Microstructures of admixed amalgams produced from Pd-containing dispersants.

Blended Pd-containing dental amalgams were developed by substituting Pd for up to 20 w/o Ag or Cu in the Ag-Cu eutectic alloy. Melted ingots were lathe-comminuted to a particle size distribution of 1-45 microns. Alloy blends were created from two parts of a traditional amalgam and one part of experimental Ag-Cu-Pd particles. Amalgams with from 0.42 to 1.67 w/o Pd were fabricated by trituration of alloys and mercury at a Hg/alloy ratio of 1:1 with a mechanical triturator at 5000 rpm for 10 s and hand-condensed. XRD studies of these amalgams revealed the suppression of eta' (Cu6Sn5) phase with Pd addition and no gamma 2 (Sn8Hg) phase found. At 3.3 w/o Pd, the eta' (Cu6Sn5) concentration of the amalgam was below the detection limit of the instrumentation (1%). SEM micrographs revealed that reaction zones around eutectic particles decreased with increased Pd concentration.     

A caries preventive programme for Robertson school children--baseline data.

This study describes the baseline caries experience of a cohort school children in the Robertson area who were selected to take part in a longterm school-based preventive programme. On the whole baseline DMFT values for the various age groups did not differ significantly except for the 13-year-olds at Vergesig who had significantly higher values than those obtained at the other two schools. The D-component predominated with a moderate M-component and no filled teeth. The teeth at risk for the respective age groups did not differ significantly between the schools. The frequency of caries experience decreased from the molars to the central incisors except for the canines which were least vulnerable. The DMFT values were high and warrant the search for the most suitable preventive measures to facilitate reduction towards the WHO goal of 3 for 12-year-olds by the year 2000.     

Retrograde root filling with composite and a dentin-bonding agent. 2.

Abstract Investigations on retrograde root filling using a composite resin, Retroplast, bonded to the root surface with the dentin-bonding agent Gluma have been described. Here, detailed information is given about the surgical procedures. The aim was to obtain a thin retrograde composite filling on the root apex, made slightly concave, sealing the main root canal, accessory canals as well as dentinal tubules. Hemostasis was obtained primarily by applying 1% adrenaline and by using a needle suction tip, and care was taken not to damage the surrounding tissues by the various chemicals. The healing results, after up to 1 year, of 388 cases of various tooth types, treated with either retrograde composite or with amalgam were compared. The healing classification included four categories: 1) complete healing; 2) fibrous healing; 3) uncertain; and 4) failures. In the composite group, the healing rates were as follows: 74% showed completely healing, 4% fibrous healing, 15% uncertain and 7% were failures. In the amalgam group, 59% showed complete healing, 3% fibrous healing, 30% uncertain, and 8% were failures. Complete healing occurred significantly more often after filling with Retroplast than after filling with amalgam (p<0.00005). Significantly fewer proportion to other tooth types. The number of immediate postoperative complications did not differ significantly between the composite and the amalgam groups.     

The effects of resin-bonded and conventional fixed partial dentures on the periodontium: restoration type evaluated

The purpose of this study was to compare the long-term and short-term periodontal response to three different modalities of fixed prosthodontic tooth replacement. Posterior proximal sites adjacent to abutment teeth supporting etched metal and two designs of conventional fixed partial dentures (FPDs) were assessed 6 months to 5 years after insertion. For the long-term observation, the etched metal resin-bonded FPDs had significantly greater plaque scores than both of the conventional designs. The resin-bonded FPD group had statistically, but not clinically, significant increased probing depths than the supragingival FPD group. In spite of the increased levels of supragingival plaque associated with the etched metal FPD, this type of fixed prosthesis was no more injurious to the periodontium than the subgingival conventional FPD designs.     

Vertical root fracture and dentin deformation in curved roots: the influence of spreader design

The effect of lateral condensation using different tapered spreaders was evaluated. Curved mesiobuccal roots of maxillary molars were step-back prepared. Strain gauges applied to the root surfaces measured dentin deformation (distortion) during controlled lateral condensation with either fine finger or D11 spreaders. After obturation, roots were cross sectioned and analyzed under the stereomicroscope to detect the presence and pattern of fractures. The results showed no statistical difference between spreader designs as to mean distortion and the incidence of fractures; however several specimens in the D11 group showed high root distortion measurements. When fractures occurred, there were no consistent patterns of fracture in either spreader group. In conclusion, although there were no significant differences in mean deformation or fracture incidence in curved roots between the spreaders, the roots showing high deformation readings in the D11 group may be more susceptible to future vertical root fractures.     

Root canal system of the maxillary central incisor

To better assess the efficacy of mechanical preparation of root canals, transparent specimens of 510 extracted maxillary central incisors were investigated for thickness and curvature of the root canal, condition of any accessory canals, and location of the apical foramen. Over 60% of the specimens showed accessory canals that are impossible to clean mechanically. Most lateral branches were small, 80% were the size of a #10 reamer or less, and only 3% were thicker than a #40 reamer. Apical foramina located away from the apex were observed in 45% of the teeth, although nearly 80% of all foramina were within approximately 0.5 mm of the apex, and 95% were within approximately 1.0 mm. Data on the thickness and curvature of the main canal showed that normally it is adequately prepared when reached with a #60 reamer to the apical constriction and supplemented by flare preparation.     

Infrequent clinicopathological findings in 108 ameloblastomas

One hundred and eight ameloblastomas diagnosed in a rural black Africa population were analysed for clinicopathologic findings other than those classically described. One patient had a polycystic ameloblastoma adjacent to an ameloblastic fibroma. Two other polycystic ameloblastomas showed aneurysmal bone cyst formation and one mandibular tumour was diagnosed as a keratoameloblastoma. Microscopic changes resembling an adenomatoid odontogenic tumour were present in association with two unicystic ameloblastomas and a HPV18-positive verrucous lesion occurred in the lining of a cystic space of a polycystic ameloblastoma. Two ameloblastomas contained eosinophilic granules in all tumor cells and melanocytes were diffusely present in another. One case exhibited a focus of mucous cell metaplasia. Two polycystic ameloblastomas showed diffuse interstitial ossification. One mandibular tumor was diagnosed as a desmoplastic ameloblastoma and another as an odontoameloblastoma. This study demonstrated that although ameloblastomas are regarded as a fairly homogeneous group of neoplasms, detailed investigations prove clinicopathologic diversity in a significant number of lesions.     

Masticatory performance with mandibular implant-retained overdentures

It was investigated in a clinical trial whether the masticatory performance of complete-denture wearers depended on the support for their mandibular dentures by implants or mucosa. The trial involved the provision of a new maxillary denture and either a new conventional mandibular denture (mucosa-borne), a mandibular overdenture retained by two IMZ-implants (implant-mucosa-borne), or a mandibular overdenture on a transmandibular implant (TMI; mainly implant-borne). In comparison with mandibular implant-retained overdentures, subjects with conventional dentures needed 1.5 to 3.6 times more chewing strokes for an equivalent reduction in particle size. No differences in masticatory performance were found between subjects with IMZ-implants and those with TMI. This suggests that the increased stability of the mandibular denture with implants determines the wearer's masticatory performance, rather than the support by implants.     

Sotos syndrome with hypodontia

Sotos syndrome, or cerebral gigantism, is a rare genetic condition characterized by tall stature, gigantism, dolichocephaly, advanced bone age and learning disability. The purpose of this case report is to highlight the dental management of a 10-year-old boy with Sotos syndrome who presented with hypodontia and dental caries.     

Undifferentiated pleomorphic sarcoma of the orbital region

Undifferentiated pleomorphic sarcoma (formerly known as malignant fibrous histiocytoma) has been established as an entity in the WHO-classification of soft tissue tumors since 2002. Before this the term "malignant fibrous histiocytoma" has been a collective term for soft tissue malignancies that had no distinct components and included most soft tissue sarcomas (40%). With the new classification they account for only about 5%, and tumors arising in the head and neck contribute only about 1-3% of all undifferentiated pleomorphic sarcomas. We report a rare case in which the orbital region was involved.