Two-body wear behavior of human enamel versus monolithic zirconia, lithium disilicate, ceramometal and composite resin

PURPOSE: To investigate and compare the surface roughness (SR), weight and height of monolithic zirconia (MZ), ceramometal (CM), lithium disilicate glass ceramic (LD), composite resin (CR), and their antagonistic human teeth enamel. MATERIALS AND METHODS: 32 disc shaped specimens for the four test materials (n=8) and 32 premolars were prepared and randomly divided. SR, weight and height of the materials and the antagonist enamel were recorded before and after subjecting the specimens to 240,000 wear-cycles (49 N/0.8 Hz/5℃/50℃). SR, height, weight, and digital microscopic qualitative evaluation were measured. RESULTS: CM (0.23 + 0.08 µm) and LD (0.68 + 0.16 µm) exhibited the least and highest mean difference in the SR, respectively. ANOVA revealed significance (P=.001) between the materials for the SR. Paired T-Test showed significance (P < .05) for the pre- and post-SR for all the materials. For the antagonistic enamel, no significance (P=.987) was found between the groups. However, the pre- and post-SR values of all the enamel groups were significant (P < .05). Wear cycles had significant effect on enamel weight loss against all the materials (P < .05). CR and MZ showed the lowest and highest height loss of 0.14 mm and 0.46 mm, respectively. CONCLUSION: MZ and CM are more resistant to SR against the enamel than LD and CR. Enamel worn against test materials showed similar SR. Significant variations in SR values for the tested materials (MZ, LD, CM, and CR) against the enamel were found. Wear simulation significantly affected the enamel weight loss against all the materials, and enamel antagonist against MZ and CM showed more height loss.

Effect of anatomic, semi-anatomic and non-anatomic occlusal surface tooth preparations on the adaptation of zirconia copings

PURPOSE: To compare the accuracy of marginal and internal adaptation of zirconia (Zr) copings fabricated on anatomic (A), semi-anatomic (SA) and non-anatomic (NA) occlusal surface preparations. MATERIALS AND METHODS: 45 extracted bicuspid teeth were prepared for receiving zirconia crowns, with different occlusal preparation designs A=15, SA=15 & NA=15. The Zr copings were fabricated by using CAD4DENT, CAD/CAM. The copings were adjusted, cemented and were cross sectioned centrally from buccal cusp tip to lingual cusp tip into mesial and distal halves. The copings were examined under electron microscope at x200 magnification and the measurements were recorded at 9 predetermined areas in micrometers. RESULTS: Overall mean gap values for the three groups was found to be 155.93+/-33.98 microm with Anatomical Occlusal preparation design having the least gap value of 139.23+/-30.85 microm showing the best adaptation among the groups. Post Hoc Tukey's test showed a statistically significant difference (P=.007) between the means of gap for A & NA preparation designs. Measurements recorded at 9 predetermined points showed variations for the three groups. CONCLUSION: Anatomical occlusal preparation designs resulted in better marginal and internal adaptation of Zr copings. There is a considerable variation between the measured marginal and internal gap values for the Zr copings fabricated by the (CAD4DENT-CAD/CAM). This variation may be associated with the lack of standardization of the preparation of teeth, computerized designing of the coping for each tooth, cement used, uniform pressure application during the cementation of the copings, sectioning of the copings and the microscopic measurements.

Awareness of tooth shade selection principles among dental students, interns, genral dentists and specialists

The purpose of this survey was to determine the knowledge and awareness about the principles of tooth shade selection among final year dental students, interns, general dentists and specialist prosthodontists I restorative dentists in Riyadh, Saudi Arabia. A self-administrative questionnaire especially designed for this study, was distributed among a conveniently selected sample. A total of292 [response rate of 83%] questionnaires were completed. The results of this study showed that the specialists have a better awareness about the principles of tooth shade selection. There was a significant [p<. 05] difference between the final year dental students, general dentists and specialists -regarding the shade selection methods, timings, lighting conditions, surrounding factors, removal of stains, shade distribution charts and knowledge of the shade guide. On the other hand, no significant difference [p>.05] was found between the groups in relation to factors as using visual method, shade selection prior to procedure, position of the patients, seeking second opinion and patients' opinion during the shade selection. Further analyses indicated that specialist dentists have better understanding about the principles of tooth shade selection as compared to final year students, interns and general dentists

Scientific and artistic principles of tooth shade selection: a review

Modern dentistry is facing growing demands for esthetic tooth-colored restorations, whether in composite, porcelain or acrylic systems. This makes shade selection, on the chair-side and its accurate formulation in the laboratory, the key determinant to the overall success of these restorations. The process of shade selection itself is based on scientific, artistic and physiological principles, which should be properly understood to avoid any shade mismatches and consequent remakes. Hence, the aim of this article was to review the basic principles involved in the shade selection process and present them in an easy-to-understand manner. For this, an electronic search was carried out in PubMed and PakMedinet databases and journal websites, supplemented by a hand search of the published literature and standard textbooks of Prosthodontics to gather all relevant information. It is hoped that this article shall provide useful knowledge to the dental community on the science behind the art of successful shade selections

Comparison of patients satisfaction with replacement complete dentures fabricated by copy denture technique versus conventional technique

To compare the level of patients satisfaction with replacement complete dentures fabricated by copy denture technique versus conventional technique. This was a Quasi experimental comparative study [Phase 2 trial]. Conducted from May 2005 to May 2006 at the Department of Prosthodontics, AFID, Rawalpindi. First 60 patients seeking replacement complete dentures were registered and divided into two groups. Group -A patients were given dentures fabricated by copy denture technique and Group-B patients were given dentures fabricated by conventional denture fabrication technique. The patients satisfaction level was assessed after 6 weeks of denture insertion with the help of a questionnaire. Questions about appearance, looseness of dentures, ability to chew food, ability to taste foods, speech and comfort of the patients were asked from each of the patients. Each of the questions had three answers [a] Good [b] Fair and [c] Poor. Good was given a scoring rate of 3, fair a scoring rate of 2 and poor a scoring rate of 1. The maximum scoring rate was 18 and minimum was 6. The patients who had a rate of 15 to 18 were categorized as highly satisfied, from 11-14 were categorized as fairly satisfied and from 06 to 10 were categorized as poorly satisfied. In group A, 10 patients [33%] were highly satisfied, 11 patients [36%] were fairly satisfied and 7 patients [23%] were poorly satisfied. Chi-square test was applied for the comparison of satisfaction level of the two groups. Differences in satisfaction scores between the subjects belonging to the two groups were statistically significant. The p value was 0.002. Copy denture technique is a valid, biologically acceptable and cost effective treatment modality

Denture induced stomatitis in edentulous population

Denture stomatitis is a commonly recurring problem of denture wearers. The aetiology is said to include infection, trauma and possibly a defect in the host's defence mechanism. The extent of interplay of these factors is still a controversy. Literature seems to indicate that age of the denture, denture hygiene and denture wearing habits influence the initiation and progression of denture stomatitis. These factors have been studied in Caucasian. Whether these factors have any bearing on our local people, who differ from Caucasians in social, cultural, dietary and genetic make up, has yet to be investigated. The duration of the study was 6 months. A cross-sectional comparative study was done at Department of Prosthodontics, Armed forces Institute of Dentistry, Rawalpindi. Seventy five edentulous patients all wearing maxillary complete dentures were divided into two groups: Dentrue Induced Stamotitis [DIS] Present and Absent. The DIS present group comprised of 36 patients [14 male and 22 female] with type II denture stomatitis. The DIS absent group comprised of 39 subjects [14 male and 22 female] with type II denture stomatitis. The DIS absent group comprised of 39 subjects [14 male and 25 female] with clinically healthy palatal mucosa. A standardised interview and clinical appraisal were carried out. The dye disclosing method was used to assess denture cleanliness and the resultant staining pattern scored. SPSS version 10 was used to analyze the data. There was a significant difference [P<0.05] regarding denture hygiene habits of the DIS Present and DIS absent subjects. Continuous wearing was more common in patients with denture stomatitis [P<0.01]. Denture cleanliness was far better in the DIS absent group than in the DIS present group [P<0.01]. Differences between the denture stomatitis group and the DIS present group were statistically significant for the following factors: denture hygiene habits, denture wearing habits and denture cleanliness