Alveolar Bone Density Reduction in Rats Caused by Unilateral Nasal Obstruction

Effect of breathing patterns on mandibular cortical bone quality in children and establishment of a preliminary screening model

OBJECTIVE

This retrospective study analyzed breathing patterns and age subgroups effect on cortical bone quality of the mandible in growing subjects, aiming to explore the application value of facial skeletal pattern combined with cortical bone density detection in early screening diagnosis of mouth breathing.

METHODS

One hundred twenty-six participants were divided into four groups: mouth breathing group (7-9, 10-12 years old) and nasal breathing group (7-9, 10-12 years old). The mandibular anterior, middle, and posterior cortical bone mineral density (CBMD), cortical bone width (MCW), ANB, and FMA values were measured. Independent T-test and Mann-Whitney U test were used to compare the measured values. Binary logistic regression was employed to analyze the correlation between measured variables and the children's breathing patterns. ROC analysis was used to determine the ability of the cortical bone density measurements in early screening diagnosis of MB.

RESULTS

Mouth breathing had a negative impact on CBMD and MCW of the pre-mandibular (Pog) in subjects aged 7-9 years and also impacted the development of (Pog) and submandibular (Me) sites in subjects aged 10-12 years. Older children in the nasal breathing group have higher CBMD, MCW, and SNB values and lower FMA values. Single-factor and multiple-factor logistic binary regression analysis showed that FMA, MSPogCBMD, MSPogMCW, and ANB are correlated factors for children at risk of mouth breathing.

CONCLUSION

Mouth breathing pattern is closely associated with decreased mandibular CBMD and MCW values in children aged 7-12, where the anterior (Pog) and inferior (Me) sites of anterior mandible are more significantly affected. Furthermore, in combination with facial skeletal pattern, it provides a basis for the early warning diagnosis of mouth breathing.

Effects of Hypoxic Environment on Periodontal Tissue through the ROS/TXNIP/NLRP3 Inflammasome Pathway

There is low evidence for the possible association between obstructive sleep apnea-hypopnea syndrome (OSAHS) and periodontitis, necessitating further research. This study was aimed at investigating this association. For the in vitro study, 8-day-old Wistar rats were divided into the unilateral nasal obstruction group (UNO) and the sham surgery group (SHAM). Rats in the former group were subjected to UNO by cauterization of the external nostril at the age of 8 days. Immunofluorescence analysis, quantitative real-time polymerase chain reaction, and western blot were performed to assess the expression of thioredoxin-interacting protein (TXNIP), NLR family pyrin domain-containing 3 (NLRP3) inflammasome-associated factors, and interleukin-1β (IL-1β). Throughout the experimental period, the weights of rats in the two groups were similar. The mRNA and protein expression of TXNIP and IL-1β was significantly higher in the UNO than in the SHAM groups. Compared with SHAM, NLRP3 inflammasome-associated factors were activated in the UNO group. For the in vitro study, a cellular hypoxia model was established by treating human periodontal ligament cells (HPDLCs) with cobalt chloride. The studies showed that hypoxia can induce an excessive production and accumulation of reactive oxygen species (ROS) in HPDLCs and induce abnormal expression of TNXIP, NLRP3 inflammasome-related factors, and IL-1β. More importantly, N-acetylcysteine induced reduction of ROS in HPDLCs, downregulated TXNIP expression, inhibited the expression and aggregation of NLRP3 inflammasome-related factors, and abrogated the inflammatory response to hypoxia. In conclusion, hypoxia-induced ROS can activate the TXNIP/NLRP3 inflammasome signaling pathway in response to oxidative stress, resulting in the increased expression of inflammatory factors in HPDLCs. Our findings provide evidence for the mechanism underlying the possible association between OSAHS and periodontal disease.

Nasal obstruction promotes alveolar bone destruction in the juvenile rat model

Background/purpose

Nasal obstruction leads to oral breathing and consequently hypoxia. The purpose of this study was to determine the influence of hypoxia on inflammatory response and the effect on alveolar bone development in a rat model in which mouth breathing was induced by nasal obstruction.

Materials and methods

Unilateral nasal obstruction was performed by injecting a Merocel sponge into the nasal cavity of 8-week-old Sprague Dawley (SD) rats. After 3 and 6 weeks of nasal obstruction, rats were sacrificed, the organs were weighed, and the changes in mandibular bone quality were examined by micro-computed tomography (μ-CT). The stereomicroscope was used for the morphological analysis of alveolar bone loss in response to nasal obstruction. Hematoxylin and Eosin (H&E) and immunohistochemical staining were employed to examine inflammation and bone remodeling induced by hypoxia.

Results

Nasal obstruction led to a delay in overall growth and organ development. The bone mineral density (BMD) and bone volume/total volume (BV/TV) of the mandible were reduced due to nasal obstruction, and the loss of the alveolar bone was confirmed morphologically. Our nasal obstruction method was observed to be successful in inducing hypoxia along with an increase in hypoxia-inducible factor 1-alpha (HIF-α). Oral hypoxia induced by nasal obstruction increased inflammatory response, and increased expression of receptor activator of nuclear factor kappa-Β ligand (RANKL) led to bone destruction.

Conclusion

This study demonstrated that nasal obstruction induced mouth breathing led to hypoxia in a rat model. Under hypoxic conditions, an increase in osteoclast differentiation induced by activation of the inflammatory pathway causes destructive changes in the alveolar bone.

Potential impact of pediatric obstructive sleep apnea on mandibular cortical width dimensions

STUDY OBJECTIVES

To analyze differences in mandibular cortical width (MCW) among children diagnosed with obstructive sleep apnea (OSA) or at high- or low-risk for OSA.

METHODS

A total of 161 children were assessed: 60 children with polysomnographically diagnosed OSA, 56 children presenting symptoms suggestive of high-risk for OSA, and 45 children at low risk for OSA. Children at high- and low-risk for OSA were evaluated through the Pediatric Sleep Questionnaire. MCW was calculated using ImageJ software from panoramic radiograph images available from all participants. Differences between MCW measurements in the 3 groups were evaluated using analysis of covariance and Bonferroni post-hoc tests, with age as a covariate. The association between MCW and specific cephalometric variables was assessed through regression analysis.

RESULTS

The participants' mean age was 9.6 ± 3.1 years (59% male and 41% female). The mean body mass index z-score was 0.62 ± 1.3. The polysomnographically diagnosed OSA group presented smaller MCW than the group at low-risk for OSA (mean difference = -0.385 mm, P = .001), but no difference with the group at high-risk for OSA (polysomnographically diagnosed OSA vs high-risk OSA: P = .085). In addition, the MCW in the group at high-risk for the OSA was significantly smaller than the group at low-risk for the OSA (mean difference = -0.301 mm, P = .014). The cephalometric variables (Sella-Nasion-A point angle (SNA) and Frankfort - Mandibular Plane angle (FMA)) explained only 8% of the variance in MCW.

CONCLUSIONS

Reductions in MCW appear to be present among children with OSA or those at high-risk for OSA, suggesting potential interactions between mandibular bone development and/or homeostasis and pediatric OSA.

CITATION

Fernandes Fagundes NC, d'Apuzzo F, Perillo L, et al. Potential impact of pediatric obstructive sleep apnea on mandibular cortical width dimensions. J Clin Sleep Med. 2021;17(8):1627-1634.