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Purpose: The aim of this study was to investigate the prevalence and length of the anterior loop (AL), the distance from this landmark to the alveolar crest and its relation with the shape of the foramen and emergency pattern in the Spanish population on helical computed tomography scan (helical CT scan) through tridimensional reconstructions., Methods: Helical CT scan images of 41 patients aged 65 or older were analyzed. A total of 82 human hemi-mandibles were examined in this study. A tridimensional reconstruction of each mandible and Inferior Alveolar Nerve canal was created in AMIRA ® software (AMIRA, Mercury Computer Systems, Berlin, Germany). Prevalence, length and distance between the AL, mental foramen and alveolar ridge were measured. This retrospective observational study was performed according to the STROBE guidelines., Results: Prevalence of the AL was 53.7 % (n = 44) and the mean length was 1.3 ± 0.64 mm. The mean distance from the highest point of the loop to the alveolar ridge was 13.4 ± 2.8 mm. The mean diameter of the mental foramen was 3.5 ± 0.65 mm and the proportion of the oval-shaped was 62.2 % (n = 51) and round-shaped was 37.8 % (n = 31). The study found that patients with type 1 pattern emergency pattern had a higher prevalence of the AL (p = 0.03)., Conclusions: Prevalence, location and length of the anterior loop can be overlooked if only two-dimensional pre-surgical studies are performed. Therefore, three-dimensional imaging and modeling of anatomic structures should be used for the pre-operative examination of the interforaminal area. Given the wide variability of the emergency pattern of the mental nerve and the prevalence and location of the anterior loop, it should be studied in every patient individually.

The objectives of this study were to evaluate the survival after 5 years of implants placed using inferior alveolar nerve (IAN) lateralization in cases of mandibular atrophy and to determine the incidence of complications. Twenty-seven patients received 74 implants by means of the IAN lateralization technique. Implant survival after 5 years of loading was 98.6%. Eighteen months after surgery, the recovery of sensitivity was complete in 26 cases. Implant placement with IAN lateralization was seen to be a satisfactory and predictable technique. IAN lateralization requires a high level of technical skill, and strict criteria should be applied when prescribing this treatment., (Copyright © 2016 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.)

The aim of this retrospective radiological study was to evaluate the variability of the mandibular anatomy in the presence and absence of teeth and to consider how it could influence implant planning. 187 mandibular CT DentaScans were selected from our department archive according to the inclusion criteria. The axial height, vertical height, angulation of the bone crest, and the bone available for ideal implant placement were measured. The analysis of the data shows that the mandible contour presents a constant degree of angulation. The variation of angulation in the absence of teeth was statistically significant only in the region between the canine and the first premolar and in that between the second premolar and the first molar. The difference between the crest height and the available distance to place the implant was greater in the region of the second molar while in the other regions the implant planning was made complex by postextraction resorption. Alveolar bone resorption after tooth loss can be considered as a risk factor for lingual cortical perforation during the insertion of an implant. To avoid potential intra/postoperative complications, 3D radiographic examination is recommended in order to study the mandibular anatomy and identify the risk areas.

The ontogenetic development of the mental region still poses a number of unresolved questions in human growth, development and phylogeny. In our study we examine the hypotheses of DuBrul & Sicher (1954) (The Adaptive Chin. Springfield, IL: Charles) and Enlow (1990) (Facial Growth, 3rd edn. Philadelphia, PA: Saunders) to explain the presence of a prominent mental region in anatomically modern humans. In particular, we test whether the prominence of the mental region and the positioning of the teeth are both correlated with the developmental relocation of the tongue and the suprahyoid muscles inserting at the lingual side of the symphysis. Furthermore, we test whether the development of the mental region is associated with the development of the back of the vocal tract. Using geometric morphometric methods, we measured the 3D mandibular and tooth surfaces in a cross-sectional sample of 36 CT-scanned living humans, incorporating the positions of the tongue and the geniohyoid and digastric muscle insertions. The specimens' ages range from birth to the complete emergence of the deciduous dentition. We used multivariate regression and two-block partial least squares (PLS) analysis to study the covariation among the mental region, the muscle insertions, and the teeth both across and within age stages. In order to confirm our results from the 3D cross-sectional sample, and to relate them to facial growth and the position of the cervical column and the hyoid bone, we used 46 lateral radiographs of eight children from the longitudinal Denver Growth Study. The 3D analysis demonstrates that the lingual side of the lower border of the symphysis develops downwards and forwards. These shape changes are significantly correlated with the relocation of muscle insertion sites and also with the vertical reorientation of the anterior teeth prior to emergence. The 2D analysis confirms the idea that as the mental region prominence develops, the space of the laryngopharynx becomes restricted due to upper mid-face retraction and the acquisition of upright body posture. In agreement with the hypotheses of DuBrul & Sicher (1954) and Enlow (1990), our results suggest that the presence of a prominent mental region responds to the space restriction at the back of the vocal tract, and to the packaging of the tongue and suprahyoid muscles in order to preserve the functionality of the laryngopharynx during respiration, feeding and speech., (© 2012 The Authors Journal of Anatomy © 2012 Anatomical Society.)