Chewing side preference and laterality in patients treated with unilateral posterior implant-supported fixed partial prostheses.

BACKGROUND: It is not clear to what extent chewing is improved by unilateral oral rehabilitation with implant-supported fixed partial prostheses (ISFPPs). OBJECTIVES: This study aimed to investigate whether patients treated with unilateral ISFPPs in the maxilla use their prostheses during mastication to the same extent as they used their contralateral natural teeth. A further aim was to investigate whether there is a correlation between preferred chewing side and laterality. METHODS: Chewing side preference was assessed in 15 participants treated with unilateral ISFPPs in the maxilla. The first, second, third, fifth and tenth chewing cycles were assessed, and the test was repeated 10 times. All participants also answered a questionnaire about their chewing side preference. RESULTS: Most of the participants presented bilateral chewing, but two (13%) chewed only on the ISFPP. There was no statistically significant association between the objectively assessed chewing side and dental status (natural teeth or ISFPPs) during any of the recorded chewing cycles (p > .1). There were statistically significant correlations between both the subjectively reported usually preferred chewing side and the subjective chewing side preference during the test and the objectively assessed chewing side for the first three chewing cycles (p < .01). No correlation was found between handedness and the objectively assessed chewing side. CONCLUSION: In the present study, most participants chewed bilaterally, and chewing was performed both on the ISFPP and on the natural teeth. No correlation was found between the preferred chewing side, objectively or subjectively determined and laterality.

Effects of Chronic and Experimental Acute Masseter Pain on Precision Biting Behavior in Humans.

Chronic pain in the orofacial region is common worldwide. Pain seems to affect the jaw motor control. Hence, temporomandibular disorders (TMD) are often accompanied by pain upon chewing, restricted mouth opening and impaired maximal bite forces. However, little is known on the effects of pain, in particular the effects of chronic jaw muscle pain on precision biting. The aim of the study was to investigate the effect of chronic and acute jaw muscle pain on oral motor control during precision biting in humans. Eighteen patients with chronic masseter muscle pain and 18 healthy participants completed the experiment. All participants were examined according to the Diagnostic Criteria for TMD. Experimental acute pain was induced by bilateral, simultaneous sterile hypertonic saline infusions into the healthy masseter muscles. A standardized hold and split biting task was used to assess the precision biting. The data was analyzed with non-parametric statistical tests. The results showed no significant differences in the hold forces, split forces, durations of split or peak split rates within or between the pain and pain-free conditions. The mean split rate increased significantly compared to baseline values both in the chronic patients and the pain-free condition. However, this increase was not evident in the experimental acute pain condition. Further, there were no significant differences in the mean split rates between the conditions. The data suggest that jaw muscle pain does not seem to alter precision biting in humans, however, the possibility that a nociceptive modulation of spindle afferent activity might have occurred but compensated for cannot be ruled out.

Perturbed oral motor control due to anesthesia during intraoral manipulation of food.

Sensory information from periodontal mechanoreceptors (PMRs) surrounding the roots of natural teeth is important for optimizing the positioning of food and adjustment of force vectors during precision biting. The present experiment was designed to test the hypothesis; that reduction of afferent inputs from the PMRs, by anesthesia, perturbs the oral fine motor control and related jaw movements during intraoral manipulation of morsels of food. Thirty healthy volunteers with a natural dentition were equally divided into experimental and control groups. The participants in both groups were asked to manipulate and split a spherical candy into two equal halves with the front teeth. An intervention was made by anesthetizing the upper and lower incisors of the experimental group while the control group performed the task without intervention. Performance of the split was evaluated and the jaw movement recorded. The experimental group demonstrated a significant decrease in measures of performance following local anesthesia. However, there was no significant changes in the duration or position of the jaw during movements in the experimental and control group. In conclusion, transient deprivation of sensory information from PMRs perturbs oral fine motor control during intraoral manipulation of food, however, no significant alterations in duration or positions of the jaw during movements can be observed.

Fine motor control of the jaw following alteration of orofacial afferent inputs.

OBJECTIVE: The study was designed to investigate if alteration of different orofacial afferent inputs would have different effects on oral fine motor control and to test the hypothesis that reduced afferent inputs will increase the variability of bite force values and jaw muscle activity, and repeated training with splitting of food morsel in conditions with reduced afferent inputs would decrease the variability and lead to optimization of bite force values and jaw muscle activity. MATERIAL METHODS: Forty-five healthy volunteers participated in a single experimental session and were equally divided into incisal, mucosal, and block anesthesia groups. The participants performed six series (with ten trials) of a standardized hold and split task after the intervention with local anesthesia was made in the respective groups. The hold and split forces along with the corresponding jaw muscle activity were recorded and compared to a reference group. RESULTS: The hold force and the electromyographic (EMG) activity of the masseter muscles during the hold phase were significantly higher in the incisal and block anesthesia group, as compared to the reference group (P < 0.001). However, there was no significant effect of groups on the split force (P = 0.975) but a significant decrease in the EMG activity of right masseter in mucosal anesthesia group as compared to the reference group (P = 0.006). The results also revealed that there was no significant effect of local anesthesia on the variability of the hold and split force (P < 0.677). However, there was a significant decrease in the variability of EMG activity of the jaw closing muscles in the block anesthesia group as compared to the reference group (P < 0.041), during the hold phase and a significant increase in the variability of EMG activity of right masseter in the mucosal anesthesia group (P = 0.021) along with a significant increase in the EMG activity of anterior temporalis muscle in the incisal anesthesia group, compared to the reference group (P = 0.018), during the split phase. CONCLUSIONS: The results of the present study indicated that altering different orofacial afferent inputs may have different effects on some aspects of oral fine motor control. Further, inhibition of afferent inputs from the orofacial or periodontal mechanoreceptors did not increase the variability of bite force values and jaw muscle activity; indicating that the relative precision of the oral fine motor task was not compromised inspite of the anesthesia. The results also suggest the propensity of optimization of bite force values and jaw muscle activity due to repeated splitting of the food morsels, inspite of alteration of sensory inputs. CLINICAL RELEVANCE: Skill acquisition following a change in oral sensory environment is crucial for understanding how humans learn and re-learn oral motor behaviors and the kind of adaptation that takes place after successful oral rehabilitation procedures.

Can short-term oral fine motor training affect precision of task performance and induce cortical plasticity of the jaw muscles?

The aim was to test the hypothesis that short-term oral sensorimotor training of the jaw muscles would increase the precision of task performance and induce neuroplastic changes in the corticomotor pathways, related to the masseter muscle. Fifteen healthy volunteers performed six series with ten trials of an oral sensorimotor task. The task was to manipulate and position a spherical chocolate candy in between the anterior teeth and split it into two equal halves. The precision of the task performance was evaluated by comparing the ratio between the two split halves. A series of "hold-and-split" tasks was also performed before and after the training. The hold force and split force along with the electromyographic (EMG) activity of jaw muscles were recorded. Motor-evoked potentials and cortical motor maps of the right masseter muscle were evoked by transcranial magnetic stimulation. There was a significant effect of series on the precision of the task performance during the short-term oral sensorimotor training (P < 0.002). The hold force during the "hold-and-split" task was significantly lower after training than before the short-term training (P = 0.011). However, there was no change in the split force and the EMG activity of the jaw muscles before and after the training. Further, there was a significant increase in the amplitude of the motor-evoked potentials (P < 0.016) and in the motor cortex map areas (P = 0.033), after the short-term oral sensorimotor training. Therefore, short-term oral sensorimotor task training increased the precision of task performance and induced signs of neuroplastic changes in the corticomotor pathways, related to the masseter muscle.

Motor behavior during the first chewing cycle in subjects with fixed tooth- or implant-supported prostheses.

OBJECTIVES: Appropriate sensory information from periodontal mechanoreceptors (PMRs) is important for optimizing the positioning of food and adjustment of force vectors during precision biting. This study was designed to describe motor behavior during the first cycle of a natural chewing task and to evaluate the role of such sensory input in this behavior. MATERIAL AND METHODS: While 10 subjects with natural dentition, 11 with bimaxillary fixed tooth-supported prostheses (TSP) and 10 with bimaxillary fixed implant-supported prostheses (ISP) (mean age 69 [range 61-83]) chewed a total of five hazelnuts, their vertical and lateral jaw movements were recorded. Data obtained during the first chewing cycle of each hazelnut were analyzed. RESULTS: The amplitude of vertical and lateral mandibular movement and duration of jaw opening did not differ between the groups, indicating similar behavior during this part of the chewing cycle. However, only 30% of the subjects in the natural dentate group, but 82% of those in the TSP and 70% in the ISP group exhibited slippage of the hazelnut during jaw closure in at least one of five trials. The TSP and ISP groups also exhibited more irregular and narrower patterns of motion (total lateral/vertical movement = 0.15 and 0.19, respectively, compared to 0.27 for the natural group). CONCLUSIONS: Subjects with fixed tooth- or implant-supported prostheses in both jaws show altered behavior, including inadequate control of the hazelnut, during the first chewing cycle. We propose that these differences are due to impairment or absence of sensory signaling from PMRs in these individuals.

Effects of experimental craniofacial pain on fine jaw motor control: a placebo-controlled double-blinded study.

The aim of the experiment was to test the hypothesis that experimental pain in the masseter muscle or temporomandibular joint (TMJ) would perturb the oral fine motor control, reflected in bigger variability of bite force values and jaw muscle activity, during repeated splitting of food morsels. Twenty healthy volunteers participated in four sessions. An intervention was made by injection of either 0.2 ml of monosodium glutamate/isotonic saline (MSG/IS) (randomized) in either the masseter or TMJ (randomized). The participants were asked to hold and split a flat-faced placebo tablet with their anterior teeth, thirty times each at baseline, during intervention and post-intervention. Pain was measured using a 0-10 visual analog scale. The force applied by the teeth to "hold" and "split" the tablet along with the corresponding electromyographic (EMG) activity of the jaw muscles and subject-based reports on perception of pain was recorded. The data analysis included a three-way analysis of variance model. The peak pain intensity was significantly higher during the painful MSG injections in the TMJ (6.1 ± 0.4) than the injections in masseter muscle (5.5 ± 0.5) (P = 0.037). Variability of hold force was significantly smaller during the MSG injection than IS injection in the masseter (P = 0.024). However, there was no significant effect of intervention on the variability of split force during the masseter injections (P = 0.769) and variability of hold and split force during the TMJ injections (P = 0.481, P = 0.545). The variability of the EMG activity of the jaw muscles did not show significant effects of intervention. Subject-based reports revealed that pain did not interfere in the ability to hold the tablet in 57.9 and 78.9 %, and the ability to split the tablet in 78.9 and 68.4 %, of the participants, respectively, during painful masseter and TMJ injections. Hence, experimental pain in the masseter muscle or TMJ did not have any robust effect in terms of bigger variability of bite force and jaw muscle activity, during repeated splitting of food morsels.

Optimization of jaw muscle activity and fine motor control during repeated biting tasks.

OBJECTIVE: To investigate if repeated holding and splitting of food morsel change the variability of force and jaw muscle activity in participants with natural dentition. METHODS: Twenty healthy volunteers (mean age=26.2±3.9 years) participated in a single session divided into six series. Each series consisted of ten trials of a standardized behavioural task (total 60 trials) involving holding and splitting a flat-faced tablet (8mm, 180mg) placed on a bite force transducer with the anterior teeth. The hold and split forces along with the electromyographic (EMG) activity of the left and right masseter (MAL and MAR), left anterior temporalis (TAL) and digastric (DIG) muscles were recorded. A series (ten trials) of natural biting tasks was also performed before and after the six series of the behavioural task. RESULTS: The mean hold force (P<0.001) but not the mean split force (P=0.590) showed significant effect of number of series. No significant effect of series was seen on the variability of hold and split force and the EMG activity except for the variability of EMG activity for MAL during the hold phase (P=0.021) and DIG during the split phase (P<0.001). The behavioural task had no effect on the EMG activity of the natural biting task. CONCLUSION: There was no evident optimization of jaw motor function in terms of reduction in the variability of bite force values and muscle activity, when this simple task was repeated up to sixty times in participants with normal intact periodontium.

Alterations in intraoral manipulation and splitting of food by subjects with tooth- or implant-supported fixed prostheses.

OBJECTIVES: Sensory information provided by the periodontal mechanoreceptors (PMRs) is used by the nervous system to optimize the positioning of food, force levels, and force vectors involved in biting. The aim of this study was to describe motor performance during a novel manipulation-and-split task and to assess the extent to which control of this performance involves information from the PMRs. MATERIALS AND METHODS: A total of 10 subjects with natural teeth, 10 with bimaxillary tooth-supported fixed prostheses (TSP) and 10 with bimaxillary implant-supported fixed prostheses (ISP) (61-83 [mean 69] years of age) were asked to perform an intraoral manipulation-and-split task that involved positioning a spherical chocolate dragée between the front teeth and then splitting it into two parts of equal size. The vertical jaw movement, sound of food cracking and masseter muscle activity were monitored during this task and the accuracy of the split was evaluated. RESULTS: The group with natural teeth was significantly better than the other groups at splitting the candy with high precision. The jaw movements were similar between groups, but the contact phase prior to the split was significantly longer for those with natural dentition. CONCLUSIONS: The present findings support the conclusion that the nervous system collects rich information about contact between the teeth and food from the PMRs prior to powerful jaw action. Impairment (TSP) or absence (ISP) of this information alters motor behavior and impairs performance during the natural biting task employed here.

Clinical advantages of computer-guided implant placement: a systematic review.

OBJECTIVES: To systematically scrutinize the current scientific literature regarding the clinical advantages of computer guidance of implant placement. MATERIALS AND METHODS: Four electronic databases were searched using specified indexing terms. The reference lists of publications were also searched manually. For inclusion, publications had to meet pre-established criteria. RESULTS: The searches yielded 1028 titles and abstracts. After data extraction and interpretation, 28 publications and 2 systematic reviews remained for inclusion. Fifteen studies were prospective observational and four were retrospective observational. Nine studies included a control group (controlled clinical trials) of which seven were prospective and two retrospective. Only three of the prospective studies were randomized (RCT's). A total of 852 patients were treated with 4032 implants using computer-guided implant surgery. The number of patients included in each study ranged from 6 to 206. The age ranged from 16 to 92 years and the follow-up period varied between 1 and 49 months. CONCLUSIONS: The limited scientific evidence available suggests that guided placement has at least as good implant survival as conventional protocols. However, several unexpected procedure-linked adverse events during guided implant placement indicate that the clinical demands on the surgeon were no less than those during conventional placement. A clinical advantage with flapless guided surgery is that the technique is likely to decrease pain and discomfort in the immediate postoperative period.

Impaired force control during food holding and biting in subjects with tooth- or implant-supported fixed prostheses.

AIM: Our goal here was to assess the ability of subjects with their natural teeth (natural), bimaxillary tooth-supported bridges (bridge) and bimaxillary implant-supported bridges (implant) to control the low contact and high biting forces associated with holding and splitting food between the teeth. MATERIALS AND METHODS: Ten subjects in each of these groups performed a task involving holding and splitting morsels of food with different degrees of hardness (biscuits and peanuts) between a pair of opposing central incisors. RESULTS: The hold force employed by the implant group was significantly higher and more variable than the corresponding force exerted by the bridge group, whereas the natural group used lowest and least variable force. For all three groups, the split force was higher and the split phase duration longer with peanuts than for biscuits. In the case of the natural group, a significantly higher rate of force increase (peak force rate) was observed when splitting peanuts when compared with biscuits, whereas no such difference could be seen for the other two groups. CONCLUSION: These findings demonstrate that individuals with bimaxillary tooth- or implant-supported bridges (in whom sensory information provided by the periodontal mechanoreceptors is impaired or missing) are unable to apply low-hold forces at the levels of individuals with natural teeth or to adapt the rate of the split force to the hardness of the food. We thus conclude that adequate sensory information from periodontal mechanoreceptors is essential for normal control of both low contact and high biting forces.

Regulation of bite force increase during splitting of food.

The purpose of the study was to analyze how increases in the bite force, during the splitting of food morsels of different hardness, are modulated, and to evaluate the role of periodontal mechanoreceptors in this control. Fifteen subjects were instructed to hold and split food morsels of different hardness (peanuts and biscuits) between a pair of opposing central incisors before and during anesthesia of the teeth. The split occurred at an average bite force of 9 N for biscuits and at an average bite force of 18 N for peanuts. The duration of the split phase was longer, and the split force rate higher, for peanuts compared with biscuits. Furthermore, a steeper force trajectory was observed for the peanut. During anesthesia of the teeth, the duration of the split phase increased and the mean split force rate decreased for peanuts. Force trajectories for peanuts and biscuits were indistinguishable during anesthesia. The present results show that when higher bite forces are needed to split a morsel, both the duration and the rate of the bite force produced is increased. Furthermore, adaptation of the bite force rate to the hardness of the food is dependent on information from periodontal mechanoreceptors.

Forces applied by anterior and posterior teeth and roles of periodontal afferents during hold-and-split tasks in human subjects.

Hold-and-split tasks were performed by 20 subjects (12 females and 8 males) using the right central incisors, canines, 2nd premolars, and 1st molars, respectively. Half a peanut was positioned on a transducer-equipped plate and the subject was instructed to hold the plate with the peanut between two antagonistic teeth, and not using more force than necessary. After ca. 3 s the subject was instructed to split the peanut in a natural manner. Each session consisted of a series of three in which the subject performed the hold-and-split task five times for each tooth. Thus, in total, data were obtained from 60 trials for each subject. The magnitude of the forces and the force rates used to split the peanut increased distally along the dental arch. However, the duration of the split phase was similar for the various teeth examined. During anesthesia of the periodontal ligament (four subjects), no significant changes were seen in the split phase. The forces used to hold the peanut between the teeth also increased distally along the dental arch: 0.60 N for the incisor, 0.77 N for the canine, 1.15 N for the 2nd premolar, and 1.74 N for the 1st molar. The difference in hold forces for the various teeth can be explained by the different sensitivity characteristics of the periodontal afferents innervating anterior and posterior teeth. During periodontal anesthesia, the magnitude and variability of the hold forces increased for all types of teeth, thus supporting the suggestion that periodontal afferent information is used in the regulation of the level of forces used to hold and manipulate morsels between the teeth.

Impaired masticatory behavior in subjects with reduced periodontal tissue support.

BACKGROUND: Mechanoreceptors situated in the periodontal ligament provide detailed information about intensive and spatial aspects of tooth loads, which support the neural control of masticatory forces. We asked whether a reduced periodontal ligament due to periodontitis, and, thus, an altered mechanoreceptive innervation of the teeth, would affect masticatory behavior when subjects used incisors to hold and split food. METHODS: We tested 11 subjects with reduced periodontal tissue support that rendered 30% to 70% alveolar bone loss for at least one pair of opposing anterior incisors. Forces were recorded when subjects used their affected incisors to hold half of a peanut for approximately 4 seconds and then split it. Age- and gender-matched healthy subjects served as the control group. None of the participants showed acute oral symptoms or massive periodontal inflammation. RESULTS: The test group used greater force when holding food between the teeth (1.1+/-0.4 N [ mean+/-1 SD]) compared to the control group (0.4+/-0.2 N). Hold forces used by subjects in the test group were also more variable, both within and between trials. The increase in bite force applied to split the peanut was slower and more hesitant for subjects in the test group compared to the control group. CONCLUSIONS: Reduced periodontal tissue support accompanies impaired regulation of masticatory forces. Faulty mechanoreceptive innervation of the periodontal ligament explains the elevated hold force, whereas a change in biting strategy due to the weakened support of the teeth may account for the more defensive food-splitting behavior.