Differences of Craniofacial Characteristics in Oral Breathing and Pediatric Obstructive Sleep Apnea.

BACKGROUND: Oral breathing (OB) was considered associated with specific craniofacial structures and same for pediatric obstructive sleep apnea (OSA). This study aimed to investigate the differences of craniofacial structures between OB and OSA. METHODS: In this retrospective study, 317 children under age 18 years were recruited and divided into OB group, OSA group, and control group. OSA group (15 boys, 4 girls) were referred from qualified sleep center and diagnosed as pediatric OSA with full-night polysomnography. OB group (10 boys, 10 girls) were mostly referral from pediatric or ENT department, some of whom undertook polysomnography and were not OSA. Control group consisted of orthodontic patients within the same period. Lateral cephalograms were obtained in all groups and their parameters were compared with Chinese normal values and each other. RESULTS: R-PNS of OB group (18.04 ±â€Š2.49 mm) was greater than OSA group (14.27 ±â€Š4.36 mm) and even control group (16.22 ±â€Š3.91 mm) (P < 0.01). U1-NA was also the greatest in OB group (7.15 ±â€Š2.92 mm), followed by OSA group (4.88 ±â€Š2.66 mm), while control group was the smallest (5.71 ±â€Š2.94 mm) (P < 0.05). In addition, OB group presented the smallest adenoids and tonsils among three groups. Bony nasopharynx development, mandibular length and growth direction of mandible of OB group were all better than OSA group. CONCLUSION: Despite of oral breathing, anatomical morphology (well-developed dentoalveolar structures; mild adenotonsillar hypertrophy) might protect children from developing OSA.

[Histological changes in the circum-maxillary sutures during alternate maxillary expansions and constrictions in a rat model].

OBJECTIVE: To investigate changes in the circum-maxillary sutures during alternate maxillary expansions and constrictions in a rat model. METHODS: Twenty-two male Sprague-Dawley rats (6 weeks old) were used and divided into three groups. In maxillary expansion (ME) group (n=9), an expander was activated for 5 d, and then sacrificed. In alternate maxillary expansions and constrictions (Alt-MEC) group (9 animals), an alternate expansion and constriction protocol (5 d expansion and 5 d constriction for one cycle) was conducted for 2.5 cycles (25 d total), and then sacrificed. The control group comprised 4 animals with no appliances used, each of two sacrificed on day 5 and day 25, respectively. Circum-maxillary sutures (mid-palatal, maxillopalatine, premaxillary, zygomaticotemporal, and frontonasal suture) in each group were characterized histologically. RESULTS: Histological findings of circum-maxillary sutures: in control group, the normal sutures were divided into 5 zones, the center was polygon mesenchyme zone, the lateral was mature chondrocyte zone, the next lateral was bone tissue. In ME group, the mid-palatal suture was expanded after ME, the fibre and connective tissue were extracted and invaded into cartilage zone. Osteoblast hyperplasia and new bone formation occurred. The orientation of the new bone trabecula was consistent with force. The osteoclast appeared in some area. Findings of other sutures were similar with those of control group, osteogenesis was active in some area without obvious reconstruction in Alt-MEC group, mid-palatal suture and other sutures in some area were widened after Alt-MEC with much more osteoblast hyperplasia and new bone formation. Fibre and connective tissue were extracted, distorted or even broken. Sutures in some areas were narrowed with osteoblast cytopenia and osteoclast hyperplasia. Fibre and connective tissue compressed because of the different force and orientation. Osteoclast count results showed that compared with the control group, the number of the osteoclast was increased only in the palatal suture in ME group (P<0.05). Other sutures did not show obvious changes (P>0.05). In Alt-MEC group, the numbers of the osteoclast in circum-maxillary sutures were the most, and had statistical significances (P<0.05). CONCLUSION: These RESULTS suggested that circum -maxillary sutures were actively reconstructed after Alt-MEC. while only midpalatal suture had active reaction after ME.

Comparative characterization of maxillary expansion and alternate maxillary expansions and constrictions in rats.

The purpose of this study was to evaluate whether the cranial and circumaxillary sutures react differently to maxillary expansion (ME) and alternate maxillary expansions and constrictions (Alt-MEC) in a rat model. Twenty-two male Sprague-Dawley rats (6 weeks old) were used and divided into three groups. In ME group (n=9), an expander was activated for 5 days. In Alt-MEC group (9 animals), an alternate expansion and constriction protocol (5-day expansion and 5-day constriction for one cycle) was conducted for 2.5 cycles (25 days total). The control group comprised 4 animals with no appliances used, each of two sacrificed on day 5 and day 25 respectively. Midpalatal suture expansion or constriction levels were assessed qualitatively and quantitatively by bite-wing X-rays and cast models. Distances between two central incisors and two maxillary first molars were measured on cast models after each activation. Circumaxillary sutures (midpalatal, maxillopalatine, premaxillary, zygomaticotemporal and frontonasal suture) in each group were characterized histologically. Results showed that midpalatal suture was widened and restored after each expansion and constriction. At the end of activation, the widths between both central incisors and first molars in Alt-MEC group were significantly larger than those in ME group (P<0.05). Histologically, all five circumaxillary sutures studied were widened in multiple zones in Alt-MEC group. However, only midpalatal suture was expanded with cellular fibrous tissue filling in ME group. Significant osteoclast hyperplasia was observed in all circumaxillary sutures after alternate expansions and constrictions, but osteoclast count increase was only observed in midpalatal suture in ME group. These results suggested that cranial and circumaxillary sutures were actively reconstructed after Alt-MEC, while only midpalatal suture had active reaction after ME.

[Influence of the mandibular second premolar extraction on the angulation of the mandibular third molar].

OBJECTIVE: To compare the angular changes in the developing mandibular third molars in the mandibular second premolar extraction and non-extraction cases and to determine whether the mandibular second premolar extraction causes favorable rotational changes in the angulations of the developing mandibular third molars and benefits its later eruption. METHODS: Pretreatment and posttreatment panoramic radiographs were taken from 45 subjects who had been treated by the extraction of the mandibular second premolars and 48 subjects who had been treated without extraction. The horizontal reference plane was used to measure and compare the changes in the angulations of the developing mandibular third molars. RESULTS: The mean uprighting of the mandibular third molars seen in the extraction group was (5.9±2.5) degrees on the right side and (8.0±3.4) degrees on the left side following treatment. For the nonextraction group the mean uprighting was (1.8±2.4) degrees on the right side and (1.5±2.1) degrees on the left side. There was a statistically significant difference between the groups (P<0.05). CONCLUSION: Mandibular second premolar extraction might be a helpful procedure on the angulations of the developing mandibular third molars.