Showing papers in "Journal of Oral Rehabilitation in 1994"

Elution of leachable components from composites.

Abstract: A significant amount of residual monomer or short chain polymers remain unbound in set composite material. Due to its potential impact on both the biocompatibility and the structural stability of the restoration, many investigators have studied the elution of these unbound molecules into aqueous media. The results of these studies suggest that elution of leachable components from composites is rapid, with the majority being released within a matter of hours. Weight losses of up to 2% of the mass of the composite have been reported under certain conditions. The studies have also shown that the extent and rate of elution of components from composites is dependent upon several factors. The quantity of leachables has been correlated to the degree of cure of the polymer network. The composition and solubility characteristics of the extraction solvent influence the kinetics and mechanism of the elution process. Elution is generally thought to occur via diffusion of molecules through the resin matrix, and is therefore dependent upon the size and chemical characteristics of the leachable species.

A 6-year follow-up study of oral function in shortened dental arches. Part II: Craniomandibular dysfunction and oral comfort.

Abstract: In this clinical 6-year follow-up study subjects with shortened dental arches (SDA, n = 55), characterized by the absence of molar support, are compared with subjects with complete dental arches (CDA, n = 52) with respect to items concerning craniomandibular dysfunction and oral comfort. In addition, a small group of subjects with SDA and removable partial dentures in the lower jaw (SDA + RPD, n = 19) is included in this study. Oral comfort is defined using the following criteria: (i) absence of pain and distress, meaning the absence of signs and symptoms of craniomandibular dysfunction: (ii) chewing ability; and (iii) appreciation of the appearance of the dentition in relation to absent posterior teeth. Additionally, complaints about the free-end RPD are described. It is concluded that: (i) a SDA (consisting of 3-5 occlusal units, OU) is not a risk factor for CMD and is able to provide long-term sufficient oral comfort; and (ii) free-end RPD (in the lower jaw) in SDA do not prevent CMD and do not improve oral function in terms of oral comfort.

Cytotoxicity of components of resins and other dental restorative materials

Abstract: Cytotoxicity testing of dental restorative materials must be viewed as an assessment of hazards, that is the potential of the material to cause pulpal problems. In this context, composites, glass ionomers, amalgams, zinc-based cements and peroxide bleaching agents are all possible hazards to the pulp. The risks that these materials will cause pulpal toxicity in vivo can be partly estimated by assessing the cytotoxicity of the substances which are released from these materials in vitro and comparing these cytotoxic concentrations with those concentrations that are present in vivo. The resin components of composites, metal ions and hydrogen peroxide, all of which are released from dental restorative materials, have been shown to be cytotoxic in vitro in sufficient concentrations. The potencies of these substances are quite diverse. However, the cytotoxicity of these substances in usage tests, and therefore the risks of pulpal toxicity, depends on their ability to diffuse through the dentine and accumulate in the pulp.

Reflections on the Michigan occlusal splint

Abstract: Specific features related to the development, design and use of the Michigan splint have been described. Additional benefits from the Michigan splint beyond what can be expected from conventional stabilization splints and bite planes have been suggested. Important aspects of corrections and maintenance care of the Michigan splint have been stressed.

A 6-year follow-up study of oral function in shortened dental arches. Part I: Occlusal stability

Abstract: In this clinical 6-year follow-up study subjects with shortened dental arches (SDA, n = 55), characterized by the absence of molar support, are compared with subjects with complete dental arches (CDA, n = 52) with respect to occlusal stability. In addition, a small group of subjects with SDA and removable partial dentures in the lower jaw (SDA+RPD, n = 19) is included in this study. The aim of this study was to describe effects regarding occlusal stability in subjects with SDA during a 6-year period. The applied parameters for occlusal stability are: number of occlusal contacts in the anterior region, overbite, interdental spacing and alveolar bone support. The results of this study show that: (i) SDA do provide durable occlusal stability; (ii) free-end RPD do not contribute to occlusal stability in SDA; and (iii) SDA with periodontally involved teeth show continuing periodontal breakdown.

Symptomatology of patients with oligodontia.

Abstract: The aims of the present study were: (i) to identify the association of patterns of congenitally missing teeth with combinations of ectodermal symptoms occurring in patients with oligodontia; and (ii) to propose a diagnostic scheme for the general practitioner. For this study 167 patients with oligodontia, both isolated and as part of a syndrome, and 135 healthy controls were interviewed and documented. Chi-square tests, logistic regression and correspondence analysis were used to evaluate and test differences between the groups and associations between the congenitally missing teeth and ectodermal symptoms. No significant differences were found between the control group and the patients with isolated oligodontia with exception of the skin. It could be concluded from the present study that there were no clear associations between congenitally missing teeth, either individually or patterns, and the ectodermal symptoms or combinations of ectodermal symptoms. However, it could be concluded that if the most stable teeth are missing, or if the number of missing teeth is large the patient should be examined carefully for symptoms of ectodermal dysplasia. Using logistic regression a patient could be classified as having isolated oligodontia or oligodontia as part of a syndrome with a specificity and sensitivity of 88.2%.

Effect of dentine on release of TEGDMA from resin composite in vitro.

Abstract: Triethylene glycol dimethacrylate (TEGDMA) is a component of some resin composites which contributes to their cytotoxicity. The presence of dentine between resin composite and test cells reduces the cytotoxicity in vitro. To determine why dentine has this protective effect, the diffusion of TEGDMA from a composite resin through dentine to the pulp space was compared with release directly into aqueous solution in vitro. Both release rate and total cumulative release of TEGDMA for the two groups, at times up to 100 days, were determined using reversed-phase HPLC. Release rate directly into water was highest in the minutes immediately after immersion and declined thereafter. However, in the tooth model, using an equivalent mass and surface area of composite resin, no TEGDMA was detectable in the pulp space until 43 min after restoration placement. The rate of diffusion through dentine from that time until day 1 was less than 1% of the highest (initial) direct release rate. The rate declined thereafter. It is relevant, however, that by day 3 the total cumulative release of TEGDMA through dentine was 60% of the direct release. Dentine therefore appears to exert its protective effect principally by retarding or 'damping' the initial high release of TEGDMA to a substantial degree.

Permeability of biological and synthetic molecules through dentine

Abstract: Summary The diffusion through dentine by a number of biological and synthetic molecules, including resins and dyes, is reported. In vitro measurements were derived by experiments with a modified ‘split-chamber device’. Diffusion was found to be indirectly proportional to dentine thickness for all molecules. Permeability of water-soluble molecules and ethanol-soluble molecules was proportional to the molecular weights, except for fluorescein, hydrogen peroxide (H2O2) and urethane dimethacrylate. The resin components tested are not soluble enough in an aqueous medium to diffuse through 0.5 mm dentine at sufficient concentrations to cause cytotoxicity to pulpal cells.

Processing dentures using a microwave technique.

Abstract: In this research the technique of curing denture base acrylic resins by microwave energy was investigated with respect to polymerization method, hardness, mechanical and physical properties. Twenty-one different polymerization methods were used by varying radiation power and curing time. The Vickers hardness test was applied to the samples which were polymerized. The average value was found to be 22.46 VHN (Vicker hardness number), that is, almost the same as conventionally cured acrylic. The recommended polymerization method of curing acrylic was 3 min at 550 W in a microwave oven. Mechanical and physical tests were applied to the samples which were cured by the recommended polymerization method. The average transverse load to fracture value was found to be 7.6 kg, and the transverse deflection value was 1.5 mm at 3500 g, and 2.9 mm at 5000 g. Water sorption of acrylic resin cured by microwave energy was 0.72 mg cm-2 and the solubility rate in water was 0.038 mg cm-2. Results conformed with the ADA specification. The findings showed that acrylic resin cured by microwave energy is more resistant to mechanical failure than conventionally cured acrylic and this technique can safely be applied to the production of denture bases.

Social and functional impact of reduced posterior dental units in older adults.

Abstract: Summary The number of teeth needed to maintain adequate dental function in older adults is unknown. The purpose of this study was to examine the relationship between oral function and the number of opposing pairs of posterior teeth. We identified 338 subjects with complete anterior dentitions from an interview and examination survey of Ontario adults aged 50 and over; 261 had no partial denture and 77 had removable partial dentures (RPD). Oral function was measured using questions assessing chewing ability, mandibular function and socio-psychological impact. Subjects with no partial dentures were further allocated to five groups, based on their dental status: complete dental arch (n= 69); 5–7 functional units-pairs of opposing posterior teeth (n= 109); 3 or 4 functional units (n= 48) and 0–2 functional units (n= 35). Oral function problems increased with decreasing functional units being markedly more prevalent among the groups with 0–2 functional units. 34% of subjects in the 0–2 group reported one or more problems with chewing ability compared to 6–17% in the other groups (χ2P= 0.001 d.f. = 3). The 77 subjects who wore removable partial dentures, reported social and dental function at levels comparable to those with no dentures. From these results, there appears to be little socio-functional need to replace lost posterior teeth with a partial denture until the person has fewer than, 3 posterior functional units. The low number of partial denture wearers limited our ability to detect a lasting benefit from RPD treatment.

Assessment of chewing efficiency: a comparison of particle size distribution determined using optical scanning and sieving of almonds.

Abstract: Particle sizes obtained with progressive chewing cycles were quantified by use of an optical scanning device and compared with the sieving method. The aim of this study was to validate the optical method by comparison with sieving using a natural test food, almond. Masticatory efficiency was assessed in six dentate subjects. The almonds were chewed for 1, 4, 8, 16 and 32 chewing strokes. Each experiment was replicated. The chewed material was sieved through a 1 mm aperture sieve on a Buchner funnel and dried after washing with water and 100% alcohol. The dried particles were weighed and scanned by an optical scanning device for number and size. The same samples were sieved and weighed with a conventional sieve method. The results of both methods were described by particle size distributions based on the volume of particles. The results derived from the optical scanning and sieving showed similarity. It can be concluded that the optical method is simple to use, faster than sieving and needs little skill in the use of equipment. The comparison of the results validates both methods.

The attenuation of radiation by porcelain and its effect on polymerization of resin cements

Abstract: The influence of porcelain thickness and opacity on the polymerization of two dual activated (microfine and hybrid) and one light irradiated (hybrid) resin cements was assessed by hardness measurements. The surface microhardness values of the upper and lower surface of 1 mm thick resin cement specimens were determined. Specimens were polymerized using 40s irradiation beneath different thicknesses and opacities of porcelain discs. The results showed that increasing the thicknesses and opacity of the porcelain produced a statistically significant decrease in microhardness of the resin-based cements. The effect of attenuation is less for the microfine cement than for the hybrids. In the case of hybrid cements, the light activated material performed better than the dual activated cement.

Periodontal status of teeth in contact with denture in removable partial denture wearers

Abstract: The aims of the study were to determine the periodontal status of the teeth in contact with removable partial dentures (RPDs) and to compare them with other teeth in the opposing arch not related to any prosthesis. The periodontal status was also assessed in relation to the age of the dentures. Four hundred and twenty-seven patients treated with RPDs from 1981 to 1986 were recalled for examination. Prior to prosthetic treatment they were given periodontal treatment and fillings when required. Initially all were given oral hygiene instructions and motivation. They were reviewed regularly only on a short-term basis. Eighteen patients were suitable for the present study comprising of eight males and 10 females whose mean age was 41 years. The RPDs were in use from 1.5 to 8 years (mean 4.6 years). The following parameters were assessed: Plaque index (P1I), Gingival index (GI), loss of attachment (LA) and tooth mobility. The wearing of RPDs resulted in higher P1I, GI and LA compared to the controls and these differences were statistically significant. There was an increased frequency of higher P1I, GI and LA with the increase in denture age. Minor changes in tooth mobility were observed. It was concluded that the wearing of RPDs was detrimental to periodontal health in patients whose oral hygiene was less than adequate.

Masticatory electromyographic activity in healthy young adults and myogenous craniomandibular disorder patients.

Abstract: Summary The electromyographic (EMG) activity of the masseter and the anterior temporalis muscles were compared between 60 healthy controls and 61 myogenous craniomandibular disorder (CMD) patients. Subjects were asked to clench at 10% and at 50% of their maximum voluntary clenching level. The effects of CMD, age and gender were statistically analysed with the use of the analysis of covariance. The correlations between EMG asymmetries and the lateral slide from the retruded contact position to the intercuspal position and the asymmetry in the number of post-canine tooth contacts between the left and the right side were investigated. The CMD patients showed lower masseter EMG activities than the controls, whereas the anterior temporalis EMG activity was not different between the two groups. The activity index, relating the anterior temporalis EMG activity to the activity of the masseter muscles, confirmed the presence of a relatively high temporalis activity in the CMD group. No significant differences were found in the EMG asymmetries between the controls and the CMD patients. Males showed higher masticatory EMG activities than females. These gender effects were significant for the anterior temporalis at the 10% and 50% level and for the masseter muscle at the 10% level. The anterior temporalis EMG activity declined with age. No age related effects were observed in the masseter EMG. The lateral slide was larger and more prevalent in the CMD group. A significant correlation between the lateral slide and the anterior temporalis EMG was found for the CMD group at the 10% level. No correlation was found between the EMG asymmetry and the asymmetries in post-canine tooth contacts. In conclusion: significant CMD, age and gender effects were observed in the masticatory EMG activities of a group of myogenous CMD patients and a control group.

Interexaminer reliability of six orthopaedic tests in diagnostic subgroups of craniomandibular disorders

Abstract: Summary Interexaminer reliability is defined as the degree of consistency among examiners when making observations of the same clinical variable. In the present study, the interexaminer reliability of six orthopaedic tests was determined in a group of 79 patients with signs and/or symptoms of craniomandibular disorders (CMD), subdivided into three subgroups of patients with a mainly myogenous, a mainly arthrogenous, and a combined myogenous and arthrogenous disorder. Multi-test scores were composed for each test and combinations of tests for the three main symptoms of CMD, viz. pain, joint noises and restriction of movement. Although the orthopaedic tests showed different reliability scores, overall reliability of the determination of these three main symptoms of CMD was satisfactory. In the subgroups, arthrogenous signs and symptoms could be determined reliably with the set of six tests, whereas the reliability of the tests in determining pain and joint noises in the myogenous group was rather low. It may be concluded that the tests are well suited to evaluate arthrogenous signs and symptoms, but that the clinician should be aware of erroneous results of the tests in evaluating pain of a myogenous origin.

Growth and/or acid production of Candida albicans on soft lining materials in vitro

Abstract: Summary Effects of soft lining materials on the growth and/or acid production of Candida albicans were investigated using a simplified method monitoring the pH change in the growth medium. Reverse sigmoidal pH curves were observed with all samples and, as compared with acrylic, all soft lining materials inhibited fungal growth or acid production in the following way, i.e. delay of the beginning of a rapid and linear decline in pH, decreases in the rate of linear change in pH and increases in minimum pH. Further examinations using a surface-modified glass tube revealed that the order of Candida growth agreed with the relative hydrophobicity and adherence capacity of substrates, suggesting that this adherence capacity affected the yeast growth on their surfaces. Besides adherence capacities of substrates, the powder, liquid and plasticizer of some soft lining materials directly inhibited Candida growth. Thus, the results obtained here revealed that several factors within soft lining materials affected Candida growth and/or acid production.

Dual cure luting composites--Part II: Clinically related properties.

Abstract: Thirteen dual cure luting composites were compared in function of film thickness, consistency, and working time by using the American National Standard/American Dental Association (ANS/ADA) specifications for zinc phosphate cement and direct filling resins. The effect of temperature and setting reaction on the film thickness was also evaluated for some representative products. All three clinically related properties varied widely among the products investigated. A strong linear correlation was found between film thickness and consistency. This relation is supported by the temperature dependence of film thickness of dual cure luting composites. Cooling of the material increased the consistency, resulting in a larger film thickness, while heating reduced the film thickness because of the lower consistency. However, one product with a rather short working time at room temperature occasionally exhibited a dramatically enlarged film thickness after heating, probably caused by accelerated chemical polymerization. No correlation emerged between film thickness and maximum filler size or between consistency and filler weight content. Maximum filler size and filler weight content had been measured previously in Part I of this study. Scanning electron microscope (SEM) analysis of the cured film thickness samples revealed that the largest filler particles had been crushed under the heavy load pressure during film thickness measurement. The lack of correlation between consistency and filler weight content can be explained by the multifactorial determination of the consistency. It is concluded that the great diversity in the currently available luting composites makes clear specifications with regard to the optimum composition of luting composites urgently needed. Furthermore, more adequate methods for testing the film thickness of luting composites are also required.

Psychosocial aspects of craniomandibular dysfunction. An assessment of clinical and community findings.

Abstract: Summary This study was performed to assess whether subgroups of patients with signs and symptoms of craniomandibular dysfunction (CMD) and a control group of dental patients with and without signs of CMD can be characterized by psychosocial variables, and whether there is evidence of stress-induced muscle hyperactivity as a contributing factor in the development of signs and symptoms of CMD. A group of 127 care-seeking patients and a control group of 158 dental patients completed a Questionnaire Battery (QB) designed to measure external stressors, stress-related emotional reactions (anxiety and depression) and personal factors such as coping styles, health locus of control and personality. Patients with CMD with both a myogenous and an arthrogenous component reported more stress and stronger stress-related emotional reactions than patients with either an arthrogenous or a myogenous CMD. However, patients with arthrogenous CMD did not differ on psychosocial variables from patients with myogenous CMD. In contrast to expectations, controls with signs of CMD reported more stress than patients with CMD. Compared with controls, CMD-patients experienced less personal control over their health and they considered health to be determined by chance or fate. CMD-patients also reported to cope differently with stress than controls. Analyses of covariance showed that the results were not influenced by differences in age, sex or pain reported in the head, neck and/or shoulders. Results were interpreted with regard to the psychophysiological theory of the development of signs and symptoms of CMD as a consequence of the progression of stress-induced muscle hyperactivity. Differences between patients and controls in personal factors were interpreted with regard to treatment need for CMD.

Location of implants in the interforaminal region of the mandible and the consequences for the design of the superstructure.

Abstract: Summary The location and the number of implants to support an overdenture is of major importance for the superstructure design. Sometimes, jaw bone anatomy or posteriorly placed implants enforce the use of an angular bar to achieve a position above the alveolar ridge. Loads on such a bar may introduce a moment on the implants which can result in high bone stresses and eventually the loss of the implants. This study on stress distribution in the bone around the implants in an edentulous mandible was performed using a three-dimensional finite element model. One model with two implants placed just anteriorly of the mental foramen and connected with an anteriorly placed bar, following the curvature of the alveolar ridge, was compared with two other designs. First with a similar model but now without a bar and secondly with a model with four implants connected with straight bars. It is concluded that loading a bar, which is placed anteriorly of the interconnecting line between two implants, causes extremely large compressive and tensile stress concentrations in the bone around the implants. Therefore, in those cases, it is advised not to connect the implants or, in case a bar-clip attachment is preferred, to place additional implants in the frontal region.

Influence of dentine on the pulpward release of eugenol or acids from restorative materials

Abstract: The diffusion gradient which develops across dentine and the clearance into the capillary circulation at the pulpal side of the tissue both reduce the concentration of potential toxins applied to dentine, thus protecting pulpal cells. The data presented on eugenol indicates that when release of a potential toxin from a solid material is hydrolytic the limited wetness of dentine, i.e. the limited availability of water for hydrolysis, contributes to the protective effect of the tissue. The data on strong acids indicates that a third protective mechanism, buffering by hydroxyapatite, can contribute to dentine's protective effect in situations where the potential toxin is strongly acid. There may be other mechanisms by which dentine protects the pulp against chemical toxins from restorative materials. However, the three described: diffusion limitation; limited wetness for hydrolysis; and buffering by dentinal hydroxyapatite, appear to allow the relatively safe use of a wide range of tooth restorative materials.

Multidimensional evaluation of craniomandibular dysfunction. I: Symptoms and correlates

Abstract: To standardize clinical history taking, a comprehensive anamnestic questionnaire was developed (Screen). Screen includes questions about (i) pain, (ii) other symptoms of CMD, (iii) correlates of CMD, (iv) psychosocial factors, and (v) general health. Variables discriminating between subgroups of clinical cases and controls were described successively. This study was performed to assess whether subgroups of patients with signs and symptoms of craniomandibular dysfunction (CMD), and a control group of dental patients with and without signs and symptoms of CMD, can be characterized by differential report of signs and symptoms of CMD, as reported in Screen. Results indicate that Screen can be used to discriminate between (i) subgroups of subjects with signs or symptoms of CMD (both clinical cases and controls) and controls without signs or symptoms of CMD; (ii) subgroups of clinical cases and controls with signs and/or symptoms of CMD; and (iii) patients with CMD with mainly a myogenous component and patients with CMD with mainly an arthrogenous component. Differences between patients and controls are interpreted with regard to the correct classification of patients with CMD with mainly a myogenous component and patients with CMD with mainly an arthrogenous component, and with regard to the subjective treatment need for CMD. The results of logistic regression analyses indicate that subsets of items of Screen correctly classified up to 80% of patients with myogenous or arthrogenous CMD. Implications for further research were discussed.

Thermocycling--the effects upon the compressive strength and abrasion resistance of three composite resins.

Abstract: The purpose of this investigation was to examine the effects of thermocycling upon the compressive strength and abrasive wear resistance of three commercial composites Fulfil, P-50 and Herculite-XR. Specimens of each material were divided into five treatment groups comprising a control, and four different cycling and storage regimes. Tests for compressive strength and wear resistance were carried out. Prior to testing all specimens were stored in distilled water for 1 week. Three groups were stored at a temperature of 37 degrees C and the remaining two at 60 degrees C. Thereafter all groups that were thermocycled were subjected to 750 cycles of a thermocycling regime consisting of the cycle ACAB where A and B represent the fixed temperatures of 37 degrees C and 5 degrees C, and C, depending upon the treatment group, either 50 degrees C or 60 degrees C. One-way analyses of variance upon the compressive strength and wear factor data following the treatments highlighted significant differences in the mean compressive strength for all materials (Fulfil (P < 0.05), P-50 and Herculite-XR (P < 0.01)) and in the wear factor values for only Fulfil and P-50 (P < 0.001). Surprisingly, thermocycling P-50 with an upper temperature limit of 50 degrees C had catastrophic consequences upon the measured properties. It is concluded that some of the observed behaviour may have potentially detrimental consequences upon the long-term clinical durability of the materials tested.

Front tooth replacement with Tübingen (Frialit®) implants

Abstract: 127 Tubingen (Frialit) implants have been clinically evaluated for a 10 year period. The implants were placed in the anterior region of the maxillae of 101 patients to replace lost incisors, cuspids and premolars. Seventy-seven implants were placed within 3 months after loss of a natural anterior tooth, resulting in the preservation of the volume of the alveolar ridge and the contour of the surrounding soft tissues. This preservation of the volume of the alveolar ridge was due to the fact that the Tubingen implants have conical shapes and sizes, equal to those of the roots of natural teeth. The dentine-like colour and the biological properties of the bio-inert Al2O3 implant-material, in most of the cases was an advantage to the aesthetics of the prosthetic restorations and to the condition of the soft tissues in the permucosal area. The Tubingen implant is placed with a one-phase technique implying special care for the temporary restorations to avoid premature loading. Also prevention of overloading the ceramic material by the fixed restoration needs special attention in the construction of posts, cores and crowns. The overall survival-rate in this study with a mean follow-up of 4.5 years was 87%. Patient and dentist satisfaction was high.

Mandibular advancement with dental appliances in obstructive sleep apnoea

Abstract: The purpose of this study was to compare the effects of a modified Herbst appliance (mHA) and a muscle relaxation appliance (MR) on nocturnal breathing and body movement activity in patients with obstructive sleep apnoea syndrome (OSAS). To increase the airway space posterior to the tongue base without severely affecting the craniomandibular joint, the mHA was adjusted to anchor the mandible at 50% of maximum protrusion. MR producing an occlusal coverage but no protrusion served as a control appliance. All-night static charge-sensitive bed (SCSB) and finger oximeter recordings were done to six male patients in three conditions: first without dental device and then with mHA and with MR, in a random order, after a 2 month period of habituation. The oxyhaemoglobin desaturation events were 44.7 h-1 of recording observed during the control night, 29.6 h-1 with mHA (P = 0.087). The frequency of body movements decreased from 34.9 to 20.4 h-1 (P = 0.0079), respectively. MR had no significant effects either on the frequency of the desaturation events or the frequency of body movements, but the increased respiratory resistance breathing, indicating presence of partial upper airway obstruction, was reduced from 14.3 to 6.9% of the time in bed (P = 0.022). We conclude that 50% protrusion chosen for these experiments, produced with a mHA, brought about some alleviation of upper airway obstruction in our preselected patients, but did not lead to sufficient control of apnoea. The reduction of partial upper airway obstruction induced with a MR warrants further studies in a larger patient population.

Effect of polylactic acid on osteoinduction of demineralized bone: preliminary study of the usefulness of polylactic acid as a carrier of bone morphogenetic protein

Abstract: To evaluate the usefulness of polylactic acid (PLA), a bioabsorbable and plastic polymer, as a carrier of bone morphogenetic protein (BMP), a preliminary study has been carried out to investigate any negative effect of PLA on osteoinduction of demineralized bone (DB). PLA (10,600 mol. wt) was mixed with DB particles (1-1.5 mm square) prepared from rat femurs and laid subcutaneously on the intercostal muscle of 4-week-old Wistar rats. The PLA/DB pellets were harvested at 2, 4, 8 and 24 weeks after the operation, and prepared for light microscopic examination. Histological examination revealed cartilage formation at 2 weeks and new bone formation at 4 weeks. Extensive bone and marrow formation were observed at 24 weeks. PLA was gradually absorbed and completely disappeared at 24 weeks to be replaced by connective tissue. These results demonstrate that PLA does not have a negative influence on the osteoinductive activity and that PLA could well be a promising bioabsorbable carrier of BMP.

Masseter and temporalis surface electromyography in patients wearing complete dentures comparing anterior and posterior occlusal concepts--a pilot study.

Abstract: Summary The activity of jaw elevator muscles (masseter and anterior temporal muscle) was studied by surface electromyography in 17 patients wearing complete dentures with anterior-canine guidance. Baseline electromyography was recorded with the dentures and compared to recordings obtained with two different splints adapted to the upper denture, one providing anterior guidance leading to immediate disclusion of the posterior teeth during any jaw movement, the other providing posterior guidance buccally on the working side and lingually on the non-working side (bilaterally balanced occlusion). Recordings were obtained during a sequence of different jaw movements: postural position, maximal tooth contact in intercuspal position, protrusive movement of the mandible (under tooth contact) and during lateral excursions, also carried out under tooth contact. Muscle activity was not significantly different as recorded with dentures only versus with the splints providing anterior guidance. However, a significant increase in activity was observed with bilaterally balanced occlusion. The results of this study in edentulous people are similar to those found in patients with natural teeth.

Multidimensional evaluation of craniomandibular dysfunction. II: Pain assessment.

Abstract: Summary To standardize clinical history taking, a comprehensive anamnestic questionnaire was developed (Screen). Screen includes questions about: (i) pain, (ii) other symptoms of craniomandibular dysfuntion (CMD), (iii) correlates of CMD, (iv) pychosocial factors, and (v) general health. The current study focuses on variables in Screen concerning pain reported somewhere in the head, neck and/or shoulders. This study was performed to assess whether subgroups of patients with signs and symptoms of CMD and a control group of dental patients with and without signs and symptoms of CMD can be characterized by differences in areas reported to be painful, in quantitative and qualitative characteristics of pain, and in factors exacerbating pain. Results indicate that several characteristics of pain as measured in Screen can be used to discriminate between: (i) subgroups of subjects with signs and/or symptoms of CMD and controls without signs or symptoms of CMD, (ii) subgroups of clinical cases and controls with signs or symptoms of CMD, and (iii) patients with CMD with mainly a myogenous component and patients with CMD with mainly an arthrogenous component. The results of logistic regression analysis indicate that four adverbs describing pain correctly classified 75% of patients with CMD-myo and patients with CMD-arthro. Differences between patients and controls are interpreted with regard to the correct classification of patients with CMD with a mainly myogenous component and patients with CMD with a mainly arthrogenous component and the subjective treatment need for CMD. Implications for further research are discussed.

Variations in oral temperature

Abstract: This study investigated the temperature of healthy oral mucosa and underlying bone. Using a fine thermocouple and digital thermometer, four groups of temperatures were measured: (i) adjacent to unerupted third molars before and after surgical removal (n = 51); (ii) at the same site in patients not undergoing surgery (n = 30); and (iii) at the buccal incisor mucosa (n = 30). In each group sublingual temperatures were measured in order to calculate the temperature differential between measurement site and sublingual temperature to compensate for variations between sites and individuals. In the final group (iv) (n = 10) sublingual temperature was recorded in a closed mouth. Mean alveolar bone temperature was 5 degrees C cooler than overlying mucosa, and mean post-operative mucosal temperature was some 2.5 degrees C cooler than before operation (t = 2.32, P < 0.001). Sublingual temperature, in a closed mouth, remained relatively constant. In an open mouth, in both anterior and posterior regions, there were statistically significant decreases in sublingual temperature and in mucosal temperature differentials. Significant differences were also found between temperature differentials calculated using sublingual temperature measured at baseline and after 10 min. This indicates that sublingual temperature should be measured just prior to measuring a mucosal site.

Temporomandibular joint osteoarthritis: a comparative clinical and tomographic study pre- and post-treatment.

Abstract: Nineteen patients with definite and suspected temporomandibular joint (TMJ) osteoarthritis participated in this study. All patients were treated by dental care including bite plane therapy. By comparing the pre-treatment clinical symptoms and TMJ tomograms with those post-treatment, efficacy of the dental treatment applied for these patients has been assessed. Since TMJ pain and limitation of mouth opening were considerably improved in almost all patients post-treatment, this suggests that the clinical prognosis of TMJ osteoarthritis can be favourable. On the other hand, radiographic changes post-treatment were variable. The longitudinal changes found in the TMJ tomograms were classified into four types. The frequency of Type 2 and Type 3, which indicate the occurrence of TMJ remodelling during the observation period, was fairy high (20 TMJs and 14 patients).

Incidence of temporomandibular joint disorders in patients seen at a hospital emergency room

Abstract: A retrospective survey of a hospital emergency room population seen at an oral and maxillofacial surgery clinic during a 6-month period found 62 patients (2.7% of the total population) with temporomandibular joint disorders. The diagnoses were myofascial pain-dysfunction/temporomandibular joint dysfunction (MPD/TMJ) syndrome (70.9% of the cases) and dislocation (luxation) (22.5% of the cases). The chief complaint was well defined in relation to the diagnoses: facial pain in the MPD/TMJ syndrome cases, and displacement of the mandible in the dislocation cases.