Familial cases of missing mandibular incisor: three case presentations

Hypodontia is the congenital absence of one or more teeth because of agenesis. The most commonly missing teeth are the third molars, the maxillary lateral incisors and the second premolars. Cases are presented of three patients with a missing mandibular incisor

Orthognathic surgery in the University of Malaya

This is the first review on orthognathic surgery in Malaysia. The records of a total of 84 patients seen between 1977 and 1999 in the Department of Oral and Maxillofacial Surgery of the Faculty of Dentistry, University of Malaya were analysed. Skeletal III deformity formed 85 of the sample with a female dominance of 2 to 1. The patients' age ranged from 17 to 36 years, with a mean of 25.3 years. The common surgical techniques used were combined bilateral sagittal split and Le Fort I osteotomy. The predominant ethnic group was Chinese (n=58, 69); followed by Malay (n=14, 17) and Indian (n=12, 14)

Is there a "safety zone" in the mandibular premolar region where damage to the mental nerve can be avoided if periapical extrusion occurs?

The mandibular premolars are located close to the mental foramina (Fig. 1). As such, various events affecting these teeth, such as odontogenic infection1 and orthodontic, endodontic, periodontal or surgical misadventure, may result in neurosensory disturbance of the mental nerves.2-4 In one retrospective study, the incidence of mental paresthesia resulting from periapical infection or pathology was 0.96. In another 0.24 of cases in the same study, mental paresthesia was a complication of root canal treatment (caused by severe overfill in one case and iatrogenic perforation of mechanical instrumentation through the root and into the mental nerve in the second case).1 The incidence of mental paresthesia resulting from orthodontic, periodontal and surgical misadventure cannot be determined but is presumably low, as most such cases have been reported as individual case reports. In endodontology, elimination of infection from the pulp and dentin followed by adequate intracanal preparation and proper sealing constitute the basic principles of root canal treatment. Ideally, mechanical preparation and filling should be limited to the root canal, as overinstrumentation or extrusion of chemical fillings beyond the apical foramen to the adjacent nerve may give rise to neurosensory disturbances such as anesthesia, paresthesia or dysesthesia.5 Unfortunately, cases of endodontic extrusion of various filling or irrigation agents continue to be reported, despite recent advances in endodontology

Decompression of inferior alveolar nerve: case report comment

Paresthesia as a result of mechanical trauma is one of the most frequent sensory disturbances of the inferior alveolar nerve. This case report describes surgical treatment for paresthesia caused by a compressive phenomenon within the mandibular canal. The cause of the compression, a broken instrument left in the patient's mouth during previous endodontic therapy, was identified during routine radiography and computed tomography. Once the foreign object was removed by surgery, the paresthesia resolved quickly. This case highlights the potential for an iatrogenic mechanical cause of paresthesia. Comment : The article by Marques and Gomes (J Can Dent Assoc 2011;77:b34) caught my attention. For your information, there is almost an almost similar case reported recently, but with dysesthesia.1 It is fortunate that the patient in the current case has less severe symptoms (occasional numbness of her left lip and a small part of her chin, and a tingling sensation in the vestibular gingival). What I can deduce from the radiographs shown is that the file was actually lodged onto the wall of the periapical defect and the mandibular canal, and because of this the inferior alveolar nerve (IAN) was spared direct injury. Ikeda et al.2 had shown that there is room between the IAN and the canal. However, as reported by the Marques and Gomes, her symptoms were more aggravated in the morning and during stressful situations. This may be a result of fluid accumulation in the morning, or during any sympathetic (stressful) event, that may result in vasodilatation, and hence compression within the narrow mandibular canal that usually average 3.4 + 0.5 mm in diameter. 2,3 I hope this opinion is of help. Thank you

Making your own retrograde carrier

One of the problems faced by manufacturers is the difficulty in constructing a robust and reliable, angled applicator tip. This can be overcome by handmaking your own retrograde carrier. The applicator tip may be bent to about 50 degrees and, if a kink occurs while bending the tip, it can be replaced easily by a new modified needle. Because the wire used is flexible, it can adapt to the bend without a problem. Narrower carriers can also be made using a 20-G needle, perhaps more suitable for retrograde fillings of molar apices. Because the carrier is designed to be used once only, the problems of it being difficult to load and liable to blockages should not arise

A temperature overshoot on a catalyst pellet

An unexpected temperature overshoot was found for a Pd on alumina catalyst pellet in its course towards a new steady state, after a change in concentration of one of the reactants. The reaction mixture consisted of ethylene, hydrogen and nitrogen as inert. A speculative model is introduced, which can explain these overshoots by a slow adsorption of one of the reactants on the active sites of the catalyst

Material characterization at high strain by adapted tensile tests

The strength of materials at high strain levels has\ud been determined using the so-called Continuous-Bendingunder-\ud Tension (CBT) test. This is a modified tensile test\ud where the specimen is subjected to repetitive bending at the\ud same time. This test enables to create high levels of uniform\ud strain. A wide variety of materials has been tested this way.\ud The strength of the material after CBT testing has been\ud measured in different ways: by secondary tensile tests, by\ud interrupted CBT tests, and directly from the fracture in the\ud CBT test. All methods yield similar results: the strength is\ud largely unaffected by the cyclic pre-deformation and mainly\ud depends on the overall increase in length. Only for multiphase\ud materials the strength shows a minor influence of\ud CBT test conditions. The hardening follows the extrapolated\ud hardening observed in a conventional tensile test, except for\ud brass. This test method can potentially be used for measuring\ud hardening curves at high strain levels

Contact effects in bending affecting stress and formability

If a strip is pulled over a curved tool there is a contact stress acting on the strip. This contact stress changes the stress state in the material, which is analysed with a simple model. One effect is that the yield stress in tension is reduced. Predictions by the model agree with observation from a 90-degree bending test found in literature, and indirectly with observation from a stretch-bend test also found in literature. Another effect is that a change in stress state also affects the formability. This is analyzed by applying the maximum force condition on this situation. The predictions agree with a more thorough analysis of the effect of thickness stress in general, but the predictions of both methods are lower than actually observed in tests. There may be other mechanisms at work, and one candidate is presented