Chronic dietary supplementation with kynurenic acid, a neuroactive metabolite of tryptophan, decreased body weight without negative influence on densitometry and mandibular bone biomechanical endurance in young rats.

Kynurenic acid (KYNA) is a neuroactive metabolite of tryptophan. KYNA naturally occurs in breast milk and its content increases with lactation, indicating the role of neonatal nutrition in general growth with long-term health effects. KYNA is also an antagonist of ionotropic glutamate receptors expressed in bone cells. The aim of this study was to establish the effects of chronic KYNA supplementation on bone homeostasis in young rats, using mandible as a model bone. Female and male newborn Wistar rats were divided into control and KYNA-administered groups until 60 days of age (25x101 mg/L or 25x102 mg/L in drinking water). Hemimandibles were subjected to densitometry, computed tomography analysis and mechanical testing. Rats supplemented with KYNA at both doses showed a decrease in body weight. There were no effects of KYNA administration and mandible histomorphometry. In males, a significant quadratic effect (P < 0.001) was observed in the densitometry of the hemimandible, where BMD increased in the group supplemented with 2.5x101 mg/L of KYNA. Analysis of mechanical tests data showed that when fracture forces were corrected for bone geometry and rats body weight the improvement of bone material properties was observed in male and female rats supplemented with lower dose of KYNA. This study showed that chronic supplementation with KYNA may limit weight gain in the young, without adversely affecting the development of the skeleton.

Masticatory properties in pre-modern Holocene populations from Northern China.

Recent studies indicate that evolution of the craniofacial skeleton is influenced by dietary behavior, which in turn alters masticatory efficacy and temporomandibular joint (TMJ) stability. In this study the mechanical properties of the masticatory system and the integrity of the TMJ in human populations from Northern China, dated to between 3800 BCE and 100 CE, were assessed. The results demonstrate that the mechanical efficiency is comparable to other modern human populations, though variations are present across different populations. While the ratio of overall weighted muscle efficiency for incisor loading vs. molar loading in pastoral and some recent agricultural groups is similar to early Homo sapiens, the ratio in more ancient agricultural groups is similar to the ratio in populations with heavy anterior paramasticatory activities, such as Neandertals, Inuits, and Native Americans. The TMJ vulnerability negatively correlates with the maxillary dental arch size, and positively with the condylar size. These findings suggest that there are multi-directional strategies in adaptation to heavy anterior teeth loading, such as increasing anterior teeth loading efficiency, increasing facial height, increasing facial breath and facial orthognathy, or decreasing anterior facial length. Furthermore, populations or individuals with a smaller dental arch and high biting efficiency could more easily injure the TMJ during unilateral loadings, which may explain the higher prevalence of TMJ disorders in modern humans, especially in women. These findings further reflect the impact of diachronic changes of the masticatory apparatus and lifestyle and their impact on oral health during recent human history.

Reliability in Mandibular Movement Evaluation Using Photogrammetry in Patients With Temporomandibular Disorders.

OBJECTIVE: The purpose of this study was to propose a quantitative evaluation for mandibular opening-closing movement asymmetries and to verify the intraexaminer and interexaminer reliability using photogrammetry in individuals with and without myogenic temporomandibular disorders. METHODS: Forty-nine female participants between ages 18 and 40 were enrolled in this study. They were assigned to 2 different groups: a temporomandibular disorder group, (n = 25; 28.1 ± 3.6 years) and an asymptomatic group (n = 24; 25.6 ± 5.1 years). Data were collected through photogrammetry using Corel Draw X3 software (Corel Corp, Ottawa, Ontario, Canada) for angle measurements. Reliability analysis was done on the total sample, and the photographs were obtained by a singular examiner on 2 occasions (intraexaminer) 1 month apart and from measurement made by another examiner (interexaminer) on different days. The intraclass correlation coefficient (ICC) was applied with a significance level of 5%. RESULTS: The photogrammetry had excellent intrarater and inter-rater reliability for the evaluation of opening and closing movements of the jaw (intrarater: opening ICC = 0.99; closing ICC = 0.98; inter-rater: opening ICC = 0.89 and closing ICC = 0.82). Photogrammetry also demonstrated excellent intra- and inter-rater reliability in the evaluation of head posture (intra-rater: head deviation ICC = 0.96; head position ICC = 0.75; inter-rater: head deviation ICC = 0.98; head position ICC = 0.98). CONCLUSION: Under these experimental conditions, most angular values presented excellent intra- and interexaminer reliability.

Serum Concentration of Macro-, Micro-, and Trace Elements in Silver Fox (Vulpes vulpes) and Their Interrelationships with Morphometric, Densitometric, and Mechanical Properties of the Mandible.

The optimal content of macro-, micro-, and trace elements in tissues ensures proper systemic growth and development and optimal health status in animals and humans. However, very little is known on the elemental content in the plasma compartment in Silver fox. The aim of this study was to determine the content of selected elements in serum obtained from 8-month-old female (N = 8) and male (N = 7) silver foxes. Moreover, relationships of the evaluated elements with the morphological, densitometric, and mechanical parameters of the mandible were determined. Serum content of 12 different elements was measured using inductively coupled plasma-atomic emission spectrometry. The morphometric and densitometric properties of the mandible were determined using quantitative computed tomography method, while mechanical endurance was tested using a three-point bending test. Serum concentration of calcium was significantly higher by 20% in male foxes (P = 0.01), while manganese concentration was significantly lower in males by over 17% (P = 0.03). Positive correlations of serum concentration of calcium, phosphorus, and magnesium with the morphological traits of the mandible such as weight, length, and bone volume were stated (P < 0.05). In the group of elements playing regulatory functions, the positive relationships between serum concentrations of selenium, chromium, manganese, copper, and cobalt were found (P < 0.05). The elaborated experimental model may serve for further studies on foxes, especially focused on nutritional factors affecting elemental homeostasis, whole-body metabolism, and systemic growth and development. Daily diet formulation and precise delivery for farm foxes, together with relatively large animal population maintained at the same environmental conditions, regularly subjected to slaughter procedure, enable economical experimentation with various dietary and pharmacological manipulations.

Hypericum perforatum L. treatment restored bone mass changes in swimming stressed rats.

UNLABELLED: Stress, via corticosteroids release, influences bone mass density. Hypericum perforatum (Hp) a traditional remedy possess antidepressive activity (serotonin reuptake inhibitor) and wound healing properties. Hp preparation contains mainly hypericin, hyperforin, hyperoside and flavonoids exerting oestrogen-mimetic effect. Cold swimming represents an experimental model of stress associating mental strain and corporal exhaustion. OBJECTIVES: This study investigates the Hp effect on femur and mandible bone mass changes in rats under cold forced swimming procedure. METHODS: 30 male Wistar rats were randomized into three groups. Group A was treated with Methanolic extract of Hp (Jarsin®) via gastroesophageal catheter, and was submitted to cold swimming stress for 10 min/daily. Group B was submitted to cold stress, since group C served as control. Experiment duration was 10 days. Haematocrite and serum free fatty acids (FFA) were estimated. Furthermore volume and specific weight of each bone as well as bone mass density via dual energy X-Ray absorptiometry (DEXA) were measured. Statistic analysis by t-test. RESULTS: Hp treatment restores the stress injuries. Adrenals and bone mass density regain their normal values. CONCLUSIONS: Injuries occurring by forced swimming stress in the rats are significantly improved by Hp treatment. Estrogen-like effects of Hp flavonoids eventually may act favorable in bone remodeling.

Influence of a Magnetic Field and Laser Therapy on the Quality of Mandibular Bone During Distraction Osteogenesis in Rabbits.

PURPOSE: This study evaluated the use of low-level laser therapy (LLLT) and exposure to a magnetic field (MF) during distraction osteogenesis. MATERIALS AND METHODS: The sample consisted of 18 rabbits divided into 3 groups of 6 animals each: control, MF exposure (briefly, magnetized gold-coated washers were placed next to the distractor device), and LLLT exposure (830 nm applied every 48 hours over 4 points [dose, 5 J/cm2] during the consolidation period). The same distraction osteogenesis protocol was used in all 3 groups (0.5 mm every 12 hours for 1 week). RESULTS: Quantitative microscopic analysis of sections stained with hematoxylin and eosin showed a statistically significant difference in the amount of newly formed bone in the MF group compared with the LLLT group (P = .006). The number of cells with more than 3 argyrophilic nucleolar organizer regions also was significantly different between the LLLT and control groups (P = .038). CONCLUSION: Distraction osteogenesis effectively promoted bone lengthening. The LLLT group exhibited a larger amount of newly formed bone and a larger number of osteoblasts in the cell division phase, but the difference was not statistically relevant compared with the control group.

[Behavior of the periodontium during leveling of the mandibular incisors: what precautions are needed?]. / Comportement du parodonte au cours du nivellement des incisives mandibulaires : précautions à prendre∗.

Since the position of the mandibular incisors is one of the keys to successful treatment, most orthodontic treatments focus on control but take no special precautions regarding the periodontal environment. Can we trust the lateral headfilm alone when evaluating such slender quantities of bone surrounding the mandibular incisors? What is the true bone situation prior to treatment and above all, following alignment, leveling and uprighting of the incisors? We performed a prospective 3-year study on 50 patients to assess the periodontal behavior of the mandibular incisors following a leveling phase by means of a clinical approach using periodontal and radiologic probing based on measurements of bone thickness obtained by cone beam. The bone loss observed was not inconsiderable given the thinness of the initial bone. In the face of this clinical situation, we need to adapt our treatment by performing a pre-orthodontic periodontal check-up and by supplementing the diagnosis with 3D examinations for at-risk patients and by checking the incisal axes during the leveling phase. The advent of cone beam has provided us with a valuable tool making it possible to individualize orthodontic treatment and view the posttreatment bone environment and root positions.

Mechanical properties of bone tissues surrounding dental implant systems with different treatments and healing periods.

OBJECTIVES: The objective of the current study was to examine whether the nanoindentation parameters can assess the alteration of bone quality resulting from different degrees of bone remodeling between bone tissue ages around the dental implant interface with different treatments and healing periods. MATERIALS AND METHODS: Dental implants were placed in mandibles of six male dogs. Treatment groups included: resorbable blast media-treated titanium (Ti) implants, alumina-blasted zirconia implants (ATZ), alumina-blasted zirconia implants applied with demineralized bone matrix (ATZ-D), and alumina-blasted zirconia implants applied with rhBMP-2 (ATZ-B). Nanoindentation modulus (E), hardness (H), viscosity (η), and viscoelastic creep (Creep/P max) were measured for new and old bone tissues adjacent to the implants at 3 and 6 weeks of post-implantation. A total of 945 indentations were conducted for 32 implant systems. RESULTS: Significantly lower E, H, and η but higher Creep/P max were measured for new bone tissues than old bone tissues, independent of treatments at both healing periods (p < 0.001). All nanoindentation parameters were not significantly different between healing periods (p > 0.568). ATZ-D and ATZ-B implants had the stiffer slope of correlation between E and Creep/P max of the new bone tissue than Ti implant (p < 0.039). CONCLUSIONS: Current results indicated that, in addition to elastic modulus and plastic hardness, measurement of viscoelastic properties of bone tissue surrounding the implant can provide more detailed information to understand mechanical behavior of an implant system. CLINICAL RELEVANCE: Ability of energy absorption in the interfacial bone tissue can play a significant role in the long-term success of a dental implant system.

The Low Mandible Maneuver and Its Resonential Implications for Elite Singers.

Many elite singers appear to frequently drop the posterior mandible while singing to optimize resonance production. This study investigated the physiology of the Low Mandible Maneuver (LMM) through the use of magnetic resonance imaging (MRI), ultrasound (US), and spectrographic analysis. The study of elite singers has been hampered by the paucity of internal imagery. We have attempted to address this problem by using portable US equipment that we could transport to the homes, studios, or dressing rooms of such ranking singers. With the US and acoustic data gathered in fairly brief sessions, we were able to ascertain the resonance gains garnered from the technique's use. The study featured two phases: I--MRI study of the maneuver and its physiological effect on surrounding structures (in collaboration of the Medical University of Graz, Austria) and II--US investigation that studied tongue shape during the maneuver. The LMM has significant ramifications for resonance production by enabling a concomitantly lowered larynx and increased resonance space in the pharyngeal and oral cavities. Measurements of the LMM ranged between 0.7 and 3.1 cm and showed a boost in the first harmonics as well as an enhancement in the singers formant. Its use also has a rather significant effect on the tongue shapes required for all sung phonemes. The advantage of using US for this study was the ability to produce real-time videos of the singer in action and then, through the use of stop action, precisely study both individual phoneme production and phoneme-to-phoneme transitions during the LMM.

Combined Mandibular Guidance Therapy in the Management of a Hemimandibulectomy Patient.

This case history report describes two different devices, maxillary ramp prostheses (MRP) and mandibular guide flange prostheses (MGFP), prescribed for managing a hemimandibulectomy patient's deviated mandible. The patient was given muscle reprogramming exercises with coordinated use of both guidance prostheses for 2 months, leading to improvements in both postsurgical mandibular deviation and occlusal equilibration. A successful intercuspal position was eventually accomplished through the use of the combination therapy. MRP and MGFP can be a useful approach to avoid mandibular deviation and compromised function following a partial mandibular resection.

Management of sleep bruxism in adults: a qualitative systematic literature review.

This paper updates the bruxism management review published by Lobbezoo et al. in 2008 (J Oral Rehabil 2008; 35: 509-23). The review focuses on the most recent literature on management of sleep bruxism (SB) in adults, as diagnosed with polysomnography (PSG) with audio-video (AV) recordings, or with any other approach measuring the sleep-time masticatory muscles' activity, viz., PSG without AV recordings or electromyography (EMG) recorded with portable devices. Fourteen (N = 14) papers were included in the review, of which 12 were randomised controlled trials (RCTs) and 2 were uncontrolled before-after studies. Structured reading of the included articles showed a high variability of topics, designs and findings. On average, the risk of bias for RCTs was low-to-unclear, whilst the before-after studies had several methodological limitations. The studies' results suggest that (i) almost every type of oral appliance (OA) (seven papers) is somehow effective to reduce SB activity, with a potentially higher decrease for devices providing large extent of mandibular advancement; (ii) all tested pharmacological approaches [i.e. botulinum toxin (two papers), clonazepam (one paper) and clonidine (one paper)] may reduce SB with respect to placebo; (iii) the potential benefit of biofeedback (BF) and cognitive-behavioural (CB) approaches to SB management is not fully supported (two papers); and (iv) the only investigation providing an electrical stimulus to the masseter muscle supports its effectiveness to reduce SB. It can be concluded that there is not enough evidence to define a standard of reference approach for SB treatment, except for the use of OA. Future studies on the indications for SB treatment are recommended.

Health-related quality of life after segmental resection of the lateral mandible: Free fibula flap versus plate reconstruction.

OBJECTIVES: Segmental resection of the mandible causes functional, aesthetic and social problems affecting health-related quality of life (HRQoL). It is often assumed that reconstruction with composite free flaps guarantees better function and aesthetics than bridging the defect with reconstruction plates. METHODS: Using the European Organization for Research and Treatment of Cancer questionnaires (EORTC QLQ-C30 version 3.0 and EORTC QLQ-H&N35), we compared HRQoL in patients who received free fibula flaps versus reconstruction plates after segmental resection of the lateral mandible. RESULTS: Thirty-seven completed questionnaires (18 fibula reconstructions and 19 patients with reconstruction plates) were available. Reconstruction with a free fibula flap did not provide clear additional benefit to bridging the defect with a reconstruction plate after segmental resection of the lateral mandible. In particular aspects known to have the most impact on HRQoL like swallowing, speech and chewing were not influenced by the type of reconstruction. CONCLUSIONS: Reconstruction of segmental defects of the lateral mandible with free fibula flap and reconstruction plate resulted in comparable HRQoL. If dental rehabilitation by means of dental implants is not anticipated in the fibula, then plate reconstruction with adequate soft tissue remains a suitable technique for the reconstruction of segmental defects of the lateral mandible.

The impact of premature birth on the mandibular cortical bone of children.

SUMMARY: Children born prematurely often have reduced skeletal mineralization. The aim in this study was to compare the cortical thickness of the lower jaw on radiographs of 8- to 10-year-old children with histories of preterm or full term births. There were no significant differences in cortical thickness between full term and preterm children at this age. INTRODUCTION: The purpose of this study was to compare the cortical thickness of the mandible on panoramic radiographs of 8- to 10-year-old children with histories of preterm or full term births. METHODS: Panoramic radiography was performed on 36 extremely preterm, 38 very preterm and 42 full term children at the age of 8 to 10 years. Five observers independently measured the mandibular cortical width on the panoramic radiographs at four defined sites bilaterally. Altogether, 928 sites were available. Measurements were performed twice on a random 24% of the sites by four observers. One-way analysis of variance with Tukey's post hoc test was used to test differences between groups. Intraclass correlation coefficient (ICC) was calculated for interobserver agreement while intra-observer agreement was expressed as measurement precision. RESULTS: Significant differences of mandibular cortical width were found between extremely preterm and very preterm children for five of the eight measurement sites with the very preterm showing the highest value. No significant differences were found between full term and either very preterm or extremely preterm except for one measurement site, with the extremely preterm showing the lowest value. ICC varied between 0.30 and 0.83 for the different sites (mean 0.62). The precision of a single measurement varied between 0.11 and 0.45 mm (mean 0.25 mm). CONCLUSIONS: From the evidence that very preterm children had significantly thicker mandibular cortices than extremely preterm children, we suggest that these findings may reflect the effect of mineral supplementation provided to premature infants, causing a 'shifting up' of bone mineral status relative to the full term peer group while maintaining the difference between very preterm and extremely preterm born children.

Assessment of mandibular movements in 10 to 15 year-old patients with and without temporomandibular disorders

El objetivo del presente trabajo fue establecer valores de referencia de movimientos mandibulares en niños de 10-15 años sin disfunción; compararlos con los de pacientes de la misma edad con trastornos temporomandibulares (TTM) y con los hallados anteriormente en un grupo menor de 11 años sinTTM. Niños de ambos sexos que acudieron a la Cátedra Odontología Integral Niños de UBA en 2013 y cuyos responsables brindaron consentimiento fueron evaluados con CDI/TTM por odontopediatras estandarizados (Kappa 0.88) conformándose 3 grupos en función del resumen diagnóstico; C: sin TTM, Ia: con dolor miofacial e Ib: dolor con limitación de la apertura bucal, para el análisis de las siguientes variables: edad, sexo y movimientos mandibulares. La muestra quedó constituida por169 pacientes de 12.5±1.76 años. El 62.36 por ciento no presentó TTM (C) y en el 37.27 por ciento se estableció un diagnóstico de trastorno muscular (29.58 por ciento Ia y 7.69 por ciento Ib). En C se registraron lossiguientes valores en mm: Apertura máxima no asistida: 48.28±6.14; Lateralidad derecha 8.78±2.50; izquierda: 9.60±2.64; Protrusión: 4.94±2.58 y Sobremordida: 2.98 ± 2.5sin variaciones en relación al sexo, pero con diferencias en los registros de todos los movimientos comparados con losobtenidos en dentición mixta. (p=0.0001). El análisis de los valores medios de los movimientos mandibulares entre los 3 grupos sólo reveló diferencias para la apertura máxima no asistida (p= 0.0317). En relación al sexo, los TTM fueron másfrecuentes en niñas siendo significativa la diferencia entre C e Ia (p=0.019). En los niños sin disfunción se estableció unaapertura máxima promedio de 48.28±6.14mm, observándose valores inferiores en los pacientes con TTM. Los movimientos mandibulares en pacientes pediátricos sin TTM mostrarondiferencias significativas en función del tipo de dentición y la edad...

Assessment of the effect of low-energy diode laser irradiation on gamma irradiated rats' mandibles.

OBJECTIVE: The purpose of the present study was to evaluate the biostimulative and regenerative effects of low intensity laser irradiation (LILT) (applied before or after initiation of radiotherapy) on gamma irradiated rats' jaw bones. METHODS: Forty eight male Albino rats were equally divided into two groups: group 1, in which the left side of the mandible was subjected to three successive sessions of laser (LILT) prior to whole body gamma radiation (2Gy/3 fractions/week) and group 2, received whole body gamma radiation (2Gy/3 fractions/week) prior to three successive sessions of laser applied to left side. The right side of both groups was used as gamma irradiated non-lased control group. Each group was then subdivided into four equal subgroups (a, b, c, d) according to the time of scarification (3, 7, 14, 21 days respectively). Specimens were subjected to histological, histomorphometric and scanning electron microscopic examinations. RESULTS: Thin irregular bone trabeculae and widened marrow spaces were identified in the control group. The lased sides of groups 1 and 2 demonstrated regular, thick and continuous bone trabeculae. Ultrastructurally, collagen fibres of the control group appeared irregularly arranged and more spaced compared to groups 1 and 2. Normal-sized osteocytic lacunae were seen in the lased groups, as compared to the wide lacunar spaces noted in the control group. Histomorphometric analysis showed a significant increase in the area of bone trabeculae, as well as the width of compact bone, for the lased groups. CONCLUSIONS: LILT seemed to attenuate the radiation-related damage in alveolar bones.

Orthodontic-surgical treatment: neuromuscular evaluation in skeletal Class II and Class III patients.

OBJECTIVES: The aim of this study was the evaluation of the neuromuscular response to treatment according to diagnostic phases, as a follow-up of patients under surgical orthodontic treatment. The patient sample was subdivided into sub-samples, according to clinical characteristics. MATERIALS AND METHODS: All of the patients who underwent orthognathic surgery in the Department of Orthodontics (University of Milan) were subjected to periodic electromyographic evaluation of the masticatory muscles (masseter and anterior temporal muscles), and to electrokinesiographic evaluation of the mandibular movements. The patient sample comprised 80 patients (37 males; and 43 females) at the end of growth. The electromyographic instruments used in the study included a Freely and a K6-I electromyography. Statistical evaluation was carried out with the Student's t-tests for independent samples. RESULTS: There are many differences between the skeletal Class II and skeletal Class III patients that are shown through the analysis of these data obtained. In the beginning phases of the treatment the muscular activities were higher in the Class II patients than in the Class III patients. Nevertheless this difference was reversed at the end of the treatment. A similar difference could be found in the mandibular kinesiology, in fact the maximum mandibular opening movement was greater in the skeletal Class II patients than in the skeletal Class III patients at the beginning of the treatment. At the end of the treatment this difference was lost. At the beginning of the treatment the Class II patients showed a greater protrusive movement of the mandibular than the Class III patients. At the end the treatment however this gap was reduced without being reversed. CONCLUSIONS: Functional evaluation in patients in surgical orthodontic therapy is an important element in the diagnostic-therapeutic recordings, so as to reduce as much as possible any incorrect neuromuscular activity that can result in relapse.

A preliminary study of hardness and modulus of elasticity in sheep mandibles submitted to distraction osteogenesis and low-level laser therapy.

OBJECTIVES: To investigate the quality of newly formed bone in sheep mandibles submitted to distraction osteogenesis and low-level laser therapy (LLLT), based on hardness and modulus of elasticity values. The ideal moment for laser application (during the latency/activation period vs. during the bone consolidation period) was also evaluated. Computed tomography imaging was used to assess relapse as a result of early device removal. STUDY DESIGN: Extraoral distraction devices were placed in five sheep so as to achieve 1.5 cm of lengthened bone in 60 days. Distraction devices were removed 50, 40, and 33 days after surgery. Four animals were treated with LLLT, at different times, and one was used as control (no LLLT). RESULTS: When applied during the bone consolidation period, LLLT caused an increase in hardness and modulus of elasticity values. On the other hand, animals irradiated with LLLT during the latency/activation period presented a delay in bone healing. A period of consolidation of 13 days (early device removal) was associated with relapse. CONCLUSIONS: Nanoindentation tests were able to detect slight abnormalities in bone metabolism and proved to be important tools for the assessment of bone quality following distraction osteogenesis. LLLT provided increased benefits when applied during the bone consolidation period, once it promoted an increase in hardness and modulus of elasticity values. According to our results, the bone consolidation period should be of at least 3 weeks, so as to prevent relapse.

A comparative mechanical and bone remodelling study of all-ceramic posterior inlay and onlay fixed partial dentures.

OBJECTIVES: Comparative studies of bone remodelling and mechanical stresses between inlay and onlay fixed partial dentures (FPD) are rather limited. The purpose of this paper was to evaluate the biological consequence in posterior mandibular bone and the mechanical responses in these two different prosthetic configurations. METHODS: Three-dimensional (3D) finite element analysis (FEA) models are created to explore the mechanical responses for the inlay and onlay preparations within the same oral environment. Strain induced bone remodelling was simulated under mastication. The remodelling adopted herein relates the strain in the bone to the change of Hounsfield Unit (HU) value in proportion to the surface area density (SAD) of bony morphology, which allows directly correlating to clinical computerised tomography (CT) data. RESULTS: The results show that both FPD designs exhibit a similar resultant change in bone mineral density (BMD) though the onlay configuration leads to a more uniform distribution of bone density. The inlay design results in higher mechanical stresses whilst allowing preservation of healthy tooth structure. CONCLUSIONS: This study provides an effective means to further clinical assessment and investigation into biomechanical responses and long-term restorative outcome with different FPD designs. CLINICAL SIGNIFICANCE: Quantifying in vivo stress distributions associated with inlay/onlay FPDs can further supplement clinical investigations into prosthetic durability, FPD preparation techniques (i.e., taper angles, material development), consequent stress distributions and the ongoing biomechanical responses of mandibular bone.

Chemical detoxification vs mechanical removal of host plant toxins in Eucalyptus feeding sawfly larvae (Hymenoptera: Pergidae).

The essential oils that characterize the eucalypts and related Myrtaceae pose a challenge for herbivores. Phytophagous insects that feed on oil-rich Myrtaceae have developed specific mechanisms to deal with these oils, some of which are notoriously toxic (e.g. 1,8-cineole). Some of the eight Australian subfamilies in the sawfly family Pergidae are associated exclusively with Eucalyptus and Melaleuca species that often have high concentrations of essential oils. Unexpectedly, the Perginae and Pterygophorinae use different mechanisms to deal with the same toxic components in their respective host plants. Larvae of the Perginae have the inner surface of their mandibles equipped with soft brush-like structures that are unique among phytophagous insects in general. The proposed role of these ancillary mandibular structures in separating leaf oils from nutritive plant matter could be confirmed in experiments with larvae of two pergine species. The oil sequestration is, however, incomplete and chemical gut content analyses by gas-chromatography (GC) revealed that 1,8-cineole does enter the midgut and is metabolised to hydroxycineole. Although the related Pterygophorinae also feed mainly on oil-rich Myrtaceae, they do not sequester the oil and lack morphological structures on their mandibles. Chemical analysis of the gut content of two pterygophorine species showed that they rely solely on chemical detoxification of the relevant plant compounds, with GC demonstrating that the 1,8-cineole is removed far more rapidly and completely than in the pergine species.

Behavior analysis of electromyographic activity of the masseter muscle in sleep bruxers.

The effects of occlusal splint on the electric activity of masseter were studied in 15 women who presented sleep bruxism using surface electromyography. Sleep bruxism was defined by its clinical characteristics. The signal acquisition was done during mandible occlusion without clenching and maximum voluntary contraction in two situations. The first was after a workday without using the occlusal splint; and the second, after a sleeping night using occlusal splints. Evaluating masseter muscles during mandible occlusion without clenching, it could be observed that lower values were noticed after splint wearing in both sides. The same results were verified in maximum voluntary contraction (MVC). These results confirmed that the use of occlusal splints reduced the electromyographic activity of the right and left masseters, showing its myorelaxing effect.