Cone Beam Computed Tomographic Measurement of Maxillary Central Incisors to Determine Prevalence of Facial Alveolar Bone Width ≥2 mm

Background: The initial thickness of maxillary bone has significant impact on the responding level of facial bone and soft tissue after extraction and immediate implant placement. A prevailing notion is that following implant placement in fresh extraction sites, at least 2 mm of facial bone is needed to prevent soft tissue recession, fenestration, and dehiscence. Purpose: The purpose of this study was to use cone beam computed tomography (CBCT) to measure horizontal width of facial alveolar bone overlying healthy maxillary central incisors and to determine prevalence of bone thickness ≥2 mm. Materials and Methods: Tomographic data from 101 randomly selected patients were evaluated by two independent observers. Assessments were made of facial bone width at levels 1.0 to 10.0 mm apical to the bone crest. Results: Healthy maxillary central incisors (n = 202) were measured from 101 patient scans. The percent of teeth with facial bone ≥2 mm at levels 1, 2, 3, 4, and 5 mm from the bone crest was 0, 1.5, 2.0, 3.0, and 2.5%, respectively. Overall mean thickness of the bone was 1.05 mm for right and left central incisors combined. The range of individual measurements for all levels was 0 to 5.1 mm. The occurrence of ≥2 mm thickness bone measurements increased with increasing depth. However, mean widths observed at levels 6 to 10 mm from the crest ranged only 1.0 to 1.3 mm because of apparent fenestration occurrence (0 mm bone) in approximately 12% of teeth. Overall, no significant differences in bone thickness were found between ethnic, gender, age, or scan groups. Conclusions: Using CBCT, occurrences of ≥2 mm maxillary facial alveolar bone were found on no more than 3% of root surfaces 1.0 to 5.0 mm apical to the bone crest in this sample of maxillary central incisors. The study evidenced prevalence of a thin facial alveolar bone (<2 mm) that may contribute to risk of facial bone fenestration, dehiscence, and soft tissue recession after immediate implant therapy.     

采用锥形束CT测量健康上前牙唇侧骨板形态及牙长轴倾角的变化

目的 采用锥形束CT（CBCT）图像数字化测量的方法,测量健康上前牙唇侧骨板厚度、釉牙骨质界（CEJ）到骨嵴顶距离及牙长轴倾角,并探讨可能的影响因素。方法 分析由Newtom VGI ^? CBCT机拍摄获得的345例CBCT影像,使用NNT软件分别在上颌中切牙、侧切牙和尖牙的正中矢状平面上测量CEJ下4 mm、根中点和根尖水平的唇侧骨板厚度,CEJ距骨嵴顶距离和牙长轴倾角,记录各牙位CEJ下4 mm水平唇侧骨板厚度≥1 mm的例数。结果 1）中切牙的牙长轴倾角,CEJ距骨嵴顶距离,CEJ下4 mm、根中点和根尖水平的骨板厚度均值分别为15.2°±6.2°、（1.5±1.0）mm、（0.8±0.4）mm、（0.6±0.4）mm和（1.3±0.7）mm;侧切牙和尖牙的上述5项测量值分别为16.2°±8.8°、（1.6±1.0）mm、（0.7±0.5）mm、（0.4±0.6）mm和（1.1±0.7）mm;19.0°±6.2°、（1.8±1.0）mm、（0.9±0.6）mm、（0.4±0.6）mm和（1.2±0.7）mm。2）345例患者中,中切牙、侧切牙和尖牙CEJ下4 mm水平骨板厚度≥1 mm者分别占28.3%、25.8%和42.7%。3）中切牙、侧切牙和尖牙CEJ到骨嵴顶距离与年龄高度相关,相关系数分别为0.42、0.50、0.62（P<0.01）。结论 健康上前牙唇侧骨板厚度较薄,CEJ到骨嵴顶距离随着年龄的增加而增加,牙长轴较牙槽突长轴舌倾,充分考虑这些特点有利于提高相关口腔治疗方案的安全性和预后。     

采用锥形束CT测量健康上前牙唇侧骨板形态及牙长轴倾角的变化

目的 采用锥形束CT（CBCT）图像数字化测量的方法,测量健康上前牙唇侧骨板厚度、釉牙骨质界（CEJ）到骨嵴顶距离及牙长轴倾角,并探讨可能的影响因素。方法 分析由Newtom VGI ^? CBCT机拍摄获得的345例CBCT影像,使用NNT软件分别在上颌中切牙、侧切牙和尖牙的正中矢状平面上测量CEJ下4 mm、根中点和根尖水平的唇侧骨板厚度,CEJ距骨嵴顶距离和牙长轴倾角,记录各牙位CEJ下4 mm水平唇侧骨板厚度≥1 mm的例数。结果 1）中切牙的牙长轴倾角,CEJ距骨嵴顶距离,CEJ下4 mm、根中点和根尖水平的骨板厚度均值分别为15.2°±6.2°、（1.5±1.0）mm、（0.8±0.4）mm、（0.6±0.4）mm和（1.3±0.7）mm;侧切牙和尖牙的上述5项测量值分别为16.2°±8.8°、（1.6±1.0）mm、（0.7±0.5）mm、（0.4±0.6）mm和（1.1±0.7）mm;19.0°±6.2°、（1.8±1.0）mm、（0.9±0.6）mm、（0.4±0.6）mm和（1.2±0.7）mm。2）345例患者中,中切牙、侧切牙和尖牙CEJ下4 mm水平骨板厚度≥1 mm者分别占28.3%、25.8%和42.7%。3）中切牙、侧切牙和尖牙CEJ到骨嵴顶距离与年龄高度相关,相关系数分别为0.42、0.50、0.62（P<0.01）。结论 健康上前牙唇侧骨板厚度较薄,CEJ到骨嵴顶距离随着年龄的增加而增加,牙长轴较牙槽突长轴舌倾,充分考虑这些特点有利于提高相关口腔治疗方案的安全性和预后。     

Dimension of the facial bone wall in the anterior maxilla: a cone-beam computed tomography study

Objective: To determine the thickness of the facial bone wall in the anterior dentition of the maxilla and at different locations apical to the cemento‐enamel junction (CEJ). Material and methods: Two‐hundred and fifty subjects, aged between 17 and 66 years, with all maxillary front teeth present were included. Written informed consents were obtained. Cone‐beam computed tomography scans were performed with the iCAT unit. This examination included all tooth and edentulous sites in the dentition. The images were acquired by means of the iCAT software and processed by a computer. Measurements of the (i) distance between the CEJ and the facial bone crest and (ii) the thickness of the facial bone wall were performed. The bone wall dimensions were assessed at three different positions in relation to the facial bone crest, i.e., at distances of 1, 3, and 5 mm apical to the crest. Results: The measurements demonstrated that (i) the distance between the CEJ and the facial bone crest varied between 1.6 and 3 mm and (ii) the facial bone wall in most locations in all tooth sites examined was ≤1 mm thick and that close to 50% of sites had a bone wall thickness that was ≤0.5 mm. Conclusion: Most tooth sites in the anterior maxilla have a thin facial bone wall. Such a thin bone wall may undergo marked dimensional diminution following tooth extraction. This fact must be considered before tooth removal and the planning of rehabilitation in the anterior segment of the dentition in the maxilla. To cite this article:
Januário AL, Duarte WR, Barriviera M, Mesti JC, Araújo MG, Lindhe J. Dimension of the facial bone wall in the anterior maxilla: a cone‐beam computed tomography study.
Clin. Oral Impl. Res. 22 , 2011; 1168–1171
doi: 10.1111/j.1600‐0501.2010.02086.x.
10.1111/j.1600‐0501.2010.02086.x     

Assessment of gingival biotype and facial hard/soft tissue dimensions in the maxillary anterior teeth region using cone beam computed tomography

ObjectiveThis study sought to assess the relationship between facial gingival and bone dimensions in maxillary anterior teeth region using cone beam computed tomography (CBCT).DesignThis study assessed 621 maxillary anterior teeth in 144 patients. In the sagittal plane, facial bone thickness (BT) and gingival thickness (GT) were measured at the crestal level and at 2, 4 and 6 mm apical to the cementoenamel junction (CEJ). The dentogingival complex (DGC) dimensions and the distance from the CEJ to bone crest were also measured on CBCT scans. To determine the gingival biotype, GT at 2 mm apical to the gingival margin was measured and GT <1.5 mm was categorized as thin while GT ≥1.5 mm was categorized as thick. The data were analyzed using SPSS version 21 via repeated measures ANOVA and the Cochrane’s Q, chi-square and independent samples t-tests.ResultsThe BT around the maxillary central and lateral incisors and canine teeth at 4 and 6 mm apical to the CEJ was significantly different in thick and thin gingival biotypes (P < 0.05). The mean GT at 2 and 4 mm apical to the CEJ was significantly different around central and lateral incisors (P < 0.05). Thickness of crestal bone was significantly different between the two gingival biotypes around central and lateral incisors (P < 0.05).ConclusionThe two gingival biotypes had significantly different mean BT; different biotypes and their relationship to BT varied around anterior maxillary teeth.     

下颌前牙唇侧骨壁厚度及倾斜角度对即刻种植术前设计的影响

目的: 利用锥形束CT（cone-beam CT,CBCT）对下颌前牙唇侧骨壁厚度及倾斜角度进行测量分析,为下颌前牙区的即刻种植术前设计提供参考依据。方法: 选取青岛大学附属医院口腔科135例（男67例,女68例）下颌恒牙列完整的CBCT资料,分别测量牙槽嵴顶处（P1）、牙根中点处（P2）、根尖处（P3）3个位点的唇侧骨壁厚度、下前牙长轴与牙槽骨长轴的角度。采用SPSS 23.0软件包对数据进行统计学分析。结果: 下颌中切牙、侧切牙、尖牙唇侧牙槽嵴顶处骨板厚度分别为（0.65±0.24）mm、（0.66±0.28）mm、（0.57±0.29）mm,根中处骨板厚度分别为（0.58±0.35）mm、（0.47±0.23）mm、（0.58±0.30）mm,根尖处骨板厚度分别为（3.45±1.28）mm、（3.87±1.25）mm、（4.60±1.32）mm;下颌中切牙、侧切牙、尖牙牙体长轴与牙槽骨长轴角度分别为5.43°±2.30°、7.22°±3.12°、6.28°±2.65°;相同牙位左右侧之间、不同性别之间各测量值之间无显著差异。结论: 下颌前牙唇侧骨壁厚度菲薄,下颌前牙倾斜角度较小,可为下颌前牙区的即刻种植术前设计的制定提供参考依据。     

安氏I类错儿童上颌切牙唇腭侧齿槽厚度的CBCT研究

目的:采用CBCT影像测量安氏I类错患儿上颌前牙唇倾度及前牙唇腭侧齿槽骨的厚度,探讨上颌切牙与其支持骨的空间位置关系。方法:选取深圳市儿童医院口腔正畸科2010.1～2012.1年间就诊的正畸患儿25名,年龄11～14岁,平均12.5岁,男9例,女16例。Angle I类轻度错畸形。上前牙排列良好,无严重拥挤。所有病例均拍摄CBCT影像,在重建后的图像下进行定量测量。测定上切牙唇腭向的倾斜度,上切牙不同层面唇腭侧齿槽骨的厚度,上切牙根尖上方唇侧齿槽骨的曲度以及上切牙根尖距唇侧齿槽骨最凹点的距离。测量得到的数据采用SPSS13.0软件进行统计分析。结果:釉牙骨质界下2 mm唇侧骨板的厚度:中切牙(0.96±0.32)mm,侧切牙(0.78±0.32)mm。釉牙骨质界下2 mm腭侧骨板的厚度:中切牙(1.53±0.40)mm,侧切牙(1.12±0.48)mm。中切牙与腭平面的角度为114.59°±5.25°,侧切牙与腭平面的角度为111.75°±5.98°。切牙根尖上方唇侧齿槽骨的曲度:中切牙145.70°±11.09°,侧切牙156.92°±8.33°。切牙根尖距其上方唇侧齿槽骨最凹点的距离:中切牙(2.88±1.49)mm,侧切牙(2.69±0.99)mm。结论:上颌中切牙较侧切牙更加唇倾,切牙唇侧骨板均较薄,腭侧骨板相对较厚。切牙根尖位置更接近齿槽骨的唇侧。     

牙龈厚度与上前牙唇侧骨板厚度的相关性研究

目的：测量分析上前牙牙龈厚度与唇侧骨板厚度及牙槽嵴顶到釉牙骨质界距离的相关性。方法：对30位青年受试者用间接显影法进行 CBCT 扫描,测量并记录以下数据并进行统计分析：龈缘下2 mm 牙龈厚度,牙槽嵴顶下2、4、6 mm 骨板厚度,牙槽嵴顶到釉牙骨质界的距离。CBCT 测量的准确性用直接测量法进行检测。结果：牙龈厚度与牙槽嵴顶下2、4、6 mm 处骨板厚度相关系数（r）分别为0．493、0．383、0．342（P ＜0．001）,牙龈厚度与牙槽嵴顶至釉牙骨质界距离相关系数（r）为－0．213（P ＜0．01）。CBCT 扫描法测量与直接测量法之间差异无统计学意义（t ＝－0．521,P ＝0．603）结论：上前牙唇侧中央牙龈厚度与对应牙槽骨骨板厚度正相关,与牙槽嵴顶到釉牙骨质界的距离呈负相关。     

Dimensions of the dentogingival unit in maxillary anterior teeth: a new exploration technique (parallel profile radiograph)

This study sought to develop and evaluate a radiographic exploration technique (parallel profile radiograph [PPRx]) for measuring the dentogingival unit on the buccal surfaces of anterior teeth, and to provide additional information on the dimensions of the dentogingival unit in humans. In 88 periodontally healthy individuals, a PPRx was made of the maxillary left central incisor. Over these images, the components of the dentogingival unit were measured. PPRx was a highly reproducible exploratory technique. Mean dentogingival measurements on the buccal surfaces of the teeth were 2.05 +/- 0.87 mm for distance between the CEJ and bone crest; 2.00 +/- 0.72 mm for biologic width; 1.75 +/- 0.24 mm for thickness of connective tissue attachment; 1.12 +/- 0.24 mm for thickness of free gingiva at its base; 0.45 +/- 0.20 mm for thickness of bone plate at crest level; and 1.41 +/- 0.62 mm for gingival overlap on enamel surface. A statistically significant relationship was observed between free gingival width and thickness of connective attachment, and the depth of the gingival sulcus. These results corroborate the notion that the dimensions of the dentogingival unit are highly variable in humans. The thicknesses of both the connective tissue attachment and free gingiva, however, showed less variability than did the thickness of the bone crest, distance between CEJ and bone crest, and biologic width. The results suggest that gingival dimensions are correlated to dentogingival unit dimensions.     

Anthropometric analysis of maxillary anterior buccal bone of Korean adults using cone-beam CT

PURPOSE

The aim of this study was to evaluate the thickness of buccal and palatal alveolar bone and buccal bony curvature below root apex in maxillary anterior teeth of Korean adults using Cone-beam CT images.

MATERIALS AND METHODS

The 3D image was reconstructed with dicom file obtained through CBCT from 20 - 39 year old Korean subjects (n = 20). The thickness of buccal and palatal plate, root diameter, the buccal bony curvature angle below root apex and the distance from root apex to the deepest point of buccal bony curvature were measured on maxillary anterior teeth area using OnDemand3D program.

RESULTS

Mean thickness of buccal plate 3 mm below CEJ was 0.68 ± 0.29 mm at central incisor, 0.76 ± 0.59 mm at lateral incisor, and 1.07 ± 0.80 mm at canine. Mean thickness of palatal plate 3 mm below CEJ was 1.53 ± 0.55 mm of central incisor, 1.18 ± 0.66 mm of lateral incisor, 1.42 ± 0.77 mm of canine. Bucco-lingual diameter 3 mm below CEJ was 5.13 ± 0.37 mm of central incisor, 4.58 ± 0.46 mm of lateral incisor, and 5.93 ± 0.47 mm of canine. Buccal bony curvature angle below root apex was 134.7 ± 17.5° at central incisor, 151.0 ± 13.9° at lateral incisor, 153.0 ± 9.5° at canine. Distance between root apex and the deepest point of buccal bony curvature of central incisor was 3.67 ± 1.28 mm at central incisor, 3.90 ± 1.51 mm at lateral incisor, and 5.13 ± 1.70 mm at canine.

CONCLUSION

Within the limitation of this study in Korean adults, the thickness of maxillary anterior buccal plate was very thin within 1mm and the thickness of palatal plate was thick, relatively. The buccal bony curvature below root apex of maxillary central incisor was higher than that of lateral incisor and canine and it seems that the buccal bony plate below root apex of central incisor is most curved.     

数字化技术评估上颌前牙区唇侧牙龈厚度与骨板厚度的相关性研究

目的 通过CBCT结合口腔扫描手段,分析青年人上颌前牙区唇侧牙龈厚度与骨板厚度相关性以及釉牙骨质界(CEJ)至牙槽嵴顶(ARC)的距离与牙龈生物型之间的相关性。方法 对30名受试者进行CBCT拍摄、口内数字化扫描,两组数据配准重建后测量釉牙骨质界至牙槽嵴顶的距离、唇侧CEJ下4 mm处牙龈厚度及对应骨板厚度。结果 厚中薄三种牙龈生物型对应釉牙骨质界至牙槽嵴顶的距离差异无统计学意义(F=1.886,P>0.05);CEJ下4 mm处牙龈厚度与骨板厚度在中切牙及侧切牙区存在负相关(r=-0.319;r=-0.292,P<0.01),在尖牙区无明显相关性(r=-0.197,P>0.05)。结论 牙龈生物型分型与釉牙骨质界-牙槽嵴顶的距离之间无显著相关性;上颌前牙区唇侧牙龈厚度及骨板厚度均较薄,两者之间相关性尚未明确。     

Thickness of the anterior maxillary facial bone wall-a retrospective radiographic study using cone beam computed tomography

The purpose of this retrospective radiographic study was to analyze the thickness of the facial bone wall at teeth in the anterior maxilla based on cone beam computed tomography (CBCT) images, since this anatomical structure is important for the selection of an appropriate treatment approach in patients undergoing postextraction implant placement. A total of 125 CBCT scans met the inclusion criteria, resulting in a sample size of 498 teeth. The thickness of the facial bone wall in the respective sagittal scans was measured perpendicular to the long axis of the tooth at two locations: at the crest level (4 mm apical to the cementoenamel junction; MP1) and at the middle of the root (MP2). No existing bone wall was found in 25.7% of all teeth at MP1 and in 10.0% at MP2. The majority of the examined teeth exhibited a thin facial bone wall (< 1 mm; 62.9% at MP1, 80.1% at MP2). A thick bone wall (? 1 mm) was found in only 11.4% of all examined teeth at MP1 and 9.8% at MP2. There was a statistically significant decrease in facial bone wall thickness from the first premolars to the central incisors. The facial bone wall in the crestal area of teeth in the anterior maxilla was either missing or thin in roughly 90.0% of patients. Both a missing and thin facial wall require simultaneous contour augmentation at implant placement because of the well-documented bone resorption that occurs at a thin facial bone wall following tooth extraction. Consequently, radiographic analysis of the facial bone wall using CBCT prior to extraction is recommended for selection of the appropriate treatment approach.     

微种植体支抗辅助内收上切牙后牙槽骨改建的锥形束CT研究

目的:探索运用微种植体支抗结合高位牵引钩大量内收上颌切牙后牙槽骨的改建情况。方法:以22例青少年上颌前突拔牙矫治患者,上颌切牙内收前、内收完成后的锥形束CT（cone-beam CT,CBCT）为研究样本,应用Mimics 15.0行CBCT影像三维重建,明确上颌切牙移动方式,利用Invivo5.0三维定点测量唇、腭侧牙槽骨厚度和高度变化。采用SPSS19.0 软件包对测量数据进行配对t 检验。结果:上颌切牙切缘与根尖均发生水平舌侧移动,但切缘的移动距离大于根尖;切缘点发生向下移动,根尖点出现明显的向上移动。上切牙腭侧牙槽骨厚度及唇腭侧总厚度在根颈1/3和根中1/3均显著减小（P<0.05）,而根尖1/3显著增加（P<0.05）,腭侧牙槽骨高度显著降低（P<0.05）。结论:青少年上颌前突患者微种植体支抗结合高位牵引钩可以实现受控制的倾斜移动。大量内收上颌切牙后,其腭侧牙槽骨吸收远大于唇侧增生,牙槽骨并没有完全跟随牙的移动而改建,提示正畸矫治时不宜过度内收前牙。     

上颌前牙唇侧牙龈厚度、牙槽骨厚度及牙根牙槽骨交角的相关性研究

目的 运用锥形束CT测量上颌前牙唇侧牙龈厚度、牙槽骨厚度以及牙根与牙槽骨的位置关系,分析三者之间的相关性,为口腔美学修复、种植方案选择、预后判断及疗效评估提供依据。方法 选取40名牙周健康的志愿者,男性16名,女性24名,年龄范围23~34岁,平均（26.30±2.29）岁。运用锥形束CT间接显影法测量受试者的上颌前牙区唇侧釉牙骨质界处牙龈厚度,牙槽嵴顶根方1、3、5 mm处牙槽骨厚度,以及牙根与牙槽骨所成交角。结果 上颌前牙唇侧牙龈平均厚度为（1.08±0.34） mm,牙槽骨平均厚度为（0.79±0.29） mm,牙根与牙槽骨交角均值为18.01°±8.96°;上颌前牙唇侧牙槽骨厚度与牙龈厚度有正相关关系（r=0.293,P=0.001）,尖牙处唇侧牙槽骨厚度与牙根牙槽骨交角呈正相关关系（r=0.457,P=0.003）。结论 上颌前牙唇侧牙槽骨薄,牙根与牙槽骨存在一定角度,唇侧牙龈厚度与牙槽骨厚度具有相关性;种植治疗时应充分考虑种植位点牙龈厚度、牙槽骨厚度及牙根在牙槽骨内的位置方向,选择合理的术式以期获得良好的种植功能及美学效果。     

The influence of non-matching implant and abutment diameters on radiographic crestal bone levels in dogs

BACKGROUND: It has been shown that different implant designs and different vertical implant positions have an influence on crestal bone levels. The aim of the present study was to evaluate radiographic crestal bone changes around experimental dental implants with non-matching implant-abutment diameters placed submucosally or transmucosally at three different levels relative to the alveolar crest. METHODS: Sixty two-piece dental implants with non-matching implant-abutment diameters were placed in edentulous spaces bilaterally in five foxhounds. The implants were placed submucosally or transmucosally in the left or the right side of the mandible. Within each side, six implants were randomly placed at three distinct levels relative to the alveolar crest. After 12 weeks, 60 crowns were cemented. Radiographs were obtained from all implant sites following implant placement, after crown insertion, and monthly for 6 months after loading. RESULTS: Radiographic analysis revealed very little bone loss and a slight increase in bone level for implants placed at the level of the crest or 1 mm above. The greatest bone loss occurred at implants placed 1 mm below the bone crest. No clinically significant differences regarding marginal bone loss and the level of the bone-to-implant contact were detected between implants with a submucosal or a transmucosal healing. CONCLUSIONS: Implants with non-matching implant-abutment diameters demonstrated some bone loss; however, it was a small amount. There was no clinically significant difference between submucosal and transmucosal approaches.     

Decoronation of an ankylosed tooth for preservation of alveolar bone prior to implant placement*

Abstract – A 12‐year‐old patient sustained avulsions of both permanent maxillary central incisors. Subsequently, both teeth developed replacement resorption. The left incisor was extracted alio loco. The right incisor was treated by decoronation (removal of crown and pulp, but preservation of the root substance). Comparison of both sites demonstrated complete preservation of the height and width of the alveolar bone at the decoronation site, whereas the tooth extraction site showed considerable bone loss. In addition, some vertical bone apposition was found on top of the decoronated root. Decoronation is a simple and safe surgical procedure for preservation of alveolar bone prior to implant placement. It must be considered as a treatment option for teeth affected by replacement resorption if tooth transplantation is not feasible.     

Root exposure in the primary dentition studied in human skulls

The aims of the present study were to examine, on the primary dentition of 75 human dried skulls, the distance from the cemento-enamel junction (CEJ) to the alveolar bone crest, and to evaluate its relation to developmental age, bone morphology and attrition. The measurements from the CEJ to the alveolar crest were longer for the maxillary teeth, the second molars showed the shortest measurements, while the cuspids showed the longest. Significant positive partial correlations were found between age and the distance from the CEJ to the alveolar crest when controlling for attrition (r = 0.64), and between age and attrition when controlling for the distance from the CEJ to the alveolar bone crest (r = 0.54). The partial correlation between migration and attrition when controlling for age proved to be not significant (r = 0.13). Significant correlations were found between age and the distances from the mental foramen to: the alveolar crest (r = 0.90), and to the lower border of the mandible (r = 0.97). These findings suggest that root exposure takes place in the primary dentition, as the result of continuous eruption at a faster rate than formation of alveolar bone, presumably to compensate for facial growth.     

Rotated palatal flap in immediate implant procedures. Clinical evaluation of 26 consecutive cases

Immediate implant placement after tooth extraction is a successful treatment modality. Primary flap closure is important for satisfactory final results in these procedures. The purpose of this article was to evaluate a surgical approach that would enable predictable primary soft tissue closure over implants placed into fresh extraction sockets. In 24 patients, 26 consecutive implants were placed immediately following extraction of one anterior or premolar maxillary tooth. Primary closure was achieved by a surgical technique based on a rotated palatal flap (RPF), covering the implant. Deproteinized bovine bone was used as grafting material. The apicocoronal distance between the buccal alveolar crestal bone and the coronal aspect of the implant body was measured at time of implant placement (mean 2.6 mm, SD 1.72) and at second stage surgery (mean 0.6 mm, SD 0.70). The difference between both records was calculated. The mean gain in crestal bone was 2.0 mm (SD 1.69, P < 0.001). In 1 patient, where the implant cover screw became exposed early, crestal bone loss was noted. This technique offers a predictable valuable treatment approach to achieve and maintain primary soft tissue coverage and crestal bone regeneration over implants immediately placed within a bony envelope, after extracting maxillary teeth, without the use of barrier membranes.     

Hard and soft tissue changes after crestal and subcrestal immediate implant placement

Background: The purpose of this study is to assess the influence of the placement level of implants with a laser‐microtextured collar design on the outcomes of crestal bone and soft tissue levels. In addition, we assessed the vertical and horizontal defect fill and identified factors that influenced clinical outcomes of immediate implant placement. Methods: Twenty‐four patients, each with a hopeless tooth (anterior or premolar region), were recruited to receive dental implants. Patients were randomly assigned to have the implant placed at the palatal crest or 1 mm subcrestally. Clinical parameters including the keratinized gingival (KG) width, KG thickness, horizontal defect depth (HDD), facial and interproximal marginal bone levels (MBLs), facial threads exposed, tissue–implant horizontal distance, gingival index (GI), and plaque index (PI) were assessed at baseline and 4 months after surgery. In addition, soft tissue profile measurements including the papilla index, papilla height (PH), and gingival level (GL) were assessed after crown placement at 6 and 12 months post‐surgery. Results: The overall 4‐month implant success rate was 95.8% (one implant failed). A total of 20 of 24 patients completed the study. At baseline, there were no significant differences between crestal and subcrestal groups in all clinical parameters except for the facial MBL (P = 0.035). At 4 months, the subcrestal group had significantly more tissue thickness gain (keratinized tissue) than the crestal group compared to baseline. Other clinical parameters (papilla index, PH, GL, PI, and GI) showed no significant differences between groups at any time. A facial plate thickness ≤1.5 mm and HDD ≥2 mm were strongly correlated with the facial marginal bone loss. A facial plate thickness ≤2 mm and HDD ≥3 were strongly correlated with horizontal dimensional changes. Conclusions: The use of immediate implants was a predictable surgical approach (96% survival rate), and the level of placement did not influence horizontal and vertical bone and soft tissue changes. This study suggests that a thick facial plate, small gaps, and premolar sites were more favorable for successful implant clinical outcomes in immediate implant placement.     

骨劈开技术在上颌前牙区种植术中的应用

目的：评价骨劈开术在上颌前牙区种植术中的临床应用效果。方法：42例患者,缺失上前牙1-4颗,牙槽嵴可利用骨高度〉10mm,宽度3-5mm。采用骨劈开术形成唇侧骨瓣,在腭侧骨板与唇侧骨瓣之间植入直径3.5mmAnkyl os种植体83枚,劈开部位应用GBR技术,6个月后行二期手术和固定修复。结果：二期手术时所有种植体稳固,1例（2枚种植体）唇侧骨板部分吸收,产生2.0mm种植体颈部唇侧暴露。其余种植体被骨质完全包绕,牙槽嵴宽度增加2.8-4.1 mm,平均增宽3.5mm。83枚种植体完成固定修复,经过2年的追踪观察,无一种植体松动或脱落。结论：上颌牙槽嵴骨宽度为3-5mm时,采用骨劈开术能有效增加骨量,获得满意的临床疗效。