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Excessive gag reflex could be problematic for adequate dental care. Although various factors may increase the susceptibility to gagging, its contributing factors have not been fully determined. This study aimed to determine whether gag reflex was associated with tactile sensitivity and psychological characteristics. Fifteen volunteers of healthy males and females each were recruited for this study. After completing a questionnaire describing the self-perceived gag reflex activity, a disposable saliva ejector was inserted along the palate into the mouth until gagging was evoked. The ratio of the insertion depth to the palatal length was used as an index for the gagging threshold. The two-point discrimination (TPD) and Semmes-Weinstein monofilament (SWM) tests were performed to assess the tactile sensitivity of the palatal regions (hard palate, anterior and posterior soft palate). The Symptom Checklist-90-Revised was used to investigate the relationship between the gagging threshold and the psychological status. Our findings showed that the gagging threshold had a significant positive correlation with the TPD and SWM thresholds on the hard palate. The psychological profiles of psychoticism and hostility score were also significantly correlated with the gagging threshold. However, there were no significant differences in the tactile and gagging thresholds, as well as the psychological profiles, between males and females. Our results suggested that the tactile sensitivity of the anterior palate is a determining factor for the gagging threshold and implied that the initial response of the oral entry site to stimulation may lead to the development of gag reflex.

One of the greatest challenges to modern dentistry is the progressive destruction of tooth material due to chemical erosion. Dental erosion is the loss of dental hard tissue, without the action of bacteria, in which demineralisation of enamel and dentine results due to a decrease in intra-oral pH. The aim of this review was to appraise the scientific literature on the factors that can affect intra-oral pH. The review will examine (i) the protective role of human saliva, in terms of its mineral composition, flow rates and buffering systems and (ii) sources of in-mouth acids such as extrinsic acids, which are derived from the diet and environment, as well as intrinsic acids, which are related to disorders of the gastro-oesophageal tract. This review may assist clinicians to identify the risk factors for tooth wear and to recommend adequate preventive measures to patients.

Tooth wear is a multifactorial condition, leading to the loss of dental hard tissues. Many grading scales are available to assess the amount of tooth wear, one of which is the tooth wear evaluation system (TWES). A grading scale can be used chairside, on casts and on photographs. The aim was to test whether the grading scales of the TWES, used on casts and on photographs, resulted in comparable scores. In addition, it was tested whether these scales can be used to assess tooth wear reliably on photographs. Of 75 tooth wear patients, sets of casts and series of photographs were obtained and graded. Comparison of the grading on casts and on photographs revealed equal median values and percentiles for both occlusal/incisal grading and non-occlusal/non-incisal grading. The grading on casts and on photographs showed a high correlation for the occlusal/incisal grading and a low correlation for the non-occlusal/non-incisal grading (Spearman's rho = 0·74 and rho = 0·47; P < 0·001). Concerning the grading on photographs, the interexaminer reliability was fair-to-good (ICC = 0·41 to ICC = 0·55) while the intra-examiner reliability was fair-to-good to excellent (ICC = 0·68 to ICC = 0·86) for the occlusal/incisal grading. For the non-occlusal/non-incisal grading, the interexaminer reliability was poor to fair-to-good (ICC = 0·22 to ICC = 0·59), while the intra-examiner reliability was fair-to-good to excellent (ICC = 0·64 to ICC = 0·82). It was concluded that the scores obtained with the grading scales of the TWES on casts and on photographs are comparable. The grading scales can be used in a reliable way on photographs, which is especially the case for occlusal/incisal grading.

To describe a novel approach for continuous measurement of intra-oral pH and temperature in individuals carrying out normal daily activities over 24 h. We designed, validated and constructed a custom-made appliance fitted with a pH probe and a thermocouple. Six subjects wore the appliance over a 24-h period for two non-consecutive days, while the intra-oral pH and temperature were measured continuously and recorded. Intra-oral pH and temperature were very similar across different recording days, the difference being not statistically significant (P ≥ 0.14). There was a noticeable difference in the pattern of variation of pH between day and night. During the day, the mean pH was 7.3 (±0.4) and dropped markedly only after consumption of acidic food and drinks. The intra-oral pH decreased slowly during sleep with an average pH of 6.6 (±0.4) being recorded. The difference between day and night was statistically significant (P = 0.002). The mean intra-oral temperature was 33.9 °C (±0.9) during daytime and 35·9 °C (±0·5) during sleep (P = 0.013) with minor fluctuations occurring over 24 h. The continuous and simultaneous intra-oral pH and temperature measurement system described in this report is reliable, easy to construct, able to measure variables over a sustained period and may serve as a future diagnostic tool in a number of applications.

The choice of correct tooth shade for the fabrication of a restoration remains a challenge, even for experienced clinicians. The aim of this research was to evaluate and compare the precision of two different shade determination methods in terms of repeatability. Maxillary right central incisor of 10 patients was evaluated visually with the use of Vitapan Classical shade guide by five observers and instrumentally with the Vitapan classical shade guide values of ShadeEye NCC intra-oral colourimeter three times consecutively. The in vivo repeatability of methods were analysed with the spectrophotometric L*, a*, b* values of the shade guide (Vitapan Classical). Within the limitations of this study, the repeatability of instrumental (intra-oral dental colourimeter) and visual shade determinations were acceptable.

In this study we suggest that the presence of abrasives in food items lead to physiologic responses that reduce the amount of tooth loss because of abrasion. Subjects were presented with two pairs of two-colour chewing gum, one sample had 0.5 g of an abrasive powder added. Subjects were instructed to chew for 10 or 20 chewing strokes and then remove the gum. After removal the chewing gum was placed in a plastic bag and flattened. Each pair of gums was compared on the basis of the amount of mixing observed. In all cases the addition of the abrasive powder resulted in slower chewing and less mixing. Salivary flow rate increased from a resting value of 0.6 to 0.9 mL min(-1) when stimulated by the non-abrasive gum to 1.1 mL min(-1) with the abrasive gum. This difference was significant (P < 0.05). We conclude that when abrasive particles are detected in the mouth, less bolus manipulation is performed and more saliva is secreted. These responses would have the effect of reducing loss of tooth substance at the expense of reduced cominution of the food.

Ceramic fractures are serious and costly problems in dentistry. Moreover, they pose an aesthetic and functional dilemma both for the patient and the dentist. This problem has created demand for the development of practical repair options which do not necessitate the removal and remake of the entire restoration. Published literature on repair techniques for fractured fixed partial dentures, concentrating on the data obtained both from in vitro and in vivo studies, reveals that the repair techniques based on sandblasting and silanization are the most durable in terms of adhesive and cohesive failures compared with those using different etching agents.

SUMMARY Sensory input from sensory receptors regarding food morsels can affect jaw motor behaviours during mastication. The aim was to clarify the effects of intra-oral sensory input on the food-comminuting and food-mixing capacities of dentate subjects. Eleven dentate subjects without sensory dysfunction in their oro-facial region participated in this study. Local anaesthesia was achieved on the periodontal structures and on the oral mucosa of the subjects’ preferred chewing side by injecting a lidocaine solution with adrenalin. At baseline (control) and after anaesthesia, data on the subjects’ food-comminuting and food-mixing capacities were gathered. The food-comminuting capacity was quantified by measuring the degree of pulverisation of peanuts (objective hardness; 453 [Newton, N]) after a prescribed 20 chewing strokes. The food-mixing capacity was measured as the degree of immixture of a two-coloured paraffin wax cube after 10 chewing strokes. Wax cubes of three different hardness levels were used (soft, medium and hard: 203, 326 and 755 [N], respectively) and were chewed in random order. After anaesthesia, the subjects’ food-comminuting capacity significantly decreased (P < 0001), as did the food-mixing capacity for each hardness level of the wax cubes (P < 001). A significant correlation was observed between the objective hardness values and the anaesthesia effects for the foodmixing capacity (P < 005), indicating that after anaesthesia, deterioration of the mixing capacity increased as the hardness increased. In conclusion, intra-oral sensory input can affect both foodcomminuting and food-mixing capacities.

The dose of gamma irradiation sufficient to sterilize enamel samples to be used for intra-oral cariogenicity tests (ICT) without alteration to the structure or solubility of the enamel was determined. Each bovine incisor used was cut vertically into eight portions and each portion assigned to one of eight groups. Group 1 was used as control while other groups were subjected to respective doses of gamma irradiation from a cobalt-60 source. Following sterilization, both control and experimental groups were incubated in nutrient broth for 7 days at 37 degrees C under aerobic and anaerobic conditions. Caries-like lesions were subsequently produced in each specimen using acidic buffer solution, and mineral loss quantified using transverse microradiography. Data were analysed statistically. There was no significant difference in mineral loss between the control and experimental groups, but the numerical value of mineral loss was lower in groups irradiated with> 4080 Gy, in addition to full sterilization and enamel discoloration to cream colour observed in these groups. Microbial growth was observed in the control group and in groups irradiated with

Reliability of the intra-oral method which orientates the occlusal plane to terminate at the upper level of the retromolar pad was studied. Thirty individuals all with natural teeth and 34 complete denture wearers participated in the study. Stone casts were mounted in the S.A.M. 2 articulator by a quick mount face bow transfer. The angle between the occlusal plane and the articulator horizontal plane was measured in both groups. The angle was 9.42 degrees +/- 4.1 degrees in dentate individuals and 8.53 degrees +/- 2.8 degrees in complete denture wearers. No statistically significant difference was found between the groups (t = 0.72, P > 0.05). Therefore, the method can be advocated for a wide clinical use, as it is a simple method and places the artificial occlusal plane very close to the position of the natural plane of occlusion.

There has been limited published research assessing the range of oral temperature that the dental hard and soft tissues are exposed to. The temperatures that tooth structure and dental restorations encounter affect the performance of dental materials within the oral environment. This study therefore assessed the range of temperatures that a selected group could tolerate when drinking and also assessed the range of temperatures encountered in various intra-oral sites. These temperature fluctuations are for very brief periods of time but have a wide and varied range. Miniature dataloggers allowed for accurate measurements and recording of temperature from selected sites. The range of temperature recorded amongst the individuals tested shows the protection afforded to the dental hard tissues by the soft tissues of the oral cavity. The maximum and minimum mouth temperatures recorded show that hot fluids can raise the intra-oral temperature of the front teeth to around 70 degrees C and the consumption of iced drinks lowers the same teeth to around 0 degrees C. The range of temperature of hot fluids that can be tolerated by a selected group vary, but this does not seem to be the case for cold fluids. The thermistor beads mounted on the buccal surface of the lower front teeth and the palatal of the upper front teeth are exposed to the greatest temperature fluctuations during drinking fluids from a cup. The importance of these temperatures recorded in terms of dental materials testing and the role of material conductivity warrants further investigation.

Biofilms accumulate on hard and soft surface in the oral cavity. Accumulation of biofilms on orthodontic appliance bear scientific and clinical interest. The objection of this study was to examine the formation of dental biofilm by Streptococcus sobrinus on different types of orthodontics appliances, using a model consisting of host and bacterial constituents. The adsorption pattern of saliva to the orthodontics appliances was determined by means of gel electrophoresis coupled with computerized densitometry techniques. The amount of salivary proteins adsorbed onto the surfaces was measured using the Bradford method. Sucrose-dependent bacterial adhesion to the saliva-coated orthodontics appliances was tested by radioactive-labelled S. sobrinus. Our results show different adsorption patterns of salivary proteins to the various orthodontic appliances as modules, brackets, springs and intra oral elastics. Modules and brackets demonstrated the most affinity to salivary proteins. A surface dependent adhesion profile was recorded, showing a high affinity of albumin and amylase to modules. Bacterial accumulation was the highest on modules compared with springs which demonstrated the least bacterial adhesion. Our study demonstrates the specificity of biofilm formation on the different orthodontic appliances. Formation of a variety of dental biofilms has a significant impact on the progression of dental diseases associated with orthodontic treatment.

The breakdown of food in the mouth during mastication can be described in terms of two parameters: a breakage function, which describes the fragmentation of food after a bite, and a selection function which defines the probability of particle fracture. The non-zero value of the selection function depends on the manipulation of food particles by the tongue. Little, however, is known about this. As a first step, this study investigated the manipulation of wax sheets of differing sizes and shapes by the tongue after ingestion. It was found that subjects tended to orientate rectangular and square wax wafers so that the long axis of the particle was parallel to the tooth row, independent of the initial orientation given when they were introduced into the mouth. Circular wafers were randomly oriented relative to initial orientation. If this could be extrapolated to the start of mastication, then it suggests that the tongue tends to align food particles so that the post-canines produce close to the greatest surface area possible by fragmenting them along their longest axis.

One of the major aims of the dental profession is the maintenance of oral function, specifically chewing ability. However, there are no generally accepted measures of chewing ability or even general agreement as to what level of tooth loss is deemed to require clinical intervention. There is therefore a need for simple objective tests of oral function. In this study a modification of the two-colour chewing gum test devised by Liedberg & Owall (1991), 1995) is described. In this test chewing gum containing two contrasting colours is chewed. On removal from the mouth the bolus is placed in a transparent plastic bag, flattened and a digital image is taken. Several image processing techniques are described and evaluated as measures of the amount of mixing present in the chewed gum. Flattening the gum was found to increase the accuracy of subjective evaluation, which was similar to that achieved by the image processing techniques.

Summary Objective diagnosis of occlusal relationships is possible with the aid of a new instrument called the ‘Functiograph’. It enables recordings of both the free and tooth-guided mandibular movements to be made intra-orally on the same tracing plate. A series of twenty cases has been undertaken and a number of selected examples are illustrated. Occlusal equilibration under the control of tooth-guided movement records enables the estimation of the results of occlusal correction in an objective and methodical way.

Summary A comparison between bone height scores from long-cone paralleling radiographic surveys and orthopantomographs (Panex-EC) of forty-one patients was made. Intra-examiner reliability and inter-examiner objectivity of the measuring method (Schei ruler) proved to be very good (r = 0.954 and r = 0.923 respectively for the intra-oral surveys; r = 0.928 and r = 0.916 respectively for the orthopantomographs). Distribution and frequency of the non-measurable surfaces were evaluated. In each technique an attempt was made to discern the main cause of non-measurability: overlapping of adjacent structures, absence of the surface and absence of the apical region on the image. For twenty of the thirty-six surfaces significant differences were found between bone height scores for corresponding surfaces in the long-cone survey and in the orthopantomograph. In periodontal, prosthetic and conservative dentistry the long-cone paralleling technique should be considered as the best radiographic technique.

A new pattern of screwjack for assessing the vertical dimension for occlusion utilizing an edentulous patient's proprioceptive sensation is described. It provides a greater range of movement than other, giving infinitely variable heights between 9 and 21 mm. The elements being captive, it cannot come to pieces in use. Laboratory experiments were contrived to define the magnitude of reading errors and the play in the screw threads. It was found that, only in instances where a graduation related closely to the datum mark, did errors of interpretation arise. These were found to exceed the height set for test purposes by 0-1 mm consistently. An error of this order is of no practical significance clinically and is no impediment to such an application of the device. Mean play in the new pattern jacks was 0-01 mm compared to 0-05 mm in the Timmer versions. In a clinical experiment the performance of the screw was compared to that of Timmer. Statistical evidence was found which suggested a functional difference between the two, the new pattern being significantly more accurate.