bluuebunny/crossref_metadata_2025 huggingface dataset:
The influence of the condensation instrument on the clinical behaviour of amalgam restorations*
Authors: LETZEL H. , VAN'T HOF M. A. , VRIJHOEF M. M. A.
Published: June 2007

The influence of the condensation instrument on the behaviour of amalgam restorations was investigated in a clinical study for which in a group of forty‐nine patients, 125 Class I or II amalgam restorations were made by each of two operators. The restorations were made in series of five per patient. For each restoration within a series, the amalgam was condensed with a different instrument (hand condensation, Amalgam Condensaire, Speedomatic, Bergendal Vibrator and Electro‐mallet). For a period of 2.5 years the restorations were checked at half‐year intervals for failures. The marginal integrity of the restorations was assessed half‐yearly with a six‐point photo rating scale. The discolouration, roughness formation and the marginal integrity of the restorations were assessed clinically with four‐point rating scales. The number of failures and the assessments were analysed for the effect of the condensation instrument, the patient and the operator.

After 2.5 years, 12% of the restorations had failed, which is too few for the tracing of a condensation instrument and a patient effect. The operator, however, had an influence on the failure percentage. The condensation instrument had no influence on the clinical behaviour of the restorations, however the patient had. The operator only had an influence on the marginal integrity. This suggests that clinically the condensation results depend more on the operator rather than the instrument.
Comparative study of clinical examination, occlusal analysis and new radiological imaging procedures in patients with functional TMJ disorders
Authors: REULING N.
Published: June 2007

A comparative study was made in fifty‐three patients with functional diseases of the stomatognathic system and twelve healthy probands by means of anamnestic exploration, clinical examination, occlusal analysis, computed tomography (CT) and magnetic resonance imaging (MRI). Connections between functional and structural changes of the diseased stomatognathic system were found. The results showed the possibilities and applications of CT and MRI as supplementary diagnostic methods in the diagnosis of functional TMJ disorders.
The mandibular rest position and electromyography—a review
Authors: WATKINSON A. C.
Published: June 2007

The objective of clinical methods for the establishment of the rest position of the mandible is to establish a position at which masticatory muscle activity is minimal. Several methods are in clinical use but these methods may not elicit a position which is coincident with the lowest level of muscle activity as determined electromyographically.
Helkimo's index: a scale or just a set of symptoms?
Authors: VAN DER WEELE L. Th. , DIBBETS J. M. H.
Published: June 2007

This article discusses the validity of indices, exemplified by Helkimo index, by means of a critical analysis of the assumptions that should be made for constructing an index. General principles of scale construction are applied to test the adequacy of the scale‐values used for five common clinical symptoms in the Helkimo Di index. These general principles postulate that in addition to identifying patients correctly, an effective scale should also discriminate normal subjects. It is concluded that there is insufficient evidence to support the general applicability of this index. Further research concerning the properties of the index is needed. It is suggested that, since Helkimo's DI index contains many valuable elements, the discussion should be directed to improving the existing scale rather than trying to construct a new one.
Experiences with resin—bonded bridges and splints—a retrospective study
Authors: MARINELLO C. P. , KERSCHBAUM Th. , HEINENBERG B. , HINZ R. , PETERS S. , PFEIFFER P. , REPPEL P. D. , SCHWICKERATH H.
Published: June 2007

In a joint evaluation of 496 resin‐bonded bridges and splints anchored by various retention principles and composites, the initial experiences of seventeen clinicians were compiled. The main indications for treatment were congenital anodontia and loss of teeth due to caries and trauma. After 3 months, 95% of the bridges were still in place without need of reattachment procedure. After 6 months the figure was 91%, after 1 year 81.5% and after 1½ years 73%. Seventy‐five per cent of the loosened bridges were attached successfully a second time. The success rate for splints was significantly lower.
Resistance to horizontal forces of dowel and amalgam‐core restorations: a comparative study
Authors: GORDON M. , METZGER Z.
Published: June 2007

Four designs of amalgam‐core anchorage were compared in a laboratory study for the inability to withstand the horizontal component of occlusal force. Amalgam cores were constructed for extracted teeth with either composite resin‐cemented Dentatus dowels, or with Para‐post or Flexi‐post dowels cemented with phosphate cement. All the posts were of comparable length and diameter. These anchorage designs were compared with each other and to a self‐threading (TMS) pin‐retained amalgam core, by application of horizontal force and recording forces causing failure. Flexi‐post‐retained amalgam cores failed at a mean force of 36·5 (±8·5) kg while Dentatus‐retained and Para‐post‐retained cores failed at 41·7 (±8·0) kg and 46·6 (±11·4) kg, respectively. TMS‐retained cores resisted forces up to a mean force of 53·5 (±4·5) kg. Patterns of failure varied widely among these groups. Composite resin‐cemented Dentatus dowels were retained in the tooth in nine out of ten samples, while none of the ten Flexi‐post dowels and only one of the ten Para‐post dowels did so. Tooth fracture on, failure occurred in seven out of ten Flexi‐post‐retained cores, while only three out of ten of the Para‐post‐retained cores and none of the Dentatus dowel‐retained cores presented this unrepairable type of failure. Possible reasons for these differences are discussed.
Ability of edentulous human beings to adapt to changes in vertical dimension
Authors: HELLSING G. , EKSTRAND K.
Published: June 2007

The ability of ten edentulous patients and one patient with a full upper removable denture and a full arch (16–26) lower fixed denture to adapt to sudden change of the interocclusal distance was tested. An upper acrylic bite splint was inserted which, on average, increased the vertical dimension of the face by approximately twice the mean interocclusal distance during relaxation. After this procedure all patients quickly acquired an unstrained new postural position of the mandible. Directly after insertion, when instructed to relax, all patients hit the lower surface of the splint. They seemed, however, to need only one such experience to adapt to the increased interocclusal distance. The second time they repeated the procedure none of them touched the splint. Instead a new postural position was established with a mean interocclusal distance of 3.3 mm.

This fast re‐programming of jaw muscle tonus and length is assumed to be a response to different peripheral receptor discharge converging to the cerebellum and other programming centres. The present study on edentulous patients shows that afferent discharge from periodontal receptors is not a necessary prerequisite. It also confirms that the old concept of consistency of the mandibular postural position (Thompson, 1946) is erroneous.
Clinico‐pathological study on denture stomatitis
Authors: MORIMOTO K. , KIHARA A. , SUETSUGU T.
Published: June 2007

The clinical and pathological study was performed in order to determine the histo‐pathological and cytoimmunological characteristics of denture stomatitis. All specimens were biopsy materials from seventeen patients with denture stomatitis. Normal palatal mucosae from ten patients served as the control. In addition to the usual staining methods, naphtol AS‐D chloroacetate esterase stain and peroxidase‐antiperoxidase method were used to detect mast cells and plasma cells.

Denture stomatitis could be divided into atrophic and hyperplastic types. The former showed a smooth and atrophic mucosa. The latter showed a large number of exophytic projections which were composed of marked acanthosis and submucosal fibrosis, and was further subdivided into granular and papillary subtype according to the size of projections. In the present study, there were six cases of the atrophic type, and eleven cases of the hyperplastic type (consisting of seven granular and four papillary subtypes).

The hyperplastic type was more frequently observed in patients with partial dentures compared with complete dentures and was associated frequently with ill fitting of the denture base as well as agglutination of denture plaque.

Cytoimmunological study revealed that there was a pronounced increase of plasma cells, especially IgG‐ and IgA‐producing cells, and a moderate increase of lymphocytes as well as mast cells in both types of denture stomatitis. Mast cells were always noted in the area with marked plasma cell infiltration, suggesting an intimate relation between both cells. These findings suggest that the immunological reactions play some role in the pathogenesis of denture stomatitis.
Anatomical and electromyographic studies of the digastric muscle
Authors: WIDMALM S.‐E. , LILLIE J. H. , ASH M. M.
Published: June 2007

The techniques and sites for EMG recordings from the digastric muscles are controversial. To re‐evaluate old techniques for recording from the digastric muscles, especially the posterior bellies, the morphology of the muscles was studied by conventional dissections and by examination of specimens sectioned in the frontal and the horizontal planes. Based on these anatomical findings, recording sites and approaches to them were developed for the anterior and posterior bellies of the digastric muscles. EMG recordings from the two bellies of the muscle were obtained from five healthy subjects. The EMG recordings were ranked according to muscle activity level and the activity within single muscles and between muscles compared using the Wilcoxon signed rank test. The anterior and posterior bellies had synchronized activity in all mandibular movements but were silent or had negligible activity with the mandible in the rest position, when the head was rotated, and while clenching. Both bellies had marked to very marked activity during jaw opening, and moderate to marked activity during protrusion, retrusion and lateral movements. During swallowing the anterior and posterior bellies had patterns characterized by bursts of activity of high amplitude and short duration. The two bellies were not, however, always synchronously active.
First experiences with resin‐bonded bridges and splints—a cross‐sectional retrospective study, part II
Authors: MARINELLO C. P. , KERSCHBAUM Th. , HEINENBERG B. , HINZ R. , PETERS S. , PFEIFFER P. , REPPEL P. D. , SCHWICKERATH H.
Published: June 2007

This second report establishes that the success of treatment with resin‐bonded bridges was dependent upon many factors. Factors controlled by the clinician, such as case selection and treatment planning greatly influence the clinical success. It was possible to show that framework preparation and the amount of available enamel were significant factors, whereas isolation technique, type of retention mechanism and type of adhesive used were of less importance. Longitudinal studies are needed to confirm these observations.

Seventeen clinicians placed 496 resin‐bonded bridges and splints with different retention mechanisms and bonding agents. These reconstructions were examined in regard to the failure rate and in regard to reattachment problems. Ninety‐seven per cent of the bridges and 90% of the splints were still in place after 1 year. For bridges and splints a 90% success rate was ascertained after 2 years.
Force–displacement properties of a modified cross‐linked silicone compared with facial tissues
Authors: FARAH J. W. , ROBINSON J. C. , HOOD J. A. A. , KORAN A. , CRAIG R. G.
Published: June 2007

A dimethyl siloxane triacetoxy terminated silane, Type A adhesive, was modified with the base component of a medium grade polydimethyl siloxane with vinyl groups, MDX 4–4210, to produce a more pliable maxillofacial prosthesis. Force–displacement curves of various ratios of Type A adhesive/MDX 4‐4210 were determined and compared with force–displacement curves obtained from human subjects. Within the force range of 0.4 to 1.2 N, the force–displacement slopes obtained on human subjects compared favourably with some of the Type A adhesive/ MDX 4‐4210 test specimens. The force–displacement slopes for the elastomers and humans were not in agreement for forces below 0.4 N.
The use of an electronic thermometer in intraoral temperature measurement
Authors: HARUN Z. , STAFFORD G. D. , HUGGETT R.
Published: June 2007

The applicability of an electronic thermometer CRAFTEMP® in taking intraoral temperatures was determined. Sublingal temperatures in ten young subjects with complete natural dentitions, and the temperatures at the denture base–mucosa interface and on the polished surface of both maxillary and mandibular complete dentures in ten elderly patients were measured. The results showed that there was a temperature difference between the polished surface of the maxillary denture and the denture base–mucosa interface. This was statistically significant in the female but not in the male subjects. No temperature difference could be demonstrated with any of the mandibular dentures. The CRAFTEMP® was found to be a convenient and reliable method for intraoral temperature measurement.
Fixed restorations produced by commercial dental laboratories in Vancouver and Geneva
Authors: MACENTEE M. I. , BELSER U. C.
Published: June 2007

A survey of commercial dental laboratories in Geneva and Vancouver has been carried out using both questionnaires and telephone enquiries. It was concerned with the types of fixed prostheses constructed and the impact of recent technical developments.

The results of the study revealed that cosmetic factors played a major role in deciding the use of new techniques. Porcelain was used on the occlusal surface of most restorations and metal margins were preferred on PFM crowns. Precious and base alloys were used frequently to cast PFM protheses in Vancouver, whereas semi‐precious alloys were favoured in Geneva. Most of the laboratories used precious alloys for all‐metal restorations.
Oxidation of a gold‐palladium PFM alloy
Authors: VRIJHOEF M. M. A. , VAN DER ZEL J. M.
Published: June 2007

In this study, the influence of oxygen pressure, as well as oxidation time and temperature, on the oxide formation of a gold‐palladium‐indium‐gallium alloy was investigated. After oxidation (vacuum/air, 1–10 min, 940–1020°C) the oxides were removed selectively by means of leaching in 37% hydrochloric acid. Concentrations of the metallic parts of the oxide layers were determined by means of an emission spectrometer. The composition of the oxide layer was computed on the basis of these measurements.

Palladium oxide was not found. The formation of In2O3 and Ga2O3 was detected. The oxidation time did not influence the composition of the oxide layer. A higher oxidation temperature gave a slightly greater In2O3 concentration. Oxidation in vacuum resulted in a much higher Ga2O3 content. Under all conditions gallium oxidized preferentially.
The subjective experience of mastication in subjects with shortened dental arches
Authors: AUKES J. N. S. C. , KÄYSER A. F. , FELLING A. J. A.
Published: June 2007

In this study the perception of chewing is investigated in forty‐three subjects with a shortened dental arch (SDA) by means of an interview. A group of fifty‐four subjects with a complete dentition was used as a control group. The aim was: (i) do subjects with a SDA have a higher risk of chewing problems, and (ii) do they have different food perception and food selection leading to change in their diet?

The results show that for subjects with a SDA the chewing function, food perception, food selection and actual food consumption are hindered within an acceptable degree.
Electromyographic biofeedback and sustained masseter muscle contraction in man
Authors: WATKINSON A. C.
Published: June 2007

Twenty‐two human subjects performed sustained voluntary contractions of the mandibular elevator muscles firstly without and secondly with visual biofeedback. The level of electromyographic activity of the masseter muscle during the second clench exceeded that during the first clench by a mean of 36%. This differential indicates the ability of the subjects to override the central factors which normally limit muscle activity during a fatiguing contraction.
Prevalence of signs and symptoms of mandibular dysfunction among adults aged 25, 35, 50 and 65 years in Ostrobothnia, Finland
Authors: TERVONEN T. , KNUUTTILA M.
Published: June 2007

The prevalence of objective signs and subjectively perceived symptoms of mandibular dysfunction were studied in a sample comprising 1600 subjects, 400 each aged 25, 35, 50 and 65 years. Eighty per cent of the subjects were examined clinically. The prevalence figures were higher among the females than among the males, and a slight tendency for higher frequencies of clinical signs was observed with increasing age. In view of the severity of clinical signs preference should be given for a total of 27% of the subjects when considering the need of treatment. The number of remaining teeth in subjects with natural teeth and no additional removable dentures had no marked influence on the prevalence of mandibular dysfunction, but subjects with complete dentures had signs and symptoms of dysfunction more often than those with natural dentition. The sex and age differences can partly be explained by the higher frequency of complete dentures in females than in males and in the older age groups.
The effects of muscle fatigue on the silent period of the masticatory muscles
Authors: NAGASAWA T. , TAMURA H. , TSURU H.
Published: June 2007

Thirteen healthy adults performed sustained clenching at 50% maximum clenching level judged electromyographically. Electromyograms were recorded from both anterior temporal and masseter muscles during clenching and the silent period latency and duration were measured. As the result of muscle fatigue, the silent period latency significantly decreased, whilst the duration significantly increased up to 3 min from the beginning of clenching.
Factors influencing the bond strength between glass polyalkenoate (ionomer) cements and dentine
Authors: WALLS A. W. G. , McCABE J. F. , MURRAY J. J.
Published: June 2007

A series of investigations have been performed to study some factors influencing the tensile bond strength of glass polyalkenoate cements to dentine. The measured bond strength was affected by the method of storage of the teeth prior to testing, the nature of the dentine and the type of cement used for the tests. The most consistent results for bond strength measurements were obtained with teeth stored in neutral buffered formalin for more than 1 month after extraction, and then stored in distilled water for 4 weeks prior to bond strength determinations. The mean value obtained with this storage regime (1·62 MPa) was not different from that obtained using freshly extracted teeth (1·74 MPa). The bond strength to deciduous dentine (0·72 MPa) was significantly less than that to permanent dentine (1·62 MPa). There were significant differences between the measured bond strengths of the three materials tested, with Ketac‐Fil giving the lowest result (1·62 MPa), then Ketac‐Silver (2·41 MPa), ChemFil II formed the strongest bonds (4·65 MPa).
Quantitative observations on maximum static work efforts and associated pain of the human masseter muscle
Authors: CHRISTENSEN L. V.
Published: June 2007

The single case experimental design was used to study day‐to‐day variations in the onset (PL), tolerance (PT), and intensity (VAS) of masseter muscle pain. Pain was induced by maximum voluntary teeth clenching, with no artificial feedback‐control of the level of isometric activity, and static work efforts were quantified by cumulative electromyography. A continual effort to produce maximum static work, about 40% increase from baseline work, elicited in 30–40s an initial sensation of muscular pain that had an intensity of about 25% of maximum possible score. A further increase in maximum static work effort, about 60% increase from baseline work, caused in about 2min an intolerable increase in the intensity of muscular pain, about 50% of maximum possible score. Whereas PL showed day‐to‐day variation, PT and the ratio PL:PT did not. Intensity (VAS) scores and maximum static work efforts showed no day‐to‐day variations. Onset (PL) and tolerance (PT) showed no linear associations with VAS scores, and VAS scores showed no linear associations with maximum static work efforts; if anything, the latter associations tended to resemble a cubic parabola. Two different central neural processes, not associated with maximum static work efforts in a simple linear manner, might have been instrumental in: (i) the establishment of criteria for onset and tolerance of pain, and (ii) the discrimination of variable levels of pain intensity.
The effect of contact area morphology on operative dental procedures
Authors: LONG T. D. , SMITH B. G. N.
Published: June 2007

Measurements of the contact and embrasure areas of adjacent extracted teeth set in plaster blocks were made before groups of dentists undertook preparations on them. The prepared and adjacent teeth were examined and the findings related back to these measurements.

Damage to the adjacent teeth was a common finding with both mesial–occlusal–distal (MOD) and complete crown preparations. There was some evidence that easier access to the contact area reduced the frequency of damage to teeth adjacent to MOD preparations. The taper of complete crown preparations did not conform to commonly recommended designs.

This investigation highlights the need for greater consideration of approximal tooth surfaces when undertaking preparations and questions the practicality of achieving traditional features of complete crown preparation design. In teaching, greater emphasis should be placed on clinical reality rather than on theoretical, but unachievable ideals.
Mechanical properties of elastomeric impression materials
Authors: SALEM N. S. , COMBE E. C. , WATTS D. C.
Published: June 2007

Dental elastomeric impression materials of different consistencies, representing addition and condensation silicones, polysulphides and a polyether, were studied to determine their mechanical properties in terms of tearing energy, tensile properties and modulus determined at high strain rates. Whilst the polysulphides had the greatest resistance to tearing, they were more extensible, had lower moduli of elasticity and lower tensile strengths than the silicones. The polyether resembled the silicones in many respects.
Effects of experimental defects of the articular disc of the temporomandibular joint in rats
Authors: LEKKAS C. , HONEE G. L. J. M. , VAN DEN HOOFF A.
Published: June 2007

Triangular defects were made in different locations of the disc in rat temporoman‐dibular joints. After 3 months the following effects were observed. Central defects had become rounded without gross changes in the mandibular head. Peripheral defects were enlarged towards the centre, occasionally accompanied by condylar hyperplasia. Microscopically the cartilagenous covering of the mandibu‐lar head in all operated cases was characterized by thickening, dispersion of cells normally closely packed in the intermediate zone, and the constant appearance of a tear parallel to the surface.
The effect of removable partial dentures on the oral function in shortened dental arches*
Authors: WITTER D. J. , van ELTEREN P. , KÄYSER A. F. , VAN ROSSUM M. J. M.
Published: June 2007

In this study the effect of free‐end removable partial dentures (RPD) on oral function was investigated by comparing subjects with shortened dental arches (SDA, n=55) and a group of subjects with SDA and RPD (n=25). In addition, a group of subjects were selected who had worn an RPD in the past (n=19). All subjects had a remaining natural dentition consisting of an intact front region and three to five occlusal units (OU) in the posterior area.

On the whole, subjects with RPD had less natural OU compared with subjects without RPD. However, this is also true for those who had worn an RPD in the past. The oral functions of subjects with SDA did not differ significantly when compared with subjects with SDA and RPD.

Significantly more subjects who had an RPD in the past reported a limited mobility of the mandible, an impaired chewing capacity and chewing with the front teeth. They also reported more aesthetic complaints due to missing posterior teeth.

It is concluded that within the populations investigated in this study oral function is not evidently improved by the insertion of a free‐end RPD.
Value of EMG analysis of mandibular elevators in open‐close‐clench cycle to diagnosing TMJ disturbance syndrome
Authors: CHONG‐SHAN S. , HUI‐YUN W.
Published: June 2007

The EMGs of the temporal and masseter muscle, in sixty patients with temporomandibular joint disturbance syndrome (TMJDS) and thirty normal controls, were recorded during rhythmical open‐close‐clench cycle movement and before and after occlusal splint therapy. The duration of the muscle contraction before initial tooth contact (DMC), the latent period (LP) and the silent period (SP) of the myoelectrical activity were used as indices for exploring their diagnostic value. In contrast with the controls, DMC, LP and SP lengthened in the patients. The DMC was prolonged in those patients where there were TMJ sounds, the inter‐cuspated position did not coincide with the muscular contact position and there was deviated mandibular movement. An increase of the SP was related to tooth contact on the balancing side. After treatment, the DMC and SP in the patients returned to the level of the controls. It was found that the internal correction rate of Fisher's linear discriminate function established for the DMC and SP of the temporal and masseter muscles was 80.9% and 85.1% respectively. The results show that the DMC and SP of the temporal and masseter muscles have some value in diagnosing muscular dysfunction and discriminating therapeutic effectiveness.
Postural and maximum activity in elevators during mandible pre‐ and post‐occlusal splint treatment of temporomandibular joint disturbance syndrome
Authors: CHONG‐SHAN SHI , HUI‐YUN WANG
Published: June 2007

Electromyograms (EMGs) of the temporal and masseter muscles in sixty patients with temporomandibular joint disturbance syndrome (TMJDS) and thirty controls were recorded and integrated on‐line in the postural position and during maximum clenching, before and after occlusal splint therapy. Contrasting with the controls, the myoelectrical activity of the patients was higher in the postural position and lower during maximum clenching, whilst the former in percentage terms increased when compared to the latter. After treatment, the EMG indexes in some patients returned partially, and in others completely, to a normal level. Tenderness in the mandibular elevators, deviated opening and organic change in the TMJ increased the postural myoelectrical activity, in percentage terms, against that of maximum clenching. The myoelectrical activity of the mandibular elevators in the postural position and during maximum clenching was smaller in patients with the occlusal splint than in those without. The results show that the mandibular elevators in the patients with TMJDS were hyperactive and tense, and that the occlusal splint was useful for treating such dysfunction.
Short‐term effect of a stabilization splint on the asymmetry of submaximal masticatory muscle activity
Authors: McCARROLL R. S. , NAEIJE M. , KIM Y. K. , HANSSON T. L.
Published: June 2007

Ten healthy subjects continuously wore equilibrated maxillary full‐arch stabilization splints in the retruded position for 7 days. The muscular activity balance of the masseter muscles during submaximal isometric clenching at 10% and 50% of the maximum voluntary contraction (MVC) did not change immediately on insertion of the splint, but was improved at the 50% level after 7 days (P<0.05). While the muscular balance of the anterior temporal muscles was not affected, either immediately on splint insertion, or after wearing it for 7 days, temporal muscle activity at 10% of the MVC was greater on the side to which the mandible moved from the retruded contact position (RCP) to the inter‐cuspal position (ICP), both before (P<0.025) and after (P<0.01) wearing the splint. Splint removal after 7 days resulted in increased awareness of interferences in the ICP and increases in masseter muscle asymmetry (10%, P<0.025; 50%, P<0.05) when the electromyograms in the ICP after splint removal were compared with those on the stabilization splint before removal. After wearing the splint, the masseter muscle activity at the 10% level was greater on the side where premature contacts were present in the RCP (P<0.01).

The use of masticatory muscle asymmetry indices in the evaluation of splint treatment for craniomandibular dysfunction is indicated since submaximal masticatory muscle activity is related to occlusal stability, premature contacts in the RCP and the direction of lateral slides from the RCP to the ICP.
The use of a cone and plate viscometer for determination of flow properties of unfilled resins and etching gels
Authors: TAVAS M. A. , WATTS D. C.
Published: June 2007

A cone‐plate viscometer was employed for studying the rheological characteristics of certain unfilled resins and etching gels. Of these, BIS‐GMA monomer and its diluted mixtures exhibited Newtonian, dilatant and thixotropic behaviour depending on the shear rate. Other unfilled resins also exhibited various types of behaviour. At high shear rates reproducible hysteresis loops were obtained for etching gels which may be useful in characterization.
A 2‐year electromyographic study of patients with an immediate complete upper and a partial lower denture
Authors: TRYDE G. , TALLGREN A. , MIZUTANI H.
Published: June 2007

A longitudinal electromyographic (EMG) investigation was performed on thirty subjects provided with an immediate complete upper and a partial lower denture. Electromyographic recordings in maximal clench, light tapping and postural position were obtained from the anterior temporal and masseter muscles before final extractions and 7 weeks, 6 months, 1 year and 2 years after denture insertion.

The maximal clench activity of the jaw closing muscles showed an average tendency to decrease upon insertion of the dentures, but thereafter significant increases in mean voltages were observed during the first year of denture wear. During the second year no significant changes in EMG clenching force were noted. At the 2‐year stage most of the muscles showed significantly greater clench activity than at the post‐insertion stage, but did not exceed the pre‐extraction level.

The jaw muscle activity in light tapping showed no significant mean changes during the observation period. The postural activity tended to decrease during the period of denture wear, the decrease being significant for some of the muscles at the 2‐year stage.
Alveolar ridge augmentation with bioactive glass ceramics: a histological study
Authors: SHAOAN WANG , ANYU CHEN , ZINENG YU , ZHANJIE HUANG , YUNMAO WAO
Published: June 2007

A particulate BGC (bioactive glass ceramics), has been developed as a new bone graft biomaterial for alveolar ridge augmentation and has been evaluated by simulated animal models. Five beagle dogs were used in this investigation. Prior to augmentation the mandibular posterior teeth of the animals were extracted. Three months after the extractions, the porous BGC particles were packed into the subperiosteal tunnels in the ridges with a special syringe. The animals were killed at different time intervals and the specimens were examined by light microscopy, scanning electron microscopy (SEM), and X‐ray energy dispersive analysis (EDAX), respectively. The results of this study indicate that the BGC particles are firmly combined with the adjacent hard and soft tissues by the bone bonding interface between the implants and the alveolar bone, and by the ingrowth of bone or fibrous connective tissue into the interspaces and the pores of the particles. The results have demonstrated that particulate BGC with pores is an excellent implant material for alveolar ridge augmentation because of its very good biocompatibility.
Ultrastructure of the peri‐implant junctionalepithelium on single‐crystal sapphire endosseous dental implant loaded with functional stress
Authors: HASHIMOTO M. , AKAGAWA Y. , NIKAI H. , TSURU H.
Published: June 2007

To elucidate the Ultrastructure of peri‐implant junctional epithelium (IJE) on singlecrystal sapphire dental implants connected to the adjacent teeth by a metal superstructure, the peri‐implant gingivae of ten monkeys were examined using a transmission electron microscope (TEM) at 3, 6 and 12 months after implant insertion. At the time of examination, the ultrastructural features of the IJE were almost identical to those of junctional epithelium (JE) attached to natural teeth, i.e. developed Golgi complexes, rough‐surfaced endoplasmic reticulum, numerous free ribosomes and mitochondria. The innermost cells of IJE were attached to the implant surface by means of basal lamina‐like structures (500–1000 Å in thickness) and hemidesmosomes, but lacked a dental cuticle as seen on teeth. Such epithelial attachment of the IJE was often indistinct or absent at the apical portion of the IJE which terminated at the level of alveolar crest. A continuous basal lamina‐like structure was also present along basal cells at the interface between the IJE and gingival connective tissue except at its apical portion.
Experimental studies on masseter muscle grafts in rats: comparison of donor muscles
Authors: MONG F. S. F.
Published: June 2007

Experimental studies were performed in rats to explore the feasibility of using limb muscles to replace masticatory masseter muscles. The results showed that if several small fusiform muscles such as the extensor digitorum longus (EDL), soleus (SOL) and plantaris (PLT) were used for the grafting, the graft regenerated and matured fully in the masseter bed, although the weights were lower than those of contralateral control masseter muscles. If a multipennate muscle such as the gastrocnemius was used for the grafting, the graft also regenerated but later degenerated due to the lack of innervation. This is probably due to the excessive amount of connective tissue in the multipennate muscle. The connective tissue proliferates faster than the regeneration of muscle fibres and, thus, renders the innervation of muscle fibres difficult. Other factors pertinent to the possible clinical application of muscle transplantation in oral region are discussed.
The temporomandibular ligament and the articular eminence as constraints during jaw opening
Authors: OSBORN J. W.
Published: June 2007

It is generally thought that during symmetrical jaw opening the mandible rotates about an axis passing through the centres of the two mandibular condyles, and translates down the articular eminence. The author argues that there are no data to support this assumption. The true combination of movements can only be understood by understanding the constraints that operate during jaw opening and these are the articular eminence and the temporomandibular (TM) ligament. The TM ligament is pulled taut during jaw opening, and so acts like the chains of a swing: the mandible rotates about the lowest attachment of the TM ligament to the condyle and swings about the most posterior attachment to the articular tubercle. The effects of combining the swing and rotation are demonstrated by a simple mechanical model. The functional advantage of the TM ligament is that it keeps the condyle close to the temporal bone during jaw opening, until the condyle passes under the articular eminence. The constraints described in this paper may have important implications related to the diagnosis and treatment of some disorders of the TM joint (to be described in a later paper).
Consistency, working time and setting time of elastomeric impression materials
Authors: JAMANI K. D. , HARRINGTON E. , WILSON H. J.
Published: June 2007

This paper describes the development of an instrument for determining consistency, working time and setting time of elastomeric impression materials. The operating principle involves the application of a fixed compressive strain and the resulting stress is measured. This instrument has been called a Comprheometer. Temperature control is achieved by water circulation so that simulated room or open‐mouth temperatures can be used. Values of consistency and working time are presented for a range of elastomeric materials at room temperature. Also, setting times determined under oral conditions are recorded.
Survival studies of dental restorations: criteria, methods and analyses
Authors: LEEMPOEL P. J. B. , VAN'T HOF M. A. , DE HAAN A. F. J.
Published: June 2007

The longevity of dental restorations is an important health concern for the patient, the dentist, and the various forms of insurance systems. In this article several methods of evaluating survival time are described and the different ways of presenting the findings of survival studies are discussed. It is stated that only longitudinal studies are appropriate to give an exact insight in the longevity of restorations. A large amount of information is available in dental records and the way these data can be analysed is presented in this paper. It appears that Cox's proportional hazard model is the appropriate way of demonstrating the influence of several factors on the survival rate. An example is provided of the results from a recent survival study of crowns in The Netherlands.
A study of surfaces developed on composite resins in vivo during 4.5 years; observations by SEM
Authors: HENGCHANG XU , TONG WANG , VINGERLING P. A. , SHIQING SONG
Published: June 2007

In this study seven commercial composite resins, one experimental composite and one dental amalgam were investigated. These materials were inserted into the cavities of denture molar teeth in different patients. After clinical service for 3,9,12,24 and 54 months the specimens were removed and observed by scanning electron microscopy. The wear patterns of the filling materials and their changes with continuing clinical service for 4.5 years suggest that the abrasive mechanism of conventional composite resin is as follows. The softer resin matrix is worn away and inorganic filler particles are exposed, thereafter they loosen and fall off. As this process proceeds the composite resin is worn away. This process continues with time. In the case of microfilled composite, the organic fillers and resin matrix are worn away at the same rate. After long‐term clinical service some cracks could be seen on the wear surface between the organic filler agglomerates and the resin matrix.
A laboratory and clinical evaluation of three dental luting cements
Authors: KNIBBS P. J. , WALLS A. W. G.
Published: June 2007

The loss of material from specimens of three luting cements was measured after continuous erosion cycling in the laboratory. The glass ionomer luting cement showed significantly less material loss than the zinc polycarboxylate and zinc phosphate luting cements.

Two hundred and fifty restorations cemented with one of the three materials were studied clinically for marginal integrity and retention over 3–5 years. The data were tested using survival analysis. Zinc phosphate cement gave the best clinical performance. Possible explanations for the poor correlation between the findings in the laboratory and clinical study are discussed.
Increase in compressive strength of glass ionomer restorative materials with respect to time: a guide to their suitability for use in posterior primary dentition
Authors: WILLIAMS J. A. , BILLINGTON R.W.
Published: June 2007

Glass ionomer restorative cements have been used in anterior restorations for a number of years but have not been considered strong enough for use in posterior restorations. The compressive strengths of a number of materials currently available were measured at 30min, 1 hour and 24 hours. It was concluded that some of the materials might be considered for posterior restorations in deciduous teeth where no other considerations, such as radiopacity, apply.
Effect of substrate age on microleakage of dentine adhesive agents
Authors: CRIM G. A.
Published: June 2007

The present investigation was performed to determine the effect of substrate age on the microleakage of two new dentine adhesive agents. Class 5 preparations were placed at the cemento‐enamel junctions of two groups of extracted human molar teeth which had been stored in water for less than 3 months or for approximately 18 months. Silux Plus was used to restore cavities that had been primed with either Scotchbond 2 or GLUMA. The restored teeth were thermally stressed for 100 temperature cycles and placed in a dye solution for 24 h. Leakage was measured under a microscope at ×50 magnification. Under the experimental conditions, there was no significant difference in microleakage which could be attributed to the two different post‐extraction tooth storage periods.
Studies in oral galvanism: mercury and copper levels in urine, blood and saliva in submerged electrically cutting divers
Authors: ÖRTENDAHL T. W. , HOLLAND R. I. , RÖCKERT H. O. E.
Published: June 2007

The aim of the study was to analyse the concentration levels of mercury and copper in urine, blood/blood plasma and saliva in relation to intra‐oral electrical activity. Five Swedish Navy divers took part in the study in order to determine whether working submerged with electrical cutting equipment produced changes in the presence and level of oral galvanism and whether this posed a serious occupational health risk.

The investigation concluded that the risk of seriously increased intra‐oral electrical activity during welding or cutting activities was small. Development of the study is suggested, with long‐term sampling of urine and blood samples of divers supported.
Finite element analysis of three‐ and four‐unit bridges
Authors: FARAH J. W. , CRAIG R.G. , MEROUEH K. A.
Published: June 2007

A two‐dimensional finite element model of a mandibular quadrant was used to examine differences in magnitude of the principal stresses from the placement of three‐ and four‐unit bridges. The area of interest spanned the first premolar to the second molar. Loading conditions were (i) vertical and distributed and (ii) 30° to the vertical and concentrated. The principal stresses were calculated and compared for: (i) the first molar removed with the remaining bone either cancellous or cancellous surrounded by a cortical shell; (ii) as in (i) but with the second premolar and first molar removed; (iii) a three‐unit bridge spanning the second premolar to the second molar; and (iv) a four‐unit bridge spanning the first premolar to the second molar. Each tooth was supported by periodontal ligaments, cortical and cancellous bone with each assigned the appropriate physical constants. Removal of the first molar resulted in considerable variation of the stresses especially when the cortical shell was replaced by cancellous bone. Because of the lower modulus of cancellous bone and its lower load‐bearing capabilities the stresses were three to ten times lower and more uniform within the cancellous bone. Generally, the addition of a bridge resulted in lower and better distributed σmin stresses. The bridge also resulted in higher tensile stresses distal to the abutment teeth which theoretically could result in bone deposition. No significant differences in magnitude were observed between the three‐ and four‐unit bridge. From a stress standpoint the bridges resulted in more uniform stress distribution around the abutments and an increase in the tensile stresses distal to the abutments. Such findings support the placement of a fixed bridge to maintain bone in an edentulous area.
A laboratory examination of the behaviour of cast cobalt‐chromium clasps
Authors: GHANI F. , MAHOOD M.
Published: June 2007

Cast cobalt‐chromium clasps, long and short, tapered and untapered, were studied. It is shown that the behaviour of apparently identical clasps is inconsistent. Permanent deformation appears to commence during the first month of wear, and after 6 months' wear the retentive quality of almost all of the clasps is impaired.
A preliminary electromyographic study of bite force and jaw‐closing muscle fatigue in human subjects with advanced tooth wear
Authors: LYONS M.F. , BAXENDALE R.H.
Published: June 2007

The maximum bite force was recorded in five experimental volunteers with advanced tooth wear and five control volunteers who showed no abnormal wear. All subjects were then asked to maintain a force of 50% of the maximum for as long as possible while surface electromyograms from the masseter and temporalis muscles were recorded. The bite force and endurance time were found to be slightly increased in the experimental group, but no conclusions could be drawn regarding the state of fatigue. Two significant problems with regard to fatigue studies of the jaw‐closing muscles emerged from the study, namely the use of the canine position for recording of the force, and the thickness of the force meter.
Occlusal force distribution in lower complete overdentures
Authors: OGATA K. , AOKI T. , MATSUNAGA T. , UCHIDA K.
Published: June 2007

A space between the denture base and a root cap can effectively control the distribution ratio of occlusal force to abutment teeth and an alveolar ridge. The purpose of this study on abutments was to analyse the effect of variation in space (0 mm (no space), 0–3 mm and 0–6 mm) on the above ratio.

Six subjects, 38–65 years of age, each with an edentulous maxilla and several teeth remaining in the mandible, were selected for this experiment. The lower experimental denture had embedded a transducer which could detect a change in the vertical force applied to the experimental tooth. This transducer was capable of changing the vertical space between a denture base and an experimental tooth. Each subject was asked to increase the occlusal force applied to the denture from zero to the maximum loading rate of 5 kgf s−1. The occlusal force and the force exerted on the experimental tooth were recorded in each space 1 month after insertion of new dentures. The following results were obtained: (i) when the occlusal force was applied to the artificial tooth just above the abutment tooth, the mean ratio in the 0 mm space was 60% of the force applied to the denture, the ratio in the 0–3 mm space was 50%, and the ratio in the 0–6 mm space was 30%; (ii) if the occlusal force was applied to the point 10 mm distant from the point just above the experimental tooth, the magnitude of the ratio was decreased by 60–80%.
The prevalence of sensitivity to constituents of dental alloys
Authors: NAMIKOSHI T. , YOSHIMATSU T. , SUGA K. , FUJII H. , YASUDA K.
Published: June 2007

Ninety‐five participants were epicutaneous patch tested in order to determine the prevalence of sensitivity to components of dental alloys. Seventeen individuals (17.9%) developed allergic reactions, which were caused by mercury (10.5%), copper (2.1%), nickel, cobalt, tin, gold and zinc (1.1%). Eight of 17 allergic responders had a history of dermatitis from metal contact. The results show that there is a need for careful immunological considerations during the selection of suitable alloys, particularly in the case of patients with lesions suspected of being caused by dental alloys.