[The effect of occlusal force on the formation of experimental cervical wedge-shaped defects on human teeth]

Nine pairs of premolar from 7 patients were divided into three groups according to different occlusal forces. Every tooth was tested with pH5 or pH7 water bath by an electric toothbrushing machine and an electric occlusal force fatigue machine alternatively. Only the buccal surface of every tooth suffered from brushing test. There were 600 000 strokes of occlusal force fatigue test and/or 800 000 cycles of cross-brushing test for every tooth throughout the experiment with 4 intervals. During every interval, the depth at the profile of the cervical defect on each replica of tested tooth was measured and the shape of every defect was recorded with a computerized Seescan image analysis system. The findings suggested that the occlusal force played an important role in the formation of experimental cervical wedge-shaped defects. Occlusal force alone could produce cervical tooth defect in very slow rate. When the occlusal force associated with acid erosion and tooth-brushing abrasion, the depth of cervical defect increased significantly and the wedge-shaped defects were formed.

Reinforcement of weakened cusps by adhesive restorative materials: an in-vitro study

Pairs of extracted premolar teeth were prepared with MOD cavities reducing the lingual cusp at its base to one of five widths: 1.25-2.25 mm. One of each pair was then restored with one of five adhesive restorative techniques and the weakened cusp of both teeth fractured by a force applied to the cusp at an angle of 30 degrees to the long axis of the tooth. At all cusp widths a layered restorative technique in which the cavities were filled to the enamel-dentine junction with glass-ionomer cement and the enamel replaced by composite, reinforced the weakened cusp more than the other restorative materials tested. This combination of materials to reinforce weakened cusps is worth considering as a cost effective alternative to removing the cusp entirely and making a crown or protecting the cusp with a cuspal coverage gold inlay.

Polysaccharide composition of unlignified cell walls of pineapple [Ananas comosus (L.) Merr.] fruit

The polysaccharides of cell walls isolated from the fleshy, edible part of the fruit of the monocotyledon pineapple [Ananas comosus (L.) Merr.] (family Bromeliaceae) were analyzed chemically. These cell walls were derived mostly from parenchyma cells and were shown histochemically to be unlignified, but they contained ester-linked ferulic acid. The analyses indicated that the noncellulosic polysaccharide composition of the cell walls was intermediate between that of unlignified cell walls of species of the monocotyledon family Poaceae (grasses and cereals) and that of unlignified cell walls of dicotyledons. Glucuronoarabinoxylans were the major non-cellulosic polysaccharides in the pineapple cell walls. Xyloglucans were also present, together with small amounts of pectic polysaccharides and glucomannans (or galactoglucomannans). The large amounts of glucuronoarabinoxylans and small amounts of pectic polysaccharides resemble the noncellulosic polysaccharide composition of the unlignified cell walls of the Poaceae. However, the absence of (1-->3,1-->4)-beta-glucans, the presence of relatively large amounts of xyloglucans, and the possible structure of the xyloglucans resemble the noncellulosic polysaccharide composition of the unlignified cell walls of dicotyledons.

The distribution of erosion in the dentitions of patients with eating disorders

Anorexia and bulimia nervosa (the eating disorders) are potentially life threatening and are becoming more prevalent. This paper reviews the effects of these disorders on dental erosion and reports a study to assess the effects of the eating disorders on the erosion of teeth relating the severity of erosion to factors such as the frequency of self-induced vomiting (SIV). One hundred and twenty-two eating disorder patients and an equal number of age, sex, and social class matched controls were studied. The study population was divided into subgroups according to the eating disorder. All the subgroups had significantly more abnormal toothwear than the controls (P < 0.005), with the differences being most marked in the SIV groups. Further analysis did not find any consistent relationships to the frequency or duration of SIV.

Clinical and radiographic diagnosis of occlusal caries: a study in vitro

Various methods of diagnosing occlusal caries have been described, but only visual, clinical examination and radiographic examination are commonly used in dental practice. This laboratory study investigated the ability of 12 examiners to detect the presence or absence of occlusal caries in 48 extracted molar teeth using these two techniques. The presence or absence of caries was subsequently verified by sectioning the teeth. Diagnosis from visual examination was poor, only 48.7% of lesions in dentine being detected. Radiographic diagnosis was better with 62.2% of dentine lesions being found. However, this increase in sensitivity of the diagnosis was accompanied by a decrease in specificity with the number of false positive diagnoses increasing when the radiograph was used. Therefore, although the bite-wing radiograph may be regarded as a safety net for the diagnosis of occlusal caries, it must be interpreted with caution bearing in mind the possibility of false positive diagnoses.

The dental impact of eating disorders

Our self-perceptions are all influenced to some extent by the media. The increase in sales of diet plans immediately after Christmas only serves to highlight the fact that many people (consciously or subconsciously) are aware of the effect that advertisements have on our lives. The weight of most people is controlled by a combination of diet and homoeostatic control and remains relatively constant, but weight loss has a more profound and sinister effect for others. Unexplained dental erosion can occasionally be found during dental examinations and, despite careful questioning, a definitive diagnosis may prove elusive. In these patients, once the more common causes of dental erosion have been eliminated, the eating disorders should be considered. In this paper, the effects of psychological conditions affecting the diet on the dentition will be discussed.

The effect of restorative materials on the wear of human enamel

The wear of human dental enamel against amalgam, Concise composite, SR-Isosit Inlay/Onlay composite, Vitadur-N glazed porcelain, unglazed IPS Empress ceramic, and enamel (control) was investigated by use of a modified stress cycling machine. Testing was carried out in water and in citric acid (pH 4) and the enamel-material couples were subjected to 25,000 cycles of wear with a maximum load of 40 N. Tooth profile reduction was measured at baseline and at 5000 cyclic intervals with a computer image analysis program. The depth of the wear scars on material specimens was analyzed with a profilometer. All materials produced increased enamel wear in acid. Vitadur-N glazed porcelain was found to be the most destructive to human dental enamel, and this was closely followed by Empress and enamel.

Early MR imaging of lower-extremity physeal fracture-separations: a preliminary report

Magnetic resonance imaging (MRI) was used to evaluate physeal fracture-separations in children soon after at-risk lower-extremity fractures. MRI scans taken during the "acute" period (within 10 days of fracture) resulted in a change in three of four of the Salter-Harris classifications from the injury radiographs. Twelve children had MRI scans performed in the "early" period (3-17 weeks following fracture). Physeal narrowing or tethering and the absence of Harris arrest lines were found in those patients who subsequently required late surgical intervention. Acute MRI provides the most accurate evaluation of the physeal fracture anatomy. Early MRI can demonstrate transphyseal bridging or altered arrest lines in physeal fracture before they become manifest on radiographs.

Audit in restorative dentistry

Auditing activity requires patient data to be collected and analysed to allow comparisons to be made and conclusions drawn. Within the General Dental Services the Dental Practice Board regularly collects practitioner specific clinical data and distributes this to allow dentists to compare their own clinical activity with local and national means. In hospital dentistry, a software package has been developed to enable orthodontic audit to be performed in hospital practice. The package is now being piloted in several centres. A similar software package is required for auditing restorative dentistry activity in units where consultant services are provided. Hospital patient administration systems provide demographic data and appointment systems predominantly with little opportunity for patient specific clinical analysis. Carefully designed software will allow appropriate clinical data and analysis. To ensure compliance and accurate recording both by clinical and support staff it is essential that any software system should be easy to use.

Comparison of the effect of fluoride and non-fluoride toothpaste on tooth wear in vitro and the influence of enamel fluoride concentration and hardness of enamel

The effect of the presence of fluoride in toothpaste on tooth wear was investigated in extracted human premolar teeth collected from two geographic areas with different fluoride concentrations in the public water supply. Nine teeth from each area were divided bucco-lingually into matched pairs and subjected to a wear regime in vitro. The regime consisted of 5 minutes immersion in 6% citric acid buffered at pH 3.5, followed by 200 cycles of linear tooth-brushing in a slurry of either a fluoride or a non-fluoride toothpaste, the whole process repeated 720 times. Teeth collected from subjects in Birmingham (public water supply fluoridated at 1 ppm) had a higher fluoride concentration in the surface enamel (P < 0.01) and greater hardness (P < 0.001) than teeth collected from subjects in London (non-fluoridated water supply). The results showed that less wear was produced in the presence of the fluoride toothpaste than in the presence of the non-fluoride toothpaste with an otherwise identical formulation (P < 0.001), and that the amount of tooth wear in vitro was not significantly affected by differences in fluoride concentration and hardness of enamel.

Replacement of missing cusps: an in vitro study

One of the commonest methods of replacing a missing cusp, a pinned amalgam restoration, was compared with three adhesive restorative techniques, two of them with additional pin retention. All the teeth were subjected to occlusal/lateral forces and loaded to fracture in an Instron testing machine. A layered restoration of glass ionomer cement replacing the dentine, and resin composite replacing the enamel, without pins required more force to fracture than any of the other techniques including the pinned amalgam restoration. A composite restoration with dentine bonding agent and additional pin retention was second best and significantly better than the pinned amalgam restoration. A cermet restoration with additional pin retention required slightly less force to fracture than pin-retained amalgam restorations, but not significantly so.

Clinical techniques for producing and monitoring minor axial tooth movement

In this second article a range of clinical techniques for producing minor axial tooth movement is described, including the simple, cemented metal anterior bite-plane which has proved to be one of the most useful of the techniques. Methods of monitoring and measuring the relative tooth movements are also described.

Minor axial tooth movement in preparation for fixed prostheses

In this first of two articles the theory and practice of creating occlusal clearance for restorative procedures without the removal of tooth tissue is discussed. Earlier techniques for producing minor axial tooth movement are reviewed, together with the relevant literature on continuous eruption and occlusal stability. The indications for axial tooth movement and alternative treatment options are also considered.

Toothwear histories: a sensitive issue

Wear of the surface of the teeth is a natural consequence of ageing, but various conditions can render it pathological. In this article the authors describe two strategies for obtaining sensitive, personal information from patients who may be reluctant to disclose such details to a stranger.

Identification of a high risk subgroup of grade 1 transitional cell carcinoma using image analysis based deoxyribonucleic acid ploidy analysis of tumor tissue

The use of deoxyribonucleic acid (DNA) cytometry to identify a subset of patients with grade 1, stage Ta or T1 transitional cell carcinoma at high risk for death or recurrence was investigated in a retrospective study using paraffin blocks from 88 low grade transitional cell carcinomas of the bladder with an absorptiometric video-based image analysis system. Tumors were evaluated for ploidy (70 diploid, 16 aneuploid and 2 tetraploid) and the presence of cells with greater than 5C DNA. Survival analysis of 62 patients with adequate followup (15 to 20 years) showed that 43 of 62 (69%) suffered recurrences and 13 (21%) died of bladder cancer. The single most important predictors of death and recurrence were stem line aneuploidy and the presence of cells with greater than 5C DNA, respectively.

Some facets of tooth wear

Tooth wear seems to be an increasing problem, particularly amongst older patients who are retaining their teeth for longer. Having survived the ravages of caries and periodontal disease, they are then at risk of wearing out their dentition. Diagnosis and a full understanding of the aetiology is crucial to the effective management of unacceptable levels of tooth wear. Monitoring over a long period is helpful in planning life long management. There are specific treatment techniques which are useful in restoring badly worn teeth.

Regurgitation erosion as a possible cause of tooth wear in ancient British populations

Clinically, in modern populations, tooth wear can be differentiated into three main types--attrition, abrasion and erosion, acting either separately or together. Anthropologists generally have not recognized erosion as a factor affecting the teeth of past populations. This study compares the patterns of wear known to be associated with erosion in present-day dental patients with those found in some British, pre-Conquest, skeletons. It is concluded that erosion may have been a major factor causing the extensive tooth wear in some 20 of 151 individuals.

Prevalence of pathological tooth wear in patients with chronic alcoholism

Although chronic alcoholism is a very common condition, with potentially harmful consequences for the sufferer, there has been little emphasis in the literature on its effects on the teeth. This study of 37 alcoholic patients showed that their teeth had significantly more wear than age and sex matched controls. The tooth wear was most marked in males, and those whose alcohol consumption was continuous rather than in the form of episodic binges. The wear appeared to be erosive in nature, and in 40% of the sample it affected the palatal surfaces of the upper anterior teeth. It is therefore suggested that general dental practitioners should bear in mind the possibility of chronic alcoholism in cases of unexplained dental erosion.

Professional negligence in dentistry

Society is becoming more litigious, and dentistry has not been exempt. However, by following correct and prudent professional procedures at all times, dentists may sensibly expect to avoid serious litigation. In the first of an irregular series on dento-legal topics, Bernard Smith reviews the thorny subject of negligence in dentistry, and gives advice on both how to prevent and how to respond to accusations. Other articles in the series will look at particular legal problems in the dental specialties.

Diagnosis of caries and treatment decisions in approximal surfaces of posterior teeth in vitro

The diagnosis of caries and treatment planning decisions have been reported to vary widely between individual dentists. However, opinions differ as to whether, in general, this results in too much or too little treatment. Eighty-six dentists, mainly attending post-graduate meetings, participated in this study. They were asked to make diagnostic and treatment planning decisions on a selection of extracted teeth set in realistic contact with each other. These decisions were compared with the appearance of the proximal surfaces before setting the teeth in contact, and the histological appearance of the teeth that were sectioned after the dentists had made their decisions. Opinions as to whether caries was present and whether it required treatment showed a wide distribution. However, had the decisions been acted upon, between 1-6% of the sound surfaces would have been filled, but 20-68% of teeth with clearly cavitated surfaces or histological evidence of dentine involvement would not have been filled.

Bond strengths of three chemical adhesive cements adhered to a nickel-chromium alloy for direct bonded retainers

Sandblasted surfaces of a beryllium-free, nickel-chromium alloy were bonded with one of three chemical adhesives. After either immersion in water for up to 6 months or thermal cycling between 5 degrees and 60 degrees C for 500 cycles, the bonded specimens were tested for both shear and tensile strength. The highest values of tensile and shear bond strengths were found with Panavia Ex material, and these values showed no significant changes after thermal cycling. For ABC cement and for Super-Bond C & B material, the strength of the bond was significantly improved with thermal cycling. However, immersion in water for 6 months caused a significant decrease in the strength of the bond of specimens adhered with ABC cement.

A longitudinal study of the value of a spatial relations test in selecting dental students

Potential academic ability, practical skill and personality characteristics should all be assessed in selecting dental students. Of these, practical skill commonly receives the least attention, largely because valid and reliable predictive tests are not available. The Spatial Relations Test, which might be used for this purpose, was administered to 1391 applicants to a dental school. There was little correlation between the results of the test and GCE 'A' level grades, showing that the test measured different abilities. However, there was a strong relationship between poor scores on the test and the number of students resigning from the course or failing to graduate on time.

Dental erosion in patients with chronic alcoholism

Tooth wear attributed to the physical wear of teeth by clenching and grinding (attrition) has been described previously in alcoholic patients. However, the pattern of wear seen in the series of cases reported here is more consistent with chemical damage (erosion) than attrition. A possible mechanism for this process is suggested, and it is further suggested that erosion is likely to play a more important role in the wear of the teeth in chronic alcoholic patients than attrition.