Light Body Polyvinyl Siloxane Research Articles

A method of impressing flabby ridge

Flabby ridge remained a challenge in dental clinical practice to obtain an accurate impression for edentulous patients. During the traditional impression making process, the excessive and displaceable soft tissue are usually compressed. In this article, we presented an impression method by using a modified special stock tray, impression compound and polyvinyl siloxane impression materials.•the suitable stock tray was modified with holes about 5 mm diameter in the corresponding area to the crest of the flabby ridge.•the primary impression was made by position the modified tray with the softened compound impression on the edentulous ridge, avoiding the area of the flabby ridge.•the final accurate impression was obtained by using the light body polyvinyl siloxane impression material.

Precision Prosthodontic Rehabilitation of Flabby Ridge with a Modified Window Technique: Case Report

Flabby ridge, also known as a soft (mobile), movable, or displaceable ridge, presents a common clinical challenge in dental practice. It primarily affects the alveolar ridges of the upper (maxillary) or lower (mandibular) arches. The anterior region of the maxilla is especially susceptible in edentulous patients. The flabby ridge lacks the firmness and stability required, leading dentures to become loose and unstable. Consequently, this instability can result in discomfort, speech and eating difficulties, and reduced quality of life for denture wearers. The flabby ridge often does not provide the necessary contour and resilience needed to establish an effective seal and maintain suction between the denture base and the underlying tissues. This compromises denture retention, making them susceptible to dislodgement during typical oral functions. Therefore, rehabilitating a completely edentulous patient with flabby tissue presents a formidable challenge for prosthodontists, as it undermines the retention, stability and support of complete dentures. Methods for managing flabby ridges encompass surgical removal, ridge augmentation, specialized impression techniques, balanced distribution of occlusal loads and implant therapy. Various impression techniques have been proposed to address the complexities of such cases. By carefully applying the principles of complete denture construction, a palliative treatment approach can be achieved. Special impressions often employ the window technique to capture a static impression of the flabby area, which introduces its own set of challenges. This innovative case report introduces a modified window technique that incorporates precise record transfer of the flabby ridge using tissue (blotting) paper. Specifically designed for the anterior mandibular flabby ridge, the technique employs a custom tray with a window positioned over the flabby tissues. A mucostatic impression material is utilized to minimize pressure on the flabby tissue, thereby reducing potential tissue distortion during the impression process. The procedure is executed in two steps: first, stable structures are recorded, followed by capturing the mobile tissues using light-body polyvinyl siloxane (PVS) elastomeric impression material within the window area. This method ensures an accurate record of the denture-supporting structures while maintaining the contour and details of the flabby tissues without displacement. Importantly, the technique is crafted for straightforward implementation by general dental practitioners within a primary dental care setting.

Influence of the Crystallization Firing Process on Marginal and Internal Adaptation of Silicate-based Glass-ceramic Inlays Fabricated With a CAD/CAM Chairside System.

Computer-aided design/computer-aided manufacturing (CAD/CAM) systems are widely used in dental treatment. Clinicians can use chairside CAD/CAM technology, which has the advantage of being able to fabricate inlays on the same day. We aimed to evaluate the effects of crystallization firing processes, fabrication methods (one-step and two-step), and materials on marginal and internal adaptations of silicate-based glass-ceramic all-ceramic inlays fabricated with CAD/CAM chairside systems. Ten artificial mandibular left first molars were prepared with standardized ceramic class II mesial-occlusal (MO) inlay cavities. Optical impressions were obtained using CEREC Omnicam Ban. IPS e-max CAD (IE), (Ivoclar Vivadent, Schaan, Liechtenstein), Initial LiSi Block (LS) (Hongo, Bunkyoku, Tokyo, Japan), VITA Suprinity (SP), (Vita Zahnfabrick, Bad Säckingen, Germany), and Celtra Duo (CD) (Ivoclar Vivadent, Schaan, Liechtenstein) (n=10) were milled using CEREC MC XL (Bensheim, Germany). IE and SP were crystallization-fired using CEREC Speed Fire. The silicone replica technique was used for the measurement of internal (axial and pulpal walls) and marginal (cervical and occlusal edge) adaptations. The adaptations were measured using a thin layer of light-body polyvinyl siloxane impression material placed between the master tooth inlay preparation and restoration. Marginal and internal adaptations of IE, LS, SP, and CD were measured using a stereomicroscope (500×). For IE and SP, marginal and internal adaptations were measured before and after the crystallization firing process. Data analyses were conducted using one-way ANOVA and the Tukey test. For IE and SP, marginal and internal adaptations before and after the crystallization firing process were analyzed using the t-test. The significance level was set at α=0.05. One-way ANOVA revealed statistically significant differences in occlusal and cervical edge marginal adaptations among the material groups (p<0.001). The Tukey HSD test revealed a significant difference in marginal occlusal and cervical edge adaptations between LS and CD groups and IE and SP groups (p≤0.05). For IE and SP inlays, the t-test revealed a significant difference between occlusal and cervical edge adaptations before the crystallization firing process and those after the crystallization firing process, with the latter group showing a more significant discrepancy in adaptation than the former group (p≤0.05). Fabrication methods (one- and two-step) affected the marginal adaptation compatibility but not internal compatibility of MO inlays. The crystallization firing process affected the marginal adaptation of inlays using lithium silicate or lithium disilicate glass-ceramics. However, adaptation to the cavity was considered clinically acceptable for all materials.

Adaptation of Relined Fiber Post Using Discontinuous Short Fiber-Reinforced Resin Composite to Restore Weakened Endodontically-Treated Premolars

Abstract Objective This study aimed to investigate the effect of relining prefabricated fiber-reinforced composite (FRC) posts using bulk-fill, flowable, discontinuous short fiber-reinforced composite (SFRC) on intracanal adaptation in weakened endodontically-treated premolar teeth. Materials and Methods Forty extracted human premolar teeth were selected and randomly allocated to five groups (n = 8) according to the canal preparation method and restorative technique after endodontic treatment: Group 1 (control): nonflared, closed apex root canals; group 2, 4: flared, open-apex root canals; group 3, 5: flared, closed apex root canals. Groups 1 to 3 were restored with standard RelyX fiber post size #1, while groups 4 and 5 were restored with customized RelyX fiber post size #1 and relined with bulk-fill flowable SFRC (everX Flow, GC, Tokyo, Japan). To evaluate intracanal adaptation, the empty root of each sample with the corresponding fiber post (standard or customized) inserted was measured twice using a micro-digital scale and the average value was calculated. The post was then removed, followed by the insertion of a light body polyvinyl siloxane (PVS) impression material into the canal, followed by reinsertion of the post and removal of excess material once the PVS was set. Finally, the sample weight was recorded, and the data were analyzed using one-way analysis of variance and the Bonferroni post hoc test (p-value = 0.05). Results A statistically significant difference (p &lt; 0.05) in PVS material weight was identified between the groups. Group 1 (control) had the lightest weight of PVS material, followed by groups restored with customized fiber posts (groups 4 and 5) and standard fiber posts (groups 2 and 3). Conclusion Anatomically-customized fiber posts with bulk-fill flowable SFRC provided better intracanal adaptation compared with standard fiber posts in teeth with compromised root canals.

The trueness of an intraoral scanner in scanning different post space depths

ObjectivesThe purpose of this in vitro study was to evaluate the trueness of scanning the post space up to 20 mm with an intraoral scanner (IOS). MethodsWe captured 20-, 18-, 16-, 14-, 12-, and 10-mm length post space scans using an IOS (Primescan) eight times each by shortening the apical 2 mm end of the same mandibular canine tooth. The reference impressions of each length group were taken using a light-body polyvinyl siloxane impression material and were scanned with an extraoral scanner. The recorded standard tessellation language (STL) data of all impressions were uploaded to a 3D matching program for the trueness evaluation via the root mean square (RMS) calculation. For the statistical analysis, the Kruskal-Wallis and post-hoc Mann-Whitney U nonparametric tests were performed to compare the differences among the groups (α=0.05). ResultsThe median RMS values increased in direct proportion to the length of the post space from 10 mm (357.1 µm) to 20 mm (897.5 µm). We noted a significant difference among groups (p< 0.001). In the pairwise comparisons, there were no significant differences between the 14 mm and 16 mm groups (p=0.431) or between the 18 mm and 20 mm groups (p=0.036), while other paired groups showed significant differences (p=0.001). ConclusionsThe scanned space depth affected the trueness of the IOS (Primescan). If the post depth was below 14 mm, and the minimum diameter was 2.2 mm, Primescan could be used for impressions of the post-core structure, simplifying the impression procedure. Clinical significanceIOS seems to be a promising technology for taking digital impressions of post spaces, but cannot be recommended as a routine procedure at its present stage, as final results are highly dependent on the clinical situation. Further studies with different IOS systems are needed to gain sound evidence.

Modified functional ocular impression of post-enucleation socket: A case report

Introduction: The disfigurement associated with the loss of an eye can cause significant physical and psychological problems. Therefore, a good ocular prosthesis is needed to restore the patient's quality of life. One of the factors that determine the quality of an ocular prosthesis is accurately impression. In the case of enucleation where the eyes socket has a soft and movable tissue bad will result inaccurate impression. The difficulty of post enuclation impression in such case is the compression of the tissue eyes socket. This case report will discuss the modification in functional impression technique using a modified custom tray. Case: A 39-year-old male patient came to Dental Hospital Universitas Sumatera Utara with chief complaint an unaesthetic and loose left stock eye that had been used for 10 years. Clinical examination shows moderate depth eye socket with soft and movable tissue. Management: The functional impression technique was modified using a self-curing clear acrylic sclera without handle as a custom tray with 2 mm reduction on the intaglio surface and light body polyvinyl siloxane as impression material. Discussion: The aim of this modification is to avoid the tendency of the eye socket to compress during impression taking and to achieve a natural contour of the eyelid convexity because of the absence of the tray handle so the patient can close their eyes. Conclusion: This technique produces an ocular prosthesis that has a good retention with excellent aesthetic result.

Evaluation of Elastomeric Impression Materials' Hydrophilicity: An in vitro Study.

IntroductionHydrophilicity of dental impression materials is crucial for obtaining an accurate impression and necessary for the production of a well-fitting cast restoration. The most common technique for evaluation of hydrophilicity is a contact angle measurement. The aim of the present in vitro study was to compare the water contact angles of four groups of elastomeric impression materials, before and during setting.Material and methodsFlattened specimens (n=10) of tested impression materials were prepared by the use of a Teflon mold with specific dimensions. A 5μl droplet of deionized water fell on the specimen, and photos were taken using a Nikon D3200 DSLR camera and a 105 mm macro lens (Nikorr, Nikon) in specific time points.ResultsThe CAD/CAM material showed the highest contact angle measurements. The light body polyvinylsiloxane (PVS) material 1, polyether and vinylsiloxanether material showed comparable contact angle measurements especially at the initial time point. A statistically significant reduction of contact angles was reported during setup time for all PVS, PE and vinylsiloxanether materials, while the most expressed reduction of contact angle measurements, and thus the most significant increase of hydrophilicity were reported for light wash PVS material 2.ConclusionsThe CAD/CAM impression material showed the most hydrophobic behavior. PVS materials showed excellent hydrophilicity. Polyether and polyvinyloxanether impression materials presented lower contact angle measurements, and thus superior hydrophilicity, compared with other tested materials initially and during setting. All tested impression materials presented a stepwise development of hydrophilicity during the setting stage.

Quantitative analysis of the selective pressure impression technique using CAD-CAM technology: A pilot clinical study

Statement of problemQuantitative 3D clinical analysis of the selective pressure impression technique directly measuring tissue displacement during impression making for complete maxillary dentures is lacking. PurposeThe purpose of this clinical study was to digitally compare impressions made of the edentulous maxillary ridge by using the selective pressure impression technique with different amounts of relief incorporated into custom tray designs. Material and methodsNine participants receiving maxillary complete dentures were enrolled in the study. An initial custom tray was fabricated in urethane dimethacrylate by using the alternative border molding technique without relief and scanned to create a standard tessellation language (STL) file from which 3 groups of custom trays were designed and 3D printed with 0.0-mm (no relief), 1.0-mm, and 3.0-mm relief over the anterior ridge and median palatal suture. Definitive impressions using each of the 4 custom trays were made with a consistent volume of light-body polyvinyl siloxane impression material. The definitive impressions were scanned, and the STL files were superimposed to investigate the topographical differences among the groups, each with respect to the no relief, 3D-printed custom tray definitive impression. Mean volumetric differences for all 3 groups were measured in areas where relief was used and statistically analyzed with the Friedman test (α=.05). ResultsNo significant difference was found among any of the 3 groups of superimposed impressions in areas of no relief, 1.0-mm, and 3.0-mm relief (P=.558). The mean difference ±standard deviation for each comparison in regions of the anterior ridge and median palatal suture were 0.07 ±0.06 mm for no relief, -0.03 ±0.07 mm for the 1.0-mm tray relief, and -0.04 ±0.09 mm for the 3.0-mm tray relief. The negative values in mean difference indicated less compression of underlying tissues compared with the reference border molded urethane dimethacrylate custom tray impression. ConclusionsAlthough results showed less compression when compared with that of the control group, custom tray relief of 1.0 mm and 3.0 mm over the anterior residual alveolar ridge and median palatal suture did not significantly impact the resulting impression topography when compared with no relief custom trays.

Prosthetic Management of Flabby Ridge Tissues with Different Grades of Displaceability: A Case Series

Flabby ridges/displaceable tissues are a common finding in edentulous patients. Careful management is mandatory, failing which flabby ridges adversely affect the retention, stability and support of complete dentures. This article described a series of three clinical cases, which incorporated varied impression techniques and materials for recording this condition. Window technique with light body polyvinyl siloxane impression for maxillary ridge and double spacer with additional relief holes and light body polyvinylsiloxane impression for mandibular ridge were used for the first case, window technique with impression plaster for maxillary ridge was employed in the second case, and double spacer with additional relief holes and zinc oxide eugenol impression were used in the third case. From the conventional to the latest techniques utilised, the decision to consider which material is appropriate for a particular situation still remains in question. Moreover, the advent of newer dental materials also adds to this confusion. The proper diagnosis and planning is required for selecting the material and technique according to the displaceability of the tissues.

Fractal analysis at varying locations of clinically failed zirconia dental implants

ObjectivesPrevious studies have shown that the fracture toughness of ceramics can be determined from the fractal dimensions (D) of their fracture surfaces and that the surface should be leveled to obtain an accurate D measurement. This study was to determine the effects of leveling operations and distance from the failure origin on the D values. MethodsTwelve clinically failed zirconia implants from four different manufacturers: Axis Biodental (n=7), Z-Systems (n=3), Straumann (n=1), and Swiss Dental Solutions (n=1) were obtained from one of the authors and thoroughly cleaned. Epoxy replicas were made of three locations along the crack path in the center region of each fracture surface (near origin (O), hackle (H), and near compression curl (CC)) using a light body polyvinyl siloxane impression material. Surfaces were scanned in ScanAsyst mode with a scan size of 5μm×5μm and a scan rate of 0.592Hz using the atomic force microscope. The surface scans were then leveled using 1st order flattening operation in the AFM analysis software. The height data before and after the operation were imported into a custom MathCAD script, and FRACTALS software was used to determine the D value by Minkowski Cover algorithm, which was shown previously to be the algorithm with the highest precision. A Wilcoxon signed-rank test, two-way repeated-measures ANOVA, and one-way repeated-measures ANOVA were performed as detailed below. ResultsThe data were not normally distributed (S-W p≤0.05), so a non-parametric repeated measures test (Wilcoxon signed-rank test) was selected. The median D values before and after leveling were 2.161 and 2.174, respectively. There was a significant difference before and after leveling (p<0.001). The two-way repeated-measures ANOVA showed no significant difference among the D values for different implant brands (p=0.66) and scanning locations on the fracture surface (p=0.83). After eliminating the implant brand as a factor, the data passed normality and equal variance tests (S-W p=0.88, BF p=0.15). The mean D values and standard deviations from the three locations (O, H, CC) were 2.183±0.031, 2.179±0.024, and 2.175±0.018, respectively. One-way repeated measures ANOVA showed no significant effect of scanning location (p=0.74). SignificanceThe leveling operation successfully removed the tilt without decreasing surface tortuosity, as it increased the D values significantly. The fractal dimension was the same at the three locations on the fracture surfaces. This means that hackle and compression curl regions can be used to determine fracture toughness when the failure origin has been lost.

A Comparative Analysis on the Accuracy of Special and Prefabricated Impression Trays Using Additional Silicone in a Laboratory Model

Introduction: Impression technique plays a pivotal role in fixed prosthodontic treatments; one of the main steps of impression is selection and preparation of an appropriate tray. Impression technique with insufficient accuracy causes distortions and complications that consequently result in treatment failure. The present study compares the impression accuracy of special and prefabricated trays in a laboratory model. This article compares the accuracy of special and prefabricated impression trays for achieving better impression and finally better crowns with good adaptation. Materials and Methods: In this study, a laboratory-fabricated resin model, resembling a mandibular first molar, was used on a dental arch and prepared by standard method for full crown restorations with a finish line of 1-mm depth and 3° to 4° convergence angle. Impression was made from a laboratory-fabricated resin model, 40 times with monophase medium-body polyvinyl siloxane in special trays and 40 times with putty and light-body polyvinyl siloxane using double-mix impression technique without spacer in prefabricated trays. To measure marginal gap, distance between the restoration margin and preparation finish line was vertically determined on each die in the mesial, distal, buccal, and lingual regions. Statistical analysis was performed and data were analyzed by SPSS 20 software using independent samples t-test. The data were significantly different at P 0.05). However, a significant difference was reported between the techniques in the lingual and distal regions.Conclusion: The present study indicated a higher accuracy for the special tray impression than prefabricated tray impression.

A modified shark-fin test simulating the single-step/double-mix technique: A comparison of three groups of elastomers.

The shark-fin test was modified to convey the clinical application of a single-step/double-mix technique assessing the behavior of two viscosities applied at one point in time. A medium and light body polyether (PE), a medium and light body polyvinylsiloxane (PVS), and a medium as well as heavy and light body vinyl polyether silicone (PVXE) impression material were analyzed solely, and in a layered mixture of 1:1 and 3:1 at working times of 50, 80, and 120 s. The fin heights were measured with a digital ruler. The wettability was measured 50 and 80 s after mixing by drop shape analysis. The results showed a synergistic effect of the medium and light body PE. This was not observed in PVXE and PVS. Interestingly, PVXE showed an antagonistic flow behavior in 3:1 mixture with medium body. PVXE was more hydrophilic than PE and PVS. Future rheological studies should clarify the detected flow effects.

Intracanal Adaptation of a Fiber Reinforced Post System as Compared to a Cast Post-and-Core.

The purpose of this study was to compare the adaptation of fiber reinforced composite post system and cast post-and-core. 17 extracted human permanent maxillary central incisors were endodontically treated following the standard protocol. 17 fiber reinforced composite post had been fabricated and adapted to the prepared parallel root canals. A light body poly vinyl siloxane (EXAMIX NDS, Japan) impression material was inserted into the root canals followed by the post. A digital scale was used to measure the weight of the remaining material that filled the gap between the post and the canal wall. The adaptation was indicated by the weight difference before and after impression material insertion. The same procedures were repeated with 17 cast post-and-core in the same teeth specimens. The mean difference for the weight of the material within the group was statistically significant (P-value <0.001) with the value of 6.1mg(± 2.7mg) for cast metal post and 6.4mg(± 2.7mg) for fiber reinforced composite post. However, the mean difference was not statistically significant when compared with both materials (P-value>0.05). Both cast post-and-core and fiber reinforced composite post systems showed similar adaptation to the canal.

Materials and Bioactive Factors in Dental Restoration and Periodontal Therapy.

Dental restoration and periodontal therapy have undergone tremendous expansion over the past few decades. Improvements have been made in basic and applied material science but also in clinical considerations of functional, esthetic, reparative, and regenerative aspects of materials and bioactive factors. This special issue offers a wide range of topics, broadening knowledge of researchers, dental specialists, and general dental practitioners. Dentin-adhesive bond remains a challenge in modern adhesive dentistry due to the complex composition and morphology of dentin. Different treatment modalities have been proposed to improve the dentin-adhesive bond and increase its longevity. Among these, conditioning dentin with ethylenediaminetetraacetic acid (EDTA) along with carbodiimide pretreatment have shown potential in preserving bond strength to dentin of self-etch adhesives over time. Impression materials should withstand tear and tensile forces and be able to recover fully for an ideal impression of intricate details of dental and oral structures. A number of hydrophilic elastomeric impression materials are available on the market. In vitro testing of tensile properties of heavy-body, medium-body, and light-body polyvinylsiloxane, polyether, and vinylpolyether silicone commercial products offers scientific data for clinical selection of impression materials for specific applications. Platelet-rich fibrin membranes seem to improve the healing process in periodontal regenerative treatments. Leukocyte- and platelet-rich fibrin (L-PRF) is considered a second-generation platelet concentrate, able to form strong fibrin matrices. Early L-PRF membranes have shown stronger mechanical properties, namely, tensile strength, modulus of elasticity, and toughness, than membranes obtained using platelet rich in growth factors (PRGF)/Endoret® technology, indicating potential clinical advantages. Titanium and titanium alloys are nowadays considered the material of choice for dental implant applications in the replacement of missing teeth. Numerous studies focus on the mechanisms of interaction between the surface of titanium or titanium alloys and host tissues. Recently, the role of titanium oxide surface layer in osteoblast differentiation has been studied in terms of alkaline phosphatase (ALP) activity. Increased ALP activity suggests that titanium oxide acts as a bioactive factor involved in osteoblast differentiation and subsequent osseointegration. Finite element analysis (FEA) has been used in assessment of stress distribution induced by occlusal loading in diverse dental tissues, restorations, implants, and surrounding alveolar bone (cancellous and cortical). FEA may be particularly useful in designing dental implants. Extensive numerical simulation reveals complex stress distribution in and around dental implants with different thread designs and abutment angulations restored with porcelain crowns and subjected to a number of occlusal loading conditions. Vesna Miletic Tihana Divnic-Resnik Natasa Nikolic Jakoba Andrija Petar Bosnjak Paulo Henrique Perlatti D'Alpino

“Grab the flab” window impression technique: A case report

Aims and objective: Making of a definitive, secondary or wash/final impression of displaceable flabby tissues with minimum or no displacement of tissue by using window impression technique. Background: Denture fabrication on flabby ridges is testing situations for a clinician as it adversely affects retention and stability of complete dentures. The difficulties encountered in these patients need to be overcome by modified techniques in denture fabrication that are not time consuming and make use of materials that are easy to use. Materials and Methods: This window impression technique, uses a custom tray with a window over flabby tissues and a mucostatic impression material to minimize distortion of tissues while making a impression. First, an accurate record of the denture supporting and limiting structures is made except for the mobile tissues which are recorded in second step using light body Polyvinyl siloxane impression material in the window area of special tray. Conclusion: The use of window impression technique helps in maintaining the contour and recording the details of the tissues without displacing the flabby tissues. Hence, it improves the prognosis for complete denture without surgical removal of hyperplastic tissues.

Pressure Produced on the Residual Maxillary Alveolar Ridge by Different Impression Materials and Tray Design: An In Vivo Study

Increased ridge resorption may occur due to inappropriate pressure applied during final impression making phase of complete denture fabrication. This study was done to evaluate the pressure applied on the residual ridge while making impressions with two tray designs (with and without spacer) using, zinc oxide eugenol and light body polyvinyl siloxane impression material. Five edentulous subjects were randomly selected. For each of the five subjects four maxillary final impressions were made and were labelled as, Group A-Impression made with tray without spacer using zinc oxide eugenol impression, Group B-Impression made with tray with spacer using zinc oxide eugenol impression material, Group C-Impression made with tray without spacer using light body polyvinyl siloxane impression material, Group D-Impression made with tray with spacer using light body polyvinyl siloxane impression material. During the impression procedure a closed hydraulic system was used to remotely measure the pressures produced in three areas. The pressure produced were calibrated according to the micro strain record. Statistical comparisons of readings were done using t test and ANOVA. The acquired data revealed that ZOE produced an average pressures value of 26.534 and 72.05 microstrain, while light body PVS produced 11.430 and 37.584 microstrain value with and without spacer respectively. Significantly high values were recorded on the vault of the palate when using trays without spacer. The use of light body polyvinyl siloxane and zinc oxide eugenol impression material showed insignificant difference. Within the limitations of this study, tray design has a significantly effected on the pressures produced, while the impression materials does not have any significant difference.

Internal fit of two all-ceramic systems and metal-ceramic crowns

Objectives The aim of this study was to investigate the internal fit (IF) of glass-infiltrated alumina (ICA - In-Ceram Alumina), yttria-stabilized tetragonal zirconia polycrystals (Y-TZP - IPS e.max ZirCAD), and metal-ceramic (MC - Ni-Cr alloy) crowns. Material and Methods Sixty standardized resin-tooth replicas of a maxillary first molar were produced for crown placement and divided into 3 groups (n=20 each) according to the core material used (metal, ICA or Y-TZP). The IF of the crowns was measured using the replica technique, which employs a light body polyvinyl siloxane impression material to simulate the cement layer thickness. The data were analyzed according to the surfaces obtained for the occlusal space (OS), axial space (AS) and total mean (TM) using two-way ANOVA with Tukey's multiple comparison test (p<0.05). Results No differences among the different areas were detected in the MC group. For the Y-TZP and ICA groups, AS was statistically lower than both OS and TM. No differences in AS were observed among the groups. However, OS and TM showed significantly higher values for ICA and Y-TZP groups than MC group. Comparisons of ICA and Y-TZP revealed that OS was significantly lower for Y-TZP group, whereas no differences were observed for TM. Conclusions The total mean achieved by all groups was within the range of clinical acceptability. However, the metal-ceramic group demonstrated significantly lower values than the all-ceramic groups, especially in OS.

Lip impressions: a new method for monitoring morphological changes in orofacial granulomatosis

To develop and evaluate an objective method for assessing lip size and treatment-related morphological changes in orofacial granulomatosis (OFG) patients. Patients with swollen lips because of OFG (n=21) were enrolled. A light-body polyvinylsiloxane material was used to take lip impressions before and after treatment (n=10), or during treatment (n=11). Plaster models were cast from the impressions and the lips were measured using callipers. The intra-examiner and inter-examiner reproducibility of the technique were assessed. OFG patients had significantly larger lips than controls (P<0.0001). The coefficient of variation on repeated measurements of the same impression was 1.6% and for duplicate impressions was 2.6%. Significant reduction in lip size was shown in all 10 patients after diet restriction (P<0.002). Seven of 11 patients whose impressions were taken at least 3 months after the initiation of cinnamon- and benzoate-free diet also showed reduction in lip size during follow up (P<0.002). Serial lip impressions appear to be reliable for routine quantification of morphological changes of the lips in OFG patients. We present a new reproducible and sensitive method for assessing changes in lip size in response to treatment in OFG.

Evaluation of internal adaptation in ceramic and composite resin inlays by silicon replica technique

This study was aimed at investigating the internal adaptation of a ceramic (Ceramco II) and two composite resin inlay materials (SureFil and 3M Filtek Z 250) using silicon replica technique as an indicator. Forty-five standard mesial-occlusal-distal (MOD) cavities were prepared into brass moulds by using computer numerically controlled system. Inlays were prepared according to manufacturers' instructions with indirect methods. Replicas of the prepared cavities and inlays were produced with a polyvinyl siloxane material (Elite H-D). The spaces between inlays and cavities were filled by different coloured light-body polyvinyl siloxane material. Two parallel slices (mesio-distally) were obtained from the replicas with a sharp blade. Different coloured polyvinyl siloxane material thickness between cavity and inlay was measured at seven points (mesial, occlusal and distal). The data were evaluated with anova and Tukey's honestly significantly different (HSD) statistical tests. In the SureFil and Ceramco II groups, the sizes of the contraction gaps at mesial and distal gingival floors were greater than that of the occlusal marginal walls. In comparison of gap formation at occlusal regions, while the 3M composite group showed highest gap values (204.33 +/- 75.45 microm), the Ceramco II group revealed the lowest (141.17 +/- 23.66 microm) (P < 0.05). At the gingival floors, gap formation of Ceramco II group was the highest (227.08 +/- 51.95 microm). Neither the 3M Filtek Z250 nor SureFil group showed any statistical difference between gap values of their self-occlusal and gingival floors (P > 0.05). In conclusion, our results showed that ceramic inlays did not confer any big advantage for internal adaptation over the composite inlays.

Iatrogenic damage to approximal surfaces in contact with Class II restorations

Objectives: This study investigated the frequency of iatrogenic damage to approximal surfaces in contact with Class II restorations.Methods: Patients (n=28) with a Class II restoration in contact with an unrestored surface had elastic separators fitted interproximally. Contralateral (unrestored) control surfaces were also separated. Impressions (light body polyvinylsiloxane) of the separated surfaces were taken 3–6days later. Interproximal impressions (28 paired, seven unpaired) were examined by binocular microscope and scanning electron microscope (SEM) for iatrogenic damage, attrition and cavitation due to caries.Results: 49–60% of surfaces adjacent to Class II restorations had been iatrogenically damaged. The most frequent types of damage were vertical grooves (26%), extensive damage (17%), indentations (6%) and scratches (6%). Damage was more frequent in maxillary teeth (61%) than mandibular teeth (25%), in permanent teeth (60%) more than deciduous teeth (20%). Qualified dentists produced more iatrogenic damage (64%) than undergraduate students (23%).Conclusion: The frequency of iatrogenic damage to approximal surfaces following Class II preparations was 49%, and possibly as much as 60% when questionably damaged surfaces were included. Protection of the adjacent enamel is of paramount importance during Class II cavity preparation.