Identification of the gene for disaggregatase from Methanosarcina mazei

The gene sequences encoding disaggregatase (Dag), the enzyme responsible for dispersion of cell aggregates of Methanosarcina mazei to single cells, were determined for three strains of M. mazei (S-6(T), LYC and TMA). The dag genes of the three strains were 3234 bp in length and had almost the same sequences with 97% amino acid sequence identities. Dag was predicted to comprise 1077 amino acid residues and to have a molecular mass of 120 kDa containing three repeats of the DNRLRE domain in the C terminus, which is specific to the genus Methanosarcina and may be responsible for structural organization and cell wall function. Recombinant Dag was overexpressed in Escherichia coli and preparations of the expressed protein exhibited enzymatic activity. The RT-PCR analysis showed that dag was transcribed to mRNA in M. mazei LYC and indicated that the gene was expressed in vivo. This is the first time the gene involved in the morphological change of Methanosarcina spp. from aggregate to single cells has been identified.

Autotransplantation of a maxillary third molar to replace a maxillary premolar with vertical root fracture

AIM

To report the successful autotransplantation of a fully developed third molar that required nonsurgical and surgical interventions for tooth adaptation.

SUMMARY

This case report describes the autotransplantation of a third molar with complete root development after the loss of a fractured premolar in a 47-year-old male. To allow better adaptation of the donor tooth, the buccal roots of the third molar were removed using a diamond bur and the canal entrances were filled. Recall examination 6 years after completion of root-canal treatment showed normal periodontal healing with absence of infection, ankylosis or progressive resorption. The transplantation of a third molar is seen as a promising method to replace a lost permanent tooth, and to restore aesthetics and function.

KEY LEARNING POINTS

*Autotransplantation is a viable option for the treatment of a missing tooth or for replacement of traumatized tooth when there is a donor tooth available. *Fully developed third molars are potentially reliable candidates in the absence of other suitable donor teeth.

The thickness of the roof of the glenoid fossa in the temporomandibular joint: relationship to the MRI findings

OBJECTIVES

The purpose of this study was to clarify the relationship between the thickness of the roof of the glenoid fossa (RGF) and magnetic resonance imaging (MRI) findings of temporomandibular joint (TMJ) disorders (TMDs).

METHODS

Eighty-seven patients with symptoms and indications of TMD in one or both TMJs were referred for MRI. Cone-beam CT (3DX) was used to measure the thickness of the RGF at its thinnest point. Linear measurements were made three times on the monitor by three separate investigators and the mean values obtained were used for the statistical analyses.

RESULTS

The joints were categorised as normal (70 joints), anterior disc displacement with reduction (ADWR; 53 joints) or anterior disc displacement without reduction (ADWOR; 51 joints). The joint disorders were also categorised into the following subgroups: with osteoarthritis (OA) (21 joints), without OA (153 joints), with disc deformation (33 joints), without disc deformation (141 joints), with joint effusion (JE) (61 joints) and without JE (113 joints). The average minimum thickness of the RGF was 0.85 mm for normal joints, 0.90 mm with ADWR, 0.93 mm with ADWOR, 0.99 mm with OA, 0.87 mm without OA, 0.87 mm with disc deformation and 0.89 mm without disc deformation. There was no significant difference between these figures. There was a significant difference in the thickness of the RGF with (0.97 mm) and without (0.84 mm) JE.

CONCLUSIONS

These results suggest that RGF thickness is influenced by JE, but is unaffected by disc position and configuration.

Adhesive bonding of a lithium disilicate ceramic material with resin-based luting agents

This study evaluates the bonding characteristics of a lithium disilicate-based ceramic material (IPS Empress 2). Two sizes of disk specimens of the material were made, and three groups of disk pairs were separately surface-prepared using three techniques; etching with phosphoric acid, etching with hydrofluoric acid, and air-abrasion with alumina. Each group was further divided into four sub-groups; group (i) was bonded with the Variolink II composite, (ii) was treated with the Monobond-S silane primer and bonded with the Variolink II composite, (iii) was bonded with the Super-Bond acrylic adhesive and (iv) was treated with the Porcelain Liner M silane primer and bonded with the Super-Bond acrylic adhesive. Shear bond strengths were determined before and after 100 000 thermocycles. Bond strength varied from 10.6 to 71.5 MPa before thermocycling, whereas post-thermocycling bond strength ranged from 0 to 61.2 MPa. Among the three surface preparations, hydrofluoric acid etching (HF) was most effective in enhancing bond strength of both luting materials, especially for unsilanized specimens. Application of the silane primer elevated bond strength of both luting agents regardless of surface preparation method. It can be concluded, for both luting agents, that durable bond to the Empress 2 ceramic material can be achieved through the combined application of HF and the proprietary silane primer.

Marginal fermi liquid theory in the Hubbard model

We find marginal-Fermi-liquid- (MFL) like behavior in the Hubbard model on a square lattice for a range of hole doping and on-site interaction parameter U. Thereby we use a self-consistent projection operator method. It enables us to compute the momentum and frequency dependence of the single-particle excitations with high resolution. The Fermi surface is found to be holelike in the underdoped regime and electronlike in the overdoped regime. Our calculations concern normal state properties of the system. When a comparison is possible, we find consistency with finite temperature quantum Monte Carlo results. We also find a discontinuous change with doping concentration from a MFL to a Fermi-liquid behavior resulting from a collapse of the lower Hubbard band. This renders Luttinger's theorem inapplicable in the underdoped regime.

A new all-ceramic post and core system: clinical, technical, and in vitro results

Root-filled teeth with fractured or discolored coronal aspects invariably need to be restored by crowns. The prepared abutment tooth is usually reinforced by a metallic post and core system. The grayish discoloration of the root, and consequently of the gingiva, caused by the metal color may be an enormous esthetic disadvantage in the anterior teeth. In 1993 ceramic posts made of zirconia were introduced by the authors, allowing a new all-ceramic concept for nonvital abutment teeth. A new ceramic post and core system has now been developed with the idea of further improving esthetic appearance. In this system the core material is heat pressed directly onto the zirconia post. This article describes the material and the fabrication procedures (chairside and in the laboratory) of the system. Clinical results are presented. The retention of the core material is evaluated by in vitro tests.

Microstructure of etched "IPS Empress" heat-pressed ceramics observed by SEM

A valuable characteristic of the "IPS Empress" used for producing all ceramic dental restorations is that it is a prefired ceramic ingot. The ingot is heated, softened and press-injected into the cavity, and ceramic restorations are fabricated by the lost wax casting method. The leucite crystal present in the ingot are scattered and distributed into the glassy phase in a more homogeneous manner through this pressing procedure, and the resulting ceramics are of higher flexural strength than conventional ones. The present study was carried out to clarify the microstructure of Empress ceramics by etching, and to observe the etched surface by scanning electron microscopy, in comparison with several other conventional ceramics. It was shown that the form and distribution of the leucite crystals in Empress ceramics are quite different before and after pressing, and that the staining and layering ceramics are also different from conventional ceramics. The method of surface treatment of ceramics prior to etching, such as fracturing or grinding, the kind of etching material used, the concentration and the etching time are important factors for revealing, observing and evaluating the microstructure of ceramics containing leucite crystals.

[Study on determination of the imaginary axis of the tooth crown in anterior teeth: 1]

1. The state of inclination and the change under various conditions of the imaginary axis of the tooth crown of upper jaw anterior teeth can be determined by the image measuring system and method of this study. 2. The measurement error of this system was not more than 0.3 degree. This value was sufficient for the purpose of this study. 3. The imaginary axis of the tooth crown of anterior teeth was determined on the study cast with 1 to 3 degrees in mesiodistal direction and 2 to 4 degrees in labiopalatal direction as standard deviation. 4. The imaginary axis of the tooth crown of anterior teeth was determined toward labial in the random position and toward patient's right and palatal in Standing Posture. 5. It was confirmed that the determination of the imaginary axis of tooth crown was effected by the position of the patient relative to the operator, limitation or direction of view, and approach direction.

[The influence of the operating positions on the prepared abutment contour of full cast crowns. Unanatomical artificial teeth for fixed bridge]

With a view to research the effect of the crown form, we made the unanatomical artificial teeth and some doctors to do the abutment tooth preparation with full cast crowns for the maxillar left fixed prosthodontics three-unit bridge in random position. After that, following are the results of a study made on the influence to the prepared tooth form. The prepared teeth are the second premolar and the second molar (The "second premolar" is abbreviated to "5" and the "second molar" is abbreviated to "7"). 1. The reductions of occlusal surface was excessively larger at 5 and 7 buccal cusp regions, while it was excessively smaller at central groove area. 2. The reductions of axial surface and subgingival area were excessively smaller at 5 and 7. 3. As for the degree of axial taper, its was steeper toward the buccal and distal surfaces at 5 and 7. 4. As for the relative degree of axial taper, it get the largest in degree on both sides between 5 medial surface and 7 distal surface. The results of this experiment are similar to the results that used anatomical artificial teeth. These results are affected by the operating posture.

[Study on determination of the imaginary axis of the tooth crown. 1. Measuring procedure]

The state of inclination and the change under various conditions of the imaginary axis of the tooth crown of upper jaw and lower jaw right and left first molar can be determined by the measuring apparatus and method of this study. 2. The measurement error of this method was not more than 0.1 degree. This value was sufficient for the purpose of this study.

Juxtapapillary retinochoroiditis with a psychiatric disorder possibly caused by toxoplasma

A 32-year-old man suffered from juxtapapillary retinochoroiditis in the right eye and a psychiatric disorder. The diagnosis of toxoplasmosis was supported by the clinical ocular findings, serologic examinations, and isolation of the organism from the cerebrospinal fluid. As the retinochoroidal lesion absorbed, the psychiatric symptoms also disappeared during the course of six weeks.