Loss of Masticatory Function Affects Growth and Development of the Mandibular Condyle in Rats

The effects of childhood masticatory function loss and soft foods on the mandibular condyle have been the subject of much research. However, the corresponding bone turnover is not fully understood. The purpose of the present study was to clarify the effects of a lack of teeth and a soft food diet during the growth period on bone turnover in the mandibular condyle. We divided 3-week-old Wistar rats into the following three groups: 1) Extraction group: The maxillary molars were extracted at the age of 4 weeks, and animals were fed powdered standard feed. 2) Powder group: Animals were fed powdered standard feed without tooth extraction. 3) Control group: Animals were fed solid standard feed without tooth extraction. Non-decalcified thin-slice specimens of sagittal sections of the mandibular condyle were obtained at the age of 20 weeks for histological analysis. We used micro-CT analysis and bone histomorphometry to measure bone volume (BV), bone mineral content (BMC), bone mineral density (BMD), bone microstructure, bone resorption, and osteogenesis in the mandibular condyle, and we compared the results among groups. In the extraction and the powder groups, we found deformation and disruption of the arrangement of chondrocytes, coagulation of chondrocytes, and duplication of the tidemark in the cartilage. We also found an increase in multinuclear osteoclasts in the cancellous bone. We found a reduction in BV, BMC, and BMD in the extraction and powder groups compared to the control group, as well as a reduction of bone volume, a lowering of osteogenesis parameters, and an increase in bone resorption parameters in the secondary cancellous bone. These results suggest that a lack of teeth and a soft food diet during the growth period cause a decline in bone microstructure, a decrease in osteogenesis, and an increase in bone resorption.

Validation of a novel imaging approach using multi-slice CT and cone-beam CT to follow-up on condylar remodeling after bimaxillary surgery

The main goal of this study was to introduce a novel three-dimensional procedure to objectively quantify both inner and outer condylar remodelling on preoperative multi-slice computed tomography （MSCT） and postoperative cone-beam computed tomography （CBCT） images. Second, the reliability and accuracy of this condylar volume quantification method was assessed. The mandibles of 20 patients （11 female and 9 male） who underwent bimaxillary surgery were semi-automatically extracted from MSCT/CBCT scans and rendered in 3D. The resulting condyles were spatially matched by using an anatomical landmark-based registration procedure. A standardized sphere was created around each condyle, and the condylar bone volume within this selected region of interest was automatically calculated. To investigate the reproducibility of the method, inter- and intra-observer reliability was calculated for assessments made by two experienced radiologists twice five months apart in a set of ten randomly selected patients. To test the accuracy of the bone segmentation, the inner and outer bone structures of one dry mandible, scanned according to the clinical set-up, were compared with the gold standard, micro-CT. Thirty-eight condyles showed a significant （P〈O.05） mean bone volume decrease of 26.4%_ 11.4% （502.9 mm3＋ 268.1 mm3）. No significant effects of side, sex or age were found. Good to excellent （ICC〉 0.6） intra- and inter-observer reliability was observed for both MSCT and CBCT. Moreover, the bone segmentation accuracy was less than one voxel （0.4 mm） for MSCT （0.3 mm __. 0.2 mm） and CBCT （0.4 mm _ 0.3 mm）, thus indicating the clinical potential of this method for objective follow-up in pathological condylar resorption.

Comparison of computed tomography and magnetic resonance imaging for the detection of mandibular condylar osteochondroma

Objective The purpose of this study was to compare computed tomography(CT) and magnetic resonance imaging(MRI) for the detection of mandibular condylar osteochondroma.Methods Preoperative CT and MRI of 33 patients with unilateral condylar osteochondroma were reviewed. The morphology, location, continuity with the parent bone, cartilage cap, perichondrium of tumors, and changes in soft and hard tissues adjacent to the lesions were investigated by two reviewers. Data were analyzed using Mc Nemar test. A P value < 0.05 was considered significant.Results Among the 33 condylar osteochondromas, 11 were of the diffuse type, 10 were of the sessile type, and 12 were of the pedunculated type. Continuity with the cortex and marrow of the host condyle was observed on both CT and MRI. Both modalities had identical detection rates of surface reconstruction of the temporal bone joint, condylar dislocation, and pseudarthrosis formation. However, MRI showed significantly higher detection rates of the cartilage cap and perichondrium than CT(P < 0.05). Furthermore, MRI showed ipsilateral and contralateral temporo-mandibular joint(TMJ) disc displacement in 4 cases and 6 cases, respectively, and ipsilateral and contralateral TMJ effusion in 20 cases and 14 cases, respectively.Conclusion CT can intuitively display the morphology and spatial location of condylar osteochondromas through three-dimensional reconstruction. MRI may be superior to CT in the detection of cartilage cap, perichondrium of the condylar osteochondroma, and changes in the TMJ and adjacent soft tissues.

Ultrasonic piezotome surgery: is it a benefit for our patients and does it extend surgery time? A retrospective comparative study on the removal of 100 impacted mandibular 3rd molars

Aim of the study was to evaluate if there is a constant and significant reduction in traumaticity when mas- sively traumatic oral surgical procedures such as the removal of third molars are conducted with only ul- trasonic surgical devices (Piezotomes) expressed in a reduction of postsurgical pain and swelling on the patient’s side since such clinical experiences by the authors suggested this. Since oral surgeons criticize a higher time consumption for surgeries with Piezoto- mes also the objective time consumption was evalu- ated and compared to the traditional methods. Mate- rial and Methods: 56 female and male patients were selected that already underwent a removal of an im- pacted third mandibular molar on one side with rota- ry instruments by bone destructive burring with a still persisting comparable third mandibular molar on the contralateral side complaining about recur- rent pain episodes and were already documented for pain and swelling before. The ultrasonic surgical re- moval with the Piezotome was conducted with a buc- cal osteotomy of the compacta lateral to the impacted third molar, preservation of the resected compacta in saline solution, removal of the third molar by single or multiple dentotomy and full anatomical restitution of the surgical site with the preserved buccal com- pacta. The swelling was documented by kephalome- try 24/48/72 hours and 1 week post surgery, the pain index by the total consumption of ibuprofen-400 mg—tablets. Lesions of the mandible nerve were documented. Netto surgery time was taken from the first incision to the last suture of the procedure. Re-sults: 6 patients had to be excluded from evaluation due to incomplete post surgical follow up. A signify-cant (***, p > 0.999) decrease in pain and swelling of 50% was detected both for the parameters swelling and pain with Piezotome-surgery. No lesions of the mandible nerve were detected with Piezotome sur- gery whereas surgery with rotary instruments re- sulted in 16% hypesthesia at least up to one week. Although netto surgery time was approximately 50% longer when done with the Piezotome at the begin-ning the time consumption normalized with the growing experience of the surgeons back to the time schedule when surgery was performed with rotary instruments revealing no significant differences (-, p < 0.73). Conclusions: The results of this retrospective study suggest that Piezotome-surgery is superior in atraumaticity and soft-tissue safety compared to tra- ditional procedures with burs and grants the patients significantly less post surgical pain and swelling. Al- though—as it is with all new surgical tools and pro- tocols—surgery time is longer at the beginning when purely working with ultrasonic surgical devices time consumption reduces to normal values after a learn- ing curve.

Computer-Assisted Surgery for Mandibular Reconstruction Using a Patient-Specific Titanium Mesh Tray and Particulate Cancellous Bone and Marrow

Craniomaxillofacial surgery is difficult due to the complexity of the regional anatomy. Computer-assisted surgery is a promising tool aiming to improve the safety and precision of such surgery. A computer-assisted surgical navigation approach for reconstruction of mandibular defects using a patient-specific titanium mesh tray and particulate cancellous bone and marrow (PCBM) harvested from bilateral anterior ilia is proposed. This case report involves a large multicystic ameloblastoma affecting the right mandible of a 31-year-old male patient. Following detailed clinical examination, radiological interpretation, and histopathological diagnosis, computer-assisted surgical simulation with a virtual 3-dimensional (3-D) model was designed using surgical planning software based on the pre-operative computed tomography data. Long-span segmental resection of the mandible was planned, and the defect was analyzed for reconstruction using a patient-specific reconstruction titanium mesh tray mediated with computer-aided design and manufacturing (CAD/CAM) techniques. During the actual surgery, the ultrasonic bone cutting instrument in the surgeon’s hand was connected to the navigation system to touch an anatomical position on the patient. Therefore, osteotomies were performed finely and smoothly according to the navigation images of the cutting bone line by sequentially moving the instrument. Finally, a CAD/CAM-mediated titanium mesh tray condensed by PCBM was adapted to the remaining mandibular fragments. Six months postoperatively, the patient had a good mandibular configuration and facial contour. Integration of different technologies, such as software planning and 3-D surgical simulation, combined with intraoperative navigation and CAD/CAM techniques, provides safe and precise mandibular reconstruction surgery.

The Effect of Acupuncture on Post-operative Oral Surgery Pain

An important problem in the eviluation of acupuncture has been the difficulty in defining and designingan appropriate control group.In order to examine our methodoly for a control group,patientswith one mandibular third molar extraction were randomly assigned to an acupuncture group or aplacebo acupuncture group.The following acupuncture points were used in which the needles werePlaced ipsilateral to the tooth extraction side:Hegu（LI4）,Jiache（ST 6）,Xiaguan（ST

Hyoid Bone Position as an Etiological Factor in Mandibular Divergence and Morphology

Objectives: The objective is to determine whether there are differences in the position of the hyoid bone at rest in natural head position in subjects with mandibular hyperdivergence and to evaluate whether there are differences in hyoid position and antegonial notch depth in mandibular hyperdivergent males and females. Methods and Materials: This is a retrospective cohort study involving a review of lateral cephalometric radiographs of 45 adult men and women with mandibular hyperdivergency. Hyperdivergency was determined by cephalometric ranges of: SN-GoGn as least +2 SD from normal, Y-axis, PP-GoGN, and gonial angle greater than +1SD from normal. A group of 45 normodivergent adults served as a control, with cephalometric ranges of: SN-GoGn within ±1 SD of normal, with only one measurement of the other three between +1 and +1.5 standard deviations. A custom digital cephalometric analysis, the Hyoid Analysis, was designed, to measure the vertical and horizontal position and inclination of the hyoid and the antegonial notch depth. Results: In hyperdivergent subjects, the posterior aspect of the hyoid is located lower and more posterior, compared to the control group, while there is no difference in position of the anterior surface of the hyoid and the antegonial notch is 0.6 mm deeper. In males, the posterior aspect of hyoid is lower by 8.5 mm, while the anterior surface is located 9.0 mm lower. In males, the hyoid is inclined more steeply than in females by 4.4 degrees and the antegonial notch is deeper than in females by 0.6 mm. Conclusions: There are differences in hyoid bone position and mandibular morphology in hyperdivergent subjects compared to normodivergent subjects and in males compared to females.

Stable,dynamic,elastic miniplate osteosynthesis in cranio-maxillofacial surgery:evolution of concepts,biomechanical study and applications

An osteosynthesis of the mandible should be called stable when this type of treatment does not need to be supported by intermaxillary fixation,without disturbing the healing process.In that intention,many techniques of osteosynthesis based on different concepts were proposed during the last century.A classification of these concepts was formulated.The adaptive osteosynthesis which is pragmatically i.e.empirical,wherein the goal is immobilizing the fracture by bringing the fragments together and fixing them with rigid screwed plates.The rigid compressive osteosynthesis which is an extrapolation of the ideas of Lane proposed in 1912.The stable dynamic elastic osteosynthesis whose principles,equipment and technique as their applications were developed exclusively through biomechanical studies.The basic principle was the recovery of mobility by neutralization of detrimental distraction stresses,and reestablishment of favorable compressive stresses providing dynamic physiological stimulations.The biomechanical characteristics of the plates and the screws made possible the use of the fixation of all types of fractures or orthognathic procedures in mandibular surgery.With the application of mini or microplates in other facial bones and the skull,the art of fracture treatment and of reconstructive surgery of the craniomaxillofacial skeleton,including orthognathic and reconstructive surgery with or without bone grafting,has profoundly changed.At the present time,metal plates are sometimes superseded by resorbable plates and screws.Nevertheless,the fundamental biomechanical principles of osteosynthesis and bone healing remain unchanged.

RESEARCH OF BASIFACIAL CONTOURING SCULPTURE BY MANDIBULAR ANGLE OSTECTOMY

Objective Mandibular angle ostectomy is usually applied to the facial contouring sculpture. We evaluated the various techniques in order to enhance the precision and avoid unnecessary damage. Methods Before operation the area and quantity resected bone were designed according to facial measurement, mandible pantomagraphy and orthophoria and lateral localized radiograph of skull. The Incises of mandibular angle ostectomy included intraoral, retroauricular or intraoral associated with retroauricular. Howerer, the sagittal resection of mandible outer table was necessary in all intraoral incise. Results Single mandibular angle ostectomy was not satisfactory for the patients having mandible hypertrophy with over-width basifacial contouring. Mandibular angle ostectomy combined with the sagittal resection of outer table of mandibular angle were required. Good symmetry and appearance were gained in 206 cases. One case had facial paralysis. Two patients occured mandibular fracture during the operation. Three cases complicated angled deformity at mandible body. Conclusion Reduction mandibuloplasty should be selected depends on varied types of mandibular angle hypertrophy before operation.

Combined Therapy for Mandibular Prognathism:Sagittal Split Osteotomy with Excision of Tongue

In the evaluation of the beauty and functional integrity of the lower face, the oral cavity, teeth, mandible, maxilla, and the size and position of the tongue are important. The tongue locates forward and is larger than normal in prognathism, in which the jaw protrudes from the skull. It is not clear whether an enlarged tongue causes the open bite, protrusion or dental arch misalignment, or is a result of them. Here, we report two patients with mandibular prognathism and relative macroglossia, which were treated by mandibular setback surgery using a bilateral sagittal split osteotomy (BSSO) and excision of the tongue. This procedure achieved aesthetic improvement of the face and dentition.

成人下颌发育不足的外科矫治

下颌发育不足是牙颌面畸形的常见类型之一,严重影响患者的面部美观和咬合功能。外科矫治是目前最有效的治疗方法,可以通过手术治疗改变下颌骨位置和形态,恢复患者正常面部外形。本文从外科治疗的角度,将颞下颌关节这一关键因素纳入成人下颌发育不足的诊疗设计中,阐述成人下颌发育不足的常用矫治方法,包括正颌外科手术、颞下颌关节外科手术、正畸-正颌联合治疗和牵张成骨技术等,总结不同类型成人下颌发育不足的治疗流程。为临床医生治疗该疾病提供参考,提高这一疾病的治疗水平。

基于下颌运动轨迹的正颌外科术中下颌骨髁突定位方法及初步精度验证

目的:基于下颌运动轨迹建立正颌手术下颌骨髁突位置的术前规划和术中定位技术流程,并对其定位准确性进行评价。方法:通过大视野锥形束计算机体层摄影术(cone beam computed tomography,CBCT)和口内扫描分别获得面部骨组织和牙齿的三维数据,采用下颌运动记录仪记录患者下颌生理状态下各方向运动时的下颌运动轨迹。使用IVSPlan l.0.25软件,通过数据分割、三维重建得到上、下颌骨的三维模型,通过标志点配准将牙列数据与颌骨数据融合,将下颌运动记录仪得到的数据转化为下颌骨相对于上颌骨的矩阵变换方程组,通过下颌骨三维数据的矩阵变换得到不同时刻下颌骨髁突的坐标位置,并通过软件可视化呈现其三维运动轨迹。由一名具有颞下颌关节病诊治和正颌外科手术双专业背景的高年资口腔颌面外科医师在可视化界面上筛选合适的下颌骨髁突位置作为近心骨段的术后位置,常规进行正颌外科设计,基于咬合关系和面型设计远心骨段位置,将近、远心骨段数据融合得到术后下颌骨形态,通过3D打印得到实体模型。在实体模型上预成型钛板、打孔,设计下颌骨髁突定位导板。手术中,通过下颌骨髁突定位导板和预成型钛板引导包含下颌骨髁突的近心骨段就位于术前设计位置。通过10例骨性Ⅱ类牙颌面畸形患者验证该流程在双侧下颌升支矢状劈开截骨术(sagittal split ramus osteotomy,SSRO)中定位下颌骨髁突的准确性。误差的计算方法为术前设计与术后2周CBCT实际下颌骨髁突表面距离的均方根(root mean square,RMS)。结果:术前设计下颌骨髁突位置与术后2周的实际位置相比,下颌骨髁突表面平均距离的RMS为(1.59±0.36)mm,95%CI:1.35~1.70 mm,小于2 mm的专家共识建议值(P<0.05)。结论:下颌运动轨迹对正颌外科手术设计中确定包含下颌骨髁突的近心骨段位置可能具有指导作用,使用下颌骨髁突定位装置和预成型钛板术中引导下颌骨髁突就位的精度可以满足临床需求。

正颌外科规划软件中下颌运动交互模块的初步构建

目的:基于下颌运动轨迹构建数字化正颌外科规划软件中的下颌交互模块并进行临床验证。方法:基于CCMF Plan正颌规划软件,使用空间矩阵算法解算下颌运动轨迹数据,实现下颌运动的还原,根据距离重要性采样算法拟合患者个性化的下颌旋转轴并验证模拟下颌运动的精确性。使用下颌旋转轴指导手术规划,验证术中髁突位置实现的准确性。结果:开发出可再现患者下颌运动,以下颌旋转轴指导升支旋转的下颌运动交互模块。该模块还原模拟的下颌运动轨迹与真实轨迹误差约1 mm,同一开口度时的下颌骨模型表面距离均方根值(root mean square,RMS)值约0.3 mm。其指导的正颌手术术后髁突的角度偏差约为3°,距离偏差约1.5 mm。结论:该下颌运动交互模块可以较为精确地拟合下颌旋转轴,并还原患者个性化的下颌运动,术后髁突位置实现的精确性满足临床的要求。

骨性Ⅲ类错[牙合]畸形下颌偏斜患者正颌手术前后髁突形态变化的研究

目的:探讨正颌手术对骨性Ⅲ类错[牙合]畸形下颌偏斜患者髁突形态的影响,以及不同偏斜程度患者髁突形态和变化的差异。方法:选取20例骨性Ⅲ类错[牙合]畸形伴下颌偏斜患者,根据颏下点偏离值(menton deviation,MD)分为A组(轻度偏斜组:4 mm≤MD<10 mm)和B组(重度偏斜组:MD≥10 mm),每组各10例。将患者术前(T1)、术后6个月(T2)颅面部CT数据导入Proplan CMF软件,三维重建获得髁突模型,读取髁突体积、表面积,计算髁突形态学指数(morphometric index,MI)。结果:T2时A组偏斜侧(the deviated side,DS)与非偏斜侧(the non-deviated side,NDS)髁突体积与表面积均减小(P<0.05);2组T1、T2时NDS髁突体积、表面积、MI均大于DS,双侧差异的统计学意义,B组更显著;A组各指标数值大于B组,2组DS各指标的差异有统计学意义(P<0.05);T2较T1时髁突变化幅度不同,2组DS体积、表面积变化幅度差异有统计学意义(P<0.05)。结论:正颌手术会导致术后髁突体积与表面积减小,且术后6个月时轻度偏斜组髁突体积与表面积减小的统计学差异更加显著。患者DS髁突体积、表面积及MI小于NDS,轻度偏斜者DS髁突体积、表面积及MI大于重度偏斜者,术后髁突形态变化与偏斜程度相关。

颞下颌关节退行性改变与颅面形态及颞下颌关节形态结构的关联

颞下颌关节退行性关节病在影像学上多表现为髁突骨质破坏、增生、硬化、囊样变或者髁突形态上的短小畸形,其病因复杂。相关临床研究发现,骨性Ⅱ类或高角骨面型的个体多见颞下颌关节退行性变,偏颌人群中的患病率也较高;同样有较多的研究提示,髁突骨质退行性改变与不可复性关节盘移位等颞下颌关节形态结构存在关联,其中的因果关系目前尚不完全明确。本文主要从解剖学特征方面综述颞下颌关节退行性改变与颅面形态的相关性及与关节内部形态结构的相关性,最后从生物力学的角度来探讨颞下颌关节退行性改变的可能原因,以期为临床工作者了解该疾病及制订临床决策提供参考。

下颌骨髁突骨折45例回顾性分析

目的:总结基于新分类的下颌骨髁突骨折手术治疗及保守治疗的临床效果。方法:回顾性分析2012年1月—2021年12月期间,南京大学医学院附属苏州医院及苏州九龙医院口腔科收治的45例(57侧)下颌骨髁突骨折患者的临床资料,分析患者受伤原因、骨折分类、治疗方法、并发症及随访结果。结果:45例患者中男性34例、女性11例,平均年龄34.67岁(16~76岁)。交通事故(56%)为主要致伤原因。髁头骨折(囊内骨折) 26例(35侧),其中A型13例(13侧)、B型7例(11侧)、C型1例(1侧)、M型3例(6侧)、无移位2例(4侧);髁颈骨折12例(13侧);髁突基底部骨折7例(9侧)。10例髁头骨折(B型4例、C型1例、M型3例、无移位2例)及3例髁颈骨折共13例行保守治疗;16例髁头骨折(A型13例、B型3例)、9例髁颈骨折及7例髁突基底部骨折共32例行手术治疗。所有患者中,5例失访,40例随访6个月以上。保守治疗者中,3例关节区长期酸痛、1例关节弹响、1例张口受限;手术治疗者1例髁突吸收、2例面神经颞支麻痹。结论:下颌骨髁突骨折应结合骨折分类及患者全身情况综合考虑,选择合理的个性化治疗方案。

正颌手术治疗骨性Ⅲ类错[牙合]畸形对颞下颌关节髁突影响的研究现状

正颌外科手术是治疗骨性Ⅲ类错[牙合]畸形最常用的治疗方式,髁突是评价患者正颌术后复发及稳定性的重要因素,对正颌术后髁突位置如何变化及改建学者们意见不一。本文就骨性Ⅲ类错[牙合]畸形患者髁突位置、形态特点以及正颌术后髁突位置变化和改建三个方面进行简要综述。

数字化口腔虚拟仿真培训系统在阻生下颌第三磨牙拔除教学中的应用

目的探讨数字化口腔虚拟仿真培训系统在阻生下颌第三磨牙拔除教学中的应用效果。方法选择2022年5月—2023年5月于南昌大学第二附属医院口腔颌面外科基地轮转的113名医学生作为教学对象,按照随机数表法分为试验组和对照组,其中试验组57名,对照组56名。对照组接受传统教学模式(即观摩带教老师操作+教师的椅旁教学)培训,试验组接受传统教学模式结合数字化口腔虚拟仿真培训系统进行阻生下颌第三磨牙拔除的培训。轮转结束前3天,比较2组的理论知识考核、临床技能考核和教学效果。结果试验组的理论考核成绩为(79.14±6.55)分,高于对照组的(76.84±5.63)分,差异有统计学意义(P<0.05)。试验组的技能考核成绩为(81.02±5.21)分,高于对照组的(78.71±5.67)分,差异有统计学意义(P<0.05)。试验组的提高知识掌握程度[(7.56±0.66)分]、增进临床技能水平[(7.80±0.67)分]、激发学习兴趣[(7.77±0.68)分]和学习效果满意度[(7.75±0.71)分]评分高于对照组[(7.32±0.54)分、(7.50±0.69)分、(7.50±0.60)分、(7.45±0.63)分],差异有统计学意义(P<0.05)。结论相较于单一的传统教学模式,数字化口腔虚拟仿真培训系统可以作为一种提升阻生下颌第三磨牙拔除术理论知识掌握度和临床技能操作水平的有效辅助手段。

下颌神经管分支在下颌骨内的走行

目的 通过观察胶东地区成年人口腔锥形束CT(cone beam computed lomography, CBCT)结果,对下颌神经管的分支在下颌骨内走行进行分析统计,为口腔医学临床工作尤其是牙槽外科、口腔种植科操作提供准确的临床影像数据。方法 选取2021年12月到2022年1月期间在烟台市口腔医院拍摄CBCT影像且符合纳入标准的188例成年人(男性78人,女性110人,年龄18~59岁)患者的口腔CBCT数据,应用NNT图像系统分析观察,汇总统计分支发生率。结果 下颌神经管分支发生率为52.12%,侧别发生率为43.35%,其中Ⅰ、Ⅱ、Ⅲ、Ⅳ、Ⅴ型的发生率分别为11.70%、9.30%、9.84%、6.38%、6.11%。男性和女性左侧和右侧下颌神经管分支的发生率的差异无统计学意义(P>0.05)。结论 CBCT相较于平片更能够清晰显示下颌神经管及其分支的解剖特征,对于牙槽外科及口腔种植科进行手术时,可以更细致进行术前设计,避免损伤神经分支。

下颌第二磨牙牙冠延长术后疗效观察及其风险因素分析

目的:观察下颌第二磨牙牙冠延长术后治疗效果,确定其风险因素;探讨风险因素个数对其疗效的影响。方法:纳入2019~2021年于天津市口腔医院接受牙冠延长术的下颌第二磨牙314颗。6周复查时,按照拟定标准将其分为效果良好组和效果欠佳组。筛选影响两组患牙疗效的风险因素,并分析其数量与治疗效果的相关性。结果:314颗患牙中,成功者占88.54%,失败者为11.46%。龈缘-断端距离(P<0.01)、术前断端-嵴顶距离(P=0.032)及牙根形态(P=0.006)是影响术后疗效的风险因素。随着风险因素数量的增加,手术失败率呈线性增长的趋势,风险因素达到3个时,失败风险明显增高(P<0.01)。两者之间呈正相关(P<0.01)。结论:龈缘-断端距离、术前断端-嵴顶距离及牙根形态是影响冠延长疗效的风险因素,其数量与手术失败率之间呈正相关,风险因素达到3个时,失败风险明显增高,需谨慎选择适应证。