Cementum – a dynamic structure uday.pptx

Guided by Presented by

Dr. shrutima R.uday bhaskar

CEMENTUM

CONTENTS

• INTRODUCTION

• DEFINITION

• PHYSICAL PROPERTIES

• CLASSIFICATIONS

• COMPOSITION OF CEMENTUM

• PROTIENS

• TOOTH DEVELOPMENT

• CEMENTOGENESIS

• THEORIES

• ANATOMY

• INTERMEDIATE CEMENTUM

• CEMENTO-DENTINAL JUNCTION

• CEMENTO-ENAMEL JUNCTION

• ROLE OF CEMENTUM IN PERIODONTAL HEALTH

• AGE CHANGES

• RESORPTION AND REPAIR

• CHANGES IN DISEASED CEMENTUM

• CEMENTUM REGENERATION

• SYSTEMIC DISEASES CAUSING DEFECTIVE CEMENTUM FORMATION

• CLINICAL CONSIDERATIONS

• CONCLUSION

INTRODUCTION

Cementum

• The term cementum is derived from the Latin term “caementum” meaning quarried stone or chips of stone used for making mortar

• It is also called as Substantia Ossea

• It is the hard avascular connective tissue that covers roots of the teeth and serves primarily to invest and attach the principal periodontal ligament fibers.

CEMENTUM IS VERY SIMILAR TO BONE.

• Diseases that affect the properties of bone, often alter cementum’s properties as well.

• The composition of cementum is similar to that of bone. Cementum is approximately 50% hydroxyapatite and 50% collagen and noncollagenous proteins.

CEMENTUM DIFFERENT FROM BONE

• NOT

• Innervated,

• Exhibit little or no remodeling

• Avascular

PHYSICAL PROPERTIES

1.Colour - Pale yellow

2.Softer and more permeable than dentin

3.Relatively brittle

4.Distinguished from enamel due to its darker hue and luster

5.The relative softness of cementum, combined with its thinness

cervically, means that it is readily removed by abrasion when gingival

recession exposes the root surface to the oral environment

COMPOSITION OF CEMENTUM

Organic – 50% Inorganic – 50%

• 90% organic – Type I Collagen Mainly apatite crystals

• Type III – high concentration during Mainly calcium and development and regeneration phosphorous

• Type XII – bind Type I with non collagenous Trace element-highest fluoride matrix protiens content among all the

mineralized

• Trace amounts of Type V,VI, XIV tissues

COLLAGEN

• Functions:

• Interacts with the non collagenous proteins and provide a scaffold

for the accommodation of mineral crystals.

• Promotes cell attachment

• Maintains the integrity of both soft and hard connective tissues,

during development as well as in repair.

NON COLLAGENOUS PROTEINS

• Bone sialoprotein and osteopontin

• Osteonectin ( SPARC)

• Fibronectin (FN) and tenascin

• Osteocalcin

• BMPs

• Cementum- derived attachment protein (CAP)

• Cementum-derived growth factor

ROLE OF NON – COLLAGENOUS PROTEINS

• Matrix deposition

• Initiation and regulation of mineralization.

• Matrix remodeling.

DEVELOPMENT OF CEMENTUM

divided into

pre-functional functional

Occurs during root development.

During this time, primary distribution of main cementum varieties is determined.

Commences when the tooth reaches the occlusal plane.

Adaptive and reparitive processes are carried out.

TOOTH DEVELOPMENT

HERTWIGS EPITHELIAL ROOT SHEATH

• Cementogenesis

CEMENTOCYTE

• The spaces that the cementocytes, occupy in cellular cementum are called lacunae, and the channels that their processes extend along are the canaliculi

• They communicate with each other through a network of cytoplasmic processes (arrows) running in canaliculi in the cementum.

• The cementocytes also communicate with the cementoblasts on the surface through cytoplasmic processes.

• The presence of cementocytes allows transportation of nutrients through the cementum, and contributes to the maintenance of the vitality of this mineralized tissue.

• CEMENTOID

• CEMENTOID TISSUE

THEORIES

• Classical theory

• Von Brunn’s Theory (1891)

• Phenotypic Transformation

• Stahl and Slavkin Theory (1972)

• Cementoblasts that derive from follicular cells express osteopontin,

osteocalcin. Those derive from HERS express osteopontin only.

SEQUENCES OF CEMENTOGENESIS

1. Proliferation of hertwig's epithelial root sheath cells;

2. Differentiation of odontoblasts from ectomesenchymal cells (cranial neural

crestderived) of the dental papilla mesenchyme;

3. Deposition of dentine matrix (e.G. Type I collagen and dentine

phosphoproteins) and mineralization;

4. Degeneration of epithelial sheath cells;

5. The formation of cell-matrix interactions between mineralized dentine and

mesenchymal cells of the dental sac resulting in the differentiation of

cementoblasts; and

6. The initial deposition of cementum matrix by mesenchyme-derived

cementoblasts and subsequent mineralization

FACTORS REGULATING CEMENTOGENESIS

• GROWTH FACTORS -TRANSFORMING GROWTH FACTORβ

PDGF, IDGF,

FIBROBLAST GROWTH FACTOR

• ADHESION MOLECULES – BONE SIALOPOTIEN

OSTEOPONTIN

• ENAMEL/EPITHELIAL PROTIENS

• COLLAGEN

• GLA PROTIENS

• TRANSCRIPTION FACTORS – RUNx-2 (Run related transcription)

OSTERIX

• SIGNALLING MOLECULES – OSTEOPROTEGRIN,RANKL

CLASSIFICATION

• Classification based on the nature and origin of the organic matrix

• Classification based on the presence or absence of cells

• Classification based on the presence or absence of cells and on the nature and origin of the organic matrix

EXTRINSIC FIBRES & INTRINSIC FIBRES.

CELLULAR AND ACELLULAR CEMENTUM

Acellular cementum covers the root adjacent to

the dentine, also called primary cementum

Cellular cementum is found mainly in the apical area

and overlying the acellular cementum, also called

secondary cementum

cellular cementum develops, the formative cells

(the cementoblasts) become embedded in the

tissue as cementocytes.

Schroeder’s (1992) classification

• Acellular Afibrillar Cementum (AAC)

• Acellular Extrinsic Fiber Cementum (AEFC)

• Cellular Intrinsic Fiber Cementum (CIFC)

• Acellular intrinsic Fiber Cementum (AIFC)

• Cellular Mixed Stratified Cementum (CMSC)

ACELLULAR AFIBRILLAR CEMENTUM

• Believed to be A developmental

anomaly

• When cementocytes meet the smooth

surface of enamel it produces AAC.

• Thickness : 1-15 µ m

• Location : coronal cementum

• Consists of mineralized ground

substance produced by cementoblasts

ACELLULAR EXTRINSIC FIBER CEMENTUM (AEFC)Aligning of the cementoblast on the

newly formed dentin.Secretion of collagen in unipolar

manner Inter digitation of the collagen with

dentinal collagen, which was not yet mineralised

Continuation of deposition – lengthening and thickening of collagen

Secretion of non collagenous proteins – fills the space between collagen fibers and regulate mineralization.

• Activity continues until about 15-20 µ of cementum is formed

• Thereafter secretion of non collagenous proteins only.

• No cementoid exists on the surface of acellular extrinsic fiber

cementum

• Growth rate of AEFC is 0.005-0.01 µ / day

• Overall mineralization is about 45 – 60%.

• Location : cervical 3rd of root

• It is a product of fibroblasts and cementoblasts

CELLULAR INTRINSIC FIBER CEMENTUM (CIFC) It is formed only after at least half

the root is formed (not in incisors and canines)

It is formed more rapidly (about 30 times than acellular cementum)

Similar to acellular cementum this cementum forming cementoblast extend cell processes to unmineralized predentin and deposit collagen fibrils

Intermingling of collagen fibrils.Secretion of non collagenous

proteins.

In contrast to acellular cementum cementoid is seen

Cells secrete in relatively rapid multipolar mode

As cementum formation progresses cementoblasts become entrapped

Collagen fibrils are haphazard during rapid formation but later they get oriented parallel to the root surface.

It is a product of cementoblasts

CELLULAR MIXED STRATIFIED CEMENTUM

• Location – apical 3rd and in furcation areas

• It is aproduct of fibroblasts and cementoblasts

• Thickness 100-1000µ m

ANATOMY

• Thickness – 20-50µ at cervical region

150-200µ – apical region

INCREMENTAL LINES

• The appearance of incremental lines in

cementum is mainly due to differences in the

degree of mineralisation

•Cementum is deposited in an irregular rhythm,

resulting in unevenly spaced incremental lines

• In acellular cementum, incremental lines tend to

be close together, thin and even.

• In cellular cementum, the lines are further apart,

thicker, and more irregular.

CEMENTO-DENTINAL JUNCTION

INTERMEDIATE CEMENTUM

Consists of cellular remnants of HERS embedded in a calcified ground substance

Cementum

Intermediate cementum

Root dentin

CEMENTO-ENAMEL JUNCTION

ROLE OF CEMENTUM IN PERIODONTAL HEALTH

• Supporting tooth

• Width of PDL space

• Repair

• Maintaining occlusal relationship

• Role in orthodontic treatment

AGE CHANGES

CONTINUOUS DEPOSITION

• Cementum formation on the roots of human teeth continues throughout life

• More cementum is formed apically

• PERMEABILITY

• Diminishes with age

DEVELOPMENTAL AND ACQUIRED ANOMALIES ASSOCIATED WITH CEMENTOGENESIS

Enamel projection:

• Occur in localized areas

• particularly in furcations of mandibular teeth.

• It is suggested that projections may predispose the teeth to periodontal defect involving the furcation.

Enamel Pearls:

• This anomaly consists of globules of enamel on the root surface in the cervical region.

• They resemble small pearls up to several millimeters in diameter.

• They appear to form as a result of localized failure of Hertwig's root sheath to separate from the dentin surface.

• They mimic calculus clinically and radigraphicall y, they cannot be sealed off and elimination can only be accomplished by grinding.

• Large pearls may contain pulp extensions.

• CEMENTICLES:

•These are globular masses of acellular cementum, generally less than 0.5 mm in diameter which form within periodontal ligament

•Cause : Extra stress on sharpeys fibers causes a tear in cementum

Micro Trauma

• Common in the apical and middle third of the root and in root furcation areas.

HYPERCEMENTOSIS:

Local factors

• Abnormal occlusal trauma,

• Unopposed teeth (e.g. impacted, embedded, without antagonist)

• Adjacent inflammation

Systemic factors

• Acromegaly and pituitary gigantism

• Arthritis

• Paget’s disease (Generalized hypercementosis)

• Rheumatic fever

• Thyroid goiter

• Vitamin A deficiency

ANKYLOSIS

• Ankylosis may occur at any age clinically they are most common

• The most commonly involved tooth is primary first molar, the majority of cases occuring in the mandible.

• A sharp, solid sound may be noted on percussion of the involved

teeth.• Radiographically, absence of periodontal ligament space may be noted

RESORPTION AND REPAIR

• Cementum formation --- continuous process

• More cementum is deposited apically than cervically. Thicker layers

may form in the root surface grooves & in furcations.

• In the cementum of impacted teeth, sharpey’s fibres may be nearly

completely absent & may be built up mainly of intrinsic fibres

arranged parallel to the root surface.

• In the posterior teeth, cementum deposition is thicker on the distal

side than on the mesial, indicating a relationship to mesial drift

RESORPTION

Local factors

• Trauma from occlusion

• Orthodontic movement

• Pressure from malaligned teeth, cysts and tumors

• Teeth without functional antagonist

• Embedded teeth

• Replanted and transplanted teeth

• Periapical disease

• Periodontal disease

Systemic conditions

• Calcium deficiency

• Hypothyroidism

• Hereditary fibrous osteodystrophy

• Paget’s disease.

• Microscopic appearance:

• Baylike concavities in the root surface.

• Multinucleated giant cells and large mononuclear macrophages are

present adjacent to cementum undergoing active resorption.

• Cementoclasts: They resemble osteoclasts and are occasionally found in

normal functioning periodontal ligament.

• They are responsible for extensive root resorption that leads to primary

teeth exfoliation and localized cemental resorptions seen in adult dentin.

REPAIR

• After resorption has ceased, the damage is usually repaired

• Anatomic repair

• Functional repair.

HOW CEMENTUM IS RESISTANT TO RESORPTION?

• Avascular

• Fluoride

• Densely packed collagen

• Parathormone

CEMENTUM REGENERATION

• Most common outcome is the formation of new tissue that resembles

cementum or bone

• Does not interdigitate with the root surface

• Periodontal regeneration

• Systemic and local factors

• The role of local factors is especially relevant in cementum

• The recruited cells will be induced to differentiate into cementoblasts

SYSTEMIC DISEASES CAUSING DEFECTIVE

CEMENTUM FORMATION

PAPILLON-LEFÈVRE SYNDROME

• Rare inherited condition

• Characterized by hyperkeratotic skin lesions

• Microscopic changes reported include marked chronic inflammation of the lateral wall of the pocket

• Extremely thin cementum.

HYPOPHOSPHATASIA

• Rare familial skeletal disease

• Reduced Serum alkaline phosphatase

• Gingival inflammation

• Reduced cementum formation.

CLEIDOCRANIAL DYSPLASIA

• Developmental anomaly - affecting the skeleton and teeth (affects

the skull, clavicle and dentition).

• A paucity or complete absence of cementum due to defective

formation of cellular cementum on both erupted and un erupted teeth

• Prolonged retention of deciduous teeth, subsequent delayed eruption

of succedaneous teeth as well as numerous un erupted supernumerary

teeth.

HYPOPITUTARISM

• Reduced pituitary hormones ----- the growth hormone

• Dwarfism but have a relatively well proportioned body.

• Decreased cementum formation is associated with hypopituitarism.

ALTERATIONS RESULTING FROM PERIODONTAL PATHOLOGY

ROOT SURFACE CHANGES IN POCKET

• In normal cementum the collagen fibers are embedded in the

cementum.

• These fibers are destroyed in pathological pocket wall with the

exposure of cementum. Collagen remnants of Sharpey’s fibers in

cementum undergo degeneration creating a environment favorable

for penetration of bacteria.

• Viable bacteria have been found in the roots of 87% of periodontally

diseased non carious teeth.

• Bacterial penetration into the cementum can be found as deep as the

CDJ and may also enter the dentinal tubules.

• Bacterial products such as endotoxins have been detected in the

cementum wall of the periodontal pocket.

• These changes manifested clinically as softening of cementum

surface which is usually asymptomatic but painful when probe

penetrates the area.

EXPOSURE TO THE ORAL ENVIRONMENT

Hypermineralization

• Areas of increased mineralization at cemental saliva interface.

• The mineral content of exposed cementum increases. Microhardness

remains unchanged. This hypermineralized surface increases the

tooth resistance to decay.

CLINICAL CONSIDERATIONS

ORTHODONTIC MOVEMENT

• Orthodontic movements when in proper magnitude do not affect the cementum because cementum, with its slow metabolism is not damaged by a pressure equal to that exerted on bone.

• when the forces exceed, cemental resorption occurs on the pressure side while deposition takes place on the tension side.

ROOT PLANING

• Root Planing – arrests disease progression, remove infection

• According to Jan Lindhe & H. Rylander, ‘Root Planing’ removes

the softened cementum, resulting in a hard & smooth root surface.

• Ruben, et al., (1975) suggested that the therapeutically debrided &

planed root surface initially undergoes superficial demineralization

& resorption of the cemental matrix that involves embedded

collagens & reticular fibers.

• This is because of the acidic & enzymatic activity of post surgical

inflammation, occurring 48 hrs after surgery.

ROOT BIOMODIFIERS

• Root planing / Root conditioning -- antecedent to mesenchymal cell migration & attachment onto the exposed root surface.

• Root conditioning can be done by using:

• Acids (citric acid, HCL, Lactic acid & EDTA)

• Fibronectin

• Enamel matrix proteins.

CONCLUSION

• Cementum is probably the least understood of all dental tissues. But this does not lessen it’s role in the periodontal attachment apparatus. With the development of newer concepts of regenerative cementogenesis and role of cementum in implants, the need for us to better understand this basic tissue should be understood and implemented.

REFERENCES

• Text book of Clinical Periodontology; 10th edition. Carranza

• Cementum &Periodontal Wound Healing and Regeneration – Wojciech.J.Grzesik, A .S.narayanan

• Critical reviews of oral biology and medicine 2002;13(6) 474-84.

• Oral Cells and Tissues – P. R. Garant

• Biology of the Periodontal Connective Tissues,Bartold, Mark and Narayanan, A. Sampath.

• Orban's Oral Histology and Embryology

• Ten Cate's Oral Histology Development, Structure, and Function

• Cementum : A Dynamic structure,Periodontology 2000, Vol. 41, 2006, 196–217

THANK YOU

DIFFERENCE B/W BONE AND CEMENTUM

NOT

• Innervated,

• Exhibit Little Or No Remodeling

• Avascular

•

2 Unique Cementum Molecules: Cementum

Attachment Protein (Cap) And Igf

PHYSIOLOGICAL ACTIVITY OF CEMENTOCYTES

• Deposition of cellular intrinsic fiber cementum is characterized by the entrapment of cementoblasts

• cementum on human teeth is, however, much lower than in bone tissue.

• Cementocytes close to the cementum surface may resemble cementoblasts

• In deeper layers of cellular intrinsic fiber cementum lacunae may appear empty.

PHYSIOLOGICAL TOOTH MOVEMENT AND OCCLUSAL FORCES

• occlusal forces are not necessary to stimulate cementum deposition.

• mesial drift

• Tensional forces

• orthodontic tooth movement

• Appositional layers of bone lining

• Dynamically responsive

DO ENAMEL ASSOCIATED PROTIENS REGENERATE CEMENTUM ?

• mimic the way these materials behave in normal tooth development

• Schonfield and Slavkin in 1977

• enamel like material was formed in the root surface prior to cementum formation

• cellular cementum contains proteins

• coronal cementogenesis

• Hammarstrom in a buccal dehiscence monkey model in 1977

• human experimental defect by Heijl in 1997

• cellular cementum in experimentally prepared root surfaces

CAN GUIDED TISSUE REGENERATION AND BONE GRAFTING REGENERATE CEMENTUM??

• Millipore membranes

• First guided tissue regeneration membranes

• Grafting material

• Question ??

• Cellular cementum that is usually poorly attached to the dentin surface

• Periodontal healing with guided tissue regeneration

therapy occurs in two stages.

• first stage

• Second phase

• Conclusion

CELLULAR TISSUE ENGINEERING FOR CEMENTUM REGENERATION

• recolonization of periodontal ligament cells

• Therapeutic approach –removal of cells from PDL

• pilot study

• bone marrow mesenchymal stem cells

• Hertwig’s epithelial root sheath

• Cementoblasts

 PERI-IMPLANT CEMENTAL SURFACE

• The absence of cementum in the implant surface

• Buser and associates

• Further research is now going on an attempt to obtain a layer of cementum around the implant and thus improve it’s longevity.

EFFECT OF NUTRITION ON DEFECTIVE

CEMENTUM FORMATION

VITAMIN D DEFICIENCY

• Calciferol

• Deficiency

• Periodontal tissues

PROTEIN DEFICIENCY

Hypoproteinemia

CERVICAL ROOT RESORPTION.

• Large root resorption defects

• Hyperplastic gingivitis

MIGRATION

• Fibronectin

• Laminin

ATTACHMENT

1. Integrins

2. Fibronectin

3. Bone sialo protein and Osteopontin

4. Laminin

PROLIFERATION

• TGF-β

• IGF and GH

DIFFERENTIATION

• Bone morphogenetic protein-3

• Insulin-like growth factor and proteoglycans

• Transcription factor, core binding transcription factor 1/osteoblast-specific transcription factor 2/RunX2/ Cbfa1