Labial endodontic access opening for mandibular incisors: endodontic and restorative considerations

A labial access opening is suggested for endodontic treatment of mandibular incisors. This approach facilitates the identification and instrumentation of two canals, if present, and enhances achievement of complete obturation. More coronal tooth structure is preserved, enabling an optimum dowel core design for bracing the root.     

不同开髓方法对下颌恒切牙根管预备的影响

目的研究下颌切牙采用唇侧和舌侧开髓方法进行根管预备后管壁清洁度的差异。方法 18对离体下颌切牙随机分为A、B两组,每组中每对牙齿1颗采用唇侧开髓,另1颗采用舌侧开髓。A组用镍钛器械进行根管预备,B组用不锈钢器械进行根管预备,在扫描电镜下观察比较管壁清洁度。结果①各组的管壁清洁度均为根冠1/3>根中1/3>根尖1/3;②在根冠1/3段,各组间清洁度均无显著性差异(P>0.05)。③在根中1/3段,B组采用舌侧开髓法的管壁清洁度最差(P<0.05),其它各组间无显著性差异(P>0.05);④在根尖1/3段,A组管壁清洁度优于B组(P<0.05),B组中舌侧开髓法的预备效果最差(P<0.05)。结论下颌切牙采用唇侧开髓法有助于提高根管预备的效果,结合镍钛器械可取得最佳的根管预备效果。     

下颌恒切牙采用不同开髓方法进行根管探查的体外研究

目的:评价唇侧开髓法和舌侧开髓法对下颌切牙双根管发现率的影响。方法:82个离体下颌切牙先后采用舌侧开髓(A组)和唇侧开髓(B组)两种方式进行根管探查并记录根管数目。然后将所有牙齿横断,在体视显微镜下观察根管数目和根尖孔数目(C组)并与A、B两组进行比较。结果:①下颌切牙双根管率为30.49%;②同一医师采用同种方法进行下颌切牙根管探查的结果相对稳定(P>0.05);③同一医师采用不同的开髓方法进行下颌切牙根管探查的结果不同,唇侧开髓法的双根管发现率和可靠性都较高(P<0.05)。结论:下颌切牙双根管率为30.49%,双根管分叉的部位多位于根管中下段。采用唇侧开髓法双根管的发现率高,且其探查双根管的可靠性高于传统舌侧开髓法。     

不同开髓方向对探查下领切牙双根管的影响

目的：观察不同开髓方向对探查下切牙双根管的影响。方法：选取150颗临床拔除的下颌切牙，随机分为两组，一组进行传统舌侧开髓不损伤切缘；另一组按照近远中垂直向X光片根管影所划直线进行开髓，不考虑对切缘的影响。结果：传统方法发现1．33％双根管；另一组发现12．0％双根管。结论：传统方法进行开髓遗漏了大部分舌侧根管，临床应改进这一传统方法。     

Fracture behavior of human mandibular incisors following endodontic treatment and porcelain veneer restoration

PURPOSE: Because of existing controversy, the present study investigated the individual and combined effects of endodontic treatment and porcelain veneer restoration on the fracture behavior of human mandibular incisors. MATERIALS AND METHODS: Forty extracted intact human mandibular incisors were assigned to four groups of ten with a similar range of labiolingual widths at the cementoenamel junctions. Group A consisted of intact teeth; group B consisted of endodontically treated teeth; group C teeth were restored with labial porcelain veneers; and those of group D were endodontically treated and had labial porcelain veneers. All teeth were subjected to a slow continuous loading test at 30 degrees to the long axis of the teeth and 1 mm below the incisal edge on the labial side. RESULTS: Fracture forces were 415 +/- 220 N, 370 +/- 89 N, 420 +/- 128 N, and 448 +/- 156 N for groups A, B, C, and D, respectively. Root fracture was the most common mode of failure. There were no statistically significant differences between the groups in terms of fracture forces and modes of failure. CONCLUSION: Human mandibular incisors with endodontic treatment and/or porcelain veneer restorations were able to withstand the same magnitude of oblique loading as intact teeth. Endodontic treatment and/or porcelain veneer restoration did not affect the mode of failure of mandibular incisors.     

The effect of mesio-distal chamber dimension on access preparation in mandibular incisors

Because the pulp chamber of a young mandibular incisor flares coronally in a mesio-distal dimension, the access form pictured by a number of authors is triangular in shape. As a person ages, the chamber recedes and the access shape becomes oval in form consistent with a canal system that is primarily bucco-lingual in orientation. Endodontic literature generally recommends either the triangular or oval access shape without acknowledging that both are appropriate at a given time in the life of the individual. The question addressed by this study is when does the pulp chamber loose its coronal flare to become primarily oval in shape, and as a consequence of this change, when should the access form go from triangular to oval. It was concluded that by the age of 40 the canal has decreased in size sufficiently to justify in routine cases an oval preparation of less than 2 mm mesio-distal width.     

Root canal morphology of mandibular incisors.

In this study, 100 mandibular central and lateral incisors were used to determine the number of root canals and their types, the ramifications of the root canal, the location of apical foramina, and the frequency of apical deltas. The teeth were immersed in India ink, decalcified, and cleared. The examination of root canal systems of the teeth was based on Vertucci's classification. Two more root canal types which are not defined in that classification have also been determined and grouped as new types.     

Avoiding perforation during endodontic access.

Planning for endodontic access should be as precise as possible and the dentist should consider several factors in his preoperative evaluation of teeth to avoid perforations. Anatomical characteristics of teeth can be helpful in establishing endodontic access, and valid and invalid points for orientation have been discussed. Seven suggestions have been offered for the establishment of access on difficult teeth. The ideal in establishing endodontic access can only be achieved by the deliberate, conscious application of a thorough knowledge of dental anatomy, and of possible variations from the norm, coupled with a thorough preoperative examination of the tooth. Although a casual approach may not be unsuccessful, precision will certainly yield a higher percentage of successful cases.     

Intracoronal bleaching of nonvital discolored mandibular incisors.

Intracoronal bleaching of pulpless discolored mandibular incisors is a valuable treatment modality currently disregarded by many clinicians because of the potentially disastrous consequence of cervical resorption. A patient-administered, intracoronal carbamide peroxide bleaching technique is described. This modified, walking bleaching method minimizes the risks because treatment time is reduced to days, as opposed to weeks with the original walking bleaching protocol, the concentration of the hydrogen peroxide is markedly reduced, and residual hydrogen peroxide is completely eliminated with the use of catalase prior to the definitive restoration.     

Delayed endodontic and prosthetic treatment of two traumatized incisors.

This case report describes the delayed endodontic and prosthetic treatment of two maxillary central incisors in a 16-year-old patient. Both teeth had been traumatized eight years previously. The examination revealed arrested root formation with wide open apices, periapical inflammation and inflammatory resorption. Endodontic treatment with calcium hydroxide led to formation of hard tissue barriers in both teeth so that definite obturation could be performed. One tooth was lost due to a deep crown-root-fracture and replaced by an intraosseous implant, whereas the other incisor was retained for nearly four years.     

Congenitally missing mandibular incisors and mandibular symphysis morphology

OBJECTIVE: To explore the association between congenital absence of permanent mandibular incisors and craniofacial and mandibular symphysis morphology in Japanese orthodontic patients. MATERIALS AND METHODS: A total of 27 girls with one or two congenitally absent mandibular incisors (group M) were selected and divided into group 1M (16 girls with the absence of one incisor) and group 2M (11 girls with the absence of two incisors). In addition, 20 other Japanese girls without hypodontia and with little or no mandibular incisor crowding were enrolled as a control (group C). Using the lateral cephalogram of each subject, 17 angular, 8 linear, and 3 area measurements were made for evaluation of craniofacial and mandibular symphysis morphology. The cephalometric data thus obtained were statistically analyzed and compared between the groups. RESULTS: A significantly greater retroclination of the retained mandibular incisors was found in group 1M than in group C. Groups 1M and M showed a significantly greater retroclination of mandibular alveolar bone than group C. Groups 2M and M exhibited a significantly smaller mandibular symphysis area than group C. CONCLUSION: The retroclination of the mandibular incisors and alveolar bone and the reduced mandibular alveolar bone area should be taken into consideration in planning orthodontic treatment on patients with congenitally missing permanent mandibular incisors.