微种植钉近中移动下颌第二磨牙关闭第一磨牙拔牙间隙

目的探讨微种植钉近中移动下颌第二磨牙关闭第一磨牙缺隙的正畸治疗效果。方法对5例第一磨牙缺失患者使用微种植钉近中移动下颌第二磨牙关闭其间隙。结果矫治后尖牙、磨牙中性关系,前牙覆盖、覆袷正常,后牙袷关系良好,下颌第一磨牙拔牙间隙关闭,第二磨牙近中移动量为11．7mm。疗程为18．5～31．0个月,平均为26．1个月。结论在下颌第一、第二双尖牙间采用微种植钉近中移动第二磨牙,能有效地关闭第一磨牙拔牙间隙。     

Alveolar bone changes after molar protraction in young adults with missing mandibular second premolars or first molars

ObjectivesTo assess the changes in alveolar bone of the mandibular second molars following molar protraction and investigate the factors associated with the alveolar bone changes.Materials and MethodsCone-beam computed tomography of 29 patients (mean age 22.0 ± 4.2 years) who had missing mandibular premolars or first molars and underwent molar protraction were reviewed. Alveolar bone level was measured as the distance from the cementoenamel junction at six points, buccal, lingual, mesiobuccal (MB), mesiolingual (ML), distobuccal (DB), and distolingual (DL), of the second molars at pretreatment (T0) and after molar protraction (T1). Factors associated with alveolar bone changes at the distal and mesial of the second molars were assessed.ResultsMean alveolar bone changes ranged from −1.2 mm (bone apposition) to 0.8 mm (bone resorption). The presence of a third molar impaction at T0 (P < .001), third molar angulation at T0 (P < .001), and Nolla''s stage of third molar at T0 (P = .005) were significantly associated with alveolar bone level changes distal to the second molars. Treatment duration (P = .028) was significantly associated with alveolar bone level changes mesial to the second molar.ConclusionsPatients with impacted third molars, third molars at an earlier stage of development, and mesially angulated third molars at pretreatment may have less alveolar bone resorption distal to the second molars following protraction. Patients with increased treatment time may have reduced alveolar bone resorption mesial to the second molars.     

Factors associated with spontaneous mesialization of impacted mandibular third molars after second molar protraction

Objectives:To investigate factors associated with spontaneous mesialization of impacted third molars after second molar protraction to close the space caused by a missing mandibular first molar (L-6) or retained deciduous mandibular second molars with a missing succedaneous premolar (L-E).Materials and Methods:Panoramic radiographs of patients treated with mandibular second molar protraction to close the space due to missing L-6 or L-E (14 males, 36 females, mean age = 18.6 ± 4.4 years) were analyzed before treatment (T1) and after second molar protraction (T2). Factors associated with the amount of third molar mesialization were investigated using regression analyses.Results:Mandibular second molars were protracted by 5.1 ± 2.1 mm and 5.8 ± 2.7 mm, measured at the crown and root furcation, respectively. After second molar protraction, third molars showed spontaneous mesialization by 4.3 ± 1.6 mm and 3.8 ± 2.6 mm, measured at the crown and root furcation, respectively. Nolla''s stage of the third molar at T1 (B = 0.20, P = .026) and second molar protraction time (B = 0.04, P = .042) were significantly associated with the amount of third molar mesialization.Conclusions:Greater third molar mesialization was observed when Nolla''s stage of the third molar was higher before treatment and when the second molar protraction time was longer.     

Root resorption of mandibular second molar teeth associated with the presence of the third molars

Although pressure resorption of second molars is associated with impacted and/or erupting third molars, the relationship between pressure resorption and age is unclear. In order to investigate this relationship, 3883 dental radiographs were studied in 3174 individuals of various ages. The incidence of superimposition of the second molar on the third molar was not elevated in any subgroup except that of women of 16-40 years of age. There were no age or sex differences for the incidence of second molar root resorption. In older individuals, root resorption associated with a completely impacted third molar was more frequent than with a partially impacted third molar, and root resorption at the apex was mainly seen in individuals over 50 years of age. There was a higher incidence of superimposition and root resorption in men than women. Apical root resorption may be seen long after the formation of completely impacted third molars in both genders.     

Management of unilaterally deep impacted first, second, and third mandibular molars

Simultaneous impactions of first, second, and third permanent molars comprises a very rare clinical situation with diverse therapeutic approaches and is a difficult challenge for dentists. Early diagnosis and treatment of eruption disturbances contributes to optimal outcomes. This article reports the treatment of a teenager with severe impaction of right mandibular first, second, and third molars, which hinders the masticatory function and dental arch integrity. A decision-making process and a simple orthodontic technique are described. To shorten the treatment time and simplify the procedures, the impacted right mandibular third and second molars were orthodontically uprighted with an innovative tip-back cantilever. Subsequently, the deeply impacted right mandibular first molar was extracted with minimal obstacles. The combined surgical-orthodontic approach resolved a challenging clinical problem and eliminated the need for prosthetic or dental implant replacement of the impacted molars. Good occlusion, normal function, and a healthy periodontium of the patient were also achieved.     

Nonsurgical and nonprosthetic camouflage treatment of skeletal Class II open bite with bilaterally missing lower first molars

This report illustrates the successful nonsurgical and nonprosthetic camouflage treatment of a skeletal Class II open bite malocclusion combined with missing mandibular first molars bilaterally. In the mandible, the second and third molars were uprighted and protracted, substituting for the missing first molars. In the maxilla, anterior bodily retraction and full-arch intrusion were achieved following premolar and second molar extraction, which also induced autorotation of the mandible. The treatment outcome and prognosis were confirmed with three-dimensional superimposition techniques, along with long-term stability.     

Risk factors for root resorption of second molars associated with impacted mandibular third molars

External root resorption (ERR) affecting mandibular second molars (M2) may occur when the adjacent third molar (M3) is impacted in close proximity. This retrospective cohort study aimed to assess the presence, severity, and location of ERR on M2 due to M3 using cone beam computed tomography (CBCT) scans and to identify associated factors. The angle between the axis of M2 and M3 was measured. ERR on M2 was classified as absent, slight, moderate, or severe. The location of contact between M3 and M2, the size of the dental follicle, and patient demographic characteristics were recorded. A total of 433 patients with 640 M3 were included. A male predilection was found with regard to ERR (P = 0.0004). ERR was identified on 31.9% of M2 and was slight in 30.2%, moderate in 1.4%, and severe in 0.3% of cases. The presence of ERR was associated with direct contact between M2 and M3 (P < 0.0001), the angle between M2 and M3 (P < 0.0001), the inclination of M3 (P = 0.001), and the location of contact (P = 0.0005). This study showed ERR to be a frequent finding. ERR is associated with a mesioangular position of M3 in more than one third of cases, and a proximity ≤0.5 mm between M2 and M3 favours ERR.     

Treatment of a patient with unerupted mandibular molars, lateral open bite, and class II subdivision malocclusion

This case report describes the treatment of a patient with three unerupted mandibular right molars and a lateral open bite in a Class II subdivision malocclusion with mandibular arch asymmetry. Sequential uprighting and traction of the three mandibular unerupted teeth with a compressed open-coil spring, reverse sliding jig, and light force system was used in the treatment and are described in detail. The results remained stable during the 8-year 6-month posttreatment and 4-year postretention periods.