Stress Distribution on Prepared Tooth With Shoulder and Radial Shoulder Margin to Receive Crowns of Three Different Materials: A Finite Element Analysis.

Aim and background This study aims to determine the stress distribution on the prepared tooth at the margins with shoulder and radial shoulder finish lines when an occlusal load of 300N was applied to ceramic, zirconia, and polyether ether ketone (PEEK) crowns. Materials and methods Six models of mandibular first molar teeth were fabricated. The tooth models were subdivided into two groups with shoulder and radial shoulder margins, respectively (n = 18). The teeth were restored with three different prosthetic crown materials (ceramic, zirconia, and PEEK). To simulate the typical forces experienced by a prosthetic crown material in a lower posterior tooth during chewing and biting, an occlusal load of 300N was applied to each of the samples, and the maximum principal stress (Pmax) and von Mises stress were calculated, respectively. These samples were then compared and evaluated to determine the material best suited as a prosthetic crown material of choice for a lower posterior tooth. Results Among the materials used, the maximum principal stress value was the least in PEEK crowns. The von Mises stress value was highest for the zirconia crown with shoulder margin and was least for the PEEK crown with a similar margin. Conclusion PEEK as a crown material was found to be a better choice for lower posterior teeth as there was the least maximum principal stress at the margin, irrespective of either shoulder or radial shoulder finish line used.

Assessment of Patients' Experience and Perception Toward Dentinal Hypersensitivity for Its Diagnosis and Management: A Cross-Sectional Study.

Background Dentinal hypersensitivity (DH) is a common clinical finding that varies greatly in prevalence. An appropriate impulse that detonates noxious stimuli in the pulp/dentin boundary causes the typical DH pain, which is sudden, short, sharp, and of rapid onset. The objective of this research was to ascertain the incidence of DH in Keralites and evaluate some contributory factors, along with other initiating stimuli. Methodology Over three months, from June 2022 to August 2022, a cluster sampling technique was employed to conduct the study in 14 districts of Kerala. Patients from five clinics from each district who reported having DH and were aged 25 to 65 years were chosen at random. Using Google Survey forms, a 20-question, closed-ended survey was mailed to patients. The data were collected, evaluated, and analyzed using SPSS Version 23.0 (IBM Corp., Armonk, NY, USA). The statistical difference in the distribution of DH and the patient's age was determined using analysis of variance (ANOVA). A chi-square test was carried out to test the association between dentinal hypersensitivity, gender, and other parameters; P < 0.05 was considered to be statistically significant. Results Among the 2,520 persons to whom questionnaires were mailed, 2,321 responded, with an unresponsive rate of 7.89%. The study revealed a sensitivity predilection among females (54%), although statistically insignificant. Respondents aged 25 to 35 years (41.01%) were commonly reported to have DH, the age distribution of which was found to be highly significant statistically (P < 0.01). Teeth whitening resulted in 82.98% of the sensitivity, whereas 47.99% accepted poor oral hygiene as an additional contributory factor. DH was reported in 52.01% of the patients with gastritis and 63.03% of the patients with gingival recession. Further, blame for poor dental treatment (88.88%) and climate change (82.92%) were also found relevant. The quality of life was claimed to be afflicted in 90.99% of the patients. Desensitizing agents were used by 68.97% of the patients, with which 68.03% reported satisfaction. Of the subjects who underwent professional treatment, 87.03% reported being satisfied. Oral prophylaxis-induced sensitivity was reported in 57.99%, indicating enhanced oral health awareness among Kerala residents. There was a statistically highly significant difference in the patient distribution based on the exposure to DH, and their perception of the causes and factors affecting DH (P < 0.01). Conclusions DH is a frequently and widely prevalent dental malady. Respondents demonstrated that they were conversant with DH. The quality of life and enjoyment of daily activities are both impacted by dentin hypersensitivity, and many patients are unaware that it is a treatable illness. Various desensitizing substances are also available and can be applied quickly to sensitive areas. Patients prefer this procedure as it is simpler to apply these agents and the effects are pleasant and beneficial.

Effect of Thermocycling on Shear Bond Strength of PEEK-A Comparative Study of Resin Luting Cements: An In-Vitro Study.

Introduction: Thermocycling is an in-vitro process; it may affect the bonding strength between tooth and resin which is depending upon the adhesive system. Aim and Objectives: To evaluate and compare the thermocycling effect on shear bond strength of RelyX Unicem and G-CEM Linkace to polyether ether ketone (PEEK) surface. Materials and Methods: A total of 40 PEEK disk-shaped specimens were fabricated with dimensions of 10 × 3 mm and randomly allocated into two groups. Group A was cemented with Rely X Unicem material and Group B was cemented with G-CEM Linkace. About 10 specimens from each group were thermocycled 500 times at 5°C and 55°C. By applying force at the speed of 1 mm/min using a universal testing machine, shear bond strength was measured. Results: The mean bond strength was compared using paired t test. There was a significant difference even before and after thermocycling. Conclusion: In this experiment, Shear bond strength (SBS) of G-CEM Linkace showed more even before and after thermocycling when compared to RelyX. Also bond strengths of two cements decreased after thermocycling.

Assessment of Survival Rate of Dental Implants in Patients with Bruxism: A 5-year Retrospective Study.

BACKGROUND: Dental implants are associated with failure such as early or late failure. Systemic conditions such as diabetes, hypertension, and bruxism affect the success rate. The present study was conducted to assess complications in dental implants in bruxism patients. MATERIALS AND METHODS: This 5-year retrospective study was conducted on 450 patients (640 dental implants) who received implants during the period and followed up for 5 years from June 2010 to June 2016. Among these patients, 124 had bruxism habit. Dental radiographs or patients' recalled records were evaluated for the presence of complications such as fracture of implant, fracture of ceramic, screw loosening, screw fracture, and decementation of unit. RESULTS: In 240 males and 210 females, 380 implants and 260 implants were inserted, respectively. The difference was statistically nonsignificant (P = 0.1). A total of 145 screw-type and 130 cemented-type fixations had complications. The difference was statistically nonsignificant (P = 0.5). Complications were seen in single crown (45), partial prostheses (125), and complete prostheses (105). The difference was statistically significant (P = 0.012). The common complication was fracture of ceramic (70) in cemented-type fixation and fracture of ceramic (85) in screw-type fixation. The difference was statistically significant (P = 0.01). Forty-two single crowns showed decementation, 85 partial prostheses had fracture of ceramic/porcelain, and 50 complete prostheses showed fracture of ceramic/porcelain. The failure rate was 42.9%. Survival rate of dental implants in males with bruxism habit was 90% after 1 year, 87% after 2 years, 85% after 3 years, 75% after 4 years, and 72% after 5 years. Survival rate of dental implants in females with bruxism habit was 92% after 1 year, 90% after 2 years, 85% after 3 years, 75% after 4 years, and 70% after 5 years. The difference among genders was statistically nonsignificant (P = 0.21). CONCLUSION: Bruxism is a parafunctional habit which affects the survival rate of dental implants. There is requirement to follow certain specific protocols in bruxism patients to prevent the developing complications.

Disinfectant Efficacy of 0.525% Sodium Hypochlorite and Epimax on Alginate Impression Material.

AIM: Species of Streptococcus, Escherichia coli, Staphylococcus, Actinomyces, Pseudomonas, Klebsiella, and Candida are commonly seen in the oral cavity. Impression materials are commonly contaminated with microorganisms. The present study was conducted to assess the disinfection efficacy of Epimax and 0.525% sodium hypochlorite on alginate impression over a period of 10 minutes. MATERIALS AND METHODS: This study was conducted in the Department of Prosthodontics in the year 2015. An alginate impression material was prepared. For each bacteria species, 15 samples were used. Out of 15 samples, 3 were used by 0.525% sodium hypochlorite for disinfection for 5 minutes and 3 others for 10 minutes. Similarly, 3 samples were used by Epimax for 5 minutes and other 3 for 10 minutes. Three samples were used as controls. Each sample was polluted with Candida albicans, Pseudomonas aeruginosa, and Staphylococcus aureus strains. RESULTS: There was no statistical difference in P. aeruginosa and C. albicans after 5 minutes, whereas S. aureus showed significant difference (p < 0.05). Epimax was found to be more effective in removing S. aureus as compared with other disinfectants. Both Epimax and 0.525% sodium hypochlorite did not show significant difference against P. aeruginosa and C. albicans, whereas significant difference was found between both agents against S. aureus (p < 0.05). It was seen that Epimax eliminated S. aureus after 5 minutes and P. aeruginosa after 10 minutes and 99.8% C. albicans after 10 minutes. About 0.525% sodium hypochlorite eliminated 99.1% of C. albicans after 10 minutes, whereas 98.5 and 99% of S. aureus and P. aeruginosa were eliminated after 10 minutes respectively. CONCLUSION: Both Epimax and 0.525% sodium hypochlorite can disinfect the alginate impression material against C. albicans, P. aeruginosa, and S. aureus strains. However, Epimax was found to be more effective against S. aureus as compared with 0.525% sodium hypochlorite. CLINICAL SIGNIFICANCE: Efficacy of disinfection of sodium hypo-chlorite and Epimax on alginate impression.

In vitro Assessment of Influence of Various Bleaching Protocols on the Strength of Ceramic Orthodontic Brackets bonded to Bleached Tooth Surface: A Comparative Study.

INTRODUCTION: Esthetics is one of the common issues because of which patients consult dental orthodontic treatment. Two ways of tooth bleaching are available these days, which includes in-office bleach and home bleach. Various bleaching protocols are available these days for treating the tooth surfaces. Hence, we planned the present study for investigating the impact of various intracoronal bleaching protocols on shear bond strength of ceramic brackets bonded to tooth surface after bleaching. MATERIALS AND METHODS: The present study included assessment of 100 extracted maxillary central incisors with the integrated buccal surface. A resin block was made and individual teeth were embedded in each block. Root canal therapy procedure was performed in all the teeth, after which 2 mm short of tooth apex up to the level of cementoenamel junction, removal of the root canal filling was done. All the samples were broadly divided into four study groups with 25 samples in each group. Bleaching procedure was carried in all the samples intracoronally followed by testing of shear bond strength using universal force testing machine. Following the modified adhesive remnant index (AI), assessment of remaining adhesive on the brackets was done. All the results were compiled and analyzed by Statistical Package for the Social Sciences (SPSS) software version 17.0. RESULTS: In the control group, mean shear bond strength was found to be 17.9 MPa. While comparing the carbamide peroxide (CP) group with sodium perborate study group, we observed a statistically significant difference. Nonsignificant results were obtained while comparing the shear bond strength in between sodium perborate group and hydrogen peroxide (HP) group. CONCLUSION: Intracoronal bleaching does affect the shear bond strength of ceramic brackets. Sodium perborate bleaching influences shear bond strength more strongly than other bleaching agents such as CP and HP. CLINICAL SIGNIFICANCE: In patients undergoing orthodontic treatment, HP is a preferred agent where bleaching has to be followed by orthodontic bonding to the tooth surface.

A Clinical Study to Examine the Effect of Complete Denture on Head Posture/Craniovertical Angle.

INTRODUCTION: Edentulous patients show some significant changes in ridge relationship caused by resorption of alveolar ridge. The changes are characterized by an upward rotation of mandible, increase in mandibular prognathism that ultimately results in change of natural head posture. AIM: This clinical study was planned to know the effect of complete denture on head posture in different age groups of Indian completely edentulous population, after placement of complete denture at various time intervals. MATERIALS AND METHODS: The sample consisted of completely edentulous patients without previous experience of the dentures. They were divided into 2 age groups: Group A (45-60) and Group B (61-75). During placement of complete denture craniovertical angle was measured with the help of custom made ruler protector device. Readings were taken before denture placement, immediately after denture placement, 30 minutes, 24 hours and 30 days after dentures placement. RESULTS: The results of this study indicated that in most of the patients (90%) despite their age, change in head posture (extension) occurred immediately after the denture placement. Thereafter reading remains same for measurement at 30 minutes and 24 hours of denture placement. However after 30 days, observation revealed that all the patients showed reduced craniovertical angle (flexion). Even though the values of craniovertical angle remain higher than its baseline in both groups, significant changes were noticed only in Group A. CONCLUSION: Findings revealed that head posture was significantly altered by the placement of dentures in completely edentulous patients. Within the time interval of 30 minutes and 24 hours extension of head posture remained constant with slight variation. Although after 30 days, changes remained significant for group 'A', but no significant changes were observed in the subjects of group 'B'.

In-vitro Evaluation of Transverse Strength of Repaired Heat Cured Denture Base Resins without Surface Treatment and with Chemical and Mechanical Surface Treatment.

BACKGROUND: Denture repair involves joining two parts of a fractured denture with a denture repair material. Hence, a substantial repairing system for denture base fracture should be there to elude frequent fracture. MATERIALS AND METHODS: Surface treatment of conventional heat cure denture base resin with different surface treatments (chemical ethyl acetate, and mechanical roughening with bur), with control group formed without surface treatment. Specimens were repaired with auto polymerizing acrylic resin using sprinkle on technique. The testing of the transverse strength of the repaired specimens was evaluated with three-point bending test on universal testing machine. RESULTS: The study revealed that surface chemical treatment with ethyl acetate improved the transverse strength of repaired heat cure denture base when compared with mechanical and control group. A two-way analysis of variance revealed that there was statistically significant difference in mean strengths of the three groups. CONCLUSION: Surface chemical treatment with ethyl acetate improved the transverse strength of the repaired heat cure denture base when compared with mechanical roughening with bur and group without surface treatment.

Evaluation of Bond Strength of Acrylic Teeth to Denture Base using Different Polymerization Techniques: A Comparative Study.

BACKGROUND: Acrylic teeth have long been used in the treatment of a complete denture. One of the primary advantages of acrylic teeth is their ability to adhesively bond to the denture base resins. Although the bonding seems satisfactory, however, bond failures at the acrylic teeth and denture base resin interface are still a common clinical problem in prosthodontics. The purpose of this study was to evaluate the bond strength of acrylic teeth to denture base using different polymerizing techniques. MATERIALS AND METHODS: Acrylic resin teeth were bonded to heat cure acrylic resin and were polymerized by conventional water bath and microwave energy. The samples are then retrieved from the flask; trimmed and polished. The samples were then subjected to tensile forces till failure by using the Instron Universal testing machine. The machine used a direct pull on the incisal portion of the lingual surface in a labial direction at a height above the denture base resin bar with a crosshead speed of 0.5 mm/min. RESULTS: In the present study, it was found that conventionally cured specimens exhibited higher bond strength than microwave cured specimens and majority of fractures occur within the body of the tooth. It was found that debonding occurs within the body of the tooth rather than tooth acrylic interface, so there is no need of surface treatment of ridge lap surface. CONCLUSION: Conventionally cured specimens possess statistically higher bond strength than microwave cured specimens.

Effect of saliva contamination on the shear bond strength of a new self-etch adhesive system to dentin.

AIMS AND OBJECTIVES: To evaluate the effect of saliva contamination on the shear bond strength of a new two-step self-etch adhesive (P90 system adhesive) to dentin and to determine the effect of contaminant removing treatments on the recovery of bond strengths. MATERIALS AND METHODS: The buccal surfaces of 40 human premolars were ground to expose dentin. The specimens were randomly divided into four groups. Group 1 is uncontaminated and serves as the control group. Further groups were divided based on the step in the bonding sequence when the contamination had occurred as follows: Group 2 (primer, saliva contamination, rinse and dry), group 3 (after procedure of group 2, reapplication of primer), and group 4 (after procedure like in control group, saliva contamination, rinse and dry). Filtek P90 composite resin cylinders of 3 mm diameter and 3 mm length were fabricated on the surfaces. Shear bond strength testing was done in an Instron Universal Testing Machine and the data were subjected to one-way analysis of variance (ANOVA) and Student's t-test. RESULTS: With P90 system adhesive, group 2 and group 4 showed lower shear bond strength than group 1 (control) and group 3 (P < 0.05). CONCLUSION: Saliva contamination significantly decreased the shear bond strength of the adhesive to dentin.

Stress distribution among periodontally compromised abutments: A comparative study using three-dimensional finite element analysis.

AIMS: The aim of the study was to evaluate the stress distribution patterns in teeth and supporting structures of fixed prosthesis and design modifications in a fixed prosthesis with either normal or reduced bone support of an additional abutment. Study was also undertaken to disprove Ante's law. MATERIALS AND METHODS: Main models and variations of main models (modification 1, 2, 3, 4, 5, 6, 7, 8) were subjected to 200 N at angulations of 90° and 15° on functional cusps. Results for each loading were obtained as stress distribution color images and numerical values were recorded. A three-dimensional finite element analysis study of variations of normal models was performed using two finite element softwares, namely PRO-Engineer wildfire version 1.0 manufacturer: Parametric technology corporation, Needham, MA 02494 U.S.A. RESULTS: When periodontal compromised abutment teeth was splinted with an additional abutment an increase of stress was observed in periodontally compromised abutments so an additional abutment is not required. Eventhough the pericemental area of compromised abutments with an additional abutment (canine) was more than the combined pericemental area of pontics to be replaced, stress generated was more on abutments. This disproves Ante's law. Hence, it may be a reference, but should not be the ultimate criterion in determining the number of multiple abutments. CONCLUSIONS: When periodontal compromised abutment teeth was splinted with an additional abutment an increase of stress was observed in periodontally compromised abutments so an additional abutment is not required. Even though the pericemental area of compromised abutments with an additional abutment (canine) was more than combined pericemental area of pontics to be replaced, stress generated was more on abutments. This disproves Ante's law. Hence, it may be a reference, but should not be the ultimate criterion in determining the number of multiple abutments.