Electromyographic Evaluation of the Influence of Denture Adhesive on Retention and Stability of Complete Dentures

Improving retention and stability of complete dentures is of considerable interest in prosthetic dentistry. Approaches to this problem over the years have included overdentures, implants and denture adhesives. Although denture adhesives are widely used, there are few quantitative data on the effects of an adhesive on denture retention and stability during normal functional activities. The purpose of this investigation was to study the influence of denture adhesive on the surface EMG activity of the masticatory muscles in a sample of complete denture wearers. In this study 6 denture wearers were investigated. Surface EMG recordings were obtained from left and right anterior temporal and masseter muscle and from the sub-mandibular group in the region of the anterior belly of the digastric muscle on the left and right side. Data were recorded during standardized jaw positions that included clenching in the position of maximal intercuspation of teeth (at 100%, 50% and 25% of the maximum activity), lateral eccentric positions, maximal lateral eccentric positions, protrusion, maximal protrusion and wide opening. The results demonstrated higher digastric muscle activity in protrusion with the teeth at an edge-toedge position after the use of adhesive (p0.05). This investigation demonstrated that patients were able to produce greater levels of muscle activity in protrusive and laterotrusive positions with the use of adhesive

Optical Identification of Inaccuracies Caused by Improper Handling on Type IV Gypsum Casts

Type IV gypsum (stone gypsum) is an essential material in prosthetic treatment. Improper handling can change hardness, expansion and compressive strength and it is the most common reason for inaccurate casts. In that case even the most perfect impressions will result in inadequate prosthetic treatment. Using optical instruments-digital camera (2.5 million pixels) and digital microscope we attempted to identify the visual appearance of inadequate casts and relate them to specific causes. All casts were poured in highly controlled conditions and only one factor, whose influence we tried to determine, was changed during the procedure. Most common mistakes are: outdated gypsum, incorrect powder to water ratio, mixing without a vacuummixer, pourring without a vibrator and etching by alginate acid. All the mistakes were visualised, easily recognized and categorized by using digital optical equipment

Measurement of Factors Influencing Mandibular Function in Dental Students in Croatia

The aim of this study was to measure main variables influencing mandibular function-movements of mandible during chewing, speech and breathing. Measurements taken were: vertical and horizontal overlap of central incisives, side shift from centric relation (CR) to maximal intercuspation (MI) measured in the sagittal and frontal plain, maximal mouth opening, maximal mouth opening using force, maximal dextrotrusion and sinistrotrusion. Method used included the same number of subjects and examiners. This was achieved by educating final year dental students before the measurement took place. They were both examiners and subjects for each other. Comparison of this method to single examiner and multiple experienced examiner methods revealed no statistically different results. Measurements were divided by gender, dental status, and the number of signs and symptoms related to temporomandibular dysfunctions (TMD) that were then statistically analyzed. There were no significant differences between the results of this study and findings in current literature

Prosthetic Dentistry on the Internet

Since the late sixties when the ARPANET- first computer network was developed, Internet has had a great impact on the way of thinking, buying, teaching, learning and everyday life, including dentistry. The beginning of internet in science and research, has proved to be irreplaceable way of communication between researchers all over the word. Currently (April 2002) one of the most popular search engines on the net (Google) indexed about 2 billion web pages, 35 million of non HTML documents and 700 million Usenet messages, which makes the Internet the greatest information service ever. The purpose of this study was to investigate which part of the web space is taken by prosthetic dentistry and the importance which it gains on the Internet. The method used was standard Internet search engine keyword queries preformed using six web search engines: Google, Lycos, Infoseek, AltaVista, Northern Light, HotBotand Excite. Research results suggest that there is currently (May 2002) about 30 thousand pages (0.0015% of searched web space) which contain terms: prosthetic dentistry or prosthodontics and about one thousand web pictures connected to these terms. Content analysis suggests that quality and real informative value of the majority of those pages is low. To conclude-informative space on the Internet concerning prosthetic dentistry is still in development and the need for confirmation and authorized information is obvious

Alveolar Bone Loss on Abutment and Non-Abutment Teeth as Related to Removable Partial Denture Wearing. A Six Month Follow up Study

Loss of interdental alveolar bony septum can be determined directly from a radiograph as a percentage length of the interdental bony crest of the alveolus to the distance from cemento-enamel junction of the tooth to the tooth apex. The aim of this study was to measure the height of interdental alveolar bone around the abutment and nonabutment teeth in removable partial denture wearers (RPD) on dental panoramic radiographs (DPR) through a period of six months. Twenty RPD patients (5 males, 15 females participated in the study. The alveolarbone loss measurement was performed on DPRs, using Shei index, on each mandibular abutment and non-abutment tooth on its mesial and distal side, after the RPD delivery and six months later. Recordings of plaque index (PlI) were made at the mid-buccal, mid-palatal, mesio- and disto-palatal surfaces of each abutment and non-abutment teeth after the RPD delivery and six months later. The results revealed a decrease of Shei index values on both abutment and non-abutment teeth, which reached a statistically significant level for distal Shei index values of the abutment teeth and mesial and distal Shei index values of the non-abutment teeth (p<0.05) in a 6 month period. There was no statistically significant difference in PlI values between the first and the second measurement (p>0.05). We concluded that the decrease in bone support on both abutment and non-abutment teeth was attributed to the high levels of PlI and low level of oral hygiene than to RPD loading. Supported by the Ministry of Science and Technology, Republic of Croatia, Project No. 065911

Electromyographic evaluation of mastication and swallowing in elderly individuals with mandibular fixed implant-supported prostheses

This study evaluated the effect of implant-supported oral rehabilitation in the mandible on the electromyographic activity during mastication and swallowing in edentulous elderly individuals. Fifteen patients aged more than 60 years were evaluated, being 10 females and 5 males. All patients were edentulous, wore removable complete dentures on both dental arches, and had the mandibular dentures replaced by implant-supported prostheses. All patients were submitted to electromyographic evaluation of the masseter, superior orbicularis oris muscles, and the submental muscles, before surgery and 3, 6 and 18 months postoperatively, using foods of different textures. The results obtained at the different periods were analyzed statistically by Kruskal-Wallis non-parametric test. Statistical analysis showed that only the masseter muscle had a significant loss in electromyographic activity (p<0.001), with a tendency of similar response for the submental muscles. Moreover, there was an increase in the activity of the orbicularis oris muscle during rubber chewing after treatment, yet without statistically significant difference. Mandibular fixed implant-supported prostheses in elderly individuals revealed a decrease in electromyographic amplitude for the masseter muscles during swallowing, which may indicate adaptation to new conditions of stability provided by fixation of the complete denture in the mandibular arch