva.

Healing   The graft will swell initially, then shrinkage occurs (Figure 24-18 d). The graft receives blood and nutrients from the underlying connective tissue. Complete healing with keratinization occurs in about one month.

[Figure 24-18. (a) Mandibular central and right lateral incisors have no attached gingiva (Miller classification III) (b) A free gingival graft was harvested from the palate and (c) sutured into place at the recipient site. (d) Posttreatment healing of the grafted site. Increased width of attached gingiva was achieved. Note that root coverage was not obtained using this type of grafting procedure.]

Subepithelial Connective Tissue Graft

The subepithelial connective tissue graft is the procedure of choice for root coverage of single or multiple teeth. The subepithelial connective tissue graft was first described

by Langer and Calagna (1982) as having several advantages over the other grafts: 
(1) There is no open wound on the palate as in a free gingival graft, 
(2) the graft has a better blood supply coming from both the underlying connective tissue and the overlaying flap, and 
(3) better aesthetics and tissue and color blend are seen.

Indications   The subepithelial connective tissue graft may be used for both single and multiple adjacent teeth with gingival recession and root exposure (Chambrone & Chambrone, 2006). It is limited by the amount of donor tissue able to be harvested.

Rapid Dental Hint

The free gingival graft donor site will heal by secondary intention (open wound). It may be painful.

Technique   (Figures 24-19, 24-20) After local anesthesia is obtained, a split-thickness flap is raised at the recipient site using a surgical blade. A flap is raised at the donor site on the palate, and connective tissue is harvested while leaving the epithelium on the outside of the flap. This palatal flap is sutured into place. The connective tissue is placed on the recipient site and sutured in place with absorbable sutures. A periodontal dressing may be applied. Postoperative instructions are given to the patient, and the patient returns in one to two weeks (see Table 24-1). At one to two weeks, the dressing and

[Figure 24-19. (a) Pretreatment view of the mandibular right central incisor area. There is gingival recession and exposed root surfaces (Miller classification II). A connective tissue graft was selected to cover the root surfaces. (b) The subepithelial connective tissue graft was harvested from the palate. Incisions were made, and the epithelium was reflected. Note the vascular connective tissue underlying the epithelium. (c and d) The graft was sutured to the recipient site and the flap sutured. (e) Flap at donor site is sutured.]

[Figure 24-20. (a) Pretreatment view of the maxillary canine. Miller classification II. Gingival recession occurs beyond the mucogingival junction. The patient complained that the area was sensitive to cold and was not aesthetic. (b) Incisions made on the palate to obtain subepithelial connective tissue. This is the donor site. (c) The connective tissue graft is sutured in placed and then covered by the flap. (d) Healing at two weeks.]

sutures are removed, and the area is either left uncovered or redressed for another week.

Healing   Healing occurs through a double blood supply. Both the connective tissue from the recipient site and the overlying flap aid in healing of the soft tissue graft. Complete healing occurs in approximately one month (Figure 24-20 d).

Guided Tissue Regeneration for Root Coverage

Guided tissue regeneration (GTR) will be discussed further in Chapter 25. Essentially, GTR involves the use of a barrier membrane that is designed to prevent the gingival tissue from establishing contact with the root surface, creating a space for the formation of a new attachment and new bone rather than a long junctional epithelial attachment. This concept was intended originally for the treatment of class II buccal furcation defects and certain infrabony defects. A newer application is for the treatment of gingival recession and for root coverage (Pini Prato et al., 1992).

Alloderm^® is a biomaterial that is processed from human tissue. The process removes all epidermal and dermal cells (acellular dermal matrix), while preserving the remaining biological dermal matrix. All cells are removed to remove the risk of rejection or inflammation. This material is indicated for recession defects and for periodontal sites that have little to no attached gingiva where the goal is to increase the amount of keratinized/attached gingiva and to obtain root coverage (Gapski, Parks, & Wang, 2005; Tal, Moses, Zohar, Meir, & Nemcovsky, 2002).

AlloDerm is used in a similar way that a tissue graft from the patient's mouth (e.g., free gingival graft or connective tissue graft) is used except there is no harvesting of donor tissue (e.g., palatal tissue) and thus less pain is involved. At the time of surgery, AlloDerm is rehydrated in sterile saline before it is sutured in place on the recipient bed. AlloDerm acts like a scaffold to support regeneration of the patient's own tissue. Six to eight months postsurgery, AlloDerm becomes integrated into the patient's own soft tissue. A surgical case using AlloDerm is presented in Figure 24-21.

A clinical study showed that treatment with a coronally positioned graft plus AlloDerm significantly increased gingival thickness when compared with a coronally positioned flap alone. Coverage of a recession defect was significantly improved with the use AlloDerm (Woodyard et al., 2004).

Technique   After local anesthesia is obtained, a full-thickness flap is raised at the recipient site. Root planing is completed on the root surface. A barrier membrane is placed over the recession and bone and sutured. The flap is positioned coronally covering both the membrane and the enamel. If the membrane is resorbable, it is not removed and will resorb in about six to eight weeks after surgery. The flap sutures are removed after two to four weeks. Patients should not brush the area for at least six weeks and are recommended to rinse with chlorhexidine gluconate.

[Figure 24-21. (a) Preoperative view of the mandibular right quadrant. Note the gingival recession (Miller Classification I). (b) Flap reflected exposing underlying bone. (c) Placement of AlloDerm at recipient site. Flap sutured in place, covering the AlloDerm. (d) Three weeks post-op. Note the root coverage obtained.]

PERIODONTAL REGENERATION

Top of Form

Principles of Periodontal Surgery: Periodontal Regeneration - 

Introduction

The goals of periodontal therapy have long included arresting the disease process, preventing disease recurrence, and providing for the regeneration of periodontium lost as a result of the disease. Over the past four decades, great strides have been made in the field ofperiodontal regeneration. Periodontal regeneration is defined as healing after periodontal surgery that results in the reconstruction of lost tissues, including supporting alveolar bone, cementum, and a functionally oriented periodontal ligament (American Academy of Periodontology, 2001). Guided bone regeneration is defined as healing after periodontal surgery that results in the formation of only new bone and includes use of a barrier membrane. This procedure is usually performed to increase the height or width of bone before implant placement. This chapter provides a review of the various regenerative therapies and materials currently in use today (Box 25-1). Future directions in this ever-changing field also will be discussed. Techniques currently in use include open flap debridement, the use of bone grafts and bone substitutes, guided tissue regeneration, combination techniques, and root surface treatment, and the use of biomimetics and growth factors.

Box 25-1   Procedures Used to Enhance Periodontal Regeneration

• Bone and bone substitute grafting to fill the periodontal defect

• Prevention or retardation of junctional epithelial downgrowth and selective cell repopulation: Guided tissue regeneration (GTR)

• Guided bone regeneration (GBR)

• Acid conditioning of the root surface

• Application of enamel matrix protein derivatives

• Growth factor application to promote specific cell proliferation

Periodontal Regenerative Surgery

Objectives

Once inflammation of the gingiva is resolved with initial therapy (e.g., periodontal debridement and oral hygiene self-care instruction), the periodontitis component still must be treated. Periodontitis is characterized by apical migration of the junctional epithelium resulting inperiodontal pocket formation, loss of clinical attachment (connective tissue fibers attached to the tooth surface), and alveolar bone loss.Periodontal tissue regeneration involves surgery using bone grafts, bone substitute materials, and/or barrier membranes and modulators of tissue healing are aimed at regenerating the periodontal attachment apparatus lost due to periodontitis .

The primary goal of regenerating lost attachment is the preservation of the natural tooth. Secondary goals of using such bone-replacement materials as bone grafts and bone substitutes in infrabony defects include the following: (1) a reduction in probing depths, (2) a gain in clinical attachment level (this refers to a reduction in probing depth caused by decreased penetration of the probe at the base of the pocket), (3) filling of the osseous defects with new bone, and (4) regeneration of new supporting alveolar bone, new cementum, and a functionally oriented periodontal ligament . The latter can only be determined by histologic examination of the healed periodontal tissues.

Regenerative surgery significantly differs from osseous resective procedures, in which the osseous (bony) walls are removed surgically to eliminate the intraosseous component of the defect. Often, the morphology of the defect requires the removal of too much bone to obtain complete elimination of the defect (parabolic interdental bone), which would further compromise the affected tooth. Periodontalregenerative surgery involves "adding" bone (bone fill) into the intraosseous defect instead of its removal. Certain bony defects are more amenable to regeneration than others (Table 25-1). The type of periodontal defects that respond best to the use of bone grafts include three-wall, two-wall, and combination-type intraosseous defects. This is because the remaining bony walls contain and hold the bone graft in the defect. The depth and width of these infrabony type defects influence the amount of bone and connective tissue attachment gain. For example, an infrabony defect that is deep and narrow will most likely achieve better regeneration than a defect that is deep and wide . Moreover, the additional surrounding bony walls provide more surface area upon which bone can form. Horizontal patterns of bone loss, loss of buccal or lingual plates of bone, and furcation defects cannot be treated predictably with bone graft and bone substitute materials alone. Furcation defects are more predictably treated with GTR. Class II buccal furcation defects on the mandibular molars are most predictable types of furcation defects for periodontal regeneration.
Table 25-1. Bony Defects: Response to Regeneration


Defects That Heal Best After Regeneration 
Three-wall infrabony defect                        

Class II buccal furcation involvement on mandibular molars                                                      

Deeper bony defects (deeper than 3 mm)

Defects with a Lower Chance for Regeneration

One-wall infrabony defect

Class III furcation involvement

Shallower bony defects

Rapid Dental Hint
To diagnosis an infrabony defect, the clinician must probe the area and evaluate the radiographs.

The following are different types of regenerative techniques.

Rapid Dental Hint

Remember that an "infrabony" defect is the generic term used for a vertical defect in the alveolar bone while an "intrabony" defect is a special type of three-wall defect with cancellous bone between the cortical lining and the cortical plate.

Rapid Dental Hint

Class II buccal furcation defects and three-wall vertical bony defects are most amenable to regenerative procedures.

Surgery: Open Flap Debridement

As a surgical technique, open flap debridement (OFD), in which a flap is reflected and the roots and pocket area are debrided without the addition of any bone or bone substitute material, has been used primarily as a control for comparison in assessing other treatment modalities (Laurell, Gottlow, Zybetz, & Persson, 1998). In most histologic studies, open flap debridement resulted in repair rather than regeneration of periodontal tissues. A greater recurrence of probing depth over time has been shown with open flap debridement alone when compared with traditional osseous resective procedures. A review of the literature shows that OFD results in an average clinical attachment level gain of 1.5 mm and average bone fill of 1.1 mm .

Surgery: Bone Grafts and Bone Substitutes

Bone grafts and their substitutes are classified into four categories: autografts, allografts, alloplasts, and xenografts. Bone graftsrefer to naturally occurring autografts and allografts . Despite the benefits of autografts and allografts, the limitations of each have necessitated the pursuit of alternatives. Many of these alternatives, or bone substitutes (also referred to as bone replacement materials), can be synthetic (manufactured, not naturally occurring) materials (alloplasts), including natural and synthetic polymers and ceramics or natural and recombinant growth factors  or materials processed from the bone of other species (xenografts). Table 25-2 describes the different types of bone graft materials.

table 25-2. Types of Bone Grafts/Bone Replacement Materials
Name	Features
Autografts	Bone harvested from one part of the body and grafted to another part of the same patient's body. The bone can be obtained from an intraoral site such as the maxillary tuberosity area, edentulous area, chin, ramus, healing extraction site, or mandibular torus during implant placement or an extraoral site (e.g., tibia, femur). Osteogenic
Allografts	Bone material obtained from other individuals of the same species but genetically different. Donors include human cadavers. Allografts are obtained from bone banks. The main forms of bone allografts used in clinical practice are demineralized freeze-dried bone (DFDBA) and freeze-dried bone (FDBA). Osteoinductive
Alloplasts	Made of biocompatible, inorganic, inert materials including synthetic hydroxyapatite, calcium sulfate, bioactive glass, and tricalcium phosphate. Osteoconductive
Xenografts	A type of natural bone substitute derived from a genetically different species (e.g., bovine). Osteoinductive

Autografts (Autogenous Grafts)

Autogenous bone is living bone derived directly from the patient's own body. This has shown the best potential of any of the bone fill material for periodontal regeneration and bone fill. This bone is often mixed with the patient's blood. However, when a sufficient amount of bone is not available intraorally, or if the patient does not want bone obtained from extraoral sites such as the hip, other materials must be considered. Autogenous bone has long been considered to be the gold standard of grafting materials in terms of stimulating new bone formation.

A bone blend is a mixture of cancellous and cortical bone. When cortical bone is mixed with the patient's blood, it becomes an osseous coagulum.

Allografts (Allogeneic Grafts)

Allografts such as demineralized freeze-dried bone (DFDBA) obtained from human cadavers have demonstrated bone-forming properties. Bone allografts are obtained from bone banks. The issue of safety (e.g., nontransmission of hepatitis, HIV, and other known diseases) when using allografts has been well established, thus minimizing this factor as a concern (Marx & Carlson, 1993; Mellonig, Preuett, & Moyer, 1992). Controlled clinical studies have shown greater bone fill in sites treated with DFDBA than in nongrafted controls, with DFDBA reporting a mean bone fill of 2.6 mm (65% defect fill) compared with 1.3 mm (30% defect fill) in nongrafted controls (Mellonig, 1984). A recent review of the literature concluded that both autogenous bone and DFDBA support the formation of a new attachment apparatus (Reynolds, Aichelmann-Reidy, Branch-Mays, & Gunsolley, 2003).

Alloplasts (Alloplastic Grafts)

Alloplastic bone substitutes are manufactured synthetic materials. They are classified as implant material. Alloplasts (implants) are differentiated from grafts, which are defined as "any tissue or organ used for implantation or transplantation" (Hallmon, Carranza, Drisko, Rapley, & Robinson, 1996). Advantages of alloplasts include zero risk of disease transmission as compared with allografts and no additional surgical sites required in the mouth or body to harvest bone (as with autografts). However, alloplasts are not as effective in forming bone as are graft materials. Alloplasts are inert (nonliving) materials acting as a bone "filler" in the defect, and when effective, they act as a scaffold for bone to form around them. (Osteoconductive)

Rapid Dental Hint

Bone grafts and substitutes are indicated for infrabony (vertical) defects, and not for sites with horizontal bone loss.

A number of alloplastic materials have been introduced in an attempt to create a readily available material for bone fill of infrabonyperiodontal defects. Synthetic alloplasts may be divided into ceramic and nonceramic categories. These may be further divided into absorbable and nonabsorbable materials. Absorbable materials will absorb or dissolve (it may take years) and be replaced with new bone, whereas nonabsorbable grafts may never absorb. Ceramic alloplasts are materials that include calcium phosphate such as hydroxyapatite and tricalcium phosphate. The most commonly used ceramic materials are nonporous hydroxyapatite, porous hydroxyapatite, and tricalcium phosphate. Frequently, these materials result in a repair that evidences a long junctional epithelium to the root surface and/or adhesion of connective tissue fibers oriented parallel to the root (Yukna, 1993).

Bioactive glass is another type of alloplast. In a clinical study of the treatment of infrabony periodontal defects, a bioactive glass showed significant clinical superiority in gain of clinical attachment and defect fill compared with sites that were treated with open flap debridement alone (Froum, Weinberg, & Tarnow 1998). Bioactive glass particles contain silicon dioxide, sodium oxide, calcium oxide, and phosphorus pentoxide. Advantages of this material include the ability to bond to both hard and soft tissue (Hench, 1988), its cohesiveness (Hench & West, 1996), and its ability to inhibit the apical migration of junctional epithelium (Fetner, Martigan, & Low, 1994). One human histological study showed the clinical improvement to be a repair rather than a regenerative response (Nevins et al., 2000).

While many of these materials serve as scaffolds or fillers that allow bone from the surrounding area to grow over and into them, to date alloplasts have failed to demonstrate human histologic evidence of new cementum and a functionally oriented periodontal ligament. From a clinical standpoint, these materials appear to be biocompatible, nontoxic, nonallergenic, noncarcinogenic, and noninflammatory.

Xenografts (Xenogeneic Grafts)

Heterografts or xenografts are taken from a donor of another species. Bio-Oss (Osteohealth Co., Shirley, NY) and Osteograf/N (CeraMed Dental, Lakewood, CO) are types of natural bone mineral obtained from the cow (bovine). This bone is anorganic and deproteinated. A histological study showed that Bio-Oss used in periodontal osseous defects has the potential to regenerate lost periodontal support (Camelo et al., 1998). The safety of these materials has also been demonstrated in regard to causing mad cow disease.

Properties of Bone Grafts and Bone Substitutes

Bone grafts and bone replacement materials are divided into their properties of osteogenesis, osteoinduction, and osteoconduction. Osteogenic bone contains bone cells called osteoblasts that make new bone and obtain a bone fill in the defect. Autogenous bone (e.g., bone from the host—intraoral or extraoral) is an example of osteogenic bone and it is considered the gold standard that bone alternatives must meet. Autogenous bone directly lays down new bone during wound healing after it is placed in the periodontal defect. This is ideal; however, there are many limitations to autogenous bone including limited amounts obtained and donor site morbidity.

Osteoinductive agents are bone grafts and bone graft substitutes, generally proteins, which induce the transformation of immature stem cells into bone-producing osteoblasts which make new bone through growth factors that are found only in living bone (Fox, 1997). This bone does not contain osteoblasts as autogenous bone. Examples of osteoinductive agents include demineralized freeze-dried bone (DFDBA) from cadavers, bone morphogenic proteins (BMPs), and growth factors (platelet derived growth factor).

This differs from alloplastic grafts, which, when placed into a periodontal defect, at best function as osteoconductive material. In these situations, the alloplastic graft acts as a scaffold or framework to allow bone cells from the surrounding bone in the defect to lay down bone against its surface. Additionally, the porous surface of the graft material provides for bone in growth from bone adjacent to the bone material. Such osteoconductive materials require the presence of existing bone, and the more bone there is (greater number of bony walls in an intraosseous defect), the greater is the chance of a successful bone fill (Fox, 1997). These materials are not osteoinductive and do not produce new bone. The size and shape of the bone substitute particles influence their osteoconductive capacity. Eventually, the particles of material are either replaced by bone growing over them or incorporated into the new bone.

Biologics and Devices

Biologics is a rapidly developing field that is generating new clinical studies. Wound healing is a complex, well-orchestrated sequence of events. In studying the dynamics of cell-to-cell and cell-to-tissue interaction, scientists discovered the presence of growth factors. Attempts have been made to use these factors to enhance wound healing (repair and regeneration).

Growth factors are naturally occurring proteins that mediate or regulate cellular events such as cell proliferation. Growth factors are found only in living tissue in cells such as bone, platelets, and macrophages. The most widely studied growth factor has been platelet-derived growth factor (PDGF). Platelet derived growth factor is a potent wound healing growth factor and stimulates the proliferation and recruitment of periodontal ligament cells and bone cells. The incorporation of PDGF in bone allograft (product is available as GEM21—Osteohealth, NY) may induce periodontal regeneration during wound healing when placed in a periodontal defect .


Other proteins called bone morphogenic proteins (BMPs) are normally found in bone and can induce new bone formation. Recently a bone graft material composed of recombinant (genetically manufactured) BMP-2 and a bovine collagen sponge (available as Infuse Bone Graft—Medtronic, TN) has been used in periodontal defects to stimulate bone formation in the bony defect.

There are still questions about the concentration of growth factors when they are used by themselves or in combination with other factors. The variability of growth factor responses locally and systemically is still unknown (Nevins, et al., 2007).

Another material referred to as enamel matrix proteins (amelogenins) are retrieved from the developing teeth in pigs (porcine). This product, Emdogain (Straumann, Switzerland, Chicago), is used in periodontal regenerative techniques. Clinical studies have shown improved clinical results and gain in clinical attachment and bone fill in sites treated with Emdogain versus open flap debridement (Froum, Weinberg, Rosenberg, & Tarnow, 2001). Multicenter studies have been performed with this material and verify the safety of multiple uses in the same patient (no allergies or immunologic problems) (Froum, Weinberg, Novak, Mailhot et al., 2004). After flap reflection and debridement, EDTA (ethylenediaminetetraacetic acid) is applied to the root surface to remove the smear layer. This is then washed off with sterile water or saline. Emdogain is applied to the root surface which promotes attachment of certain cells that will eventually encourage the formation of cellular cementum and bone. Emdogain is available in a premixed, one-vial preparation. After flap reflection and debridement of the infrabony defect, Emdogain is syringed onto the root surface and the flap is sutured.

Bone Grafts and Bone Substitutes: Surgical Procedure

For bone grafting, intracrevicular incisions are made, and a gingival flap is reflected. The root surface and osseous defect are debrided to remove all granulomatous (diseased) tissue (Table 25-3). A combination of power-driven and hand instruments is commonly used to ensure that all calculus and plaque as well as altered cementum are removed from the root surface (Brunsvold & Mellonig, 1993). The defect is filled and packed with bone or a bone replacement material. The flap is replaced and sutured in an attempt to fully cover the material (Figures 25-1, 25-2, 25-3). A periodontal dressing may be placed if desired. The patient returns seven to fourteen days later for suture removal, light debridement, and oral hygiene instruction during the first postoperative visit.

Rapid Dental Hint

Many bone materials are either mixed with the patient's blood or sterile saline before it is placed in the defect. Some products such as Emdogain are already premixed.

Figure 25-1. (a) A 6-mm combination one-two-three-wall intraosseous defect on the mandibular second molar. (b)After flaps are reflected and the roots and defect thoroughly debrided, demineralized freeze-dried bone autograft (DFDBA) (c,d) was placed into the defect and the flap sutured to cover the bone (e).

Figure 25-2. (a)A 9-mm intraosseous periodontal defect is present on the mesial aspect of the maxillary cuspid.  (b) Following reflection of a periodontal flap and defect and root debridement, a bone blend is mixed consisting  of autogenous bone and the patient's blood and (c) placed into the defect.  (d) The replaced flap is sutured with silk sutures to cover the graft material.

Figure 25-3. (a) Probing between the mandibular second premolar and first molar. 
(b) Probing of the deep defect after flap reflection. 
(c) After thorough tooth and root debridement, Perioglas^® was placed into the defect and the flaps were sutured with silk sutures to cover the graft material. 
(d) Flap sutured with interrupted sutures. 
(e) Reentry of the site six months later shows that the bony defect has been filled in with new bone (also there is slight crestal resorption). The interproximal bone is flat, not cratered. Compare with Figure 25-3 b.

Guided Tissue Regeneration

Cells Involved in Regeneration

The periodontal unit can be divided into five tissue components: the gingival epithelium, the gingival connective tissue, the periodontalligament (PDL), the supporting alveolar bone, and cementum. In 1976 it was theorized that the type of tissue that predominates in the healing wound after periodontal surgery determines whether the response is either repair (e.g., long junctional epithelial attachment or connective tissue adherence) or regeneration (e.g., new bone, new cementum, and new periodontal ligament) (Melcher, 1976; Zeichner-David, 2006).

Did You Know?

Hydroxyapatite for bone grafting comes from coral from the ocean.

Epithelium is the fastest growing tissue, migrating at a rate of 0.5 to 1.0 mm per day. A periodontal wound in which unimpeded epithelial migration is allowed to occur results in repair with a long junctional epithelium. This type of healing occurs after open flap debridement and osseous resective surgical procedures. Regeneration does not occur when either gingival (junctional) epithelium or gingival connective tissues (e.g., tissue inside the flap) contact the root surface during healing. In order for regeneration to occur, cells capable of forming new cementum, PDL, and supporting alveolar bone must migrate into the periodontal osseous defect and produce these tissues. It is believed that these cells come from the PDL (osteoblasts, fiberblasts, and cementoblasts) and/or alveolar bone remaining around the tooth (Melcher, McCulloch, Cheong, Nemeth, & Shiga, 1987). In order for these cells to migrate into the periodontal defect, apical epithelial migration must be delayed, and the gingival connective tissue from the gingival flap must be excluded. If the flap makes contact with the tooth surface, a long junctional epithelium forms along the root and may prevent the necessary regenerative cells from gaining access to the periodontal defect. This concept led to the theory of selective cell repopulation or guided tissue regeneration(GTR) (Gottlow, Nyman, Karring, & Wennstrom, 1986; Nyman, Gottlow, Karring, & Lindhe, 1982).

This concept has been the basis for clinical techniques using barrier membranes inserted between the gingival flap and the root surface. The membrane maintains a "space" between the tooth and the flap. This procedure is designed to retard apical migration of the junctional epithelium and exclude the gingival connective tissue cells from making contact with the root surface and defect. This then allows cells originating from the PDL space and/or alveolar bone cells to migrate coronally into the defect to form new bone, cementum, and attachment (Figure 25-4).

Figure 25-4. Schematic illustration of a guided tissue regeneration procedure. 
(a) The periodontal defect with the junctional epithelium on the root surface. 
(b) After a flap is raised and the defect debrided, a barrier membrane is placed over the defect to create a space for the defect to heal. The periodontal ligament and bone cells attempt to migrate coronally (arrows) into the defect to produce new cementum, periodontal ligament, and supporting alveolar bone. The flap is then sutured over the membrane covering it. 
(c) Healing by regeneration. (d) The result of therapy after healing.


Surgical Procedure

Barrier membranes have been used in the treatment of Grade II buccal furcation defects in both maxillary and mandibular molars and in two- and three-wall interproximal infrabony periodontal defects as well as for guided bone regeneration (GBR) applications. Optimal results are obtained in patients who are healthy nonsmokers who demonstrate good oral home care.

Clinically, GTR techniques are performed by making intrasulcular incisions and full-thickness flap reflection. Following debridement of theperiodontal defect and the root surface, a membrane barrier is placed on the tooth so as to cover the periodontal bony defect (Figures 25-5, 25-6). The membrane is situated between the inner flap and the tooth and bone. The flap is sutured so that the membrane is fully covered and not exposed to the oral cavity. Frequently, a bone graft is first placed into the periodontal defect to prevent the membrane from collapsing into the defect and to aid in regeneration.

Figure 25-5. Bone + membrane: infrabony defect on the canine. Flaps are reflected and surgical debridement performed until the defect is visualized. Bio-Oss is placed into the defect and BioGide placed on top of the bone graft. Then the flaps are sutured to cover both the   bone and membrane.

Figure 25-6. Mandibular right quadrant: initial incisions on the buccal (a) and lingual (b). (c) Full-thickness flap is reflected showing circumferential bony defects (bone destruction from the interproximal to the lingual surface) and furcation involvement. (d) After debridement, the bony defects are grafted with DFDBA (demineralized freeze-dried bone) and (e) an absorbable membrane is sutured over the defect. (f) The flaps are sutured. (g) One week postoperative; sutures removed and (h) four weeks postoperative with the membrane still in place. (Courtesy of Dr. James B. Fine, Columbia University College of Dental Medicine)




Types of Barrier Membranes

Nonabsorbable Membranes

Membranes are classified as nonabsorbable or absorbable. Nonabsorbable membranes were the first to be used and studied clinically. Since the body does not absorb (degrade) a nonabsorbable membrane, it has to be removed. A second surgical procedure, therefore, is performed a minimum of six to eight weeks later to remove the barrier. The most commonly used nonabsorbable barrier membrane is expanded polytetrafluoroethylene (e-PTFE). Examples of an e-PTFE membrane are Gore-Tex^® and Gore-Tex^® Regenerative Membrane Titanium Reinforced, in which the titanium enhances the space creating ability of the membrane (Gore Associates, Flagstaff, AZ). Similar nonabsorbable barriers are TefGen-FD™ and TefGen-RE™ (Lifecore Biomedical, Chaska, MN), which are less porous than Gore-Tex^®, and thus may limit the amount of connective tissue ingrowth.

Most studies using nonabsorbable membranes in infrabony defects showed positive results. Over the past two decades, studies of infrabony defects in human beings treated with e-PTFE barriers showed definitive clinical gains in new attachment, with three-wall defects having the greatest improvement (Gottlow et al., 1986). A twelve-month study of one-, two-, and three-wall infrabony defects treated with e-PTFE barriers showed a 93% fill of three-wall defects, an 82% fill of two-wall defects, and a 39% fill of one-wall defects (Cortellini, Pini Prato, & Tonetti, 1993a, 1993b).

Absorbable Membranes

Absorbable membranes appeared half a decade after nonabsorbable membranes. These membranes have various compositions, including collagen (Bornstein, Bosshardt, & Buser, 2007). Absorbable membranes offer a distinct advantage over nonabsorbable barriers in that there is no need for a second surgery to retrieve the membrane. Macrophages, a type of phagocyte, are always involved in the degradation process. The barrier must remain in place a minimum of three to four weeks (Minabe, 1991) for proper wound healing. Several membranes are available commercially.

Table 25-4. Absorbable Barrier Membranes
Material		Product	Manufacturer
Synthetic: Polyglycolic acid, polylactic acid, and trimethylene carbonate		Gore OsseoQuest	W.L. Gore, Flagstaff, AZ; distributed by Nobel Biocare, Yorba Linda, CA
		Gore Resolut XT	W.L. Gore
Synthetic: Polyglycolic acid and trimethylene carbonate		Gore Resolut Adapt	W.L. Gore, Flagstaff, AZ; distributed by Nobel Biocare, Yorba Linda, CA
		Gore Resolut Adapt LT
Synthetic: PLA (poly-DL-lactide)		Epi-Guide	Curasan Inc., NC
		Atrisorb FreeFlow	Tolmar, Fort Collins, CO
		Atrisorb-D FreeFlow (with 4% doxycycline)	Tolmar
Natural: Collagen	(bovine)	BioMend	Zimmer Dental, Carlsbad, CA
	(bovine)	BioMend Extend	Zimmer Dental
	(porcine)	BioGide	Geistlich, Switzerland; distributed by Osteohealth Company, Shirley, NY
	(bovine)	OsseoGuard	Biomet 3i, Warsaw, IN
	(porcine)	Ossix Plus	OraPharma, Warminster, PA

The general consensus seems to be that furcation closure in a horizontal dimension is better with absorbable membranes (Garrett, 1996). The clinician must choose the appropriate barrier for the appropriate defect. Although nonabsorbable barriers do not have breakdown products that can interfere with tissue healing, the need for a second procedure to remove the membrane is a distinct disadvantage to wound healing.

The membrane should be covered completely by the flap to prevent bacterial colonization on the outer part of the membrane. Membrane exposure may lead to early infection and poor results. Unfortunately, membrane exposure to the oral cavity occurs with both barrier types. Tissue management when membrane exposure occurs with nonabsorbable barriers may be a problem. Bacteria from the oral cavity may contaminate the exposed membrane by attaching to it. If complete flap closure is not possible, absorbable membranes may be the best choice.

Although GTR using nonabsorbable and absorbable membranes has revolutionized clinical practice, the technique is not as yet predictable for class II, class III, and horizontal bone defects. More research in regeneration of furcation and interproximal defects is needed.

Barrier membranes need to be secured around the tooth to hold them in place and prevent them from moving. Either sutures or bone tacks can be used to attach and immobilize the membrane. A mallet is used to secure the tacks in place. The bone tacks are either stainless steel or titanium. Most are nonabsorbable, thus a second surgery is needed to remove the tacks. Osteo-Pin (Osteohealth, Shirley, NY) is a bioabsorbable fixation pin that does not need to be removed.

Several bacteria, including A. actinomycetemcomitans and P. gingivalis, have been shown to attach to bioabsorbable membranes, which could cause a bacterial infection. Additionally, these bacteria produce and release proteolytic bacterial enzymes that may take part in the degradation of collagen barrier membranes such as Bio-Gide and Biomend (Sela et al., 2003).

Rapid Dental Hint

Do not probe or do subgingival scaling for at least six months in areas that have a bone graft or barrier membrane placed either around a tooth or implant.

Regenerative Surgery: Postoperative Care

The patient's oral home care is of utmost importance for a desirable outcome. The dental hygienist should provide the patient with thorough home care instructions. Guidelines for postoperative care are outlined in Table 25-5 (Becker & Becker, 1993; Garret & Bogle, 1993; Yukna, 1993). An antimicrobial mouthrinse such as chlorhexidine gluconate may be prescribed. The patient may be prescribed an antibiotic before and after the surgery to prevent infection. The first postoperative visit is within seven to fourteen days.

Table 25-5. Periodontal Regenerative Surgery: Postoperative Care

Surgical Procedure	Postoperative Home Care	In-Office Reevaluation Procedures
Bone grafting	• If a periodontal dressing is placed, instruct the patient not to brush the area. Instruct the patient to rinse with 0.12% chlorhexidine gluconate twice a day.     • Following suture removal the patient may start to brush (soft or ultrasoft brush) surgical site gently with a circular technique. Bleeding may occur but will gradually lessen, and the patient should continue to brush.     • If an antibiotic was prescribed, instruct the patient to continue until all medication is finished.	• At the postoperative visit (seven to fourteen days), carefully remove the dressing (cut sutures if embedded in dressing), wipe off the white film (this consists of dead epithelial cells); and irrigate the area with sterile water or saline.     • Reapply dressing if needed (especially if sutures and dressing are removed before ten days).     • Periodontal probing should not be done prior to six months after surgery.     • Final prosthetic restorations should not be completed until six months or more after surgery.     • Initial appointments for professional plaque removal should be every two to three weeks for the first month, then every month for four visits, followed by every three months (alternate with visits to the general dentist).
Guided tissueregeneration	• A periodontal dressing is usually not placed. Instruct the patient not to floss or brush around the surgical area for six weeks after the surgery. However, a soft or ultrasoft toothbrush may be used for coronal brushing of the surgical area.     • Rinse with 0.12% chlorhexidine gluconate twice a day, and use cotton swabs saturated with chlorhexidine around the surgical area.     • Instruct the patient to continue to take the prescribed antibiotic until finished.	• At the first postoperative visit (one to two weeks), the surgical area is inspected.     • The patient should be seen every two to three weeks for supragingival scaling and tooth polishing with sterile water.     • Between four and six weeks, the membrane-attached sutures are removed.     • At 8 to 12 weeks, an incision is made to remove the nonabsorbable membrane.     • Periodontal probing should not be done prior to six months after surgery.     • Final prosthestic restorations should not be completed prior to six months after surgery.

Professional maintenance and plaque control have been repeatedly shown to correlate with successful clinical results of regenerative therapies including open flap debridement (Froum et al., 1982; Nyman, Lindhe, & Rosling, 1977;

Rosling, Nyman, & Lindhe, 1976), bone grafting (Rosen, Reynolds, & Bowers, 2000), and guided tissue regeneration (Cortellini, Pini Prato, & Tonetti, 1994). The hygienist thus plays a key role in the short-and long-term success of regenerative therapy.

Complications can occur during the healing period after GTR surgery

Table 25-6. Complications After Periodontal Regenerative Surgery
Complication	Procedures to Follow
Membrane becomes uncovered	Instruct the patient to call the office. Most often the membrane will become exposed within a few weeks after surgery. If there is no infection, instruct patient to keep optimal oral hygiene. Monitor the area. Instruct the patient not to disrupt the membrane. Bacteria associated with exposed membranes include A. actinomycetemcomitans and P. gingivalis. Aggressive antimicrobial therapy may be necessary, including chlorhexidine mouthrinses and antibiotics such as metronidazole alone or combined with amoxicillin.
Gingival recession at the surgical site	If recession occurs, it will usually happen within one to three weeks after surgery. Since increased plaque accumulation may result, optimal plaque control is stressed.
Pus	If an infection develops, it is most likely at the fourth and fifth postoperative visit. Remove the membrane and place the patient on an antibiotic. If the patient is already on an antibiotic, change to another antibiotic in a different classification.

Root Surface Treatment

Animal studies have shown that the root surface becomes contaminated by bacteria, bacterial by-products, and endotoxins that will prevent connective tissue attachment and regeneration (Garrett, 1977). The classic method of scaling and root planing, while effective in removing endotoxins from the root (Smart, Wilson, Davies, & Kieser, 1990), in most cases will not result in new connective tissue attachment, but rather a long junctional epithelium. Use of an acid solution such as citric acid or tetracycline HCl has been studied to determine if a new connective tissue attachment results. The proposed purposes of using acidic solutions on contaminated root surfaces are to detoxify the root and expose collagen fibers for a connective tissue attachment. However, two recent reviews ofperiodontal regeneration studies with and without the use of citric acid root conditioning showed no clinical advantage to its use (Garrett, 1996; Mariotti, 2003).

Risk Factors for Regenerative Therapy

The same contraindications for any surgical periodontal therapy apply to regenerative therapies. These include any acute or chronic uncontrolled systemic diseases that put the patient at risk (e.g., diabetes mellitus), inadequate plaque control, and smoking (especially more than one pack per day). Smoking has been shown to have a negative influence on the results of regenerative therapy. Using GTR therapy, smokers had less than 50% gain in attachment levels compared to results in nonsmokers (Tonetti, Pino Prato, & Cortellini, 1996). Of the failures with GTR, the majority (80%) occurred in smokers (Rosenberg, Dent, & Cutles, 1984).

Dental Hygiene Notes

Today, the role of periodontics in dentistry focuses not only on arresting the progression of inflammatory periodontal diseases but also on the regeneration of periodontal structures (cementum, PDL, supporting alveolar bone) that were destroyed by disease. Periodontalregenerative therapy uses bone replacement materials and guided tissue regeneration (GTR) techniques. The use of growth factors (e.g., bone morphogenic proteins, platelet-derived growth factor, and tissue modifiers) holds great promise. These factors most likely will be the next addition to periodontal regenerative techniques.

Key Points

• Periodontal regeneration is defined as healing after periodontal surgery that results in the reproduction of cementum, PDL, and supporting alveolar bone that was lost or destroyed by periodontal diseases.

• Ideally, after periodontal surgery, healing by regeneration is preferred over repair.

• Periodontal regenerative techniques include the use of bone grafts, synthetic bone substitutes, guided tissue regeneration (GTR), and a combination of these.

• Bone-replacement materials may contribute to new bone formation or serve as a filler material for bone formation that starts from the adjacent bone and grows into the defect.

• GTR is used to delay apical migration of the junctional epithelium and exclude gingival connective tissue (inner flap) from the surgical site. The goal is to allow periodontal regenerative cells to repopulate the wound first.

• A barrier membrane is placed over the osseous defect and root to create a space for the migration of cells from the PDL and alveolar bone to repopulate the wound.

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