Debonding of Leucite-reinforced Glass-ceramic Veneers Using Er, Cr:YSGG Laser Device: Optimizing Speed with Thermal Safety.

CLINICAL RELEVANCE: Removing laminate veneers on anterior teeth by using an Er,Cr:YSGG dental laser can be completed faster than previously reported while maintaining thermal safety.

Stress analysis during jaw movement based on vivo computed tomography images from patients with temporomandibular disorders.

The purpose of this study is to develop three-dimensional (3D) finite element models of temporomandibular joints (TMJs) and to investigate stress distributions. To determine the causes of temporomandibular disorders (TMDs), the magnitude and location of the maximum stresses under physiological loading must be considered. Stress analysis TMD models were reconstructed from computed tomography (CT) data. Several studies have investigated finite element TMJ models, but few have used a bilateral mandible model that includes jaw closing and maximum opening. In this study, the authors defined an asymmetry index for the different stress values on each side joint; this index has not yet been investigated. According to clinical observation, one joint affects the other side joint during mastication. Three symptom-free volunteers and three symptomatic patients were selected as the control group (CG) and TMD group (TG), respectively. For the TG, data analysis indicated that the condyle was asymmetrical during jaw closing, while both the condyle and disc were slightly asymmetrical during jaw opening. The maximum stresses did not significantly differ between the CG and TG for either closing or opening of the jaw. The results of this study have a potential clinical benefit in terms of proving superior biomechanical behaviour.

Effect of damping properties on fracture resistance of root filled premolar teeth: a dynamic finite element analysis.

AIM: To evaluate the ex vivo effects of damping on stress concentration in root filled premolar teeth. METHODOLOGY: Damping ratios of maxillary premolar teeth that had undergone root canal treatment were tested in a laboratory model. In addition, two-dimensional finite element (FE) models were established for dynamic analysis. RESULTS: The mean-damping ratio was significantly lower in premolar teeth that had undergone root canal preparation (8.50 +/- 0.53%) than in unprepared teeth (14.42 +/- 2.17%) (P < 0.05). However, root filling had a significant positive effect on the damping ratio of the tooth (10.84 +/- 1.70%) (P < 0.05). When the damping ratio was taken into consideration, FE analysis revealed that peak stresses in the apical one-third of the root on the buccal side were reduced by 31.8% when mastication forces were applied on the palatal cusp and occlusal fossa. CONCLUSION: Pulp tissue plays an important role in providing protective effects when teeth are subjected to a dynamic load. However, root filled teeth do not provide such protective effects.

Detection of the furcation involvement of a multi-rooted molar using natural frequency analysis: a numerical approach.

The aim of this study was to evaluate the potential for using the natural frequency (NF) as a parameter to detect vertical bone loss at the furcation of human molars as well as to assess the role that the surrounding bone plays in maintaining molar stability. A three-dimensional finite element model of the human maxillary molar was built. The NF values of the molar modal were calculated with one-sided, two-sided, and three-sided vertical bone loss. It was found that the change in the NF was less than 25 per cent in molars with a one-sided defect when the bone level varied by 10 mm from the cementoenamel junction. However, when a three-sided bony defect was simulated, the change in the NF ranged from 40 to 60 per cent. In addition, it was found that bone loss that had reached the furcation entrance (4 mm) resulted in a sharp change in the NF value. Furthermore, it was found that bone loss involving the mesial and distal surfaces resulted in a larger decrease in the NF value compared with bone loss involving the buccal and palatal surfaces. These results demonstrated that the bone surrounding the mesial and distal sides plays a more important role in maintaining molar stability than does the bone surrounding the buccal and palatal sides.

Natural frequency analysis of tooth stability under various simulated types and degrees of alveolar vertical bone loss.

The aim of this study was to test natural teeth stability under various simulated types and degrees of alveolar vertical bone loss, as well as to assess the role that the surrounding bone played for maintaining tooth stability. A three-dimensional finite element model of the human maxillary central incisor with surrounding tissue, including periodontal ligament, enamel, dentin, pulp, and alveolar bone, was established. One side and multiple vertical bone loss were simulated by means of decreasing the surrounding bone level apically from the cemento-enamel junction in 1 mm steps incrementally downward for 10 mm. Natural frequency values of the incisor model with various types and degrees of bone loss were then calculated. The results showed that, with one-sided bone resorption, the model with labial bone loss had the lowest natural frequency decreasing rates (8.2 per cent). On the other hand, in cases of multiple bone loss, vertical bone resorption at the mesial and distal sides had more negative effects on tooth stability compared to vertical bone losses on facial and lingual sides. These findings suggest that the natural frequency method may be a useful, auxiliary clinical tool for diagnosis of vertical periodontal diseases.

Design of a stability-detecting device for dental implants.

Resonance frequency (RF) analysis technology was used to design a dental implant stability detector. The device uses a miniature-sized electromagnetic triggering rod to elicit vibration in a dental implant. Vibrational signals were recorded via an acoustic receiver. To assess the in vivo performance of the test apparatus, animal models were used. Implants were placed in the left tibia of 12 rabbits using a conventional surgical procedure. Standard 3.2 mm x 8 mm implants were placed in each test tibia with pre-tapping cavities of 3.2 mm and 3.7 mm diameters to simulate either a 'well-fitting' or a 'loosely fitting' situation. The RF values of the test implants were detected by the newly developed device which was directly mounted on the healing abutments of the implants. The results showed that the RF values of the implants under well-fitting conditions significantly increased (p < 0.01) 3 weeks after surgery and reached a plateau at around 6-7 weeks. Meanwhile implants with higher initial RF values had shorter healing times and higher final RF values at the plateau. Based on these findings, it was concluded that the idea of using the current designed device for detecting the degree of bone healing during the osseointegration process seems feasible.

Comparative allergenicity studies of native and recombinant Blomia tropicalis Paramyosin (Blo t 11).

BACKGROUND: The complementary DNA (cDNA) encoding for Blo t 11, a 102 kD allergen from Blomia tropicalis (Bt) was isolated, expressed and characterized previously. This study aimed to isolate the native Blo t 11 allergen and compare its allergenicity with the recombinant forms. METHODS: Native Blo t 11 (nBlo t 11) was isolated from crude Bt extract by immuno-affinity chromatography, analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blot, and verified by MALDI-TOF MS. Recombinant full-length Blo t 11 (rFL-Blo t 11) and its immunodominant peptide (fD) were expressed as glutathione S-transferase (GST)-fusion proteins in Escherichia coli. Immunoglobulin E (IgE) reactivity of the Blo t 11 allergens were determined by enzyme-linked immunosorbent assay (ELISA) and skin prick test. The inhibition capacity of the nBlo t 11 against fD and vice versa was determined by absorption studies. RESULTS: Affinity purified nBlo t 11 was susceptible to degradation with the major degraded product resolved at approximately 66 kD. The nBlo t 11 was confirmed by immunoblot analysis and MALDI-TOF MS that generated 13 peptides with complete identity to the deduced amino acid sequence of Blo t 11. Comparative in vitro and in vivo allergenicity tests and the cross inhibition studies between the native and recombinant Blo t 11 showed that recombinant fD, but not the rFL-Blo t 11, has comparable IgE reactivity with the native counterpart. CONCLUSIONS: This comparative study confirmed that the recombinant peptide fD contains the main immunodominant region of Blo t 11. This recombinant peptide, instead of the full-length protein, is a good candidate for diagnostic and therapeutics development for mite allergy.

Immunochemical characterization of edible bird's nest allergens.

BACKGROUND: We have previously described anaphylaxis induced by edible bird's nest (BN) and demonstrated that this condition is IgE mediated. OBJECTIVES: This study aimed at describing the immunochemical properties of the BN allergens. Comparative studies between 3 commercially available sources (according to the country of origin) of BN were also made. METHODS: Crude extracts of commercially available processed BN from Sarawak (Malaysia), Thailand, and Indonesia and fresh unprocessed BN from the caves of Sarawak were obtained by means of aqueous extraction. Specific IgE toward these sources were determined by using fluorescence allergosorbent tests (FASTs). Cross-reactivity studies between the 3 sources of commercially available processed BN were carried out by means of FAST inhibition. Immunochemical characterization by means of IgE immunoblot, periodate treatment, and heat stability studies were carried out on fresh unprocessed BN from Sarawak. RESULTS: Serum from allergic patients showed differences in IgE binding to the 3 sources of commercially available BN, with the highest levels of specific IgE recorded with the Sarawak source (P <.0001). Of these, only the Sarawak and Thailand sources showed considerable cross-reactivity. Further work on the unprocessed fresh Sarawak source identified a putative 66-kd major allergen containing several isoforms. Periodate treatment resulted in loss of IgE binding. Despite a progressive decline in the molecular weights of allergens on SDS-PAGE with increasing periods of boiling, IgE binding, as assessed by means of FAST, was not affected. N-terminal sequence of the major putative allergen (66 kd) showed homology to a domain of an ovoinhibitor precursor in chicken (SWISS-PROT accession No. P10184). CONCLUSIONS: We have described the immunochemical properties of BN allergens. Edible BN from different sources are allergenically dissimilar. The putative major allergen is a 66-kd protein.