Alveolar bone defects in adults reporting for orthodontic treatment - A CBCT study

Identifying alveolar bony fenestration and dehiscence preceding orthodontic treatment, especially arch expansion, is needed. An unrevealed and undiagnosed buccal alveolar bone defect leads to treatment relapse and further loss of bony support. The aim of this study was to determine the extent of posterior alveolar bony dehiscence and fenestration in adults undergoing orthodontic treatment. A total of 20 subjects in the age range 18-35 years were selected for this study randomly and their CBCT records were retrieved from the Department of Orthodontics, Saveetha dental college. All statistical analysis was performed using SPSS. Chi-square test was used to determine the association of extent of fenestrations and dehiscence between males and females. Females presented with wider and extensive dehiscence defects than males (p=0.019, p<0.05). On the other hand, there was a statistically non-significant association of fenestration severity between males and females. (p=0.178, p>0.05) Within the limits of this study, it was observed that females presented with more severe bony alveolar dehiscence than males.


INTRODUCTION
Diagnosis of alveolar bony defects such as fenestration and dehiscence before orthodontic treatment is bene icial for orthodontists due to several reasons (Leung et al., 2010). Studies have reported that the incidence of alveolar bone dehiscence and fenestration may cause a gingival recession, decrease bony support of teeth (Zachrisson and Alnaes, 1974;Xu et al., 2013). An unrevealing and undiagnosed buccal alveolar bone defect leads to a greater potential for treatment relapse (Rothe et al., 2006). This leads to unaesthetic inishing of orthodontic treatment and can lead to tooth sensitivity (Samantha and Sridharan, 2016). Orthodontic treatment if not carried out properly, can lead to fenestration and dehiscence (Arvind and Jain, 2020).
Recognition of alveolar bony dehiscence and fenestration was not feasible with traditional 2dimensional imaging (Krishnan et al., 2015). With the advent of CBCT, it's now possible to view these defects three-dimensionally (Christopher et al., 2018). Timock et al. reported that the precision and reliability of the buccal bone height, as well as thickness measurements from CBCT, are sustainable and appropriate (Timock et al., 2011;Vikram et al., 2017;Jain et al., 2014). Studies have examined the alveolar bony dehiscence using CBCT in patients with cleft lip and palate and those undergoing rapid maxillary expansion and in different malocclusions (Buyuk et al., 2016;Baysal et al., 2013;Yagci et al., 2012).
However, there has not been signi icant literature examining alveolar bony defects in adults undergoing orthodontic treatment (Kamisetty et al., 2015;Viswanath et al., 2015). It's essential that orthodontists should know the anatomical limits of tooth movement to make them aware of potential periodontal problems that could worsen during orthodontic treatment (Coşskun and Kaya, 2019;Hwei and Thomas, 2014). CBCT has shown to have high speci icity and negative predictive value for dehiscence as well as fenestration but a low positive predictive value (Sun et al., 2015). Leung et al. reported that CBCT value has relatively high accuracy in diagnosing dehiscence and fenestration (Leung et al., 2010). Orthodontists using bony defects data as a precaution prior to treatment should be viewed as an exaggeration to the side of caution rather than giving misinformation. Given that CBCT users comprehend the extent of its accuracy, clinicians can still use the bony defect information within the boundaries of the overestimation limit (Murugesan and Jain, 2020).
The aim of this study was to determine the prevalence of posterior alveolar bony dehiscence and fenestration in adults undergoing orthodontic treatment.

Study design
This was a retrospective study. 20 Adults subjects aged from 18 to 35 years old were chosen from DIAS and their CBCTs were retrieved. Only subjects in whom good quality CBCT were available Inclusion criteria 3. History of previous orthodontic treatment.
After applying the inclusion and exclusion criteria, 10 males and 10 females were included in the study.

Sampling method
To minimize sampling bias, simple random sampling was carried out. The investigator A.T. did not have access to the demographic information of the subjects CBCT DICOM iles until the study had not been completed.

Bony defect measurement method
All CBCT images were observed and measured using dolphin imaging 11.8 premium software by the same investigator (A.T). The image was aligned using the FH line in such a way that the FH plane is parallel to the loor and the midsagittal plane was perpendicular to the FH plane. The posterior quadrant was observed in a multiplanar view with magni ication up to 3 times. Once enlarged, the posterior segment was aligned anteroposteriorly on the axial view.
For the lesion to be identi ied as dehiscence, it had to be equal to or greater than 2mm in the vertical distance from CEJ. This was done in order to eliminate counting normal bone level as dehiscence, which is usually 1.5-2mm below the CEJ. There was no minimum requirement lesion size to be counted as fenestration. If any amount of bone was denuded on root surface but was not found to be continuous to the marginal bone, it was counted and measured as a fenestration.

Statistical Analysis
All statistical analysis was performed in SPSS. A Chi-square test was done to determine the association of the alveolar bony defects between males and females.

RESULTS AND DISCUSSION
A tooth was counted as the one with bony defect when there was the presence of a defect on one side, either mesial or distal, or on both sides. Table 1 depicts the mean widths and standard deviation of bony defects. Table 2 depicts the association of extent of fenestrations and dehiscence in males and females. Figure 1 and Figure 2 represents the association of fenestration and dehiscence in males and females.
In Figure 1, The X-axis represents the width of the dehiscence and Y-axis represents gender. Pearson's chi-square value-5.49, p value-0.019(<0.05) hence its statistically signi icant. In Figure 2 The Xaxis represents the width of the fenestration and Yaxis represents gender. Pearson's chi-square value-1.818, p-value-0.178(>0.05) hence its not signi icant.
In the present study, all measurements were done    on CBCTs patients requiring orthodontic treatment.
On studying the extent of fenestration and dehiscence in males and females, it was reported that there was a signi icant association of more severity and extent of dehiscence in females than in males. There was no statistically signi icant association of extent of fenestration between males and females. With regard to patient selection, growing patients had not been included in the study because previous studies have reported that hormonal and functional changes associated with age in luence cortical bone thickness Usui et al. (2007); Papadopoulos (2014). In our study, CBCT was used since it is the imaging of choice in orthodontics nowadays since a 3-dimensional view of the entire dentition and craniofacial structures but due radiation concerns, CBCT should not routinely be considered in orthodontics (Meena and Kowsky, 2014).
Rupprecht et al. conducted a prevalence study of dehiscence and fenestration in modern American skulls and reported that African-American males and Caucasian females were signi icantly more likely to have dehiscences, while African-American females were signi icantly more likely to have fenestrations but this was a craniometric study whereas the present study involved CBCT (Leung et al., 2010). Similarly, Ana et al. reported that the percentage of teeth with considerable bone loss was higher in females, but was not signi icantly associated (Malčić et al., 2011). Choi et al. reported that adults in crossbite reported higher prevalence to total bony defects and dehiscence, but an association was not performed between males and females (Choi et al., 2020).
The overall consensus in the available literature on this topic agrees with the indings of the present study. The limitation of this study was a small sample size. Since this was a retrospective study, the settings of the CBCT images could not be controlled. As dehiscence and fenestrations do not have a speci ic geometric shape, changing the orientation of the image can lead to a slight change in the measurements on measuring vertical diameter.
Future scope indicates that investigations should be carried out pre-and post-orthodontic treatment. Study larger sample size, more no. of teeth should be evaluated, and type of malocclusion should be taken into consideration.

CONCLUSION
Within the limitations of this study, it can be concluded that in females dehiscence defects were wider than males, but no gender association was seen for fenestration.