Clinical significance of sleep bruxism on several occlusal and functional parameters

The aim of this study was to evaluate the association between various functional and occlusal parameters and sleep bruxism. Thirty-nine (39) sleep bruxism patients and 30 controls participated in this investigation. The assessment of sleep bruxism was performed using the Bruxcore Bruxism-Monitoring Device (BBMD) combined with a new computer-based analyzing method. Sixteen functional and/or occlusal parameters were recorded. With a mean slide of 0.95 mm in the sleep bruxism group and a mean slide of 0.42 mm in the control group (Mann Whitney U test; p<0.003), results solely demonstrated a significant group difference regarding the length of a slide from centric occlusion to maximum intercuspation. The results suggest that the slightly pronounced slide could be of clinical importance in the development of increased wear facets in patients with current sleep bruxism activity. Following further evaluation including polysomnographic recordings, the BBMD combined with this new analyzing technique seems to be a clinically feasible instrument that allows the practitioner to quantify abrasion over a short period.     

第一磨牙缺失不同修复方法的咬合接触特征研究

目的 针对单个第一磨牙缺失的病例,研究种植及可摘局部义齿（RPD）种不同修复方法所恢复的牙列咬合接触特征。方法 选择15名单个第一磨牙缺失的患者作为实验组,15名正常牙列人群作为对照组,其中,实验组每位患者同时进行种植及RPD修复,应用TeeTester咬合分析仪,测试对照组和实验组在未修复、RPD修复及种植义齿修复后3种状态下分别做正中咬合及咀嚼运动,分析其咬合接触特征(总咬合力、总接触面积、不平衡指数、单次咀嚼循环时间,OT/DT比值),并进行统计学分析。结果 患者做正中咬合时,在总咬合力、总接触面积、不平衡指数方面,患者未修复时分别为（48.76±12.82）kg,（317.59±58.47）mm2,（24.78±7.40）,行RPD修复时分别为（54.36±10.59）kg,（355.81±77.43）mm2,（18.29±8.42）,行种植修复时分别为（61.94±12.36）kg,（398.17±83.86）mm2,（17.80±6.69）;患者咀嚼运动时在总咬合力、总接触面积、不平衡指数、单次咀嚼循环时间及T0/Td方面,患者行种植修复时分别为（52.14±16.53）kg,（348.08±81.76）mm2,（15.69±9.16）,（0.4072±0.10）s,（1.718±0.26）。统计学分析表明,RPD、种植义齿修复和对照组的部分咬合接触特征结果无显著性差异,但与未修复前结果有显著性差异。单次咀嚼循环时间及T0/Td在各组间均无显著性差异。结论 在恢复咬合力及咬合接触面积方面,种植义齿优于RPD,较接近天然牙列,并明显优于不修复。正中咬合时全牙列的总咬合力及总接触面积明显大于咀嚼运动时,但不平衡指数无明显统计学差异。     

青年夜磨牙症患者经弹性牙合垫治疗前后咬合变化特征的研究

目的：：测量并分析夜磨牙症患者使用弹性垫治疗前后各项咬合数据变化。方法：使用弹性垫对青年夜磨牙症患者(n=10)进行治疗,并在治疗前和治疗后6个月使用T-Scan咬合检测仪进行咬合检测,观察和记录实验组闭合时间、分离时间、力中心位置、力不对称指数的变化,与对照组( n=10)进行对比和研究,并观察临床疗效。结果：治疗前实验组闭合时间及左、右侧分离时间均比对照组长(P<0.05),治疗后均无统计学差异(P>0.05);治疗前、后2组前伸分离时间差别无统计学意义(P>0.05);治疗前实验组和对照组力中心位置左右向偏移和右侧力百分比及力不对称指数比较均有统计学差异(P<0.05),治疗后比较均无统计学差异(P>0.05)。实验组治疗后闭合时间及左、右侧分离时间均比治疗前缩短(P<0.05);实验组治疗前、后右侧力百分比值有统计学差异(P<0.05),前伸分离时间、力中心位置偏移、左侧力百分比及力不对称指数治疗前后比较均无统计学差异(P>0.05)。结论：早接触、侧方干扰、全牙列力中心的偏移等咬合因素与磨牙症有十分密切的关系。使用弹性垫治疗磨牙症,可以有效地改善上述问题,使关系更加协调和稳定。     

磨牙症患者（牙合）接触特征的研究

目的 :研究磨牙症患者牙合接触的特征 ,探索牙合因素与磨牙症的关系。方法 :用T -scanII型咬合分析仪对 2 3名磨牙症患者与 13名对照者分别进行正中牙合位、前伸及侧方运动的咬合检查 ,测量闭合接触时间、前伸与侧方牙合分离时间 ,观察平衡侧牙合干扰出现的情况。结果 :磨牙症患者的闭合时间小于对照组 ;侧方牙合分离时间比对照组长 ;与对照组相比多数磨牙症患者出现平衡侧牙合干扰。结论 :平衡侧牙合干扰可能是与磨牙症有密切关系的重要的牙合因素     

Comparison of the occlusal vertical dimension after processing complete dentures made with lingualized balanced occlusion and conventional balanced occlusion

STATEMENT OF PROBLEM: An increase in occlusal vertical dimension (OVD) may occur after processing complete dentures. Although many factors that generate this change are known, no information is available in the dental literature regarding the effect that the occlusal scheme may have on the change in OVD. PURPOSE: This in vitro study compared the increase in OVD, after processing, between complete dentures with teeth arranged in lingualized balanced occlusion and conventional balanced occlusion. MATERIAL AND METHODS: Thirty sets of complete dentures were evaluated as follows: 15 sets of complete dentures were arranged in conventional balanced occlusion (control) and 15 sets of complete dentures were arranged in lingualized balanced occlusion. All dentures were compression molded with a long polymerization cycle. The occlusal vertical dimension was measured with a micrometer (mm) before and after processing each set of dentures. Data were analyzed using an independent t test (alpha=.05). RESULTS: The mean increase in the OVD, after processing, was 0.87 +/- 0.21 mm for the control group and 0.90 +/- 0.27 mm for the experimental group. There was no significant difference between the groups. CONCLUSION: After processing, dentures set in lingualized balanced occlusion showed an increase in OVD similar to those set in conventional balanced occlusion. CLINICAL IMPLICATIONS: Although the 2 occlusal concepts resulted in similar increases in the OVD after processing, the lingualized balanced occlusion may result in easier occlusal adjustments, as the less complicated occlusal scheme uses a smaller number of centric occlusion contact points.     

Does the facebow affect the outcome of CAD/CAM occlusal splint. Randomized clinical trial

BackgroundOcclusal appliances can distribute aggressive loads which are generated by bruxism and can reduce their frequency. The facebow record, when used in the construction of occlusal appliances, helps in minimizing occlusal discrepancies. This study aimed to compare the effect of CAD/CAM stabilization occlusal splint made with and without facebow for management of bruxer patients.Method24 Patients who were diagnosed as bruxers were randomly assigned into two equal groups and obtained maxillary CAD/CAM occlusal stabilizing splint recorded with centric relation either with or without using a facebow. The patient satisfaction using the visual analog scale (VAS) was recorded at baseline, one month and three months’ follow-up periods. The adjustment time of both splints, from the start of splint delivery until becoming well-fitted and occlusally adjusted, was calculated using a stopwatch.ResultsThe CAD/CAM occlusal splints with or without the use of facebow improved the patient's satisfaction with no statistically significant difference between both groups at baseline, one month and three months with p values of 0.73, 0.24 and 0.45 respectively. The comparison between the two modalities regarding the adjustment time showed no statistically significant difference between both groups (P = 0.06).ConclusionAccording to the results of this study; no difference was detected in patient satisfaction and the time required for adjustment of CAD/CAM occlus.     

平衡对全口义齿咀嚼效能影响的研究

目的:研究平衡对全口义齿咀嚼效能的影响。方法:采用吸光度法来测定20例全口义齿戴用者在正中选磨前、正中选磨后以及正中与非正中选磨后的咀嚼效能。结果:(1)正中选磨后的咀嚼效能明显高于选磨前的咀嚼效能(p<0.05);(2)正中与非正中选磨后的咀嚼效能略高于仅正中选磨后的咀嚼效能,但无统计学上的意义(p>0.05)。结论:(1)平衡是决定全口义齿修复效果的重要因素之一,全口义齿修复后进行系统选磨是非常必要的;(2)咀嚼效能测定可作为评价全口义齿平衡的功能性检测手段之一。     

A clinical diagnosis of diurnal (non-sleep) bruxism in denture wearers

The purpose of this study was to establish a clinical method for diagnosing diurnal bruxism in denture wearers by recording masseter and anterior temporal electromyograph (EMG) activity. Seven suspected bruxists and five normal patients who wore complete dentures and/or distal extension base removable partial dentures were selected for participation. EMG activity in both the masseter and the anterior temporal muscles was recorded bilaterally during silent reading (10 min), maximal voluntary clenching (MVC), tapping in centric occlusion, lateral movements, chewing and swallowing. No significant differences of EMG activity were found between the groups during tapping, lateral movement, chewing and swallowing (P> 0.05). However, during 10 min of silent reading, a significant difference was found between the groups when comparing masseter muscle activity (P < 0.05). A threshold of 10% of MVC of at least 3-s duration was used to define an individual bruxism event. When the muscle activity recorded during silent reading was further analysed using these criteria, the control group displayed no bruxing activity while the suspected bruxist group displayed a mean frequency of six bruxism events (range 2-10). It was concluded that: (a) masseter muscle activity recorded during 10 min of silent reading showed significant difference between the groups; (b) the criteria selected in this study for the detection of sleep bruxism can also be used to assess diurnal bruxism; and (c) it is possible to diagnose diurnal bruxism in denture wearers by measuring the masseter EMG activity during 10 min of silent reading.     

Temporomandibular joint function and its effect on concepts of occlusion.

Many of the premises of dentistry that have evolved empirically have been re-evaluated in the light of newly-developed concepts of TMJ function. Centric relation, although duplicable, may not necessarily be correct. A "functional" centric relation exists when the TMJ radiographs can be correlated with the occlusal findings, in which case, the retruded classical centric relation should be used. When a "dysfunctional" centric relation is present (no correlation between the TMJ radiographs and occlusal findings), the most retruded position should not be used and a therapeutic centric occlusion should be created by the dentist. Subclinical TMJ dysfunction occurs more frequently than commonly thought, because TMJ radiographs are not routinely used. Retruded condylar displacements can be easily overlooked, because the lateral pterygoid muscle has relatively few stretch receptors compared to the elevator muscles of the mandible. Condylar retrusion, therefore, would not necessarily cause lateral pterygoid spasm as might be expected. The exact mechanism of the TMJ suspension system is unknown, although experimental evidence has shown that the condyle can be displaced superiorly with posterior unsupported muscle force. This indicates that the immutability of the condylar path under varying clinical conditions is questionable. Due to the superior displacement characteristics of the TMJ, the condyle does not act as the fulcrum in mandibular kinetics. The fulcrum, therefore, shifts to the teeth and/or bolus, depending on the specific situation. In either instance, whether considering bruxism or mastication, for most patients, an occlusion based on group function is preferable to a canine-protected occlusion to insure TMJ health. Scientifically, no one scheme of occlusion or articulation has been proven to be superior to any other scheme; therefore, the choice is a matter of the personal preference of the dentist.     

Controversies in occlusion

The tissues and structures of the stomatognathic system adapt in different ways but in a coordinated manner to functional forces. This adaptive capacity differs from individual to individual and tends to cloud the picture as to how these mechanisms function. This leads to many areas of disagreement as to the role of occlusal trauma in the etiology of periodontal disease; the importance of centric, bite collapse versus arch collapse; the role of incisal guidance in maintaining occlusal stability; canine protected-guided occlusion versus group function; the use of appliances in occlusal therapy; prophylactic versus interceptive occlusal adjustment; and the role of bruxism and other parafunctional habits in occlusal trauma. An attempt is made in this article to clarify these issues.     

Occlusion and orthodontics.

The importance of considering the functional aspects as well as the static concepts of an occlusion was demonstrated in the case of an 11-year-old girl with postorthodontic temporomandibular joint muscle pain dysfunction. The following characteristics of an ideal occlusion were discussed as they relate to the entire masticatory system: 1. There should be no slide in centric; that is, there should be a stable jaw relationship when occlusal contact is made in centric relation closure. 2. There should be freedom in centric, that is, freedom for the mandible to move from centric relation to centric occlusion and slightly anterior to centric occlusion without interference. 3. Centric relation should be at the same contact vertical dimension as centric occlusion. 4. There should be no buccolingual thrust or impact to any tooth on closure to contact in centric relation or to centric occlusion. 5. Between centric relation and centric occlusion there should be an unrestricted glide with maintained occlusal contact. 6. Complete freedom for smooth-gliding occlusal contact movements in various excursions from both centric occlusion and centric relation. 7. Occlusal guidance should be on the working or functioning side rather than on the balancing or nonfunctioning side. 8. There should be no soft-tissue impingment from occlusal contacts. In effect, the occlusion should be related to centric relation and centric occlusion prior to, during, and at the completion of active treatment. The final occlusion should provide unhindered closure in centric relation, smooth-sliding lateral and protrusive movements, and an optimal bilateral vertical contact dimension. Orthodontic treatment must include proper occlusal adjustment procedures to obtain the goals of an ideal occlusion in most instances.     

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??Abstract??Objective To discuss the effect of occlusal reduction on the postoperative pain level after one-visit endodontic treatment for acute pulpitis. Methods Totally 44 cases of acute pulpitis of mandibular molar were selected and divided into the experiment and control groups. The experiment group included 22 cases receiving total occlusal reduction in both centric and lateral occlusion after the root canal therapy. The control group included 22 cases without reduced occlusion. The rate of pain response and VAS ??Visual Analogue Scale/Score???? which was evaluated 7 days?? 1 time per day??were recorded after operation. A comparison of the pain response and VAS results was done between the two groups. Results There was no statistically significance between the groups regarding the rate of pain response after operation ??the experiment group 36.36%?? the control group 40.91%?? P > 0. 05??. The VAS of the experiment group was slightly lower than the control group?? the difference having statistical significance ??P < 0.05??. Conclusion Occlusal reduction has no effect on the rate of pain response?? whereas it might diminish the pain degree following acute pulpitis in one-visit root canal therapy.     

Biologic laws governing functions of muscles that move the mandible. Part IV. Degree of jaw separation and potential for maximum jaw separation.

Accurate diagnosis and treatment of the gnathostomatic system require an understanding of both its biomechanics and its physiology. Clinically, the treatment consists of modifying the existing occlusal program to relieve stress from distressed tissues. The objective of treatment is to effect a neuromuscular release of the mandible. This may be accomplished by (1) equilibration of the natural occlusion, (2) orthodontics, (3) restorative procedures, or (4) surgery. Most frequently, however, the treatment entails some combination of these procedures. The criteria for success of treatment are not determined by the method or technique employed but by the neuromuscular response that the treatment produces. The purpose of this article is not to suggest which occlusal scheme produces the most favorable muscle response in the gnathostomatic tissues. Neither is an objective of this article to teach the mandible-manipulation techniques that are needed to identify occlusal irritants, perform occlusal equilibrations, or obtain accurate centric relation recores. The objective of this article is to emphasize that there are definite principles by which the muscles respond to occlusal contacts. Occlusal contacts can excite bruxism and the sequelae to bruxism. Knowledge of the laws which govern functions of the muscles that move the mandible enables the dentist to acquire the mandibular-manipulation skills that are necessary for the effective diagnosis and treatment of occlusal conditions.     

A change of occlusal conditions after splint therapy for bruxers with and without pain in the masticatory muscles

Bruxism has been suggested as an initiating or perpetuating factor in a certain subgroup of temporomandibular disorders (TMD), however, the exact association between bruxism and TMD remains unclear. This study aimed to demonstrate the difference in responses between bruxism and a subgroup of TMD to a full-arch maxillary stabilization splint from the standpoint of an occlusal condition. This study was conducted to verify the null hypothesis that there were no differences between bruxer groups with and without myofascial pain (MFP) with respect to the changes in occlusal conditions after the use of a splint. Thirty bruxers with MFP and 30 without MFP participated. Occlusal conditions were examined before and after splint therapy, and occlusal changes following the use of a splint were compared between the two groups. The frequency of occlusal changes after splint therapy was significantly higher in the MFP bruxer group than the non-MFP bruxer group (p < 0.05) for the occlusal conditions investigated in the present study. However, no statistical differences were found with regard to each occlusal condition. This result may show the variety of splint effects and may demonstrate a heterogeneous aspect to bruxism and myofascial pain.     

Computerized analysis of occlusal contacts in bruxism patients treated with occlusal splint therapy

PURPOSE

Occlusal splints are commonly used to prevent tooth wear caused by bruxism. However, the effects of splints on occlusion are still unclear. Although it is rarely alluded in literature, splints can provoke severe occlusal alterations and other complications. This study was aimed to identify differences in the responses of individuals with bruxism and healthy individuals to a full-arch maxillary stabilization splint in terms of occlusal changes.

MATERIALS AND METHODS

Occlusal contacts in 20 (5 male, 15 female) bruxism patients and 20 (5 male, 15 female) controls with normal occlusion were evaluated before and after occlusal splint therapy. T-Scan III, a computerized occlusal analysis system, was used to simultaneously measure occlusion and disclusion times as well as left-right and anterior-posterior contact distributions before splint therapy and 3 months after therapy. Wilcoxon and Mann-Whitney U tests were used for statistical analyses (α=.05).

RESULTS

No differences were found in the posterior contact of bruxism patients before and after stabilization splint treatment. However, differences in posterior contact were observed between bruxists and normal individuals prior to treatment, and this difference disappeared following treatment.

CONCLUSION

The results of this study showed the use of a stabilization splint may not have an effect on occlusion. However, the area of posterior occlusal contact among bruxists was found to be greater than that of normal individuals. According to this study, the clinical use of splints may be harmless.     

全口义齿平面前点确定方法的光弹性研究

目的 探讨全口义齿平面前点的确定方法与光弹性效果。方法 选择2015年2月—2017年7月到我院诊治的10例牙列缺失患者作为研究对象,同时制作了由哥特式弓轨迹顶点(义齿A组)、自然咬合法(义齿B组)确定平面前点的全口义齿,测定义齿的咬合指标、光弹性效果与应力情况。结果 调前,义齿A组的咬合接触时间多于义齿B组,左右侧力百分比差值与力中心距离到中线的距离少于义齿B组,对比都有统计学意义(P＜0.05);调后两组上述指标对比都无统计学意义(P＞0.05)。义齿A组与义齿B组测定都显示牙尖工作斜面与平面的夹角呈越向远中越大的趋势,相邻角度差值也有向远中增大的趋势,组间对比无差异(P＞0.05)。义齿A组与义齿B组模型的光弹性材料符合模型实验的基本要求,两组的舌向集中的正中与前伸最大应力值均小于解剖(P＜0.05),在两组对比无差异(P＞0.05)。结论 采用哥特式弓轨迹顶点与自然咬合法确定全口义齿平面前点能维持义齿平衡,其中哥特式弓轨迹顶点确定平面前点的全口义齿的咬合能达到更好的咬合关系。     

In vivo evaluation of noncarious cervical lesions in sleep bruxism subjects

STATEMENT OF PROBLEM: Occlusal load has frequently been suggested to be involved in the development of a noncarious cervical lesion (NCL). However, there is a lack of clinical studies evaluating NCLs and occlusal parameters in sleep bruxism (SB) subjects. PURPOSE: The purpose of this clinical study was to assess the frequency of NCLs and determine potential occlusal differences between SB subjects and healthy control subjects. MATERIAL AND METHODS: A total of 91 volunteers, 58 women and 33 men, with a mean (SD) age of 28.37 (4.89) years (range of 20 to 39 years), participated in this investigation. The clinical assessment of SB was based on the criteria of the American Academy of Sleep Medicine. The participants were divided into 2 groups; 58 subjects were assigned to the SB group and 33 subjects to the control group, following a thorough dental examination that was performed by a single trained dentist. Additionally, the following parameters were recorded: mean number of teeth present, existence/absence of NCLs, frequency of NCLs relating to the type of tooth, type of occlusal guidance scheme, existence of a slide from centric occlusion (CO) to maximum intercuspation (MI), length of the slide, and report of tooth hypersensitivity. Group differences were statistically analyzed using chi-square tests for the qualitative variables and Mann-Whitney U tests for the quantitative variables (alpha=.05). RESULTS: NCLs were significantly more prevalent in SB subjects (39.7%) than in the control subjects (12.1%) (P=.006). In SB subjects, the first premolars were the teeth most affected, and in control subjects, the first molars were most affected. Tooth hypersensitivity was reported in 62.1% of the SB subjects and in 36.4% of the control subjects (P=.018). The evaluation of occlusal guidance schemes revealed no significant difference between the groups. In SB subjects (70.7%), a slide from CO to MI was significantly more prevalent than in control subjects (42.4%) (P=.008). Moreover, SB subjects demonstrated a significantly longer mean (SD) slide of 0.77 (0.69) mm compared to that of control subjects of 0.4 (0.57) mm (P=.008). CONCLUSIONS: Within the limitations of this study, SB subjects demonstrated significantly more NCLs than the control group; whereas, the type of occlusal guidance scheme seems to be of minor importance in the development of NCLs.     

Examination of the relationship between mandibular position and body posture

The purpose of this study was to evaluate the effect of changing mandibular position on body posture and reciprocally, body posture on mandibular position. Forty-five (45) asymptomatic subjects (24 males and 21 females, ages 21-53 years, mean age 30.7 years) were included in this study and randomly assigned to one of two groups, based on the table of random numbers. The only difference between group I and group II was the sequence of the testing. The MatScan (Tekscan, Inc., South Boston, MA) system was used to measure the result of changes in body posture (center of foot pressure: COP) while subjects maintained the following 5 mandibular positions: (1) rest position, (2) centric occlusion, (3) clinically midlined jaw position with the labial frena aligned, (4) a placebo wax appliance, worn around the labial surfaces of the teeth and (5) right eccentric mandibular position. The T-Scan II (Tekscan, Inc., South Boston, MA) system was used to analyze occlusal force distribution in two postural positions, with and without a heel lift under the right foot. Total trajectory length of COP in centric occlusion was shorter than in the rest position (p < 0.05). COP area in right eccentric mandibular position was larger than in centric occlusion (p < 0.05). When subjects used a heel lift under the right foot, occlusal forces shifted to the right side compared to no heel lift (p < 0.01). Based on these findings, it was concluded that changing mandibular position affected body posture. Conversely, changing body posture affected mandibular position.     

降低咬合对急性牙髓炎一次性根管治疗术后疼痛影响的研究

目的探讨降低咬合对急性牙髓炎一次性根管治疗术后疼痛的影响。方法选择2012年1—8月汕头市金平区中医医院口腔科门诊收治的下颌磨牙急性牙髓炎患者44例（共44颗患牙）,按就诊顺序随机分为试验组和对照组,每组22例（22颗患牙）。试验组患牙在行一次性根管治疗术后作降低咬合处理,使其在正中、侧方咬合位均无咬合接触;对照组患牙在行一次性根管治疗术后不作降低咬合处理。记录两组患者术后疼痛发生情况,并在术后7d内每天1次记录疼痛的视觉模拟评分（visual analogue scale／score,VAS）分值。比较两组患者术后疼痛发生率及疼痛VAS分值的差异。结果试验组患者术后疼痛发生率为36_36％,对照组为40．91％,两组患者的术后疼痛发生率差异无统计学意义（P〉0．05）。两组患者术后7d内的疼痛VAS分值比较,实验组均比对照组略低,但差异并无统计学意义（P〉0．05）。两组患者中发生术后疼痛者7d内的疼痛VAS分值比较,试验组均比对照组低,且差异均有统计学意义（P〈0．05）。结论单纯降低咬合对急性牙髓炎一次性根管治疗术后疼痛发生率无明显影响,但对于会发生术后疼痛的患者,可以减轻其疼痛的程度。