Influence of pharyngeal airway respiration pressure on Class II mandibular retrusion in children: A computational fluid dynamics study of inspiration and expiration.

OBJECTIVES: To examine the influence of negative pressure of the pharyngeal airway on mandibular retraction during inspiration in children with nasal obstruction using the computational fluid dynamics (CFD) method. SETTING AND SAMPLE POPULATION: Sixty-two children were divided into Classes I, II (mandibular retrusion) and III (mandibular protrusion) malocclusion groups. MATERIAL AND METHODS: Cone-beam computed tomography data were used to reconstruct three-dimensional shapes of the nasal and pharyngeal airways. Airflow pressure was simulated using CFD to calculate nasal resistance and pharyngeal airway pressure during inspiration and expiration. RESULTS: Nasal resistance of the Class II group was significantly higher than that of the other two groups, and oropharyngeal airway inspiration pressure in the Class II (-247.64 Pa) group was larger than that in the Class I (-43.51 Pa) and Class III (-31.81 Pa) groups (P<.001). The oropharyngeal airway inspiration-expiration pressure difference in the Class II (-27.38 Pa) group was larger than that in the Class I (-5.17 Pa) and Class III (0.68 Pa) groups (P=.006). CONCLUSION: Large negative inspiratory pharyngeal airway pressure due to nasal obstruction in children with Class II malocclusion may be related to their retrognathia.

Asymmetry in the condylar long axis and first molar rotation.

Asymmetric growth occurs frequently in the mandibulofacial region, but little attention has been given to asymmetry in the temporomandibular joint. The purpose of this study was to clarify the feature of asymmetry in the condylar long axis and its relation to upper first molar rotation. Records of 148 pre-orthodontic patients were used. The angle of the condylar long axis and that of the molar rotation were both larger on the left side than on the right side. Positive correlations were found between the corresponding bilateral measurements of condylar long axes and also between those of molar rotations, whereas no correlation was found between the condylar long axis and molar rotation. These findings were found in most subgroups classified by dental age, skeletal pattern, bite force balance, or gender. These results suggest that consistent left-right differences in the condylar long axis and first molar rotation are common.

The use of small titanium screws for orthodontic anchorage.

The use of conventional dental implants for orthodontic anchorage is limited by their large size. The purpose of this study was to quantify the histomorphometric properties of the bone-implant interface to analyze the use of small titanium screws as an orthodontic anchorage and to establish an adequate healing period. Overall, successful rigid osseous fixation was achieved by 97% of the 96 implants placed in 8 dogs and 100% of the elastomeric chain-loaded implants. All of the loaded implants remained integrated. Mandibular implants had significantly higher bone-implant contact than maxillary implants. Within each arch, the significant histomorphometric indices noted for the "three-week unloaded" healing group were: increased labeling incidence, higher woven-to-lamellar-bone ratio, and increased osseous contact. Analysis of these data indicates that small titanium screws were able to function as rigid osseous anchorage against orthodontic load for 3 months with a minimal (under 3 weeks) healing period.

A clinical and histological evaluation of titanium mini-implants as anchors for orthodontic intrusion in the beagle dog.

The aim of this study was to determine the anchorage potential of the titanium mini-implant for orthodontic intrusion of the mandibular posterior teeth. Six mini-implants were surgically placed around the mandibular third premolars on each side in 3 adult male beagle dogs. On the buccal site, three mini-implants were placed distal to the apex of the distal root of the third premolar, at the interradicular septa of the third premolar, and mesial to the apex of the mesial root of the third premolar, as linearly as possible. The same procedure was performed at the lingual site on both sides of the mandibular third premolars in each dog. Bilateral interradicular mini-implants on both the buccal and the lingual sites were used as the anchorage for the intrusion of the third premolars (loaded implants) and the other mini-implants were used as control (unloaded) implants. In 6 weeks, an intrusive force (150 g) was applied between the interradicular implants on the buccal and the lingual sites by closed coil springs run across the crowns of the third premolars. After 12 to 18 weeks of orthodontic intrusion, the animals were killed and their mandibles were dissected and prepared for histologic and fluorescent observation. The results indicated that the mandibular third premolars intruded 4.5 mm, on average, after 12 to 18 weeks of orthodontic force application, with mild root resorption at the furcation area as well as the root apex. All the mini-implants remained stable during orthodontic tooth movement without any mobility or displacement. The morphometrical findings indicated that the calcification of the peri-implant bone on the loaded implants was equal to or slightly greater than those of the controls. In addition, 6 of the 36 mini-implants were removed after tooth movement, and all of them were easily removed with a screwdriver. These findings suggest that mini-implants are effective tools for the anchorage of orthodontic intrusion in beagle dogs.

Very early face mask therapy in Class III children.

The purpose of this study was to examine the effects of very early face mask therapy in children with Class III malocclusion. At pretreatment (T0), 40 female subjects who were eventually treated showed a more severe Class III pattern (ANB 0.1 degrees) than did 28 skeletal Class III female subjects who remained untreated (ANB 0.4 degrees), as observed in the Wits analysis. Posttreatment results (T1) showed significant (p<0.01) anterior advancement of the maxillary components, backward rotation of the mandible without increased lower anterior facial height, and an improved incisor relationship. Comparison of posttreatment (T1) and postretention (T2) records, however, revealed no increase in SNA in the treated group. SNA did increase in the untreated group, with no significant difference in ANB angle. The x-components of B-point and Me showed a significant (p<0.05) difference between the two groups. At postretention (T2), N-S-Ba, N-S-Ar, and CC-Ba tended to increase more in the treated group than in the untreated group.

Uprighting the mandibular molars stimulates mandibular growth during treatment of class II malocclusion.

We hypothesized that uprighting of the mandibular molars creates a counter-clockwise rotation of the mandible and stimulates mandibular forward growth during the treatment of a Class II malocclusion. This investigation used 33 longitudinal lateral cephalometric radiographs of Class II, Division 1 female patients. All cases were treated with non-extraction. Treatment was started in early adolescence with .018 slot edgewise Alexander appliances. High-pull head-gear and Class II elastics were used. Seventeen cases that showed more than 5 degrees of uprighting of the mandibular first molars were selected as the uprighted group. Cases that showed less than 5 degrees of uprighting of the mandibular first molars were selected as the non-uprighted group. There was a significant correlation coefficient between the uprighted degree of the mandibular first molars and the degree of clockwise rotation of the mandibular plane to FH.

The differences in the chronology and calcification of second molars between angle Class III and Class II occlusions in Japanese children.

The purpose of this study was to examine the differences in the times of eruption and calcification of the permanent dentition between skeletal class III and class II groups. (And also to examine the relationship between the time of eruption and the type of malocclusion) Fifty-three children, ages seven to ten years, were selected. Of these, twenty-six children (twelve boys and fourteen girls) were Angle class III with minus ANB and twenty-seven children (eleven boys and sixteen girls) were Angle class II with five or more ANB. Panoramic radiographs and cephalometric radiographs were used. The panoramic radiographs showed that the calcification of the maxillary second molars in class II were earlier than in class III using Nolla's classification. There was no statistically significant difference, however, for mean values of calcification stages, using Nolla's classification, between boys and girls. The cephalometric and panoramic radiographs showed that the times of eruption and calcification were earlier in the maxillary second molars than in the mandibular second molars for class II. In contrast, the times of eruption and calcification were earlier in the mandibular second molars than in the maxillary second molars for class III. The times of eruption and calcification of the maxillary molars were significantly related to the length of the ANS-PNS. The longer the ANS-PNS, the earlier were the times of eruption and calcification. There was a significant relationship between the ANB angle and the time of eruption, as well as the ANB angle and calcification. The larger ANB had earlier calcification and chronology of maxillary second molars.

Oral morphology and tongue habits.

Human beings ingest food, transform the food into the energy needed for existence, and communicate through speech, thus forming society. The oral cavity plays an essential role in these functions. When ingesting food, appropriate biting, mastication and swallowing must be conducted, and when speaking, words must be pronounced accurately. There is no doubt that the cooperative movements of the lips, teeth and tongue form the principal axis for each of these activities. The positions into which the teeth naturally erupt and align themselves are the points of balance between the opposing forces exerted by the tongue and by the lips. For instance, if the forward extension of the tongue is strong and the tension of the lips is weak, the teeth will protrude slightly forward; conversely, if the strength of the lips is strong and that of the tongue is weak, it is believed that the teeth will be inclined toward the direction of the tongue. Also, as the tongue is a mass of muscle, its shape at rest is often a manifestation of its functional characteristics. Likewise, the lips are composed of tissue surrounding muscle, and thus the shape of the lips can often reveal their function. Based on these observations, we conducted a survey of the relationships between the shape and form of the tongue and lips, versus the inclinations of the dental axes of the front teeth of the upper and lower jaw.

[Application of composite resin inlays to deciduous molars--a clinical observation of the resin onlay].

Although composite resin has been used as an aesthetic restorative material, wear and fracture of the resin of fracture of the tooth structure are likely to occur when the size of the dental cavities are large. In addition to the lack of the aesthetic value, clinical results of prefabricated metal crown revealed several problems which were caused by the wear of the metal and the ill-adaptation of the cervical margin. In the present study, 50 devitalized deciduous molars were treated with composite resin onlays which were designed to cover the entire occlusal surface of the deciduous molar, and the clinical results were evaluated for a 6 month period. Additionally, for the purpose of simplification of the laboratory process for making resin onlays, ready-made occlusal shells were fabricated. The variety of the prepared shell size consisted of 7 sizes for the first deciduous molar, 9 sizes for the upper second deciduous molar and 10 sizes for the lower deciduous molar. The following results were obtained. 1) A partial resin fracture at the peripheral area of the mesio-buccal cuspid was found in five cases out of 50. 2) A glossy appearance on the surface of the onlay which was created by coated unfilled resin disappeared after 6 months of observation. 3) In relation to the resin onlay, when the antagonistic tooth was restored with prefabricated metal crowns, holes were made by attrition on all the crowns within a 3-4 month period.(ABSTRACT TRUNCATED AT 250 WORDS)

Morphological characteristics of the teeth of Newar children.

The morphology of the teeth of Newar children was investigated in order to determine racial characteristics of the teeth in comparison with those of Japanese. The results were as follows. 1) The incidence of a C type labial surface pattern on the maxillary incisors was greater in Newars than Japanese for both the maxillary central and lateral incisors. 2) The total incidence of shovel-shaped and semi-shovel-shaped maxillary incisors was greater than 80% in Japanese, although at most about 25% in Newars. 3) The incidence of interstitial tubercles on the maxillary premolars in Newars was less than in Japanese. 4) The incidence of the cusp of Carabelli on maxillary first molars was greater in Newars than in Japanese. 5) Although the incidence of protostylids on the mandibular first molars was less in Newars than in Japanese, the incidence of the + type occlusal groove pattern was higher in Newars. Even though four-cusp mandibular first molars were more common in Newars than in Japanese, the incidence of a sixth cusp was lower in Newars. Also, the incidence of a sixth cusp was lower in Newars. Also, the incidence of medial of medial lingual accessory tubercles was slightly higher in Newars than in Japanese. Examination of the Newar teeth confirmed previous findings that they are racially Caucasoid, although they have some similarities with Japanese.