Chapter 2 Material and methods
Material and methods Summary This chapter describes the subjects and methods being used in this study. Between 1986 and 1997 9 expeditions were undertaken in remote areas of Indonesia and almost 2400 patients were operated of whom 267 patients, who were considered to be unoperated adults, have participated in the present study. The patients were divided into 4 groups of clefts: unilateral cleft lip and alveolus (UCLA), bilateral cleft lip and alveolus (BCLA), unilateral cleft lip, alveolus and palate (UCLP), and bilateral cleft lip, alveolus and palate (BCLP). From these patients maxillary and mandibular impressions were made and dental casts were fabricated. Dental casts of 24 non-cleft individuals, selected at random from the surrounding population, were used as a control group. The dental casts of the cleft and non-cleft group were digitized three-dimensionally, using an industrial coordinate measuring machine. Means and standard deviations were calculated for transverse dimensions of the upper and lower jaw, palatal shelf width and palatal shelf angle. The t-test was conducted to determine whether the mean values of the cleft groups showed significant differences from each other and from the control group. The level of significance was set at p<0.05. 27
Chapter 2 2.1 Cleft mission For the present study, dental casts of adult unoperated cleft patients were collected in remote areas of Indonesia during several expeditions for the treatment of cleft lip and palate individuals. In these remote areas no proper medical or dental care is available and in the small regional hospitals only basic medical care can be offered. Rudimentary dental care is provided by young dentists who only have basic dental equipment and material; in fact only emergency dental care is possible. An expedition can only be organized after sufficient money has been collected to perform a cleft mission. Contact between the expedition leaders and the local authorities is of paramount importance in order to receive the necessary permission for the treatment of the patients. Contact was also made with the authorities of the small local hospitals in order to provide the necessary infrastructure for the treatment of the cleft patients. Religious leaders and social workers were contacted in order to announce the arrival of the expedition to the isolated small villages throughout the region. The same persons assisted the expedition members in finding housing for them as well as for the patients and for the accompanying members of their family. The patients and members of the family were mostly in a poor general condition, therefore they received a small amount of money for the daily needs during the period of hospitalization. During this preliminary contact a registration of the patients with cleft lip, alveolus and palate took place, giving the expedition leader a rough calculation of the number of patients who would like to be treated. This made it possible to estimate the necessary budget and to provide medical equipment for the expedition. All necessary equipment and material was brought to the target area together with the members of the expedition. The expedition consisted of medical and paramedical personnel necessary for a preoperative screening, for surgery and postoperative care. Therefore besides plastic surgeons and oral maxillofacial surgeons also ENT specialists, paediatricians, specialists in internal medicine, anaesthetists, and radiologists were included in the team. The supporting paramedical personnel consisted of laboratory assistants, nurses, operation room assistants, recovery room assistants and laboratory doctors and assistants. After arrival of the expedition at a given hospital, all patients who were registered previously were operated as soon as possible. The expedition as a whole moved then to the next hospital where the following group of patients 28
Material and methods was treated, and so on, until all registered patients of the area were treated. The final control of the operated patients was left to the regular doctors/residents of the local hospitals. 2.2 Patient definitions A patient is considered to be adult from the age of 13 years. Although facial growth at that age is still not fully complete, in the literature on unoperated clefts this age is generally used as the start of the adulthood stage. In our target area the patients or their family sometimes did not know the exact age of the patient. Therefore the patients were considered to be 13 years or older when the permanent dentition had erupted into full occlusion, including the second permanent molar. A patient was considered to be unoperated if he had not undergone any kind of surgical or orthodontic treatment previously. A patient was considered to have a cleft lip (CL) only when clinically and on the dental cast no defect of the alveolar process was visible. These patients were excluded from the investigation as they were not the target of this study. Figure 2.1 Patient with UCLA. Figure 2.2 Patient with BCLA. Individuals were considered to be affected by a cleft lip and alveolus, unior bilateral, when besides a cleft of a lip also the alveolar process showed clear signs of a cleft at one or both sides. The extension of the cleft could range from a small notch or depression of the alveolar process at the cleft 29
Chapter 2 area to a considerable gap of the alveolar process. In this thesis, these patients are referred to as UCLA (figure 2.1) or BCLA (figure 2.2) for a unilateral or bilateral cleft lip and alveolus, respectively. Figure 2.3 Patient with UCLP. Figure 2.4 Patient with BCLP. An individual was considered to be a cleft lip, alveolus and palate patient when a complete cleft of the lip, alveolus and palate with or without Simonart s band was diagnosed. Patients with a cleft lip and alveolus combined with a cleft of the palate with normal fused tissue in between were excluded from the sample. In this thesis these patients are referred to as UCLP (figure 2.3) or BCLP (figure 2.4) for a unilateral or bilateral cleft lip, alveolus and palate respectively. Only a few of the presented patients had an isolated cleft palate. These were also excluded from the present study, because the number was too small for analysis. 2.3 Collection of the sample 2.3.1 Cleft sample The material for this study was collected through the cooperation between the University of Brawijaya, Faculty of Medicine (Malang, Indonesia), Universitas Indonesia, Faculty of Dentistry (Jakarta, Indonesia) and the University Medical Centre Leiden, Department of Oral & Maxillofacial 30
Material and methods Surgery (Leiden, The Netherlands). During 9 expeditions, spread over 10 years (1986-1997), almost 2400 cleft patients were treated surgically. Among them there were 337 adult unoperated cleft patients registered prior to surgical treatment. From these patients, impressions of the upper and lower jaw were made with alginate (CA 37), and the impressions were poured out in stone within 5 minutes after they had been taken. For inclusion in the study the following criteria were applied: not too many extractions because these would compromise the measurements on the dental casts no damaged or broken dental cast permanent dentition including, if present, second molars in occlusion cleft present according to the definitions in paragraph 2.2 Based on these inclusion criteria 12 dental casts were excluded because the patients were found to be too young as the second permanent molar was not yet in full occlusion. Another 14 dental casts, initially classified as cleft lip and alveolus, were excluded because no defect of the alveolar process was found and therefore they were classified as cleft lip only. Another 7 dental casts were excluded because for them no clear cleft classification was possible. In these 7 patients the cleft lip and alveolus were combined with a cleft palate, but the 2 clefts were separated by a small area of normal fused palate. Furthermore 37 dental casts were excluded from the examination for reasons of damage of the model, missing teeth, multiple carious teeth or periodontal problems. In this category 2 individuals were also included because they were fully edentulous. Finally 267 patients (159 males and 108 females) participated in the study. The distribution of the final sample according to cleft type and age is given in table 2.1. Table 2.1 and age. Distribution of the unoperated cleft sample (N = 267) according to cleft type Age UCLA UCLP BCLA BCLP Total N Perc N Perc N Perc N Per c N Perc 13-20 94 35.2 29 10.9 10 3.7 10 3.7 143 53.6 21-30 49 18.4 26 9.7 8 3.0 2 0.8 85 31.8 31-40 18 6.7 9 3.4 0 1 0.4 28 10.5 41-50 5 1.8 3 1.1 0 0 8 3.0 51-60 2 0.8 1 0.4 0 0 3 1.1 Total 168 62.9 68 25.5 18 6.7 13 4.9 267 100.00 31
Chapter 2 The minimum age of the participating patients was 13 and the maximum 57 years. From table 2.1 it can be seen that the greatest number of patients is concentrated in the ages up to 40. Above that age very few patients were registered. The explanation for this may be that cleft patients have a lower life expectancy than non-cleft individuals of the same age and because life expectancy is only 57.5 years in this part of the world. In table 2.2 the distribution of the cleft sample is given according to gender. The gender distribution is in accordance with epidemiological data showing that males are more often affected than females (Derijcke et al, 1996). Table 2.2 Distribution of the unoperated cleft sample (N=267) according to gender. Gender Number Percentage Male 159 59.5 % Female 108 40.5 % Total 267 100 % 2.3.2 Control sample The control group consisted of 24 randomly selected non-cleft individuals from the same population. Table 2.3 shows the distribution of the control group according to age and table 2.4 according to gender. From the control group impressions and dental casts were made as described for the cleft sample in paragraph 2.3.1. Table 2.3 Distribution of the control group according to age. Age Number Percentage 13-20 16 66.7 % 21-30 7 29.2 % 31-40 1 4.1 % Total 24 100 % Table 2.4 Gender distribution in the control group. Gender Number Percentage Male 9 37.5 % Female 15 62.5 % Total 24 100 % 32
Material and methods 2.4 Dental cast analysis The dental casts were digitized three-dimensionally using an industrial coordinate measuring machine (=CMM) (Zeiss Numerex; Carl Zeiss, Stuttgart, Germany) (figure 2.5). With this bridge-type system accurate single-point data acquisition is possible by using a touch probe. The linear accuracy is up to 0.002 mm. Figure 2.5 Zeiss Numerex coordinate measuring machine. As a base for the orientation of the dental cast the occlusal plane was used. Firstly, the occlusal contacts between upper and lower molars were established by mutual agreement between two experienced investigators. Then wooden sticks with a diameter of 2 mm were fixed on the upper and lower dental cast when the dental casts were in occlusion, connecting both models. The ventral stick was fixed in the midline between the incisors, the midline of the mandible was used as the midline for both models. The lateral sticks were placed on the outmost point of the second molar on both sides. When the second molar was absent the sticks were fixed at the outmost point of the first molar. The wooden sticks were cut at the level of the occlusion with a rotating saw of 0.1 mm thickness. In the incisor area, the wooden stick was cut half way the distance between the occlusal edges of the upper and lower incisors. In this way the dental cast of the maxilla was separated from this of the mandible. The center of each wooden stick (cut-off) was used as a reference 33
Chapter 2 point. This procedure resulted in an upper and lower cast with three reference points through which the computer could calculate the occlusal plane either of the maxilla or the mandible. Then the dental casts were fixed on the measurement table of the CMM for registration of the reference points on the casts. Figure 2.6a and 2.6b show the points on the dental casts that were digitized. The points related to teeth are described with the number of the proper teeth, followed by the numbers 1, 2, or 3 indicating the position of the point on the tooth. The definition of the recorded points is given by Moyers et al (1976). The points, numbered 4, are located at the cleft margins on an imaginary line connecting the points 3 at left and right side of the maxilla for each tooth (in UCLP and BCLP only). In the control group the points 4 of the left and right side coincide in the midline of the palate. Figure 2.6 a. Maxillary dental cast (UCLP) reference points indicated. b. Mandibular dental cast with the reference points indicated. Between these points the following distances / angles were calculated: In the maxilla: 171-271 distance between distal cusps of the right and left second molar. 172-272 distance between mesial cusps of the right and left second molar 161-261 distance between distal cusps of the right and left first molar 162-262 distance between mesial cusps of the right and left first molar 163-164 palatal shelf width right side (in UCLP, BCLP and Control) at the level of the first molar 34
Material and methods 263-264 palatal shelf width left side (in UCLP, BCLP and Control) at the level of the first molar 151-251 distance between buccal cusps of the right and left second premolar 153-154 palatal shelf width right side (in UCLP, BCLP and Control) at the level of the second premolar 253-254 palatal shelf width left side (in UCLP, BCLP and Control) at the level of the second premolar 141-241 distance between buccal cusps of the right and left first premolar 143-144 palatal shelf width right side (in UCLP, BCLP and Control) at the level of the first premolar 243-244 palatal shelf width left side (in UCLP, BCLP and Control) at the level of the first premolar 131-231 distance between cusps of the right and left canine 133-134 palatal shelf width right side (in UCLP, BCLP and Control) at the level of the canine 233-234 palatal shelf width left side (in UCLP, BCLP and Control) at the level of the canine 163-164 / occlusal plane: palatal shelf elevation at the right side, defined as the angle between the occlusal plane and the line 163-164, representing the palatal shelf at the right side (see above). 263-264 / occlusal plane: palatal shelf elevation at the left side, defined - 264, as the angle between the occlusal plane and the line 263 representing the palatal shelf at the left side (see above). In the mandible: 371-471 distance between distal cusps of the right and left second molar 372-472 distance between mesial cusps of the right and left second molar 361-461 distance between distal cusps of the right and left first molar 362-462 distance between mesial cusps of the right and left first molar 351-451 distance between buccal cusps of the right and left second premolar 341-441 distance between buccal cusps of the right and left first premolar 331-431 distance between cusps of the right and left canine. Missing teeth and missing cusps were registered using a code indicating that a cusp or a tooth was missing. 35
Chapter 2 Arch depth calculations were not performed, as the position of the incisor, especially the central incisor, was often so extreme that arch depth measurements related to this incisor would produce unreliable results. 2.5 Statistics 2.5.1 Measurement error To determine the measurement error 40 dental casts were digitized twice by two independent observers. Intra- and interobserver measurement errors were calculated according to Dahlberg s formula (1940). The intra- and interobserver errors for the transversal distances were small ranging from 0.10 mm to 0.27 mm. The median measurement error was 0.15 mm. For the palatal shelf width these values ranged from 0.14 mm to 0.35 mm. The median error was 0.2 mm. The measurement error for the palatal shelf angle was 0.3º. The measurement errors were in agreement with earlier studies performed by our group but using other measuring devices (Kuijpers- Jagtman, 1985; Derijcke et al, 1994). 2.5.2 Statistics Means and standard deviations were calculated for all variables to describe the subgroups. Eight comparisons were made to find the influence of UCLA, UCLP, BCLA, and BCLP using the t-test i.e. UCLA versus Control UCLP versus Control BCLA versus Control BCLP versus Control UCLA versus UCLP BCLA versus BCLP UCLA versus BCLA UCLP versus BCLP The difference between the cleft and the non-cleft side (in the unilateral group only) was studied using the paired t-test. The level of significance was set at p<05. No alpha correction was made for multiple comparisons. The calculations were performed using SSPS version 11.0. 36
Material and methods 2.6 References DAHLBERG G. Statistical methods for medical and biological students. New York: Interscience Publications; 1940. DERIJCKE A, KUIJPERS-JAGTMAN AM, LEKKAS C, HARDJOWASITO W, LATIEF B. Dental arch dimensions in unoperated adult cleft-palate patients: an analysis of 37 cases. J Craniofac Genet Dev Biol 1994;14:69-74. KUIJ PERS-JAGTMAN AM. Changes in maxillary arch dimensions and occlusion in unilateral cleft lip and palate subjects. In: Studyweek Dutch Society for the Study of Orthodontics. Noordwijkerhout: NVOS; 1985. MOYERS RE, VAN DER LINDEN FPGM, RIOLO ML, McNAMARA JJ JR. Standards of human occlusal development. Ann Arbor (USA): Center for Human Growth and Development; 1976. 37