The erosive effects of saliva following chewing gum on enamel and dentine: an ex vivo study.

OBJECTIVES: The primary objective was to determine the erosive effect of expectorated saliva, following chewing acidic gum, on enamel and dentine samples, using a non-acidic gum as a negative control. Secondary objectives were to determine the effect of brushing enamel and dentine samples and the effect of individual saliva pH and buffering. DESIGN: A single-centre, single-blind, placebo-controlled, two-way crossover study. SETTING: A clinical trial, involving healthy participants, undertaken at Bristol Dental School and Hospital. METHODS: Eight healthy participants expectorated saliva onto prepared enamel and dentine samples while chewing gum (strawberry flavoured acidic gum [active] or peppermint flavoured non-acidic gum [control]). Half of the enamel and dentine samples were brushed before measurement by contact profilometry. MAIN OUTCOME MEASURES: Mean enamel and dentine erosion, with and without brushing and the relationship to salivary buffering.Results At 10 days, mean depth of surface loss from dentine samples (95% CI), following chewing of acid-containing gum and subsequent brushing, was -11.34 µm (2.22 µm) and from un-brushed dentine samples was -11.02 µm (1.71 µm). No significant erosion was noted for other groups. CONCLUSIONS: Frequent chewers of acid-containing gums are susceptible to dentine erosion even in the presence of good salivary buffering. Enamel erosion was insignificant within the time constraints of the present study but warrants further investigation.

Comparative stain removal properties of four commercially available denture cleaning products: an in vitro study.

OBJECTIVES: Formulations of commercially available denture cleaners vary widely. Unfortunately, comparative data to suggest which products are the most effective can become invalid as newer products are introduced or formulations are changed. The aim of this in vitro study was to measure the stain removal properties of four currently available denture cleaners. METHODS: Stain was deposited on multi-well polystyrene saliva coated microplates using multiple chlorhexidine and tea solutions. Following drying, each stained well was exposed to a solution of denture cleaner, dried again and the amount of stain remaining measured using a microplate reader. The cleaning procedure was repeated with further multiple exposures of the wells to solutions of the denture cleaners. RESULTS: All denture cleaners removed stain better than water used as a control. At five cleaning cycles only one of the cleaners (Superdrug Cleaning Powder) had removed 100% of the stain. At 30 cycles three of the cleaners had removed 100% of the stain. CONCLUSIONS: All the commercial denture cleaners removed stain. Superdrug Cleaning Powder, which contains sodium percarbonate and sodium lauryl sulphate, was particularly effective.

Evaluation of the strength and radiopacity of Portland cement with varying additions of bismuth oxide.

AIM: To study the effect of addition of various proportions of bismuth oxide on compressive strength and radiopacity of Portland cement. METHODOLOGY: The compressive strength of white Portland cement and cement replaced with 10, 15, 20, 25 and 30% bismuth oxide was evaluated by testing cylinders 6 mm in diameter and 12 mm high. Twelve cylinders were tested for each material under study. The radiopacity of the cements tested was evaluated using an aluminium step-wedge and densitometer. The optical density was compared with the relevant thickness of aluminium (Al). Statistical analysis was performed using Analysis of Variance (ANOVA) with P = 0.05 and Tukey test to perform multiple comparison tests. RESULTS: Various additions of bismuth oxide had no significant effect on the strength of the material when compared with the unmodified Portland cement (P > 0.05). The radiopacity of the cements tested ranged from 2.02 mm Al for Portland cement to 9.79 mm Al for the highest bismuth replacement. CONCLUSIONS: Addition of bismuth oxide did not affect the compressive strength of Portland cement. All the bismuth oxide cement mixtures had radio-opacities higher than 3 mm thickness of aluminium.

The effect of a range of disinfectants on the dimensional accuracy and stability of some impression materials.

Disinfection of dental impressions should be considered as a routine procedure in dental surgeries and dental laboratories. Disinfectants can have deleterious effects on some properties of impression materials. The aim of this study was to evaluate the dimensional accuracy and dimensional stability of a model dental stone, reproduced from five commonly used impression materials (Aquasil soft putty/Aquasil Ultra LV; Aquasil Monophase; Aquasil Ultra Heavy; Impregum F and Provil putty/Provil Light CD wash) retained by their adhesives in acrylic resin trays and exposed to three disinfectant solutions (Perform ID; Haz-Tabs and MD 520). Two hundred models were used to investigate the effect of the three disinfectants on the dimensional accuracy of the five impression materials. Five impressions were taken for each impression material for each disinfection treatment group. Measurements were carried out using a High Precision Reflex Microscope. All materials demonstrated a percentage change in dimensions when subjected to no disinfection when compared to the brass master die and all materials demonstrated a percentage change in dimension when subjected to the different disinfection procedures. The results of this study have demonstrated that for all of the materials investigated, the changes in dimensional stability were small in the order of microns. These changes may however be of clinical significance for procedures requiring a high degree of accuracy, for example fixed prosthodontics. The materials respond differently depending on the disinfectant used and it may therefore be appropriate that manufacturers recommend the use of particular disinfectants for their products in order to ensure optimum dimensional accuracy and stability.

The effect of a range of disinfectants on the dimensional accuracy of some impression materials.

In this study the dimensional accuracy of two model materials; dental stone and plaster of Paris, reproduced from three commonly used impression materials; alginate, polyether and addition-cured silicone, retained by their adhesives in acrylic resin trays and exposed to four disinfectant solutions was evaluated. Ninety casts were used to investigate the effect of the four disinfectants on the dimensional accuracy of alginate, polyether and addition-cured silicone impression material. For each impression material 30 impressions were taken, half were poured in dental stone and half in plaster of Paris. The disinfectants used were Dimenol, Perform-ID, MD-520, and Haz-tabs. Measurements were carried out using a High Precision Reflex Microscope. For the alginate impressions only those disinfected by 5-minute immersion in Haz-tabs solution and in full-strength MD 520 were not adversely affected by the disinfection treatment. All polyether impressions subjected to immersion disinfection exhibited a clinically acceptable expansion. Disinfected addition-cured silicone impressions produced very accurate stone casts. Those disinfected by spraying with fill-strength Dimenol produced casts that were very similar to those left as controls, but those treated by immersion disinfection exhibited negligible and clinically acceptable expansion. The results of the studied demonstrated that the various disinfection treatments had different effects on the impression materials. It is important that an appropriate disinfectant is used for each type of impression material.

The prevalence of dentine hypersensitivity in a hospital clinic population in Hong Kong.

OBJECTIVES: Dentine hypersensitivity is a common clinical finding with a wide variation in prevalence values. The aim of this study was to establish the prevalence of dentine hypersensitivity and to examine some associated aetiological factors in a cross-sectional study of patients visiting the Periodontology and Oral Hygiene Clinic at Prince Phillip Dental Hospital, Hong Kong over a three-week period. METHODS: 226 patients were examined over a three-week period using a triple syringe to administer a blast of cold air to confirm the diagnosis of dentine hypersensitivity. Additional factors such as smoking habits, initiating stimuli, gingival recession and cervical tooth surface loss were noted. RESULTS: 153 patients were diagnosed as having dentine hypersensitivity, giving a prevalence figure of 67.7%. The commonest teeth affected were the lower incisors and the commonest initiating factor was cold drinks. CONCLUSIONS: The prevalence of dentine hypersensitivity in a hospital periodontology clinic population in Hong Kong was 67.7%.

Accuracy of adaptation of thermoformed poly(methyl methacrylate).

Thermoformed poly(methyl methacrylate) (PMMA) sheet is used to produce a number of different dental appliances such as stents, occlusal splints and baseplates for occlusal rims. The purpose of the present study was to measure the accuracy of adaptation of Perspex PMMA sheet and to determine the effect of annealing on the accuracy of the thermoformed specimens. The results of the study showed that PMMA can produce specimens that are accurately adapted to the cast. Immersion in water resulted in an increase in the space between the cast and the specimen for both thermoformed and thermoformed and annealed acrylic resin. Annealing of the thermoformed specimens had significantly less increase in space between the cast and the specimens when immersed in water over a period of 3 months.

Online orthodontic advice: a protocol for a pilot teledentistry system.

A prototype teledentistry service was established that incorporated a PC-based expert system designed to assist in orthodontic cases. It guided the general dental practitioner (GDP) through the assessment of a patient's malocclusion and helped ensure that all relevant clinical observations were made and details recorded. The resulting data file, containing radiographic images and clinical data, was then transferred via the Internet to a dental specialist. The specialist's recommendations were returned by the same route or, where appropriate, a realtime videoconference was conducted. During an eight-month trial, six GDPs referred 158 cases through the teledentistry system; another 24 cases were referred directly to a local consultant. The protocol used during the trial worked satisfactorily. The GDPs found that it was straightforward and covered all aspects of the cases they submitted.

The effect of the addition of surface treated chopped and continuous poly (methyl methacrylate) fibres on some properties of acrylic resin.

Poly (methyl methacrylate), the material most commonly used in the construction of dentures, is not without limitations particularly in terms of mechanical strength, such as flexural and fatigue strength. The Dental Practice Board for England statistics show that many dentures fail as a result of fracture. This study investigated the self-reinforcement of acrylic resin through the addition of surface treated poly (methyl methacrylate) fibres in chopped and continuous form. The effect of the addition of fibres on transverse and impact strengths was investigated. The addition of surface treated chopped or continuous fibres to acrylic resin did not improve the transverse or impact strengths. The addition of surface treated poly (methyl methacrylate), in the present form, to acrylic resin cannot be recommended as a method of reinforcement.

Is paediatric day case tonsillectomy desirable? The parents' perspective.

Tonsillectomy is the most commonly performed otolaryngological procedure in most units. There is considerable financial pressure to perform paediatric tonsillectomy as a day case. Responding to concern that day case tonsillectomy might not be welcomed by parents or felt to be in the best interests of the patients, we carried out an audit of paediatric tonsillectomy, by means of a questionnaire for parents and nursing staff to complete while 32 consecutive patients underwent tonsillectomy as inpatients. Although eight parents (25%) felt that day surgery should be an option, none of those surveyed felt that on this occasion their child was well enough to be discharged home six hours postoperatively. Furthermore, no child in the audit fulfilled all the essential discharge criteria at six hours. In this area, at least, it appears parents do not uniformly welcome paediatric day case tonsillectomy.

Sudden parotid swelling due to spontaneous haemorrhage.

This paper presents an interesting case of a severe spontaneous haemorrhage within the parotid gland in an adult. A rapidly enlarging parotid mass with absence of causative trauma, inflammation or vascular abnormality, raised the suspicion of a neoplasm. Ultrasound, computed tomography (CT) and tissue biopsy, however, have shown only changes suggestive of previous haemorrhage and no evidence of malignancy. A 30-year review of the literature revealed no similar case reported previously.

Appropriate use of the day care unit for rigid endoscopy of the upper aerodigestive tract.

There is increasing pressure for more day surgery to be undertaken in the health service. In this retrospective study of 325 rigid upper aerodigestive tract endoscopies performed in the Day Care Unit of The Royal National Throat Nose and Ear Hospital, London, there were no post-discharge complications and only four patients required admission, none were, in our opinion, the direct result of day case rigid endoscopy. In our unit, the day case rate for microlaryngeal surgery is 44.8%, showing that rates significantly higher than published national rates of 17.1% (1993/1994) are achievable. We conclude that day case microlaryngeal surgery and diagnostic rigid endoscopy of the upper aerodigestive tract is safe if performed by suitably qualified staff in dedicated specialist units with patients selected according to existing day case criteria.

A clinic for the rapid processing of patients with neck masses.

Neck masses are common and may have serious underlying pathology. There is much anxiety and confusion in primary care as to which hospital department will provide the patient with the best service and the swiftest diagnosis. A clinic was set up at Wexham Park hospital to enable patients with neck masses to be seen early, and to undergo a one-stop specialist evaluation, ultrasound scan and fine needle aspiration biopsy. The clinic has yielded a wide variety of benign and malignant pathology. The first 100 patients are discussed and evaluated.

Congenital anosmia.

Congenital anosmia is well described in conjunction with various sexual and other developmental abnormalities and has been reported to run in families. Congenital anosmia occurring as an isolated defect in a single family member is extremely rare, and tends to present late. We describe a case of a five year old girl with congenital anosmia and we outline the investigations which should be undertaken in such cases.

An assessment clinic for routine paediatric otolaryngological surgery.

In the current climate of medical practice clinicians are under constant pressure to come up with new ways of increasing efficiency and throughput whilst maintaining a high standard of patient care. Assessment clinics are not a new idea and are widely practised in the National Health Service. The novel feature of the clinic we are describing is that all relevant professionals are present: consultant otolaryngologist, audiologist, paediatric nurse, playleader and preassessment nurse. The Wexham Park Paediatric Otolaryngology Preassessment Clinic has now been running for six years, and in this time we have experienced a marked decrease in both the waiting times for surgery and the non-attendance rate.

The incidence and detection of HPV in the upper aerodigestive tract using brush and biopsy techniques.

The association between human papillomavirus (HPV) and squamous carcinoma is well established. In the polymerase chain reaction (PCR) we have an effective technique for detecting small quantities of viral DNA, but the assay requires tissue taken at endoscopy to reveal the presence or absence of HPV. Brushings have been used effectively elsewhere in the body to obtain cytological material. This study set out to ascertain if sufficient viral DNA could be obtained, using a laryngeal brushing and the PCR, to detect the presence or absence of HPV. Six patients with squamous carcinoma of the larynx and seven controls who were having laryngoscopy for other reasons underwent laryngeal biopsy. In addition, in the patients with carcinoma, biopsies were taken at the tumour margins and brushings from both sites. The samples were tested for the presence of HPV types 6, 11, 16, 18 and 31 by means of the PCR. The distribution of HPV types was as expected in the biopsy specimens, but only one brushing detected any HPV type at all. We conclude that laryngeal brushing is an inadequate technique for assessing the presence of HPV in the larynx.

The effect of surface treated UHMWPE beads on some properties of acrylic resin denture base material.

UHMWPE in the form of experimental surface treated beads was added to acrylic resin denture base material in various percentages to form a composite material. The influence on doughing and manipulation times, and transverse and impact strength was examined. The results indicated that the manipulation times, were not significantly affected as the percentage of UHMWPE beads in the acrylic resin powder increased. Increasing the percentage of incorporated UHMWPE beads resulted in an inconsistent decrease in the modulus of rupture and no effect on the impact fracture resistance. It was concluded that the use of treated UHMWPE beads is of no significant benefit to the properties of acrylic resin.

Clinical informatics and the dental curriculum. A review of the impact of informatics in dental care, its implications for dental education.

The origins of informatics lie in the development of computers and data processing techniques since the 1950s. The subsequent application of these to the practice of healthcare continues to the present day, so that information technology now holds the potential to revolutionise healthcare through more rapid and efficient management of an ever increasing quantity of clinical information. In dentistry, no less than in medicine, electronic systems can make an extremely valuable contribution to clinical practice. For these systems to be clinically useful, however, they need to be properly understood by clinicians. This review paper outlines the scope of clinical informatics and argues that a grounding in clinical informatics is now essential for today's undergraduates to equip them to meet the challenge of practice in the 21st century.

Wear: mechanisms, manifestations and measurement. Report of a workshop.

OBJECTIVE: The purpose of this workshop was to bring together a tribologist (T.A.S.), a clinician (L.H.M) and a dental materials scientist (R.W.V) to discuss the fundamental mechanisms of wear and how these relate to the manifestations and measurement of wear in dentistry. Eighty delegates contributed to a valuable discussion led by the workshop chairman (C.H.L.). KEY POINTS: Wear is the net result of a number of fundamental processes: abrasion, adhesive effects, fatigue and corrosive effects which act in different combinations on the various classes of materials. In ceramics, sliding compression and surface corrosion greatly increase wear, whereas the ability to deform either plastically or elastically influences the wear of polymers. The filler particle distribution is a major variable influencing the wear of composites. In the mouth, wear can be considered in terms of its site, timing and mechanism. The latter may involve direct contact between surfaces or result from the action of slurries; both of which are affected by surface corrosion (erosion). Although wear can be categorized at the chairside, its precise measurement involves the use of replica models and surface contouring. Laboratory simulation is useful to study fundamental wear mechanisms; but it is not able to predict clinical wear. CONCLUSIONS: The management of clinical wear requires a proper understanding of the underlying mechanisms. This can only be achieved through close co-operation between all the disciplines which seek to understand and manage wear. The attendance of so many delegates at this workshop indicates the willingness to participate in this process.