Radiographic healing patterns after tooth-borne distraction in canine model

Background

The osteogenesis distraction technique applied to the craniofacial skeleton is an alternative treatment for dentofacial deformities. Despite the advantages of tooth-borne distractors, few studies have evaluated their clinical implementation in sagittal dentoskeletal deformities. This study aimed provide a radiographic assessment of the effect of two different activations of tooth-borne distraction in the lengthening of the mandible in canines.

Material and Methods

Ten male beagle dogs, approximately one year old, were used for this experimental study. Three remained as a control group and seven underwent a mandibular tooth-borne distraction protocol with single daily activation in one hemimandible and two daily activations in the other, during ten days. The consolidation period took 12 weeks. Occlusal radiographs were performed immediately pre- and postoperatively.

Results

After the distraction period, the host bone margins presented very well-defined outlines with regular contours. Concerning the consolidation period, between the second and fourth weeks, all hemimandibles showed small rectangular radiopaque regions with parallel orientation to the distraction axis. At the twelfth week, all hemimandibles presented an entire mineralization of the distraction gap with no axial deviations of the anterior and posterior host bone, nine of which with both margins showing corticalization.

Conclusions

Radiographic analysis showed bone regeneration in order to achieve the original bone architecture, especially in the group of multiple distraction. Tooth-borne distraction allowed successful sagittal lengthening of the mandible in a canine model.

Key words:Orthodontics, osteogenesis, distraction, mandibular advancement, orthodontic appliance design.

Relationships of maxillofacial morphology and malocclusion with handgrip strength in adult women

OBJECTIVES

Maxillofacial morphology and malocclusion are related to maximum occlusal force (MOF). Although it has been reported that MOF was related to handgrip strength (HS), the relationships between maxillofacial morphology/malocclusion and HS remain unclear. This study aimed to examine the relationships between maxillofacial morphology, malocclusion and HS.

SETTING AND SAMPLE POPULATION

Eighty-five women with malocclusion, aged 18-40 years, were selected.

MATERIALS AND METHODS

Lateral cephalometric radiographs (SNA, SNB, ANB, mandibular plane-FH, and gonial angles, overjet and overbite), the Peer Assessment Rating (PAR) index and HS were measured. Subjects were classified by the Japanese normal mean value of cephalometric analysis or the reference value which was defined by degree of malocclusion in each PAR index measurement item (small/low: value < mean/reference value, large/high: value ≧ mean/reference value). Measurements were then compared between groups.

RESULTS

HS of the large-gonial angle group was lower than that of the small-gonial angle group. In the small-overbite group or high-transverse (PAR index score showing crossbite/scissor bite in the canine and molars) group, HS in the large-gonial angle group was significantly lower than that in the small-gonial angle group.

CONCLUSIONS

Our results suggest that gonial angle is the largest factor affecting HS. HS may be especially low in those subjects with a large gonial angle and a small overbite or a crossbite/scissor bite in the molar section.

BMAL1 Deficiency Contributes to Mandibular Dysplasia by Upregulating MMP3

Skeletal mandibular hypoplasia (SMH), one of the common types of craniofacial deformities, seriously affects appearance, chewing, pronunciation, and breathing. Moreover, SMH is prone to inducing obstructive sleep apnea syndrome. We found that brain and muscle ARNT-like 1 (BMAL1), the core component of the molecular circadian oscillator, was significantly decreased in mandibles of juvenile SMH patients. Accordingly, SMH was observed in circadian-rhythm-disrupted or BMAL1-deficient mice. RNA sequencing and protein chip analyses suggested that matrix metallopeptidase 3 (MMP3) is the potential target of BMAL1. Interestingly, in juvenile SMH patients, we observed that MMP3 was obviously increased. Consistently, MMP3 was upregulated during the whole growth period of 3-10 weeks in Bmal1-/- mice. Given these findings, we set out to characterize the underlying mechanism and found BMAL1 deficiency enhanced Mmp3 transcription through activating p65 phosphorylation. Together, our results provide insight into the mechanism by which BMAL1 is implicated in the pathogenesis of SMH.

Extraction treatment of a class II division 2 malocclusion with mandibular posterior discrepancy and changes in stomatognathic function

This case report describes the successful extraction treatment of a Class II division 2 malocclusion with mandibular posterior discrepancy and a congenitally missing maxillary lateral incisor on the left side. The posterior space in the mandibular arch was small, and the mandibular second molars were impacted, with distal tipping. The discrepancies in the maxillary and mandibular arches were resolved by extraction of the maxillary lateral incisor on the right side and the mandibular second premolars on both sides. The mesial movement of the mandibular first molars occurred appropriately, with the second molars moving into an upright position. A lip bumper was used with a preadjusted edgewise appliance in the maxillary dentition to reinforce molar anchorage and labial movement of the retroclined incisors. Despite the extraction treatment, a deep bite could be corrected without aggravation as a result of the lip bumper and utility arch in the mandibular dentition. Thus, an Angle Class I molar relationship and an ideal overbite were achieved. The occlusal contact area and masticatory muscle activities during maximum clenching increased after treatment. The maximum closing velocity and the maximum gape during chewing increased, and the chewing pattern changed from the chopping to grinding type. The findings in the present case suggest that the correction of a deep bite might be effective for improving stomatognathic function.

Improvement of asymmetric stomatognathic functions, unilateral crossbite, and facial esthetics in a patient with skeletal Class III malocclusion and mandibular asymmetry, treated with orthognathic surgery

Patients with a dentofacial skeletal deformity have not only esthetic and morphologic problems related to facial proportions and dentition, but also problems of stomatognathic functions. Therefore, in addition to morphologic analysis, functional analysis is important for the diagnosis and evaluation of treatment in these patients. However, no reports have described longitudinal simultaneous evaluations of stomatognathic functions, and the comprehensive effects of surgical orthodontics on the stomatognathic functions are unclear. A patient was diagnosed as having a skeletal Class III jaw-base relationship, mandibular asymmetry, unilateral crossbite, asymmetric stomatognathic functions, and a temporomandibular disorder. She was treated with a combination of surgery and orthodontic therapy. As a result, facial proportions and occlusion improved; in particular, asymmetric stomatognathic functions, including masticatory muscle activity, condylar movement, and occlusal force, became symmetric between the left and right sides. Moreover, after 2 years of retention, the activity of the masticatory muscles and the values of occlusal force and occlusal contact area exceeded those at pretreatment. These results suggest that improvement of asymmetric stomatognathic functions can be achieved by correction of dentofacial morphology by surgical orthodontic treatment in patients with mandibular asymmetry.

Patient with oligodontia treated with a miniscrew for unilateral mesial movement of the maxillary molars and alignment of an impacted third molar

This report describes the treatment of a 20-year-old woman with a dental midline deviation and 7 congenitally missing premolars. She had retained a maxillary right deciduous canine and 4 deciduous second molars, and she had an impacted maxillary right third molar. The maxillary right deciduous second molar was extracted, and the space was nearly closed by mesial movement of the maxillary right molars using an edgewise appliance and a miniscrew for absolute anchorage. The miniscrew was removed, and the extraction space of the maxillary right deciduous canine was closed, correcting the dental midline deviation. After the mesial movement of the maxillary right molars, the impacted right third molar was aligned. To prevent root resorption, the retained left deciduous second molars were not aligned by the edgewise appliance. The occlusal contact area and the maximum occlusal force increased over the 2 years of retention. The miniscrew was useful for absolute anchorage for unilateral mesial movement of the maxillary molars and for the creation of eruption space and alignment of the impacted third molar in a patient with oligodontia.

Orthodontic-surgical treatment: neuromuscular evaluation in skeletal Class II and Class III patients

OBJECTIVES

The aim of this study was the evaluation of the neuromuscular response to treatment according to diagnostic phases, as a follow-up of patients under surgical orthodontic treatment. The patient sample was subdivided into sub-samples, according to clinical characteristics.

MATERIALS AND METHODS

All of the patients who underwent orthognathic surgery in the Department of Orthodontics (University of Milan) were subjected to periodic electromyographic evaluation of the masticatory muscles (masseter and anterior temporal muscles), and to electrokinesiographic evaluation of the mandibular movements. The patient sample comprised 80 patients (37 males; and 43 females) at the end of growth. The electromyographic instruments used in the study included a Freely and a K6-I electromyography. Statistical evaluation was carried out with the Student's t-tests for independent samples.

RESULTS

There are many differences between the skeletal Class II and skeletal Class III patients that are shown through the analysis of these data obtained. In the beginning phases of the treatment the muscular activities were higher in the Class II patients than in the Class III patients. Nevertheless this difference was reversed at the end of the treatment. A similar difference could be found in the mandibular kinesiology, in fact the maximum mandibular opening movement was greater in the skeletal Class II patients than in the skeletal Class III patients at the beginning of the treatment. At the end of the treatment this difference was lost. At the beginning of the treatment the Class II patients showed a greater protrusive movement of the mandibular than the Class III patients. At the end the treatment however this gap was reduced without being reversed.

CONCLUSIONS

Functional evaluation in patients in surgical orthodontic therapy is an important element in the diagnostic-therapeutic recordings, so as to reduce as much as possible any incorrect neuromuscular activity that can result in relapse.

Experimental evaluation of acute molding of the regenerate in mandibular distraction osteogenesis in a rabbit model

OBJECTIVES

The aim of this study was to investigate the possible effect of acute regenerate molding (ARM) on bone healing in mandibular distraction osteogenesis (DO).

STUDY DESIGN

Nine white New Zealand rabbits underwent unilateral mandibular lengthening via DO. Three groups were created: The first underwent 15° ARM, the second group underwent 30° ARM after the distraction period, and the third group served as control without molding. After 1 month of consolidation, all of the animals were killed and histomorphometric evaluation was performed.

RESULTS

New bone formation was uneventful in all of the groups. In the ARM groups, the amounts of osteoblasts and newly formed bone areas were higher in compressed areas than in stretched ones (P < .05). The regenerates in the control group and stretched regenerate areas of the ARM groups were similar regarding new bone formation (P > .05).

CONCLUSION

Acute regenerate molding could be safely applied immediately after the distraction period to correct postdistraction deformities without compromising bone healing.