Evaluation of the effect of dentin surface treatment by air abrasion and Er:YAG laser on the retention of metal crowns luted with glass ionomer cement in teeth with reduced crown height: An in vitro study.

AIM AND OBJECTIVES: The purpose of this study was to investigate the effect of dentin surface treatment with aluminum oxide air abrasion and Er:YAG laser on tensile bond strength of metal crowns. Metal crowns were luted with conventional glass ionomer cement (GIC) in the teeth with reduced crown height, where preparation geometry did not provide optimal retention form. MATERIALS AND METHODS: Forty-eight human premolars were prepared to receive metal crowns and were randomly divided into four groups for tensile bond strength testing. Group A: Untreated dentin luted with self-adhesive composite resin cement as positive control; Group B: Untreated dentin luted with GIC as negative control; Group C: Surface treatment with 50 µm aluminum oxide air abrasion and luted with GIC; Group D: Surface treatment with Er:YAG laser (λ =2.94 mm) with a total energy 84.88 J/cm2 of (60 mJ/pulse, 10 Hz, 60 pulses, and 100 µs pulse width) and luted with GIC. The cemented specimens were thermocycled and later subjected to axial load in a universal testing machine at 0.5 mm/min cross-head speed for tensile testing. Scanning electron microscopic evaluation of dentin surface treatment and cement-dentin interface was also done in representative specimens. RESULTS: One-way analysis of variance showed statistically significant difference among/within the groups (P < 0.001). Tukey's post hoc test presented significant increased tensile bond strength of Er:YAG laser group. Air abrasion group showed no significant increase in tensile bond strength values (P = 0.033). CONCLUSION: Dentin surface treatment with Er:YAG laser significantly improved the tensile bond strength of luting GIC compared to air-abraded and untreated dentin.

Stress distribution & deflection in an Aramany class II obturator fabricated with cobalt-chromium & titanium alloys - 3D FEA.

PURPOSE/OBJECTIVES: The aim of the research was to develop a model that accurately represents an Aramany class II defect and its obturator prostheses fabricated with Cobalt Chromium alloy & Titanium alloy to compare the deflection and the stress distribution in the rehabilitated area. METHODS: Aramany class II defect and the obturator prostheses was generated geometrically utilizing ANSYS 14.5, both overlaid on each other to impressionist prostheses and the maxilla as one element. Meshing of models was carried out utilizing HYPERMESH software & materialistic properties were assigned. The 120 N load was constituted on the teeth in different directions. RESULTS: The stress distribution & deflection executed by ANSYS provided results that enabled the tracing of Von Mises stress and deflection field in the form of color veiled bands with standards in Mega Pascal (MPa). CONCLUSION: The study shows that Von Mises stresses are higher for the frame work fabricated with cobalt chromium alloy compared to Titanium alloy. The framework made of titanium alloy showed more deflection than cobalt chromium alloy. CLINICAL IMPLICATIONS: 3D FEA can be performed on a computer without putting any stress on the human body from technical materials, which is especially difficult for maxillectomy patients.

A Three Month Comparative Evaluation of the Effect of Different Surface Treatment Agents on the Surface Integrity and Softness of Acrylic based Soft Liner: An In vivo Study.

INTRODUCTION: Acrylic based soft liners are cost effective, yet are inferior in durability as compared to silicone based liners. Hence, this study was conducted to evaluate if the softness and surface integrity of acrylic based soft liner can be maintained by using different surface treatment agents. AIM: To comparatively evaluate the effects of Varnish, Monopoly and Kregard surface treatment agents on the surface integrity and softness of acrylic based soft liner at baseline, at one month and after three months. MATERIALS AND METHODS: A total of 37 participants who required conventional maxillary dentures were selected according to the determined inclusion and exclusion criteria of the study. In the maxillary denture on the denture bearing surface, eight palatal recesses (5 mm x 3 mm) were made and filled with acrylic based soft liner (Permasoft). The soft liners in these recesses were given surface treatment and divided as control (uncoated), Varnish, Monopoly and Kregard groups. The hardness and surface integrity were evaluated with Shore A Durometer and Scanning Electron Microscope (SEM) respectively at baseline, one month and three months interval. Surface integrity between groups was compared using Kruskal-Wallis test. Intergroup comparison for hardness was done using ANOVA and Tukey's HSD post-hoc tests. RESULTS: Amongst all the groups tested, surface integrity was maintained in the Kregard group, as compared to control, Varnish and Monopoly groups for all three time intervals (p< 0.001). Kregard treated samples also demonstrated significantly higher softness at all the time intervals (p<0.001). CONCLUSION: Surface treatment with Kregard demonstrated better surface integrity and softness at all the time intervals.

Comparative evaluation of the amount of gingival displacement produced by three different gingival retraction systems: An in vivo study.

STATEMENT OF PROBLEM: Tetrahydrozoline has been introduced as new gingival retraction agent but its clinical efficacy with widely used conventional retraction agents has not been tested. PURPOSE: The study was designed to clinically evaluate efficacy of newer retraction agent tetrahydrozoline with two widely used retraction systems i.e., Expasyl retraction system and medicated retraction cords on basis of amount of gingival retraction. MATERIALS AND METHODS: 30 subjects were selected according to inclusion and exclusion criteria. Maxillary Impressions were made with irreversible hydrocolloid for all subjects. Tray material was used for making the special tray. Latin Block Design was Used in the Study to avoid tissue fatigue. Retraction was done with aluminium chloride; Tetrahydrozoline and Expasyl according to Latin block design. Impressions were poured with die stone. Casts were retrieved and sections were made with die cutter. 3 mm thin slices were obtained. Each slice was used to measure the amount of retraction under stereomicroscope under 20x and images were transferred to image analyser. RESULTS: The amount of gingival retraction obtained by using aluminium chloride as gingival retraction agent was maximum (148238.33 µm(2)) compared to tetrahydrozoline (140737.87 µm(2)) and Expasyl (67784.90 µm(2)).

A comparative analysis of the effect of three types of denture adhesives on the retention of maxillary denture bases: an in vivo study.

There are many factors involved in the success of a good quality complete dentures, one of them is retention. There are some forcing situations where providing optimal retention may be a problem, in which use of denture adhesives is recommended. In the present study, primary and secondary impressions were made on 20 completely edentulous patients, master cast was fabricated. Master cast was duplicated; heat-cured denture base was fabricated. The retention test for control group, powder group, wafer group, paste group was done using a customized force sensor device. Readings was subjected to ANOVA followed by post hoc test. Results show that the retention force value of the paste group was the maximum, followed by powder group, wafer group and the least retention force value was observed with control group. Within the limitations of the study it can be concluded that the paste form of denture adhesive has the best retentive property compared to the powder and wafer.

Alternatives for restoration of a hemisected mandibular molar.

Hemisection is a common conservative treatment option for periodontally or endodontically compromised teeth. It is most likely to be performed on mandibular molars with class II or III furcation involvement. Their restoration is more critical than implant surgery to ensure the ability to masticate along with the ability to maintain good oral hygiene. There are various alternatives to restore such types of teeth: the remaining root restored as an individual tooth, restoring individual roots with either a molar or premolar morphology using the adjacent tooth as an abutment in a full coverage fixed partial denture, restoring individual roots with either molar or premolar morphology using an inlay type of restoration on the adjacent abutment tooth. This article reports two cases, one treated with molar morphology and an inlay type of restoration and the other with a premolar morphology and a full coverage fixed partial denture.

A clinical study of the variation in horizontal condylar guidance obtained by using three anterior points of reference and two different articulator systems.

BACKGROUND AND OBJECTIVES: For mounting the maxillary cast to articulator, minimum three reference points not on single line, decide the plane to which maxillary cast is mounted. Variations exist in condylar guidance when different anterior reference points are used to mount the cast. Type of articulator may have influence on condylar guidance. A clinical study was planned to evaluate the effects of different anterior points of reference and two different articulator systems on condylar guidance. MATERIALS AND METHODS: Total 15 subjects were selected. Six sets of maxillary casts were obtained. Face bow record was made using orbitale as anterior point of reference and the record was transferred to the Arcon and Non-Arcon articulator. The second and third mounting on Arcon and Non-Arcon articulator were done using Superior and inferior annular groove on incisal pin of articulator. Protrusive interocclusal records were made for all the subjects. Two lateral cephalograms one in maximum intercuspation and the other in protrusion for left and right side were taken. Anatomic condylar guidance of the subject were obtained from radiograph tracing. Arcon and Non-arcon articulator were programmed with Protrusive interocclusal record of the subjects and the condylar guidance was tabulated for right and left side. The procedure was repeated for all three mountings for both the articulators. RESULTS: The orbitale is the best reference point which mounts maxillary cast closer to anatomic position. Inferior annular groove can also be used as anterior point of the reference. The superior annular groove is not recommended anterior point of reference.

Indirect laminate veneer: a conservative novel approach.

Various treatment options and materials are available for restoration of an endodontically treated tooth. Laminate veneer is conservative treatment usually employed for aesthetic correction or improvement. The indirect composite is available in a wide range of shades and specific characterisation is easily performed chair side in the operatory area, which makes it a quick procedure and time saving for both the patient and the dentist. The physical properties and optical properties are good enough to use it as indirect restorative material, so in this particular case it was the material of choice for fabrication of laminate veneer on anterior tooth. In this case, the endodontically treated tooth with a fractured incisal edge was restored with indirect composite material.

Complete denture with pharyngeal bulb prosthesis.

Velopharyngeal dysfunction is the inability of the soft palate to affect complete seal with the posterior or lateral pharyngeal walls. Rehabilitation of these patients with palatal defects is challenging for both surgical and prosthetic fields of dentistry. The development of sophisticated surgical techniques and procedures has greatly enhanced the rehabilitation of congenital or acquired palatal defects. However, some of these patients may present oral or systemic factors contraindicating surgical intervention. In addition, since total elimination of these defects surgically has not yet become a reality, there exists a patient population for whom non-surgical rehabilitation must be approached with the help of prosthesis and such prosthesis must restore the basic functions of mastication, deglutition and speech production. Here a non-surgical approach of rehabilitation of such defect is presented in the form of a case report of pharyngeal bulb prosthesis given for a patient with a soft palate defect.

Effect of the impression margin thickness on the linear accuracy of impression and stone dies: an in vitro study.

The space available for impression material in gingival sulcus immediately after the removal of retraction cord has been found to be 0.3-0.4 mm. However after 40 s only 0.2 mm of the retracted space is available. This is of concern when impression of multiple abutments is to be made. Hence a study was planned to determine the minimum width of the retracted sulcus necessary to obtain a good impression. Five metal dies were machined to accurately fit a stainless steel block with a square cavity in the center with spaces, 1 mm deep and of varying widths (0.11-0.3 mm) away from the block. Polyvinyl siloxane impressions were made and poured using a high strength stone. Using traveling microscope, length and widths of abutment, impression and die were measured and compared for linear accuracy and completeness of impression. Results showed 1.5-3 times greater mean distortion and larger coefficient of variance in the 0.11 mm group than in the wider sulcular groups. ANOVA test for distortion also showed statistically significant differences (P < 0.05). 75 % of impressions in 0.11 mm group were defective compared to less than 25 % of impressions in other width groups. It is not always possible to predictably obtain accurate impressions in sulcus width of 0.11 mm or lesser. Dimensionally accurate and defect free impressions were obtained in sulcus width of 0.15 mm and wider. Hence clinicians must choose retraction methods to obtain a width greater than 0.35 mm. Further immediate loading of the impression material after cord removal may improve accuracy.

Coronomaxillary space and its significance in complete denture retention--case reports.

The coronomaxillary space defines the distal-most extension of the maxillary denture border, and it usually is tightened during mouth opening. It has been reported that its adequate filling or overfilling is helpful in prosthesis retention. Two types of individual anatomical variations can affect the size of this space: vertical or lateral. With vertical variations, the space increases or does not vary when the mouth is opened; therefore, the prosthesis border must be thicker to obtain adequate retention. With lateral variations, the coronomaxillary space is reduced when the mouth is opened; therefore, the prosthesis border must be thin. The case reports presented here show how complete denture retention can be augmented by the careful recording of the coronomaxillary space dimensions.

A comparative evaluation of effect of upper lip length, age and sex on amount of exposure of maxillary anterior teeth.

AIM: The aim was to evaluate the relationship of age, sex and lip length to the amount of exposure of maxillary incisors and canine teeth. MATERIALS AND METHODS: Two-hundred subjects were enrolled in the study. All subjects were grouped according to the lip length and age. The exposure of maxillary central incisor and canines was measured with flexible millimeter ruler. Teeth exposure beyond the lower border of the upper lip was considered as positive exposure and the unexposed teeth were considered as negative exposure. RESULT: In females of age group 20 to 29, 30 to 39, 40 to 49 and 50 to 59 years, the mean exposure of central incisor was 2.16, 2.1, 2.18 mm and that of canine was 0.04, -0.36, -0.44 mm. For male of age group 20 to 29, 30 to 39, 40 to 49 and 50 to 59 years exposed 2.04, 2.04, 1.84, 1.76 mm of central incisor respectively and 0.08, -0.52, -0.4 and -0.4 mm exposure of canine. Female subjects with lip length 10 to 15, 15 to 20, 21 to 25, 25 to 30 and 31 to 35 mm showed 3.7, 3.4, 2.3, 0.9, 0.25 mm exposure of central incisor and 0.35, -0.15, -0.7, -0.8, -0.6 mm exposure of canine, respectively. Male subjects exposed 3.4, 3.3, 2.05, 0.7, 0.15 mm of central incisor and 0.4, 0.3, -0.6, -0.95, -0.7 mm of canine respective to lip length. CONCLUSION: The range of exposure of maxillary central incisors was wider than that of canine. The average dimensions for maxillary canines relating to age and sex were closer to the extremes of the range. The canine position relative to the maxillary lip appeared to be a more predictable determinant. CLINICAL SIGNIFICANCE: The result of the study can be used as a reference according to the age, sex and the lip length of the patient to correctly place maxillary anterior teeth in prosthesis.