下颌阻生智齿相关第二磨牙牙根外吸收：曲面断层片与CBCT对比研究

目的 比较曲面断层片和CBCT在诊断下颌阻生智齿相关第二磨牙牙根外吸收的差异。方法 回顾性分析2019年1月—2020年12月于南京医科大学附属口腔医院就诊的832例(1 074颗)近中/水平下颌阻生智齿病例,分别应用曲面断层片和CBCT评估下颌第二磨牙远中牙根外吸收发生率,并分析曲面断层片诊断错误的相关因素。结果 以CBCT影像学结果判定为标准,下颌智齿相关第二磨牙牙根外吸收的发生率为33.15%(356/1 074),曲面断层片诊断正确率为66.39%。经多因素Logistic回归分析发现：中低位、Ⅲ类阻生智齿,下颌阻生智齿与第二磨牙牙根重叠,下颌阻生智齿与第二磨牙牙根接触是导致曲面断层片诊断错误的危险因素(P<0.05)。结论 曲面断层片诊断下颌阻生智齿相关第二磨牙牙根外吸收正确性较低,推荐选用CBCT检测。     

下颌智齿阻生类型及其邻牙远中邻面患龋情况的对称性初探

目的 调查下颌第三磨牙生长情况的对称性及其对相邻第二磨牙远中邻面龋患病情况的影响,为临床早期预防性拔除下颌智齿提供依据。方法 纳入2019年11月1日至2019年11月23日在上海交通大学医学院附属仁济医院口腔科拍摄的全景片196张,调查其双侧下颌第三磨牙的对称性,通过卡方检验分析不同阻生类型的下颌第三磨牙与相邻第二磨牙远中邻面龋患病情况之间的关系。结果 双侧下颌第三磨牙对称者187例,占比95.41%。Winter分类中垂直阻生对称性（79.2%）显著高于近中阻生（47.6%）与水平阻生（59.1%）（P=0.001）; Winter分类为近中阻生（46.4%）和水平阻生（38.4%）的下颌第三磨牙,其相邻第二磨牙远中邻面龋发生率显著高于垂直阻生（23.6%）（P=0.001）。结论 下颌智齿具有对称性;为预防相邻第二磨牙远中邻面龋,近中阻生及水平阻生的下颌第三磨牙应在临床上早期预防性拔除。     

第三磨牙阻生引起相邻第二磨牙牙根外吸收的回顾性研究

目的　研究第三磨牙阻生与相邻第二磨牙牙根外吸收（external root resorption，ERR）的关系，并为此类病例的防治处理提供依据。方法　回顾性分析南方医科大学深圳口腔医院2013—2017年收治的85例第三磨牙阻生患者的105颗阻生牙及相邻第二磨牙ERR情况。利用CBCT对第二磨牙ERR进行检测。采用χ2检验或Fisher确切概率法分析第二磨牙ERR检出率及其严重程度与临床特征的关系。结果　第二磨牙ERR的检出率为44.8%，男、女差异无统计学意义（P＞0.05）；各年龄组比较发现，≤20岁组与＞20～30岁、＞30～40岁和＞40岁三组之间的差异有统计学意义（P＜0.05），而后三组间差异无统计学意义（P＞0.05）。第二磨牙ERR的检出率随第三磨牙阻生角度的变大和位置的变深逐渐增加。第二磨牙ERR的严重程度在上、下颌之间的差异有统计学意义（P＜0.05）；在性别、年龄、阻生第三磨牙类型的差异无统计学意义（P＞0.05）。结论　第二磨牙ERR检出率无性别差异，与年龄及阻生第三磨牙位置、角度、深度相关。发生于下颌的第二磨牙ERR要比上颌的严重。对于造成第二磨牙ERR的阻生第三磨牙要积极拔除，特别是发生于下颌者。     

Third molar impaction in the Jazan Region: Evaluation of the prevalence and clinical presentation

ObjectiveTo provide information on the prevalence and clinical features of impacted third molar teeth in the South-Western region of Saudi Arabia.Material and methodsIn this cross-sectional study, 1200 panoramic radiographs (50% males and 50% females) were retrieved from the electronic clinical records of patients at the College of Dentistry, Jazan University from December 2014 to December 2016, and impacted third molars were evaluated. Data on clinical and radiographic presentation were analyzed.ResultsOverall, there were 291 (24.3%) patients with impacted third molars among 1200 radiographs. The distribution of impacted third molars according to the number of impacted teeth was as follows: one impaction in 121 (41.6%); two impactions in 90 (30.9%); three impactions in 42 (14.4%); and four impactions in 38 (13.1%) patients. There was a high prevalence of all impaction types among females (54.5%). Maxillary vertical angulation was most common (50%) followed by mandibular mesioangular angulation (48.3%). The depth of impaction in maxillary teeth was higher than in mandibular teeth. Pain was uncommon (4.5% of patients).DiscussionClinically, vertical impaction in the maxilla was present in 50% of patients because of limited posterior space, and mesioangular angulation in the mandible was present in 48% of patients because of inadequate space between the ramus and the second molar. These findings are similar to other reports. Vertical impaction of the maxillary wisdom tooth is mostly related to the discrepancy between the mesiodistal size of the tooth crown and the limited retromolar space.ConclusionNoiseless presentation of an impacted third molar requires raising the population’s awareness about the need for diagnosis and treatment of the problem to avoid any further complications. The study can be to guide surgical procedures. This study documented the prevalence, pattern, and clinical features of impacted third molars in South Western region of Saudi Arabia.     

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.     

第三磨牙近中阻生对邻近第二磨牙龈沟液中MMP8和TIMP1的影响

目的:探讨第三磨牙近中阻生对邻近磨牙龈沟液中MMP8和TIMP1的影响。方法:选择64例口腔科就诊的战士,分为4组,A组下颌第二磨牙伴第三磨牙近中阻生,第三磨牙无冠周炎病史,龈瓣颜色正常;B组下颌第二磨牙伴第三磨牙近中阻生,6个月内第三磨牙有冠周炎病史,龈瓣颜色正常;C组下颌第二磨牙伴第三磨牙近中阻生,有冠周炎;D组无下颌第三磨牙,第二磨牙作为对照。收集下颌第二磨牙龈沟液,检测MMP8和TIMP1水平,同时测定第二磨牙龈沟出血指数、探诊深度和菌斑指数等指标。结果:MMP8和TIMP1各组间均有统计学差异(C组>B组>A组>D组)。MMP8/TIMP1 B组和A组之间无明显差别,其余各组间差异有统计学意义。临床指标中,C组的菌斑指数明显高于D组,A、B、C组的探诊深度大于D组。结论:第三磨牙近中阻生在无炎症状态时可引起第二磨牙龈沟液MMP8、TIMP1、MMP8/TIMP1和探诊深度等牙周炎潜在致病因素的变化,出现冠周炎症时变化更加显著。     

Vertical eruption patterns of impacted mandibular third molars after the mesialization of second molars using miniscrews

Objective:To investigate (1) whether vertical eruption of impacted third molars improves after mesialization of second molars and (2) what factors affect the vertical eruption of impacted third molars when space caused by missing molars is successfully closed by mesialization of the second molar using miniscrews.Materials and Methods:The treatment group (Group 1) included 52 patients who had (1) missing mandibular first molars (ML-6) or missing deciduous mandibular second molars (ML-E), (2) initially impacted mandibular third molars, and (3) successful space closure of the edentulous area with orthodontics. Panoramic radiographs at start of treatment (T1) and at time of space closure (T2) were collected. The control group (Group 2) included 46 nonedentulous patients with impacted mandibular third molars without molar protraction treatment. Panoramic radiographs with similar T1/T2 treatment times were selected. Nine measurements were obtained regarding horizontal available space, vertical eruption, and third molar angulation.Results:Third molars erupted vertically an average of 2.54 mm in Group 1 compared with 0.41 mm in Group 2. Age, gender, Nolla stage, and angle of the third molars did not show significant correlations with the vertical change of the impacted third molars, whereas the depth of third molar impaction and available space showed significant correlations.Conclusions:Impacted mandibular third molars vertically erupt as a result of uprighting with mesialization of the second molar, and vertical eruption is affected by the initial vertical location of impacted third molars and available space.     

Pre-operative assessment of relationship between inferior dental nerve canal and mandibular impacted third molar in Saudi population

ObjectiveTo study the correlation between the position of the inferior dental (ID) nerve canal and the angulation of impacted mandibular third molars using dental cone beam computed tomography (CBCT).Materials and methodsThe study considered 100 impactions in 85 patients (60 males, 25 females), for whom an initial panoramic radiographic assessment had revealed that the ID canal and the lower 3rd molar were in close proximity. A CBCT scan of each patient was carried out to assess how the ID nerve canal position influenced the class and position of impaction, angulation of impaction, and bone contact.ResultsClass I position B impactions were found in the majority of cases, where the position of the ID canal was approximate to the lingual plate and inferior to the 3rd molar (85.7%). The results were statistically significant (p = 0.001). 96% of the ID canals showed bone contact. Of these, 77.1% of ID canals exhibited lingual bone contact, inferior to impaction. The results were statistically significant (p = 0.001). Horizontally angulated impactions were most common in the mandible, and significantly associated with lingual and inferior positioning of the ID canal (76.2%).ConclusionsOur sample population most commonly exhibited horizontally angulated class I position B impactions of the mandible. The position of the ID canal significantly influenced the type of impaction and bone contact.     

Effect of premolar extraction on mandibular third molar impaction in young adults

Objective:To test the null hypothesis that orthodontic therapy with or without premolar extraction does not result in any difference in third molar impaction.Materials and Methods:Two groups were formed: 22 patients in one group with first premolar extractions and 22 patients in the other group without extractions. All patients were nongrowing subjects who had normal gonial angles and were skeletal Class I at the beginning of treatment. The available space for third molars, inclination of second and third molars, and angle between the second and third molars were evaluated. Also, the correlation of measured parameters and type of orthodontic therapy with the eruption of third molars was evaluated.Results:Of the third molars, 81.8% were impacted in the nonextraction group and 63.6% were impacted in the extraction group. Impaction of mandibular third molars was significantly correlated to the pretreatment and posttreatment inclination of third molars and the angle between the second and third molars. In the extraction therapy group, the retromolar distance increased significantly with a mean of 1.30 ± 1.25 mm.Conclusions:When the inclination of the third molar is inconvenient, the tooth may remain impacted even if there is enough retromolar space.     

下颌磨牙阻生的正畸治疗

目的探讨下颌前倾、水平阻生磨牙的正畸治疗方法，评估其效果。方法采用固定矫治器结合磨牙带环焊多曲推簧，推14颗水平阻生或前倾阻生的下颌磨牙远中向、[牙合]向移动，引导其竖直、萌出。结果前倾、水平阻生的下磨牙全部竖直萌出到正常的[牙合]平面并有良好的[牙合]接触关系。X线片显示原阻生牙牙冠所占位置被正常牙槽骨组织所代替。竖直治疗时间为6～12个月，平均7．4个月。结论带环焊多曲推簧的磨牙竖直技术能有效地使前倾、水平阻生的下颌磨牙产生快速的远中向、[牙合]向旋转运动，具有创伤小、操作简单、患者易适应等优点。     

下颌前倾或水平阻生磨牙的简捷快速竖直

下颌前倾或水平阻生的磨牙临床上多予以拔除,笔者对于牙列较整齐、下颌第二磨牙阻生或经正畸减数治疗后上颌第三磨牙位置正常、下颌第三磨牙阻生者仅采用与阻生磨牙相邻的磨牙作支抗牙,黏接焊接了多曲推簧的磨牙带环,推阻生磨牙向远中、牙合向移动,引导前倾或水平阻生的下磨牙竖直、萌出.结果显示前倾或水平阻生的下颌磨牙较快地被竖直、萌出到正常的牙合平面,建立良好的牙合关系,X线曲面断层片示原阻生牙冠所占的位置为正常牙槽骨组织所代替.该方法能有效地使前倾或水平阻生的下颌磨牙产生快速的远中牙合向旋转运动,具有无须手术暴露阻生磨牙颊面、操作简单、竖直时间短、患者无明显不适和创伤小等优点.     

下颌阻生第三磨牙分段切割拔除术的选择

目的 探讨用涡轮机分段切割法拔除下颌中、低位阻生的第三磨牙的效果及适应证。方法 对481例675颗曲面体层片显示中、低位阻生的下颌第三磨牙用涡轮机分段切割法拔除。其中327颗实施二段切割法;348颗实施三段切割法。结果 下颌阻生第三磨牙均完全拔除;手术时间5~20 min（平均16 min）;术后发生短暂下唇麻木症状3例（3颗）,发生术后感染15例（15颗）。结论 二段切割法适用于中位近中阻生的下颌第三磨牙,三段切割法适用于中/低位近中、水平阻生的下颌第三磨牙。     

Risk factors for lingual plate fracture during mandibular third molar extraction

Objective

The aim of this study was to predict the risk of lingual plate fracture during mandibular third molar (M3) extraction.

Materials and methods

Cone beam computed tomography (CBCT) data from 264 mandibular M3s (erupted and impacted) from 264 patients (104 males and 160 females; age range, 17–75 years) were retrospectively analyzed. Lingual plate thicknesses at the levels of the mid-root and root apex of the M3s were measured and defined as “thicker” (bone thicker than 1 mm), “thinner” (bone thinner than 1 mm), or “perforated” (bone perforated by the M3 root). These measurements were correlated with potential risk factors for thinner and perforated lingual plates: tooth position of the mandibular M3, morphology of the lingual plate, and patient characteristics (age and sex).

Results

The mean thickness of the lingual plate was 1.49 ± 1.38 mm at the mid-root of the M3s, and 2.35 ± 2.03 mm at the root apex. Multivariate regression analyses revealed that mesioangularly and horizontally impacted M3s were significantly associated with thinner and perforated lingual plates at the mid-root (P < 0.001), whereas the M3s in infra-occlusion positions (in infra-occlusion when compared with the adjacent second molar) had thinner lingual bone at the root apex (P = 0.022 and P = 0.027, depending on the level of impaction). Female patients were less likely to have lingual plate perforation (P = 0.036).

Conclusions

Mesioangulation, infra-occlusion, and male sex were risk factors for lingual plate fracture.

Clinical relevance

When the risk of lingual plate fracture is high, a sufficiently large flap, osteotomy, and tooth section by bur or piezosurgery are recommended to create a good operative field and avoid excessive pressure on the lingual plate.

     

The surgical-orthodontic management of combined impacted maxillary second and third molars

Background

A correlation between impacted maxillary third molars on the eruption potential of the maxillary second molar has been identified. There is little published evidence available in the literature regarding a treatment modality for this presentation.

Aims 

The aim of this case series is to propose a joint surgical and orthodontic approach for the management of such cases.

Method 

A retrospective search of all patients treated for impacted second and third maxillary molars from 2014 to 2020 revealed 24 cases. Surgical planning was facilitated with the use of a CBCT to help orientate the teeth in 3-D and assess any associated pathology to nearby structures. Twenty-three cases were treated via surgical removal of the impacted third molar and subsequently monitored for spontaneous maxillary second molar eruption.

Conclusion

 All treated cases showed complete or partial spontaneous eruption followed by orthodontic repositioning if required.

     

Anatomical considerations for the spread of odontogenic infection originating from the pericoronitis of impacted mandibular third molar: computed tomographic analyses

OBJECTIVES: The aims of the present study were to clarify the anatomy of impacted mandibular third molars in relation to surrounding structures and to investigate the pathway of infection originating from pericoronitis of this tooth. STUDY DESIGN: Computed tomography (CT) images were evaluated in 87 patients with uninfected mandibular third molar impaction and in 12 patients with infection originating from an impacted mandibular third molar. In uninfected patients, bony features around the impacted crown were investigated together with the relationship between the crown and surrounding muscles. In infected patients, involvements of bony and soft tissue structures were evaluated according to the disappearance of cortices and lateral asymmetry of density and shape in the spaces and muscles. RESULTS: In uninfected patients, the disappearance of the lingual cortical plate was observed in 48 (35.3%) impacted molars, while only in 11 (8.1%) teeth for buccal cortices. The cortical thickness was thinner on the lingual side than the buccal side. Sixty-five percent of the masseter muscle horizontally overlapped the crown, while almost all of the medial pterygoid muscle was posteriorly situated apart from the crown. The mylohyoid muscle horizontally overlapped the crown at below or intermediate vertical positions. In infected patients, the involvement of lingual structures was more frequently observed than that of buccal structures. The mylohyoid muscle was involved in 10 (83.3%) of 12 patients. Among them, 8 showed submandibular space involvement. CONCLUSION: CT findings supported the clinical observations of infection spread in patients with pericoronitis of the impacted mandibular third molar. CT appeared to be an effective tool for investigating the pathway of infection originating from the pericoronitis of impacted mandibular third molars.     

Mandibular third molar space in different antero-posterior skeletal patterns

Retromolar space has long been identified as a major factor in the aetiology of mandibular third molar impaction. The aims of this study were to compare mandibular third molar space between the different antero-posterior (A-P) skeletal patterns, between erupted and impacted third molars in the different A-P skeletal patterns, and to report on the status of third molar eruption/impaction among the studied subjects. A total of 432 mandibular third molars in 270 subjects (132 females and 138 males) were investigated from dental pantomograms (DPTs) and lateral cephalograms (LC). The average age for the total sample was 20.80 ± 2.03 years. The subjects were divided into three groups according to their ANB angle as follows: skeletal Class I (144 third molars in 90 subjects), skeletal Class II (145 third molars in 95 subjects), and skeletal Class III (143 third molars in 85 subjects). Each group was subdivided into impacted and erupted subgroups. DPT and LC were traced and the following variables were measured: retromolar space width, third molar width and angulation, β angle, second molar angulation, mandibular length, and gonial angle. Independent t-test, analysis of variance, and chi-square test were used for statistical analysis. Retromolar space width in the Class III subjects was smaller than in the Class I subjects (P?相似文献   

下颌阻生第三磨牙与下颌管重叠时的三维位置关系与拔除方法研究

目的 探讨曲面体层X线片示下颌阻生第三磨牙根尖部与下颌管重叠时的三维位置关系分类,以指导临床采用恰当方法拔出下颌阻生第三磨牙.方法 选取在曲面体层X线片上牙根与下颌管有重叠的57颗下颌阻生第三磨牙,行锥形束CT(cone beam computed tomography,CBCT)检查,了解两者间的三维位置关系,拟定安全的拔除手术方案.结果 55例患者的57颗患牙的CBCT影像中,22颗患牙牙根(38.6％)突破下颌管壁位于下颌管内;30颗患牙(52.6％)的牙根位于下颌管的舌侧,未与下颌管发生接触;4颗患牙(7.0％)的牙根位于下颌管的颊侧,未与下颌管发生接触;1颗患牙(1.8％)的双根跨于下颌管间.57颗患牙均顺利完成拔牙手术,1例患者(1.8％)出现短暂的下唇麻木于术后1个月后恢复.结论 曲面体层X线片上下颌阻生第三磨牙根尖部与下颌管重叠的病例中,下颌第三磨牙的根尖多位于下颌管的舌侧或位于下齿槽神经管内,CBCT检查对拟定正确安全的拔除术式和降低下齿槽神经损伤发生率具有重要的意义.     

下颌第二、第三磨牙并列阻生的正畸矫治

目的探讨下颌第二、三磨牙并列阻生的正畸治疗方法,评估其效果。方法选择下颌第二、第三磨牙并列阻生患者6例、共8对,拔除下颌阻生第三磨牙,采用固定矫治器结合磨牙带环焊多曲推簧直立装置,对水平阻生的第二磨牙进行竖直,使第二磨牙远中直立移动。结果水平阻生第二磨牙全部被直立,达到正常的殆平面,获得良好功能邻接关系及根平行。X线片示原阻生牙冠所占空间为正常牙槽骨组织所修复。下颌阻生磨牙竖直时间为5～14个月,平均为8．63个月。结论在下颌第二、三磨牙并列阻生患者中,拔除下颌第三磨牙,有利于第二磨牙的直立。自制带环焊多曲推簧及粘接拉钩的磨牙竖直技术能有效地使水平阻生的第二磨牙产生快速的远中直立移动。     

改良舌弓矫治下颌第二磨牙近中倾斜的临床应用

目的 评价改良舌弓矫治下颌近中倾斜第二磨牙的疗效。 方法 选择5例下颌第二磨牙近中倾斜病例,采用改良舌弓远中牵引、直立近中倾斜的第二磨牙,观察其临床效果,通过曲面断层片测量评价其疗效。 结果 5例近中倾斜磨牙均远中直立,建立了良好咬合关系,平均疗程5个月。 结论 改良舌弓能有效直立近中倾斜的第二磨牙。     

Third molar angulation during and after treatment of adolescent orthodontic patients

The purpose of this study was to analyse the effect of premolar extraction therapy on third molar angulation during active treatment, and to test the significance of such changes on subsequent impaction of the third molars. Lateral cephalograms made before (T1) and after (T2) treatment and at long-term follow-up (T3) of 157 patients treated non-extraction (non-ex) or with extraction of four premolars (ex), all accurately diagnosed for impaction versus eruption of at least one third molar at T3, were evaluated. Linear regression models demonstrated that the maxillary third molars uprighted more from T1 to T2 (P < 0.05) and were less distally angulated at T2 (P < 0.01) in the ex than in the non-ex patients. No such differences were detected in the mandible (P > 0.05). The regression models also showed similar uprighting of the maxillary and mandibular third molars from T1 to T2 and similar angulation of the maxillary third molars at T2 in those patients with subsequent eruption and impaction (P > 0.05), but more mesially angulated mandibular third molars at T2 in the impaction patients (P < 0.01). Chi square testing demonstrated a higher frequency of distal tipping of the maxillary third molars from T1 to T2 in the impaction patients (P < 0.01), while mesial tipping from T1 to T2 of the mandibular third molars occurred with similar frequency in the two patient groups (P > 0.05). Chi square analysis also showed a higher frequency of greater than 30 degree distal angulation as well as an amount mesial angulation of the maxillary third molars at T2 (P < 0.01), and a higher frequency of greater than 40 degree mesial angulation of the mandibular third molars at T2 (P < 0.01) in patients with impaction than in those with eruption.