Quintessence International, 10/1996

Nonaxial implant alignment often predicates the use of cemented or screw-retained angled abutments with inherent disadvantages, including reduced retrievability on screw lossening. The purposes of this article are to review the relative merits of cemented and screw-retained angled abutments and to present a method of ensuring retrievability of cemented angled abutments.

The long-term bonding of dental materials to dentin remains an area of great controversy and the results of in vitro testing do not always reflect those found in vivo. The clinician is faced with a large number of dentinal bonding agents that have had limited testing in vivo and are frequently replaced before any long-term clinical testing has been completed. Glass-ionomer cements, although having a longer history of good adhesion to dentin, are not suitable for use in high-stress-bearing areas. The selection of materials for specific clinical situations has become more and more difficult. This paper gives a personal view of the history and evolution of both resin bonding agents and glass-ionomer cements and their potential in clinical use.

Some teeth can best be treated by a combination of enamel microabrasion and resin composite bonding. This article outlines a protocol for treating patients with such teeth and documents one case, showing 5-year results.

Sensitivity after cementation of a crown with glass-ionomer cement is often attributed to an adverse effect on the pulp by the luting agent. Most permanent restorative materials in common use today do not tend to irritate the pulp; the main cause of pulpal damage is infection, the bacteria originating in the smear layer or deep in the dentinal tubules, inaccessible to caries-excavating procedures. A poorly fitting provisional crown may expose cut dentin to the oral fluids, and mechanical trauma caused by frictional heat during preparation may also damage the pulp. The following precautions are recommended during precementation procedures to reduce the risk of an inflammatory response in the pulp: (1) The provisional crown should be well fitting, covering cervical dentin but not impinging on the periodontal tissues. The permanent crown should be cemented as soon as possible. (2) The superficial smear layer should be removed and the dentinal surface should be treated with an antibacterial solution before the provisional crown is placed. (3) To decrease dentinal permeability under the provisional crown, the dentinal surface should be covered with a liner that can be easily removed before final cementation. (4) To ensure optimal micromechanical bonding, the dentinal surface should be thoroughly cleaned, and the dentin should be kept moist until cementation. (5) The occlusion should be carefully checked before cementation of the crown.

Proper management of a malocclusion relies on a basic understanding of the development of the dentition and the craniofacial complex. Diagnosis should only be formulated after all the relevant diagnostic records, including clinical examination and history, are reviewed. Armed with this information, the dentist forms the treatment plan. The mere occurrence of a malocclusion does not constitute a need for treatment. Injudicious intervention can be counterproductive or destructive. Through a case report, the deleterious effects of improper case management and questionable treatment mechanics are highlighted. The subsequent orthodontic management emphasizes the principles and techniques for the successful treatment of the patient in question.

Intentional replantation is an accepted endodontic procedure for treatment of teeth in which conventional surgical endodontic treatment is contraindicated. This article persents a rare case of intentional replantation of a mandibular molar that had severe periodontal destruction resulting from iatrogenic perforation of the furcation. A 17-month follow-up evaluation revealed an asymptomatic and functional tooth with no radiographic signs of pathosis. The favorable results obtained might be attributed to the preservation of the vitality of the periodontal ligament; the absence of damaging perssure during extraction; the minimal extraoral treatment time; the use of nonrigid splinting; and the immediate repair of the perforation during a one-visit endodontic procedure. The results obtained with this tooth may indicate the possibility of a successful surgical technique for this otherwise hopeless complication of endodontic therapy.

In the past, chronic periodontal abscess was treated by conventional gingivectomy, flap access procedures, or by extraction of the affected tooth. A modified technique for the treatment of the chronic periodontal abscess is described. A surgical approach is combined with root conditioning with doxycycline. Application of this technique has resulted in rapid, uneventful hearling in which neither further tissue breakdown or recurrence of the abscess has occurred.

Two-dimensional finite-element analysis was used to study levels and distribution patterns of stress within three-unit f ixed partial dentures (mandibular first premolar to first molar) constructed of different materials (Type III gold alloy, Dicor, and In-Ceram) and with different connector heights (3.0 mm versus 4.0 mm). In the computer models, 10 MPa of stress was applied centrally to the prosthesis. Resultant von Mises stresses were concentrated within the connectors; the greatest stress occurred at the axial location of the connector. Stresses were 40% to 50% lower for 4.0-mm connectors. Patterns of stress distribution were similar for premolar and molar connectors. Stress levels within In-Ceram models were lower than for the other two materials and represented a lower percentage of the ultimate strength of the material. Based on a two-dimensional finite-element analysis model, In-Ceram would appear to be the best choice for posterior fixed partial dentures.

The aim of this study was to determine whether the use of a topical surfactant (Hydrosystem), designed for clinical use, improved the quality of the impression surface of two poly(vinyl siloxane) materials used in vivo. Before impressions were taken, Hydrosystem was applied to the maxillary left or right premolar teeth, allocated at random, in 50 subjects. The untreated side acted as a control for each subject. The impressions were examined for quality of reproduction and number of surface defects. Hydrosystem was found to significantly improve the quality of reproduction.

The shear strength of human incisors, canines, premolars, and molars and bovine incisors in the region of the dentinoenamel junction were tested. The median shear strength of all human teeth, 38.99 MPa, was not significantly different from that of bovine teeth, 37.40 MPa. Among the groups of human teeth, the highest median shear strength was obtained from mandibular premolars (46.15 MPa), and the lowest from mandibular canines (32.63 MPa). Physical treatments (cooling or drying) led to a significant reduction in shear strengths. A similar effect was found after exposure to amino butyrate (a caries-removing agent) but not after exposure to sodium hypochlorite (used in endodontic treatment). In all investigated groups of teeth, the fracture areas were mainly in dentin and never exactly at the dentinoenamel junction; indicating that the cohesion of dentin, not the adhesion between dentin and enamel, is the limiting factor in the shear strength.