Oral perception and proprioception: a review of the literature and its significance to prosthodontics

Correlation of Bite Force Interpretation in Maximal Intercuspal Position among Patient, Clinician, and T-Scan III System

OBJECTIVE

 The main purpose of this article was to determine the correlation of bite force in maximal intercuspal position (MIP) among patient's perceptions, clinician subjective interpretation, and T-Scan III system.

MATERIALS AND METHODS

 Forty-three dental students at Naresuan University (Phitsanulok, Thailand) participated in the study. Subjects were positioned by Frankfurt horizontal plane paralleled to the horizontal plane and asked to bilaterally clenched in MIP. Patient's perception was evaluated by asking which side of the jaw had heavier bite force (right, left, or equally on both sides). Then, the clinician subjective interpretation was assessed using traditional occlusal indicators. Furthermore, patient's bite force was analyzed using T-Scan III.

STATISTICAL ANALYSIS

 Cohen's weighted kappa test was used to evaluate the correlation of bite force.

RESULTS

 The best correlation between patient's perception and T-Scan III was at the ± 7.5% cutoff range with 15 subject agreements. While the best correlation between clinician subjective interpretation and T-Scan III was at ± 5.0% cutoff range with 23 subject agreements. Cohen's weighted kappa indicated slight agreement between T-Scan III and patient's perception and fair agreement between T-Scan III and clinician.

CONCLUSIONS

 Clinician subjective interpretation is more clinically reliable than patient's perception when T-Scan III is used as a gold standard.

Sensorial Ability, Mastication and Nutrition of Single-Implant Overdentures Wearers

Abstract The use of two-implant overdentures improves mastication of edentulous elderly patients. However, little is known about the effects of single-implant overdentures (SIO) on oral perception and masticatory function in such elders. This study compared the effects of conventional complete dentures (CD) and SIO on the oral sensorimotor ability (OSA), masticatory function, and nutritional intake of elderly people with residual alveolar mandibular height classified as Class III or IV according to the American College of Prosthodontics. Twelve elders first received new conventional CD, which were later converted to SIO. All variables were evaluated after use of each prosthesis for 2 months. To evaluate OSA, elders closed their eyes and orally identified test pieces prepared from raw carrots. A kinesiographic device was used to measure chewing movements during mastication of a test material (Optocal). Masticatory performance (MP) was determined with the sieving method, and a 3-day food diary verified nutrient intake based on a standard Brazilian Food Composition Table. Data were analyzed using the Wilcoxon signed rank test and Student’s paired t test (P < 0.05). OSA results did not differ according to prosthesis type. However, opening and closing velocities during chewing and MP increased after SIO insertion (P < 0.05). Although no difference was observed in the intake of most nutrients, sodium ingestion decreased after SIO insertion (P < 0.05). SIO use had no effect on OSA, but significantly improved mastication and sodium intake of elders with decreased residual ridges height (Brazilian Registry of Clinical Trials #RBR-3kgttj).

Overdenture Prostheses with Metal Copings: A Retrospective Analysis of Survival and Prosthodontic Complications

PURPOSE

To retrospectively evaluate complications associated with overdentures and abutment teeth restored with metal copings, including post-procedural and prosthetic problems; also to analyze the frequency and influencing factors associated with these problems.

MATERIALS AND METHODS

A total of 80 subjects (48 females, 32 males, mean age 62 years) wearing root-supported overdentures were enrolled in the study. All participants were thoroughly examined by a single examiner, and appropriate maintenance care was performed. The 80 subjects had 270 abutments, which were endodontically treated teeth. All 80 subjects were carefully interviewed, inspected, and evaluated for post-procedural and clinical problems with their overdentures for an observation period of up to 5 years.

RESULTS

Of the post-procedural problems evaluated, the most common problems were gingival inflammation (69%) and root caries (36%) because of poor oral hygiene (41%) and loss of metal copings (34%), followed by overdenture base fracture over abutment teeth (34%). Other post-procedural problems reported were loss of overdenture stability (23%), incidence of overdenture repair (20%), poor retention (18%), incidental finding of root fragments (unplanned) in the jaws (15%), and up to two grade net change in the mobility of overdenture abutments (8%). All prostheses were in use at the time of data collection and observation up to 5 years.

CONCLUSIONS

Overdenture therapy was satisfactory; however, post-procedural and prosthetic complications and aftercare maintenance must not be underestimated.

Evaluation of oral stereognostic ability after rehabilitating patients with complete dentures: in vivo study

Stereognosis has been defined as the appreciation of the form of objects by palpation. Whilst this definition holds good for the manual exploration of objects, it is possible for the shape of objects to be explored intra orally referred to as oral stereognosis. To better understand patients' relative satisfaction with complete dentures, differences in oral stereognostic perception, based on the identification of 6 edible objects was analyzed in a group of 30 edentulous individuals at 3 stages, namely, just before (pre-treatment), 30 min after (30 min post-treatment) and 1 month after (1 month post-treatment) the insertion of new dentures. The time required to identify each object was recorded and the correctness of identification of each object was scored using oral stereognostic score. Descriptive statistics, Wilcoxon signed rank test, Spearman's rank correlation test, Pearson Chi square test was used to statistically analyze the data obtained. OSA scores was significantly increased 1 month post-treatment compared to 30 min post-treatment (p < 0.05). It was found that Oral stereognostic test is reliable for measuring patients' oral stereognostic perception and may be used as one of the clinical aids in appreciating the functional limitations imposed by the prostheses.

Precision attachment: retained overdenture

Precision attachments are small interlocking devices to connect prosthesis and abutments that offer a variety of solutions to the challenge of balance between functional stability and cosmetic appeal. Precision attachments have wide applications, used in fixed removable bridge, removable partial dentures, overdentures, implant retained overdentures, and maxillofacial prosthesis. Attachment retained overdentures helps in distribution of masticatory forces, minimizes trauma to abutments and soft tissues, attenuate ridge resorption, improves the esthetics and retains proprioception. The following case report discusses the use of resilient stud attachments to retain maxillary and mandibular overlay complete dentures.

Evaluation of minimum interdental threshold ability in dentate female temporomandibular disorder patients

Minimum interdental threshold is the smallest thickness that can be detected between teeth during an occlusion and has an influence on the occlusal force and on the control of mandibular movements. The aim of this study was to assess the possible association of the signs and symptoms of temporomandibular disorders (TMD) with the ability to detect a minimum interdental threshold. Two hundred women were equally divided into four groups: asymptomatic (control), subjects with masticatory muscle pain, with articular [temporomandibular joint (TMJ)] pain and mixed (muscular and articular pain). Evaluation of the ability to detect a minimum interdental threshold was performed using aluminium foils with 0.010, 0.024, 0.030, 0.050, 0.080 and 0.094 mm of thickness in the premolar region. A total of 20 tests with each thickness for each patient were performed, starting with the thickest foil (0.094 mm) and ending with the thinnest one. The myogenic pain and articular groups presented significantly higher threshold values (0.020 and 0.022 mm, respectively), when compared to the control. Both groups reached the level of certain perceptiveness only at 0.030 mm. No significant correlation was found between minimum interdental threshold and age. These results suggest that discrimination of thicknesses can be disturbed as a consequence of TMD manifestations and not the cause of it. Clinicians should, therefore, be aware that changes on muscles and TMJ can secondarily lead to occlusion changes. The mechanisms involved in this process, however, are not well understood and warrant further investigation.

Influence of age on mastication: effects on eating behaviour

The present review covers current knowledge about the ageing of oral physiology related to mastication and its effects on eating behaviour. Mastication is the first process undergone by a food during feeding. It has a key role in the maintenance of nutritional status in two respects. First, the perceptions of food's sensory properties elicited during chewing and swallowing are one of the major determinants of the pleasure which drives us to eat; second, the properties of the swallowed bolus are affected by oral conditions and this may modulate the subsequent phases of digestion. Ageing in healthy dentate subjects induces moderate changes in oral physiology. Changes in neuromuscular activity are partly compensated by changes in chewing behaviour. No clear age effect is seen in texture perception, although this does impact on food bolus properties. In contrast, great alterations in both chewing behaviour and food bolus properties are observed when ageing is associated with a compromised dentition, general health alterations and drug intake. Eating behaviour is far more complex than just chewing behaviour and the concerns of the elderly about food cannot be explained solely by oral physiology. Discrepancies are often noticed with older subjects between various objective measurements of oral performance and corresponding measures of self-perception. In addition, although more foods are recognised as hard to chew with increasing age, there is no clear shift in preference towards food that is easy to chew. Food choices and food consumption are also driven by memory, psychology and economic factors. Advances in the understanding of food choice in the elderly need a sustained collaborative research effort between sensory physiologists, nutritionists, and food scientists.

Implant-retained removable prosthesis with ball attachments in partially edentulous maxilla

This clinical report presents a restorative option for the partially edentulous maxilla utilizing an implant-retained removable partial denture without retentive clasps. This approach required (1) fewer patient visits and laboratory procedures; (2) the use of minimal number of implants; (3) lower financial obligations; and (4) no sinus elevation surgery. The use of O-ring attachments provided excellent retention and stability. The detachable prosthesis over implants allows easier oral hygiene by the patient and provides superior esthetics and phonetics in cases involving advanced ridge resorption.

The influence of dentures on nasalance values in speech

OBJECTIVE

The purpose of this study was to investigate the effects of maxillary dentures on nasalance values in normal elderly individuals.

DESIGN

A three-factor within-subjects experimental design was employed to analyze the nasalance scores obtained.

PARTICIPANTS

Twenty English-speaking women aged 61 to 81 years, who wore complete maxillary dentures, participated in the study.

INTERVENTION

A Nasometer was used to collect nasalance data. Participants read three standard passages aloud, three times each, in two conditions: with and without their maxillary dentures.

RESULTS

Results revealed that nasalance values were significantly lower with the maxillary dentures removed (p<.01), although the difference in nasalance between the two denture conditions averaged no more than 2%. Nasalance scores obtained both with and without maxillary dentures fell within one standard deviation of the mean for a reference group of comparably aged English-speaking women.

CONCLUSIONS

The results suggest that the existing collection of normal reference data for nasalance may be safely used for elderly individuals regardless of their status with respect to natural or prosthetic maxillary dentition.

Oral stereognosis in edentulous subjects rehabilitated with complete removable dentures

Oral stereognosis was analysed in a group of edentulous subjects rehabilitated with complete removable dentures. Stereognosis was evaluated with and without the denture in place. The results showed that the older subjects had poorer stereognostic ability than the younger ones, whereas the duration of edentulism appeared not to influence this ability. The presence of a correct prosthetic rehabilitation appeared to improve stereognostic ability. Subjects with poorer stereognostic ability appeared more satisfied with their rehabilitation than did those with better stereognostic ability.

Quantitative and somatotopic mapping of neurones in the trigeminal mesencephalic nucleus and ganglion innervating teeth in monkey and baboon

Neurones of the trigeminal mesencephalic nucleus (Mes V) and ganglion innervating the periodontium of incisor, canine and molar teeth in 10 monkeys and 10 baboons were counted and mapped using the horseradish peroxidase (Hrp), retrograde axonal transport method. Periodontal afferent neurones of all these teeth were well represented in the Mes V, although the incisors had a significantly higher number of labelled neurones than the canines or molars. The primary cell bodies of the periodontal afferents were located mainly in the caudal part of the ipsilateral Mes V from the level of the inferior colliculus to the floor of the fourth ventricle in the pons. The caudal periodontal Mes V neurones may be favourably located to make collateral connections with the trigeminal motor nucleus for jaw reflexes. Incisors and canines had a large and predominantly ipsilateral representation of Hrp-labelled neurones in the ganglion. In contrast, molar representation in the ganglion was sparse and all labelled neurones supplied ipsilateral teeth. The maxillary and mandibular teeth had a somatotopic distribution within the respective maxillary (middle) and mandibular (posterolateral) compartments of the trigeminal ganglion. It is suggested that the anterior teeth with greater connections to the Mes V and the ganglion may impart greater sensory perception and be involved in jaw reflexes to ensure a good occlusal relation during mastication, while the afferent connections of the molars may initiate complex jaw reflexes during the occlusal phase of mastication.

Overdentures with roots or implants for elderly patients: a comparison

Roots maintained under the denture base preserve the alveolar ridge, provide sensory feedback and improve the stability of the dentures. Furthermore, with the use of copings and precision attachments, retention of the denture is provided. Overdentures are a favored treatment modality for elderly patients with few remaining teeth because adaptation to wearing dentures is facilitated. Recently, overdenture treatment with the use of implants has become popular for edentulous elderly patients who are maladaptive to complete dentures. Although the biologic basis of implants installed in the bone is different from roots surrounded by a periodontal membrane, the prosthetic concept is similar. Tactile sensibility is reduced because of the absence of periodontal receptors. However, oral function with overdentures supported by roots or implants is comparable and does not seem to depend on the presence of a periodontal membrane. Comparison of studies demonstrates a higher tendency for success when overdentures are supported by implants than by roots. This is particularly true for mandibular overdentures, whereas for maxillary implants, more frequent failures are observed with low bone quality and short implants. This study discusses results and special applications with regard to an elderly population who will profit from the benefit of overdenture therapy.

Role of periodontal ligament receptors in the tactile function of teeth: a review

The tactile function of the human periodontal mechanoreceptors has mostly been studied by psychophysical approaches. It was concluded that periodontal mechanoreceptors play a major role in the tactile function of teeth. It must be noted however that the interocclusal tactile threshold is not solely determined by periodontal mechanoreceptors but also by pulpal, muscular or articular receptors. While temporomandibular joint receptors play a minor role, muscular receptors are important in the discriminatory ability for a mouth opening of 5 mm and more. To discriminate between the contribution of periodontal and other receptors in the oral tactile function, future studies should use appropriate psychophysical methodologies and well-defined stimulus parameters.

The immediate effect of the variation of anteroposterior laterotrusive contacts on the elevator EMG activity

A unilateral maxillary splint divided into three occlusal blocks was built for eight healthy young adults. The three blocks allowed the anteroposterior location of the laterotrusive contacts to vary and to distribute the occlusal force over equivalent periodontal surfaces. The ipsilateral masseteric and temporalis electromyogram (EMG) activities were recorded with surface electrodes during maximal voluntary clenching. The elevator EMG activity with the anterior occlusal block in place was significantly lower than with the intermediate or posterior blocks. The reduction for both elevators with the intermediate block in place did not show a significant variation in comparison to the posterior block of the three blocks inserted. The elevator activity with the three occlusal blocks did not differ from that recorded with the posterior block alone. Neurophysiologic and biomechanical explanations are given related to this laterotrusive elevator muscular behavior.

Blocking of periodontal afferents with anesthesia and its influence on elevator EMG activity

The effect of anesthetic blocking of the periodontal afferents of the canine teeth was studied in order to determine its influence on any changes in the jaw elevation activity. Unilateral integrated EMG recordings were made of the masseter and anterior temporal muscles during maximal voluntary clenching in centric occlusion and laterotrusive position with canine contact. After anesthetic blocking of the periodontal afferents of one or both ipsilateral canines, a significant increase was observed of the EMG activity of both jaw elevator muscles studied, in centric occlusion as well as with canine contact. The elevator activity increase was of a greater magnitude when antagonistic canines were anesthetized. These findings thus support the hypothesis that high threshold periodontal receptors exert an inhibitory effect on jaw elevator muscular activity.

Influence of variation in anteroposterior occlusal contacts on electromyographic activity

A full upper stabilization splint divided into three pairs of occlusal bilateral blocks was made for eight healthy young adult subjects. The three pairs of blocks allowed the location of the centric occlusal contacts to vary and to be distributed over equivalent periodontal surfaces. The electromyographic activity of the masseter and temporal muscles was recorded with surface electrodes during maximum voluntary clenching over the centric occlusal blocks. The electromyographic activity from the elevator muscles with the anterior blocks was significantly less than with the intermediate and posterior occlusal blocks. With use of the intermediate blocks, the activity from the elevator muscles was significantly less than with the posterior blocks. The elevator activity with the posterior blocks was similar to that with the full coverage splint.

Influence of group function and canine guidance on electromyographic activity of elevator muscles

A comparative EMG study was done between two types of occlusal guidances: group function and canine guidance. The purpose was to determine which of the two occlusal schemes causes a greater reduction in muscle activity and thereby a decrease in muscle tension in eccentric mandibular positions. Full-coverage occlusal splints were made for six test subjects with normal function of the stomatognathic system. Left- and right-side integrated EMG recordings were made of the masseter and temporal muscles during static (clenching) and dynamic (lateral excursion and clenching) maximal contractions. The results showed an EMG activity reduction of the elevator muscles with group function relative to their activity in centric occlusion. A more marked reduction was observed on the mediotrusive side, mainly in the temporal muscle. With canine guidance, the reduction in elevator muscle activity is much greater, more significant, and mainly in the temporal muscle of the mediotrusive side. The clinical implications of this study suggest the use of canine guidance in laterotrusion for therapy with full-coverage occlusal splints.

Bite force discrimination by individuals with complete dentures

The purpose of this study was to determine whether differences existed in interincisor bite force discrimination between a group of subjects wearing complete dentures and a group of dentate individuals. It was hypothesized that biting force is monitored at least in part by the sensory mechanism within the PDL and that the absence of the PDL would result in reduced bite force discrimination. A specially designed strain gauge scale was constructed for the measurement of bite force. Bite force discrimination was assessed at three different standards including 500, 1000, and 3000 gm. Data analysis revealed that, overall, bite force discrimination was not significantly different for the two groups. However, at the lightest standard of 500 gm, the dentate group performed significantly better (p less than .05) than the denture wearers. It is concluded that the sensory system within the PDL plays a role in monitoring bite force discrimination.

Magnetic retention units for overdentures

Mechanical attachments used to improve retention of overdentures have their limitations. With the recent development of the cobalt-samarium magnet an alternative method of achieving increased overdenture retention is offered. The most suitable form of magnet appears to be of a reverse split pole design with a ferromagnetic disc or keeper which will ensure a closed magnetic field. Clinical techniques involve conventional endodontic therapy, and the basic method of overdenture construction can be followed with only minor modification.

The absence of proprioceptive nerve endings in the human periodontal ligament: the role of periodontal mechanoreceptors in the reflex control of mastication

A review of the literature was conducted to determine the presence or absence of proprioceptive nerve endings in the human periodontal ligament. A histologic review of the periodontal ligament innervation concluded that nerve endings found were those mediating pain, pressure, or touch and that there is no histologic evidence of any "classic" proprioceptive nerve ending in the periodontal ligament. A summary is given concerning the precise role of nerve endings in the periodontal membrane, their afferent pathways, and the role of masticatory muscle proprioception, jaw reflexes, and the temporomandibular joint in the coordinated control of mastication and mandibular proprioception.

A clinical study of rest position using the Kinesiograph and Myomonitor

The clinical study was designed to study the vertical dimension of rest position and mandibular closure to maximum intercuspation of the teeth before, during, and after relaxation procedures on 14 subjects with stable dentitions. The findings call attention to the potential of both the Myomonitor and the Kinesiograph for research and clinical use, to the physiologic need for flexibility of the vertical dimension of rest position, and to the importance of measuring all three dimensions when examining the rest position.

Alveolar bone loss in overdentures: a 5-year study

The results of a 5-year clinical study show that patients treated with complete maxillary dentures and mandibular overdentures demonstrate less vertical alveolar bone reduction than patients with complete maxillary and mandibular dentures.

Effects of occlusal therapy on pantographic reproducibility of mandibular border movements

A clinical experiment was undertaken to study the relationship between occlusal therapy and pantographic reproducibility. Twenty-six subjects were categorized according to their ability to reproduce pantographic border movements and were put into either a control nonreproducible, control reproducible, or experimental nonreproducible group. From each subject a sequence of five pantographic surveys consisting of two morning and two afternoon pantographic recordings was taken. Each survey period lasted a minimum of 30 days. The experimental subjects alone were given occlusal splint therapy and occlusal adjustment therapy during the sequence of recall periods. The relationship between the effect caused by occlusal therapy and pantographic reproducibility was analyzed. For the purpose of analysis, the pantographic recordings were assessed a numerical score using a pantographic reproducibility index. A double-blind technique was used until all data were collected.

Influence of immediate dentures on oral motor skill and speech

An investigation was designed to test whether the precision of finely coordinated orofacial movements is influenced by the transition from natural to artificial dentition. The oral motor skill of 16 patients was tested before extraction and within 2 weeks of wearing immediate dentures. Speech recordings were employed to detect changes in voice quality and speech sound production. Results showed that the loss of natural teeth and the wearing of immediate dentures did not alter sensorimotor pathways significant to the precision of oral motor skills. It was also determined that physical characteristics of dentures are significant factors in the production of acceptable speech.

Dolder bar joint mandibular overdenture: a technique for nonparallel abutment teeth

A mandibular overdenture technique has been presented that utilizes the Dolder bar joint attachment. Endodontically treated lower canines were retained as abutments. Two techniques for attaching the bar to teeth with divergent root canals were discussed: (1) the Schubiger screw system for those teeth with extremely divergent canals and (2) the Stutz pivots system for teeth with only slightly divergent root canals. The use of the Dolder bar joint offers periodontally involved teeth an improved crown/root ratio and splinting of the teeth. Because the bar is close to the alveolar bone, forces of mastication exert much less leverage to the teeth. Finally, the bar joint offers slight vertical and rotational movement of the denture as well as a stressbreaker action.

Sensory perception in overdenture patients

The discussion of overdentures has been confined to their capacity to use abutment teeth to improve neuromuscular control of mandibular movement. Use of overdentures has been favored often because of their mechanical advantages, but seldom because of the sensory role of the retained abutment teeth. Even though the retained teeth may be periodontally diseased, they still may provide sufficient support for the transmission of masticatory pressures and sufficient periodontal ligament receptors to initiate a jaw opening reflex. Whereas conflicting evidence shows that the periodontal nerve receptors play a role in mandibular positional sensibility (proprioception), pressure perception by the periodontal ligament remains a primary stimulus for the jaw opening reflex. Additional investigations will be essential to a complete understanding of the role of the periodontal ligament receptors. However, recognition of the importance of the periodontal ligament receptors to the overdenture patient as a source of sensory input is vital.

Clinical, radiographic, and histological study of endodontically treated retained roots to preserve alveolar bone

Endodontically treated, submerged roots in two Macaca speciosa monkeys were studied clinically, radiographically, and histologically. The roots were successfully covered by soft tissue, except in two areas. In several sites, radiographic evidence of bone formation was observed; this was confirmed by histologic examination. Bone formation coronal to the submerged roots was not a predictable occurrence. Even though epithelium and inflammation commonly occurred over the amputation sites, their presence did not seem to affect bone formation.