POSTGRADUATE PERIODONTOLOGY - THEORY EXAMINATION NOTES

CLASSIFY OSSEOUS DEFECTS & DIFFERENTIATE BETWEEN SUPRABONY AND INFRABONY POCKETS

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SECTION I: INTRODUCTION AND DEFINITIONS

"Different types of bone deformities can result from periodontal disease. These usually occur in adults and have been reported in human skulls with deciduous dentitions. Their presence may be suggested on radiographs, but careful probing and surgical exposure of the areas are required to determine their exact conformation and dimensions."

• Carranza's Clinical Periodontology, 10th Edition (Ch. 28)
• Newman and Carranza's Clinical Periodontology and Implantology, 14th Edition (Ch. 22)

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SECTION II: FACTORS DETERMINING BONE MORPHOLOGY IN PERIODONTAL DISEASE

1. The thickness, width, and crestal angulation of the interdental septa
2. The thickness of the facial and lingual alveolar plates
3. The presence of fenestrations and dehiscences
4. The alignment of the teeth
5. Root and root trunk anatomy
6. Root position within the alveolar process
7. Proximity with another tooth surface

• Carranza's 10th Ed. (Ch. 28) and Newman 14th Ed. (Ch. 22)

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SECTION III: CLASSIFICATION OF OSSEOUS DEFECTS

FLOWCHART: CLASSIFICATION OF OSSEOUS DEFECTS (Text Format)

OSSEOUS DEFECTS IN PERIODONTAL DISEASE
                    |
    ________________|_________________
    |                                 |
BONE LOSS PATTERNS               BONE DEFORMITIES
    |                                 |
    |____Horizontal Bone Loss         |____Vertical/Angular Defects (Intrabony)
    |                                 |        |___One-wall (Hemiseptum)
    |                                 |        |___Two-wall
    |                                 |        |___Three-wall (originally "Intrabony defect")
    |                                 |        |___Combined Osseous Defect
    |                                 |        |___Circumferential Defect
    |                                 |
    |                                 |____Osseous Craters (Two-wall specific type)
    |                                 |
    |                                 |____Reversed (Negative) Architecture
    |                                 |
    |                                 |____Bulbous Bone Contours (Exostoses/Lipping)
    |                                 |
    |                                 |____Ledges
    |                                 |
    |                                 |____Furcation Involvement (Grade I-IV)

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A. HORIZONTAL BONE LOSS

• Carranza's 10th Ed. (Ch. 28)

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B. VERTICAL (ANGULAR) DEFECTS - PRIMARY CLASSIFICATION

• Carranza's 10th Ed. (Ch. 28) - uses term "intrabony"
• Newman 14th Ed. (Ch. 22) - uses term "infrabony" (recent terminology change - see Section VIII)

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GOLDMAN AND COHEN'S CLASSIFICATION OF ANGULAR (VERTICAL) DEFECTS

(Based on Number of Osseous Walls)

• "Vertical defects increase with age"
• "Approximately 60% of persons with interdental angular defects have only a single defect"
• "Vertical defects detected radiographically have been reported to appear most often on the distal surfaces and mesial surfaces"
• "Three-wall defects are more frequently found on the mesial surfaces of upper and lower molars"
• Carranza's 10th Ed. (Ch. 28) and Newman 14th Ed. (Ch. 22)

"Angular bony defects were directly associated with the apical extension of bacterial plaque. Waerhaug stated that an angular defect forms when the subgingival plaque front on one tooth surface in an interproximal region advances further apically than does the plaque front on the adjacent tooth." - Periodontics Medicine Surgery Implants

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SPECIFIC DEFECT TYPES (Detailed)

1. ONE-WALL DEFECT (HEMISEPTUM)

• "The one-wall vertical defect is also called a hemiseptum." - Carranza's 10th Ed.
• "Hemiseptal defects are one- or two-wall osseous defects that often are found around mesially tipped teeth." - Newman 14th Ed. (Ch. 48)
• Only one bony wall remains: the distal wall only (in the described example: Figures 28-16C and 22.40C)
• Poorest regenerative potential

2. TWO-WALL DEFECT

• Two walls remain; distal (1) and lingual (2) walls present; buccal wall absent
• Carranza's 10th Ed. (Ch. 28) - Figure 28-16B; Newman 14th Ed. - Fig. 22.40B

3. THREE-WALL DEFECT

• "The three-wall vertical defect was originally called an intrabony defect." - Carranza's 10th Ed.
• Three bony walls: distal (1), lingual (2), and facial (3) - appears most frequently on the mesial aspects of second and third maxillary and mandibular molars
• Best prognosis for regeneration
• Newman 14th Ed. states: "Three-wall osseous defects are amenable to pocket reduction with orthodontic tooth movement..." (Ch. 48)

4. COMBINED (MIXED) OSSEOUS DEFECT

• "The number of walls in the apical portion of the defect may be greater than that in its occlusal portion, in which case the term combined osseous defect is used."
• "Because the facial wall is half the height of the distal (1) and lingual (2) walls, this is an osseous defect with three walls in its apical half and two walls in the occlusal half." - Carranza's 10th Ed. (Fig. 28-20); Newman 14th Ed. (Fig. 22.43)

5. CIRCUMFERENTIAL DEFECT

• "Continuous defects that involved more than one surface of a tooth, in a shape that is similar to a trough, are called circumferential defects." - Newman 14th Ed. (Ch. 22)
• Carranza's 10th Ed. Figure 28-19: "Circumferential vertical defect in relation to the upper premolar and canine."

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C. OSSEOUS CRATERS

• "Craters have been found to make up about one third (35.2%) of all defects and about two thirds (62%) of all mandibular defects"
• "Occur twice as often in posterior segments as in anterior segments"
• "The heights of the facial and lingual crests of a crater have been found to be identical in 85% of cases, with the remaining 15% being almost equally divided between higher facial crests and higher lingual crests"

1. The interdental area collects plaque/biofilm and is difficult to clean
2. The normal flat or even concave faciolingual shape of the interdental septum in lower molars may favor crater formation
3. Vascular patterns from the gingiva to the center of the crest may provide a pathway for inflammation

• Carranza's 10th Ed. (Ch. 28); Newman 14th Ed. (Ch. 22)

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D. REVERSED (NEGATIVE) ARCHITECTURE

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E. BULBOUS BONE CONTOURS

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F. LEDGES

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G. EXOSTOSES

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H. BUTTRESSING BONE FORMATION (LIPPING)

• "When it occurs within the jaw, it is termed central buttressing bone formation."
• "When it occurs on the external surface, it is referred to as peripheral buttressing bone formation."
• "The latter may cause bulging of the bone contour, termed lipping, which sometimes accompanies the production of osseous craters and angular defects." - Carranza's 10th Ed. (Ch. 28)

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I. FURCATION INVOLVEMENT

• Carranza's 10th Ed. (Ch. 28) and Newman 14th Ed. (Ch. 22)

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SECTION IV: RELATIONSHIP OF THE POCKET TO BONE - DEFINITION OF POCKET TYPES

DEFINITION FROM NEWMAN 14TH ED. (Ch. 22):

DEFINITION FROM CARRANZA'S 10TH ED. (Ch. 27):

DEFINITION FROM PERIODONTOLOGY FOR THE DENTAL HYGIENIST (4th Ed., Ch. 7):

DEFINITION FROM PERIODONTOLOGY FOR THE DENTAL HYGIENIST (Ch. 14):

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SECTION V: TABLE OF DISTINGUISHING FEATURES - SUPRABONY vs. INFRABONY/INTRABONY POCKET

TABLE 27-2 / TABLE 22.2 - DISTINGUISHING FEATURES OF SUPRABONY AND INTRABONY/INFRABONY PERIODONTAL POCKETS

• Carranza's 10th Ed. Table 27-2 (Ch. 27); Newman 14th Ed. Table 22.2 (Ch. 22)

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SECTION VI: ADDITIONAL DIFFERENTIATING CHARACTERISTICS

Glickman's Zone Theory (Clinical Periodontology and Implant Dentistry, 6th Ed. - Lindhe)

• Clinical Periodontology and Implant Dentistry, 6th Ed. (Ch. 16 - Lindhe)

Waerhaug's Concept (opposing Glickman):

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SECTION VII: COMPREHENSIVE COMPARISON TABLE

Cross-Reference: How Different Textbooks Describe Key Points

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SECTION VIII: RECENT TERMINOLOGY CHANGES

CRITICAL EXAMINER KEYWORD: Terminology Change - "Intrabony" vs. "Infrabony"

• Newman 14th Ed. (Ch. 22): uses "infrabony" throughout
• Carranza's 10th Ed. (Ch. 27): uses "intrabony" throughout
• Periodontology for the Dental Hygienist (4th Ed.): "Suprabony periodontal pockets occur above the crest of the alveolar bone and intrabony pockets extend apically..." but also uses "infrabony" in Ch. 14

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SECTION IX: CLINICAL CORRELATION - TREATMENT IMPLICATIONS

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SECTION X: RAPID-REVIEW SUMMARY TABLE - OSSEOUS DEFECT TYPES

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SECTION XI: KEY EXAMINER KEYWORDS (HIGHLIGHTED)

1. Goldman and Cohen - classifiers of angular defects based on number of osseous walls
2. Intrabony (Carranza 10th) vs. Infrabony (Newman 14th) - TERMINOLOGY CHANGE
3. Hemiseptum - one-wall vertical defect
4. Three-wall defect - originally called "intrabony defect" by Prichard
5. Osseous craters - "specific type of two-wall defect" (Newman 14th); 35.2% of all defects; 62% mandibular
6. Combined osseous defect - three walls apically, two walls coronally
7. Circumferential defect - trough-like, involves multiple surfaces
8. Reversed/Negative architecture - more common in maxilla
9. Horizontal bone loss - most common; associated with suprabony pockets
10. Vertical/Angular bone loss - associated with infrabony pockets
11. Transseptal fibers - horizontal in suprabony; oblique in infrabony/intrabony pockets
12. Buttressing bone formation/Lipping - central vs. peripheral types
13. Furcation grades I-IV - Grade III = through-and-through (not visible); Grade IV = with gingival recession
14. Enamel projections - in 13% of multirooted teeth (furcation factor)
15. Waerhaug vs. Glickman - opposing concepts on angular defect pathogenesis
16. Zone of irritation vs. Zone of co-destruction (Glickman)
17. Regenerative approaches for contained infrabony (multi-wall) defects
18. Resective procedures (gingivectomy, osseous surgery) for suprabony pockets
19. 60% of angular defect cases have only a single defect
20. Vertical defects increase with age

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SECTION XII: SOURCES USED

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• Horizontal bone loss
• Goldman and Cohen's wall-based classification of angular defects (1-wall/hemiseptum, 2-wall, 3-wall, combined, circumferential) with a comparison table
• Osseous craters with all statistics (35.2%, 62% mandibular, 85% equal heights)
• Reversed/negative architecture
• Bulbous bone contours, ledges, exostoses, buttressing/lipping
• Furcation involvement Grades I-IV

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LANDMARK AND IMPORTANT STUDY ARTICLE NOTES

Topic: Classification of Osseous Defects & Differentiation of Suprabony and Infrabony Pockets in Periodontology

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ORGANIZATION OF NOTES

1. Foundational/Classification Papers (historical landmarks)
2. Epidemiology/Prevalence Studies (how common and how distributed)
3. Pathogenesis Papers (how they form - plaque vs. occlusal trauma debate)
4. Treatment Outcomes Papers (systematic reviews informing management)

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GROUP 1: FOUNDATIONAL LANDMARK PAPERS

(Classification and Definition of Osseous Defects)

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PAPER 1 - THE DEFINING CLASSIFICATION PAPER ⭐⭐⭐⭐⭐

• FIRST systematic classification of the infrabony pocket based on the number of remaining osseous walls
• Established the one-wall, two-wall, three-wall, and four-wall osseous defect terminology that remains in use to this day
• Introduced the concept that the number of remaining bony walls determines the prognosis for treatment - specifically that contained (multi-wall) defects have a better healing potential
• Distinguished the infrabony pocket from the suprabony pocket as a distinct pathological entity requiring different surgical management
• First to propose the "intrabony technique" as a predictable surgical procedure for managing infrabony defects
• Established that infrabony pockets have a vertical (angular) bone destruction pattern, as opposed to the horizontal bone destruction of suprabony pockets
• The classification is eponymously cited in every major periodontology textbook as the "Goldman and Cohen classification" of angular osseous defects

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PAPER 2 - THREE-WALL (INTRABONY) DEFECT TECHNIQUE ⭐⭐⭐⭐⭐

• Prichard coined the term "intrabony defect" (synonymous with the three-wall defect) and was the first to establish its surgical management as a predictable procedure
• His classification of osseous defects caused by periodontal disease included: interproximal craters, inconsistent margins, hemisepta, furca invasions, intrabony defects (infrabony defects with three osseous walls), and combinations
• Distinguished fenestrations (denuded bone areas with intact marginal bone) from dehiscences (denuded areas involving marginal bone) as additional anatomic aberrations
• Established that the three-wall intrabony defect had the greatest potential for bone fill and new attachment following surgery
• His subsequent 1960 paper ("A technique for treating infrabony pockets based on alveolar process surgery") further refined the surgical approach

1. Interproximal craters
2. Inconsistent margins
3. Hemisepta
4. Furca invasions
5. Intrabony defects (three osseous walls)
6. Combinations of the above
7. Complicated by: thick marginal ledges, exostoses, tori, fenestrations, and dehiscences

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PAPER 3 - KARN ET AL. TOPOGRAPHIC CLASSIFICATION ⭐⭐⭐

• Proposed a topographic classification system of alveolar process deformities - a complement to the Goldman-Cohen wall-based system
• Classified defects based on the topographic/anatomic relationship of bone to teeth
• Provided a different organizational framework for understanding how defects manifest across different root surfaces and interproximal regions

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GROUP 2: EPIDEMIOLOGY AND PREVALENCE STUDIES

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PAPER 4 - PREVALENCE IN DRY MANDIBLES ⭐⭐⭐⭐

• Examined 100 dry mandibles (South African Negroes) for intrabony defects
• 231 intrabony defects detected out of possible occurrences (4.1%)
• Established the distribution of defect types: 35.8% one-walled, 49.6% two-walled, 15% three-walled
• Found 51 craters, 19 of which (37%) were associated with distal surfaces of second molars
• Found that 84.3% of craters had higher lingual than buccal walls (contradicting the Carranza textbook finding of "identical in 85% of cases" - examiner can contrast this with clinical studies)
• Found that interproximal root surfaces were far more commonly involved with defects than buccal or lingual surfaces
• 39.4% of one-walled pockets formed hemisepta against interproximal root surfaces
• Confirmed that mesial surfaces of canines were most commonly involved with hemisepta
• Found that frequency of intrabony pockets increased from anterior to posterior zones of mandible

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PAPER 5 - CLINICAL PREVALENCE IN ADULT PERIODONTITIS ⭐⭐⭐⭐

• Comprehensive clinical study using direct surgical observation during periodontal surgery (gold standard method)
• 286 patients with moderate/advanced adult periodontitis; 5476 teeth examined after full-thickness mucoperiosteal flap reflection
• 981 defects detected: 533 maxilla (15.4% of teeth), 448 mandible (22.4% of teeth)
• Posterior mandibular segment had the highest percentage of teeth with defects (33.8%), followed by posterior maxillary segment (19.9%)
• Defects were classified as interdental craters, hemisepta, and infrabony defects with 1, 2, 3, or 4 walls
• Craters accounted for nearly half of all defects - confirmed as the most prevalent defect type, more common in posterior segments
• Hemisepta formed the lowest proportion of defects
• Confirmed that anatomical variations in alveolar bone shape between the maxilla and mandible and between anterior/posterior regions were responsible for the observed differences in defect distribution
• The highly significant difference (p=0.00001) in defect rates between maxilla and mandible in posterior segments, but no difference in anterior segments, is a key finding

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PAPER 6 - CBCT CLASSIFICATION OF BONE DESTRUCTION PATTERNS ⭐⭐⭐

• First study using cone-beam computed tomography (CBCT) to classify periodontal bone defect prevalence - important for modern radiographic diagnosis
• Classified remaining alveolar bone into six main groups based on CBCT evaluation of four aspects and furcation areas
• Key findings: Horizontal bone defects were most common (71.4%), while three-walled vertical bone defects were least common (1.9%)
• Osseous craters found in 6.7% of interdental alveolar bone assessments
• Dehiscence: 2.7%; Fenestration: 3.3%
• In furcation areas: no furcation involvement in 61.4% of teeth; Grade II involvement most common (26.2%) among involved teeth
• Reinforces that CBCT provides three-dimensional assessment of defect morphology not possible with conventional radiography, aiding in precise treatment planning

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GROUP 3: PATHOGENESIS PAPERS

(The Plaque vs. Occlusal Trauma Debate for Infrabony Pocket Formation)

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PAPER 7 - GLICKMAN'S CO-DESTRUCTION THEORY ⭐⭐⭐⭐⭐

• Glickman, I. (1965). Occlusion and the periodontium. Journal of Dental Research, 44(1), 16-21.
• Glickman, I. (1967). Clinical significance of trauma from occlusion. Journal of the American Dental Association, 70, 607-618.

• Proposed the "Zone of Irritation" and "Zone of Co-Destruction" theory - the most cited framework for explaining why infrabony pockets form
• Zone of Irritation: Marginal and interdental gingiva; responds only to plaque; produces horizontal bone loss and suprabony pockets
• Zone of Co-Destruction: Cementum, PDL, and alveolar bone; if exposed to both plaque AND excessive occlusal forces simultaneously, produces angular bone defects and infrabony pockets
• Proposed that excessive occlusal forces alter the pathway of spread of plaque-induced inflammation from a periosteal route (horizontal) to a PDL route (vertical) - hence the angular pattern
• Coined the term "co-destructive factor" for occlusal trauma in the pathogenesis of infrabony pockets
• This concept was widely accepted for two decades and remains frequently cited and debated

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PAPER 8 - WAERHAUG'S CHALLENGE TO CO-DESTRUCTION THEORY (Part 1) ⭐⭐⭐⭐⭐

• Directly challenged Glickman's co-destruction concept using extracted teeth from patients with advanced periodontal disease
• Used stereomicroscopy with staining of subgingival plaque and remaining attachment fibers - highly precise methodology
• Key finding: In the depth of infrabony pockets, there was close congruence between the front of subgingival plaque and the border of remaining attachment fibers (0.2-2.0 mm distance)
• Found close relationship between subgingival plaque front and the alveolar crest (1-3 mm)
• "There was no evidence to indicate that trauma from occlusion had been involved in the pathogenesis of the infrabony pockets"
• Tooth mobility adjacent to infrabony pockets was: normal in 42%, slightly increased in 31%, excessively increased in only 11% - demonstrating no direct correlation
• After hemisection and periodontal treatment, 8 of 12 remaining roots functioned for 1-10 years without further angular defect formation when plaque was controlled
• Established that infrabony pockets are invariably associated with subgingival plaque downgrowth - not occlusal forces

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PAPER 9 - WAERHAUG'S CHALLENGE (Part 2) - THE PLAQUE-ANGULAR DEFECT RELATIONSHIP ⭐⭐⭐⭐⭐

• Examined 64 sets of human teeth with bite analysis, radiographs, and mesiodistal sections - methodologically comprehensive
• Five landmark observations:
  1. Before attachment loss, the configuration of the interdental septum is entirely dependent on the CEJ location of neighboring teeth - if CEJs are at different levels, the bone crest is oblique even before disease
  2. Loss of attachment was invariably related to the apical growth of subgingival plaque (lysis of attachment fibers within 0.2-1.8 mm of the plaque front)
  3. Alveolar crest height was determined by the level of the plaque on the two neighboring tooth surfaces - if plaque reached the same level on both sides = horizontal bone crest; if different levels = angular/oblique crest = ANGULAR DEFECT FORMATION
  4. "In the present material no evidence was found to indicate that functional (traumatic) forces can act as a co-factor in the causation of angular defects" - they occurred equally often adjacent to traumatized and non-traumatized teeth
  5. Infrabony pockets were invariably associated with downgrowth of subgingival plaque

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PAPER 10 - ROSLING ET AL. - BONE REGENERATION IN INFRABONY POCKETS REQUIRES PLAQUE CONTROL ⭐⭐⭐⭐⭐

• Landmark RCT by the Gothenburg school (Rosling, Nyman, Lindhe) - 24 patients with advanced periodontal disease, randomized into test and control groups
• Both groups: oral hygiene instruction + modified Widman flap surgery
• Test group: Recalled every 2 weeks for professional tooth cleaning for 2 years
• Control group: Recalled every 12 months only
• Test group result: ALL osseous defects were refilled with bone over the 2-year period
• Control group result: Could not maintain oral hygiene; exhibited progressive deterioration of periodontal tissues
• Established that infrabony defects can exhibit spontaneous bone repair (without grafts or membranes) when plaque is optimally controlled after surgery
• Proved the direct role of subgingival plaque in the maintenance of infrabony defects (consistent with Waerhaug's concept)
• This study was the clinical validation of the concept that plaque control is the prerequisite for bone regeneration in infrabony pockets
• Is frequently cited as showing that infrabony defects are not irreversibly destructive - they can heal with adequate plaque control

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GROUP 4: TREATMENT OUTCOMES - SYSTEMATIC REVIEWS

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PAPER 11 - SYSTEMATIC REVIEW: DEFECT MORPHOLOGY AND REGENERATIVE OUTCOMES ⭐⭐⭐⭐⭐

• The only systematic review specifically examining how defect morphology affects regenerative outcomes - directly relevant to the examination question
• Meta-analysis of 15 publications: Initial defect depth influenced radiographic bone gain at 12 months; narrower angles and increased number of walls influenced BOTH radiographic bone gain AND CAL gain at 12 months
• Key finding: "Deeper defects with narrower angles and increased number of walls exhibit improved CAL and radiographic bone gain at 12 months post-regenerative surgery"
• These associations occurred irrespective of the biomaterials used - demonstrating that defect morphology itself is the primary determinant of regenerative potential, not just the treatment used
• Provides the systematic evidence base for the clinical principle that 3-wall > 2-wall > 1-wall defects in terms of regenerative potential
• Also highlighted the lack of standardized reporting of defect morphology in periodontal literature - a methodological gap

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PAPER 12 - SYSTEMATIC REVIEW: REGENERATIVE VS. ACCESS FLAP ⭐⭐⭐⭐⭐

• The largest and most comprehensive systematic review on the treatment of intra-bony (infrabony) defects - 79 RCTs published 1990-2019
• All regenerative procedures provided adjunctive benefit in terms of CAL gain (1.34 mm; 95% CI: 0.95-1.73) compared with open flap debridement alone
• Both EMD (enamel matrix derivative) and GTR (guided tissue regeneration) were superior to OFD alone
  • EMD: CAL gain 1.27 mm (95% CI: 0.79-1.74)
  • GTR: CAL gain 1.43 mm (95% CI: 0.76-2.22)
• Addition of DBBM (deproteinized bovine bone mineral) improved outcomes of both GTR with resorbable barriers and EMD
• Papillary preservation flaps enhanced clinical outcomes
• Conclusion: "EMD or GTR in combination with papillary preservation flaps should be considered the treatment of choice for residual pockets with deep (≥3 mm) intra-bony defects"
• This review justifies the clinical principle that contained infrabony defects (multi-wall) should be managed regeneratively, while non-contained (one-wall) defects may require resective approaches

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PAPER 13 - SYSTEMATIC REVIEW: MEDIUM AND LONG-TERM BENEFITS ⭐⭐⭐⭐

• Long-term data (3-20 years post-treatment) on regenerative/reconstructive procedures for intrabony defects
• OFD was clearly the least efficacious; regenerative treatments produced significantly shallower residual PD in 4 of 8 comparisons (range: -2.37 to -0.60 mm) and larger CAL gain in 6 of 8 comparisons (range: 1.26 to 2.66 mm)
• Combination approaches appeared most efficacious (graft + membrane ± growth factors)
• Tooth loss was significantly lower after regenerative/reconstructive treatment (0.4%) compared with OFD alone (2.8%)
• Established that regenerative treatment of intrabony defects translates into high rates of tooth survival on a medium (3-5 years) to long-term (5-20 year) basis
• Key implication: Proper classification of osseous defects is essential because contained multi-wall defects justify regenerative investment - the long-term tooth survival data supports this clinical decision

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SUMMARY TABLE: ALL LANDMARK PAPERS AT A GLANCE

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EXAMINER'S QUICK REFERENCE: MOST FREQUENTLY ASKED ABOUT PAPERS

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• Goldman & Cohen (1958) - The original 1-2-3-wall classification of infrabony pockets - the single most cited paper in this topic
• Prichard (1957, 1960) - Coined "intrabony defect" for three-wall defects; established surgical predictability
• Karn et al. (1984) - Topographic classification system

• Tal (1984) [PMID 6584590] - 100 dry mandibles; 2-wall defects most common (49.6%); craters had higher lingual walls in 84.3%
• Vrotsos et al. (1999) [PMID 9923510] - 5476 teeth; craters = ~50% of all defects; posterior mandible most affected
• Ozcan & Sekerci (2017) [PMID 28891547] - First CBCT study; horizontal defects most common (71.4%)

• Glickman (1965/1967) - Zone of irritation/co-destruction; occlusal forces create infrabony pockets
• Waerhaug (1979) x2 [PMID 381633 + 287677] - Differential plaque downgrowth creates angular defects; no role for occlusal trauma
• Rosling, Nyman, Lindhe (1976) [PMID 767366] - All infrabony defects refilled with bone under strict plaque control (RCT)

• Nibali et al. (2021) [PMID 33025619] - More walls + deeper + narrower angle = better regenerative outcome
• Nibali et al. (2020) [PMID 31860134] - EMD or GTR + papillary preservation flap = treatment of choice
• Stavropoulos et al. (2021) [PMID 33289191] - 3-20 year follow-up; regeneration gives 0.4% tooth loss vs. 2.8% with OFD