Feasibility of mini-implant insertion between mesial and distal buccal roots of a maxillary first molar: A cone-beam computed tomography imaging study.

INTRODUCTION: Mini-implant insertion in the maxillary posterior region can be influenced by anatomic limitations, thus increasing the failure rate. We explored the feasibility of a new implantation site: the region between the mesial and distal buccal roots of the maxillary first molar. METHODS: Cone-beam computed tomography data from 177 patients were collected from a database. The maxillary first molars were morphologically classified by analyzing the angle and morphology of the mesial and distal buccal roots. Next, 77 subjects were randomly selected from the 177 patients to measure and analyze the hard-tissue morphology in the maxillary posterior region. RESULTS: We devised the Morphological Classification on the Mesial and Distal Buccal Roots of Maxillary First Molar (MCBRMM), divided into 3 types: MCBRMM-I, II, and III. In all subjects, MCBRMM-I, II, and III accounted for 43%, 25%, and 32%, respectively. At 8 mm from the mesial cementoenamel junction of maxillary first molars, the interradicular distance between the maxillary first molar's mesiodistal buccal roots of MCBRMM-I was 2.6 mm, showing an upward trend from the cementoenamel junction to the apex. The distance from the buccal bone cortex to the palatal root was >9 mm. The buccal cortical thickness was >1 mm. CONCLUSIONS: This study provided a potential site for mini-implant insertion in the maxillary posterior region: the alveolar bone of maxillary first molars in MCBRMM-I.

Investigation of periodontal status and bacterial composition aroundmini-implants.

INTRODUCTION: Mini-implants are now widely used in orthodontic treatment. Soft-tissue inflammation around the mini-implant is an important factor affecting its stability. This study aimed to investigate the periodontal status and the bacterial composition around mini-implants. METHODS: A total of 79 mini-implants in 40 patients (aged 18-45 years) were evaluated in this study. The mini-implant probing depth (mPD), mini-implant gingival sulcus bleeding index (mBI), mini-implant plaque index (mPLI), and the composition of the supragingival and subgingival plaque around the mini-implants were recorded. After Congo red staining, the bacteria were classified and counted under a light microscope. RESULTS: The mPLI and mBI around mini-implants in the infrazygomatic crest were higher than those in the buccal shelf and interradicular area. The mPD was higher on the coronal site of the mini-implant than on the mesial, distal, and apical sites in the infrazygomatic crest. The mPLI around the mini-implant was positively correlated with the mBI, and the mBI was positively correlated with the mPD. The supragingival and subgingival bacterial composition around the mini-implants was similar to that of natural teeth. Compared with supragingival bacterial composition, the subgingival bacteria of mini-implants had a significantly lower proportion of cocci and a higher proportion of bacilli and spirochetes. CONCLUSIONS: The bacteria composition of the plaque and the location are important factors in the inflammation around mini-implants. Similar to natural teeth, mini-implants require health maintenance to prevent inflammation of the surrounding soft tissue and maintain stability.

Success rate of fractured teeth receiving modified crown lengthening surgery and restorations.

BACKGROUND: Whether to preserve a structurally compromised tooth or remove it is a dilemma often encountered by clinicians. The aim of this study was to assess the long-term success rate of fractured teeth preserved by modified crown lengthening surgery and restorations. METHODS: Thirty-nine patients with a total of 45 fractured teeth who had received modified crown lengthening surgery were recruited and examined. Numbers of teeth lost were recorded, and the criteria for successful teeth were defined. Kaplan-Meier estimator was used to determine the success rate. Possible risk factors were compared between successful and unsuccessful groups by a Cox regression analysis to explore the potential predictors of failure with a significant level at α = 0.05. RESULTS: The mean ± SD of success time without considering variants was 6.2 ± 0.6 years (95% CI 5.1-7.7). The mean survival rates ± SD at 1.0-, 2.0-, 3.0-, 5.0-, 7.0-, and 9.0-year intervals was 97.8 ± 2.2%, 92.2 ± 4.4%, 72.8 ± 7.9%, 68.2 ± 8.6%, 60.7 ± 10.5%, and 40.4 ± 13.6%, respectively. Failure cases in teeth with poor plaque control and step-shaped fracture margin were significantly more than those with good plaque control and knife-shaped fracture margin (HR = 7.237, p = 0.011; HR = 15.399, p = 0.006; respectively). CONCLUSIONS: Fractured teeth treated with modified crown lengthening surgery are anticipated to have a high clinical success rate for 6.2 ± 0.6 years. Plaque control and fracture morphology appeared to be significantly associated with the success of the multidisciplinary treatment approach.

[Different multidisciplinary approaches of two traumatic teeth fractures in the esthetic zone: a case report].

In this article, different methods to deal with teeth fractures were discussed by presenting a case of traumatic crown-root fracture in the anterior esthetic zone. The traumatic crown-root fracture is a common problem in clinic. When a fracture line locates in close proximity to or below the alveolar bone crest, the fracture most likely involve the junctional epithelium and the connective tissue attachment. This type of fracture becomes a challenge for restorative dentists because it involves biologic, functional, and esthetic considerations, especially when the fracture occurs in an esthetic area. In this case, a young patient presented with two fractured upper anterior teeth to the Department of Periodontics, Peking University School and Hospital of Stomatology. After the comprehensive clinical evaluation, the right central incisor was decided to extract for implant therapy and the right lateral incisor was decided to retain by one modified crown lengthening surgery. The most common technique applied to save a retained root is a clinical crown lengthening procedure. However, the aggressive alveolar bone resection of both target and adjacent teeth to reestablish the bone width and periodontal health may compromise functional and esthetic outcomes. To reduce loss of excessive osseous tissue during osteotomy procedure, the modified crown lengthening of the right lateral incisor was performed, including minor bone resection and root reshaping. Regarding the right central incisor, the retained root was all located below the alveolar bone crest. The extraction and implant procedure, combined with guided bone graft were performed to avoid the damage to neighbor teeth during traditional restorative therapy and to reshape a preferable buccal contour. At the last visit, the patient was recalled with healthy periodontium, normal tooth function and favorable esthetic results.