Reproducible Reference Point Research Articles

Tomographic Evaluation of Alveolar Ridge Preservation Using Bone Substitutes and Collagen Membranes-A Retrospective Pilot Study.

Alveolar ridge preservation (ARP) reduces dimensional changes following tooth extraction. We evaluated the changes in alveolar ridge dimensions after ARP using bone substitutes and collagen membranes. Objectives included the tomographic evaluation of sites prior to extraction and six months after ARP and the assessment of the extent ARP preserved the ridge and reduced the need for additional augmentation at the time of implant placement. A total of 12 participants who underwent ARP in the Postgraduate Periodontics Clinic (Faculty of Dentistry) were included. Cone beam computed tomography images were used to retrospectively assess 17 sites prior to and six months after dental extraction. Alveolar ridge changes were recorded and analysed using reproducible reference points. The alveolar ridge height was measured at buccal and palatal/lingual aspects, whilst width was measured at crestal level, 2 mm, 4 mm and 6 mm below the crest. Statistically significant changes were found in alveolar ridge width at all four heights, with mean reduction differences ranging from 1.16 mm to 2.84 mm. Likewise, significant changes in the palatal/lingual alveolar ridge height (1.28 mm) were observed. However, changes of 0.79 mm in buccal alveolar ridge height were not significant (p = 0.077). Although ARP reduced dimensional changes following a tooth extraction, some degree of alveolar ridge collapse could not be avoided. The amount of resorption on the buccal aspect of the ridge was less compared to the palatal/lingual after ARP. This indicated that the use of bone substitutes and collagen membranes was effective in reducing changes in the buccal alveolar ridge height.

The Use of a Gothic Arch Tracing to Record Centric Relation in the Construction of Complete Dentures

The establishment of a fixed and reproducible reference point (centric relation) is critical when reorganizing the occlusion in a dentate patient or constructing complete dentures in an edentulous patient. There are many techniques for guiding the patient's mandible into centric relation and recording the relationship between the maxilla and mandible in this position. Some patients are resistant to being manipulated into this position and have an unreproducible habitual path of closure. A gothic arch tracing is considered to be the most reliable and predictable method of determining centric relation. The present article describes the gothic arch tracing technique and illustrates its use in an edentulous patient during the construction of complete dentures. CPD/Clinical Relevance: The gothic arch technique can be used to predictably locate centric relation in both dentate and edentulous patients.

A reproducible reference point for the common peroneal nerve during surgery at the posterolateral corner of the knee: a cadaveric study

BackgroundThis is an experimental study conducted to assess whether the fibular head is a reliable reference point to identify the position of the common peroneal nerve at the posterolateral corner of the knee.Materials and methodsTwelve cadaveric knees were dissected through the lateral approach. The common peroneal nerve was identified and traced. The location where the common peroneal nerve crossed the posterior border of the biceps femoris and the posterior border of the fibular neck were designated as points B and N, respectively. The tip of the fibular head was designated F. Distances FB and FN were measured and the triangular area FBN was calculated at various degrees of knee flexion.ResultsDuring knee motion, distance FN showed minimal change and was not affected by variation in degrees of knee flexion (p = 0.131). Distance FB and distance BN were affected by variation in degrees of knee flexion (p < 0.001). Triangular area FBN increased in size up to 60° of knee flexion measuring 621.22 mm2 and subsequently decreased with further knee flexion.ConclusionThe common peroneal nerve can consistently be found at approximately 20.7 ± 1 mm on the fibular neck with respect to the tip of the fibular head. The tip of the fibular head is a consistent landmark that can be used to predict the position of the exit point of the common peroneal nerve at the posterolateral corner of the knee.

Quantification of facial asymmetry by 2D analysis – A comparison of recent approaches

IntroductionSymmetry has been found to play a crucial role in attractiveness assessment and so its restoration is an essential problem in oral maxillofacial surgery. This paper presents an overview of recent 2D asymmetry analysis techniques. These are techniques which are based on the evaluation of two-dimensional data, like photos. The aim of this paper is to find the most precise and practical techniques to investigate facial asymmetry. Materials and methodsFor this purpose studies addressing symmetry investigations are collected and categorized by the type of data they extract from the photos. The reference points on the facial surface, which are frequently used in these studies, are presented and calculation methods are described. ResultsThree kinds of techniques using vertical or horizontal reference lines or centres of bilateral points appear to be most appropriate. Recommendations are made, which aspects should be taken into account when calculating symmetry/asymmetry indices from photos. Advantages and disadvantages of the three selected methods are summarized in a table. ConclusionsUsing one of the three recommended approaches denoted by FA, AI and z-score allows calculating meaningful asymmetry values. The proper selection and identification of reference points is crucial. For highest accuracy, a sufficient number of evenly distributed and reproducible reference points should be used.

The pectoralis major tendon as a reference for restoring humeral length and retroversion with hemiarthroplasty for fracture

The success of anatomic reattachment of the tuberosities in proximal humeral fractures, treated with hemiarthroplasty, correlates with functional results. The purpose of this study was to determine the value of the upper edge of the pectoralis major insertion (PMI) as a landmark to establish the proper height and version of hemiarthroplasty implanted for proximal humeral fractures. Twenty cadaveric humeri were studied by CT scan to analyze the relationship between the PMI and humeral height and retroversion. The mean distance from the PMI to the tangent to the humeral head was 5.64 cm. The mean distance of the PMI to the posterior fin of the prosthesis was 1.06 cm. The mean angle between the PMI and the posterior fin of the prosthesis was 24.65 degrees. The upper edge of the pectoralis major insertion constitutes a reproducible reference point to restore proper humeral height and retroversion in hemiarthroplasty for proximal humeral fracture.

Three-dimensional analysis of models articulated in the seated condylar position from a deprogrammed asymptomatic population: A prospective study. Part 1

The seated condylar position (SCP), also known as centric relation (CR), is considered the most reliable and reproducible reference point for accurately recording the relationship of the mandible to the maxilla. Therefore, a determination of the SCP/CR is a prerequisite for the analyses of the dental interarch, condylar position, and skeletal relationships. The purpose of this prospective study was to statistically evaluate the 3-dimensional nature of dental interarch displacement and condylar displacement between the SCP/CR and maximum intercuspation or centric occlusion (MIC/CO). The records of 596 consecutive asymptomatic patients having routine orthodontic treatment in a private practice were used. The initial premature occlusal contact and 3-dimensional dental interarch displacement were measured by the analysis of models, mounted on an articulator (Panadent, Grand Terrrace, Calif) in the SCP/CR, by using the modified (nonmanipulated) 2-piece wax SCP/CR recording method with deprogramming. Three-dimensional condylar displacement was measured by analysis of the graphic registrations, produced by condylar position instrumentation, and evaluated for frequency, direction, and magnitude of displacement. The dental interarch discrepancy in the SCP/CR was significantly different from that observed in MIC/CO, with posterior premature contacts (94.0%), increased overjet, decreased overbite, midline differences, and Angle classification changes. A difference in condylar position between the SCP/CR and MIC/CO in at least 1 plane was detected for every asymptomatic patient and every condyle. The most prevalent types of directional change in condylar position were inferior (down) (97.0%) and distal (posterior) (66.7%) when the teeth were brought into MIC/CO. The mean difference in condylar position between the SCP/CR and MIC/CO was .86 mm in the horizontal plane, 1.80 mm in the vertical plane, and .26 mm in the transverse plane. No correlation was found between a patient's age or sex and the magnitude of condylar displacement. There is a significant difference in the occlusion when it is dictated by the teeth and when it is dictated by the condyles. This difference is quantifiable at both the occlusal and condylar levels.

Le bloc coracoïdien : mise en évidence ďune voie ďabord simple utilisant le petit pectoral

Despite their recognized advantages, infraclavicular blocks, especially with the pericoracoid approach, are underutilized because the lack of simple anatomical landmarks. The goal of this study is to determine a simple, reliable and reproducible reference point by means of magnetic resonance imaging (MRI), using the anterior extremity of the coracoid process, and the pectoralis minor as a tactile reference point.Sagittal and para-sagittal MRI sections at the coracoid process were performed on 11 patients. The relationships between the coracoid process, the nerve-vessel bundle, the pectoralis minor and the skin were measured.The optimal puncture point for a needle introduced strictly in an anterio-posterior direction in a supine, alert patient is located 2 cm within and 2.5 cm below the coracoid process. The injection point, defined as the distance between the skin and the tip of the needle lying in the centre of the visualized nerve-vessel bundle, is located an average of 5 cm from the skin (mean 5.02 cm, with a standard deviation of 1.03 and a confidence interval of 0.91). This injection point goes from 0.4 cm (at the most anterior part of the bundle) and 1.75 cm (at the most posterior part), with an average 1 cm from the posterior surface of the pectoralis minor (tactile reference point). Neither body mass index nor sex influence significantly the variables measured.The reference points defined here could allow easy and reproducible performance of this relatively simple block and make it more effective.

A simple noninvasive stereotactic device for routine MR head examinations.

A simple device to define reproducible reference points in MR examinations was designed. The device can be worn like a pair of eyeglasses and has reference structure visible in MR images. Combined with a specially designed algorithm, the imaging plane can be aligned to a predefined coordinate system in one step, using a single slice through the device. The device can be produced at low cost and is suitable for routine examinations as well as surgical planning.

Early palatal changes in complete and incomplete cleft lip and/or palate.

Early palatal development in various complete and incomplete forms of cleft lip and/or palate (CLP) was studied from birth to 3 months of age by means of dental casts. Palatal morphology (shape) and dimensions--based on reproducible reference points--were determined in a group of 128 CLP children and 68 normal children who served as controls. Substantial normal palatal growth during the first 3 months of life was observed. Round arch forms changed into oval arch forms. Growth mainly takes place in the sagittal direction (+4 mm) (transverse: +1 mm). Palates of CLP children differed significantly dependent on the type of cleft and whether the cleft was complete or incomplete. Cleft lip and alveolus children and bilateral cleft lip and palate children had more elongated palatal arches, whereas unilateral cleft lip and palate children and cleft palate children had wider palatal arches than the control group. Incomplete clefts differed from the control group in the same direction as their complete cleft forms, though less distinctly. Preoperative orthopedics used in CLP patients does not stimulate growth. On the contrary, it even restricts growth.

Sagittal and Coronal Image Reconstruction

The application of coronal and sagittal image reconstruction in the display of the normal pancreas and peripancreatic region is illustrated. The use of standard reproducible reference points for multiplanar reconstruction is suggested. Reconstruction computed tomography displays more anatomic structures in the coronal and sagittal planes than ultrasonography and accurately displays the craniocaudad extent of pancreatic pathology.

Possible role of histones in regulation of nucleic acid synthesis

ALTHOUGH this paper will be concerned principally with our studies on the possible role of histones in regulation of nucleic acid synthesis, it seems pertinent to comment first upon the gel electrophoresis of histones. Butler has stated that the most satisfactory way of characterizing histones is the application of starch gel electrophoresis [S, 10, 111. We have found [ 121 that polyacrylamide gels are superior to starch gels in the separation of histones, and Reisfeld et al. [ 131 have reported success with this gel system in the electrophoresis of other cationic proteins. The gels are formed by mixing buffered tetramethy-ethylenediamine catalyst with 60 per cent acrylamide and 0.4 per cent N,N’-methylenebisacrylamide followed by addition of ammonium persulfate. The gels are formed in glass tubes and have a pH of 3 after polymerization. Samples are applied directly upon the gels in a density-stabilized layer, and electrophoresis is conducted in a glycine buffer at pH 4 for 4.5 hr at 15 ma. per tube. The gels are stained in amido black, and excess stain is removed electrically. Patterns obtained by electrophoresis of calf thymus histones are shown diagrammatically in Fig. 1 in comparison with patterns obtained by electrophoresis in starch gels. The bands shown in Fig. 1 C were found consistently by electrophoresis in polyacrylamide gels, and the bands are designated by Roman numerals. Bands II and IV, found in all calf thymus histone preparations examined in this laboratory, stained more heavily than the other bands and provided easily recognized and very reproducible reference points. The inclusion of a sample of unfractionated histone in each electrophoretic run of 6 samples facilitated the assignment of band identities in preparations of histone fractions. Band II was arbitrarily assigned a relative mobility (1~‘)

Use and Abuse of pH Measurements

The development of the concept of pH from its invention by Sorenson in 1909 to the present-day National Bureau of Standards' pH scale is reviewed. The liquid junction potential problem involved in the use of the pH meter is discussed in detail. The magnitude of the error due to the junction potential depends upon the pH, ionic strength, nature of the solutes, nature of solvent, presence of colloids, temperature--in fact, anything that affects the mobilities of charged particles. Whether the junction potential error can be ignored depends upon the use to which the pH measurement is put. Some estimates from the literature as to the probable magnitude of this error are presented and discussed. Under certain relatively simple conditions an approximate relationship may be considered to exist between the pH meter reading and the hydrogen ion concentration. Under other conditions, the ph meter reading must be considered as simply a reproducible reference point having no theoretical significance. Under some conditions, the meter reading cannot even be considered as a reproducible reference point. These points are developed in detail.

Superconductivity of Lead

Numerous determinations of the zero-field transition temperature of lead have been made. All of these observations except that of Daunt were made by the direct measurement of electrical resistance. Daunt`s method involved the shielding effect of persistent currents in a hollow cylinder. In the authors work on columbium to be described in a forthcoming paper an a.c. induction method was used for the measurement of superconducting transitions. The superconductor was mounted as a cylindrical core of a coil which functioned as the secondary of a mutual inductance. The primary coil was actuated by an oscillator which provided a maximum a.c. field within the secondary of 1.5 oersteds at a frequency of 1000 cycles per second. The secondary e.m.f. which was dependent for its magnitude on the permeability of the core was amplified, rectifie, and observed on a recording potentiometer. During the application of this method to the study of columbium it appeared that a further check on the zero-field transition temperature of lead would be worth while especially if agreement between results for very pure samples could be obtained using this method. Such result would help in establishing the lead transition temperature as a reasonably reproducible reference point in themore » region between 4 deg and 10 deg K.« less