Prevalence and significance of minor anomalies in children with impaired development.

AIM: To compare the prevalence of Waldrop's minor physical anomalies in children with developmental disorders (mental retardation, hearing and visual impairment) and healthy schoolchildren. METHODS: The study was carried out on a sample of 469 children (223 children with developmental disorders and 246 healthy schoolchildren). RESULTS: Significant differences were found between the children with developmental disorders and the healthy children with regard to the number of minor anomalies and their weighted scores according to Waldrop. Multivariate discriminant analysis with two discriminative functions explained as much as 96.51% of the total variability and significantly distinguished the healthy children from the children with developmental disorders. However, no clear distinction was found between the mentally retarded children and those with visual impairment. Interrelation of the number and sum of the weighted scores of minor anomalies showed similar minor anomalies in the mentally retarded children (mean per person 3.65 and 3.82, respectively), the children with visual impairment (3.24 and 3.50), the children with hearing impairment (3.84 and 3.67) and the control group (1.70 and 1.46), although at different levels. CONCLUSIONS: The high prevalence of multiple minor anomalies in children with developmental disorders suggests that during early development, factors which cause the specific developmental disorder and the occurrence of a minor anomaly have a joint effect.

Amorphous alloys resistant to corrosion in artificial saliva solution.

The tailoring of new corrosion-resistant alloys with specific properties has recently been performed mostly by the sputter deposition technique. The aim of this work was to investigate corrosion resistance of aluminum-tungsten (Al-W) amorphous alloys in artificial saliva solution, pH=5.5, based on the electrochemical methods of cyclic voltammetry and linear polarization. Thin alloy films were prepared on a sapphire substrate by magnetron codeposition. Completely amorphous films were obtained in the Al(80)W(20)-Al(67)W(33) composition range. Amorphous Al-W alloys exhibit very high corrosion resistance due to their homogeneous single-phase nature. The passive films spontaneously formed at their surface are uniform with characteristics of an insulator film and prevent corrosion progression in the bulk in a very demanding oral environment. The mechanism of increasing resistivity of Al-W alloys to pitting corrosion and generalized corrosion has been discussed in the view of increasing tungsten content in the alloy. Considering these exceptional corrosion properties and microhardness which falls in the range 7.5+/-1.6 Pa, Al-W alloys represent promising materials for dental applications.

Tooth loss and the condition of the prosthodontic appliances in a group of elderly home residents.

The study assessed the number of missing teeth, the state of the existing prosthodontic appliances and the need for their replacement. Dental status and anamnesis were taken on a group of 120 elderly home residents by trained examiners. Prosthodontic appliances were evaluated according to the Karlsson's index for the crowns and bridges, and according to the modified Nevalainen et al. index for the evaluation of the complete dentures, as well as the need for prosthetic treatment. The most persistent teeth in both jaws were lower canines, while the most commonly missing teeth were lower first molars. On average, the crowns were older and in poorer condition than the bridges. Lower complete dentures had better stability but were also less retentive in comparison with the upper complete dentures. More than 82% of the subjects were in need of either fixed, removable or combined prosthodontic treatment. The high prevalence of needs for prosthodontic treatment pointed to the requirement for frequent dental check ups within elderly home residents in order to better identify and meet their dental needs.

Bond strengths of silicoated and acrylic resin bonding systems to metal.

STATEMENT OF PROBLEM: The Kevloc bonding system is based on the bond of acrylic resin with the metal surface, in contrast to the Silicoater system, which covers the metal surface with a SiOx-C layer. Bonding prevents the occurrence of the marginal gap between the metal and the resin, which causes weaker bond strengths and discoloration. PURPOSE: This investigation examined the bond strength values achieved by using the Kevloc technique on Ag-Pd and Co-Cr alloys, and compared them with those obtained by the Silicoater technique. After artificial aging, shear testing of the specimens was performed. MATERIAL AND METHODS: A microscope image analyzer measured the thickness of bonding layers to reveal any marginal gap. RESULTS: No marginal gap was noticed for either technique. The Kevloc technique provided better results than Silicoater regardless of alloy used. Immersion in water (7.64 to 8. 05 MPa) and thermocycling (6.12 to 6.95 MPa) reduced the initial bond strength values (12.52 to 12.94 MPa), but the breakdown occurred between the opaque layers or between the opaque and the resin, thus giving a cohesive type of failure. CONCLUSION: The dental alloy used did not affect bond strengths and artificial aging caused reduction in bond strengths. The Kevloc bonding system exhibited higher bond strengths than Silicoater, but the marginal gap was not seen for either bonding system.

The fatigue strength of the interface between Ag-Pd alloy and hydrothermal ceramic.

OBJECTIVE: The purpose of this paper was to investigate the fatigue strength of a hydrothermal ceramic fused to Ag-Pd alloy. This study compared the values with those of other metal-ceramic systems previously reported by other authors. METHODS: This investigation was performed on 48 specimens made of Ag-Pd alloy frames (45 x 12 x 4 mm) on which the hydrothermal ceramic was fused (25 x 12 x 2 gmm). The specimens were divided into two groups. The first group of specimens was dynamically loaded immediately after casting and fusing, while the other group of specimens was thermocycled (1000 times at 0 degree C and 55 degrees C) before dynamic loading. The dynamic loading tests were carried out by using a modified three-point load method in a universal testing machine. RESULTS: The determined dynamic loading limit was up to 550 N for thermocycled, and up to 850 N for non-thermocycled specimens. These results are very respectable in comparison with other metal-ceramics. A statistically significant difference between maximal dynamic forces and number of loading cycles for thermocycled and non-thermocycled samples was determined. SIGNIFICANCE: From the data obtained in this study and current literature profiles, it is concluded that the tested metal-ceramic system is more durable than other metal-ceramic systems.

Evaluation of the precision of dimensional measurements of the mandible on panoramic radiographs.

The purpose of this study was to evaluate the precision of dimensional measurements of the mandible on orthopantomographic images and thus to evaluate their dimensional reliability. Different distances denoted by metal markers were measured on 25 dry mandibles. The same mandibles were then positioned in an orthopantomographic machine, and radiographic images of them were made. Measurements of the same distances were made on the panoramic images and then compared with the results of the measurements on the dry mandibles. All results were statistically analyzed. The results showed significant difference between the magnification factor listed by the manufacturer and calculated magnification factors, the latter being closer to 1.00. The study also showed that linear measurements made on only one side of the panoramic image of a mandible were very close to the actual dimensions of the dry mandible, whereas measurements that extended across the midline of the mandible were greatly enlarged because of large magnification factors; therefore, such measurements should not be made.

Early antibacterial effect of Pd-Ag dental alloy on aerobic and microaerophilic flora in oral cavity.

Early effect of Pd-Ag alloy on aerobic and microaerophilic flora from healthy oral cavity was studied. Normal microbial flora was sampled from saliva, dental plaque and gingival crevice from healthy individuals without any prosthodontic appliances or periodontal diseases. Such samples were inoculated into liquid media and were left in thermostat (37 degrees C) in aerobic condition. In some samples one or two sterile Pd-Ag alloy pieces were inoculated, while some samples were left without that pieces to be a control group. Both were kept in a thermostat for 24 and 48 hrs and after that were examined for bacterial dehydrogenic activity to reveal the amount of active bacteria in a sample. Dehydrogenic activity was registered after incubation of 0.1 ml of 3-phenyltetrazolynchloryde (TTC) into samples. TCC changes a colour of a liquid media because of bacterial dehydrogenic activity and therefore samples were analysed in a spectroscope. Statistical analysis revealed lower bacterial activity (lower TTC distinction) in samples with one or two Pd-Ag alloy pieces than in a control group. These results indicate the existence of initial inhibitory effect of Pd-Ag alloys on aerobic flora in the mouth, which might give space for anaerobic strains to increase ther growth. Presence of periodontal changes in a gingival crevice with Pd-Ag alloy crowns is probably due to anaerobic micro-organisms, as mostly anaerobic strains are responsible for periodontal disease.

Dimensional measurements on the human dental panoramic radiographs.

The objective of this study was to evaluate the precision of the horizontal and vertical linear dimensional measurements on orthopantomographic images. Different horizontal and vertical distances denoted by metal markers were measured on 25 dry mandibles. The same mandibles were then positioned in an orthopantomographic machine and their radiographic images were made. Measurements of the same distances were repeated on the panoramic images and compared to the results of the measurements on the dry mandibles. All results were statistically analyzed. The results showed significant difference between the magnification factor listed by the manufacturer and the calculated magnification factors, the latter being closer to 1.00. The study also showed that linear measurements made only on one side of panoramic images of mandibles were close to actual dimensions of dry mandibles, while the measurements which extended across the midline of mandibles were greatly enlarged due to large magnification factors.

Modification of the angle of the lower third of the face.

Determination of vertical dimension of occlusion by roentgencephalometric method, with the help of the angle of the lower third of the face, has been described in literature. The aim of this study was to modify the angle of the lower third of the face and correlate its determination with reference planes for orientation of casts in the articulators space, to determine mean value and measures of variability of the modified angle in a random sample, and the possibility to use this angle as a control value for establishing the height of the lower third of the face. On a sample of 131 roentgenograms in L-L projection, with teeth in maximal intercuspation, points: N, IS47, THA, SNA, SNP, Xi and Pg were traced down. By the use of this points the angle of the lower third of the face (angle K) was constructed. The values of the angle were measured and statistically analyzed. Mean value of the angle was 48.5 degrees, with standard deviation of 4.41 and coefficient of variation 9.09%. The investigated angle can serve as a control value for determination of intermaxillary relationships and should not be accepted as an strict norm.

The tooth reduction and abrasion in a group of elderly home residents.

The degree of tooth loss and abrasion was the objective of the study on a group of 73 partially dentate elderly home residents, with particular interest in the type of missing and abraded tooth and the type of the interocclusal contacts according to the Eichner classification. The patients were examined by a dental mirror and a probe. The obtained data of dental status as well as medical and dental history were recorded in a specially designed questionnaire according to the WHO recommendations. The results confirmed the hypothesis about the molars being the most commonly missing teeth, with average values of 4.49 present teeth in lateral section and 5.82 present teeth in frontal section of the dental arch. The Eichner index class III was the most often interocclusal relationship found within 74% of the elderly home residents. Lower teeth were abraded more often than the upper teeth, showing higher abrasion degrees (class 2 and 3).

Comparative review of gnathometric characteristics in total dentures and eugnathic subjects.

The problem of determining the position and lining of the teeth in total dentures is presented by a comparative examination of gnathometric variables in eugnathic subjects and in those wearing total dentures. The material consisted of 51 plaster casts of eugnathic subjects and 49 subjects wearing total dentures. The following were examined: upper total number of incisors (T1), anterior width (AW), posterior width (PW), anterior length (AL) and posterior length (PL) of models. Analysis of the investigated variables was carried out by means of sliding calipers MECANIC Type 6901 (IVOCLAR, Lichtenstein) with a scale of 0-130 mm, and reading accuracy 97.5%. A three-dimensional pair of compasses according to Korhaus (Dentaurum, Germany) was used to measure the anterior and posterior lengths of models, with a scale 10-60 mm and reading accuracy 95%. No significant difference was observed between the eugnathic subjects and subjects wearing total dentures (p > 0.05). The results of this comparative gnathometric analysis of examined variables (Tl, AW, PW, AL and PL) are a contribution to the rules when lining anterior and posterior teeth in total dentures.

The response of human premolars to cyclic loading.

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 statically significant difference was found (P < 0.05) between the magnitude of cyclic loads and the different types of specimens tested.

Comparative investigation of dynamic loading of prepared and intact human premolars.

The aim of this study was to obtain some data on the dynamic strength of premolar teeth. Experiments were performed on three groups of human premolars: intact teeth, teeth prepared for partial veneer crowns with flat occlusal surfaces, and teeth prepared for partial veneer crowns with rounded occlusal surfaces. The loading procedure was performed in a modified Amslers high-frequency pulsator. The greatest dynamic strength was exhibited by the intact specimens. The highest continual (unlimited number of loading cycles) dynamic stress withstood by all three groups of premolars was about 300 N. A statistically significant negative correlation was found between Fmax and the number of cycles in all three tested groups.

Follow-up of the intracranial supernumerary tooth.

A rare case of an intracranially located supernumerary tooth was described, observed over a period of 14 years, where movement was established laterally in relation to the referent Carthesian coordinate system, down and forward with rotation around the anteroposterior axis. During skull growth, the skull base angle changed by 20 degrees, but this movement only affected the change in tooth position slightly. During the observation period, no further changes in the neurological findings were observed.

The influence of arm position on the pinch grip strength of female dentists in standing and sitting positions.

The objective of this study was to measure and compare hand pinch grip forces in standing and sitting postures for a group of 77 healthy female dentists of 25 to 55 years old. The equipment used consisted of a gripping device with strain gauges, a measuring device and a printer. The results can be described as follows. With respect to absolute values the hand pinch forces are higher when the subject is standing with her arm supported, than when she is sitting. In the standing position the measured forces were maximum when the forearm was at 60 degrees angle towards the frontal position, while in the sitting position the pinch grip forces were maximum with the forearm vertical (90 degrees ) with respect to the frontal position. The above data can be used to design the dentist's working area.

A comparative investigation of the influence of certain arm positions on hand pinch grips in the standing and sitting positions of dentists.

Hand pinch grips in the standing and sitting positions on a group of 46 healthy males of 20 to 26 years old were measured. The results were as follows: 1. Hand pinch grip forces are higher when the subject is standing than when he is sitting. 2. Hand pinch grip forces, depending on the position of the arm in the working space, are higher when the arm is supported than the corresponding forces of the unsupported arm. 3. There is an effect due to the position of the arm in relation to the frontal position of the subject's thorax. In the standing position, the forces are maximum when the forearm has a 60 degrees angle towards the frontal position, while in the sitting position pinch grip forces are maximum when the forearm is perpendicular (90 degrees ) to the frontal position. 4. A handle which permits all fingers to be spread in a pinch grip is capable of having an applied force 50% greater than if the thumb and either forefinger or middlefinger grips the handle. In such a handle each finger is required to apply less force to contribute to the total needed for the task, and therefore there is a diminished likelihood of the onset of fatigue.

[Investigation of hand grasps of women-dentist in standing position]. / Istrazivanje zahvatnih sila sakom u stojecem polozaju zena-stomatologa.

The authors investigated the magnitude of hand grasping forces in certain positions of the arm in standing position of women dentists. The investigation concerned a sample of 39 female dentists. The research consisted of 3 devices: the grasping device with electroresistant tape; the measuring device and the printer for graphical registration of deformations. In conclusion the authors pointed out the effect of hand position in relation to the frontal plane of the dentist. Grasping forces of the hand increased with the increase of the angle between the upper arm and the forearm. Higher values of grasping forces in standing position suggested the need of use of the former position during grasps which required big forces in addition to the technique. (e.i. too the extraction).

[Assessment of the amount of palladium-silver alloy used for cast posts and veneer crowns]. / Utrosak paladij srebrne legure za lijevanje nadogradnje i fesetirane krunice.

Average amounts of palladium-silver alloy were assessed in a sample of 966 veneer crowns and 667 casted posts. The mean weight values of the samples under study were compared in relation to particular types of anterior teeth. The specimens cast in Auropal SE were weight by the precise balance, Tehtnica, type 6215. Results were analyzed by weight according to the type of the sample under study, and classified according to age, and to the anterior teeth of the upper and lower jaws. On an average, the heaviest posts and veneer crowns were measured on upper canines, whereas the lighest were those on lower incisors. A cast post was found to be by about 40% heavier than a veneer crown on the same tooth.