Technical assessment of shear bond strength at ceramo-alloy interface after various surface treatment combinations and application of metal bonding agent.

BACKGROUND: Bonding between metal and ceramic is one of the most important aspects of a successful prosthesis. Various methods have been recommended for preparing the metal surface to enhance the bond between metal and ceramic including the use of a metal bonding agent. OBJECTIVE: This study aims to evaluate and compare the shear bond strength of the metal-ceramic (M-C) interface after combinations of various surface treatments including the application of a metal bonding agent. METHOD: 40 Ni-Cr alloy specimens were made and divided into 4 groups of 10 each based on the combination of surface treatments. Sandblasting, surface grinding, and Oxidation heat treatment (OHT) were performed on specimens from Group 1 (Control). In addition, Group 2 specimens received ultrasonic cleaning, Group 3 steam cleaning, and Group 4 metal bonding agent application. Following surface treatments on all specimens, porcelain build-up was performed, and shear bond strength was tested in a Digital Universal testing machine. The statistical tests used were independent t-test and ANOVA. RESULTS: Results revealed that Group 4 specimens had the highest mean value of shear bond strength of 39.087 MPa while Group 3 specimens showed the least mean shear bond strength of 18.154 MPa with highly statistically significant results (p< 0.001). CONCLUSION: The surface treatments and application of bonding agent to metal prior to porcelain application resulted in increased shear bond strength of the metal-ceramic interface.

Dimensional Stability of Light-Activated Urethane Dimethacrylate Denture Base Resins.

An accurate and dimensionally stable trial denture base is required for a successful denture. The aim of this in vitro study was to assess the dimensional stability of a light-activated urethane dimethacrylate (UDMA) visible light cure (VLC) denture base with three fabrication techniques and different curing cycles. Forty-five VLC denture base samples were divided evenly into three groups. Group A used a conventional fabrication technique with a curing cycle of 5 min. Group B used a modified fabrication technique with two 4-min curing cycles. Group C used a multi-step fabrication technique with three curing cycles (4 min, plus 4 min, plus 2 min). The samples were sectioned and observed under a stereomicroscope to measure the discrepancy between the sample and the master cast. The mean dimensional discrepancy (mm) at the molar region at mid-palate, after 24 h in Group A, B and C was 0.790 mm, 0.741 mm and 0.379 mm, respectively; at the right ridge crest, it was 0.567, 0.408 and 0.185, while at the left ridge crest it was 0.475, 0.331 and 0.125, respectively. Statistical analysis showed significantly different dimensional discrepancies among the groups at all three sites; right ridge crest (F = 93.54, p < 0.001), left ridge crest (F = 105.96, p < 0.001) and mid-palate (F = 125.53, p < 0.001). Within the limitations of this laboratory study, it can be concluded that the denture base using a multi-step fabrication technique with three curing cycles provides better adaptation than the conventional technique. The significance of the study is that clinicians should consider performing denture base fabrication using a multi-step technique to enhance adaptation and hence the stability of the dentures for patients.

Clinical analysis of CAD-CAM milled and printed complete dentures using computerized occlusal force analyser.

BACKGROUND: Digital complete dentures (CDs) by computer-aided designing and computer-aided manufacturing (CAD-CAM) techniques (milling and three-dimensional (3-D) printing) have been evaluated clinically and provided satisfactory results. But clinical studies assessing occlusal forces by digital dentures are lacking. OBJECTIVES: To compare the occlusal force parameters in complete dentures (CDs) fabricated by milling, 3-D printing and conventional techniques having 3 commonly used occlusal schemes, using computerized occlusal force analysis system (Tech-Scan III- T-Scan III). METHODS: A total of 45 CDs were fabricated for 5 patients. Nine sets of CDs were made for each patient and were divided into 3 groups: Conventional CDs (CCD), Milled CDs (MCD), and 3-D printed CDs (3-DP CD). The CDs in each group were further divided into 3 sub-groups based on occlusion schemes - bilateral balanced (BBO), lingualized (LO) and mono plane (MP). Occlusal force analysis [percentage (%) of occlusal force applied on the right and left sides of the arch difference between them, centralization of forces and % of maximum occlusal/bite force] was done using computerized occlusal analysis system (T-Scan III) at the time of denture insertion. Univariate regression analysis and logistic regression analysis were performed (p< 0.05). RESULTS: The intergroup comparison of force distribution on right and left side in CDs fabricated by various techniques showed insignificant differences (p> 0.05) but statistically significant differences (p< 0.01) were found in right-left side force difference, maximum bite force % and centralization of forces. The maximum force difference on right and left side was observed CCD with MO (37.48 ± 1.03 N) and maximum occlusal-bite force % was observed for 3-DPCD with LO (95.40 ± 1.30 N). In comparison to 3-DP CD, the chances of centre of force out of ellipse (centralization of forces) was 3.36 and 2.15 times more in CCD and MCD techniques made CDs respectively. CONCLUSIONS: The occlusal parameters in CDs were affected by the fabrication techniques and occlusal schemes of CDs. The digital CDs retain adjusted occlusal schemes better and 3-DP CDs with BBO and LO occlusal schemes provided centralization of forces, better distribution and high maximum occlusal force % respectively.

Computerized occlusal forces analysis in complete dentures fabricated by additive and subtractive techniques.

BACKGROUND: Fabrication of complete dentures by computer-aided designing and computer-aided manufacturing (CAD-CAM) techniques are now common. Subtractive and Additive are the two principal CAD-CAM techniques used for this purpose. However, studies that evaluated the occlusal forces by CDs manufactured by these techniques are lacking. OBJECTIVES: To compare the occlusal forces in complete dentures fabricated by additive, subtractive and conventional techniques with different occlusal schemes, using computerized occlusal force analysis system [Tech-Scan III (T-Scan III)]. METHODS: Three groups (Gr) were made on the basis of techniques of fabrication of CDs: Conventional CDs (CCD), Subtractive CDs (SCD), and Additive CDs (ACD). Each group CDs were further divided into three sub groups based on occlusion schemes: bilateral balanced occlusion (BBO), lingualized occlusion (LO) and mono plane occlusion (MO). A total of 45 CDs were made: 15 in each group with 5 CDs of each occlusal scheme. For all samples, occlusal force analysis (percentage of occlusal force applied on the right and left sides of the arch, centralization of forces and percentage of maximum occlusal force) was done using computerized occlusal analysis system: T-Scan III. Univariate regression analysis and logistic regression analysis were used to find the effects of the technique of fabrication and occlusion scheme over the occlusal forces (p< 0.05). RESULTS: The intergroup comparison revealed statistically significant differences (p< 0.01) in right-left side force difference, maximum bite force in CDs fabricated by various techniques and with different occlusion schemes. Though the effect of occlusion scheme was more than the technique of fabrication (according to effect size estimation). The maximum force difference between right-left side was observed in combination of CCD technique and MO scheme (36.88 ± 2.82 N). Furthermore, the maximum bite force was observed for SCD technique (89.14 ± 6.08 N) and LO scheme (92.17 ± 3.22 N). In comparison to ACD, the chances of centre of force out of ellipse was 2.53 time more in CCS and 0.75 times less in SCD techniques and in comparison to MO, the chances of out of ellipse was 0.298 times less in BBO and 0.396 times less in LO schemes, though these chances were not statistically significant (p> 0.05). CONCLUSIONS: The digital CDs fabricated by subtractive technique were proved to be superior to additive technique in terms of occlusal force analysis on tested parameters. However, further research is needed on patients to determine the exact superiority of one technique over the other.

Four narrow dental implants and conventionally cast bar-supported removable hybrid acrylic complete denture as a therapeutic modality for terminal dentition.

The report portrays four narrow implants and cast bar-supported removable hybrid acrylic complete dentures and other terminal dentition treatment options in the maxilla. The therapeutic module could be efficient and satisfactory to patients.

Predoctoral dental implant education techniques-students' perception and attitude.

PURPOSE: Dental implant (DI) therapy is in high demand and can only be rendered efficiently to graduating dentists by effective teaching methodologies. This study aimed to assess the perceptions and attitudes of dental graduates towards predoctoral DI education techniques and rehabilitation by DI. METHODS: A total of 26 well-structured questionnaires were distributed to 120 final-year students. Modified advanced teaching methodologies such as e-learning, small-group teaching-problem-based learning (SGT-PBL), and team-based learning were implemented for teaching DI. Its effects were assessed using a questionnaire set: the first section (DI Rehabilitation) with 12 questions and the second (DI teaching methods) with 14 questions. Statistical analysis was done using the Chi-square test, and a P-value < 0.05 was considered statistically significant. RESULTS: The response rate was 95.83%. Seventy-five percent of the students recommended DI for patients, and 78% of them agreed to it themselves. On comparing teaching methods for DI, on and before level 12, small-group teaching (PBL) was significantly at a higher proportion (P = 0.002), followed by seminars (P < 0.001). Students preferred small-group teaching PBL (60%), followed by e-learning (15%) and demonstration (10%). Ninety-two percent of the students agreed that DI is an important subject in the "bachelor of dental surgery" (BDS) program, but 78% of them felt that time was insufficient to complete the DI syllabus. CONCLUSIONS: The modified teaching methodologies used at level 12 for teaching DI enhanced students' interest and knowledge. The SGT-PBL teaching method was the most preferred. It is recommended that dental implantology topics should be started early in the undergraduate curriculum, and the topics should be widely divided throughout BDS.

Oral rehabilitation of a cleft palate patient with tooth-supported, telescopic magnetic overdenture.

A 49-year-old male patient with residual cleft palate and missing pre-maxilla presented with an ill-fitting and unaesthetic maxillary denture. The posterior teeth were periodontally sound but crowded and had defective restorations and secondary caries. We restored the bilateral maxillary canines and first premolars with conical telescopic crowns having magnetic keepers. A metal-reinforced acrylic overdenture with magnetic attachments corresponding to the keepers of the telescopic crowns was fabricated. The telescopic crowns provided a single path of insertion, retention and stability to the prosthesis. The magnetic attachments provided additional retention and self-centring properties. The prosthesis effectively sealed the oronasal communication and enhanced the function, aesthetics and oral hygiene. The 6-month and 1-year follow-ups revealed that the patient was delighted, and the prosthesis provided excellent obturation and function. Periodic follow-up, maintenance, patient education and meticulous oral hygiene are vital for long-term success of such prostheses.

Marginal and internal fit of provisional crowns fabricated using 3D printing technology.

BACKGROUND: Clinicians routinely provide provisional crowns following teeth preparation. Three-dimensional (3D) printing technology could be used over conventional methods for better fit as lack of adequate fit would result in plaque accumulation, micro-leakage, teeth sensitivity, caries and periodontal diseases. OBJECTIVE: The aim of the study was to evaluate the marginal and internal fit of provisional crowns fabricated using 3D printing technology and to compare it with that of compression molding and milling methods. METHODS: Ninety study models were fabricated by duplicating metal master models of the maxillary first premolar molar with three different finish line chamfer, rounded shoulder and rounded shoulder with bevel. On each study model, provisional crowns were fabricated using compression molding (Mo. group, n= 30 - by over impression technique), milling (Mi. group, n= 30 - by 5-axis dental milling machine), and 3D printing method (3D-P. group, n= 30 - by 3D printer). Marginal and internal fit of the samples were evaluated by measuring gap using a scanning electron microscope with a magnification of 27 ×, at 7 zones A-G on different finish line models. The data were statistically analysed using one-way analysis of variance (ANOVA) at the 0.05 significance level. The p-values were calculated using Dunnett's test. RESULTS: The marginal gap was minimal for the 3D-P. group for each finish line with lowest for rounded shoulder with bevel at zone A 30.6 ± 5.3 and at zone G 32.8 ± 5.4. In axial area, i.e. zones B and F, the minimum gap was noticed for the Mo. group and in Occlusal area (cusp and fossa), for zones C-E maximum gap was determined in Mi. group followed by Mo. and 3D-P. groups. CONCLUSIONS: 3D printed provisional crowns have better marginal and internal fit compared to milled and molded provisional crowns.

Implant-supported fixed hybrid acrylic complete dentures opposing fully restored mandibular metal ceramic restorations.

This report presents a full-mouth rehabilitation case. A patient came with a failing dentition in maxilla, and after the treatment, the patient had a shortened full-arch, implant-supported, screw-retained hybrid acrylic complete denture in the maxilla and full-arch metal ceramic restorations in the mandible. The report describes the steps involved in the prosthodontic rehabilitation; a cost-effective treatment plan, the restoration of vertical dimension, an immediate denture, an implant-level impression, a verified-master cast, the fabrication of definitive prosthesis, the occlusal scheme and multiple follow-ups in 6 months. We discussed the merits/demerits of screw-retained prosthesis, impression techniques and various types of fixed complete dentures. We learnt the difficulty in hygiene measures and dissatisfaction of the patient with the hygienic gaps under the acrylic fixed dentures.

Hydrophilic titanium surface-induced macrophage modulation promotes pro-osteogenic signalling.

OBJECTIVES: As biomaterial-induced modulation of mediators of the immune response may be a potential therapeutic approach to enhance wound healing events, the aim of this study was to delineate the effects of titanium surface modification on macrophage phenotype and function. MATERIAL AND METHODS: Rodent bone marrow-derived macrophages were polarized into M1 and M2 phenotypes and cultured on micro-rough (SLA) and hydrophilic modified SLA (modSLA) titanium discs. Macrophage phenotype and cytokine secretion were subsequently assessed by immunostaining and ELISA, respectively. Osteoblast gene expression in response to culture in the M1 and M2 macrophage conditioned media was also evaluated over 7 days by RT-PCR. RESULTS: M1 macrophage culture on the modSLA surface promoted an M2-like phenotype as demonstrated by marked CD163 protein expression, Arg1 gene expression and the secretion of cytokines that significantly upregulated in osteoblasts the expression of genes associated with the TGF-ß/BMP signalling pathway and osteogenesis. In comparison, M2 macrophage culture on SLA surface promoted an inflammatory phenotype and cytokine profile that was not conducive for osteogenic gene expression. CONCLUSIONS: Macrophages are able to alter or switch their phenotype according to the signals received from the biomaterial surface. A hydrophilic micro-rough titanium surface topography elicits a macrophage phenotype associated with reduced inflammation and enhanced pro-osteogenic signalling.

An In Vitro Evaluation of Fracture Resistance Strength of Different Post Systems in Endodontically Treated Teeth.

AIM: This study aimed to evaluate the fracture resistance strength of different post systems in endodontically treated teeth. MATERIALS AND METHODS: Freshly extracted 60 single-rooted first premolars were selected for this study. Conventional step-back technique was used to prepare a canal for all the teeth. Obturation was carried out and post space was created using a Peeso reamer. All teeth were randomly divided into three groups of 20 samples in each group: Group I, teeth inserted with prefabricated carbon posts; Group II, teeth inserted with prefabricated zirconia posts; and Group III, teeth inserted with prefabricated everStick posts. Core buildup was performed using light-cured composite resin. Compressive load required to fracture the tooth was measured using a universal testing machine. RESULTS: The compressive strength of zirconia posts was highest with a mean of 796.10 ± 20.78 followed by carbon posts (628.22 ± 18.11) and lower compressive strength was exhibited by everStick posts (534.13 ± 19.98). An analysis of variance revealed a statistically highly significant difference (P < 0.005) among the different posts used, and a statistically significant difference between carbon posts vs. zirconia posts, carbon posts vs. everStick posts, and zirconia posts vs. everStick posts (P < 0.05). CONCLUSION: Zirconia posts show the maximum fracture resistance than the carbon posts and everStick posts.

An In Vivo Study to Compare Location of Neutral Zone Recorded with Two Materials.

AIM: To establish a relationship between the crest of the alveolar ridge and neutral zone and to compare its location recorded by two different material. METHODS AND MATERIALS: Thirty subjects were selected, and the location of the neutral zone was compared with the mandibular alveolar ridge crest. For each subject neutral zone was recorded by two different recording materials-Low fusing impression compound and tissue conditioner. After neutral zone recording, the relation between mandibular ridge crest and neutral zone location examined radiographically. The data so collected were checked for normality, descriptive statistics and the Mann-Whitney U test was used. RESULTS: Position of neutral zone was found towards lingual in the posterior, labial side in anterior and almost near to the alveolar ridge crest in premolar region. The thermoplastic flow of the material effects the position of neutral zone but no significant difference was noted in the positions of neutral zone recorded by the two materials in relation to the alveolar ridge crest. CONCLUSION: Location of the neutral zone is not affected by the material used in recording it. CLINICAL SIGNIFICANCE: The location of the neutral zone varies from subject to subject and mainly depends upon their musculature and can be recorded accurately by using correct technique irrespective of the materials used.

The Effect of Platelet Proteins Released in Response to Titanium Implant Surfaces on Macrophage Pro-Inflammatory Cytokine Gene Expression.

BACKGROUND AND PURPOSE: Platelets are one of the earliest cell types to interact with surgically inserted titanium implants. This in vitro study investigated the effect of titanium surface-induced platelet releasate on macrophage cytokine gene expression. MATERIALS AND METHODS: To mimic the in vivo temporal sequence of platelet arrival and protein production at the implant surface and the subsequent effect of these proteins on mediators of the immune response, the levels of platelet attachment and activation in response to culture on smooth polished, sandblasted and acid-etched (SLA), and hydrophilic-modified SLA (modSLA) titanium surfaces were first determined by microscopy and protein assay. The subsequent effect of the platelet-released proteins on human THP-1 macrophage cytokine gene expression was determined by polymerase chain reaction array after 1 and 3 days of macrophage culture on the titanium surfaces in platelet-releasate conditioned media. RESULTS: Platelet attachment was surface dependent with decreased attachment observed on the hydrophilic (modSLA) surface. The platelet releasate, when considered independently of the surface effect, elicited an overall pro-inflammatory response in macrophage cytokine gene expression, that is, the expression of typical pro-inflammatory cytokine genes such as TNF, IL1a, IL1b, and CCL1 was significantly up-regulated whereas the expression of anti-inflammatory cytokine genes such as IL10, CxCL12, and CxCL13 was significantly down-regulated. However, following platelet exposure to different surface modifications, the platelet releasate significantly attenuated the macrophage pro-inflammatory response to microrough (SLA) titanium and hastened an anti-inflammatory response to hydrophilic (modSLA) titanium. CONCLUSIONS: Theses results demonstrate that titanium surface topography and chemistry are able to influence the proteomic profile released by platelets, which can subsequently influence macrophage pro-inflammatory cytokine expression. This immunomodulation may be an important mechanism via which titanium surface modification influences osseointegration.

Titanium surface hydrophilicity enhances platelet activation.

Titanium implant surface modification is a key strategy used to enhance osseointegration. Platelets are the first cells that interact with the implant surface whereupon they release a wide array of proteins that influence the subsequent healing process. This study therefore investigated the effect of titanium surface modification on the attachment and activation of human platelets. The surface characteristics of three titanium surfaces: smooth (SMO), micro-rough (SLA) and hydrophilic micro-rough (SLActive) and the subsequent attachment and activation of platelets following exposure to these surfaces were determined. The SLActive surface showed the presence of significant nanoscale topographical features. While attached platelets appeared to be morphologically similar, significantly fewer platelets attached to the SLActive surface compared to both the SMO and SLA surfaces. The SLActive surface however induced the release of the higher levels of chemokines ß-thromboglobulin and platelet factor 4 from platelets. This study shows that titanium surface topography and chemistry have a significant effect on platelet activation and chemokine release.

Titanium surface hydrophilicity modulates the human macrophage inflammatory cytokine response.

Increased titanium surface hydrophilicity has been shown to accelerate dental implant osseointegration. Macrophages are important in the early inflammatory response to surgical implant placement and influence the subsequent healing response. This study investigated the modulatory effect of a hydrophilic titanium surface on the inflammatory cytokine expression profile in a human macrophage cell line (THP-1). Genes for 84 cytokines, chemokines, and their receptors were analyzed following exposure to (1) polished (SMO), (2) micro-rough sand blasted, acid etched (SLA), and (3) hydrophilic-modified SLA (modSLA) titanium surfaces for 1 and 3 days. By day 3, the SLA surface elicited a pro-inflammatory response compared to the SMO surface with statistically significant up-regulation of 16 genes [Tumor necrosis factor (TNF) Interleukin (IL)-1ß, Chemokine (C-C motif) ligand (CCL)-1, 2, 3, 4, 18, 19, and 20, Chemokine (C-X-C motif) ligand (CXCL)-1, 5, 8 and 12, Chemokine (C-C motif) receptor (CCR)-7, Lymphotoxin-beta (LTB), and Leukotriene B4 receptor (LTB4R)]. This effect was countered by the modSLA surface, which down-regulated the expression of 10 genes (TNF, IL-1α and ß, CCL-1, 3, 19 and 20, CXCL-1 and 8, and IL-1 receptor type 1), while two were up-regulated (osteopontin and CCR5) compared to the SLA surface. These cytokine gene expression changes were confirmed by decreased levels of corresponding protein secretion in response to modSLA compared to SLA. These results show that a hydrophilic titanium surface can modulate human macrophage pro-inflammatory cytokine gene expression and protein secretion. An attenuated pro-inflammatory response may be an important molecular mechanism for faster and/or improved wound healing.