Dental stability and radiographic healing patterns after mandibular symphysis widening with distraction osteogenesis

Distraction osteogenesis is the biological process of new bone formation between bone segments that are gradually separated by incremental traction. The purpose of this study was to assess dental stability and radiographic healing patterns following mandibular symphysis widening with distraction osteogenesis (MSDO) in 19 non-syndromic patients (10 males, 9 females: mean age at the time of surgery 20 years 11 months). To evaluate dental stability, 13 landmarks were measured on the study models of all patients and healing patterns were classified for 11 subjects according to healing times on periapical or occlusal radiographs at three time points: pre-distraction (T1), post-distraction (T2), and follow-up (T3; average 1 year 6 months). Paired t-tests were used to evaluate the change between T2-T1, T3-T2, and T3-T1. The results of this study showed that although there was a decrease in expansion during treatment, the total amount of surgical expansion was maintained. Arch length was significantly increased and irregularity was significantly decreased (both P<0.001). There was evidence of mineralization of the distraction gap in 11 patients within 3 weeks of the end of activation. Radiographically, healing patterns for the distraction gap were diverse, but radiopacity increased over time. MSDO is dentally stable and the distracted gap is mineralized with time, indicating that MSDO is an efficient and stable treatment method in subjects with skeletal mandibular transverse deficiency.     

Solitary osteochondroma of the mandibular symphysis

Osteochondroma is a benign neoplasm that usually develops in long bones and very rarely occurs in craniofacial bones. Nearly all reported mandibular osteochondromas have arisen in the condyle and the coronoid process, and occurrence in other locations is extremely rare. We describe a case of osteochondroma arising from the inferior border of the mandibular symphysis.     

A developmental defect of the mandibular symphysis

A case in reported of coincidental abnormalities of development of both the premaxilla and anterior mandible. The defect in the mandible presented certain radiographic features frequently observed in cystic or neoplastic lesions. Histological examination revealed it to be of a developmental nature. The importance of adequate examination of tissue removed from lesions of the jaws is emphasized.     

Neurosensory disturbances following bone harvesting in the symphysis: a prospective clinical study

OBJECTIVE: To analyse the occurrence and resolution of neurosensory disturbances following bone harvesting from the symphysis. MATERIAL AND METHODS: In 30 patients, skin sensitivity of the chin/lower lip area and pulp sensitivity of all mandibular anterior teeth were assessed preoperatively, at the time of suture removal, at 6 and 12 months postoperatively. In addition, bone defect dimensions of the donor site were measured intraoperatively, and distances from defect margins to adjacent anatomical structures, such as root apices, mental foramen and inferior border of mandible, were assessed postoperatively on a panoramic radiograph. RESULTS: Pulp sensitivity changes were found in 18.6% of adjacent teeth at the time of suture removal. At the 6-month follow-up, 8.1% of teeth, and at the 12-month re-examination, 0.6% of teeth presented with altered sensitivity. This decrease over time of the number of affected teeth per patients with sensitivity changes was significant (P=2.35e-007). Lower lip hypaesthesia was only observed in one patient postoperatively, with complete resolution at the 6-month follow-up. Radiographic measurements of distances between donor defect and adjacent anatomical structures only reached significant difference for one parameter in patients with sensitivity changes compared with patients without sensitivity changes. CONCLUSIONS: Patients must be informed about possible transient and long-term sensitivity changes of adjacent teeth and soft tissues following bone harvesting from the chin. However, by correctly placing mucoperiosteal incisions and bone cuts, the risk of sensitivity changes can be minimized.     

颏与正畸美学的关系

颏是人类面部容貌特征之一,从审美角度来看,其是面下1／3的重要美学参考,鼻、唇、颏关系的和谐,是容貌美的重要标志之一。形态良好的颏部,不仅被视为容貌美的一项标志,还象征智慧与魅力,颏部过于前突或后缩,均会影响脸型的完美。故颏部在医学与美学领域都具有不可忽视的重要意义。颏部形态在正畸诊断中有何意义？正畸治疗能否改变颏部形态？怎样的颏部更符合侧貌容貌美？诸多问题尚待探讨。本文从颏部的解剖、进化、生长发育,颏部与正畸的关系及颏部的审美作一综述。     

Comparative study of two evaluation methods on radiographic bone loss at the mandibular canines and incisors

Abstract – The approximat bone loss of the mandibuLar canines and incisors was scored with two different units of measurement on 30 sets of standardized paralleling radiographs: 1) with absolute values ("true" millimeter) unrelated to casual variables and 2) with relative values (i.e. percentage of the root length). Absolute bone loss scores revealed that the space between the canines and the lateral incisors of the present material seemed to be more susceptible to bone loss than the spaces between the incisors, with a tendency towards the mesiai bone loss of the canines being still greater than the distal bone loss of the laterals. There was a high degree of correspondence between absolute bone loss scores at different teeth and corresponding gingival pocket depths of a previous analysis by the present authors. Relative bone loss scores led to divergent and partly direct-opposite results compared with the absolute scores. The correspondence between percentage bone loss scores and gingival pocket depths at corresponding tooth surfaces was poor. When investigating the susceptibility of different teeth to periodontal breakdown it seerns as if bone loss should be expressed in absolute values in the same way as are gingival pocket depths and loss of attachment. If a common standard is being used the results of different investigations may be compared. However, when studying the inception and advancement of the disease at the same tooth over a period of time, or when evaluating the remaining bone support the percentage bone loss method may be of clinical importance.     

The intraosseous course of the mandibular incisive nerve in the mandibular symphysis.

The use of the mandibular symphysis as a source of autogenous bone grafting material has been well documented. Currently, no references in the literature describe the intraosseous distribution of the neurovascular complex anterior to the mental nerve with respect to its position buccolingually and apicocoronally. The objective of this study was to evaluate the distribution of the incisive nerve and measure its location buccolingually and apicocoronally in the anterior mandible and determine its possible significance to clinical practice. According to macroscopic dissection, the mandibular incisive nerve is a normal structure that typically extends closer to the midline than previously reported. To reduce postoperative neurovascular morbidity, this should be considered when using the mandibular symphysis as a source of autogenous bone or during placement of implants in the anterior mandible.     

The prevalence and significance of anatomic variance in the mandibular symphysis: a retrospective study

As computerized tomography (CT) becomes more widespread in implant treatment planning, dentists are bound to encounter more uncharacteristic anatomical conditions in the jaws. This retrospective study examined the prevalence of one such anatomic variance on 78 CT scans of human mandibles. Irregular heterogeneous circular radiopacities with internal radiolucencies were present in a majority (97.4%) of the CT scans examined; however, the phenomenon only appeared pronounced in 28.9% of this group. Bone radiodensity was higher in the regions with the phenomenon as compared with adjacent bone without the phenomenon, which suggested no adverse indications for implant placement.     

Relationship between the apices of the lower molars and mandibular canal--a radiographic study

The study was performed on forty-six randomly chosen dry mandibles. The molar areas of each mandible were radiographed by the paralleling technique, and an additional radiograph at -20 degrees angulation of the same area was taken. Measurements of the distance between the upper border of the mandibular canal and the root apices of the first and second molars were taken. The location of the mandibular canal in the buccolingual plane was determined. The obtained data were statistically evaluated. Statistically significant symmetry of the relationship of the mandibular canal to the root apices was established between the right and left sides of the same mandible. In the majority of cases the mandibular canal was buccal to the apices of the second molar, and in the first molar area the canal was lingual to the root apices in almost half of the cases. Most frequently, the upper border of the mandibular canal was located 3.5 to 5.4 mm below the root apices of both first and second molars. In no case was the mandibular canal found in close proximity, both in the vertical and in the buccolingual planes, to the first and second molar apices.     

下颌骨颏部正中骨折二维与三维坚强内固定的三维有限元研究

目的:用有限元法分析比较下颌骨颏部正中骨折小型钛板二维与三维坚强内固定的稳定性。方法:用ANSYS软件建立下颌骨颏部正中骨折坚强内固定模型,比较使用不同钛板数目、不同空间位置进行坚强内固定时各种工况下骨折段位移、骨折断层及接骨板固定钉的应力分布情况。结果:各种固定方法在各种功能咬合工况下,骨断端位移均小于0.15 mm,三维固定时骨折断端的位移均小于二维固定。各种固定时骨折断层和接骨板固定钉的应力分布均在允许值范围内。结论:下颌骨下缘下方骨面钛板加唇颊面钛板的三维固定方法在多数工况下优于传统二维内固定方式。     

Developmental significance of delayed closure of the mandibular symphysis.

The unique finding of a midline suture at the mandibular symphysis in cleidocranial dysplasia is presented and discussed in regard to its relation to facial skeletal development.     

A preliminary radiographic study of mandibular para-radicular third molar radiolucencies

OBJECTIVES: To determine the frequency and describe a poorly documented radiographically observed variation of normal associated with the roots of mandibular third molars--the mandibular third molar para-radicular radiolucency (MPR). STUDY DESIGN: A systematic random sample of 822 dental school surgery and emergency charts was reviewed for radiographic evidence of the MPR. The frequency was determined and the variation in radiographic appearance was described. Clinical signs and symptoms were correlated with the presence of an MPR. RESULTS: The frequency of the MPR was 7.8% with a female-to-male ratio of 2.6:1.0. Of 6 bilateral cases (9.4%) all occurred in female patients. The most common location was the distal surface of the mandibular third molar. Most (58.6%) were oval in shape. CONCLUSION: This radiographic finding most likely represents a variation of normal anatomy and based on this retrospective study does not appear to require treatment.     

Reconstruction of maxillary alveolar defects with mandibular symphysis grafts for dental implants: a preliminary procedural report.

Partially edentulous patients with alveolar defects contraindicating implant placement were treated with bone grafts obtained from the mandibular symphysis. Complications encountered were minor and uneventful. Evaluation 4 months after surgery revealed minimal graft resorption, thus implant placement was possible in all potential sites. Advantages of the symphysis graft include easy access, availability of greater quantities of bone over other intraoral donor sites, low morbidity, no hospitalization, minimal discomfort, no alteration in ambulation, and no cutaneous scar. Compared with other bone regenerative methods for implant placement, a superior quality of bone was found and a shorter healing period is required. Results of this preliminary clinical investigation demonstrate that chin grafts offer a viable alternative for reconstruction of alveolar defects prior to dental implant placement.