Relationship between orthodontic anomalies and masticatory function in adults

Insights into the digestive processes of normal and high-amylose rice using realistic boluses formed in the bio-inspired oral mastication simulator (iBOMS-III)

Mastication is essential for preparing food bolus for swallowing and digestion. This study employed the bio-inspired oral simulator (iBOMS-III) to investigate the effects of mastication on physical properties and starch hydrolysis of normal rice (NR) and high-amylose rice (HR), while validating its results through comparison with in vivo data from human subjects. The median particle size (d50) of NR (1.266, 0.931, 0.776 mm) and HR (1.32, 1.04, 0.928 mm) boluses from iBOMS-III at 12, 14, and 20 cycles closely matched human boluses at the swallowing threshold, particularly after 14 and 20 cycles. Starch hydrolysis in NR increased from 76.6 % to 91.3 %, while HR hydrolysis ranged from 63.4 % to 73.3 %. Boluses from iBOMS-III with 14 and 20 cycles showed starch digestibility consistent with in vivo data (84.2 % for NR, 71.3 % for HR). These findings demonstrate that iBOMS-III effectively replicated human mastication behaviors, producing boluses comparable to those observed in vivo.

Does malocclusion affect ingestion: a systematic review

OBJECTIVES

The multifactorial aspect of malocclusions and their consequences on ingestion function is rarely described in the literature. The aims of this review are (i) to investigate the relationship between oral ingestion and malocclusion and (ii) to gather malocclusion tools that could help screen subjects at risk of malocclusion-related ingestion disorders.

MATERIAL AND METHODS

A systematic review was performed following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis Protocol (PRISMA-P 2015) guidelines. The analysis methods and inclusion criteria have been documented in a protocol published in the Prospective International Register of Systematic Reviews (PROSPERO) under the registration number CRD42023395840. The bibliographic search involved the PubMed®, Cochrane and PROSPERO databases.

RESULTS

A total of 29 articles published between 2007 and 2023 were retained by the search criteria for the qualitative synthesis. Twenty of the studies found that the severity of malocclusion has a negative impact on oral ingestion. This review highlights that malocclusion and ingestion impairments are associated but it is not possible to determine causality due to the observational approach of many of the studies.

CONCLUSION

Malocclusion has a negative impact on ingestion function. During orthodontic consultations, particular interest should be directed towards chewing, biting, and swallowing disorders, which can affect patients' nutritional status. This review offers arguments for designing further studies assessing the extent to which malocclusions may affect nutritional status.

CLINICAL RELEVANCE

Orthodontic treatment should focus on improving patients' ingestion.

Masticatory performance in patients with jaw muscle pain: A case control study

Introduction

Masticatory function is often impaired in patients with painful temporomandibular disorders (TMD) therefore more detailed studies on comminution and mixing ability are warranted in well-defined TMD patients with chronic myalgia. Moreover, there is a need to explore the correlation between any changes in perceived pain or fatigue in such patients and the masticatory function.

Materials and methods

Self-assessments using questionnaires regarding pain, oral health, jaw function, masticatory ability, fear of movement and psychosocial signs were answered by all the participants. A series of chewing tasks involving viscoelastic food and two-colored gum was performed. Optical imaging and analyzing was conducted. Bite force as well as characteristics of pain and fatigue were assessed.

Results

In patients, the fragmented soft candy particles were less in number and had larger median of area and minimum Feret's diameter after standardized chewing compared to healthy individuals (P = 0.02). Surprisingly, the two-colored Hue-Check gum was less mixed by the healthy controls since they displayed a greater variance of the hue (P = 0.04). There were significant differences between the patients and the healthy controls in the self-assessed masticatory ability mainly regarding pain-related variables.

Conclusions

Objectively, TMD patients with chronic myalgia exhibited an impaired masticatory performance with less efficiency in comminuting soft viscoelastic food compared to the pain-free healthy control group. There was an agreement between the patients' self-assessed masticatory ability and the efficiency of their masticatory function.

The consequences of living with a severe malocclusion: A review of the literature

AIM

To facilitate the orthognathic shared decision-making process by identifying and applying existing research evidence to establish the potential consequences of living with a severe malocclusion.

METHODS

A comprehensive narrative literature review was conducted to explore the potential complications of severe malocclusion. A systematic electronic literature search of four databases combined with supplementary hand searching identified 1024 articles of interest. A total of 799 articles were included in the narrative literature review, which was divided into 10 themes: Oral Health Related Quality Of Life; Temporomandibular Joint Dysfunction; Masticatory Limitation; Sleep Apnoea; Traumatic Dental Injury; Tooth Surface Loss; Change Over Time; Periodontal Injury; Restorative Difficulty; and Functional Shift and Dual Bite. A deductive approach was used to draw conclusions from the evidence available within each theme.

RESULTS

The narrative literature review established 27 conclusions, indicating that those living with a severe malocclusion may be predisposed to a range of potential consequences. With the exception of Oral Health Related Quality Of Life, which is poorer in adults with severe malocclusion than those with normal occlusions, and the risk of Traumatic Dental Injury, which increases when the overjet is >5 mm in the permanent and 3 mm in the primary dentition, the evidence supporting the remaining conclusions was found to be of low to moderate quality and at high risk of bias.

CONCLUSION

This article summarises the findings of a comprehensive narrative literature review in which all of the relevant research evidence within a substantive investigative area is established and evaluated. Notwithstanding limitations regarding the quality of the available evidence; when combined with clinical expertise and an awareness of individual patient preferences, the conclusions presented may facilitate the orthognathic shared decision-making process and furthermore, may guide the development of the high-quality longitudinal research required to validate them.

Gastric emptying rate of a solid meal in patients with anterior open bite malocclusion: A preliminary study

Objectives:

The objective of the study was to investigate the relationship between anterior open bite (AOB) malocclusion and digestion by evaluating mastication and gastric emptying (GE) of a solid meal.

Material and Methods:

We recruited 26 female participants and divided them into two groups according to their occlusion status: The control group with normal occlusion (n = 11; age: 25.2 ± 2.8 years; and body mass index [BMI]: 21.1 ± 1.9 kg/m2) and the AOB group with AOB malocclusion (n = 15; age: 23.2 ± 5.5 years; BMI: 21.0 ± 1.6 kg/m2). GE, chewing, and occlusion were assessed simultaneously. A food questionnaire survey was also administered on the same day.

Results:

A significant positive correlation was noted between open bite and the occlusal analysis findings. Negative correlations were found between the food questionnaire score and both the open bite and occlusal analysis findings, which confirmed that AOB affects mastication. However, no significant difference in the GE rate parameters was observed between the two groups.

Conclusion:

Adaptive mechanisms may have a compensatory effect on the GE rate. However, the lack of tooth contact in the anterior occlusal region resulted in reduced masticatory ability. Orthodontic treatment should thus be considered, regardless of the presence of digestive problems, to improve mastication.

Oral Health Status of Hearing-Impaired Students Attending Special Need Schools in Amhara Region, Ethiopia: A Cross-Sectional Study

Background

Oral health care is the most common unmet need among individuals with a disability. Individuals with a disability may have compromised oral health needs due to neglect from parents, socioeconomic problems, and communication barriers. In Ethiopia, there is a lack of data on oral health status of the hearing-impaired population. Therefore, this study aimed to assess the oral health status of hearing-impaired students in the Amhara region, Ethiopia.

Methods

A cross-sectional study was conducted from November 2020 to April 2021 on hearing-impaired students in Amhara region, Ethiopia. Data were collected using a pretested interview administered questionnaire and clinical examination. Oral cavity was evaluated using the simplified oral hygiene index, decayed, missed and filled teeth, and community periodontal index. Data analysis was done using SPSS 26.0, and logistic regression analysis was done to identify the risk factors of dental caries and periodontal disease.

Results

A total of 149 hearing impaired students with an age range of 7–30 years were involved in the study. The prevalence of periodontal disease and dental caries was 22.8% (95% CI: 16.8, 30.4) and 38.9% (95% CI; 32.2, 46.9), respectively. Being grade 1–4 student (AOR = 3.94, 95%: 1.16, 13.38), lack of formal education (AOR = 4.98, 95% CI: 1.00, 24.65), dental caries (AOR = 2.51, 95% CI: 1.08, 5.08) and bleeding on probing (AOR = 9.98, 95% CI: 3.69, 26.64) were statistically significant with periodontal disease. Grade level, parents’ support during brushing, oral health status, and medication intake were independent factors for dental caries.

Conclusion

In the present study, a significant number of hearing-impaired students had periodontal disease and dental caries. School oral health programs and caregivers assisted oral hygiene practices are essential to combat oral health problems in hearing-impaired students. Moreover, a nationwide prospective study with a large sample size will be required to reflect the oral health status of hearing-impaired individuals in the country.

Relationship between dental caries, oral hygiene and malocclusion among Syrian refugee children and adolescents: a cross-sectional study

BACKGROUND

Little is known about the oral disease burden in refugee children and associated risk factors. This cross-sectional study aimed to explore the oral hygiene status and prevalence of caries, and to investigate their association with malocclusion characteristics in a child refugee population.

METHODS

606 Syrian refugee children and adolescents aged 7-19 years, registered as refugees in Jordan and residing in Zaatari camp, were recruited to the study. Oral hygiene and caries status were recorded using DMFT (mean of decayed, missing, and filled permanent teeth) and OHI-S (Simplified Oral Hygiene Index) according to WHO criteria. Oral health results were then cross tabulated with previously reported malocclusion traits for the same study sample (crowding, spacing, contact point deflection and IOTN) to detect any associations. Statistical analysis was conducted using chi-square test, independent sample t-test, one-way ANOVA, Welch test and Post Hoc testing (Gabriel and Games-Howell).

RESULTS

Overall DMFT and OHI-S were 4.32 and 1.33 respectively with no difference between males and females. Around 40% of the sample showed ≥ 5 DMFT score. 96.1% of the sample either do not brush or brush occasionally: females showed better oral hygiene practices (P = 0.002). No significant differences in DMFT scores were noted for gender or age, other than the 7-9.9 year old group having significantly higher mean DMFT scores than all other age groups (P < 0.01);the mean of OHI-S was not significantly different between different age groups (P = 0.927). Subjects with malocclusion, specifically crowding, contact point deflection and IOTN grades 3, 4 and 5 had higher scores in both arches for OHI-S and DMFT than subjects without malocclusion traits, although this was not statistically significant for DMFT scores. Overall, patients with generalized spacing had a significantly lower OHI-S score than those without spacing (P = 0.021). Significant correlations were found between parameters of intra-arch and inter-arch relationships and oral health indices (DMFT and OHI-S).

CONCLUSION

Malocclusion may increase the risk of caries and periodontal disease; the magnitude of this risk is amplified in populations with poor oral health and limited access to oral healthcare services, highlighting the need for preventive and curative oral health programs.

Orthodontic Status and Orthodontic Treatment Need of 12- and 15-Year-Old Greek Adolescents: A National Pathfinder Survey

The purpose of this research was to assess the orthodontic status and orthodontic treatment needs of 12- and 15-year-old schoolchildren in Greece, in relation to sociodemographic factors and parental education level. A total of 1102 12-year-old children and 1131 15-year-old adolescents across Greece were assessed using the Modified Dental Health component (DHC) of the Index of Orthodontic Treatment Need (IOTN). An amount of 38.7% of 12-year-olds and 33.7% of 15-year-olds were in definite need of orthodontic treatment. The most common etiologic factors were tooth eruption and position anomalies. A higher rate of orthodontic treatment need was recorded among subjects with lower parental education level. Class I malocclusion was found in 50.9%, Class II in 38.4% and Class III in 10.8% of the total sample. A higher incidence of dental trauma was found in the 12-year-olds presenting with a Class II molar relationship and >3 mm overjet. The need for orthodontic treatment in Greece was higher, in comparison to other European countries, with one out of two children presenting a severe overjet associated with a high incidence of dental trauma. One out of three adolescents were still judged as having a need for orthodontic treatment by the age of 15.

Prevalence of Occlusal Features and Their Relation to Sociodemographic Variables in Northwest Ethiopia: A Cross-Sectional Study

BACKGROUND

Malocclusion affects the chewing, dental aesthetics, jaw development, and overall attractiveness of individuals. The negative impact of malocclusion is high, particularly in adolescents who can be the target of teasing, intimidation, and name-calling. Even if, malocclusion is a common problem in developing countries, there was a paucity of data in Ethiopia. Therefore, this study aimed to determine the prevalence and associated factors of malocclusion in northwest Ethiopia.

METHODS

This cross-sectional study was done at the University of Gondar comprehensive hospital from December 1, 2019, to October 30, 2020. Four hundred seventy-six study participants were selected using a systematic random sampling method. Data collection was done using a structured interviewer-administered questionnaire. Qualified dental professionals examined malocclusion traits according to the WHO oral health survey tool and evaluated for the presence of malocclusion in terms of angles classification, open bite, crossbite, spacing, and crowding. Data entry was done using Epi-Info 7, and analyzed by SPSS 26. Descriptive statistics and logistic regression was done to analyze the data.

RESULTS

A total of 476 subjects were included in the study with a mean age of 29.83 (SD±14.013). The prevalence of malocclusion was 55.9% (95% CI: 51.39-60.28). The common occlusal traits were class-I malocclusion with minor discrepancy (34.9%), anterior crowding (22.9%), and anterior open bite (21.6%). The prevalence of anterior crossbite, posterior crossbite, class-II, and class-III malocclusion was 5.9%, 3.8%, 10.9%, and 8.0%, respectively. Males (AOR=1.6, 95% CI: 1.11, 2.30), urban residents (AOR=1.64, 95% CI: 1.06, 2.56), monthly income of ≤2500 Ethiopian Birr (AOR=1.27, 95% CI: 1.02, 1.59) and mouth breathers (AOR=2.50, 95% CI: 1.72, 2.63) were significantly associated with malocclusion.

CONCLUSION

Significant amount of the study participants had malocclusion. Males, urban residents, low monthly income, and mouth breathing habits were independent factors for a malocclusion. Therefore, early attention to the development of the dentition and occlusion, and necessary functional correction during childhood are important to reduce its prevalence and lifelong adverse effect. Moreover, publicly financed orthodontic treatment should be scheduled, and supplied to individuals in desperate need of orthodontic care.

Prevalence of malocclusion and assessment of orthodontic treatment needs among Syrian refugee children and adolescents: a cross-sectional study

Background

There is a scarcity of data concerning the prevalence and pattern of malocclusion and orthodontic treatment needs in Syrian refugee. In this study, extra and intra-oral features of malocclusion and the dental health component of the Index of Orthodontic Treatment Need (IOTN) were reported.

Methods

Examination of 606 Syrian children/adolescents refugees attending Zaatari clinic was carried out (males = 280, females = 326, mean age = 11.84 ± 2.1 years). Subjects not within the age limit, with a history of orthodontic treatment, or with craniofacial anomalies were excluded. Both extra and intra-oral features of malocclusion were assessed. Intra-oral features included inter- and intra-arch occlusal characteristics: crowding, spacing, crossbite, overjet, overbite, molar and canine relationship, incisor relationship, and centerline shift. In addition, the dental health component (DHC) of the Index of Orthodontic Treatment Need (IOTN) was recorded. Gender and age variations in malocclusion characteristics and IOTN grading were tested using chi-square and nonparametric tests respectively (P < 0.05).

Results

The prevalence of malocclusion was 83.8% (52.6% class I, 24.2% class II, 7% class III). The most common features of malocclusion were crowding (71.1%) followed by centerline shift (52.1%), increased overjet (36.1%), high vertical proportions (34%) and deep overbite (31.2%); there were significant gender and age differences for a number of occlusal traits. The prevalence of moderate to severe need for orthodontic treatment was 67.7%.

Conclusions

This study provides baseline data on the prevalence of malocclusion in Syrian refugee children/adolescents in Zaatari camp where data concerning oral health of this population are lacking. The prevalence of orthodontic treatment need was high warranting the need for a comprehensive interceptive orthodontic program to prevent increasing oral health problems in the future. This high burden of oral diseases has a negative financial impact on the hosting country which can be reduced through public health interventions and implementing community-based dental healthcare for this underprivileged population.

Impact of post-orthodontic dental occlusion on masticatory performance and chewing efficiency

BACKGROUND

Whether precise orthodontic detailing of occlusion impacts masticatory function is unknown. In this study, we aimed to assess the impact of post-orthodontic dental occlusion on masticatory performance and chewing efficiency.

MATERIALS AND METHODS

Fifty-four adults who completed orthodontic treatment were categorized into two groups using the American Board of Orthodontics (ABO) model grading system: one meeting ABO standards (ABO, N = 29), the other failing to meet them (non-ABO, N = 25). The electromyographic (EMG) signals of the anterior temporalis (AT) and superficial masseter muscles were recorded bilaterally during static (clenching) and dynamic (gum chewing) tests. Chewing efficiency was measured by calculating the median particle size (MPS) and broadness of particle distribution (BPD) after five chewing trials of experimental silicone food at a standardized chewing rate.

RESULTS

Participants of the ABO group had a slightly more symmetric activation of the AT muscles during clenching (P = 0.016) and chewed a gum at a slower rate (P = 0.030). During the standardized chewing test with silicone food, ABO subjects had slightly greater EMG potentials at all muscle locations than non-ABO individuals (all P < 0.05). MPS and BDP did not differ significantly between groups (all P > 0.05).

LIMITATIONS

The severity of the initial malocclusion of the study participants was not in the statistical model as a potential confounder on the outcome measures.

CONCLUSIONS

Meeting ABO standards contributes to a slightly more balanced activation of the temporalis muscles during clenching and more efficient muscle recruitment during chewing but does not improve chewing efficiency.

Masticatory Adaptation to Occlusal Changes

This review deals with the frequent wide variability of masticatory capacity/incapacity. Neither researchers nor clinicians have taken sufficient account of this variability despite its implications for nutrition. Mastication in normal healthy oral conditions is first described, followed by a short presentation of the mechanisms of masticatory adaptation in the nervous system. Capacity, incapacity, and successful compensatory adaptation of mastication are then defined, along with the different methods used for their evaluation. Examples of adaptation needs are given, such as those concomitant with dental wear or occlusal changes. Finally, given its vital importance for deeply impaired mastication/deglutition function, the impact of masticatory adaptation processes on nutrition is examined.

Gastric emptying rate before and after orthodontic treatment examined with the [13C] breath test: A pilot study

INTRODUCTION

Orthodontic patients with malocclusion have significantly lower masticatory and gastrointestinal digestive function than persons with normal occlusion. Although several studies have suggested that masticatory function is improved after orthodontic treatment, the relationship between such improvement and change in gastrointestinal symptoms has not been quantitatively evaluated. In this study, we aimed to investigate the change in masticatory function and the gastric emptying rate in patients with malocclusion, before and after orthodontic treatment.

METHODS

Seven women with malocclusion, before (pretreatment group) and after orthodontic treatment (posttreatment group), and 7 healthy dentate female volunteers (control group) underwent a ¹³C-acetate breath test (¹³CO₂) with a liquid meal and the color changeable gum test, along with completing the frequency scale for symptoms of gastroesophageal reflux and a questionnaire on food intake. Between-group differences were evaluated.

RESULTS

The pretreatment group had significantly longer maximum ¹³CO₂ exhalation time and lower masticatory function, quantified using a higher red-color value on the gum test and the questionnaire on food intake, than did the posttreatment and control groups. No significant differences were identified between the posttreatment and the control groups.

CONCLUSIONS

We provide evidence of improvement of masticatory function after orthodontic treatment, which was associated with a faster rate of gastric emptying.

Assessing Angle's malocclusion among cleft lip and/or palate patients in Jammu

OBJECTIVE

The study was conducted to examine the patients with abnormalities of cleft lip and/or palate and its association with different types of malocclusion.

MATERIALS AND METHODS

This descriptive study was done among 168 patients with abnormalities of cleft lip and/or palate. Angle's classification of malocclusion was applied for assessment of occlusion as Class I, Class II, and Class III. The types of oral clefts classification such as cleft lip unilateral and cleft lip bilateral, cleft palate (CP), unilateral cleft lip with palate (UCLP) and bilateral cleft lip with palate (BCLP) was considered. Chi-square test was applied to analyze the data at P < 0.05.

RESULTS

The study showed different categories of clefts patients as cleft lip (81), CP (31), and both cleft lip and palate (53). The occurrence of unilateral cleft lip (44) was maximum among the sample followed by UCLP (39), and bilateral cleft lip (31). Maximum subjects with Class II (10.7%) and Class III (4.9%) malocclusion were seen with unilateral cleft lip deformities. None of the patients with UCLP had Class III malocclusion.

CONCLUSION

Cleft lip was the most commonly observed deformity and high frequency of Class II and III malocclusion was evident. Therefore, patients with such abnormalities should be screened timely.

Prevalence of caries and malocclusion in an indigenous population in Chiapas, Mexico

OBJECTIVES

To assess the prevalence of caries and malocclusion in Mayan Mexican adolescents, 14-20 years of age, living in Chiapas, Mexico.

METHODS

This was a cross-sectional, population-based, quantitative, epidemiological study. Sites were chosen to capture subjects representative of the state's Mayan population. A total of 354 subjects were recruited. Caries experience was quantified, via visual inspection, using the Decayed, Missing and Filled Surface (DMFS) index. Malocclusion was quantified using the Index of Complexity, Outcome and Need (ICON).

RESULTS

Our data showed that 99% of the population had caries experience, with a median DMFS score of 8. Of the 99% with caries experience, over half had caries affecting more than five tooth surfaces. Thirty-seven per cent of the students had unmet orthodontic treatment need, and 46.46% presented a Class II, and 39.09% a Class III, anterior-posterior relationship.

CONCLUSIONS

Less than 1% of the population had any exposure to orthodontics, demonstrating the lack of access to care. Likewise, only 1% of the population was found to have no caries experience, exhibiting a large unmet treatment need. The median DMFS score of 8 was also high in comparison with the median DMFS in the USA of 6. Our data suggest a correlation between the lack of access to care and high prevalence of caries and malocclusion in Mexican Mayans who inhabit Chiapas, Mexico.

Prevalence of malocclusion and orthodontic treatment need in schoolchildren - An epidemiological study

BACKGROUND

To ascertain the prevalence of malocclusion and orthodontic treatment need in schoolchildren dependent on armed forces personnel. To review the overall oral health using DMFT index and to evaluate any relation between increased DMFT index to existing orthodontic problems.

METHOD

Five schools were randomly selected among Army/KV/AF schools and a random sample of 1200 children aged 10-15 years old attending these schools dependant on armed forces personnel were selected. A survey form was filled up after the examination of children by the principal worker and need for orthodontic treatment was assessed using index for orthodontic treatment need (IOTN) and overall oral health status by DMFT index and totaled. Frontal intra oral photograph in centric occlusion were taken. Dental Health Component (DHC) of IOTN for all the patients was marked by one set of orthodontists. The most severe occlusal trait was identified by the examiner for any particular patient and the patient was then categorized according to this most severe trait. AC of the IOTN was assessed by second orthodontist, individual and a layperson.

RESULTS

It was observed that prevalence of malocclusion in the sample was 53.7%. 32.8% (239 males & 154 females) of samples are in need of orthodontic treatment. 55.1% of samples shown no caries risk, 38.1% had moderate caries risk and 6.8% had high caries risk.

CONCLUSION

Significant percentage of the samples are in need for orthodontic treatment. There is significant relation between higher DMFT index and orthodontic treatment need. It was found that IOTN is a reliable and user-friendly index, which can be used for orthodontic surveys.

Occlusal stability

Occlusion is the foundation for clinical success in fixed, removable, and implant prosthodontic treatment. Understanding those principles is critical when restoring a patient's occlusion. Many philosophies, devices, and theories of occlusion have evolved based on anecdotal clinical observations and applied geometric perceptions. The literature has reported these classic and contemporary occlusal concepts. As evidence-based dentistry emerged, it championed scrutiny of previously held beliefs, resulting in the abandonment of many pragmatic, yet beneficial occlusal procedures. The impetus toward scientific discovery, whereby factual information might be universally applied in dental education and clinical practice, has renewed interest in occlusal studies.

Validity assessment and determination of the cutoff value for the Index of Complexity, Outcome and Need among 12-13 year-olds in Southern Chinese

To validate the use of the Index of Complexity, Outcome and Need (ICON) in assessing orthodontic treatment need among 12–13 year-olds in southern China, we determined the threshold value of ICON based on Chinese orthodontists' judgments. The samples consisted of 335 students in grade 7 from 16 randomly selected middle schools in Chengdu, China. Three associate professors provided ICON scores for each participant and the results were compared with the gold standard judgments from 25 experts on treatment needs. Based on the gold standard, 195 casts belonged to the treatment category, while the rest 140 belonged to the no-treatment category. With the international cutoff point of 43, the sensitivity and specificity of the ICON score were 0.29 and 0.98. The best compromise between sensitivity and specificity in Chengdu, compared with the gold standard, was found at a cutoff point of 29, and the sensitivity and specificity were 0.88 and 0.83. When used to evaluate the treatment need of 12–13 year-olds in southern China, the international ICON cutoff value did not correspond well with Chinese orthodontists' judgments; a lower cutoff value of 29 offered a greater sensitivity and specificity with respect to expert orthodontists' perception of treatment need.

Association between normative and self-perceived orthodontic treatment need among 12- to 15-year-old students in Shiraz, Iran

Self-perception of dental attractiveness is an important factor affecting orthodontic treatment need. The purpose of this study was to investigate the association between normative and self-perceived orthodontic treatment need and to evaluate the influence of gender and socioeconomic background such as family size, parental education and father's employment. The subjects were 900 male and female junior high school students (450 males, 450 females) aged 12-15 years, from four districts in the city of Shiraz, Iran. The participants were asked to complete a questionnaire and then underwent a dental examination. Normative treatment need was assessed clinically using the Dental Aesthetic Index (DAI) according to the World Health Organization guidelines. Statistical analysis was undertaken using t- and chi-squared tests. There was no statistically significant correlation between DAI scores and demographics. The results showed a significant correlation between DAI scores and a subject's awareness of malocclusion and their satisfaction with dental appearance. There were no differences between genders concerning the questionnaire data. The results suggest that the DAI score might reflect a self-perceived need for orthodontic treatment.

The masticatory normative indicator

There is no established quantitative, objective method to differentiate individuals with good masticatory function from those lacking this attribute. The aim of this study was to specify a normal range of median particle size values for masticated raw carrots collected just before being swallowed. The masticatory normative indicator (MNI) value thus obtained was based on seven studies carried out by different investigators using different methods for measuring particle size in carrot boluses. A simple mathematical transformation of variables and the choice of an interval of +/-1.96 times the standard deviation gave 4.0 mm as the upper limit of normal median particle size for carrots in a population of young persons with good oral health. This value identifies boluses that may be considered as resulting from impaired mastication, as illustrated in healthy individuals with experimentally hampered mastication, denture wearers, and individuals presenting with obesity or Down syndrome.

Is the goal of mastication reached in young dentates, aged dentates and aged denture wearers?

The objective of the present study was to assess the impact of age and dentition status on masticatory function. A three-arm case-control study was performed. Group 1 (n 14) was composed of young fully dentate subjects (age 35.6 +/- 10.6 years), group 2 (n 14) of aged fully dentate subjects (age 68.8 +/- 7.0 years) and group 3 (n 14) of aged full denture wearers (age 68.1 +/- 7.2 years). Mastication adaptation was assessed in the course of chewing groundnuts and carrots to swallowing threshold. Particle size distribution of the chewed food, electromyographic (EMG) activity of the masseter and temporalis muscles during chewing, and resting and stimulated whole saliva rates were measured. Aged dentate subjects used significantly more chewing strokes to reach swallowing threshold than younger dentate subjects (P < 0.05), with increased particle size reduction, longer chewing sequence duration (P < 0.05) and greater total EMG activity (P < 0.05) for both groundnuts and carrots. In addition, aged denture wearers made significantly more chewing strokes than aged dentate subjects (P < 0.001) to reach swallowing threshold for groundnuts. Particle size reduction at time of swallowing was significantly poorer for denture wearers than for their aged dentate counterparts, despite an increase in chewing strokes, sequence duration and EMG activity per sequence. Masticatory function was thus adapted to ageing, but was impaired in denture wearers, who failed to adapt fully to their deficient masticatory apparatus.