Incidence of the middle mesial canals in mandibular permanent molars in a Romanian population by cone-beam computed tomography.

INTRODUCTION: Untreated middle mesial canals (MMCs) of mandibular permanent molars can result in endodontic treatment failure. AIM: The aim of this retrospective study was to investigate the incidence of MMC of mandibular molars in a Romanian population. PATIENTS, MATERIALS AND METHODS: In total, there were evaluated 144 mandibular first permanent molars and 140 mandibular second permanent molars by using cone-beam computed tomography (CBCT) scans. RESULTS: The MMC was identified in 5.67% of mandibular first permanent molars, respectively in 4.28% of mandibular second permanent molars. The male∕female ratio of MMC presence was 1:3 of mandibular first molars and inverted for mandibular second molars (5:1). The presence of MMC in mandibular first molars was associated in all cases of our study with a second distal canal, unlike the mandibular second molars where no second distal canal was associated with a MMC. CONCLUSIONS: In Romanian population, the MMC of mandibular first molars, when present, is commonly associated with a second distal canal, unlike the mandibular second molars where the occurrence of a MMC was associated with only one distal canal. When performing the preoperative evaluation, it has also to be considered the patient gender, since the male∕female ratio of MMC was 1:3 in mandibular first molars and 5:1 in mandibular second molars.

Middle mesial canal of the permanent mandibular first molars: an anatomical challenge directly related to the outcome of endodontic treatment.

To effectively clean and shape the mandibular permanent first molars it is mandatory to understand in detail their complex internal anatomy. The middle mesial canal is an additional canal located between the usual mesiobuccal and mesiolingual canals in the mesial root of mandibular first molars. The incidence of the middle mesial canal, its relationship with main canals of the mesial root and the possibility for it to be negotiated is an important practical issue in endodontics. To identify the presence of this canal is mandatory. Accordingly, a modified endodontic access, the use of the operating microscope and periapical radiographs in two different horizontal projections are indicated to enhance the long-term favorable outcome of the endodontic treatment.

Occurrence of invasive cervical resorption after the completion of orthodontic treatment.

The invasive cervical resorption (ICR) is an irreversible and progressive loss of tooth hard tissues involving coronal and root dentine that usually affects single permanent teeth. The aim of this study was to present the pattern of ICR lesions detected in three patients with no contributory medical and dental anamnesis, at different time periods after orthodontic tooth movements. Conventional radiographs and cone-beam computed tomography (CBCT) images were obtained by X-Mind™ (Satelec), respective 3D Accuitomo (Morita). The present clinical study confirmed that orthodontic forces might be a key factor for generating an ICR and the risk of lesion occurrence is increased in long movements of the teeth because the orthodontic forces act continuously an extended time. However, it should not be overlooked the synergistic effect of additional factors such as traumatic injuries, periodontal inflammation, clenching, and grinding. The more advanced ICR lesions found in our study, described as Heithersay Class 3 and Class 4, appeared on conventional radiographs as irregular, diffuse, mottled radiolucencies extended both to the crown and deeply into the tooth root. CBCT proved to have a superior accuracy in detection and assessing the severity of ICR, since the conventional intraoral radiographs cannot afford an early and proper identification of the resorptive defect. Moreover, the CBCT image allows an accurate inspection of all surfaces of tooth due to the slices in sagittal, axial and coronal planes, and to avoid erroneous diagnostic conclusions. Currently, due to CBCT scan, the nature and extension of ICR lesion into the tooth structures can be exactly evaluated.

An optical investigation of dentinal discoloration due to commonly endodontic sealers, using the transmitted light polarizing microscopy and spectrophotometry.

The aim of this study was to establish the degree of tooth crown staining by commonly used endodontic sealers. Crown discolorations by tooth canal sealers [AH Plus (Dentsply DeTrey Gmbh, Konstanz, Germany); Endofill (Produits Dentaires SA, Vevey, Switzerland); Apexit (Dentsply DeTrey Gmbh, Konstanz, Germany); and MTA Fillapex (Angelus, Londrina, Brazil)] were tested on extracted human premolars. The samples were divided into five groups of five samples each, after root canal sealing. Five teeth were used as control groups. The spectrophotometric method was performed in order to quantify in terms of color change of the coronal part (it was also recorded a track on how the color changes over time). For the microscopic study of the extracted dental specimens subjected to this study, polarized transmitted light microscopy was used. This method involves the development of special microscopic preparations, called "thin sections". In our case, the thin section was performed on 20 prepared and obturated recently extracted teeth. The degree of discoloration was determined after one week and three months using spectrophotometry and polarized light microscopy. All sealers usually cause some degree of discoloration on the cervical aspect of the crowns that increases in time. AH Plus and Endofill caused the greatest discoloration, followed by Apexit and MTA Fillapex.

Endodontic treatment of a mandibular canine with two roots.

Lower canine is a tooth with a robust, long root and very good implantation, making it a valuable abutment tooth for any type of prosthetic treatment. In order to treat it conservatively and to prevent its loss from the dental arch it is necessary to accomplish a correct and complete endodontic treatment, which involves knowledge of all its morphological variation. The mandibular canine usually presents one root with a single large canal centrally located. The possible anatomical variations are the existence of a single root with two canals and of two different roots, each having a canal. The incidence of lower canines with two roots is usually low, as described in various studies, but their presence in everyday practice shows that the clinician must consider them if he wants to prevent dental endodontic treatment failure. This article presents a relatively rare case of a patient whose right mandibular canine has two roots and two canals. Although the frequency of mandibular canines with two roots is very low, we must not forget that we can deal with such cases, which can obviously occur even in patients in our country, as the ones described in foreign specialty literature.