Bone dimensions in the posterior mandible: a retrospective radiographic study using cone beam computed tomography. Part 1--analysis of dentate sites

This retrospective radiographic study analyzed the dimensions of the alveolar bone in the posterior dentate mandible based on cone beam computed tomography (CBCT) images. A total of 56 CBCT images met the inclusion criteria, resulting in a sample size of 122 cross sections showing posterior mandibular teeth (premolars and molars). The thickness of the buccal and lingual bone walls was measured at two locations: 4 mm apical to the cementoenamel junction (measurement point 1, MP1) and at the middle of the root (measurement point 2, MP2). Further, alveolar bone width was assessed at the level of the most coronal buccal bone detectable (alveolar bone width 1, BW1) and at the superior border of the mandibular canal (alveolar bone width 2, BW2). The vertical distance between the two as well as the presence of a lingual undercut were also analyzed. There was a steady increase in buccal bone wall thickness from the first premolar to the second molar at both MP1 and MP2. BW1 at the level of the premolars was significantly thinner than that for molars. Alveolar bone height was constant for all teeth examined. For the selection of an appropriate postextraction treatment approach, analysis of the alveolar bone dimensions at the tooth to be extracted by means of CBCT can offer valuable information concerning bone volume and morphology at the future implant site.

The Semantics and Typology of Yes/No Particles (A Cross-Linguistic Study)

Taking the three basic systems of Yes/No particles the group looked at the relative deep and surface structures, and asked what types of systems are present in the Georgian, Polish and Armenian languages. The choice of languages was of particular interest as the Caucasian and Indo-European languages usually have different question-answering systems, but Georgian (Caucasian) and Polish (Indo-European) in fact share the same system. The Armenian language is Indo-European, but the country is situated in the southern Caucasus, on Georgia's southern border, making it worth analysing Armenian in comparison with Georgian (from the point of view of language interference) and with Polish (as two relative languages). The group identified two different deep structures, tracing the occurrence of these in different languages, and showed that one is more natural in the majority of languages. They found no correspondence between relative languages and their question-answer systems and demonstrated that languages in the same typological class may show different systems, as with Georgian and the North Caucasian languages. It became clear that Georgian, Armenian and Polish all have an agree/disagree question-answering system defined by the same deep structure. From this they conclude that the lingual mentalities of Georgians, Armenians and Poles are more oriented to the communicative act. At the same time the Yes/No system, in which a positive particle stands for a positive answer and a negative particle for a negative answer, also functions in these languages, indicating that the second deep structure identified also functions alongside the first.

Regional structural characteristics of bovine periodontal ligament samples and their suitability for biomechanical tests

Mechanical testing of the periodontal ligament requires a practical experimental model. Bovine teeth are advantageous in terms of size and availability, but information is lacking as to the anatomy and histology of their periodontium. The aim of this study, therefore, was to characterize the anatomy and histology of the attachment apparatus in fully erupted bovine mandibular first molars. A total of 13 teeth were processed for the production of undecalcified ground sections and decalcified semi-thin sections, for NaOH maceration, and for polarized light microscopy. Histomorphometric measurements relevant to the mechanical behavior of the periodontal ligament included width, number, size and area fraction of blood vessels and fractal analysis of the two hard-soft tissue interfaces. The histological and histomorphometric analyses were performed at four different root depths and at six circumferential locations around the distal and mesial roots. The variety of techniques applied provided a comprehensive view of the tissue architecture of the bovine periodontal ligament. Marked regional variations were observed in width, surface geometry of the two bordering hard tissues (cementum and alveolar bone), structural organization of the principal periodontal ligament connective tissue fibers, size, number and numerical density of blood vessels in the periodontal ligament. No predictable pattern was observed, except for a statistically significant increase in the area fraction of blood vessels from apical to coronal. The periodontal ligament width was up to three times wider in bovine teeth than in human teeth. The fractal analyses were in agreement with the histological observations showing frequent signs of remodeling activity in the alveolar bone - a finding which may be related to the magnitude and direction of occlusal forces in ruminants. Although samples from the apical root portion are not suitable for biomechanical testing, all other levels in the buccal and lingual aspects of the mesial and distal roots may be considered. The bucco-mesial aspect of the distal root appears to be the most suitable location.

Anterior Stafne's bone cavity mimicking a periapical lesion of endodontic origin: report of two cases

INTRODUCTION: This report of 2 cases describes the diagnostic procedures used to identify 2 Stafne's bone cavities (SBC) found in unusually anterior locations in the mandible, both mimicking periapical lesions of endodontic origin. METHODS: In the first patient, a 47-year-old man, an SBC was diagnosed in the area of teeth #27, 28, and 29. In the second patient, a 62-year-old man, the SBC was a fortuitous finding, because this patient was referred for dental implant therapy. RESULTS: In both cases, the final diagnosis was achieved by using limited cone beam computed tomography (CBCT) and magnetic resonance imaging (MRI). In both patients, the lingual bone cavity was found to be occupied by accessory salivary gland tissue. CONCLUSIONS: The combination of CBCT and MRI as noninvasive diagnostic techniques seems ideal to avoid surgical explorations, incisional biopsies, or enucleations of the lesion for diagnostic purposes.

[The mental foramen or "the crossroads of the mandible." An anatomic and clinical observation]

This paper presents a clinical and anatomical review of the mental foramen (MF) based on recent publications (since 1990). Usually, the MF is located below the 2nd premolar or between the two premolars, but it may also be positioned below the 1st premolar or below the mesial root of the 1st molar. At the level of the MF, lingual canals may join the mandibular canal (hence the term "crossroads"). Accessory MF are frequently described in the literature with large ethnic variations in incidence. The emergence pattern of the mental canal usually has an upward and posterior direction. The presence and extent of an "anterior loop" of the mental canal may be overestimated with panoramic radiography. Limited cone-beam computed tomography currently appears to be the most precise radiographic technique for assessment of the "anterior loop". The mental nerve exiting the MF usually has three to four branches for innervation of the soft tissues of the chin, lower lip, facial gingiva and mucosa in the anterior mandible. The clinician is advised to observe a safety distance when performing incisions and osteotomies in the vicinity of the MF.

Complication sévère d’une contention collée linguale mandibulaire

Le collage d’un fil torsadé souple sur les faces linguales des six dents antérieures mandibulaires est une modalité de contention couramment utilisée. Les complications sont rares mais peuvent être assez sérieuses pour provoquer des dégâts biologiques. Cet article présente une complication sérieuse d’un fil de contention torsadé souple, collé en lingual. Quatre ans après son traitement orthodontique, un homme de 20 ans a consulté pour la rupture d’un fil de contention torsadé souple. L’examen clinique a montré un torque radiculo-vestibulaire d’environ 35° d’une dent. Une image en tomographie volumique à faisceau conique (Cone-Beam Computed Tomography ou CBCT) a montré que la racine et l’apex de la dent étaient presque totalement hors de l’os du côté vestibulaire. Étonnamment, la vitalité de la dent était préservée. La dent a été ramenée presque jusqu’à sa position initiale; cliniquement, seule une récession gingivale a persisté. Les orthodontistes et les dentistes devraient être conscients des complications possibles des contentions collées. Les patients devraient être clairement informés de la manière dont les problèmes peuvent être détectés à un stade précoce.

Indication and timing of soft tissue augmentation at maxillary and mandibular incisors in orthodontic patients. A systematic review.

OBJECTIVE To assess the indication and timing of soft tissue augmentation for prevention or treatment of gingival recession when a change in the inclination of the incisors is planned during orthodontic treatment. MATERIALS AND METHODS Electronic database searches of literature were performed. The following electronic databases with no restrictions were searched: MEDLINE, EMBASE, Cochrane, and CENTRAL. Two authors performed data extraction independently using data collection forms. RESULTS No randomized controlled trial was identified. Two studies of low-to-moderate level of evidence were included: one of prospective and retrospective data collection and one retrospective study. Both implemented a periodontal intervention before orthodontics. Thus, best timing of soft tissue augmentation could not be assessed. The limited available data from these studies appear to suggest that soft tissue augmentation of bucco-lingual gingival dimensions before orthodontics may yield satisfactory results with respect to the development or progression of gingival recessions. However, the strength of the available evidence is not adequate in order to change or suggest a possible treatment approach in the daily practice based on solid scientific evidence. CONCLUSIONS Despite the clinical experience that soft tissue augmentation of bucco-lingual gingival dimensions before orthodontic treatment may be a clinically viable treatment option in patients considered at risk, this treatment approach is not based on solid scientific evidence. Moreover, the present data do not allow to draw conclusions on the best timing of soft tissue augmentation when a change in the inclination of the incisors is planned during orthodontic treatment and thus, there is a stringent need for randomized controlled trials to clarify these open issues.

Bone dimensions in the posterior mandible: a retrospective radiographic study using cone beam computed tomography. Part 2- analysis of edentulous sites.

A precise radiographic evaluation of the local bone dimensions and morphology is important for preoperative planning of implant placement. The purpose of this retrospective study was to analyze dimensions and morphology of edentulous sites in the posterior mandible using cone beam computed tomography (CBCT) images. This retrospective radiographic study measured the bone width (BW) of the mandible at three locations on CBCT scans for premolars (PM1, PM2) and molars (M1, M2): at 1 mm and 4 mm below the most cranial point of the alveolar crest (BW1, BW2) and at the superior border of the mandibular canal (BW3). Furthermore, the height (H) of the alveolar process (distance between the measuring points BW1 and BW3), as well as the presence of lingual undercuts, were analyzed. A total of 56 CBCTs met the inclusion criteria, resulting in a sample size of 127 cross sections. There was a statistically significant increase from PM1 to M2 for the BW2 (P < .001), which was not present for BW1 and BW3 values. For the height of the alveolar process, the values exhibited a decrease from PM1 to M2 sites. Sex was a statistically significant parameter for H (P = .001) and for BW1 (P = .03). Age was not a statistically significant parameter for bone width (BW1: P = .37; BW2: P = .31; BW3: P = .51) or for the height of the alveolar process (P = .41) in the posterior mandible. Overall, 73 (57.5%) edentulous sites were evaluated to be without visible lingual undercuts; 13 (10.2%) sites exhibited lingual undercuts classified as influential for implant placement. Precise evaluation of the alveolar crest by cross-sectional imaging is of great value to analyze vertical and buccolingual bone dimensions in different locations in the posterior mandible. In addition, CBCTs are valuable to diagnosing the presence of and potential problems caused by lingual undercuts prior to implant placement.

Susceptibility of enamel to initial erosion in relation to tooth type, tooth surface and enamel depth

This study aimed at assessing the susceptibility of different tooth types (molar/premolar), surfaces (buccal/lingual) and enamel depths (100, 200, 400 and 600 μm) to initial erosion measured by surface microhardness loss (ΔSMH) and calcium (Ca) release. Twenty molars and 20 premolars were divided into experimental and control groups, cut into lingual/ buccal halves, and ground/polished, removing 100 μm of enamel. The initial surface microhardness (SMH 0 ) was measured on all halves. The experimental group was subjected to 3 consecutive erosive challenges (30 ml/tooth of 1% citric acid, pH 3.6, 25 ° C, 1 min). After each challenge, ΔSMH and Ca release were measured. The same teeth were consecutively ground to 200, 400 and 600 μm depths, and the experimental group underwent 3 erosive challenges at each depth. No difference was found in SMH 0 between experimental and control groups. Multivariate nonparametric ANOVA showed no significant differences between lingual and buccal surfaces in ΔSMH (p = 0.801) or Ca release (p = 0.370). ΔSMH was significantly greater in premolars than in molars (p < 0.05), but not different with respect to enamel depth. Ca release decreased significantly with increasing depth. Regression between Ca release and ΔSMH at 100 μm depth showed lower slope and r 2 value, associated with greater Ca release values. At 200-600 μm depths, moderately large r 2 values were observed (0.651-0.830). In conclusion, different teeth and enamel depths have different susceptibility to erosion, so when Ca release is used to measure erosion, the depth of the test facet in enamel should be standardized, whereas this is less important if ΔSMH is used.

Periodontal regeneration - furcation defects: a consensus report from the AAP Regeneration Workshop

BACKGROUND Treatment of furcation defects is a core component of periodontal therapy. The goal of this consensus report is to critically appraise the evidence and to subsequently present interpretive conclusions regarding the effectiveness of regenerative therapy for the treatment of furcation defects and recommendations for future research in this area. METHODS A systematic review was conducted before the consensus meeting. This review aims to evaluate and present the available evidence regarding the effectiveness of different regenerative approaches for the treatment of furcation defects in specific clinical scenarios compared with conventional surgical therapy. During the meeting, the outcomes of the systematic review, as well as other pertinent sources of evidence, were discussed by a committee of nine members. The consensus group members submitted additional material for consideration by the group in advance and at the time of the meeting. The group agreed on a comprehensive summary of the evidence and also formulated recommendations for the treatment of furcation defects via regenerative therapies and the conduction of future studies. RESULTS Histologic proof of periodontal regeneration after the application of a combined regenerative therapy for the treatment of maxillary facial, mesial, distal, and mandibular facial or lingual Class II furcation defects has been demonstrated in several studies. Evidence of histologic periodontal regeneration in mandibular Class III defects is limited to one case report. Favorable outcomes after regenerative therapy for maxillary Class III furcation defects are limited to clinical case reports. In Class I furcation defects, regenerative therapy may be beneficial in certain clinical scenarios, although generally Class I furcation defects may be treated predictably with non-regenerative therapies. There is a paucity of data regarding quantifiable patient-reported outcomes after surgical treatment of furcation defects. CONCLUSIONS Based on the available evidence, it was concluded that regenerative therapy is a viable option to achieve predictable outcomes for the treatment of furcation defects in certain clinical scenarios. Future research should test the efficacy of novel regenerative approaches that have the potential to enhance the effectiveness of therapy in clinical scenarios associated historically with less predictable outcomes. Additionally, future studies should place emphasis on histologic demonstration of periodontal regeneration in humans and also include validated patient-reported outcomes. CLINICAL RECOMMENDATIONS Based on the prevailing evidence, the following clinical recommendations could be offered. 1) Periodontal regeneration has been established as a viable therapeutic option for the treatment of various furcation defects, among which Class II defects represent a highly predictable scenario. Hence, regenerative periodontal therapy should be considered before resective therapy or extraction; 2) The application of a combined therapeutic approach (i.e., barrier, bone replacement graft with or without biologics) appears to offer an advantage over monotherapeutic algorithms; 3) To achieve predictable regenerative outcomes in the treatment of furcation defects, adverse systemic and local factors should be evaluated and controlled when possible; 4) Stringent postoperative care and subsequent supportive periodontal therapy are essential to achieve sustainable long-term regenerative outcomes.

Visor Osteotomy of the Anterior Mandible

Current techniques for three-dimensional correction of the chin in patients with mandibular retrusion may increase mentolabial fold depth, but have limited effect on the lips. The authors present a single surgical technique to support the mentolabial fold and improve labial competence. The visor osteotomy is performed from canine to canine. The bone fragment pedicled to the lingual periosteum is coronally mobilized and fixed in the new position. Preserved vascularization is supposed to minimize the amount of bone resorbed. Visor osteotomy of the anterior mandible may improve the existing treatments for micrognathia by creating an aesthetic mentolabial fold and a competent lip seal.

Space requirement of a prefabricated bar on two interforaminal implants: a prospective clinical study

OBJECTIVES This clinical study measured the dimensional changes of existing lower complete dentures due to the integration of a prefabricated implant bar. Additionally, the impact of this dimensional change on patient satisfaction and oral function was analyzed. METHODS Twenty edentulous patients (10 men/10 women; aged 65.9 ± 11.8 years) received two interforaminal implants. Subsequent to surgery, a chair side adapted, prefabricated bar (SFI Bar(®), C+M, Biel, Switzerland) was inserted, and the matrix was polymerized into the existing lower denture. The change of the denture's lingual dimension was recorded by means of a bicolored, silicone denture duplicate that was sectioned in the oro-vestibular direction in the regions of the symphysis (S) and the implants (I-left, I-right). On the sections, the dimensional increase was measured using a light microscope. Six months after bar insertion, patients answered a standardized questionnaire. RESULTS All dentures exhibited increased lingual volume, more extensively at S than at I (P = 0.001). At S, the median diagonal size of the denture was doubled (+4.33 mm), and at I, the median increase was 50% (I-left/-right = +2.66/+2.62 mm). The original denture size influenced the volume increase (P = 0.024): smaller dentures led to a larger increase. The amount of denture increase did not have negative impact on either self-perceived oral function or patient satisfaction. Approximately, 95% of the patients were satisfied with the treatment results. CONCLUSIONS The lingual size of a lower denture was enlarged by the integration of a prefabricated bar without any negative side effects. Thus, this attachment system is suitable to convert an existing full denture into an implant-supported overdenture.