bluuebunny/crossref_metadata_2025 huggingface dataset:
The influence of canine guidance and condylar guidance on mandibular lateral movement
Authors: KOYANO K. , OGAWA T. , SUETSUGU T.
Published: August 2010

summary
This Study investigates the definite influence of the working‐side canine and balancing‐side condylar guidances on mandibular lateral movement. Lateral movements were measured on 40 young adults (22 males and 18 females), using the three‐dimensional mandibular movement analysing system. The inclinations of the paths were calculated on the working‐side canine, incisor, balancing‐side first and second molars and balancing‐side condylar points in the frontal plane. Multiple regression analysis enabled quantitative evaluation of the influence of the canine path and condylar path on the path of each tooth. The canine path showed greater influence than the condylar path even on the balancing‐side second molar path. There was no difference between male and female subjects in the influential ratio of the canine guidance to the condylar guidance on any tooth path. It was concluded that the influence of the anterior and posterior guidance on the lateral movement varied according to the type of tooth, but not to the gender of the subject. This functional characteristic was confirmed by the morphological finding that the relative location of the molars in relation to canine and condyle does not differ between the sexes. The difference in the guiding system between the protrusive and lateral movement is also described in this paper.
A microscopic survey of the human temporomandibular joint disc
Authors: MINARELLI A. M. , LIBERTI E. A.
Published: August 2010

summary
The articular disc of the temporomandibular joint was studied in a foetuses and children group (GI), a dentate group of adults (GII) and an edentulous, elderly group of humans (GIII) by light microscopy. The main, constituent bundles of type I collagen fibres are stratified and are orientated sagittally, transversely and obliquely in the middle portion of the disc. In the thick, posterior portion, transverse bundles constitute the main feature. In the anterior portion of the disc, the fibres are sagittally and obliquely orientated. Type III collagen fibres, intermingled with type I collagen fibres are present in all groups. The disc is cellular in nature in foetuses and children, becoming more fibrous with age. Chondroid cells are observed in all portions of the discs in groups GII and GIII. Elastic fibres are numerous in GI discs and decrease in number in the disc with age. These fibres lie parallel to the collagen fibres in all three portions of the three groups.
Mechanical properties of endodontic posts
Authors: LAMBJERG‐HANSEN H. , ASMUSSEN E.
Published: August 2010

summary
Twenty‐two commercially available endodontic posts were examined with regard to stiffness, elastic limit and resistance to fracture. Differences in mechanical properties were explained by differences in width, shape and surface structure. In the selection of an endodontic post, its stability rather than its retention should be of primary clinical concern. Accordingly, the authors advocate the use of endodontic posts that have a cylindrical coronal portion and a conical apical portion.
Effect of 4‐META adhesive on the bond strength of different metal framework designs and acrylic resins
Authors: CANAY S. , HERSEK N. , TULUNOǦLU İ. , UZUN G.
Published: August 2010

summary
The effect of relining the 4‐META adhesive resin onto metal alloy of a partial denture framework was tested. Seventy‐two metal frameworks with three different retentive patterns were designed. Half of the specimens were treated with 4‐META, the other group was left untreated. Thirty‐six specimens were first divided into three groups in which 12 samples had different designs of retention, i.e. mesh, ring‐shaped and flat plane. Then, each different retentive design was divided into two groups and in one group Lucitone 199 and the other QC acrylic resin were processed. Finally they were subjected to shear test. While samples with adhesive exhibited greater bond strength than the others, samples without adhesive may be ranked in the order mesh, ring‐shaped and flat planes with regard to shear bond strength. In samples with adhesive, the flat plane ones displayed better results. Statistically significant differences were observed in the relationships between the groups.
Electric versus magnetic transcranial stimulation of the trigeminal system in healthy subjects. Clinical applications in gnathology
Authors: FRISARDI G. , RAVAZZANI P. , TOGNOLA G. , GRANDORI F.
Published: August 2010

summary
This investigation is focused on the analysis of the masseter responses evoked by means of magnetic and electric stimulation of the cortex and root of the trigeminal system of 20 healthy subjects. Moreover, in order to determine jaw elevation in centric occlusion, the analysis also focused on the motor response of the trigeminal bilateral roots evoked simultaneously using two stimulators. The masseter responses show a high level of symmetry in both latency and amplitude. The difference between the hinge axis in natural centric occlusion (CO) and in centric relation (CR) as determined by electric and magnetic transcranial stimulation is lesser than 2.5 mm. This is due to two main factors: (i) the response is evoked from the trigeminal motor neural pool involving all the masticatory muscles and hence simulating the natural ‘muscular coactivation’; (ii) there is no manual manipulation to guide the jaw into the centric relation (CR). This method could be of some help for diagnosis in patients suffering from TMJ dysfunction who have lost stereognostic control over the jaw and display obvious signs of deviation during closure of the mandible.
Methods for minimizing the errors in mandibular model mounting on an articulator
Authors: ADRIEN P. , SCHOUVER J.
Published: August 2010

summary
The study examines the errors that occur in mandibular mounting on a hinge‐axis articulator using impression wax and an arbitrary hinge axis. The transfer of the model positions on the articulator was analysed mathematically. The error varied considerably as a function of the real hinge axis localization. It was influenced by the orientation of the occlusion plane and especially by the thickness of the impression wax. Analysis of the results provided clinical conclusions that help minimize localization errors.
Application of a three‐dimensional reconstruction method to analysis of the residual ridge
Authors: KAWAHATA N. , ONO H. , KAMASHITA Y. , HAMANO T. , NAGAOKA E.
Published: August 2010

summary
The purpose of this study was to develop a new method of analysing the shape of the residual ridge. The line of the residual ridge crest was regarded as the reference for artificial tooth arrangement and a method of determining it was evaluated. The shape of a plaster model was measured with a contact‐type shape measurement system. The measurement data in each frontal section were interpolated by cubic splines. The points corresponding to the residual ridge crest were calculated and superimposed onto the image of the plaster model on a monitor screen of an image processor. Using these points and the image of the plaster model, the line of the residual ridge crest was marked on the plaster model. It was concluded that this method could be used to determine the line of the residual ridge crest on a plaster model.
A comparative study of flexible (Polyactive®) versus rigid (hydroxylapatite) permucosal dental implants. I. Clinical aspects
Authors: MEIJER G.J. , CUNE M.S. , VAN DOOREN M. , DE PUTTER C. , VAN BLITTERSWIJK C. A.
Published: August 2010

summary
Recently, an elastomeric polyethylene‐oxide polybutylene‐terephthalate (PEO:PBT) copolymer (Polyactive®) was introduced, which exhibits bone‐bonding characteristics. In contrast to ceramics, bioglass, titanium and other metals, PEO:PBT copolymers are flexible materials that could reduce undesirable peak stresses along the neck of a permucosal implant. The application of three types of Polyactive®permucosal dental implants (one dense and two porous types) and one dense hydroxylapatite (HA) implant were clinically tested and compared during 30 weeks of loading in a dog experiment. With respect to the porous Polyactive® implants, it was observed that the pore diameter had decreased to such an extent that optimal bone ingrowth was not achieved. Polyactive® is known to expand due to water uptake, and, as a consequence, the sizes of the pores of the press‐fit inserted implants had decreased to a large extent. This feature explained the high loss of the implants with the porous outer layer (6 out of 22). None of the dense Polyactive® implants and only one of the HA implants were lost. Statistical analysis was performed solely on the dense Polyactive® and the HA implants. At the lingual sites, plaque scores, gingiva indices, bleeding indices and corresponding pocket depths were statistically significantly lower for both implant types, when compared to the corresponding values at the buccal, mesial and distal sites, irrespective of the observation period. Differences between the dense Polyactive® and the HA implants were not observed. A considerable difference in mobility was registered between the Polyactive® and the hydroxylapatite implants, as measured by the Periotest®. The dense Polyactive® implants functioned adequately and had mobility resembling natural teeth. As such, these dense flexible materials showed a favourable clinical function and they seem promising for reducing undesired peak stresses when applied as a dental implant.
The response of human premolars to cyclic loading
Authors: ĆTOVIĆ A. , KRALJEVIĆ K. , JEROLIMOV V. , CELEBIĆ A. , KOVAČIĆEK F. , VALENTIĆ‐PERUZOVIĆ M.
Published: August 2010

summary
The aim of the study was to obtain data on the dynamic strength of both intact and prepared premolars for partial veneer crowns. Cyclic loading was performed in a modified Amslers high‐frequency pulsator with varying force (between 400 and 1400 N). The greatest dynamic strength was exhibited by the intact samples. The greater the load the fewer the cycles necessary to fracture the tooth. A stastically significant difference was found (P < 0.05) between the magnitude of cyclic loads and the different types of specimens tested.
Antifungal effect of zeolite‐incorporated tissue conditioner against Candida albicans growth and/or acid production
Authors: NIKAWA H. , YAMAMOTO T. , HAMADA T. , RAHARDJO M.B. , MURATA H. , NAKANODA S.
Published: August 2010

summary
A new antimicrobial material, Ag‐zeolite (Zeomic°), was combined with a commercial tissue conditioner (GC‐Soft Liner (GC); 1–5%) and, through monitoring the pH of the growth medium, examined for effects on the in vitro growth and/or acid production of Candida albicans on protein‐free and saliva‐coated specimens. The effect of incorporation of this agent on the physical property of the lining material was also examined according to the ISO penetration test. Comparison studies were carried out using GC, Coe Comfort (CC) or undecylenate combined GC (1–5%) specimens. Although the pH changes in the media varied depending upon the materials on which the Candida was grown, reverse sigmoidal pH curves were observed with most samples. As compared with GC, the soft lining materials showed, to some extent, an inhibitory effect on the acid production and/or the growth of C. albicans. These inhibitory effects consisted of a delay in the onset of rapid pH decline, decreases in the rate of pH change and increases in minimum pH. In most cases, the inhibitory effects of test specimens were dose‐dependent, and zeolite specimens showed a significantly higher antifungal effect, followed by CC and undecylenate‐combined GC; GC showed the least antifungal effect. The inhibitory effects of these materials on fungal growth were decreased by the presence of a saliva‐coat, particularly with zeolite specimens and CC. However, four of eight 5%‐Zeomic° specimens still exhibited perfect growth inhibition in the presence of the salivary pellicle. Furthermore, test specimens containing 2–5% Zeomic° showed a significantly greater effect on the delay in rapid decline of pH, as compared with the other specimens examined. In addition, the significantly higher minimum pH was observed where the yeasts were grown on 4%‐ and 5%‐Zeomic° specimens. The physical properties of all the test specimens conformed with the ISO standard as examined by penetration test. These results taken together suggest that an antimicrobial zeolite‐combined tissue conditioner would be a potential aid in denture plaque control.
Silver and fluoride ion release from metal‐reinforced glass‐ionomer filling materials
Authors: WILLIAMS J. A. , BILLINGTON R. W. , PEARSON G.
Published: August 2010

summary
This study was undertaken to examine whether a relationship exists between the composition of metal‐containing glass‐ionomer cements and ion release from these materials. Conflicting data on silver release from this type of material has been reported and it was felt that further investigation was desirable in view of the increasing use of these materials. In this study, the release of ions, particularly of silver and fluoride, into deionized water and artificial saliva was nieasured for up to one year. Low levels of silver and copper ions were found in both media. The amounts released from alloy‐containing materials were dependent on the amount of alloy present; lesser amounts were leached from cermets. Fluoride ion release was less material‐dependent but still lowest for cermets. The use of artificial saliva reduced ion release as did increasing the maturation time prior to immersion in either liquid.
Studies of changes in occlusion after the insertion of complete dentures* (Part II)
Authors: UTZ K.‐H.
Published: August 2010

summary
The aim of this clinical experimental study was to investigate whether, and what, changes in occlusion occur between 3 weeks and 1 year after insertion of complete dentures. Twenty‐six edentulous patients, who already had their jaw relation registered for part I of this study some 357 days before, were re‐examined. The same special non‐arcon measuring articulator was used for determination of any positional differences between the presently recorded central condylar position with inter‐occlusal gap and the equilibrated intercuspal position, from approximately 1 year previous. Differences were recorded electronically in the condylar area in three dimensions. The position of the condylar balls of the measuring articulator in maximum intercuspation had shifted, since the previous recording, by about 0.62 ± 0.04 mm (0.04–1.76 mm) in the sagittal and 0.89 ± 0.72 mm (0.01–3.06 mm) in the vertical direction. Whereas the differences measured in maximum intercuspation scattered in the sagittal plane uniformly around the centric condylar position, in the vertical plane they were shifted cranially about an average of 0.77 ± 0.85 mm (1.06 mm caudally to 3.06 mm cranially). The results indicate that in half of the patients from the present sample the occlusion did not remain stable, which is assumed to be mainly caused by resorption of alveolar bone and abrasion of the acrylic teeth. Therefore, at each check‐up visit not only the health of the denture‐bearing tissues and the fit of the dentures, but also the mandibular posture and the occlusion should be examined carefully.
Failure of dental bridges. IV. Effect of supporting periodontal ligament
Authors: FAYYAD M. A. , AL‐RAFEE M. A.
Published: August 2010

summary
The relationship between bridge failure and the periodontal ligament area of their abutments was studied in 156 dental bridges constructed for 132 patients. Of the bridges constructed at the College of Dentistry, King Saud University, 26.9% did not meet the published criteria of Ante's Law while 50.0% of those made in general dental practice did not meet the same criteria. However, radiographic evaluation of abutment teeth in 56 failed bridges revealed that there were only two cases with evidence of overloading the abutments.
Re‐examination of incisal tooth wear in children and adolescents
Authors: SILNESS J. , BERGE M. , JOHANNESSEN G.
Published: August 2010

summary
The material presented in this report was derived from a longitudinal study of the development and progress of incisal tooth wear in children and adolescents. The study group was established in 1991–1992 (baseline examination) and consisted of participants between 8 and 15 years of age. They were re‐examined in 1993 (interim examination) and in 1994 (final examination). In all, 77 school children (3O females and 47 males) participated in the three examinations. The timespan between baseline and interim was on average 15 months and the period between interim and final examination averaged 16 months. The total observation period was approximately 32 months. Assessments of incisal wear was made on stone casts using the incisal wear index which was shown to have good reproducibility. The results demonstrated that the prevalence and severity of incisal wear had increased significantly with age. In general the rate of incisal wear progression was higher between baseline and interim than between interim and final examination. In this respect certain differences between the tooth types seemed to exist. At baseline the relationship between age and incisal wear was positive and statistically significant for all tooth types. At the final examination the strength of this relationship had decreased for maxillary and mandibular central and lateral incisors. For canine teeth of both jaws the relationship between age and incisal wear was no longer statistically significant at the final examination.
Effect of complete denture renewal on oral health—a survey of 42 patients
Authors: PELTOLA M. K. , RAUSTIA A. M. , SALONEN M. A. M.
Published: August 2010

summary
The effect of complete denture renewal on oral health was evaluated both subjectively and clinically at follow‐up 30 months (range 19–36 months) after completion of treatment in 42 edentulous patients (31 women and 11 men, aged 34–76 years) treated by dental students during 1989–1992. Ninety per cent of the patients were satisfied with the new appearance of their dentures and 71% with the way they functioned. When comparing the base data and results from follow‐up it seems that general health and medication, anatomical circumstances, salivary flow rates and denture wearing habits in edentulous subjects do not change significantly over a few years. The main effects of denture renewal are seen in patient satisfaction, and clinically in the improved condition of oral mucosa and better fit and acceptable occlusion of dentures.
Effect of cleaning dentine with soap and pumice on shear bond strength of dentine‐bonding agents
Authors: BACHMANN M. , PAUL S. J. , LÜTHY H. , SCHÄRER P.
Published: August 2010

summary
in vitro study reports on the cleaning effect of different soaps on the shear bond strength of various dentine‐bonding agents. Human teeth were coated with provisional cements for 24 h or for 14 days. After removing the provisional cements with a scaler, the dentinal surface was cleaned with a cotton pellet and non‐fluoridated flour of pumice and soap for 10 sec. Different dentine‐bonding agents and a luting resin were bonded to the dentinal surface according to manufacturers'instructions with the bonding agent and the composite material being light‐cured at the same time. The bonding agents were tested under intrapulpal pressure and with thermal cycling to imitate physiological conditions. Compared with cleaning the dentine with water and pumice, all soaps investigated in this study decreased the shear bond strength values of the tested dentine‐bonding agents considerably.
Electromyographic evidence for a digastric reflex evoked by perioral stimuli in humans
Authors: CADDEN S.W. , NEWTON J.P. , YEMM R.
Published: August 2010

summary
Electromyographic recordings (EMGs) were made using skin surface electrodes placed over the anterior digastric muscle in seven subjects. In every case, short bursts of electrical stimuli to the upper lip produced a response in the EMG that had a minimum latency of 62.0 ± 10.8 ms (mean ± SD). By contrast, no responses were seen when single pulse stimuli were applied. In 6/7 subjects, the minimum stimulation intensity that produced the reflex was described as being sharp or painful. In three additional experiments, single motor units were recorded within the digastric muscle using needle electrodes. In two of these experiments, there was evidence of reflex activity 60–110 ms after the application of painful electrical stimuli to the lip. These findings confirm that perioral stimuli can evoke a digastric reflex in humans and suggest that this reflex requires the summation that results from successive volleys of impulses in a large number of nociceptive afferent neurones.
Chewing activity and activities of daily living in the elderly
Authors: MIURA H. , ARAKI Y. , UMENAI T.
Published: August 2010

summary
The present study was conducted in order to determine the statistical relationship between chewing activity and activities of daily living (ADL) in the elderly. Subjects which took part were 79 elderly individuals (37 males, 42 females) ranging in age from 65 to 74 years. Based on questionnaires regarding diet, a mastication score was determined to evaluate chewing activity in each subject. This score was scaled from 0 to 100%. ADL levels were determined using two indices: the guidelines of the Ministry of Health and Welfare of Japan and the Tokyo Metropolitan Institute of Gerontology (TMIG) index. The TMIG index is a multidimensional 13‐item index of competence in which scores range from 0 to 13 points. According to the guidelines of the Ministry of Health and Welfare, the independence level of each subject was evaluated as independent, home‐bound, or bedridden. These independence levels showed a significant correlation with the mastication score (P < 0.01). The mastication score also significantly correlated with the TMIG index, showing a Spearman coefficient of correlation of 0.63 in males (P < 0.01) and 0.71 in females (P < 0.01). These results suggest that chewing activity is related to ADL levels in elderly subjects.
Subjective pain report and the outcome of several orthopaedic tests in craniomandibular disorder patients with recent pain complaints
Authors: HESSE J.R. , VAN LOON L.A.J. , NAEIJE M.
Published: August 2010

summary
A comparison between a subjective pain report and the outcome of the combined dynamic and static pain tests, and several other orthopaedic tests, was investigated in craniomandibular disorder (CMD) patients with recent pain complaints and in control subjects. Thirty‐two CMD patients who clearly reported pain in the masticatory muscle region or in the temporomandibular joint region by means of a symptom report questionnaire (SRQ), participated in the study. The investigators performing the symptom report interview and the clinical tests were blinded to each other. A high correspondence was shown between the patients reporting joint or muscle pain (by means of SRQ) and the classification into arthrogenous and myogenous pain patients, based on the outcome of the dynamic and static pain tests (P=0.0003). The outcome of four other orthopaedic tests: passive maximum mouth opening (PMMO; P=0.0001), palpation of the temperomandibular joint (TMJ) and the masticatory muscles (P=0.0002), TMJ‐play (P=0.0001), and TMJ‐compression (P=0.0138) demonstrated significant differences between the patients reporting joint and muscle pain.
Recognition of veneer restorations by dentists and beautician students
Authors: MEIJERING A.C. , ROETERS F.J.M. , MULDER J. , CREUGERS N.H.J.
Published: August 2010

summary
Three types of veneer restorations (VRs) were evaluated for recognition by two groups of observers to study the aesthetic result. The different types of VRs were: porcelain, direct resin composite and indirect resin composite. One month after insertion of the VRs, colour transparencies were made of smiling patients randomly selected from a group of 112 patients participating in a clinical trial. The slides were evaluated by five dentists who were not familiar with the patients and by 25 beautician students (BS). Dentists were asked to locate the VRs which were present in the patients and to specify the type of VR. BS were only asked to locate the VRs. To trace a possible relationship between the aesthetic result of the treatment and a number of variables, ANOVA was applied to evaluate the variables:‘discolouration of the teeth’before treatment, ‘type of VR’ and ‘number of VRs’. Agreements in judgement were expressed in Cohen–Kappa coefficients. The results showed that the dentists could locate the VRs quite well (Kappa coefficient 0.64 ± 0.28) but for BS this was lower (Kappa coefficient 0.43 ± 0.27). The more VRs were made in one patient, the more difficult it was to locate them correctly. The other variables had no significant effect on the recognition of the VRs. It was not possible for the dentist observers to differentiate between the types of VRs.
Bonding of hybrid composite resin to the surface of gold–alloy used in porcelain‐fused‐to‐metal restorations
Authors: VALLITTU P. K .
Published: August 2010

summary
The aim of this study was to determine the bond strength of hybrid composite resin to the surface of a gold alloy used in porcelain‐fused‐to‐metal restorations. The surface of the gold alloy was either ground with a sintered diamond burr, sandblasted with Al2O4 or ground with a silicon‐carbide stone. The composite resin was bonded to the surface of the gold alloy with or without a commercial silane primer. Bond strength was tested with a three‐point loading test, and the elemental composition of the surface of the gold alloy after various mechanical treatments was analysed by SEM/EDS method. Replicas of the fracture surface of the test specimens were examined by SEM to determine whether or not composite resin particles left on the surface had adhered after the loading test. The results showed that mechanical treatment of the surface of the gold alloy affects the bond strength of the composite resin (P < 0·001) but that silane treatment of the surface did not affect the bond strength (P= 0·217). SEM/EDS analysis showed evenly distributed aluminium on the surface of sandblasted gold alloy and silicon on the surface that had been ground with the silicon‐carbide stone. This study suggests that sandblasting of the gold alloy surface considerably enhances the strength of its bond to hybrid composite resin.
Personality traits in a group of subjects with long‐standing bruxing behaviour
Authors: KAMPE T. , EDMAN G. , BADER G. , TAGDAE T. , KARLSSON S.
Published: August 2010

summary
The personality pattern of 29 subjects, 10 men and 19 women, with a mean age of 37.7 years (range 23–68) was studied by means of a personality inventory (KSP) and compared with the personality traits of a ‘normal population’. The bruxers had significantly higher scores in the somatic anxiety and muscular tension scales and lower scores in the socialization scale; that is, the bruxers were more anxiety‐prone, had higher vulnerability for psychosomatic disorders and were less socialized. The frequent clenchers (once to twice a week) comprised a special subgroup within the material with higher values in the somatic anxiety, psychic anxiety and muscular tension scales. A strong correlation was found between high values in the muscular tension scale and headache; aching neck, back, throat or shoulders; tooth clenching; number of muscles tender at palpation and the clinical dysfunction index (Di). The results of this study indicate a possible aetiological relationship between personality, tooth clenching and craniomandibular dysfunction (CMD). However, the material was small and some precaution must be taken prior to generalization of the results. Studies on larger material are needed and especially more studies in sleep laboratories.
In vitro adherence of bacteria to bleached or unbleached enamel surfaces
Authors: GÜORGAN S. , BOLAY S. , ALAÇAM R.
Published: August 2010

summary
The purpose of this in vitro study was to evaluate the effects of three 10% carbamide peroxide bleaching agents on adherence of bacteria to tooth enamel surface. Enamel specimens were subjected to one of three carbamide peroxide solutions for 8 h per day for 30 days. Control specimens were kept in saline solution. Profilometer evaluation of surface roughness was performed on all specimens. The adherence of Streptococcus mutans was determined bacteriologically. There was no significant difference in surface roughness between the untreated and treated enamel specimens but a statistically significant difference was found in the adherence of S. mutans to bleached and unbleached enamel specimens. Specimens treated with Opalescence° showed the highest adherence.
A long‐term study of transverse stability of maxillary teeth in patients with unilateral complete cleft lip and palate
Authors: RAMSTAD T. , JENDAL T.
Published: August 2010

summary
The aim of this study was to investigate the long term post‐treatment transverse stability of the maxillary dental arch in subjects with unilateral complete cleft lip and palate (UCLP) treated by the Harvold/Bøhn method of orthodontic expansion and prosthodontic retention. The treatment of 22 consecutive patients, primarily operated on during the period 1957–60, was completed at a mean age of 18.1 years by the provision of a fixed partial retention prosthesis across the cleft using the cleft side central incisor and canine only as abutment teeth. The cleft side lateral incisor was missing in each case. Dental casts were made at the time of abutment preparation and at six subsequent times with the final observation 13·5 years after treatment completion. Measurements of any shift in the transverse position of cleft side and non‐cleft side canines, premolars and first molars were made on standardized photographs of the casts. A constructed antero‐posterior palatal line served as ‘midline’ reference. A mean reduction of width at the final observation, as recorded from the palatal surface to the reference line, was for the cleft side canine: −0·4 mm, the premolar immediately distal to the prosthesis and the first molar: both −1·2 mm. The corresponding mean width reductions on the noncleft side were: canine −0·9 mm, premolar −1·2 mm, first molar −1·6 mm. The rate of movement towards the midline decreased linearly with in(time) for all variables (P < 0·02) but for the cleft side canine.
The relation of canine guidance with laterotrusive movements at the incisal point and the working side condyle
Authors: Yang Y. , Yatabe M. , Ai M. , Soneda K.
Published: August 2010

The effect of different types of canine guidance on the patterns of laterotrusive tracing at the incisal point and the relationship between the laterotrusive inclinations and the working side condylar movements were investigated in 42 young subjects. The subjects were divided into M and D groups according to their mesial and distal canine guidance, and were also divided into protrusive laterotrusion (PL) and retrusive laterotrusion (RL) groups according to their laterotrusive tracing patterns. No differences of laterotrusive inclinations and working side condylar movements were found between the M and D groups. The laterotrusive tracing pattern had no corresponding association with the type of canine guidance. In relation to the movements of the working side condyles, significant differences were found between the PL and RL groups. The condyles moved laterally and posteriorly in the RL group, but moved lateral and inferior in the PL one. The distance of condylar movement in the X direction was correlated with the horizontal and sagittal inclinations of laterotrusion. The results indicate that the movements of the working side condyle were affected functionally by the laterotrusion, but not by either the mesial or the distal type of canine guidance.
Changes in jaw‐jerk on different levels of jaw closure and teeth‐clenching in humans
Authors: Fukuyama E. , Fujita Y. , Soma K.
Published: August 2010

We investigated how the jaw‐jerk in the human masseter muscle is modulated in relation to the level of jaw closure (JC) and teeth clenching. Electromyographic (EMG) activity was recorded with surface electrodes. Background EMG activity of the masseter muscle was kept at three low teeth clenching levels with visual feedback. The level of JC was changed in six steps along the habitual path of closure relative to the mean maximal jaw opening during gum chewing by inserting a bite block between the upper and lower molars. The jaw‐jerk was evoked by applying mechanical stimulation of about 20 N with a hammer to the bite‐fork placed on the lower molars on one side in each condition of combination of a level of JC with a level of teeth‐clenching. At the resting condition the excitability of the jaw‐jerk increased with JC, while at weak voluntary teeth clenching it then decreased and increased again as the jaw was progressively closed. It is suggested that the excitability of the jaw‐jerk would increase toward the occlusal position, which in turn would contribute to smooth masticatory movements. In addition, the mode of modulation of the jaw‐jerk was studied in a subject with skeletal malocclusion.
Biomechanical calculation of human TM joint loading with jaw opening
Authors: Kuboki T. , Takenami Y. , Maekawa K. , Shinoda M. , Yamashita A. , Clark G. T.
Published: August 2010

A three‐dimensional, static mathematical calculation of the stomatognathic system was done to predict total temporomandibular joint (TMJ) loading at different levels of jaw opening. The model assumed that muscle forces acting on the mandible could be simulated by a combination of contractile components (CCs) and elastic components (ECs) and that static equilibrium existed within the body of the mandible. The model also imposed the constraint that any generated joint reaction force would act on the centre of the condyle. The results of the model demonstrated that under all conditions of opening and for all values of the elastic modulus selected, the forces between the TMJ condyle and the articular eminence were compressive in nature. The compressive force magnitude increased from 2·7 to 27·6 N incrementally as the jaw opened from 10 to 40 mm. Overall data in this study indicated that the TMJ tissues undergo low levels of compression at open positions up to 40 mm. Finally, the condition of trismus (increased jaw closing activation with opening) was simulated, the joint reaction force at 20 mm opening increased from 7·7 to 64·9 N with only a 20% activation of the closers.
Influence of previous restoration of the tooth on prognosis of crowns with dowels
Authors: Näpänkangas R. , Salonen M. A. M. , Raustia A. M.
Published: August 2010

Due to extensive loss of tooth substance the restoration of endodontically treated tooth requires intracanal dowels to give an efficient strength for the crown. The aim of our study was to investigate whether the previous type of restoration of the tooth, i.e. composite restoration with screw post versus one‐piece dowel crown, has an effect on the prognosis of crowns with dowels. The material consisted of 111 single crowns and as a previous restoration there were 83 composite restorations with screw posts and 28 one‐piece dowel crowns. The mean follow‐up time was 78 months (range 6–163 months). The cumulative survival was 87% for one‐piece dowel crowns and 84% for composite resins with screw posts. There were six root fractures, four losses of cement retention and one tooth extraction due to caries in crowns with previous composite resin with screw posts. In one‐piece dowel crowns as a previous restoration there were two root fractures and one tooth extraction for periodontal reasons. In conclusion, it seems that the previous restoration has no marked effect on the prognosis of crowns with dowels when studying a composite resin restoration with screw post and a one‐piece dowel crown.
Factors affecting the ability of dental cements to alter the pH of lactic acid solutions
Authors: Patel M. , Tawfik H. , Myint Y. , Brocklehurst D. , Nicholson J. W.
Published: August 2010

Two related studies have been carried out to determine the effect of (a) powder:liquid ratio and (b) relative amounts of cement on the extent of buffering of a lactic acid storage solution using zinc polycarboxylate and glass–ionomer cements (both water‐activated). The effect of varying the powder:liquid ratio was found to be slight and not statistically significant. On the other hand, increasing the numbers of specimens in a given volume of storage solution was found to have a significant influence on the final pH (at the 0·0005 level of significance). The fact that powder:liquid ratio did not affect the final pH led to the conclusion that attack occurs mainly at the matrix of these cements, confirming previous findings about the acid erosion process. The finding that increasing the relative amount of cement to acid storage solution strongly influenced pH suggested that, under clinical conditions, buffering would be important. When five specimens were used, the final pH corresponded to that of arrested caries, from which it was concluded that these cements have the ability to be cariostatic in vivo.
Measuring system for lip movements using two video trackers
Authors: Sekita T. , Minakuchi S. , Hirano Y. , Kobayashi K. , Nagao M.
Published: August 2010

Movements of soft tissues surrounding the oral cavity, especially lips and cheeks, have a strong influence on mastication and phonetics. They also influence the relationship between a denture and its oral environment. The purpose of this study was to develop a three‐dimensional measuring system for soft tissue movement. This system consisted of two video trackers placed stereographically and a computer. In addition, one video tracker was connected for measuring mandibular movements. The accuracy of this system was evaluated using computerized XYZ pulse stage. The resolution of this system was 0·10×0·10×0·10 mm, when the measurement was carried out in the area of the 24·0 (X)×20·0 (Y)×20·0 (Z) mm with a working distance of 500 mm and a frequency of 120 Hz. In the present study, the lip movements of a dentulous subject with mandibular movements during chewing peanuts were analysed using this system. The new system demonstrated its value for analysing soft tissue movement.
Rehabilitation of biting abilities in patients with different types of dental prostheses
Authors: Miyaura K. , Morita M. , Matsuka Y. , Yamashita A. , Watanabe T.
Published: August 2010

This study investigated the masticatory rehabilitation of subjects wearing different types of prostheses. Biting abilities per person (biting force, biting pressure and occlusal contact area) were assessed with a pressure detecting sheet (Prescale®). Five hundred and ninety volunteers were divided into four groups according to the type of posterior dentition: complete denture, removable partial denture, fixed partial denture, and full natural dentition groups. The biting forces of the fixed partial, removable partial and complete denture wearers were 80, 35 and 11% respectively, when expressed as a percentage of the subjects with a natural dentition. The complete denture wearers showed the highest biting pressure among the four groups, followed by the removable partial denture wearers. In a clinical intra‐individual study, the biting abilities of 85 subjects, without (before insertion of) and with (after insertion of) renewed prostheses, were compared. No significant differences were found between biting before and immediately after insertion of the prostheses. However, the biting force and occlusal contact area increased 2 months after insertion of the prostheses. This study confirmed past clinical studies indicating an impaired masticatory function of denture wearers. The functional adaptation to new prostheses had improved at evaluation 2 months after insertion.
Dimensional measurement and finite element analysis of I‐bar clasps in clinical use
Authors: Sato Y. , Tsuga K. , Abe Y. , Asahara S. , Akagawa Y.
Published: August 2010

An I‐bar clasp is a popular retainer for distal‐extension removable partial dentures. However, there have been almost no evidence‐based criteria on the mechanically preferable shape. The present study aimed to investigate the variations of dimension in I‐bar clasps used in patients, and to clarify the effect of the variations on stiffness and stress of I‐bar clasps by finite element analysis. Dimensions (thickness, width, taper, radius of curvature, length, relation to oral structures) of 23 I‐bar clasps were measured. A three‐dimensional finite element model was made for each measured I‐bar clasp with vertical and horizontal straight sections connected with a curved section. A concentrated load of 5 N was applied at the lowest point of the tip that contacted the abutment in the buccal direction. Maximal equivalent stress and stiffness of each clasp were evaluated. The measured dimension, stiffness, and maximum stress showed wide variations. Mean stiffness was far from the proper one, and mean stress was near the proportional limit of Co–Cr alloy. Considering the stiffness and stresses in this study, only six clasps out of 23 were appropriate. These results suggest that evidence‐based criteria of preferable shape of I‐bar clasps should be determined.
Rheological characteristics of tooth bleaching materials
Authors: Wille T. , Combe E. C. , Pesun I. J. , Giles D. W.
Published: August 2010

Tooth bleaching materials need to flow easily on insertion but should have high viscosity at low stresses to stay in place on the teeth. Some degree of elasticity may also aid retention on the teeth thereby maximizing efficacy. The present work was undertaken to study the comparative rheology of three tooth bleaching systems: two gels (Opalescence®, Ultradent; Perfecta Trio®, American Dental Hygienics) and a paste (Colgate Platinum®, Colgate). A dynamic stress rheometer (Rheometrics Scientific) with cone and plate geometry was used, with the materials maintained at 37·0±0·1 °C with a vapour hood to minimize volatilization. Stress creep and recovery experiments were carried out. Steady shear viscosity for all three systems was high (>106 Pa s−1) for stresses <20 Pa. Between 100 and 200 Pa stress, all three materials showed a large drop in viscosity and flowed readily. The recovery portion of the data showed a marked difference where the elasticity of the gels was nearly two orders of magnitude higher than that of the paste. It was concluded that all materials would flow readily on insertion into the mouth and all have desirable high viscosity at low stress, but the paste material had the lowest elasticity. The effect of elasticity on performance needs to be determined clinically.
The relationship of bruxism with craniofacial pain and symptoms from the masticatory system in the adult population
Authors: Ciancaglini Riccardo , Gherlone Enrico F. , Radaelli Giovanni
Published: August 2010

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.
Influence of nocturnal bruxism on the stomatognathic system. Part I: a new device for measuring mandibular movements during sleep
Authors: Amemori Y. , Yamashita S. , Ai M. , Shinoda H. , Sato M. , Takahashi J.
Published: August 2010

The purpose of this study was to investigate the influence of bruxism on the stomatognathic system. A new device for measuring nocturnal mandibular movements was developed using a PIN photodiode sensor, integrated with polysomnography including electromyography (EMG), electroencephalography (EEG) and electro oculography (EOG). One bruxing event was defined depending upon EMG activities above 5% maximum voluntary contraction (MVC), and mandibular movement for each event was classified into three patterns (clenching, grinding and mix). Three subjects were selected for this study. Two of these reported a bruxing habit and one subject had some symptoms of temporomandibular dysfunction (TMD). Mandibular movement was analysed for these subjects. Frequency and duration of the bruxism events were 4·5–10·9 and 47·8–174·9 s h–1respectively. Clenching type bruxism was most frequently observed for all three subjects and EMG activities during clenching were stronger than grinding.
The dynamic behaviour of a lower complete denture during unilateral loads: analysis using the finite element method
Authors: Takayama Y. , Yamada T. , Araki O. , Seki T. , Kawasaki T.
Published: August 2010

The purpose of this study was to analyse the correlation between the location and/or direction of unilateral load and the dynamic behaviour of a mandibular complete denture using the three‐dimensional finite element method (FEM). The FE model consisted of the body of mandible, alveolar mucosa, and a complete denture, and it could simulate the condition of contact between the surface of the mucosa and mucosal surface of a denture. Load vectors, which simulated premature contacts, were calculated on the supposition that a premature contact on an occlusal facet causes a vertical load on it. Load‐A, a load vertical to the anterior occlusal facet, caused the least displacement of the denture and less concentrated stress distribution. Load‐P, a load vertical to the posterior occlusal facet, was characterized by the stress distributed in the lingual area of the pre‐molar lesion on the contra‐lateral side of the load. Load‐B, a load vertical to the balancing occlusal facet, caused the largest displacement of the denture. The relationship between loads and stress distribution was agreed approximately with the observations previously reported, and lead to some suggestions about occlusion for complete dentures.