Background
To elucidate the anatomical features of the mandibular molar region to allow safe immediate implant placement.
Methods
Cone-beam computed tomography images of 150 patients (600 teeth) were reviewed retrospectively. The virtual implants were placed in the mandibular first and second molar region. The anatomic structures of the mandible and inter-radicular septum were both categorized into three types. The relationship between implant and inferior alveolar nerve (IAN), and the horizontal distance from the implant surface to the bone wall were analyzed. Variables were compared using a student’s t-test, or Mann–Whitney U test.
Results
Type U (39.0%) and type S (56.0%) were the most common in the first molar, while type U (67.7%) and type M (54.7%) had the highest prevalence rate in the second molar. The mean distance from the level where the virtual implant was completely surrounded by bone to IAN was 7.06 mm. The mean horizontal widths from the implant to the mesial and distal socket wall were 1.59 mm and 1.89 mm. The widths of the inter-radicular septum and the distances from implant to the buccal and lingual plate on different sections were significantly associated with tooth position (P < .05).
Conclusions
In the first molar region, the implant is suggested to be placed in the center of the inter-radicular septum, while in the second molar region, the mesial root socket could be considered. Immediate implant placement in the mandibular second molar sockets shows a high risk of IAN injury, lingual perforation, and inadequate primary stability.
The primary prerequisite for successful dental implant treatment is osseointegration, in which the primary stability of the implant is essential (Szmukler-Moncler et al., 2000). The primary stability can be evaluated by using the insertion torque value (ITV), periotest value (PT), and resonance frequency analysis (RFA). In clinical scenarios, ITV and RFA are both commonly used methods. The ITV is the maximum torque generated during implantation. A high ITV can be deemed as one of the prerequisites for a satisfying immediate loading procedure (Esposito et al., 2009), and a value of 32 N•cm for a single implant can be considered for immediate loading (Ottoni et al., 2005). RFA is
Ceramic stereolithography (SLA) was used to fabricate a ceramic. A ceramic 3D printer based on the SLA method was manufactured. In order to systematically and effectively evaluate the role of the parameters in the ceramic green body, the orthogonal test method is introduced. The placement position of the parts, the laser repetition frequency, and scanning speed are used as independent variables to be studied. The final result shows that when laser power is set, the relationship between the hardness of the part and the position of the part is not evident. The speed of laser scanning greatly influences the mechanical properties of the parts. Alumina parts with smooth surface and dense microstructure were obtained after debinding and sintering processes.
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