Short-term changes in chewing efficiency and subjective evaluation in normal dentate subjects after insertion of oral appliances with an occlusal flat table.

Oral appliances with an occlusal flat table are used as treatment dentures. However, the short-term effect of insertion of such oral appliances on chewing has not been reported. This study aimed to determine whether experimental and continuous insertion of oral appliances with an occlusal flat table has an effect on chewing efficiency and Oral Health Impact Profile (OHIP) in healthy participants. Ten participants each in the oral-appliance and control (no oral-appliance insertion) groups attended six data collection sessions for 5 consecutive days. Participants answered the OHIP questionnaire and underwent the chewing efficiency test. For each parameter, intergroup differences were investigated in terms of change from baseline to immediately after oral-appliance insertion (0 hour; P < .05) and from 0 hour to 24, 48, 72 and 96 hours after oral-appliance insertion (P < .05). There were significant differences between groups in the degree of change in chewing efficiency and OHIP scores for functional limitation, physical pain, physical disability and handicap from baseline to 0 hour (all, P < .001); among these, only OHIP scores for functional limitation and physical pain demonstrated significant differences in degree of change between the two groups at 96 hours after appliance insertion (P = .477 and .275, respectively). Differences between the two groups in the degree of change in other parameters were not significant. Insertion of oral appliances caused a decrease in chewing efficiency and an increase in OHIP scores. Continuous insertion improved functional limitation and physical pain within 96 hours.

Head position affects the direction of occlusal force during tapping movement.

Despite numerous reports describing the relationship between head position and mandibular movement in human subjects, the direction and magnitude of force at the occlusal contacts have not been investigated in relation to head position. The objective was to investigate the effect of head position on the direction of occlusal force while subjects performed a tapping movement. Twenty-three healthy adult subjects were asked to sit on a chair with their back upright and to perform 15 tapping movements in five different head positions: natural head position (control); forward; backward; and right and left rolled. The direction and magnitude of force were measured using a small triaxial force sensor. The Wilcoxon signed-rank test and Bonferroni test were used to compare head positions in each angle of the anteroposterior axis direction and the lateral axis direction with respect to the superior axis. The force element in the anteroposterior axis shifted to the forward direction in the head position pitched backward, compared with control, pitched forward and rolled left positions (P = .02, <.01 and <.01, respectively). The force direction in the lateral axis with the head position rolled to the right or left shifted to the left and right directions, respectively, compared with those in the other positions (P < .05). Results of this study suggest that the head should be maintained in a position in which a stable tapping movement can be performed in a relaxed position without anteroposterior and lateral loading.

Effect of dietary counselling with prosthetic restoration on fruit and vegetable intake in partially dentate patients: A prospective study.

The aim of this study was to investigate the effects of a counselling-based dietary intervention on nutritional status in partially dentate patients receiving removable partial dentures (RPDs). Thirty-eight patients [mean age (standard deviation): 73.2 (7.7) years] who were scheduled to receive RPDs at a dental hospital and were currently eating <350 g of vegetables per day were included in the study. A dentist provided basic dietary counselling aimed at increasing dietary fruit and vegetable intake and improving dietary habits. Patients received dietary counselling directly after treatment with new RPDs and at 1 week after a 1-month follow-up evaluation (T1). Food intake was assessed via a validated brief-type self-administered diet history questionnaire, and carotenoids and vitamin C in 6-hour fasting blood samples were measured before RPD administration, and at 1 (T1) and 3 months (T3) thereafter. Vegetable but not the fruit intake increased significantly at T1 and T3 compared to before treatment. Alpha carotene significantly increased at T3 while ß significantly increased both at T1 and T3 compared to before treatment (P < .05). The number of occlusal units on natural teeth was significantly positively associated with increased vegetable and ß-carotene intake (P < .05). Serum carotenoids and vitamin C levels measured with 6-hour fasting blood samples remained constant. These results suggest that basic dietary counselling may improve vegetable intake in partially dentate patients receiving RPD treatment, but did not lead to haematological changes. The presence of occlusion of remaining posterior teeth may be critical for improving vegetable intake.

Oral health-related quality of life in patients with non-metal clasp dentures: a randomised cross-over trial.

We investigated the efficacy of non-metal clasp dentures (NMCDs) with regard to the oral health-related quality of life (OHRQoL) and compare the findings with those for conventional metal clasp-retained dentures (MCDs). This single-centre, randomised controlled, two-phase, open label, cross-over trial included 28 partially dentate individuals. The patients were randomised to receive MCDs followed by NMCDs, or the opposite sequence (n = 14 in each group); each denture was worn for 3 months. OHRQoL was evaluated using the Oral Health Impact Profile-Japanese version (OHIP-J) at entry (T-entry; before treatment with the first denture) and at 3 months after treatment with each denture (T3). An examiner evaluated denture stability, oral appearance and surface roughness before denture delivery (T0) and at T3 and denture hygiene at T3. A total of 24 patients completed the trial. There were no complications related to the dentures, abutment teeth or denture-bearing mucosa during the follow-up periods for both dentures. The mean OHIP summary score was lower for NMCDs than for MCDs, and the difference (9 points) was greater than the minimal important difference (6 points), indicating the difference was clinically relevant. The effect size was medium (0·70). Statistical analyses with linear mixed models found a significant effect of the denture type on the OHIP summary score and scores for the Oro-facial appearance, Oro-facial pain and Psychological impact domains (NMCD < MCD; P < 0·05). The results of our study suggest that NMCDs allow for better OHRQoL compared with MCDs.

Adaptive change in chewing-related brain activity while wearing a palatal plate: an functional magnetic resonance imaging study.

Prosthodontic treatment success depends on patients' ability to adapt to an altered oral environment containing removable prostheses. We investigated adaptive chewing-related brain activity changes in response to a new oral environment. Twenty-eight fully dentate subjects (mean age: 28·6 years) wore experimental denture-base palatal plates (3 mm thick), for 7 days. We measured food mixing ability and cycle time, and assessed brain activity by functional magnetic resonance imaging during chewing at pre-insertion (Day 0), and immediately (Day 1), 3 days (Day 3) and 7 days (Day 7) after insertion. Food mixing ability significantly decreased and cycle time increased on Day 1 as compared to Day 0 (P < 0·001) and tended to recover to Day 0 level by Day 7. Brain activation in the right face primary sensorimotor cortex and putamen significantly decreased on Day 1 as compared to Day 0 (P < 0·001) and recovered to Day 0 level by Day 7. Brain activation in the left face primary sensorimotor cortex, putamen, anterior cingulate gyrus (ACG) and right posterior medial frontal cortex (pMFC) significantly decreased on Day 1 as compared to Day 0 (P < 0·001) and did not recover by Day 7. Thus, oral environment changes involving palate covering affected chewing and induced adaptive brain activity changes in the face primary sensorimotor cortex and putamen, possibly associated with motor learning. As ACG and pMFC activity remained unrecovered by 7 days after plate insertion, automatisation of chewing while wearing a palatal plate may require longer adaptation periods.

Factors associated with mucosal pain in patients with partial removable dental prostheses.

The aim of this study was to investigate factors associated with mucosal pain in patients with partial removable dental prostheses (PRDPs). In this hospital-based cross-sectional study, 333 patients wearing 500 PRDPs (mean age 71·4 years, men 33·3%) were consecutively recruited from prosthetic clinic of a dental hospital in Japan. Subjects rated pain intensity and frequency of denture-bearing mucosa. An examiner recorded age, gender and systemic diseases as well as dental, mucosa, denture, sensory, behavioural- and psychological-related characteristics that were possibly associated with the mucosal pain. Multivariate analyses were performed to analyse factors related to mucosal pain. Pain intensity was rated as more than score 0 (presence) in 34·2% (171/500) PRDPs, and pain was experienced after denture delivery in 42·8% (214/500) PRDPs. Logistic regression analyses showed that younger age, mucosal damage, poor mucosal condition, bone prominence, poor residual ridge, higher pain sensitivity, presence of awake bruxism, perception of oral dryness, interim denture wear and high number of missing teeth were significant independent predictors for the presence of the mucosal pain intensity and/or frequency (P < 0·05). Multiple factors are associated with mucosal pain in patients with PRDPs. Oral mucosal characteristics, age, pain sensitivity and behavioural factors seem to be more critical for mucosal pain than distribution of missing teeth and number of abutment teeth.

Stress distribution in root filled teeth restored with various post and core techniques: effect of post length and crown height.

AIM: To investigate interfacial stress distribution in restored root filled teeth with various post lengths and crown heights. METHODOLOGY: Three-dimensional mathematical models of a root filled mandibular premolar tooth were constructed. Parts of the tooth structures were replaced with ceramic crowns having three crown heights incorporating, either a cast post and core or a resin post and cores with fibre post or metallic post with four post lengths. Finite element linear analysis was performed to calculate equivalent and shear stress distribution at the interfaces between the teeth and post and cores under mesiodistal symmetrical boundary conditions and an oblique static load of 400 N. RESULTS: For the resin post and core with fibre and metallic posts, shear stress at the interface was greater in the cervical area than the post area, depending on the crown height. The resin post and core with metallic post had lower shear stress at the interface of cervical area than that of the fibre post model; however, the metallic post models produced a high concentration of shear stress at the interface between the post and resin composite. On the other hand, for the cast post and core, the shear stress at the interface was mainly produced in the post end area, which increased with decrease of post length. CONCLUSIONS: For the resin post and core, bonding integrity to the cervical area would play a critical role in the survival of the restored tooth, whereas for the cast post and core, the bond of the post would be essential.

Influence of intra-oral sensory impairment by anaesthesia on food comminution and mixing in dentate subjects.

Sensory input from sensory receptors regarding food morsels can affect jaw motor behaviours during mastication. The aim was to clarify the effects of intra-oral sensory input on the food-comminuting and food-mixing capacities of dentate subjects. Eleven dentate subjects without sensory dysfunction in their oro-facial region participated in this study. Local anaesthesia was achieved on the periodontal structures and on the oral mucosa of the subjects' preferred chewing side by injecting a lidocaine solution with adrenalin. At baseline (control) and after anaesthesia, data on the subjects' food-comminuting and food-mixing capacities were gathered. The food-comminuting capacity was quantified by measuring the degree of pulverisation of peanuts (objective hardness; 45.3 [Newton, N]) after a prescribed 20 chewing strokes. The food-mixing capacity was measured as the degree of immixture of a two-coloured paraffin wax cube after 10 chewing strokes. Wax cubes of three different hardness levels were used (soft, medium and hard: 20.3, 32.6 and 75.5 [N], respectively) and were chewed in random order. After anaesthesia, the subjects' food-comminuting capacity significantly decreased (P < 0.001), as did the food-mixing capacity for each hardness level of the wax cubes (P < 0.01). A significant correlation was observed between the objective hardness values and the anaesthesia effects for the food-mixing capacity (P < 0.05), indicating that after anaesthesia, deterioration of the mixing capacity increased as the hardness increased. In conclusion, intra-oral sensory input can affect both food-comminuting and food-mixing capacities.

Influence of posterior dental arch length on brain activity during chewing in patients with mandibular distal extension removable partial dentures.

It is well known that shortened dental arch decreases masticatory function. However, its potential to change brain activity during mastication is unknown. The present study investigates the effect of a shortened posterior dental arch with mandibular removable partial dentures (RPDs) on brain activity during gum chewing. Eleven subjects with missing mandibular molars (mean age, 66.1 years) on both sides received experimental RPDs with interchangeable artificial molars in a crossover trial design. Brain activity during gum chewing with RPDs containing (full dental arch) and lacking artificial molars (shortened dental arch) was measured using functional magnetic resonance imaging. Additionally, masticatory function was evaluated for each dental arch type. Food comminuting and mixing ability and the perceived chewing ability were significantly lower in subjects with a shortened dental arch than those with a full dental arch (P < 0.05). Brain activation during gum chewing with the full dental arch occurred in the middle frontal gyrus, primary sensorimotor cortex extending to the pre-central gyrus, supplementary motor area, putamen, insula and cerebellum. However, middle frontal gyrus activation was not observed during gum chewing with the shortened dental arch. These results suggest that shortened dental arch affects human brain activity in the middle frontal gyrus during gum chewing, and the decreased middle frontal gyrus activation may be associated with decreased masticatory function.

The influence of elastic modulus mismatch between tooth and post and core restorations on root fracture.

AIM: To investigate the influence of elastic modulus mismatch between tooth and post and core restorations on mechanisms of root fracture. METHODOLOGY: Three-dimensional mathematical models of a root filled maxillary premolar tooth with supporting periodontium were constructed. The tooth was restored with a cast Ni-Cr alloy or fibre-reinforced composite post and core that was bonded or nonbonded to dentine. In the nonbonded simulation, a nonlinear contact analysis was executed to simulate a friction and a potential sliding phenomenon in the interface between tooth and post and core. Risks of root fracture and debonding at the bonded interface were estimated based on the principal stress of the root and the shear stress on the interface, respectively. RESULTS: The fracture risk of the bonded cast post and core was lower than that of the composite post and core, although the cast restoration exhibited eight times greater stress than the composite. The risk of root fracture based on the tensile stress of the tooth structures was higher with the bonded composite post and core than that with the cast post and core. These stresses doubled when the restorations were not bonded to the tooth structures. The risk of debonding of the cast post and core based on the shear stress was approximately twice that of the composite post and core. CONCLUSIONS: The elastic modulus mismatch appears to be a factor responsible for the debonding of post and cores from root canals, with the potential to increase the risk of root fracture indirectly.

Recognition of endoscopic diagnosis in differentiated-type early gastric cancer by flexible spectral imaging color enhancement with indigo carmine.

BACKGROUND/AIMS: To evaluate the usefulness of flexible spectral imaging color enhancement with indigo carmine (I-FICE) in early gastric cancer (EGC) demarcation. METHODS: The study participants were 29 patients with differentiated-type EGC. The endoscope was fixed and images of the same area of EGC demarcations in each lesion were obtained using four different methods (WLE, flexible spectral imaging color enhancement (FICE), CE, and I-FICE). FICE mode at R 550 nm (Gain: 2), G 500 nm (Gain: 4), and B 470 nm (Gain: 4) was used. Four endoscopists ranked the images obtained by each method on the basis of the ease of recognition of demarcation using a 4-point system. We calculated the standard deviation of pixel values based on L*, a*, and b* color spaces in the demarcation region (Lab-SD score). RESULTS: The median ranking score for I-FICE images was significantly higher than that obtained from the other methods. Further, the average Lab-SD score was significantly higher for I-FICE images than for images obtained by the other methods. There was a good correlation between the ranking score and Lab-SD score. CONCLUSION: EGC demarcations were most easily recognized both subjectively and objectively using I-FICE image, followed by CE, FICE and WLE images.

Measurement of jerk-cost using a triaxial piezoelectric accelerometer for the evaluation of jaw movement smoothness.

Jerk-cost as a measure of jaw movement smoothness has been used to evaluate the masticatory function of patients with tooth loss and malocclusion. Jerk-cost measuring systems have thus far been unable to determine the jerk-cost of each chewing phase over time. The purposes of this study were (i) to develop a new method for measuring momentary jerk-cost of the jaw movement using a small triaxial piezoelectric accelerometer and (ii) to test the hypothesis that the lowest smoothness is seen during jaw-opening phase. The accelerometer was attached to the skin of the mentum of each subject. Vertical jaw displacement, acceleration, the jerk, and the time differential of jerk-cost during gum chewing were analysed as a function of time in five normal dentate subjects (n = 5). The system revealed intra-class correlation coefficients of intra-examiner, inter-examiner, and test-retest consistency of substantially high values (0.80-0.88). In all subjects, the highest jerk-cost was observed in the opening phase of each chewing cycle when the gum was parting from the teeth; the lowest jerk-cost was observed in the intercuspal phase throughout the chewing cycle, thus confirming the hypothesis. Significant differences were observed between the opening, closing, and intercuspal chewing phases (N = 5, P = 0.007). The smoothness measurement system used in this study evaluated the momentary smoothness of each chewing phase in the masticatory cycle. The system may serve as a diagnostic tool to evaluate the smoothness of the jaw movement in general dental practice.

A patient-based model study of fixed splinting of premolars with reduced periodontal support.

The aim of this patient-based study was to assess the effect of fixed splinting of mandibular premolars having reduced alveolar support on load distribution in the periodontium. A patient's mandibular second premolar with considerably reduced alveolar bone height was restored using a metal-ceramic restoration splinted with the adjacent first premolar; an acceptable 3-year maintenance period was observed. A patient-based three-dimensional finite element model was constructed using the morphological measurements obtained from the diagnostic cast and radiographs. The model incorporated in vivo occlusal records and was used to analyze stress and strain in the periodontium for splinted and nonsplinted simulations. Modified models were also created to explore the effects of relative bone height on the stress and strain distributions. The maximum principal stress and strain on the periodontium of the second premolar were considerably higher before splinting than after splinting and were close to strain levels indicative of potential bone microdamage. In contrast, the stress and strain in the first premolar increased after splinting. The modified models showed that the increased vertical gap of alveolar height between the splinted teeth was another factor to increase the load in the first premolar. Since the prosthodontic procedure employed is not routinely used, the results cannot be generalized. However, it is suggested that fixed splinting can decrease the periodontal load on premolars with reduced periodontal support, but may increase the load on the splinted tooth.

Insect juvenile hormone: activity of selected terpenoid compounds.

A nuimber of compounds with terpenoid skeletons attached to various functional groups were prepared and tested for their effects as a juvenile hormone in the yellow mealworm Tenebrio molitor. Several of these compounds showed high activity.

Endoscopic submucosal dissection for colorectal tumors: technical difficulties and rate of perforation.

BACKGROUND AND STUDY AIM: Endoscopic submucosal dissection (ESD) for colorectal tumors is not generally recommended because of the technical difficulties and complications, including perforation. These aspects of ESD are thoroughly analyzed in our retrospective study. PATIENTS AND METHODS: We studied 105 colorectal tumors, from 100 patients, that were treated by ESD at the Kyoto Prefectural University of Medicine or Nara City Hospital between 2005 and 2008. We analyzed tumor size, operation time, rate of en bloc resection, and complications. In addition, we thoroughly investigated the cases of perforation. RESULTS: The average tumor size was 30.4 mm; average operation time, 102 min; and rate of en bloc resection, 88.5 %. Perforation occurred in 10.4 % of the ESD procedures. Of the 11 perforations, 8 were detected during ESD and treated by clip closure during endoscopy, while 3 were evident only on subsequent routine computed tomography (CT); these were also managed conservatively. A case of postoperative hemorrhage was also observed. CONCLUSIONS: ESD effectively achieved a high rate of en bloc resection. However, the perforation rate was substantial; hence, improvement in the ESD method is required. The outcomes of ESD, especially for early colorectal malignancies, need to be assessed further.

Nonlinear finite element analyses: advances and challenges in dental applications.

OBJECTIVES: To discuss the development and current status of application of nonlinear finite element method (FEM) in dentistry. DATA AND SOURCES: The literature was searched for original research articles with keywords such as nonlinear, finite element analysis, and tooth/dental/implant. References were selected manually or searched from the PUBMED and MEDLINE databases through November 2007. STUDY SELECTION: The nonlinear problems analyzed in FEM studies were reviewed and categorized into: (A) nonlinear simulations of the periodontal ligament (PDL), (B) plastic and viscoelastic behaviors of dental materials, (C) contact phenomena in tooth-to-tooth contact, (D) contact phenomena within prosthodontic structures, and (E) interfacial mechanics between the tooth and the restoration. CONCLUSIONS: The FEM in dentistry recently focused on simulation of realistic intra-oral conditions such as the nonlinear stress-strain relationship in the periodontal tissues and the contact phenomena in teeth, which could hardly be solved by the linear static model. The definition of contact area critically affects the reliability of the contact analyses, especially for implant-abutment complexes. To predict the failure risk of a bonded tooth-restoration interface, it is essential to assess the normal and shear stresses relative to the interface. The inclusion of viscoelasticity and plastic deformation to the program to account for the time-dependent, thermal sensitive, and largely deformable nature of dental materials would enhance its application. Further improvement of the nonlinear FEM solutions should be encouraged to widen the range of applications in dental and oral health science.

Influence of alveolar support on stress in periodontal structures.

The influence of alveolar bone support on the functional capability of a tooth remains unclear. It was hypothesized that a reduction in alveolar support causes an increase of maximum stress in the periodontal structures. Mathematical models of the maxillary incisor to simulate in vivo tooth movement were constructed with periodontium of normal or reduced bone height, and normal or widened periodontal ligament (PDL) space. Under simulated bite force, the maximum tensile stress at the lingual cervical region in the PDL increased with bone height reduction, but decreased with PDL widening. The compressive stress at the cervical region in the cortical bone was no more than 22% of the yield strength of bone, and did not increase by the height reduction with widened PDL. The result suggests that the height reduction potentially causes mechanical damage to the PDL, but, of itself, is not likely to have a negative effect on the bone.

The cDNA cloning and transient expression of a chicken gene encoding a follicle-stimulating hormone receptor.

A clone, pcFSHR, containing a 3.1-kb insert was isolated from a cDNA library of chicken ovarian follicles by screening with an RT-PCR-generated cDNA probe for a putative N-terminal half-region of chicken FSH-R. The deduced amino acid sequence of pcFSHR exhibits about 84% identity to those of mammalian FSH-R and about 70% to those of mammalian LH-CG-R. Northern blot analysis for total RNA preparations from several chicken tissues revealed that transcripts detected with pcFSHR were present exclusively in ovary and testis. In a chicken ovary, the transcripts were detected in granulosa but not in theca cells. A radioligand receptor assay for the human 293 cells transfected with an expression vector containing the insert of pcFSHR demonstrated the production of a receptor which showed about 10-fold higher affinity for chicken FSH than for chicken LH. The affinity for chicken FSH was significantly higher than for human FSH. In consistency with the ligand specificity of the receptor, a significantly higher level of intracellular accumulation of cAMP was detected when the transfected cells were treated with chicken FSH than with chicken LH. From these results, we conclude that pcFSHR is a cDNA clone for the chicken FSH-R.

The cDNA cloning and transient expression of an ovary-specific 17beta-hydroxysteroid dehydrogenase of chickens.

A cDNA clone, pc17bHSD, was obtained from the chicken ovarian cDNA library by its partial homology to the cDNA sequence of the rat 17beta-hydroxysteroid dehydrogenase (17beta-HSD). The cDNA insert of pc17bHSD is 979bp long and contains an open reading frame (ORF) of 906bp. The deduced amino acid sequence of the ORF shows 48 and 50% overall identity with those of the rat and the human type-1 17beta-HSD, respectively. Five sequence regions common to the short-chain alcohol dehydrogenase superfamily are well conserved, including the YxxxK sequence motif at the active site. Northern blot hybridization detected a transcript of about 1kb only in ovaries of both sexually immature and mature female chickens. The 17beta-HSD activity, which was highly specific to the interconversion between estrone and estradiol-17beta, was detected in the cytoplasmic fraction of human 293 cells transfected transiently with an expression vector carrying the c17bHSD cDNA sequence, pcDNAI/c17bHSD. From these results, it is concluded that the pc17bHSD is the cDNA clone for the ovary-specific molecular species of 17beta-HSD in chickens.