Soft lining materials: Their status and prospects

Although soft lining materials are inadequate to their requirements, their use is widespread. This paper comprises a preliminary report of a comprehensive study of these materials, which has been undertaken in an attempt to determine which are the better materials, how best to use them and how they may be improved. In addition, some new materials have become available which may have advantages over existing materials.

Fifteen materials are under investigation. These have been analysed, their water absorption, water solubility and visco-elastic properties studied and the effect of bonding these soft lining materials to polymethyl methacrylate determined.

The study is continuing as there are many aspects of these materials which remain to be investigated.     

The mandibular pain dysfunction syndrome: an assessment of its treatment

Almost all clinicians claim successful results with their treatment of the mandibular pain dysfunction (MPD) syndrome, but longer term follow-up studies are relatively few. One hundred and nine patients whose treatment had been completed some time previously replied to a postal questionnaire which enquired into their experience of pain, limitation of jaw opening, clicks and evenness of ‘bite’. The results indicated that many patients experienced a return of discomfort, and clicking of the joints responded poorly to treatment. Limitation of jaw opening, on the other hand, showed a successful response to treatment.     

Perceptions of the value of hospital residency and clinical medicine in dental education

A survey of the outlook of 81 participating dental undergraduates concerning the value of a general hospital residency programme has been compared with the perceptions of 240 graduate health professionals (dental and medical practitioners, registered nurses and others). There is convincing statistical evidence of pan-professional support for such a general hospital residency. Better medical preparation of the dental student prior to residency is strongly favoured. Closer links between medicine and dentistry are inevitable as well as being essential for both professions and the community.     

Enamel loss during bonding, debonding, and cleanup with use of a self-etching primer

Self-etching primers have recently been introduced to simplify the orthodontic bonding process. The aim of this investigation was to compare the enamel loss at each stage of the bonding and debonding process with the use of such a product compared with the conventional two-stage etching and priming process with 37% o -phosphoric acid. In the laboratory, a planer surfometer was used to measure enamel surface height before any enamel treatment, after pumicing, after etching, and once the brackets had been debonded, after enamel clean-up with one of 4 clean-up methods. The latter included a high-speed tungsten carbide bur, a slow-speed tungsten carbide bur, debanding pliers, and an ultrasonic scaler. A change in enamel surface height was seen at each stage of the bonding and debonding process. After pumicing and conventional etching, the cumulative median enamel loss was -2.76 microm; however, the range was from -1.11 to -4.57 microm. This observed loss was much less than in previous reports on enamel loss after acid etching. With the self-etching primer, the median enamel loss was significantly lower, at -0.27 microm (range, -0.03 to -0.74 microm). At debond, there was also a significant difference in the adhesive remnant index scores between the 2 groups, with more adhesive remaining on the enamel surface in the conventional-etch group. It was during enamel clean-up that most surface loss occurred. In both the conventional and self-etch groups, most enamel loss occurred after the use of the high-speed tungsten carbide bur or the ultrasonic scaler and least with the slow-speed tungsten carbide bur or the debanding pliers.     

Dental Discomfort Questionnaire: its use with children with a learning disability

This study investigated whether the behaviors from the Dental Discomfort Questionnaire (DDQ) could help identify toothaches in children with a learning disability, who have a limited capacity to self-report. The objectives were to examine whether the behaviors from the DDQ occur more often in children with a learning disability who have caries and a toothache than in children who do not have caries and a toothache; and secondly, to examine whether two additional items increase the specificity and sensitivity of the DDQ to recognize a toothache, in this particular population of children with a learning disability.
The DDQ was completed by a convenience sample of 58 parents on behalf of their children: 31% girls, aged between 6 and 13 years (mean = 7.5, SD = 2.7).
Of the total group, 26% (n = 15) suffered from a toothache and 43% (n = 25) had carious teeth. Children with caries and a toothache had a significantly higher mean DDQ score and displayed more toothache-related behaviors (e.g., problems with chewing, problems with brushing teeth) than children without caries or toothache.
The DDQ seems to be a functional and easy-to-use instrument to alert parents to the presence of a toothache in this specific group of children with a learning disability.     

The Effects of Abutment Wall Height, Platform Size, and Screw Access Channel Filling Method on Resistance to Dislodgement of Cement-Retained, Implant-Supported Restorations

PURPOSE: Factors affecting the retention of fixed prostheses to natural abutments are well understood. In contrast, little is known concerning factors influencing the retention of fixed prostheses cemented to implant abutments. The purpose of this study was to investigate the effect that varying implant abutment wall height, platform size, and screw access channel filling method has on the retention of castings cemented to implant abutments using TempBond. MATERIALS AND METHODS: Four 15 degrees preangled abutments (Nobel Biocare Replace Select Esthetic) of each platform size--narrow (NP), regular (RP), and wide (WP)--were used. In each group of abutments the screw access axial wall was either unadjusted, one-third removed, two-thirds removed, or completely removed. The screw access channels were either fully or partially filled with Memosil, a vinyl polysiloxane impression material. For each abutment a casting was constructed that incorporated an attachment to allow removal. Castings were cemented to abutments with TempBond. The tensile force required to separate the cemented castings from the abutments was measured using an Instron Universal load-testing machine. RESULTS: The mean peak removal force for comparable abutments was significantly different ( p < 0.05): (1) where the screw access channel was completely filled with Memosil compared with those partially filled with Memosil; (2) with platform sizes--WP > RP > NP; (3) with alteration of axial wall height--1/3 removed > unadjusted = 2/3 removed > total wall removal. CONCLUSIONS: The retention of castings cemented to implant abutments with TempBond is influenced by the wall height, platform size, and the filling modality of the screw access channel.     

The use of ultrasonography in the diagnosis of neck lumps

The role of ultrasonography in the diagnosis of neck lumps is explained with particular reference to branchial cysts, chemodectomas, and abscesses.     

The nature of the interface between polymethyl methacrylate denture base materials and soft lining materials

Four of the commonly used resilient denture lining materials were investigated. They were of different chemical composition, physical forms and processing cycles. Scanning electron microscope examinations of the interface between the liners and the regular acrylic resin base material were carried out in an attempt to assess the bonding of these materials to the denture base, and to evaluate the reliability of their use. The physical and mechanical bonding properties of the resilient lining materials to acrylics were studied, which included tensile, shear, peel and compression tests to measure the efficacy of the joint between the acrylic and the lining materials and its resistance to various external damaging loads. The effect of water on the liner/denture base interface and on the liner's bonding properties to acrylics was also investigated, and the validity of roughening the tissue surface of the denture base prior to processing the liner was assessed.

The findings point to the advisability of using the acrylic type of soft liners whenever resilient liners are indicated. Roughening the fitting surface of the denture base to which the resilient lining materials are to be applied has a weakening effect on the bond between the lining and the denture base. Long-term exposure of the liners to water has a destructive effect. The infusion of the water into the material leads to swelling and stresses build up at the denture base interface and these tend to promote distortion and reduction in bonding.