Changes in masticatory mandibular movements in growing individuals: a six-year follow-up

The pattern of mandibular movement during chewing is influenced by several central and peripheral factors. The aim of the present study was to determine whether changes in masticatory function, characterized by mandibular velocity and displacement, occurred during individuals' normal growth. Forty-seven children, 9-15 years of age, were followed over a 6-year period. All had an Angle Class I occlusion with no obvious orthodontic problems. Oral motor function with respect to mandibular displacement, duration, and velocity was monitored 3-dimensionally with an opto-electronic method. The chewing cycle was divided into an opening, closing, and occlusal phase. Total body height was measured. During the follow-up period, all masticatory variables except the 3-dimensional opening distance showed significant changes. The total chewing cycle duration, the opening and occlusal time of the chewing cycle, and the 3-dimensional closing distance increased during the growth period, while the closing time of the chewing cycle, the 2-dimensional lateral and vertical distances and both the opening and closing velocity decreased. The children who grew proportionally most in height during the 6-year period, i.e. the youngest children in the group studied, showed a significantly larger decrease in the opening velocity. From this study it becomes evident that the variables of the chewing cycle undergo a continuous process of change during growth. This is possibly a reflection of anatomical changes, maturation of the central nervous system, and altered functional demands.     

Impairment of rat tooth eruption in pups born to mothers exposed to chronic stress during pregnancy

Objective

Tooth eruption is a multifactorial process in which bone tissue plays a prevailing role. In this study we evaluated the bone overlying the developing tooth germ and the degree of tooth eruption of the first mandibular molar in pups born to mothers subjected to constant light during pregnancy.

Design

Pregnant rats were divided into two groups: mothers chronically exposed to a 12:12 light/light cycle (LL) from day 10 to 20 of pregnancy and controls (C) maintained on a 12:12 h light/dark cycle. Pups from each group were euthanized at the age 3 or 15 days.Buccolingually oriented sections of mandibles were stained with haematoxylin–eosin or for histochemical detection of tartrate resistant acid phosphatase (TRAP). The histomorphometric parameters evaluated were bone volume, number of osteoclasts, TRAP+ bone surface, number of TRAP+ and TRAP− osteoclasts per mm² and degree of tooth eruption (mm).

Results

It was found an increase in bone volume (LL: 58.14 ± 4.24 vs. C: 32.31 ± 2.16; p < 0.01) and a decrease in the number of osteoclasts (LL: 3.5 ± 0.65 vs. C: 8.03 ± 1.31; p < 0.01) and TRAP+ cells (LL: 0.84 ± 0.53 vs. C: 8.59 ± 1.26; p < 0.01) in 3-day-old pups born to LL-exposed mothers. These observations are consistent with the decrease in the degree of tooth eruption observed in 15-day-old experimental pups (LL: −0.605 ± 0.05 vs. C: −0.342 ± 0.02; p < 0.0001).

Conclusion

Our results suggest that chronic constant light applied as a pre-natal stressor impairs the resorptive capacity of osteoclasts involved in the formation of the eruption pathway and consequently the degree of tooth eruption.     

The Number of Bleaching Sessions Influences Pulp Tissue Damage in Rat Teeth

Introduction

Hydrogen peroxide tooth bleaching is claimed to cause alterations in dental tissue structures. This study investigated the influence of the number of bleaching sessions on pulp tissue in rats.

Methods

Male Wistar rats were studied in 5 groups (groups 1S–5S) of 10 each, which differed by the number (1–5) of bleaching sessions. In each session, the animals were anesthetized, and 35% hydrogen peroxide gel was applied to 3 upper right molars. Two days after the experimental period, the animals were killed, and their jaws were processed for light microscope evaluation. Pulp tissue reactions were scored as follows: 1, no or few inflammatory cells and no reaction; 2, <25 cells and a mild reaction; 3, between 25 and 125 cells and a moderate reaction; and 4, 125 or more cells and a severe reaction. Results from each experimental group were compared between groups and within groups to the corresponding unbleached upper left molars and analyzed for significant differences using the Kruskal-Wallis test (P < .05).

Results

All tissue sections showed significant bleaching-induced changes in the dental pulp. After 1 bleaching session, necrotic tissue in the pulp horns and underlying inflammatory changes were observed. The extent and intensity of these changes increased with the number of bleaching sessions. After 5 sessions, the changes included necrotic areas in the pulp tissue involving the second third of the radicular pulp and intense inflammation in the apical third.

Conclusions

The number of bleaching sessions directly influenced the extent of pulp damage.     

Tooth Discoloration after the Use of New Pozzolan Cement (Endocem) and Mineral Trioxide Aggregate and the Effects of Internal Bleaching

Introduction

The aim of this study was to evaluate tooth discoloration after the use of mineral trioxide aggregate (MTA) and to examine the effect of internal bleaching on discoloration associated with MTA.

Methods

Thirty-two teeth were endodontically treated. Three-millimeter plugs of MTA, ProRoot, Angelus, or Endocem were placed on the access cavities of 24 teeth. Eight teeth served as the control group. After 24 hours, the access cavities were restored, and the tooth color was recorded at baseline and at 1, 2, 4, 8, and 12 weeks. After 12 weeks, the MTA materials were removed under a microscope, and an internal bleaching treatment was performed. After removal of the MTA materials and after a 1-week bleaching treatment, the color changes were measured, and the MTA-dentin interfaces were observed under a microscope.

Results

The ProRoot and Angelus groups displayed increasing discoloration during a period of 12 weeks. The discoloration associated with ProRoot and Angelus was observed at the MTA-dentin interface and on the interior surface of the dentin. However, the Endocem groups demonstrated no significant discoloration (P < .05). No marginal discoloration was observed around the material in the Endocem group. Removal of the discolored MTA was effective for resolving the discoloration in all of the experimental groups (P < .05). However, a subsequent internal bleaching treatment was not significantly effective compared with the removal of MTA.

Conclusions

ProRoot and Angelus caused tooth discoloration. However, Endocem did not affect the contacting dentin surface. Removing the discolored MTA materials contributed more to resolving the tooth discoloration than post-treatment internal bleaching.     

Effects of different bleaching methods on shear bond strengths of orthodontic brackets

Objective:To evaluate the effects of different bleaching methods on the shear bond strength (SBS) of orthodontic brackets.Materials and Methods:Forty-five freshly extracted premolars were randomly divided into three groups (n  =  15 per group). In group I, bleaching was performed with the office bleaching method. In group II, bleaching was performed with the home bleaching method. Group III served as the control. Orthodontic brackets were bonded with a light cure composite resin and cured with an LED light. After bonding, the SBS of the brackets were tested with a Universal testing machine.Results:Analysis of variance indicated a significant difference between groups (P < .001). The highest values for SBS were measured in group III (20.99 ± 2.32 MPa). The SBS was significantly lower in groups I and II than in group III (P < .001). The lowest values for SBS were measured in group II (6.42 ± 0.81 MPa). SBS was significantly higher in group I than in group II (P < .001).Conclusions:Both of the bleaching methods significantly affected the SBS of orthodontic brackets on human enamel. Bleaching with the home bleaching method affected SBS more adversely than did bleaching with the office bleaching method.     

An epidemiological scoring system for tooth wear and dental erosive wear

Background: The prevalence and severity of tooth wear and dental erosion is rising in children and there is no consensus about an index to be employed. Aim: To assess the reliability of an epidemiological scoring system dental wear index (DWI) to measure tooth wear and dental erosive wear. Design: An epidemiological cross‐sectional survey was conducted to evaluate and compare tooth wear and dental erosion using the dental wear index and erosion wear index (EWI). The study was conducted with randomised samples of 2,371 children aged between 4 years and 12 years selected from the State of São Paulo, Brazil. Records were used for calculating tooth wear and dental erosion; the incisal edge and canine cusp were excluded. Results: As the schoolchildren's ages increased the severity of primary tooth wear increased in canines (P = 0.0001, OR = 0.34) and molars (P = 0.0001, OR = 2.47) and erosion wear increased in incisal/occlusal (P = 0.0001, OR = 5.18) and molars (P = 0.0001, OR = 2.47). There was an increased prevalence of wear in the permanent teeth of older schoolchildren, particularly on the incisal/occlusal surfaces (P = 0.0001, OR = 7.03). Conclusion: The prevalence of tooth wear and dental erosion increased as age increased in children. The epidemiological scoring system Dental Wear Index is able to measure both tooth wear and dental erosive wear. This index should be used to monitor the progression of non‐carious lesions and to evaluate the levels of disease in the population.     

Randomized multi-centre study on the effect of training on tooth shade matching

Objectives

The aim of this study was to find out whether Toothguide Trainer, TT, and Toothguide Training Box, TTB, show any training effects, independent of the shade guide chosen.

Methods

Students from four dental schools (N = 78) were included in this study. The participants were randomized into a study, 42 students (age range: 19–27 years; 69% female, 31% male) and a control group of 36 students (age range: 19–30 years; 57% female, 43% male). The study group started with a double blind introduction test, followed by the TT and TTB training, finishing with the final test. The control group only passed the introduction and – after a break – the final test. Eight randomly chosen samples, seven of the Vita classical and one of the 3D-Master colour scale, were marked by barcodes. Colour matching was arranged by the Vita classical scale.

Results

The results of the pre- and final tests of both groups were combined. For every sample, the value ΔE was determined. The summation of all eight samples from the introduction and final tests offered a summarized ΔE value. The differences between introduction and final tests revealed the individual learning success. 47.6% of the study group showed statistically significant better results than the control group, 33% (p = 0.031).

Conclusion

TT and TTB show a positive effect of training on tooth shade matching independent of the colour scale used.

Clinical significance

Visual shade taking is the most frequent clinical method for shade determination. To increase better results in visual colour matching, TT and TTB training is used. This is the first study examining the training effect of TT and TTB using Vita classical scale.     

Extraction of Permanent Maxillary Teeth by Only Buccal Infiltration of Articaine

Objective

The aim of this study is to demonstrate whether articaine hydrochloride administered alone as a single buccal infiltration in maxillary tooth removal, can provide favourable palatal anesthesia as compared to buccal and palatal injection of lidocaine.

Study Design

The study population consisted of 30 patients who were undergoing orthodontic treatment, and who required bilateral extraction of maxillary permanent premolars as per their orthodontic treatment plan. On the experimental side, 4 % articaine/HCl was injected into the buccal vestibule of the tooth to be extracted. On the control side, 2 % lignocaine HCl was injected both into the buccal and the palatal side of the tooth to be extracted. Following tooth extraction all patients completed a 100-mm visual analogue scale (VAS) and faces pain scale (FPS) to rate the pain on extraction.

Results

According to the VAS and FPS scores, the pain on extraction between buccal infiltration of articaine and the routine buccal and palatal infiltration of lignocaine was statistically insignificant.

Conclusions

The routine use of a palatal injection for the removal of permanent maxillary premolar teeth may not be required when articaine/HCl is used as the local anesthetic.     

肿瘤坏死因子-α诱导人牙囊细胞的凋亡作用

目的：研究不同浓度肿瘤坏死因子-α（TNF-α）对体外培养人牙囊细胞凋亡的影响。方法：第五代HDFCs分别与浓度为0（对照组）、50、100、200 ng/mL的TNF-α共孵育24 h,流式细胞仪AnnexinⅤ-FITC/PI双染技术检测牙囊细胞凋亡细胞比率。结果：HDFCs的凋亡率随TNF-α浓度升高而上升,由对照组的2.3%增加到7.1%。结论：TNF-可诱导HDFCs的凋亡,这种作用可能在牙齿发育、萌出过程中起重要作用。     

氟化物与过氧化氢类漂白剂联用对大鼠牙髓影响的组织病理学观察

目的从组织学水平观察高浓度漂白剂与氟化物联用对大鼠牙髓的影响。方法将60只大鼠按处理方法不同随机分为加NaF漂白组、漂白组和空白组,其中NaF漂白组和漂白组分别按5、10和15 min 3个不同的治疗时间进行漂白处理,然后对即刻、3 d后和7 d后的牙髓情况进行组织病理学观察。结果全部受试牙中仅有1/3出现轻度牙髓反应,没有出现中度或重度牙髓反应,并且这些轻微牙髓反应在治疗结束后即可出现,一般在2周内恢复正常,NaF漂白组和漂白组之间无统计学差异。结论动物实验结果显示高浓度过氧化氢类牙齿漂白治疗可引发轻微、局限性的牙髓反应,漂白治疗术前氟化物的应用对牙髓反应等级无明显影响。