Biomedical subjects
Publications and source records attributed to A W van Pelt.
For the restoration of occlusal anatomy partial gold restorations are preferred. Adhesive techniques in combination with plastic materials can also be used and are less invasive than indirect restorations. Occlusal tooth wear is becoming a major problem all over the world. This paper describes minimal invasive techniques to restore tooth wear.
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Air abrasive technology has re-emerged in dentistry. The history, characteristics and clinical application of this approach are reviewed, including advantages and limitations for the removal of enamel, dentin and decay. Air-abrasive technology may be especially suited for use in bonded restorations as well as for repair of all types of restorations. The factors affecting adequate bond strength are discussed.
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Composite restorations shrink most during curing. In large cavities more shrinkage may be expected. The composite inlay is especially developed to overcome these disadvantages. After curing of the composite inlay causes secondary polymerization increasing several material properties such as wear resistance and stress relaxation. Clinical results are reviewed and the benefits of the composite inlay technique discussed.
Large direct composite restorations can induce shrinkage related postoperative sensitivity. Indirect resin-bonded (tooth colored) restorations may perhaps prevent these complaints. Indirect bonded ceramics are especially attractive because of their biocompatibility and esthetic performance. Several procedures and techniques are currently available for the fabrication of ceramic restorations: firing, casting, heat-pressing and milling. In this article the different systems are described. Advantages, disadvantages and clinical performance of ceramic inlays are compared and discussed.
An adhesive or resin-bonded bridge is a tooth saving construction for the replacement of a lost tooth, especially when the abutment teeth are relatively sound. In this article an overview is presented of the different types of resin-bonded bridges, their advantages and disadvantages and their indications. The direct methods are very suited for the immediate replacement of a lost anterior tooth. The all composite adhesive bridge has a survival rate that is surprisingly good.
Severe localized or generalized tooth wear will result in loss of vertical dimension. Rehabilitation of the dimensional height is often required. A causal approach is the choice of preference to prevent progression of destructive processes. However, the etiology of pathological wear is not yet clarified, so reversible and non-destructive tooth saving restorative procedures are essential. For adjustment and stabilization of the occlusion of CMD problems the philosophy and treatment approach are similar. Tooth coloured adhesive restorations can be fabricated in different manners, directly and indirectly. In this article treatment objectives for occlusal rehabilitation are described and two cases presented where tooth coloured restorations are used.
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In a prospective study 116 consecutive patients were treated according to a revised protocol to induce and control bone growth. Revisions included: 1. lengthening of the transosseous posts and cortical screws between the mental foramina so that two threads extended beyond the alveolar crest of the mandible without protruding through the mucosa; and 2. fabricating an implant borne prosthesis with a gap of 2 mm between the denture base and the mucosal tissues in the saddle areas and loading only the retromolar pads. The gap was re-opened every 8 weeks until further bone growth would prevent proper oral hygiene. Measurements of the height of the mandible were made using a digital millimeter caliper and standardized radiographs. The radiographic enlargement was calculated per radiograph for the sites to be measured. The follow-up varied from 15 up to 39 months. Bone growth had occurred in 104 of the 116 patients, while the resorption of bone had ceased in the remaining patients. The increase of bone height varied from 9 mm in patients with severe mandibular atrophy down to 2 mm for patients with mild atrophy. The revised protocol for TMI insertion and rehabilitation is advocated to promote bone growth and to cease further resorption in the atrophic mandible.
Bleaching of vital and non-vital teeth is becoming a routine procedure in esthetic dentistry. In a relative safe way many types of discoloration can be treated. Four treatment systems are available at present. For an appropriate choice it is essential to know the cause of the discoloration. Long term results are still scarce. Most treatment systems show slight to moderate side-effects, varying from demineralisation of enamel to soft tissue problems.
A better chemical bonding to metals offers the opportunity to bind composites onto metal and metals onto tooth structures. This may lead to an increase of adhesive prosthetic and cosmetic treatments. In this article some applications of this modern treatment method are described, anterior and posterior, in solitary elements as well as multiple bridge constructions.
In this paper the development of techniques to remove intrinsic vital stains are summarized. The mechanism of chemical agents is described as well as the nature of the stain and its treatment. Finally a rationale for selecting patients for treatment and its prognosis is presented and discussed.
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The kinetics of adhesion of Streptococcus sanguis CH3 from suspension to polymers with different surface free energies were studied by using three bacterial concentrations (2.5 X 10(7), 2.5 X 10(8), and 2.5 X 10(9) cells per ml-1). Substratum surface free energies (gamma s) ranged from 18 to 120 erg cm-2. The kinetics of bacterial adhesion to these surfaces showed a typical two-step adhesion process, indicating an equilibrium in both steps. In the initial adhesion step (step 1), low equilibrium numbers of adhering bacteria were counted on substrata with surface free energies lower than 55 erg cm-2. A maximal number adhered on substrata with higher surface free energies. At the lowest bacterial concentration tested, the highest number of bacteria were found on substrata with a surface free energy around 55 erg cm-2. For each substratum, step 2 started after a characteristic time interval tau, being short (30 min) for gamma s less than 50 and long (120 min) for gamma s greater than 50 erg cm-2. The relationship between the substratum surface free energy and the number of bacteria adhering at equilibrium after step 2 was similar to, although less distinct than, that during step 1 with a slight indication of a bioadhesive minimum around gamma s = 35 erg cm-2. The results are indicative of a two-step adhesion model, in which step 1 is controlled by macroscopic substratum properties.
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The adhesion of the oral bacterium Streptococcus sanguis CH3 to various polymeric surfaces with surface free energies (gamma s) ranging from 22 to 141 erg cm-2 was investigated. Suspensions containing nine different bacterial concentrations (2.5 X 10(7) to 2.5 X 10(9) cells per ml) were used. After adhesion for 1 h at 21 degrees C and a standardized rinsing procedure, the number of attached bacteria per square centimeter (nb) was determined by scanning electron microscopy. The highest number of bacteria was consistently found on polytetrafluorethylene (gamma s = 22 erg cm-2), and the lowest number was found on glass (gamma s = 141 erg cm-2) at all bacterial concentrations tested. The overall negative correlation between nb and gamma s was weak. However, the slope of the line showing this decrease, calculated from an assumed linear relationship between nb and gamma s, appeared to depend strongly on the bacterial concentration and increased with increasing numbers of bacteria in the suspension. Analysis of the data for each separate polymer showed that the numbers of attached cells on polyvinyl chloride and polypropylene were higher but that those on polycarbonate were lower than would be expected on basis of a linear relationship between nb and gamma s. Desorption experiments were performed by first allowing the bacteria to attach to substrata for 1 h, after which the substrata and attached bacteria were removed to bacterial suspensions containing 10-fold lower bacterial concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)