Evaluation of the Periotest Device as an Objective Measuring Tool for Tooth Mobility—A Clinical Evaluation Study

Abstract

Objective: The aim of this study was to allow researchers to evaluate the Periotest device as a reproducible tool that can be trusted to carry out accurately reproducible and comparable tooth mobility readings. Methods: A reproducibility test was initially conducted taking Periotest recordings for #16 every 10 min with 1 min intervals. Each time, three readings were recorded, and the average of the three was noted. This was followed by recordings for three different subject groups varying in age that were seen three times in 4 weeks, with 2-week intervals between each appointment; recordings were taken of #11, #13 and #16. Nonparametric analysis using the Wilcoxon signed-rank test was carried out. Results: For the reproducibility test, the values of all three readings for each recording session were either exactly the same or differed by up to ±2 Periotest value units. p-value results in the three patient groups showed no significant difference in Periotest values between appointments, with the minor exception of #16 in all three groups, but this was well within the limits of error of the device. Conclusions: Analysis of the Periotest readings in this study indicates that positive (higher) Periotest values correspond to increased tooth mobility.

1. Introduction

The Periotest device (Medizintechnik Gulden, Eschenweg 3, 64397 Modautal, Germany) (Figure 1) was introduced by Siemens to help dentists measure tooth mobility with ease and accuracy. It consists of a unit with an LCD screen and a handpiece, similar in form and size to a straight dental handpiece. The handpiece consists of a metal rod, housed in the tapping head, with a constant speed of 0.2 m/s (meters per second) and a known mass of 8 g [1,2]. When the rod contacts the surface of the tooth, it decelerates and electromagnetically retracts into the handpiece, drawn back to its starting position only to reaccelerate to make contact with the tooth surface again. The measurement is based on the time interval between the first impact on the tooth and when it contacts the tooth surface again. An accelerometer records the impact’s deceleration. This sequence is repeated for four seconds, with four taps per second, for a total of 16 taps [3,4].

The unit has a built-in microprocessor or microcomputer, which checks the validity of the signals and rejects the invalid ones, signaling to the dentist acoustically (a beep sound) through the speakers after checking whether the manipulation of the handpiece has been correct. An incorrect manipulation results in the absence of the acoustic signal, and the value of the measurement appears in the erroneous form of +999 (Figure 2). In recent years, the Periotest Classic has evolved into a more user-friendly device with system setting keys that were not available in older models, and a more portable device, the Periotest M, intended solely for battery use, has been created (Figure 1).

1.1. Principles of the Periotest Device

The Periotest measures the reaction of the periodontium to a reproducible and defined impact load applied to the tooth crown, but essentially, its function is the measurement of the periodontal damping characteristics [5,6], which are dependent upon the health of the periodontal tissues [7]. Tooth mobility is calculated from the state of the rebound of the tapping head. The greater the stability of the periodontium, the higher the damping effect and the faster the deceleration [8]. In other words, when the rod contacts the surface of a tooth with a healthy, firm periodontium, then the rebound of the tooth is very quick. The elastic fibers restrain the tooth, absorbing the loading of the percussion force but also causing the rod to decelerate faster.

When the periodontium is compromised with possible attachment loss, the percussion force generated by the flying rod of the handpiece moves the tooth away because the elastic fibers are no longer able to return it quickly and efficiently to its prior position. The tooth eventually returns, but the elastic fibers, due to the inflammation and attachment loss, can no longer function properly [9].

Measurements of tooth mobility using the Periotest device can also be taken in maximum intercuspation [3,4]; however, the periodontal damping capability changes because the periodontal fibers are tensed, altering their damping capability and showing lower Periotest values than teeth that are out of contact.

1.2. Periotest Values (PTVs)

The Periotest value, or PTV, constitutes a reproducible quantitative parameter for the reaction of the periodontium to a percussive stimulus, a force applied on the buccal surface of the tooth crown. It is based on a numerical scale from −8 to +50. Compared with the standard and more commonly used manual index described by Miller [10], the Periotest values are classified as seen in

Table 1. Periotest values compared to the standard classification Miller index as described by Schulte and Lukas in 1992.

Miller Index	Periotest Values	Description
class 0	−8 to +9	clinically firm teeth
class I	+10 to +19	palpable mobility
class II	+20 to +29	visible mobility
class III	+30 to +50	mobility in response to lip or tongue pressure

. Bone loss is of great importance to the calculation of the Periotest value. Alveolar bone height corresponds to lower or negative Periotest values. A negative Periotest value translates into a more reduced capacity of damping of the impact load on the tooth surface; thus, hard bone tissue surrounds the tapped tooth. Positive Periotest values mean the tooth has a greater capacity to absorb the impact load, and therefore, there is softer tissue around the tapped tooth [4].

The measurements should be taken with the handpiece placed parallel to the horizontal plane and at a 90-degree angle from the vertical plane on the middle third of the buccal surface of the tooth [3,4] (Figure 3). Any deviation from that position will result in incorrect measurement and rejection by the microprocessor of the device (Figure 4). Mesially eccentric percussion is allowed in the posterior teeth in cases where the masseter muscle does not allow proper handling. Schulte and Lukas in their 1990 [1] article stated that for the anterior teeth and the premolars, the Periotest device provides a long-term accuracy of ±1 to ±2 PTV units, but for the molars, the variation is greater, at about ±3.

1.3. Practical Applications of the Periotest

One of the most important applications of the Periotest device is the measurement of tooth mobility to identify teeth that are involved in progressive marginal inflammation at an earlier stage of the diagnostic process [11]. Combined with a clinical (pocket depth, plaque index) and a radiographic (periapical X-rays) examination, as well as follow-ups, the Periotest provides information on existing or early periodontal structure changes, and treatment for possible periodontal disease can be started much earlier [5,6,11].

Over the years, the Periotest has been used successfully in children’s dentistry [6,7], orthodontics [12], endodontics [13], restorative dentistry [14,15] and traumatology [16], and even hormonal influences on tooth mobility such as the menstrual cycle have been studied using the Periotest device [17,18]. In recent years it has been mainly used on osseointegrated implants [19,20,21,22] in order to identify and evaluate possible problems that could lead to failure. Implant mobility is an indicator of bone loss [23]. It is difficult to conclude radiographically with 100% certainty that there is no fibrous or epithelial tissue between the bone and the implant [24]. Therefore, a more reliable assessment of clinical mobility could be produced by using dynamic measurements such as implant percussion from the Periotest device [25]. Evaluating the damping characteristics of periodontal tissues surrounding osseointegrated implants produces values of between −4 and +2, lower than those for natural teeth, and non-osseointegrated implants give values much higher than those of natural teeth [26].

1.4. Aims and Objectives of the Study

The aim of this study was to examine and test the reproducibility of the Periotest device and whether it can be trusted to carry out tooth mobility readings accurately. The literature so far suggests that it is an objective tooth mobility measuring tool, as long as the manufacturer’s instructions for proper manipulation of the handpiece are followed closely. However, concerns have been voiced with readings subsequent to the first measurement and their validity [7]. The second Periotest recording was considerably lower than the first, which is attributed to the lack of sufficient time allowing the periodontium to recover to its previously functioning state.

2. Methodology

2.1. Design of the Study

Prior to any new study being launched and during its developing stages, pilot tests are being carried out to examine the reproducibility of the methods, techniques and devices that are going to be used in the study. This is an important step as it identifies potential problems or parameters that were not initially thought of and could jeopardize outcomes early on. To facilitate the statistical analysis of the data collected from the subjects, the exact same methods are required to be performed on each subject entering the study, thus making the data statistically comparable between subjects and groups. Therefore, all aspects of the methodology need to be tested and their reproducibility evaluated.

In order to achieve that, a reproducibility test (pilot study) was initially conducted using only one test subject. The results obtained provided the necessary proof that the data collected were comparable for statistical analysis. In accordance with the objectives of the study, three groups of subjects were fashioned, each targeting a specific age range.

All subjects gave their informed and signed consent for inclusion before they participated in the study. The study was conducted in accordance with the Declaration of Helsinki, and the protocol was approved by 5 separate Institutional Ethics Committees, which are listed in

Table 2. List of ethical approvals obtained before the study commenced.

Committee	Date	Ref. Number
King’s College Research Ethics Committee (CREC)	26 February 2002	CREC/01/02-40
Guy’s Research Ethics Committee	13 March 2003	03/01/08
King’s College Hospital REC	10 April 2003	04-03-108
King’s College Hospital Research and Development Committee	9 May 2003	03DS09
Guy’s Research and Development Committee	29 October 2003	RJ1:03/0271

.

2.1.1. Periotest Reproducibility Test

A test subject (patient) with full upper and lower natural dentition was selected, with no diagnosed periodontal disease, no fixed or removable restorations and no ongoing orthodontic treatment. The subject was seen in a morning session at the Team Care clinics of King’s College Dental Institute at the Denmark Hill Campus and recordings were taken by the researcher using the Periotest device on the upper right 6 molar tooth (#16). The tapping procedure was repeated 10 times, every 10 min, for the mentioned tooth, and every time, 3 readings were recorded with 1 min intervals to allow sufficient time for the periodontium to recover [1,2,3,4]. The average of the 3 readings was noted as the mean PTV of mobility for the tooth (

Table 3. Reproducibility test data in PTV units for the Periotest device.

Time Intervals	Reading #1	Reading #2	Reading #3	Average of Three
10′	3	3	2	3
20′	3	3	3	3
30′	3	2	2	2
40′	5	4	3	4
50′	0	0	−1	0
60′	3	2	3	3
70′	5	4	3	4
80′	5	5	4	5
90′	3	3	3	3
100′	3	3	2	3

). The subject was not allowed to eat or chew anything between recordings.

2.1.2. Patient Groups

Three groups of patients were seen a total of 3 times in 4 weeks, with 2-week intervals between each appointment.

• The first group (Group A1) consisted of 12 undergraduate students under the age of 30 (6 females and 6 males) who volunteered to take part in the study and had the chance to become acquainted with the Periotest device. All subjects had complete upper and lower dentitions, with no diagnosed periodontal disease and no fixed or removable restorations, and none of the subjects were undergoing any orthodontic treatment.
• The second group (Group A2) consisted of 11 members of staff over the age of 30 (5 females and 6 males) with the same criteria as Group A1; a complete upper and lower dentition, with no diagnosed periodontal disease and no removable prosthesis, and none of the subjects were undergoing any orthodontic treatment. Some of the subjects had fixed crowns on their teeth but not on any of the teeth used in the study.
• Finally, the third group (Group A3) consisted of 9 patients (3 females and 6 males) between the ages of 40 to 65 years old who, in contrast with the two previous groups, had diagnosed, treated and stable periodontal disease. Some of the subjects had fixed crowns on their teeth but not on any teeth used in this study.

Each time for every patient of all three study groups, Periotest recordings were taken of the upper right 1 (#11), upper right 3 (#13) and upper right 6 (#16) teeth. The tapping procedure was repeated three times for each tooth with 1 min intervals [1,2,3,4]. The average of the three recordings for each tooth was noted as the mean mobility of the tooth for this session (

Table 4. Tooth mobility mean values and standard deviation for the 3 consecutive visits for Groups A1, A2 and A3 and for teeth #11, #13 and #16.

Group A1		N	Baseline	2 Weeks	4 Weeks
	Mean	12	1.00	0.83	1.17
#11	Std. Deviation		2.045	1.642	1.267
	Median		0.50	0.50	1.00
	Mean	12	−1.50	−1.83	−1.75
#13	Std. Deviation		2.111	1.749	1.545
	Median		−1.50	−2.00	−2.00
	Mean	12	0.17	−0.50	−1.08
#16	Std. Deviation		2.329	2.067	2.021
	Median		0.00	−0.50	−1.50
Group A2		N	Baseline	2 Weeks	4 Weeks
	Mean	11	1.18	1.00	0.91
#11	Std. Deviation		2.089	2.646	1.868
	Median		1.00	1.00	1.00
	Mean	11	−0.64	−1.36	−1.45
#13	Std. Deviation		1.859	1.859	2.067
	Median		−1.00	−1.00	−2.00
	Mean	11	1.09	0.27	−0.55
#16	Std. Deviation		2.914	2.867	2.382
	Median		0.00	−1.00	−1.00
Group A3		N	Baseline	2 Weeks	4 Weeks
	Mean	9	3.56	3.33	3.44
#11	Std. Deviation		3.127	3.428	3.812
	Median		3.00	3.00	3.00
	Mean	9	0.56	0.11	−0.33
#13	Std. Deviation		3.283	2.713	2.915
	Median		0.00	0.00	0.00
	Mean	9	1.89	3.78	2.00
#16	Std. Deviation		5.036	4.868	5.244
	Median		0.00	4.00	0.00

).

2.2. Periodontal Assessment

Periodontal clinical assessment of all patients included bleeding on probing (BOP), clinical attachment loss (CAL) and pocket depth (PD) measurements following the criteria of the American Academy of Periodontology [27], which were used at the time. Accordingly, periodontally healthy patients (pilot test, Groups A1 and A2) were considered as those who displayed bleeding on probing <2%, no clinical attachment loss and pocket depth <3 mm. For Group A3, periodontitis was diagnosed, the subjects showed bleeding on probing >10% and a pocket depth >3 mm was detectable in ≥2 teeth. All patients participating in Group A3 were treated for periodontitis previous to participating in the study.

2.3. Statistical Analysis and Limitations of the Study

The value of the error of the Periotest device has been identified by the manufacturer as up to ±2 PTV units for the anterior teeth (incisors and canines) and up to ±3 PTV units for the posterior teeth (premolars and molars).

Regarding the reproducibility test, since it is not a comparative statistical study but a one-sample pilot study with n observations (n = 10), each observation is compared with the other observations within the same group. The diversion from the mean value of the readings is the standard error for the study, while the standard deviation is the dispersion of values.

Statistical analysis of the data for all 3 subgroups (Group A1, A2 and A3) to determine if there was a significant difference in tooth mobility between the baseline visit (visit 1) and 2 weeks later (visit 2) and the baseline visit (visit 1) and 4 weeks later (visit 3) was performed using the Wilcoxon signed-rank test through the statistical software SPSS v.15 (© 2006 SPSS Inc., Chicago, IL, USA—© 2009–2023 IBM SPSS Statistics, 1 New Orchard Road, Armonk, NY 10504-1722, USA) for Microsoft Windows OS. Due to the limited sample size, there is a lack of certainty that the data follow a normal distribution. Therefore, a nonparametric analysis was carried out. Nonparametric analysis tests do not require the same assumptions regarding the distribution of the data and are more suitable for small samples.

The Wilcoxon signed-rank test is a nonparametric test equivalent to the parametric paired sample t-test and is mostly used in cases where the statistical sample is either too small, has a wide variance or does not follow a normal distribution. Contrary to the t-tests, the Wilcoxon test examines median values with the null hypothesis, stating that both samples are the same and have median values of zero.

To consider that there is a strong indication of dependence between the variables, the value of significance, or p-value, must be lower than the predetermined significance level, which is set to 0.05; thus, the p-value = 0.05. The p-value is a type II error that expresses the possibility of a mistake in the null hypothesis, stating that there is a dependence between the variables. The lower its value, the lesser the possibility of such a mistake.

3. Results

3.1. Periotest Reproducibility Test

Taking a closer look at the readings presented in Table 3, it can be observed that the values of all three readings for each recording session are either exactly the same or differ by up to ±2 PTV units. The average PTV of the three readings is either the same between all 10 consecutive recording sessions or differs by up to ±3 PTV units. The mean PTV for the 10 recordings of the group is 3, while the standard deviation from the mean value is 1.333 and the standard error from the mean value is 0.422, which are both within the limits of the error of the device provided by the manufacturer for posterior teeth (

Table 5. Descriptive statistics and standard error in PTV units for #16.

	N	Min	Max	Mean	Standard Deviation	Standard Error
UR6	10	0	5	3	1.333	0.422

).

3.2. Patient Groups

For Group A1, the mean PTVs between the three consecutive visits were similar for all three teeth, and their standard deviation was well within the limits of error of the device (Table 4).

Statistical analysis of the Periotest recordings (

Table 6. p-value results from the Wilcoxon signed-rank test analysis for #11, #13 and #16 of Group A1 between 0 and 2 weeks, 0 and 4 weeks and 2 and 4 weeks.

	N	Asymp. Sig. (2-Tailed)
Group A1		0–2 Weeks	0–4 Weeks	2–4 Weeks
#11	12	0.516	0.608	0.157
#13	12	0.391	0.490	0.860
#16	12	0.146	0.012	0.096
	N	Asymp. Sig. (2-Tailed)
Group A2		0–2 Weeks	0–4 Weeks	2–4 Weeks
UR1	11	0.527	0.180	0.739
UR3	11	0.070	0.021	0.785
UR6	11	0.024	0.011	0.107
	N	Asymp. Sig. (2-Tailed)
Group A3		0–2 Weeks	0–4 Weeks	2–4 Weeks
UR1	9	0.589	0.785	0.655
UR3	9	0.336	0.168	1.000
UR6	9	0.016	0.892	0.125

) for #11 showed no significant difference in Periotest values and tooth mobility between the baseline visit (visit 1) and the second visit two weeks later, with a p-value larger than 0.05 (p = 0.516); the same applied for the baseline visit (visit 1) and the third visit four weeks later (p = 0.608). There was also no significant difference in Periotest value between the second and the third visit (p = 0.157), indicating no significant change in tooth mobility. Similarly, there was no significant difference in Periotest values and tooth mobility between all three pairs for #13: baseline visit (visit 1) and the second visit two weeks later (p = 0.391), baseline visit (visit 1) and the third visit four weeks later (p = 0.490) and also between the second and the third visit (p = 0.860). For #16, there was a significant difference in Periotest values and tooth mobility between the baseline visit and the third visit four weeks later (p = 0.012), while there was no significant difference between the baseline visit and the second visit two weeks later (p = 0.146) and between the second and the third visit (p = 0.096).

For Group A2, the mean PTVs between the three consecutive visits were similar for all three teeth, and their standard deviation edged above the limits of error of the device only for the first two visits for #11 (Table 4).

Following the same procedures as in Group A1, statistical analysis of the Periotest recordings (Table 6) for #11 showed no significant difference in Periotest values and tooth mobility between the baseline visit (visit 1) and the second visit two weeks later, with a p-value of 0.527; the same applied for the baseline visit (visit 1) and the third visit four weeks later (p = 0.180), and no significant difference was found between the second visit and the third visit (p = 0.739). For #13, there was a significant difference in Periotest values and evidence of tooth mobility between the baseline visit (visit 1) and the third visit four weeks later (p = 0.021), while there was no significant difference between the baseline visit (visit 1) and the second visit two weeks later (p = 0.070) and between the second and the third visit (p = 0.785). Finally, for #16, there was a significant difference in Periotest values and tooth mobility between the baseline visit (visit 1) and the second visit two weeks later (p = 0.024) and the baseline visit (visit 1) and the third visit four weeks later (p = 0.011), while there was no significant difference between the second and the third visit (p = 0.107).

Finally, for Group A3, the mean PTVs between the three consecutive visits were similar for all three teeth, except for the second visit for #16, while their standard deviation was, in all cases, above the limits of error for the device (Table 4).

Similarly, to the previous groups A1 and A2, statistical analysis of the Periotest recordings (Table 6) for #11 showed no significant difference in Periotest values and no tooth mobility between the baseline visit (visit 1) and the second visit two weeks later (p = 0.589), the baseline visit (visit 1) and the third visit four weeks later (p = 0.785) and no significant difference in tooth mobility between the second visit and the third visit (p = 0.655). For #13, there was no significant difference in tooth mobility between all three pairs: the baseline visit (visit 1) and the second visit two weeks later (p = 0.336), the baseline visit (visit 1) and the third visit four weeks later (p = 0.168) and also between the second and the third visit (p = 1.000). And for #16, there was a significant difference in Periotest values and tooth mobility between the baseline visit (visit 1) and the second visit two weeks later (p = 0.016), while there was no significant difference between the baseline visit (visit 1) and the third visit four weeks later (p = 0.892) and between the second and the third visit (p = 0.125).

4. Discussion

The Periotest device provides a way to measure tooth mobility very quickly, noninvasively and without causing the patient any discomfort or pain. It is easy and simple to use. The tapping on the surface of the teeth is very light and does not jeopardize the periodontal health of teeth nor does it increase mobility in already periodontally compromised dentitions. Where the Miller index fails, the Periotest provides a greater variety of tooth mobility values, allowing the dentist to monitor more closely the changes in compromised dentitions. There are many causes of increased and decreased tooth mobility. Having a reliable device that measures tooth mobility is useful to the clinician as a special test that can be used as required to assist in diagnosis and treatment.

The Periotest has been studied by many researchers in an attempt to evaluate its clinical use and verify the reproducibility and accuracy of the results obtained [1,3,4,6,7,12,13,14]. As mentioned, it has been found to be a noninvasive method that does not cause any discomfort or pain to the patients, and unlike the commonly used Miller index, the results obtained are automated and therefore objective, not relying solely on the practitioner’s experience and use of the method.

Various factors contribute to the success of the Periotest device as a diagnostic tool to provide correct readings of tooth mobility, most notably, the correct manipulation of the handpiece. Unsteady movements or generally incorrect manipulation of the handpiece must be avoided at all times due to the inaccuracy of the result obtained. Erroneous readings can be identified because they appear in the form of +999 [3,4], while accurate readings produce a bleeping sound from the main unit during the tapping process.

The position of the patient, sitting up or lying down, produces the same measurements without any deviations, but depending on the group of teeth examined, the head must be positioned in the right way. In all cases, and regardless of the position of the head, the handpiece should be parallel to the horizontal plane and at a 90-degree angle from the vertical plane on the buccal surface of the tooth.

Another factor that should always be considered and could be responsible for false recordings is mastication. The use of chewing gum or consumption of food prior to the recordings slightly increases the mobility of the posterior teeth. Due to the continuous forces applied on the masticatory surface of the posterior teeth, the elastic fibers of the periodontal ligaments are stretched and the results obtained are incorrect. For this reason, the general dental practitioner should always enquire, as well as always be aware, if the patient has any clenching habits or if he/she is diagnosed with bruxism before using the Periotest device, especially if the recordings are taken early in the morning. Along the same lines, teeth with extensive, old and broken-down restorations, where the forces applied on the masticatory surface are uneven, could also provide inaccurate tooth mobility recordings.

This could explain why there was a significant difference in Periotest values and subsequently tooth mobility for #16 in all three groups of patients between appointments, either the baseline visit (visit 1) and the second visit two weeks later or the baseline visit (visit 1) and the third visit four weeks later.

A very important parameter in the calculation of tooth mobility is to know the direction of the percussion force: the force used by the device to tap the surface of the tooth in order to identify any existing mobility. All measurements have to be performed with the same percussion force to all teeth otherwise the reaction of each tooth is going to be different, and the results will not be comparable. The direction of the percussive force needs to be centered on the buccal/lingual aspect of the tooth, but sometimes, due to the anatomical limitations in posterior teeth, a mesially eccentric percussion technique is used [3,4]. Unsteady movements of the handpiece must be avoided at all times due to the inaccuracy of the result obtained.

Mackie et al. (1996) [7] identified another problem that had not been mentioned in any study before. The second Periotest recording, which was taken to evaluate the reproducibility of the results, was considerably lower than the first. The only reasonable explanation given by the authors for this discrepancy is that not enough time was allowed for the periodontium to recover to its previous functioning state between the two attempts. These findings seem to be supported by Andresen et al. (2003a and 2003b) [5,6] who quantified the time intervals at no less than 15 min.

It should be noted that the Periotest as a diagnostic tool is probably impractical to use in daily routine dental treatment or to identify the presence of tooth mobility in cases of periodontitis if the practitioner is not experienced in the use of the device, as well as fully aware of its limitations. An incorrect reading requires a resting period of up to 15 min, according to Mackie [7], before a new reading is attempted, which makes it time-consuming. Although his findings are scientifically correct, it is impractical to follow his suggestions in practice or even research. If we were to abide by the suggestion that following an erroneous reading with the Periotest, a 15 min interval is necessary before a second Periotest reading is taken, then a simple tooth mobility evaluation using this device in practice could take more than an hour to complete. This is time-consuming and very often not acceptable by either the patient or the dental practitioner. Neither one can allow that much time to examine the potential presence of tooth mobility on only one tooth, especially if the same assessment needs to be performed on all the patient’s teeth.

In each recording session, the results of the reproducibility study show that subsequent readings to the first (the second and third readings of each recording session) were poorer; however, the standard deviation from the mean value of each recording session is no higher than ±2 PTV units, which is, as stated earlier, an acceptable and statistically nonsignificant error.

Taking into consideration the results from our study, it was concluded that the possible error or deviation in accuracy in tooth mobility results from the Periotest device, if we were to take readings in less than 15 min intervals, was acceptable and more practical to work with for both the researcher and the subjects/patients.

The Periotest value will correlate significantly with pocket depth, bone destruction, attachment loss and plaque index, as well as tooth mobility. It integrates the influences of the periodontal tissue changes of which 70% originate from bone changes and 30% from soft tissue changes. This does not apply to gingivitis because there is no change in the periodontal structure. Finally, restorations such as fillings, crowns or even crowded teeth have no or an insignificant bearing on the measurements. Splinted teeth or fixed–fixed bridges will produce the value of the entire block.

Further examination of the Periotest readings for this study supports the same conclusions reached by Schulte et al. (1992) [4] and Aparicio (1997) [28]; positive (higher) or negative (lower) Periotest values correspond to bone loss and alveolar bone height, respectively. Younger patient groups have significantly lower or negative values for all groups of teeth because they have less bone loss surrounding the tapped teeth. This becomes even more evident for the canine and molar teeth than the central incisors because the canines have a thick long root, while the molars are multirooted teeth with better bone support. On the other hand, anterior incisors have slimmer and often short roots, with very thin alveolar bone.

Age and oral hygiene are well-known factors negatively affecting the bone support of teeth over the years. Unsatisfactory restorations and missing teeth could also play a part in it. Positive values are mostly apparent in patients with diagnosed periodontally compromised teeth. Higher Periotest values mean a greater capacity to absorb the force of the impact and softer tissue around the tapped teeth, thus tooth mobility.

Additionally, it would be interesting to compare the Periotest device both with recently introduced technologies such as smartphone applications [29,30] and artificial intelligence [31] in order to improve data and knowledge about the reliability of such devices in daily clinical practice.

5. Conclusions

The finding from both the reproducibility test and the subject groups allows the researcher to conclude that the Periotest device is a reproducible tool that can be trusted to carry out the tooth mobility readings accurately.

• Reproducibility of the Periotest device recordings can be achieved for patients of all age groups, with or without diagnosed periodontal disease.
• Reproducibility of the Periotest device readings over a period of time depends on the correct manipulation of the handpiece and the location of the teeth in the arches.
• Younger populations present positive Periotest values, which translate into hard bone tissue surrounding the tapped teeth, while negative values are more usually observed in older populations, which translates to a greater capacity to absorb the impact force, softer tissue around the tapped teeth and, as a consequence, tooth mobility.
• All subsequent Periotest readings to the first, in the same session, were found to be different, with the majority of those being lower than the first.