Classification of Cementum According to Schroeder

Cementum is a specialized calcified tissue that covers the roots of teeth and plays a crucial role in periodontal health. According to Schroeder, cementum can be classified into several distinct types based on its cellular composition and structural characteristics. Understanding these classifications is essential for dental professionals in diagnosing and treating periodontal conditions.

Classification of Cementum

1. Acellular Afibrillar Cementum:

   • Characteristics:
     • Contains neither cells nor collagen fibers.
     • Present in the coronal region of the tooth.
     • Thickness ranges from 1 µm to 15 µm.
   • Function:
     • This type of cementum is thought to play a role in the attachment of the gingiva to the tooth surface.

2. Acellular Extrinsic Fiber Cementum:

   • Characteristics:
     • Lacks cells but contains closely packed bundles of Sharpey’s fibers, which are collagen fibers that anchor the cementum to the periodontal ligament.
     • Typically found in the cervical third of the roots.
     • Thickness ranges from 30 µm to 230 µm.
   • Function:
     • Provides strong attachment of the periodontal ligament to the tooth, contributing to the stability of the tooth in its socket.

3. Cellular Mixed Stratified Cementum:

   • Characteristics:
     • Contains both extrinsic and intrinsic fibers and may contain cells.
     • Found in the apical third of the roots, at the apices, and in furcation areas.
     • Thickness ranges from 100 µm to 1000 µm.
   • Function:
     • This type of cementum is involved in the repair and adaptation of the tooth root, especially in response to functional demands and periodontal disease.

4. Cellular Intrinsic Fiber Cementum:

   • Characteristics:
     • Contains cells but no extrinsic collagen fibers.
     • Primarily fills resorption lacunae, which are areas where cementum has been resorbed.
   • Function:
     • Plays a role in the repair of cementum and may be involved in the response to periodontal disease.

5. Intermediate Cementum:

   • Characteristics:
     • A poorly defined zone located near the cementoenamel junction (CEJ) of certain teeth.
     • Appears to contain cellular remnants of the Hertwig's epithelial root sheath (HERS) embedded in a calcified ground substance.
   • Function:
     • Its exact role is not fully understood, but it may be involved in the transition between enamel and cementum.

Clinical Significance

• Importance of Cementum:

  • Understanding the different types of cementum is crucial for diagnosing periodontal diseases and planning treatment strategies.
  • The presence of various types of cementum can influence the response of periodontal tissues to disease and trauma.

• Cementum in Periodontal Disease:

  • Changes in the thickness and composition of cementum can occur in response to periodontal disease, affecting tooth stability and attachment.

Changes in Plaque pH After Sucrose Rinse

The pH of dental plaque is a critical factor in the development of dental caries and periodontal disease. Key findings from various studies that investigated the changes in plaque pH following carbohydrate rinses, particularly focusing on sucrose and glucose.

Key Findings from Studies

1. Monitoring Plaque pH Changes:

   • A study reported that changes in plaque pH after a sucrose rinse were monitored using plaque sampling, antimony and glass electrodes, and telemetry.
   • Results:
     • The minimum pH at approximal sites (areas between teeth) was approximately 0.7 pH units lower than that on buccal surfaces (outer surfaces of the teeth).
     • The pH at the approximal site remained below resting levels for over 120 minutes.
     • The area under the pH response curves from approximal sites was five times greater than that from buccal surfaces, indicating a more significant and prolonged acidogenic response in interproximal areas.

2. Stephan's Early Studies (1935):

   • Method: Colorimetric measurement of plaque pH suspended in water.
   • Findings:
     • The pH of 211 plaque samples ranged from 4.6 to 7.0.
     • The mean pH value was found to be 5.9, indicating a generally acidic environment in dental plaque.

3. Stephan's Follow-Up Studies (1940):

   • Method: Use of an antimony electrode to measure in situ plaque pH after rinsing with sugar solutions.
   • Findings:
     • A 10% solution of glucose or sucrose caused a rapid drop in plaque pH by about 2 units within 2 to 5 minutes, reaching values between 4.5 and 5.0.
     • A 1% lactose solution lowered the pH by 0.3 units, while a 1% glucose solution caused a drop of 1.5 units.
     • A 1% boiled starch solution resulted in a reduction of 1.5 pH units over 51 minutes.
     • In all cases, the pH tended to return to initial values within approximately 2 hours.

4. Investigation of Proximal Cavities:

   • Studies of actual proximal cavities opened mechanically showed that the lowest pH values ranged from 4.6 to 4.1.
   • After rinsing with a 10% glucose or sucrose solution, the pH in the plaque dropped to between 4.5 and 5.0 within 2 to 5 minutes and gradually returned to baseline levels within 1 to 2 hours.

Implications

• The studies highlight the significant impact of carbohydrate exposure, particularly sucrose and glucose, on the pH of dental plaque.
• The rapid drop in pH following carbohydrate rinses indicates an acidogenic response from plaque microorganisms, which can contribute to enamel demineralization and caries development.
• The prolonged acidic environment in approximal sites suggests that these areas may be more susceptible to caries due to the slower recovery of pH levels.

Hormonal Effects on Periodontal Tissues

Optimal Treatment Timing

• Safest Period: Early second trimester (weeks 14-20)
• Rationale: Organogenesis complete, uterine size manageable

Clinical Manifestations

• Most Striking Feature: Pronounced ease of bleeding (pregnancy gingivitis)
• Mechanism: Increased vascular permeability due to hormonal changes

Microbial Changes

• Bacterial Shift: Increased Prevotella intermedia
• Hormonal Influence: Estrogen and progesterone serve as growth factors for certain bacteria

Periodontal Fibers

Periodontal fibers play a crucial role in maintaining the integrity of the periodontal ligament and supporting the teeth within the alveolar bone. Understanding the different groups of periodontal fibers is essential for comprehending their functions in periodontal health and disease.

1. Gingivodental Group

• Location:
  • Present on the facial, lingual, and interproximal surfaces of the teeth.
• Attachment:
  • These fibers are embedded in the cementum just beneath the epithelium at the base of the gingival sulcus.
• Function:
  • They help support the gingiva and maintain the position of the gingival margin.

2. Circular Group

• Location:
  • These fibers course through the connective tissue of the marginal and interdental gingiva.
• Attachment:
  • They encircle the tooth in a ring-like fashion.
• Function:
  • The circular fibers help maintain the contour of the gingiva and provide support to the marginal gingiva.

3. Transseptal Group

• Location:
  • Located interproximally, these fibers extend between the cementum of adjacent teeth.
• Attachment:
  • They lie in the area between the epithelium at the base of the gingival sulcus and the crest of the interdental bone.
• Function:
  • The transseptal fibers are primarily responsible for the post-retention relapse of orthodontically positioned teeth.
  • They are sometimes classified as principal fibers of the periodontal ligament.
  • Collectively, they form the interdental ligament of the arch, providing stability to the interproximal areas.

4. Semicircular Fibers

• Location:
  • These fibers attach to the proximal surface of a tooth immediately below the cementoenamel junction (CEJ).
• Attachment:
  • They go around the facial or lingual marginal gingiva of the tooth and attach to the other proximal surface of the same tooth.
• Function:
  • Semicircular fibers help maintain the position of the tooth and support the gingival tissue around it.

5. Transgingival Fibers

• Location:
  • These fibers attach to the proximal surface of one tooth and traverse the interdental space diagonally to attach to the proximal surface of the adjacent tooth.
• Function:
  • Transgingival fibers provide support across the interdental space, helping to maintain the position of adjacent teeth and the integrity of the gingival tissue.

Classification of Periodontal Pockets

Periodontal pockets are an important aspect of periodontal disease, reflecting the health of the supporting structures of the teeth. Understanding the classification of these pockets is essential for diagnosis, treatment planning, and management of periodontal conditions.

Classification of Pockets

1. Gingival Pocket:

   • Also Known As: Pseudo-pocket.
   • Formation:
     • Formed by gingival enlargement without destruction of the underlying periodontal tissues.
     • The sulcus is deepened due to the increased bulk of the gingiva.
   • Characteristics:
     • There is no destruction of the supporting periodontal tissues.
     • Typically associated with conditions such as gingival hyperplasia or inflammation.

2. Periodontal Pocket:

   • Definition: A pocket that results in the destruction of the supporting periodontal tissues, leading to the loosening and potential exfoliation of teeth.
   • Classification Based on Location:
     • Suprabony Pocket:
       • The base of the pocket is coronal to the alveolar bone.
       • The pattern of bone destruction is horizontal.
       • The transseptal fibers are arranged horizontally in the space between the base of the pocket and the alveolar bone.
     • Infrabony Pocket:
       • The base of the pocket is apical to the alveolar bone, meaning the pocket wall lies between the bone and the tooth.
       • The pattern of bone destruction is vertical.
       • The transseptal fibers are oblique rather than horizontal.

Classification of Periodontal Pockets

1. Suprabony Pocket (Supracrestal or Supraalveolar):

   • Location: Base of the pocket is coronal to the alveolar bone.
   • Bone Destruction: Horizontal pattern of bone loss.
   • Transseptal Fibers: Arranged horizontally.

2. Infrabony Pocket (Intrabony, Subcrestal, or Intraalveolar):

   • Location: Base of the pocket is apical to the alveolar bone.
   • Bone Destruction: Vertical pattern of bone loss.
   • Transseptal Fibers: Arranged obliquely.

Classification of Pockets According to Involved Tooth Surfaces

1. Simple Pocket:

   • Definition: Involves only one tooth surface.
   • Example: A pocket that is present only on the buccal surface of a tooth.

2. Compound Pocket:

   • Definition: A pocket present on two or more surfaces of a tooth.
   • Example: A pocket that involves both the buccal and lingual surfaces.

3. Spiral Pocket:

   • Definition: Originates on one tooth surface and twists around the tooth to involve one or more additional surfaces.
   • Example: A pocket that starts on the mesial surface and wraps around to the distal surface.

Anatomy and Histology of the Periodontium

Gingiva (normal clinical appearance): no muscles, no glands; keratinized

• Color: coral pink but does vary with individuals and races due to cutaneous pigmentation
• Papillary contour: pyramidal shape with one F and one L papilla and the col filling interproximal space to the contact area (col the starting place gingivitis)
• Marginal contour: knife-edged and scalloped
• Texture: stippled (orange-peel texture); blow air to dry out and see where stippling ends to see end of gingiva
• Consistency: firm and resilient (push against it and won’t move); bound to underlying bone
• Sulcus depth: 0-3mm
• Exudate: no exudates (blood, pus, water)

  Anatomic and histological structures

Gingival unit: includes periodontium above alveolar crest of bone

a. Alveolar mucosa: histology- non-keratinized, stratified, squamous epithelium, submucosa with glands, loose connective tissue with collagen and elastin, muscles.  No epithelial ridges, no stratum granulosum (flattened cells below keratin layer)

b. Mucogingival junction: clinical demarcation between alveolar mucosa and attached gingiva

c. Attached gingiva: histology- keratinized, stratified, squamous epithelium with epithelial ridges (basal cell layer, prickle cell layer, granular cell layer (stratum granulosum), keratin layer); no submucosa

• Dense connective tissue: predominantly collagen, bound to periosteum of bone by Sharpey fibers
• Reticular fibers between collagen fibers and are continuous with reticulin in blood vessels

d. Free gingival groove: demarcation between attached and free gingiva; denotes base of gingival sulcus in normal gingiva; not always seen

e. Free gingival margin: area from free gingival groove to epithelial attachment (up and over ® inside)

• Oral surface: stratified, squamous epithelium with epithelial ridges
• Tooth side surface (sulcular epithelium): non-keratinized, stratified, squamous epithelium with no epithelial ridges (basal cell and prickle cell layers)

f. Gingival sulcus: space bounded by tooth surface, sulcular epithelium, and junctional epithelium; 0-3mm depth; space between epithelium and tooth

g. Dento-gingival junction: combination of epithelial and fibrous attachment

• Junctional epithelium (epithelial attachment): attachment of epithelial cells by hemi-desmosomes and sticky substances (basal lamina- 800-1200 A, DAS-acid mucopolysaccharides, hyaluronic acid, chondroitin sulfate A, C, and B), to enamel, enamel and cementum, or cementum depending on stage of passive eruption.  Length ranges from 0.25-1.35mm.
• Fibrous attachment: attachment of collagen fibers (Sharpey’s fibers) into cementum just beneath epithelial attachment; ~ 1mm thick

h. Nerve fibers: myelinated and non-myelinated (for pain) in connective tissue.  Both free and specialized endings for pain, touch pressure, and temperature -> proprioception.  If dentures, rely on TMJ.

i.Mesh of terminal argyophilic fibers (stain silver), some extending into epithelium

ii  Meissner-type corpuscles: pressure sensitive sensory nerve encased in CT

iii.Krause-type corpuscles: temperature receptors

iv. Encapsulated spindles

i. Gingival fibers:

i.  Gingivodental group:

• Group I (A): from cementum to free gingival margin
• Group II (B): from cementum to attached gingiva
• Group III (C): from cementum over alveolar crest to periosteum on buccal and lingual plates

ii.  Circular (ligamentum circularis): encircles tooth in free gingiva

iii. Transeptal fibers: connects cementum of adjacent teeth, runs over interdental septum of alveolar bone.  Separates gingival unit from attachment apparatus.

Transeptal and Group III fibers the major defense against stuff getting into bone and ligament.

2.  Attachment apparatus: periodontium below alveolar crest of bone

Periodontal ligament: Sharpey’s fibers (collagen) connecting cementum to bone (bundle bone).  Few elastic and oxytalan fibers associated with blood vessels and embedded in cementum in cervical third of tooth.  Components divided as follows:

i. Alveolar crest fibers: from cementum just below CEJ apical to alveolar crest of bone

ii.Horizontal fibers: just apical to alveolar crest group, run at right angles to long axis of tooth from cementum horizontally to alveolar bone proper

iii.Oblique fibers: most numerous, from cementum run coronally to alveolar bone proper

iv. Apical fibers: radiate from cementum around apex of root apically to alveolar bone proper, form socket base

v. Interradicular fibers: found only between roots of multi-rooted teeth from cementum to alveolar bone proper

vi. Intermediate plexus: fibers which splice Sharpey’s fibers from bone and cementum

vii. Epithelial Rests of Malassez: cluster and individual epithelial cells close to cementum which are remnants of Hertwig’s epithelial root sheath; potential source of periodontal cysts.

viii. Nerve fibers: myelinated and non-myelinated; abundant supply of sensory free nerve endings capable of transmitting tactile pressure and pain sensation by trigeminal pathway and elongated spindle-like nerve fiber for proprioceptive impulses

Cementum: 45-50% inorganic; 50-55% organic (enamel is 97% inorganic; dentin 70% inorganic)

i.  Acellular cementum: no cementocytes; covers dentin (older) in coronal ½ to 2/3 of root, 16-60 mm thick

ii. Cellular cementum: cementocytes; covers dentin in apical ½ to 1/3 of root; also may cover acellular cementum areas in repair areas, 15-200 mm thick

iii. Precementum (cementoid): meshwork of irregularly arranged collagen in surface of cementum where formation starts

iv. Cemento-enamel junction (CEJ): 60-65% of time cementum overlaps enamel; 30% meet end-to-end; 5-10% space between

v. Cementum slower healing than bone or PDL.  If expose dentinotubules ® root sensitivity.

Alveolar bone: 65% inorganic, 35% organic

i. Alveolar bone proper (cribriform plate): lamina dura on x-ray; bundle bone receive Sharpey fibers from PDL

ii. Supporting bone: cancellous, trabecular (vascularized) and F and L plates of compact bone

Blood supply to periodontium

i. Alveolar blood vessels (inferior and superior)

A) Interalveolar: actually runs through bone then exits, main supply to alveolar bone and PDL

B) Supraperiosteal: just outside bone, to gingiva and alveolar bone

C) Dental (pulpal): to pulp and periapical area

D) Terminal vessels (supracrestal): anastomose of A and B above beneath the sulcular epithelium

E) PDL gets blood from: most from branches of interalveolar blood vessels from alveolar bone marrow spaces, supraperiosteal vessels when interalveolar vessels not present, pulpal (apical) vessels, supracrestal gingival vessels

ii. Lymphatic drainage: accompany blood vessels to regional lymph nodes (esp. submaxillary group)