endodontic and periodontal regeneration

Endodontic and Periodontal Regeneration

Mohammed Jumaa

Endo-Perio continuum………………………………………... Pathways of communications between the dental pulp and the periodontium..

Effect of endodontic disease on the periodontium………………………………...

Effect of periodontal disease on the pulp…………………………………………..

Effect of the occlusion on the periodontium and the pulp……………………….

Classification of Endodontic-Periodontic Lesions………………………………..

Periodontal and Endodontic Regeneration………………….. Membranes……………………………………………………………………………..

Growth factors…………………………………………………………………………

Graft associated regeneration……………………………………………………….

References……………………………………………………...

1

Endodontic and Periodontal regeneration 1

Endo-Perio continuum

Pathways of communications between the dental pulp and the periodontium1

The dental pulp and periodontal tissues are intimately related.

The pulp originates from the dental papilla and the PDL from the dental follicle.

They are separated by Hertwig’s epithelial root sheath.

As the tooth matures and the root is formed, three main avenues of communication between the

dental pulp and the periodontium are formed:

1- Dentinal tubules.

2- Lateral and accessory canals.

3- The apical foramen

Dentinal tubules:

Cementum acts as a protective barrier, but direct communication may be established between the

pulp and the periodontium via patent dentinal tubules if the cementum is missing.

The cementum may be missing as a result of developmental defects, disease processes or

periodontal or surgical procedure.

Recognizing the anatomy of patent dentinal tubules and the changes caused by age or periodontal

treatment is essential to the understanding of permeability of root dentin, as well as clinical

conditions as dentin hypersensitivity.

Dentin exposure plays an important role when assessing the progression of endodontic

pathogens, as well as the effect of scaling and root planning on cementum integrity, trauma and

chemically induced pathosis.

Other possible dentinal communication may be through developmental grooves both

palatogingival and apical.

Lateral and accessory canals:

Lateral and accessory canals can be present anywhere along the root, and their incidence and

location have been well documented.

It is estimated that up to 40% of all teeth have lateral and accessory canal mostly found in the

apical third of the root.

De Deus reported that 17% of the teeth examined presented lateral canals at the apical third of

the root, 9% in the middle third and less than 2% in the coronal third. 2

2


Kirkham examined 1000 human teeth with extensive periodontal disease and found only 2% of

lateral canals associated with the corresponding periodontal pocket. 3

It appears that under usual clinical conditions predictable identification of lateral and accessory

canals on the basis of radiographic interpretation may be accomplished only in a very small

number of cases.

However, several clinical aids may be helpful for their identification:

1- A radiographic image of a discrete lateral lesion associated with necrotic pulp.

2- Radiographic identification of a notch on the lateral root surface suggesting the presence

of an orifice.

3- Demonstration of root canal filling material or sealer extruding through the patient

orifices.

Apical foramen:

The apical foramen is the principal route of communication between the pulp and periodontium.

Infectious and inflammatory byproducts of a diseased pulp may permeate readily through the

apical foramen resulting in periodontal pathosis.

The apical foramen may also be a portal of entry of inflammatory elements from deep

periodontal pockets to the pulp.

Pulp inflammation or necrosis extends into the periapical tissue causing a local inflammatory

response often associated with bone and root resorption.

Elimination of the etiologic factors from the root canal is therefore essential to promote healing.

Effect of endodontic disease on the periodontium

When the pulp becomes infected, it elicits an inflammatory response of the PDL at the apical

foramen or adjacent to openings of accessory or lateral canals.

Inflammatory byproducts of pulpal origin may permeate through the apex, lateral or accessory

canals and dentinal tubules to trigger an inflammatory vascular response in the periodontium.

The result of the pulp inflammation can range in the extent from a minimal inflammatory process

confined to the PDL to extensive destruction of the PDL, tooth socket and surrounding bone.

After appropriate root canal treatment lesion resulting from pulpal necrosis resolve uneventfully

in most instances.

Subsequently the integrity of the periodontal tissue will be reestablished.

3


Certain procedures involved in root canal treatment as well as irrigants, intracanal medicaments,

sealers and filling materials have the potential to cause an inflammatory response in the

periodontium.

The inflammatory response resulting from commonly used root canal treatment methods and

materials is usually transient in nature and resolves quickly if the materials are confined within

the canal space.

Procedural errors during root canal treatment can also cause inflammatory response in the

periodontium.

Periodontal defects resulting from attachment breakdown may occur after procedural mishaps

such as perforation of the floor of the pulp chamber or the root surface apical to the gingival

attachment, strip perforations or root perforation related to cleaning and shaping procedure and

vertical root fractures associated with uncontrolled forces used for canal obturation.

Effect of periodontal disease on the pulp

The effect of periodontal inflammation on the pulp is controversial.

It has been suggested that periodontal disease has no major effect on the pulp at least until it

involves the apex. 4

In contrast several studies suggest that the effect of periodontal disease on the pulp is

degenerative in nature causing an increase in calcification, fibrosis, collagen resorption and

direct inflammatory sequalae. 5, 6

It appears that the pulp is usually not severely affected by periodontal disease until the defect has

exposed an accessory canal to the oral environment.

At these stage pathogens leaking from the oral cavity through the accessory canal into the pulp

may cause an inflammatory reaction followed by pulp necrosis.

However, if the microvasculature of the apical foramen remains intact the pulp may test positive

to pulp vitality tests.

The effect of periodontal treatment on the pulp is similar during scaling, curettage or periodontal

surgery if accessory canals are severed and/or opened to the oral environment.

Jansson et al. in a 3 years retrospective radiographic study evaluated 175 endodontically treated

single rooted teeth of 133 patients.

Patients who were more prone to periodontitis and exhibited evidence of endodontic treatment

failures showed an approximately threefold increase in marginal bone loss as compared to

patients without endodontic infection. 7

4


In addition the effect of endodontic infection on periodontal probing depth and the presence of

furcation involvement in mandibular molars were also investigated.

It was found that endodontic infection in mandibular molars was associated with more

attachment loss at the furca.

These authers suggested that endodontic infection in molars associated with periodontal disease

might enhance periodontitis progression by spreading pathogens through accessory canals and

dentinal tubules.

However other investigators failed to observe a correlation between a reduced marginal bone

support and endodontic status. 8

This issue still merits further investigation.

Effect of the occlusion on the periodontium and the pulp 9

Trauma from Occlusion:

Pathologic or adaptive changes which develop in the periodontium as a result of undue force

produced by the masticatory muscles.

Stillman (1917): A condition where injury results to the supporting structures of the teeth by the

act of bringing the jaws into a closed position

WHO (1978): Damage in the periodontium caused by stress on the teeth produced … by the

teeth of the opposing jaw.

AAP (1986): An injury to the attachment apparatus as a result of excessive occlusal force.

Trauma from Occlusion

– Primary TfO:

A tissue reaction, which is elicited around a tooth with normal height of the periodontium

(no attachment loss!)

– Secondary TfO:

Related to situations in which occlusal forces cause damage in a periodontium of reduced

height (attachment loss present)

Bone resorption in TfO should be interpreted as an adaptation of the ligament and bone to the

altered functional requirements

5


Jiggling Forces:

Combined pressure and tension zones result from jiggling

Zones are characterized by collagen resorption, bone resorption, and cementum

resorption.

Signs of increased vascularity or exudation.

Tooth shows progressive mobility.

Ligament space gradually adjusts to new situation.

No attachment loss!

Increased tooth mobility

6


Occlusal adjustment normalizes the width of the periodontal ligament.

Teeth are stabilized and regain normal mobility.

7


Reduced Height, Healthy peridontium:

Zones of combined pressure and tension exhibit

– vascular proliferation,

– exudation,

– thrombosis, and

– bone resorption

A widened periodontal ligament develops

Tooth mobility is increasing progressively

8


Ligament space gradually adjusts to new situation.

No attachment loss!

Increased tooth mobility

Ligament tissue regains normal composition

9


Supra-alveolar tissue unaffected

No further loss of attachment

Teeth hyper mobile, surrounded by tissue that adapted to the new functional

situation

Occlusal adjustment will allow the periodontal ligament to regain its normal width.

Reduced height and Diseased periodontium:

In plaque-induced inflammation, TfO may enhance the disease progression

In the case presented here, there is a healthy zone between inflamed CT and PL

10


Pathologic and adaptive reactions occur in the PL

A widened periodontal ligament and increased tooth mobility will result

No further loss of attachment is observed

11


Occlusal adjustment will result in reduction of periodontal ligament width and

Reduced (not normal!) tooth mobility

12


Presence of infrabony pocket and infiltrated connective tissue

Merging of zones of “irritation” and “co-destruction”

13


Jiggling forces lead to typical vascular and exudative reaction in ligament space

Pathologic reaction may occur within a zone that also contains (plaque-induced)

inflammatory cell infiltrate

14


In this situation, increasing tooth mobility may also be associated with an enhanced

loss of attachment and further down growth of the most apical portion of the PE

15


Occlusal adjustment will result in narrowing of the ligament space, less tooth

mobility

Regeneration of attachment cannot be expected

Loss of attachment is permanent

If plaque-induced inflammation persists, more attachment loss may occur

16


Classification of Endodontic-Periodontic Lesions • Primary Endo

• Primary Perio

• Primary Endo w/ Secondary Perio

• Primary Perio w/ Secondary Endo

• True Combined

• Concomitant Pulpal-Periodontal Two separate and distinct entities

17


Periodontal and Endodontic Regeneration

The type of healing that occurs after conventional endodontic and periodontal therapy, either repair or regeneration, is critically dependent on the cell type that repopulates the wound first. Typically, the cells with the fastest migration rate tend to dominate the initial healing phase. A classic review by Melcher introduced the idea of compartmentalization, which described 4 cell populations in the periodontium: lamina propria of the gingiva, periodontal ligament (PDL), alveolar bone, and cementum. PDL cells, alveolar bone cells, and possibly cementoblasts are all capable of periodontal regeneration, whereas epithelial cells typically produce repair and/or long junctional epithelium formation.

10

Membranes Occlusive barrier membranes are used to exclude epithelial cells and connective tissue fibroblasts from a periodontal wound. This allows other regenerative cells (eg, bone, periodontal ligament, cementoblast) to repopulate the area and promote periodontal regeneration in the area. Barrier membranes can be divided into nonresorbable and bioabsorbable categories

Nonresorbable Membranes Many materials have been used as nonresorbable barriers for GTR including bacterial (Millipore, Billerica, MA) filters and a rubber dam, but the most commonly used material is the ePTFE membrane. The first case report evaluating GTR as a therapy used a Millipore filter as a barrier membrane to regenerate the periodontium in a 9-mm defect on a hopeless tooth Three months after surgery, the tooth was extracted, and subsequent histology revealed 5 mm of connective tissue attachment coronal to the base of the defect.

11

Gottlow et al took block sections of 12 hopeless teeth treated with ePTFE membranes and found new bone growth to be an average of 5.1 mm and an average clinical attachment level (CAL) gain of 5.6 mm.

12

Recent studies showed that intrabony defects treated with ePTFE membranes can be expected to undergo between 3.0–5.0 mm of bone fill with 4.0–7.0 mm CAL gain, regardless of whether a bone replacement graft is placed concomitantly.

13-15

One study compared the use of ePTFE membranes versus no membranes in the treatment of periapical lesions after apical surgery. Radiographic analysis of the defects showed that defects treated with an ePTFE membrane healed faster and with greater quality and quantity of regenerated bone compared with controls, especially in through-and-through lesions

16

18


Although most nonresorbable membranes are biocompatible and highly effective at maintaining space, they require a second surgery to facilitate their removal. Consequently, other materials were introduced to eliminate these drawbacks.

Bioabsorbable Membranes

The search for resorbable membranes included tests with rat collagen , bovine collagen, cargile

membrane derived from the cecum of an ox, polylactic acid, vycril, synthetic skin and freeze-

dried dura mater.17-20

The most common material is collagen, which can be modified through various collagen cross-linking processing techniques to vary the resorption rate.

21

Numerous studies have shown bioabsorbable membranes to be effective at promoting regeneration in both endodontic and periodontal defects.

22-26

Because alveolar bone and the periodontal ligament contain collagen, using a collagen membrane might impart some additional advantages for GTR purposes by augmenting its native properties. Collagen facilitates hemostasis and therefore wound stability by promoting platelet aggregation in addition to promoting fibroblast migration, which could accelerate wound closure.

27

Histologic studies of bioabsorbable membranes indicate that regeneration can occur after healing, although repair was seen in a minority of instances.

28-30

The membrane can be obtained in different shapes and size to suit proximal spaces and

facial/lingual surfaces of furcations. The technique for its use is as follows:

1- Raise a mucoperiosteal flap with vertical incision extending a minimum of two teeth

anteriorly and one tooth distally to the tooth being treated.

2- Debride the osseous defect and thoroughly plane the roots.

3- Trim the membrane with sharp scissors to the approximate size of the area being treated.

The apical border of the material should extend 3 to 4 mm apical to the margin of the

defect and laterally 2 to 3 mm beyond the defect the occlusal border of the membrane

should be placed 2 mm apical to the CEJ.

4- Suture the membrane tightly around the tooth with a sling suture.

5- Suture the flap back in its original position or slightly coronal to it using independent

sutures interdentally and in the vertical incisions. The flap should cover the membrane

completely.

6- In cases of nonresorbable The membrane is removed surgically using a miniflap 4-6

weeks after the operation.

19


Growth Factors:

The application of local growth factors has been studied to enhance the healing and regeneration potential of periodontal/endodontic surgery.

Polypeptide Growth factors are polypeptide molecules released by cells in the inflamed area.

They can be considered hormones that are not released into bloodstream but have only a local

action.

These factors primarily secreted by macrophages, endothelial cells, fibroblasts and platelets

include platelet-derived growth factors (PDGF), insulin-like growth factor (IGF), basic

fibroblastic growth factor (Bfgf) and transforming growth factor (TGF)-α and –β.

PRP(platelet rich plasma), growth factors including BMPs, PDGF, and EMD are the most commonly used agents.

31,32

PRP is a highly concentrated suspension of autologous platelets, which secrete bioactive growth factors on activation. Because these growth factors are present at increased concentrations in PRP, they help to enhance key stages of wound healing and regenerative processes including chemotaxis, proliferation, differentiation, and angiogenesis.

33

PDGF is a growth factor involved in wound healing that stimulates the regenerative potential of periodontal tissues including bone, cementum, and periodontal ligament. PDGF-BB is one form of PDGF, and it has shown the most promise as a regenerative agent.

34

Howell and co-workers reported that a single application in human periodontal defects of IGF-I

resulted in significant improvement in bone fill above that obtained in controls while another

growth factor tested ((PDGF-BB) was not effective. 35

Graft associated regeneration

Perhaps the most commonly used technique for regeneration is the use of bone replacement grafts.

Bone replacement grafts can promote tissue/bone regeneration through a variety of mechanisms.

Numerous therapeutic grafting modalities for restoring periodontal osseous defects have been

investigated. Material to be grafted can be obtained from:

1- The same person (Autograft)

20


2- From a different person(Allograft)

3- From a different species (Xenograft)

4- From a synthetic or inert foreign body (Alloplast)

Bone graft are generally evaluated based on the following potentials:

1- Osteogenesis : the formation or development of newbone by cells contained in the graft.

2- Osteoinduction : a chemical process by which molecules contained in the graft (BMPs)

converts the neighboring cells into osteoblasts which in turn form bone.

3- Osteoconductive : a physical effect by which the matrix of the graft forms a scaffold that

favors outside cells to penetrate the graft and form new bone.

The considerations that govern the selection of a material have been defined as following:

1- Biologic acceptability

2- Predictability

3- Clinical feasibility

4- Minimal operative hazards

5- Minimal post operative sequelae

6- Patient acceptance

It is difficult to find a material with all these characteristics and to date there is no ideal material

or technique.

Autogenous Grafts Autogenous grafts are those obtained from a remote location within the same host and are considered the gold standard bone replacement graft

36

Sources of bone include bone from healing extraction wounds, bone from edentulous ridges,

bone trephined from within the jaw without damaging the roots, newly formed bone in wounds

especially created for the purpose and bone removed during osteoplasty and osteotomy.

Alternatively, larger grafts can be obtained extraorally from areas such as the iliac crest or tibia. Advantages to using autogenous grafts are that these grafts are osteogenic, prevent disease transmission, and are low cost. However, they do require a second surgical site at the donor site.

21


Schallhorn used iliac crest grafts in the treatment of infrabony defects and reported up to a 4-mm gain in bone height.

37

Owing to problems associated with its use such as postoperative infection, exfoliation,

sequestration, varying rates of healing, root resorption and rapid recurrence of the defect in

addition to increased patient expense and difficulty in procuring the donor material the technique

is no longer in use. 38

Allografts A bone allograft refers to a graft between genetically dissimilar members of the same species.

Bone allografts are commercially available from tissue banks.

They are obtained from cortical bone within 12 hours of the death of the donor, defatted, cut in

pieces, washed in absolute alcohol then deep frozen.

The material may then be demineralized and subsequently ground and sieved to a particle size of

250 to 750 mm and freeze dried. Finally it is vacuum sealed in glass vials.

These grafting materials have relatively high success rates and have an additional advantage in that no additional surgical procedure is required to procure bone from a donor site. Disadvantages potentially include a foreign body immune response, cost, and contamination of the graft during processing.

Undecalcified freeze-dried bone allograft (FDBA):

Several clinical studies by mellonig, bowers and co-workers reported bone fill exceeding 50% in

67% of the defects grafted with FDBA and in 78% of the defects grafted with FDBA plus

autogenous bone. 39

FDBA is considered an osteoconductive material.

Decalcified freeze-dried bone allograft (DFDBA):

Experiments by Urist and co-workers have established the osteogenic potential of DFDBA. 40, 41

Demineralization in cold, diluted hydrochloric acid exposes the components of bone matrix,

closely associated with collagen fibrils that have been termed bone morphogenic protein.

DFDBA is considered an osteoinductive graft.

Mellonig and associates tested DFDBA against autogenous materials in the calvaria of guinea

pigs and showed it to have similar osteogenic potential. 42

Laboratory studies have found that DFDBA has a higher osteogenic potential than FDBA and is

therefore preferred. 43

22


Limitations of the use of DFDBA include the possible albeit remote potential of disease transfer

from the cadaver.

Xenografts

A xenograft refers to tissue taken from one species and placed into another species. Xenografts are osteoconductive by nature. For intraoral bone replacement grafts, the most common animal sources are bovine and porcine.

Calf bone (Boplant) treated by detergent extraction, sterilized and freeze dried has been used for

the treatment of osseous defects.

Kiel bone is calf or ox bone denatured with 20% hydrogen peroxide, dried with acetone and

sterilized with ethylene oxide.

Anorganic bone is ox bone from which the organic material has been extracted by means of

ethylenediamine, it is then sterilized by autoclaving.

these grafting materials resorb very slowly and might sequester or undergo fibrous encapsulation. 44

these materials have been tried and discarded for various reasons include very slow resorbtion,

sequestration and unpredictability.

Alloplasts

An alloplast is a synthetic or inert foreign body that is implanted into host tissue. They are osteoconductive only. Alloplasts serve primarily to maintain space, and consequently they are not ideal for promoting periodontal regeneration.

Sclera:

Sclera was originally used in periodontal procedures because it is a dense fibrous connective

tissue with poor vascularity and minimal cellularity. 45

This afford a low incidence of antigenicity and other untoward reactions. 46

In addition sclera may serve to protect the blood clot during the initial healing period.

Cartilage:

Cartilage has been used for repair studies on monkeys and treatment of periodontal defects in

humans.47, 48

23


However cartilage has received only limited evaluation. 48

Plaster of paris

Plaster of paris (calcium sulfate) is biocompatible and porous thereby allowing fluid exchange

which prevents flap necrosis.

Plaster of paris resorbs completelyin 1 to 2 weeks.

It was found to be useful in one uncontrolled clinical study but other investigators have reported

that it does not induce bone formation. 49

One report suggested its use in combination with DFDBA and a Gore-Tex membrane. 50

Its usefulness in human cases has not been proven.

Plastic materials

HTR polymer is a non resorbable, microporous, bio compatible composite of

polymethylmethacrylate and polyhydroxylethylmethacrylate.

A clinical 6 months study showed significant defect fill. 51

Histologically this material is encapsulated by connective tissue fibers with no evidence of new

attachment. 52

Calcium phosphate biomaterials

Several calcium phosphate biomaterials have been tested since the mid-1970s and are currently

available for clinical use.

Calcium phosphate biomatertals have excellent tissue compatibility and do not elicit any

inflammation or foreign body response.

These materials are osteoconductive, not osteoinductive, meaning that they will induce bone

formation when placed next to viable bone but not when surrounded by non-bone-forming tissue

such as skin. 53, 54

Two types of calcium phosphate ceramics have been used:

1. Hydroxyapatite (HA) has a calcium-to-phosphate ratio of 1.67, similar to that found in bone

material. HA is generally nonbioresorbable.

24


2. Tricalcium phosphate (TCP), with a calcium-to-phosphate ratio of 1.5, is mineralogically B-

whitlockite.

TCP is at least partially bioresorbable.

Coral-derived materlals

Two different coralline materials have been used: natural coral and coral-derived porous

hydroxyapatite.

Both are biocompatible, but whereas natural coral is resorbed slowly (several months), porous

hydroxyapatite is not resorbed or takes years to do so.

Both materials have demonstrated microscopic cementum and bone formation, but their slow

resorbability or lack thereof has hindered clinical success in practice. 55, 56

25


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endodontic and periodontal regeneration

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