A comparison of arch widths in adults with normal occlusion and adults with class II, Division 1 malocclusion

This study compares arch widths and other cast and cephalometric measurements of 36 normal-occlusion subjects (19 males, 17 females) with 39 Class II, Division 1 subjects (20 males, 19 females). None of the subjects had received orthodontic treatment. Analysis of variance demonstrated that subjects with normal occlusion had larger maxillary molar widths, maxillary canine widths, and maxillary alveolar widths than subjects with malocclusion; only male subjects with normal occlusion had larger mandibular molar widths and mandibular alveolar widths than the malocclusion subjects; the normal occlusion and malocclusion groups had similar mandibular canine widths; and when the lower molar and alveolar widths were subtracted from corresponding upper widths, the remainders of the Class II group were negative instead of positive, contrary to the normal group. This revealed a posterior crossbite tendency in the Class II group.     

Long-term radiographic evaluation of hydroxylapative-augmented mandibular alveolar ridges

From six months to four years after alveolar ridge augmentation was performed, the vertical ridge heights of 74 Class III and Class IV alveolar ridge deficiency patients, who had undergone augmentation with hydroxylapatite with or without autogenous cancellous bone, were measured using panoramic radiographs adjusted for magnification errors. No statistically significant decreases in vertical ridge heights were seen when only hydroxylapatite was used, nor were there significant differences between the two types of hydroxylapatite particles used. Unlike other bone onlay procedures, the use of autogenous bone and HA together did not result in significant decreases in vertical ridge height.     

The surgical-orthodontic correction of mandibular deficiency. Part II

As discussed in Part I of this study, persons with mandibular deficiency and Class II malocclusions exhibit a wide spectrum of esthetic, cephalometric, and occlusal characteristics. In many such patients optimal overall results are best obtained via a combined orthodontic-surgical approach. In such patients a critical evaluation is essential to decide (1) the optimal operation and (2) the appropriate orthodontic-surgical sequencing. Our method of making these two basic decisions was presented in Part I. In this article the indications for mandibular advancement with or without genioplasty, total subapical mandibular advancement, superior repositioning of the maxilla, and inferior repositioning of the maxilla are discussed in detail. These alternatives are illustrated with representative cases, and the results are discussed. The intention of these two presentations is to illustrate an orthodontic-surgical approach to the correction of mandibular deficiency and Class II malocclusion that is predicated on a systematic evaluation of the individual patient rather than a standard approach.     

Alveolar ridge augmentation using nonresorbable hydroxylapatite with or without autogenous cancellous bone

A four-year prospective evaluation of the use of nonresorbable, particulate hydroxylapatite (HA) to augment deficient alveolar ridges was performed. The material was used alone and in combination with finely crushed autogenous cancellous bone. Implants were delivered subperiosteally by syringe injection, usually using local anesthesia for Class I to Class III ridges and general anesthesia for Class III and Class IV ridges. The improved ridge height and width were stable. Postoperative resorption with significant loss of ridge height, frequently seen with rib and iliac crest onlayed grafts, was not observed with HA augmentation. Permanent denture construction began as early as three weeks postoperatively and by four to six weeks if HA was combined with autogenous cancellous bone. It was possible to place mandibular staple implants simultaneously or following HA augmentation. Visor osteotomy techniques were improved by use of HA to produce a wider, more convex stable ridge. Although skin, mucosa, or dermal vestibuloplasties were performed as early as three months postoperatively in a small number of patients, there appeared to be a lesser need for vestibuloplasty after HA augmentation than after onlay bone grafting. In addition, prosthodontists performed fewer denture relines after HA augmentation than after onlay bone grafts. The authors believe the most significant factor accounting for these observations is the firm, nonmobile mucosal base resulting from augmentation with HA. The resultant stable, soft tissue base and improved ridge height and contour have contributed to a comfortable, retentive, stable denture for these patients. The prosthetic and surgical procedures are easier to perform and have produced superior, more permanent results than onlay bone grafts and alloplasts. Preliminary studies also point to exciting possibilities for use of HA as a bone substitute/marrow extender in maxillary and mandibular defects, cysts, and clefts and in osteotomies for orthognathic surgery.     

Adsorption of human plasma proteins to modified titanium surfaces

OBJECTIVES: The aim of this study was to examine the effect of modified titanium (Ti) surfaces on the initial events of plasma proteins adsorption. MATERIALS AND METHODS: 'Ti disks' with three types of surface modifications were compared: machined, acid-etched and acid-etched and blasted. Physical and chemical characterizations of the surfaces were performed via scanning electron microscopy (SEM), atomic force microscopy (AFM) used for analysis of surface topography, characterization of the titanium oxide (TiO2) layer was carried out by X-ray photoelectron spectroscopy (XPS) and characterization of surface energy by the determination of contact angles. Evaluation of plasma proteins' adsorption to the treated Ti surfaces was performed by mass spectrometry, confocal laser scanning microscopy and XPS. Quantitative proteins' assessment was carried out by enzyme-linked immunosorbent assay. RESULTS: SEM images revealed major differences in the topography of the examined surfaces. Acid-etched and blasted Ti surfaces were found to have higher roughness values and a thicker TiO2 layer as compared with acid-etched and machined surfaces. Moreover, acid-etched and blasted surfaces showed high surface area differentiation, pointing to a high increase in the three-dimensional (3D) surface area over the 2D surface area compared with the other surfaces. Adsorption of plasma proteins to the acid-etched and blasted Ti surfaces was both qualitatively and quantitatively more intense compared with the machined and acid-etched surfaces. This was shown for each examined protein, total proteins and by the removal degree of the protein coat. CONCLUSIONS: The preferential adsorption of plasma proteins to the acid-etched and blasted Ti surfaces may be explained by its topographical characteristics and by the increase of the 3D surface area of this modified surface.     

Periodontal regeneration of transplanted rat teeth subcutaneously after cryopreservation

The periodontal regeneration of transplanted teeth after cryopreservation in liquid nitrogen overnight was previously examined using an animal model. The results showed that overnight cryopreservation did not have any severe adverse effects on periodontal healing. For clinical application, it is necessary to make the period of storage longer than in the preliminary study. In this study, the regeneration of periodontal tissues after cryopreservation for 4 weeks was examined. The maxillary molars of 4-week-old Wistar rats were extracted and transplanted into the abdominal subcutaneous tissue either immediately or after cryopreservation in a deep freezer at -80 degrees C. The donor teeth were frozen in a rate-controlling freezer. At 1, 2 and 4 weeks after transplantation, they were excised and observed under light microscopy. The cryopreserved teeth had acellular cementum with a rough surface at 1 week. With an increase in cementoblasts and the appearance of periodontal ligament and alveolar bone, the surface had become smooth at 2 weeks. There was no progressive root resorption. Although the process took somewhat more time, the teeth cryopreserved for 4 weeks showed regeneration that was similar to that of the immediately transplanted teeth.     

Microtensile bond strength of different components of core veneered all-ceramic restorations. Part II: Zirconia veneering ceramics.

OBJECTIVES: The purpose of this research was to investigate microtensile bond strength between one type of zirconia substrate and various commercial veneer ceramics. The effect of an optional liner material between the core and veneer was also evaluated where applicable. METHODS: Bilayered zirconia veneer discs were fabricated from five layering and two pressable veneer ceramics. Additionally, discs from each veneer ceramic were prepared. The discs were cut into microbars of 6 mm in length and 1mm in cross-section. The microtensile bond strength was tested in a universal testing machine. The fracture surfaces of the microbars were examined with scanning electron microscopy (SEM) and EDAX. RESULTS: The microtensile strength of Rondo Dentine and Lava Dentine veneer ceramics were significantly higher than the other tested veneer ceramics. Furthermore, the layered systems Rondo Dentine and Ceram Express were significantly stronger than the other tested core-veneer ceramics. The application of liner material dramatically affected the bond strength and failure mode, which was also material dependent. SEM analysis showed that two pressable veneers and one type of layering veneer ceramic failed entirely cohesively in veneer side while the remaining test groups had higher percentage of interfacial failure. SIGNIFICANCE: Selection of stronger veneer ceramics which have good bond strength with zirconia can reduce the chances of chipping and delamination under function. The liner material should only be used with some layering veneers but not in combination with pressable veneers as it will result in weakening of the microtensile bond strength.     

Opinions and attitudes of the UK's GDPs and specialists in oral surgery, oral medicine and surgical dentistry on oral cancer screening

OBJECTIVE: To survey two broad areas of oral cancer awareness and management of patients at risk of oral cancer by specialists in oral surgery, oral medicine, surgical dentistry and general dental practitioners (GDPs) in the UK. The first of these included knowledge and awareness of aetiological factors, changing patterns of disease, and screening/detection programmes including their effectiveness. The second included oral cancer detection methods, advice on avoidance of high-risk activity and self-examination, and referral pattern of GDPs. DESIGN AND METHOD: A pretested, 44-item questionnaire, a covering letter, a brief outline of the research protocol and return, stamped envelope were mailed in March 2003. A sample of 200 GDPs whose names were obtained from the General Dental Council's main list and 305 dental specialist names obtained from specialist's list in surgical dentistry, oral medicine and oral surgery were selected randomly. Information on oral cancer awareness and practice, screening practice and education was obtained. RESULTS: The response rate was 66.9%. The knowledge of the dental specialists was consistent with that in reports of current aetiological studies on oral cancer. However there were gaps in the GDP's knowledge and ascertainment of oral cancer risk factors. Over 70% of the dental specialists provided counselling advice on the risks of tobacco and alcohol habits compared with 41.2% of GDPs. More GDPs (52.4%) than specialists (35.4%) believed that oral cancer screening on a national basis would be effective in decreasing the mortality of oral cancer. Over 95% of all respondents used a visual examination for oral cancer screening and 89.9% of all respondents strongly believed that visual screening is effective in the early detection of oral cancer. CONCLUSION: The results showed that GDPs had knowledge gaps in their awareness of oral cancer risk factors and the application of preventive measures. Most dental health providers in the UK perform visual screening of the oral mucosa for their patients. Opinion was equivocal as to whether a nationally based screening programme similar to cervical cancer would be effective in improving the mortality and morbidity of oral cancer.     

Increased Young's modulus and hardness of Col1a2oim dentin

Mice harboring the Col1a2(oim) mutation (oim) express dentinogenesis imperfecta. To determine the effect of Col1a2 genotype on tissue mechanical properties, we compared Young's modulus and hardness of dentin in the 3 Col1a2 genotypes. Upper incisors were tested by nanoindentation. Genotype had a significant effect on Young's modulus, but there was not a simple mutant allele dosage relationship. The effect of genotype on hardness did not reach significance. Hardness and Young's modulus were greater near the dento-enamel junction than near the pulp chamber. Greater hardness and Young's modulus values near the dento-enamel junction reflected continued mineralization of the dentin following its initial synthesis. Analysis showed the mechanical data to be consistent with Fourier transform infrared and backscattered electron microscopy studies that revealed increased mineralization in oim bone. Analysis of the data suggests that clinical fragility of teeth in oim mice is not due to deficiencies of hardness or Young's modulus, but may be due to defects in post-yield behavior or resistance to fatigue damage.     

Histochemical analysis of pathological alterations in oral lichen planus and oral lichenoid lesions

Lichen planus is a dermatologic disease of unknown etiology characterized by keratotic plaques on the skin. Many patients also harbor white lesions of the oral mucosa. The literature contains numerous reports of lichen planus-like lesions evolving in conjunction with the administration of a variety of pharmacologic agents. It is difficult, if not impossible, to distinguish such lesions from one another. The present study evaluated the epithelial and basement membrane thickness, mast cells (intact cells and degranulated cells subepithelially) and the presence or absence of blood vessels in oral lichen planus and oral lichenoid lesions. The evaluation was done using the periodic acid-schiff (PAS) and toluidine blue staining techniques on 20 cases each of oral lichen planus and oral lichenoid lesions and 5 control specimens of normal buccal mucosa. The results showed an increased number of degranulated mast cells in areas of basement membrane degeneration, increased vascularity and increased PAS-positive basement membrane thickness in oral lichen planus as compared with oral lichenoid lesions. Reduced epithelial thickness was found in oral lichen planus. The present study emphasizes the importance of these parameters in differentiating oral lichen planus from oral lichenoid lesions using special staining techniques.