Influence of temperature and foil hardness on interocclusal tactile threshold

Determinations of interocclusal tactile threshold levels so far have involved neither appropriate psychophysical approaches nor an assessment of the mechanical and thermal properties of the foils used. Twenty subjects (12 females) aged 18 to 50 (mean age 35) were tested for their absolute threshold level (RL). Both the method of limits and the staircase method were applied to determine the active or passive RL. For the active RL assessment, foils of different thicknesses were placed between edge-to-edge opposed incisors during gentle biting. Inner ear receptors of the blindfolded subjects were blocked by broad band noise applied through earphones, because vibrations induced by occlusal contact and conducted through bone might be perceived by these receptors. The foils presented were aluminum (Al), tin (Sn), polyester (PE) and calibrated steel (St) (thickness ranging from 8 to 50 microns) which offer different physical and thermal properties. The range of RL of the group varied between 8 microns for aluminum to 46 microns for polyester for 50% correct assessments. Increasing the foil temperature from room temperature (20 degrees C) to body temperature (35 degrees C) significantly increased the RL for conducting materials (one-way blocked ANOVA). These results indicate that temperature exchange takes place while presenting conducting foils at 20 degrees C (cold stimulus) interocclusally, which influences the RL by activating thermosensitive receptors. The passive RL determination with classical von Frey-hairs resulted in a mean axial RL of 3.0 g. Both psychophysical RL assessments (method of limits, staircase method) gave reproducible and similar results as ascertained by ANOVA. Furthermore, a positive correlation was established between active and passive RL (Pearson correlation test).(ABSTRACT TRUNCATED AT 250 WORDS)     

Occupational changes in manual tactile sensibility of the dentist

Summary The aim of this study was to find out if the use of vibrating tools (drill, ultrasonic scaler …) in dental practice has negative side effects on the manual tactile sensibility of the dentist. The sensory tests were performed on 50 subjects, who were allocated to three different groups according to their occupation and the length of their working experience. The first test group consisted of 20 dentists, who had more than 25 years of work experience. As a control group, 20 non‐dentists were recruited to obtain a similar age distribution as the former test group. A final group consisted of 10 dentists with more than 1 year of work experience. All subjects underwent three tests: light‐touch sensation test, two‐point discrimination test and thermal sensation test on the thumb and the index finger of the working and non‐working hands. Results showed significant differences, especially for the light‐touch sensation test. The study showed more specifically that the tactile sensibility of the working hand of the dentists with more than 25 years of work experience was significantly diminished with respect to the non‐working hand and to the working hand of non‐dentists. In the test group of young dentists, there was no noticeable reduction of manual tactile sensibility.     

Reliability of tactile perception using sharp and dull explorers in marginal opening identification

PURPOSE: The most direct method to clinically evaluate marginal openings in fixed partial dentures is to use manual explorers for tactile perception. The purpose of this in vitro study was to establish the reliability of different instruments for discovering marginal openings. MATERIALS AND METHODS: The materials used in this study included a dull stylet and a sharp-tipped explorer as well as a metal cylinder surface featuring 9 "V"-shaped circumferential grooves ranging in size from 20 to 165 microns. A group of 42 subjects were asked to discover the grooves using both instruments. RESULTS: The data revealed high reliability in the use of the sharp-tipped explorer. With this instrument, a defect of 36 microns could be perceived by 95% of the subjects. The dull, worn instrument gave significantly inferior results (P < 0.05). CONCLUSION: Using a sharp-tipped explorer on a smooth metal surface, tactile perception is a reliable means of detecting open margin defects up to 36 microns wide. As has been suggested in previous studies, the difficulty seems to be not in defect detection but in the evaluation of the clinical acceptability once it is detected.     

Tactile sensibility of single-tooth implants and natural teeth

AIM: The purpose of this randomized split-mouth clinical trial was to determine the active tactile sensibility between single-tooth implants and opposing natural teeth and to compare it with the tactile sensibility of pairs of natural teeth on the contralateral side in the same mouth (intraindividual comparison). MATERIAL AND METHODS: The hypothesis was that the active tactile sensibilities of the implant side and control side are equivalent. Sixty two subjects (n=36 from Bonn, n=26 from Bern) with single-tooth implants (22 anterior and 40 posterior dental implants) were asked to bite on narrow copper foil strips varying in thickness (5-200 microm) and to decide whether or not they were able to identify a foreign body between their teeth. Active tactile sensibility was defined as the 50% threshold of correct answers estimated by means of the Weibull distribution. RESULTS: The results obtained for the interocclusal perception sensibility differed between subjects far more than they differed between natural teeth and implants in the same individual [implant/natural tooth: 16.7+/-11.3 microm (0.6-53.1 microm); natural tooth/natural tooth: 14.3+/-10.6 microm (0.5-68.2 microm)]. The intraindividual differences only amounted to a mean value of 2.4+/-9.4 microm (-15.1 to 27.5 microm). The result of our statistical calculations showed that the active tactile sensibility of single-tooth implants, both in the anterior and posterior region of the mouth, in combination with a natural opposing tooth is similar to that of pairs of opposing natural teeth (double t-test, equivalence margin: +/-8 microm, P<0.001, power >80%). Hence, the implants could be integrated in the stomatognathic control circuit.     

Changes in passive tactile sensibility associated with dental implants following their placement

PURPOSE: This study investigated the changes that might occur in passive tactile sensibility during a period of 3 months following Implant placement in a group of edentulous subjects treated with dental implants. The effect of changing the velocity of force application on passive tactile sensibility was also investigated. MATERIALS AND METHODS: Five edentulous subjects who had been treated (as a part of an immediate loading study) with 2 or more Nobel Biocare dental implants in the anterior mandible were studied. Pushing forces were applied directly and perpendicular to the long axes of the abutments until the subjects felt the first sensation of pressure, using a computer-controlled, custom-made device. The force was measured with an integral transducer. The applied force had a ramped staircase pattern, which was used at 2 different tip velocities. The measurements were taken on 4 occasions: 1, 2, 4, and 12 weeks after fitting the abutments. RESULTS: Statistical analysis, using multilevel modeling, demonstrated that there was a significant decrease In the tactile threshold over successive weeks following implant placement. It also demonstrated that high velocity exhibited a higher threshold than low velocity. DISCUSSION AND CONCLUSION: It could be concluded that there was a significant increase In passive tactile sensibility during the healing phase following implant placement.     

Distributions of symmetric and asymmetric patterns of caries attack in human permanent mandibular incisor teeth: Genetic implications

Data were analysed from the records of dental surgeons practising in three areas: The North-east of England, Gloucestershire in the South of England, and Belfast in Northern Ireland. Studies were made of the distribution of caries experience among the mesial and distal surfaces of all four mandibular incisor teeth, in persons aged 15 yr and above. Some 63 patterns of caries experience were considered, ranging from the involvement of a single surface, up to all eight mesial and distal surfaces. Certain patterns were therefore symmetric with respect to the median plane and others asymmetric. Relative frequencies were found to have similar characteristics, in each community. Distributions of caries experience among the mesial and distal surfaces were found to be highly non-random. The data support the hypothesis that the site-specificity of dental caries in these surfaces is determined by complex genetic factors.     

Passive tactile sensibility in edentulous subjects treated with dental implants: a pilot study

STATEMENT OF PROBLEM: Edentulous patients treated with implant-supported prostheses have shown increased passive tactile sensibility compared with those using conventional complete dentures. This is thought to be due to the close mechanical coupling between the implant and bone via the osseointegrated interface, yet the phenomenon has received little attention. PURPOSE: The purpose of this study was to measure passive tactile sensibility in a group of edentulous subjects treated with dental implants, and to relate the measured sensibility to a range of factors thought to be of possible relevance, namely, patient age, gender, time since implant placement, implant length, and implant separation.MATERIAL AND METHODS: Twenty edentulous subjects successfully treated with 2 or more Nobel Biocare dental implants in the anterior mandible were studied. The inclusion criteria were : (1) age of less than 50 years, (2) a period of at least 12 months since implant placement, (3) implant length of at least 10 mm and of standard diameter (excluding narrow and wide platform designs), and (4) implant separation of at least 18 mm. Using a computer-controlled custom-made device, pushing forces (2.1, 2.4, 2.7, and 3.0 N/s) were applied directly and perpendicular to the long axes of the implant abutments until the subjects felt the first sensation of pressure. The magnitude of these forces was measured with an integral transducer. The applied force had a ramped staircase pattern, and force application rates were varied between 2.1 and 3.0 N/s. Multilevel modeling was used to analyze the collected data (alpha=.05). RESULTS: The threshold values of passive tactile sensibility ranged between 3.1 and 15.7 N (mean 10.9; SD 3.9). Analysis failed to show any significant association between passive tactile sensibility and the variables studied. CONCLUSION: Within the limitations of this study, which included a small sample size, no relationship was found between passive tactile sensibility associated with long-standing implants and any of the variables studied (age, gender, time since implant placement, implant length, and implant separation).     

Studies on adaptation to complete dentures. Part II: Oral stereognosis and tactile sensibility

summary High oral perception is thought to contribute to poor adaptation to new dentures. The aim of this study was to evaluate the oral stereognosis and tactile sensibility in edentate subjects and relate these to patient age and capability of adaptation to new prostheses. A total of 67 patients were provided with new complete dentures 2-3 weeks before the experiment. In 54 subjects, the oral stereognosis was evaluated by 12 different test-pieces, which were placed unseen on the tongue and had to be recognized. In 38 patients, the oral tactile sensibility was determined in the premolar area using copper foils. The capability of adaptation was evaluated by a questionnaire.
Denture retention was assessed by clinical examination. The number of correctly identified test-pieces and the average identification time were related to the age, but no relation was found to patients'capability of adaptation. The tactile sensibility was found to be impaired with age and diminished capability of adaptation. Both adaptation and oral tactile sensibility were significantly lower in subjects with poor lower-denture retention. In conclusion, the results cannot support a relationship between high oral stereognosis and adaptation problems. However, good denture retention facilitates the adaptation process.     

天然牙触觉阈限的测量及临床意义

目的 检测天然牙6个正交方向的被动触觉阈限,分析其影响因素,以指导临床个性化调(牙合).方法 利用牙齿触觉功能数字测试系统,测试20名健康受试者(平均年龄25岁,男女各10名)的218颗天然牙(上下颌中切牙至第一磨牙)的6个正交方向(即唇或颊、舌、近中、远中4个水平方向,根方和冠方2个轴向)的被动触觉阈限,利用多水平模型(multilevel modeling,MLM)分析被动触觉阈限的影响因素.结果 前牙、前磨牙和磨牙被动触觉阈限的中位数(四分位数间距)分别为16(18)、38(57)和105(115)mN,MLM分析显示,受试者间天然牙被动触觉阈限的个体差异明显(P＜0.05),受牙列分区、性别和受力方向3个因素的影响(P＜0.01),其影响作用的大小依次递减.结论 天然牙具有灵敏的触觉功能,被动触觉阈限能达到10 mN的水平,被动触觉阈限存在个体差异,受牙列分区、性别和受力方向的影响.     

导弓式可摘矫治器矫治乳前牙反机制的探讨

目的探讨导弓式可摘矫治器矫治乳前牙反的机制。方法 37例3.5～5.0岁乳前牙反患者,随机分为2组,一组使用导弓式可摘矫治器,18例,另一组使用垫式可摘矫治器,19例。结果导弓式可摘矫治器戴用组反纠正快于垫矫治器组,经t检验P<0.05;导弓式可摘矫治器组除上前牙唇倾,下前牙舌倾、下颌后移较垫式可摘矫治器组明显。结论导弓式可摘矫治器矫治乳前牙反的机制是推上前牙唇倾、引导下前牙舌倾,荡下颌向后,缩短了治疗时间。     

Threshold of tactile sensitivity perceived with dental endosseous implants and natural teeth

The aim of this study was to determine the threshold of tactile perception of endosseous dental implants and to assess the relative difference of that threshold between implants and teeth. Twenty‐two subjects with implants of the ITI® Dental Implant System were included in the study. All implants served as abutments for single tooth crowns and had been in function for a minimum of 1 year. A strain gauge glued to the shaft of an amalgam plugger served as a force sensor. It transformed the elastic deformation exerted onto the shaft into an electronic signal for recording. By use of the amalgam plugger, a continuously increasing force was exercised on the implants or teeth until the first sensation of touch was indicated by the patient. Statistical analysis revealed threshold values for the implants ranging from 13.2 to 189.4g (1g=0.0lN)(mean 100.6; SD 47.7), while a range of 1.2 to 26.2g (mean 11.5; SD 11.5) was found for control teeth. Thus, the mean threshold values for implants were 8.75 times higher than for teeth. This difference was highly statistically significant. A general linear models procedure was applied to determine the influence of patient age, jaw, implant position and the threshold values of teeth on the measurements obtained for implants. Only gender and the threshold values for contralateral teeth had a significant influence. These 2 parameters together explained 27% of the variability in threshold measurements. It is concluded that a more than 8‐fold higher threshold value for tactile perception exists for implants compared with teeth.     

A tactile method for canal length determination in teeth with open apices

Aim  To present a tactile method for working length determination in teeth with open apices and to determine its accuracy and repeatability.
Methodology  Ninety teeth with 129 root canals were prepared to create open apices. The correct working length (CWL) for each canal was determined by introducing a file into the root canal until it was visible at the apex. Consequently, the tactile working length (TWL) was determined by the 'Tactile Method' using a K-file that was bent at the tip. Two operators repeated the measurement once in each root canal. The accuracy of the TWL was determined by comparing the TWL with the CWL. The mean of the absolute differences and the corresponding 99% confidence interval (CI) were calculated. Both the repeatability and inter-operator agreement of the tactile method were determined by performing paired analysis of the differences between repeated measurements and the two operators.
Results  Overall, 97% (CI: 91–99) of the TWL were within 0.5 mm from the CWL, the mean of absolute differences was 0.1 mm (CI: 0.1–0.2). The maximum difference between repeated measurements was 0.2 mm and between the two operators was 0.6 mm.
Conclusions  The tactile method may provide an accurate determination of canal length in teeth with open apices.     

The ability of pulp sensibility tests to evaluate the pulp status in primary teeth

BACKGROUND. Accurate determination of the pulp status is the most important part of conservative pulp therapy. AIM. The aim of this study was to assess the ability of thermal and electrical pulp tests to assess the pulp status in primary teeth. DESIGN. Seventy-eight primary molar teeth in 36 children were investigated. Fifty-six teeth had unknown pulp status in need of endodontic treatment, and 22 were intact teeth with no signs of pulp disease. Cold, hot and electrical pulp testing (EPT) were performed on each tooth. The gold standard was established by direct inspection of the pulp after an access cavity had been made. The sensitivity, specificity, positive and negative predictive values for each test and different sequential combinations of pulp testing were calculated. Sequential combination test analysis was used for data analysis. RESULTS. The highest accuracy was found for EPT, followed by heat and cold tests. No significant difference was found between the accuracy of EPT and the heat test (P-values > 0.05); however, the accuracy of EPT was significantly higher than that of the cold test (P-value< 0.05). CONCLUSION. Based on this study, EPT can be used as a reliable test for diagnosing the pulp status in primary teeth.     

Pulp sensibility and vitality tests for diagnosing pulpal health in permanent teeth: a critical review

The aim of this review was to critically appraise the literature related to pulp vitality and sensibility testing in order to determine the diagnostic accuracy of pulp tests with reference to a gold standard or control group. Implications of the results for research and clinical practice are also explored. The MEDLINE (Ovid), MEDLINE (PubMed), Embase and Cochrane databases were searched for English‐language clinical trials in humans in which in vivo studies were designed to evaluate or compare the accuracy of selected pulp sensibility and pulp vitality tests in determining the state of pulpal health in permanent teeth. Studies were included only if the results were compared to a control group or to a valid gold or reference standard. Eight studies were identified. Shortcomings in research design were found to influence the findings. The limited number of studies investigating pulp vitality tests was insufficient to answer the research question. It was concluded from this critical appraisal of the literature that laser Doppler flowmetry appeared to be the most accurate method for diagnosing the state of pulpal health and came closest to serving as a gold standard. Pulp vitality tests proved superior to pulp sensibility tests for early and accurate assessments of the pulpal health of traumatized teeth. When accurately used and interpreted, pulp sensibility tests provide valuable diagnostic information, particularly when an electric pulp test is used in combination with either CO₂ snow or Endo‐Ice.