In Vitro Evaluation of marginal adaptation of polyether ether ketone and zirconia copings

Background

Polyether ether ketone (PEEK) has emerged as a new thermoplastic material with potential applications as a restorative material. Aim: This study aimed to evaluate the marginal adaptation of PEEK copings compared to zirconia copings using field emission scanning electron microscopy.

Materials and Methods

A freshly extracted maxillary central incisor was prepared for a full-coverage restoration following standard principles of tooth preparation. The tooth was sent to a laboratory for fabrication of samples using computer-aided design and manufacturing (CAD/CAM). Twenty samples of polyether ether ketone (PEEK) copings (group A) and 20 of zirconia copings were fabricated (group B). The copings were scanned under a field emission scanning electron microscope and measurements were taken at four distinct points. The marginal adaptation over the buccal, lingual, mesial, and distal margins for both groups was evaluated. One-way analysis of variance (ANOVA) and independent t test were applied.

Results

Our findings indicate that PEEK showed better marginal adaptation than zirconia at all measurement points. The mean marginal gap value of the PEEK group was 33.99 ± 8.81 μm and of the zirconia group was 56.21 ± 15.07 μm. On comparing marginal adaptation among the mesial, distal, buccal, and lingual aspects, PEEK showed better adaptation on all four margins, with the best adaptation on the buccal margin that had the lowest mean gap value of 29.27 ± 6.07 μm. The zirconia group adapted best at the distal margin, with a lowest mean gap value of 53.58 ± 15.25 μm (P ≤ 0.05).

Conclusion

PEEK copings had better marginal adaptation and fit compared to zirconia copings. It may have applications as a restorative material in fixed prostheses.

Antibacterial Efficacy and Surface Characteristics of Boron Nitride Coated Dental Implant: An In-Vitro Study

This in vitro study evaluated bacterial cell proliferation and biofilm adhesion on titanium discs with and without antibacterial surface treatment to reduce the chances of peri-implant infections. Hexagonal boron nitride with 99.5% purity was converted to hexagonal boron nitride nanosheets via the liquid phase exfoliation process. The spin coating method was used for uniform coating of h-BNNSs over titanium alloy (Ti6Al4V) discs. Two groups of titanium discs were formed: Group I (n = 10) BN-coated titanium discs and Group II (n = 10) uncoated titanium discs. Two bacterial strains, Streptococcus mutans (initial colonizers) and Fusobacterium nucleatum (secondary colonizers), were used. A zone of inhibition test, microbial colony forming units assay, and crystal violet staining assay were used to evaluate bacterial cell viability. Surface characteristics and antimicrobial efficacy were examined by scanning electron microscopy with energy dispersion X-ray spectroscopy. SPSS (Statistical Package for Social Sciences) version 21.0 was used to analyze the results. The data were analyzed for probability distribution using the Kolmogorov-Smirnov test, and a non-parametric test of significance was applied. An inter-group comparison was done using the Mann-Whitney U test. A statistically significant increase was observed in the bactericidal action of BN-coated discs compared to uncoated discs against S. mutans, but no statistically significant difference was found against F. nucleatum.

Comparative evaluation of osteogenic cell growth on titanium surface and titanium coated with boron nitride surface: An in vitro study

Context

To promote better biological response and osseointegration continuous research is going on to modify the titanium (Ti) implant surface for successful implant treatment modality.

Aims

This study aims to evaluate the osteogenic cell growth upon the uncoated Ti discs and boron nitride (BN) coated Ti to assess osseointegration and clinical success of dental implants.

Settings and Design

This is an descriptive experimental study which includes coating of uncoated titanium alloy suraface with boron nitride in the form of hexagonal boron nitride sheets. Than comparative evaluation of osteogenic cell growth upon both coated and uncoated titanium surfaces was done using specific cell growth determinants.

Materials and Methods

In this descriptive experimental study, both BN-coated and uncoated Ti discs were assessed for osteogenic cell growth using 3-(4, 5-dimethyl thiazolyl-2)-2, 5-diphenyltetrazolium bromide assay, 4',6-diamidino-2-phenylindole, is a fluorescent stain assay, and cell adhesion assay.

Statistical Analysis Used

As this study is a descriptive experimental analysis between two variables only so there is no need of statistical analysis or p-value.

Results

Overall good cell adhesion, cell differentiation, and cell proliferation occurred in the BN-coated Ti discs as compared to uncoated Ti discs.

Conclusions

To promote osseointegration of dental implants, surface coating with BN proved to be an effective approach toward better osseointegration and long-duration success of dental implants as a single unit or implant-supported prosthesis BN which is a biocompatible graphene material with advantages in chemical and thermal stability. BN promoted better osteogenic cell adhesion, differentiation, and proliferation. Hence, it can be used as a new promising Ti implant surface-coating material.

Comparison of Stress Distribution in Fixed Partial Prosthesis Restored with Different Combination of Support: A Finite Element Study

AIM

This study was conducted to evaluate the distribution of stress in the bone around the natural tooth, endodontically treated tooth having post and core, and implant as an abutment in different combinations in fixed partial prosthesis using two-dimensional finite element analysis (FEA).

MATERIALS AND METHODS

Six models were simulated using ANSYS Modeller19. All six models were divided into 12 zones and 4 lines, and stress values were calculated and compared. The study combinations were - tooth supported fixed partial prosthesis, fixed partial prosthesis having the combination of tooth and post- and core-treated tooth, fixed partial prosthesis with the combination of tooth and implant, fixed partial prosthesis having the combination of implant and post- and core-treated tooth, fixed partial prosthesis with the combination of post- and core-treated tooth on both sides, and fixed partial prosthesis having the combination of implant on both sides.

RESULT

On comparing the stress values, the maximum stress value was observed in fixed partial prosthesis having the combination of implant on both sides (306.2434 MPa) followed by Model 4 (223.1255 MPa), Model 3 (154.3952 MPa), Model 5 (136.9041 MPa), Model 2 (116.2034 MPa), and least stress seen in Model 1 (99.6209 MPa), and minimum in tooth supported fixed partial prosthesis (99.6209 MPa).

CONCLUSION

This study concluded that stress concentration in bone was maximum when the implant was used as an abutment in fixed partial prosthesis. The least stress was seen in bone around the natural tooth due to the dampening effect of the periodontal ligament. Further, the modulus of elasticity of a post acts as a vital parameter in the distribution of stress in post- and core-treated tooth.

CLINICAL SIGNIFICANCE

The stress concentration in the bone around the abutments affects the longevity of the prosthesis, hence, the clinically appropriate combination of the abutments should be considered for a fixed partial prosthesis.

Comparison of Tensile Bond Strength of Fixed-Fixed Versus Cantilever Single- and Double-Abutted Resin-Bonded Bridges Dental Prosthesis

Resin-bonded fixed dental prostheses (RBFDP) are minimally invasive alternatives to traditional full-coverage fixed partial dentures as they rely on resin cements for retention. This study compared and evaluated the tensile bond strength of three different resin-bonded bridge designs, namely, three-unit fixed-fixed, two-unit cantilever single abutment, and three-unit cantilever double-abutted resin-bonded bridge. Furthermore, the study attempted to compare the tensile bond strengths of the Maryland and Rochette types of resin-bonded bridges. Based on the inclusion and exclusion criteria, a total of seventy-five extracted maxillary incisors were collected and later were mounted on the acrylic blocks. Three distinct resin-bonded metal frameworks were designed: three-unit fixed-fixed (n = 30), two-unit cantilever single abutment (n = 30), and a three-unit cantilever double abutment (n = 30). The main groups were further divided into two subgroups based on the retainer design such as Rochette and Maryland. The different prosthesis designs were cemented to the prepared teeth. Later, abutment preparations were made on all specimens keeping the preparation as minimally invasive and esthetic oriented. Impression of the preparations were made using polyvinyl siloxane impression material, followed by pouring cast using die stone. A U-shaped handle of 1.5 mm diameter sprue wax with a 3 mm hole in between was attached to the occlusal surface of each pattern. The wax patterns were sprued and cast in a cobalt-chromium alloy. The castings were cleaned by sandblasting, followed by finishing and polishing. Lastly, based on the study group, specimens for Rochette bridge were perforated to provide mechanical retention between resin cement and metal, whereas the remaining 15 specimens were sandblasted on the palatal side to provide mechanical retention (Maryland bridge). In order to evaluate the tensile bond strength, the specimens were subjected to tensile forces on a universal testing machine with a uniform crosshead speed. The fixed-fixed partial prosthesis proved superior to both cantilever designs, whereas the single abutment cantilever design showed the lowest tensile bond strength. Maryland bridges uniformly showed higher bond strengths across all framework designs. Within the limitations of this study, the three-unit fixed-fixed design and Maryland bridges had greater bond strengths, implying that they may demonstrate lower clinical failure than cantilever designs and Rochette bridges.

Analysis of Denture Base Displacement between Conventional Acrylic Removable Partial Dentures and Click Fit Partials for Kennedy's Class I and II Situations: An In Vitro Study

AIM/OBJECTIVE

The aim of this study was to evaluate the displacement of the denture base of conventional acrylic dentures and Click Fit partials in Kennedy's class I and II situations in the mandibular arch.

MATERIALS AND METHODS

Four removable partial dentures-two conventional clasp dentures and two attachment dentures (Click Fit)-were designed. The two conventional clasp dentures were retained by C (conventional) clasps, and the two attachment dentures were retained by rigid precision attachments. The displacement of denture bases and the movements of denture bases were investigated, and the influences of denture design were studied.

RESULT

The values obtained were statistically analyzed by using independent t-tests. For all statistical purposes, a p-value of ≤0.001 was considered significant. The results showed that mean vertical displacements (mm) of the conventional acrylic removable partial denture base for Kennedy's class I mandibular arch under 50, 75, and 100 N forces were 0.0317, 0.04377, and 0.06392, respectively, and those for Kennedy's class II mandibular arch under 50, 75, and 100 N forces were 0.04922, 0.09849, and 0.1522, respectively. Vertical displacements (mm) of the Click Fit removable partial denture base for Kennedy's class I mandibular arch under 50, 75, and 100 N forces were 0.02185, 0.03436, and 0.005365, respectively, and those for Kennedy's class II mandibular arch under 50N, 75N, and 100N forces were 0.0445, 0.07851, and 0.14457, respectively. The difference between the groups was statistically significant (p ≤0.001).

CONCLUSION

The vertical displacement of the denture base retained by conventional C clasps was more than that of the denture base retained by rigid precision attachment. The displacement of the denture base tended to be less when the denture was designed with a rigid connection for the retainer and with cross-arch stabilization as in Kennedy's class I case.

CLINICAL IMPLICATIONS

This research evaluated the vertical denture base displacement using different designs and retention types. Hence, it helped predict the prognosis of different removable partial denture base designs in various clinical conditions.

Rehabilitation of unilateral loss of eye with customized ocular prosthesis: Case series

A patient who is suffering from complete loss of one eye or one phthisical eye due to injury, inflammation, or tumor experiences lot of physical and psychological trauma. Ocular prostheses are used in the management of a wide variety of acquired and congenital anopthalmia. Several techniques have been used in fitting and fabricating artificial eyes. These eyes can be prefabricated or custom made, but a prosthesis that is lifelike in appearance provides a sense of psychological security to the patient, which is better achieved with custom ocular prosthesis. This article discusses series of cases made by utilizing one of the latest techniques of iris duplication (digital imaging) and also aims at enhanced awareness of the cosmetic benefits of custom designed ocular prosthesis when compared with stock eye.

Effect of Alcohol and Tea on Solubility of Soft-liner and Polymethyl Methacrylate Resin: An In Vitro Study

AIM

To evaluate solubility of soft denture liner material and acrylic denture base resin when stored in 8% and 50% concentration of alcohol and tea(with milk and green tea) at an interval of 4,7,11 and 15 days.

MATERIALS AND METHODS

An in vitro study wasdone on 75 standardized samples in disk form (15 mm × 2 mm), each for soft-liner and acrylic denture base resin. Samples were divided into 5 groups (15 per group/per material) and stored in distilled water (A), 8% alcohol (B), 50% alcohol (C), tea with milk (D) and green tea (E). Solubility was determined at each time interval by dividing difference of weight (taken after drying the sample in a desiccator) from day 1 divided by surface area of the specimen. For each day (i.e., 4, 7, 11 and 15),one-way analysis of variance (ANOVA) test was used to determine if the distribution of mean solubility was similar in five groups followed by post-hoc Tukey's test for pair-wise comparisons.

RESULTS

Mean solubility of soft-liner was the highest tea with milk (D) followed by green tea (E), then 50% and 8 % alcohol (C and B) and was least in group A at each time of measurement. Mean solubility of an acrylic resin was highest for 8% alcohol (B) and all other groups it was similar.

CONCLUSION

This study shows increased solubility for soft-liners when immersed in tea with milk, green tea, and alcohol at 8% and 50% concentration. The solubility of acrylic resin also increases at 8% alcohol concentration.

CLINICAL SIGNIFICANCE

Drinks/beverages used in our study are commonly consumed, the results of this study caution for restricting the frequency of intake. However, this needs to be confirmed by in-vivo studies designed to prove the association of denture life with the consumption pattern of these drinks/ beverages.

The effect of microwave processing and use of antimicrobial agent on porosity of conventional heat cured denture base resin: An in vitro study

Statement of Problem:

The occurrence porosity in polymethyl methacrylate, the most commonly used denture base material is a problem. The occurrence of oral candidiasis and other infections has also been reported in denture users.

Purpose:

The aim of this study was to evaluate the effect of addition of an antimicrobial agent, silver zeolite on the porosity of denture base resin, which will be an effective tool in the prevention of oral candidiasis among denture wearers. This study also aims to analyze the effect of polymerization technique on porosity in zeolite incorporated dentures to develop a denture base resin which will be easy to process with optimal mechanical and antimicrobial properties.

Materials and Methods:

Eighty rectangular resin specimens (65 mm × 40 mm × 5 mm) were divided into one control group (A) and three experimental groups (B – Microwave cured denture base resin specimens, C – Conventionally cured denture base resin incorporated with antibacterial zeolites, D – Microwave cured denture base resin incorporated with antibacterial zeolites) porosity was calculated by measurement of the specimen volume before and after its immersion in water. Data were analyzed using one-way analysis of variance.

Results:

The mean values of the percent mean porosity were: A = 0.9555%, B = 0.9590%, C = 0.9630%, D = 0.9695%. No significant differences were found in mean porosity among the groups evaluated.

Conclusion:

Within the limitations of this study, it could be concluded that the addition of zeolites did not result in significant porosity and that the use of microwave processing is a viable option for denture processing.

Effects of fluconazole, chlorhexidine gluconate, and silver-zinc zeolite on flexural strength of heat-cured polymethyl methacrylate resin

Aim:

We evaluated the effect of incorporating Fluconazole, Chlorhexidine Gluconate, and Silver-Zinc Zeolite as bioactive materials (10% of mass) on the flexural strength of commercially available heat-cured polymethyl methacrylate (PMMA; Travelon).

Materials and Methods:

The following four groups were compared; Group 1: Control group with pure PMMA, Group 2: Antibacterial drug group with chlorhexidine gluconate in powder form + PMMA, Group 3: Antifungal drug group with fluconazole in powder form + PMMA, Group 4: Antimicrobial agent group with silver zinc zeolite in powder form + PMMA. After processing, the specimens were subjected for flexural strength testing using three-point bending test in a universal testing machine.

Results:

A significant (P < 0.0001) decrease in flexural strength following incorporation of Fluconazole, Chlorhexidine Gluconate, and Silver-Zinc Zeolite to heat polymerized acrylic resin was observed when compared with the control group. The decrease in mean flexural strength was minimal in the fluconazole group.

Conclusion:

Although the addition of a bioactive material to PMMA acrylic is desirable, it is not practical as it reduces flexural strength of the acrylic base.

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.

Sniffing out pain: An in vivo intranasal study of analgesic efficacy

BACKGROUND

Orofacial pain is a common encounter in dentistry (affecting 12% of the population) and is a primary reason for patients seeking emergency care. Dentists often prescribe oral analgesics, which have disadvantages of decreased absorption rates and delayed onset. Intranasal (IN) delivery takes advantage of a large surface area of mucosal tissue for rapid absorption. The purpose of this study was to evaluate the efficacy of IN ketorolac for endodontic pain using a randomized, double-blind, placebocontrolled parallel design study.

MATERIALS & METHODS

Twenty patients presenting with moderate to severe endodontic pain were selected to receive IN treatment with placebo (n = 10) or ketorolac (n = 10) 30 minutes before endodontic treatment was started and immediately after the completion of endodontic treatment. Baseline pain levels were recorded before IN treatment. Pain levels were also recorded at 15 and 30 minutes after the initial IN dosing (before endodontic treatment); 30 minutes after completion of endodontic treatment; and 4, 8, and 12 hours after the initial IN spray.

RESULTS

IN ketorolac alone or with endodontic treatment showed significantly better pain relief compared with IN placebo spray alone or with endodontic treatment at 30 minutes after the first or second intranasal dose and at 4 hours after the first intranasal dose.

CONCLUSIONS

These results suggest that IN ketorolac may provide a novel and efficacious method for pain relief in endodontic pain patients. How to cite the article: Maroli S, Srinath HP, Goinka C, Yadav NS, Bhardwaj A, Varghese RK. Sniffing out pain: An in vivo intranasal study of analgesic efficacy. J Int Oral Health 2014;6(1):66-71.

Morphological and Dimensional Characteristics of Dental Arch among Tribal and Non-tribal Population of Central India: A Comparative Study

BACKGROUND

Differences in the dental arch among Bhil Aboriginals were investigated and compared with non-tribal individuals residing in a tribal zone of Central India. Plaster models (120) were made with the help of alginate impression of tribal adults as well as non-tribal adults residing in the same area. The supposition as aboriginals being primitive due to dietary practices maxillary arch size and mandibular arch size is distended in comparison to the non-tribal population as adaptation of soft refined diet has disrupted the growth of the jaws. Hence, an attempt was made to evaluate the arch widths of tribal population and to associate it with non-tribe population in the same area of Central India.

MATERIALS AND METHODS

Difference in morphology and dimension of the maxillary and mandibular arches was aimed at Bhil tribes as well as non-tribal residents of tribe rich zone of Central India. The study was steered amid 120 individuals both tribal and non-tribe equally around 60 each through a well-organized out-reach program intermittently. Study models were made of dental arches of all participants. All measurements of the arch dimension were patent on the study casts using an electronic digital sliding caliper. Pair t-test was applied by using SPSS software version-19.0.

RESULTS

In the maxillary arch, on appraisal the non-tribal and Bhil tribe's subjects, it showed a statistically significant difference in inter-incisor width (2.95 mm), inter-canine width (2.60 mm), arch depth (3.25 mm). While inter premolar width (0.20 mm) and inter molar width (0.80 mm) anterior arch length (0.60 mm), and posterior arch length (0.10 mm) showed statistically not significant difference between non-tribal population and Bhil tribe subjects. In the mandibular arch, it showed a statistically significant difference in inter-canine width (1.00 mm). Although, inter-incisor width (0.72 mm), inter-molar width (0.80 mm), arch depth (0.90 mm), anterior arch length (0.30 mm), posterior arch length (0.35 mm), and curve of Spee (0.13 mm) showed statistically not significant difference between general population and Bhil tribe subjects.

CONCLUSION

When associated non-tribal population to Bhil tribes subjects, for the morphological and dimensional characteristics of dental arches Bhil tribe subjects exhibited: A narrower and shorter maxilla; reduced mandible size; smaller incisor widths for the maxillary and mandibular arches.

Evaluation and comparison of dimensional accuracy of newly introduced elastomeric impression material using 3D laser scanners: an in vitro study

AIM

Aim of the present study was to comparatively evaluate dimensional accuracy of newely introduced elastomeric impression material after repeated pours at different time intervals.

MATERIALS AND METHODS

In the present study a total of 20 (10 + 10) impressions of master model were made from vinyl polyether silicone and vinyl polysiloxane impression material. Each impression was repeatedly poured at 1, 24 hours and 14 days. Therefore, a total of 60 casts were obtained. Casts obtained were scanned with three-dimensional (3D) laser scanner and measurements were done.

RESULTS

Vinyl polyether silicone produced overall undersized dies, with greatest change being 0.14% only after 14 days. Vinyl polysiloxane produced smaller dies after 1 and 24 hours and larger dies after 14 days, differing from master model by only 0.07% for the smallest die and to 0.02% for the largest die.

CONCLUSION

All the deviations measured from the master model with both the impression materials were within a clinically acceptable range.

CLINICAL SIGNIFICANCE

In a typical fixed prosthodontic treatment accuracy of prosthesis is critical as it determines the success, failure and the prognosis of treatment including abutments. This is mainly dependent upon fit of prosthesis which in turn is dependent on dimensional accuracy of dies, poured from elastomeric impressions.

A comparative evaluation of flexural strength of commercially available acrylic and modified polymethylmethacrylate: an in vitro study

AIM

The purpose of this study was to evaluate and compare the flexural strength of commercially available acrylic (trevalone) and modified polymethylmethacrylate (PMMA).

MATERIALS AND METHODS

Four groups were tested; Group 1- control group regular MMA, group 2-2% methacrylic acid, 88% MMA, group 3-16% methacrylic acid, 84% MMA group 4- 20% methacrylic acid, 80% MMA 15 resin specimens of each group were polymerized. After processing, the specimens were subjected for flexural strength testing using three point bending test in a Universal Testing Machine. All data was statistically analyzed with one-way ANOVA, differences within the groups were analyzed by Scheffe's analysis.

RESULTS

As the ratio of incorporated methacrylic acid to PMMA increased, the flexural strength decreased. Analysis of data revealed a significant decrease in flexural strength of specimens (p < 0.000) after incorporation of 12%, 16%, 20% methacrylic acid to heat polymerized acrylic resin, when compared with the control group. Lowest flexural strength was observed with specimens containing 20% methacrylic acid and highest flexural strength was observed with specimens containing conventional monomer without methacrylic acid.

CONCLUSION

It was observed that as the concentration of methacrylic acid in heat polymerized acrylic resin increases, the flexural strength decreases. Lowest flexural strength was observed with specimens containing 20% methacrylic acid and highest flexural strength was observed with specimens containing conventional monomer without methacrylic acid.

CLINICAL SIGNIFICANCE

The major advantages of addition of methacrylic acid to polymethylmethacrylate could be for the elderly people with restricted manual dexterity or cognitive disturbances, especially for patients who do not follow an adequate denture cleansing protocol and diabetic patients who are more susceptible for denture stomatitis.

Alliance of oral hygiene practices and abrasion among urban and rural residents of Central India

OBJECTIVES

To attain alliance between the oral hygiene practices with prevalence of tooth abrasion among urban and rural adult population of Central India. To plan dental care services in inaccessible areas and to suggest appropriate remedial measures to prevent this avertable and self-inflicted injury of teeth in this cross-sectional study.

MATERIALS AND METHODS

A sum of 1045 adult residents both from Urban (529) and rural (516) parts of Bhopal district (Central India) was selected on a random basis. The multistage sampling technique was adopted to ascertain the sample size. In urban area the study population consisted of 240 males, 289 females and 201 males and 315 females in rural area respectively. All residents above 18 years of age from the Bhopal district were included in cross-sectional study. Assessment form comprises of questionnaire and general information on oral hygiene practices, dietary habits and medical history. Abrasion was assessed using diagnostic criteria recommended by Smith and Knight (modified). Chi- square test was used to test associations between categorical variables at 5% level of significance. Regression analysis attempted to define for risk factors causing abrasion. Literature on the prevalence of abrasion is very sparse, so attempt is made to correlate the etiological factors and recommend to prevent tooth wear.

RESULTS

Investigation of this cross-sectional study was aggregate of 1045 residences. Result shows high prevalence of abrasion 70.2%. Higher prevalence concomitant with diffident habits related to oral hygiene maintenance was recorded more among rural (76.9%) when compared to urban dwellers (63.7%). Presence of abrasion verifies statistical significance in relation to age, rural urban difference and variations in habit of oral hygiene care. Stated in the present study, avertable and self-inflicted is tooth abrasion, recurrently resulted by the reprehensible brushing method and common use of indigenous material for the maintenance of oral hygiene.

CONCLUSION

Shows significant liaisons with the presence of abrasions in relation to Urban and rural dwelling, age, material used and mode of brushing and duration of brushing. Indigenous and course material causes high amount of enamel wear and with the advancement in age abrasion tend to increase. Prevalence of abrasion does not show any gender predilection. Cultural believes, lifestyle and transition reflects in deviating presence of abrasion in populations.

A comparative study of impression procedures for distal extension removable partial dentures

AIM

This study was carried out with the purpose of comparing three impression methods as to which of them placed tissues most favorably.

METHODS

The methods used were Hindels method, selective tissue placement method and functional reline method. The measurements obtained were analyzed to determine which of the three impression methods placed the mucosal tissues maximally. To compare and measure tissue placements, autopolymerizing acrylic resin platforms were constructed to the height of the occlusal surfaces of the remaining teeth. 15 orthodontic buccal tubes were placed on each side of the platform. They were arranged in three sets of five and attached to the platform over selected reference regions by means of autopolymerizing resin. The selected reference areas were in anterior, middle and posterior areas of the ridge on either side.

RESULTS

No significant difference was seen in tissue placement in the anterior middle and posterior regions in each of the three methods when each method was assessed separately. Selective tissue placement method placed the tissues maximally (7.547 mm) followed by Hindels method (7.2110 mm) and the least placement was by functional reline method (5.856 mm). Tissue placement was significantly higher in Hindels method as compared to functional reline method (p < 0.001).

CONCLUSION

Tissue placement was maximum in the posterior region, followed by the middle region and least in the anterior region of the mandibular ridge for all three methods. Selective tissue placement method showed the maximum overall tissue placement followed by the Hindels method and minimum placement was by functional reline method.

CLINICAL SIGNIFICANCE

Selective tissue placement method provided maximum overall tissue placement and can be a preferred technique for impression making for bilateral distal extension removable partial denture fabrication.

Short direct repeats flank the T-DNA on a nopaline Ti plasmid

Crown gall disease results from the insertion of a segment of the Agrobacterium Ti plasmid, called T-DNA, into host plant nuclear DNA. We have subjected to sequence analysis the border regions of pTi T37 (ends of T-DNA) and one left T-DNA/plant DNA border fragment isolated from BT37 tobacco teratoma by molecular cloning. These sequence studies, taken together with published sequence of a right T-DNA/plant DNA border fragment, allowed us to identify the positions of left and right borders at the DNA sequence level. Comparison of left and right border regions of the Ti plasmid revealed a "core" direct repeat of 13 of 14 bases (12 contiguous) precisely at the borders of T-DNA. An extended repeat of 21 of 25 bases overlaps this core repeat. T-DNA on the Ti plasmid exhibits no longer direct or inverted repeats in the border regions, based on Southern hybridization studies. The physical structure of T-DNA differs from that of known prokaryotic and eukaryotic transposable elements but bears a structural resemblance to the prophage of bacteriophage lambda.

Cloning of a higher-plant plastid omega-6 fatty acid desaturase cDNA and its expression in a cyanobacterium

Oligomers based on amino acids conserved between known plant omega-3 and cyanobacterium omega-6 fatty acid desaturases were used to screen an Arabidopsis cDNA library for related sequences. An identified clone encoding a novel desaturase-like polypeptide was used to isolate its homologs from Glycine max and Brassica napus. The plant deduced amino acid sequences showed less than 27% similarity to known plant omega-6 and omega-3 desaturases but more than 48% similarity to cyanobacterial omega-6 desaturase, and they contained putative plastid transit sequences. Thus, we deduce that the plant cDNAs encode the plastid omega-6 desaturase. The identity was supported by expression of the B. napus cDNA in cyanobacterium. Synechococcus transformed with a chimeric gene that contains a prokaryotic promoter fused to the rapeseed cDNA encoding all but the first 73 amino acids partially converted its oleic acid fatty acid to linoleic acid, and the 16:1(9c) fatty acid was converted primarily to 16:2(9c, 12) in vivo. Thus, the plant omega-6 desaturase, which utilizes 16:1(7c) in plants, can utilize 16:1(9c) in the cyanobacterium. The plastid and cytosolic homologs of plant omega-6 desaturases are much more distantly related than those of omega-3 desaturases.

Cloning of higher plant omega-3 fatty acid desaturases

Arabidopsis thaliana T-DNA transformants were screened for mutations affecting seed fatty acid composition. A mutant line was found with reduced levels of linolenic acid (18:3) due to a T-DNA insertion. Genomic DNA flanking the T-DNA insertion was used to obtain an Arabidopsis cDNA that encodes a polypeptide identified as a microsomal omega-3 fatty acid desaturase by its complementation of the mutation. Analysis of lipid content in transgenic tissues demonstrated that this enzyme is limiting for 18:3 production in Arabidopsis seeds and carrot hairy roots. This cDNA was used to isolate a related Arabidopsis cDNA, whose mRNA is accumulated to a much higher level in leaf tissue relative to root tissue. This related cDNA encodes a protein that is a homolog of the microsomal desaturase but has an N-terminal extension deduced to be a transit peptide, and its gene maps to a position consistent with that of the Arabidopsis fad D locus, which controls plastid omega-3 desaturation. These Arabidopsis cDNAs were used as hybridization probes to isolate cDNAs encoding homologous proteins from developing seeds of soybean and rapeseed. The high degree of sequence similarity between these sequences suggests that the omega-3 desaturases use a common enzyme mechanism.

Local thermo-radiotherapy in carcinoma cervix: improved local control versus increased incidence of distant metastasis

In 1986, 50 patients with stages II and III carcinoma of the cervix were entered into this prospective randomized study. Twenty-five cases (Group I) were treated only by radical radiation whereas remaining 25 cases (Group II) received local hyperthermia in addition to radical radiation. Hyperthermia was delivered by intracavitary brachyhyperthermia approach using an endotract applicator. Both the groups were followed up for a minimum period of 18 months. Group II patients achieved better local control (14 out of 20 evaluable cases) than the Group I patients (11 out of 22 evaluable cases). A disturbing observation was the increased incidence of distant metastasis in Group II (4 out of 23 cases) as compared to Group I (1 out of 23 cases), though most of them remained disease free locally. The increasing use of hyperthermia in the management of various cancers needs to be reviewed in this context.

Comparison of increased expression of wild-type and herbicide-resistant acetolactate synthase genes in transgenic plants, and indication of posttranscriptional limitation on enzyme activity

Genes encoding wild type acetolactate synthase (ALS) and a sulfonylurea herbicide-resistant form of the enzyme, isolated from Arabidopsis thaliana, were expressed in transgenic Nicotiana tabacum plants under the control of their native promoters or of the highly active cauliflower mosaic virus 35S promoter. Expression of the wild type coding region from the 35S promoter resulted in a small, threefold increase in sulfonylurea tolerance above the levels measured in tissue expressing the native wild type gene. A much larger, 300-fold increase in herbicide tolerance was conferred by the mutant gene encoding a herbicide-resistant ALS. An additional 10-fold increase in tolerance was attained by expressing this coding region from the 35S promoter. The increase in both wild type and mutant gene expression directed by the 35S promoter resulted in over 25-fold higher levels of ALS messenger RNA in some transformants as compared with those expressing the native genes. However, ALS specific activity increased at most twofold, indicating that the amount of functional enzyme and messenger RNA are not correlated.

Side-effects of local hyperthermia: results of a prospectively randomized clinical study

In 1986, 25 patients with stage II and III carcinoma of the cervix were treated by a combination of radiation and local hyperthermia using an endotract intravaginal applicator. Another 25 patients were treated with radiation alone. Both groups were followed up for a minimum period of 18 months. The acute and long-term toxicity of local hyperthermia was closely monitored. Our study shows that whereas local hyperthermia adds significantly to the local control achieved with radiation alone, it is not in any way associated with any significant short- or long-term toxicity, and does not enhance the radiation reactions.

Tubulin from cultured tobacco cells: isolation and identification based on similarities to brain tubulin

The microtubule protein, tubulin, was isolated from most other proteins of cell suspension cultures of Nicotiana tabacum L. by its copolymerization with cow-brain tubulin. Cow-brain tubulin was added to the soluble protein fraction of extract from (35)S-labeled tobacco cells and subjected to two cycles of temperature-dependent assembly-disassembly (copolymerization). When analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) about 70% of the radioactivity in the twice copolymerized protein was found in a prominent doublet migrating close to the doublet of brain tubulin. When analyzed by two-dimensional isoelectric-focusing-SDS-PAGE the radioactive doublet behaved like the doublet of brain tubulin. Limited proteolysis of the individual polypeptides of the coublets showed that, while the peptide maps of the leading radioactive band and of the β-subunit of brain tubulin were virtually indistinguishable, the maps of the trailing radioactive band and of the α-subunit of brain tubulin, though similar, were not identical. Most of the copolymerized (35)S-labeled protein also behaved like brain tubulin during gel filtration and ion-exchange chromatography. It is concluded that the doublet of radioactive polypeptides isolated by copolymerization with brain tubulin are tobacco tubulin polypeptides that have, in their native as well as denatured forms, properties very similar to, but not identical with, cow brain tubulin. Apparently, tubulin has been highly conserved during evolution.