In vivo evaluation of occlusalcontact area and maximum bite force in patients with various types of implant-supported prostheses

Abstract

Objective. To determine the effects of various implant retained and/or supported prostheses on number of occlusal contacts (NOC), occlusal contact area (OCA)and maximum bite force (BF). Patients and methods: In total, 56 patients were included in the study; five test groups and two control groups. The patients in the treatment groups received implant-supported/retained prosthesis; over-dentures retained with two individual attachments in occlusion with complete denture, with four individual attachments in occlusion with complete denture, with four individual attachments in occlusion with fixed partial dentures or natural dentition, 6-implant retained fixed bridges in occlusion with natural dentition and 8-implant retained fixed bridges in occlusion with natural dentition. The patients in control group 1 were wearing conventional complete maxillary and mandibular dentures, whereas in control group 2 they had fixed full-arch porcelain-fused to metal restorations prostheses for both arches. Dental Pre-scale was used measure the NOC, BF and OCA. Results. There was no statistically significant difference between the treatment and control groups, among the groups with regards to NOC. OCA demonstrated different results among the removable and fixed reconstruction groups. With regards to BF, removable dentures supported with four implants showed higher bite force values than controls and two implant over-dentures. Also, a fixed reconstruction using eight implants showed higher BF values than a fixed reconstruction using six implants. Conclusion. Use of implants for removable dentures and fixed reconstructions improve occlusal contact area and bite force.     

Wear mechanisms of resin and porcelain denture teeth

The aim of this investigation was to describe the wear mechanism in occlusal contact areas of porcelain and acrylic resin denture teeth opposing different dental materials. A 55-year-old man with earlier extensive wear was given two complete dentures, as identical as possible, in the upper jaw. One of the dentures had diatoric teeth in cross-linked resin and the other denture had diatoric teeth in porcelain. The dentures were antagonizing a new gold-acrylic fixed bridge from 46 to 36. Two contralateral segments of the bridge were made as removable double crowns. The removable segments were made in different materials: gold, porcelain, light-cured resin, and heat-cured resin. Wear of the denture teeth was studied by scanning electron microscopy on replica models made after 1 and 2 months of antagonizing contact with the various materials. Wear of both porcelain and modern cross-linked resin teeth was mainly a fatigue type of wear. Abrasion was observed when hard particles were assumed to be part of the wear debris.     

先天性缺牙患儿可摘义齿修复61例总结

目的 探讨先天性缺牙患儿可摘义齿修复的方法及特点。方法 对1998—2018年间61例3~12岁先天性缺牙患儿镶配可摘义齿,其中男59例,女2例。根据患儿特点及口内萌出牙的情况,设计可摘义齿。用传统制作方法完成全口义齿21例42件,单颌全口义齿、对颌可摘局部义齿20例40件,上、下颌均为可摘局部义齿20例40件,共计122件。结果 患儿戴用可摘义齿修复后,咀嚼、发音等功能和外貌均得到明显改善。结论 虽然先天性缺牙的病因尚未完全清楚,但均可早期镶配可摘义齿,解决患儿的进食困难,改善外貌及发音,促进患儿的生长发育和身心健康。     

Cantilevered fixed partial dentures in a geriatric population: preliminary report

This study has shown that treatment with distally extending cantilever fixed partial dentures is a favorable alternative to treatment with removable partial dentures in elderly patients with reduced dentition. In patients with anterior teeth and one or two premolar teeth remaining in the mandible, sufficient occlusal stabilization for a maxillary complete denture was provided by a two- or three-unit cantilever fixed partial denture. A pronounced improvement in chewing function and stability of the maxillary denture was expressed, even by patients who were previously well adapted to wearing removable partial dentures.     

Avoiding osseous grafting in the atrophic posterior mandible for implant-supported fixed partial dentures: a report of 2 cases

Bone atrophy occurs after tooth extraction in the posterior mandible, placing the mandibular canal and its neural, arterial, and venous contents closer to the osseous facial aspect and the coronal crest. This proximity places the structure in danger of damage when dental implants are surgically placed to support fixed or removable prostheses. Several options are available to treat these areas for implant-supported fixed and removable complete or partial dentures. Osseous grafting and ridge expansion are surgical options that enable acceptance of standard sized dental implants but have serious morbidities. Additionally, vertical osseous augmentation is not predictable at this time. Narrow diameter dental implants can be placed to avoid the mandibular canal, but some bone volume situations preclude this. Very wide and very short (6.5 × 5 mm) dental implants may be placed at an angle in atrophic sites to successfully support fixed partial dentures. An anterior guidance occlusal scheme may be used in maxillary dentate patients or group function in maxillary complete denture patients. A 100 micron occlusal relief in fixed partial dentures in dentate patients may be required to account for natural tooth intrusion and to prevent occlusal overload of the implant-supported partial denture.     

Custom metal occlusal surfaces for acrylic resin denture teeth

A simple step-by-step procedure has been presented for the fabrication of custom metal occlusal surfaces for acrylic resin denture teeth. This technique works equally well with complete or removable partial dentures and provides the patient with a long-lasting prosthesis and minimal postinsertion problems due to occlusal changes and wear.     

Replacement of missing teeth in a southern region of Vietnam — a descriptive dental laboratory study

Aim : To explore whether tooth replacement in a southern region of Vietnam is in line with the primary health care approach, aiming at health services for all people at affordable costs. Methods : Tooth replacement was investigated by means of prostheses as delivered by four dental laboratories of which the output was considered representative. Information was based on dental casts related to the prostheses. Results : Prostheses replaced almost all missing teeth, irrespective of the types (interrupted or shortened dental arches) and numbers of missing teeth in the dental arch they were made for. Acrylic removable partial dentures were the most common prostheses delivered (65% of removable partial dentures). Conclusion : It cannot be stated that dental arch conditions in this study were representative for the southern Vietnamese population. However, it is concluded that dental practitioners tend to provide complete dental arches by tooth replacements. This morphologically based approach might introduce over treatment. In line with primary oral health care, a functionally oriented treatment management, including the shortened dental arch concept, should be implemented.     

Nd—YAG激光在可摘局部义齿基牙预备的应用

为了解决可摘局部义齿修复过程中牙本质过敏基牙预备的困难和戴牙后加重磨耗等问题，于１９９１年起，对２０例（３０颗）牙本质过敏基牙在预备前、后进行了Ｎｄ－ＹＡＧ激光治疗。经过０．５～４年的临床观察，结果表明该疗法可以明显减轻患者在基牙预备时的敏感与不适，使得基牙预备顺利完成且无副作用，治疗后支托窝与隙卡沟均无明显磨耗。根据本研究结果，建议将Ｎｄ－ＹＡＧ激光治疗作为对可摘局部义齿的牙本质过敏基牙预备的常规方法，对健康基牙亦可在预备后应用。     

Precision metal occlusal surfaces for removable partial dentures

The prosthodontist is often limited in developing the desired occlusal pattern when integrating removable partial dentures with natural dentitions or fixed partial dentures. A technique that allows the development of an esthetic, accurate metal occlusal surface for a removable partial denture is described. The occlusion developed allows an occlusal harmony with the removable partial denture that is not possible with stock denture teeth or metal occlusal surfaces developed with stock denture teeth.     

Chewing performance and occlusal contact area with the shortened dental arch

The aim of this study was to investigate the effect of the loss of posterior teeth on the effectiveness of mastication. To evaluate this, chewing performance and occlusal contact area were investigated in 10 edentate subjects having implants stabilising a mandibular overdenture. A copy of the original lower denture was made for each subject, with removable teeth, which could be separated to convert a complete dental arch to a shortened dental arch, an extremely shortened dental arch, or a broken dental arch. Both post canine occlusal contact area and chewing performance demonstrated significant differences between the different arches. It was concluded that chewing performance is reduced by removing posterior teeth from implant stabilised mandibular complete dentures.     

Fabrication of a functionally generated, implant-retained fixed partial denture

Partially edentulous patients are frequently restored with implant-supported restorations between and opposing natural teeth. Differences in horizontal and vertical mobility of teeth and dental implants necessitate occlusal contact modification to create prostheses that harmonize with the opposing dentition. This article describes a functionally generated path technique to achieve optimal articulation between an implant-retained fixed partial denture and the patient's dentition.     

Influence of mandibular free-end partial edentulism on the force exerted on maxillary anterior teeth

PurposeThe purpose of this study was to determine the influence of mandibular free-end partial edentulism and the wearing of removable partial dentures in the partially edentulous area on the force exerted on maxillary anterior teeth.MethodsA commercially available jaw model with exchangeable teeth was used. Seven experimental conditions of mandibular free-end edentulism were set up and a distal extension removable partial denture to replace missing posterior teeth was fabricated. Strain gauges were attached to the root surface of the maxillary left central incisor, canine, first premolar and first molar, and the force exerted on them was calculated based on the calibration coefficient. An occlusal load of 49 N was applied and the forces were compared with the Kruskal–Wallis test (P < 0.05).ResultsThe force exerted on the maxillary anterior teeth increased significantly as the number of remaining teeth decreased. The force exerted on the maxillary anterior teeth decreased significantly with use of a removable partial denture.ConclusionsWhen the number of remaining teeth decreases in mandibular free-end partial edentulism, the burden on the maxillary anterior teeth increases. Our findings suggest that for patients with mandibular free-end partial edentulism, wearing a removable partial denture is effective in preserving the remaining teeth by reducing excessive stress.     

咬合重建相关病例回顾及修复流程研究

目的根据咬合异常的不同临床表现，应用不同的修复方法进行咬合重建，评价临床效果，讨论与咬合重建相关疾病的临床诊断及修复设计流程。方法64例咬合异常患者按照修复前检查-诊断-修复设计-咬合重建修复-修复后评价的临床步骤，进行固定修复、固定-可摘局部义齿修复及可摘局部义齿修复咬合重建，于修复前后分别检查颞颌关节健康状况、义齿使用情况与咀嚼效能。结果咬合重建修复1年后，30例颞颌关节紊乱病患者中的25例治愈，对关节区疼痛与关节弹响的疗效差异有统计学意义：全部患者对咬合重建修复的临床效果满意，与可摘局部义齿修复相比较，固定修复、固定-可摘局部义齿修复在义齿舒适度（X^2=5．25，P〈0．05）和对发音影响（X^2=10．86，P〈0．05）等方面的满意度较高，差异有统计学意义；不同种类修复之间及选用不同种类修复咬合重建修复前（F=9．248，P〈0．05）和修复后（F=4．858，P〈0．05），患者咀嚼效能的差异有统计学意义。总结和制定与咬合重建相关疾病的临床诊断流程及修复设计流程。结论运用系统化的临床诊断流程及修复设计流程，能保障获得准确的诊断与针对性的修复设计，保证咬合重建诊疗修复取得成功。     

Electromyographic analysis of masticatory and neck muscles in subjects with natural dentition, teeth-supported and implant-supported prostheses

Objectives: To compare the electromyographic (EMG) characteristics of masticatory and neck muscles in patients with natural dentition, teeth‐supported prostheses and implant‐supported prostheses. Materials and methods: Twenty‐five subjects aged 40–80 years were examined. Five patients had maxillary and mandibular implant‐supported fixed prostheses; five patients had mandibular implant‐supported fixed prosthesis and maxillary removable complete denture; seven patients had implant‐supported fixed prosthesis (one arch) and natural dentition or full‐arch tooth‐fixed prosthesis (one arch); and eight control subjects had natural dentition or single tooth‐fixed prostheses. Surface EMG of masseter, temporal and sternocleidomastoid muscles was performed during maximum teeth clenching and unilateral gum chewing. Interarch dental contacts were assessed with shim stocks. Results: All groups had similar interarch dental contacts (P>0.05). During clenching, patients with maxillary and mandibular implant‐supported fixed prostheses had unbalanced standardized masseter and temporalis anterior activities (74%), with significantly larger values found in the other patients and control subjects (all mean values larger than 86%, P=0.017). All patients chewed with significantly larger muscular potentials than control subjects (on average, 1434–2100 μV s vs. 980 μV s, P=0.04), and had altered muscular patterns (left side, P=0.021). The patients with one arch with natural dentition/tooth fixed prostheses had chewing muscular patterns similar to the control subjects. Conclusions: Clenching with the analyzed prostheses was performed with a relative increment of temporalis activity. Neuromuscular coordination during chewing was larger in patients who maintained their teeth or dental roots, independently from the number of dental contacts.     

Factors associated with mucosal pain in patients with partial removable dental prostheses

The aim of this study was to investigate factors associated with mucosal pain in patients with partial removable dental prostheses (PRDPs). In this hospital‐based cross‐sectional study, 333 patients wearing 500 PRDPs (mean age 71·4 years, men 33·3%) were consecutively recruited from prosthetic clinic of a dental hospital in Japan. Subjects rated pain intensity and frequency of denture‐bearing mucosa. An examiner recorded age, gender and systemic diseases as well as dental, mucosa, denture, sensory, behavioural‐ and psychological‐related characteristics that were possibly associated with the mucosal pain. Multivariate analyses were performed to analyse factors related to mucosal pain. Pain intensity was rated as more than score 0 (presence) in 34·2% (171/500) PRDPs, and pain was experienced after denture delivery in 42·8% (214/500) PRDPs. Logistic regression analyses showed that younger age, mucosal damage, poor mucosal condition, bone prominence, poor residual ridge, higher pain sensitivity, presence of awake bruxism, perception of oral dryness, interim denture wear and high number of missing teeth were significant independent predictors for the presence of the mucosal pain intensity and/or frequency (P < 0·05). Multiple factors are associated with mucosal pain in patients with PRDPs. Oral mucosal characteristics, age, pain sensitivity and behavioural factors seem to be more critical for mucosal pain than distribution of missing teeth and number of abutment teeth.     

Repair of a Removable Partial Denture Using Gold Occlusals

Limited interarch space causes maintenance problems with removable partial dentures. The problem of abrasion and breakage of acrylic resin teeth, the concomitant supraeruption of opposing natural teeth, and possible decrease of vertical dimension of occlusion can be prevented or minimized with cast-gold occlusals. Use of metal occlusals has been advocated on newly constructed removable partial dentures, but not on existing prostheses with severely worn or broken denture teeth. This article describes a repair procedure for a removable partial denture where minimal interarch distance resulted in wear and breakage of denture teeth. A thin, abraded denture tooth that had been repaired numerous times was prepared and covered with a cast gold restoration. The problem of abrasion and breakage of the acrylic resin tooth was solved and the service life of the prosthesis was extended.     

Clinical evaluation of removable partial denture rest seat adaptation

The clinical relationship between the removable partial denture cast occlusal rest and the corresponding rest seat was examined. Under the conditions of the study, it was found that rests of mandibular Class I and II removable partial dentures fit significantly better than those of mandibular Class III and IV prostheses. No significant difference was noted between similar types of maxillary removable partial dentures in this regard. In evaluating the fit of specific portions of the occlusal rest, it was found that the marginal ridge zone was more closely adapted to the rest seat than other zones for all types of removable partial dentures. However, contact, as defined in this analysis, was found to exist on a random basis in all four quadrants of the occlusal rests evaluated. In spite of this fact, one fifth of the occlusal rests did not contact the opposing rest seat at any point. Improved fit with length of service was not substantiated by a cross-sectional analysis. Suggestions were made to assist the clinician in achieving a better fit between the framework and dentition in removable partial dentures.     

Present status of titanium removable dentures--a review of the literature

Although porcelain and zirconium oxide might be used for fixed partial dental prostheses instead of conventional dental metals in the near future, removable partial denture (RPD) frameworks will probably continue to be cast with biocompatible metals. Commercially pure (CP) titanium has appropriate mechanical properties, it is lightweight (low density) compared with conventional dental alloys, and has outstanding biocompatibility that prevents metal allergic reactions. This literature review describes the laboratory conditions needed for fabricating titanium frameworks and the present status of titanium removable prostheses. The use of titanium for the production of cast RPD frameworks has gradually increased. There are no reports about metallic allergy apparently caused by CP titanium dentures. The laboratory drawbacks still remain, such as the lengthy burn-out, inferior castability and machinability, reaction layer formed on the cast surface, difficulty of polishing, and high initial costs. However, the clinical problems, such as discoloration of the titanium surfaces, unpleasant metal taste, decrease of clasp retention, tendency for plaque to adhere to the surface, detachment of the denture base resin, and severe wear of titanium teeth, have gradually been resolved. Titanium RPD frameworks have never been reported to fail catastrophically. Thus, titanium is recommended as protection against metal allergy, particularly for large-sized prostheses such as RPDs or complete dentures.     

Shortcomings of prosthodontic rehabilitation of patients living in long‐term care facilities

Removable dentures are a non‐invasive, cost‐effective prosthodontic solution for the reduced dentition. Their intended purpose is the rehabilitation of harmonious oral function and aesthetics on a long‐term basis. The prevalence of removable dentures among patients of advanced age is high and the quality of the dentures is often poor. The aim of this study was to find the most important shortcomings of removable dentures and address the main targets for improving the quality of prosthodontic rehabilitation. The records from dental check‐ups in Austrian residential homes were analysed retrospectively. Dental anamnesis questionnaires and data from the clinical examinations of 105 denture wearers were analysed. The functional condition and retention of 192 dentures had been assessed, as well as the impact of the dentures on the intra‐oral tissues. Insufficient denture retention was very common, particularly in the lower jaw (56·0%). Problems with the masticatory function were reported by 26.7% of the denture wearers, 11·4% were dissatisfied with the denture aesthetics, and 4·8% had difficulties with phonetics. Traumatic ulcers were found in 18·1%. Cracks, broken pieces (6·3%) or missing denture teeth (2·1%) were rare. It may be assumed that the findings of the present study also apply to a great percentage of community‐dwelling seniors. The most important issues in prosthodontic rehabilitation with removable dentures are denture retention and masticatory function. Regular dental check‐ups, denture adjustment and, when necessary, relining can maintain the primary denture quality and prevent damages of the oral tissues caused by ill‐fitting dentures.