Influence of the maxillary canine on mandibular fracture.

The length of the root of the mandibular canine tooth has been considered by many authors as being a source of weakness in the mandible. It has also been suggested that a direct blow or a bending force around this tooth can result in traumatic injury. We advance a theory that implicates the maxillary canine tooth as directly contributing to the mandibular canine region fracture pattern.     

Prosthodontic principles in surgical planning for maxillary and mandibular resection patients.

Discussion between the surgeon and prosthodontist on surgical planning is important. It is necessary that they each be aware of the other's problems. Only in this way can continuity be established between surgical and prosthetic procedures. This will provide a maximum level of treatment for the maxillofacial patients, thereby returning them to society most expeditiously.     

A new guide to mandibular resection for oral squamous cell carcinoma based on the Cawood and Howell classification of the mandible

A new guide for mandibular resection in the management of oral squamous cell carcinoma based on the Cawood and Howell classification of the jaws is suggested. This was a retrospective review of case records and pre-operative orthopantomograms (OPG), bone scintigraphy and magnetic resonance imaging (MRI). The classification of the mandible was based on the residual bone height as measured in the molar region of the OPG to be equivalent to the Cawood and Howell classification of the mandible (Class I-II dentate or immediate post-extraction), Class III-IV >20mm well-rounded or knife-edge ridge, and Class V-VI <20mm (flat or depressed ridge form). Of the 77 patients, 58% (22/38) of Class I-II, 43% (9/23) of Class III-IV and 6% (1/16) of Class V-VI were treated with a marginal (rim) resection of the mandible. The predictability of the pre-operative investigations was more accurate in the edentulous mandible (Class III-VI). A simple guide is suggested for mandibular resection taking into account the pre-operative investigations, the estimation of invasion clinically, and the Cawood and Howell classification of ridge resorption.     

Validity of the examination method of occlusal contact pattern relating to mandibular position

OBJECTIVE: This study was based on the hypothesis that conflicting findings and inconclusive consensus regarding the role of occlusal factors in the masticatory system are due to the variations in the definitions and methods used to describe and examine the occlusal factors. The object of this study was to determine whether contact patterns during lateral movement vary with mandibular positions and whether the contact pattern in lateral positions close to the maximum intercuspation has characteristics distinct from those in an edge-to-edge position. METHODS: Occlusal contacts of 86 young adults were examined using shim stock in regulated lateral positions: 0.5, 1, 2 and 3 mm from the maximum intercuspation, where the 0.5, 1 and 2 mm positions were defined as lateral positions close to the maximum intercuspation and the 3 mm position as an edge-to-edge position. RESULTS: The occlusal contact pattern in the 0.5 mm position showed a marked prevalence of posterior tooth contacts on the working and the non-working sides, compared with the 1, 2 and 3 mm positions. The occlusal contact pattern in the 3 mm position predicted the presence or absence of the occlusal contact in the 1 and 2 mm positions (sensitivity > 0.7) but not in the 0.5 mm position (sensitivity < 0.6). CONCLUSION: The occlusal contact patterns during lateral movement varied greatly with mandibular positions. The examination method of the occlusal contact pattern in one unregulated position will be invalid. It is necessary to distinguish the occlusal contact patterns between a position close to the maximum intercuspation and an edge-to-edge position when investigating its role in the masticatory system and in oral disease.     

上颌埋伏尖牙CT影像分型系统的建立和分析

目的 利用螺旋CT三维重建技术建立适合上颌埋伏尖牙的影像学分型系统。方法 选择102例上颌埋伏尖牙患者为研究对象,共121颗上颌埋伏尖牙。所有患者均接受标准的螺旋CT扫描,数据均导入MIMICS 10.01软件采用表面遮盖成像法进行三维重建。通过对121颗上颌埋伏尖牙的三维空间位置进行分析建立上颌埋伏尖牙的影像学分型系统。结果 本研究建立了一个上颌埋伏尖牙的三维CT影像学数据库。研究结果显示在X轴方向上,最常见的分型是牙尖近中伴根尖正常。在Y轴方向上,样本中所有埋伏尖牙只存在3种分型即根尖均处于高位,牙尖分别处于高、中、低位。在Z轴方向上,最常见的分型是牙尖和根尖均处于唇侧,约占总数的三分之一。结论 本研究利用螺旋CT建立了一个适合上颌埋伏尖牙的三维影像学分型系统,具有一定的临床诊断价值。     

The effects of overbite on the maxillary and mandibular morphology

The aim of this study was to investigate the differences in the maxillary and mandibular morphology related to the overbite. A total of 80 untreated subjects were divided into 4 groups with normal overbite, edge-to-edge bite, open bite, or deep bite and were compared with one another. Differences between the overbite groups and between genders were assessed by means of variance analysis and the least significant difference test. In addition, correlation coefficients between the overbite and other variables were calculated. The results showed that there are statistically significant differences in the maxillary and mandibular morphology among the overbite groups.     

The use of fresh frozen allogeneic bone for maxillary and mandibular reconstruction.

The use of fresh frozen bone (FFB) alone, or in combination with autogenous bone (AB), for bony augmentation of the maxilla and mandible in preparation for dental reconstruction with endosseous implants has been studied. Ten patients received FFB +/- AB for augmentation of a severely atrophic mandible (n = 6) or for reconstruction of a jaw defect secondary to trauma or tumor resection (n = 4). Average follow-up was 26.3 +/- 5.4 months. At the time of implant placement, the bone grafts were found to be firm in consistency, well incorporated, and well vascularized in all 10 patients. Twenty-nine endosseous implants were placed an average of 8.3 +/- 3.1 months following bone grafting. One implant failed and was replaced, and one implant remains buried as a nonfunctional unit. All patients have been restored prosthetically by means of 28 of the 29 implants. This preliminary study indicates that FFB may be used alone or in combination with autogenous bone for augmentation or reconstruction of the atrophic maxilla and mandible. The resultant ridge is adequate to support loaded endosseous implants. A potential disadvantage is the minimal risk of disease transmission.     

Determination of approximate size of maxillary anterior denture teeth when mandibular anterior teeth are present. Part III: Relationship of maxillary to mandibular central incisor widths

The average width of a natural maxillary central incisor is 8.92 mm. This value is determined from the results of three studies of natural dentitions. The average width of a mandibular central incisor is 5.5 mm. The average ratio produced by dividing the average maxillary central incisor width by the average mandibular incisor width is 1.62. The factor of 1.5 times the width of a mandibular central incisor produces a maxillary central incisor width that is too narrow. The width of a mandibular central incisor plus half the width of the mandibular lateral incisor also produces a maxillary central incisor width that is too narrow. There may be a tendency to undersize the maxillary prosthetic dentition. The ratio of 1.62 can be used to select the appropriate width for a missing maxillary central incisor when given the width of the mandibular central incisor. This ratio of 1.62 is also valuable to verify the dimension of a selected artificial maxillary central incisor when the patient complains that the tooth is too large. If substitutions or adjustments are made in the mold, the desired canine-to-canine measurement produced by the ratio range of 1.3 to 1.38 reported in Parts I and II of this study should be maintained.     

The maxillary rotation: Its relation to the cranial base and the mandibular corpus. An implant study.

A material of 22 patients with metallic implants was used in a longitudinal study, based on lateral head-plates, of the relationship between: 1) the maxillary rotation and the cranial base 2) the maxillary rotation and the different mandibular rotations. No connection has been found between the variation of the maxillary rotation and the growth of the cranial base. The correlation between the maxillary and the mandibular rotations is the highest when the rotation of the corpus is considered. A strong correlation is found between the variation of the condylar growth direction and the variation of the maxillary rotation.     

Vascularized cranial bone grafts for mandibular and maxillary reconstruction. The parietal osteofascial flap

The authors have performed 13 cases of vascularized cranial bone grafts for reconstruction of maxillofacial defects since 1986. Two types of flaps were used: the parietal osteofascial flap pedicled to the parieto-temporal fascia based on the superficial temporal artery and the temporalis osteomuscular flap pedicled to the temporalis muscle based on the deep temporal artery. Zygomatico-orbital complex, maxilla and mandible were reconstructed and hemifacial microsomia was also treated. The results of vascularized cranial bone grafts pedicled to fascia were as good as those of grafts pedicled to muscle. There were no major complications. Two types of vascularized cranial bone grafts seem to be useful in reconstruction of maxillofacial defects with avascular recipient beds because of their good blood supply. The parietal osteofascial flap has additional advantages including easy rotation of the flap to the defect, particularly a mandibular defect, and versatile use of fascia without bulkiness for reconstruction of soft tissue defects. This flap can be designed as a full- or partial-thickness cranial bone graft with good vascularity. In this paper, our technique for mandibular and maxillary reconstruction using the parietal osteofascial flap is introduced, and the results compared with our temporalis osteomuscular flap technique are reported.     

Posterior palatal seal location and preparation on the maxillary complete denture cast

A technique for the precise location and preparation of the posterior palatal seal on the master cast has been described. The technique provides a distinct landmark, which aids in finishing the posterior border of the denture and creates a posterior palatal seal that is physiologically acceptable to the patient because its depth and extent are determined by the displaceability of the tissues.     

Validation study of a new method for sexual prediction based on CBCT analysis of maxillary sinus and mandibular canal

ObjectiveThe aim of this study was to evaluate the accuracy of two craniometric methods for sexual prediction (SP) using cone-beam computed tomography (CBCT) in the Dutch population and to construct a formula for each method and then the two combined.DesignOne-hundred sixty CBCT images were selected from a Dutch database (80 males and 80 females). The images were analyzed by two examiners taking seven measurements in the maxillary sinus (MS) region (first method) and nine in the mandibular canal (MC) region (second method). The most predictive measurements in both methods were used to develop an equation to determine the accuracy of each method.ResultsAll measurements showed statistical difference between genders. Logistic regression results showed two variables with greater SP index with 75% accuracy in the first method and four variables with 71.9% accuracy in the second. The two methods combined showed another four variables with 78.5% accuracy.ConclusionAll measurements showed statistically significant differences between sexes. The SP accuracy values were 75% for first 71.9% for the second method. When the two methods were combined, the accuracy increased to 78.5%. The formulas developed in this study can be applied as a complementary method for human identification in the Dutch population.     

Eruption of the permanent maxillary canines in relation to mandibular second molar maturity

Objective:To evaluate the timing of spontaneous maxillary canine eruption in relation to stages of mandibular second molar maturation. Potential confounding effects from such factors as age, growth phase, and facial features were also explored.Subjects and Methods:A sample of 106 healthy subjects (48 females and 58 males; age range, 9.4–14.3 years) with both permanent maxillary canines during the final phase of intraoral eruption were included. Mandibular second molar maturation (stages E to H) was assessed according to the method of Demirjian. Skeletal maturity was determined using the cervical vertebral maturational (CVM) method. Facial vertical and sagittal relationships were evaluated by recording the Sella-Nasion/mandibular plane (SN/MP) angle and the ANB angle. An ordered multiple logistic regression was run to evaluate adjusted correlation of each parameter with the mandibular second molar maturational stage.Results:Overall, the prevalence of the different second molar maturational stages was 36.8%, 37.8%, and 27.4% for stages E, F and G, respectively. According to the regression model, this relation was not influenced by sex, CVM stage, SN/MP angle, and ANB angle.Conclusions:Irrespective of sex, growth phase, and facial features, the maturational stage of the mandibular second molar may be a reliable indicator for the timing of spontaneous eruption of the maxillary canine.