Distance of the contact glide in the closing masticatory stroke during mastication of three types of food

Summary  This study was designed to characterize the distance of the contact glide in the closing masticatory stroke in healthy adult subjects, during chewing of three types of food (crustless bread, chewing gum and peanuts). Mandibular movements (masticatory movements and laterality movements with dental contact) were registered using a gnathograph (MK-6I Diagnostic System) on the right and left side during unilateral chewing of the three food types. Length of dental contact was measured in masticatory cycle, which is defined as where the terminal part of the chewing cycles could be superimposed on the pathways taken by the mandible during lateral excursions with occlusal contacts. The length of dental contact during mastication of chewing gum is 1·46 ± 1 mm, during chewing of soft bread is 1·38 ± 0·7 mm and during chewing of peanuts is 1·45 ± 0·9 mm. There is no significant difference in the lengths of dental contact during mastication of three types of foods that enable direct tooth gliding.     

Colour compatibility between teeth and dental shade guides in Quinquagenarians and Septuagenarians

Summary  The aim of this investigation was to determine colour compatibility between dental shade guides, namely, VITA Classical (VC) and VITA 3D-Master (3D), and human teeth in quinquagenarians and septuagenarians. Tooth colour, described in terms of L * a * b * values of the middle third of facial tooth surface of 1391 teeth, was measured using VITA Easyshade in 195 subjects (48% female). These were compared with the colours ( L * a * b * values) of the shade tabs of VC and 3D. The mean coverage error and the percentage of tooth colours being within a given colour difference (Δ E _ab ) from the tabs of VC and 3D were calculated. For comparison, hypothetical, optimized, population-specific shade guides were additionally calculated based on discrete optimization techniques for optimizing coverage. Mean coverage error was Δ E _ab  = 3·51 for VC and Δ E _ab  = 2·96 for 3D. Coverage of tooth colours by the tabs of VC and 3D within Δ E _ab  = 2 was 23% and 24%, respectively, (Δ E _ab  ≤ 2 as clinically acceptable match). The hypothetical guides performed better and would only need seven to eight tabs to reach the same results as VC and 3D. Both guides had a mean coverage error that was too high and coverage that was too low according to an acceptable colour difference of tooth colour for these subjects. The optimized hypothetical, population-specific guides performed better indicating the possibility for improvement in colour compatibility of the guides with tooth colour in future shade guide development, allowing acceptable shade matching for most of the patients in clinical routine.     

Efficacy of alpha lipoic acid in burning mouth syndrome: a randomized, placebo-treatment study

Summary  To study the efficacy of alpha lipoic acid (ALA) in a group of patients with burning mouth syndrome (BMS). Sixty BMS patients, 30 treated with ALA (Thioderm^®) 800 mg day⁻¹ for 8 weeks and 30 patients on the same protocol with a placebo. The symptomatology was measured on a Visual Analogue Scale (VAS). Sixty patients (54 females and 6 males, mean age 64·37 ± 11·61 years) were included. Thirty-nine patients completed the treatment (23 with ALA and 16 with a placebo). Reviews were carried out at 0, 1 and 2 months. No statistically significant differences were found in the average pre- and post-treatment values for pain with the VAS scores, obtained in the placebo (6·6 ± 2·5 − 2·8 ± 25 = 3·8 ± 3·7) versus ALA (6·3 ± 2·8 − 4·0 ± 2·7 = 2·2 ± 2·6). Only one patient pertaining to the group treated with ALA abandoned because of adverse gastrointestinal side effects. The results showed no significant differences between the two groups.     

Decrease of γ1 lattice constant with time in dental silver amalgam

Abstract— As a measure of the mercury content of the γ₁ phase in dental silver amalgam, the lattice constant of this phase in different amalgams was determined at various times after trituration. The lattice constants of amalgams prepared from alloys with a high silver content have lower values and show a steeper decline with time than amalgams with a low Ag-content. Therefore, since a higher lattice constant presumably is associated with increased mercury vapor, the mercury vapor emission from amalgams with a low Ag-content probably is greater than from amalgams with a high Ag-content, especially during the first weeks after trituration.     

The effects of lavender scent on dental patient anxiety levels: a cluster randomised-controlled trial

Kritsidima M, Newton T, Asimakopoulou K. The effects of lavender scent on dental patient anxiety levels: a cluster randomized-controlled trial. Community Dent Oral Epidemiol 2010; 38: 83–87. © 2009 John Wiley & Sons A/S   Abstract – 
Objectives:  To review the effect of lavender scent on anticipatory anxiety in dental participants.
Methods:  In a cluster randomized-controlled trial, patients' ( N  = 340) anxiety was assessed while waiting for a scheduled dental appointment, either under the odor of lavender or with no odor. Current anxiety, assessed by the brief State Trait Anxiety Indicator (STAI-6), and generalized dental anxiety, assessed by the Modified Dental Anxiety Scale (MDAS) were examined.
Results:  Analyses of variance ( anova s) showed that although both groups showed similar, moderate levels of generalized dental anxiety (MDAS F _(1,338) = 2.17, P  > 0.05) the lavender group reported significantly lower current anxiety (STAI: F _(1,338) = 74.69, P  < 0.001) than the control group.
Conclusions:  Although anxiety about future dental visits seems to be unaffected, lavender scent reduces state anxiety in dental patients.     

Proliferative activity of cells from remaining dental pulp in response to treatment with dental materials

Background:  The biological examination of pulp injury, repair events and response of dental pulp stem cells to dental restorative materials is important to accomplish restorative treatment, especially to commonly used dental materials in paediatric dentistry, such as glass ionomer cement (GIC) and calcium hydroxide (Ca(OH)₂) lining cement.
Methods:  Healthy patients aged between 9 to 11 years with carious primary molars without pulp exposure were selected and divided into two groups: Group 1 (teeth restored with GIC) and Group 2 (teeth lined using Ca(OH)₂ and restored with GIC). The proliferative activity of stem cells of teeth between these two groups was compared using colourimetric cell proliferation reagent, alamarBlue. Immunocytochemistry and flow cytometry confirmation were performed using mesenchymal stem cell markers, CD105 and CD166.
Results:  The proliferative activity using alamarBlue™ assay showed that cells derived from the remaining dental pulp of exfoliated deciduous teeth were positive for CD105 and CD166 and exhibited no difference between the two groups.
Conclusions:  It can be concluded that the use of Ca(OH)₂ or GIC as a lining material in indirect pulp capping procedures has the same effect on cells derived from the remaining dental pulp of exfoliated deciduous teeth which have responded favourably to the restorative treatments.     

Load-bearing capacity of all-ceramic posterior inlay-retained fixed dental prostheses

The purpose of this in vitro study was to compare the quasi-static load-bearing capacity of all-ceramic resin-bonded three-unit inlay-retained fixed dental prostheses (IRFDPs) made from computer-aided design/computer-aided manufacturing (CAD/CAM)-manufactured yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) frameworks with two different connector dimensions, with and without fatigue loading. Twelve IRFDPs each were made with connector dimensions 3 × 3 mm² (width × height) (control group) and 3 × 2 mm² (test group). Inlay-retained fixed dental prostheses were adhesively cemented on identical metal-models using composite resin cement. Subgroups of six specimens each were fatigued with maximal 1,200,000 loading cycles in a chewing simulator with a weight load of 25 kg and a load frequency of 1.5 Hz. The load-bearing capacity was tested in a universal testing machine for IRFDPs without fatigue loading and for IRFDPs that had not already fractured during fatigue loading. During fatigue testing one IRFDP (17%) of the test group failed. Under both loading conditions, IRFDPs of the control group exhibited statistically significantly higher load-bearing capacities than the test group. Fatigue loading reduced the load-bearing capacity in both groups. Considering the maximum chewing forces in the molar region, it seems possible to use zirconia ceramic as a core material for IRFDPs with a minimum connector dimension of 9 mm². A further reduction of the connector dimensions to 6 mm² results in a significant reduction of the load-bearing capacity.     

Effect of immediate intracanal placement of Ledermix Paste® on healing of replanted dog teeth after extended dry times

Abstract  – Ledermix Paste^® is a paste containing triamcinolone and demeclocycline with demonstrated anti-inflammatory activity that may slow down resorptive processes after severe traumatic injuries to the dentition. A total of 29 premolar roots of six mongrel dogs were extracted and instrumented with rotary nickel titanium files. Fifteen of these roots were then filled with a calcium hydroxide (Ca(OH)₂) slurry and 14 roots were filled with Ledermix Paste^® paste. All accesses were sealed with glass ionomer and the roots replanted after an extraoral dry time of 60 min. After 4 months, the dogs were killed and the roots prepared for histological evaluation. Five-micrometer thick cross-sections of the root and surrounding tissue taken every 90 µm were evaluated for healing. In addition, residual root mass was also measured to determine the extent of root structure loss for each treatment method. The Ledermix Paste^®-treated roots had statistically significantly more healing and less resorption than the roots treated with Ca(OH)₂. Root filling with Ledermix Paste^® also resulted in significantly less loss in root mass due to resorption compared to those roots filled with Ca(OH)₂. Immediate intracanal placement of Ledermix Paste^® at the emergency visit after an avulsion injury appears to decrease resorption and increase favorable healing.     

Effect of rhBMP-2 with PLGA/gelatin sponge type (PGS) carrier on alveolar ridge augmentation in dogs

Summary  Recombinant human bone morphogenetic protein-2 has been shown to promote bone formation because of its osteoinductive property. The purpose of this study was to evaluate the efficacy of rhBMP-2 delivered on a poly ( d , l -lactic-co-glycolic acid) copolymer/gelatin sponge (PGS) in vertical alveolar ridge augmentation on height-reduced edentulous mandible to verify the retention of rhBMP-2 withstanding the pressure of soft tissues. Coronal defects of the alveolar bone were created in six adult beagle dogs. After a healing period of 9 weeks, PGSs with or without rhBMP-2 (0 or 0·4 mg mL⁻¹) were implanted on the defects(6 mm in height, 30 mm in length, 8 mm in width). Sixteen weeks after implantation, the bone mineral content (BMC) and the total bone area were measured by peripheral quantitative computed tomography. The BMC and the total bone area of the defect sites with rhBMP-2 group were significantly greater (133 ± 33 mg mm⁻¹, 277 ± 54 mm², respectively) than those of the control group (80 ± 19 mg mm⁻¹, 155 ± 49 mm², respectively) ( P  <   0·01, P  <   0·0001, respectively; paired t -test). From the histological analyses, the height of newly formed bone in the experimental group was greater than that of the control group (4·3 ± 0·9 mm, 0·22 ± 0·28 mm, P  <   0·0001, n  = 6, paired t -test). These results indicate that PGS has characteristics of effective bone graft substitutes for implantation of rhBMP-2 on vertical alveolar ridge augmentation in huge defect of mandibles in dogs.     

Accelerated corrosion analysis of dental amalgams

Abstract – The corrosion of powdered conventional and high Cu dental amalgam was studied in vitro under fixed conditions (100% oxygen, pH 4, and constant weak mechanical action). Results were retrieved from X-ray diffraction of samples of amalgam and solid corrosion products Formed, in combination with recording of the HC1 consumed to maintain the fixed pH. In the conventional amalgam no corrosion of γ₁ occurred until all γ₂ had corroded, whereas in the high Cu amalgam corrosion of γ₁ occurred from the beginning, concurrent with corrosion of ε and ń. Corrosion products found were AgCl, Hg₂Cl₂, CuCl₂-3Cu(OH)₂, and SnO₂. The results may be interpreted as follows: in the conventional amalgam the matrix phase γ₁ is anodically protected against corrosion as long as any γ₂ remians; in the high Gu amalgam the least noble phases ε and ń do not protect γ₁ in a similar way.     

Behaviours of three-dimensional compressive and tensile forces exerted on a tooth during function

Summary  The 3-D tensile and compressive forces exerted on a tooth were measured in vivo during function using a force-measuring device including a piezoelectric transducer. The device was mounted on the maxillary left second molar of a healthy male subject; the subject tooth had been endodontically treated and prepared for metal abutment and a crown. The 3-D forces were expressed as a vector of the coordinates based on the Frankfort horizontal ( x – y ) and sagittal ( y – z ) planes. The device captured the sequential changes in the forces. The directions of the forces changed during not only chewing a caramel or a peanut but also maximum voluntary clenching (MVC). As the magnitudes of the force increased during both MVC and caramel chewing (CaC), the force vector tended to correspond to the direction of the palatal root, medially and posteriorly. The compressive forces during MVC and caramel and peanut chewing were 173·29 ± 15·32, 146·3 ± 14·7 and 57·7 ± 35·7 N, respectively. The force vector during MVC was directed from the crown to the root medially at an angle of 10·27 ± 1·00° from the y – z plane and posteriorly at an angle of 3·18 ± 0·85° from the x – z plane to the perpendicular line of the F-H plane. There were significant differences in the behaviour of the compressive forces between clenching and chewing. The tensile force was recorded during CaC, not peanut chewing.     

Periodontal repair in dogs: effect of recombinant human transfornning growth factor-β1 on guided tissue regeneration

Abstract. This study evaluated alveolar bone and cementum regeneration following surgical implantation of recombinant human transforming growth factor- β₁ (rhTGF-β₁) in conjunction with guided tissue regeneration (GTR). Supraalvcolar, critical size, periodontal defects were surgically created around the 3rd and 4th mandibular premolar teeth in right and left jaw quadrants in 5 beagle dogs. Alternate jaw quadrants in consecutive animals received rhTGF-β₁ in a CaCO₃/ hydroxyethyl starch carrier with GTR, or carrier with GTR alone (control), 20μg of rhTGF-/A in buffer solution was incorporated into approximately 0.8 ml of carrier for each defect scheduled to receive rhTGF-β₁. Animals were sacrificed at week 4 postsurgery and tissue blocks were harvested and processed for histo-metric analysis. Clinical healing was generally uneventful. Minor membrane exposures were observed. Defects with membrane exposure displayed an inflammatory infiltrate underneath the membrane. Bone regeneration of trabecular nature, apparent in all animals, was generally limited to the very apical aspect of the defects. Cementum regeneration was limited without obvious differences between experimental conditions. Comparing rhTGF-β to control defects, statistically significant differences were found for area (1.8±0.4 and 1.3±0.6 mm², respectively: p<0.05) and density (0.3±0.1 and 0.2±0.03. respectively: p<0.05) of alveolar bone regeneration. Observed differences are small and represent a clinically insignificant potential for enhanced regeneration in this preclinieal model. Within the limitations of study, it may be concluded that rhTGF-β₁ has a restricted potential to enhance alveolar bone regeneration in conjunction with GTR.     

Activity pattern of swallowing-related muscles, food properties and body position in normal humans

Summary  Activity patterns of the swallowing-related muscles were examined in normal subjects at different four body positions during swallowing of foods with different textural properties. Surface electromyograms were recorded from two muscle groups, the anterior tongue and suprahyoid muscles. The T _P technique we developed was applied to the electromyograms for quantitative analysis of the activity patterns. Three test foods were prepared by dissolving 2·0% (low), 5·7% (middle) and 9·1% (high concentration) of a thickening agent into distilled water. Each subject was delivered randomly, one of the test foods to swallow at one of the four body positions i.e. horizontal supine, 30° inclined, 60° inclined and upright. In this study, T ₅₀ values were calculated in activity data of the two muscle groups, and the T ₅₀ values were statistically examined analysis of variance with a linear model including four fixed effects of 'concentrations', 'body positions', 'subjects' and 'sessions'. Three major findings obtained were that (i) the activity pattern of the anterior tongue was altered from a decrementing discharge pattern to an incrementing discharge pattern by shifting from the upright to the horizontal supine position, (ii) the activity pattern of the suprahyoid muscles was altered from a decrementing discharge pattern to an incrementing discharge pattern by shifting from the low concentration food to the higher ones and (iii) two subgroups were detected in subjects with the significant effects of 'concentrations' and 'body positions'. These findings lead a conclusion that activity patterns of the swallowing-related muscles are affected by food properties and body positions.     

Creep of dental amalgam as a function of heat treatment

abstract — The creep of dental amalgam was measured as a function of heat treatment of the amalgam. The treatment significantly reduced the creep rate. The β₁ (Ag-Hg) phase was detected in the heat-treated amalgam by X-ray diffraction and metallographic methods, and it appeared that the reduction in creep rate was due to the γ₁→β₁ transformation.     

γ2 phase in conventional dental amalgams — discrete clumps or continuous network? A review

A bstract — Six different types of sources of evidence are examined to study the controversy of whether the γ ₂ phase in conventional dental amalgams occurs in discrete clumps or as a continuous network.
Evidence obtained from corrosion studies, volume-fraction analysis studies and amalgam microstructure studies and evidence associated with the alloy type, the structure of the γ ₂ phase and manipulative techniques are investigated.
Although, under certain conditions, the γ ₂ phase may form a continuous network there is evidence to indicate that, using a conventional Ag₃Sn-based alloy and techniques providing adequate mercury removal, the γ ₂ phase occurs in discrete clumps.     

Stability values of titanium dioxide-blasted dental implants in edentulous maxillas: a 3-year pilot study

Summary  The purpose of this follow-up study was to measure the resonance frequency of Astra Tech TiO₂ blasted implants at second surgery, at one and 3 years of loading. Secondly, it was investigated whether resonance frequency at second surgery could discriminate between successful implants and those that will fail over a 3-year period. Fifty titanium dioxide-blasted implants in eight consecutive patients with edentulous maxillas seeking fixed rehabilitations, were included in the study at abutment connection after 6 months of healing. Resonance frequency, clinical and radiographic records were obtained at abutment connection and after one and 3 years of loading. The cumulative survival rate after 3 years was 100%. The mean resonance frequencies were 65 ± 4·8 implant stability quotient (ISQ) at second surgery (range 50–78 ISQ), 66 ± 3·4 ISQ after 1 year of loading (range 53–76 ISQ) and 64 ± 3·8 ISQ after 3 years of loading (range 53–77 ISQ). No significant differences resulted between these three time points. The marginal bone level decrease of 0·6 mm between the second surgery and the 3-year follow-up was observed. One limitation of the study is that no late failures were encountered in this relatively small sample. Consequently, it was not possible to establish a cut-off ISQ for implants that, after abutment connection, would maintain their stability over a 3-year period. Nevertheless, it might be concluded that following the first year of loading the range of 53–76 ISQ describes the stability of osseointegrated Astra Tech TiO₂ blasted implants.     

Partial pulpotomy on caries-free teeth using enamel matrix derivative or calcium hydroxide: a randomized controlled trial

Aim  To compare the effect of enamel matrix derivative (EMD) and calcium hydroxide [Ca(OH)₂] on exposed human pulp.
Methodology  Fifteen pairs of human contralateral premolars were intentionally and partially pulpotomized. The exposed pulps were randomly capped with either EMDgel (Emdogain^®) or a mix of Ca(OH)₂ and sterile water. The subjects recorded pain or discomfort during the first 10 days and were also interviewed and examined by a blinded examiner at 1 day, 2 weeks, 3 and 6 months post-operation. Periapical radiographs were taken prior to the operation, and 3 and 6 months post-operation. After 6 months, the teeth were extracted and processed for histological evaluation. The data were described and analysed using McNemar test and Kaplan–Meier survival analysis.
Results  The EMDgel-treated teeth had significantly less tooth hypersensitivity than the Ca(OH)₂-treated teeth during the first 2 weeks ( P  =   0.031) but were not significantly different after 2 weeks ( P  =   0.125). No detectable periapical radiographic changes were observed in any teeth and radiographic evidence of dentine bridge formation from both groups were not significantly different during the follow-up periods ( P  >   0.05). Histological evaluation demonstrated that the Ca(OH)₂-treated teeth had less inflammation and more dentine bridge formation than those in the EMDgel-treated teeth.
Conclusions  After 6 months, healthy pulps capped with Ca(OH)₂ had more favourable results than counterparts capped with EMDgel. However, similar clinical and radiographic results were seen in both groups.     

Vitamin D and tissue non-specific alkaline phosphatase in dental cells

Dental epithelium comprises different cell populations, including ameloblasts and stratum intermedium cells. Ameloblasts are vitamin D targets, and at least five proteins undergo specific modulation of their expression following the addition of 1 α ,25(OH)₂ vitamin D₃[1 α ,25(OH)₂D₃]. Stratum intermedium cells have not been studied in any great detail regarding vitamin D impact. Interestingly, in these cells, the tissue non-specific alkaline phosphatase (TNAP) is overexpressed. On the other hand, TNAP is a reliable bone marker of vitamin D action, similar to calbindins in kidney and intestine, previously used for studies of vitamin D activity in ameloblasts. Here, TNAP expression and activity were investigated in vivo in the microdissected epithelium and mesenchyme of mandible incisors. Physiological doses of 1 α ,25(OH)₂D₃ injected in control rats failed to modify TNAP activity in both dental epithelium and mesenchyme. No significant differences were observed in the steady-state levels of TNAP mRNAs of dental tissues from wild-type and vitamin D nuclear receptor (VDRnuc)-deficient mice of the same litters. These data suggest that, in contrast to ameloblasts, stratum intermedium cells are not sensitive to 1 α ,25(OH)₂D₃. An explanation for such a responsiveness of stratum intermedium cells to 1α,25(OH)₂D₃ is proposed based on the respective expressions of both vitamin D receptors (VDRnuc and 1,25D₃-[MARRS]) and the Dlx2 homeobox gene.     

Correlations between Color Differences Based on Three Color-Difference Formulas Using Dental Shade Guide Tabs

Purpose: The purpose of this study was to determine the correlation among color-difference values based on three formulas between shade tab pairs from two shade guides [Vita Lumin (VITA) and Chromascop (CHRO)].
Materials and Methods: The color of shade tabs was measured relative to the standard illuminant D₆₅ under the 8° standard observer function, and distributions for CIE L *, a *, and b * values were compared. One hundred and twenty shade pairs from VITA and 190 shade pairs from CHRO were used to calculate color differences using CIELAB, DIN99, and CIEDE2000 formulas (Δ E*_ab , Δ E ₉₉, and Δ E ₀₀, respectively). A paired t- test was used to determine the difference between each pair of the three color-difference values (α= 0.01). Regression analysis was used to determine the correlations between the color differences (α= 0.01).
Results: For both shade guides, there were significant differences between Δ E*_ab and Δ E ₀₀, Δ E*_ab and Δ E ₉₉, and Δ E ₉₉ and Δ E ₀₀ ( p < 0.01). Δ E*_ab and Δ E ₀₀, and Δ E*_ab and Δ E ₉₉ were strongly correlated (r²= 0.90 to 0.94, p < 0.05). Although a simplified a * rescaling function of the CIE a * axis has been added in the CIEDE2000 formula, the influence of the opposite signs in the a * value were found to be irrelevant to the Δ E ₀₀ value.
Conclusion: Δ E*_ab, Δ E ₉₉, and Δ E ₀₀ can be used interchangeably for the evaluation of color difference of shade tabs.     

Changes in the expression of αv integrins in oral squamous cell carcinomas

Integrins are cell surface adhesion molecules that regulate normal cellular interactions; aberrant integrin expression is believed to play a role in tumour invasion and metastasis. The α_v subunit is capable of forming heterodimers with several β subunits but not all the heterodimers expressed in oral epithelium have been investigated. We have examined the distribution of α_v integrins in normal buccal mucosa and seventeen oral squamous cell carcinomas. Antibodies to the α_v subunit and α_vβ₅ heterodimer stained normal epithelium, with strong expression in the basal layers and weaker staining in the more superficial layers. The β₃ and β₆ subunits were not expressed in normal epithelium. Anti-α_v and anti-α_vβ₅ antibodies stained all the squamous cell carcinomas, but the pattern of expression was variable both within and between tumours. Poorly differentiated tumours showed the weakest staining and often had areas showing loss of expression. β₆, was expressed in all of the carcinomas, indicating new expression of the α_vβ₆ integrin in malignant oral epithelium. These results suggest that alterations in α_v integrins may contribute to the behaviour of malignant epithelium and that α_vβ₆ expression may play a role in tumour progression.