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Introduction The occlusal relationship of primary dentition plays a vital role in predicting malocclusion in permanent dentition because primary dentition is the stepping stone for permanent dentition. Aim The aim of the study was to assess the occlusal relationships between the primary canine and the primary molar in the primary dentition in centric occlusion and also spacing in primary dentition among a group of 3- to 6-year-old children. Materials and methods The survey was based on examination of the primary dentition of 100 school children aged 3-6 years from Chennai, Tamil Nadu, India. The examination was done using pen light and mouth mirror. The occlusal assessment was done only on children who are healthy and free from extensive caries. The primary molar relationship and the canine relationship were assessed using Foster and Hamilton criteria with the teeth in centric occlusion. Results The study showed that, out of 100 school children, the molar relationship 56% had mesial step followed by 36% with flush terminal relationship and 8% with distal step relationship and out of 100 children, the canine relationship 61% of children had class III relationship followed by 27% class I relationship and 12% class II relationship. And around 54% had spacing out of which, maximum spacing was found only in the upper anteriors. Conclusion The survey concluded showing that the mesial step primary relationship was more common among 5- to 6-year-old children followed by flush terminal relationship and distal step relationship. The class III primary canine relationship was more common followed by classes I and II. Spacing was found more common in upper anteriors. How to cite this article Kumar D, Gurunathan D. Primary Canine and Molar Relationships in Centric Occlusion in 3 to 6-year-old Children: A Cross-sectional Survey. Int J Clin Pediatr Dent 2019;12(3):201-204.

Purpose To establish a complete digital workflow for the design and manufacture of sports mouthguards and to observe preliminary clinical effects. Materials and methods Eighteen healthy participants were included in this study. The self-controlled method was applied, and all participants were provided with two types of mouthguards. Digital mouthguards were designed and milled using CAD/CAM with polyetheretherketone, and conventional mouthguards were fabricated using the vacuum pressure-forming method with ethylene vinyl acetate. The order of wearing was determined using a random number table, and the washout period between was set as 1 month. Degrees of satisfaction in terms of retention, appearance, occlusal comfort, and labial comfort were evaluated. Distribution of occlusal force was tested using the T-scan analysis system. Participants were also asked to choose one mouthguard for future use. Results The complete workflow of digitally designed and manufactured sports mouthguards was successfully established. No significant difference was noted in retention between the types of mouthguard. The appearance score (P = .025), occlusal comfort score (P = .030), and labial side comfort score (P = .003) of the digital mouthguard group were significantly higher compared to the conventional mouthguard group. T-scan analysis results showed that in centric occlusion, participants exhibited occlusal contact in the second molar alone while wearing conventional mouthguards, while the occlusal force was uniformly distributed with digital mouthguards. Sixteen participants selected the digital mouthguard for future use. Conclusion Digital design and manufacture of sports mouthguards improved the occlusal design and greatly simplified and optimized the conventional fabrication process.

Purpose: Additional grafting procedures for the treatment of extremely atrophic jaws may be demanding, expensive, and sometimes require long time and multiple surgical sessions, which may reduce patient's acceptance and quality of life. This study evaluated the outcomes of 10 patients with extensive alveolar bone defects in the posterior jaws, treated in a single surgical session with grafting and implants. Materials and Methods: Ten consecutive patients were treated within 3 months of extraction. After ridge exposure, implants were positioned in 4-wall defects without contact with pristine bone, and mineralized particulate allograft packed around to stabilize them. Sites were covered with resorbable membranes and soft tissues were sutured tension-free. Five months later, implants were restored in centric occlusion. Results: At uncovering, newly formed bone filled all defects and all implants resisted at 30 Ncm of reverse torque. No complication was recorded throughout the study; survival rate was 100% for both implants and grafts. After 24 months of follow-up, mean periimplant bone level change was 0.15 ± 0.53 mm and mean bone gain at the defect site was 11.62 ± 1.04 mm. Conclusion: Rehabilitation of wide postextraction defects may achieve successful outcomes using allograft and a special implant design, even in the absence of optimal primary stability.

Correct occlusal relationships are part of the successful prosthetic treatment for edentulous patients. Fabrication of complete dentures comprises of clinical and laboratory procedures that should be executed accurately for achieving success with fabricated dentures. Errors occurring during the clinical and laboratory procedures of a denture may subsequently lead to the occlusal errors in the final prosthesis. These occlusal errors can be corrected in two ways: i) in patient's mouth ii) by recording new centric relation and remounting dentures on an articulator. The latter method is more feasible because the mobility of denture base on the mucosa in oral cavity does not permit the identification of premature contacts in centric occlusion and tooth guided eccentric excursions. This article describes a modest and effective clinical chair-side remount procedure using customized mounting platforms.

Background: The concept of scalloped implants to maintain the natural contour of the alveolar ridge has been a source of controversy for many years. Purpose: This study examined the long-term clinical performance of the scalloped NobelPerfect implant in a one-stage procedure (immediate loading in the esthetic zone). Materials and Methods: In 20 patients, immediate prosthetic restorations were placed on 31 NobelPerfect implants in a private practice and followed for up to 78 months. Twenty-one implants were placed immediately after extraction, seven implants were placed after osseous consolidation of the extraction sockets, and three implants were placed secondary to extended alveolar ridge augmentation procedures. All implants were provisionalized on the day of implant placement and adjusted to clear all contacts in centric occlusion and during eccentric movements. Outcome variables were success rates, marginal bone levels, and pink esthetic score (PES) assessed per implant. Results: One implant failed after 1.4 months. Five patients with six implants in total were scored in the 5-year follow-up as dropouts. Mean follow-up period of remaining 24 implants was 65 months (range, 55–78 months). Cumulative success rates according to the criteria specified by Smith and Zarb were 96.8%. Marginal bone levels averaged 1.1 mm above the first thread. Mean PES ratings were 10.5 (range, 3–13). Conclusions: Survival rates, marginal bone levels, and esthetic results suggest proof of principle for the preservation of the interproximal bony lamella with a scalloped implant design in long-term data.

Objective : To provide information on the state of occlusion and the spaces available after complete eruption of the primary dentition and to compare the characteristic features of the primary dentition in Chennai and Hyderabad, two of the metropolitan cities in South India. Materials and Methods : Children in the age range between 3 and 5 years were selected from different schools of both Chennai and Hyderabad, with a complete set of primary dentition. Study casts were obtained and assessment of spacing in the primary dentition and the primary molar relationship were recorded in centric occlusion. The data obtained was subjected to statistical analysis. Results : The mean values and standard deviations for the primary molar relationship and spacing in primary dentition are given in the tables. Conclusion : Bilateral flush terminal plane relationship of the second primary molars and spaced dentition was most frequent in primary dentition of the children in both Chennai and Hyderabad groups. Significant differences were not found among both groups and genders.

Purpose The purpose of this study was to compare the muscle activity of jaw-closing muscles during chewing of a wax cube used for mixing ability test with that of peanuts used for masticatory performance test. Methods Twenty subjects with complete dentitions (mean age 24.1 years) were directed to perform a mixing ability test and a masticatory performance test. Surface electromyograms (EMGs) were recorded from the masseter and temporalis muscles on right and left sides. Muscle work, maximal voltage and duration were measured on the integrated EMG signal in each muscle. In addition, muscle work was normalized with EMG activity during maximum voluntary clenching at centric occlusion. The mean of the 2nd to 5th cycle in each parameter was employed for statistical analysis. Results Repeated measures one-way multiple analysis of variance found a significant effect of chewing test on muscle work, normalized muscle work and maximal voltage ( P P =0.07). Muscle work, normalized muscle work and maximal voltage for the mixing ability test were significantly less than for the masticatory performance test in all muscles (paired t -test, P Conclusion The results of this study suggest that muscle activity of jaw-closing muscles in the mixing ability test is less than that in the masticatory performance test using peanuts as test food.

Purpose This article describes the laboratory and the prosthetic steps required for the fabrication of the provisional immediate load prosthesis used in guided surgical treatment protocols. Materials and Methods NobelGuide software (Nobel Biocare, Gothenburg, Sweden) was used to fabricate a surgical guide. The surgical guide in turn was used to develop a master model and fabricate the provisional bridge that will be secured to the implants immediately after their placement using the guided surgery template. Results Using this protocol, the fabrication of the provisional fixed prosthesis for immediate loading patients using the NobelGuide software was possible. The fit of the prosthesis to the implants required minimal adjustment. The patients were able to achieve a comfortable centric occlusion needing only minor adjustments following the securing of the prosthesis to the implants. Conclusion This protocol allows for the predictable fabrication of provisional immediate load prosthesis.

Statement of problem A variety of treatment philosophies persist concerning the need for coincidence of centric occlusion (CO) and maximum intercuspation (MI) in prosthodontic restoration; however, no consensus exists. Purpose The purpose of this study was to determine the philosophies of dental educators throughout the United States at both the predoctoral and postdoctoral levels and to compare their attitudes toward desirable maxillomandibular relationships in defined clinical situations. Material and methods A survey was constructed with 5 clinical scenarios presented describing patients with a difference between maximum intercuspation and centric occlusion. The survey was mailed to 171 dentists involved in either predoctoral or postdoctoral dental programs in the United States; including 56 dental schools; the Army, Navy, and Air Force postdoctoral programs; 8 Department of Veterans Affairs postdoctoral programs; and 7 hospital-based programs. Descriptive statistics of the responses were provided. Chi-squared (α=.05) and Fisher's exact test analyses (α=.05) comparing predoctoral and postdoctoral program responses for each question were performed. Results Forty-three predoctoral dental school program responses were received. Forty-one postdoctoral program directors, including the dental school–based programs, 3 armed service branches, 2 Veterans Administration programs, and 1 hospital-based program responded to the survey. Fifteen respondents indicated that they represented both predoctoral and postdoctoral programs, and these data were deleted from the sample. Summarized results for each question reflect on whether the clinicians philosophically believed patients were better off with the elimination of an existing occlusal interference between MI and CO or not. There was no statistically significant difference seen between the predoctoral and postdoctoral responses. Conclusion The controversy regarding the preferred mandibular position for treatment of dentulous and partially edentulous patients continues among dental educators at both the predoctoral and postdoctoral levels in the United States.

Force distribution on mandibular implants supporting overdentures was registered in viva by means of piezo-electric transducers that allow for simultaneous force measurements in 3 dimensions. The anchorage device for connecting the overdenture to the implants was a Ushaped bar to which distal extensions were soldered bilaterally. Force patterns were analyzed under different test conditions such as maximum force when biting in centric occlusion, maximum biting with the unilateral use of a bite plate, parafunction and chewing bread. Maximum force measured in centric occlusion and on the ipsilateral implant with the use of bite plate was increased in the vertical dimension, compared to transverse dimensions. On the contralateral implant, equally low values were found, in all 3 dimensions. Transverse force components reached 5 to 35% of the vertical magnitudes. With the use of the bite plate on the ipsilateral implant, force magnitudes in the vertical direction and in the backward-forward direction were significantly higher (P 95%) or exclusive force direction in the vertical dimension, registered on both implants was downward. However, with the unilateral use of the bite plate, upward directions were found on the contralateral implant as an effect of distal bar extensions. This was in contrast to previous results where upward force directions were not found. In transverse dimensions, the specific influence of bar extensions was recognised in backward directions on the contralateral implant. In comparison with previous results, it was concluded that, in vivo, the effect of distal bar extensions was of much lesser influence regarding force magnitudes and force directions than was expected.

Purpose This study aims to investigate the effects of four different lateral occlusion schemes and different excursions on peri-implant strains of a maxillary canine implant. Materials and methods Four metal crowns with different occlusion schemes were attached to an implant in the maxillary canine region of a resin model. The included schemes were canine-guided (CG) occlusion, group function (GF) occlusion, long centric (LC) occlusion, and implant-protected (IP) occlusion. Each crown was loaded in three sites that correspond to maximal intercuspation (MI), 1 mm excursion, and 2 mm excursion. A load of 140 N was applied on each site and was repeated 10 times. The peri-implant strain was recorded by a rosette strain gauge that was attached on the resin model buccal to the implant. For each loading condition, the maximum shear strain value was calculated. Results The different schemes and excursive positions had impact on the peri-implant strains. At MI and 1 mm positions, the GF had the least strains, followed by IP, CG, and LC. At 2 mm, the least strains were associated with GF, followed by CG, LC, and IP. However, regardless of the occlusion scheme, as the excursion increases, a linear increase of peri-implant strains was detected. Conclusion The peri-implant strain is susceptible to occlusal factors. The eccentric location appears to be more influential on peri-implant strains than the occlusion scheme. Therefore, adopting an occlusion scheme that can reduce the occurrence of occlusal contacts laterally may be beneficial in reducing peri-implant strains.

A recording device termed a "Kleinrok Functiograph" was introduced to simultaneously document condylar- and tooth-guided mandibular movements on the same plate. The Functiograph instrument permitted objective monitoring of mandibular movement without tooth contact, with all tooth contacts, and allowed analysis of the correlation of these two recordings. After 10 years of conducting investigations on centric occlusion using the Functiograph instrument combined with clinical, radiographic, and electromyographic studies, it was possible to differentiate the horizontal Functiograph recordings of normal and disturbed centric occlusion at a clinically acceptable vertical dimension. Two types of centric occlusal disturbances were classified to accelerate diagnosis and standardize communication.

Temporomandibular joint (TMJ) reconstruction with a TMJ Concepts total joint prosthesis (TMJ Concepts, Ventura, USA) requires a precise 3D model of the jaws in centric occlusion. The authors present a virtual procedure for repositioning the lower jaw in centric occlusion to obtain a precise stereolithographic model for TMJ reconstruction using a custom-made total joint prosthesis in a case of TMJ ankylosis and anterior open bite.

An alternative procedure for discrimination of contacts in centric occlusion and lateral excursion was introduced for eliminating premature contacts in lateral excursion without the alteration of other intercuspations. This procedure involves the application of red paper for the evaluation of lateral excursive contacts and blue paper for centric occlusion holding contacts to provide improved visibility of occlusal contacts.

A computerized diagnostic system was tested for its capability to evaluate the occlusal equilibrium of complete dentures. Its electronic sensor foil was calibrated to intraorally compute a load index for the left and right sides of the denture. The index is calculated by the measured force and number of occlusal contacts. Perfect equilibrium is given by a ratio of load left-to-load right of 1:1. Centric occlusion of complete dentures was examined before and after remounting. A good correlation between load index and the occlusal relationship on the articulator could be observed. The system appears to be suitable for verifying the need for occlusal adjustment. However, improvements concerning the hardware and software are necessary.

Two bilateral Schuller's position radiographs were made of 10 edentulous patients with complete dentures. In one radiograph, the complete dentures were in place in centric occlusion. For the other radiograph, the complete dentures were removed and the maxillary and mandibular residual ridges approximated as closely as possible. This position is referred to as the edentulous position of the temporomandibular joint (TMJ). Findings indicate that in the edentulous position the average size of the upper and posterior TMJ spaces and the distance from the center of the condyle to the center of the glenoid fossa on the Y axis of the TMJ are smaller than measurements in the intercuspal position. The size of the anterior space and the distance between the two centers on the X axis are larger in the edentulous position. Because vertical dimension is reduced in the edentulous position, the mentum is in a superior and protrusive position. The study indicates that when the maxillary and mandibular residual ridges are approximate there is a pathologic position of the TMJ and the mandible caused by the loss of all teeth. The study shows that the condyle has the potential to move backward and upward excessively. As a result of the study, the concept of the edentulous position of TMJ is introduced. This concept is important in determining the proper position of the condyle in the glenoid fossa and the correct vertical and horizontal jaw relationship of an edentulous patient when complete dentures are made.

Research has indicated that the suspension mechanism of the condyle in the fossae is muscular rather than ligamentous. Therefore, in a normal condyle-disk-fossa relationship, variations in muscle tone influence condylar position and function. The proprioception of the muscles, tendons, periodontal membrane, and temporomandibular joints influence the muscle programming of centric occlusion. In many patients the usual chairside muscle deconditioning procedures are too weak and inefficient to overcome habitual closure. The role of long-term and short-term muscle deconditioning for the occlusal correction of centric relation deflective contacts has been discussed.

Variability of closest speaking space was compared with that of interocclusal distance in 30 dentulous subjects to the nearest 0.1 mm on the screen of a mandibular kinesiograph. Postural rest position was elicited by the subjects saying /M/ and relaxing the jaw. Closest speaking space was defined as the vertical difference in the position of the mandible from the immediate end of rapid counting from 60 to 66 to centric occlusion. The two variables were measured in random order 20 times each. The subjects were examined for two data collecting sessions. The variance of the closest speaking space was smaller than the variance for interocclusal distance for 26 of 30 subjects. The difference between the mean variances was statistically significant, p greater than 0.1 (t 3 and t 3.41, df 29).

Twenty dentulous subjects were selected at random. A Hight tracer, fixed on the labial surface of the teeth by special clutches, was used to indicate a record of centric relation and centric occlusion. The Myo-Monitor centric position was recorded and compared to centric occlusion and centric relation in anteroposterior and lateral dimensions. This study indicated that: 1. Myo-Monitor centric position is always anterior to centric relation, with an average of 3.8 min. 2. Myo-Monitor centric position is always anterior to centric occlusion, with an average of 1.8 mm. 3. In 18 of 20 subjects, the Myo-Monitor registration was to the right or to the left side of the line between centric relation and centric occlusion. 4. In all subjects, centric occlusion was an average of 2.2 mm. anterior to centric relation.

The kinesiometric and electromyographic findings from the evaluation of mandibular resting posture in 30 individuals with diverse vertical dentofacial morphology can be summarized as follows: 1. The RVD and TESP of the mandible are two distinctly different biologically dynamic neuromuscular entities. They differ with respect to their spatial position in that the RVD is 2.6 mm closer to centric occlusion than TESP. 2. The intrapersonal reproducibility of the RVD and TESP at various time intervals predictably demonstrated some biologic variability. 3. The occlusal neuromuscular mechanism apparently maintains a functional tone in the masticatory musculature at the RVD as a result of stimuli from the periodontal mechanoreceptors following tooth contact. 4. A physiologic range of neuromuscular adaptability exists within each diverse morphologic group. Adaptations are apparently mediated by the central nervous system and the musculoskeletal complex. 5. The interocclusal distance at the TESP is inversely related to the vertical dentofacial morphology. 6. Sophisticated computerized morphometrics in combination with the kinesiometric and electromyographic findings of this study demonstrate the dentoalveolar nature of VME and VMD and suggest that correction of these dentofacial deformities by various biologically compatible means will tend to normalize neuromuscular-skeletal relations.

A cephalometric-electromyographic method to analyze tooth contacts in centric occlusion and at terminal hinge contact has been presented. A positional difference between centric occlusion and centric relation was demonstrated in all subjects. However, temporal and masseter muscle activity during maximal isometric contraction did not differ significantly at these two positions. The study is being continued employing young male subjects with complete dentitions as subjects.

Use of a double arch, closed-mouth technique as described in this article enables dentists to obtain cast and die placement in centric occlusion in a single step. Complete closure of the teeth is mandatory for registering the interocclusal relationship correctly. The accuracy of the interocclusal relationship is more likely because of the decreased number of steps in the technique. Several different trays are available for the double arch impression technique. The more rigid trays buttress the impression material and reduce the possibilities of distortion in the final impression. Several variations in the double arch impression technique are possible, and tray selection is dependent on the demands of each patient.

Although TMJ click is common, its relationship to subjective and objective evaluation and the position of the click within the envelope of motion is not fully understood. This study attempted to correlate these entities in 21 patients. Although specific conclusions are difficult to make from this study, the findings suggest the following: The most important etiologic factors in the click are bruxism, clenching, an occlusal slide from centric relation to centric occlusion of more than 1 mm, and lateral deviation. The most important clinical sign of TMJ clicking is palpable soreness in the lateral pterygoid and temporal muscles. Over 50% of patients with a click have bilateral click. A click occurs least often in retruded closing movement (7%) and most often in habitual movement (37%). Although it appears that closure in the retruded position may avoid click, further evaluation of the presence of click in retruded opening movement is indicated. A mean mandibular lateral deviation of 2.2 mm anteriorly is observed at the time of click.

Fabrication of interocclusal splint at a thickness determined by the vertical dimension at which the jaw muscle EMG amplitude is minimum has been recommended. However, the effect of prior jaw motion and the effect of the recording site on the EMG amplitudes and on the vertical dimension of minimum EMG activity have not been documented. IEMG amplitudes at various static jaw positions achieved during opening and during closing were analyzed in nine subjects. Surface IEMGs were recorded over the left anterior temporal muscle, left masseter and left suprahyoids muscles, and by nonspecific EMG recording as described by Rugh and Drago. The jaw position was recorded in 5 mm increments by a kinesiograph. After 30 seconds of relaxation, 10 successive IEMG reading at 4-second integration times were obtained at each recording site. These 10 recordings at each requested jaw position were averaged and analyzed. The IEMG activity changed with different jaw position. As the jaw opened from centric occlusion, the IEMG from jaw closing muscles decreased to a minimum and then increased with further opening. Moreover, the IEMG for a particular jaw position differed depending on the history of the jaw movement, that is, whether the position was achieved after an opening step or after a closing step. Two factors, the amount of jaw opening and the history of jaw movement to reach that position, seemed to influence the IEMG differently in each of the recorded muscles.

The least complicated approach in treatment should be the guiding principle in occlusal reconstruction. Such an approach initially requires one to develop a philosophy of occlusion. Most dentists have developed a philosophy as a result of experience or have built on a philosophy presented to them in dental school. The philosophy suggested by the authors requires (1) centric occlusion to be established at centric jaw relation, (2) an absence of deflective occlusal contacts in lateral and protrusive movements, (3) a posterior tooth form with enough cusp height to permit adjustment of the occlusion by selective grinding, and (4) a natural and pleasing appearance in the restoration. Once the conditions of a philosophy have been established, the dentist must then choose a concept of occlusal treatment. Balanced or nonbalanced occlusal contacts are the two concepts most often proposed in providing complete denture service. Balanced occlusion is defined as “an occlusion of teeth which presents a harmonious relation of occluding surfaces in centric and eccentric positions within the functional range.“2 A nonbalanced concept strives for a maximum planned contact or intercuspation of the teeth at centric occlusion without emphasizing the contact relationship in the eccentric positions. Most dentists usually become

Two complete fixed prostheses built with the occlusion in centric relation and with occlusion in the subject's existing centric occlusal position were tested with telemetry under conditions of actual use. The findings indicate that the subject did not use the centric relation position but accepted the prosthesis built to her preexisting centric occlusion. These findings are consistent with our previous results of telemetric studies conducted on patients with three-unit fixed prostheses.

A landmark on the surface of the skin has been determined and described which locates the articular surface of the condyle that is in closest proximity with the inferior surface of the articular fossa of the temporal bone when the teeth are in centric occlusion. This reference point can be used to record the spatial relationship between the condyle-disc-articular fossa and the maxillae for transfer to the articulater.

Impressions were made from the anterior segment of the mouth in 25 subjects with their teeth in centric occlusion. Measurements were made on each impression to determine the relation of the maxillary and mandibular vestibular folds and of the anterior teeth to the maxillary and mandibular mucolabial reflections. The mean distance between the depth of the mucolabial reflections in the canine region was 36.70 mm for the right side and 36.94 mm for the left side. The mean distances for the right and left central incisor regions were 34.20 mm and 34.06 mm. The variations in the measurements of different teeth confirmed the anatomic individuality of each patient. Nevertheless, the findings of this study will be helpful as guides in the initial placement of the maxillary and mandibular anterior teeth and in the initial determination of the vertical dimension of occlusion.

The changes and inaccuracies resulting from physical manipulations of the waxed set-up of the dentures through the flasking, processing, trimming, and removing processes affect the occlusal vertical dimension, centric occlusion, and occasionally the esthetic ensemble as originally set. Some of these changes are inevitable, and others may be reduced or prevented. In any event, significant changes can be corrected by the use of the split-cast method, with greater potential of accuracy inherent in the use of metal split-cast remounting plates. The technique and advantages of this desirable control mechanism have been described.

The average 5 year reduction of the occluding vertical dimension (nasion to menton) for 45 patients was 3.2mm. (2.8 mm. for the anatomic group, 3.2 mm. for the semianatomic group, and 3.6 mm. for the nonanatomic group, each constituting 15 patients). Mandibular physiologic resting face height became foreshortened on the average only one third as much as the morphologic centric occlusion face height. Tabulation of adjustments for sore spots indicated that: the fewest postinsertion appointments were required for the anatomic group of patients; three fourths of 604 denture base alterations were on lower dentures; for upper and lower denture base alterations, one third were made on the borders and two thirds, on the basal seat; one sixth of all alterations were made at routine recall examinations; the fewest upper denture base alterations were for the nonanatomic patients; and the fewest adjustments of the lower denture base on the tissue surface and on the borders were done for the anatomic group of patients. This investigation has been underway for 18 years, and several more re

Excursive movements were not characteristic of most masticatory strokes by the complete denture wearers in this study. Excursive movements occurred less often with full-cusped teeth than with flat-cusped teeth, and more often from centric position to lateral position when they did occur. The reverse is generally assumed. The majority of closures occurred directly into centric occlusion with some direct closures into lateral or medial positions. Retention and stability did not seem to be a factor in the incidence of lateral excursions. There appears to be some neuromuscular preference for direct centric closures, particularly with dentures with full-cusped teeth.

Inconsistencies exist in the literature concerning the relationship of functional mandibular movements and border tracings recorded by pantographs. This study was undertaken to determine the relationship of functional movement and border tracings. A pantograph was assembled to clutches attached to anterior teeth. Chewing studies were performed on four subjects using different test foods. The functional movements of two subjects contacted the border tracing frequently from centric relation while the functional movements of two subjects were restricted to the tracings made from centric occlusion and influenced by occlusal interferences. The occlusion of one of the subjects with restricted functional movements was adjusted, and subsequently, the functional movements frequently contacted the border tracings. This study suggests that occlusion in harmony with border tracings may be the most physiologic.

1. Both artificial cusp and flat cuspless occlusal forms present disadvantages when they are used for complete dentures. 2. Although the objectives of natural occlusion and prosthetic occlusion are the same, the aims of prosthetic occlusion must be achieved by mechanical means. 3. A cuspless occlusal pattern which incorporates the principle of concentric curvatures of the same radius is suggested as a means of accomplishing the aims of prosthetic occlusion in complete denture construction. 4. This cuspless occlusal pattern is characterized by a curved three-dimensional occlusal surface rather than by a flat, two-dimensional occlusal surface. It is bio-mechanical and meets with the biologic and mechanical requirements of occlusion in complete denture construction. 5. A simplified procedure for obtaining balanced occlusion has been described. The teeth are set to fixed lateral and protrusive positions, thereby obtaining proper working, balancing, and centric occlusion.

An occlusal analysis in relation to the TMJ radiographs will reveal factors that should be added to the purely clinical definition of centric relation. It has been previously established that bilateral asymmetric TMJ spaces and condylar retrusion or protrusion are most often associated with disc derangement and/or palpable muscle spasm. 4 Conversely, bilateral TMJ space symmetry and condylar concentricity (condyle centered in the superior portion of the glenoid fossa) are associated with joint and muscle health. All TMJ radiographs are obtained with the teeth in the acquired centric occlusion. Centric relation is considered functional when the magnitude and direction of the centric relation deflective slide to the acquired centric occlusion correlate with the condylar displacement observed on the TMJ radiographs. For example, if the patient has a 2 mm. deflective slide straight forward, the centric relation is considered functional when the TMJ radiographs reveal equal condylar protrusion proportional to the mandibular deflection. In the judgment of the dentist, the occlusal correction of the deflective contacts will result in bilateral condylar concentricity. Conversely, centric relation is dysfunctional when the magnitude and direction of the centric relation deflective slide to the acquired centric occlusion do not correlate with condylar position in the TMJ radiographs. When no deflective slide is present, both condyles should be concentrically located in each fossa with bilateral symmetrical joint spaces in order for centric relation to be considered functional. Dysfunctional centric, relation is often associated with disc derangement and/or palpable muscle spasm. When the centric relation is functional, the most retruded jaw position should be used. If the centric relation is dysfunctional, a therapeutic or treatment centric occlusion must be established by the dentist, utilizing the TMJ radiographs as a guide. In this situation, the most retruded position would be harmful to the patient.

The relationship between occlusal disharmony and pain in the temporomandibular joint and adjacent muscles was tested clinically and electromyographically before and after occlusal adjustment on 32 patients. Various degrees of bruxism associated with psychic tension and occlusal interferences were observed in all of the patients. Clinically, all patients experienced relief of the pain and discomfort after complete occlusal adjustment. Electromyographically, a harmonious and well-synchronized contraction pattern of the temporal and masseter muscles was recorded after the adjustment. Any type of occlusal interference was found to trigger muscle spasms and pain, but the most consistent and significant interference was a discrepancy between centric relation and centric occlusion. The muscle disharmony was displayed electromyographically mainly in swallowing. The second most significant occlusal disharmony was balancing side interference. The balancing side contact had to be lighter than the working side contacts to establish a harmonious masticatory pattern. The patients' symptoms subsided without altering the vertical dimension. A close correlation was observed between the clinical and electromyographic recordings of occlusal interferences and muscle disharmony. However, electromyographic evidence of muscle balance in rest position could be obtained in more than one-half of the patients in spite of occlusal interference and temporomandibular joint pain. Masticatory contacts were seldom observed posterior to centric occlusion. However, the occlusal contacts in swallowing apparently occurred between centric occlusion and centric relation. The occlusal stability in centric relation was found to be of extreme importance for muscle harmony during swallowing. Rest position determined by conventional clinical methods did not always correspond to minimal, harmonious muscle activity electromyographically. A slight opening from the clinically determined rest position often facilitated the recording of an even, minimal contraction of the temporal and masseter muscles. The mandible could be opened from this position about 1/2 inch further (a resting range) without eliciting any increased muscle activity from these muscles.

Jaw movements of a selected group of subjects were studied by clinical observation, examination of wax occlusal records and mounted casts, photoelectric mandibulography, and oscilloscopic tracings. Subjects were found to have substantially consistent and reproducible patterns of jaw movement during empty and functional chewing exercises. However, the individual patterns could not be predicted from analysis of occlusal status. Mean values of (1) the chewing cycle time, (2) the pause at centric occlusion, (3) maximum opening, (4) maximum movement to the right and left of the midline, and (5) maximum jaw point velocity while opening, closing, and moving to the right and left were obtained for 22 subjects chewing a single peanut on the right and the left sides. Great diversity in chewing patterns was observed, but in general, individual subjects exhibited specific and repetitive patterns. All subjects exhibited a pause in centric occlusion at the end of a closing masticatory stroke. A substantially constant jaw point velocity was observed for most of a chewing cycle when the open-close, close-open, left-right, and right-left components of jaw movements were analyzed separately.

The maxillomandibular tooth relationship when the mandible is in its terminal hinge position is fundamental in treatment planning. This tooth position is termed centric occlusion. Centric occlusion is fundamental to a study of the functional movements of the mandible and is related to all factors of occlusion. An analysis of the direction of stresses in centric closures versus that of eccentric closures discloses one of the important causes of pathologic wear of teeth and the resultant effect on the supporting structures. The objective is a treatment plan that restores harmonious cusp relationships within physiologic limits and one that is correlated with the condylar guidances.

A relining technique for complete dentures has been described. Wax impressions are made in the denture bases with the use of centric relation as a guide for positioning the dentures. The correct vertical dimension of occlusion is reestablished while a new interocclusal centric relation record is made. Centric occlusion is preserved by correctly positioning the lower denture to the upper denture after the casts have been mounted on the articulator. Hard Klinging Liner Plastic is used as the final relining material.

A relining technique has been described that permits the restoration of the proper vertical dimension of occlusion and also the centric occlusion that was originally built into the dentures. This technique has been used successfully for many patients, and from 2 to 14 mm. of lost vertical dimension (measured at the incisors) can be restored in a single procedure. The muscles are permitted to freely dictate maxillomandibular relations, and there is no need to be concerned about the "hinge axis" or "temporomandibular joint relations" when this technique is employed. This technique is not applicable to dentures made with plastic teeth which have become grossly abraded; neither can this procedure correct faulty occlusion that was built into the dentures or other errors or omissions of original construction.

Ten patients had three “Myo-Monitor centric” records made at each of three appointments. Terminal hinge axis determination and interocclusal registration of centric relation were used to accurately mount maxillary and mandibular casts on a modified articulator. The characteristics of “Myo-Monitor centric” were investigated by: evaluation of the reproducibility of “Myo-Monitor centric” records; comparison of “Myo-Monitor centric” position to centric relation contact position and centric occlusion; comparison of the tooth contact on hinge closure from “Myo-Monitor centric” with centric relation contact; evaluation of the effect of the anteroposterior head position on the number and location of tooth contacts during “Myo-Monitor centric” mandibular closure; and a comparison of the anteroposterior relationships among “Myo-Monitor centric,” centric relation, and centric occlusion. Examination and appropriate statistical analysis of the data revealed several characteristics of “Myo-Monitor centric”: The axis of rotation determined by “Myo-Monitor centric” was always anterior and inferior to the patient's terminal hinge axis; “Myo-Monitor centric” registrations within individuals were non-reproducible; with “Myo-Monitor centric” registrations, centric relation contacts on the mandible were anterior to both centric relation and centric occlusion contacts on the maxillae; variation of anteroposterior head position affected Myo-Monitor-produced mandibular closure; and eight of ten patients had “Myo-Monitor centric” contact anterior to their centric relation contact.

One hundred dentulous subjects were recorded cinematically in order to investigate the relationship between the occlusal pattern, centric relation, centric occlusion, and temporomandibular joint dysfunction. The majority of the subjects (81 per cent) exhibited lateral working side cuspal contact; only 19 per cent had a canine-protected occlusion. A 2 mm. discrepancy between centric relation and centric occlusion was found in only one subject of the working side contact group, whereas more than half of the canine-protected group had this degree of “hit and slide.” This evidence suggests the possibility of an association between a canine-protected occlusion and large discrepancies between centric relation and centric occlusion. Three subjects of the 4 with temporomandibular joint dysfunctions were found in the canine-protected occlusion group. However, 2 mm. discrepancies between centric relation and centric occlusion in each subject with temporomandibular joint disturbances leads to the association of centric occlusal disharmony with joint pathology. However, it would be premature to relate the canine-protected occlusion directly to temporomandibular joint dysfunction.

“Centric” is an old term that would be almost impossible to eliminate from dental terminology. It seems prudent, then, that the term be used correctly and that simple, usable definitions of centric relation and centric occlusion be employed. The word “centric” is an adjective that should not be made to function as a noun. Centric relation is a bone-to-bone (mandible to maxillae) relation. Centric occlusion is a tooth-to-tooth relation (mandibular teeth to maxillary teeth). Therefore, centric relation and centric occlusion are not the same by definition; however, often they both can exist at the same time.

Mandibular movements made with the teeth in contact were investigated in 4 different subjects by means of a new technique. These movements were lateral movements to right and left from the position of centric occlusion and return, retrusion from the position of centric occlusion and return, and protrusion from the position of centric occlusion and return. Thus, sixteen different movements in all were investigated, or twenty, if the two stages of protrusion are considered separately. All of these movements were found to be rotary about fixed axes, the positions of which were located and are described.

Monitoring the occlusion with miniaturized intraoral radio transmitters revealed that contacts of teeth during swallowing occurred more often in centric occlusion rather than in centric relation with ratio of 182 to 5.

We can conclude from the evidence we have, that free-way space is a physiologic necessity. We cannot successfully insert splints, be they removable or fixed, or increase vertical dimension by crown and bridge prosthesis, unless the normal free-way space is maintained after the treatment. Therefore, many cases of mutilated occlusion must be rehabilitated without increasing the vertical dimension of centric occlusion. Establishing a more normal plane of occlusion and restoring a more normal occlusal anatomy will result in bringing the case to a successful conclusion.

1. In a person with a full complement of natural teeth, centric occlusion is determined by neuromuscular, “neuroarticular,” and “neuroperiodontal” function. 2. Centric relation is determined by neuromuscular and “neuroarticular” function. 3. Centric occlusion in persons with complete dentures is determined by neuromuscular, “neuroarticular,” and “neuromucosal” function. 4. Occlusal patterns of artificial teeth should be given a form that will contribute to the psychologic and functional adaptation to the dentures. 5. Centric relation should be recorded as a means to establish centric occlusion in complete dentures. 6. If necessary, the occlusal pattern of complete dentures should be remodeled by grinding until optimal neuromuscular, “neuroarticular,” and “neuromucosal” function is attained.

2. The condyle of the mandible consists of a rounded, elliptical, bony head with a neck which is usually tilted forward. The upper and anterior surface of the condyle in centric occlusion articulates with the posterior surface of the articular eminence. Articular cartilage covers the surface of this condyle. 3. The articular disc or meniscus is an oval structure which is a relatively thin plate of fibrocartilage. Its lower surface is concave and its upper surface is convex conforming to the shape of the structures it approximates. 4. The two synovial membranes or sacs are placed one above and one below the articular disc. The superior membrane, which is the larger and looser of the two, extends from the inferior of the mandibular fossa and articular eminence onto the superior surface of the disc. The inferior membrane passes from the inferior surface of the disc onto the neck of the condyle.