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 Most common mistakes are: outdated gypsum, incorrect powder to water ratio, mixing without a vacuummixer, pourring without a vibrator and etching by alginate acid.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

Relationship Between Attrition Faces and Signs of TMD

Smatra se da su brusne fasete znak funkcijskih i parafunkcijskih aktivnosti, te ih nalazimo na okluzalnim i incizalnim plohama zuba obično kao posljedicu procesa atricije. Brusne fasete razlikuju se opsegom i pozicijom na zubima. Bruksizam, kao parafunkcijska aktivnost, smatra se jednim od etioloških čimbenika za nastanak disfunkcije stomatognatoga sustava. Cilj rada bio je istražiti moguću povezanost između pojavnosti brusnih faseta, kao znak bruksizma, i znakova temporomandibularne disfunkcije. Temeljem nalaza brusnih faseta nakon izvršena kliničkog pregleda izdvojeno je 100 ispitanika, određenih za daljnje istraživanje. Opsežnost brusnih faseta procjenjivana je modificiranim indeksom Pullingera i Seligmana: stupanj 0 = nema vidljive atricije; 1 = minimalna atricija kvržica ili incizalnih bridova (u caklini); 2 = fasete usporedne s normalnim područjima kontura ploha (caklina); 3 = zamjetna zaravnjenja kvržica ili incizalnih bridova (caklina); 4 = potpuni gubitak kontura ploha/bridova i ekspozicija dentina do polovice visine nekadašnje krune zuba; 5 = potpuni gubitak kontura i ekspozicija dentina za više od polovice nekadašnje krune zuba. Svi ispitanici podvrgnuti su kliničkim ispitivanjima kako bi se utvrdilo postojanja znakova TMD-a. Rezultati su pokazali da ne postoji statistički znatna povezanost između znakova TMD-a i pojavnosti brusnih faseta te ni između znakova TMD-a i opsežnosti brusnih faseta. Rezultati ovoga istraživanja slažu se s ostalim recentnim studijama da brusne fasete nisu pouzdan pokazatelj za procjenjvanje funkcijskog stanja stomatognatoga sustava. Ovim istraživanjem nije utvrđeno postojanje povezanosti između pojavnosti brusnih faseta i znakova temporomandibularne disfunkcije.Attrition faces are usually seen on the occlusal or incisal surfaces of teeth worn by attrition. They are considered to be a sign of functional and parafunctional activities, and can differ by wideness and position on the teeth. Bruxizm, as a parafunctional activity, is considered to be a risk factor for dysfunction of the masticatory system. The aim of the study was to investigate the possible relationship between attritional faces, as a sign of bruxizm, and signs of temporomandibular dysfunction. By clinical examination, a group of 100 subjects was selected for trial, based on findings of attritional faces. The severity of attrition faces was quantified on a fivepoint scale ( modified assessment for determination of incisal tooth wear according to Pullinger and Seligman: 0 = no visible tooth wear; 1 = minimal wear of cusps or incisal tips (enamel); 2 = faces parallel to normal planes of contour (enamel); 3 = noticeable flattening of cusp or incisal edges (enamel); 4 = total loss of contour and dental exposure when identifiable (dentin exposure up to half of former crown of tooth): 5 = total loss of contour and dental exposure over half of former crown of tooth). Selected subjects were then examined by standard procedure to investigate the presence of TMD signs. Results showed that there was no statistical significance between signs of TMD and presence of attrition faces, and neither between signs of TMD and severity of attrition faces. Results of this study are compatible with other recent investigations, which show that attrition faces are not a reliable sign for assessing the functional status of the masticatory system. According to this investigation there is no association between attrition faces and signs of temporomandibular dysfunction

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

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

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

The Patient’s and the Therapist’s Evaluation of Complete Denture Therapy

A total of 222 patients were studied. In a questionnaire patients graded their complete dentures of different age and quality, depending on the level of satisfaction, using the modified analogue-visual scale from 1 to 5. The dentist assessed the same dentures, as well as the denture bearing area. The patients’ assessments were surprisingly high, the grades were bigger than the therapist’s (p < 0.05), but in disappointed patients the grades were smaller than the therapist’s (p < 0.05). It seems that the dentist is more critical in assessments than the patient. No significant difference existed between chewing and denture stability and between stability and the comfort of wearing lower full denture (p > 0.05). Unstable denture aggravates chewing and causes pain and discomfort on the bearing area. It seems that subjective factors in patients, expectations of the denture or the number of previous dentures play a role in satisfaction, not only the quality of denture bearing area and the quality of a denture

The EMG Activity of Masticatory Muscles During Different Chewing Tasks

Mastication is a highly coordinated neuromuscular function that involves fast effective movements of the jaw and continuous modulation of muscle force. To understand the relationship between muscles during mastication it is necessary to know the position and direction of movement of the mandible. MATERIAL AND METHODS: Twenty-four young healthy adults, age ranged 17 to 27, participated in this study. They were chosen among dental students of School of Dental Medicine University in Zagreb and had to be free of sign and symptoms of TMD. Surface EMG recordings were obtained from left and right anterior temporal muscle, left and right masseter muscle and from left and right digastric muscle on the 8 channel PC based EMGA-1, apparatus for simultaneous recording of myoelectrical activity (6 differential EMG channels, input impedance 100 MW, CMRR> 95 dB at 50 Hz, bandwidth 2 Hz-1 kHz, programmable input sensitivity from 100mVpp to 20 mVpp, an 8 bit resolution A/D conversion, 2 kHz sampling rate) - occlusal sound (2 audio channels), specially designed and developed for the purpose of kinesyological examinations of stomatognathic system’s function. The disc electrodes (Ag/AgCl, diameter 10 mm) were placed 2 cm apart in the main direction of the muscle fibres. RESULTS: 1. Main effect of factor "functional movement" was significant at p<0.01, and values were the highest for gum chewing, and the lowest for empty chewing except fordigastric muscle which had lowest values at continuous isometric contraction. 2. Main effect of factor “muscles” was significant at p<0.01 for all muscles involved, values were similar for the same muscles on left and right side. 3. Main effect of factor “time” was statistically significant p<0.05 for all cases showing decreasing trends except in last minute during functional movements. 4. Interactions between factors “functional movement” and “time” were present at significance p<0.01

The Satisfaction with the Removable Partial Denture Therapy in the Croatian Adult Population

Little is known about the outcomes of treatment and patient’s satisfaction with removable partial dentures in adult Croatian population. Therefore patient’s satisfaction with their partial dentures in relation to some socio-economic variables was studied. Patient’s satisfaction with denture retention, speech, aesthetics, comfort of wearing dentures, chewing ability was also studied in relation to different denture classification, construction, material, denture base shape (major connectors), denture support and the number of missing teeth. A total of 165 patients, 59 males and 105 females between 38 and 87 years took part in this study. A questionnaire, devised for a purpose of the study, was divided into three parts. In the first part, patients answered questions about age, gender, marital status, education, general health, socio-economic status, self-supporting life, period of tooth loss and number of previous denture experiences and in the second part, patients graded their partial dentures, depending on the level of satisfaction, by using a scale from 1 to 5. In the third part a dentist determined Kennedy classification and their modifications, denture material and denture support, denture base shape and the number of missing teeth and graded a denture construction. Influence of these factors on patient’s satisfaction was analyzed. A majority of the examined patients were satisfied with the partial prosthesis, but a small amount of dissatisfaction existed. More then half of them scored all the examined parameters to the best score category. Considering chewing with lower partial dentures, women were more satisfied than men (p <0.05). Patients with more missing teeth gave lower grades for the comfort of wearing dentures (p<0.05). Patients of higher education gave lower grades (p<0.05) for the aesthetics. Patients were not satisfied with speech if the dentist graded a construction of alower partial denture low (p<0.05). Dissatisfaction was related to mastication, aesthetics, number of missing teeth and ability of speech. These findings can aid a clinician in discussing a treatment plan and help a patient understand the risk of dissatisfaction in the presence of certain factors