Khadry Galil

Bonding to porcelain and gold

To test the effectiveness of bonding orthodontic attachments to porcelain, edgewise brackets were bonded to 160 lower incisor, porcelain denture teeth by means of two different resin systems and three different porcelain bonding agents. Bonding to porcelain was found to be not only effective, but the use of a porcelain primer before bonding resulted in shear strengths comparable to those achieved with conventional acid-etch enamel bonding when the same resin was used. Roughening the porcelain surface and bonding with a heavily filled resin without a porcelain primer provided shear strengths (30.6 lbs) comparable to conventional acid-etch enamel bonding with a lightly filled resin (28.8 lbs). Roughening the porcelain surface before bonding, adding porcelain primers, and using highly filled resins all added significantly to bond strength, but caused a progressively greater risk of porcelain fracture during debonding. One of three methods to polish porcelain completely restored a roughened porcelain surface to its former appearance. The porcelain bonding primers failed to provide a significant increase in bond strength when bonding to gold. However, a roughened gold surface bonded with a heavily filled resin provided shear strengths (27.3 lbs). comparable to conventional acid-etch enamel bonding by means of a lightly filled resin (28.8 lbs). The use of a highly filled resin on an intact, glazed porcelain surface without using a porcelain primer may provide sufficient bond strength clinically. If more bond strength is needed, the use of Reliance porcelain primer on an intact glaze is preferable to Ormco porcelain primer or Fusion. Still greater bond strength can be developed by roughening the porcelain surface before application of a primer and use of a highly filled resin. The potential for porcelain fracture in debonding, however, is much increased and it is questionable whether bond strengths of this magnitude are required clinically.

An in vitro evaluation of a visible light-cured resin as an alternative to conventional resin bonding systems

An in vitro study of 69 premolars was conducted to evaluate a visible light-cured resin system used in orthodontic bonding. The material was evaluated under various parameters to determine its relative value as an alternative to the conventional chemically activated resin systems. The 30-hour bond strength for the visible light-cured resin system was approximately one half of that found for a chemically cured resin system. Initial 1-hour bond strength of the visible light-cured resin system was found to be only 26% of the 30-hour bond strength. Enamel loss associated with debonding and subsequent cleanup of the visible light-cured resin was approximately one half of that found with the chemically cured, heavily filled resin. With the visible light-cured resin system, cleanup of remaining resin required the use of hand scalers only.

The effect of incisal bite force on condylar seating

The purpose of this study was to investigate the relationship between different incisal biting forces and condylar seating. Bite force was measured with strain gauges at the incisors in 22 adult subjects. The subjects were positioned with mandibles in retruded centric and with an opening not exceeding the range of hinge axis movement. Condylar movement was measured using standard true hinge axis location procedures. Condylar position was measured with no force, then with bite forces of 4.5 kg, 7.5 kg and a comfortable maximum. Biting force significantly affected condylar movement (p < 0.001). As incisal bite forces increased, so did the amount of condylar seating to an average of 0.49 mm anteriorly and 0.27 mm superiorly using maximum biting force. Therefore, when taking a centric relation record, a technique involving an anterior stop and sufficient biting force should seat the condyles more fully.

A Three-dimensional Analysis of Zygomatic Symmetry in Normal, Uninjured Faces

AbstractCurrent approaches to facial reconstruction are based on the assumption of facial symmetry, though this has yet to be established in the literature. Through quantitative and qualitative analysis, symmetry of normal, male faces is examined here using the zygomatic complex as a bellwether for the rest of the facial skeleton. Three-dimensional models reconstructed from the computed tomography scans of 30 adult male patients displaying normal facial skeletal anatomy were analyzed. Seven zygomatic landmarks were identified on all craniofacial models, and asymmetry scores were calculated based on the average deviation distance upon reflection of 1 hemiface across the midfacial plane. Deviation maps were then generated for each zygomatic pair to enable visualization of the asymmetry. All landmarks displayed a slight (<3 mm) deviation from perfect symmetry, and analysis of zygomatic form asymmetry revealed an average of 0.4 mm of surface deviation between hemifaces. The presence of such slight asymmetries in the zygoma warrants further investigation as to the clinical relevance of such skeletal asymmetries from both an esthetic and biomechanical consideration to provide insight as to the proper approach to zygomatic restoration in cases of zygomatic fracture.

Ultrasound-Guided Greater Palatine Nerve Block: A Case Series of Anatomical Descriptions and Clinical Evaluations

BACKGROUND:Greater palatine nerve (GPN) block is commonly performed for maxillary and palatal anesthesia by using bony landmarks. Ultrasound (US) can be used to consistently identify greater palatine foramen (GPF) as a defect in the bony palate enabling US-guided injections near the foramen. METHODS:We scanned and injected 16 undissected well-embalmed hemisectioned cadaveric heads after excluding major anatomical malformations. A linear high-frequency hockey stick probe (7–13 MHz) positioned in long axis to the hard palate visualized GPF as a discontinuity in the hard palate. US-guided injections of 0.1 mL India ink were made in an oblique plane. Specimens were dissected immediately after injection, and dye distribution was noted. The success rate of identification of GPF, number of attempts, and number of successful injections were recorded. The technique was evaluated clinically in 7 patients undergoing dental procedures. Five patients had US-guided injections, and 2 patients received US-assisted greater palatine canal blocks. RESULTS:GPF was successfully identified in 16 hemisectioned heads (n = 16). In 7 of 16 hemisectioned cadaveric specimens (n = 7/16), needle pass was seen on the US and traces of India ink were found within the greater palatine canal and pterygopalatine fossa. In the remaining heads (n = 9/16), the dye was observed in the mucosal tissue of the hard palate anterior to the GPF or in the soft palate. Clinical evaluation reconfirmed successful identification of GPF by US in 6 of 7 patients (n = 6/7). US-guided injections were successful in 6 of the 8 attempted blocks (n = 6/8) with median number (range) of attempts being 2 (1–4). US-assisted injections were successful in 2 patients (n = 2/2). CONCLUSIONS:US has the potential to successfully locate and characterize GPF in normal and edentulous maxilla. US-guided GPN blocks can be technically challenging. The clinical applicability of US guidance or assistance for GPN block needs further evaluation in a larger sample of patients.