Root Face Research Articles

A scanning electron microscopic evaluation of root surfaces and the gutta-percha interface following root-end resection in vitro.

The aim of this study was to evaluate the effects that various commonly used instruments have on root surface morphology, the obturating material, and the interface between the obturation and the root canal walls following root-end resection in vitro. Sixty human single-rooted teeth with fully formed apices were collected and decoronated. The root canals were instrumented, and then obturated with thermoplasticized gutta-percha using AH-26 as the sealer. The roots were randomly divided into 12 different groups, and apical root-end resections were performed using eight different instrument configurations, and two different directions in which the bur moved across the root face in relation to its direction of rotation. Epoxy resin replicas of the resected root ends were examined using scanning electron microscopy. Each instrument produced a characteristic surface finish on the resected root end that mirrored its cutting profile. Irrespective of the design of the bur used, smearing and shredding of the gutta-percha across the root face occurred only when the handpiece was moved across the root face in reverse direction in relation to the direction of rotation of the bur. To ensure minimal disruption and distortion of the root filling and to prevent shredding of the gutta-percha interface, care should be taken to ensure that the final pass of the bur across the root canal is in the correct direction in relation to its direction of rotation.

Incidence of root face alteration after ultrasonic retrograde cavity preparation

Problem. Ultrasonic root end preparation is now a recognized clinical procedure. Advantages claimed include improved access to the surgical site (because of reduced root end bevel), and faster more conservative preparation of the root end cavity. However, cracking of the root face has been reported after preparation.Objectives. The aim of this study was to determine the incidence of root end cracking at varying ultrasonic power levels with a replica technique and scanning electron microscopy.Study design. The root canals of 55 single-rooted teeth were prepared to size 40 apically and obturated with laterally condensed gutta perch and sealer. Root ends were resected at 90 degrees 3 mm from the apex. Class 1 cavities (n = 5) were prepared with retro tips in a Neosonic handpiece with different power settings. Time of preparation and load applied were constant. Another experimental group (n = 5) was prepared with a no. 1 rotary bur. A replica technique with addition-cured silicone impression material and epoxy resin was used to prevent drying artefacts. Specimens were viewed under scanning electron microscope for alterations of the root face.Results. Results showed no root face cracking across the full range of instrument power settings, although chipping of the retrograde cavity margins was observed. No cracking was noted in bur-prepared teeth.

Controlling dentine penetration in computer microleakage tracer mapping

Objectives: Microleakage tracer penetration tests in dentine with simple sectioning are often confounded by dentine tubule penetration into the interface, leaching of water soluble tracers on wet sectioning, lack of standardized cavity dimensions affecting stresses, inadequate sectioning missing important tracer regions and airlocks obstructing tracer entry. The present aim was to create high resolution maps of stained interfaces without these confounding factors. Methods: Ten intact extracted permanent upper central incisors were horizontally sectioned through the upper root, one third of the root length from the mid-buccal enamel limit. A dentine-bonded resin composite (Scotchbond MP, Z100, 3M) restoration was placed in a cylindrical cavity milled centrally in the root face of the coronal portion of five teeth. Tubules were angled at a mean of 12.5 ± 4.8 ° to the root face, and travelled approximately radially from the interface, such that tubule penetration was directed sufficiently radially outward to be distinguished from vertical interface penetration. Waterfast silver nitrate staining was applied with initial vacuum at 30 mmHg. A precision grinding machine serially removed approximately 100 μm increments of the tooth until no tracer remained, and computer image analysis data for the 18 revealed surfaces were used to construct detailed interface tracer maps. Results: Control specimen tubule penetration was directed sufficiently radially outward to permit tubule penetration to be isolated from vertical interface penetration in test specimens, and ignored. Interface penetration ranged from approximately 0.3 to 1.6 mm in depth, and 0.90 to 5.09 mm 2 in area. Conclusions: This method provided quantitative standardized high resolution mapping of interface tracer penetration, unconfounded by dentine penetration. None of the interfaces was fully sealed.

Ｈｅ‐ＤＣＥＮティグ全姿勢自動溶接法のアルミニウム配管への適用 アルミニウム配管における高品位溶接施工法の検討

According to the rule of high pressure gas in Japan, it is limited strictly to generate the weld defects in weld zone. In this report, on high pressure gas piping of aluminium, an automatic all position welding process without blowhole is investigated. The following results were obtained in this study.It was found that the quality of weld zone by using He-DCEN·TIG is better than that of Ar-AC·TIG. In He-DCEN·TIG, shielding gas flow conditions influence on generating blowhole, but back shielding gas has no effect on it. In brushing treatment of root face, many weld defects such as aluminium oxide inclusion are produced. On the other hand, in the case of mechanical treatment that the root face becomes fiine smooth, occurrence of these defects decreases.

Dichromatic Sums Revisited

In a previous paper the author studied an enumerating power seriesΦin six variables. The typical term was the sum of a dichromatic polynomial over all rooted planar maps of given numbers of vertices and faces and given valencies for the root face and root vertex. Loops and multiple joins were allowed. The polynomial was the one now commonly called the “Tutte polynomial” by other writers. An equation forΦwas obtained. It made possible a recursive calculation of coefficients in the order of increasing edge number. The present paper arose out of the observation that the equation forΦtakes a particularly simple form when the variablesxandyof the dichromatic polynomial are each given the value 1. The value of the polynomial is then the number of spanning trees of the map concerned. In that special case a theoretical solution is obtained. It is stated in terms of a remainder obtained when a certain power series in the four remaining variables, slightly transformed, is divided by a certain polynomial.

Impregnation by dentine bonding agents into instrumented root-face dentine

Objectives: To examine the penetration of unfilled resin into instrumented root-face dentine, facilitated by five commercially available dentine bonding agents. Methods: Upper third molar teeth were decoronated, and a given dentine bonding agent and resin composite applied to the instrumented root face, according to the manufacturer's instructions. A control specimen was similarly prepared but no dentine primer was applied prior to resin composite. The teeth were sectioned longitudinally and the sectioned surface demineralized and deproteinated. Specimens were examined by scanning electron microscopy (SEM) for resin tag length and density in different areas of the root face. Results: Specimens treated with dentine bonding agent systems exhibited minimum resin penetration of peripheral root-face dentine and much longer penetration of resin tags in dentine above the pulp chamber. A possible ‘hybrid’ layer of resin-impregnated dentine was observed in all specimens where a dentine bonding agent system had been used but was not observed in control specimens. Resin tags were also more sparsely observed in control specimens. Conclusion: Resin tag penetration is superior in both density and length of penetration in dentine overlying and adjacent to the pulp chamber, with shorter and sparser penetration exhibited in peripheral root-face dentine. The possible clinical implications of these observations are discussed.

An auto-programming system of MAG welding parameters for vision-based robot

The on-line auto-programming of MAG welding parameters for a vision-based robot mainly aims at improving the adaptability of a welding robot in a complex welding environment, and it is a new kind of intelligent control method of weld quality. The authors developed an experimental system of an MAG welding robot with 3-D vision according to the requirements of real-time auto-programming of welding parameters. In the system, the scam geometry parameters, i.e., root gap and root face in a single V-groove, are used as input variables, while the welding process parameters, i.e., welding current and speed, are used as output variables. The relation between input and output variables is described by a fuzzy model. Experimental results show that the system can result in increased weld quality.

Management of the resected root end: a clinical review

Careful management of the resected root end during endodontic surgery is critical to the overall success of the case. After resection, the root structure presents with multiple anatomical variations and considerations at both a macroscopic and microscopic level. These include root outline, canal anatomy, dentinal tubule configuration, presence of a smear layer and root canal filling material. Proper assessment of these variables will dictate the best methods for root-end management, along with the attainment of an anatomically compatible root face for optimal healing of the periradicular tissues.

The Lattice Structure of Flow in Planar Graphs

Flow in planar graphs has been extensively studied, and very efficient algorithms have been developed to compute max-flows, min-cuts, and circulations. Intimate connections between solutions to the planar circulation problem and with “consistent” potential functions in the dual graph are shown. It is also shown that the set of integral circulations in a planar graph very naturally forms a distributive lattice whose maximum corresponds to the shortest path tree in the dual graph. Further characterized is the lattice in terms of unidirectional cycles with respect to a particular face called the root face. It is shown how to compactly encode the entire lattice and it is also shown that the set of solutions to the min-cost flow problem forms a sublattice in the presented lattice.

コンポジットレジンによる支台築造の実験的研究 その２ 根菅内象牙質処理法がレジンコアの維持力と辺縁封鎖性に及ぼす影響

In this study we investigated the effect of two different dentin pretreatments on the retention of prefabricated posts and on the microleakage of the composite resin cores.The dentin surfaces of both post space and root face of extracted human single-rooted teeth were treated with either 1) 37% phosphoric acid solution or 2) 37% phosphoric acid solution and then 10% sodium hypochlorite solution. Then, a prefabricated post (AD Post®, Kuraray Co.) was cemented with an adhesive resin cement (Panavia EX®, Kuraray Co.) after application of dentin bonding agent (Clearfil New Bond®, Kuraray Co.). And a composite resin core was built up with light-cured composite resin (Clearfil Photo Core®, Kuraray Co.).The retention of prefabricated posts was measured after one day immersion into 37°C water, 5, 000 times and 10, 000 times of thermalcycles between 4° and 60°C of water bath. The microleakage was measured after 2, 500 times of thermalcycles between 4° and 60°C in 0.2% aqueous solution of basic fuchsin dye.The results obtained indicated that phosphoric acid etching was ineffective both on the retention and on the marginal sealing of posts and composite resin cores. Meanwhile, removing of the collagen layer exposed by phosphoric acid etching (30 s) with sodium hypochlorite solution (60 s or 120 s) effectively increased adhesive strength of the adhesive resin to dentin, i. e. the retention of prefabricated posts significantly increased and the microleakage of the composite resin cores was significantly reduced.These results were supported by SEM observation of interface between adhesive resin and dentin.

The adaptation and sealing ability of light‐cured glass ionomer retrograde root fillings

The adaptation and sealing ability of a light-cured glass ionomer cement when used as a retrograde root filling was assessed using a confocal optical microscope with and without a fluorescent dye. This material was compared with a conventional glass ionomer cement and amalgam. The root canals of 60 extracted human single-rooted teeth were prepared and filled with gutta-percha and sealer. All the teeth were apicected, retrograde cavities were prepared, and then divided into three groups of 20 teeth each and filled with the test materials. The light-cured glass ionomer cement was well adapted to the retrograde cavity and apicected root surface. Within the retrograde cavity the cement was often well adapted to one wall, but gaps were found on the opposite cavity wall. This was probably caused by the polymerization contraction of the material. In contrast, the amalgam retrograde root fillings were poorly adapted to the cavities, with gaps between the cavity walls and amalgam. This group exhibited the poorest sealing ability as measured by the extent of dye penetration. The conventional glass ionomer cement was often found smeared over the root face, and there were unfilled voids at the base of some retrograde cavities. The results of the dye leakage study were analysed statistically. The sealing ability of the light-cured glass ionomer cement was significantly better than that of amalgam (P less than 0.001). The dye penetration around the light-cured glass ionomer cement and the conventional glass ionomer cement was not significantly different (P greater than 0.05). However, the sealing ability of the conventional glass ionomer cement was significantly better than that of amalgam (P less than 0.05).

Face sizes of 3-polytopes

Let R n be the root face valency of a random, rooted n-edged 3-polytope, X n the valency of a randomly selected face from the faces of n-edged 3-polytopes, and Y n the valency of a randomly selected face from the faces of a randomly selected n-edged 3-polytope. Then for each fixed j Prob(X n=j)∼ Prob(Y n=j)∼4 Prob(R n=j) j and lim n→∞ Prob(X n=j)∼9( 6 jπ ) 1 2 2 −j as j→∞ Also, there exists a B( ϵ) such that Prob(R n=j)<B(ε)( 1 2 +ε) f for all n, j, ϵ>0.

The restoration of endodontically treated teeth: An update

W ith increasing numbers of teeth being retained by endodontic therapy there is a concomitant need for the dentist to have the knowledge and skills to restore them. The restorative method depends on the amount’ of supported coronal tooth structure that remains. If a substantial part of the crown is intact, a conservative approach may be used. If little or no coronal tooth structure remains, provision must be made for creating a core, a synthetic crown preparation such as gold, amalgam, composite, or glass ionomer, over which a crown can be placed. Ideally a post inserted in a preparation within the confines of the root by using the canal as a guide provides optimum support for the core. This post may be supplemented with one or more TMS pins (Whaledent International, New York, N.Y.) to increase retention. However, there are instances when the use of a retentive post may be prohibited by (1) a curve in the root that prevents the placement of a post of adequate length to provide necessary retention, (2) the presence of a silver point that cannot be removed to the desired depth, and (3) the presence of a previous post that cannot be removed. In these instances, if sufficient horizontal root face is present, pins may be used to support the core. If neither a post nor pins can be used, the restorative effort is nullified and extraction is necessary.

A technique to reinforce weakened roots with post canals.

Abstract A method to strengthen the weakened coronal portion of roots with post canals is described. The apical portion of the root canal is prepared using a Dormer twist drill to fit a matching Wiptam wire post. After removal of the Wiptam wire, the root canal of the weakened coronal portion of the root is prepared and acid‐etched. The Wiptam wire, lubricated with petroleum jelly, is repositioned into the root canal, and after painting the coronal root den tin with bonding agent, radiopaque composite resin is syringed around the wire into the coronal defect. Following polymerization of the composite material, the wire is removed, leaving a reinforced root with a patent post canal. Preparation of the root face is completed for restoration with a post crown.

Further studies on heat generation during obturation techniques involving thermally softened gutta-percha.

Summary. A study in vitro investigated the heat generated at the root face of human single‐rooted canine teeth during the use of thermally softened gutta‐percha root‐filling techniques. The temperature rise was recorded at two points on the outer surface of each tooth using thermocouples linked to a chart recorder. Four groups of specimens were used in the study. In the first group, the teeth were root filled using a plugger at a rotational speed of 8000 rev/minute. In the second group, the teeth were obturated with a plugger of the same design but at a rotational speed of 16,000 rev/minute. The third group was root filled with a combination of lateral condensation of gutta‐percha and mechanical compaction, and in the final group, filling was carried out using the Unitek Obtura system. The results showed that significant temperature rises occurred in the four groups and that these rises were greater at the central point than apically. An increase in the rotational speed of compaction caused an increased temperature rise at the apical region. The heat generated by the injection of thermally softened gutta‐percha was slower to dissipate than with the other techniques. The results of these investigations would indicate that the temperature rises generated during the use of thermally softened gutta‐percha in endodontic obturation lie within the range likely to cause tissue damage.

Effect of proteolytic enzymes on caries lesion formation in vitro

This study investigates enzyme degradation of collagen at various pH levels and is designed to obtain information pertaining to the effect of proteolytic enzymes on caries-like lesion formation and progression. One hundred and eight sections of human teeth with exposed areas on enamel and root face, were placed into an enzyme/buffer system maintained at pH levels of 4.0, 5.5 and 7.0. Periodically, throughout the experimental period, sections were removed and examined histologically for caries-like lesion formation. Results showed consistent surface erosion occurring on the root face only at a pH level of 5.5 in buffer containing enzymes. Sections placed in pH 5.5 buffer only, which served as controls, showed obvious lesion formation on the root face, but with histologically intact surfaces. This interaction occurring between enzymatic activity and acid demineralization suggests that enzymes may have a contributory effect on caries lesion formation in root surfaces.

Root face caries in patients with periodontal diseases: associations between oral and periodontal hygiene: Raetzke P. (1985) Dtsch Zahnaertzl. Z, 40, 775–777

Root face caries in patients with periodontal diseases: associations between oral and periodontal hygiene: Raetzke P. (1985) Dtsch Zahnaertzl. Z, 40, 775–777

ルート割れ発生部の局部水素濃度について

The local hydrogen concentration in the heat-affected-zone where the root cracking occurred has been investigated using the finite difference method. The effect of groove and weld metal shapes on the local hydrogen concentration was basically examined. It is clear that the local hydrogen related with the cold cracking is not determined by the time factor, but by the thermal factor, namely, throat depth does not become a main factor. The root face, the root angle and the bond line shape are important factors of the local hydrogen concentration.

Management of a vertically fractured endodontically treated tooth

The case of a vertically fractured endodontically treated tooth in which an amalgam platform was constructed on the root face is presented. A modified post crown was erected on this base. No exploratory endodontic surgery was performed. Over a 2-year follow-up period, neither the clinical nor the radiographic appearance of the tooth had deteriorated.

Two-part coping, dowel, and core

M aking a dowel, core, and crown restoration for a root where the adjacent teeth form an undercut, presents a vexatious problem. The situation generally arises where teeth have tilted. The result is a distance between the contact surfaces of the adjacent teeth which is less than the mesiodistal distance between the roots. The two-part coping, dowel, and core technique was devised to overcome the problem of constructing a crown where a prepared root face cannot receive a vertically inserted restoration (Fig. 1).