Adaptation of cobalt chromium frameworks fabricated by conventional versus selective laser melting techniques: An in vitro and clinical assessment.

STATEMENT OF PROBLEM: Three-dimensional (3D) printing of cobalt chromium (Co-Cr) removable partial dentures (RPDs)by selective laser melting (SLM) has been claimed to be less challenging than by conventional casting and provides significant improvements. However, the adaptation and fit of the SLM framework and the optimum build orientation are still unclear. PURPOSE: The purpose of this in vitro and clinical study was to evaluate the effect of different build orientations on the adaptation of removable partial denture frameworks fabricated by SLM technology in vitro and to compare the adaptation of the SLM and conventional RPD frameworks clinically. MATERIAL AND METHODS: A master model simulating a maxillary arch of Kennedy class III modification 1 was scanned and duplicated to create a virtual 3D cast and reference cast. Four groups (n=40) of Co-Cr RPD frameworks were fabricated. For the SLM groups, the Co-Cr framework was virtually designed and exported for SLM printing. The SLM printing was done in 3 different build orientations: 0-degree (n=10), 45-degree (n=10), and 90-degree (n=10) groups. Other Co-Cr frameworks were conventionally cast (n=10). All Co-Cr frameworks were scanned and virtually superimposed with the master model using a surface-matching software program. The gap under 9 selected points in the palatal major connectors was analyzed and calculated. A smaller gap indicates more surface adaptation and close contact between the palatal major connector and the master model. The data were analyzed using the Kruskal-Wallis and Dunnett T3 tests (α=.05). Three patients with a partially dentate maxillary arch were enrolled in the clinical part based on inclusion criteria. Two RPD frameworks were provided for each patient (conventional casting and SLM printing). The adaptation of each framework was assessed by measuring the gap between the palatal major connector of the framework and the palate with light-body silicone. The differences in adaptation between the conventional and SLM frameworks were compared by using independent t tests (α=.05). RESULTS: The in vitro study identified significant differences in the adaptation of the palatal major connector among the 4 groups (P<.001), except for conventional and 0-degree SLM printing (P=.999). The conventional and 0-degree SLM frameworks exhibited the best adaptation, with the lowest gap underneath the palatal major connector of the RPD framework (0.01 ±0.02 mm and 0.01 ±0.01 mm, respectively). In the clinical part of the study, no significant difference was found between the adaptation of SLM and the conventional framework (P=.430) CONCLUSIONS: The adaptation of SLM printing can be maximized with less gap under the palatal major connector of the RPD framework when using the 0-degree build orientation. Co-Cr frameworks produced with SLM printing technology were comparable with conventionally produced frameworks; hence, SLM printed frameworks can be an alternative for clinical applications when optimum SLM parameters are applied.

Is microbial adhesion affected by the build orientation of a 3-dimensionally printed denture base resin?

STATEMENT OF PROBLEM: How the build orientation of a 3-dimensionally (3D) printed denture affects microbial adhesion is unclear. PURPOSE: The purpose of this in vitro study was to compare the adherence of Streptococcus spp. and Candida spp. on 3D-printed denture bases prepared at different build orientations with conventional heat-polymerized resin. MATERIAL AND METHODS: Resin specimens (n=5) with standardized 28.3 mm2 surface area were 3D printed at 0 and 60 degrees, and heat-polymerized (3DP-0, 3DP-60, and HP, respectively). The specimens were placed in a Nordini artificial mouth (NAM) model and exposed to 2 mL of clarified whole saliva to create a pellicle-coated substratum. Suspensions of Streptococcus mitis and Streptococcus sanguinis, Candida albicans and Candida glabrata, and a mixed species, each at 108 cfu/mL were pumped separately into the model for 24 hours to promote microbial adhesion. The resin specimens were then removed, placed in fresh media, and sonicated to dislodge attached microbes. Each suspension (100 µL) was aliquoted and spread on agar plates for colony counting. The resin specimens were also examined under a scanning electron microscope. The interaction between types of specimen and groups of microbes was examined with 2-way ANOVA and then further analysis with Tukey honest significant test and Kruskal-Wallis post hoc tests (α=.05). RESULTS: A significant interaction was observed between the 3DP-0, 3DP-60, and HP specimen types and the groups of microbes adhering to the corresponding denture resin specimens (P<.05). The difference was statistically significant among 3DP-0, 3DP-60, and HP specimens (P<.05). The adherence of candida was 3.98-times lower on the 3DP-0 than that of HP (P<.05). However, adherence of the mixed-species microbes and streptococci on the 3DP-60 were 1.75 times and 2-fold higher, respectively (P<.05). The scanning electron micrographs showed that 3DP-0 exhibited the lowest microbial adherence compared with HP and 3DP-60. CONCLUSIONS: Adherence affinity of denture base resin is affected by the build orientation rather than by the group of different microbes. Three-dimensionally printed denture base resin fabricated at a 0-degree build orientation exhibited low affinity for microbial adhesion. Three-dimensionally printed dentures may reduce microbial adhesion when printed at a 0-degree build orientation.

Physicomechanical properties of cobalt-chromium removable partial denture palatal major connectors fabricated by selective laser melting.

STATEMENT OF PROBLEM: Additive manufacturing by selective laser melting (SLM) has been claimed to be less challenging than conventional casting of cobalt-chromium (Co-Cr) removable partial dentures (RPDs), providing significant improvements. However, how the physicomechanical properties of Co-Cr RPDs fabricated by SLM compare with those fabricated by conventional casting is unclear. PURPOSE: The purpose of this in vitro study was to evaluate the physicomechanical properties of Co-Cr RPD palatal major connectors fabricated by SLM compared with those fabricated by conventional casting. MATERIAL AND METHODS: A master die simulating a maxillary arch of Kennedy class III modification 1 was scanned to create a virtual 3-dimensional (3D) cast. Two groups of 5 Co-Cr RPD major connectors were fabricated. In the 3D printing group, the Co-Cr major connector was virtually designed and exported for direct SLM 3D printing. For the conventional group, Co-Cr major connectors were constructed conventionally. The Co-Cr major connectors were virtually superimposed with the master die for surface adaptation analysis. Additional comparative analyses of surface roughness, relative density, microhardness, and microstructure of the 2 groups were performed. Data were analyzed by using independent t tests (α=.05). RESULTS: The overall volumetric and linear discrepancies were significantly higher (P<.05) in the 3D printing group. Significant differences in the surface roughness (P<.05) and microhardness (P<.05) were observed, with the 3D printing group having higher surface roughness and microhardness than the conventional group. Unlike conventional connectors, the microstructure of 3D-printed connectors showed fine homogeneous granules. CONCLUSIONS: Compared with the conventional casting technique, SLM 3D printing enabled the fabrication of Co-Cr RPD major connectors with higher microhardness and fine homogenous microstructure. However, the surface adaptation and surface roughness of SLM 3D printing Co-Cr connectors were worse than those produced conventionally. Both techniques showed similar relative densities.

Digital workflow for articulating maxillary and mandibular 3D arch models using an open source 3D modeling software program.

Virtual planning in digital dentistry enables easier communication between technicians, clinicians, and patients, and faster performance. Dental computer-aided design (CAD) software programs have been used for this purpose. One of the most crucial steps in virtual planning is mounting and articulating the maxillary and mandibular arch 3D models to simulate and evaluate the occlusion as a part of the virtual mock-up. The aim of this article was to describe a more cost-effective digital technique utilizing a scanned interocclusal record for articulating the cast models virtually. For this purpose, the open source Autodesk Meshmixer software program was used.

Assessment of masticatory function of mandibular implant-supported overdenture wearers: A 3-year prospective study.

STATEMENT OF PROBLEM: Wearers of mandibular complete dentures (CDs) often complain of retention and stability problems resulting in poor masticatory function. Evidence suggests that a mandibular overdenture (MOD) stabilized by 2 implants represents the treatment of choice to improve stability and masticatory function. Measurements are needed of the improvement in masticatory function after providing mandibular implant-stabilized overdentures. PURPOSE: The purpose of this prospective clinical study was to evaluate the changes in masticatory function from baseline (T0) to 3 months (T1) and 3 years (T2) in participants with MODs and to assess the effect of baseline mandibular bone height and volume on masticatory function after 3 years. MATERIAL AND METHODS: Participants were assessed for masticatory function by using masticatory performance involving paraffin wax cubes as an objective measure and by using masticatory ability involving a questionnaire as a subjective measure. Edentulous individuals presenting for replacement dentures were provided with conventional mucosa-supported prostheses and evaluated for masticatory function after a 3-month settling-in period (baseline measure). Before implant placement, baseline measures of bone height and volume were recorded from cone beam computed tomography (CBCT) images. The prostheses were then converted to implant-stabilized mandibular overdentures while any maxillary prostheses remained supported by the mucosa. Masticatory function was reassessed at 3 months and 3 years after insertion of the mandibular overdentures, and the mean changes from baseline were analyzed with the Wilcoxon signed-rank test. The effect of variables on masticatory function was determined by using multivariate linear regression analyses. RESULTS: A total of 23 participants were included in the study, with only 1 participant not completing the 3-year assessment. Significant improvement was observed in the masticatory performance (mixing ability index) (P<.01) and masticatory ability score (P<.001) from baseline to 3 months and baseline to 3 years. Bone height and volume had no significant effect on the improvement of masticatory function after conversion to an implant-stabilized mandibular overdenture. CONCLUSIONS: Masticatory function significantly improved after 3 months and was maintained over 3 years in participants with implant-stabilized mandibular overdentures. However, baseline bone height and volume had no significant effect on these changes in masticatory function after 3 years.

Accuracy of a new elastomeric impression material for complete-arch dental implant impressions.

AIM: The aim of the present study was to assess the accuracy of multi-unit dental implant casts obtained from two elastomeric impression materials, vinyl polyether silicone (VPES) and polyether (PE), and to test the effect of splinting of impression copings on the accuracy of implant casts. METHODS: Forty direct impressions of a mandibular reference model fitted with six dental implants and multibase abutments were made using VPES and PE, and implant casts were poured (N = 20). The VPES and PE groups were split into four subgroups of five each, based on splinting type: (a) no splinting; (b) bite registration polyether; (c) bite registration addition silicone; and (d) autopolymerizing acrylic resin. The accuracy of implant-abutment replica positions was calculated on the experimental casts, in terms of interimplant distances in the x, y, and z-axes, using a coordinate measuring machine; values were compared with those measured on the reference model. Data were analyzed using non-parametrical Kruskal-Wallis and Mann-Whitney tests at α = .05. RESULTS: The differences between the two impression materials, VPES and PE, regardless of splinting type, were not statistically significant (P>.05). Non-splinting and splinting groups were also not significantly different for both PE and VPES (P>.05). CONCLUSIONS: The accuracy of VPES impression material seemed comparable with PE for multi-implant abutment-level impressions. Splinting had no effect on the accuracy of implant impressions.

Virtual Treatment Planning for Implant-Retained Nasal Prosthesis: A Clinical Report.

Osseointegrated craniofacial implants have improved retention and patients' perceptions of implant-retained nasal prostheses; however, the determination of the available bone sites for implant placement post-rhinectomy is difficult. This case report describes the use of cone beam computed tomography scanning and computer-assisted virtual planning in conjunction with digital photographs for rehabilitation of a facial defect with an implant-retained silicon nasal prosthesis. Two implants were planned in the anatomical area with adequate bone volume to achieve favorable cosmetic outcomes and accessibility for hygiene maintenance. The implant-retained nasal prosthesis resulted in a meaningful improvement in the esthetics without the need for plastic surgery. In such cases, the post-rhinectomy reconstruction surgery should be limited to preparation of the surgical defect area for an implant-retained prosthesis. Silicone prostheses are reliable alternatives to surgery and should be considered in selected cases.

Finite element analysis and clinical complications in mandibular implant-overdentures opposing maxillary dentures.

Denture fracture is a common clinical complication caused by improper material selection, design, or fabrication technique. This study aimed to investigate the effect of two attachment systems on fracture risk of the implant-overdentures (IOD) via finite element analysis (FEA), using the force distributions obtained from patients' occlusal analyses and to compare the obtained results with the clinical complications associated with these attachments. A three-dimensional jaw model comprised of the edentulous bones was constructed. Three types of mandibular prostheses including complete denture (CD) (model LCD), IOD with Locator attachment (model LID-L), and IOD with telescopic attachment (model LID-T), as well as a maxillary CD (model UCD) were assembled. The vertical occlusal forces at anterior and posterior quadrants were obtained from the patients wearing mandibular CDs or IODs. The FEA results were further compared with the mechanical failures of different prostheses observed at patient recalls. In overall, the fracture risk of mandibular prostheses was lower than the maxillary compartments. The UCD opposing LCD underwent higher strains than that opposing LID-L and LID-T, which was mostly concentrated at the anterior mid-palatal polished surface. On the other hand, LID-L showed the lowest strain, followed by LID-T, and LCD. The obtained results were consistent with the clinical complications observed in the patient recalls.

Patient-reported outcome and its association with attachment type and bone volume in mandibular implant overdenture.

OBJECTIVE: To determine oral health-related quality of life (OHRQoL) and denture satisfaction (DS) in patients provided with mandibular implant-supported overdentures (ISOD) retained by two different attachment types, and the association of mandibular bone volume with the change in patient-reported outcome, before and after implant treatment. MATERIAL AND METHODS: Thirty-four patients (mean age 60.70 â€¯±â€¯ 8.7 years) received telescopic crown or locator attachments for ISOD and completed OHIP-14 (Malaysian version) and DS questionnaires, at baseline (T0 ) with new conventional complete dentures (CCD) and 3 months (T1 ) and 3 years (T2 ) after ISOD conversion. Mandibular bone volume was calculated from cone beam computed tomography (CBCT) datasets using Mimics software. Mean changes (MC) in OHIP-14 and DS at intervals were analyzed using the Wilcoxon signed-rank test and effect size (ES). The association of bone volume, implant attachment type, and other patient variables with the change in OHIP-14 and DS were determined using multivariate linear regression analysis. RESULTS: The MC in OHIP-14 and DS scores from T0 to T1 and T2 showed significant improvement with moderate and large ES, respectively. Regression analyses for the change in OHIP-14 score from T0 to T2 showed significant association with implant attachment type (P = 0.043), bone volume (P = 0.004), and baseline OHIP-14 (P = 0.001), while for DS, the association was only significant with baseline DS score (P = 0.001). CONCLUSION: Improvement in patients' OHRQoL and satisfaction with ISOD was associated with their baseline ratings. Mandibular bone volume had a stronger association for improvement in OHRQoL compared to type of attachment.

Impact of mandibular implant prostheses on the oral health-related quality of life in partially and completely edentulous patients.

OBJECTIVE: To assess the oral health-related quality of life (OHRQoL) of patients provided with mandibular implant fixed partial prostheses (IFPP) for rehabilitation of two adjacent missing posterior teeth and complete denture patients provided with mandibular implant-supported overdenture (ISOD). The response to change in OHRQoL with implant prostheses was additionally compared. MATERIAL AND METHODS: In this prospective study, 20 IFPP (mean age 47.0; SD 12.9 years) and 28 ISOD (mean age 61.5; SD 9.1 years) patients received 2 mandibular implants. Metal ceramic nonsplinted fixed prostheses were provided in IFPP group, while in ISOD group, the mandibular overdentures were retained by nonsplinted attachments. Patients rated their oral health-related quality of life using OHIP-14 Malaysian version at baseline (T0), 2-3 months (T1) and 1 year (T2) postimplant treatment. Mean OHIP-14 for total and domain scores between groups and intervals was analysed using repeated-measures ANOVA and t-test. Mann-Whitney and Wilcoxon signed-rank tests were used for the comparison of mean score change and effect size, while the association between pre- and post-treatment scores was determined using multivariate linear regression modelling. RESULTS: The total OHIP and domain scores before implant treatment were significantly higher (lower OHRQoL) in IFPP than in ISOD groups, except for physical pain where this domain showed similar impact in both groups. Postimplant scores between groups at T1 and T2 showed no significant difference. The mean score changes at T0-T1 and T0-T2 for total OHIP-14 and domains were significantly greater in IFPP except in the domains of physical pain and disability which showed no difference. Large effect size (ES) was observed for total OHIP-14 in IFPP while moderate in ISOD. Improved OHRQoL was dependent on the treatment group and pretreatment score. CONCLUSION: Improvement in OHRQoL occurred following both mandibular implant-supported overdentures and implant fixed partial prostheses.

Ocular Defect Rehabilitation Using Photography and Digital Imaging: A Clinical Report.

Ocular disorders occasionally necessitate surgical intervention that may lead to eye defects. The primary objective in restoring and rehabilitating such defects with an ocular prosthesis is to enable patients to cope better with associated psychological stress and to return to their accustomed lifestyle. A series of detailed steps for custom-made ocular prosthesis fabrication using the advantages of digital photography to replace the conventional oil paint and monopoly iris painting technique are presented in this article. In the present case, a digital photograph of the patient's iris was captured using a digital camera and manipulated on a computer using graphic software to produce a replica of the natural iris. The described technique reduces treatment time, increases simplicity, and permits the patient's natural iris to be replicated without the need for iris painting and special artistic skills.

Patient-based and clinical outcomes of implant telescopic attachment-retained mandibular overdentures: a 1-year longitudinal prospective study.

PURPOSE: The purpose of this study was to evaluate and compare Oral Health-Related Quality of Life (OHRQoL), denture satisfaction, and masticatory performance in edentulous patients provided with mandibular implant-supported overdentures (ISODs) retained with telescopic attachments and those of conventional complete dentures (CCDs). Peri-implant soft tissue changes were also evaluated at various intervals during a 1-year observation period. MATERIALS AND METHODS: Participating patients received new CCDs and later received two mandibular interforaminal implants and had their mandibular CCDs converted into ISODs with telescopic attachments. Questionnaires were used to assess OHRQoL (Shortened Oral Health Impact Profile-14, Malaysian version) and denture satisfaction at different stages of treatment with CCDs and ISODs. Objective masticatory performance with the CCDs and ISODs was recorded with a mixing ability test. Evaluations were carried out at 3 months with the new CCDs, 3 months after mandibular ISOD provision, and 1 year after receiving the ISOD. Peri-implant parameters were additionally assessed at specific intervals during the treatment period. The data obtained were statistically analyzed and compared. RESULTS: In the 17 patients who completed the protocol, significant improvements were observed in OHRQoL and patient satisfaction when CCDs were modified to ISODs, after 3 months, and at 1 year. Significantly better mixing ability with the ISOD was noted, with the highest values observed at 1 year. Statistically insignificant differences were observed for all the peri-implant parameters, except for gingival recession, for which significant changes were observed 6 months after ISOD delivery (values had stabilized by 1 year). CONCLUSION: Telescopic crown attachment-retained mandibular ISODs improved OHRQoL, dental prosthesis satisfaction, and masticatory performance compared to CCDs. Peri-implant soft tissue response and implant stability were found to be favorable after 1 year.

Short dental implants: an emerging concept in implant treatment.

OBJECTIVE: Short implants have been advocated as a treatment option in many clinical situations where the use of conventional implants is limited. This review outlines the effectiveness and clinical outcomes of using short implants as a valid treatment option in the rehabilitation of edentulous atrophic alveolar ridges. DATA SOURCES: Initially, an electronic search was performed on the following databases: Medline, PubMed, Embase, Cochrane Database of Systematic Reviews, and DARE using key words from January 1990 until May 2012. An additional hand search was included for the relevant articles in the following journals: International Journal of Oral and Maxillofacial Implants, Clinical Oral Implants Research, Journal of Clinical Periodontology, International Journal of Periodontics, Journal of Periodontology, and Clinical Implant Dentistry and Related Research. Any relevant papers from the journals' references were hand searched. Articles were included if they provided detailed data on implant length, reported survival rates, mentioned measures for implant failure, were in the English language, involved human subjects, and researched implants inserted in healed atrophic ridges with a follow-up period of at least 1 year after implant-prosthesis loading. CONCLUSION: Short implants demonstrated a high rate of success in the replacement of missing teeth in especially atrophic alveolar ridges. The advanced technology and improvement of the implant surfaces have encouraged the success of short implants to a comparable level to that of standard implants. However, further randomized controlled clinical trials and prospective studies with longer follow-up periods are needed.

Passive Fit in Screw Retained Multi-unit Implant Prosthesis Understanding and Achieving: A Review of the Literature.

One of the considerable challenges for screw-retained multi-unit implant prosthesis is achieving a passive fit of the prosthesis' superstructure to the implants. This passive fit is supposed to be one of the most vital requirements for the maintenance of the osseointegration. On the other hand, the misfit of the implant supported superstructure may lead to unfavourable complications, which can be mechanical or biological in nature. The manifestations of these complications may range from fracture of various components in the implant system, pain, marginal bone loss, and even loss of osseointegration. Thus, minimizing the misfit and optimizing the passive fit should be a prerequisite for implant survival and success. The purpose of this article is to present and summarize some aspects of the passive fit achieving and improving methods. The literature review was performed through Science Direct, Pubmed, and Google database. They were searched in English using the following combinations of keywords: passive fit, implant misfit and framework misfit. Articles were selected on the basis of whether they had sufficient information related to framework misfit's related factors, passive fit and its achievement techniques, marginal bone changes relation with the misfit, implant impression techniques and splinting concept. The related references were selected in order to emphasize the importance of the passive fit achievement and the misfit minimizing. Despite the fact that the literature presents considerable information regarding the framework's misfit, there was not consistency in literature on a specified number or even a range to be the acceptable level of misfit. On the other hand, a review of the literature revealed that the complete passive fit still remains a tricky goal to be achieved by the prosthodontist.

A simple procedure for retrieval of a cement-retained implant-supported crown: a case report.

Retrieval of cement-retained implant prostheses can be more demanding than retrieval of screw-retained prostheses. This case report describes a simple and predictable procedure to locate the abutment screw access openings of cementretained implant-supported crowns in cases of fractured ceramic veneer. A conventional periapical radiography image was captured using a digital camera, transferred to a computer, and manipulated using Microsoft Word document software to estimate the location of the abutment screw access.

Evaluation of accuracy of complete-arch multiple-unit abutment-level dental implant impressions using different impression and splinting materials.

PURPOSE: This in vitro study evaluated the accuracy of multiple-unit dental implant casts obtained from splinted or nonsplinted direct impression techniques using various splinting materials by comparing the casts to the reference models. The effect of two different impression materials on the accuracy of the implant casts was also evaluated for abutment-level impressions. MATERIALS AND METHODS: A reference model with six internal-connection implant replicas placed in the completely edentulous mandibular arch and connected to multi-base abutments was fabricated from heat-curing acrylic resin. Forty impressions of the reference model were made, 20 each with polyether (PE) and polyvinylsiloxane (PVS) impression materials using the open tray technique. The PE and PVS groups were further subdivided into four subgroups of five each on the bases of splinting type: no splinting, bite registration PE, bite registration addition silicone, or autopolymerizing acrylic resin. The positional accuracy of the implant replica heads was measured on the poured casts using a coordinate measuring machine to assess linear differences in interimplant distances in all three axes. The collected data (linear and three-dimensional [3D] displacement values) were compared with the measurements calculated on the reference resin model and analyzed with nonparametric tests (Kruskal-Wallis and Mann-Whitney). RESULTS: No significant differences were found between the various splinting groups for both PE and PVS impression materials in terms of linear and 3D distortions. However, small but significant differences were found between the two impression materials (PVS, 91 µm; PE, 103 µm) in terms of 3D discrepancies, irrespective of the splinting technique employed. CONCLUSIONS: Casts obtained from both impression materials exhibited differences from the reference model. The impression material influenced impression inaccuracy more than the splinting material for multiple-unit abutment-level impressions.

Closed hollow bulb obturator--one-step fabrication: a clinical report.

A method is described for the fabrication of a closed hollow bulb obturator prosthesis using a hard thermoforming splint material and heat-cured acrylic resin. The technique allowed the thickness of the thermoformed bulb to be optimized for weight reduction, while the autopolymerized seal area was covered in heat-cured acrylic resin, thus eliminating potential leakage and discoloration. This technique permits the obturator prosthesis to be processed to completion from the wax trial denture without additional laboratory investing, flasking, and processing.

Zygomatic implant-retained fixed complete denture for an elderly patient.

Dental rehabilitation of a completely edentulous geriatric patient has always been a challenge to the clinician, especially in treating those with higher expectations and demands. Treatment duration and the amount of residual alveolar bone available are often important considerations when planning for dental implant-based fixed treatment for these patients. With the introduction of zygomatic implants, a graftless alternative solution has emerged for deficient maxillary bone with provision for immediate loading. This article describes the treatment of a completely edentulous elderly patient using zygomatic implants in conjunction with conventional implants. The implants were immediately loaded using a definitive acrylic resin fixed denture reinforced with a cast metal framework, to provide function and aesthetics.

The effect of bur preparation on the surface roughness and reline bond strength of urethane dimethacrylate denture base resin.

BACKGROUND: The clinical success of relining depends on the ability of reline resin to bond to denture base. Surface preparations may influence reline bond strength of urethane-based dimethacrylate denture base resin. AIM: To investigate the effect of bur preparation on the surface roughness (R a ) of eclipse denture base resin and its shear bond strength (SBS) to an intra-oral self-curing reline material. The mode of reline bonding failure was also examined. MATERIALS AND METHODS: Twenty-four cylindrical Eclipse™ specimens were prepared and separated into three groups of eight specimens each. Two groups were subjected to mechanical preparation using standard and fine tungsten carbide (TC) burs and the third group (control) was left unprepared. The R a of all specimens was measured using a contact stylus profilometer. Subsequently, relining was done on the prepared surface and SBS testing was carried out a day later using a universal testing machine. RESULTS: One-way ANOVA revealed significant differences (P<0.05) in R a and SBS values for all the groups. Post-hoc Tukey's HSD test showed significant differences (P<0.05) between all the groups in the R a values. For SBS also there were significant differences (P<0.05), except between standard bur and control. CONCLUSIONS: 1) There was a statistically significant difference in the R a of Eclipse™ specimens prepared using different carbide burs (P<0.05). 2) There was a statistically significant difference in the relined SBS (P<0.05) when prepared using different burs, but the difference between the standard bur and the control group was not statistically significant.

Effect of cavity preparation on the flexural strengths of acrylic resin repairs

OBJECTIVE: To investigate the effect of cavity preparation on the flexural strength of heat-curing denture resin when repaired with an auto-curing resin. MATERIAL AND METHODS: Ninety-six rectangular specimens (64x10x2.5 mm) prepared from heat-curing denture base resin (Meliodent) were randomly divided into four groups before repair. One group was left intact as control. Each repair specimen was sectioned into two; one group was repaired using the conventional repair method (Group 1). Two groups had an additional transverse cavity (2x3.5x21.5 mm) prepared prior to the repair; one repaired with (Group 2) and one without glass-fiber reinforcement (Group 3). A three-point flexural bending test according to the ISO 1567:1999 specification8 for denture base polymers was carried out on all groups after 1, 7 and 30 days of water immersion. Statistical analysis was carried out using two-way ANOVA, Kruskal Wallis and post-hoc Mann Whitney tests. RESULTS: The highest flexural strength was observed in the control group. Control and conventional repairs group (Group 1) showed reduction in the flexural strength 30 days after water immersion. No significant change in the strength was observed for Groups 2 and 3 where the repair joints were similarly prepared with additional transverse cavity. CONCLUSION: Repaired specimens showed lower flexural strength values than intact heat-curing resin. Cavity preparation had no significant effect on the flexural strength of repair with water immersion.