Immunolocalization of PTCH protein in odontogenic cysts and tumors

The human patched gene (PTCH) functions in both embryologic development and tumor suppression. PTCH mutations have been found in odontogenic keratocysts. However, the expression and localization of the protein product of the gene have not been determined in odontogenic tumors and cysts. We investigated 68 odontogenic lesions by immunohistochemistry, and compared their PTCH expression with that in basal cell carcinomas. All odontogenic lesions, including two keratocysts with truncating mutations, were positive for PTCH. Different types of lesions had different amounts of staining. Lack of staining was noted in the majority of basal cell carcinomas. Taken together, these data suggest that odontogenic keratocysts arise with heterozygous mutations of the PTCH gene.     

Effetto della contaminazione ematica sul distacco di tre differenti tipi di brackets autoleganti: studio sperimentale in vitro

Objectives

To assess the effect of blood contamination on the bonding and bond-failure site of 3 different types of self-ligating bracket.

Materials and methods

Two hundred forty bovine permanent mandibular incisors were randomly divided into 12 groups, each containing 20 specimens. Three different self-ligating brackets (Smart Clip - 3 M Unitek, Monrovia, California, USA; Damon - Ormco, Glendora, California, USA; and Quick - Forestadent, Pforzheim, Germania) were bonded to the teeth with Orthosolo primer (Ormco, Glendora, California, USA) and Trasbond XT composite (3 M Unitek, Monrovia, California, USA). Bonding was tested under different surface enamel conditions: dry, contaminated with blood before priming, contaminated with blood after priming, and contaminated with blood before and after priming. After bonding, all samples were stored in distilled water at room temperature for 24 hours. Shear bond strength was then evaluated with a universal testing machine (Mod. 4301, Instron Corp., Canton, Massachussets, USA). After bond failure, the bracket bases and the enamel surfaces were examined under an optical microscope (Stereomicroscope SR, Zeiss, Oberkochen, Germany) at 10 x magnification, and the amount of adhesive left on the enamel surface was rated with the adhesive remnant index (ARI). All the data were statistically analyzed (Chi-square test; level of significance p < 0.05).

Results and conclusions

ARIs of 2 were more frequent among samples bonded to dry enamel, whereas samples bonded to blood-contaminated enamel (before, after, or before and after priming) exhibited a higher frequency of ARI 0. However, there were no significant differences between the ARI scores for the 3 conditions of contaminated enamel or for those related to the 3 types of self-ligating brackets tested.     

Assessment of polymerization contraction stress of three composite resins.

OBJECTIVES: The purpose of this study was to measure the development of contraction stress of three composite resin restorative materials during photo-polymerization: a micro-hybrid composite (Filtek Z250, 3M ESPE, St. Paul, MN, USA); a nano-filled composite (Filtek Supreme, 3M ESPE, St. Paul, MN, USA); and a low-shrinkage composite (AElite LS, Bisco Inc., Schaumburg, IL, USA). METHODS: Curing shrinkage stress was measured using a stress-analyzer. Composites were polymerized with a halogen-curing unit (VIP, Bisco Inc., Schaumburg, IL, USA) for 40 s. The contraction force (N) generated during polymerization was continuously recorded for 150 s after photo-initiation. Contraction stress (MPa) was calculated at 20, 40, 60 and 150 s. Data were statistically analyzed. RESULTS: The low-shrinkage composite AElite LS exhibited the lowest stress values compared to other materials (p<0.05). Statistical analysis did not show significant differences between Filtek Z250 and Filtek Supreme. SIGNIFICANCE: The low-shrinkage composite showed lower contraction stress than micro-hybrid and nano-filled composite. Ideally, non-shrinking resins would represent the ultimate solution to overcome polymerization contraction and stress-related problems.     

Fracture resistance of implant-supported screw- versus cement-retained porcelain fused to metal single crowns: SEM fractographic analysis.

OBJECTIVES: The present in vitro study aimed at evaluating the fracture resistance of both implant-supported screw- and cement-retained porcelain fused to metal (PFM) single crowns. A scanning electron microscope (SEM) evaluation of the mode of failure of the specimens was also performed. METHODS: Forty PFM premolar-shaped identical single crowns were realized. The restorations were divided into two groups: cement-retained (group 1) and screw-retained (group 2) prostheses. Compressive loading tests and SEM fractographic analyses were performed. The data were statistically analysed by means of the Student's t-test, with a confidence interval of 95%. RESULTS: The mean fracture load value was 1657 (+/-725) N in group 1 and 1281 (+/-747) N in group 2; the statistical analysis pointed out no significant differences between the two groups (p=0.115). The mean work at maximum load value was 0.775 (+/-0.619) J in group 1 and 0.605 (+/-0.526) J in group 2; the statistical analysis pointed out no significant differences between the two groups (p=0.355). All the samples were affected by cohesive fractures of the porcelain. Screw-retained crowns showed microcracks at the level of the occlusal access to the screw and extensive fractures in the whole thickness of the ceramics. On the contrary, cement-retained restorations were affected by less wide paramarginal fractures of the porcelain. SIGNIFICANCE: A stronger implant-prosthetic connection was noticed in cemented restorations group than in screw-retained single crowns. Even though negatively influenced by the presence of the occlusal access to the screw, the metal-ceramics bond can be considered predictable in both the implant-prosthetic connection systems analysed.     

Matrix metalloproteinase-2 expression induced by two different adhesive systems on human pulp fibroblasts

Introduction

This study evaluated the expression of matrix metalloproteinase-2 (MMP-2) in primary cultures of human pulp fibroblasts (HPFs) when exposed to extracts from dentin-bonding systems.

Methods

Polymerized resin disks of the bonding agent of a 2-step self-etch adhesive (TechBond, Isasan, Rovello Porro, Italy) or of the primer/bonding agent a 2-step etch-and-rinse adhesive (Optibond Solo; Sybron-Kerr, Orange, CA) were immersed in HPF culture medium for 24 or 96 hours. HPFs were incubated in the adhesive-conditioned or control (untreated) culture medium for 24 hours. Western blot and immunofluorescence analyses were performed to assay MMP-2 expression.

Results

MMP-2 expression levels in HPFs cultured for 24 hours in culture medium were similar in both the control and experimental media groups showing a faint band at 67 kDa. Conversely, the HPFs incubated in the medium that contain polymerized resin disks for 96 hours showed increased MMP-2 expression compared with the untreated medium. The self-etch adhesive displayed the most pronounced induction of MMP-2 expression. These findings were confirmed by immunofluorescence analysis.

Conclusions

HPFs display increased MMP-2 expression after 96 hours of conditioning of the HPF culture medium with polymerized disks of dentin bonding systems. This MMP-2 expression/activation may represent a defence mechanism exhibited by HPFs towards monomers eluted from the dentin bonding systems.     

The number of implants required to support a maxillary overdenture: a systematic review and meta-analysis

Purpose

The number of implants needed to support a maxillary overdenture is still a controversial issue. The aim of this systematic review was to investigate the number of implants required to support a maxillary overdenture in order to obtain optimal treatment outcomes in terms of implant survival, overdenture longevity and patient satisfaction.

Early loading of sandblasted, acid-etched implants in the posterior maxilla and mandible: a 1-year follow-up report from a multicenter 3-year prospective study

PURPOSE: The aim of the present study was to evaluate the concept of an immediate loading protocol in the posterior maxilla and mandible through analysis of implant survival at 1 year. MATERIALS AND METHODS: One year follow-up data of a multicenter study are reported. Eighty-two ITI sandblasted, acid-etched (SLA) implants in 40 patients were loaded between 0 and 11 days after implant placement (mean 4.3 +/- 2.8 days). The restorations consisted of either 2 splinted crowns or a 3-unit fixed prosthesis. All restorations were put into full functional occlusion. Periapical radiographs were evaluated for changes in crestal bone level from baseline to 1 year postloading. Primary stability of the implants was checked initially and before the fitting of the definitive prosthesis. The restorations were evaluated by the practitioners for retention, stability, and esthetics. RESULTS: Three patients' implants were not loaded because of lack of primary stability, and a fourth patient was excluded from the study because of a protocol violation (more than 4 implants were used). All 4 patients were successfully treated outside the protocol. The overall survival rate of the remaining implants at 1 year was 98.8%. The mean bone loss at 1 year was 0.52 +/- 0.98 mm, which is within the reported limits of less than 1 mm (range 0.4 to 1.4 mm) loss in the first year. DISCUSSION AND CONCLUSION: The early results from this study indicate that early and immediate loading of 2 implants in the posterior maxilla and mandible may be suitable in selected patients. On the basis of 1 year of observation, the results appear similar to those achieved with a delayed procedure.     

A study of the septa in the maxillary sinuses and the subantral alveolar processes in 30 patients

The objective of this paper is to study the incidence of septa in the maxillary sinus and measure the height of the underlying alveolar process using panoramic radiography and computerized tomography (CT scans). Thirty patients who were going to be treated with dental implants were submitted to panoramic radiographs and CT scans. Sixty maxillary sinuses were analysed and divided into 2 groups: group 1 (totally edentulous) and group 2 (partially edentulous). The sinuses were divided into 3 regions (anterior, middle, and posterior), the septa were analysed, and the heights of the alveolar processes were calculated in these 3 areas. Of the 30 patients, 36.5% had maxillary sinuses, and 25% of these sinuses had septa, and 11.8% of the panoramic radiographs were false-negatives. In the panoramic radiographs of 10 patients, 3 had bilateral septa, 5 had a septum in only one sinus, and 2 patients had 2 unilateral septa. In the CT scans of 11 patients, 4 patients had a bilateral septa, 5 had a septum in only 1 sinus, and 2 patients had 2 unilateral septa. Therefore, 2 more septa were observed in the CT scans. In the study of the height of the subantral alveolar process, the least amount of difference between both techniques occurred in the middle region of the sinus. The CT scan is more reliable than the panoramic radiograph in diagnosing maxillary septa because of its greater accuracy. In the panoramic radiograph, the middle portion of the alveolar process in the posterior subantral segment was the least distorted of the three portions measured.     

EFFECT OF CAST RECTIFIERS ON THE MARGINAL FIT OF UCLA ABUTMENTS

Objectives:

This study assessed the effect of cast rectifiers on the marginal misfit of cast UCLA abutments compared to premachined UCLA abutments. The influence of casting and porcelain baking on the marginal misfit of these components was also investigated.

Methods:

Two groups were analyzed: test group – 10 cast UCLA abutments, finished with cast rectifier and submitted to ceramic application; control group – 10 premachined UCLA abutments, cast with noble metal alloy and submitted to ceramic application. Vertical misfit measurements were performed under light microscopy. In the test group, measurements were performed before and after the use of cast rectifiers, and after ceramic application. In the control group, measurements were performed before and after casting, and after ceramic application. Data were submitted to statistical analysis by ANOVA and Tukey''s test (α= 5%).

Results:

The use of cast rectifiers significantly reduced the marginal misfit of cast UCLA abutments (from 25.68μm to 14.83μm; p<0.05). After ceramic application, the rectified cylinders presented misfit values (16.18μm) similar to those of premachined components (14.3 μm). Casting of the premachined UCLA abutments altered the marginal misfit of these components (from 9.63 μm to 14.6 μm; p<0.05). There were no significant changes after porcelain baking, in both groups.

Conclusion:

The use of cast rectifiers reduced the vertical misfit of cast UCLA abutments. Even with carefully performed laboratory steps, changes at the implant interface of premachined UCLA abutments occurred. Ceramic application did not alter the marginal misfit values of UCLA abutments.     

骨性二类错患者上、下颌骨矢状结构病因机制分析

目的:研究我国骨性二类错患者的病因机制是以上颌前突为主,还是下颌后缩为主,根据其病因机制找出合理的治疗方法。方法:在头颅定位侧位X线片上,以ANB角大于5°作为判定标准,随机选取56例骨性二类错患者为研究样本,以SNA、SNB为分析指标,分析上、下颌在矢状方向上的突、凹程度代表的结构特征,以分析骨性二类错形成的病因机制。结果:所研究的骨性二类错患者中92.9%的患者不存在上颌前突病因机制,67.9%的患者存在下颌后缩病因机制,而且这种上、下颌骨病因机制方面的差异性是有显著的统计学意义的。结论:我国骨性二类错患者是以下颌后缩为主要机制的,提示要注重对于这种骨性二类错患者的早期下颌前移矫治,而在对于生长发育高峰期已过的患者,要注意使用能代偿这种下颌后缩骨性机制的矫治设计方案。