Cervical wear and occlusal wear from a periodontal perspective

Summary The aim of this study was to investigate whether cervical wear was associated with occlusal wear and clinical periodontal parameters in relatively older adults. A total of 30 patients, with multiple non‐carious cervical lesions (NCCLs) and without a disease or condition that could cause heavy tooth wear, were included in the study. The periodontal parameters including plaque index, probing pocket depth, gingival recession (GR) and tooth mobility were obtained from 641 teeth of which 475 (74·1%) displayed NCCLs. The levels of cervical wear and occlusal wear were determined according to a tooth wear index. Premolars were more likely to develop cervical wear than canines, molars and incisors. Cervical wear was significantly associated with less plaque accumulation and the presence of shallow pockets. The teeth with advanced GR and without increased mobility were 2·583 and 1·715 times more likely to develop deeper cervical lesions, respectively. Age and the level of occlusal wear were not linked to the bucco‐lingual depth of cervical wear. In conclusion, the significant association of advanced cervical wear with the relatively healthy periodontal status suggested the role of abrasion and its possible combined action with erosion in the aetiology of NCCLs. The rate of GR and the lack of tooth mobility could constitute predisposing factors for the progression of cervical wear because the exposed root surfaces could be more susceptible to abrasion and/or erosion, and the non‐mobile teeth resisting strongly against frictional forces, thus abrasive effects, could possibly develop cervical wear.     

Correlations of noncarious cervical lesions and occlusal factors determined by using pressure-detecting sheet

OBJECTIVES: The purpose of this clinical study was to examine the relationships of v-shaped noncarious cervical lesion (NCCL) formation with occlusal factors. METHODS: A total of 159 male self-defense force officials with a mean age of 36.2 years participated in this study. All present teeth were examined for the presence and type of NCCL using the Tooth Wear Index (TWI). The subjects were then interviewed about bruxing and toothbrushing habit. Finally, occlusal force, occlusal contact area and average pressure were measured using a pressure-detecting sheet. Subject-level logistic regression was carried out to assess the associations of factors with presence of v-shaped NCCL teeth. Subjects without v-shaped NCCL were designated as control subjects. RESULTS: Totally, 4518 teeth were examined. Seventy-eight subjects (49.1%) had one or more teeth with typical v-shaped NCCL (259 teeth). The number of teeth with v-shaped NCCL of grade 2 (defect less than 1mm in depth) was 195 (4.3%), and the number of teeth with v-shaped NCCL of grade 3 (defect 1-2mm in depth) was 54 (1.2%). The prevalence of teeth with v-shaped NCCL was significantly higher in the maxilla than in the mandible. Most of the NCCL teeth were premolars. There was no significant difference between teeth with NCCL on the right side and those on the left side. Subject-level logistic regression analysis revealed that age (OR=1.11), toothbrushing pressure (400g, OR=2.43) and occlusal contact area (>23.0mm(2), OR=4.15) were associated with the presence of NCCL teeth. CONCLUSIONS: It is concluded that aging, toothbrushing pressure and occlusal contact area are associated with the presence of NCCLs.     

A cross‐sectional study: non‐carious cervical lesions,cervical dentine hypersensitivity and related risk factors

The present survey aims to study the prevalence and clinical characteristics of non‐carious cervical lesions (NCCLs) and cervical dentine hypersensitivity (CDH), as well as their possible risk factors in a general population in China. A total of 1023 subjects were included in the present study. Each subject completed a structured interview, and all teeth of each subject were examined by a practitioner to determine NCCLs and CDH. Teeth with NCCLs and CDH were diagnosed according to the tooth wear index and by a blast of air from a triple syringe, respectively. Binary logistic regression was completed by analysing the association of risk factors with the occurrence of NCCLs and CDH. Loss of attachment (LOA) and gingival recession (GR) of teeth with NCCLs and/or CDH were measured using Williams periodontal probe. The diagnoses of NCCLs and CDH established following a clinical assessment yielded an overall prevalence of 61·7% and 27·1%, respectively. The 60–69 age group had the greatest proportion of subjects with NCCLs or CDH. The pre‐molars were the most commonly affected teeth type with NCCLs or CDH. The proportion of teeth with CDH associated with NCCLs increased significantly with age, but the proportion of teeth with CDH only associated with LOA or GR decreased slowly with age. The single variables and interactive effects of variables associated with the occurrence of NCCLs include the following: age group, occupation type, method of toothbrushing, frequency and method of toothbrushing, and method of toothbrushing and duration of a toothbrush used. Gender, age group, occupation type and frequency of toothbrushing were associated with the occurrence of CDH. The current study presented higher prevalence of NCCLs and CDH in a general Chinese population. Both diseases were closely associated with age and periodontal status. The portion of the population with NCCLs or CDH had different risk factors.     

Comparison of pattern of failure of resin composite restorations in non-carious cervical lesions with and without occlusal wear facets

Objectives

Many studies have reported the clinical problems associated with resin composite restorations in NCCLs. None has compared these clinical problems in NCCLs with and without occlusal wear facets. The present study sets out to determine the proportion of NCCLs that presents occlusal wear facets, and to compare the failure pattern of resin composite restorations in NCCLs with and without occlusal wear facets.

Methods

Teeth with NCCLs were classified into two groups, those with and without occlusal wear facets. Both groups were restored using micro hybrid resin composite. The restorations were evaluated at the end of 2 years concerning post-operative sensitivity, retention, marginal integrity, marginal discolouration, wear, and secondary caries, using the USPHS criteria. Statistical analysis compared the ratings of each criterion between the two groups using Pearson's χ² or Fisher's exact test.

Results

About one-third (33.8%) of teeth with NCCLs presented with occlusal wear facets, more NCCLs with occlusal wear facets in mandibular teeth (44.7%) than maxillary teeth (24.5%). Retention rate of composite resin restorations in NCCLs with and without occlusal wear facets was 63.9% and 74.4% respectively at the end of 2 years. More marginal discolouration and defects were observed in restorations in NCCLs with occlusal wear facets, the differences were not statistically significant (p > 0.05).

Conclusions

The decline in ratings of marginal discolouration and defects, and the lower retention rate of restorations in NCCLs with occlusal wear facets may support the role of occlusal stress and tooth flexure as a cause of failure of restorations in NCCLs.

Clinical significance

The ability to distinguish between stress induced lesions (with occlusal wear facets) and other cervical lesions will have important ramifications for the success of their restorations because they are not subjected to the same physical forces that are responsible for the deterioration of the restoration.     

The prevalence and severity of non-carious cervical lesions in a group of patients attending a university hospital in Trinidad

Non-carious cervical lesions (NCCLs) are often encountered in clinical practice and their aetiology attributed to toothbrush abrasion, erosion and tooth flexure. This paper aims to determine the prevalence and severity of NCCLs in a sample of patients attending a university clinic in Trinidad and to investigate the relationship with medical and dental histories, oral hygiene practices, dietary habits and occlusion. Data were collected via a questionnaire and clinical examination. Odds ratios were used to determine the association of the presence of lesions and the factors examined. One hundred and fifty-six patients with a mean age of 40.6 years were examined of whom 62.2% had one or more NCCLs. Forty five per cent of the lesions were sensitive to compressed air. Younger age groups had a significantly lower correlation with the presence of NCCLs than older age groups. Other significant factors included patients who reported heartburn, gastric reflux, headaches, bruxism, sensitive teeth and swimming or had a history of broken restorations in the last year. There was also significant correlation of NCCLs in patients who brushed more than once a day or used a medium or hard toothbrush. Patients with vegetarian diets and those who reported consuming citrus fruits, soft drinks, alcohol, yoghurt and vitamin C drinks were associated with the presence of lesions. Significant associations were also found in patients with group function, faceting, clicking joints or those who wore occlusal splints.     

Non‐carious cervical lesions (NCCLs) in a random sampling community population and the association of NCCLs with occlusive wear

This study investigated the prevalence, risk factors and association of occlusive wear with non‐carious cervical lesions (NCCLs) in the general Chinese population. A total of 1320 subjects were recruited, and multistage and random sampling methods of survey spots were performed. All age groups comprised similar numbers of participants and equal numbers of males and females. Each subject completed a structured interview, and all teeth of each subject were examined by a practitioner to determine NCCLs and occlusive wear. Binary logistic regression was conducted by analysing the association of risk factors with the occurrence of NCCLs. Bivariate correlation analysis was performed by determining the association of NCCLs dimension or depth with the range of occlusive wear facets. Clinical assessment showed that the overall prevalence of subjects diagnosed with NCCLs was 63%. The proportion of subjects or teeth with NCCLs significantly increased with age. Pre‐molars were the most commonly affected teeth. Single variables and interactive effects of variables associated with the occurrence of NCCLs include the following: age group, intensity of toothbrushing, frequency of fresh fruit consumption and interactive effect between intensity of toothbrushing and frequency of fresh fruit consumption. A weak positive correlation of the grading index was found between NCCLs dimension, size or depth and range of occlusive wear facets. This study reported the higher prevalence of NCCLs in the general Chinese population. Implementation of a combined strategy to reduce risk factors of NCCLs could be more effective than individual techniques; meanwhile, the occurrence of NCCL could be related to the wear degree of occlusive defects in the population studied.     

The prevalence and morphological types of non-carious cervical lesions (NCCL) in a contemporary sample of people

Non-carious cervical lesions (NCCLs) were examined in 6541 extracted human teeth and classified based on the morphology of the lesions. As a result, NCCLs were found on 38.7% of teeth (41.6% on maxillary teeth and 36.0% on mandibular teeth), and were most frequent on canines and first premolars. According to the new method of classification, the morphology of NCCLs was classified both by the surface contour (SC) and by the cross-sectional contour (CC). Three types of NCCLs appeared to be dominant. The causes of these NCCLs were discussed based on their morphologies, positions where these NCCLs were frequently found, and the results of previous studies. NCCLs with a horizontal oval SC and a round CC (Type I), which were frequent on the labial surfaces of maxillary canines and buccal surfaces of maxillary first premolars, may be associated with wear by friction and chemical degradation. NCCLs with a vertical oval SC and a round CC (Type II), which were frequent on the lingual surfaces of mandibular incisors and canines, might be mainly related to chemical degradation. NCCLs with a horizontal oval SC and a wedge shape CC (Type III), which were extensively found on the buccal surfaces of maxillary premolars, had formed most probably due to wear by friction and microstructural loss by stress. This new method can classify the morphology of NCCLs more precisely and deduce the mechanisms of the formation of NCCLs more clearly than former methods.     

Noncarious cervical lesions: Morphology and progression,prevalence, etiology,pathophysiology, and clinical guidelines for restoration

Purpose

To synthesize the literature regarding noncarious cervical lesions (NCCLs) and propose clinical guidelines when lesion restoration is indicated.

Material and methods

A PubMed search was performed related to NCCL morphology, progression, prevalence, etiology, pathophysiology, and restoration.

Results

NCCLs form as either rounded (saucerlike) depressions with smooth, featureless surfaces that progress mainly in height or as V-shaped indentations that increase in both height and depth. Prevalence ranges from less than 10% to over 90% and increases with age. Common locations are the facial surfaces of maxillary premolars. They have a multifactorial etiology due to personal habits such as excessive horizontal toothbrushing and consumption of acidic foods and drinks. Occlusal factors have been identified as contributing to the prevalence of NCCLs in some studies, whereas other studies indicate there is no relationship. The concept of abfraction has been proposed whereby mechanical stress from occlusal loading plays a role in the development and progression of NCCLs with publications supporting the concept and others indicating it lacks the required clinical documentation. Regardless of the development mechanism, demineralization occurs and they are one of the most common demineralization diseases in the body. Treatment should be managed conservatively through preventive intervention with restorative treatment delayed until it becomes necessary due to factors such as lesion progression, impact on patient's quality of life, sensitivity, poor esthetics, and food collection may necessitate restoration. Composite resins are commonly used to restore NCCLs although other materials such as glass ionomer and resin-modified glass ionomer are also used. Sclerotic dentin does not etch like normal dentin and therefore it has been recommended to texture the dentin surface with a fine rotary diamond instrument to improve restoration retention. Some clinicians use mechanical retention to increase retention. Beveling of enamel is used to increase the bonding area and retention as well as enhance the esthetic result by gradually creating a color change between the restoration and tooth. Both multistep and single-step adhesives have been used. Dentin etching should be increased to 30 seconds due to the sclerotic dentin with the adhesive agent applied using a light scrubbing motion for 20 seconds but without excessive force that induces substantial bending of a disposable applicator. Both flowable and sculptable composite resins have been successfully used with some clinicians applying and polymerizing a layer of flowable composite resin and then adding an external layer of sculptable composite resin to provide enhanced resistance to wear. When caries is present, silver diamine fluoride has been used to arrest the caries rather than restore the lesion.

Conclusions

Noncarious cervical lesions (NCCLs) form as smooth saucerlike depressions or as V-shaped notches. Prevalence values as high as 90% and as low as 10% have been reported due to habits such as excessive toothbrushing and an acidic diet. Occlusal factors have been proposed as contributing to their presence but it remains controversial. Publications have both supported and challenged the concept of abfraction. They are one of the most common demineralization diseases in the body. Conservative treatment through prevention is recommended with restorative treatment delayed as long as possible. When treatment is needed, composite resins are commonly used with proposed restorative guidelines including texturing the sclerotic dentin, beveling the enamel, potential use of mechanical retention, 30 seconds of acid etching, and use of either multistep or single-step adhesives in conjunction with a light scrubbing motion for 20 seconds without excessive force placed on disposable applicators.     

Diet and dental erosion in young people in south-east Brazil

Background. The regular consumption of acidic foods and drinks may be associated with dental erosion, and soft drink consumption appears to be increasing both in developed and developing countries. Dentists are aware that an acidic diet can contribute to the development of erosion; however, there may be confusion within the profession concerning the general health message of eating five portions of fruits and vegetables each day. Objective. The aim of this study was to investigate associations between dental erosion and the consumption of acidic foods and beverages in schoolchildren in south-east Brazil. The objective was to gather information, by means of a dietary questionnaire, on frequency of intake and patterns of consumption of acidic foods and drinks in a group of schoolchildren. The hypothesis was that the experience of dental erosion among the study sample was associated with the frequency and pattern of consumption of soft drinks, fruit juices, fruits, and yogurt. Methods. A cross-sectional study was conducted in Três Corações, south-east Brazil. A sample of 458 schoolchildren, mean age 13.8 (SD 0.39) years, completed the study. Information about potential dietary risk factors for dental erosion was collected through a questionnaire survey completed by the schoolchildren. For the dental examinations, the subjects were examined for dental erosion in a school room. Associations between dental erosion and the variables under study were investigated through processes of bivariate and multivariate analyses. The statistical significance level was set at 5%. Results. Analysis of the questionnaire surveys showed that the frequency of consumption of sugared carbonated drinks was the only variable independently associated with the erosive process, with subjects who had a daily consumption of such drinks having a greater likelihood of having erosion (P = 0.015, odds ratio 1.752, 95% confidence interval 1.116–2.750). Conclusions. Of all tested factors in this sample of schoolchildren the consumption of sugared carbonated drinks is most associated with dental erosion.     

Effect of long-lasting clenching on dental occlusion

Durable clenching on a particular occlusal area may affect the masticatory muscle activity and induce transitional deformation of the dentoalveolar, mandibular and temporomandibular tissues. These effects may provide detectable alterations in the occlusal contact pattern. The aim of this study was to evaluate the subsequent effect of clenching on the number and location of occlusal contacts. This study was carried out on 16 volunteers with correct occlusion and sharply demarcated occlusal contact pattern. The patient closed to intercuspal position with maximal biting force and the occlusal contacts were revealed with a 12 microns thick occlusal foil. Then a gnathometer was placed between the upper and lower incisors and the mouth was closed for two minutes with about 50 N closing force. After that the occlusal contacts were evaluated again. Paired t-test was used to evaluate the data. Both before and after clenching the highest average number of contacts was recorded on the surface of first molars. They were followed in decreasing order by the second molars, second premolars, first premolars, and finally the canines. When the number of contacts was compared in tooth groups, the first molars and the second premolars had more contacts than the second molars and the first premolars. On the surfaces of molars more occlusal contacts were registered after clenching than before. Significant differences were found in case of the left second molar only. It was concluded that durable clenching on a particular occlusal area might change transitionally the distribution of occlusal contacts.     

Silent period and initial occlusal sliding time in patients with premature contacts

This study was designed to examine the relationship between frequency of silent period and initial occlusal sliding time. The subjects consisted of three volunteers with normal occlusal contacts and three patients with premature contacts. Electromyograms of the bilateral masseter muscles, initial occlusal contacts and jaw movements during the habitual tapping (20-25) were synchronously recorded and replayed using Takamatsu's technique. Results were as follows: 1. The frequency of silent period in the bilateral masseter muscles was 95-100% in subjects with normal occlusal contacts and 34-53% in patients with premature contacts. 2. The silent period latency in three normal subjects was 8.9 +/- 1.3 msec in the left masseter and 13.9 +/- 2.2 msec in the right masseter. The silent period latency in three patients with premature contacts was 12.4 +/- 2.6 msec in the left masseter and 13.9 +/- 8.2 msec in the right masseter. 3. The duration of silent period in three normal subjects was 12.4 +/- 2.6 msec in the left masseter and 11.1 +/- 3.7 msec in the right masseter. The duration of silent period in three patients with premature contacts was 9.1 +/- 1.7 msec in the left masseter and 11.1 +/- 5.6 msec in the right masseter. 4. Initial occlusal sliding time in three subjects with normal occlusal contacts was less than 30 msec, and 98% of all slidings lasted for less than 15 msec. Initial occlusal sliding times in patients with premature contacts were distributed between 6 and 80 msec (40%: 6 to 15 msec, 60%: greater than 15 to 80 msec).(ABSTRACT TRUNCATED AT 250 WORDS)     

侧方咬合运动中接触型及其分布特征

目的观察侧方咬合运动中接触点的分布特征,并对尖牙尖对尖颌位时的侧方型进行分类。方法利用T-ScanII咬合分析系统记录85名个别正常者侧方咬合运动过程中的接触信息,并进行统计分析。结果尖牙尖对尖颌位时的接触形式有六类:尖牙保护(44.1%)、组牙功能(20.6%)、工作侧多组前牙接触(2.9%)、仅工作侧第一前磨牙接触(8.8%)、工作侧前后牙同时存在接触(20.0%)、工作侧非工作侧同时存在接触(3.5%)。结论自然牙列侧方接触形式除尖牙保护与组牙功能外还存在其它一些型。     

Noncarious cervical lesions among a non-toothbrushing population with Hansen's disease (leprosy): initial findings.

OBJECTIVE: The purpose of this preliminary investigation was to examine the presence of noncarious cervical lesions (NCCLs) among a convenience sample of non-toothbrushing subjects with Hansen's disease (leprosy). METHOD AND MATERIALS: A cross-sectional sample of 102 non-toothbrushing subjects (20 to 77 years of age) was examined. The clinical parameter of interest for this study was the presence or absence of NCCLs and their probable etiology as it relates to the subjects' diet, occlusion, and use of medication. Subjects were examined clinically and interviewed according to study protocol. RESULTS: NCCLs were found in 48 subjects (47% of the studied sample). Widespread consumption of acidic foods and beverages acting as corrodents, signs of parafunction, and use of medication that causes xerostomia were also noted. Thus, all may be contributing factors in the etiology of NCCLs in this population. CONCLUSION: This preliminary report suggests that toothbrush/dentifrice abrasion was not a factor in the etiology of NCCLs in the population studied. The authors intend to expand their study among these non-toothbrushing     

Dentine hypersensitivity in a private practice patient population in Australia

Summary Although dentine hypersensitivity (DH) has been widely investigated, studies based on randomly selected general practice populations are scarce. This study aimed to examine the intra‐oral distribution of DH and its association with age, sex, symptoms, stimuli, pre‐disposing factors and management strategies in a private practice patient population in Australia. A randomly selected sample of 800 Australian private dental practice dentists was invited to participate in a questionnaire‐based survey. A log diary about the total number of patients seen during a typical week in practice and the details of patients with DH were recorded. The details included teeth and sites involved with DH and the age and sex of people affected, symptoms, stimuli, pre‐disposing factors and management strategies. The prevalence of DH was 9·1% among patients seen over the typical week with 2·3 teeth/person and 1·2 surfaces/tooth affected. Women (60·7%) were more affected than men (39·3%) whilst 30‐ to 49 ‐year‐olds (48·8%) were the most common among those affected. Premolars (36·5%) and buccal surfaces (54·8%), respectively, were the most commonly affected teeth and tooth sites. Although cold stimulation (80·1%) was the commonest stimulus, dietary acid was the only stimulus that was significantly associated with DH. Gingival recession and erosion emerged as significant pre‐disposing factors, whereas using desensitising toothpastes was the most important management strategy. The findings suggested that dietary acid, gingival recession and erosion were significantly associated with DH, while desensitising toothpastes was the key management strategy used for DH in this patient population.     

楔状缺损与咬合力关系的研究

目的 临床研究楔状缺损与He力的关系。方法 将123例患不同程度楔状缺损的中老年患者，按楔状缺损的程度分为无、轻、中、重度4组；使用电阻应变式咬合力计测量上颌尖牙、第一、二双尖牙、第一磨牙牙齿咬合力；用光He法测定上颌牙齿最高He接触强度。结果 楔状缺损患牙的咬合力低于无楔状缺损牙。上颌第一双尖牙的楔状缺损患牙的最高He接触强度高于未患牙、楔状缺损组中的第一磨牙和第一双澡牙相对于其邻牙的最高He接触强度增高。结论 He力与楔状缺损的发生有关。     

Raman spectroscopic study of noncarious cervical lesions

The surface of noncarious cervical lesions (NCCLs) consists of sclerosed dentin. This type of dentin may affect the ability of adhesive restorative materials to bond well to its surface, but little information exists on the chemical nature of this dentin surface and how it may be affected during acidic treatment. The inorganic part of normal dentin and dentin from NCCLs before and after acid conditioning with phosphoric acid or polyacrylic acid was investigated. Ten premolars with NCCLs and four human third molars (control) were used. Replicas of NCCLs were examined using scanning electron microscopy (SEM). Surfaces and longitudinal sections of four NCCLs and control dentin discs were analyzed using Raman spectroscopy. The discs and NCCLs were sectioned, and treated with 35% phosphoric acid or 20% polyacrylic acid/3% aluminum chloride, and Raman spectra obtained. The area under phosphate ν₁ of the dentin spectrum was computed to obtain a ratio with the area under the second-order spectrum of a silicon phonon comparative standard. Mean phosphate ν₁ and silicon phonon ratios from normal dentin and NCCLs were compared using a linear model with repeated measurements and Tukey’s pairwise tests. Mean ratios from different locations of the NCCLs were compared using one-way analysis of variance (ANOVA) and Tukey’s pairwise tests. SEM micrographs of NCCL surfaces showed variation from relatively smooth with no dentinal tubule openings to surfaces with occluded tubules. The mean phosphate ν₁ and silicon phonon ratios for NCCLs were higher than those of normal dentin in all treatment groups (P < 0.05). Ratios from the untreated specimens were higher than those of the polyacrylic acid-treated specimens, and those for the phosphoric acid-treated group were the lowest (P < 0.05). The ratios obtained for the surfaces of NCCLs were higher than those halfway towards the pulp, and those adjacent to the pulp were the lowest (P < 0.05).     

The effects of alcoholic beverages on composite wear.

OBJECTIVES: In vivo wear of composite restorative materials appears to be, in part, dependent on various patient factors. Specifically, consumption of alcoholic beverages has the potential for increasing the degradation rate. The hypothesis tested in this experiment was that composite wear is dependent on the type of alcohol-containing liquid the materials are exposed to during three-body abrasive wear. METHODS: To test this hypothesis, composite wear experiments were performed using the ACTA three-body wear machine. Abrasive slurries containing either beer, wine, 9 vol% ethanol or water were used during the wear experiments. The data were analyzed using ANOVA and Tukey's test. RESULTS: The wine and ethanol solutions caused significantly more wear compared to the beer and water. There was no significant differences in the wear between the wine and 9 vol% ethanol groups, and the beer groups were not significantly different from the water groups. Furthermore, there was no significant interaction between the composite type and the various abrasive slurries. SIGNIFICANCE: These results indicate that alcoholic beverages with at least 9 vol% ethanol will increase the wear of composite. The observed increase in wear of composite by the wine was caused primarily by the ethanol content of the wine. Other constituents in the wine do not appear to have an effect on composite wear. The ethanol effect was consistent among different composite types.     

Occlusal tooth wear in Chinese adults with shortened dental arches

To assess associations between occlusal tooth wear and shortened dental arches (SDA) in Chinese 40 years and older subjects. From a sample of 1462 urban and rural adults, those presenting with SDA (n = 150) were compared with a control group of 65 randomly selected subjects with complete dentitions (CDA). Occlusal wear was assessed using a modified Smith and Knight index – the occlusal tooth wear index (OWTI) – and analysed using multivariate (logistic) regression. There was no significant effect from SDA on severe occlusal wear (OTWI score 3 or 4: OR = 2·016; 95% CI = 0·960–4·231; P = 0·064). Higher age was associated with severe occlusal wear (P values ≤0·007) and with higher mean OTWI scores; urban had less often severe occlusal wear than rural residents (OR = 0·519; P = 0·008). Higher mean OTWI scores were associated with rural residents, except for anterior teeth. Females had lower mean OTWI score for anterior teeth (effect = ?0·153; P = 0·030). Premolars in SDA had higher mean OTWI scores compared with those in CDA (effect = +0·213; P = 0·006). In SDA, more posterior occluding pairs (POPs) were associated with lower mean OTWI sores for anterior teeth (effect: ?0·158; P = 0·008) and higher scores for molars (effect: +0·249, P = 0·003). Subjects with SDA or CDA presented comparable occlusal wear, but premolars in SDA tend to have higher probability for having occlusal wear. Fewer numbers of POPs were associated with more wear in anterior teeth.     

In vivo horizontal forces on implants depending on the type of occlusion

Minimizing horizontal forces on implants is one of the important aims of an occlusal design. Therefore, several proposals have been made in literature, e.g. flat cuspal slopes or narrow occlusal surfaces. Our aim was to test how these occlusal designs would influence horizontal forces. Ten healthy subjects with unilateral partially edentulous arches were provided with fixed partial dentures (FPD) on two ITI‐implants. The opposing jaw was fully dentate. After an adaptation of 6 month measurement setups with a measuring FPD were put into the mouth. The sensoring device, which consisted of two abutments equipped with strain gauges, evaluated the forces in three dimensions. For each person three FPDs were made with a different design of the occlusal surface. The first FPD exhibited cusps with steep slopes (S), the second showed flat cusps (F) and the third had a narrow occlusal surface (N). The peak forces of the chewing cycles of each patient were evaluated. While chewing wine gum the average values of the vertical forces of the three different FPDs showed no significant differences and amounted to between 253·8 N (s.d. 85·7 N) and 273·9 N (s.d. 63·7 N). With the first FPD (S) mean horizontal forces of 47·9 N (s.d. 34·8 N) were found whereas with the flat surface an average force of 47·4 N (s.d. 37·1 N) was measured. The narrow occlusal surface was associated with an average reduction of the horizontal forces of about 50·9% to a mean value of 24·4 N (s.d. 10·6 N) (P < 0·005). The inclination of occlusal slopes did neither affect vertical nor horizontal forces significantly. However, narrowing of the occlusal surface in the oro‐vestibular direction by 30% showed a significant reduction of the lateral forces exerted on the implants by more than 50%. A reduced oro‐vestibular width of the occlusal surface is recommended especially for diameter‐reduced implants, in case of an unfavourable relationship between implant and crown length or for implants that are strongly inclined to the occlusal plane.     

The prevalence of dentine hypersensitivity in the general population in China

Summary Dentine hypersensitivity (DH) is a common condition that is frequently encountered in dental practice. The aim of this multi‐centre and cross‐sectional study was to establish the prevalence of DH in the general population in China. A total of 6843 subjects were questioned and examined using a triple syringe with a blast of cold air to confirm the diagnosis of DH. The sensitive surface, loss of attachment and gingival recession of sensitive teeth were measured and recorded. Of the 2932 subjects reporting hypersensitive symptoms, 2363 subjects were further diagnosed as DH, giving an overall prevalence of 34·5%. The greatest number of subjects with DH were within the 50–59 years age group (P < 0·01). The most commonly affected teeth were the premolars and the most provoking factor was the presence of a cold stimulus. The prevalence of DH in a representative sample of the general population in China was 34·5%, indicating that DH is a common oral problem. Therefore, the recognition of the condition and subsequent treatment by the dentist is therefore essential if the condition is to be managed correctly.