Shingo Kuroda

Severe Anterior Open-Bite Case Treated Using Titanium Screw Anchorage

Anterior open bite is often caused by a downward rotation of the mandible and/or by excessive eruption of the posterior teeth. In such cases, it is difficult to establish absolute anchorage for molar intrusion by traditional orthodontic mechanics. This article reports the successful treatment of a severe skeletal anterior open-bite case using titanium screw anchorage. A female patient 33 years eight months of age had open bite of -7.0 mm and increased facial height. The titanium screws were implanted in both the maxilla and the mandible, and an intrusion force was provided with elastic chains for 13 months. After active treatment of 19 months, her upper and lower first molars were intruded about 3.0 mm each, and good occlusion was achieved. Her retrognathic chin and convex profiles were improved by an upward rotation of the mandible. Our results suggest that titanium screws are useful for intrusion of molars in anterior open-bite cases.

Biomechanical and biochemical characteristics of the mandibular condylar cartilage

The human masticatory system consists of a mandible which is able to move with respect to the skull at its bilateral temporomandibular joint (TMJ) through contractions of the masticatory muscles. Like other synovial joints, the TMJ is loaded mechanically during function. The articular surface of the mandibular condyle is covered with cartilage that is composed mainly of collagen fibers and proteoglycans. This construction results in a viscoelastic response to loading and enables the cartilage to play an important role as a stress absorber during function. To understand its mechanical functions properly, and to assess its limitations, detailed information about the viscoelastic behavior of the mandibular condylar cartilage is required. The purpose of this paper is to review the fundamental concepts of the biomechanical behavior of the mandibular condylar cartilage. This review consists of four parts. Part 1 is a brief introduction of the structure and function of the mandibular condylar cartilage. In Part 2, the biochemical composition of the mandibular condylar cartilage is summarized. Part 3 explores the biomechanical properties of the mandibular condylar cartilage. Finally, Part 4 relates this behavior to the breakdown mechanism of the mandibular condylar cartilage which is associated with the progression of osteoarthritis in the TMJ.

Distal Movement of Maxillary Molars Using Miniscrew Anchorage in the Buccal Interradicular Region

OBJECTIVE To quantify the treatment effects of interradicular miniscrew anchorage and to confirm the validity of the clinical usage of interradicular miniscrews in the distal movement of maxillary molars in nonextraction treatment. MATERIALS AND METHODS Twenty-four maxillary molars were moved to the distal using miniscrews placed in the interradicular space between the second premolar and the first molar at an oblique angle of 20 to 30 degrees to the long axis of the proximal tooth. The teeth were evaluated as to how the molars were moved to the distal with the use of lateral cephalograms and dental casts. RESULTS Maxillary molars were moved to the distal by 2.8 mm with distal tipping of 4.8 degrees and intruded by 0.6 mm. Maxillary incisors were moved to the distal by 2.7 mm with palatal tipping of 4.3 degrees. Molar extrusion and/or consequent mandibular rotation was not observed in any patient. CONCLUSION Miniscrews placed in the maxillary interradicular space provide successful molar distal movement of 2.8 mm without patient compliance and with no undesirable side effects such as incisor proclination, clockwise mandibular rotation, or root resorption.

Comparison of the intrusion effects on the maxillary incisors between implant anchorage and J-hook headgear

INTRODUCTION Recently, miniscrews have been used to provide anchorage during orthodontic treatment, especially for incisor intrusion. Miniscrews during incisor intrusion are commonly used in implant orthodontics. Traditionally, effective incisor intrusion has been accomplished with J-hook headgear. In this study, we compared the effect of incisor intrusion, force vector, and amount of root resorption between implant orthodontics and J-hook headgear. METHODS Lateral cephalometric radiographs from 8 patients in the implant group and 10 patients in the J-hook headgear group were analyzed for incisor retraction. The estimated force vector was analyzed in the horizontal and vertical directions in both groups. Root resorption was also measured on periapical radiographs. RESULTS In the implant group, significant reductions in overjet, overbite, maxillary incisor to palatal plane, and maxillary incisor to upper lip were observed after intrusion of the incisors. In the J-hook headgear group, significant reductions in overjet, overbite, maxillary incisor to upper lip, and maxillary incisor to SN plane were observed after intrusion of the incisors. There were significantly greater reductions in overbite, maxillary incisor to palatal plane, and maxillary incisor to upper lip in the implant group than in the J-hook headgear group. Estimated force analysis resulted in significantly more force in the vertical direction and less in the horizontal direction in the implant group. Furthermore, significantly less root resorption was observed in the implant group compared with the J-hook headgear group. CONCLUSIONS The maxillary incisors were effectively intruded by using miniscrews as orthodontic anchorage without patient cooperation. The amount of root resorption was not affected by activating the ligature wire from the miniscrew during incisor intrusion.

Class II malocclusion treated with miniscrew anchorage: Comparison with traditional orthodontic mechanics outcomes

INTRODUCTION Anchorage control in patients with severe skeletal Class II malocclusion is a difficult problem in orthodontic treatment. In adults, treatment often requires premolar extractions and maximum anchorage. Recently, incisor retraction with miniscrew anchorage has become a new strategy for treating skeletal Class II patients. METHODS In this study, we compared treatment outcomes of patients with severe skeletal Class II malocclusion treated using miniscrew anchorage (n = 11) or traditional orthodontic mechanics of headgear and transpalatal arch (n = 11). Pretreatment and posttreatment lateral cephalograms were analyzed. RESULTS Both treatment methods, miniscrew anchorage or headgear, achieved acceptable results as indicated by the reduction of overjet and the improvement of facial profile. However, incisor retraction with miniscrew anchorage did not require patient cooperation to reinforce the anchorage and provided more significant improvement of the facial profile than traditional anchorage mechanics (headgear combined with transpalatal arch). CONCLUSIONS Orthodontic treatment with miniscrew anchorage is simpler and more useful than that with traditional anchorage mechanics for patients with Class II malocclusion.

Three-dimensional finite element analysis of cartilaginous tissues in human temporomandibular joint during prolonged clenching.

OBJECTIVE Bruxism, the parafunctional habit of nocturnal grinding of the teeth and clenching, is associated with the onset of joint degeneration. Especially prolonged clenching is suggested to cause functional overloading in the temporomandibular joint (TMJ). In this study, the distributions of stresses in the cartilaginous TMJ disc and articular cartilage, were analysed during prolonged clenching. The purpose of this study was to examine if joint degradation due to prolonged clenching can be attributed to changes in stress concentration in the cartilaginous tissues. DESIGN Finite element model was developed on the basis of magnetic resonance images from a healthy volunteer. Condylar movements recorded during prolonged clenching were used as the loading condition for stress analysis. RESULTS At the onset of clenching (time=0s), the highest von Mises stresses were located in the middle and posterior areas (6.18MPa) of the inferior disc surface facing the condylar cartilage. The largest magnitude of the minimum principal stress (-6.72MPa) was found in the condylar cartilage. The stress concentrations were relieved towards the superior disc surface facing the temporal cartilage. On the surfaces of the temporal cartilage, relatively lower stresses were found. After 5-min clenching, both stress values induced in the TMJ components were reduced to 50-80% of the stress values at the onset of clenching, although the concomitant strains increased slightly during this period. CONCLUSIONS It is suggested that both the condylar and temporal cartilage layers along with the TMJ disc, play an important role in stress distribution and transmission during prolonged clenching due to tissue expansion. Furthermore, our study suggests that a development of stress concentrations in the TMJ during prolonged clenching and risk factors for the initiation of TMJ degeneration could not be confirmed.

Skeletal Anchorage for Orthodontic Correction of Maxillary Protrusion with Adult Periodontitis

Because the number of adult patients seeking orthodontic treatment is increasing, orthodontists are becoming more likely to encounter patients with adult periodontitis. However, it is sometimes difficult to establish anchorage because of poor periodontal tissues in patients with adult periodontitis. This article reports the successful use of skeletal anchorage to treat a maxillary protrusion case complicated by severe adult periodontitis. A female patient aged 50 years seven months showed a skeletal Class II jaw base relationship. A spacing of five mm in the upper anterior teeth with an overjet of 7.5 mm and overbite of four mm was observed. She had generalized horizontal bone loss in both arches, with vertical bone loss in the posterior segment. After periodontal treatment, miniplates were placed in the zygomatic process, and retraction and intrusion of the maxillary incisors were performed. After active treatment for 21 months, the upper incisors had been inclined 9.5 degrees lingually, intruded two mm at the apex, and good anterior occlusion was achieved. Acceptable occlusion and periodontal tissue were maintained after a retention period of two years. Our results suggest that skeletal anchorage is useful for retraction and intrusion of upper incisors in cases of maxillary protrusion with severe adult periodontitis.

CTGF and Apoptosis in Mouse Osteocytes Induced by Tooth Movement

It is known that experimental tooth movement stimulates the gene expression of connective tissue growth factor (CTGF) and induces apoptosis in osteocytes in rats. We hypothesized that there is a relationship between CTGF expression and the induction of apoptosis in osteocytes, to play a significant role in triggering bone remodeling during experimental tooth movement. In this study, CTGF mRNA expression was detected at 2 hours in osteocytes on the pressure side, followed by apoptosis at 6 hours after tooth movement in mice. The number of empty lacunae significantly increased on day 1 after mechanical stimulation. Thereafter, the number of osteoclasts significantly increased on the pressure side of the alveolar bone on day 3. Tooth movement increased rapidly on day 10. These findings suggest that CTGF expression, followed by apoptosis in osteocytes in response to mechanical stimulation, might play a significant role in triggering bone remodeling during tooth movement.

Skeletal Class lll Severe Openbite Treatment Using Implant Anchorage

A female patient with a skeletal Class III severe anterior openbite was treated using miniplates as the anchorage. The patient was 15 years and 10 months of age when she reported to our university hospital with a chief complaint of anterior openbite and reversed occlusion. The patient had an anterior openbite with an overjet of -3.0 mm and overbite of -5.0 mm and a Class III molar relationship. The cephalometric analysis showed a skeletal Class III relationship (ANB 0 degrees ). After the extraction of the bilateral mandibular third molars, miniplates were placed in the mandibular external oblique line. The mandibular dentition was retracted using elastic chain and miniplates. After treatment, an Angle Class I molar relationship was achieved and overjet and overbite had become 2.0 mm and 1.5 mm. A good facial appearance and occlusal relationship were obtained. The total active orthodontic treatment period was 23 months. Wrap-around type retainers were placed on both jaws and a lingual bonded retainer was also attached in the mandibular incisors. After 1 year of retention, the occlusion was stable, and a good facial profile was also retained. The mandibular deviation to the left was improved and the strain in the circumoral musculature during lip closure disappeared. An appropriate interincisal relationship was achieved by the uprighting of mandibular dentition without changing the vertical intermaxillary relationship. A panoramic radiograph showed no marked root resorption. Our results suggest that implant anchorage is useful for correction of skeletal Class III severe anterior openbite cases.

Class III malocclusion with complex problems of lateral open bite and severe crowding successfully treated with miniscrew anchorage and lingual orthodontic brackets

In this article, we report the successful use of miniscrews in a patient with an Angle Class III malocclusion, lateral open bite, midline deviation, and severe crowding. Simultaneously resolving such problems with conventional Class III treatment is difficult. In this case, the treatment procedure was even more challenging because the patient preferred to have lingual brackets on the maxillary teeth. As a result, miniscrews were used to facilitate significant asymmetric tooth movement in the posterior and downward directions; this contributed to the camouflage of the skeletal mandibular protrusion together with complete resolution of the severe crowding and lateral open bite. Analysis of the jaw motion showed that irregularities in chewing movement were also resolved, and a stable occlusion was achieved. Improvements in the facial profile and dental arches remained stable at the 18-month follow-up.