EFFECT OF ANTERIOR IMPLANT POSITION ON BIOMECHANICAL PERFORMANCE IN THE MAXILLARY ALL-ON-FOUR TREATMENT: A 3-D FINITE ELEMENT ANALYSIS

In the all-on-four concept, the positions of both posterior and anterior implants can affect stress distribution. The aim of this study was to examine the effect of the position of anterior implants on stress distribution in the implant, the bone around the implant, and prosthetic components in the resorbed maxilla using the all-on-four concept. All-on-four designs were prepared with three different anterior implant positions in a fully edentulous maxilla. Anterior implants were placed axially in the central incisor area in model 1, in the lateral incisors area in model 2, and in the canine area in model 3, forming three groups. The von Mises and principal stresses in the bone tissue and the von Mises stresses in the implant and prosthetic components were evaluated by three-dimensional finite element analysis. There were more stresses on the cortical bone than cancellous bone. The stresses on the bone tissue and implant components were generally concentrated around the posterior implant, whereas the stresses on the prosthetic components were generally concentrated in the anterior region. Changing the anterior implant positions from the central tooth to the canine tooth reduced the stress on the bone around the implant. The highest von Mises stresses occurred in the prosthetic superstructure in all models, whereas the lowest stresses occurred in the cancellous bone. Changing the position of the anterior implants from the central tooth to the canine area in the maxillary all-on-four concept created a favourable stress distribution.

Radular morphology by using SEM in Pugilina cochlidium (Gastropoda: Melongenidae) populations, from Thondi coast-Palk Bay in Tamil Nadu-South East coast of India

Radula in all melongeninae species is rather uniform and characterized by bicuspid lateral teeth with strongly curved cusps and sub rectangular rachidians, bearing usually 3 cusps. The aim of the present study was to describe the radula of 2 Pugilina cochlidium populations using SEM. The radula in 2 species proves itself as a rachiglossate type showing the radular formula of 1 + R + 1. The first population hasthe central tooth wide with sharp cusps equal in length, emanate from posterior margin of tooth base. The lateral teeth have 2 cusps and are long, sharp, pointed and bent towards the rachidian tooth. Whereas the second population, the central tooth is narrow with sharp cusps equal in length, emanate from posterior margin of tooth base. The lateral teeth have 2 cusps and are broad, longer, sharp, pointed and bent towards the rachidian tooth. They are typically sickle shaped with broad strong base. In both populations the rachidian tooth is subquadrate with 3 big cusps in the middle, but in the second population the base of the rachidian is concave while in the first population it is straight. In the present study the median rachidian of the second population, has a broad basal region when compared to first. This similar observation has been made in Chicoreus virgineus ponderosus and Siratus virgineus ponderosus. In the present study, since 2 populations exhibit the same generalized rachiglossate pattern it does not offer much scope for systematic diagnosis below generic level.

Cleaning efficacy of polyetheretherketone tips in eliminating cement remnants around implants with different abutment heights

The excess cement not removed following the cementation of fixed implant-supported restorations may cause loss of peri-implant attachment or adjacent bone. The aims of this study were to evaluate the amount of residual cement at different abutment-crown connection levels and to test the cleaning efficacy of poly-ether-ether-ketone (PEEK) ultrasonic tips after cementation. One implant was placed in an anterior central tooth position 5 mm below the gingival margin in an acrylic model, and 32 stone models were obtained with implant analogs. Abutment heights of 1-2 mm and 2.5-4 mm were used on the vestibular and lingual sides, respectively. Crowns were cemented and cleaned, and half of the samples were cleaned again using PEEK tips. The abutment-crown suprastructure was then disconnected, and cleaning efficacy was evaluated. Varying amounts of excess cement were found on all specimens except for the PEEK group with abutment-crown connections 1 mm below the gingival margin. An increase of undetected cement remnants was observed when the restoration margins were located deeper subgingivally. Various amounts of excess cement associated with margin location were detected on the abutment-restoration complex despite meticulous cleaning efforts. Ultrasonic PEEK tips were effective at cleaning the cement remnants around implants to a certain depth.

Morphological Disparity of the Mouthparts in Polyphagous Species of Largidae (Heteroptera: Pentatomomorpha: Pyrrhocoroidea) Reveals Feeding Specialization

Mouthpart structures were observed in four species of Largidae using scanning electron microscopy to investigate their morphological disparity, and linked to changes in feeding specialization. The examined species are pests that feed mainly on seeds and plant sap of forbs, shrubs, and trees. Their external mouthparts are described in detail for the first time herein. The cone-like labrum and four-segmented tube-like labium are shorter in Physopelta species than in Macrocheraia grandis (Grey). The labium surface in all studied species bears nine types of sensilla (St1-St2, Sb1-3, Sch, Sca1-2, Sm). The distributions of sensilla on particular labial segments varies among the studied species. The tripartite apex of the labium consists of two lateral lobes and an apical plate that is partly divided in Physopelta species, and not divided in Macrocheraia. Each lateral lobe possesses a sensillar field with 10 thick-walled uniporous sensilla basiconica, one multiporous sensillum styloconicum, and one long non-porous hair sensillum. Each mandibular stylet tip in M. grandis has a central tooth placed anteriorly and pairs of teeth arranged dorso-laterally. In Physopelta, there are one or two central teeth placed anteriorly but two pairs of teeth dorso-laterally. In all studied species, the inner surfaces of the mandibular stylets have scale-like projections. A left–right asymmetry of the maxillary stylets is noticeable; the external end of the right maxillary stylet is smooth and slightly tapered in M. grandis and evidently wider (spoon–like) in the three species of Physopelta, while the left end of the stylets is straight and narrow in M. grandis in contrast to Physopelta, in which the end is straight and wide. No differences in the internal structure of the maxillary stylets were observed among the studied species. Based on structural differences, we inferred that the mandibles and maxillae are more adapted for seed-sucking in Physopelta species than in M. grandis. M. grandis has the ends of the maxillae more narrowed, a trait more adapted for sucking sap from phloem or parenchymal cells.

Morphological and molecular diversity of rissoellids (Mollusca, Gastropoda, Heterobranchia) from the Northwest Pacific island of Hokkaido, Japan

This study deals with four species of marine microgastropods of the family Rissoellidae. Rissoella elatior (Golikov, Gulbin & Sirenko, 1987), R. golikovi (Gulbin, 1979), R. japonica n. sp., and Rissoella sp. 1 were collected in different locations around the island of Hokkaido, Japan. Light and scanning electron microscopy (SEM) were used to study the general morphology of the shell and radula, and a region of the mitochondrial cytochrome c oxidase subunit I (COI) gene was amplified for 26 specimens. Rissoella elatior is morphologically characterized by a highly asymmetrical radula with a deep notch encircled by 10–13 minute secondary cusps on the left dorsal margin of the central tooth. Rissoella golikovi is characterized by a skeneiform shell and possession of three teeth per row on the radula. Rissoella japonica n. sp. shows five teeth per row on the radula; central tooth higher than wide; lateral and marginal teeth narrow with an outer lateral projection at the base; all teeth presenting numerous small cusps on the cutting edge. Rissoella sp. 1 is distinguished from R. japonica n. sp. in having i) very short oral lobes, ii) a mantle with a large, black patch and whitish blotches inside, and iii) different color patterns associated with the visceral mass. Although Rissoella sp. 1 probably represents an undescribed species, additional specimens are needed to complete its description. This study represents a first molecular approach to the family Rissoellidae. Studies of traditional morphological characters indicated four species, the addition of COI data raised the count to eight potential species, suggesting the occurrence of cryptic species among rissoellids.

Systematization and comparative scheme analysis of mechanisms of planetary rotary hydraulic machines

The systematization of planetary rotary hydraulic machines (PRHM) with floating rollers is presented in the article. This systematization is carried out according to such structural features as: the number of waves that have central tooth gears with internal and external teeth, the character of the leading link motion; selection of a supporting (fixed) link; selection of the link containing the channels. The systematization allows us to list all essentially different schemes of PRHM and conduct their comparative analysis. The comparison is based on such technical parameters as: symmetry of schemes; absence of dead spots; PRHM performance, pulsation of instantaneous performance; channel cross-sectional area. The comparison showed that based on a set of indicators, the schemes with the numbers of central wheel waves 2×4; 4×6; 6×8 are preferred, in which the rotor performs a purely rotary motion.

Perawatan Estetik pada Insisivus Sentral Maksila dengan Perforasi Apikal

Masalah estetik dapat diatasi dengan pendekatan restorasi, ortodontik maupun kombinasi keduanya. Perawatan restorasi dapat dilakukan jika pasien menolak untuk dilakukan perawatan ortodontik. Perawatan restorasi mencakup pembuatan ilusi perubahan arah gigi tanpa merubah lokasi akar gigi. Kecelakaan iatrogenik yang disebabkan oleh hilangnya panjang kerja dapat menyebabkan perforasi apikal. Salah satu manajemen perawatan perforasi apikal adalah dengan Ca(OH)2. Tujuan dari artikel ini adalah menginformasikan keberhasilan perawatan restorasi untuk perbaikan estetik serta keberhasilan perawatan perforasi apikal menggunakan Ca(OH)2. Laki – laki berusia 20 tahun datang dengan fraktur gigi insisivus akibat kecelakaan 7 tahun yang lalu. Gigi insisivus maksila pertama kanannya telah dilakukan perawatan saluran akar dan direstorasi dengan resin komposit. 6 tahun kemudian, pasien merasakan sakit pada giginya, perkusi dan palpasi positif serta ditemukan mobilitas. Pasien juga merasakan gigi depannya berubah warna dan berjejal. Pada pemeriksaan radiografis ditemukan material obturasi yang overfilling disertai pelebaran ligamen periodontal. Perawatan perforasi apikal untuk gigi insisivus maksila pertama kanan dilakukan menggunakan Ca(OH)2, dilakukan juga perawatan saluran akar pada gigi insisivus maksila pertama kiri. Berjejalnya gigi depan diperbaiki dengan restorasi menggunakan resin komposit direk dengan penguat pasak fiber. Masalah estetik gigi depan dapat diperbaiki menggunakan pendekatan restoratif, serta perawatan saluran akar dengan perforasi apikal dapat dilakukan dengan menggunakan Ca(OH)2. ABSTRACT: Aesthetically Compromized Maxillary Central Incisor with Apical Perforation. Aesthetical problem may be corrected restoratively, orthodontically or with combination of both approaches. Restorative treatment could be done for a patient due to several reasons; one of them is when patients refuse orthodontic treatment. Restorative alternatives create the illusion of movement without altering the location of the tooth root. Iatrogenic accident as a result of the loss of working length could lead to apical perforation. One of the management for apical perforation is Ca(OH)2. The aim of this case report is to present the success of repairing aesthetically compromised tooth with fiber reinforced composite and root canal retreatment with apical perforation using Ca(OH)2 as a repair and sealing material. A 20 year old male patient had a fractured incisor following a traumatic incident 7 years previously. The maxillary right central incisor was endodontically treated and restored with composite resin. 6 years later, the patient felt pain in his two central incisor teeth and tenderness to percussion; palpation was positive and mobility was detected. The patient also felt discoloration and misalignment of his central incisor. The radiographic examination reveals an overfilling of obturation material with enlargement of periodontal ligament. A root canal retreatment for maxillary right central incisor with apical perforation using Ca(OH)2 as repair and seal material and root canal treatment for maxillary left central incisor was conducted. The aesthetically compromised maxillary central tooth was corrected restoratively using fiber reinforced composite. The aesthetically compromised central tooth was proven to be successfully corrected using fiber reinforced composite and the apical perforation successfully sealed using Ca(OH)2.

Intraradicular Splinting with Endodontic Instrument of Horizontal Root Fracture

Introduction. Root fractures, defined as fractures involving dentine, cementum, and pulpal and supportive tissues, constitute only 0.5–7% of all dental injuries. Horizontal root fractures are commonly observed in the maxillary anterior region and 75% of these fractures occur in the maxillary central incisors.Methods. A 14-year-old female patient was referred to our clinic three days after a traffic accident. In radiographic examination, the right maxillary central incisor was fractured horizontally in apical thirds. Initially, following local infiltrative anesthetics, the coronal fragment was repositioned and this was radiographically confirmed. Then the stabilization splint was applied and remained for three months. After three weeks, according to the results of the vitality tests, the right and left central incisors were nonvital. For the right central incisor, both the coronal and apical fragments were involved in the endodontic preparation.Results. For the right central tooth, both the coronal and apical root fragments were endodontically treated and obturated at a single visit with white mineral trioxide aggregate whilst the fragments were stabilized internally by insertion of a size 40 Hedstrom stainless-steel endodontic file into the canal.Conclusion. Four-year follow-up examination revealed satisfactory clinical and radiographic findings with hard tissue repair of the fracture line.

Management of an Intruded Tooth and Adjacent Tooth Showing External Resorption as a Late Complication of Dental Injury: Three-Year Follow-Up

Treatment and prognosis of intrusive luxation can vary depending on the age of the patient, type of dentition, stage of root development, and time and severity of the trauma. Some studies have demonstrated that intrusions of up to 3.0 mm have an excellent prognosis, whereas teeth with severe intrusion or teeth that are intruded more than 6.0 mm present an unfavorable prognosis because of the occurrence of inflammatory resorption and pulp necrosis. The aim of this case report is to present an 11-year-old male patient with complete intrusion of the permanent maxillary left lateral incisor, associated with the adjacent central tooth presenting external resorption, treated by immediate surgical repositioning and root canal treatment with a favorable prognosis. After long-term (3-year) clinical and radiographic follow-up, the teeth appeared normal and the patient was pleased with the outcome.