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 Table of Contents  
Year : 2022  |  Volume : 17  |  Issue : 4  |  Page : 990-995

Unraveling the quantification of intrabony defect

Department of Periodontics and Implant Dentistry, Tamil Nadu Government Dental College and Hospital, Chennai, Tamil Nadu, India

Date of Submission25-Aug-2022
Date of Acceptance12-Sep-2022
Date of Web Publication10-Feb-2023

Correspondence Address:
Dr. Rajakumari Natarajan
No. 1, Sathyamoorthy Colony, Thiruvalleswarar Nagar, Thirumangalam, Chennai - 600 040, Tamil Nadu
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jdmimsu.jdmimsu_377_22

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Periodontitis a chronic inflammatory disease caused by dysbiotic plaque biofilm is characterized by the destruction of periodontal supporting structures. Based on the direction and angle, interproximal bone loss can either be horizontal or vertical. The identification and evaluation of these defects are imperative to ascertain therapeutic intervention. In this review, a detailed discussion about various methods adopted in evaluating interproximal bone defect is scrutinized.

Keywords: Intrabony defect, periodontitis, techniques for measurement

How to cite this article:
Natarajan R, Arunachalam M, Krishnamurthi M, Raj SS. Unraveling the quantification of intrabony defect. J Datta Meghe Inst Med Sci Univ 2022;17:990-5

How to cite this URL:
Natarajan R, Arunachalam M, Krishnamurthi M, Raj SS. Unraveling the quantification of intrabony defect. J Datta Meghe Inst Med Sci Univ [serial online] 2022 [cited 2023 Nov 29];17:990-5. Available from: https://journals.lww.com/dmms/pages/default.aspx/text.asp?2022/17/4/990/369499

  Introduction Top

Periodontitis, a chronic inflammatory disease is characterized by the destruction of periodontal supporting structures. A classical feature of periodontitis is alveolar bone loss. The unmitigated analysis of alveolar bone loss is essential for the therapeutic management of periodontitis. Several methods, both invasive and noninvasive techniques are being used for the analysis of alveolar bone loss. However, noninvasive radiographic techniques are the commonly employed method for assessing alveolar bone loss. In this review, we will discuss in detail about various methods adopted in evaluating interproximal bone defect (BD).

  Alveolar Bone Loss Top

An equilibrium between bone deposition and bone resorption is crucial for an ideal intact alveolar bone. When there is a shift in this equilibrium either due to increase in bone resorption or decrease in bone deposition, bone loss occurs. Alveolar bone loss has two components, cortical bone loss and trabecular bone loss. Cortical bone loss prevails by an increase in cortical porosity, whereas trabecular bone loss betides due to depletion of bony trabeculae.[1] Based on the direction and angle, interproximal bone loss can either be horizontal or vertical. The vertical bone loss is further classified into one wall, two walls, three walls, or combined defects. The quantitative assessment of the amount of bone loss that occurred is exacting, however they are an indispensable requirement for periodontal regenerative surgery.

  Interproximal Bone Defect Top

Evaluation of bone loss is done based on the linear measurements between anatomic landmarks such as cementoenamel junction (CEJ), alveolar bone crest (AC), and BD level. Bone loss can be appraised in terms of the following parameters

  1. Vertical (Height of the defect)
  2. Horizontal (Mesiodistal width, buccolingual width of the defect)
  3. Defect angle.

These measurements can be taken either clinically or radiographically. Periodontal BDs can be assessed in the following ways,

  1. Probes
  2. Radiographic methods

    • Intraoral periapical radiograph (IOPA) and digital imaging
    • Bitewing
    • Circular tomosynthesis
    • Orthopantomogram (OPG)
    • Computed tomography (CT)
    • Cone-beam CT (CBCT)

  3. Recent advancement

    • Ultrasonography.

  4. Gold standard

  • Intrasurgical (IS).


Clinically BDs can be appraised using calibrated manual periodontal probes. Under local anesthesia, the probe is pushed through the gingival sulcus and the following landmarks should be recorded

  • CEJ
  • Alveolar bone level
  • The deepest area of penetration where strong resistance is met by probe on contact with bone. This is recorded as the base of the BD.[2]

Subsequently following linear measurements should be determined, the distance from CEJ to the alveolar bone crest (AC) and the distance from CEJ to the base of the defect (BD). By subtracting (CEJ–AC) from (CEJ–BD) the infrabony component of the BD can be obtained.[3] These measurements are made at the line angles of the tooth.[4]


  • Abolfazli et al. in their study reported a difference of 0.27 mm and 0.9 correlation on comparing bone probing with the direct surgical assessment[5]
  • Savitha et al. have suggested a difference of 0.25 ± 0.02 mm and 0.97 correlation between bone probing and IS assessment.[6]


Several authors such as Greenberg et al. in their study have shown that there is a close correlation between measurements of bone probing level and surgically confirmed bone level.[7] However, there are certain pitfalls in this technique,

  • Burnett et al. and Suomi et al. suggested in their study that there is an underestimation of actual bone loss level in this technique[8],[9]
  • Moreover, this method measures only the vertical component of the BD, they neither evaluate horizontal or angular measurements
  • Most of all clinician's expertise is crucial.

Radiographic methods

Measurement of bone defect


Linares et al. in their study have estimated the intrabony defect by scanning the routine periapical radiograph with high definition scanner.[10] Based on Schei et al.'s[11] and Bjorn et al.'[12] criteria, Linares et al. obtained the following landmarks

  • CEJ
  • Coronal most portion of the alveolar bone crest in the intrabony defect as BC
  • Apical most portion of the bone destruction where still normal periodontal ligament space is maintained as the bottom of the defect (BD)
  • In case of tooth with restorations, apical most margin of the restoration is considered the fixed reference point rather than CEJ.

A linear measurement of CEJ–BD and CEJ–BC is obtained and intrabony defect depth is obtained by (CEJ–BD) – (CEJ–BC).

Defect angle measurement

Linares et al.[10] also measured defect angle in the radiograph by drawing two lines, a vertical line which represents the root surface of the affected tooth, and a second line representing the BD surface. An angle between these two lines was measured as baseline defect angle.


The horizontal dimension of a defect includes mesiodistal width and buccolingual width of the defect.

Two dimensions

IOPA and digital images

The most commonly used noninvasive radiographic technique for evaluating BDs are IOPA and bitewing. Silver grains in the emulsion of these radiographs helps in acquiring grayscale values (predominantly ranging from 0.3 to 2 optical density units). These grayscale values are converted into digital code which is exploited in the computer as a digital image. This process is called digitization or quantization. For a quantitative alveolar bone measurement in the digital image, an optima pixel size of 50 μm2 with spatial resolution of 262,144 pixels (512 rows × 512 columns) and 256 shades of gray (28 = 1, byte = 8 bit) are advised.[13] On these images, vertical, horizontal, and angular measurements can be done. On IOPA, linear measurements are appraised using vernier caliper.

Linares et al.[10] in their study have estimated the intrabony defect by scanning the routine periapical radiograph with high definition scanner. To estimate the distortion between consequent radiographs, an anatomic nonvariable distance, i.e. the root length (the distance from CEJ to root apes [RA]) should be measured in all radiographs. The correction factor can be calculated by


  • In a study conducted on comparing the conventional radiograph (IOPA) technique and digital radiograph (radiovisiography) technique on assessing alveolar bone in periodontitis, it was said that there is no significant difference between these two techniques. However, when comparing these two techniques with IS measurement, there was nonsignificant underestimation in terms of horizontal bone loss, whereas vertical bone loss showed a statistically nonsignificant difference[14]
  • However, Wolf et al. in their study have suggested that digitized image radiographs are close in assessment to IS rather than conventional radiographs which are digitized with flatbed scanner[15]
  • Eickholz et al. compared the radiographic assessment and IS assessment of bone loss in intrabony defects utilizing linear measurements. There was an underestimation in the amount of bone loss in radiographic assessment when compared to surgical evaluation (1.41 ± 2.58 mm)[16]
  • Several authors have suggested that the defect angle influences wound healing [Table 1].
Table 1: Defect angle and wound healing

Click here to view


  • These techniques help to measure the vertical and angular measurement of the defect. However, it is impossible to measure the buccolingual width of the defect size, thereby leading to ambiguity in evaluating defect volume
  • As these are two-dimensional radiographic techniques, they are bound to have superimposition among buccal and lingual alveolar bone
  • Aforementioned radiographs are specific but they lack sensitivity as bone loss of >30% can only be detected in radiographs[20]
  • Radiation exposure
  • Diagnosis can be affected exposure condition and contrast and density of the image.

Digital subtraction radiography

Digital subtraction radiography demonstrated by Zeides des Plantes enhances the qualitative and quantitative visualizations of bone density. Thereby providing a high degree of correlation in alveolar bone density changes. About 1%–5%/unit volume of alveolar bone loss can be detected.[21] However, they still provide only a two-dimensional image which impedes the complete measurement of a periodontal defect.

Computer-assisted densitometric image analysis introduced by Bragger et al. is a type of subtraction radiography.[22] Two serial images which are obtained with standardized projection geometry are compared and equalized to analyze the density differences in the images. It quantifies images by comparative analysis of radiographic images.


  • The depth of the defect in the buccolingual plane can be analyzed[22]
  • Helps to quantitatively analyze the alveolar bone density changes over time[23]
  • More sensitive than IOPA and subtraction radiography
  • To assess the outcome after guided tissue regeneration.[24]


OPG produces a single tomographic image of facial structures such as the maxilla, mandible, and dentition and the supporting structures. Vadiati Saberi et al. in their cross-sectional study have compared the diagnostic value of OPG using a digital caliper and digital ruler measurements with direct surgical measurement in assessing the depth of vertical BD. They have reported a high correlation of 0.89 between values measured in digital ruler and direct surgical measurement. A lower correlation value of 0.79 between digital caliper and surgical method.[25]


  • OPG is generally not suggested for assessing periodontal disease as there is an underestimation of marginal bone destruction and overestimation of extensive destruction
  • Less clear and lower resolution compared to IOPA
  • The density of small defects is not visible
  • Superimposition can lead to underestimation of actual BD
  • Diagnosis can be affected by exposure condition and contrast and density of the mage
  • High exposure can lead to crestal bone burn out thereby leading to increased defect size measurement.

Three dimensions

Computed tomography

A three-dimensional image analysis which has the potential for precise measurement of intrabony defects. As it depicts structures in an axial section which helps in the interpretation of the width of the defect.

The measurement of BD was compared among two-dimensional radiographs, CT, and direct IS measurements. For appraising BD using CT, the slices were analyzed for separate measures, as base of the defect and alveolar crest will be located in different slices. The results of this study determined that CT scan has a maximum correlation (-0.218, +0.358) with direct surgical measurement. However, CT underestimated the maximum percentage of sites for detecting osseous destruction of infrabony compartments and they overestimated the depth of vertical osseous defects (71.0%) as alveolar crest and base of the defect assessment are performed in different axial sections.[3]

MicroCT provides cross sections of a three-dimensional object. Micro implies the pixel size of the cross-sectional image. It provides higher spatial resolution than conventional CT. Rosenstein SW et al. in their study demonstrated a difference of 25% among the calculation between two-dimensional and micro-CT scans.[26]

Dental CT scan – A software which provides axial, panoramic, and oblique sagittal planes of CT image of the maxilla and mandible. It helps in observing the bone density, quality, height, and buccolingual dimension of periodontal BD.[27]


  • Overexposure to radiation[28]
  • Unnecessary overprescription.

Cone-beam computed tomography

CBCT is a three dimensional image analysis alternative to CT. It has the advantage of less radiation exposure on comparing to CT and it also brings forth variable fields of view, providing an ideal field of view for each region of interest. Moreover, they also provide a submillimeter isotropic voxel resolution helping in nonorthogonal sectioning of the data.[29] Anter et al. conducted a systematic review on the accuracy of CBCT in measuring periodontal BDs. He reported a minimum error of 0.19 ± 0.11 mm and maximum error of 1.27 ± 1.43 mm while comparing to the gold standard.[30] However, they had no agreement on whether the direction of deviation is over or underestimation.

Several studies have been conducted on the direction of deviation in CBCT in terms of over or underestimation [Table 2].
Table 2: Studies on direction of deviation in cone-beam computed tomography in terms of over or underestimation

Click here to view

  Recent Advancement Top


Current systematic reviews have indicated CBCT as the most accurate method in evaluating intrabony defects next to the gold standard IS assessment.[36] However, they are not routinely used due to radiation exposure and high financial cost. Ultrasonography utilizes ultrasound signal echoes to image the structure of tissues. It is a noninvasive and nonionizing imaging technology. Recently, ultrasonography is being used to analyze bone tissue on estimating cortical bone thickness and in children with scoliosis to imagine the spine.[37],[38]

In a systematic review, ultrasonography and CBCT were compared. Data suggested a difference of 0.071 to 0.68 mm (1.6%–8.8%) in ultrasound values from CBCT. Moreover, ultrasonography underestimates CBCT measurements.[39]


In ultrasonography, the thickness of the alveolar bone cannot be determined since the amount of incident energy which reaches the bottom of the alveolar bone is less due to scattering and attenuation.[40],[41]

  Gold Standard Top

Intrasurgical measurement

This is the gold standard method of assessing intrabony defects. Under local anesthesia a full-thickness mucoperiosteal flap raised and debridement should be done. Then, a calibrated probe should be inserted parallel to the long axis of the root surface, with the tip of the probe located at the apical most point of the defect. Distance from CEJ to the base of the defect (CEJ–BD) is measured. Similarly, another probe should be placed perpendicular to the tooth axis along the root surface, at the crest of the alveolar bone. The distance measured from the intersection of the two probes to the base of the defect is noted as the depth of the defect. The mesiodistal width of the defect is calculated as the distance (horizontal) from the root surface to the mesial edge or distal edge of the defect. The buccolingual width of the defect is measured as the distance from the inner wall of the buccal edge to the inner wall of the lingual edge of the defect at the level of the bone crest. This can be done if the walls of the defect are at the same level. If they are at different levels, then one probe should be placed horizontally at relatively higher defect wall, and the distance from the junction of these two probes to the level of high bone crest to be measured.[36]

  Conclusion Top

Contemporary advances in imaging modalities have empowered periodontists to visualize bone changes more precisely. Digital two-dimensional radiography, CT, and CBCT have already become a reality in periodontics. Present day, bone scanning or radionuclide imaging to analyze the biochemical alteration in alveolar bone is utilized. However, the selection of techniques to analyze the BD pertinent to the case still remains a conundrum. Hence, this review has attempted to summarize various methods to evaluate interproximal BD.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

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  [Table 1], [Table 2]


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