Showing papers in "Journal of Oral Rehabilitation in 2001"

Bruxism is mainly regulated centrally, not peripherally.

Abstract: Bruxism is a controversial phenomenon. Both its definition and the diagnostic procedure contribute to the fact that the literature about the aetiology of this disorder is difficult to interpret. There is, however, consensus about the multifactorial nature of the aetiology. Besides peripheral (morphological) factors, central (pathophysiological and psychological) factors can be distinguished. In the past, morphological factors, like occlusal discrepancies and the anatomy of the bony structures of the orofacial region, have been considered the main causative factors for bruxism. Nowadays, these factors play only a small role, if any. Recent focus is more on the pathophysiological factors. For example, bruxism has been suggested to be part of a sleep arousal response. In addition, bruxism appears to be modulated by various neurotransmitters in the central nervous system. More specifically, disturbances in the central dopaminergic system have been linked to bruxism. Further, factors like smoking, alcohol, drugs, diseases and trauma may be involved in the bruxism aetiology. Psychological factors like stress and personality are frequently mentioned in relation to bruxism as well. However, research to these factors comes to equivocal results and needs further attention. Taken all evidence together, bruxism appears to be mainly regulated centrally, not peripherally.

Water sorption and solubility of dental composites and identification of monomers released in an aqueous environment

Abstract: Water sorption and solubility of six proprietary composite resin materials were assessed, and monomers eluted from the organic matrix during water storage identified. Water sorption and solubility tests were carried out with the following storage times: 4 h, 24 h and 7, 60 and 180 days. After storage, water sorption and solubility were determined. Eluted monomers were analysed by high performance liquid chromatography (HPLC). Correlation between the retention time of the registered peak and the reference peak was observed, and UV-spectra confirmed the identity. The results showed an increase in water sorption until equilibrium for all materials with one exception. The solubility behaviour of the composite resin materials tested revealed variations, with both mass decrease and increase. The resin composition influences the water sorption and solubility behaviour of composite resin materials. The HPLC analysis of eluted components revealed that triethyleneglycol dimethacrylate (TEGDMA) was the main monomer released. Maximal monomer concentration in the eluate was observed after 7 days. During the test period, quantifiable quantities of urethanedimethacrylate (UEDMA) monomer were observed, whereas 2,2-bis[4-(2-hydroxy-3-methacryloyloxypropoxy)-phenyl]propane (Bis-GMA) was only found in detectable quantities. No detectable quantities of bisphenol-A were observed during the test period.

Degree of conversion and temperature rise during polymerization of composite resin samples with blue diodes.

Abstract: To ensure an adequate clinical composite filling light source for photopolymerization is of great importance. In everyday clinical conditions commonly used unit for polymerization of composite material is halogen curing unit. The development of new blue superbright light emitting diodes (LED) of 470 nm wavelengths comes as an alternative to standard halogen curing unit of 450-470 nm wavelengths. The purpose of this study was to compare the degree of conversion (DC) and temperature rise of four hybrid composite materials: Tetric Ceram, Pertac II, Valux Plus and Degufill Mineral during 40 s illumination with standard halogen curing unit Heliolux GTE of 600 mW cm(-2) intensity, Elipar Highlight soft-start curing unit of 100 mW cm(-2) (10 s) and 700 mW cm(-2) (30 s) intensity and 16 blue superbright LED of minimal intensity of 12 mW cm(-2) on the surface and 1 mm depth. The results revealed only a little bit higher DC values in case of polymerization with even 66 times stronger halogen curing units which showed twice higher temperature than blue diodes. Temperature and DC obtained are higher on the surface than on 1 mm depth regardless on the light source used.

Quantitative study of bite force during sleep associated bruxism

Abstract: Nocturnal bite force during sleep associated bruxism was measured in 10 subjects. Hard acrylic dental appliances were fabricated for the upper and lower dentitions of each subject. Miniature strain-gauge transducers were mounted to the upper dental appliance at the right and left first molar regions. In addition, thin metal plates that contact the strain-gauge transducers were attached to the lower dental appliance. After a 1-week familiarization with the appliances, nocturnal bite force was measured for three nights at the home of each subject. From the 30 recordings, 499 bruxism events that met the definition criteria were selected. The above described system was also used to measure the maximum voluntary bite forces during the daytime. The mean amplitude of detected bruxism events was 22.5 kgf (s.d. 13.0 kgf) and the mean duration was 7.1 s (s.d. 5.3 s). The highest amplitude of nocturnal bite force in individual subjects was 42.3 kgf (15.6-81.2 kgf). Maximum voluntary bite force during the daytime was 79.0 kgf (51.8-99.7 kgf) and the mean ratio of nocturnal/daytime maximum bite force was 53.1% (17.3-111.6%). These data indicate that nocturnal bite force during bruxism can exceed the amplitude of maximum voluntary bite force during the daytime.

Comparison of photo-activation versus chemical or dual-curing of resin-based luting cements regarding flexural strength, modulus and surface hardness.

Abstract: This study investigated the efficiency of chemical activation of dual-cure resin-based luting cements as compared with light- and dual-curing. Curing was performed by (i) mixing base and catalyst without subsequent irradiation (chemical curing=CC), (ii) mixing base and catalyst with direct irradiation (dual-cure=DC) or with (iii) irradiation through 2.5 mm of leucite-reinforced glass-ceramics (IPS Empress, Ivoclar) (dual-cure through porcelain=DCtP), (iv) using only the base paste with direct irradiation (light-curing=LC) or with (v) irradiation through porcelain (light-curing through porcelain=LCtP). Specimens of four fine-hybrid DC resin composites and one self-cure hybrid resin composite (only CC) were prepared and tested after 24 h for flexural strength, modulus of elasticity (ISO 4049) and surface hardness (Vickers). For all materials and parameters, dual-curing produced higher values than LC, even when irradiation was performed through porcelain. Following self-curing without photo-activation, flexural strength was 68.9-85.9%, the modulus 59.2-94.5% and Vickers hardness 86.1-101.4% of the corresponding values obtained by dual-curing with direct irradiation. Light-curing through porcelain as compared with direct irradiation reduced the values for most parameters and materials. In contrast, dual-curing maintained flexural strength for all, the modulus for three and the hardness for one of the materials. The mechanical properties of the self-curing resin cement ranged between those of the DC materials.

Obturator prostheses for hemimaxillectomy patients.

Abstract: Maxillary defects are created by surgical treatment of benign or malignant neoplasms, congenital malformation and by trauma. The size and location of the defects influence the degree of impairment and difficulty in prosthetic rehabilitation. Lack of support, retention, and stability are common prosthodontic treatment problems for patients who have had a maxillectomy. A prosthesis used to close a palatal defect in a dentate or edentulous mouth is referred to as an obturator. The obturator prosthesis is used to restore masticatory function and improve speech, deglutition and cosmetics for maxillary defect patients.

The effect of pH on the erosion of dentine and enamel by dietary acids in vitro

Abstract: The reported incidence of tooth erosion caused by acidic soft drinks has been increasingly documented. Citric and phosphoric acids are the two main dietary acids present in these soft drinks. Many variables need to be determined in order to assess risk factors for dental erosion caused by beverage consumption including pH, titratable acidity, pKa, buffering capacity, hence the aim of these in vitro investigations. Methodologies included profiling flat enamel and dentine samples (< +/- 0.3 microm profile) from unerupted human third molars. Groups of five specimens were placed in acidic solutions adjusted with alkali over the available pH range; citric, phosphoric and hydrochloric acid were adjusted with sodium hydroxide and citric acid with trisodium citrate. Tissue loss was calculated by profilometry. Results showed that under these conditions citric acid caused far more erosion over the pH range employed than phosphoric acid for both tissue types. Citric acid compared with hydrochloric acid highlighted dissolution and chelation effects. Phosphoric acid caused minimal erosion over pH 3 for enamel and pH 4 for dentine. These factors could be considered in order to reduce the erosivity of acidic soft drinks.

Fluoride release from glass-ionomer cements, compomers and resin composites.

Abstract: The short and long-term fluoride release of 16 products (seven conventional glass-ionomers, five light-activated glass-ionomers, two polyacid-modified resin composites and two resin composites) commercialized as fluoride-releasing materials were measured. A potential link between the material type and its level of fluoride release was researched. The fluoride release was evaluated after different time intervals. Initial fluoride release from all materials was highest during the first 24 h and decreased sharply over the first week. Some groups of materials appeared to be significantly different after, respectively, 7 and 91 days. However, it was impossible to correlate the fluoride release of the materials by their type (conventional or resin-modified glass-ionomers, polyacid-modified resin composite and resin composite) except if we compared the products from the same manufacturer. The link between fluoride release and an acid-base reaction seems to be confirmed. The glass-ionomer composition (glass particles and polyacid's type, powder/liquid ratio) should have more influence on fluoride release than material type.

Effect of different acid treatments on a porcelain surface.

Abstract: The objective of this study was to determine the effect of selected surface treatments on the surface texture of a feldspathic porcelain. The three different etchant treatments were, acidulated phosphate fluoride (APF) applied for 10 min and hydrofluoric acid (HF) applied for 1 and 4 min. After acid treatment, half of the specimens from each group were cleansed with water and others were subjected to ultrasonic cleaning and then dried. Half of the specimens cleansed with two different methods were treated with silane. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to characterize the effects of such treatments. Etching with APF displays shallow patterns. Etching for 1 min with HF displays deep channels, pores and precipitates on the surface and as the etching time increased these channels were replaced by larger channels. EDS analyses show that the crystalline precipitates on the etched surfaces, which were not readily soluble in water, were the reaction products of Na, K, Ca, Al, etc. HF displayed a more roughened surface than the APF gel. However, the precipitates remain on the surface after acid application, they can only be removed by ultrasonic cleaning and cannot be removed by rinsing.

Use of optical coherence tomography for assessment of dental caries: quantitative procedure.

Abstract: A method for quantitative assessment of dental caries using optical coherence tomography (OCT) was demonstrated. Development of caries lesions in 15 bovine teeth, by demineralization in acidic buffer solution, was quantitatively assessed daily for 3 days, using OCT. An OCT system which can collect A-scans (depth versus reflectivity curve), B-scans (longitudinal images) and C-scans (transverse images at constant depth) was used. While the B- and C-scans qualitatively described the lesion detected, the A-scan which showed the depth (mm) resolved reflectivity (dB) of the tooth tissue was used for the quantitative analysis. After a simple normalization procedure to determine the actual depth the light travelled into the tooth tissue, the area (R) under the A-scan was quantified as a measure of the degree of reflectivity of the tissue. The result showed that R (dB mm) decreased with increasing demineralization time. The percentage reflectivity loss (R%) in demineralized tissue, which related to the amount of mineral loss, was also calculated, and it was observed that R% increased with increasing demineralization time. It was concluded that with the above procedure, OCT could quantitatively monitor the mineral changes in a caries lesion on a longitudinal basis.

Chemical degradation of composite restoratives.

Abstract: The chemical environment is one aspect of the oral environment, which could have an appreciable influence on the in vivo degradation of composite restoratives. The effects of chemical media on surface hardness of four composite restoratives (Silux [SX], Z100 [ZO], Ariston [AR] and Surefil [SF]) were investigated. The relationship between hardness and the thickness of the degradation layer was also studied. Thirty six specimens (3 x 4 x 2 mm) were made for each material. Following polymerization, the specimens were stored in artificial saliva at 37 degrees C for 24 h. The specimens were then randomly divided into six groups of six, subjected to microhardness testing (load = 500 gf, dwell time = 15 s) and stored in the following chemicals for 1 week at 37 degrees C: artificial saliva (S), distilled water (W), 0.02 N citric acid (C), 0.02 N lactic acid (L), heptane (H) and 75-25% ethanol-water solution (E). After conditioning, the specimens were again subjected to hardness testing and sectioned. Change in hardness (DH) was computed and the thickness of the degradation layer (DL) was measured using a computerized image analysis system at 600x magnification. Results of statistical analysis (ANOVA/Scheffe's [P all other mediums; ZO - W > C; and AR - S, W, E > H (> indicates significantly greater hardness change). No significant difference in DH was observed between the different chemicals for SF. The effects of chemical media on DH were found to be material dependent. A significant but weak positive correlation (Pearson's correlation [P < 0.05]) exists between change in hardness and thickness of the degradation layer.

Bactericidal effect of dentin primer containing antibacterial monomer methacryloyloxydodecylpyridinium bromide (MDPB) against bacteria in human carious dentin.

Abstract: The aim of this study was to investigate the bactericidal effect of a dentin primer incorporating the antibacterial monomer 12-methacryloyloxydodecylpyridinium bromide (MDPB) against bacteria in human dentinal carious lesions. To evaluate the antibacterial activity of MDPB against anaerobes, the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) against obligate anaerobes and facultative anaerobic strains of lactobacilli were determined. Bacteria were recovered from carious dentin samples obtained from the teeth of patients, and the bactericidal activities of the experimental primer containing 5% MDPB and three commercially available primers were compared by counting the number of viable cells after contact with diluted solutions of each primer for 30 s. MDPB showed strong antibacterial activity against anaerobes, the MIC and MBC values ranging from 3.9 to 31.3 micrograms/ mL-1 and 15.6-125 micrograms/ mL-1, respectively. Experimental primer containing MDPB was the most bactericidal among the materials tested (ANOVA, Fisher's PLSD test, P < 0.05) and was able to kill the bacteria completely even when diluted 40 times, while the three commercial products exhibited little activity at 40 times dilution. These results indicate that incorporation of MDPB into dentin primer could be beneficial for eliminating the residual bacteria in cavities.

Oral habits among adolescent girls and their association with symptoms of temporomandibular disorders

Abstract: SUMMARY Aim: To evaluate the contribution of certain parafunctional activities to the presence of temporomandibular disorder (TMD) symptoms among teenage girls, with special emphasis to gum chewing and jaw play. Methods: A total of 323 girls, aged 15‐16 years, were randomly selected from a religious junior high school. The girls responded to a questionnaire on oral habits and TMD symptoms. Results: Gum chewing was a very prevalent habit (62AE4%), performed daily (mean chewing time 3AE95 h day )1 ). Girls who chewed intensively (more than 4 h day )1 ) showed associations with pain in the ear area during function and at rest, as well as with joint noises. Jaw play, although reported by only 14AE3%, was significantly associated with pain in the ear area during function and at rest, feeling of tiredness of the jaw while chewing, joint noises, catch and lock. All oral parafunctions, except chewing gum, were associated with jaw play and with each other. Conclusions: Jaw play was the most detrimental habit in TMD; intensive gum chewing was a potentially contributing factor for joint noises and pain. Oral parafunctions (except chewing gum) were significantly associated between themselves and suggest a behavioural pattern of ‘jaw hyper

Comparison of the erosive potential of gastric juice and a carbonated drink in vitro.

Abstract: The aim of this study was to compare the erosive effect of gastric juice and a carbonated drink on enamel and dentine by measuring release of calcium from 30 hemisectioned teeth in vitro. In addition, the titrable acidity (mL of 0.05 M sodium hydroxide required to neutralize) and pH of the fluids was estimated. The mean pH of the seven gastric acid samples was 2.92 (range 1.2-6.78) and mean titratable acidity 0.68 mL (range 0.03-1.64). Both the pH and the titratable acidity of the gastric juice varied between patients all of whom suffered from symptoms of reflux disease. The carbonated drink had a pH of 2.45 and a titratable acidity of 0.29 mL. The median amount of calcium released by the gastric acids from enamel was 69.6 microg L-1 (interquartile range 5.4-144) and 62.4 microg L-1 (2.2-125.3) from dentine. The carbonated drink released 18.7 microg L-1 (13.4-23.4) and 18.6 microg L-1 (11.9-35.3), respectively. The differences in calcium release by gastric juice and the carbonated drink were statistically significant for both enamel (P < 0.005) and dentine (P < 0.01). It is concluded that gastric juice has a greater potential, per unit time, for erosion than a carbonated drink.

Pain measurement in TMD patients: evaluation of precision and sensitivity of different scales

Abstract: The aim of this study was to evaluate the precision and sensitivity of four different pain rating scales in 59 temporomandibular disorders (TMD) patients. The capacity of describing changes in symptoms during treatment was also addressed. All patients were asked to answer four pain scales: Visual Analogue Scale (VAS), Numerical Scale (NS), Behaviour Rating Scale (BRS) and Verbal Scale (VS). Two measurements were taken before any treatment. After beginning it, follow-ups and repeated measurements were taken 1 week, 15 days, and every month for 6 months. Statistical analysis showed significant differences (P 0.05), when the two initial measurements were analysed. Regarding the sensitivity, all pain scales demonstrated general symptom improvement of 30-50%, when initial and final figures were compared (P < 0.01). Also, the most significant improvement occurred in the first 2 months after beginning the management programme. Authors concluded that the NS was more accurate to measure reproducibility of pain. As for the capacity of expressing changes during the treatment, all scales demonstrated symptom decrease of 30-50% in a period of 6 months. Caution when analysing the results is recommended because of the subjective aspect of pain measurement, the absence of a 'gold standard' for comparison and the natural fluctuation of TMD symptoms.

An investigation into the importance of the periodontal ligament and alveolar bone as supporting structures in finite element studies.

Abstract: Many finite element analyses studies have been published in the dental literature. Some of these have analysed just the crown of the tooth, others have included part or all of the root, while others have included the supporting periodontal ligament and alveolar bone. The aim of this study was to examine which of the supporting structures was important to the model when analysing the stress distribution within a tooth. A two-dimensional plane strain finite element model of a lower second pre-molar was developed, which included the supporting periodontal ligament and alveolar bone. Two 50 N loads were applied to simulate the effect of a load in centric occlusion. The nodal x, y and shear stresses were recorded along two horizontal planes, one in the crown and one in the cervical region. Each of the supporting structures was systematically removed and the remaining structures reanalysed. It was found that it was particularly important to include both the periodontal ligament and alveolar bone when undertaking the finite element analyses of teeth.

The influence of fibre placement and position on the efficiency of reinforcement of fibre reinforced composite bridgework.

Abstract: The effect of placement of ultra-high molecular weight polyethylene (UHMWPE) fibres on the flexural properties and fracture resistance of a direct dental composite was investigated. The UHMWPE fibres are increasingly being used for the reinforcement of laboratory fabricated resin composite crown and bridgework. The aim of this study was to assess the effect of a commonly used laboratory fabrication variable on the in vitro strength of beam shaped specimen simulating a three-unit fixed bridge. Four groups (10 specimens per group) of Herculite XRV were prepared for flexural modulus and strength testing after reinforcement with UHMWPE fibres. Two groups of control specimens were prepared without any fibre reinforcement. Half the specimen groups were stored in distilled water and the other groups were stored dry, both at 37 degrees C for 2 weeks before testing. The results of this study showed that placement of fibre at or slightly away from the tensile side improved the flexural properties of the composite in comparison with the unreinforced control specimen groups whilst the mode of failure differed according to fibre position. Scanning electron microscope (SEM) investigation revealed that placement of the fibre slightly away from the tensile side favoured crack development and propagation within the resin bridging the interfibre spaces in addition to debonding parallel to the direction of fibre placement. Laboratory fabrication variables may effect the strength of fibre reinforced bridgework significantly.

Effectiveness of exercise therapy in patients with internal derangement of the temporomandibular joint.

Abstract: SUMMARY This study intended in evaluating the effectiveness of exercise therapy in patients with craniomandibular disorders (CMD). Twenty consecutive patients suffering from CMD with anterior disc displacement without reduction consulting a CMD service were included in the study if they met following criteria: (i) pain in the temporomandibular region, (ii) reduced incisal edge clearance (<35 mm), (iii) magnet resonance imaging confirmed anterior disc displacement without reduction and (iv) evidence of postural dysfunction. All patients were assigned to a waiting list, serving as a no-treatment control period, according to a before‐ after trial. The treatment consisted of active and passive jaw movement exercises, correction of body posture and relaxation techniques. A total of 18 patients completed the study, no adverse effects occurred. Following main outcome measures were evaluated: (1) pain at rest (2) pain at stress (3) impairment (4) mouth opening at base-line, before and after treatment and at 6 month follow-up. As a result of treatment pain, impairment and mouth opening improved significantly more than during control period (paired samples t-test P <0 AE05). After treatment four patients had no pain at all (chisquare: P <0 AE05) and only seven patients revealed an impaired incisal edge clearance after treatment. (chi-square Test, P <0 AE001). At follow up, seven patients had no pain and experienced no impairment. Exercise therapy seems to be useful in the treatment of anterior disc displacement without

The relationship of bruxism with craniofacial pain and symptoms from the masticatory system in the adult population.

Abstract: The association of bruxism with craniofacial pain and symptoms of dysfunction of the masticatory system was assessed in a sample of 483 adult subjects, aged 18-75 years and selected from the general population living in the municipality of Segrate, a metropolitan area in northern Italy. Subjects were interviewed by a questionnaire about oral conditions, occurrence of symptoms of masticatory disturbances, craniofacial and neck pain. The overall prevalence of bruxism was 31;4% (95% confidence interval (CI): 27;3-35;5%). At univariate analysis bruxism was significantly associated with craniofacial pain, difficulty in closing the mouth, difficulty in opening the mouth wide or in locking the mouth, temporomandibular joint sounds, pain on movement, a feeling of stiffness or fatigue of the jaws, and neck pain. After adjustment for reciprocal influences and confounding variables, logistic regression analysis disclosed a strong independent association of bruxism with difficulty in closing the mouth (adjusted odds ratio, (OR): 2;84, 95% CI: 1;68-4;48), and a weaker relationship with craniofacial pain (adjusted OR: 1;84, 95% CI: 1;16-2;93) and temporomandibular joint sounds (adjusted OR: 1;64, 95% CI: 1;00-2;69). The findings show that in the general adult population there is a complex connection among bruxism, craniofacial pain and symptoms of masticatory disturbances. Furthermore, they suggest that the most direct relationship of bruxism may be with difficulties in mouth movements, but also an independent association may exist with craniofacial pain and other symptoms of temporomandibular disorder.

Multifactorial analysis of an MOD restored human premolar using auto-mesh finite element approach.

Abstract: The use of an mesial-occlusal-distal (MOD) restoration in repairing a large carious lesion depends on many factors. Biomechanical performance is one of the most important. It has been recognized that resistance to restoration failure is not solely a biological concern (e.g. toxicity), but that the cavity shape, dimensions, and the state of stress must all be taken into account. In the present study, a newly developed auto-mesh program was used to generate 30 three-dimensional (3D) finite element (FE) models simulating the biomechanics for multiple factorial design of the MOD gold restoration in a maxillary second premolar. Stress levels were related to individual design factors (e.g. pulpal wall depth [P], isthmus width [W] and interaxial thickness [T]) and to their interactions under the worst physiological scenario: a concentrated bite force acting on lingual cusp with debonded interfaces between cavity walls and restorations. The results showed that enlarging the volume of the MOD cavity significantly increased stresses in enamel but did not intentionally affect stresses in dentin. The alternation of individual design parameters significantly changed the peak stresses (P < 0.05). For all three parameters, except for the width, the peak stress increased as the cavity dimension increased. Stress elevation rate (termed as 'volumetric stress rate'--stress elevation by increasing one unit volume of the restored materials) was different among three design factors. Depth was the most critical factor governing the stress elevation in enamel (1.76 MPa mm(-3)) while length (interaxial thickness) was the most important parameter in dentin (0.49 MPa mm(-3)). Width was the least compromising factor to the remaining tooth, 0.32 MPa mm(-3) for enamel and -0.23 MPa mm(-3) for dentin. The findings, at its core, did not fully agree with the traditional concept that the preservation of tooth substances will reduce risk of tooth fracture. This study leaves open possibility for the structural optimization of the MOD restoration.

The effects of oxalate-containing products on the exposed dentine surface: an SEM investigation

Abstract: In-office products containing oxalates have been claimed to be clinically effective in reducing dentine sensitivity, although there has been limited supporting clinical data. The rationale for their use appears to be based on their potential to act as occluding and/or nerve desensitizing agents. Four commercially available oxalate-containing products were applied to etched dentine discs and the extent of tubule occlusion was observed by scanning electron microscopy. Tenure Quick (aluminium oxalate), Sensodyne Sealant (ferric oxalate) and MS Coat (oxalic acid) covered the dentine surface and occluded the tubules. However, Butler Protect (potassium oxalate) did not cover the surface to any great extent but provided some occlusion. The presence of oxalates after application to glass slides and dentine discs was examined using thin film X-ray diffraction. From samples on glass, only potassium oxalate could be clearly identified (JCPDS 14-0845). No oxalate was detected on dentine discs in either thin film geometry or standard theta two theta mode. We have demonstrated that professionally applied in-office products containing oxalate are capable of covering the dentine surface and/or occluding the tubules to varying degrees. However, X-ray diffraction analysis was unable to confirm the oxalate profile for all products as described in the available commercial literature.

Effect of desensitizers on bond strength of adhesive luting agents to dentin.

Abstract: The current study investigates the influence of three dentin hypersensitivity treating agents (Gluma CPS, MS Coat and Saforide) on bond strength to dentin of two luting agents (Panavia Fluoro Cement and Super-Bond C & B). Sixty bovine dentin substrates were divided into 12 combinations of four treatment conditions (Gluma CPS, MS Coat, Saforide and control) and three adhesive systems (AD Gel sodium hypochlorite + Panavia Fluoro Cement, Panavia Fluoro Cement without AD Gel and Super-Bond C & B). After bonding the treated teeth to steel rods, 24-h tensile bond strengths were determined, and average values (n=5) were compared by analysis of variance (ANOVA). Without application of the desensitizers, bond strengths of the two groups (Super-Bond C & B, 10.2 MPa; AD Gel + Panavia, 11.5 MPa) were comparable, and they were greater than the group bonded with the Panavia material with no AD Gel conditioning (7.1 MPa). Application of the Saforide ammoniated silver fluoride desensitizer reduced bond strength of both the Super-Bond and Panavia luting agents, whereas the MS Coat polymeric agent negatively affected bond strength of the Panavia cement only. The use of the Gluma desensitizer did not affect bond strength of any of the three adhesive systems, and the bond strength of the Panavia cement with the AD Gel conditioning was not reduced by application of any of the three desensitizers. The four combinations of two desensitizers (MS Coat and Gluma CPS) and two adhesive systems (Super-Bond C & B and AD Gel + Panavia) are deemed to be applicable to fixed prosthodontic treatment.

Comparison of maximum bite force and dentate status between healthy and frail elderly persons

Abstract: The purpose of the present study was to (1) determine the standard value of maximum bite force and to (2) compare the maximum bite force of the elderly between healthy and frail subjects. Subjects included 349 healthy elderly individuals (149 males, 200 females) and 24 frail elderly individuals (seven males, 17 females) ranging from 65 to 74 years of age. Maximum bite force was evaluated using a Dental Prescale system. The maximum bite force of the healthy subjects was significantly higher than that of the frail subjects in both males (P=0.020) and females (P=0.015). However, no significant difference was observed in the number of present teeth between the healthy and frail subjects. Median of maximum bite force in healthy males was 408.0 N, and that of the healthy females was 243.5 N. These results suggest that the frail elderly have latent bite force problems.

Prevalence of temporomandibular dysfunction in Turkish children with mixed and permanent dentition

Abstract: This study was carried out to determine the prevalence of temporomandibular joint (TMJ) dysfunction in mixed and permanent dentition and to evaluate the sex distribution in Turkish children. One hundred and eighty-two children with mixed dentition and 212 with permanent dentition were selected for the study, which used a questionnaire and clinical examination. Children with one or more signs (TMJ sounds, TMJ tenderness, muscle tenderness, restricted mouth opening) and/or symptoms (TMJ pain during mastication and mouth opening, restriction of the jaw opening and TMJ sounds) met the criterion of TMJ dysfunction. The total prevalence of signs and symptoms of TMJ dysfunction in the studied population was 68% (68% in girls and 68% in boys) in mixed dentition and 58% (61% in girls and 56% in boys) in permanent dentition. The Z-test and analysis of variance (ANOVA) were used for statistical analysis of the difference between the results. The total prevalence of signs and symptoms of TMJ dysfunction in mixed dentition was found to be higher than in permanent dentition (P < 0.05). No statistically significant difference was found in the total prevalence of TMJ dysfunction between girls and boys.

Surface roughness and wettability of enamel and dentine surfaces prepared with different dental burs.

Abstract: The aim of dental adhesive restorations is to produce a long lasting union between the restoration and the tooth structure. This bond depends on many variables including the geometry of the preparation and the type of bonding agent or luting cement. It is therefore suggested that the topography of the tooth surface may influence the wettability and the bonding quality of adhesive systems. This study measured the surface roughness and wettability of enamel and dentine after preparation with different dental burs. The mesial and distal surfaces of 15 extracted sound human premolar teeth were prepared with a tungsten carbide crown bur, a diamond bur and a tungsten carbide finishing bur and finished in enamel or dentin, respectively. The prepared surfaces were analysed with a surface profilometer and scanning electron microscopy (SEM). The contact angle of distilled water on each of the prepared surfaces was used as the measure of wettability. The differences in average surface roughness (Ra) were significant between the rotary instrument groups, as revealed by a two-way ANOVA test. No differences were detected between enamel and dentine surfaces prepared with the same type of dental bur. The smoothest surfaces were those completed with tungsten carbide finishing burs. The diamond bur preparations were intermediate in the roughness assessment and the tungsten carbide crown burs gave the roughest surfaces. There were no significant differences in the contact angle measurements for the various groups. It was concluded that the surface roughness of enamel and dentine prepared by different rotary instruments had no significant influence on the wettability of distilled water on these surfaces.

Heat‐cured acrylic resin repaired with microwave‐cured one: bond strength and surface texture

Abstract: This study evaluated the influence of chemical surface treatments in the repair strength of a heat-cured acrylic resin (Lucitone 550, (LU)). A total of 70 specimens were made with LU according to American Dental Association (ADA) specification No. 12. Of these, 14 remained intact and were used as a control group (GI). A total of 56 specimens were selected randomly. These specimens were cut in the middle (10 mm), repaired with a microwave acrylic resin (Acron MC (AC)), and processed in a microwave oven for 3 min at 500 W. Prior to the repair, the surface of the cut ends received different chemical treatments (GIII = AC monomer dipping/30 s; GIV = acetone dipping/30 s; GV = acetone dipping/15 s + blast of air + AC monomer dipping/15 s; GVI = no wetting treatment). However, 14 intact specimens made with AC formed a second control group (GII). The effect of the chemical treatments on the surface texture of LU was observed with scanning electron microscopy. Flexural test results were submitted to paired t-test and showed statistical differences (P < 0.05) only between the pairs GIV-GV and GIV-GVI. Strength mean values of repaired specimens were statistically lower (79-90%) than GII mean values. Strength mean values of GVI and GIV were 93 and 106%, respectively, of GI mean, showing no statistical differences. Scanning electron microscopic observations revealed various effects of the chemical treatments on the denture base resin surface. In conclusion, the wetting surface treatments affected the bond strength between the two acrylic resins, and no statistical differences in strength were observed between intact heat-cured denture base material and the same material repaired with microwave acrylic resin.

Improved bonding of adhesive resin to sintered porcelain with the combination of acid etching and a two‐liquid silane conditioner

Abstract: This study determined the bond strengths of adhesive resins joined to a feldspathic porcelain (VMK 68) for the purpose of developing the most durable surface preparation for the porcelain. Three porcelain surfaces-ground, air-abraded with alumina, and etched with hydrofluoric acid-were prepared. A two-liquid porcelain conditioner that contained both 4-methacryloyloxyethyl trimellitate anhydride (4-META) and a silane coupler (Porcelain Liner M) was used as the priming agent. Each of the two liquid components of the conditioner was also used individually in order to examine the effects of the respective chemical ingredients on adhesive bonding. Two methyl methacrylate (MMA)-based resins initiated with tri-n-butylborane (TBB) either with or without 4-META (MMA-TBB and 4-META/MMA-TBB resins) were used as the luting agents. Shear bond strengths were determined both before and after thermocycling. Shear testing results indicated that thermocycling was effective for disclosing poor bonding systems, and that both mechanical and chemical retention were indispensable for bonding the porcelain. Of the combinations assessed, etching with hydrofluoric acid followed by two-liquid priming with the Porcelain Liner M material generated the most durable bond strength (33.3 MPa) for the porcelain bonded with the 4-META/MMA-TBB resin (Super-Bond C&B).

Influence of thermal cycles in water on flexural strength of laboratory-processed composite resin.

Abstract: Recently a new generation of laboratory-processed composite resins containing submicron glass fillers was introduced, with claims of high strength. The purpose of this study was to evaluate the effect of thermal cycling in water on the flexural strength and hardness of several laboratory composite systems. The flexural strength of the new laboratory processed composite resins (Artglass [AG], Targis [TR] and Estenia [ES]) was significantly higher than that of conventional resins (Dentacolor [DC] and Cesead II [CS]). Thermocycling caused a reduction of the flexural strength but not a reduction of the hardness for most of materials tested. It was concluded that thermocycling affected the properties of the laboratory-processed hybrid type composite resin, ES, AG and TR. However, the changes of these properties were smaller than those of microfine type composite resin DC. Thus, ES, AG and TR may maintain better properties during service compared with DC.

Determination of elastic properties of metal alloys and dental porcelains.

Abstract: This study aimed to determine Young's modulus, shear modulus and Poisson's ratio of some metal alloys and dental porcelains used in fixed prosthodontics using the technique of impulse excitation of vibration. It also aimed to compare Young's modulus values of these materials with those obtained using the other two methods: the four-point flexural test and the indentation test using the ultra micro-indentation system (UMIS). Five types of metal alloys and four types of dental porcelains were tested. The samples were prepared to a rectangular shape of approximately 8 x 30 x 1.5 mm. Frequency of vibration in a sample was read when a singular elastic strike was made with an impulse tool. The elastic constants were calculated from the frequency of vibration, dimension and mass of each sample. Young's modulus values resulting from the impulse excitation of vibration are not significantly different (P<0.05) from those obtained using the flexural test and the UMIS test in most metal alloys but are different in titanium, titanium alloy and most of the dental porcelains. The technique of impulse excitation of vibration has proven to be an accurate method and is simple to operate. The elastic properties of these alloys and porcelains are essential for determining the other mechanical properties (fracture toughness) and are relevant in clinical application.

Bonding strength between a hard chairside reline resin and a denture base material as influenced by surface treatment

Abstract: Direct relining of dentures made with hard chairside reline resins is faster than laboratory-processed reline systems and the patient is not without the prosthesis for the time necessary to perform the laboratory procedures. However, a weak bond between the autopolymerizing acrylic reline resins and the denture base material has been observed. This study evaluated the effect of six different surface treatments on the bond strength between a hard chairside reline acrylic resin and a heat-cured acrylic resin. Specimens of the heat-cured acrylic resin were divided into seven groups. One of these groups remained intact. In the other groups, a 10-mm square section was removed from the centre of each specimen. The bonding surfaces were then treated with (i) methyl methacrylate monomer, (ii) isobutyl methacrylate monomer, (iii) chloroform, (iv) acetone, (v) experimental adhesive and (vi) no surface treatment -- control group. Kooliner acrylic resin was packed into the square sections and polymerized. The bonding strength was evaluated by a three-point loading test. The results were submitted to one-way analysis of variance (ANOVA) followed by a Tukey multiple range test at a 5% level of significance. No significant difference was found between the surface treatment with Lucitone 550 monomer or chloroform, but both were stronger than the majority of the other groups. The bond strength provided by all the surface treatments was lower than that of the intact heat-cured resin.