Analyzing dental occlusion for implants: Tekscan's TScan III

Though no single, specific occlusal pattern has been developed that is ideal for oral implantology, research suggests some general criteria for deciding on a particular occlusal pattern that will help reduce cuspal interferences and lessen horizontal or lateral forces on the fixtures. Anticipated occlusal and chewing forces need to be taken under consideration for any implant-supported prosthesis. In addition, opposing dentition, as well as potential parafunctional mandibular movements, should be noted. Tekscan's T-Scan Occlusal Analysis System can help clinicians meet the needs of their patients for reliable measurements of occlusal biting forces. The T-Scan III System is Tekscan's most recent attempt to help dental clinicians obtain consistent and useful occlusal data for the placement, analysis, and repair of dental implants.     

Early and late electromyographic response to treatment with activators.

An EMG analysis of twenty Class II cases treated with activators shows that: 1. During daytime use of activators, the protractor muscles of the mandible are stimulated, while the retractors are inhibited. 2. During nightime use of activators, no functional stimulation can be recorded. The activator appears to be operated mainly by tissue stretching and the accompanying elastic rebound. 3. Before treatment, as well as after the treatment, Class II cases show a balanced EMG pattern during closure in the intercuspal position. 4. A narrow upper arch should be expanded before treatment in order to avoid occlusal interferences and to make it easier for the lower arch to adapt itself to a protruded position.     

Recurrence: mechanisms and treatments

An original analysis by computer has been imagined. Etiological diagnosis in recurrence's cases is based on asymmetry. Different levels were investigated: dental arch, ridge, basal bone and mandibular position. Dental shift, deformed bone, eccentric mandibular and occlusal distortion were found. Each molar is independently moving. Mandibular basal bone is stabilized in the transverse dimension. Mandibular deviation induces compression or stretching in temporo-mandibular articulation. Occlusal interferences involve distortion of cuspal plans. To reach stable objectives, molars require symmetrical position below one millimeter discrepancy, molar locking is to be had for the disto-vestibular cusp and ovoid arch. A special anchor apparatus allows to correct every wrong position of each individual molar, in each three-directional space. Mini-positioner or mini-splint perfect anterior misalignment. Sometimes, thermical memory archs are required. Ten fundamental rules that regulate occlusal and mandibular stability have been checked after treatment.     

Results of a clinicopsychological study of diseases of the temporomandibular joint.

Patients' complaints relating to disorders of the temporomandibular joint appear to be becoming more frequent and to be occurring in younger age groups. In many cases no organic cause affecting the joint or the masticatory system can be identified as the sole cause of the symptoms. An investigation was therefore undertaken to determine whether psychological causes might also be implicated. Two questionnaires were used to establish a complete picture of patients from a number of countries who suffered from disorders of the temporomandibular joint. The first questionnaire sought particulars of the dental condition, family status, type of education, satisfaction with job and pay etc. The second was a personality questionnaire which had originally been prepared for the Olympic Games in Munich. Although the extensive data collected has not yet been fully evaluated it is clear that in addition to the well established dental causes such as shortened dental arches, deep overbite and cuspal interferences, a psychosomatic element is superimposed in many cases. It is hoped to develop a means by which those whose symptoms require a psychotherapeutic approach, either alone or in conjunction with dental treatment, can be identified.     

Occlusal interferences in orthodontic patients before and after treatment,and in subjects with minor orthodontic treatment need

Different opinions have been expressed concerning the effect of orthodontic treatment on mandibular function. One factor discussed is occlusal interferences. The aim of this study was to establish the prevalence of occlusal interferences in 210 orthodontic patients before (mean age 12 years 8 months) and after (mean age 16 years 10 months) treatment and to compare them with subjects with minor orthodontic treatment need. The results showed a decrease in retruded contact position/intercuspal position (RCP/ICP) interferences in all morphological deviations, age, and gender groups. The prevalence of mediotrusion interferences decreased in some types of malocclusions whilst in others there was no change. One reason for this is that treatment was started when the majority of the patients had no second or third molars erupted. At the final registration, the second molars were erupted in all patients, and the third molars were erupted in approximately 25 per cent. Mediotrusion interferences were more consistent with basal morphological deviations, for example, Class III relationships and anterior open bite were more consistent in the same person, and more difficult to eliminate than RCP/ICP interferences. RCP/ICP interferences, often caused by dental deviation in position, size, and shape, were easier to correct. Optimal orthodontic treatment, if necessary, including selective grinding, will decrease the prevalence of occlusal interferences.     

Mandibular function in children with a lateral forced bite

Open-close-clench cycles have been studied in 12 children with a lateral forced bite in order to investigate how the neuromuscular system of the mandible adapts itself in the presence of occlusal interferences. The mandibular movements were registered in a frontal plane at the central incisors with an opto-electronic registration technique. Series of 35 cycles were recorded to intercuspal position, against flat occlusal splints constructed in intercuspal raised and retruded positions, and against splints with occlusal stops in a retruded position. Average lateral displacements of the mandible during cycle series against flat occlusal splints were measured relative to cycle series to intercuspal position and relative to series against splints with occlusal stops in the retruded position. The lateral mandibular displacements were registered at maximal tooth-tooth or tooth-splint contact and at 7, 14, and 21 mm mouth-opening. It was found that the mandible in the subjects investigated is displaced to the forced bite side both during cycle series into intercuspal position as well as when occlusal contacts are eliminated by the use of flat occlusal splints.     

Stability of the implant/abutment joint in a single-tooth external-hexagon implant system: clinical and mechanical review

Rigorous efforts have recently been made to reduce the recurrence of implant/abutment joint failure in single‐tooth implant restorations. However, the current knowledge about the stability of implant/abutment joints in an external hexagon implant system is incomplete. We reviewed clinical data regarding single‐tooth implant treatment with Brånemark implants, specifically the CeraOne abutment system (Nobel Biocare AB, Göteborg, Sweden). In vitro studies on joint stability were systematically assessed. Bending overload and the presence of misfit at the implant/abutment joint interface are the critical mechanical conditions that can make the joint unstable. Appropriate joint fitness and proper alignment of the implant should be assessed, and occlusal adjustment by narrowing the restoration width and flattening cuspal inclination should be applied to avoid bending moments caused by the lateral component of occlusal forces. Sufficient clinical reports of longer duration that evaluate and verify longer‐term success of the newly manufactured joint components were unavailable.     

In vitro posterior composite polymerization recovery following hygroscopic expansion

Post-operative pain has been associated with composite polymerization shrinkage. This study aimed to quantify the cuspal deflection resulting from the initial shrinkage and the subsequent hygroscopic expansion of a standard posterior composite resin. Thirty hydrated permanent molars were marked on the buccal and lingual cusp tips. Standardized conventional Class II preparations were made and restorations with composite resin were placed and: (A) polymerized as one complete unit; (B) polymerized in gingivo-occlusal increments; (C) polymerized in buccolingual increments. Ten untreated teeth were marked and acted as controls. All specimens were placed in water. Pre-operative, post-operative and 6-month photographs were projected on a digitizer pad and measured by two independent investigators. The mean cuspal deflection (micron) immediately post-operatively and 6 months respectively, was: (A) 22.4, 8.7; (B) 12.4, 5.3; (C) 9.8, 3.0. The percentage of natural tooth dimensional recovery, following hygroscopic expansion was: (A) 97.5%; (B) 98.6%; (C) 99.4%. Buccolingual incremental polymerization led to significantly less initial cuspal deflection and the most cuspal recovery after hygroscopic expansion. The technique of resin placement therefore may provide a decrease in post-operative sensitivity.     

Seven-year clinical evaluation of painful cracked teeth restored with a direct composite restoration

The purpose of this study was to investigate long-term clinical effectiveness of treating painful cracked teeth with a direct bonded composite resin restoration. The hypothesis tested was that cracked teeth treated with or without cuspal coverage showed the same performance. Forty-one patients attended a dental practice with a painful cracked tooth that was restored with a direct composite resin restoration. Twenty teeth were restored without and 21 with cuspal coverage. After 7 years, 40 teeth could be evaluated. Three teeth without cuspal coverage needed an endodontic treatment, of which 2 failed as a result of fracture. No significant differences were found for tooth or pulp survival. Three more repairable restoration failures were recorded. Mean annual failure rate of restorations without cuspal coverage was 6%; no failures in restorations with cuspal coverage occurred (P = .009). A direct bonded composite resin restoration can be a successful treatment for a cracked tooth.     

Prevalence of symptoms of functional disturbances of the masticatory system in Swedish men

Subjective and clinical symptoms of mandibular dysfunction and cuspal interferences were studied in 389 Swedish men (median age 32 years). Impaired chewing function was noted in about 10%, different types of parafunction in 26%, frequent headaches in 5 %, TMJ or muscle pain in 3 % and difficulties in mouth opening in 10% of the men. Locking or luxation of the mandible was the most prevalent clinical symptom (24%), followed by reduced movement capacity and deviation on opening of the mandible, TMJ-sounds and muscle tenderness. Sixty per cent of the men had one or more clinical symptoms of dysfunction. Subjective symptoms of dysfunction were positively correlated with reduced movement capacity of the mandible and tenderness of the masticatory muscles and temporomandibular joints upon palpation. Positive correlations were found between subjective symptoms of dysfunction and non-working side interference as well as single tooth contact on the working side. Locking or luxation of the mandible and TMJ-sounds were positively correlated with single tooth contact on the working side and TMJ-sounds and muscle tenderness with interferences in the retruded position of the mandible.     

The implications of bracket selection and bracket placement on finishing details

It is this clinician’s opinion that the concept of anterior interferences has not received adequate attention in our clinical management of orthodontic patients. Much has been written on the subject of occlusal interferences in the posterior teeth during occlusal function. This article will deal with the impact that anterior interferences have in the possible causation of specific temporomandibular disorders and the impact of this information on how orthodontic cases should be finished. The effect of anterior interferences on occlusal dysfunctions is discussed. Finally, we will review the possible control of anterior interferences during fixed appliance mechanics. Five specific clinical sequela are identified, and their clinical implications in orthodontic treatment are reviewed.     

A reappraisal of the incremental packing technique for light cured composite resins

The cuspal flexure caused by a direct placement composite resin was measured using a technique that did not interfere with cuspal movement. Twenty upper premolar teeth with mesial-occlusal-distal (MOD) cavity preparations were restored using a posterior composite resin. Ten teeth were restored using a bulk packing technique and 10 were restored using three 'U' shaped bucco-lingual increments. Total cuspal movement was measured 1 h following the initiation of curing. Bulk placement of the composite resin produced slightly more cuspal movement (12.5 microm) compared with the incremental placement of composite (11.3 microm). This difference was not statistically significant. The technique of incremental packing to reduce cuspal flexure is therefore questioned.     

An onlay technique for teeth in supraversion

A technique for onlaying teeth in supraversion has been described. Through proper selection and preparation, teeth in supraversion may be restored to normal function on a favorable plane of occlusion. Proper preparation procedures assure maximum retention and stability through the use of intracoronal and extracoronal parallel walls and line angles. Hygienic restoration margins result from placement above the free gingival margins, and desired tooth contours are produced more readily because the enamel remains on the buccal and lingual surfaces. The thickness of the gold in cuspal areas and the requirements for pulp protection have been stipulated.     

Application of the Functionally Generated Path Technique to Restore Mandibular Molars in Bilateral Group Function Occlusion

The functionally generated path (FGP) is a static representation of the opposing cusps’ dynamic eccentric movements from a centric position to achieve optimal articulation and occlusal harmony. When understood and appreciated, use of the FGP technique is a straightforward and practical method to achieve harmonious occlusal anatomy of restorations with the anterior determinant/anterior guidance, the posterior determinant/condylar guidance, existing occlusal and cuspal anatomy, and the neuromuscular system. Although the FGP technique is normally used in the fabrication of maxillary posterior indirect restorations, it is described and applied here in the fabrication of mandibular posterior restorations that maintained the patient's bilateral group function occlusion while eliminating the nonworking side and protrusive interferences. This novel procedure involved the use of a stone crib to intraorally construct a stone core that captured the FGP recording while simultaneously indexing to the contralateral and ipsilateral mandibular dentition. This technique lends additional stability to the stone core to minimize error during the mounting process.     

Sixty-eight years of experimental occlusal interference studies: what have we learned?

STATEMENT OF PROBLEM: Understanding is needed regarding the effect that occlusal interferences have on the teeth, periodontium, and especially on jaw function. PURPOSE: This article summarizes research in which experimental occlusal interferences have been placed on the teeth of animals and human volunteers. MATERIAL AND METHODS: Data from 18 human and 10 animals studies were reviewed. Experimental occlusal interferences were grouped into those that alter intercuspal position and those contacting on lateral jaw movement only. The outcome of these interferences were analyzed according to their local pulpal-periodontal, jaw function, or bruxism effects. RESULTS: Experimental occlusal interferences in maximum intercuspation had a deleterious effect on periodontal and pulpal tissues of the affected tooth; sometimes this produces a disruption of smooth jaw function and occasionally jaw muscle pain and clicking. Experimental occlusal interferences that contact only in a lateral jaw movement are infrequently harmful to jaw function. Furthermore, no reliable evidence demonstrates that occlusal interferences can cause nocturnal bruxism, or stop it. CONCLUSION: Transient local tooth pain, loosening of the tooth, a slight change in postural muscle tension levels, chewing stroke patterns, and sometimes a clicking joint can be induced by an experimental occlusal interference. Because such findings are present in relatively asymptomatic patients, these data do not prove that occlusal interferences are causally related to a chronic jaw muscle pain or temporomandibular joint dysfunction problems.     

Anatomy of cusps of posterior teeth and their fracture potential

Fracture of cusps on posterior teeth, especially those carious or restored, is a major cause of tooth loss, Nonfunctional cusps fracture more often than the functional; mandibular cusps fracture more often than maxillary cusps. This study examined functional and nonfunctional cusps of the maxillary and mandibular posterior teeth in four different parameters; (1) buccolingual width, (2) angle of cuspal inclination, (3) thickness of enamel, and (4) angle of inclination of the dentinoenamel junction. Measurements of functional cusps, except those in maxillary premolars established differences that may explain the frequency of frequency of fracture. These parameters of functional and nonfunctional cusps suggest that the cuspal anatomy has a relationship to the fracture potential of cusps.     

Assessment of occlusal interferences

The variability in the assessment of occlusal variables was investigated in eight subjects by the repeated registrations of four observers. The following variables were investigated in three different ways: sliding between the RCP (retruded contact position) and the ICP (inter-cuspal contact position) in the sagittal, vertical and lateral plane. Interferences during lateral movements on the working and balancing sides as well as interferences causing deviation of the mandible during protrusive movements were recorded. The intra- and inter-observer error for the measurement of sagittal and vertical distance RCP-ICP was within acceptable limits. There was no significant difference between the three methods used. The intra- and inter-observer agreement between duplicate recordings of the lateral distance RCP-ICP was high and there were no differences between the different measurement modalities. The inter-observer agreement was lower than the intra-observer agreement concerning presence/absence of balancing side interferences, and positive inter-observer agreement was only found on lateral movement more than 3 mm from the RCP or the ICP. The observer error for the variable working side interferences should be acceptable for future research, while the observer error for measurement of lateral deviation of the mandible upon protrusion was somewhat larger.     

An in vivo study of voluntary mandibular lateral translation concerning its existence, magnitude, and timing

Statement of problem. The existence of mandibular lateral translation and the approaches to its measurement and interpretation by using a pantograph are controversial. Purpose. This study evaluated the validity of using a pantograph to measure mandibular lateral translation and analyzed human pantographic tracings to determine whether they exhibited mandibular lateral translation. Material and methods. A pantograph was modified by adding 2 posterior horizontal recording tables and styli at the transverse horizontal axis. Pantographic tracings of 25 human subjects were compared with the corresponding theoretically determined values for tracings that exhibited only rotation with no translation. Differences in the tracings at 2 pantographic recording table locations, relative to the transverse horizontal axis, were also compared. Results. The character of the lateral component of 100 pantographic tracings all differed from the lateral component of theoretically determined values for pure rotation. In 64% of tracings, over 50% of the total mandibular lateral translation occurred by the first 1 mm of forward movement of the nonworking side condyle. In 94% of tracings, more than 50% of the translation had occurred in the first 3 mm of forward movement. For the pantographic system used, the amount of mandibular translation represented in the tracing was not changed by altering the posterior horizontal recording table position in the anterior-posterior direction, relative to the transverse horizontal axis. Conclusion. All subjects showed evidence of mandibular lateral translation. New definitions for timing of mandibular lateral translation are proposed. Of the tracings, 64% were classified as exhibiting early translation, 30% as intermediate, and 4% as late mandibular lateral translation. (J Prosthet Dent 1998;80:672-9.)     

An investigation of cuspal deformation and delayed recovery after occlusal loading

OBJECTIVE: The purpose of this study was to investigate the extent of progressive cuspal displacement during prolonged occlusal loading (either continuous or cyclic) and delayed cuspal recovery following removal of the load. METHODS: Extracted maxillary premolars with extensive MOD cavity plus endodontic access were subjected to an occlusal load applied to both cusps, followed by a recovery period. Two types of loading were applied: (a) continuous load of 100, 200 and 300 N for 0.1--1000 s; (b) cyclic loading of 300 N at 0.83 Hz for 1--1000 cycles. Cuspal displacement during loading and subsequent recovery were measured with an extensometer attached to both cusps. RESULTS: Continuous loading led to progressive cuspal displacement that was both time- and load-dependent. After removal of the load, complete recovery from cuspal deformation was prolonged up to 20 min, also in a time- and load-dependent manner. Cyclic loading resulted in a cumulative increase in cusp displacement but to only a very small extent (approximately 1 microm after 1000 cycles). CONCLUSIONS: Progressive cuspal displacement and delayed recovery occur with prolonged continuous or cyclic occlusal loading. Continuous loading (e.g. as in clenching) is potentially more damaging than cyclic loading (as in chewing).     

The influence of cavity preparation design on fracture strength and mode of fracture of laboratory-processed composite resin restorations

STATEMENT OF PROBLEM: Removal of large amounts of sound tooth structure may result in a weakened restored tooth. Nevertheless, removal of tooth structure for cuspal coverage has been recommended to protect teeth restored with laboratory-processed composite resin (LPCR) from fracture. PURPOSE: The purpose of this study was to evaluate the influence of different cavity preparation designs on fracture strength and modes of fracture of teeth restored with LPCR. MATERIAL AND METHODS: Ninety anatomically similar human third mandibular molars were selected. There were 2 experimental factors, occlusal isthmus width (narrow versus wide) and cuspal coverage (inlay, 1-cusp onlay, 2-cusp onlay, and all-cusp onlay), and 1 control group that received no treatment, resulting in 9 groups (n=10). Indirect composite resin (SR Adoro) restorations were manufactured and adhesively cemented with Adper Single Bond 2 and Rely-X ARC. A compressive loading test (0.5 mm/min) was performed. The modes of fracture were classified according to 4 categories. One-way and 2-way ANOVA followed by Tukey-HSD test were used to statistically analyze the fracture load data (alpha =.05). RESULTS: The statistical analysis failed to show significant differences among restored groups but showed differences between these groups and the control group (P = .001). Two-way ANOVA failed to show any difference when considering the occlusal isthmus width alone (P = .98), cuspal coverage (P = .273), or the interaction between these factors (P = .972). Several teeth had fractures affecting a great amount of both restoration and tooth structure. CONCLUSIONS: This in vitro study showed restored teeth having similar fracture strength and fracture modes, suggesting that with the tested preparation designs, there is no advantage of cuspal coverage to protect LPCR restored teeth from fracture.